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  • 251.
    Farzaneh, Amirfarrokh
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    An in-situ ATR-FTIR Study of the Adsorption Properties of MFI Type Zeolites for Upgrading of Biofuels2014Licentiatavhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    With the depleting reservoirs of fossil fuels, increasing environmental concerns for flue-gas emissions from fossil-fuel combustion and growing world population, the need for the development of new sustainable fuels is higher than ever. However, to be able to compete with today’s mature technologies for production of fuels from fossil sources, new efficient processing alternatives for upgrading of biofuels must be developed. Bio-fuels produced by e.g. fermentative processes are promising alternatives to traditional chemicals and fuels produced from fossil sources. Recovery of biofuels by selective membranes and adsorbents has been identified as promising energy efficient recovery routes. In this work, the adsorption of water and butanol vapor in silicalite-1 and ternary adsorption of methane, water and carbon dioxide in zeolite Na-ZSM-5 were studied using in-situ ATR-FTIR spectroscopy in order to understand the adsorption properties of these zeolites. Single component adsorption isotherms of butanol and water vapor were determined at different temperatures using ATR-FTIR spectroscopy. The Langmuir model was successfully fitted to experimental data, and the fitted parameters obtained in this work were in very good agreement with values reported in the literature. The butanol/water adsorption selectivity determined was as high as 107 for a model ABE vapor mixture which shows that the adsorption of butanol silicalite-1 was very favorable compared to that of water. Biogas (methane) is another promising biofuel that is commonly produced by anaerobic degradation of biomass. However, before it may be used, contaminants have to be removed from the gas; two of the most abundant contaminants in biogas are carbon dioxide and water vapor. Adsorption of a ternary mixture of methane, carbon dioxide and water vapor in zeolite Na-ZSM-5 has been studied at various compositions and temperatures using ATR–FTIR spectroscopy. The amount adsorbed determined from experimental data were compared to predictions by the Ideal Adsorbed Solution Theory (IAST). For a model biogas mixture with the composition of 66, 0.4 and 33.6 mol % of CH4, H2O and CO2, respectively, the H2O/CH4, H2O/CO2 and CO2/CH4 selectivities were determined to be 2600, 130 and 20 respectively, showing that the zeolite showed the highest affinity for water followed by carbon dioxide. This result confirms that Na-ZSM-5 could be a promising membrane material for upgrading of biogas.

  • 252.
    Farzaneh, Amirfarrokh
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    DeJaco, Robert F.
    Department of Chemical Engineering and Materials Science and Department of Chemistry and Chemical Theory Center, University of Minnesota , Minneapolis.
    Ohlin, Lindsay
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Holmgren, Allan
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Siepmann, J. Ilja
    Department of Chemical Engineering and Materials Science and Department of Chemistry and Chemical Theory Center, University of Minnesota , Minneapolis.
    Grahn, Mattias
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Comparative Study of the Effect of Defects on Selective Adsorption of Butanol from Butanol/Water Binary Vapor Mixtures in Silicalite-1 Films2017Inngår i: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 33, nr 34, s. 8420-8427Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A promising route for sustainable 1-butanol (butanol) production is ABE (acetone, butanol, ethanol) fermentation. However, recovery of the products is challenging because of the low concentrations obtained in the aqueous solution, thus hampering large-scale production of biobutanol. Membrane and adsorbent-based technologies using hydrophobic zeolites are interesting alternatives to traditional separation techniques (e.g., distillation) for energy-efficient separation of butanol from aqueous mixtures. To maximize the butanol over water selectivity of the material, it is important to reduce the number of hydrophilic adsorption sites. This can, for instance, be achieved by reducing the density of lattice defect sites where polar silanol groups are found. The density of silanol defects can be reduced by preparing the zeolite at neutral pH instead of using traditional synthesis solutions with high pH. In this work, binary adsorption of butanol and water in two silicalite-1 films was studied using in situ attenuated total reflectance-Fourier transform infrared (ATR-FTIR) spectroscopy under equal experimental conditions. One of the films was prepared in fluoride medium, whereas the other one was prepared at high pH using traditional synthesis conditions. The amounts of water and butanol adsorbed from binary vapor mixtures of varying composition were determined at 35 and 50 °C, and the corresponding adsorption selectivities were also obtained. Both samples showed very high selectivities (100-23 000) toward butanol under the conditions studied. The sample having low density of defects, in general, showed ca. a factor 10 times higher butanol selectivity than the sample having a higher density of defects at the same experimental conditions. This difference was due to a much lower adsorption of water in the sample with low density of internal defects. Analysis of molecular simulation trajectories provides insights on the local selectivities in the zeolite channel network and at the film surface.

  • 253.
    Farzaneh, Amirfarrokh
    et al.
    School of Engineering, University of Boras, Boras, SE 501 90, Sweden.
    Richards, Tobias
    School of Engineering, University of Boras, Boras, SE 501 90, Sweden.
    van Heiningen, Adrian
    School of Chemical Technology, Aalto University, Espoo, FI-02150, Finland.
    Sklavounos, Evangelos
    School of Chemical Technology, Aalto University, Espoo, FI-02150, Finland.
    A Kinetic Study of CO2 and Steam Gasification of Char from Lignin Produced in the SEW Process2014Inngår i: BioResources, ISSN 1930-2126, E-ISSN 1930-2126, Vol. 9, nr 2, s. 3052-3063Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The reaction kinetics of gasification are important for the design of gasifiers using biomass feedstocks, such as lignin, produced in biorefinery processes. Condensed and uncondensed lignin samples used in the present study were prepared using the SEW (SO2-ethanol-water) fractionation process applied to spruce wood chips: the dissolved lignin is precipitated during the recovery of SO2 and ethanol from the spent fractionation liquor. The gasification of char made from condensed and uncondensed SEW lignin was investigated using thermogravimetric analysis (TGA) at atmospheric pressure using either CO2 or steam. The main aim of this study was to quantify the reaction rate during the gasification process, which was found to be best described as zero-order. All experiments were performed at constant temperatures between 700 and 1050 °C to obtain the necessary information for describing the reaction rate equation in an Arrhenius form; the heating rate was 20 °C/min for both samples. The experiments led to almost similar results for both samples. The activation energies of CO2 gasification were approximately 160 kJ/mol and 170 kJ/mol for uncondensed and condensed lignin char, respectively. The activation energies of steam gasification were approximately 90 kJ/mol and 100 kJ/mol for uncondensed and condensed lignin char, respectively.

  • 254.
    Farzaneh, Amirfarrokh
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Zhou, Ming
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Antzutkin, Oleg
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Bacsik, Zoltan
    Department of Materials and Environmental Chemistry, Stockholm University.
    Hedlund, Jonas
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Holmgren, Allan
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Grahn, Mattias
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Adsorption of Butanol and Water Vapors in Silicalite‑1 Films with a Low Defect Density2016Inngår i: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 32, s. 11789-11798Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Pure silica zeolites are potentially hydrophobic and have therefore been considered to be interesting candidates for separating alcohols, e.g., 1-butanol, from water. Zeolites are traditionally synthesized at high pH, leading to the formation of intracrystalline defects in the form of silanol defects in the framework. These silanol groups introduce polar adsorption sites into the framework, potentially reducing the adsorption selectivity toward alcohols in alcohol/water mixtures. In contrast, zeolites prepared at neutral pH using the fluoride route contain significantly fewer defects. Such crystals should show a much higher butanol/water selectivity than crystals prepared in traditional hydroxide (OH−) media. Moreover, silanol groups are present at the external surface of the zeolite crystals; therefore, minimizing the external surface of the studied adsorbent is important. In this work, we determine adsorption isotherms of 1-butanol and water in silicalite-1 films prepared in a fluoride (F−) medium using in situ attenuated total reflectance−Fourier transform infrared (ATR−FTIR) spectroscopy. This film was composed of well intergrown, plate-shaped b-oriented crystals, resulting in a low external area. Single-component adsorption isotherms of 1-butanol and water were determined in the temperature range of 35− 80 °C. The 1-butanol isotherms were typical for an adsorbate showing a high affinity for a microporous material and a large increase in the amount adsorbed at low partial pressures of 1-butanol. The Langmuir−Freundlich model was successfully fitted to the 1-butanol isotherms, and the heat of adsorption was determined. Water showed a very low affinity for the adsorbent, and the amounts adsorbed were very similar to previous reports for large silicalite-1 crystals prepared in a fluoride medium. The sample also adsorbed much less water than did a reference silicalite-1(OH−) film containing a high density of internal defects.The results show that silicalite-1 films prepared in a F− medium with a low density of defects and external area are very promising for the selective recovery of 1-butanol from aqueous solutions.

  • 255.
    Farzaneh, Amirfarrokh
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Zhou, Ming
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Potapova, Elisaveta
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Bacsik, Zoltan
    Department of Material and Environmental Chemistry, Stockholm University, SE-106 91 Stockholm, Sweden.
    Ohlin, Lindsay
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Holmgren, Allan
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Hedlund, Jonas
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Grahn, Mattias
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Adsorption of Water and Butanol in Silicalite-1 Film Studied with in-situ ATR-FTIR Spectroscopy2015Inngår i: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 31, nr 17, s. 4887-4894Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Biobutanol produced by, e.g., acetone–butanol–ethanol (ABE) fermentation is a promising alternative to petroleum-based chemicals as, e.g., solvent and fuel. Recovery of butanol from dilute fermentation broths by hydrophobic membranes and adsorbents has been identified as a promising route. In this work, the adsorption of water and butanol vapor in a silicalite-1 film was studied using in situ attenuated total reflectance–Fourier transform infrared (ATR–FTIR) spectroscopy to better understand the adsorption properties of silicalite-1 membranes and adsorbents. Single-component adsorption isotherms were determined in the temperature range of 35–120 °C, and the Langmuir model was successfully fitted to the experimental data. The adsorption of butanol is very favorable compared to that of water. When the silicalite-1 film was exposed to a butanol/water vapor mixture with 15 mol % butanol (which is the vapor composition of an aqueous solution containing 2 wt % butanol, a typical concentration in an ABE fermentation broth, i.e., the composition of the gas obtained from gas stripping of an ABE broth) at 35 °C, the adsorption selectivity toward butanol was as high as 107. These results confirm that silicalite-1 quite selectively adsorbs hydrocarbons from vapor mixtures. To the best of our knowledge, this is the first comprehensive study on the adsorption of water and butanol in silicalite-1 from vapor phase.

  • 256. Fasanya, O. O.
    et al.
    Atta, A. Y.
    Myint, M. T. Z.
    Dutta, Joydeep
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik.
    Jibril, B. Y.
    Effects of synthesis methods on performance of CuZn/MCM-41 catalysts in methanol steam reforming2021Inngår i: International journal of hydrogen energy, ISSN 0360-3199, E-ISSN 1879-3487, Vol. 46, nr 5, s. 3539-3553Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    CuZn-based catalysts are active in production of hydrogen by methanol steam reforming. However, there is a need to have further insight on their physico-chemical properties to improve selectivity to hydrogen. Therefore, a series of CuZn/MCM-41 catalysts was synthesized by four different routes; one pot hydrothermal synthesis (OPMCM), co-impregnation (COMCM), serial impregnation (SRMCM) and copper impregnated on Zn-MCM-41 (ZNMCM). Samples of catalysts were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM) coupled with energy dispersive X-ray spectroscopy (EDS), inductively coupled plasma (ICP) emission spectrometry, Fourier transform infrared (FTIR) spectroscopy, thermogravimetric analysis (TGA) and X-ray photoelectron spectroscopy (XPS). XRD revealed disruption in the ordered pore network typical in MCM-41 for all catalysts synthesized and also showed that the one pot synthesis catalyst had wide spread dispersion of Cu and Zn. SEM micrographs captured irregularly shaped particles of different sizes. While XPS showed that different Cu and Zn species were formed within the catalyst matrix. XPS also confirmed that there was wide spread dispersion and interaction of Cu and Zn with MCM-41 matrix in the OPMCM catalyst. COMCM and OPMCM demonstrated the highest activity with 88 and 65% methanol conversion with corresponding H2 selectivity of 91 and 86% respectively. They are better than SRMCM and ZNMCM which had average H2 selectivity of 19% and 31% respectively. CO selectivity was less than 1.8% for the COMCM and OPMCM catalysts. While SRMCM and ZNMCM had CO selectivity's as high as 8.9% and 7.2% respectively. The data generated shows that catalytic activity is largely affected by the nature of Cu species within the catalyst matrix.

