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  • 1. Agrell, J.
    et al.
    Germani, G.
    Järås, Sven G.
    KTH, Superseded Departments, Chemical Engineering and Technology.
    Boutonnet, Magali
    KTH, Superseded Departments, Chemical Engineering and Technology.
    Production of hydrogen by partial oxidation of methanol over ZnO-supported palladium catalysts prepared by microemulsion technique2003In: Applied Catalysis A: General, ISSN 0926-860X, E-ISSN 1873-3875, Vol. 242, no 2, p. 233-245Article in journal (Refereed)
    Abstract [en]

    Selective production of hydrogen by partial oxidation of methanol, using air as oxidant, was studied over a series of ZnO-supported Pd catalysts. Microemulsion-assisted synthesis and conventional impregnation techniques were used for preparation of catalysts containing Pd particles of different sizes. Catalyst characterisation included BET, XRD and TEM analyses. The influence of Pd particle size on catalytic activity and product distribution was studied by carrying out activity measurements at temperatures between 230 and 300 degreesC using a stoichiometric feed composition. All catalysts performed well with respect to methanol conversion and hydrogen yield. Both methanol conversion and hydrogen selectivity increased with increasing reaction temperature, the latter at the expense of water formation. Oxygen conversion was complete throughout the examined temperature range. These selectivity trends, with a strong dependence of hydrogen and carbon monoxide selectivities on methanol conversion and reaction temperature, support a reaction scheme consisting of consecutive methanol combustion, steam reforming and decomposition. More importantly, a correlation between Pd particle size and carbon monoxide selectivity was found. When the microemulsion catalysts are compared, carbon monoxide formation increases with increasing particle size. This was not observed over the impregnated reference catalysts, which exhibited high carbon monoxide-levels throughout the examined temperature range. Bimetallic PdZn particles were detected in spent catalysts by means of XRD and it is suggested that the catalytic activity is dependent on the formation of PdZn, the catalytic function being different from that of Pd-0.

  • 2. Agrell, J.
    et al.
    Hasselbo, K.
    Jansson, K.
    Järås, Sven G.
    KTH, Superseded Departments, Chemical Engineering and Technology.
    Boutonnet, Magali
    KTH, Superseded Departments, Chemical Engineering and Technology.
    Production of hydrogen by partial oxidation of methanol over Cu/ZnO catalysts prepared by microemulsion technique2001In: Applied Catalysis A: General, ISSN 0926-860X, E-ISSN 1873-3875, Vol. 211, no 2, p. 239-250Article in journal (Refereed)
    Abstract [en]

    Production of hydrogen by partial oxidation of methanol, using air as oxidant. has been studied over a series of Cu/ZnO catalysts prepared by microemulsion technique. The catalytic activity was compared to that of a reference catalyst prepared by conventional co-precipitation. The BET surface areas of the microemulsion catalysts (30-70 wt.% Cu) ranged from 22 to 36 m(2)/g and were considerably lower than that of the reference (60 m(2)/g). Nevertheless, the microemulsion catalysts were more active in the partial oxidation reaction and exhibited high hydrogen and carbon dioxide selectivities. At a molar O-2/CH3OH ratio of 0.1, hydrogen production was initiated at about 185 degreesC over the microemulsion catalysts. Over the reference, hydrogen production began at 215 degreesC under the same conditions. The catalytic activity was Found to be strongly dependent on the partial pressure of oxygen, which also plays an important role in determining the product distribution. By increasing the O-2/CH3OH ratio, the methanol conversion and carbon dioxide selectivity increase. while production of water occurs at the expense of hydrogen. By TEM and TPR, it was observed that Cu is less well-dispersed in the microemulsion catalysts than in the reference. The higher catalytic activity is not expected considering the lower number of exposed Cu sites, i.e, the turnover frequencies are substantially higher over the microemulsion catalysts. It is possible that, a strong interaction between a small part of CuO and the ZnO lattice is responsible for the higher turnover frequencies of the microemulsion catalysts, or that particular crystallographic Cu planes or surface imperfections are the active sites of the reaction.

  • 3.
    Andersson, Robert
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology.
    Boutonnet, Magali
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology.
    Järås, Sven
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology.
    Correlation patterns and effect of syngas conversion level for product selectivity to alcohols and hydrocarbons over molybdenum sulfide based catalysts2012In: Applied Catalysis A: General, ISSN 0926-860X, E-ISSN 1873-3875, Vol. 417, p. 119-128Article in journal (Refereed)
    Abstract [en]

    The focus of the present study was to investigate the effect of the operation conditions, space velocity and temperature, on product distribution for a K-Ni-MoS2 catalyst for mixed alcohol synthesis from syngas. All experiments were performed at 91 bar pressure and constant H-2/CO=1 syngas feed ratio. For comparison, results from a non-promoted MoS2 catalyst are presented. It was found that the CO conversion level for the K-Ni-MoS2 catalyst very much decides the alcohol and hydrocarbon selectivities. Increased CO conversion by means of increased temperature (tested between 330 and 370 degrees C) or decreased space velocity (tested between 2400 and 18,000 ml/(g(cat) h)), both have the same effect on the product distribution with decreased alcohol selectivity and increased hydrocarbon selectivity. Increased CO conversion also leads to a greater long-to-short alcohol chain ratio. This indicates that shorter alcohols are building blocks for longer alcohols and that those alcohols can be converted to hydrocarbons by secondary reactions. At high temperature (370 degrees C) and low space velocity (2400 ml/(g(cat) h)) the selectivity to isobutanol is much greater than previously reported (9%C). The promoted catalyst (K-Ni-MoS2) is also compared to a non-promoted (MoS2) catalyst: the promoted catalyst has quite high alcohol selectivity, while almost only hydrocarbons are produced with the non-promoted catalyst. Another essential difference between the two catalysts is that the paraffin to olefin ratio within the hydrocarbon group is significantly different. For the non-promoted catalyst virtually no olefins are produced, only paraffins, while the promoted catalyst produces approximately equal amounts of C-2-C-6 olefins and paraffins. Indications of olefins being produced by dehydration of alcohols were found. The selectivity to other non-alcohol oxygenates (mostly short esters and aldehydes) is between 5 and 10%C and varies little with space velocity but decreases slightly with increased temperature. Very strong correlation patterns (identical chain growth probability) and identical deviations under certain reaction conditions between aldehyde and alcohol selectivities (for the same carbon chain length) indicate that they derive from the same intermediate. Also olefin selectivity is correlated to alcohol selectivity, but the correlation is not as strong as between aldehydes and alcohols. The selectivity to an ester is correlated to the selectivity to the two corresponding alcohols, in the same way as an ester can be thought of as built from two alcohol chains put together (with some H-2 removed). This means that, e.g. methyl acetate selectivity (C-3) is correlated to the combination of methanol (C-1) and ethanol (C-2) selectivities.

  • 4.
    Andersson, Robert
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology.
    Boutonnet, Magali
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Järås, Sven
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology.
    Effect of CO2 in the synthesis of mixed alcohols from syngas over a K/Ni/MoS2 catalyst2013In: Fuel, ISSN 0016-2361, E-ISSN 1873-7153, Vol. 107, p. 715-723Article in journal (Refereed)
    Abstract [en]

    An unsupported K-Ni-MoS2 catalyst for higher alcohol synthesis from syngas (H-2/CO) has been studied during 360 h on stream. It shows a gradual increase in activity with time on stream and some possible reasons for this are discussed in the paper. The main focus of this paper was to study the on the effect of CO2-containing syngas, relative CO2-free syngas under identical reaction conditions and identical inlet H-2 and CO partial pressures (340 degrees C, 100 bar, GHSV = 6920 ml/(g(cat) h)). The effect of increased partial pressure of H-2 and CO was also studied, and to a minor extent also the effect of changed gas hourly space velocity (GHSV). Under the studied conditions, addition of CO2 was found to greatly decrease total product yield, while the selectivities to alcohol and hydrocarbons (C%, CO2-free), respectively, were unchanged. CO2 addition, however, led to a great change in the distribution within the alcohol and hydrocarbon groups. With CO2 added the methanol selectivity increased much while selectivity to longer alcohols decreased. For hydrocarbons the effect is the same, the selectivity to methane is increased while the selectivity to longer hydrocarbons is decreased. It has earlier been shown that product selectivities are greatly affected by syngas conversion level (correlated to outlet concentration of organic products, i.e. alcohols, hydrocarbons etc.) which can be altered by changes in space velocity or temperature. This means that alcohol selectivity is decreased in favor of increased hydrocarbon selectivity and longer alcohol-to-methanol ratio when syngas conversion is increased. At first it might be thought that the selectivity changes occurring when CO2 is present in the feed, just correlate to a decreased organic product concentration in the reactor and that the selectivities with CO2-containing and CO2-free syngas would be identical under constant concentration of organic products in the reactor. However, CO2-addition studies where space velocity was varied showed that significantly lower alcohol selectivity (mainly ethanol selectivity) and increased hydrocarbon selectivity (mainly methane) were found at similar organic outlet concentrations as when CO2-free syngas was feed. Comparing addition of extra H-2 or extra CO, it was found that a high H-2/CO ratio (H-2/CO = 1.52 tested in our case) favors maximum product yield, especially methanol formation, while a lower H-2/CO ratio (H-2/CO = 0.66 tested in our case) leads to higher yield of higher alcohols simultaneously minimizing hydrocarbon and methanol formation.

