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Abstract: A Cu/CeO2/Al2O3 catalyst prepared by a single-step sol–gel method was studied for methanol steam reforming (SRM) to gain information on the oxidation state of Cu and the role of oxidized Cu species. The catalyst was tested in a new laboratory-made flow apparatus that allowed on-line analysis of the products and measurement of the oxidation state and dispersion of Cu in situ. The catalyst pre-reduced in H2 was more active and selective than the not pre-reduced one. The oxidation state, evaluated after SRM tests, suggested the presence of a layer of oxygen atoms on the metallic Cu surface. Treating the pre-reduced catalyst with H2O vapour at 250°C caused dissociative H2O chemisorption and led to a partial oxidation of Cu. The H2O oxidized sample reacted with CH3OH producing CO2 and H2 as long as oxygen was present on the Cu surface. The results support an oxidation–reduction mechanism. [Copyright &y& Elsevier]

Abstract: Cu/ZnO/Al2O3 catalysts (5–45 Cu at.%) derived from layered double hydroxide (LDH) precursors were studied for oxidative steam reforming of methanol (OSRM). The precursors were prepared by homogeneous precipitation with urea. The catalysts were obtained by thermal decomposition of the precursors and subsequent reduction in H2 stream. XRD, SEM, N2 adsorption, TPR and NH3 TPD techniques were employed for characterization. Catalytic activity tests were carried out in a fixed bed flow reactor at T =200–400°C, H2O/CH3OH/O2 molar ratios=1.1/1/0.12 (CH3OH concentration=17.8%), GHSV=6×104 h−1. Tests of simple steam reforming (SRM), partial oxidation (POM) and CH3OH decomposition (DEC) were also carried out. TPR measurements showed that redox properties depended on the composition of the samples and on the nature of the phases present in the precursors. The area of metallic Cu, measured by N2O passivation method, was correlated to Cu content. The size of Cu particles was smaller than 10nm for Cu content up to 18at.%. NH3 TPD measurements showed acid sites with a wide strength distribution, the strongest ones being mainly related to Al2O3 or Zn aluminate. Catalytic activity was influenced by the chemical composition: kinetic constants for OSRM varied unevenly with Cu surface area, while those for SRM increased with Cu surface area. A reaction mechanism agreeing with OSRM, SRM and DEC data was hypothesized. The mechanism involved an oxidation-reduction cycle of Cu and also the participation of the oxide matrix. [Copyright &y& Elsevier]

Abstract: A Cu/CeO2/Al2O3 catalyst (6.6% Cu, 13.8% Ce) based on a structurally organized mesoporous alumina was prepared by a new single-step sol–gel method starting from Al butoxide and Ce and Cu stearates. The sample was characterized by N2 adsorption, XRD, TPR and Cu dispersion measurements and tested as catalyst for the SRM (methanol steam reforming) and OSRM (methanol autothermal reforming) reactions. The material showed a huge surface area (360m2 g−1) and resulted to contain very dispersed CeO2 and CuO phases on a poorly crystalline alumina matrix. A highly dispersed Cu metallic phase was obtained after a reductive treatment with H2. Catalytic tests showed that the unreduced material was fairly active for the OSRM process, but the activity increases appreciably after the pre-reduction treatment. The activity for the OSRM process resulted high, in terms of hydrogen production rate, if compared with data on similar Cu/Ce/Al systems, but the activity for SRM, in the absence of oxygen was, on the other hand, very low. This behaviour was explained either considering the occurrence of H spillover or the CeO2 assisted oxidation of Cu to Cu+. [Copyright &y& Elsevier]