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  • 1. Bernardini, A.
    et al.
    Gemo, N.
    Biasi, P.
    Canu, P.
    Mikkola, J. P.
    Salmi, T.
    Lanza, Roberto
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology.
    Direct synthesis of H2O2 over Pd supported on rare earths promoted zirconia2015In: Catalysis Today, ISSN 0920-5861, E-ISSN 1873-4308, Vol. 256, p. 294-301Article in journal (Refereed)
    Abstract [en]

    In this work Pd (0.3 or 0.6 wt.%) was supported on both ZrxM1-xO2 (M = La, Y, Ce) and on mechanical mixtures of CeO2 and ZrO2. The synthesized catalysts were characterized by XRD, TPR, AAS and CO chemisorption and tested for the direct synthesis of hydrogen peroxide in a high pressure semibatch apparatus. The reactants conversion was limited in order to avoid mass-transfer limitations. No selectivity enhancers of any kind were used and the all the materials were halide free. Small metal particles were obtained (1-2.6 nm). Supports with smaller pore diameters leaded to larger Pd particles, which in turn were found to preferentially support the formation of the peroxide. Moreover, supports with higher reducibility favored the production of H2O2, probably due to an easier reduction of the active metal, essential to achieve high selectivity. Notwithstanding the absence of enhancers, the specific activity and selectivity recorded were very high.

  • 2. Bersani, Marco
    et al.
    Gupta, Kalyani
    Mishra, Abhishek Kumar
    Lanza, Roberto
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Taylor, S. F. Rebecca
    Islam, Husn-Ubayda
    Hollingsworth, Nathan
    Hardacre, Christopher
    de Leeuw, Nora H.
    Darr, Jawwad A.
    Combined EXAFS, XRD, DRIFTS, and DFT Study of Nano Copper Based Catalysts for CO2 Hydrogenation2016In: ACS Catalysis, ISSN 2155-5435, E-ISSN 2155-5435, Vol. 6, no 9, p. 5823-5833Article in journal (Refereed)
    Abstract [en]

    Highly monodispersed CuO nanoparticles (NPs) were synthesized via continuous hydrothermal flow synthesis (CHFS) and then tested as catalysts for CO2 hydrogenation. The catalytic behavior of unsupported 11 nm sized nanoparticles from the same batch was characterized by diffuse reflectance infrared fourier transform spectroscopy (DRIFTS), extended X-ray absorption fine structure (EXAFS), X-ray diffraction (XRD), and catalytic testing, under CO2/H-2 in the temperature range 25-500 degrees C in consistent experimental conditions. This was done to highlight the relationship among structural evolution, surface products, and reaction yields; the experimental results were compared with modeling predictions based on density functional theory (DFT) simulations of the CuO system. In situ DRIFTS revealed the formation of surface formate species at temperatures as low as 70 degrees C. DFT calculations of CO2 hydrogenation on the CuO surface suggested that hydrogenation reduced the CuO surface to Cu2O, which facilitated the formation of formate. In situ EXAFS supported a strong correlation between the Cu2O phase fraction and the formate peak intensity, with the maxima corresponding to where Cu2O was the only detectable phase at 170 degrees C, before the onset of reduction to Cu at 190 degrees C. The concurrent phase and crystallite size evolution were monitored by in situ XRD, which suggested that the CuO NPs were stable in size before the onset of reduction, with smaller Cu2O crystallites being observed from 130 degrees C. Further reduction to Cu from 190 C was followed by a rapid decrease of surface formate and the detection of adsorbed CO from 250 degrees C; these results are in agreement with heterogeneous catalytic tests where surface CO was observed over the same temperature range. Furthermore, CH4 was detected in correspondence with the decomposition of formate and formation of the Cu phase, with a maximum conversion rate of 2.8% measured at 470 degrees C (on completely reduced copper), supporting the indication of independent reaction pathways for the conversion of CO2 to CH4 and CO that was suggested by catalytic tests. The resulting Cu NPs had a final crystallite size of ca. 44 nm at 500 degrees C and retained a significantly active surface.