  • 257. Fatehi, Hesameddin
    et al.
    Qu, Zhechao
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik.
    Schmidt, Florian M.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik.
    Bai, Xue-Song
    Effect of Volatile Reactions on the Thermochemical Conversion of Biomass Particles2017Inngår i: 8th International Conference on Applied Energy (ICAE2016) / [ed] Jinyue Yan, Fengchun Sun, SK Chou, Umberto Desideri, Hailong Li, Pietro Campana, Rui Xiong, Elsevier, 2017, Vol. 105, s. 4648-4654Konferansepaper (Fagfellevurdert)
    Abstract [en]

    A numerical and experimental study on the conversion of a biomass particle is carried out to quantify the effect of homogeneous volatile combustion on the biomass pyrolysis. The numerical domain consists of a particle and its surrounding and the model considers detailed chemical kinetic mechanism for reaction of pyrolysis products. A detailed pyrolysis model is employed which provides the composition of pyrolysis products. The effect of gas phase reaction on the conversion time and temperature of the particle is analyzed and it was shown that the gas phase reactions results in shorter pyrolysis time. H2O mole fraction and temperature above a biomass pellet from wheat straw (WS) and stem wood (SW) were experimentally measured using tunable diode laser absorption spectroscopy (TDLAS) while recording the particle mass loss. The TDLAS data were used to validate the numerical model developed for biomass conversion. The results showed that by considering the gas phase reactions a good agreement between the measurement and the model prediction for mass loss and temperature can be achieved. For H2O mole fraction on top of the particle, on the other hand, some discrepancy between the model prediction and the experimental data was observed. Nevertheless, the difference in H2O mole fraction would be much larger by neglecting the gas phase reaction at the particle boundary.

    Fulltekst (pdf)
    fulltext
  • 258. Fatehi, Hesameddin
    et al.
    Schmidt, Florian M.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik.
    Bai, Xue-Song
    Gas phase combustion in the vicinity of a biomass particle during devolatilization: model development and experimental verification2018Inngår i: Combustion and Flame, ISSN 0010-2180, E-ISSN 1556-2921, Vol. 196, s. 351-363Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A numerical and experimental study on the devolatilization of a large biomass particle is carried out to quantify the effect of homogeneous volatile combustion on the conversion of the particle and on the temperature and species distribution at the particle vicinity. A global chemical kinetic mechanism and a detailed reaction mechanism are considered in a one dimensional numerical model that takes into account preferential diffusivity and a detailed composition of tar species. An adaptive moving mesh is employed to capture the changes in the domain due to particle shrinkage. The effect of gas phase reactions on pyrolysis time, temperature and species distribution close to the particle is studied and compared to experiments. Online in situ measurements of average H2O mole fraction and gas temperature above a softwood pellet are conducted in a reactor using tunable diode laser absorption spectroscopy (TDLAS) while recording the particle mass loss. The results show that the volatile combustion plays an important role in the prediction of biomass conversion during the devolatilization stage. It is shown that the global reaction mechanism predicts a thin flame front in the vicinity of the particle deviating from the measured temperature and H2O distribution over different heights above the particle. A better agreement between numerical and experimental results is obtained using the detailed reaction mechanism, which predicts a wider reaction zone.

  • 259.
    Fatima, Nowshir
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Holmgren, Allan
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Marklund, Pär
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Mathew, Aji P.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Larsson, Roland
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Degradation mechanism of water contaminated automatic transmission fluid (ATF) in wet clutch system2013Konferansepaper (Fagfellevurdert)
    Fulltekst (pdf)
    fulltext
  • 260.
    Fatima, Nowshir
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Holmgren, Allan
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Marklund, Pär
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Minami, Ichiro
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Larsson, Roland
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Degradation Mechanism of Automatic Transmission Fluid by Water as a Contaminant2015Inngår i: Proceedings of the Institution of mechanical engineers. Part J, journal of engineering tribology, ISSN 1350-6501, E-ISSN 2041-305X, Vol. 229, nr 1, s. 74-85Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The degradation mechanism of water contaminated Automatic Transmission Fluids (ATF) was experimentally investigated. Water contaminated ATF was tribotested in a full-scale wet clutch test rig to monitor the friction durability during clutch ageing, and was also statically aged in oven to evaluate the interaction of ATF with water. The bulk properties and chemical nature of the ATF were analysed using viscosity measurements, Fourier Transform Infrared Spectroscopy (FTIR) and Thermogravimetric Analysis (TGA). It was shown that water presence in the ATF can increase the mean friction coefficient over a short time period, though in the long term perspective there is a higher loss of mean friction. Phase separation of the water-in-oil emulsion by centrifugation at 20000 rpm made it possible to examine the water phase using infrared 2spectroscopy. The spectroscopic analysis revealed the hydrophilic nature of certain ATF constituents, although the impact of water on the bulk properties like lubricant viscosity and thermal stability was insignificant. The analysis of the tribotests showed that the friction increase for water contamination was a short-term effect and likely due to the interaction between polar surface active additives and water. Even though no significant change has been found for thermal degradation or in bulk properties of the lubricant, the initially changed action of the water soluble additives and generation of high friction resulted in a total deterioration of the clutch performance during long term use.

  • 261.
    Fatima, Nowshir
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Minami, Ichiro
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Holmgren, Allan
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Marklund, Pär
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Berglund, Kim
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Larsson, Roland
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Influence of water on the tribological properties of zinc dialkyl-dithiophosphate and over-based calcium sulfonate additives in wet clutch contacts2015Inngår i: Tribology International, ISSN 0301-679X, E-ISSN 1879-2464, Vol. 87, s. 113-120Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Usually the wet clutch lubricant properties vary with different formulations of base oil types and additives. The aim of this paper was to evaluate the effect of water on the performance of additives in ATF. Simplified lubricants, ZDDP and over-based Ca-sulfonates detergent additives in an API Group I mineral base oil, were employed to compare with the commercial fully-formulated automatic transmission fluid (DEXRON®VI) during water-contamination. A full-scale wet clutch test rig was used to evaluate the frictional response due to water contamination of the lubricants. Fourier Transform Infrared Spectroscopy was utilized to evaluate the variation in the solubility of these polar organic additives in the water phase and Karl-Fischer titration was utilized to evaluate the post-test water content for different formulations.

  • 262.
    Fatima, Nowshir
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Minami, Ichiro
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Holmgren, Allan
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Marklund, Pär
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Larsson, Roland
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Adsorption of ATF additives on wet clutch friction interfaces under water contaminated lubricant conditions2014Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Stable friction and positive slope of friction-speed is the typical criterion for a good clutch performance. Lubricated friction interfaces used for wet clutches produces different friction behavior depending on the lubricant conditions. Usually the lubricant conditions vary for different automatic transmission fluid (ATF) formulations implying e.g. water contamination and these conditions might influence the deterioration of the clutch plates. The aim of this paper is to verify additive adsorption on friction interfaces and ageing of the friction material in wet clutch system for a water contaminated commercial ATF (DEXRON® VI). Standard clutch plates are employed in an automated wet clutch test rig to evaluate the friction characteristics of the tested lubricant. For controlled test conditions (speed, contact pressure, oil temperature) and specific number of test cycles, the mean friction coefficient and the friction vs. speed relations are monitored during sliding test. The resultant tribofilms on the tested friction interface surfaces are characterized by means of Scanning Electron Microscopy-Energy Dispersive X-ray spectroscopy (SEM- EDS), Attenuated Total Reflectance -Fourier Transform Infrared Spectroscopy (ATR-FTIR) and X-ray Photoelectron Spectroscopy (XPS analysis). The spectroscopic techniques were used to analyse adsorbed additives on friction interfaces and made it possible to correlate measured data to the specific friction behavior obtained after water contamination of the ATF.

  • 263.
    Fatima, Nowshir
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Minami, Ichiro
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Holmgren, Allan
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Marklund, Pär
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Larsson, Roland
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Adsorption of ATF additives on wet clutch friction interfaces under water contaminated lubricant conditions2014Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Stable friction and positive slope of friction-speed is the typical criterion for a good clutch performance. Lubricated friction interfaces used for wet clutches produces different friction behavior depending on the lubricant conditions. Usually the lubricant conditions vary for different automatic transmission fluid (ATF) formulations implying e.g. water contamination and these conditions might influence the deterioration of the clutch plates. The aim of this paper is to verify additive adsorption on friction interfaces and ageing of the friction material in wet clutch system for a water contaminated commercial ATF (DEXRON® VI). Standard clutch plates are employed in an automated wet clutch test rig to evaluate the friction characteristics of the tested lubricant. For controlled test conditions (speed, contact pressure, oil temperature) and specific number of test cycles, the mean friction coefficient and the friction vs. speed relations are monitored during sliding test. The resultant tribofilms on the tested friction interface surfaces are characterized by means of Scanning Electron Microscopy-Energy Dispersive X-ray spectroscopy (SEM- EDS), Attenuated Total Reflectance -Fourier Transform Infrared Spectroscopy (ATR-FTIR) and X-ray Photoelectron Spectroscopy (XPS analysis). The spectroscopic techniques were used to analyse adsorbed additives on friction interfaces and made it possible to correlate measured data to the specific friction behavior obtained after water contamination of the ATF.

    Fulltekst (pdf)
    FULLTEXT01
  • 264.
    Fatima, Nowshir
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Minami, Ichiro
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Holmgren, Allan
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Marklund, Pär
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Larsson, Roland
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Surface chemistry of wet clutch influenced by water contamination in automatic transmission fluids2016Inngår i: Tribology International, ISSN 0301-679X, E-ISSN 1879-2464, Vol. 96, s. 395-401Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Lubricated friction interfaces used for wet clutches produces different friction behaviour depending on the lubricant conditions. Usually the lubricant conditions vary for water contamination in automatic transmission fluid (ATF). The presence of water retards the ATF performance by increasing the friction and can influence the deterioration of the clutch plates. Water as a polar contaminant can change the absorbability of the surface active additives, which might cause the characteristic friction behaviour. The aim of this paper is to verify the surface chemistry of tribotested standard friction interfaces lubricated with water contaminated commercial ATF (DEXRON® VI). The evidences of the influence of water on ATF performances were shown by surface analyses

  • 265.
    Faust, Robin
    et al.
    Department of Chemistry and Chemical Engineering, Chalmers University of Technology, Gothenburg, Sweden.
    Hannl, Thomas Karl
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Berdugo Vilches, Teresa
    Department of Chemistry and Chemical Engineering, Chalmers University of Technology, Gothenburg, Sweden.
    Kuba, Matthias
    Bioenergy2020+ GmbH, Güssing, Austria.
    Öhman, Marcus
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Seemann, Martin
    Department of Space, Earth and Environment, Chalmers University of Technology, Gothenburg, Sweden.
    Knutsson, Pavleta
    Department of Space, Earth and Environment, Chalmers University of Technology, Gothenburg, Sweden.
    Layer Formation on Feldspar Bed Particles during Indirect Gasification of Wood. 1. K-Feldspar2019Inngår i: Energy & Fuels, ISSN 0887-0624, E-ISSN 1520-5029, Vol. 33, nr 8, s. 7321-7332Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The choice of bed material for biomass gasification plays a crucial role for the overall efficiency of the process. Olivine is the material conventionally used for biomass gasification due to the observed activity of olivine toward cracking of unwanted tars. Despite its catalytic activity, olivine contains high levels of chromium, which complicates the deposition of used bed material. Feldspar has shown the same activity as olivine when used as a bed material in biomass gasification. As opposed to olivine, feldspar does not contain environmentally hazardous compounds, which makes it a preferred alternative for further applications. The interaction of bed material and ash heavily influences the properties of the bed material. In the present study interactions between feldspar and main ash compounds of woody biomass in an indirect gasification system were investigated. Bed material samples were collected at different time intervals and analyzed with SEM-EDS and XRD. The obtained analysis results were then compared to thermodynamic models. The performed study was divided in two parts: in part 1 (the present paper), K-rich feldspar was investigated, whereas Na-rich feldspar is presented in part 2 of the study (DOI: 10.1021/acs.energyfuels.9b01291). From the material analysis performed, it can be seen that, as a result of the bed materials’ interactions with the formed ash compounds, the latter were first deposited on the surface of the K-feldspar particles and later resulted in the formation of Ca- and Mg-rich layers. The Ca enriched in the layers further reacted with the feldspar, which led to its diffusion into the particles and the formation of CaSiO3 and KAlSiO4. Contrary to Ca, Mg did not react with the feldspar and remained on the surface of the particles, where it was found as Mg- or Ca-Mg-silicates. As a result of the described interactions, layer separation was noted after 51 h with an outer Mg-rich layer and an inner Ca-rich layer. Due to the development of the Ca- and Mg-rich layers and the bed material–ash interactions, crack formation was observed on the particles’ surfaces.