  • 5.
    Andersson, Robert
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Boutonnet, Magali
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Järås, Sven
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Higher alcohols from syngas using a K/Ni/MoS2 catalyst: Trace sulfur in the product and effect of H2S-containing feed2014In: Fuel, ISSN 0016-2361, E-ISSN 1873-7153, Vol. 115, p. 544-550Article in journal (Refereed)
    Abstract [en]

    Two types of experiments have been performed related to the higher alcohol synthesis from syngas over a K-Ni-MoS2 catalyst which beforehand has been operated for 1000 h on stream in sulfur-free syngas. In the first experimental part, sulfur-free syngas was used as feed and the condensed liquid product was found to contain 67 ppmw sulfur, while the sulfur concentration in the gas was 19 ppmv. The gas phase was found to contain mainly COS and H2S, while the liquid phase contained methanethiol (13.8 ppmw S), ethanethiol (10.6 ppmw S), dimethyl sulfide (21.3 ppmw S), ethyl methyl sulfide (12.2 ppmw S), unidentified sulfur compounds (7.9 ppmw S) together with some dissolved COS (0.5 ppmw S) and H2S (1.2 ppmw S). In the second experimental part, the effect of feeding syngas containing 170 ppm H2S compared to a sulfur-free syngas was studied, while all products were carefully monitored online. The presence of H2S in the syngas was found to increase CO conversion, but the largest change was found in product selectivity. The hydrocarbon selectivity greatly increased at the expense of alcohol selectivity, while the alcohol distribution shifted towards longer alcohols (increased C2+OH/MeOH ratio). From product yields it became clear that most of the increased CO conversion with H2S in the feed was due to increased methane formation (and CO2 formation due to the water-gas shift reaction). The presence of H2S in the feed greatly increased the concentration of all sulfur compounds. Together with COS, formation of thiols (methanethiol and ethanethiol) was especially favored by the presence of H2S. The thioether concentration also increased, however, to a much lower extent.

  • 6.
    Andersson, Robert
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology.
    Boutonnet, Magali
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Järås, Sven
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology.
    On-line gas chromatographic analysis of higher alcohol synthesis products from syngas2012In: Journal of Chromatography A, ISSN 0021-9673, E-ISSN 1873-3778, Vol. 1247, p. 134-145Article in journal (Refereed)
    Abstract [en]

    An on-line gas chromatographic (GC) system has been developed for rapid and accurate product analysis in catalytic conversion of syngas (a mixture of H-2 and CO) to alcohols, so called "higher alcohol synthesis (HAS)". Conversion of syngas to higher alcohols is an interesting second step in the route of converting coal, natural gas and possibly biomass to liquid alcohol fuel and chemicals. The presented GC system and method are developed for analysis of the products formed from syngas using alkali promoted MoS2 catalysts, however it is not limited to these types of catalysts. During higher alcohol synthesis not only the wanted short alcohols (similar to C-2-C-5) are produced, but also a great number of other products in smaller or greater amounts, they are mainly short hydrocarbons (olefins, paraffins, branched, non-branched), aldehydes, esters and ketones as well as CO2, H2O. Trace amounts of sulfur-containing compounds can also be found in the product effluent when sulfur-containing catalysts are used and/or sulfur-containing syngas is feed. In the presented GC system, most of them can be separated and analyzed within 60 min without the use of cryogenic cooling. Previously, product analysis in "higher alcohol synthesis" has in most cases been carried out partly on-line and partly off-line, where the light gases (gases at room temp) are analyzed on-line and liquid products (liquid at room temp) are collected in a trap for later analysis off-line. This method suffers from many drawbacks compared to a complete on-line GC system. In this paper an on-line system using an Agilent 7890 gas chromatograph equipped with two flame ionization detectors (FID) and a thermal conductivity detector (TCD), together with an Agilent 6890 with sulfur chemiluminescence dual plasma detector (SCD) is presented. A two-dimensional GC system with Deans switch (heart-cut) and two capillary columns (HP-FFAP and HP-Al2O3) was used for analysis of the organic products on the FIDs. Light inorganic gases (H-2, CO, CO2, N-2) and methane were separated on packed columns and quantified with the TCD. The "sulfur GC" was optimized for on-line trace level sulfur analysis in hydrocarbon matrices and used to understand to which degree sulfur is released from the catalyst and incorporated into the liquid product, and if so in which form. The method provides excellent quantitative measurements with a carbon material balance near 99.5% (carbon in/carbon out) for individual measurement points.

  • 7.
    Barrientos, Javier
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Garcilaso, Victoria
    Venezia, Baldassarre
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Aho, Atte
    Antonio Odriozola, Jose
    Boutonnet, Magali
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Järås, Sven
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Fischer-Tropsch Synthesis Over Zr-Promoted Co/gamma-Al2O3 Catalysts2017In: Topics in catalysis, ISSN 1022-5528, E-ISSN 1572-9028, Vol. 60, no 17-18, p. 1285-1298Article in journal (Refereed)
    Abstract [en]

    Two Zr-modified alumina supports were synthetized containing the same amount of Zr but a different distribution of this modifier over the alumina surface. These supports, together with the unmodified alumina carrier, were used to prepare three cobalt-based catalysts which were characterized and tested under relevant Fischer-Tropsch conditions. The three catalysts presented very similar porosity and cobalt dispersion. The addition of Zr nor its distribution enhanced the catalyst reducibility. The catalyst activity was superior when using a carrier consisting of large ZrO2 islands over the alumina surface. The use of a carrier with a homogeneous Zr distribution had however, a detrimental effect. Moreover, a faster initial deactivation rate was observed for the Zr-promoted catalysts, fact that may explain this contradictory effect of Zr on activity. Finally, the addition of Zr showed a clear enhancement of the selectivity to long chain hydrocarbons and ethylene, especially when Zr was well dispersed.

  • 8.
    Barrientos, Javier
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Gonzalez, Niklas
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Boutonnet, Magali
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Järås, Sven
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Deactivation of Ni/gamma-Al2O3 Catalysts in CO Methanation: Effect of Zr, Mg, Ba and Ca Oxide Promoters2017In: Topics in catalysis, ISSN 1022-5528, E-ISSN 1572-9028, Vol. 60, no 17-18, p. 1276-1284Article in journal (Refereed)
    Abstract [en]

    Catalyst deactivation is one of the major concerns in the production of substitute natural gas (SNG) via CO methanation. Catalysts in this application need to be active at low temperatures, resistant to polymeric carbon formation and stable at high temperatures and steam partial pressures. In the present work, a series of alumina-supported nickel catalysts promoted with Zr, Mg, Ba or Ca oxides were investigated. The catalysts were tested under low temperature CO methanation conditions in order to evaluate their resistance to carbon formation. The catalysts were also exposed to accelerated ageing conditions at high temperatures in order to study their thermal stability. The aged catalysts lost most of their activity mainly due to sintering of the support and the nickel crystallites. Apparently, none of these promoters had a satisfactory effect on the thermal resistance of the catalyst. Nevertheless, it was found that the presence of Zr can reduce the rate of polymeric carbon formation.

