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

摘要

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 H-2 and N2O for metallic area determination, XDR (calcined and in situ reduced samples), TPR-H-2, TPD-NH3, MET/EDX e TPO-O-2. 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 degrees C, demonstrated high H-2 yield and stability, except for the IE catalyst at 500 degrees C, which favored the ethylene formation by ethanol dehydration. The main route for H-2 obtainment in all cases was ethanol decomposition. The temperature increasing up to 500 degrees 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 H-2/CO2 ratio, less than 5% of CH4, and no CO, which makes it the best candidate for hydrogen production by ethanol steam reforming. (C) 2016 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.