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The effect of Ag (1 wt%) and Au (1 wt%) on the catalytic properties of Ni/Al 2 O 3 (7 wt% Ni) for methane steam reforming (MSR) was studied in parallel with the effect of CeO 2 (6 wt%) and La 2 O 3 (6 wt%) addition. The addition of 1 wt% Ag to the alumina supported nickel catalyst drastically decreased its catalytic properties at temperatures lower than 600°C, due to the blockage of metal catalytic centers by silver deposition. The addition of Au and CeO 2 (La 2 O 3 ) to the nickel catalyst improved the methane conversion, CO 2 selectivity and hydrogen production at low reaction temperatures (t \ 600°C). At 700°C under our working conditions, the additives have no important effect in hydrogen production by MSR. The best hydrogen production at low temperatures was obtained for Ni-Au/Al 2 O 3 , due to the higher CO 2 selectivity, cumulated with slightly higher methane conversion in comparison with Ni/CeO 2 -Al 2 O 3 . At high temperature, Ni/CeO 2 -Al 2 O 3 is stable for 48 h on stream. are mainly deactivated due to the temperature effect on Au and Ag nanoparticles and less through coke formation. On , crystalline, graphitic carbon was deposited after 48 h of reaction leading to catalyst partial deactivation. On the Ni/CeO 2 -Al 2 O 3 surface, a porous amorphous form of deposited carbon was found, which does not decrease its catalytic activity after 48 h of reaction.Electronic supplementary material The online version of this article (

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Ni/oxide-SiO2 (oxide: MgO, CeO2­, La2O3, 10 wt.% target concentration) catalyst samples were prepared by successive impregnation of silica matrix, first with supplementary oxide, and then with Ni (10 wt.% target concentration). The silica matrix with multimodal pore structure was prepared by solvothermal method. The catalyst samples were structurally characterized by N2 adsorption-desorption, XRD, SEM/TEM, and functionally evaluated by temperature programmed reduction (TPR), and temperature programmed desorption of hydrogen (H2-TPD), or carbon dioxide (CO2-TPD). The addition of MgO and La2O3 leads to a better dispersion of Ni on the catalytic surface. Ni/LaSi and Ni/CeSi present a higher proportion of moderate strength basic sites for CO2 activation compared to Ni/Si, while Ni/MgSi lower. CO2 methanation was performed in the temperature range of 150–350 °C and at atmospheric pressure, all silica supported Ni catalysts showing good CO2 conversion and CH4 selectivity. The best catalytic activity was obtained for Ni/LaSi: CO2 conversion of 83% and methane selectivity of 98%, at temperatures as low as 250 °C. The used catalysts preserved the multimodal pore structure with approximately the same pore size for the low and medium mesopores. Except for Ni/CeSi, no particle sintering occurs, and no carbon deposition was observed for any of the tested catalysts.