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We present a Pt/ZrO2 catalyst that can operate in the harsh conditions of methane oxidation without being deactivated by SO2. XPS analysis of 1%Pt/ZrO2 catalyst revealed the presence of stable Pt2+–Pt4+ and Pt2+–Zr4+ bifunctional catalytic sites of dipolar nature at the Pt–ZrO2 interface. These sites increase the probability of CH4 polarization, increasing the strength of their collision with the catalyst surface, lowering the C–H bond energy and facilitating the abstraction of the first hydrogen in adsorbed CH4. The resistance of the catalyst to deactivation by sulfur poisoning is explained considering the stronger interaction of SO2 with Pt2+–Zr4+ dipolar sites, presenting a higher dipolar electric potential than Pt2+–Pt4+, on which CH4 adsorption and oxidation occur.

Hydrogen production from ethanol steam reforming over xNi/15 %La2O3–10 %CeO2–γ-Al2O3 (x = 5, 10 and 15 wt %) catalysts was investigated with an ethanol:water = 1:3 feed composition. The results of catalysts characterization suggest that Ni metal particles have a strong metal support interaction with the promoters on the surface. Ethanol was completely converted to hydrogen and C1 products (CO, CO2, CH4) even at 723 K due to the remarkable C–C bond cleavage capacity and resistance to coke formation conferred by the promoters at low metal loadings. The increase of Ni particle size decreases the stability and selectivity; catalyst deactivation during 24 h on stream was attributed to coke deposition.

The hydrogenation of CO to hydrocarbons is investigated over zirconia iron-based catalysts prepared by co-precipitation. These catalysts, in which the Fe-content varied between 0 and 100 %, were tested in the CO hydrogenation reaction under fixed reaction conditions (H2/CO = 2, T = 250 °C, P = 20 bar, GHSV = 0.0083 L/g.s.). The resulting activity data indicated that CO conversion is strongly dependent on the iron contents of the catalysts. The lowest CO conversion (, M. Al-Dossary gratefully acknowledges financial support from SABIC-Saudi Arabia for PhD program.

Recently, gold has been proposed as an active phase for the hydrogenation of nitro-arenes. This metal has been rarely used in hydrogenation reactions because gold does not possess hydrogen chemisorption capacity. However, small gold particles behave differently and they may be able to chemisorb hydrogen to same extent, leading to possible activity in hydrogenation reactions. This may provide an advantage because the reactions catalyzed by highly dispersed gold particles may be better controlled. In this work, TiO2 and SiO2 supported Au catalysts were prepared by the deposition–precipitation method using urea and NaOH to precipitate the metallic component at different temperatures and hydrogen pressures. The metal loading for all the catalysts was 1 wt%. The catalysts were characterized by X-ray diffraction, high resolution transmission electron microscopy among others. The catalysts were then evaluated in the hydrogenation of nitrobenzene in a batch type reactor at 25 °C. All the catalysts were active in the hydrogenation reaction and the major obtained product was aniline.Gold Nitrobenzene Hydrogenation Heterogeneous, The authors thank the Project FONDECYT 1100259 for funding this research. C. Torres and C. Campos are grateful to CONICYT for their doctoral Fellowship. We also thanks to REDOC.CTA Universidad de Concepción.

The synergistic effect between Co//Mo and Co//W stacked bed systems in the hydrodesulphurization (HDS) of 4,6-dimethyldibenzothiophene (4,6-DMDBT) was studied. The reaction was carried out in a high-pressure continuous-flow microreactor at 3 MPa and 300 °C. The observed synergism can only be explained by the action of hydrogen spillover (HSO). The selectivity in hydrogenation over direct desulphurization pathways (HYD/DDS) of Mo/γ-Al2O3 and W/γ-Al2O3 catalysts increased when the reaction was carried out in Co//Mo and Co//W stacked bed systems, respectively. The changes in selectivity can be explained by the fact that hydrogen spillover does not only create more active sites, but it also modifies the sites, favouring the HYD pathway. Differences in synergistic effect between Co//Mo and Co//W stacked bed systems were related to the higher degree of sulphurization of the molybdenum compared to the tungsten phase, as detected by XPS.

