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  • 301.
    Korelskiy, Danil
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Ye, Pengcheng
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Zhou, Han
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Mouzon, Johanne
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Hedlund, Jonas
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Reprint of: An experimental study of micropore defects in MFI membranes2014Inngår i: Microporous and Mesoporous Materials, ISSN 1387-1811, E-ISSN 1873-3093, Vol. 192, 69-75 s.Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In the present work, two ultra-thin MFI membranes, prepared using hydroxide and fluoride ions as mineralizing agents, respectively, were carefully examined by permporometry. The amount of micropore defects, as determined by permporometry, differed significantly between the two different membranes. For the first time, it was demonstrated that the micropore defects determined by permporometry were most likely open grain boundaries. The results were verified by direct observation of the open grain boundaries by a state-of-the-art XHR-scanning electron microscopy instrument. In addition, the permporometry data were also consistent with permeation data using 1,3,5-trimethylbenzene (TMB) as a probe molecule, separation data using an equimolar mixture of n-hexane and TMB, and nitrogen adsorption data

  • 302.
    Korelskiy, Danil
    et al.
    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.
    Mouzon, Johanne
    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.
    An experimental study of micropore defects in MFI membranes2013Konferansepaper (Fagfellevurdert)
  • 303.
    Kornmann, Xavier
    et al.
    Luleå tekniska universitet.
    Berglund, Lars A.
    Luleå tekniska universitet.
    Sterte, Johan
    Giannelis, E.P.
    Department of Materials Science and Engineering, Cornell University Ithaca.
    Nanocomposites based on montmorillonite and unsaturated polyester1998Inngår i: Polymer Engineering and Science, ISSN 0032-3888, E-ISSN 1548-2634, Vol. 38, nr 8, 1351-1358 s.Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The concept of nanoscale reinforcement provides opportunity for synthesis of new polymer materials with unique properties. Montmorilonite (MMT) was derived from bentonite, purified, activated by sodium ions and mixed with reacting unsaturated polyester (UP). X-ray and transmission electron microscopy data were in support of the formation of a partially delaminated nanocomposite material. At an MMT content of only 1.5 vol%, the fracture energy, GQ of the nanocomposite was doubled, 138 J/m2 as compared with 70 J/m2 for the pure UP.

  • 304.
    Koroidov, Sergey
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Anderlund, Magnus F
    Styring, Stenbjörn
    Thapper, Anders
    Messinger, Johannes
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    First turnover analysis of water-oxidation catalyzed by Co-oxide nanoparticles2015Inngår i: Energy & Environmental Science, ISSN 1754-5692, E-ISSN 1754-5706, Vol. 8, nr 8, 2492-2503 s.Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Co-oxides are promising water oxidation catalysts for artificial photosynthesis devices. Presently, several different proposals exist for how they catalyze O-2 formation from water. Knowledge about this process at molecular detail will be required for their further improvement. Here we present time-resolved O-18-labelling isotope-ratio membrane-inlet mass spectrometry (MIMS) experiments to study the mechanism of water oxidation in Co/methylenediphosphonate (Co/M2P) oxide nanoparticles using [Ru(bpy)(3)](3+) (bpy = 2,2'-bipyridine) as chemical oxidant. We show that O-16-Co/M2P-oxide nanoparticles produce O-16(2) during their first turnover after simultaneous addition of (H2O)-O-18 and [Ru(bpy)(3)](3+), while sequential addition with a delay of 3 s yields oxygen reflecting bulk water O-18-enrichment. This result is interpreted to show that the O-O bond formation in Co/M2P-oxide nanoparticles occurs via intramolecular oxygen coupling between two terminal Co-OHn ligands that are readily exchangeable with bulk water in the resting state of the catalyst. Importantly, our data allow the determination of the number of catalytic sites within this amorphous nanoparticular material, to calculate the TOF per catalytic site and to derive the number of holes needed for the production of the first O-2 molecule per catalytic site. We propose that the mechanism of O-O bond formation during bulk catalysis in amorphous Co-oxides may differ from that taking place at the surface of crystalline materials.

  • 305. Kumar, N.
    et al.
    Shojaee, Maryam
    KTH, Skolan för kemivetenskap (CHE).
    Spivey, J.J.
    Catalytic bi-reforming of methane: From greenhouse gases to syngas2015Inngår i: Current Opinion in Chemical Engineering, ISSN 2211-3398, Vol. 9, 8-15 s.Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The bi-reforming reaction to produce syngas from CH<inf>4</inf> and CO<inf>2</inf> offers significant advantages over dry reforming and oxy-CO<inf>2</inf> with respect to catalyst deactivation by carbonization. This approach has potential for powerful new alternatives and is entering the stage of increasing advanced research toward commercialization of the technology. Research is ongoing to develop catalysts that are resistant to high temperatures and the presence of a more oxidative environment due to steam. All current research on bi-reforming catalysis is focused on Ni-based catalysts, a logical extension based on commercial materials on steam/methane reforming and dry reforming. However, recent work on thermally stable crystalline oxides has promise, particularly in resisting carbon deposition while remaining stable at the demanding conditions of bi-reforming.

  • 306.
    Kyprianidis, Konstantinos
    et al.
    Mälardalens högskola, Akademin för ekonomi, samhälle och teknik, Framtidens energi.
    Skvaril, JanMälardalens högskola, Akademin för ekonomi, samhälle och teknik, Framtidens energi.
    Developments in Near-Infrared Spectroscopy2017Collection/Antologi (Fagfellevurdert)
    Abstract [en]

    Over the past few decades, exciting developments have taken place in the field of near-infrared spectroscopy (NIRS). This has been enabled by the advent of robust Fourier transform interferometers and diode array solutions, coupled with complex chemometric methods that can easily be executed using modern microprocessors. The present edited volume intends to cover recent developments in NIRS and provide a broad perspective of some of the challenges that characterize the field. The volume comprises six chapters overall and covers several sectors. The target audience for this book includes engineers, practitioners, and researchers involved in NIRS system design and utilization in different applications. We believe that they will greatly benefit from the timely and accurate information provided in this work.

  • 307.
    Lai, Kwok Kei
    et al.
    Hong Kong University of Science and Technology, Clear Water Bay, P. R. China .
    Renneberg, Reinhard
    Hong Kong University of Science and Technology, Clear Water Bay, P. R. China .
    Mak, Wing Cheung
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Biosensorer och bioelektronik. Linköpings universitet, Tekniska fakulteten.
    High efficiency single-step biomaterial-based microparticle fabrication via template-directed supramolecular coordination chemistry2016Inngår i: Green Chemistry, ISSN 1463-9262, E-ISSN 1463-9270, Vol. 18, nr 6, 1715-1723 s.Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Biomaterial-based microparticles have attracted much attention for medical and biological applications such as pharmaceutics, bioseparation and cosmetics. Emerging technologies enable versatile and facile fabrication of microparticles, with key features being purity, precise size control, mild preparation conditions and minimal processing. Here, an innovative approach combining template synthesis, biomolecule assembly and partial-purification within a single step for high efficiency fabrication of pure biomaterial-based microparticles is reported. This concept is based on facile co-precipitation of biomolecules within CaCO3 templates and simultaneous crosslinking of entrapped biomolecules via Ca2+ driven supramolecular coordination chemistry, followed by template removal. Carbohydrate (alginate) and proteins (casein and fresh milk) are used as models of biomolecules. The process driven by selective crosslinking automatically excludes non-specific materials from the template and thus provides the additional function of partial-purification, as demonstrated using highly complexed fresh milk. This green approach to fabrication of biomaterial-based microparticles offers three critical advantages (i) mild conditions to preserve the chemical and secondary structures of biomolecules; (ii) single processing step to facilitate scale-up production; and (iii) partial-purification without the need for upstream raw material purification. This innovative approach not only addresses fundamental issues in fabrication techniques, but also marks progress in energy and environmental conservation during manufacturing processes.

  • 308.
    Lantto, Jonas
    KTH, Skolan för kemivetenskap (CHE).
    Analytical model of mass transfer through supported liquid membranes2015Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [en]

    This report details the development and validation of a model for the simulation of supported liquid membrane processes, as applied to the extraction of lanthanides. Supported liquid membranes are systems where two phases, usually aqueous, are separated by a third phase, typically organic, which acts as a membrane, in order to separate solutes from one phase to the other. The model employs an analytical solution to the diffusion equation for the organic phase and linear approximations of the resistances to mass transfer in the aqueous phase boundary layers. The goal of this model is to underline the importance of taking these boundary layer resistances into account.

