Production of hydrogen from bioethanol in Cu–Ni/NbxOy catalysts obtained by different preparation methods

• Hydrogen production without CO.
• Novel CuNi–Nb co-precipitated catalyst for ethanol steam reaction.
• Little quantity of CH4 is the only by-product on ethanol steam reaction.
• Presence of Cu2O on reduced catalyst was responsible for no CO formation.

Ethanol steam reforming for hydrogen production was evaluated using Cu–Ni/NbxOy catalyst prepared by ion exchange (IE), wet impregnation (WI) and co-precipitation (CP). The catalysts were characterized by textural analysis, chemisorption of H2 and N2O for metallic area determination, XDR (calcined and in situ reduced samples), TPR-H2, TPD-NH3, MET/EDX e TPO-O2. Differences in crystal structure and metal-support interaction have altered the reducibility of the catalysts, besides metal surface area and crystallite size of Cu and Ni. The catalytic tests, using ethanol:water molar ratio of 1:10, temperature of 450 and 500 °C, demonstrated high H2 yield and stability, except for the IE catalyst at 500 °C, which favored the ethylene formation by ethanol dehydration. The main route for H2 obtainment in all cases was ethanol decomposition. The temperature increasing up to 500 °C favored the by-product CH4 reforming. The weakest metal-support interaction on WI catalyst provided the fully reduced metal phase, however, support characteristics achieved by this preparation method led to the filamentous coke formation. TEM images showed that different crystalline structures of the support modified the mechanism of the reaction and consequently the type of coke deposited on the surface. The CP catalyst showed low coke deposition and no metal sintering, stoichiometric H2/CO2 ratio, less than 5% of CH4, and no CO, which makes it the best candidate for hydrogen production by ethanol steam reforming.