  • 266.
    Fernandez, Hanna
    et al.
    KTH, Skolan för kemivetenskap (CHE).
    Johansson, Tova
    KTH, Skolan för kemivetenskap (CHE).
    Renholm, Pontus
    KTH, Skolan för kemivetenskap (CHE).
    Stauber Alfredsson, Malin
    KTH, Skolan för kemivetenskap (CHE).
    Design och tillverkning av automatiserat bryggverk2016Independent thesis Basic level (degree of Bachelor), 10 poäng / 15 hpOppgave
    Abstract [sv]

    Alkoholhaltiga drycker har konsumerats länge i Sverige, idag är öl en av de mest förekommande dryckerna. Med tanke på hur få ingredienser öl innehåller och att smaken trots detta kan varieras i det oändliga är det lätt att förstå att alla delsteg måste genomföras med precision. De olika delstegen i ölbryggningsprocessen är mältning, mäskning, lakning, humlekokning och jäsning.

    Ett försök till att bygga ett automatiserat bryggverk har gjorts. Komponenter till bryggverket har köpts in och bryggverket har byggts från grunden. Det var inte möjligt att göra alla delsteg i processen automatiserade, till exempel flödesstyrningar och tillsats av ingredienser. Detta gjorde att manuella insatser krävdes. För att styra bryggningen programmerades mikrokontrollerkortet Arduino Uno i programmeringsspråket C. Med hjälp av programmeringen har de delsteg av bryggningen, som går att automatisera, automatiserats.

    Vid testbryggningen uppstod praktiska problem som inte kunde förutsägas i teorin, exempelvis gick pumpen torrt ibland, reläerna fungerade inte som tänkt samt att en oväntad temperaturgradient uppstod. Dessa problem kan eventuellt lösas med ytterligare insatser i framtida försök. Vidare genomfördes tester innan bryggningen med endast vatten i kärlen för att undersöka temperaturregleringen. Det visade sig dock vara stora skillnader mellan vatten och mäsk, vilket gjorde att dessa tester inte kunde förutsäga alla problem. Trots detta resulterade bryggningen i en besk men drickbar öl.

    Fulltekst (pdf)
    fulltext
  • 267.
    Ferreira, Jorge A.
    et al.
    Högskolan i Borås, Akademin för textil, teknik och ekonomi.
    Lennartsson, Patrik R.
    Högskolan i Borås, Akademin för textil, teknik och ekonomi.
    Taherzadeh, Mohammad J
    Högskolan i Borås, Akademin för textil, teknik och ekonomi.
    Airlift bioreactors for fish feed fungal biomass production using edible filamentous fungi2017Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Airlift bioreactors are generally considered to be better alternatives for cultivation of filamentous fungi in comparison to stirred-tank bioreactors or bubble columns bioreactors. The reason for the former includes fungal growth around all internal parts including impellers, baffles or pH, temperature and oxygen probes limiting mass transfer, whereas the latter is limited by air flow rates that can be applied before the system provides deficient mixing and so mass transfer rates. Spent sulphite liquor, a by-product from the paper pulp industry, was used for cultivation of edible Rhizopus sp., a strain isolated from Indonesian tempeh used as human food, using a 26 L airlift bioreactor. Increasing the aeration rate from 0.15 to 1 vvm led to increased biomass production (1 vs 7 g/L). The aeration rate was also found to influence fungal morphology and metabolite production during batch cultivation. Rhizopus sp. shifted from mycelial suspensions at 0.15 and 0.5 vvm to small compact pellets of regular size at 1 vvm. The production of ethanol and lactic acid, a proof of sub-optimal aeration conditions, was also reduced when increasing the aeration rate from 0.15 to 1 vvm. The produced biomass was found to be composed, on a dry weight basis, of 30-50% protein, 2-7% lipids, and 3-9% glucosamine. Considering the edible character of the fungus used as well as its biomass nutritional characteristics, there is a potential for its use as fishmeal replacement within the increasing aquaculture sector.

  • 268.
    Filippov, Andrei
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Dvinskikh, Sergey V.
    Royal Institute of Technology.
    Khakimov, Aidar
    Kazan (Volga Region) Federal University, Kazan.
    Grahn, Mattias
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Zhou, Han
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Furo, Istvan
    Royal Institute of Technology.
    Antzutkin, Oleg
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Hedlund, Jonas
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Dynamic properties of water in silicalite-1 powder2012Inngår i: Magnetic Resonance Imaging, ISSN 0730-725X, E-ISSN 1873-5894, Vol. 30, nr 7, s. 1022-1031Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Self-diffusion of D 2O in partially filled silicalite-1 crystals was studied at 25°C by 2H nuclear magnetic resonance (NMR) with bipolar field gradient pulses and longitudinal Eddy-current-delay. For the first time, reliable experimental diffusion data for this system were obtained. Analysis of NMR diffusion decays revealed the presence of a continuous distribution of apparent self-diffusion coefficients (SDCs) of water, ranging from 10 -7 to ~10 -10 m 2/s, which include values much higher and lower than that of bulk water (~10 -9 m 2/s) in liquid phase. The observed distribution of SDC changes with variation of the diffusion time in the range of 10-200 ms. A two-site Kärger exchange model was successfully fitted to the data. Finally, the water distribution and exchange in silicalite-1 pores were described by taking into account (a) a gas-like phase in the zeolite pores, a gas-like phase in mesopores and an intercrystalline gas-like phase and (b) intercrystalline liquid droplets with intermediate exchange rate with the other phases. The other phases experience fast exchange on the NMR diffusion time scale. Diffusion coefficients and mean residence times of water in some of these states were estimated

  • 269.
    Flores Ituarte, Iñigo
    et al.
    Department of Materials and Production, Section of Sustainable Production, Faculty of Engineering and Science, Aalborg University, Copenhagen, Denmark.
    Wiikinkoski, Olli
    Department of Mechanical Engineering, School of Engineering, Aalto University, Espoo, Finland.
    Jansson, Anton
    Örebro universitet, Institutionen för naturvetenskap och teknik.
    Additive Manufacturing of Polypropylene: A Screening Design of Experiment Using Laser-Based Powder Bed Fusion2018Inngår i: Polymers, E-ISSN 2073-4360, Vol. 10, nr 12, artikkel-id 1293Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The use of commodity polymers such as polypropylene (PP) is key to open new market segments and applications for the additive manufacturing industry. Technologies such as powder-bed fusion (PBF) can process PP powder; however, much is still to learn concerning process parameters for reliable manufacturing. This study focusses in the process–property relationships of PP using laser-based PBF. The research presents an overview of the intrinsic and the extrinsic characteristic of a commercial PP powder as well as fabrication of tensile specimens with varying process parameters to characterize tensile, elongation at break, and porosity properties. The impact of key process parameters, such as power and scanning speed, are systematically modified in a controlled design of experiment. The results were compared to the existing body of knowledge; the outcome is to present a process window and optimal process parameters for industrial use of PP. The computer tomography data revealed a highly porous structure inside specimens ranging between 8.46% and 10.08%, with porosity concentrated in the interlayer planes in the build direction. The results of the design of experiment for this commercial material show a narrow window of 0.122 > Ev > 0.138 J/mm3 led to increased mechanical properties while maintaining geometrical stability.

    Fulltekst (pdf)
    FULLTEXT01
  • 270.
    Flores Ituarte, Iñigo
    et al.
    Department of Materials and Production, Section of Sustainable Production, Faculty of Engineering and Science, Aalborg University, Copenhagen, Denmark.
    Wiikinkoski, Olli
    Department of Mechanical Engineering, School of Engineering, Aalto University, Espoo, Finland.
    Jansson, Anton
    Örebro universitet, Institutionen för naturvetenskap och teknik. Department of Mechanical Engineering.
    Additive Manufacturing of Polypropylene: A Screening Design of Experiment Using Laser-Based Powder Bed Fusion2018Inngår i: Polymers, E-ISSN 2073-4360, Vol. 10, nr 12, artikkel-id 1293Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The use of commodity polymers such as polypropylene (PP) is key to open new market segments and applications for the additive manufacturing industry. Technologies such as powder-bed fusion (PBF) can process PP powder; however, much is still to learn concerning process parameters for reliable manufacturing. This study focusses in the process–property relationships of PP using laser-based PBF. The research presents an overview of the intrinsic and the extrinsic characteristic of a commercial PP powder as well as fabrication of tensile specimens with varying process parameters to characterize tensile, elongation at break, and porosity properties. The impact of key process parameters, such as power and scanning speed, are systematically modified in a controlled design of experiment. The results were compared to the existing body of knowledge; the outcome is to present a process window and optimal process parameters for industrial use of PP. The computer tomography data revealed a highly porous structure inside specimens ranging between 8.46% and 10.08%, with porosity concentrated in the interlayer planes in the build direction. The results of the design of experiment for this commercial material show a narrow window of 0.122 > Ev > 0.138 J/mm3 led to increased mechanical properties while maintaining geometrical stability.

    Fulltekst (pdf)
    fulltext
  • 271.
    Forsberg, Oscar
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser.
    Påverkan av sena tillsatser på medföljande slagg och dess viskositet i LD-processen2020Independent thesis Advanced level (professional degree), 300 hpOppgave
    Abstract [sv]

    Vid SSAB Europé i Luleå produceras höghållfaststål. För att uppnå sådan kvalité måste renligheten i stålet vara god i hela processen. Risken att få förhöjda värden av exempelvis vanadin efter LD-processen vid deoxidationssteget, då medföljande vanadininhållande slagg som återreduceras till stålet är hög.

    Det finns olika system som jobbar för att förhindra medföljande slagg vid tappning av LD-konvertern. På SSAB i Luleå används IR-kamera för att identifiera slagg vid tappning och en mekanisk slaggstoppare som blockerar tapphålet samt tvingar flödet tillbaka in i konvertern med hjälp av kvävgas.

    Ett annat möjligt system att använda skulle kunna vara slaggens viskositet, då en högviskös slagg skulle fungera som en vortexinhibitor och därigenom reducera mängden medföljande slagg. Målet med examensarbetet har varit att undersöka sena tillsatsers påverkan av medföljande slagg, där de sena tillsatserna syftar till att öka viskositeten på slaggen genom att skapa fasta partiklar.

