Transfer hydrogenation of cellulose-based oligomers over carbon-supported ruthenium catalyst in a fixed-bed reactor

Abstract

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. Fix that bed: The catalytic conversion of cellulose to sugar alcohols in high yield in a continuous flow fixed-bed reactor through hydrolytic transfer hydrogenation is described. Ru supported on activated carbon catalyses direct hydrogen transfer from 2-propanol to glucose without the involvement of hydrogen gas. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.