  • 9.
    Barrientos, Javier
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    González, N.
    Lualdi, Matteo
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Boutonnet, Magali
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Järås, Sven
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    The effect of catalyst pellet size on nickel carbonyl-induced particle sintering under low temperature CO methanation2016In: Applied Catalysis A: General, ISSN 0926-860X, E-ISSN 1873-3875, Vol. 514, p. 91-102Article in journal (Refereed)
    Abstract [en]

    Abstract The present work aims to evaluate the effect of catalyst pellet size on deactivation due to nickel carbonyl-induced particle sintering. For that purpose, a γ-Al2O3-supported nickel catalyst was prepared and tested under low temperature and high CO partial pressure. A total of four different pellet sizes were employed in the present study. It was found that the deactivation rate decreases with increasing pellet size. A very severe deactivation was observed when using small pellets. Large pellets exhibited instead a more stable performance. This difference in catalyst stability was explained by X-ray diffraction analyses which revealed that the growth of the nickel particles was very severe when using small pellets. An evaluation of heat and mass transfer phenomena in these four pellets was also conducted. It was found that, under the present low temperature reaction conditions, the temperature at the catalyst external surface can greatly differ from that in the bulk gas when using sufficiently large pellets. It was also shown that, for large pellets, the major part of the interior of the catalyst is exposed to negligible CO partial pressures and high temperatures, fact that can reduce the potential for nickel carbonyl formation.

  • 10.
    Barrientos, Javier
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Lualdi, Matteo
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Boutonnet, Magali
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Järås, Sven
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Deactivation of supported nickel catalysts during CO methanation2014In: Applied Catalysis A: General, ISSN 0926-860X, E-ISSN 1873-3875, Vol. 486, p. 143-149Article in journal (Refereed)
    Abstract [en]

    Deactivation of Ni-based catalysts was investigated during CO methanation over different supported catalysts. X-ray diffraction and temperature-programmed hydrogenation analyses were used to investigate nickel particle sintering and carbon formation during the first 24 h on stream. Titania-supported catalysts presented high resistance towards carbon deposition and nickel particle growth in comparison with the other tested catalysts. Particle size effects on these two deactivation causes were also evaluated. It was shown that carbon formation rates are higher on bigger crystal particles. However, it was found that titania-supported nickel catalysts reduced at high temperatures show the opposite effect. This difference is most probably due to a stronger interaction between nickel and TiOx (x < 2) species on smaller crystals which changes the CO dissociation properties and, in consequence, carbon formation rates.

  • 11.
    Barrientos, Javier
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Montes, V.
    Boutonnet, Magali
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Järås, Sven
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Further insights into the effect of sulfur on the activity and selectivity of cobalt-based Fischer–Tropsch catalysts2016In: Catalysis Today, ISSN 0920-5861, E-ISSN 1873-4308, Vol. 275, p. 119-126Article in journal (Refereed)
    Abstract [en]

     A sulfur poisoning study was performed by ex situ poisoning of a platinum-promoted cobalt/alumina catalyst with different sulfur amounts. The poisoned catalyst samples were tested at relevant Fischer–Tropsch reaction conditions and at the same CO conversion in order to evaluate the effect of sulfur on catalyst activity and product selectivity. It was found that the activity and the selectivity to long-chain hydrocarbons decrease with increasing sulfur content. Moreover, it was found that sulfur has no significant effect on the CO2 selectivity. It was also shown that sulfur significantly enhances olefin hydrogenation. Finally, a deactivation model relating the catalyst activity and the sulfur to cobalt active site ratio was proposed and used to describe the experimental results.

  • 12. Berg, M.
    et al.
    Johansson, E. M.
    Järås, Sven G.
    KTH, Superseded Departments, Chemical Engineering and Technology.
    Catalytic combustion of low heating value gas mixtures: comparison between laboratory and pilot scale tests2000In: Catalysis Today, ISSN 0920-5861, E-ISSN 1873-4308, Vol. 59, no 02-jan, p. 117-130Article in journal (Refereed)
    Abstract [en]

    Catalytic combustion of low heating value fuels is a promising method for electricity production combining the use of a renewable fuel with ultra-low emissions. In the present work, catalytic combustion of a low heating value gas has been studied over monolithic catalysts in an atmospheric 30 kW pilot catalytic combustor connected to a wood pellet gasifier. The results have been compared to similar tests with a model gas mixture and a series of test in a laboratory scale reactor for monolithic samples. Various catalyst configurations have been tested, such as precious metal-based catalyst impregnated on modified alumina washcoats and hexaaluminate washcoats. Cordierite monoliths with various cells per square inch were used as supports, but hexaaluminate extruded monoliths were also used. The catalysts were combined in different segment series. The results show that it is possible to ignite the low heating value gas at compressor outlet temperatures without the use of pre-burners over precious metal catalysts. Generally, trends and phenomena obtained in laboratory reactor operating close to isothermal could be confirmed in the pilot operating at close to adiabatic conditions. Further results, such as deactivation by sulphur compounds, fuel-NOx conversion and emissions of carbon monoxide and total hydrocarbons, are addressed in the paper.

  • 13.
    Birgersson, Henrik
    et al.
    KTH, Superseded Departments, Chemical Engineering and Technology.
    Boutonnet, Magali
    KTH, Superseded Departments, Chemical Engineering and Technology.
    Järås, Sven G.
    KTH, Superseded Departments, Chemical Engineering and Technology.
    Eriksson, L.
    Deactivation and regeneration of spent three-way automotive exhaust gas catalysts (TWC)2004In: Topics in catalysis, ISSN 1022-5528, E-ISSN 1572-9028, Vol. 30-1, no 1-4, p. 433-437Article in journal (Refereed)
    Abstract [en]

    The effect of oxidation, oxy-chlorination and reduction treatments at elevated temperatures on the dispersion of palladium (Pd) and rhodium (Rh) for commercially aged three-way automotive exhaust gas catalysts (TWC) has been investigated. The catalytic activity of treated samples was compared with a reference sample, which was taken from the corresponding aged TWC and tested using a 'mini-cuts' reactor simulating real driving conditions. In the case of oxygen, the improvement of the noble metal dispersion on the catalysts was dependent on the noble metal loading and the degree of metal sintering. Adding chlorine to the oxygen atmosphere facilitates the restructuring of the metals with an improved increase in the noble metal dispersion. The temperature and the composition of the gas used during these thermal treatments proved to be of importance not only to increase the metal dispersion, but also to prevent possible losses of noble metals, in the form of volatile MOxCly compounds. TEM-EDS techniques indicated changes in the size of the largest noble metal agglomerates of Lip to 100 nm in size after thermal gas treatment. BET porosity and XRD analyses were employed to investigate restructuring of the washcoat and showed a decrease in pore size distribution and an increase in surface area.

  • 14.
    Birgersson, Henrik
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Eriksson, L
    Boutonnet, Magali
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Järås, Sven
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Regeneration of spent commercial automotive three-way exhaust gas catalysts (TWC)Article in journal (Other academic)
  • 15.
    Birgersson, Henrik
    et al.
    KTH, Superseded Departments, Chemical Engineering and Technology.
    Eriksson, L
    Boutonnet, Magali
    KTH, Superseded Departments, Chemical Engineering and Technology.
    Järås, Sven
    KTH, Superseded Departments, Chemical Engineering and Technology.
    Thermal gas treatment to regenerate spent automotive three-way exhaust gas catalysts (TWC)2004In: Applied Catalysis B: Environmental, ISSN 0926-3373, E-ISSN 1873-3883, Vol. 54, p. 193-200Article in journal (Refereed)
    Abstract [en]

    The effect of regeneration on the metal dispersion and catalyst activity of commercial automotive three-way catalysts (TWC) in oxygen, hydrogen and oxy-chlorine at elevated temperatures has been investigated. In addition, characterisation of the catalysts has been performed using XRD, TEM, TPR, CO chemisorption and BET surface area measurements. Activity tests on monolith fragments were conducted in a micro-reactor supplied with real exhaust gases. An increase in activity was observed with oxygen treatment on catalysts showing heavy sintering as well as a high noble metal loading. Hydrogen proved to be an ineffective treatment procedure, whereas the addition of chlorine to the oxygen stream resulted in an activity increase even on catalysts less sintered and with lower noble metal contents. A comparison of the XRD and BET profiles showed no or small changes in the washcoat structure compared to fresh catalysts after successful regeneration. The TEM, TPR and CO chemisorption measurements suggest a decrease in the size of the largest noble metal agglomerates on the catalyst surface, as well as some Pd and RhO restructuring. The oxy-chlorine regeneration procedure is shown to be the most efficient, both regarding the catalyst activity and the metal dispersion. An increase in the amount of noble metal particles with a size of 20-70 nm, coupled with a decrease in size of larger clusters up to 100 nm in size, was observed for this treatment.

