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  • 51.
    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.
    Di Carlo, G.
    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.
    Venezia, A. M.
    Blekkan, E. A.
    Holmen, A.
    Evidence for diffusion-controlled hydrocarbon selectivities in the fischer-tropsch synthesis over cobalt supported on ordered mesoporous silica2011In: Topics in catalysis, ISSN 1022-5528, E-ISSN 1572-9028, Vol. 54, no 16-18, p. 1175-1184Article in journal (Refereed)
    Abstract [en]

    A series of four cobalt-based catalysts (two of which promoted with ruthenium) supported on SiO2 or SBA-15 were prepared and tested in the Fischer-Tropsch synthesis at industrially relevant process conditions (483 K, 20 bar, H2/CO ratio = 2.1, pellet size: 53-90 μm). The catalysts were characterized by N2-adsorption, X-ray diffraction (XRD), temperature-programmed reduction (TPR), H2-chemisorption and transmission electron microscopy (TEM). Ru as promoter enhanced the activity but not the selectivity to long-chain hydrocarbons ({S}-{C}-{ 5+}). The {{S}}-{{C}}-{5+}} values of the SBA-supported catalysts were very low, especially at low conversion levels (i.e. low water partial pressure), suggesting that CO diffusion limitation increased the H2/CO ratio inside the 1-dimensional (1-D) porous network. A superimposition of the selectivity results on the correlations found in our recent study, derived for Co-based catalysts supported on γ-Al2O3, α-Al2O3 and TiO2 free from diffusion limitations, was made. While the SiO2-supported catalysts with a 3-D porous structure followed the correlations, the SBA-catalysts deviated significantly at low conversions, giving a further indication that the selectivity results of these catalysts were affected by CO diffusion limitations. Hence, it may be concluded that the kinetically significant diffusion distances (i.e. those long enough to cause an intrapore H 2/CO ratio higher than that of the bulk gas phase) are probably much shorter for 1-D porous networks than for conventional 3-D supports. This is explained by a significantly lower effective diffusivity in 1-D porous networks. The potential of using the correlations between non-ASF distributed hydrocarbons and C5+, to give insight on the occurrence of diffusion limitations, was confirmed by superimposing data from the literature that were anticipated to be influenced by CO diffusion limitations.

  • 52.
    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.
    Regali, Francesco
    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.
    Investigation of mixtures of a Co-based catalyst and a Cu-based catalyst for the fischer-tropsch synthesis with Bio-Syngas: The importance of indigenous water2011In: Topics in catalysis, ISSN 1022-5528, E-ISSN 1572-9028, Vol. 54, no 13-15, p. 977-985Article in journal (Refereed)
    Abstract [en]

    A series of different mechanical mixtures of a narrow-pore Co/γ-Al2O3 catalyst and a Cu-based WGScatalyst has been investigated in the low-temperature Fischer-Tropsch synthesis (483 K, 20 bar) with a model bio-syngas (H2/CO = 1.0) in a fixed-bed reactor. The higher the fraction of WGS-catalyst in the mixture, the lower is the Co-catalyst-time yield to hydrocarbons. This is ascribed to a strong positive kinetic effect of water on the Fischer-Tropsch rate of the Co-catalyst, showing the importance of the indigenously produced water, especially in fixed-bed reactors where the partial pressure of water is zero at the reactor inlet. A preliminary kinetic modeling suggests that the reaction order in PH2O is 0.3 for the Co/γ-Al2O3 catalyst in the range of the studied reactor-average partial pressures of water (i.e., 0.04-1.2 bar).

  • 53.
    Lögdberg, Sara
    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.
    Walmsley, John C.
    Järås, Sven
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Holmen, Anders
    Blekkan, Edd A.
    Effect of water on the space-time yield of different supported cobalt catalysts during Fischer-Tropsch synthesis2011In: Applied Catalysis A: General, ISSN 0926-860X, E-ISSN 1873-3875, Vol. 393, no 1-2, p. 109-121Article in journal (Refereed)
    Abstract [en]

    The effect of partial pressure of water on the Fischer-Tropsch (FT) rate of six cobalt-based catalysts supported on three different carrier materials (gamma-Al2O3, alpha-Al2O3, TiO2) with varying Co particle sizes was investigated in a fixed-bed reactor by changing space velocity and by external water vapour addition. A typical catalyst pellet size (<100 mu m) for industrial slurry-bed FT reactors was used. Water was found to have a positive kinetic effect, at least up to moderate amounts, on the FT rate of all catalysts in the present study, including the gamma-Al2O3-supported catalyst with pores smaller than similar to 10 nm. The reason for the apparent negative effect on the space-time yield at a direct exposure of Co supported on narrowpore gamma-Al2O3 to high partial pressures of water is due to a rapid and extensive deactivation. This could be ascribed to formation of hard-to-reduce oxidized cobalt species. The choice of support material was found to have a major effect on the response to changes in partial pressure of water, both with respect to deactivation behaviour and kinetics. However, there is a minor Co-particle size effect on the magnitude of the kinetic effect of water, larger Co particles showing a more positive response. Different extents of mass transfer limitations and/or differences in fugacities of H-2, CO and water among the six catalysts could be ruled out as causes for the observed differences.

  • 54.
    Lögdberg, Sara
    et al.
    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.
    Boutonnet, Magali
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology.
    Study of th selectivity-governing parameters in the cobalt-catalysed Fischer-Tropsch reactionArticle in journal (Refereed)
  • 55.
    Lögdberg, Sara
    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.
    Järås, Sven
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Walmsley, John C.
    Blekkan, Edd A.
    Rytter, Erling
    Holmen, Anders
    On the selectivity of cobalt-based Fischer-Tropsch catalysts: Evidence for a common precursor for methane and long-chain hydrocarbons2010In: Journal of Catalysis, ISSN 0021-9517, E-ISSN 1090-2694, Vol. 274, no 1, p. 84-98Article in journal (Refereed)
    Abstract [en]

    A total of 36 cobalt-based supported catalysts were investigated in the Fischer-Tropsch reaction at industrially relevant process conditions: 483 K, 20 bar, molar H-2/CO ratio = 2.1, pellet size: 53-90 mu m. The effect of adding water vapour to the feed was investigated for 20 of the catalysts, and a H-2/CO ratio of 1.0 was used for a few catalysts. The catalysts differed in support material, Co loading, promoters, Cl content, Co particle size (larger than similar to 6 nm), morphology, degree of reduction and preparation technique and showed a large variation in selectivity. For each set of process conditions, a linear relationship seems to exist between the selectivity to methane (and other light products) and C5+ indicating a common precursor, i.e. a common monomer pool, for all hydrocarbon products. A high selectivity to C5+ is mainly an effect of a high intrinsic chain-growth probability and unlikely to be a result of an enhanced cc-olefin readsorption. The universal effect of external water addition on the hydrocarbon selectivities is limited to a decrease in the methane selectivity. A small proportion of the catalysts developed "pure methanation" sites upon exposure to high partial pressures of water.

  • 56.
    Lögdberg, Sara
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Tristantini, Dewi
    Chalmers Tekniska högskola.
    Borg, Öyvind
    Norwegian University of Science and Technology (NTNU).
    Ilver, Lars
    Chalmers Tekniska högskola.
    Gevert, Börje
    Chalmers Tekniska högskola.
    Järås, Sven
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Blekkan, E.A
    Norwegian University of Science and Technology (NTNU).
    Holmen, Anders
    Hydrocarbon production via Fischer-Tropsch synthesis from H-2-poor syngas over different Fe-Co/gamma-Al2O3 bimetallic catalysts2009In: Applied Catalysis B: Environmental, ISSN 0926-3373, E-ISSN 1873-3883, Vol. 89, no 1-2, p. 167-182Article in journal (Refereed)
    Abstract [en]

    Fischer-Tropsch synthesis (FTS) at 20 bar. and 483 K, with H-2-poor syngas (H-2/CO ratio = 1.0) in order to simulate gasified biomass, was performed over Al2O3-supported catalysts with various ratios of Fe:Co (12 wt% bimetal) prepared by co-impregnation. Co was found to be incorporated into the Fe2O3 phase after calcination, at least for the iron-rich samples, while no evidence of Fe incorporated into Co3O4 was found. Upon reduction, most probably FeCo alloys were formed in the iron-rich bimetallic samples. The degree of reduction of the catalysts showed a non-linear behavior with respect to the Fe:Co ratio, but it is obvious that Co increases the reducibility of Fe. Alloying Co with small/moderate amounts of Fe improved the FT activity compared to the 100% Co catalyst at low conversion levels. Alloying Fe with small/moderate amounts of Co lowered the FT activity, but increased the relative water-gas-shift (WGS) activity compared to the 100% Fe catalyst. However, the overall WGS activity was very low for all catalysts, even with external water addition to the feed, resulting in low FT productivities (per gram catalyst) due to the low partial pressure of H-2. A higher Fe:Co ratio in the bimetallic catalyst generally resulted in higher relative WGS activity, but did not lower the H-2/CO usage ratio to the desired value of 1.0. For the Fe-containing catalysts, the space-time yield of hydrocarbons (HCs) decreased with increasing partial pressure of water or reduced space velocity, indicating an inhibition of water on the FT activity, most often resulting in low FT productivity under the conditions with highest relative WGS activity (usage ratios closest to the inlet H-2/CO ratio). Moreover, the co-impregnation technique resulted in a surface enrichment of Fe, at least for the Co-rich samples, covering the Co sites. For the bimetallic catalysts, both FT and WGS activities rapidly declined at high partial pressure of water due to deactivation by oxidation and sintering. However, the results indicate that WGS and FT proceeded over sites of different nature in the bimetallic catalysts.The bimetallic catalysts showed essentially no synergy effects with respect to HC selectivities and olefin/paraffin ratios, which partly can be explained by the use of a sub-stoichiometric H-2/CO ratio as feed. The higher the Fe content, the lower were the C5+ selectivity and C-3 olefin/paraffin ratio. Water addition increased the C5+ selectivity and C-3 Olefin/paraffin ratio and reduced the CH4 selectivity.

