Zn-promoted synthesis of diphenyl carbonate via transesterification over Ti–Zn double oxide catalyst

Abstract

An environmentally friendly heterogeneous catalyst, Ti–Zn double oxide, was prepared using a sol–gel method and firstly used for the synthesis of diphenyl carbonate (DPC) via the transesterification of phenol and dimethyl carbonate. The catalyst exhibited excellent catalytic activity. Moreover, the effects of Ti to Zn molar ratio, calcination temperature and catalyst amount on the catalytic performances of Ti–Zn double oxide have been investigated. The characterization results of XRD, TGA–DSC, ICP-AES and NH3-TPD showed that amorphous TiO2 was the active sites, and amorphous ZnO was the promoter. Also the amount of Zn remarkably affected the acid amounts of the catalysts, and the calcination temperature not only influenced the acid amount, but also affected the acid strength. Besides, the weak surface acid sites were responsible for the synthesis of MPC and DPC, whereas the strong acid sites favored the formation of a by-product, anisole. The phenol conversion and the transesterification selectivity reached 41.2 and 98.2% over 0.3 g 5TiZn-250 for 8 h, respectively. Furthermore, the prepared catalyst could be reused for three runs without drastic decrease in activity. The slight decreased activity was attributed to the phase change of Ti–Zn double oxide and the leaching of Ti.