  • 16.
    Elm Svensson, Erik
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Boutonnet, Magali
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Järås, Sven
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    High-surface-area lanthanum hexaaluminates by carbon templatingArticle in journal (Other academic)
  • 17.
    Elm Svensson, Erik
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology.
    Boutonnet, Magali
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology.
    Järås, Sven
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology.
    Preparation of hexaaluminate2008Patent (Other (popular science, discussion, etc.))
    Abstract [en]

    A method for preparing a hexaaluminate. The method comprises the steps of a) providing a porous template material, wherein pores having a pore size of about 5-200 nm form at least about 50% of the total pore volume; b) impregnating the material with a liquid comprising metal elements corresponding to the elements of said hexaaluminate to provide an impregnated material; c) drying the impregnated material to provide a dried material; d) optionally, repeating at least once step b), using the dried material, and step c); e) calcining the dried material in an inert atmosphere to provide a calcined material; and f) recovering the hexaaluminate by removing template material from the calcined material. A composition obtainable by such a method. A catalyst composition comprising a hexaaluminate, wherein the composition has an average surface area of at least about 9 m2/g after ageing of the composition in a moist high-temperature atmosphere. A supported catalyst comprising such a composition. Use of such a composition as a catalyst in a high-temperature application.

  • 18.
    Elm Svensson, Erik
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Boutonnet, Magali
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Järås, Sven
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Stability of hexaaluminate-based catalysts for high-temperature catalytic combustion of methane2008In: Applied Catalysis B: Environmental, ISSN 0926-3373, E-ISSN 1873-3883, Vol. 84, no 1-2, p. 241-250Article in journal (Refereed)
    Abstract [en]

    Lanthanum hexaaluminate with a nominal composition of LaAl11O18 Was used to support 20 wt.% of LaMnO3 and CeO2. LaAl11O18 was prepared through co-precipitation of metal nitrates within the water phase of an isooctane/CFAB/1-butanol microemulsion. The stabilities of the prepared catalysts were assessed by measuring the activities for combustion of methane before and after aging at 1000 degrees C for 100h in air with 10 vol.% H2O. The activities were compared with LaMnAl11O19, due to its well-documented stability. It was shown that by using hydrothermal treatment of the microemulsion, a significantly higher surface area was obtained for the LaAl11O18. For LaMnO3, the reference support (Al2O3) was shown to be superior to LaAl11O18 as support, both in terms of activity and stability. Reactions between LaMnO3 and support were observed for all supports included in the study. For CeO2, LaAl11O18 was superior to Al2O3 as support. Deactivations of the CeO2 catalysts were linked to crystal growth of CeO2. LMHA deactivated strongly during aging; LaMnO3 on Al2O3 and several of the catalysts with CeO2 supported on LaAl11O18 showed a much more stable behavior.

  • 19.
    Elm Svensson, Erik
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Boutonnet, Magali
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Järås, Sven
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Synthesis of barium hexaaluminate by co-precipitation in microemulsionIn: Materials Chemistry and Physics, ISSN 0254-0584, E-ISSN 1879-3312Article in journal (Other academic)
  • 20.
    Elm Svensson, Erik
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Lualdi, Matteo
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Boutonnet, Magali
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Järås, Sven
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Catalytic combustion of methane over perovskite supported on lanthanum hexaaluminate prepared through the microemulsion method2007In: Studies in Surface Science and Catalysis, ISSN 0167-2991, Vol. 172, p. 465-468Article in journal (Refereed)
  • 21.
    Elm Svensson, Erik
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Nassos, Stylianos
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Boutonnet, Magali
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Järås, Sven
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Microemulsion synthesis of MgO-supported LaMnO3 for catalytic combustion of methane2006In: Catalysis Today, ISSN 0920-5861, E-ISSN 1873-4308, Vol. 117, no 4, p. 484-490Article in journal (Refereed)
    Abstract [en]

    Catalysts with 20% LaMnO3 supported on MgO have been prepared via CTAB-1-butanol-iso-octane-nitrate salt microemulsion. The preparation method was successfully varied in order to obtain different degrees of interaction between LaMnO3 and MgO as shown by TPR and activity tests after calcination at 900 degrees C. Activity was tested on structured catalysts with 1.5% CH4 in air as test gas giving a GHSV of 100,000 h(-1). The activity was greatly enhanced by supporting LaMnO3 on MgO compared with the bulk LaMnO3. After calcination at 1100 degrees C both the surface area and TPR profiles were similar, indicating that the preparation method is of little importance at this high temperature due to interaction between the phases. Pure LaMmO(3) and MgO were prepared using the same microemulsion method for comparison purposes. Pure MgO showed an impressive thermal stability with a BET surface area exceeding 30 m(2)/g after calcination at 1300 degrees C. The method used to prepare pure LaMnO3 appeared not to be suitable since the surface area dropped to 1.1 m(2)/g already after calcination in 900 degrees C.

  • 22.
    Eriksson, Sara
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology.
    Boutonnet, Magali
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology.
    Järås, Sven
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology.
    Catalytic combustion of methane in steam and carbon dioxide-diluted reaction mixtures2006In: Applied Catalysis, ISSN 0166-9834, E-ISSN 1873-3867, Vol. 312, p. 95-101Article in journal (Refereed)
    Abstract [en]

    Supported palladium catalysts have been tested for methane combustion under lean conditions in the temperature range of 200-800 degrees C. The effect of diluting the reaction mixture with high amounts of water and carbon dioxide was studied in order to simulate a combustion process with exhaust gas recirculation. The influence of support material, i.e. ZrO2 or doped CeO2, on the catalytic performance was also investigated.

    The catalyst support material was found to influence the light-off temperature significantly, which increased in the following order: Pd/ZrO2 < Pd/Zr-CeO2 < Pd/La-CeO2. The order of activity changed at higher temperatures resulting in Pd/La-CeO2 being the most active catalyst above 670 degrees C. This catalyst also shows a more stable performance with no distinct deactivation occurring at higher temperatures during cooling.

    Both water and CO2 were found to have a negative influence on the catalytic activity. The inhibitory effect was, however, more pronounced for water. This inhibitory effect was present in the entire temperature range investigated. Adding CO2 in the presence of water resulted in conversions similar to the ones observed when feeding water alone for Pd/ZrO2 and Pd/La-CeO2, On the contrary, the activity of Pd/Zr-CeO2 was further decreased when co-feeding water and CO2.

  • 23.
    Eriksson, Sara
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology.
    Nilsson, Martita
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology.
    Boutonnet, Magali
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology.
    Järås, Sven
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology.
    Partial oxidation of methane over rhodium catalysts for power generation applications2005In: Catalysis Today, ISSN 0920-5861, E-ISSN 1873-4308, Vol. 100, p. 447-451Article in journal (Refereed)
    Abstract [en]

    The partial oxidation of methane (POM) to syngas, i.e. H-2 and CO, over supported Rh catalysts was investigated at atmospheric pressure. The influence of support material, Rh loading and the presence of water vapor on the methane conversion efficiency and the product gas composition was studied. The catalysts containing ceria in the support material showed the highest activity and formation of H2 and CO. By increasing the Rh loading, a decrease of the ignition temperature was obtained. The addition of water vapor to the reactant gas mixture was found to increase the ignition temperature and the formation of hydrogen, which is favorable for combustion applications where the catalytic POM stage is followed by H-2-stabilized homogeneous combustion.