  • 57.
    Lögdberg, Sara
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Yang, J.
    Lualdi, Matteo
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Walmsley, J. C.
    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.
    Blekkan, E. A.
    Rytter, E.
    Holmen, A.
    Further insights into methane and higher hydrocarbons formation over cobalt-based catalysts with γ-Al2O3, α-Al2O3 and TiO2 as support materials2017In: Journal of Catalysis, ISSN 0021-9517, E-ISSN 1090-2694, Vol. 352, p. 515-531Article in journal (Refereed)
    Abstract [en]

    A range of cobalt-based catalysts varying in Co loading and prepared by incipient wetness impregnation of traditional support materials (γ-Al2O3, α-Al2O3 and TiO2), have been studied in the Fischer-Tropsch reaction at industrially relevant process conditions (483 K, 20 bar, H2/CO = 2.1). A high selectivity to C5+ hydrocarbons (SC5+) is to a great extent connected with a high site activity, but not exclusively. We propose that the ratio of monomer-production rate to C–C coupling rate of a catalyst determines chain-growth probability by means of governing the coverage of the monomer on the cobalt surface. We speculate that this ratio depends on e.g. shape, strain and size of the Co crystallites and, therefore, is highly dependent on the choice of support material. No general relationship between Co particle size and SC5+ is found, but individual correlations exist for each support material. Within each support material, there are indications of negative correlations between the chain-growth probability of the C1 ∗ surface intermediate (αC1) and the higher αCn values. This can be rationalized by assuming that the majority of methane is formed by a different mechanism, separate from chain growth, but connected with chain growth through a common carbon pool. We propose that the monomers and the majority of methane are produced at sites different from the ones involved in chain growth. There is no general correlation between αC1 and SC5+ for catalysts with different support materials, possibly due to small differences in cobalt surface coverage of hydrogen. For the TiO2-supported catalysts, a dramatically increased αC1 value observed for catalysts with Co particles smaller than approx. 15 nm, is probably associated with strong metal-support interactions (SMSI). This phenomenon apparently limits the effect (reduction) on the SC5+ when moving toward smaller Co particles.

  • 58.
    Manrique Carrera, Arturo
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Jayasuriya, Jeevan
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Fakhrai, Reza
    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.
    Järås, Sven
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology.
    Catalytic Combustion of Gasified Biomass for Gas Turbine Applications: Experimental Investigation at High Pressure2005In: Proceedings of the 6th International Workshop on Catalytic Combution, 2005, Vol. 100, p. 9-14Conference paper (Refereed)
  • 59. Montes, V.
    et al.
    Boutonnet, M.
    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.
    Lualdi, Matteo
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Marinas, A.
    Marinas, J. M.
    Urbano, F. J.
    Mora, M.
    Preparation and characterization of Pt-modified Co-based catalysts through the microemulsion technique: Preliminary results on the Fischer-Tropsch synthesis2014In: Catalysis Today, ISSN 0920-5861, E-ISSN 1873-4308, Vol. 223, p. 66-75Article in journal (Refereed)
    Abstract [en]

    The influence of the addition of small amounts of platinum (0.1-0.25% wt) to cobalt-based systems on Fischer-Tropsch synthesis was investigated. The solids were synthesized through microemulsion technique using TiO2 as the support. The best catalytic performance was achieved using Synperonic 13/6.5 as the surfactant. In all cases, the presence of platinum led to an increase in CO conversion which could be ascribed to the promotion of cobalt reducibility as evidenced by XPS. Moreover, the simultaneous reduction of cobalt and platinum precursors during synthetic procedure (ME1) was preferable to the consecutive one (ME2) probably as a result of a better Co-Pt interaction in the former case, as evidenced by TPR. TPR, Raman and XPS data also suggested that not only the presence of Co-0 but also the appearance of Co-TiO2 interactions favor the catalytic performance and that in general those interactions are stronger for ME1 solids.

  • 60. Montes, V.
    et al.
    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.
    Marinas, A.
    Marinas, J. M.
    Urbano, F. J.
    Selective transformation of glycerol into 1,2-propanediol on several Pt/ZnO solids: Further insight into the role and origin of catalyst acidity2015In: Catalysis Today, ISSN 0920-5861, E-ISSN 1873-4308, Vol. 257, p. 246-258Article in journal (Refereed)
    Abstract [en]

    Microemulsion technique allowed us to synthesize different ZnO solids with similar particle sizes and textural properties. Platinum was subsequently incorporated by deposition-precipitation and impregnation methods and solids tested for glycerol selective transformation into 1,2-PDO. Incorporation of platinum led to the creation of new (mainly Lewis) acid sites. A good correlation between conversion and acidity of Pt/ZnO solids was obtained. Interestingly, despite exhibiting some acidity, supports alone were inactive in the process which evidenced the role of the metal in dehydration of glycerol into acetol. Furthermore, as the reaction proceeded some chlorine coming from the precursor (H2PtCl6) was leached which led to the disappearance of the strongest acid sites, associated to side reactions (catalytic cracking) thus resulting in an increase in selectivity to 1,2-PDO. Eventual formation of Pt-Zn alloy upon reduction of the systems at ca. 400 degrees C was beneficial to 1,2-PDO selectivity.

  • 61. Montes, V.
    et al.
    Checa, M.
    Marinas, A.
    Boutonnet, Magali
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Marinas, J. M.
    Urbano, F. J.
    Järås, Sven
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Pinel, C.
    Synthesis of different ZnO-supported metal systems through microemulsion technique and application to catalytic transformation of glycerol to acetol and 1,2-propanediol2014In: Catalysis Today, ISSN 0920-5861, E-ISSN 1873-4308, Vol. 223, p. 129-137Article in journal (Refereed)
    Abstract [en]

    Different systems consisting of diverse metals (Au, Pt, Pd, Rh) supported on ZnO (5% by weight) were synthesized through the microemulsion technique (ME) and tested for glycerol hydrogenolysis, the main products being hydroxyacetone (acetol) and 1,2-propanediol (1,2-PDO). The solids synthesized using sodium borohydride as the reducing agent (B series) had smaller particle sizes as compared to the use of hydrazine (H series) which, in turn, resulted in a better catalytic performance. This synthetic method allowed us to obtain similar metal particle sizes (2-4 nm) for Pt, Pd and Rh solids in B series, whereas average gold metal particle was higher (> 8 nm) which probably accounts for Au-containing systems being inactive under our experimental conditions. Reactivity order followed the sequence Rh > Pt > Pd. A comparison of the systems synthesized in the present paper through ME technique with those obtained in a previous work through the deposition-precipitation process revealed a higher activity and selectivity to acetol for the former solids which could be related to the presence of surfactant. Moreover, results suggested that metal sites could participate not only in hydrogenation of acetol to 1,2-propanediol but also in the previous dehydration step of glycerol to acetol.