     

  • 309.
    Lanza, Roberto
    et al.
    Università di Padova.
    Canu, Paolo
    Universita` di Padova, Dipartimento di Principi e Impianti di Ingegneria Chimica.
    Dalle Nogare, Daniela
    Universita` di Padova, Dipartimento di Principi e Impianti di Ingegneria Chimica.
    Gas Phase Chemistry in Cellulose Fast Pyrolysis2009Inngår i: Industrial & Engineering Chemistry Research, ISSN 0888-5885, E-ISSN 1520-5045, Vol. 48, nr 3, 1391-1399 s.Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We experimentally and theoretically studied cellulose pyrolysis at high temperature and short residence time. We investigated the gas phase chemistry with dedicated experiments and feeding intermediates. Results have been also compared with equilibrium calculations, both single (gas) phase and allowing for solid C formation. Our aim was to understand the cellulose degradation mechanism and particularly the role of gas phase chemistry. We provided evidence of a simplified mechanism, where CO formation is a first, fast step that can be related to levoglucosan ring opening, while H(2) comes from a totally different route, based on hydrocarbon reforming reactions, which also provide further CO. In addition, butadiene was identified as a key intermediate in the decomposition sequence. The different paths and rates of CO formation and H2 formation explain why the ratio of CO to H(2) is not constant, particularly at short residence time. A two-stage process or longer contact time is required, if aiming at syngas production.

  • 310.
    Lanza, Roberto
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Kemisk teknologi.
    Velasco, Jorge
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Kemisk teknologi.
    Järås, Sven
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Kemisk teknologi.
    Recent developments and achievements in partial oxidation of methane with and without addition of steam2011Inngår i: Catalysis / [ed] James J. Spivey, Royal Society of Chemistry, 2011, 23, 50-95 s.Kapittel i bok, del av antologi (Fagfellevurdert)
    Abstract [en]

    The latest works on catalytic partial oxidation of methane (CPO) have beenconsidered and reviewed to give an updated frame of the state of the art inthis topic. Papers published since 2008 have been considered, dealing withthe process both without and with addition of steam. Particular attentionwas dedicated to Ni and Rh, that are the most used metals. The mechanismfollowed by the reaction was also considered as well as new and promisingtechnologies such as SOFCs, membrane reactors and plasma systems.

  • 311.
    Larsson, Ann-Charlotte
    et al.
    Växjö universitet, Fakulteten för matematik/naturvetenskap/teknik, Institutionen för teknik och design. Bioenergiteknik.
    Einvall, Jessica
    Växjö universitet, Fakulteten för matematik/naturvetenskap/teknik, Institutionen för teknik och design. Bioenergiteknik.
    Andersson, Arne
    Lund University.
    Sanati, Mehri
    Växjö universitet, Fakulteten för matematik/naturvetenskap/teknik, Institutionen för teknik och design. Bioenergiteknik.
    Physical and chemical characterisation of potassium deactivation of a SCR catalyst for biomass combustion2007Inngår i: Topics in catalysis, ISSN 1022-5528, E-ISSN 1572-9028, Vol. 45, nr 1-4, 149-152 s.Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The deactivation of a commercial Selective Catalytic Reduction (SCR) catalyst, of V2O5-WO3/TiO2 type, has been studied through comparisons with results from a full-scale biomass combustion plant to that with laboratory experiments. In the latter, the catalyst was exposed to KCl and K2SO4 by both wet impregnation with diluted salt solutions and deposition of generated submicrometer aerosol particles by means of an electrostatic field. The reactivity of fresh and deactivated samples was examined in the SCR reaction. Chemical and physical characterizations were focusing on internal structures and chemical composition. Deposition of submicrometer sized particles on the monolithic SCR catalyst was shown to induce deactivation with characteristics resembling those obtained in a commercial biomass combustion plant.

  • 312.
    Larsson, Ann-Charlotte
    et al.
    Växjö universitet, Fakulteten för matematik/naturvetenskap/teknik, Institutionen för teknik och design. Bioenergiteknik.
    Einvall, Jessica
    Växjö universitet, Fakulteten för matematik/naturvetenskap/teknik, Institutionen för teknik och design. Bioenergiteknik.
    Andersson, Arne
    Lund University.
    Sanati, Mehri
    Växjö universitet, Fakulteten för matematik/naturvetenskap/teknik, Institutionen för teknik och design. Bioenergiteknik.
    Targeting by Comparison with Laboratory Experiments the SCR Catalyst Deactivation Process by Potassium and Zinc Salts in a Large-Scale Biomass Combustion Boiler2006Inngår i: Energy & Fuels, ISSN 0887-0624, E-ISSN 1520-5029, Vol. 20, nr 4, 1398-1405 s.Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The deactivation of a commercial selective catalytic reduction (SCR) catalyst of type V2O5−WO3/TiO2 has been studied in this work through comparisons of results from a full-scale biomass combustion plant with those from laboratory experiments. In the latter, the catalyst was exposed to KCl, K2SO4, and ZnCl2 by both wet impregnation with diluted salt solutions and deposition of generated submicrometer aerosol particles by means of an electrostatic field. The reactivity of freshly prepared and deactivated catalyst samples was examined in the SCR reaction, for which the influence of the different salts and the method of exposure were explored. Chemical and physical characterizations of the catalyst samples were carried out focusing on surface area, pore volume, pore size, chemical composition, and the penetration profiles of potassium and zinc. Particle-deposition deactivation as well as commercially exposed catalyst samples were shown to impact surface area and catalyst activity similarly and to have penetration profiles with pronounced peaks. Salt impregnation influenced pore sizes and catalyst activity more strongly and showed flat penetration profiles. Deposition of submicrometer-sized particles on the monolithic SCR catalyst has been shown to induce deactivation of the catalyst with characteristics resembling those obtained in a commercial biomass combustion plant; the laboratory process can be used to further assess the deactivation mechanism by biomass combustion.

  • 313.
    Larsson, Ann-Charlotte
    et al.
    Växjö universitet, Fakulteten för matematik/naturvetenskap/teknik, Institutionen för teknik och design. Bioenergiteknik.
    Einvall, Jessica
    Växjö universitet, Fakulteten för matematik/naturvetenskap/teknik, Institutionen för teknik och design. Bioenergiteknik.
    Sanati, Mehri
    Växjö universitet, Fakulteten för matematik/naturvetenskap/teknik, Institutionen för teknik och design. Bioenergiteknik.
    Physical and Chemical Characterisation of Potassium Deactivation of an SCR Catalyst for Biomass Combustion2006Inngår i: 12th Nordic Symposium in Catalysis-May 28-30-Trondheim-Norway, 2006, 198-199 s.Konferansepaper (Annet vitenskapelig)
  • 314.
    Larsson, Mårten
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Energiprocesser.
    Görling, Martin
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Energiprocesser.
    Alvfors, Per
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Energiprocesser.
    Bio-methane upgrading of pyrolysis gas from charcoal production2013Inngår i: Energy Conversion and Management, ISSN 0196-8904, E-ISSN 1879-2227, Vol. 3, 66-73 s.Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This article presents a novel route for bio-methane synthesis utilizing pyrolysis gas from charcoal production. It is a retrofit option that may increase overall process efficiency in charcoal production while adding a valuable product. The pyrolysis gas from charcoal production can be used for bio-methane production instead of burning, while the required heat for the charcoal production is supplied by additional biomass. The aim is to evaluate the energy efficiency of bio-methane upgrading from two types of charcoal plants, with and without recovery of liquid by-products (bio-oil). Aspen simulations and calculations of the energy and mass balances are used to analyse the system. The yield of bio-methane compared to the import of additional biomass is estimated to be 81% and 85% (biomass to bio-methane yield) for the syngas case and the pyrolysis vapour case, respectively. When the biomass necessary to produce the needed electricity (assuming ηel = 33%) is included, the yields amount to 65% and 73%. The results show that the suggested process is a competitive production route for methane from lignocellulosic biomass.

  • 315.
    Lassebro, Joakim
    Linköpings universitet, Institutionen för fysik, kemi och biologi.
    Förstudie till rengöringsvalidering av produktionssystem för handdesinfektionsmedlet AHD 20002017Independent thesis Basic level (degree of Bachelor), 10,5 poäng / 16 hpOppgave
    Abstract [sv]

    Vid tillverkning av produkter avsedda för medicinalt bruk är det viktigt att minska mängden av korskontaminering som kan överföras från tillverkningen av en produkt till en annan. Genom att utföra en rengöringsvalidering utvärderar man rengöringsprocessens effektivitet och fastställer vad som behöver göras för att hålla sig inom de nivåer som krävs.

    I detta examensarbete planeras och genomförs en förstudie till en rengöringsvalidering av det produktionssystem där handdesinfektionsmedlet AHD 2000 tillverkas.

    Inledningsvis genomfördes en genomgång av produktionssystemet och ett antal så kallade kritiska punkter valdes ut. Dessa punkter är områden där rengöringsprocessens effektivitet bedöms kunna variera. För att mäta effektiviteten genomfördes tre olika tester: svabbtest, sköljtest och en visuell kontroll. För svabb- och sköljtestet analyserades provernas totala organiska innehåll (TOC) och dess förbrukning av kemiskt bundet syre (COD). Erhållna analysresultat jämfördes med beräknade gränsnivåer, dvs. nivåer som kan accepteras för de två testerna. Dessa gränsnivåer är beräknade baserat på en generell nivå som vanligtvis ligger på mellan 10-500 ppm av tillverkad batch. För den visuella kontrollen gjordes en fysisk inspektion för att bedöma synliga spår av produktrester.

