The Reaction Mechanism of Bio-oil Model Compound Steam Reforming for Hydrogen Production Over an Ni-Co/Ce-Zr-O Catalyst

Abstract

Ni-Co/Ce-Zr-O catalyst was prepared by incorporating sol-gel and wet impregnation methods. Meanwhile, mechanism of methanol and acetone (model compound derived from bio-oil) catalytic steam reforming over Ni-Co/Ce-Zr-O catalyst were studied. The results indicated that methanol was first absorbed by Ce at the catalyst Ni-Co/Ce-Zr-O and transformed into methoxyl species. Methoxyl group further dehydrogenation produced formate. Part of the formate separating from the Ce atom was combined with the absorbed H atoms to form formic acid. The others were transformed into absorbed CO2 after further liberating hydrogen. Finally, absorbed CO2 separated from the catalyst. The mechanism of acetone catalytic steam reforming is as follows: first of all, the water molecule is broken up into OH and H under the synergic effect of the carrier and the metal. The OH species is then absorbed by Ce3+, and the H species is absorbed by active metal. Next, the carbonyl group of acetone is absorbed by OH, which is linked to Ce atom, while the methyl of acetone is absorbed by Ni atom; meanwhile hydrogen is released. After that, CO2 releases by breaking of the Ce–O bond, then part of the methyls absorbed from the neighboring Ni atoms polymerize to produce C2H4; the others, after water assisted decomposition, produce CO2 and H2.