The catalytic transfer hydrogenation (CTH) of glucose to sorbitol has been studied using a wide collection of different biomass-derived alcohols and diols as hydrogen donors. Catalytic activity results reflect the feasibility to conduct this transformation in the presence of conventional, commercially available Raney Ni-type sponges as catalysts. Sacrificial diols displayed a superior performance as hydrogen donors as compared to short-chain alcohols, including secondary alcohols. Among them, terminal diols such as 1,4-butanediol and 1,5-pentanediol were revealed as excellent hydrogen donors, providing a high selectivity in the conversion of glucose into sorbitol. As for the catalysts, molybdenum promotion provided a very high catalytic activity to sponge nickel catalysts, even under mild temperature conditions. The transformation was also studied in a fixed-bed reactor under continuous-flow operation conditions. Results demonstrate that the catalysts are highly stable and able to operate for at least 550 h on stream with a high selectivity in the CTH of glucose to sorbitol.

Sn-USY materials have been prepared through an optimized post-synthetic catalytic metalation procedure. These zeolites displayed, upon ion exchange with alkaline metals, an outstanding activity in the direct transformation of glucose into methyl lactate, yielding more than 70% of the starting glucose as the target product, and an overall combined retro-aldol condensation product yield above 95% in a short reaction time (<4 h). This outstanding catalytic performance is ascribed to the neutralization of Brønsted acid sites, the consequent depression of side reactions, and a higher population of tin open sites in the ion-exchanged Sn-USY zeolites. Reusability tests evidenced some loss of catalytic activity, partially caused by the closing of tin sites, although the use of small amounts of water in the reaction media demonstrated that this deactivation mechanism can be, at least, partially alleviated.

Long-term liquid phase studies of the activity in the formic acid-mediated hydrogenation of MA to SA were conducted in a fixed bed continuous reactor for two relevant situations: neutralising maleic...