    Resultatet för svabbtestet visade att alla provsvar vid respektive kritiska punkt låg under den beräknade gränsnivån vilket betyder att kriteriet för svabbtestet är uppnått. För sköljtestet hamnade provresultaten något över den beräknade gränsnivån men har trots det bedömts vara inom rimliga gränser. Vid den visuella kontrollen noterades inga synliga spår och detta kriterium var alltså uppfyllt.

    Slutsatsen är alltså att alla tre kriterier för validering av rengöringsprocessen är uppfyllda vilket betyder att rengöringsprocessen är tillräckligt effektiv för att avlägsna spår av tidigare tillverkad produkt.

  • 316.
    Lassinantti, Magdalena
    Luleå tekniska universitet.
    Synthesis, characterization and properties of zeolite films and membranes2001Licentiatavhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    The work presented in this thesis was aimed to synthesize zeolite films in the absence of organic additives to avoid the potentially detrimental calcination procedure. Furthermore, the support surface was seeded with colloidal seed crystals prior to film growth. This technique has previously been used to prepare thin zeolite films. The films were characterized by Scanning electron microscopy (SEM), X-ray diffraction (XRD) and gas permeation experiments. Films of three different types of zeolites were synthesized in this work; FAU-type zeolite, ZSM-5 and zeolite NaA. The thickness of the FAU-type zeolite films could be controlled by varying the synthesis temperature and duration. However, a maximum film thickness was found. Prolonged hydrothermal treatment caused the film thickness to decrease due to the transformation of FAU into zeolite P. The adsorbed seeds were oriented with the <111> pyramid parallel to the surface of the support. During growth, the crystals constituting the films became randomly oriented. The ZSM-5 films were tested as membranes for the separation of butane isomers. The selectivity for n-butane/i-butane had a maximum value of 17.8 at 220°C. Furthermore, the ZSM-5 membranes were found to be catalytically active, converting ethanol into diethylether and ethylene. The growth of silicious species into the porous support during zeolite NaA membrane synthesis was examined. Higher temperatures of synthesis resulted in relatively more growth into the porous support compared to the film growth on top of the support. By using a multi-step synthesis procedure at low temperature, thicker films with less growth into the support could be prepared.

  • 317.
    Lassinantti, Magdalena
    et al.
    Luleå tekniska universitet.
    Hedlund, Jonas
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Sterte, Johan
    Effects of synthetsis parameters on intra-pore zeolite formation in a zeolite A membrane2001Inngår i: Zeolites and mesoporous materials at the dawn of the 21st century: proceedings of the 13th Internationa Zeolite Conference, Amsterdam: Elsevier, 2001, 292- s.Konferansepaper (Fagfellevurdert)
  • 318.
    Lassinantti, Magdalena
    et al.
    Luleå tekniska universitet.
    Hedlund, Jonas
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Sterte, Johan
    Faujasite-type films synthesized by seeding2000Inngår i: Microporous and Mesoporous Materials, ISSN 1387-1811, E-ISSN 1873-3093, Vol. 38, nr 1, 25-34 s.Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Thin and continuous Faujasite-type films were synthesized on α-alumina wafers using a seeding technique. Surface modified wafers were seeded with colloidal zeolite Y crystals prior to film growth in a synthesis mixture. The effects of hydrothermal treatment on film thickness, morphology and preferred orientation of the crystals constituting the film were investigated using scanning electron microscopy and X-ray diffraction. During hydrothermal treatment a precipitate formed rapidly, leaving an almost clear solution in the upper part of the reactor. Experiments at 60–100°C were performed with the sample placed in the upper part of the synthesis solution. An increase in the film growth rate with increasing temperature was observed. Adsorbed seeds were shown to be oriented with the {1 1 1} pyramid, parallel to the substrate surface. A change in the orientation with film growth was noted, probably due to the attachment of secondary crystals to the growing film surface. In one experimental series, film growth was effected at the bottom of the tube at 100°C. Faster film growth and multilayered films were obtained. A decrease in the film thickness after prolonged hydrothermal treatment was observed in all experimental series. This is probably due to the dissolution of the film and formation of zeolite P in the synthesis solution. The thicknesses of the films synthesized in this work are in the range of 150–2700 nm. The films are promising candidates for use in membrane applications.

  • 319.
    Lassinantti, Magdalena
    et al.
    Luleå University of Technology.
    Hedlund, Jonas
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Sterte, Johan
    Synthesis of thin zeolite Y films on polished α-alumina wafers using a seeding technique1999Inngår i: Porous materials in environmentally friendly processes: proceedings of the 1st International FEZA Conference / [ed] I. Kiricsi, Amsterdam: Elsevier, 1999, 181-187 s.Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Zeolite Y films were synthesized on polished α-alumina wafers by using a seeding technique which includes surface modification, seed adsorption and growth of the seed crystals into a dense film. The film thickness was found to be a linear function of synthesis duration up to a certain point. Further treatment reduced the film thickness. Continuous and crack free films with thicknesses in the range 210 to 2670 nm were synthesized in this work.

  • 320.
    Lassinantti, Magdalena
    et al.
    Luleå tekniska universitet.
    Jareman, Fredrik
    Luleå tekniska universitet.
    Hedlund, Jonas
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Creaser, Derek
    Luleå tekniska universitet.
    Sterte, Johan
    Preparation and evaluation of thin ZSM-5 membranes synthesized in the absence of organic template molecules2001Inngår i: Catalysis Today, ISSN 0920-5861, E-ISSN 1873-4308, Vol. 67, nr 1-3, 109-119 s.Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Porous α-alumina supports with a pore size of 100 nm were seeded with colloidal TPA-silicalite-1 crystals with a size of 120 nm. The seeded supports were calcined and treated in a synthesis solution free from organic template molecules to form ZSM-5 films on the supports. According to SEM images, the films were about 2 μm thick and no defects could be found on the as-synthesized membranes. Single gas permeation data was collected and good quality membranes (defined as having a non-detectable permeance of SF6 after drying at 100°C) were further evaluated using binary/ternary gas mixtures. The selectivity for n-butane/i-butane had a maximum value of 17.8 at 220°C. Water was selectively separated from a helium-diluted vaporized water/ethanol azeotrope with a maximum selectivity of 12.4.

  • 321.
    Lassinantti-Gualtieri, Magdalena
    et al.
    Luleå tekniska universitet.
    Alessandro, Gualtieri
    Dipartimento di Scienze della Terra, Universita di Modena e Reggio Emilia.
    Hedlund, Jonas
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Jareman, Fredrik
    Luleå tekniska universitet.
    Sterte, Johan
    Dapiaggi, M.
    Dipartimento di Scienze della Terra, Università di Milano.
    Accurate measurement of the thermal expansion of MFI zeolite membranes by in situ HTXRPD2004Inngår i: Recent advances in the science and technology of zeolites and related materials. Part A: proceedings of the 14th International Zeolite Conference, Amsterdam: Elsevier, 2004, 703-709 s.Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Template removal by calcination of MFI type membranes is often accompanied by crack formation. The thermal behavior of MFI type membranes, synthesized with and without masking, was studied to understand the mechanism. Masking prevents growth of zeolite in the interior of the Support during membrane synthesis. Rietveld refinements of powder diffraction data collected in situ at high temperature allowed to accurately determine the change in thermal expansion of the MFI film and the porous alpha-alumina support. During heating, a relatively large contraction of the cell volume during template removal occurred in the zeolite powder and in the film of the membrane prepared with masking. The much smaller decrease in the non-masked sample indicates that this membrane is under stress during heating and as a consequence, cracks are formed. The stress imposed in the membrane prepared without masking may be due to the opposite thermal behavior of the Substrate in combination with strong bonds between the membrane and the support.

  • 322.
    Lefevr, Avlina
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013).
    Methods of Chemical and Physical Modification Used in Increasing Poor Solubility of Orally Administered Medications: -2014Independent thesis Basic level (degree of Bachelor), 10 poäng / 15 hpOppgave
    Abstract [en]

    Poor-water solubility of chemical compounds accounts for 40% and more of new medicalentities become discarded. Low solubility results in chemical substances cannot be deliveredto the target organ or cells, for that reasons there is a need to increase low water-solubilitywith various physical and chemical methods. In this paper we have examined various physicaland chemical methods of increasing poor solubility suggested in the pharmacological booksand journals and looked at how these methods can be practically used in increasing poorwater-solubility of four medications from the WHO Essential List of Medications. Thefindings of the paper are that several methods have shown good results for dissolution invivo: complexation with cyclodextrins and use of surfactants (physical methods), developmentprodrug (chemical methods). Improved medications provide a good solution for chronically illpatients who take high doses over a long period of time. Another benefit of improvedsolubility is lower cost of treatment, which is an important issue in poor regions of the world.

