Ti<sup>3+</sup> Tuning the Ratio of Cu<sup>+</sup>/Cu<sup>0</sup> in the Ultrafine Cu Nanoparticles for Boosting the Hydrogenation Reaction
Ziyang Zhang, Zhongli Wang, Kang An, Jiaming Wang, Siran Zhang, Pengfei Song, Yoshio Bando, Yusuke Yamauchi, Yuan Liu
Abstract
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 TiOCu 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+ OCu 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 CO 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 TiOCu 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.