Reaction mechanism of in-situ vaporization catalytic reforming of aqueous bio-oil for hydrogen production

In order to explore the reaction mechanism of aqueous bio-oil catalytic reforming with an in-situ vaporization strategy, eight representative components of the aqueous bio-oil were selected as models to carry out experiments with a Ni/Al2O3 catalyst. The results showed high reforming conversion rates of the eight model compounds. However, the catalysts in the reaction system of methyl acetate and furfural showed obvious deactivation from the beginning of the reaction. The gas production characteristics at the start of the reaction indicated that the oxygen atoms in these molecules adsorbed by the oxygen vacancies on the catalyst surface were the key step to trigger the reforming reaction, and the [∗OH]ads adsorbed on the catalyst surface was the fuse to ignite the reforming reaction. Ethanol and acetone were typical intermediates in the catalytic reforming process of the eight compounds and were detected in the liquid products after the reaction. The characterization of coke on the catalyst surface showed that, at least two forms of coke were produced during catalytic reforming of the aqueous bio-oil. The fibrous coke resulting in the rapid deactivation of the catalyst was primarily derived from the components rich in “CO”. [C–CO] was the smallest unit generating fibrous coke, and the presence of [∗OH]ads significantly inhibited the growth of fibrous coke. This paper revealed the trigger mechanism and coke behavior of catalytic reforming of aqueous bio-oil for hydrogen production, providing an important theoretical basis for designing efficient catalysts and the subsequent process optimization.