    I daglig drift görs ingen uppskattning av mängden medföljande slagg eller hur sena slaggtillsatser påverkar detta. Genom slaggprovtagning samt stålprover innan och efter tappning av LD-konvertern kan en massbalans göras av mängden medföljande slagg. Beräkningsämnena som passade bäst i denna studie var kisel och vanadin, två ämnen som oftast återfinns endast i slaggen.

    Utifrån resultatet av proverna visade sena tillsatser inte ha någon påverkan av mängden medföljande slagg. Ingen påvisad skillnad av viskositetsberäkningarna kunde kopplas till de sena tillsatserna, där beräkningarna gjordes i FactSage.

    Studien visade att sena tillsatser inte har den önskade effekten på medföljande slagg som man tidigare trott och skulle kunna tas bort helt. Detta för att reducera kostnaderna för tillsatser och deponi.

    Slaggen fick flytegenskaper redan vid 72% andel fasta partiklar och en temperatur på 1379°C. Vid LD-processen har slaggen 8% andel fasta partiklar och temperatur på 1739°C. Detta påvisar att det blir praktiskt omöjligt att styva upp slaggen i LD-processen med hjälp av sena tillsatser.

    Fulltekst (pdf)
    fulltext
  • 272.
    Forsling, Willis
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Sterte, Johan
    Skogsindustrin satsar på forskning och utbildning i Luleå: professur i Kemisk Apparatteknik inrättad1997Inngår i: Svensk papperstidning, Nordisk cellulosa, ISSN 1101-766X, nr 9, s. 49-50Artikkel i tidsskrift (Annet vitenskapelig)
  • 273.
    Fouladvand, Shahpar
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser.
    Study of MFI zeolite membrane for CO2 separation2016Licentiatavhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    Nowadays, the need and interest for renewable sources of energy has increased. Biogas is a renewable source of energy that can be considered as a sustainable substitute for natural gas. Biogas is mainly composed of CH4 and CO2, and normally the CO2 content of the gas has to be reduced as it decreases the calorific value of the gas and it may also cause corrosion in pipes and other equipment. Most today’s technologies used for upgrading biogas have been adapted from upgrading of natural gas. However, these technologies are best suited for large scale operation; whereas, production of biogas is typically several orders of magnitude smaller. This leads to high costs for removal of CO2 from biogas and consequently, new efficient technologies for upgrading biogas should be developed. Membrane-based separations are generally considered as energy efficient and are suitable for a wide range in scale of production due to their modular design. Zeolite membranes have been singled out as especially attractive membranes for gas separations. In this work, we therefore study separation of CO2 from CH4 and H2 using zeolite MFI membranes. 

    The performance of a high-silica (Si/Al ca. 139) MFI membrane for CO2/CH4 separation was investigated in a wide temperature range i.e. 245 K to 300 K. The separation factor increased with decreasing temperatures as is typically the case for adsorption governed separations. The highest separation factor observed was about 10 at 245 K. The CO2 permeance was very high in the whole temperature studied, varying from ca. 60 × 10-7 mol s-1 m -2 Pa-1 at the lowest temperature to about 90 × 10-7 mol s-1 m -2 Pa-1 at the highest temperature studied. The CO2 permeance was higher than that reported previously in the open literature for this separation. Modeling of the experimental data revealed that the membrane performance was adversely affected by pressure drop over the support, whereas the effect of concentration polarization was small. Removing the former effect would improve both the permeance and selectivity of the membrane. 

    In order to investigate the impact of the aluminum content on the performance of MFI membranes for the CO2/CH4 separation, MFI membranes with different Si/Al ratios were prepared. Increasing the aluminum content makes the zeolite II more polar which should increase the CO2/CH4 adsorption selectivity. Again the effect of temperature on the performance was investigated by varying the temperature in a range almost similar as above. Altering the Si/Al ratio in MFI zeolite membranes indeed changed the separation performances. At the lower temperatures the separation performance increased with increasing aluminum content in the zeolite as a result of larger adsorption selectivity. However, as the temperature was decreased, the selectivity of the membrane with the highest aluminum content went through a maximum, whereas for the other membranes the selectivity continued to increase with decreasing temperature under the conditions studied. At the same time, the CO2 permeances were high for all membranes studied and for the membrane with the highest selectivity, the CO2 permeance increased from 65 × 10-7 to 100 × 10-7 mol s-1 m -2 Pa-1 with increasing temperature. 

    High-silica MFI membranes were also evaluated for CO2/H2 separation, which is critical for syngas purification and H2 production. The highest CO2 permeance at the feed pressure of 9 bar was about 78 × 10-7 mol s-1 m -2 Pa-1 at around 300 K, which is one or two order of magnitude higher than those reported previously in the literature. By decreasing the temperature, separation factor reached its highest value of 165 at 235 K. 

    In summary, zeolite membranes show great potential for CO2 separation from industrial gases, in particular for CO2 removal from synthesis gas. For the CO2/CH4 separation the selectivity of the MFI membranes should be improved or other frameworks relying on molecular sieving e.g. the CHA framework should be explored. 

    Fulltekst (pdf)
    fulltext
  • 274.
    Fredriksson, Robert
    et al.
    AkzoNobel , Separations Products, Bohus, Sweden.
    Samuelsson, Jörgen
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörs- och kemivetenskaper (from 2013).
    Fornstedt, Torgny
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörs- och kemivetenskaper (from 2013).
    The Importance of Overloading Studies in Method Development: A Case Study2012Konferansepaper (Fagfellevurdert)
  • 275.
    Fu, Dianliang
    et al.
    Shandong University, China.
    Truong, Nguyen Le
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för byggd miljö och energiteknik (BET).
    Lai, Yanhua
    Shandong University, China.
    Lin, Leteng
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för byggd miljö och energiteknik (BET).
    Dong, Zhen
    Shandong University, China.
    Lyu, Mingxin
    Shandong University, China.
    Improved pinch-based method to calculate the capital cost target of heat exchanger network via evolving the spaghetti structure towards low-cost matching2022Inngår i: Journal of Cleaner Production, ISSN 0959-6526, E-ISSN 1879-1786, Vol. 343, artikkel-id 131022Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Ahead of heat exchanger network (HEN) design, setting an optimal pinch temperature difference for pinch analysis depends vitally on the capital cost target. Conventional methods based on the spaghetti (SPA) structure ignoring matching optimization might result in calculated cost targets of large deviations. This work evolved the SPA structure via four stages by shifting energy towards low-cost matching. The fourth structure evolved from the SPA structure (ESPA-IV structure) with the lowest-cost matching after loops elimination forms the base to establish the ESPA method. It is validated by numerical experiment and applied to a case reported in literature, meanwhile comparisons are always made to the SPA method. The numerical experiment proves that the ESPA method can obtain capital cost targets with higher accuracy than the SPA method. The target deviations (often within ±5%) given by the ESPA method are much lower than those (well above 10%) derived by the SPA method. In the case study, the given HEN is further optimized as hinted by ESPA method results. Of two target methods, the cost target indicated by ESPA method is closer to the optimum capital cost newly derived after optimization. The high accuracy of the ESPA method is further verified.

    Fulltekst (pdf)
    fulltext
  • 276.
    Galkin, Maxim
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för materialvetenskap, Nanoteknologi och funktionella material.
    Barta, Katalin
    Karl Franzens Univ Graz, Inst Chem, Heinrichstr 28, A-8010 Graz, Austria..
    Editorial: Chemical conversion of biomass to chemicals2023Inngår i: Current Opinion in Green and Sustainable Chemistry, E-ISSN 2452-2236 , Vol. 44, artikkel-id 100869Artikkel i tidsskrift (Annet vitenskapelig)
  • 277.
    Gao, Qiuju
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Edo, Mar
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Larsson, Sylvia H.
    Collina, Elena
    Rudolfsson, Magnus
    Gallina, Marta
    Oluwoye, Ibukun
    Altarawneh, Mohammednoor
    Dlugogorski, Bogdan Z.
    Jansson, Stina
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Formation of PCDDs and PCDFs in the torrefaction of biomass with different chemical composition2017Inngår i: Journal of Analytical and Applied Pyrolysis, ISSN 0165-2370, E-ISSN 1873-250X, Vol. 123, s. 126-133Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Torrefaction is a thermal pre-treatment technology used to refine biomass, mainly for energy production purposes. However, there is currently a lack of information on the potential formation of polychlorinated dibenzo-p-dioxins (PCDDs) and dibenzofurans (PCDFs) in the torrefaction process. In this study, torrefaction was conducted using five different types of feedstock: stemwood, bark, wood from a discarded telephone pole, cassava stems and particle board. The feedstock as well as the torrefied biomass (chars) and the volatiles (non-condensable and condensable) generated during torrefaction were analyzed for PCDDs and PCDFs. PCDD concentrations in the torrefaction products were about 2-5 fold of those in the feedstocks. Torrefaction of particle board resulted in extensive formation of PCDDs (7200 ng kg(-1)) compared to the other four feedstocks (13-27 ng kg(-1)). Examination of the homologue profiles suggested that the observed PCDDs in the torrefaction products partly originated from new formation and partly physical transformation from volatilization and re-condensation of PCDDs present in the feedstock. Dechlorination of highly chlorinated compounds (HpCDD and OCDD) in the feedstock to form less chlorinated PCDDs was also observed. Compared to PCDDs, the net formation of PCDFs in the torrefaction process was low, except for the telephone pole sample, for which a dramatic increase (44-fold) of PCDFs was observed. PCDDs and PCDFs were mainly retained in the chars, accounting for 76-96% and 39-74% of the total concentration, respectively. It was also found that the highly chlorinated congeners tended to be retained in the chars, whereas the less chlorinated ones were predominantly volatilized into the gas phase.

