Ti3+ Tuning the Ratio of Cu+/Cu0 in the Ultrafine Cu Nanoparticles for Boosting the Hydrogenation Reaction

Abstract Hydrogenation of diesters to diols is a vital process for chemical industry. The inexpensive Cu + /Cu 0 ‐based catalysts are highly active for the hydrogenation of esters, however, how to efficiently tune the ratio of Cu + /Cu 0 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 0 and stabilize the Cu + by the TiOCu bonds in Ti‐doped SiO 2 supported Cu nanoparticle (Cu/Ti–SiO 2 ) catalysts for the high conversion of dimethyl adipate to 1,6‐hexanediol. In the synthesis of the catalysts, the Ti 4+ OCu 2+ bonds promote the reduction of Cu 2+ to Cu + by forming Ti 3+ O V Cu + (O V : oxygen vacancy) bonds and the amount of Ti doping can tune the ratio of Cu + /Cu 0 . In the catalytic reaction, the O vacancy activates CO in the ester by forming new Ti 3+ δ O R Cu 1+ δ bonds (O R : reactant oxygen), and Cu 0 activates hydrogen. After the products are desorbed, the Ti 3+ δ O R Cu 1+ δ bonds return to the initial state of Ti 3+ O V Cu + bonds. The reversible TiOCu bonds greatly improve the activity and stability of the Cu/Ti–SiO 2 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.