The Effect of Hydrogen-Donor Agent in Catalytic Pyrolysis of Lignin to Hydrocarbons

 Xianglan Bai¹, Shuai Zhou², Robert C. Brown¹

¹Department of Mechanical Engineering, Iowa State University, Ames, IA 50011, USA

²Bioeconomy Institute, Iowa State University, Ames, IA 50011 USA

Catalytic pyrolysis of lignin using zeolite as the catalyst is known to convert lignin into aromatic hydrocarbons. However the yield of the aromatic is usually low and deactivation of catalyst is problematic. Our previous study showed that reactive phenols derived from lignin during fast pyrolysis subsequently repolymerize in the vapor phase. Therefore it is important to stabilize the reactive phenols prior to following catalytic upgrading. In the present study, lignin is co-pyrolyzed with tetralin in a tandem micropyrolyzer. Tetralin is capable of releasing hydrogen atoms at atmosphere pressure, thus high pressure is not required. The pyrolysis vapor is then sent to a downstream catalytic bed that is filled with HY or HZSM-5 zeolite. It is found that the presence of the hydrogen-donor agent promotes saturation of vinylphenol, demethoxylation and demethylation of phenols. Catalytic upgrading of the stabilized pyrolysis vapor improves hydrocarbon yield from lignin and inhibites coke formation on catalyst. Saturation of vinyl groups and demethoxylation by hydrogen-donors contributes to the observed changes.