  • 62. Nassos, S.
    et al.
    Svensson, E. Elm
    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.
    The influence of Ni load and support material on catalysts for the selective catalytic oxidation of ammonia in gasified biomass2007In: Applied Catalysis B: Environmental, ISSN 0926-3373, E-ISSN 1873-3883, Vol. 74, no 1-2, p. 92-102Article in journal (Refereed)
    Abstract [en]

    The effect of nickel (Ni) load (0, 5 and 10 wt.%) and support material (Ce0.9La0.1O2, Ce0.9Zr0.1O2 and gamma-Al2O3), together the amount of oxygen (lambda = 0.25 and lambda = 0.5) and gas hourly space velocity (50 000, 100 000 and 150 000 h(-1)) were investigated for the selective catalytic oxidation of ammonia in gasified biomass. The mixed metal oxide support materials were prepared by microemulsion, whereas the alumina was a commercial product. Ni was added to the different supports by incipient wetness. All the obtained catalysts were characterised by BET and XRD analysis. Cordierite monoliths coated with 20 wt.% catalytic material were tested in a tubular quartz reactor. For simulating the gasified biomass fuel, 500 ppm of NH3 was added to the fuel. Water was also present during the activity tests, which were carried out between 500 and 750 degrees C. The results from the activity tests at lambda = 0.25 and gas hourly space velocity of 100 000 h(-1) indicated that the 10 wt.% Ni on Ce0.9La0.1O2 was the best catalyst obtaining 65 and 97% N-2 yield at 500 and 750 degrees C, respectively. By increasing lambda to 0.5 and decreasing the gas hourly space velocity, the N-2 yield improved considerably at low temperature level (500 degrees C). Moreover, NOx emissions maintained at low levels depending on the experimental conditions. Constant conversion and negligible carbon deposition were also two other important observations from the mixed metal oxide supported catalysts. On the contrary, all the alumina-based catalysts displayed the lowest performance.

  • 63.
    Nassos, Stylianos
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology.
    Svensson, Erik Elm
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology.
    Nilsson, M.
    Järås, Sven G.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Microemulsion-prepared Ni catalysts supported on cerium-lanthanum oxide for the selective catalytic oxidation of ammonia in gasified biomass2006In: Applied Catalysis B: Environmental, ISSN 0926-3373, E-ISSN 1873-3883, Vol. 64, no 02-jan, p. 96-102Article in journal (Refereed)
    Abstract [en]

    Nickel (Ni) catalysts supported on cerium-lanthanum oxide were prepared by two different preparation techniques and have been tested in the temperature range of 500-750 degrees C for selective catalytic oxidation of ammonia to nitrogen in gasified biomass. The two different catalyst preparation methods used are the conventional and the microemulsion (water-in-oil). The effect on catalytic activity of different Ni loadings was also tested in combination with the preparation method. Catalyst characterisation was focused on BET and XRD analysis. Cordierite monoliths were used in a tubular quartz reactor for the purpose of the activity tests. For simulating the gasified biomass fuel, 400 ppm NH3 was added to the fuel. Water was also present during the activity tests, which were carried out at fuel rich conditions. Results showed that the microemulsion-prepared catalysts obtained higher performance than the conventional ones, with the best catalyst reaching 98% ammonia conversion and 99% nitrogen selectivity at 750 degrees C. The more the Ni supported on the catalyst, the higher the catalytic activity. Constant conversion and negligible carbon deposition were two other important characteristics for the microemulsion-prepared catalysts.

  • 64.
    Nylén, Ulf
    et al.
    KTH, Superseded Departments, Chemical Engineering and Technology.
    Frontela Delgado, Juana
    Järås, Sven
    KTH, Superseded Departments, Chemical Engineering and Technology.
    Boutonnet, Magali
    KTH, Superseded Departments, Chemical Engineering and Technology.
    Characterization of alkylated aromatic sulphur compounds in light cycle oil from hydrotreated vacuum gas oil using GC-SCD2004In: Fuel processing technology, ISSN 0378-3820, E-ISSN 1873-7188, Vol. 86, no 2, p. 223-234Article in journal (Refereed)
    Abstract [en]

    A light cycle oil (LCO) fraction in the boiling point range 220-337 degreesC was successfully characterized in detail with respect to 29 individual aromatic sulphur compounds and total sulphur content using high-resolution gas chromatography with sulphur chemiluminescence detection (HRGC-SCD). The resulting chromatogram, although very complex with hundreds of different alkyl-substituted aromatic sulphur derivatives, was well resolved owing to the high performance Equity-1 column and the optimised GC method. A shift in the sulphur distribution towards the heavier homologues was observed due to the origin of the LCO, derived from hydrotreated vacuum gas oil.

  • 65.
    Nylén, Ulf
    et al.
    KTH, Superseded Departments, Chemical Engineering and Technology.
    Frontela Delgado, Juana
    KTH, Superseded Departments, Chemical Engineering and Technology.
    Järås, Sven
    KTH, Superseded Departments, Chemical Engineering and Technology.
    Boutonnet, Magali
    KTH, Superseded Departments, Chemical Engineering and Technology.
    Low and high-pressure ring opening of indan over 2 wt.% Pt, Ir and bi-metallic Pt25Ir75/boehmite catalysts prepared from microemulsion systems2004In: Applied Catalysis A: General, ISSN 0926-860X, E-ISSN 1873-3875, Vol. 262, no 2, p. 189-200Article in journal (Refereed)
    Abstract [en]

    A bi-metallic 2 wt.% Pt25Ir75/boehmite catalyst has been synthesized from a microemulsion system and characterized in detail with techniques including TPR, XPS, SEM and TEM-EDX. Additional reduction treatment changes the structural phase of the support as well as the character of the metal particles. TEM-EDX revealed unexpectedly large agglomerates with platinum clusters lying on top of iridium plate-like clusters. The catalytic activity with respect to ring opening of indan was Studied at 325 degreesC and atmospheric pressure and compared with the catalytic performance of corresponding monometallic Pt and Ir/boehmite catalysts. The bi-metallic 2wt.% Pt(25)lr(75)/boehmite catalyst was also tested in a more realistic environment for industrial applications, i.e. at high pressure (40 bar). In essence, the obtained catalytic results indicated superior catalytic activity for the Ir and Pt-Ir catalysts. Concerning selectivity the product distribution varied widely, with hydrogenation and selective ring opening being the most prominent reactions for high pressure and atmospheric pressure conditions, respectively. At atmospheric pressure, all catalysts were slightly deactivated whereas at high pressure, the Pt-Ir catalyst showed a high operating stability with no deactivation.

  • 66.
    Nylén, Ulf
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology.
    Sassu, Lorenzo
    Melis, Stefano
    Järås, Sven
    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.
    Catalytic ring opening of naphthenic structures Part I. From laboratory catalyst screening via pilot unit testing to industrial application for upgrading LCO into a high-quality diesel-blending component2006In: Applied Catalysis A: General, ISSN 0926-860X, E-ISSN 1873-3875, Vol. 299, p. 1-13Article in journal (Refereed)
    Abstract [en]

    The present investigation shows the most relevant results obtained during a joint academic and industrial effort to develop new effective catalysts for upgrading light cycle oil (LCO) into a high-quality diesel-blending component. Bench-scale atmospheric pressure screening with indan over 12 different Pt-Ir-based ring-opening catalysts prepared by the incipient wetness technique showed that the relative amount of iridium and the choice of support material are factors that mainly influence the activity but also the initial and final product distribution. Moreover, TPO-TG-MS analyses of the spent catalysts revealed that for ceria-based catalysts there is a correlation between the amount of iridium, the amount of coke deposits and the resulting catalytic activity: increasing the iridium load results in less carbonaceous deposits and hence higher catalytic activity due to the intrinsic hydrogenolysis/hydrogenation properties of iridium that effectively destroy coke precursors. The catalytic properties of the chosen catalyst candidate, with the formula 2 wt.% Pt5Ir95/CeO2, were examined more closely in a pilot unit under industrially employed conditions with a tetralin/cetane model feed mixture and the real feed pre-hydrotreated LCO (HDT-LCO). As the operating pressure is increased from atmospheric to industrial high-pressure conditions, i.e. 40 bar, coking tendencies are supressed. Moreover, the dominating reaction pathway for the model feed changes from ring-opening to hydrogenation; still, ring-opening is gradually observed as the temperature exceeds approximately 300 degrees C. Simultaneously with ring-opening, consecutive cracking reactions are observed and these must be closely monitored and carefully balanced in order to reduce liquid yield losses.Results obtained at high pressure employing the HDT-LCO show that catalyst performance is slightly impaired, most likely due to sulphur poisoning. In spite of this, the catalyst candidate shows very promising catalytic properties and as the majority of current and forthcoming diesel quality specifications are exceeded, implementation of this catalyst in industrial operation is feasible.

