Catalytic transfer hydrogenation of cellulose to hydrocarbons using straight-chain aliphatic hydrocarbon as a solvent

Abstract

Catalytic transfer hydrogenation is effective for converting cellulose to liquid fuel. This method typically uses an alcohol or a cyclic compound as a liquid hydrogen resource. However, alcohol causes side reactions, and oxygen-containing compounds remain in liquid fuel. Cyclic compounds such as tetralin suppress side reactions, but negatively affect liquid fuel properties because of difficult cyclic compound-liquid fuel separation. Therefore, catalytic transfer hydrogenation of lignocellulose requires a hydrogen donor solvent that is easily separated or does not need to be separated from liquid fuel. Thus, we focused on the use of straight-chain aliphatic hydrocarbon as a solvent. When used with lignocellulose-based liquid fuel, straight-chain aliphatic hydrocarbon can remain in transportation fuel. In addition, a palladium catalyst added to this solvent is expected to behave as a hydrogen donor, because this catalyst dehydrogenates alkane while serving as a hydrogen resource. This expectation was investigated by using cellulose, a main component of lignocellulose, and hexadecane, as a straight-chain aliphatic hydrocarbon. Using this solvent for catalytic transfer hydrogenation resulted in suppressed formation of the solid residue and increased liquefied oil production. Because of this reaction, hexadecane dehydrogenation and the hydrogenation of ɤ-valerolactone and furfural from cellulose were promoted. The hydrocarbon (C10–44) yield in liquefied oil reached over 35 wt% of cellulose, and the liquefied oil was collected while still being mixed with hexadecane. Hexadecane served to extract the hydrocarbon derived from cellulose and acted as a hydrogen resource.