  • 3.
    González Arcos, Angélica Viviana
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Diomedi, Matteo
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Lanza, Roberto
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Engvall, Klas
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Effect of potassium electrochemical promotion in biomass-tar reformingManuscript (preprint) (Other academic)
  • 4.
    Haghighi Moud, Pouya
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Andersson, Klas J.
    Lanza, Roberto
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Engvall, Klas
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Equilibrium potassium coverage and its effect on a Ni tar reforming catalyst in alkali- and sulfur-laden biomass gasification gases2016In: Applied Catalysis B: Environmental, ISSN 0926-3373, E-ISSN 1873-3883, Vol. 190, p. 137-146Article in journal (Refereed)
    Abstract [en]

    Biomass conversion to syngas via gasification produces certain levels of gaseous by-products, such as tar and inorganic impurities (sulfur, potassium, phosphorus etc.). Nickel, a commonly used catalyst for hydrocarbqn steam reforming, suffers reduced reforming activity by small amounts of sulfur (S) or potassium (K), while resistance against deleterious carbon whisker formation increases. Nevertheless, the combined effect of biomass derived gas phase alkali at varying concentrations together with sulfur on tar reforming catalyst performance under realistic steady-state conditions is largely unknown. Prior to this study, a methodology to monitor these effects by precise K dosing as well as K co-dosing with S was successfully developed. A setup consisting of a 5 kW biomass fed atmospheric bubbling fluidized bed gasifier, a high temperature hot gas ceramic filter, and a catalytic reactor operating at 800 degrees C were used in the experiments. Within the current study, two test periods were conducted, including 30 h with 1 ppmv potassium chloride (KCl) dosing followed by 6 h without KCl dosing. Besides an essentially carbon-free operation, it can be concluded that although K, above a certain threshold surface concentration, is known to block active Ni sites and decrease activity in traditional steam reforming, it appears to lower the surface S coverage (theta(s)) at active Ni sites. This reduction in theta(s) increases the conversion of methane and aromatics in tar reforming application, which is most likely related to K-induced softening of the S-Ni bond. The K-modified support surface may also contribute to the significant increase in reactivity towards tar molecules. In addition, previously unknown relevant concentrations of K during realistic operating conditions on typical Ni-based reforming catalysts are extrapolated to lie below 100 mu K/m(2), a conclusion based on the 10-40 mu K/m(2) equilibrium coverages observed for the Ni/MgAl2O4 catalyst in the present study.

  • 5.
    Karatzas, Xanthias
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Jansson, Kjell
    Stockholm University.
    Dawody, Jazaer
    Volvo Technology.
    Lanza, Roberto
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Pettersson, Lars J.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Microemulsion and incipient wetness prepared Rh-based catalyst for diesel reforming2011In: Catalysis Today, ISSN 0920-5861, E-ISSN 1873-4308, Vol. 175, no 1, p. 515-523Article in journal (Refereed)
    Abstract [en]

    The role of the catalyst preparation technique was investigated for diesel reforming. Reverse microemulsion (ME) and incipient wetness (IW) techniques were used for the preparation of Rh-based monolithic catalysts that were employed for hydrogen generation of low-sulfur diesel via autothermal reforming (ATR). The washcoat of the tested catalysts consisted of 0.5 wt% Rh, 1 wt% Rh, and 1: 1 wt% Rh: Pt supported on gamma-alumina. All washcoats were deposited on 400 cpsi cordierite monoliths. The reaction condition was T(feed) = 650 degrees C, H(2)O/C similar to 2.5, O(2)/C similar to 0.49, TOS = 3 h, GHSV similar to 13 000 h(-1) and P = 1 atm. Fresh and aged powder samples of the catalyst were characterized by N(2)-BET, H(2) chemisorption, XRD, H(2)-TPR, O(2)-TPO and TEM. The activity results established that Rh and RhPt formulations, prepared by ME and IW, are highly active for ATR of diesel where fuel conversions above 92% were obtained. FTIR and NDIR analysis also showed that the highest formation of ethylene was found in the product gas stream from the bimetallic samples indicating that RhPt/Al(2)O(3) is less resistant towards carbon deposition. The latter observation was confirmed by O(2)-TPO analysis of the aged samples where high loads of coke were found both on the active metals and on the support. Interestingly, these effects were less significant on the ME samples. The characterization results clearly showed differences in morphology between the ME and the IW samples. N(2)-BET analysis showed that higher surface area, similar to 268-285 m(2)/g, was obtained with the ME samples. Also, H(2) chemisorption analysis showed that the rhodium dispersion was similar to 10% higher for the ME samples (H/Rh similar to 60-66%). XRD analysis showed that crystalline phases of gamma-alumina were present on all samples. The diffractograms also showed small traces of metallic Pt (similar to 16-30 nm) in the bimetallic samples. H(2)-TPR analysis, showed peaks ascribed to bulk rhodium oxides and rhodium aluminates. It was also noted that the addition of Pt on the support lowered the reducibility of the different rhodium species. TEM analysis performed on the fresh and aged ME and IW bimetallic samples showed mainly Rh(x)Pt(1-x) alloys with an average particle size of similar to 20-50 nm were present on the alumina support. Also, for the aged samples, no sintering effects were noted. Furthermore, rhodium was found to switch oxidation state from e. g. Rh(3+) to Rh(0) while Pt remained in the metallic state.