  • 67.
    Okoli, Chuka
    et al.
    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.
    Rajarao-Kuttuva, Gunaratna
    KTH, School of Biotechnology (BIO), Industrial Biotechnology. Albanova University Center, Sweden.
    Protein-functionalized magnetic iron oxide nanoparticles: Time efficient potential-water treatment2014In: Nanotechnology for Sustainable Development, First Edition, Springer, 2014, p. 127-136Chapter in book (Other academic)
    Abstract [en]

    Recent advances in nanoscience suggest that the existing issues involving water quality could be resolved or greatly improved using nanomaterials, especially magnetic iron oxide nanoparticles. Magnetic nanoparticles have been synthesized for the development and use, in association with natural coagulant protein for water treatment. The nanoparticles size, morphology, structure, and magnetic properties were characterized by transmission electron microscope, X-ray diffraction, and superconducting quantum interference device magnetometry. Purified Moringa oleifera protein was attached onto microemulsions-prepared magnetic iron oxide nanoparticles (ME-MION) to form stable protein-functionalized magnetic nanoparticles (PMO+ME-MION). The turbidity removal efficiency in both synthetic and surface water samples were investigated and compared with the commonly used synthetic coagulant (alum) as well as PMO. More than 90 % turbidity could be removed from the surface waters within 12 min by magnetic separation of PMO+ME-MION; whereas gravimetrically, 70 % removal in high and low turbid waters can be achieved within 60 min. In contrast, alum requires 180 min to reduce the turbidity of low turbid water sample. These data support the advantage of separation with external magnetic field (magnetophoresis) over gravitational force. Time kinetics studies show a significant enhancement in ME-MION efficiency after binding with PMO implying the availability of large surface of the MEMION. The coagulated particles (impurities) can be removed from PMO+ME-MION by washing withmild detergent or cleaning solution. To our knowledge, this is the first report on surface water turbidity removal using protein-functionalized magnetic nanoparticle.

  • 68.
    Okoli, Chuka
    et al.
    KTH, School of Biotechnology (BIO), Environmental Microbiology. 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.
    Rajarao-Kuttuva, Gunaratna
    KTH, School of Biotechnology (BIO), Environmental Microbiology.
    Protein-functionalized magnetic iron oxide nanoparticles: time efficient potential-water treatment2012In: Journal of nanoparticle research, ISSN 1388-0764, E-ISSN 1572-896X, Vol. 14, no 10, p. 1194-Article in journal (Refereed)
    Abstract [en]

    Recent advances in nanoscience suggest that the existing issues involving water quality could be resolved or greatly improved using nanomaterials, especially magnetic iron oxide nanoparticles. Magnetic nanoparticles have been synthesized for the development and use, in association with natural coagulant protein for water treatment. The nanoparticles size, morphology, structure, and magnetic properties were characterized by transmission electron microscope, X-ray diffraction, and superconducting quantum interference device magnetometry. Purified Moringa oleifera protein was attached onto microemulsions-prepared magnetic iron oxide nanoparticles (ME-MION) to form stable protein-functionalized magnetic nanoparticles (PMO+ME-MION). The turbidity removal efficiency in both synthetic and surface water samples were investigated and compared with the commonly used synthetic coagulant (alum) as well as PMO. More than 90 % turbidity could be removed from the surface waters within 12 min by magnetic separation of PMO? ME-MION; whereas gravimetrically, 70 % removal in high and low turbid waters can be achieved within 60 min. In contrast, alum requires 180 min to reduce the turbidity of low turbid water sample. These data support the advantage of separation with external magnetic field (magnetophoresis) over gravitational force. Time kinetics studies show a significant enhancement in ME-MION efficiency after binding with PMO implying the availability of large surface of the ME-MION. The coagulated particles (impurities) can be removed from PMO+ME-MIONby washing with mild detergent or cleaning solution. To our knowledge, this is the first report on surface water turbidity removal using protein-functionalized magnetic nanoparticle.

  • 69.
    Okoli, Chuka
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology. KTH, School of Biotechnology (BIO), Environmental Microbiology.
    Boutonnet, Magali
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Mariey, Laurence
    Spectrochemistry, ENSICAEN, France.
    Järås, Sven
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Rajarao, Gunaratna
    KTH, School of Biotechnology (BIO), Environmental Microbiology.
    Application of magnetic iron oxide nanoparticles prepared from microemulsions for protein purification2011In: Journal of chemical technology and biotechnology (1986), ISSN 0268-2575, E-ISSN 1097-4660, Vol. 86, no 11, p. 1386-1393Article in journal (Refereed)
    Abstract [en]

    BACKGROUND: Magnetic nanoparticles are of immense interest for their applications in biotechnology. This paper reports the synthesis of magnetic iron oxide nanoparticles from two different water-in-oil microemulsion systems (ME-MIONs), their characterization and also their use in purification of coagulant protein. RESULTS: ME-MIONs have demonstrated to be an efficient binder in the purification of Moringa oleifera protein when compared with the superparamagnetic iron oxide nanoparticles prepared from coprecipitation in aqueous media. The size and morphology of the ME-MIONs were studied by transmission electron microscopy (TEM) while the structural characteristics were studied by X-ray diffraction (XRD). The microemulsion magnetic iron oxide nanoparticles (ME 1-MION and ME 2-MION) obtained have a size range 7-10 nm. The protein and ME-MIONs interaction was investigated by Fourier transform infrared spectroscopy (FT-IR); the presence of three peaks at 2970, 2910 and 2870 cm(-1) respectively, confirms the binding of the protein. The purification and molecular weight of the coagulant protein was 6.5 kDa as analyzed by SDS-PAGE. CONCLUSION: The ME-MIONs have the advantage of being easily tailored in size, are highly efficient as well as magnetic, cost effective and versatile; they are, thus, very suitable for use in a novel purification technique for protein or biomolecules that possess similar characteristics to the Moringa oleifera coagulant protein.

  • 70.
    Okoli, Chuka
    et al.
    KTH, School of Biotechnology (BIO), Environmental Microbiology. KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Sanchez-Dominguez, Margarita
    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.
    Civera, Concepción
    Solans, Conxita
    Kuttuva Rajarao, Gunaratna
    KTH, School of Biotechnology (BIO), Environmental Microbiology.
    Comparison and Functionalization Study of Microemulsion-Prepared Magnetic Iron Oxide Nanoparticles2012In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 28, no 22, p. 8479-8485Article in journal (Refereed)
    Abstract [en]

    Magnetic iron oxide nanoparticles (MION) for protein binding and separation were obtained from water-in-oil (w/o) and oil-in-water (o/w) microemulsions. Characterization of the prepared nanoparticles have been performed by TEM, XRD, SQUID magnetometry, and BET. Microemulsion-prepared magnetic iron oxide nanoparticles (ME-MION) with sizes ranging from 2 to 10 rim were obtained. Study on the magnetic properties at 300 K shows a large increase of the magnetization similar to 35 emu/g for w/o-ME-MION with superparamagnetic behavior and nanoscale dimensions in comparison with o/w-ME-MION (10 emu/g) due to larger particle size and anisotropic property. Moringa oleifera coagulation protein (MOCP) bound w/o- and o/w-ME-MION showed an enhanced performance in terms of coagulation activity. A significant interaction between the magnetic nanoparticles and the protein can be described by changes in fluorescence emission spectra. Adsorbed protein from MOCP is still retaining its functionality even after binding to the nanoparticles, thus implying the extension of this technique for various applications.

  • 71. Persson, K.
    et al.
    Thevenin, P. O.
    Jansson, K.
    Agrell, J.
    Järås, Sven G.
    KTH, Superseded Departments, Chemical Engineering and Technology.
    Pettersson, Lars J.
    KTH, Superseded Departments, Chemical Engineering and Technology.
    Preparation of alumina-supported palladium catalysts for complete oxidation of methane2003In: Applied Catalysis A: General, ISSN 0926-860X, E-ISSN 1873-3875, Vol. 249, no 1, p. 165-174Article in journal (Refereed)
    Abstract [en]

    Alumina-supported palladium catalysts (Pd/Al2O3) have been prepared by incipient wetness (IW), grafting (G) and microemulsion techniques (ME). Two slightly different microemulsion methods have been used (ME1) and (ME2). The catalysts have been calcined at 1000 degreesC for 4 h. The catalysts have then been examined with respect to their activity for the combustion of methane, during heating and cooling ramps. Pd/Al2O3-IW and Pd/Al2O3-ME2 exhibit the highest activity whereas Pd/Al2O3-ME1 and Pd/Al2O3-G are the less active. There is not much of a difference in activity between Pd/Al2O3-IW and Pd/Al2O3-ME2, despite strong differences in palladium particle size observed by TEM analysis. TPO experiments show that Pd/Al2O3-IW and Pd/Al2O3-ME2 present a higher PdO/Pd ratio than the other samples exhibit. The preparation technique affects the reoxidation ability of palladium during cooling, hence the combustion activity of the fresh catalyst, as PdO is more active than Pd for the complete oxidation of methane under lean conditions.

  • 72.
    Persson, Katarina
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology.
    Ersson, Anders
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology.
    Colussi, S
    Trovarelli, A
    Järås, Sven G.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology.
    Catalytic combustion of methane over bimetallic Pd-Pt catalysts: The influence of support materials2006In: Applied Catalysis B: Environmental, ISSN 0926-3373, Vol. 66, p. 175-185Article in journal (Refereed)
    Abstract [en]

    The effect of support material on the catalytic performance for methane combustion has been studied for bimetallic palladium-platinum catalysts and compared with a monometallic palladium catalyst on alumina. The catalytic activities of the various catalysts were measured in a tubular reactor, in which both the activity and stability of methane conversion were monitored. In addition, all catalysts were analysed by temperature-programmed oxidation and in situ XRD operating at high temperatures in order to study the oxidation/reduction properties.