  • 24.
    Eriksson, Sara
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology.
    Schneider, A.
    Mantzaras, J.
    Wolf, M.
    Järås, Sven
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology.
    Experimental and numerical investigation of supported rhodium catalysts for partial oxidation of methane in exhaust gas diluted reaction mixtures2007In: Chemical Engineering Science, ISSN 0009-2509, E-ISSN 1873-4405, Vol. 62, no 15, p. 3991-4011Article in journal (Refereed)
    Abstract [en]

    The partial oxidation of methane/oxygen mixtures with large exhaust gas dilution (46.3 vol% H2O and 23.1 vol% CO2) has been investigated experimentally and numerically over Rh/CeO2-ZrO2, Rh/ZrO2 and Rh/alpha-Al2O3 catalysts. Experiments were carried out in a short-contact-time (similar to 8 ms) reactor at 5 bar and included exhaust gas analysis, temperature measurements along the reactor, and catalyst characterization. Additional experiments were performed in an optically accessible channel-flow reactor and involved in situ Raman measurements of major gas-phase species concentrations over the catalyst boundary layer and laser-induced fluorescence (LIF) of formaldehyde. A full elliptic two-dimensional numerical code that included elementary hetero-/homogeneous chemical reaction schemes and relevant heat transfer mechanisms in the solid was used in the simulations. The employed heterogeneous reaction mechanism, including only active Rh sites, reproduced the experiments with good accuracy. The ratio of active to geometrical surface area, deduced from hydrogen chemisorption measurements, was the single model parameter needed to account for the effect of different supports. This indicated that water activation occurring on support sites, resulting in inverse OH spillover from the support to the noble metal sites, could be neglected under the present conditions with high water dilution. An evident relationship between noble metal dispersion and catalytic behavior, in terms of methane conversion and synthesis gas yields, could be established. Both measurements and predictions indicated that an increasing Rh dispersion (in the order Rh/alpha-Al2O3, Rh/ZrO2, and Rh/CeO2-ZrO2) resulted in higher methane conversions, lower surface temperatures, and higher synthesis gas yields.

  • 25.
    Eriksson, Sara
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology.
    Wolf, M.
    Schneider, A.
    Mantzaras, J.
    Raimondi, F.
    Boutonnet, Magali
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology.
    Järås, Sven
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology.
    Fuel-rich catalytic combustion of methane in zero emissions power generation processes2006In: Catalysis Today, ISSN 0920-5861, E-ISSN 1873-4308, Vol. 117, no 4, p. 447-453Article in journal (Refereed)
    Abstract [en]

    A novel catalytic combustion concept for zero emissions power generation has been investigated. Catalysts consisting of Rh supported on ZrO2, Ce-ZrO2 or alpha-Al2O3 were prepared and tested under fuel-rich conditions, i.e. for catalytic partial oxidation (CPO) of methane. The experiments were performed in a subscale gas-turbine reactor operating at 5 bar with exhaust gas-diluted feed mixtures.The catalyst support material was found to influence the light-off temperature significantly, which increased in the following order Rh/Ce-ZrO2 < Rh/ZrO2 < Rh/alpha-Al2O3. The Rh loading, however, only had a minor influence. The high activity of Rh/Ce-ZrO2 is probably related to the high dispersion of Rh on Ce-ZrO2 and the high oxygen mobility of this support compared to pure ZrO2. The formation of hydrogen was also found to increase over the catalyst containing ceria in the support material.

  • 26. Ersson, A.
    et al.
    Kusar, H.
    Carroni, R.
    Griffin, T.
    Järås, Sven G.
    KTH, Superseded Departments, Chemical Engineering and Technology.
    Catalytic combustion of methane over bimetallic catalysts a comparison between a novel annular reactor and a high-pressure reactor2003In: Catalysis Today, ISSN 0920-5861, E-ISSN 1873-4308, Vol. 83, no 04-jan, p. 265-277Article in journal (Refereed)
    Abstract [en]

    The effects of adding a co-metal, Pt or Rh, to Pd/-gamma-Al2O3 catalysts were studied with respect to the catalytic activity for methane combustion and compared to a Pd/gamma-Al2O3 catalyst, using both a pressurized pilot-scale and a lab-scale annular reactor. Temperature programmed oxidation (TPO) experiments were also carried out to investigate the oxygen release/uptake of the catalyst materials. Palladium showed an unstable behavior both in the pilot and lab-scale experiments at temperatures well below the PdO to Pd transformation. An addition of Pt to Pd stabilized, and in some cases increased, the catalytic activity for methane combustion. The TPO experiments showed that the oxygen release peak was shifted to lower temperatures even for low additions of Pt, i.e. Pd:Pt = 2:1. For additions of rhodium only small beneficial effects were seen. The steady-state behavior of the lab-scale annular reactor correspond well to the pressurized pilot-scale tests.

  • 27.
    Ersson, Anders
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology.
    Persson, Katarina
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology.
    Adu, Isaac Kweku
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology.
    Järås, Sven G.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    A comparison between hexaaluminates and perovskites for catalytic combustion applications2006In: Catalysis Today, ISSN 0920-5861, E-ISSN 1873-4308, Vol. 112, no 04-jan, p. 157-160Article in journal (Refereed)
    Abstract [en]

    Hexaaluminates and perovskites are two promising candidates for use in catalytic combustion applications. In the present study two hexaaluminates, LaMnAl11O19 and LaCoAl11O19, were compared with two perovskites, LaMnO3 and LaCoO3, with respect to their thermal stability and catalytic activity for combustion of methane and gasified biomass. The results showed that the hexaaluminates retained a much higher surface area even after calcination at 1200 degrees C compared to the perovskites. LaMnAl11O19 showed the highest catalytic activity of all catalysts. LaCoAl11O19 generally showed low activity. Of the two perovskites, LaCoO3 was the most active, and the initial test run the activity for biomass combustion were close to that one of LaMnAl11O19 even though its surface area was only one tenth of the hexaaluminate's. However, it was severely deactivated in the second test run. Similar deactivation but less severe was also found for the other catalyst.

  • 28.
    Jayasuriya, Jeevan
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Ersson, Anders
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Fredriksson, Jan
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Fransson, Torsten
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Järås, Sven
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Ultra Low Emission Gas Turbine Combustion: An Expoerimental Investigation of Catalytically Stabilizws Lean Pre-mixed Combustion on Modern Gas Turbine Conditions2004Conference paper (Refereed)
  • 29.
    Jayasuriya, Jeevan
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Ersson, Andreas
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Fredriksson, Jan
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Fransson, Torsten
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Järås, Sven
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Catalytic Combustion Developments for Ultra Low Emission Gas Turbine Combustion2003Conference paper (Refereed)
  • 30.
    Jayasuriya, Jeevan
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Ersson, Andreas
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Fredriksson, Jan
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Fransson, Torsten
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Järås, Sven
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Experimental Investigations of High Pressure Catalytic Combustion of Methane2003Conference paper (Refereed)
  • 31.
    Jayasuriya, Jeevan
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Fredriksson, Jan
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Fransson, Torsten
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Persson, Katarina
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Thevenin, Philippe
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Järås, Sven
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Bench Scale Experimental Test Rig  for High Pressure Catalytic Combustion2002Conference paper (Refereed)
  • 32. Johansson, E. M.
    et al.
    Danielsson, K. M. J.
    Ersson, A. G.
    Järås, Sven G.
    KTH, Superseded Departments, Chemical Engineering and Technology.
    Development of hexaaluminate catalysts for combustion of gasified biomass in gas turbines2002In: Journal of engineering for gas turbines and power, ISSN 0742-4795, E-ISSN 1528-8919, Vol. 124, no 2, p. 235-238Article in journal (Refereed)
    Abstract [en]

    There is an increasing interest in Catalytic combustors fuelled by low-heating value (LHV) gases, with a LHV of 5-7 MJ/Nm(3). This is because catalytic combustion could be advantageous compared to flame combustion with respect to stable combustion of LHV-gases and low conversions of fuel-N (mainly NH3) to NOX. In the present project, funded by the EU Joule Program, catalytic combustion of gasified wood for gas turbine applications is studied. A synthetic gas mixture of H-2, CO, CO2, H2O, CH4, N-2, and NH3, that resembles the output from a fluidized bed gasifier using biomass as raw material, is used. The gas mixture is mixed with air at atmospheric pressure and combusted over wash-coated cordierite monoliths in a bench-scale laboratory quartz-reactor. The objectives of the work described here are twofold. To begin with, improvement of the thermal stability of hexaaluminate washcoats by substitutions of rare earth or transition metal compounds is being studied. Secondly, catalytic combustion of gasified biomass over these washcoats has been studied in a bench-scale unit. In. this on-going project, obtained result show that it is possible to improve the surface area of hexaaluminate compounds up to 17 m(2)/g after careful synthesis and calcination up to 1400degreesC for four hours. The selectivity of NH3-conversion to N-2 is at present at 60 percent, but varies strongly with temperature. Fuel components such as H-2, CO, C2H4, and NH3 ignite at temperatures close to compressor outlet temperatures. This means that a pilot-flame may not be needed for ignition of the fuel. A comparison between a Pd-impregnated lanthanum hexaaluminate and a Mn-substituted lanthanum hexaaluminate showed that the ignition temperature and the NOX-formation varied strongly over the two different catalysts.