  • 323.
    Leppäjärvi, Tiina
    et al.
    Department of Process and Environmental Engineering, University of Oulu.
    Malinen, Ilkka
    Department of Process and Environmental Engineering, University of Oulu.
    Korelskiy, Danil
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Hedlund, Jonas
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser.
    Tanskanen, Juha
    Oulu University.
    Maxwell-Stefan Modeling of Ethanol and Water Unary Pervaporation Through a High-silica MFI Zeolite Membrane2014Inngår i: Industrial & Engineering Chemistry Research, ISSN 0888-5885, E-ISSN 1520-5045, Vol. 53, nr 1, 323-332 s.Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The pervaporative mass transfer of pure ethanol and water through a thin (0.5 mu m) supported high-silica MFI membrane was studied experimentally at 30-70 degrees C, and modeled on the basis of the Maxwell-Stefan formalism. The temperature dependency of adsorption was described with the temperature dependency of pure component saturated vapor pressure. Two scenarios of coverage dependency, i.e., coverage-dependent and coverage-independent Maxwell-Stefan diffusivity, were applied in the modeling of the mass transfer through the zeolite film. In addition, the mass-transfer resistance of the support layers was taken into account. The derived unary models provided good representations of ethanol and water pervaporation flux. The study illustrates that pure component steady-state pervaporation flux measurements at different conditions offer a feasible basis for determining diffusion coefficients. Basically, pure component adsorption isotherms and derived diffusivities can be used in the modeling of pervaporative mass transfer of mixtures using zeolite membranes

  • 324.
    Leppäjärvi, Tiina
    et al.
    Department of Process and Environmental Engineering, University of Oulu.
    Malinen, Ilkka
    Department of Process and Environmental Engineering, University of Oulu, University of Oulu.
    Korelskiy, Danil
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Kangas, Jani
    University of Oulu.
    Hedlund, Jonas
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Tanskanen, Juha
    Department of Process and Environmental Engineering, University of Oulu.
    Pervaporation of Ethanol/Water Mixtures through a High-silica MFI Membrane: Comparison of Different Semi-empirical Mass Transfer Models2015Inngår i: Periodica Polytechnica. Chemical Engineering, ISSN 0324-5853, Vol. 59, nr 2, 111-123 s.Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Pervaporation of binary ethanol/water solutions of 5-10 wt.% ethanol was studied experimentally through a thin supported high-silica MFI zeolite membrane of hydrophobic character in the temperature range of 30-70 degrees C. The fluxes obtained were very high, 2-14 kg m(-2)h(-1) with ethanol/water separation factors of 4-7. The loss of effective driving force was significant in the supporting layers, which limited the membrane performance. The correlation between the experimental data and three different semi-empirical mass-transfer models was examined The correlation was good especially when the driving force for mass-transfer was determined based solely on bulk feed, or the bulk feed and permeate conditions together Somewhat lower correlation was observed when the driving force was corrected with the effect of support resistance. This was most likely due to the inaccuracies of the used mass transfer parameters in the support. The investigated semi-empirical models can be applied for initial stage process design purposes.

  • 325. Li, Debing
    et al.
    Hu, Wei
    KTH, Skolan för bioteknologi (BIO).
    Zhang, Junqiao
    Shi, Hui
    Chen, Qu
    Sun, Tianyang
    Liang, Lijun
    Wang, Qian
    Separation of Hydrogen Gas from Coal Gas by Graphene Nanopores2015Inngår i: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 119, nr 45, 25559-25565 s.Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We designed a series of porous graphene as the separation membrane for hydrogen gas in coal gas. The permeation process of different gas molecules (H-2, CO, CH4, and H2S) in porous graphene was evaluated under the atmospheric pressure and high pressure conditions. Our results indicate the hydrogen permeability and selectivity could be tuned by the size and the shape of the porous graphene. For graphene with bigger pores, the selectivity for hydrogen gas could decrease. In the porous graphene with same pore area, the hydrogen gas selectivity could be affected by the shape of the pore. The potential of mean force (PMF) of different gases to pass through a good separation candidate was calculated. The order of PMF for different gases to pass through the good separation candidate is H-2 < CO < CH4 approximate to H2S, which is also confirmed by the first-principle density function theory (DFT) calculation.

  • 326. Li, Hongliang
    et al.
    Yu, Xinhai
    Tu, Shan-Tung
    Yan, Jinyue
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Energiprocesser.
    Wang, Zhengdong
    Catalytic performance and characterization of Al2O3-supported Pt-Co catalyst coatings for preferential CO oxidation in a micro-reactor2010Inngår i: Applied Catalysis A: General, ISSN 0926-860X, E-ISSN 1873-3875, Vol. 387, nr 1-2, 215-223 s.Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Platinum-cobalt (Pt-Co) catalyst coatings are studied for preferential oxidation of carbon monoxide (PROX) ill hydrogen-rich gas streams. Experimental results show a role for cobalt in improving catalytic activity. The most active catalyst coating can decrease carbon monoxide concentrations from 1% to a value of less than 10 ppm for GHSV values ranging from 40,000 to 120,000 ml g(-1) h(-1). This catalyst coating can work at a wide window of operation ill terms of temperature. Transmission electron microscopy, selected-area electron diffraction, and diffuse reflectance infrared Fourier transform spectroscopy show that the addition of Co forms Pt3Co intermetallic compounds and slightly increases the average particle size. In situ laser Raman spectroscopy reveals the co-existence of Co metal and its oxides on the catalyst surface, due to gradual oxidation of Co by gas phase oxygen within the initial stage of the PROX reaction. The promotional effect of Co during PROX is confirmed and ascribed to this Pt3Co intermetallic compound and the synergetic effect of Co-0 and Co chi+. The high accessibility of the reactant to Pt3Co species appears favorable and crucial for PROX.

  • 327.
    Li Jansson, Zheng
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Träkemi och massateknologi.
    Brännvall, Elisabet
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Träkemi och massateknologi.
    Effect of Kraft Cooking Conditions on the Chemical Composition of the Surface and Bulk of Spruce Fibers2014Inngår i: Journal of wood chemistry and technology, ISSN 0277-3813, E-ISSN 1532-2319, Vol. 34, nr 4, 291-300 s.Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    By varying cooking temperature, alkali charge, ionic strength, and cooking time in Kraft pulping of spruce chips, pulps ranging between kappa numbers 20-80 were obtained. The unbleached Kraft pulp fibers were subjected to mechanical peeling in order to separate the surface material from the bulk of the fibers and the carbohydrate composition and lignin content of the two fractions were analyzed. As expected, the lignin and xylan contents were higher on the fiber surface than in the fiber wall. The percentage of xylan on the fiber surface was fairly constant, independent of different pulping conditions or degree of delignification. The lignin proportion on the fiber surface gradually decreased with decreasing kappa number. At a given kappa number, pulping at a higher temperature resulted in less lignin on the fiber surface, probably because of the higher solubility of lignin at higher temperature. Cooking at lower alkali charge also resulted in lower lignin content on the fiber surface at a given kappa number. In this case, there was more time available for degradation of the surface lignin since the lower alkali charge resulted in longer cooking time needed to reach a certain kappa number.

  • 328.
    Li Jansson, Zheng
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Träkemi och massateknologi.
    Brännvall, Elisabet
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Träkemi och massateknologi.
    Effect of kraft cooking conditions on the chemical composition ofthe surface and bulk of spruce fibers2011Manuskript (preprint) (Annet vitenskapelig)
  • 329.
    Li, Q.
    et al.
    Luleå tekniska universitet.
    Creaser, Derei
    Luleå tekniska universitet.
    Sterte, Johan
    Nucleation period for TPA-silicalite-1 crystallization determined by a two-stage varying-temperature synthesis1999Inngår i: Microporous and Mesoporous Materials, ISSN 1387-1811, E-ISSN 1873-3093, Vol. 31, nr 1, 141-150 s.Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A two-stage-varying-temperature synthesis procedure, which involves a rapid change in temperature at some point during the course of crystallization, was applied to the synthesis of discrete colloidal particles of TPA-silicalite-1. As the duration of the period at the initial synthesis temperature was extended, the crystal concentration and ultimate crystal size varied until they were approximately equal to those obtained for a complete synthesis at the initial temperature. At this point in the crystallization, it was concluded that the nucleation stage was completed. For syntheses performed at 60, 80 and 100°C, the duration of the nucleation period determined by this method was about 100 h, between 4 and 6 h and less than 2 h, respectively. Thus, nucleation, for this system, is a continuous process, and it was found that the rate of nucleation, which is initially high, declines, throughout the nucleation period. In all cases, nucleation occurred during an induction period when little or no crystal growth was observed, which explains why the syntheses yielded a product with a rather narrow crystal size distribution. If, for the two-stage syntheses, the temperature change was made after completion of the nucleation period, the second synthesis temperature controlled only the linear growth rate of the crystals and the final yield of silicalite-1 obtained