  • 278.
    Garcia, Gustavo
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Synthesis of Zeolites from Bolivian Raw Materials for Catalysis and Detergency Applications2014Licentiatavhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    Zeolites are very useful in many technological applications such as catalysis, separation and purification of gases and solvents, ion-exchange, etc. The production of zeolites is nowadays carried out with a variety of reagents, such starting materials render large scale production of zeolites expensive. Hence alternative synthesis routes for zeolite production at a lower cost are currently under investigation. One of these routes involves the use of natural aluminosilicate raw materials which have many advantages such as their availability, low price, workability, etc. The aim of the present work was to provide routes to produce synthetic zeolites of industrial attractiveness derived from non-expensive Bolivian raw materials like clays and diatomites. In particular, the work was focused on the synthesis of intermediate- and low-silica zeolites: zeolite Y and zeolite A. The raw materials as well as intermediate materials and final zeolite products were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), nitrogen gas adsorption, inductively coupled plasma mass spectrometry (ICP-SFMS), and UV-VIS spectroscopy.The first part of the study addressed the synthesis and characterization of intermediate silica zeolite Y from diatomite. Prior to synthesis, the diatomite was leached in sulfuric acid to remove impurities, but this step also resulted in dealumination. Therefore, aluminum sulfate was used as an extra source of aluminum. The raw materials were reacted hydrothermally at 373 K in aqueous medium with sodium hydroxide. Variations in parameters like the Na2O/SiO2 ratio and synthesis time were investigated. As a result, micro-sized crystals of zeolite Y were obtained. It was possible to achieve high zeolite yield at a Na2O/SiO2 ratio of 0.9, which produced zeolite Y with a SiO2/Al2O3 ratio of 3.9. Also, synthesis of almost pure zeolite Y with a SiO2/Al2O3 ratio of 5.3 in low yield at a Na2O/SiO2 ratio of 0.6 was achieved. In this respect, diatomite behaved similarly to colloidal silica in traditional syntheses, with both sources of silica having a high degree of polymerization. Zeolite Y with the latter SiO2/Al2O3 ratio might be useful for the production of ultra-stable zeolite Y for use as FCC catalyst.A similar acid leaching procedure, this time with hydrochloric acid, was used for dealumination of diatomite to increase the SiO2/Al2O3 ratio and to reduce the amount of iron in producing well-crystallized ZSM-5 from diatomite in combination with sodium hydroxide and n-butyl amine under appropriate synthesis conditions.The second part of this study dealt with the synthesis of low silica zeolite A from Bolivian montmorillonite-type clay. This clay did contain significant amounts of quartz. Hence, an alkali fusion treatment was applied to the clay by fusing the clay at high temperature with NaOH to make the material more reactive and to take advantage of all the silica present in the clay. The raw clay had a SiO2/Al2O3 ratio of 4, and sodium aluminate was added to the mixture to decrease this ratio to 2. An optimization of the synthesis time was performed. The final zeolite product exhibited high brightness despite the presence of iron in appreciable amount in the starting material and the final product. This was attributed to the magnesium in the raw material, which exerted a masking effect on iron. The latter was incorporated into extraneous magnesium aluminosilica compounds, thereby increasing brightness and strongly decreasing the overall yellowness. This simple method appears as a promising alternative to the complex and costly techniques suggested to reduce the iron content in natural raw materials, especially kaolin.To summarize, this work reports the synthesis of zeolites with promising characteristics from Bolivian raw materials. However, further optimization is required to qualify these products for industrial applications. Moreover, this study might help in the development of poor regions of the Bolivian Altiplano and open up for large scale production, since the methods developed in this work are simple and non-expensiveand other impurities for synthesis of high silica ZSM-5 zeolite. This procedure was successful in producing well-crystallized ZSM-5 from diatomite in combination with sodium hydroxide and n-butyl amine under appropriate synthesis conditions.The second part of this study dealt with the synthesis of low silica zeolite A from Bolivian montmorillonite-type clay. This clay did contain significant amounts of quartz. Hence, an alkali fusion treatment was applied to the clay by fusing the clay at high temperature with NaOH to make the material more reactive and to take advantage of all the silica present in the clay. The raw clay had a SiO2/Al2O3 ratio of 4, and sodium aluminate was added to the mixture to decrease this ratio to 2. An optimization of the synthesis time was performed. The final zeolite product exhibited high brightness despite the presence of iron in appreciable amount in the starting material and the final product. This was attributed to the magnesium in the raw material, which exerted a masking effect on iron. The latter was incorporated into extraneous magnesium aluminosilica compounds, thereby increasing brightness and strongly decreasing the overall yellowness. This simple method appears as a promising alternative to the complex and costly techniques suggested to reduce the iron content in natural raw materials, especially kaolin.To summarize, this work reports the synthesis of zeolites with promising characteristics from Bolivian raw materials. However, further optimization is required to qualify these products for industrial applications. Moreover, this study might help in the development of poor regions of the Bolivian Altiplano and open up for large scale production, since the methods developed in this work are simple and non-expensive.

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    FULLTEXT01
  • 279.
    Garcia, Gustavo
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Aguilar, Wilson
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Carabante, Ivan
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    Cabrera, Saúl
    Chemistry Research Institute IIQ, San Andres Mayor University UMSA, La Paz.
    Hedlund, Jonas
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Mouzon, Johanne
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Preparation of zeolite A with excellent optical properties from clay2015Inngår i: Journal of Alloys and Compounds, ISSN 0925-8388, E-ISSN 1873-4669, Vol. 619, s. 771-777Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Discoloration of zeolite A powder is a common problem when natural raw materials such as kaolin clay are used because of the formation of colored iron compounds. In this study, we report on a novel method to produce zeolite A with excellent optical properties, from clays. The brightness is as high as 94.5 and the yellowness is as low as 3.0. The product is comprised of intergrown zeolite A crystals with cubic habit and a length ranging between 0.5 and 2 μm. Good optical properties are obtained when the raw material contains magnesium, as some natural raw materials do, or alternatively, when a magnesium compound is added to the raw material. Magnesium probably forces iron inside colorless extraneous magnesium aluminosilicate compounds. This simple process appears very promising for the preparation of zeolite A with good optical properties from inexpensive natural raw materials.

  • 280.
    Garcia, Gustavo
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik. Solid State and Theoretical Chemistry, Chemistry Research Institute, San Andres Mayor University.
    Cabrera, Saúl
    Solid State and Theoretical Chemistry, Chemistry Research Institute, San Andres Mayor University, University Campus.
    Hedlund, Jonas
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Mouzon, Johanne
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Selective synthesis of FAU-type zeolites2018Inngår i: Journal of Crystal Growth, ISSN 0022-0248, E-ISSN 1873-5002, Vol. 489, s. 36-41Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In the present work, parameters influencing the selectivity of the synthesis of FAU-zeolites from diatomite were studied. The final products after varying synthesis time were characterized by scanning electron microscopy, energy dispersive spectroscopy, X-ray diffraction and gas adsorption. It was found that high concentrations of NaCl could completely inhibit the formation of zeolite P, which otherwise usually forms as soon as maximum FAU crystallinity is reached. In the presence of NaCl, the FAU crystals were stable for extended time after completed crystallization of FAU before formation of sodalite. It was also found that addition of NaCl barely changed the crystallization kinetics of FAU zeolite and only reduced the final FAU particle size and SiO2/Al2O3 ratio slightly. Other salts containing either Na or Cl were also investigated. Our results suggest that there is a synergistic effect between Na+ and Cl-. This is attributed to the formation of (Na4Cl)3+ clusters that stabilize the sodalite cages. This new finding may be used to increase the selectivity of syntheses leading to FAU-zeolites and avoid the formation of undesirable by-products, especially if impure natural sources of aluminosilica are used.

  • 281.
    Garcia, Gustavo
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Cardenas, Edgar
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Cabrera, Saúl
    Chemistry Research Institute IIQ, San Andres Mayor University UMSA, La Paz.
    Hedlund, Jonas
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Mouzon, Johanne
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Synthesis of zeolite Y from diatomite as silica source2016Inngår i: Microporous and Mesoporous Materials, ISSN 1387-1811, E-ISSN 1873-3093, Vol. 219, s. 29-37Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Bolivian diatomite was successfully used as a silica source for the synthesis of zeolite Y. Prior to synthesis, the diatomite was leached with sulfuric acid to remove impurities and aluminum sulfate was used as an aluminum source. The raw materials were reacted hydrothermally at 100 °C in water with sodium hydroxide and different Na2O/SiO2 ratios were investigated. The final products were characterized by scanning electron microscopy, X-ray diffraction, gas adsorption and inductively coupled plasma-atomic emission spectroscopy. Diatomites originating from different locations and therefore containing different types and amounts of minerals and clays as impurities were investigated. After optimization of synthesis time, zeolite Y with low SiO2/Al2O3 ratio (3.0–3.9) was obtained at a high yield for high alkalinity conditions (Na2O/SiO2 = 0.85–2.0). Lower Na2O/SiO2 ratios resulted in incomplete dissolution of diatomite and lower yield. Nevertheless, decreasing alkalinity resulted in a steady increase of the SiO2/Al2O3 ratio in zeolite Y. Consequently, it was possible to synthesize almost pure zeolite Y with a SiO2/Al2O3 ratio of 5.3 for a Na2O/SiO2 ratio of 0.6, albeit at a low yield. In this respect, diatomite enables the synthesis of high silica zeolite Y and behaves similarly to colloidal silica in traditional syntheses, with both sources of silica having in common a high degree of polymerization. Interestingly, the presence of minerals and clays in the starting diatomite had marginal effects on the outcome of the synthesis. However, their dissolution resulted in presence of calcium and magnesium in the zeolite Y crystals. Finally, overrun of all investigated compositions resulted in the formation of zeolite P nucleating and growing onto dissolving zeolite Y crystals, which was shown to be triggered when aluminum was completely depleted at high alkalinity

  • 282.
    Garcia Mendoza, Javier Gustavo
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser.
    Synthesis and applications of low silica zeolites from Bolivian clay and diatomaceous earth2017Doktoravhandling, monografi (Annet vitenskapelig)
    Abstract [en]

    The aim of the present work was to develop synthesis routes to produce synthetic zeolites with industrial attractiveness from non-expensive Bolivian raw materials, such as clays and diatomite. In particular, the work was focused on the synthesis of low-silica zeolites with the LTA and FAU structures. The raw materials as well as intermediate and final zeolite products were structurally characterized by different techniques, namely scanning electron microscopy (SEM), X-ray diffraction (XRD), nitrogen gas adsorption, inductively coupled plasma mass spectrometry (ICP-MS). Besides, the final properties were evaluated for intended applications i.e. brightness by UV-VIS spectroscopy for LTA-type zeolite A in detergents and the CO2 breakthrough adsorption of FAU-type zeolite X for gas separation.

     

    The first part of this study deals with the synthesis of low silica zeolite A from Bolivian montmorillonite clay (Paper I). The clay was fused at high temperature with NaOH to render the material more reactive. The raw montmorillonite had a SiO2/Al2O3 ratio of 4 and sodium aluminate was added to the mixture to decrease this ratio to 2. An optimization of the synthesis time was performed. For the sake of comparison, the same treatment was applied to commercial kaolin. The final zeolite product from Bolivian montmorillonite exhibited high brightness despite the presence of iron in appreciable amount in the starting material and the final product. It was concluded that magnesium, present in the raw material, exerted a masking effect on iron. The latter was incorporated into extraneous magnesium aluminosilica compounds, thereby increasing brightness and strongly decreasing the overall yellowness. This simple method appears as a promising alternative to the complex and costly techniques suggested to reduce the iron content in natural raw materials, especially kaolin.

     

    The second part of the study addresses the synthesis, characterization and evaluation of FAU-type zeolites i.e. Y and X from diatomite and chemical grade reagents, respectively. With regard to the synthesis of zeolite Y, the diatomite was leached in sulfuric acid to remove impurities prior to synthesis, this step also resulted in dealumination, which rendered possible the synthesis of ZSM-5 zeolite (Paper II). However, extra aluminum had to be added in the form of aluminum sulfate for the synthesis of zeolite Y (Paper III). In this case, the raw materials were reacted hydrothermally at 100°C in aqueous medium with sodium hydroxide. Variations in parameters such as the Na2O/SiO2 ratio and synthesis time were investigated. As a result, micro-sized crystals of zeolite Y were obtained at a Na2O/SiO2 ratio of 0.9, which produced zeolite Y with a SiO2/Al2O3 ratio of 3.9. Also, zeolite Y with a SiO2/Al2O3 ratio of 5.3 in low yield at a Na2O/SiO2 ratio of 0.6 was achieved. In this way, diatomite behaved similarly to colloidal silica in traditional syntheses having a high degree of polymerization. Zeolite Y with a SiO2/Al2O3 ratio of 5.3 might be useful for the production of ultra-stable zeolite Y for use as FCC catalyst. Addition of NaCl to this system was also found to completely inhibit the formation of zeolite P and to retard the effects of overrunning by a synergic effect of Na and Cl ions (Paper IV).

     

    As an innovate application, FAU-type zeolite X films were growth on steel monoliths as structured adsorbent for CO2 removal (Paper V). Thicknesses 3 and 10 µm on steel monoliths of 1600 cells per square inches (c.p.s.i.) were investigated. The produced structured adsorbents showed reasonable CO2 adsorption capacity but with a very low pressure drop compared with traditional packed beds of zeolite beads. The CO2 breakthrough fronts were very sharp and the mass transfer resistance was very low compensating the presence of less adsorbing material by reducing cycle time and increased cycle frequency to increase throughput.  

     

    To summarize, zeolites with promising characteristics were successfully synthesized from Bolivian raw materials in this thesis work. However, further characterization is required to qualify these products for industrial applications. Moreover, this study might help the development of poor regions of the Bolivian Altiplano and open up for large scale production, since the methods developed in this work are simple and non-expensive.