  • 33. Kling, Asa
    et al.
    Andersson, Christer
    Myringer, Ase
    Eskilsson, David
    Järås, Sven G.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Alkali deactivation of high-dust SCR catalysts used for NOx reduction exposed to flue gas from 100 MW-scale biofuel and peat fired boilers: Influence of flue gas composition2007In: Applied Catalysis B: Environmental, ISSN 0926-3373, E-ISSN 1873-3883, Vol. 69, no 04-mar, p. 240-251Article in journal (Refereed)
    Abstract [en]

    Deactivation of vanadium-titanium deNO(x) SCR (selective catalytic reduction) catalysts in high-dust position have been investigated in three 100 MW-scale boilers during biofuel and peat combustion. The deactivation of the catalyst samples has been correlated to the corresponding flue gas composition in the boilers. Too investigate the effect on catalyst deactivation a sulphate-containing additive was sprayed into one of the furnaces. Increased alkali content on the SCR catalyst samples decreased the catalytic deNO(x), activity. The study has shown a linear correlation between exposure time in the boilers and alkali concentration (mainly potassium) on the samples. The results imply that mainly alkali in ultra fine particles (< 100 nm) in the flue gas increased the alkali accumulation on the catalyst samples. Low correlation was found between particles larger than 100 nm and the catalyst deactivation. It was not possible to decrease the deactivation of the catalyst samples by the sulphate-containing additive. Although the additive had an effect in sulphating potassium chloride to potassium sulphate, it did not decrease the amount of potassium in ultra fine particles or the deactivation of the catalyst samples.

  • 34. Kusar, H. M. J.
    et al.
    Ersson, A. G.
    Järås, Sven G.
    KTH, Superseded Departments, Chemical Engineering and Technology.
    Catalytic combustion of gasified refuse-derived fuel2003In: Applied Catalysis B: Environmental, ISSN 0926-3373, E-ISSN 1873-3883, Vol. 45, no 1, p. 1-11Article in journal (Refereed)
    Abstract [en]

    The catalytic combustion of gasified refuse-derived fuel (RDF), i.e. a low heating-value (LHV) gas containing H-2, CO and CH4 as combustible components, has been studied and compared with the combustion of methane. Two metal oxide catalysts, i.e. a spinel and a hexaaluminate, and three noble metal catalysts were tested. The results show that the Pd-based catalysts were the most active both for the gasified waste, i.e. RDF and methane. Incorporating an active support such as LaMnAl11O19 enhances the catalytic activity for methane in gasified waste. Substituting Mn into the crystal lattice of the spinel also increased the catalytic activity for H-2 and CO, while the methane activity remained low. The formation of NOX from fuel-bound nitrogen was investigated by adding NH3 to the gas stream. The metal oxide catalysts showed a higher selectivity for oxidising NH3 into N-2 than the catalysts containing precious metals. The spinel materials have high thermal stability and are comparable to the hexaaluminates confirming that they could be promising as washcoat materials to avoiding sintering at high temperatures.

  • 35. Kusar, H. M. J.
    et al.
    Ersson, A. G.
    Vosecky, M.
    Järås, Sven G.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Selective catalytic oxidation of NH3 to N-2 for catalytic combustion of low heating value gas under lean/rich conditions2005In: Applied Catalysis B: Environmental, ISSN 0926-3373, E-ISSN 1873-3883, Vol. 58, no 02-jan, p. 25-32Article in journal (Refereed)
    Abstract [en]

    The selective catalytic oxidation (SCO) of ammonia to nitrogen has been examined over 5% Fe/Al2O3, 5% Mn/Al2O3, 20% Cuo/Al2O3, 1% Pt/20% CuO/Al2O3, 2% Rh/Al2O3 and a Fe zeolite (Fe-SH-27) under fuel-lean and fuel-rich conditions in a monolith lab-scale reactor. For simulating fuel-bound nitrogen in a low heating value (LHV) gas 400 ppm NH3 was added to the test gas. The SCO performance of the catalysts was tested both with and without water added to the gas stream. For SCO under fuel-lean conditions the Fe-zeolite catalyst exhibited the lowest NO, yield. For SCO under fuel-rich conditions the 20% CuO/Al2O3 was superior with close to zero NO, formation.

  • 36.
    Lakshmanan, Ramnath
    et al.
    KTH, School of Biotechnology (BIO), Bioprocess Technology (closed 20130101).
    Okoli, Chuka
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology. KTH, School of Biotechnology (BIO), Bioprocess Technology (closed 20130101).
    Boutonnet, Magali
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Järås, Sven
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Kuttuva Rajarao, Gunaratna
    KTH, School of Biotechnology (BIO), Bioprocess Technology (closed 20130101).
    Effect of Magnetic Iron Oxide Nanoparticles for Surface Water Treatment: Trace Minerals and MicrobesManuscript (preprint) (Other academic)
  • 37.
    Lakshmanan, Ramnath
    et al.
    KTH, School of Biotechnology (BIO), Industrial Biotechnology.
    Okoli, Chuka
    KTH, School of Biotechnology (BIO), Industrial Biotechnology. KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Boutonnet, Magali
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Järås, Sven
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Kuttuva Rajarao, Gunaratna
    KTH, School of Biotechnology (BIO), Industrial Biotechnology.
    Effect of magnetic iron oxide nanoparticles in surface water treatment: Trace minerals and microbes2013In: Bioresource Technology, ISSN 0960-8524, E-ISSN 1873-2976, Vol. 129, p. 612-615Article in journal (Refereed)
    Abstract [en]

    The existing water treatment process often uses chemicals, which is of high health and environmental concern. The present study focused on the efficiency of microemulsion prepared magnetic iron oxide nanoparticles (ME-MIONs) and protein-functionalized nanoparticles (MOCP. +. ME-MIONs) in water treatment. Their influence on mineral ions and microorganisms present in the surface water from lake Brunnsviken and örlången, Sweden were investigated. Ion analysis of water samples before and after treatment with nanoparticles was performed. Microbial content was analyzed by colony forming units (CFU/ml). The results impart that ME-MIONs could reduce the water turbidity even in low turbid water samples. Reduction of microbial content (98%) was observed at 37 °C and more than 90% reduction was seen at RT and 30 °C when compared to untreated samples from lake örlången. The investigated surface water treatment method with ME-MIONs was not significantly affecting the mineral ion composition, which implies their potential complement in the existing treatment process.

  • 38.
    Lakshmanan, Ramnath
    et al.
    KTH, School of Biotechnology (BIO), Industrial Biotechnology.
    Okoli, Chuka
    KTH, School of Biotechnology (BIO), Industrial Biotechnology.
    Boutonnet, Magali
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Järås, Sven
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Kuttuva Rajarao, Gunaratna
    KTH, School of Biotechnology (BIO), Industrial Biotechnology.
    Microemulsion prepared magnetic nanoparticles for phosphate removal: Time efficient studies2014In: Journal of Environmental Chemical Engineering, ISSN 2213-3437, Vol. 2, no 1, p. 185-189Article in journal (Refereed)
    Abstract [en]

    The present study investigates the effective removal of phosphate in sewage wastewater using magnetic iron oxide nanoparticles (MION). The microemulsion-prepared magnetic iron oxide nanoparticles (ME-MION) of around 7-10 nm was synthesized using water-in-oil microemulsion method. The interaction of ME-MION and phosphate was studied using In situ FT-IR technique. Batch experiments were carried out with wastewater to determine the conc. and time efficiency using ME-MION for removal of phosphate. The vibration peak at 1004 cm-1 and the presence of hydroxyl group (OH-) at 3673 cm-1 confirms the binding of phosphate to ME-MION. ME-MION with 0.44 g L-1 exhibited more than 95% phosphate reduction in 5 min and close to 100% in 20 min. Conversely the experimental data obtained has been fitted with Langmuir isotherm model and also exhibited high correlation coefficients. The ME-MION was regenerated and can be reused for minimum 5 consecutive times. Efficient and fast reduction of phosphate was attained while the recovery of nanoparticles was achieved by an external magnetic field. To the author's knowledge, this is the first report that underscores around 100% phosphate removal from wastewater using ME-MION in 20 min. The approach utilized in this study offers a potential technique in the reduction of phosphate in wastewater whilst, reducing the time and reuse of nanoparticles.