  • 330.
    Li, Qinghua
    Luleå tekniska universitet.
    Colloidal zeolites: from nucleation to zoned films by seeded growth2002Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    The work presented in this thesis concerns the investigation of nucleation kinetics for colloidal zeolites, especially the determination of the nucleation period during crystallization. It also concerns the use of colloidal TPA-silicalite-1 for the preparation of zoned MFI films. A novel method, a two-stage varying-temperature procedure, involving starting a crystallization at a certain temperature, and then rapidly changing temperature at some point during the crystallization, was developed for the investigation of nucleation kinetics of colloidal zeolites. As the duration of the crystallization at the initial temperature was extended, the ultimate crystal size and crystal concentration varied until they were approximately equal to those obtained for a complete synthesis at the initial temperature. At this point, the nucleation stage during the crystallization was completed. For the synthesis of colloidal TPA-silicalite- 1, the nucleation process occurred over a substantial period of time, extending over the induction period, but was completed before crystal growth was detected, independent of aging time and silica source. For the synthesis of colloidal zeolite Y, the nucleation and crystal growth processes occurred simultaneously and the nucleation period was significantly longer than the induction period. The two-stage varying-temperature synthesis procedure was used to synthesize particularly small colloidal crystals of TPA-silicalite-1 with a high yield for short synthesis time. In addition, midsynthesis addition of sodium after the nucleation of zeolite Y produced pure colloidal zeolite Y with slightly larger crystals (less than 110 nm) and a high yield. Colloidal TPA-silicalite-1 crystals with a size of 60 nm were used as seeds to prepare different types of zoned MFI films on various substrates by a two- step crystallization method. In the first step a type of MFI film was synthesized on the seeded substrate by hydrothermal treatment. In the second step crystallization of another type of MFI film was achieved by further hydrothermal treatment. The structural configuration of the films was characterized by SEM, EDS, XRD and TEM techniques. The channel continuity at the interface between two different layers depended on both the composition and synthesis conditions used and the order of the layers in the film.

  • 331.
    Li, Qinghua
    Luleå tekniska universitet.
    Crystallization of colloidal TPA-silicalite-1 by a two-stage varying-temperature synthesis2000Licentiatavhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    A novel synthesis method called a two-stage varying-temperature synthesis was developed for the investigation of kinetics and mechanism of the crystallization of discrete colloidal crystals of TPA-silicalite-1. Briefly, this method involves a rapid change in treatment temperature at some point during the crystallization. By extending the duration of the period at the initial synthesis temperature, the crystal concentration and final crystal size varied until they were approximately equal to those obtained for a complete synthesis at the initial temperature. At this point in the crystallization, it was concluded that the nucleation stage was completed. In the TPAOH-TEOS-H2O system, the nucleation was a continuous process and the rate of nucleation was initially high immediately after the start of hydrothermal treatment, but then exponentially declined throughout the nucleation period. In the TPAOH-SiO2-H2O-ethanol system, where SiO2 was colloidal amorphous silica, the nucleation was still a successive process, whereas the nucleation profile was more similar to that usually considered to occur during zeolite syntheses with an autocatalytic increase in the nucleation rate. When the synthesis conditions were identical, except for the silica source in the above two systems, the nucleation period for the TPAOH-SiO2-H2O-ethanol system was longer than that for the TPAOH-TEOS-H2O system. This was presumably due to the fact that the colloidal silica particles needed to depolymerize to reach a supersaturation concentration in order for nucleation and crystal growth to occur. Also, it was found that irrespective of silica sources, the vast majority of nucleation occurred during an induction period before linear crystal growth started. The two-stage synthesis method could also be used to produce particularly small colloidal crystals of TPA-siliclaite-1 with reduced synthesis times and high yields. Using this method involves starting a synthesis at a lower temperature and ending the synthesis at a higher temperature. After determining the nucleation stage, an elevated temperature can be used to accelerate the crystal growth and reach higher equilibrium yields controlled by the final temperature. The effects of temperature, dilution and alkalinity on the synthesis were studied to optimize syntheses. The effect of aging on the kinetics and mechanism for crystallization of colloidal TPA-silicalite-1 with varying silica source was also investigated with the two-stage synthesis procedure. With the TEOS silica source, aging for up to 15 days at room temperature had no significant effect on the nucleation and crystallization at a low synthesis temperature. Whereas with amorphous silica, aging caused the nucleation kinetics to become increasingly similar to those for syntheses with TEOS. Thus, with sufficient aging of more economical amorphous silica sources, the properties of the final products approached that with the more exotic TEOS silica source, viz., small colloidal crystals with a narrow crystal size distribution.

  • 332.
    Li, Qinghua
    et al.
    Luleå tekniska universitet.
    Creaser, Derek
    Luleå tekniska universitet.
    Sterte, Johan
    High yield synthesis of collodial crystals of zeolite Y2001Inngår i: Zeolites and mesoporous materials at the dawn of the 21st century: proceedings of the 13th International Zeolite Conference, Amsterdam: Elsevier, 2001, 140- s.Konferansepaper (Fagfellevurdert)
  • 333.
    Li, Qinghua
    et al.
    Luleå tekniska universitet.
    Creaser, Derek
    Luleå tekniska universitet.
    Sterte, Johan
    The synthesis of small colloidal crystals of TPA-silicalite-1 with short synthesis times and high yields1999Inngår i: Studies in Surface Science and Catalysis, ISSN 0167-2991, Vol. 125, 133-140 s.Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A two-stage varying-temperature crystallization procedure can be used to synthesize particularly small colloidal crystals of TPA-silicalite-1 with reduced synthesis times and high yields. Using this procedure involves starting a synthesis at a reduced temperature which favours the nucleation of a large crystal population. The reduced temperature is maintained throughout the nucleation stage, after which an elevated temperature is used to accelerate the crystal growth and reach higher equilibrium yields favoured by higher temperatures

  • 334.
    Li, Qinghua
    et al.
    Luleå tekniska universitet.
    Hedlund, Jonas
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Creaser, Derek
    Luleå tekniska universitet.
    Sterte, Johan
    Zoned MFI films by seeding2001Inngår i: Chemical Communications, ISSN 1359-7345, E-ISSN 1364-548X, Vol. 2001, nr 6, 527-528 s.Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The synthesis and characterization of zoned MFI films consisting of intergrown TPA-silicalite-1 and ZSM-5 crystals are described.

  • 335.
    Li, Qinghua
    et al.
    Luleå tekniska universitet.
    Hedlund, Jonas
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Sterte, Johan
    Creaser, Derek
    Chalmers University of Technology.
    Bons, Jan-Anton
    European Technology Center.
    Synthesis and characterization of zoned MFI films by seeded growth2002Inngår i: Microporous and Mesoporous Materials, ISSN 1387-1811, E-ISSN 1873-3093, Vol. 56, nr 3, 291-302 s.Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Supported zoned and sandwiched MFI films were prepared by a two-step crystallization procedure, using seeds. In this work, a zoned MFI film is defined as one assembled by crystals propagating from the support to the film top surface with varying Al content along the length of the crystal. A sandwiched MFI film is referred to as one assembled by at least two layers of crystals. Six types of films were prepared, both zoned and sandwiched, with a high or a low Al-content in the ZSM-5 part and with varying order of the layers, i.e. ZSM-5 coated with silicalite-1 or vice versa. The films were characterized by SEM and TEM. The Al-distribution was measured by cross-sectional EDS, and the preferred orientation of the crystals could be determined by XRD. Truly zoned films are obtained when the compositional difference between the layers is relatively small, and the synthesis conditions are similar or when the first layer is silicalite-1. If the first layer is ZSM-5 and the synthesis conditions and/or the composition vary too much, a discontinuity occurs at the interface between the layers, and sandwiched film results, where nucleation of the second layer is initiated by secondary nucleation or by applying seeds.

  • 336.
    Li, Qinghua
    et al.
    Luleå tekniska universitet.
    Mihailova, Boriana
    Bulgarian Academy of Sciences.
    Creaser, Derek
    Luleå tekniska universitet.
    Sterte, Johan
    The nucleation period for crystallization of colloidal TPA-silicalite-1 with varying silica source2000Inngår i: Microporous and Mesoporous Materials, ISSN 1387-1811, E-ISSN 1873-3093, Vol. 40, nr 1-3, 53-62 s.Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The effect of varying silica source on the nucleation and crystallization of TPA-silicalite-1 was investigated. A direct experimental method, involving a two-stage varying-temperature synthesis, was used to determine the nucleation period for colloidal crystals of TPA-silicalite-1 with different silica sources, including tetraethoxysilane (TEOS) and amorphous silica (Ludox TM and Ludox LS). For syntheses performed at 60°C with TEOS as silica source, the duration of the nucleation was about 72 h, and a very rapid increase in the crystal population occurred during the initial crystallization time. However, with the amorphous silica sources (Ludox TM or Ludox LS), the duration of the nucleation period was extended to about 120 h, and the nucleation profile consisted of a self-accelerating nucleation rate at the beginning of the nucleation period. The two-stage synthesis method could be used to determine the nucleation profile for the various silica sources. However, this technique overestimated the crystal concentration at the earliest stage of nucleation with amorphous silica. The use of amorphous silica gave rise to a broader crystal size distribution compared to that of TEOS. However, it was found that for both TEOS and amorphous silica the vast majority of the nucleation occurred during an induction period when little or no crystal growth was observed. In addition, Raman spectroscopy revealed structural differences between Ludox TM and Ludox LS which may account for differences in the nucleation processes observed for these two amorphous silicas.