Perovskite-type oxides such as La1−x Ca x NiO3 (x = 0.0, 0.05, 0.1, 0.3, 0.5 and 0.8) have been prepared from citrate precursors and characterized by XRD, TPR, TG-H2 and XPS. Catalytic experiments in the reforming of CH4 with CO2 have been carried out in a tubular reactor at 750 °C and atmospheric pressure. After the catalytic tests the catalysts were studied by TPO and SEM. Partial substitution of La by Ca was performed to stabilize Ni particles and to prevent carbon deposition. The XRD profiles showed that the perovskite structure is the only compound identified within the 0 ≤ x ≤ 0.05 range, whereas for x ≥ 0.1 compounds such as spinel-type La2NiO4, NiO and CaO were observed in addition to the perovskite oxide. On the other hand, segregation of NiO, even in the unsubstituted perovskite (x = 0.0), was confirmed by TPR and XPS. The catalytic tests showed that the replacement of La by Ca, which has a lower ionic radius, favored a higher activity and stronger resistance to carbon deposition. However, this coking resistance depended on the Ca-loading and the catalysts with x = 0.05 and x = 0.8 were the most stable against deactivation.

The effect of Re and Ge addition to Pt/Al2O3 was studied. Mono-, bi- and a trimetallic catalysts were prepared and characterized by TPR, XPS, TPO and by the n-pentane, cyclohexane (CH) and n-octane reactions. It was found that the trimetallic was the most active and stable catalyst and showed selectivities to aromatics and isomers very similar to the bimetallic germanium-based catalyst. Fil: Souza Santos, M.C.. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Investigaciones en Catálisis y Petroquímica "Ing. José Miguel Parera". Universidad Nacional del Litoral. Instituto de Investigaciones en Catálisis y Petroquímica "Ing. José Miguel Parera"; Argentina Fil: Grau, Javier Mario. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Investigaciones en Catálisis y Petroquímica "Ing. José Miguel Parera". Universidad Nacional del Litoral. Instituto de Investigaciones en Catálisis y Petroquímica "Ing. José Miguel Parera"; Argentina Fil: Pieck, Carlos Luis. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Investigaciones en Catálisis y Petroquímica "Ing. José Miguel Parera". Universidad Nacional del Litoral. Instituto de Investigaciones en Catálisis y Petroquímica "Ing. José Miguel Parera"; Argentina Fil: Parera, Jose. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Investigaciones en Catálisis y Petroquímica "Ing. José Miguel Parera". Universidad Nacional del Litoral. Instituto de Investigaciones en Catálisis y Petroquímica "Ing. José Miguel Parera"; Argentina Fil: Fierro, J.L.G.. Instituto de Catálisis y Petroleoquímica; España Fil: Figoli, Nora Susana. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Investigaciones en Catálisis y Petroquímica "Ing. José Miguel Parera". Universidad Nacional del Litoral. Instituto de Investigaciones en Catálisis y Petroquímica "Ing. José Miguel Parera"; Argentina Fil: Rangel, Maria do Carmo. Universidade Federal da Bahia; Brasil

A 10 wt% Co/SiO2 catalyst was prepared by the incipient wet-impregnation method and tested in Fischer–Tropsch synthesis in a slurry reactor under conditions approaching industrial practice. The catalyst precursor was investigated by X-ray diffraction (XRD), temperature-programmed reduction (TPR), transmission electron microscopy (TEM) and photoelectron spectroscopy (XPS). The XPS and XRD techniques revealed the presence of a crystalline Co3O4 spinel-type phase, while-in addition-TEM and XPS analyses pointed to the formation of another amorphous Co3O4 spinel phase, both species interacting weakly with the silica substrate. The influence of total pressure on the conversion, selectivity and stability of the catalyst was studied. Upon increasing the overall pressure from 20 to 40 bar, not only activity increased but also the catalyst are not deactivating. These results are explained in terms of an increase of gases solubility in the solvent, this increment of CO concentration in the liquid phase favours carbonyl species formation and the cobalt particles segregation that implies an increase in the metal surface area.