  • 39.
    Lakshmanan, Ramnath
    et al.
    KTH, School of Biotechnology (BIO), Industrial Biotechnology.
    Rajaraman, P.
    Okoli, Chuka
    KTH, School of Biotechnology (BIO), Industrial Biotechnology.
    Boutonnet, Magali
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Järås, Sven
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Kuttuva Rajarao, Gunaratna
    KTH, School of Biotechnology (BIO), Industrial Biotechnology.
    Application of magnetic nanoparticles for wastewater treatment using response surface methodology2013In: Technical Proceedings of the 2013 NSTI Nanotechnology Conference and Expo, NSTI-Nanotech 2013: Volume 3, 2013, 2013, p. 690-693Conference paper (Refereed)
    Abstract [en]

    Nanotechnology is considered as one of the key techniques that provide unique materials with high reactivity due to large surface to volume ratio and which could address the fundamental issues in water sector and environment. The present study investigates the efficiency of magnetic iron oxide nanoparticles in wastewater treatment based on Central Composite Face centered (CCF) matrix of response surface methodology for the reduction of turbidity and total nitrogen. The multiple linear regression fit (MLR) obtained for turbidity (r2 0.97) and total nitrogen reduction (r 0.94) supports the future predictions obtaining a significant model. The maximum reduction of turbidity and total nitrogen achieved was 93% and 41% respectively. Other contaminants such as color, total organic carbon, nitrate and microbial content could be reduced. The present study reveals that magnetic property, time and reduction of pollutants by magnetic nanoparticles could impart an efficient treatment process.

  • 40.
    Lakshmanan, Ramnath
    et al.
    KTH, School of Biotechnology (BIO), Industrial Biotechnology.
    Rajaraman, Premanand
    Sri Sairam Engineering College, Department of Physics.
    Okoli, Chuka
    KTH, School of Biotechnology (BIO), Industrial Biotechnology. KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Boutonnet, Magali
    KTH, School of Biotechnology (BIO), Industrial Biotechnology.
    Järås, Sven
    KTH, School of Biotechnology (BIO), Industrial Biotechnology.
    Kuttuva Rajarao, Gunaratna
    KTH, School of Biotechnology (BIO), Industrial Biotechnology.
    Application of Magnetic Nanoparticles for the removal of turbidity and total nitrogen from sewage wastewater: Modelling studiesManuscript (preprint) (Other academic)
  • 41.
    Lanza, Roberto
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Canu, P.
    Järås, Sven G.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Methane partial oxidation over Pt-Ru catalyst: An investigation on the mechanism2010In: Applied Catalysis A: General, ISSN 0926-860X, E-ISSN 1873-3875, Vol. 375, no 1, p. 92-100Article in journal (Refereed)
    Abstract [en]

    The mechanism of the partial oxidation of methane has been investigated over a bimetallic Pt-Ru catalyst. Dedicated experiments aimed to separate and quantify the relative contribution of single reactions included in the so-called "combustion and reforming" mechanism using the same catalyst. The catalyst is 0.5% Ru and 0.5% Pt (w/w) supported on mixture of alumina, ceria and zirconia (75/4.4/20.6%, w/w), washcoated on a ceramic monolith. Steam reforming, dry reforming, direct and reverse water-gas shift reactions were investigated. The temperature range investigated is 300 < T < 800 degrees C, while the space velocity range is 25.000 < GHSV < 100.000 h(-1). Conditions at which single side reactions are expected to occur during the partial oxidation process, were approximated by tuning the reactant composition. The experimental results are also compared with thermodynamic equilibrium calculations. The CO and H-2 yields of partial oxidation have been quantitatively connected with steam and dry reforming, while the persistent water-gas shift reaction always rearranges the products and intermediates.

  • 42.
    Lanza, Roberto
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Canu, P.
    Järås, Sven G.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Microemulsion-prepared ruthenium catalyst for syngas production via methane partial oxidation2008In: Applied Catalysis A: General, ISSN 0926-860X, E-ISSN 1873-3875, Vol. 337, no 1, p. 10-18Article in journal (Refereed)
    Abstract [en]

    Partial oxidation of methane (POxM) was studied over Ru catalyst supported on alumina (1%, w/w). The catalyst was prepared via microemulsion (ME) and coated onto cordierite monoliths. Samples were characterized by XRD, BET surface area, SEM-EDS and TPR and TPO analyses. The catalyst showed high methane conversion with very good selectivity towards CO and H-2 under every condition tested. The effects of GHSV and heating rate (HR) were investigated, recording composition data both during heating and cooling. This allowed to evidence hysteresis cycles and to obtain additional information on the reactions occurring within the monolith.

  • 43.
    Lanza, Roberto
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Canu, P.
    Järås, Sven G.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Partial oxidation of methane over Pt-Ru bimetallic catalyst for syngas production2008In: Applied Catalysis A: General, ISSN 0926-860X, E-ISSN 1873-3875, Vol. 348, no 2, p. 221-228Article in journal (Refereed)
    Abstract [en]

    A bimetallic catalyst (Pt-Ru 50/50) has been prepared for methane partial oxidation. Total metal load was 1 wt%. The support was alumina mixed with 25 wt% of a ceria-zirconia mixture. This because of the good performances of alumina for such applications and to exploit the oxygen buffer effect of the ceriazirconia system. The catalyst has been prepared by incipient wetness and characterized by means of XRD, BET surface area, TPR/TPO and SEM-EDS analyses. It showed good activity and high selectivity towards CO and H-2, produced in a ratio suitable for Fisher-Tropsch applications. The effect of spatial velocity (GHSV) has been investigated; ramping temperature up and down, some hysteresis has been evidenced, especially at the highest GHSV, mainly caused by thermal effects. Overall, 100% conversion of methane to H-2 and CO at the appropriate syngas ratio (2/1) can achieved easily and with stability.

  • 44.
    Lanza, Roberto
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Järås, Sven G.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Canu, P.
    Partial oxidation of methane over supported ruthenium catalysts2007In: Applied Catalysis A: General, ISSN 0926-860X, E-ISSN 1873-3875, Vol. 325, no 1, p. 57-67Article in journal (Refereed)
    Abstract [en]

    Partial oxidation of methane (POM) to synthesis gas was studied over Ru catalysts (1% (w/w)) supported on silica, alumina and ceria-zirconia. Catalyst samples were prepared by incipient wetness and characterized by BET area, XRD, ESEM-EDS, and TPR-TPO analyses. Ru on silica deactivated very fast, while Ru supported on alumina has good activity and selectivity. The mixture CeO2-ZrO2 led to low selectivity towards POM, with a higher selectivity towards complete combustion, common to all the catalysts at lower temperature. Both reduced and non-reduced catalysts were tested resulting in different behaviour in the same temperature range. We investigated the effect of different GHSVs, heating rates and also sequences of heating and cooling cycles. This allowed gaining insight into the sequence of reactions taking place in the reactor and revealed hysteresis for all reaction conditions. This can be explained through a cycling between Ru oxidation states on the surface.

  • 45.
    Lanza, Roberto
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Velasco, Jorge
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Järås, Sven
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Recent developments and achievements in partial oxidation of methane with and without addition of steam2011In: Catalysis / [ed] James J. Spivey, Royal Society of Chemistry, 2011, 23, p. 50-95Chapter in book (Refereed)
    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.

