(348c) Hydropyrolysis of Lignin Using Pd/HZSM-5

The aim of this work was to study the formation of cycloalkanes from the hydropyrolysis of lignin with HZSM-5 and Pd/HZSM-5 catalysts. Cycloalkanes are important components of jet-fuels, and hydropyrolysis is proposed as a potential route for the conversion of lignin because: 1) the hydrogen medium promotes hydrodeoxygenation reactions, leading to hydrocarbons, and 2) the hydrogen caps reactive radicals resulting from the decomposition of lignin. These radicals would, otherwise, recombine to form char. We observed that palladium supported on HZSM-5 catalyzed hydrogenation and deoxygenation reactions that converted phenolic compounds into aromatic and cycloalkane molecules. This study analyzed the effect of the catalyst-to-lignin ratio, H₂ partial pressure, and temperature on the yields of hydrocarbons with HZSM-5 and Pd/HZSM-5. Pd/HZSM-5 produced 44% more aromatic hydrocarbons than HZSM-5 at a catalyst-to-lignin ratio of 20:1, 650ºC, and a constant H₂ partial pressure of 1.7 MPa. The presence of palladium led to significant difference in yields only at 1.7 MPa H₂ partial pressure. In addition, the hydropyrolysis temperature played a substantial role in the equilibrium conversion of hydrogenation reactions that led to cycloalkanes directly from lignin. In addition, a comparison of in-situ and ex-situ hydropyrolysis on hydrocarbon yield will be presented, with further details on the effect of temperature on the mechanistic pathways of these two upgrading pathways.