Preparation of Ca–Zn–Al Oxides and Their Catalytic Performance in the One-Pot Synthesis of Dimethyl Carbonate from Urea, 1,2-Propylene Glycol, and Methanol

Abstract

A series of Ca–Zn–Al oxides were prepared by different methods and their structures, compositions, and basicities were characterized by means of X-ray diffraction (XRD), N2 adsorption–desorption, inductively coupled plasma-atomic emission spectrometry (ICP-AES), and CO2 temperature-programmed desorption (TPD). CO2 TPD analysis showed that all of the prepared Ca–Zn–Al oxides had both weak base sites and strong base sites, but their base amounts were different. The weak base sites were provided by the Zn–Al oxides, whereas the strong base sites were due to CaO. Ca–Zn–Al oxides with different base distributions could be prepared by varying the molar ratios of Zn/Al and Ca/Al. The Ca–Zn–Al oxides showed excellent catalytic performances for the one-pot synthesis of dimethyl carbonate (DMC) from urea, 1,2-propylene glycol (PG), and methanol: The yield of DMC could reach 82.9% under appropriate reaction conditions. However, the catalytic performance of the recovered catalyst decreased dramatically, mainly becaus...