  • 46.
    Lopez, Luis
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology. UMSA Universidad Mayor de San Andrés, Bolivia.
    Montes, V.
    Kušar, Henrik
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Cabrera, S.
    Boutonnet, Magali
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Järås, Sven
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Syngas conversion to ethanol over a mesoporous Cu/MCM-41 catalyst: Effect of K and Fe promoters2016In: Applied Catalysis A: General, ISSN 0926-860X, E-ISSN 1873-3875, Vol. 526, p. 77-83Article in journal (Refereed)
    Abstract [en]

    Transportation fuels such as ethanol can be obtained through thermochemical processing of biomass. Interest in the development of more selective catalysts for the conversion of biomass-derived syngas (H2 + CO) to ethanol is increasing in both academia and industry. In this work, we have evaluated the performances of K and Fe as metal promoters of a mesoporous Cu/MCM-41 catalyst and their effects on the product selectivity and especially on ethanol formation. The metal loading was 29 wt.% Cu, 2 wt.% Fe and 1.6 wt.% K. The catalysts were tested at 300 °C, 20 bar and gas-hourly-space-velocities in the range of 1500–30000 mlsyngas/gcat h; under these conditions the syngas conversion level was between 2 and 11%. The non-promoted Cu/MCM-41 catalyst showed interesting selectivity toward oxygenated compounds, mostly methanol. The addition of K as promoter increases the selectivity toward methanol even more, while the addition of Fe as promoter favors the formation of hydrocarbon compounds. When both K and Fe as promoters are incorporated into the Cu/MCM-41 catalyst, the reaction rate to oxygenated compounds is notably increased, especially for ethanol. The space time yield for ethanol for the Cu/MCM-41 catalyst is 0.3 × 10−5 carbon-mol/gcath which increases to 165.5 × 10−5 carbon-mol/gcath for the Cu-Fe-K/MCM-41 catalyst. From XPS analysis, the Cu-Fe-K/MCM-41 catalyst was found to have the following atomic composition: Cu0.34Fe0.08K0.08Si1.00. The promoting effect of both K and Fe, may be related to an increased reaction rate toward CO non-dissociation and CO-dissociation paths, respectively, which is beneficial for the ethanol formation. Further catalytic results, catalyst characterization and discussion of results are presented in this work.

  • 47.
    Lopez Nina, Luis Gagarin
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology. UMSA Universidad Mayor de San Andres, Bolivia.
    Velasco, Jorge A.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Cabrera, Saul
    Boutonnet, Magali
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Järås, Sven G.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Effect of syngas conversion and catalyst reduction temperature in the synthesis of ethanol: concentration of water vapor in mesoporous Rh/MCM-41 catalyst2015In: Catalysis communications, ISSN 1566-7367, E-ISSN 1873-3905, Vol. 69, p. 183-187Article in journal (Refereed)
    Abstract [en]

    Rh-based catalysts typically show low selectivity to CO2 in the synthesis of ethanol from syngas. However, a novel mesoporous Rh/MCM-41 catalyst shows high selectivity to CO2 in a large range of syngas conversions; 1% to 68%, regulated by adjusting the operation conditions (270-430 degrees C, 30-90 bar and 6000-40,000 ml(syngas)/gcat h). The same effect is obtained at different catalyst reduction temperatures (200 degrees C and 500 degrees C) as well as on the non-reduced catalyst. A high concentration of water vapor seems to occur in the pores of Rh/MCM-41 which may promote the water-gas-shift-reaction, producing extra CO2 and H-2. (C) 2015 Elsevier B.V. All rights reserved.

  • 48.
    Lopez Nina, Luis Gagarin
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology. UMSA Universidad Mayor de San Andrés, Bolivia.
    Velasco, Jorge
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology. UMSA Universidad Mayor de San Andrés, Bolivia.
    Montes, Vicente
    Marinas, Alberto
    Cabrera, Saul
    Boutonnet, Magali
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Järås, Sven
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Synthesis of Ethanol from Syngas over Rh/MCM-41 Catalyst: Effect of Water on Product Selectivity2015In: CATALYSTS, ISSN 2073-4344, Vol. 5, p. 1737-1755Article in journal (Refereed)
    Abstract [en]

    The thermochemical processing of biomass is an alternative route for the manufacture of fuel-grade ethanol, in which the catalytic conversion of syngas to ethanol is a key step. The search for novel catalyst formulations, active sites and types of support is of current interest. In this work, the catalytic performance of an Rh/MCM-41 catalyst has been evaluated and compared with a typical Rh/SiO2 catalyst. They have been compared at identical reaction conditions (280 degrees C and 20 bar), at low syngas conversion (2.8%) and at same metal dispersion (H/Rh = 22%). Under these conditions, the catalysts showed different product selectivities. The differences have been attributed to the concentration of water vapor in the pores of Rh/MCM-41. The concentration of water vapor could promote the water-gas-shift-reaction generating some extra carbon dioxide and hydrogen, which in turn can induce side reactions and change the product selectivity. The extra hydrogen generated could facilitate the hydrogenation of a C-2-oxygenated intermediate to ethanol, thus resulting in a higher ethanol selectivity over the Rh/MCM-41 catalyst as compared to the typical Rh/SiO2 catalyst; 24% and 8%, respectively. The catalysts have been characterized, before and after reaction, by N-2-physisorption, X-ray photoelectron spectroscopy, X-ray diffraction, H-2-chemisorption, transmission electron microscopy and temperature programmed reduction.

  • 49.
    Lualdi, Matteo
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Di Carlo, Gabriella
    Lögdberg, Sara
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Järås, Sven
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Boutonnet, Magali
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    La Parola, Valeria
    Liotta, Leonarda Francesca
    Ingo, Gabriel M.
    Venezia, Anna Maria
    Effect of Ti and Al addition via direct synthesis to SBA-15 as support for cobalt based Fischer-Tropsch catalysts2012In: Applied Catalysis A: General, ISSN 0926-860X, E-ISSN 1873-3875, Vol. 443-444, p. 76-86Article in journal (Refereed)
    Abstract [en]

    Different mesoporous SBA-15 supports doped with Ti and Al at 5 and 10 wt% have been synthesized by means of direct synthesis. The supports have been characterized by N 2-adsorption, X-ray diffraction (XRD), temperature-programmed reduction (TPR), NH 3-temperature programmed desorption (NH 3-TPD), H 2-chemisorption, X-ray photoelectron spectroscopy (XPS), field emission scanning electron microscope (FE-SEM), transmission electron microscopy (TEM). Titanium doped materials showed to have much shorter channels than the pristine SBA-15, while aluminum addition did not have a significant effect on channel length. After impregnation with 12 wt% Co, the catalysts were further characterized and tested in the Fischer-Tropsch synthesis at industrially relevant process conditions (483 K, 20 bar, H 2/CO ratio = 2.1, pellet size: 53-90 μm) with and without external water addition. The S C5 + values of the different SBA-supported catalysts were low, especially at low conversion levels (i.e. low water partial pressure), suggesting that CO diffusion limitations increased the H 2/CO ratio inside the 1-dimensional (1D) porous network. The selectivity data showed a correlation between the channel length and the extent of CO-diffusion limitations at much shorter diffusion distances than those for conventional 3D porous supports. Water partial pressure showed to increase the syngas diffusion rate (i.e. removal of diffusion limitations on reactants’ arrival), to have a positive kinetic effect on the rate and to favor longer chain hydrocarbons.

  • 50.
    Lualdi, Matteo
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Lögdberg, Sara
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Boutonnet, Magali
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Järås, Sven
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    On the effect of water on the Fischer-Tropsch rate over a Co-based catalyst: The influence of the H2/CO ratio2013In: Catalysis Today, ISSN 0920-5861, E-ISSN 1873-4308, Vol. 214, p. 25-29Article in journal (Refereed)
    Abstract [en]

    The effect of water partial pressure on the Fischer-Tropsch (FT) rate of a cobalt catalyst supported on narrow-pore γ-Al2O3 was investigated at industrially relevant process conditions (483 K, 30 bar, pellet size: 53-90 μm). Inlet water partial pressure was varied up to 9 bar by external water vapour addition at different H2/CO molar ratios ranging from 1 to 3. The effect of water was found to be positive on FT-rate independently of the H2/CO ratio, but more significantly at H 2-poor condition. Temperature-programmed hydrogenation (TPH) was used to verify the presence of unreactive carbon species on the catalyst after 22 h on stream at the different conditions with and without exposure to about 9 bar water. A higher temperature feature that could be associated to amorphous polymeric carbon was detected at H2-poor conditions but remained unchanged upon 2 h of water exposure which did not result in a change in the amount of amorphous polymeric carbon detectable by TPH.

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