Steam reforming of acetic acid over Ni/biochar catalyst treated with HNO_3: Impacts of the treatment on surface properties and catalytic behaviors

摘要

Biochar is a major product from the pyrolysis of biomass, which can be potentially used as the low costly support of nickel catalyst for steam reforming reactions. In this study, the rice husk-derived biochar supported nickel catalysts were prepared and the impacts of the treatment of the biochar support with HNO3 on catalytic performance of the Ni/biochar catalysts in steam reforming of acetic acid were investigated. The results showed that the treatment of the biochar with the varied concentration of HNO3 led to the change of the hydrophilicity, the pore structure, distribution of functionalities on surface of biochar, weakening of the interaction between nickel and biochar, increased size of metallic nickel, decreased lower nickel dispersion and enhanced abundance and strength of acidic sites. Among these aspects, the hydrophobicity showed the most significant effects on the catalytic activity for steam reforming of acetic acid. The Ni/biochar catalyst with medium hydrophobicity showed superior catalytic activity, as it showed capability for strong adsorption of the reaction intermediates with the C-O-C aliphatic structures and for gasification of the reaction intermediates with carbonyl functionalities. The Ni/biochar catalyst with too high hydrophobicity could not effectively gasifying the intermediates bearing C=O and showed the low activity and high coking tendency.