    The activity of the monometallic palladium catalyst decreases under steady-state conditions, even at a temperature as low as 470 degrees C. In situ XRD results showed that no decomposition of bulk PdO into metallic palladium occurred at temperatures below 800 degrees C. Hence, the reason for the drop in activity is probably not connected to the bulk PdO decomposition.

    All Pd-Pt catalysts, independently of the support, have considerably more stable methane conversion than the monometallic palladium catalyst. However. dissimilanties in activity and ability to reoxidise PdO were observed for the various support materials. Pd-Pt supported on Al2O3 was the most active catalyst in the low-temperature region, Pd-Pt supported on ceria-stabilised ZrO2 was the most active between 620 and 800 degrees C, whereas Pd-Pt supported on LaMnAl11O19 was superior for temperatures above 800 degrees C. The ability to reoxidise metallic Pd into PdO was observed to vary between the supports. The alumina sample showed a very slow reoxidation, whereas ceria-stabilised ZrO2 was clearly faster

  • 73.
    Persson, Katarina
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology.
    Ersson, Anders
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology.
    Jansson, K.
    Iverlund, N
    Järås, Sven
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology.
    Influence of co-metals on bimetallic palladium catalysts for methane combustion2005In: Journal of Catalysis, ISSN 0021-9517, E-ISSN 1090-2694, Vol. 231, p. 139-150Article in journal (Refereed)
    Abstract [en]

    The catalytic combustion of methane has been investigated over eight different bimetallic palladium catalysts, comprising the co-metals Co, Rh, Ir, Ni, Pt, Cu, Ag, or An. The catalysts were characterized by TEM, EDS, PXRD, and temperature-programmed oxidation (TPO). It was found that a catalyst containing both Pd and Pt was the most promising, as it had a high activity that did not decline with time. The catalyst containing Pd and Ag was also a promising candidate, but its activity was slightly lower. For PdCo and PdNi, the co-metals formed spinel structures with the alumina support, with the result that the co-metals did not affect the combustion performance of palladium. For PdRh, PdIr, PdCu, and PdAg, the co-metals formed separate particles consisting of the corresponding metal oxide. These catalysts, except PdRh, showed a stable activity. For PdPt and PdAu, the co-metals formed alloys with palladium, and both catalysts showed a stable activity.

  • 74.
    Persson, Katarina
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology.
    Ersson, Anders
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology.
    Jansson, Kjell
    Fierro, J L G
    Järås, Sven G
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology.
    Influence of molar ratio on Pd-Pt catalysts for methane combustion2006In: Journal of Catalysis, ISSN 0021-9517, Vol. 243, no 1, p. 14-24Article in journal (Refereed)
    Abstract [en]

    The catalytic oxidation of methane was investigated over six catalysts with different palladium and platinum molar ratios. The catalysts were characterised by TEM, EDS, XPS, PXRD and temperature-programmed oxidation. The results suggest that in the bimetallic catalysts, an alloy between Pd and Pt was formed in close contact with the PdO phase, with an exception for the Pt-rich catalyst, where no PdO was observed. It was found that the molar ratio between palladium and platinum clearly influences both the activity and the stability of methane conversion. By adding small amounts of platinum into the palladium catalyst, improved activity was obtained in comparison with the monometallic palladium catalyst. However, higher amounts of platinum are required for stabilising the methane conversion. The most promising catalysts with respect to both activity and stability were Pd67Pt33 and Pd50Pt50. The platinum-rich catalyst showed very poor activity for methane conversion.

  • 75.
    Persson, Katarina
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology.
    Ersson, Anders
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology.
    Manrique Carrera, Arturo
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Jayasuriya, Jeevan
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Fakhrai, Reza
    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.
    Supported palladium-platinum catalyst for methane combustion at high pressure2005In: Catalysis Today, ISSN 0920-5861, E-ISSN 1873-4308, Vol. 100, p. 479-483Article in journal (Refereed)
    Abstract [en]

    Catalytic combustion of methane over a supported bimetallic Pd-Pt catalyst and a monometallic Pd catalyst has been investigated experimentally. Two different reactor configurations were used in the study, i.e. a tubular lab-scale reactor working at atmospheric pressure and a high-pressure reactor working at up to 15 bar. The results showed that the bimetallic catalyst has a clearly more stable activity during steady-state operation compare to the palladium only catalyst. The activity of the bimetallic catalyst was slightly higher than for the palladium catalyst. These results were established in both test facilities. Further, the impact of pressure on the combustion activity has been studied experimentally. The tests showed that the methane conversion decreases with increasing pressure. However, the impact of pressure is more prominent at lower pressures and levels out for pressures above 10 bar

  • 76.
    Persson, Katarina
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology.
    Jansson, Kjell
    Järås, Sven G.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology.
    Characterisation and microstructure of Pd and bimetallic Pd-Pt catalysts duirng methane oxidation2007In: Journal of Catalysis, ISSN 0021-9517, E-ISSN 1090-2694, Vol. 245, no 2, p. 401-414Article in journal (Refereed)
    Abstract [en]

    The catalytic oxidation of methane was studied over Pd/Al2O3 and Pd-Pt/Al2O3. It was found that the activity of Pd/Al2O3 gradually decreases with time at temperatures well below that of PdO decomposition. The opposite was observed for Pd-Pt/Al2O3, of which the activity decreases slightly with time. Morphological studies of the two catalysts showed major changes during operation. The palladium particles in Pd/Al2O3 are initially composed of smaller, randomly oriented crystals of both PdO and Pd. In oxidising atmospheres, the crystals become more oxidised and form larger crystals. The activity increase of Pd-PuAl2O3 is probably related to more PdO being formed during operation. The particles in Pd-Pt/Al2O3 are split into two different domains: one with PdO and the other likely consisting of an alloy between Pd and Pt. The alloy is initially rich in palladium, but the composition changes to a more equalmolar Pd-Pt structure during operation. The ejected Pd is oxidised into PdO, which is more active than its metallic phase. The amount of PdO formed depends on the oxidation time and temperature.

  • 77.
    Persson, Katarina
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology.
    Pfefferle, Lisa D.
    Schwartz, William
    Ersson, Anders
    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.
    Stability of palladium-based catalysts during catalytic combustion of methane: The influence of water2007In: Applied Catalysis B: Environmental, ISSN 0926-3373, E-ISSN 1873-3883, Vol. 74, no 3-4, p. 242-250Article in journal (Refereed)
    Abstract [en]

    The stability of methane conversion was studied over a Pd/Al2O3 catalyst and bimetallic Pd-Pt/Al2O3 catalysts. The activity of methane combustion over Pd/Al2O3 gradually decreased with time, whereas the methane conversion over bimetallic Pd-Pt catalysts was significantly more stable. The differences in combustion behavior were further investigated by activity tests where additional water vapor was periodically added to the feed stream. From these tests it was concluded that water speeds up the degradation process of the Pd/Al2O3 catalyst, whereas the catalyst containing Pt was not affected to the same extent. DRIFTS studies in a mixture of oxygen and methane revealed that both catalysts produce surface hydroxyls during combustion, although the steady state concentration on the pure Pd catalyst is higher for a fixed temperature and water partial pressure. The structure of the bimetallic catalyst grains with a PdO domain and a Pd-Pt alloy domain may be the reason for the higher stability, as the PdO domain appears to be more affected by the water generated in the combustion reaction than the alloy. Not all fuels that produce water during combustion will have stability issues. It appears that less strong binding in the fuel molecule will compensate for the degradation.

  • 78. Pocoroba, E.
    et al.
    Johansson, E. M.
    Järås, Sven G.
    KTH, Superseded Departments, Chemical Engineering and Technology.
    Ageing of palladium, platinum and manganese-based combustion catalysts for biogas applications2000In: Catalysis Today, ISSN 0920-5861, E-ISSN 1873-4308, Vol. 59, no 02-jan, p. 179-189Article in journal (Refereed)
    Abstract [en]

    During recent years, catalytic combustion of low heating value gases has received increased attention. The purpose of the present work was to study the effect of ageing for 30 days at 1000 degrees C in air saturated with 12% steam on Pd- and Pt-impregnated as well as Mn-substituted lanthanum hexaaluminate materials. Both hexaaluminate powders and 400 cpsi cordierite monoliths, washcoated with hexaaluminate powder, were aged. Powders were characterised by BET and XRD, whereas the catalytic activity of the washcoated monoliths was evaluated in a bench-scale rig for conversion of synthetic gasified biomass. The surface areas decreased significantly during the first day of ageing, whereas further ageing had only a minor influence. The pure lanthanum-alumina sample was a mixture of the hexaaluminate LaAl11O18 phase and the less preferable perovskite LaAlO3 phase, which increased after ageing. The Mn-substituted lanthanum-alumina mainly showed pure hexaaluminate phase both before and after ageing. The catalytic activity tests showed that Pd-impregnated lanthanum hexaaluminate was the most active catalyst for combustion of carbon monoxide and hydrogen, retaining low light-off temperatures also after 30 days of ageing. However, the ignition temperature for 50% conversion (T-50) of methane was approximately 300 degrees C higher than for the fresh sample. Pt-impregnated samples were less active than the Pd ones. The Pt-loading decreased after ageing, whereas the Pd-loading remained fairly constant. However, the amount of Pd oxide decreased after ageing. Further, the Mn-substituted samples were less active than the precious metal ones. Here, the activity for the combustion of carbon monoxide was substantially affected by ageing. The formation of nitrogen oxides from ammonia was lower over the aged samples than over fresh ones; the Mn-substituted sample aged 30 days showed the lowest yield, only 30% of ammonia was converted to nitrogen oxides.