  • 337.
    Li, Qinghua
    et al.
    Luleå tekniska universitet.
    Wang, Zheng
    Luleå tekniska universitet.
    Hedlund, Jonas
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Creaser, Derek
    Chalmers University of Technology.
    Zhang, Hong
    Stockholm University.
    Zou, Xiaodong
    Stockholm University.
    Bons, Anton-Jan
    European Technology Center.
    Synthesis and characterization of colloidal zoned MFI crystals2005Inngår i: Microporous and Mesoporous Materials, ISSN 1387-1811, E-ISSN 1873-3093, Vol. 78, nr 1, 1-10 s.Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Colloidal zoned MFI crystals, i.e., continuous crystals with a compositional gradient resulting in a ZSM-5 core covered with a silicalite-1 shell, were synthesized by the addition of ZSM-5 seeds to a silicalite-1 synthesis solution. The effect of the surface aluminum content of the ZSM-5 crystals on the synthesis of the zoned MFI crystals was investigated using SEM, TEM, XPS and XRD. An acid treatment of the ZSM-5 seeds, which removed some of the aluminum at the surface, proved favorable for the synthesis of zoned MFI crystals.

  • 338.
    Li, Ying Zhen
    et al.
    RISE - Research Institutes of Sweden, Säkerhet och transport, Safety.
    Ingason, Haukur
    RISE - Research Institutes of Sweden, Säkerhet och transport, Safety.
    Analysis of Muskö tunnel fire flows with automatic sprinkler activation2017Rapport (Annet vitenskapelig)
    Abstract [en]

    The focus of the present study is analyzing the best position of a sprinkler nozzle in a tunnel cross-section in the Muskö tunnel, south of Stockholm, Sweden. Activation of the sprinklers installed along the centerline and along the sidewall is investigated through analysis of full scale experiments and by three dimensional numerical modelling. Then the tunnel velocity is analyzed by one dimensional numerical modelling for various fire locations in the Muskö tunnel. For both activating the automatic sprinklers nearby the fire and avoiding activation of the sprinklers further downstream, the automatic sprinklers are recommended to be installed along the centerline of the tunnel. It has also been found that the tunnel velocity varies significantly with the fire location. When the fire is on the left side of the tunnel, the flow velocity mostly remains in a range of 1 m/s (positive or negative) within the first 10 minutes, which helps early activation of the automatic sprinklers. When the fire is on the right side of the tunnel, the flow velocity mostly remains within a range of -1 m/s and 1 m/s within the first 5 minutes, and the velocity mostly increases to 2 m/s at around 10 min. Therefore, the scenario for fire located on the left side is better than that for fire on the right side, especially when it is located between the middle of the right section and the right portal. As one typical case with fire on the right side, the tunnel velocity maintains at 1 m/s for the first 5 min and gradually increases to 2 m/s at 10 min. Under such conditions, the automatic sprinkler system is expected to perform well. 

  • 339.
    Li, Ying Zhen
    et al.
    RISE - Research Institutes of Sweden, Säkerhet och transport, Safety.
    Ingason, Haukur
    RISE - Research Institutes of Sweden, Säkerhet och transport, Safety.
    New models for calculating maximum gas temperatures in large tunnel fires2016Rapport (Annet vitenskapelig)
    Abstract [en]

    The work presented in this report focuses on estimating maximum gas temperatures at ceiling level during large tunnel fires. Gas temperature is an important parameter to consider when designing the fire resistance of a tunnel structure. Earlier work by the authors has established correlations between excess ceiling gas temperature and effective tunnel height, ventilation rate, and heat release rate. The maximum possible excess gas temperature was set as 1350°C, independent of the tunnel structure and local combustion conditions. As a result of this research, two models have been developed to better estimate possible excess maximum gas temperatures for large tunnel fires in tunnels with differing lining materials and structure types (e.g. rock, concrete). These have been validated using both model- and full-scale tests. Comparisons of predicted and measured temperatures show that both models correlate well with the test data. However, Model I is better and more optimal, due to the fact that it is more conservative and easier to use. The fire duration and flame volume are found to be related to gas temperature development. In reality, the models could also be used to estimate temperatures in a fully developed compartment fire.

  • 340.
    Liao, Haidong
    KTH, Skolan för kemivetenskap (CHE), Kemi.
    Sol-gel Synthesis and Photocatalytic Characterization of Immobilized TiO2 Films2009Licentiatavhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

       Contamination of surface and ground water from industrial wastes and anthropogenic activities represents one of the greatest challenges to the sustainable development of human society. Heterogeneous photocatalysis, a kind of advanced oxidation process characterized by the production of highly oxidative hydroxyl radicals, is a relatively novel subject with tremendous potential in water treatment applications.

        The purpose of this research was first to develop feasible hydroxyl radical detection methods, which can be used to evaluate efficiency of photocatalytic process, and second to prepare immobilized TiO2 films with high photocatalytic activities by the sol gel method.

        The feasibility of Indigo carmine and phthalic hydrazide as OH-radical probes was investigated. The organic dye Indigo carmine absorbs visual light strongly at 610 nm and its destruction can be monitored conveniently in a spectrophotometer. Results showed that both ·OH and HO2· can bleach Indigo carmine, and the bleaching yield of ·OH was pH independent. The photocatalytic dye bleaching in black light UV illuminated Degussa P25 TiO2 aerated suspensions was then investigated. A strong pH dependency of the bleaching yield was found.  This implies that the quantum yield of OH radical at pH 3 is one fourth compared to that at pH 10. The reaction of the OH radical with phthalic hydrazide will form strongly chemiluminescent 3-hydroxyphthalic hydrazide. Using the more specific phthalic hydrazide as OH radical probe, an even stronger pH dependent quantum yield of OH radical was found. At pH 10 the quantum yield reached the same magnitude as that obtained by using Indigo carmine, whereas the quantum yields at acidic pH were close to zero. However it was found that the addition of phosphate and fluoride anions can substantially enhance the OH radical yield at acidic pH by blocking the adsorption of phthalic hydrazide onto the TiO2 surfaces. Hence the adsorption of phthalic hydrazide to TiO2 is an important factor to consider when this method is used.

        Photocatalytic TiO2 films coated on metal plates were prepared by a sol gel method using titanium isopropoxide as TiO2 precursor and isopropanol as solvent. The photocatalytic activity of the obtained films was evaluated by bleaching of indigo carmine at pH 9 under black light UV irradiation. The effect of the molar ratio of isopropanol, water and hydrochloric acid to titanium isopropoxide was studied. It was also shown that the activities of TiO2 films are considerably influenced by calcination temperature, coating cycles and the supporting materials.

  • 341.
    Lind, Mårten
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Energiprocesser.
    Opportunities and uncertainties in the early stages of development of CO2 capture and storage2009Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    The topic of this thesis is carbon dioxide (CO2) capture and storage (CCS), which is a technology that is currently being promoted by industries, scientists and governments, among others, in order to mitigate climate change despite a continued use of fossil fuels. Because of the complex nature of CCS and the risks it entails, it is controversial. The aim of this thesis is to analyse how the technology may be further developed in a responsible manner. In the first part of the thesis different methods for capturing CO2 from industrial processes as well as power plants are analysed. The aim is to identify early opportunities for CO2 capture, which is considered important because of the urgency of the climate change problem. Three potential early opportunities are studied: i) capturing CO2 from calcining processes such as cement industries by using the oxyfuel process, ii) capturing CO2 from pressurised flue gas, and iii) capturing CO2 from hybrid combined cycles. Each opportunity has properties that may make them competitive in comparison to the more common alternatives if CCS is realised. However, there are also drawbacks. For example, while capturing CO2 from pressurised flue gas enables the use of more compact capture plant designs as well as less expensive and less toxic absorbents, the concept is neither suitable for retrofitting nor has it been promoted by the large and influential corporations. The second part of the thesis has a broader scope than the first and is multidisciplinary in its nature with inspiration from the research field of Science and Technology Studies (STS). The approach is to critically analyse stakeholder percep-tions regarding CCS, with a specific focus on the CCS experts. The thesis sheds new light on the complexity and scientific uncertainty of CCS as well as on the optimism among many of its proponents. Because of the uncertain development when it comes to climate change, fossil fuel use and greenhouse gas emissions, the conclusion is that CCS has to be further developed and demonstrated. A responsible strategy for a future development of CCS would benefit from: i) a search for win-win strategies, ii) increasing use of appropriate analytical tools such as life-cycle analysis, iii) a consideration of fossil fuel scarcity and increasing price volatility, iv) funding of unbiased research and v) increasing simultaneous investments in long-term solutions such as renewable energy alternatives and efficiency improvements.