  • 6.
    Lanza, Roberto
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Bersani, Marco
    Conte, Luca
    Martucci, Alessandro
    Canu, Paolo
    Guglielmi, Massimo
    Mattei, Giovanni
    Bello, Valentina
    Centazzo, Massimo
    Rosei, Renzo
    Effect of Crystalline Phase and Composition on the Catalytic Properties of PdSn Bimetallic Nanoparticles in the PROX Reaction2014In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 118, no 44, p. 25392-25402Article in journal (Refereed)
    Abstract [en]

    We present a synthetic strategy for the preparation of palladiumtin alloy and intermetallic nanoparticles. Complexes of palladium(II) and tin(IV) precursors in oleylamine were thermally decomposed in an organic solution in the presence of reducing moieties, leading to the formation of monodispersed nanoparticles with varying crystallographic structures. We found that the nanoparticles crystalline structure closely follows the bulk material phase diagram. The nanoparticles were supported on Al2O3 and their reactivity tested as catalysts for the preferential oxidation of CO in excess of hydrogen (PROX). Different Pd/Sn and O-2/CO ratios have been investigated, and the structurereactivity correlation highlighted. With increasing tin content, the CO ignition temperature remarkably lowers and the CO conversion rate increases, up to the formation of intermetallic phases that concurrently determine a reduction in the catalyst activity; the selectivity of the pure palladium references is preserved.

  • 7.
    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.

  • 8.
    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.

  • 9.
    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.

  • 10.
    Lanza, Roberto
    et al.
    Università di Padova.
    Canu, Paolo
    Universita` di Padova, Dipartimento di Principi e Impianti di Ingegneria Chimica.
    Dalle Nogare, Daniela
    Universita` di Padova, Dipartimento di Principi e Impianti di Ingegneria Chimica.
    Gas Phase Chemistry in Cellulose Fast Pyrolysis2009In: Industrial & Engineering Chemistry Research, ISSN 0888-5885, E-ISSN 1520-5045, Vol. 48, no 3, p. 1391-1399Article in journal (Refereed)
    Abstract [en]

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

  • 11.
    Lanza, Roberto
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Eriksson, E.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Pettersson, Lars J.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    NOx selective catalytic reduction over supported metallic catalysts2009In: Catalysis Today, ISSN 0920-5861, E-ISSN 1873-4308, Vol. 147, p. S279-S284Article in journal (Refereed)
    Abstract [en]

    In this work we present the results obtained with 3 catalysts (Pt, Rh and Ag on alumina) tested in ranges of temperatures and gas hourly space velocities typical of diesel engines in real trucks. NO concentration was 500 ppm, C3H6 ranged between 500 and 2000 ppm, while oxygen was always 5%. All the catalysts were active and showed high conversions. Both Pt and Rh were active at low temperature (T-50 = 200-250 degrees C) but had quite high selectivity towards NO2. Silver was active at higher temperature, but showed very high selectivity towards N-2. A strong boosting effect on NO conversion was recorded if H-2 was added to the gas mixture.

  • 12.
    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.

  • 13.
    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.

