Hydrogen production from biomass-derived oil over monolithic Pt- and Rh-based catalysts using steam reforming and sequential cracking processes

摘要

The conversion of biomass-derived crude oil towards H2 production was investigated using continuous catalytic steam reforming and sequential cracking/reforming processes.The performances of Pt/Ce0.5Zr0.5O2 and Rh/Ce0.5Zr0.5O2 catalysts deposited on cordierite monoliths were comparatively studied.The Pt-based catalyst showed better catalytic activity than Rh for steam reforming in the whole range of steam-to-carbon molar ratios (S/C) studied,the amount of added water determining the H2 yield for both noble metals.The best H2 yield (70%,corresponding to ~49 mmol of H2/g of bio-oil) was obtained with the Pt catalyst at S/C ratio of 10 at 780 °C,with CH4 concentrations below 1%.In the case of sequential cracking,the process alternated cracking steps,during which the bio-oil is converted into H2,CO,CO2,CH4 and carbon stored on the catalyst,with regeneration steps where the deposited coke was burnt under O2.Comparison with thermal bio-oil cracking showed that the catalyst plays a major role in enhancing the H2 productivity up to 18 mmol of H2/g of bio-oil (~50% of H2 in gaseous products stream) and lowering the CH4 formation.The steam reforming offers high yields towards H2 but is highly endothermic,whereas the sequential cracking,despite lower H2 yields,offers a better control of coke formation and catalyst stability,and due to lower energy input can theoretically run auto-thermally.