On the activity of bimetallic catalysts for ethanol steam reforming

摘要

The performance of CeO_2-supported Pt-Ni and Pt-Co catalysts in the low temperature-Ethanol Steam Reforming (ESR) reaction has been evaluated studying the effect of the preparation method (impregnation/coprecipitation) and parameters such as dilution ratio, temperature, water-to-ethanol feed ratio and Gas Hourly Space Velocity (GHSV). The re-sults show that impregnated samples perform better. In particular, the Pt/Ni/CeO_2 catalyst starting from 350 ℃ leads to a products distribution very close to the equilibrium calcu-lations, with a low CO content that is ideal for fuel cells devices. In addition, the Co-based catalysts appear attractive in terms of hydrogen yield and coking tendency. For the Pt/Ni sample at 370 ℃, the analysis of products distributions vs contact time suggests a surface reaction path involving ethanol dissociative adsorption, dehydrogena-tion to acetaldehyde at short contact time (5-40 ms), followed by decomposition, reforming and CO-WGS reactions, to obtain H_2, CH_4, CO_2 and CO. The last step is the methanation reaction, occurring at contact times higher than 100 ms, which drives the system to the equilibrium.