  • 342.
    Lindgren, Maria
    et al.
    Luleå tekniska universitet.
    Skrifvars, Mikael
    SICOMP AB, Swedish Institute of Composites.
    Sandlund, Erik
    SICOMP AB, Swedish Institute of Composites.
    Pettersson, Joakim
    SICOMP AB, Swedish Institute of Composites.
    Styrene emissions from the spray-up and vacuum injection processes: A quantitative comparison2002Inngår i: AIHA journal, ISSN 1542-8117, Vol. 63, nr 2, 184-189 s.Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Styrene emissions were studied during manufacturing of two identical glass-fiber reinforced plastic boats by two different manufacturing methods. The manufacturing methods were spray-up, which is an open method, and vacuum injection, which is a closed method. Changing the manufacturing process from an open method to a closed method decreased the styrene evaporation dramatically in this particular case. By using vacuum injection, the styrene emission during the laminate application was reduced by 98% compared with the styrene emission during laminate application by spray-up. Gel coat application by spraying will remain a major source for styrene emissions. The greatest environmental benefit is achieved with closed manufacturing methods when products without gel coat are made. The whole manufacturing process can then be performed in a closed system virtually free from emissions.

  • 343.
    Lindmark, Jonas
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Modification of MFI membranes for enhanced selectivity2009Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    Zeolite membranes can potentially be used for separation of many types of mixtures. The membranes can be tailored by a number of methods to suit a specific separation application. In this work both traditional and new innovative methods were used to tailor the properties of zeolite membranes in order to enhance the selectivity for a given separation. In this work the traditional methods for tailoring of zeolite membranes by adjusting the Si/Al-ratio of, and exchanging the counterions in the zeolite have been used. In addition, two new methods have been developed: One where the impregnation concept often used in the catalysis field is adapted to tailor the properties of zeolite membranes for the first time, and another, where methylamine is used to modify the zeolite and form more and stronger basic sites. The polarity of a zeolite can be tailored by changing the Si/Al ratio in order to facilitate the separation of polar and non polar molecules. A low Si/Al ratio gives a more polar zeolite and vice versa. In the present work, separation of mixtures of water, hydrogen and n-hexane was investigated for membranes with two different Si/Al ratios (silicalite-1 and ZSM-5). The highest separation factors α-water/hydrogen were observed at 25 °C and were 14.3 and 19.7 for silicalite-1 and ZSM-5, respectively. Mixtures of methanol/ethanol, hydrogen, carbon dioxide and water were also investigated, and the highest measured methanol/hydrogen separation factor, 32, was achieved for a ZSM-5 membrane, while a silicalite-1 membrane was found to give the highest ethanol/hydrogen separation factor of 46. The polar ZSM-5 favours the separation of the polar methanol, whereas the less polar silicalite-1 is more favourable for separation of the less polar ethanol. These results confirm that the selectivity for these separations can be controlled by tailoring the polarity the zeolite. The effect of the counter ions in ZSM-5 was studied by preparing, silicalite-1 and ZSM-5 membranes with three different counter ions (Na+, Li+ and Ba2+) and evaluating these for separation of quadrupolar carbon dioxide from binary and ternary mixtures of carbon dioxide, hydrogen and water. The aim was to develop a membrane suitable for separation of carbon dioxide from synthesis gas. A separation factor α-carbon dioxide/hydrogen of 6.2 was achieved for a BaZSM-5 membrane at room temperature. In the BaZSM-5 membranes, the permeances of both carbon dioxide and hydrogen were decreased by the presence of the Ba2+counter ion, but due to enhanced adsorption of the more quadrupolar carbon dioxide the carbon dioxide permeance was decreased much less than the hydrogen permeance. By development of a new and innovative impregnation procedure, carbon dioxide selective membranes with high flux were prepared by impregnating the pores of a silicalite-1 membrane with calcium compounds to aid the adsorption of carbon dioxide. The separation experiments with mixtures of carbon dioxide and hydrogen showed that the separation factor α-carbon dioxide/hydrogen at 25 °C was drastically changed from 0.7 (hydrogen selective) to 3.7 (carbon dioxide selective) by this modification. A second new modification procedure was also developed, where MFI membranes with high Si/Al ratio were modified with methylamine to increase the carbon dioxide affinity and thus increase the carbon dioxide selectivity. These membranes were then evaluated for separation of carbon dioxide from various mixtures of carbon dioxide, hydrogen, methane and water. The modification had significant effects on both permeances and separation factors and the selectivity towards carbon dioxide was increased considerably for all the feed mixtures tested. The results of the different modifications were evaluated by techniques such as SEM, TEM, XRD, DRIFT spectroscopy and by single component permeation and mixture separation experiments. High quality membranes with few defects are critical to study the effects of membrane modification and throughout this thesis adsorption-branch permporometry is used as a standard tool to evaluate membrane quality. The permporometry technique was also studied more in detail. It is shown how the distribution of flow-through defects can be estimated from the permporometry pattern. The estimated defect distribution is supported by SEM observations. In addition the permporometry data can be used to predict the permeance of molecules diffusing through defects in the membrane in mixture separation experiments and also indicate the separation factor.

  • 344. Lindmark, Jonas
    Tailoring of MFI membranes for enhanced selectivity2006Licentiatavhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    Zeolite membranes can potentially be used for the separation of many types of mixtures. The membranes can be tailored by a number of methods to suit a specific separation application. In this work both traditional and new innovative methods were used to tailor the properties of membranes in order to enhance the selectivity for a given separation. Traditional methods to tailor zeolite membranes include; choice of zeolite framework, adjustment of Si/Al ratio and choice of counterion. In zeolite catalysts the properties are often also tailored by incorporating metal or metal oxide clusters in the zeolite pores by impregnation. In this work the traditional methods for membrane tailoring by adjusting the Si/Al-ratio and exchanging the counterions have been used. In addition, a new method where the impregnation concept often used in catalyst preparation is adapted to tailor the properties of zeolite membranes, was used. The polarity of a zeolite can be tailored by changing the Si/Al ratio, and to facilitate the separation of polar and non polar molecure e.g. H2O and H2, the Si/Al ratio should be relatively low. In the present work, separation of mixtures of H2O, H2 and n-hexane was investigated for membranes with two different Si/Al ratios (silicalite-1 and ZSM-5), in the temperature range 25 to 350 C. The highest separation factors H2O/H2 were observed at 25 C and were 14.3 and 19.7 for silicalite-1 and ZSM-5, respectively. The membranes were selective also at 100 C and the separation factors were about 3.2 and 6 for silicalite-1 and ZSM-5, respectively. These results confirm that the selectivity for this separation can be controlled by changing the polarity the zeolite. The aim of the new and innovative modification procedure was to prepare CO2 selective membranes with high flux. The pores of a silicalite-1 membrane were impregnated with calcium compounds to aid the chemisorption of CO2, which is essential to achieve a membrane which is CO2 selective even at high temperatures. The result of the impregnation was evaluated by separation of CO2 and H2. Calcined membranes were impregnated with a solution of Ca(NO3)2 in methanol and heated to 600 to thermally decompose the Ca(NO3)2 Calcium compounds were evenly distributed in the pores of the silicalite-1 film and there were also some relatively large CaCO3 crystals on the surface. The separation experiments with of mixtures of CO2 and H2 showed that the separation factor CO2/H2 at 25C was drastically changed from 0.7 (H2 selective) to 3.7 (CO2 selective) by this modification. These results show that the properties of the H2 selective silicalite-1 membrane could be tailored by impregnation to prepare a CO2 selective membrane.

  • 345. Lindmark, Jonas
    et al.
    Hedlund, Jonas
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Carbon dioxide removal from synthesis gas using MFI membranes2010Inngår i: Journal of Membrane Science, ISSN 0376-7388, E-ISSN 1873-3123, Vol. 360, nr 1-2, 284-291 s.Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A membrane processes may represent a more effective alternative compared to current technology for separation of CO2 from synthesis gas. In the present work, MFI membranes were prepared and the separation performance was evaluated. The Si/Al ratio and the counter ions in the membrane had a significant effect on both single gas permeation and mixture separation by modifying both the effective pore size and the adsorption properties of the membranes. The membranes were relatively unselective for binary mixtures of carbon dioxide and hydrogen, but when the feed also contained water, a CO2/H2 separation factor of 6.2 was achieved for a BaZSM-5 membrane at room temperature. The CO2 permeance for this membrane was as high as 13·10-7 mol · m-2 · s-1 · Pa-1. A suitable terminology for this effect, that a third component, in this case water, enhanced the separation of two other components, in this case CO2 and H2, is sorption enhanced separation. Due to the reduced adsorption of both CO2 and water at higher temperature, the CO2/H2 separation factor was always reduced as the temperature was increased. This work clearly shows that MFI membranes are promising candidates for CO2 separation from synthesis gas.

