Ti Tuning the Ratio of Cu /Cu in the Ultrafine Cu Nanoparticles for Boosting the Hydrogenation Reaction.

Hydrogenation of diesters to diols is a vital process for chemical industry. The inexpensive Cu /Cu -based catalysts are highly active for the hydrogenation of esters, however, how to efficiently tune the ratio of Cu /Cu and stabilize the Cu is a great challenge. In this work, it is demonstrated that doped Ti ions can tune the ratio of Cu /Cu and stabilize the Cu by the TiOCu bonds in Ti-doped SiO supported Cu nanoparticle (Cu/Ti-SiO ) catalysts for the high conversion of dimethyl adipate to 1,6-hexanediol. In the synthesis of the catalysts, the Ti OCu bonds promote the reduction of Cu to Cu by forming Ti O Cu (O : oxygen vacancy) bonds and the amount of Ti doping can tune the ratio of Cu /Cu . In the catalytic reaction, the O vacancy activates CO in the ester by forming new Ti O Cu bonds (O : reactant oxygen), and Cu activates hydrogen. After the products are desorbed, the Ti O Cu bonds return to the initial state of Ti O Cu bonds. The reversible TiOCu bonds greatly improve the activity and stability of the Cu/Ti-SiO catalysts. When the content of Ti is controlled at 0.4 wt%, the conversion and selectivity can reach 100% and 98.8%, respectively, and remain stable for 260 h without performance degradation.