    Fulltekst (pdf)
    fulltext
  • 283. Gavilà, Llorenç
    et al.
    Constantí, Magda
    Medina, Francisco
    Pezoa-Conte, Ricardo
    Anugwom, Ikenna
    Mikkola, Jyri-Pekka
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Lactic acid production from renewable feedstock: fractionation, hydrolysis, and fermentation2018Inngår i: Advanced Sustainable Systems, ISSN 2366-7486, Vol. 2, nr 3, artikkel-id 1700185Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In this paper, an integrated fractionation with a switchable ionic liquid (SIL), pulp hydrolysis, and lactic acid fermentation is carried out. For this, SO2-swithced SIL is used for fractionation of sugar cane (Saccharum officinarum) bagasse and giant cane (Arundo donax, AD). SIL is able to extract ≈2/3 of lignin when relatively large wood chips (≈4 mm) are used without any mechanical agitation and just 1 h of treatment time for AD. Furthermore, SIL reuse is successfully demonstrated for four runs. Subsequently, the produced pulps are hydrolyzed within 15 min in a microwave reactor, producing a glucose rich hydrolysates. Finally, these hydrolysates are used as a carbohydrate source for Lactobacillus delbrueckii fermentation, which selectively transform all glucose present into optically pure D-lactic acid. Hence, the whole chain for lactic acid production from biomass is successfully demonstrated.

  • 284.
    Gavrilovic, Ljubisa
    et al.
    Norwegian University of Science and Technology, Norway.
    Brandin, Jan
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för byggd miljö och energiteknik (BET).
    Holmen, Anders
    Norwegian University of Science and Technology, Norway.
    Venvik, Hilde
    Norwegian University of Science and Technology, Norway.
    Myrstad, R.
    SINTEF Materials and Chemistry, Norway.
    Blekkan, Edd
    Norwegian University of Science and Technology, Norway.
    Deactivation of Co-based Fischer-Tropsch catalyst by aerosol deposition of potassium salts2018Inngår i: Industrial & Engineering Chemistry Research, ISSN 0888-5885, E-ISSN 1520-5045, Vol. 57, nr 6, s. 1935-1942Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A 20%Co/0.5%Re/γAl2O3 Fischer-Tropsch catalyst was poisoned by four potassium salts (KNO3, K2SO4, KCl, K2CO3) using the aerosol deposition technique, depositing up to 3500 ppm K as solid particles. Standard characterization techniques (H2 Chemisorption, BET, TPR) showed no difference between treated samples and their unpoisoned counterpart. The Fischer-Tropsch activity was investigated at industrially relevant conditions (210 °C, H2:CO = 2:1, 20 bar). The catalytic activity was significantly reduced for samples exposed to potassium, and the loss of activity was more severe with higher potassium loadings, regardless of the potassium salt used. A possible dual deactivation effect by potassium and the counter-ion (chloride, sulfate) is observed with the samples poisoned by KCl and K2SO4. The selectivity towards heavier hydrocarbons (C5+) was slightly increased with increasing potassium loading, while the CH4 selectivity was reduced for all the treated samples. The results support the idea that potassium is mobile under FT conditions. The loss of activity was described by simple deactivation models which imply a strong non-selective poisoning by the potassium species.

  • 285.
    Gavrilovic, Ljubisa
    et al.
    Norwegian University of Science and Technology, Norway.
    Brandin, Jan
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för byggd miljö och energiteknik (BET).
    Holmen, Anders
    Norwegian University of Science and technology, Norway.
    Venvik, Hilde
    Norwegan University of Science and technology, Norway.
    Myrstad, Rune
    SINTEF Industry, Norway.
    Blekkan, Edd
    Norwegan University of Science and Technology, Norway.
    Fischer-Tropsch synthesis: Investigation of the deactivation of a Co catalyst by exposure to aerosol particles of potassium salt2018Inngår i: Applied Catalysis B: Environmental, ISSN 0926-3373, E-ISSN 1873-3883, Vol. 230, s. 203-209Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The influence of potassium species on a Co based Fischer-Tropsch catalyst was investigated using an aerosol deposition technique. This way of poisoning the catalyst was chosen to simulate the actual potassium behaviour during the biomass to liquid (BTL) process utilizing gasification followed by fuel synthesis. A reference catalyst was poisoned with three levels of potassium and the samples were characterized and tested for the Fischer-Tropsch reaction under industrially relevant conditions. None of the conventional characterization techniques applied (H2 Chemisorption, BET, TPR) divulged any difference between poisoned and unpoisoned samples, whereas the activity measurements showed a dramatic drop in activity following potassium deposition. The results are compared to previous results where incipient wetness impregnation was used as the method of potassium deposition. The effect of potassium is quite similar in the two cases, indicating that irrespective of how potassium is introduced it will end up in the same form and on the same location on the active surface. This indicates that potassium is mobile under FTS conditions, and that potassium species are able to migrate to sites of particular relevance for the FT reaction.

  • 286.
    Gavrilovic, Lubisa
    et al.
    Norwegian University of Science and Technology, Norway.
    Brandin, Jan
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för byggd miljö och energiteknik (BET).
    Holmen, Anders
    Norwegian University of Science and Technology, Norway.
    Venvik, Hild J.
    Norwegian University of Science and Technology, Norway.
    Myrstad, Rune
    SINTEF Industry, Norway.
    Blekkan, Edd A.
    Norwegian University of Science and Technology, Norway.
    The effect of aerosol-deposited ash components on a cobalt-based Fischer–Tropsch catalyst2019Inngår i: Reaction Kinetics, Mechanisms and Catalysis, ISSN 1878-5190, E-ISSN 1878-5204, Vol. 127, nr 1, s. 231-240Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The effect of ash salts on Co-based Fisher–Tropsch catalysts was studied using an aerosol deposition technique. The major elements in the ash were found to be K, S and Cl. The ash was deposited on a calcined catalyst as dry particles with an average diameter of approx. 350 nm. The loading of ash particles was varied by varying the time of exposure to the particles in a gas stream. Catalyst characterization did not reveal significant differences in cobalt dispersion, reducibility, surface area, pore size, or pore volume between the reference and the catalysts with ash particles deposited. Activity measurements showed that following a short exposure to the mixed ash salts (30 min), there were no significant loss of activity, but a minor change in selectivity of the catalyst . Extended exposure (60 min) led to some activity loss and changes in selectivity. However, extending the exposure time and thus the amount deposited as evidenced by elemental analysis did not lead to a further drop in activity. This behavior is different from that observed with pure potassium salts, and is suggested to be related to the larger size of the aerosol particles deposited. The large aerosol particles used here were probably not penetrating the catalyst bed, and to some extent formed an external layer on the catalyst bed. The ash salts are therefore not able to penetrate to the pore structure and reach the Co active centers, but are mixed with the catalyst and detected in the elemental analysis.

  • 287. Ge, Y.
    et al.
    Ding, S.
    Zhang, Wennan
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap, design och hållbar utveckling (2023-).
    Kong, X.
    Kantarelis, E.
    Engvall, K.
    Pettersson, J. B. C.
    Impacts of fresh bed materials on alkali release and fuel conversion rate during wood pyrolysis and char gasification2023Inngår i: Fuel, ISSN 0016-2361, E-ISSN 1873-7153, Vol. 353, artikkel-id 129161Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Bed materials provide efficient heat transfer and catalytic function in the thermochemical conversion of biomass, but their interactions with the fuel remain incompletely understood. In this study, the effects of bed materials on alkali release and fuel conversion during wood pyrolysis and CO2 gasification are investigated by online alkali detection combined with thermogravimetric analysis. The investigated bed materials include silica, sea sand, alumina and the natural ores olivine, ilmenite and dolomite. Only dolomite has a significant effect on fuel mass loss and alkali release during wood pyrolysis, while all bed materials influence char reactivity and alkali release during gasification. Sea sand, alumina and dolomite enhance the char gasification during the whole or most of the gasification process, which is related to alkali migration from the bed materials. All bed materials affect char reactivity and alkali release when the conversion approaches completion, and small amounts of some bed materials reduce the alkali release by an order of magnitude. The findings can be understood based on the chemical composition of the different materials. Silicon-rich materials reduce the levels of catalytically active alkali by formation of stable alkali silicates, and a similar explanation applies for ilmenite that captures alkali efficiently. Magnesium and calcium in contrast promote alkali release through their influence on alkali silicate chemistry. Analysis of char surfaces using scanning electron microscopy with energy dispersive spectroscopy indicates that low amounts of several elements are transferred from the bed material to the char where they may be directly involved in the char conversion process. The transferred elements are specific for each bed material and relates to their chemical composition. Mechanisms for material exchange between bed material and char are discussed. 

  • 288.
    Ge, Yaxin
    et al.
    Department of Chemistry and Molecular Biology, Atmospheric Science, University of Gothenburg, SE-412 96 Gothenburg, Sweden.
    Ding, Saiman
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Kemiteknik, Processteknologi.
    Zhang, Wennan
    Department of Chemical Engineering, Mid Sweden University, SE-85170 Sundsvall, Sweden.
    Kong, Xiangrui
    Department of Chemistry and Molecular Biology, Atmospheric Science, University of Gothenburg, SE-412 96 Gothenburg, Sweden.
    Kantarelis, Efthymios
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Kemiteknik, Processteknologi.
    Engvall, Klas
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Kemiteknik, Processteknologi.
    Pettersson, Jan B.C.
    Department of Chemistry and Molecular Biology, Atmospheric Science, University of Gothenburg, SE-412 96 Gothenburg, Sweden.
    Impacts of fresh bed materials on alkali release and fuel conversion rate during wood pyrolysis and char gasification2023Inngår i: Fuel, ISSN 0016-2361, E-ISSN 1873-7153, Vol. 353, artikkel-id 129161Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Bed materials provide efficient heat transfer and catalytic function in the thermochemical conversion of biomass, but their interactions with the fuel remain incompletely understood. In this study, the effects of bed materials on alkali release and fuel conversion during wood pyrolysis and CO2 gasification are investigated by online alkali detection combined with thermogravimetric analysis. The investigated bed materials include silica, sea sand, alumina and the natural ores olivine, ilmenite and dolomite. Only dolomite has a significant effect on fuel mass loss and alkali release during wood pyrolysis, while all bed materials influence char reactivity and alkali release during gasification. Sea sand, alumina and dolomite enhance the char gasification during the whole or most of the gasification process, which is related to alkali migration from the bed materials. All bed materials affect char reactivity and alkali release when the conversion approaches completion, and small amounts of some bed materials reduce the alkali release by an order of magnitude. The findings can be understood based on the chemical composition of the different materials. Silicon-rich materials reduce the levels of catalytically active alkali by formation of stable alkali silicates, and a similar explanation applies for ilmenite that captures alkali efficiently. Magnesium and calcium in contrast promote alkali release through their influence on alkali silicate chemistry. Analysis of char surfaces using scanning electron microscopy with energy dispersive spectroscopy indicates that low amounts of several elements are transferred from the bed material to the char where they may be directly involved in the char conversion process. The transferred elements are specific for each bed material and relates to their chemical composition. Mechanisms for material exchange between bed material and char are discussed.

  • 289.
    Geng, Shiyu
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Maennlein, Alexis
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Yu, Liang
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Hedlund, Jonas
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Oksman, Kristiina
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap. Mechanical & Industrial Engineering (MIE), University of Toronto, Toronto, ON, M5S 3G8, Canada.
    Monolithic carbon aerogels from bioresources and their application for CO2 adsorption2021Inngår i: Microporous and Mesoporous Materials, ISSN 1387-1811, E-ISSN 1873-3093, Vol. 323, artikkel-id 111236Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Monolithic binder-free CO2 adsorbents with high adsorption capacity, selectivity, adsorption-desorption kinetics, and regenerability are highly desired to both reduce the environmental impact of anthropogenic CO2 emissions and purify valuable gases from CO2. Herein, we report a strategy to prepare monolithic carbonaceous CO2 adsorbents from low-cost and underutilized bioresources, which enabled the formation of a delicate anisotropic, hierarchical porous structure. With optimized material composition and processing conditions, the biobased carbon adsorbent demonstrated a CO2 adsorption capacity of 4.49 mmol g-1 at 298 K and 100 kPa, relatively weak adsorbent-adsorbate affinity, good CO2/N2 selectivity, and advantageous hydrophobicity against water vapor. Moreover, the unique anisotropic porous structure provided high stiffness and good flexibility to the adsorbent in the axial and radial directions, respectively. We confirmed that this type of carbon adsorbent could be packed in a column for dynamic CO2 capture independent of any binders, indicating its promising future for further development toward widespread utilization.