  • 79.
    Regali, Francesco
    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.
    Hydrocracking of Fischer-Tropsch waxes over Pt/Pd catalysts supported on amorphous silica-alumina2011In: Abstract of Papers of the American Chemical Society, ISSN 0065-7727, Vol. 242, p. 63-PETR-Article in journal (Other academic)
  • 80.
    Regali, Francesco
    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.
    Hydrocracking of n-hexadecane on noble metal/silica-alumina catalysts2013In: Catalysis Today, ISSN 0920-5861, E-ISSN 1873-4308, Vol. 214, no SI, p. 12-18Article in journal (Refereed)
    Abstract [en]

    Bifunctional catalysts consisting of platinum or palladium on amorphous silica-alumina were prepared and tested in the hydrocracking of n-hexadecane (n-C16H34). Product selectivities toward mono-branched and multi-branched feed isomers and cracking products have been determined in a wide range of conversions, varying liquid hourly space velocity at constant operating parameters (pressure = 30 bar; temperature = 310 C; H 2/n-C16H34 feed molar ratio = 10). A simple kinetic study is presented, in which the reactions are approximated by a network of pseudo first order irreversible reaction steps. The reaction network model was fitted to the experimental data, and kinetic constants for the different reaction steps were obtained. It could be concluded that mono-branched feed isomers are primary products in the hydrocracking/hydroisomerization reaction network; multi-branched isomers are formed mainly from mono-branched as a secondary product. On the platinum catalyst cracking products were formed as primary products, and it proved to be slightly more active than the palladium based one, at the same metallic molar loading. It could be shown that the platinum catalyst yields cracking products both via a bifunctional metal/acid mechanism and by monofunctional (metal only) hydrogenolysis. This second mechanism accounted for the higher activity of the platinum catalyst.

  • 81.
    Regali, Francesco
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Liotta, Leonarda Francesca
    Istituto per lo Studio dei Materiali Nanostrutturati, ISMN CNR, Palermo, Italy.
    Venezia, Anna Maria
    Istituto per lo Studio dei Materiali Nanostrutturati, ISMN CNR, Palermo, Italy.
    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.
    Hydroconversion of n-hexadecane on Pt/silica-alumina catalysts: Effect of metal loading and support acidity on bifunctional and hydrogenolytic activity2014In: Applied Catalysis A: General, ISSN 0926-860X, E-ISSN 1873-3875, Vol. 469, p. 328-339Article in journal (Refereed)
    Abstract [en]

    Bifunctional catalysts based on platinum and amorphous silica-alumina were studied in the hydroconversion of n-hexadecane. The influence of platinum loading and support acidity on activity and selectivity were assessed. The contribution of hydrogenolysis reactions on top of bifunctional hydrocracking was shown to depend not only on metal loading, but also on the effect of support acidity on the intrinsic activity of the platinum sites. The yield of cracking products, and their linear alkane fraction, increased with metal loading, while the isomerization yield was practically independent of the metal content. On a support of high Bronsted acidity, the rate of formation of methane was proportional to the platinum surface area, indicating that dernethylation occurred by metal-cataly ed hydrogenolysis. On the other hand, the methane site-time yield was one order of magnitude lower on a catalyst with negligible Bronsted acidity. Pt-catalyzed hydrogenolysis was also investigated during selective poisoning of acid sites by cofeeding pyridine and comparing the effect of hydrogen partial pressure on reaction rates. In the presence of pyridine, total hydroconversion activity was reduced by one order of magnitude while rates to methane and linear cracking products remained relatively high. These observations indicate that acid sites do not intervene in the mechanism, but that support acidity affects the hydrogenolytic activity of platinum sites.

  • 82.
    Regali, Francesco
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Liotta, Leonarda Francesca
    Istituto per lo Studio dei Materiali Nanostrutturati, ISMN-CNR, Palermo, Italy.
    Venezia, Anna Maria
    Istituto per lo Studio dei Materiali Nanostrutturati, ISMN-CNR, Palermo, Italy.
    Montes, Vicente
    Organic Chemistry Department, University of Córdoba, Córdoba, Spain.
    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.
    Effect of metal loading on activity, selectivity and deactivation behavior of Pd/silica-alumina catalysts in the hydroconversion of n-hexadecane2014In: Catalysis Today, ISSN 0920-5861, E-ISSN 1873-4308, Vol. 223, p. 87-96Article in journal (Refereed)
    Abstract [en]

    Bifunctional catalysts consisting of palladium on amorphous silica-alumina with different metal loadings (0 wt% to 1.2 wt%) were compared in the hydrocracking/hydroisomerization of n-hexadecane. The reaction conditions were: pressure = 30 bar; temperature = 310 degrees C; hydrogen-to-hexadecane feed molar ratio = 10. Metal loading was found to have a remarkable influence on the initial deactivation rate, which could be related to the formation of carbonaceous deposits. The dependence of activity on the metal-acid site ratio was the typical one for bifunctional hydrocracking where, after reaching a threshold value, the catalytic activity does not appreciably increase with increasing metal loading. On the Pd-containing catalysts, the methane space-time-yield showed a strong dependence on conversion, but no clear relationship with metal surface area, indicating that the formation of methane might not proceed by purely metal-catalyzed hydrogenolysis.

  • 83.
    Regali, Francesco
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Suaréz París, Rodrigo
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Aho, Atte
    Åbo Akademi.
    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 a Pt/Silica–Alumina Catalyst and Effecton Selectivity in the Hydrocracking of n-Hexadecane2013In: Topics in catalysis, ISSN 1022-5528, E-ISSN 1572-9028, Vol. 56, no 9-10, p. 594-601Article in journal (Refereed)
    Abstract [en]

    The deactivation behavior of a bifunctionalcatalyst consisting of platinum on amorphous silica–aluminawas studied in the hydrocracking of n-hexadecane.The initial decline in activity and the change in selectivitywere monitored at the following reaction conditions:pressure = 30 bar; temperature = 310 C; hydrogen-tohexadecanefeed molar ratio = 10. Initially, hexadecaneconversion and selectivity to cracking products decreasedrapidly with time-on-stream, and stabilized after 40 h onstream. This could be related to an initial loss of metalsurface area, which decreased the activity of monofunctionalhydrogenolysis generating cracking products. Theacidic function seemed to be unaffected under these reactionconditions. The stable catalyst was exposed to a lowerhydrogen-to-hexadecane ratio to accelerate deactivation bycoking. A decline in the activity of both functions wasobserved. The activity of the acidic function could bealmost completely recovered by oxidative regeneration,while the metal activity was only partially recovered.

  • 84. Rojas, S.
    et al.
    Garcia-Garcia, F. J.
    Järås, Sven G.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Martinez-Huerta, M. V.
    Fierro, J. L. G.
    Boutonnet, Magali
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Preparation of carbon supported Pt and PtRu nanoparticles from microemulsion - Electrocatalysts for fuel cell applications2005In: Applied Catalysis A: General, ISSN 0926-860X, E-ISSN 1873-3875, Vol. 285, no 02-jan, p. 24-35Article in journal (Refereed)
    Abstract [en]

    A series of platinum and platinum ruthenium carbon supported electrocatalyst have been prepared by the microemulsion technique. The influence of parameters such as the preparation route, the metal loading and the PtRu stoichiometry on the morphology of the final nanoparticles has been studied. Irrespective the total metal loading, nanosized particles, displaying a narrow size distribution were obtained. In addition, particle size was found to be independent of the metal loading. Structural characteristics of these systems have been studied by XPS, X-ray diffraction, TEM, and TPR-TPO and their textural parameters by N-2 adsorption. The catalytic performance of the samples was evaluated in the electrochemical oxidation of methanol. The influence of the morphology on the catalytic performance of the catalysts is discussed in terms of their synthesis route. © 2005 Elsevier B.V. All rights reserved.

