Biomass is regarded as an appropriate energy resource for the production of hydrogen due to its carbon-neutral nature and easy availability. In general, the flash pyrolysis of biomass to bio-oil and the followed steam reforming is proposed as a viable way for hydrogen production. Bio-oil is a complex mixture of organic compounds and its steam reforming is characterized with lots of difficulties. Steam reforming of the model components in bio-oil is much easier. Moreover, it can offer much information for preparing active catalysts and optimizing experimental conditions for steam reforming of a real bio-oil. Acetic acid is one of the main components in bio-oil and a safe hydrogen carrier due to its non-inflammable nature. Because of these special characteristics, steam reforming of acetic acid has been widely performed by different research groups.

Nickel and cobalt were the most widely used transition metals for various steam reforming reactions, and both of them were suggested as suitable materials because of their superior catalytic performances. However, the detailed comparisons of Ni and Co catalysts in terms of catalytic behaviors in acetic acid reforming reactions have not yet been reported. Besides, to the best knowledge of the researchers of the current study, the catalytic performances of Co/Al2O3, Fe/Al2O3, and Cu/Al2O3 catalysts in acetic acid reforming reaction also have not been checked in detail.

Researchers at the State Key Laboratory for Oxo Synthesis and Selective Oxidation have studied the catalytic behaviors of four Al2O3-supported transition metals catalysts, namely Co/Al2O3, Fe/Al2O3, and Cu/Al2O3 catalysts in steam reforming of acetic acid.

It is found that Ni/Al2O3 and Co/Al2O3 catalysts are active for acetic acid steam reforming while Fe/Al2O3 and Cu/Al2O3 catalysts present negligible activity. The difference can be attributed to the different cracking activity of the metals toward the C–C and C–H bonds of acetic acid molecule. Detailed comparisons in terms of catalytic activity, selectivity, and stability are carried out over Ni/Al2O3 and Co/Al2O3 catalysts. Distinct product distributions were observed between them. CH4 production was favored over Ni/Al2O3 catalyst at mild temperatures while CO production was favored over Co/Al2O3 catalyst at high temperatures, which were induced by the different reaction networks over the two catalysts. Moreover, in the stability tests, Ni/Al2O3 catalyst was much more stable than Co/Al2O3 catalyst. Serious coke deposition and oxidation of metallic phase led to the fast deactivation of Co/Al2O3 catalyst. On the contrary, much slower coke formation rates and metal sintering rates as well as much higher resistivity of active metal toward oxidation guaranteed the stability of Ni/Al2O3 catalyst.

The work has received support from the National Basic Research Program (also called 973 Program). And the report of the study has been published in Applied Catalysis B: Environmental (Applied Catalysis B: Environmental 99 (2010) 289–297).

Applied Catalysis B: Environmental paper