Gold nanoclusters on TiO2 powder were prepared from adsorbed AuIII(CH3)2(C5H7O2) (dimethyl acetylacetonate gold(III)) and characterized by extended X-ray absorption fine structure (EXAFS) and X-ray absorption near edge structure (XANES) spectroscopies. The samples were tested as catalysts for CO oxidation at 298 K and atmospheric pressure and characterized by EXAFS and XANES with the catalysts in the working state. The XANES results identify Au(III) in the initially prepared sample, and the EXAFS data indicate mononuclear gold complexes as the predominant surface gold species in this sample, consistent with the lack of Au–Au contributions in the EXAFS spectrum. The mononuclear gold complex is bonded to two oxygen atoms of the TiO2 surface at an Au–O distance of 2.16 A. Treatment of this complex in He or in H2 at increasing temperatures led to formation of metallic gold clusters of increasing size, ultimately those with an average diameter of about 15 A. The data demonstrate the presence of metallic gold clusters in the working catalysts and also show these clusters alone are not responsible for the catalytic activity.

The liquid-phase stereoselective hydrogenation of phenyl alkyl acetylenics at 298 K and atmospheric pressure on Pd-supported catalysts has been studied. The catalysts were prepared by impregnation of Pd(acac)2 precursor (1 wt% of Pd) on different siliceous substrates such as amorphous SiO2, mesoporous MCM-41 and silylated MCM-41. The poisoning effect of lead incorporation on the supported palladium was also studied. All the catalysts displayed high selectivity to cis-alkene isomer, with Pd/MCM-41 being the most active catalyst. Deliberately adding lead to the base, palladium catalysts underwent changes in the selectivity to cis-alkene isomer and a significant drop in the activity. All the solids were characterized by nitrogen adsorption–desorption isotherms at 77 K, TGA, TPR, H2 and CO chemisorption, XRD, XPS, and TEM.

Zirconia-supported and bulk-mixed vanadiumantimonium oxide catalysts were used for the oxidation of o-xylene to phthalic anhydride. X-ray diffraction, Raman spectroscopy and photoelectron spectroscopy were used for characterization. It was found that vanadium promotes the transition of tetragonal to monoclinic zirconia. The simultaneous presence of Sb and V on zirconia at low coverage led to a preferential interaction of individual V and Sb oxides with the zirconia surface rather than the formation of a binary Sb-V oxide, while at higher Sb-V contents the formation of SbVO4 took place. Sb-V/ZrO2 catalysts showed high activity for o-xylene conversion and better selectivity to phthalic anhydride as compared to V/ZrO2 catalysts. However, their selectivity to phthalic anhydride was poor in comparison to a V/TiO2 commercial catalyst. The improved selectivity of the Sb-containing catalysts is attributed to the blocking of non-effective surface sites of ZrO2, the decrease of the total amount of acid sites and the formation of surface V-O-Sb-O-V structures.

Supported nickel catalysts were prepared by impregnation of La2O3, MgO and ZrO2 substrates and tested in the partial oxidation of methane to synthesis gas at atmospheric pressure. Nickel interacted strongly with La2O3 forming a deficient LaNiO3-δ perovskite structure upon calcination. Upon reduction at 973 K, the Ni/La2O3 catalysts that resulted were highly active and selective for syngas production. By contrast, a separate and readily reducible NiO phase was formed on the ZrO2 support. Because the interaction of metallic nickel particles on ZrO2 is weak, the catalysts underwent deactivation by sintering of metal particles during on-stream operation as confirmed by photoelectron spectroscopy. The relatively high activity of the Ni/MgO systems was associated with the formation of a highly stable cubic Ni-Mg-O solid solution, in which nickel remains highly dispersed during the methane partial oxidation reaction.