  • 290.
    Geng, Shiyu
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Wei, Jiayuan
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Jonasson, Simon
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Hedlund, Jonas
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Oksman, Kristiina
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap. Fibre and Particle Engineering, University of Oulu. Mechanical & Industrial Engineering (MIE), University of Toronto.
    Multifunctional Carbon Aerogels with Hierarchical Anisotropic Structure Derived from Lignin and Cellulose Nanofibers for CO2 Capture and Energy Storage2020Inngår i: ACS Applied Materials and Interfaces, ISSN 1944-8244, E-ISSN 1944-8252, Vol. 12, nr 6, s. 7432-7441Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In current times, CO2 capture and light-weight energy storage are receiving significant attention and will be vital functions in next-generation materials. Porous carbonaceous materials have great potential in these areas, whereas most of the developed carbon materials still have significant limitations, such as non-renewable resources, complex and costly processing or the absence of tailorable structure. In this study, a new strategy is developed for using the currently under-utilized lignin and cellulose nanofibers, which can be extracted from renewable resources to produce high-performance multifunctional carbon aerogels with a tailorable, anisotropic pore structure. Both the macro- and microstructure of the carbon aerogels can be simultaneously controlled by discreetly tuning the weight ratio of lignin to cellulose nanofibers in the carbon aerogel precursors, which considerably influences their final porosity and surface area. The designed carbon aerogels demonstrate excellent performance in both CO2 capture and capacitive energy storage, and the best results exhibit a CO2 adsorption capacity of 5.23 mmol g-1 at 273 K and 100 kPa, and a specific electrical double layer capacitance of 124 F g-1 at a current density of 0.2 A g-1, indicating that they have great future potential in the relevant applications.

  • 291.
    Gerger, Marcus
    KTH, Skolan för kemivetenskap (CHE).
    Centrifugal Separation of 1-Methylnaphthalene2016Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [en]

    In this report, modifications and experimental tests with an early stage test rig intended for producing a commercial solution to fractionating pyrolysis oil are described. The idea is to use centrifugal force to separate the formed aerosols from condensible gases with a lower volatility. A stacked disc centrifuge prototype built to work at high temperature was used. The experiment was done with a single component, 1-Methylnaphtalene (1-MN) to evaluate the functionality of the test rig. No separation was achieved, concluding that further work need to be done at different operating parameters with 1-Methylnaphtalene prior to including more components. The reason for the negative separation result is probably due to that the saturation ratio was to low resulting in that no aerosol was formed during the experiments. Further work includes improving the stability of the inlet stream to the centrifuge. Perform more experiments with other process parameters, recommendation is to decreasing the temperature at the inlet to the centrifuge to increase the saturation ratio. It is also suggested that an optical in situ measuring devise is added to the test rig to facilitate operation.

    Fulltekst (pdf)
    fulltext
  • 292. Ghadami Yazdi, M.
    et al.
    Moud, Pouya H.
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Kemiteknik.
    Marks, K.
    Piskorz, W.
    Öström, H.
    Hansson, T.
    Kotarba, A.
    Engvall, Klas
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Kemiteknik.
    Göthelid, M.
    Naphthalene on Ni(111): Experimental and Theoretical Insights into Adsorption, Dehydrogenation, and Carbon Passivation2017Inngår i: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 121, nr 40, s. 22199-22207Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    An attractive solution to mitigate tars and also to decompose lighter hydrocarbons in biomass gasification is secondary catalytic reforming, converting hydrocarbons to useful permanent gases. Albeit that it has been in use for a long time in fossil feedstock catalytic steam reforming, understanding of the catalytic processes is still limited. Naphthalene is typically present in the biomass gasification gas and to further understand the elementary steps of naphthalene transformation, we investigated the temperature dependent naphthalene adsorption, dehydrogenation and passivation on Ni(111). TPD (temperature-programmed desorption) and STM (scanning tunneling microscopy) in ultrahigh vacuum environment from 110 K up to 780 K, combined with DFT (density functional theory) were used in the study. Room temperature adsorption results in a flat naphthalene monolayer. DFT favors the dibridge[7] geometry but the potential energy surface is rather smooth and other adsorption geometries may coexist. DFT also reveals a pronounced dearomatization and charge transfer from the adsorbed molecule into the nickel surface. Dehydrogenation occurs in two steps, with two desorption peaks at approximately 450 and 600 K. The first step is due to partial dehydrogenation generating active hydrocarbon species that at higher temperatures migrates over the surface forming graphene. The graphene formation is accompanied by desorption of hydrogen in the high temperature TPD peak. The formation of graphene effectively passivates the surface both for hydrogen adsorption and naphthalene dissociation. In conclusion, the obtained results on the model naphthalene and Ni(111) system, provides insight into elementary steps of naphthalene adsorption, dehydrogenation, and carbon passivation, which may serve as a good starting point for rational design, development and optimization of the Ni catalyst surface, as well as process conditions, for the aromatic hydrocarbon reforming process.

  • 293.
    Ghaly, Montaser
    et al.
    National Research Centre (NRC), Chemical Engineering and Pilot Plant Department, Cairo, Egypt.
    Ali, Mohamed Eid
    National Research Centre (NRC), Water Pollution Research Department, P.O. 11312, Cairo, Egypt.
    Österlund, Lars
    FOI CBRN Defence and Security, Umeå.
    Khattab, Ibrahim
    National Research Centre (NRC), Chemical Engineering and Pilot Plant Department, Cairo, Egypt.
    Badawy, Mohamed
    National Research Centre (NRC), Water Pollution Research Department, P.O. 11312, Cairo, Egypt.
    Farah, Joseph
    National Research Centre (NRC), Chemical Engineering and Pilot Plant Department, Cairo, Egypt.
    Zaher, Fatama
    National Research Centre (NRC), Chemical Engineering and Pilot Plant Department, Cairo, Egypt.
    Al-Maghrabi, Mohammednoor
    Faculty of Engineering, King Abdul-Aziz University, Jedddah, Saudi Arabia.
    ZnO/spiral-shaped glass for solar photocatalytic oxidation of Reactive Red 1202014Inngår i: Arabian Journal of Chemistry, ISSN 1878-5352, E-ISSN 1878-5379 Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    ZnO/glass spiral (GS) was prepared by immobilization of ZnO on GS with facilemethod, and was characterized by X-ray diffraction analysis (XRD), scanning electron microscope(SEM) and the crystallite size of ZnO on GS surface was calculated. SEM showed rod-like shape ofZnO particles on GS surface. Photocatalytic activity of prepared immobilized photocatalyst wasinvestigated for decolourization and degradation of C.I. Reactive Red 120 (RR-120) dye under sunlight.The kinetics of decolourization and degradation removal has been investigated. The effect ofpH on decolourization and degradation of dye was studied. The decolourization and degradation ofdye were followed by pseudo-first order reaction. The decolourization and degradation of RR-120dye were enhanced by H2O2 addition to definite dosage beyond that the effect is diminished. Also,the reusability of immobilized ZnO on GS was tested for photocatalytic degradation of dye and itwas worth noting that it has high efficiency with slight decrease (5%) after five successive runs.

  • 294.
    Gharib Ali Jalal, Ibrahim
    et al.
    KTH, Skolan för kemivetenskap (CHE).
    Abdulaziz Ali, Abdulbasit
    KTH, Skolan för kemivetenskap (CHE).
    The Sustainability related opportunities and challenges with various transformer insulation fluids and business case on re-refining2017Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [en]

    Transformers are electrical devices used in practice to increase or decrease voltages. Transformers are of various sizes and used mainly in power distribution. To provide cooling and insulation, transformer oils are used together with cellulose that acts as a solid insulation.

    The most common type of transformer oil is mineral oil and is a product derived from the refining of crude oil. Its low cost and good compatibility with cellulose are two factors that have led to its predominant position as the common transformer oil. There are also synthetic ester based transformer oils, and following an increased interest in environmentally friendly products, transformer oils made from natural esters such as sunflower, soybean and rapeseed.

    Mineral oil is not biodegradable and is deemed as hazardous waste. The ester based oils are biodegradable and promoted as a more environmentally friendly alternative to mineral oil.

    In this thesis, the possibility of re-refining used mineral transformer oil is assessed from a financial perspective in the form of a business case and an LCA study has been done to compare the environmental impacts between ester based transformer oils and mineral based transformer oil.

    The results from the LCA study showed that from a cradle-to-gate perspective, mineral oil has a lower environmental impact than ester-based transformer oils. The re-refining of used mineral transformer oil further reduces the environmental impact. The results from the business case showed that a small scale re-refining facility is financially feasible but highly dependent on the supply and demand of used transformer oil.

    It is recommended to pursue further studies before making any decision. There is lack of data regarding the re-refining market in Eastern Europe and the accuracy of the LCA study can be further improved by having emissions data from re-refining used mineral transformer oil.

    Fulltekst (pdf)
    fulltext
  • 295.
    Ghorbani, Morteza
    et al.
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Medicinteknik och hälsosystem, Medicinsk avbildning. Mechatronics Engineering Program, Faculty of Engineering and Natural Science, Sabanci University, 34956 Tuzla, Istanbul, Turkey.
    Araz, Sheybani Aghdam
    Faculty of Engineering and Natural Sciences, Sabanci University, Tuzla, Istanbul 34956, Turkey.
    Talebian, Moein
    Mechatronics Engineering Program, Faculty of Engineering and Natural Science, Sabanci University, 34956 Tuzla, Istanbul, Turkey.
    Kosar, Ali
    Mechatronics Engineering Program, Faculty of Engineering and Natural Science, Sabanci University, 34956 Tuzla, Istanbul, Turkey ; Sabanci University Nanotechnology Research and Application Center, 34956 Tuzla, Istanbul, Turkey ; Center of Excellence for Functional Surfaces and Interfaces for Nano-Diagnostics (EFSUN), Sabanci University, Orhanli, 34956 Tuzla, Istanbul, Turkey.
    Cakmak Cebeci, Fevzi
    Faculty of Engineering and Natural Sciences, Sabanci University, Tuzla, Istanbul 34956, Turkey ; Sabanci University Nanotechnology Research and Application Center, 34956 Tuzla, Istanbul, Turkey.
    Grishenkov, Dmitry
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Medicinteknik och hälsosystem, Medicinsk avbildning.
    Svagan, Anna Justina
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi.
    Facile Hydrodynamic Cavitation ON CHIP via Cellulose Nanofibers Stabilized Perfluorodroplets inside Layer-by-Layer Assembled SLIPS Surfaces2019Inngår i: Chemical Engineering Journal, ISSN 1385-8947, E-ISSN 1873-3212Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The tremendous potential of “hydrodynamic cavitation on microchips” has been highlighted during recent years in various applications. Cavitating flow patterns, substantially depending upon thermophysical and geometrical characteristics, promote diverse industrial and engineering applications, including food and biomedical treatment. Highly vaporous and fully developed patterns in microfluidic devices are of particular interest. In this study, the potential of a new approach, which includes cellulose nanofiber (CNF)- stabilized perfluorodroplets (PFC5s), was assessed inside microfluidic devices. The surfaces of these devices were modified by assembling various sizes of silica nanoparticles, which facilitated in the generation of cavitation bubbles. To examine the pressure effects on the stabilized droplets in the microfluidic devices, the upstream pressure was varied, and the cavitation phenomenon was characterized under different experimental conditions. The results illustrate generation of interesting, fully developed, cavitating flows at low pressures for the stabilized droplets, which has not been previously observed in the literature. Supercavitation flow pattern, filling the entire microchannel, were recorded at the upstream pressure of 1.7 MPa for the case of CNF-stabilized PFC5s, which hardly corresponds to cavitation inception for pure water in the same microfluidic device.