  • 14.
    Montecchio, Francesco
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Persson, Henry
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology.
    Engvall, Klas
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Delin, Jack
    Scandinavian Centriair AB, Sweden.
    Lanza, Roberto
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology.
    Development of a stagnation point flow system to screen and test TiO2-based photocatalysts in air purification applications2016In: Chemical Engineering Journal, ISSN 1385-8947, E-ISSN 1873-3212, Vol. 306, p. 734-744Article in journal (Refereed)
    Abstract [en]

    An innovative system suitable for the abatement of VOCs (Volatile Organic Compounds), using photo catalysis under UV light, was designed and built. The design of the reactor is based on the stagnation point flow geometry and the fluid dynamics of the system was carefully investigated in order to avoid mass transfer limitations. The proportions of the elements in the reactor were adjusted in order to homogenize the UV irradiation on the catalyst surface. The supports used for the coating of the catalysts were aluminum plates in order to accurately reproduce industrial conditions. After each test, the catalytic plate was examined to evaluate the mechanical strength of the bonding between the catalyst powder and the metallic support. The coating proved to be sufficiently stable for tests in the designed set up. The potential scale-up of the features of the system was considered throughout the design and especially the power of the UV lamps was decided in order to be representative of the industrial cases. In order to evaluate the suitability of the system for catalysis investigations, various photocatalysts, both synthesized and commercial, were screened. Analyzing the activity results, using acetyl aldehyde as a model VOC, it was possible to evaluate clear differences between the samples and P90 proved to be the most active sample. All the aspects investigated in this work demonstrate that the design of the reactor is in accordance with the expectations and that the system is suitable for screening and testing of photocatalysts for VOCs removal applications.

  • 15.
    Moud, Pouya H.
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology.
    Andersson, K. J.
    Lanza, Roberto
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology.
    Pettersson, J. B. C.
    Engvall, Klas
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology.
    Effect of gas phase alkali species on tar reforming catalyst performance: Initial characterization and method development2015In: Fuel, ISSN 0016-2361, E-ISSN 1873-7153, Vol. 154, p. 95-106Article in journal (Refereed)
    Abstract [en]

    In thermochemical conversion of biomass to synthesis gas and biofuels, the effect of varying gas phase alkali concentrations on tar reforming catalyst performance in combination with gas phase sulfur and chlorine is largely unknown. The current study demonstrates a new methodology for investigating gas phase alkali adsorption and presents results for early stage adsorption on a Ni-based catalyst under realistic industrial conditions. The experiments were carried out using pine pellets as feedstock in a setup consisting of a 5 kW atmospheric bubbling fluidized bed gasifier, a high temperature hot gas filter and a catalytic reactor - all operating at 850 °C. A potassium chloride solution was atomized with an aerosol generator, and the produced submicrometer KCl particles were continuously introduced to the catalytic reactor where they rapidly evaporated to form KCl (g). The accurate dosing of gas-phase alkali was combined with elimination of transient effects in catalytic performance due to catalyst sintering and S adsorption, and results for K uptake in relation to sulfur uptake were obtained. Different KCl levels in the gas phase demonstrates different initial uptake of K on the catalyst surface, which at low K coverage (θK) is approximately linearly proportional to time on stream. The results also show a clear suppressing effect of sulfur adsorption on potassium uptake. Indications of a slow approach to K equilibration on the catalyst were observed. The potential of the developed methodology for detailed studies under close to industrial conditions is discussed.

  • 16.
    Scarabello, Andrea
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology.
    Dalle Nogare, D.
    Canu, P.
    Lanza, Roberto
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology.
    Partial oxidation of methane on Rh/ZrO2 and Rh/Ce-ZrO2 on monoliths: Catalyst restructuring at reaction conditions2015In: Applied Catalysis B: Environmental, ISSN 0926-3373, E-ISSN 1873-3883, Vol. 174-175, p. 308-322Article in journal (Refereed)
    Abstract [en]

    0.5% Rh catalysts on ZrO2 or CeO2-ZrO2, coated on monoliths were tested for partial oxidation of methane, (GHSV=100000h-1). We ran temperature cycles up to 850°C, varying the O2/CH4 ratio from 0.5 to 0.7. The catalysts were characterized by XRD, TPR/TPO, BET and chemisorption. ZrO2 required a long conditioning step, to reach stable performance, while the CeO2-ZrO2 catalyst quickly gained steady activity. The conditioning step is explained with a restructuring of the surface, with the metallic particles becoming smaller. Ceria lowers the ignition temperature by 60°C. At low temperature, ceria allows an increase in CH4 conversion and selectivity to syngas. At high temperature, the CeO2-ZrO2 catalyst significantly increases the CH4 conversion, compared to ZrO2, approaching 100%. However, the selectivity to syngas decreases below 80%. The syngas selectivity is higher at lower O2/CH4 ratio, at any temperature, but the absolute amount of syngas can be larger with more O2.

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