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

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 C6 sugar alcohol yield of 85 % was obtained in less than 1 h reaction time in a batch reactor. Optimum reaction conditions for transfer hydrogenation were determined as 180 °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 4.7 h−1. The catalytic activity did not decrease even after 12 h of the onstream reaction.