  • 85.
    Suárez París, Rodrigo
    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 G.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Effect of methanol addition on higher alcohol synthesis over modified molybdenum sulfide catalysts2015In: Catalysis communications, ISSN 1566-7367, E-ISSN 1873-3905, Vol. 67, p. 103-107Article in journal (Refereed)
    Abstract [en]

    One of the main problems in higher alcohol synthesis is the poor product distribution. Cofeeding of methanol, together with the synthesis gas, has been suggested in order to increase the yield of ethanol and higher alcohols. In this work, the effect of methanol addition on K-MoS<inf>2</inf> and K-Ni-MoS<inf>2</inf> catalysts was studied at 71 bar, 340 °C and GHSV = 6000 N mL/h · g<inf>catalyst</inf>. Under these conditions methanol recycle is not a viable option for boosting higher alcohol production. The main result was an increase in methane yield, while the effect in higher alcohols was negative or not significant.

  • 86.
    Suárez París, Rodrigo
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    L’Abbate, Mario Enrico
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Liotta, Leonarda Francesca
    Montes, Vicente
    Barrientos, Javier
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Regali, Francesco
    Aho, Atte
    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.
    Hydroconversion of paraffinic wax over platinum and palladium catalysts supported on silica–alumina2016In: Catalysis Today, ISSN 0920-5861, E-ISSN 1873-4308, Vol. 275, p. 141-148Article in journal (Refereed)
    Abstract [en]

    Two bifunctional catalysts consisting of platinum or palladium supported on amorphous silica–alumina were prepared and tested in hydrocracking/hydroisomerization of paraffinic wax. The performance of both noble metals was studied at the following reaction conditions: P = 35 bar; T = 300–330 °C; H2/wax = 0.1 wt/wt; WHSV = 1–4 h−1. The platinum sample was more active in hydrocracking of C22+ compounds and more selective to middle distillates. On the other hand, the palladium-based catalyst resulted in a higher isomerization degree of the products and lower amounts of methane and ethane. The higher production of light compounds over platinum is attributed to a monofunctional hydrogenolysis mechanism, in addition to the classical bifunctional route. Characterization studies showed that both catalysts had comparable metal and acid site distributions. These observations would indicate that the different catalyst performance is due to the different nature of platinum and palladium as hydrogenation/dehydrogenation function.

  • 87.
    Suárez París, Rodrigo
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology.
    Lopez Nina, Luis Gagarin
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology.
    Barrientos, Javier
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology.
    Pardo, Fátima
    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 G.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology.
    Catalytic conversion of biomass-derived synthesis gas to fuels2015In: Catalysis. Volume 27, Royal Society of Chemistry, 2015, p. 62-143Chapter in book (Refereed)
    Abstract [en]

    Biomass-derived fuels constitute a promising alternative for diversifying the fuel supply and reducing the consumption of fossil fuels, leading to a reduction in greenhouse gas emissions and thus mitigating global warming. Biomass can be converted to synthesis gas, which can serve as a source for various liquid and gaseous fuels. Although significant progress has been achieved in the overall process, both economic and technical challenges still need to be overcome. Many pilot plants are already in operation and the first demonstration and semi-commercial installations are under construction or starting to operate. Catalysis is a key parameter in the conversion of synthesis gas to fuels. The aim of this work is to present the latest advances in the catalytic conversion of synthesis gas to Fischer-Tropsch gasoline and diesel, synthetic natural gas, ethanol and mixed alcohols. The syntheses of methanol and dimethyl ether are also briefly reviewed.

  • 88.
    Suárez París, Rodrigo
    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.
    Higher alcohol synthesis over nickel-modified alkali-doped molybdenum sulfide catalysts prepared by conventional coprecipitation and coprecipitation in microemulsions2015In: Catalysis Today, ISSN 0920-5861, E-ISSN 1873-4308, Vol. 258, p. 294-303Article in journal (Refereed)
    Abstract [en]

    Ethanol and higher alcohols are one of the most interesting alternatives to replace fossil fuels in the transportation sector. Nickel-modified alkali-doped molybdenum sulfide is a potential catalyst for the conversion of syngas to mixed alcohols. In this work, K-Ni-MoS2 catalysts were synthetized by coprecipitation in aqueous solution or in microemulsions, followed by alkali doping. The influence of the preparation route in CO hydrogenation was investigated at 91 bar, 340/370 degrees C and GHSV= 2000-14,000 NmL/h g(catalyst). The catalysts were also characterized by TGA, ICP, XPS, nitrogen adsorption, XRD, SEM-EDX and TEM. The novel microemulsion catalyst outperformed the conventional one, resulting in higher yields of ethanol and higher alcohols. The higher activity and selectivity was attributed to a higher concentration of promoters on the microemulsion catalyst surface, together with a lower degree of crystallinity.

  • 89.
    Sven, Järås
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology.
    Sara, Lögdberg
    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.
    Method for depositing metal particles on a supportArticle in journal (Other academic)
  • 90. Thevenin, P. O.
    et al.
    Alcalde, A.
    Pettersson, Lars J.
    KTH, Superseded Departments, Chemical Engineering and Technology.
    Järås, Sven G.
    KTH, Superseded Departments, Chemical Engineering and Technology.
    Fierro, J. L. G.
    Catalytic combustion of methane over cerium-doped palladium catalysts2003In: Journal of Catalysis, ISSN 0021-9517, E-ISSN 1090-2694, Vol. 215, no 1, p. 78-86Article in journal (Refereed)
    Abstract [en]

    Various Pd-supported catalysts have been prepared using three different types of alumina as support material: (a) gamma-alumina, (b) Ba-stabilized alumina, and

  • 91. Thevenin, P. O.
    et al.
    Ersson, A. G.
    Kusar, H. M. J.
    Menon, P. G.
    Järås, Sven G.
    KTH, Superseded Departments, Chemical Engineering and Technology.
    Deactivation of high temperature combustion catalysts2001In: Applied Catalysis A: General, ISSN 0926-860X, E-ISSN 1873-3875, Vol. 212, no 02-jan, p. 189-197Article in journal (Refereed)
    Abstract [en]

    The main objective of catalytic combustion is to attain a flame temperature 300-400 Klower than in thermal or non-catalyzed combustion; this substantially reduces the direct combination of nitrogen and oxygen in air to form the so-called thermal NOx. In this way, catalytic combustion is a preventive solution to the problem of nitrogen oxides emissions. The focus of attention here is its application in gas turbines, both for power production and for transportation by road, sea and air. Any catalyst for catalytic combustion, however, has to face extreme demands: continuous operation above 1000 degreesC in the presence of oxygen and steam for preferably 30,000 h, resistance to poisons in the fuel and/or process air, and ability to withstand large thermal and mechanical shocks. While material/catalyst advances are still inadequate, systems engineering is coming to the rescue by developing multiple-monolith catalyst systems and the so-called hybrid reactors. The deactivation of catalyst supports, washcoats, and active materials is briefly reviewed here: sintering, vaporization, phase transformation, thermal shock and poisoning.

  • 92. Thevenin, P. O.
    et al.
    Menon, P. G.
    Järås, Sven G.
    KTH, Superseded Departments, Chemical Engineering and Technology.
    Catalytic processes to convert methane: partial or total oxidation - Part 11 - Catalytic total oxidation of methane2003In: CATTech, ISSN 1384-6566, E-ISSN 1572-8811, Vol. 7, no 1, p. 10-22Article in journal (Refereed)
    Abstract [en]

    The introduction of solid catalysts into a traditionally non-catalytic free-radical process such as combustion occurred in recent years under the influence of environmental pressures. The major applications of catalytic combustion are two-fold: at low temperatures to eliminate volatile organic compounds (VOCs) and at high temperatures (>1000degreesC) to reduce NOx emission from gas turbines, jet motors, etc. It is the high temperature application that is reviewed here. Some recent depolopments in high-temperature catalytic combustion are trend setters in catalysis and hence of particular interest. For instance, novel materials are being developed for catalytic applications above 1000degreesC for sustained operation longer than one year. Where material/catalyst developments are still inadequate, systems engineering is coming to the rescue by developing multiple-monolith catalyst systems and the so-called hybrid (catalytic + thermal) reactors.

  • 93. Thevenin, P. O.
    et al.
    Pocoroba, E.
    Pettersson, Lars J.
    KTH, Superseded Departments, Chemical Engineering and Technology.
    Karhu, H.
    Vayrynen, I. J.
    Järås, Sven G.
    KTH, Superseded Departments, Chemical Engineering and Technology.
    Characterization and activity of supported palladium combustion catalysts2002In: Journal of Catalysis, ISSN 0021-9517, E-ISSN 1090-2694, Vol. 207, no 1, p. 139-149Article in journal (Refereed)
    Abstract [en]

    The catalytic activity of Pd supported on gamma-Al2O3, Ba-Al2O3, and La-Al2O3 has been examined in complete oxidation of methane when operating in excess of oxygen. Two different sizes of I'd particles have been considered. Foreign ions have a strong influence with respect to the stabilization of alumina when submitted to a temperature as high as 1000 degrees C. In contrast, no specific effect can be detected when the samples are calcined at 500 degreesC. Interaction with the supported palladium particles, observed during the combustion reaction, has been investigated by X-ray photoelectron Spectroscopy and temperature-programmed oxidation. The difference in combustion activity is attributed to the difference in surface oxidation states of the Pd particles. The presence of foreign ions in the alumina structure results in surface PdO only. When supported on gamma-Al2O3, small amounts of metallic Pd can be detected, resulting in a lower ignition temperature.

