The ethanol steam reforming over Cu-Ni/SiO2 catalysts: Effect of Cu/Ni ratio

The operating conditions of SRE (steam reforming of ethanol) reaction were evaluated by thermodynamics, in considering of the application requirements in hydrogen concentration and energy consumption. Under the select operating conditions, 5% CuNi/SiO2 catalysts with different Cu/Ni ratios prepared through incipient-wetness co-impregnation were tested for SRE. The catalysts were reduced with NaBH4 at room temperature, and again reduced by H2 at 623 K prior to temperature-programmed SRE testing to remove surface oxygen. The SRE reaction products indicate a reaction scheme involving ethanol dehydrogenation to acetaldehyde, wherein acetaldehyde steam reforming and acetaldehyde decomposition compete, and with subsequent CO conversion to CO2 via water gas shift reaction. The catalysts with Cu/Ni ≥ 1 showed higher ethanol conversion, higher acetaldehyde conversion, higher selectivity of acetaldehyde steam reforming, and lower coking at temperatures below 673 K than the Ni-rich catalysts. Analyses by XRD, XPS, and EXAFS indicate that the Cu-rich catalysts had formed an alloy structure with Ni-enriched surface. The catalyst with Cu/Ni = 1 showed the highest performance in ethanol conversion, acetaldehyde conversion, the selectivity of acetaldehyde steam reforming, and the stability against particle sintering.

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• The prepared 5% CuNi/SiO2 catalysts showed the highest performance for ESR when Cu/Ni = 1.
• The CuNi/SiO2 catalyst with Cu/Ni = 1 had low coking and particle sintering tendencies during ESR.
• The relative selectivity of each reaction pathway of ESR was quantitatively analyzed.
• The CuNi/SiO2 catalyst with Cu/Ni = 1 had the smallest metal particles and Cu and Ni formed alloy.