  • 346. Lindmark, Jonas
    et al.
    Hedlund, Jonas
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Modification of MFI membranes with amine groups for enhanced CO2 selectivity2010Inngår i: Journal of Materials Chemistry, ISSN 0959-9428, E-ISSN 1364-5501, Vol. 20, nr 11, 2219-2225 s.Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Much research on zeolite membranes has been devoted to MFI type zeolite and these membranes can be prepared reproducibly with high quality by our group. However, the MFI pores are too large for separation of small molecules such as CO2, H-2 CH4, and H2O by molecular sieving and the CO2 affinity is not sufficiently strong in our current membranes with quite high Si/Al ratio to achieve CO2 selective membranes. In the present work, existing MFI membranes with high Si/Al ratio are modified with methylamine to increase the CO2 affinity and thus increase the CO2 selectivity. To the best of our knowledge, this is the first time this type of modification is reported for zeolite membranes. These membranes were then evaluated for separation of CO2 from various mixtures of CO2, H-2, CH4 and H2O. The modification had significant effects on both permeances and separation factors and the selectivity towards CO2 was increased considerably for all the feed mixtures tested. The highest separation factor was observed for a CO2/CH4/H2O mixture and alpha-CO2/CH4 was 12 at about 40 degrees C. At the same time, the CO2 permeance was as high as 9 x 10(-7) mol m(-2) s(-1) Pa-1. The separation factor for the amine-modified silicalite-1 membranes was comparable to the highest reported separation factors for MFI membranes, while the CO2 permeance was higher than reported for other selective MFI membranes.

  • 347. Lindmark, Jonas
    et al.
    Hedlund, Jonas
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Separation of CO2 and H2 with modified MFI membranes2007Inngår i: From Zeolites to Porous MOF Materials: The 40th Anniversary of International Zeolite Conference, Proceedings of the 15th International Zeolite Conference / [ed] Ruren Xu; Zi Gao; Jiesheng Chen; Wenfu Yan, Amsterdam: Elsevier, 2007, 975-980 s.Konferansepaper (Fagfellevurdert)
    Abstract [en]

    MFI membranes with equal film thickness were grown on graded alumina supports and modified by ion exchange or impregnation. Single gas permeances of CO2 and H2 were measured for all membranes. Both impregnation and ion exchange had a significant effect on the permeation properties of the membranes. The single gas CO2/H2 permeance ratios were 0.57, 0.82, 1.7 and 2.2 for silicalite-1, NaZSM-5, BaZSM-5 and silicalite-1 impregnated with Ca(NO3)2 , respectively. Selected membranes were tested for separation of a mixture of 90 kPa CO2 and 90 kPa H2 in the temperature range 25-400 °C. The separation factors at 25 °C were 0.7, 2.0 and 4.1 for silicalite-1, BaZSM-5 and impregnated silicalite-1, respectively and decreased with increasing temperature. The results show that the separation factor can be enhanced significantly by impregnation, lowering of the Si/Al ratio or ion exchange.

  • 348. Lindmark, Jonas
    et al.
    Hedlund, Jonas
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Wirawan, Sang Kompiang
    Creaser, Derek
    Chalmers University of Technology, Department of Chemical and Biological Engineering.
    Li, Mingrun
    Department of Materials and Environmental Chemistry, Berzelii Center EXSELENT on Porous Materials, Stockholm University.
    Zhang, Daliang
    Department of Materials and Environmental Chemistry, Berzelii Center EXSELENT on Porous Materials, Stockholm University.
    Zou, Xiaodong
    Department of Materials and Environmental Chemistry, Berzelii Center EXSELENT on Porous Materials, Stockholm University.
    Impregnation of zeolite membranes for enhanced selectivity2010Inngår i: Journal of Membrane Science, ISSN 0376-7388, E-ISSN 1873-3123, Vol. 365, nr 1-2, 188-197 s.Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A new method to enhance the selectivity of zeolite membranes for alternative separation tasks has been developed. Calcined MFI membranes were impregnated with a solution of Ca(NO3)2 in methanol and calcined at 600 °C to thermally decompose the nitrate. SEM and EDS data indicated that calcium compounds were evenly distributed in the entire MFI film and in addition, a few crystals of a calcium compound were observed on top of the film in some locations. A HR-TEM investigation showed that calcium compounds were present in low concentration in the sample and that the interiors of the MFI crystals remained fully crystalline after impregnation and calcination. However, the HR-TEM investigation could neither confirm nor rule out the occurrence of calcium compounds in the pores in the interiors of the crystals. In accordance with the SEM and TEM observations, XRD data showed that calcium compounds on top of the film were relatively large CaCO3 crystals and that the zeolite film remained crystalline after impregnation. However, eventual calcium compounds in the pores of the zeolite could not be studied by XRD since these would probably generate a very weak signal of amorphous material. FTIR data indicated that impregnation increased the amount of both physisorbed and chemisorbed CO2, the latter resulting in carbonate species in the film. n-Hexane/helium adsorption branch permporometry showed that the high quality of the membranes remained after modification. The single component permeance ratio CO2/H2 increased from 0.6 to 1.5 after impregnation. Calculations indicated that the increased CO2/H2 single component permeance ratios were both an effect of increased adsorption of CO2 in the film and reduced pressure drop in the support. The dual component separation factor α CO2/H2 at room temperature increased drastically from 0.7 (H2 selective) to 3.4 (CO2 selective) after impregnation. This work shows for the first time that impregnation procedures can be used to tailor the diffusion properties of zeolite membranes in a similar way as impregnation procedures are used to tailor the catalytic performance of catalysts.

  • 349.
    Liu, Jin
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Teknisk strömningslära.
    Svärd, Michael
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Teknisk strömningslära. University of Limerick, Ireland .
    Rasmuson, Åke C.
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Teknisk strömningslära. University of Limerick, Ireland .
    Influence of agitation and fluid shear on nucleation of m-Hydroxybenzoic acid polymorphs2014Inngår i: Crystal Growth & Design, ISSN 1528-7483, E-ISSN 1528-7505, Vol. 14, nr 11, 5521-5531 s.Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The influence of agitation and fluid shear on nucleation of m-hydroxybenzoic acid polymorphs from 1-propanol solution has been investigated through 1160 cooling crystallization experiments. The induction time has been measured at different supersaturations and temperatures in two different crystallizer setups: small vials agitated by magnetic stir bars, for which experiments were repeated 4080 times, and a rotating cylinder apparatus, for which each experiment was repeated five times. The nucleating polymorph has in each case been identified by FTIR spectroscopy. At high thermodynamic driving force for nucleation, only the metastable polymorph (form II) was obtained, while at low driving force both polymorphs were obtained. At equal driving force, a higher temperature resulted in a larger proportion of form I nucleations. The fluid dynamic conditions influence the induction time, as well as the polymorphic outcome. Experiments in small vials show that the agitation rate has a stronger influence on the induction time of form II compared to form I. The fraction of form I nucleations is significantly lower at intermediate agitation rates, coinciding with a reduced induction time of form II. In experiments in the rotating cylinder apparatus, the induction time is found to be inversely correlated to the shear rate. The difference in polymorphic outcome at different driving force is examined in terms of the ratio of the nucleation rates of the two polymorphs, calculated by classical nucleation theory using determined values of the pre-exponential factor and interfacial energy for each polymorph. A possible mechanism explaining the difference in the influence of fluid dynamics on the nucleation of the two polymorphs is based on differences between the two crystal structures. It is hypothesized that the layered structure of form II is comparatively more sensitive to changes in shear flow conditions than the more isotropic form I structure.

  • 350.
    Liu, Longcheng
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Kemisk apparatteknik.
    Neretnieks, Ivars
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Kemisk apparatteknik.
    Shahkarami, Pirouz
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Kemisk apparatteknik.
    Meng, Shuo
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Kemisk apparatteknik.
    Moreno, Luis
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Kemisk apparatteknik.
    Solute transport along a single fracture in a porous rock: a simple analytical solution and its extension for modeling velocity dispersion2017Inngår i: Hydrogeology Journal, ISSN 1431-2174, E-ISSN 1435-0157Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A simple and robust solution is developed for the problem of solute transport along a single fracture in a porous rock. The solution is referred to as the solution to the single-flow-path model and takes the form of a convolution of two functions. The first function is the probability density function of residence-time distribution of a conservative solute in the fracture-only system as if the rock matrix is impermeable. The second function is the response of the fracture-matrix system to the input source when Fickian-type dispersion is completely neglected; thus, the effects of Fickian-type dispersion and matrix diffusion have been decoupled. It is also found that the solution can be understood in a way in line with the concept of velocity dispersion in fractured rocks. The solution is therefore extended into more general cases to also account for velocity variation between the channels. This leads to a development of the multi-channel model followed by detailed statistical descriptions of channel properties and sensitivity analysis of the model upon changes in the model key parameters. The simulation results obtained by the multi-channel model in this study fairly well agree with what is often observed in field experiments—i.e. the unchanged Peclet number with distance, which cannot be predicted by the classical advection-dispersion equation. In light of the findings from the aforementioned analysis, it is suggested that forced-gradient experiments can result in considerably different estimates of dispersivity compared to what can be found in natural-gradient systems for typical channel widths.

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