Catalytic pyrolysis of individual components of lignocellulosic biomass

Abstract

We report on the catalytic pyrolysis of switchgrass and its three main components (cellulose, hemicellulose and lignin) over H-ZSM5 catalyst. The yields of aromatic hydrocarbons for the three components decreased in the following order: cellulose > hemicellulose ≫ lignin. Moderately higher temperature favored formation of aromatics. The results indicate that H-ZSM5 catalyst did not remove oxygen in an optimal pathway for catalytic pyrolysis of biomass. Dehydration was the dominant oxygen removal mechanism for catalytic pyrolysis, while decarbonylation to CO was favored over decarboxylation to CO₂. This suggests that higher yields of aromatics might be achieved by catalyst improvements or reactor design that optimizes deoxygenation pathway. For cellulose and hemicellulose, coke produced catalytically contributed a larger fraction of solid carbonaceous residue than char from purely thermal processes. In the case of lignin, thermal rather than catalytic processes primarily contribute to the production of solid carbonaceous residue. Product distribution from catalytic pyrolysis of switchgrass appeared to be the additive contribution of the three individual components, which indicates that there was no significant interaction among the biomass-derived products.