  • 94.
    Velasco, Jorge A.
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Fernandez, Cristhian
    Lopez Nina, Luis Gagarin
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology. UMSA Universidad Mayor de San Andres, Bolivia.
    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.
    Catalytic partial oxidation of methane over nickel and ruthenium based catalysts under low O2/CH4 ratios and with addition of steam2015In: Fuel, ISSN 0016-2361, E-ISSN 1873-7153, Vol. 153, p. 192-201Article in journal (Refereed)
    Abstract [en]

    Catalytic partial oxidation (CPO) of methane to synthesis gas at low O2/CH4 ratios and in the presence of steam was investigated over nickel and ruthenium catalysts supported on hydrotalcite-derived materials. The influence of catalyst properties and composition on activity, temperature profile and deactivation by carbon formation was examined. All catalyst presented high methane conversions, close to the values predicted by thermodynamic equilibrium and such conversions increased in proportion to the metal surface of the catalyst tested. The temperature profiles at O2/CH4 = 0.2 and H2O/CH4 = 0.3 and a constant exit temperature of 700 °C varied depending on the catalyst type; it was possible to examine catalyst deactivation from the change in the shape of the profile of each catalyst. Since the O2/CH4 and H2O/CH4 ratios were low, the risk or potential for carbon formation was thermodynamically favorable along the entire catalytic bed; however, this potential was qualitatively higher when the temperature profile of the catalyst presented a pronounced maximum peak at the inlet of the reactor. During catalytic reaction tests and methane decomposition experiments, the ruthenium catalyst did not formed appreciable amounts of carbon while a bimetallic catalyst (Ni and Ru) form only small amounts (in comparison with the nickel catalysts). For the ruthenium catalyst, a higher O2/CH4 ratio favored conversions closer to the equilibrium value. The observations presented in this work indicate that during the CPO of methane, at low O2/CH4 ratios and in the presence of steam, the catalyst properties and composition will have a substantial influence on the extent of the combustion and reforming reactions along the catalytic bed. This will in turn define the temperature profile, and therefore the risk or potential for carbon formation; this risk might effectively be overcome by the use of ruthenium-containing catalysts.

  • 95.
    Velasco, Jorge A.
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology. UMSA - Universidad Mayor de San Andrés, Bolivia.
    Lopez Nina, Luis Gagarin
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology. UMSA - Universidad Mayor de San Andrés, Bolivia.
    Cabrera, Saul
    UMSA - Universidad Mayor de San Andrés, Bolivia.
    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 gas production for GTL applications: Thermodynamic equilibrium approach and potential for carbon formation in a catalytic partial oxidation pre-reformer2014In: Journal of Natural Gas Science and Engineering, ISSN 1875-5100, E-ISSN 2212-3865, Vol. 20, p. 175-183Article in journal (Refereed)
    Abstract [en]

    The present work is focused on synthesis gas production for Gas to Liquids (GTL.) applications. A thermodynamic equilibrium approach has been chosen in order to address the methane reforming processes in presence of steam and oxygen (i.e. autothermal reforming "ATR" and catalytic partial oxidation "CPO"). The effect of operational variables on the performance of the reforming units has been analyzed at conditions typical for GTL processes. Also, the performance of a synthesis gas generation unit (SGU) comprising a CPO pre-reformer followed by an ATR reactor has been investigated. The potential for carbon formation in the CPO pre-reformer has been evaluated by applying the "equilibrated gas principle". Our results show that synthesis gas production can be strongly influenced by changes in operating variables such as the steam-to-carbon (S/C) and the oxygen-to-carbon (O-2/C) ratios, recycled gas (tail gas) compositions, and operating pressures and temperatures; however, effective operation of the SGU (CPO + ATR) requires an correct combination of these variables in order to accomplish the synthesis gas requirements of the Fischer-Tropsch synthesis. Likewise, it is shown that the risk of carbon formation in the CPO reactor can be reduced or even eliminated by a proper manipulation and combination of such variables.

  • 96.
    Velasco, Jorge A.
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Lopez Nina, Luis Gagarin
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology. UMSA Universidad Mayor de San Andres, Bolivia.
    Velasquez, Miguel
    Boutonnet, Magali
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Cabrera, Saul
    Järås, Sven
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Gas to liquids: A technology for natural gas industrialization in Bolivia2010In: Journal of Natural Gas Science and Engineering, ISSN 1875-5100, E-ISSN 2212-3865, Vol. 2, no 5, p. 222-228Article in journal (Refereed)
    Abstract [en]

    Gas-to-Liquids (GTL) technology converts natural gas, through Fischer-Tropsch synthesis, into liquid and ultra-clean hydrocarbons such as light oils, kerosene, naphtha, diesel, and wax. Bolivia has natural gas reserves that reach 48.7 trillion cubic feet and produces nearly 40.0 million cubic meters per day, from which, around 88% are exported to Brazil and Argentina. In spite of these considerable amounts of natural gas reserves and production, the country experiences a shortage of diesel which cannot be solved using conventional refining processes due the light nature of its crude oil. Thus, the GTL process seems to be a promising solution for Bolivia's diesel problems, at the same time that its natural gas reserves could be monetized. Although GTL can be considered as a well proven and developed technology, there are several aspects along the main processing steps (synthesis gas generation, Fischer-Tropsch synthesis, and product upgrading) to be considered at the time of implementing a GTL plant. The aim of this paper is to give an overall view of some relevant issues related to Gas-to-Liquids technology as an option for natural gas industrialization in Bolivia, and also to provide a landscape of Bolivian natural gas industry.

  • 97.
    Velasco, Jorge A.
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Montes, Vicente
    Organic Chemistry Department, University of Córdoba, Córdoba, Spain.
    Kusar, Henrik
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Cabrera, Saul
    Instituto del Gas Natural, San Andrés Higher University, La Paz, Bolivia.
    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.
    Methane partial oxidation and methane decomposition over Ni andNi-Ru supported catalysts for synthesis gas productionManuscript (preprint) (Other academic)
    Abstract [en]

    Nickel and nickel-ruthenium based catalysts were compared in the catalytic partial oxidation (CPO) of methane and in the equilibrium of the methane decomposition reaction. A hydrotalcite-derived material as well as α- Al2O3 and γ-Al2O3 were used as catalyst supports. The catalysts were characterized by H2 chemisorption, N2 physisorption, temperature-programmed reduction (TPR), temperature-programmed oxidation (TPO) and transmission electron microscopy (TEM). Catalyst properties and composition influenced the catalytic performance during partial oxidation (i.e. activity and temperature profiles). During methane decomposition equilibrium tests, all catalysts presented smaller equilibrium constants than those calculated on the basis of graphite; the deviation from graphite data was mainly associated with maximum nickel particle size (for both Ni and bimetallic Ni-Ru supported catalysts). Among all catalysts, the bimetallic Ni-Ru catalyst supported on hydrotalcite-derived material showed an interesting enhanced behavior; however, resistance towards catalyst deactivation, by mechanisms different than carbon formation, still needs to be improved. 

  • 98. Venezia, Anna Maria
    et al.
    La Parola, Valeria
    Liotta, Leonarda F.
    Pantaleo, Giuseppe
    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.
    Co/SiO2 catalysts for Fischer-Tropsch synthesis; effect of Co loading and support modification by TiO22012In: Catalysis Today, ISSN 0920-5861, E-ISSN 1873-4308, Vol. 197, no 1, p. 18-23Article in journal (Refereed)
    Abstract [en]

    The influence of cobalt loading and titania addition to the silica support on Fischer-Tropsch synthesis activity is investigated over two series of catalysts with Co loading of 6 wt% and 12 wt%. The pure silica support is prepared by sol-gel procedure in acid conditions. The modification by TiO2 is performed by grafting with titanium isopropoxide. The catalysts are prepared by wet-impregnation over amorphous SiO2 and over SiO2 modified by TiO2 (5 wt%). The samples, characterized by N-2-adsorption-desorption analyses, X-ray diffraction (XRD), temperature programmed reduction (TPR) and X-ray photoelectron spectroscopy (XPS), are tested in the low-temperature Fischer-Tropsch synthesis using the conditions of 483 K, 20 bar and H-2/CO = 2.1. The improved conversion rate and the increased SC5+ of the titania containing catalysts are discussed in terms of the stronger interaction between cobalt and titania affecting the cobalt oxide reducibility.

12 51 - 98 of 98
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