    Fulltekst (pdf)
    fulltext
  • 296.
    Ghorbani, Morteza
    et al.
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Medicinteknik och hälsosystem, Medicinsk avbildning. Sabanci Univ, Fac Engn & Nat Sci, Mechatron Engn Program, TR-34956 Istanbul, Turkey.
    Olofsson, Karl
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik.
    Benjamins, Jan-Willem
    Research Institute of Sweden (RISE), Chemistry, Materials and Surfaces, Box 5607, SE-114 86 Stockholm, Sweden.
    Loskutova, Ksenia
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Medicinteknik och hälsosystem, Medicinsk avbildning.
    Paulraj, Thomas
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi, Polymera material.
    Wiklund, Martin
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    Grishenkov, Dmitry
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Medicinteknik och hälsosystem, Medicinsk avbildning.
    Svagan, Anna Justina
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi.
    Unravelling the Acoustic and Thermal Responses of Perfluorocarbon Liquid Droplets Stabilized with Cellulose Nanofibers2019Inngår i: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 35, nr 40, s. 13090-13099Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The attractive colloidal and physicochemical properties of cellulose nanofibers (CNFs) at interfaces have recently been exploited in the facile production of a number of environmentally benign materials, e.g. foams, emulsions, and capsules. Herein, these unique properties are exploited in a new type of CNF-stabilized perfluoropentane droplets produced via a straightforward and simple mixing protocol. Droplets with a comparatively narrow size distribution (ca. 1–5 μm in diameter) were fabricated, and their potential in the acoustic droplet vaporization process was evaluated. For this, the particle-stabilized droplets were assessed in three independent experimental examinations, namely temperature, acoustic, and ultrasonic standing wave tests. During the acoustic droplet vaporization (ADV) process, droplets were converted to gas-filled microbubbles, offering enhanced visualization by ultrasound. The acoustic pressure threshold of about 0.62 MPa was identified for the cellulose-stabilized droplets. A phase transition temperature of about 22 °C was observed, at which a significant fraction of larger droplets (above ca. 3 μm in diameter) were converted into bubbles, whereas a large part of the population of smaller droplets were stable up to higher temperatures (temperatures up to 45 °C tested). Moreover, under ultrasound standing wave conditions, droplets were relocated to antinodes demonstrating the behavior associated with the negative contrast particles. The combined results make the CNF-stabilized droplets interesting in cell-droplet interaction experiments and ultrasound imaging.

  • 297.
    Ghorbani Shiraz, Hamid
    et al.
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Laboratoriet för organisk elektronik. Linköpings universitet, Tekniska fakulteten.
    Khan, Zia
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Laboratoriet för organisk elektronik. Linköpings universitet, Tekniska fakulteten.
    Pere, Daniel
    IMRA Europe SAS, France.
    Liu, Xianjie
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Laboratoriet för organisk elektronik. Linköpings universitet, Tekniska fakulteten.
    Coppel, Yannick
    Univ Toulouse, France.
    Fahlman, Mats
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Laboratoriet för organisk elektronik. Linköpings universitet, Tekniska fakulteten.
    Vagin, Mikhail
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Laboratoriet för organisk elektronik. Linköpings universitet, Tekniska fakulteten.
    Chmielowski, Radoslaw
    IMRA Europe SAS, France.
    Kahn, Myrtil L.
    Univ Toulouse, France.
    Berggren, Magnus
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Laboratoriet för organisk elektronik. Linköpings universitet, Tekniska fakulteten.
    Crispin, Xavier
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Laboratoriet för organisk elektronik. Linköpings universitet, Tekniska fakulteten.
    Effect of Oxygen Poisoning on the Bidirectional Hydrogen Electrocatalysis in TaS2 Nanosheets2023Inngår i: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 127, nr 12, s. 5825-5832Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Sustainable production of hydrogen gas, a green energy carrier of high density, is possible only by electrolysis of water based on the hydrogen evolution reaction (HER). Here, we report the effect of oxygen poisoning on the efficiency of hydrogen production and the consumption by the HER and the hydrogen oxidation reaction (HOR), respectively, on the interface of platinum group metal-free electrocatalyst TaS2 in pristine form and intercalated by the organic Lewis base hexylamine. The state of the surface probed by photoelectron spectroscopy was significantly altered by both Lewis base doping and oxygen poisoning. This alteration dramatically affects the hydrogen production efficiency in the HER, while the back process by the HOR was less sensitive to the changes in the surface states of the electrocatalysts. The oxygenated and intercalated electrocatalyst shows more than 2 x 105 times lower exchange current density of the HER compared to pristine oxygenated materials.

    Fulltekst (pdf)
    fulltext
  • 298.
    Gilardi, Lorenza
    KTH, Skolan för kemivetenskap (CHE).
    Removal of hydrogen sulfide from an air stream using UV light2016Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [en]

    Volatile sulfur compounds are cause of concern because, when present in high concentrations, they constitute a danger for health because of their strong toxicity. Furthermore, for low concentrations, they are often a cause of complaint, because of their low odor threshold. In this context, the purpose of this Thesis is to evaluate a new technology for the abatement of sulfur-based malodorous compounds. The investigated technology consists in the use of ozone generating low-pressure UV mercury lamps, operating at room temperature. Hydrogen sulfide is often found in industrial processes, (e.g. WWTPs (Wastewater Treatment Plants), leather production, sewage treatment, garbage disposal, etc). Moreover, it presents both a very high toxicity a low odor threshold. Thus, due to its high representativeness of the case, hydrogen sulfide was chosen as reference compound for the purposes of this project. In order to evaluate a wide range of cases, several experiments using different residence times, humidity contents and inlet concentrations of the pollutant were conducted. The obtained results show that this technology generally presents discrete conversion efficiencies, although not suffcient to be used as freestanding process. For this reason, a pretreatment is revealed to be necessary. The best conversion efficiency was obtained for low flow rates and high moisture content. At the end of the project, as side-study, a possible pretreatment using an adsorbent bed constituted by granular ferric oxide was evaluated.

     

    Fulltekst (pdf)
    fulltext
  • 299.
    Glenngård, Anton
    et al.
    KTH, Skolan för kemivetenskap (CHE).
    Helmersson, Sofia
    KTH, Skolan för kemivetenskap (CHE).
    Kessler, Amanda
    KTH, Skolan för kemivetenskap (CHE).
    Nilsson, Elisabeth
    KTH, Skolan för kemivetenskap (CHE).
    Utformning av Bränslecellsystem för Autonom Undervattensfarkost2016Independent thesis Basic level (degree of Bachelor), 10 poäng / 15 hpOppgave
    Abstract [sv]

    Avdelningen Marina System på Kungliga Tekniska Högskolan har designat och konstruerat en autonom undervattensfarkost (AUV). I dagsläget drivs farkosten drivs av ett litiumpolymerbatteri. Ett bränslecellssystem bestående utav PEM-bränslecellsstackar (Polymerelektrolytbränslecell), metallhydrid och trycksatt syrgas har designats för att byta ut det befintliga litiumpolymerbatteriet. För att få ett säkert system är det utrustat med vätgassensor, trycksensor, voltmätare samt temperatursensor. Eftersom både syrgas och vätgas måste medföras i farkosten, jämfört med landgående fordon som kan utnyttja syret från omgivande atmosfär, har olika bränslelagringsmetoder undersökts. För att lagra syrgas har trycksatt gas valts, denna lagras i en tank gjord av kolfiber och ett har ett tryck på 300 bar. Vätgasen väljs att lagras i en FeTi-metallhydrid på grund av dess volymmässiga fördel. Metallhydrid är en volymeffektiv men viktineffektiv lagringsmetod, vilket gör att den är perfekt till en undervattensfarkost. Metallhydriden förvaras i en tank gjord av aluminium. Eftersom bränslecellerna producerar vatten har olika sätt att fånga upp detta undersökts. Regenerad cellulosa (disktrasa) har hög absorptionsförmåga och har därför valts för systemet.

    De bränslecellesstackar som införskaffades har testats med hjälp av programvaran Labview. De presterade något under vad tillverkaren hävdade, något som antas bero på effektbehov hos kontroller och fläktar. Olika driftbetingelser har undersökts för att kunna använda bränslecellsstackarnas fulla potential.

    Det slutgiltiga systemet får ej plats i farkosten. En teoretisk studie för när bränsleceller blir mer volymeffektiva än batterier visar att för ett helt optimerat system går gränsen vid 3 liter, vilket motsvarar att 822 normalliter vätgas måste tas med.

    I framtiden skulle en kemisk lagringsmetod av syrgas vara att föredra, exempelvis väteperoxid. Metallhydrid är ett bra sätt att lagra vätgas men tankmaterialet skulle kunna vara exempelvis rostfritt stål istället för aluminium så att tanken blir mer volymeffektiv på grund av den högre brottgränsen hos stålet. Ett syrgasflöde till bränslecellen istället för ut i farkostens atmosfär skulle kunna öka verkningsgraden och därmed räckvidden.

    Fulltekst (pdf)
    fulltext
  • 300.
    Golets, Mikhail
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Heterogeneously Catalyzed Valorization of Monoterpenes to High Value-Added Chemicals2014Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    A potential industrial process is profitable only if it is successfully implemented by the continuously developing chemical industry. Throughout last decades heterogeneous catalysis has opened doors to the creation of various know-how products which previously were considered unfeasible. Moreover, the use of heterogeneous catalysts allows improving existing processes to shift towards more ecological and cost efficient practices. In particular, polymer or fuel compounds could be eco-friendly produced from wood extractives, as an alternative to the conventional oil resources. This goal becomes even more attractive in light of the upcoming peak-oil.

    In the Nordic pulping industry turpentine is widely available as a tonnage by-product. Despite its interesting properties and promising application possibilities this fraction is commonly burned in the recovery boilers for energy. Although the chemical composition of turpentine depends strongly on the specific pulping process, α-pinene is the predominant compound and as such most studied. The general message of this thesis is the successful implementation of the heterogeneous catalysts in one-pot value-added upgrading of crude turpentine and specific terpenes, particularly α-pinene. Concepts allowing the production of fragrances, resins, plastics and pharmaceutical compounds are presented in the current study. Both commercial (Amberlyst 70) and self-prepared (Me/Al-SBA-15 or TiO2) catalysts were studied in several reactions including: acetoxylation, isomerization, dehydroisomerisation and oxidation. Both commercially purified α-pinene and crude thermo-mechanical turpentine were used as raw materials in the catalytic one-pot synthesis of value-added compounds.

    The experiments were performed in both batch and continuous reactor systems depending on the studied reaction. Successful results were obtained in case of several reactions. As an example, upon acetoxylation of α-pinene valuable fragrances – α-terpinyl and bornyl acetates – were produced with yields of 35 and 40 wt-%, respectively. Furthermore, in the dehydroisomerisation reaction of α-pinene, a yield of around 80 wt-% of an important fragrance, solvent and plastics precursor, ρ-cymene, was obtained. In the last case, thermo-mechanical turpentine was also successfully utilized. Still, some α-pinene oxidation tests leading to α-pinene oxide and verbenone fragrances were also carried out. Upon this study, further oxidation of ρ-cymene lead to the formation of ρ-methyl-acetophenone, a product essential for perfumery, pharmaceutical and pesticide industry as well as a potent polymer precursor. In addition, isomerization reactions were performed. Additionally, the catalytic materials were thoroughly characterized and analyzed.

    Fulltekst (pdf)
    Heterogeneously Catalyzed Valorization of Monoterpenes to High Value-Added Chemicals
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