Transfer Hydrogenation of Cellulose-based Oligomers over Carbon-supported Ruthenium Catalyst in a Fixed-bed Reactor

摘要

Ru supported on activated carbon was found to be active for the transfer hydrogenation of cellulose oligomers, which were produced by the milling of acidulated microcrystalline cellulose. A C-6 sugar alcohol yield of 85% was obtained in less than 1h reaction time in a batch reactor. Optimum reaction conditions for transfer hydrogenation were determined as 180 degrees C and a pH above 2.2 using glucose as a substrate. Use of deuterium as a marker established that direct transfer of hydride species from 2-propanol to glucose occurs through the dihydride mechanism. Formation of molecular hydrogen from 2-propanol dehydrogenation was found to be a side reaction, with little influence on the glucose hydrogenation step. Conversion of cellulose oligomers to hexitols was also achieved in a continuous flow fixed-bed reactor with 36.4% yield at a liquid hourly space velocity of 4.7h(-1). The catalytic activity did not decrease even after 12h of the onstream reaction.