Hydrogenolysis Of Sorbitol To Lower Glycols Over Ru/CNFs Catalysts

It is generally accepted that the substitution of fossile hydrocarbons by biomass, especially sorbitol may possibly be a source of raw materials for the chemical industry with heavy demands for propylene glycol and ethylene glycol. Over the past decades, considerable amounts of academic researches on the hydrogenolysis of sorbitol have been reported, mainly focusing on the mechanism of bond cleavage. Previous research in our laboratory has showed that CNFs (carbon nanofibers)-surpported Ru catalyst exhibited high catalytic activity. Furthermore, the addition of base has been reported to enhance the conversion of sorbitol. However, the role of base in sorbitol hydrogenolysis is still unclear.Based on the previous work in our laboratory, the role of base was carefully investigated in sorbitol hydrogenolysis over Ru/CNFs. The effects of the kind and amount of base additives were discussed in combination with a reaction mechanism. The base additive in sorbitol hydrogenolysis was defined as a promoter. The promoting action of CaO in sorbitol hydrogenolysis was resulted from combined effects of compexation and base-catalyzed retro-aldol reaction. With detailed knowledge of the reaction mechanism and an understanding of the bases affecting selectivity, an optimum condition for higher sorbitol conversion and glycol selectivities was obtained.A series of hydrotalite precursor supported Ru catalysts were prepared and used for sorbitol hydrogenolysis in a base-free solution. With highly dispersed Ru particles and strong alkalinity, hydrotalite supported Ru catalyst exhibited high performance. Comparied with Ru/CNFs in basic solution, the selectivity to glycols is higher. What's more, the reaction mixture was easy to be processed.The effect of S on the catalystic performance of Ru/CNFs was investigated by introducing S into the system in two ways. The results indicated that Ru dispersion was decreased with the increasing amount of S, which resulted in the reduction of sorbitol conversion. It was believed that S was detrimental to sorbitol conversion due to the poisoning of Ru/CNFs by S.