Zn-Co@N-Doped Carbon Derived from ZIFs for High-Efficiency Synthesis of Ethyl Methyl Carbonate: The Formation of ZnO and the Interaction between Co and Zn

Ya-Nan Miao,Li-Jing Gao,Xiang-Hai Song,Yuan Wang,Si-Quan Xu,Dong-Hui Pan,Guo-Min Xiao

doi:10.3390/catal9010094

Abstract

In this work, a series of Zn-Co@N-doped carbon materials were prepared by pyrolysis of Co/Zn-ZIF precursors under a N2 atmosphere and used for high-efficiency synthesis of ethyl methyl carbonate (EMC) from dimethyl carbonate (DMC) and diethyl carbonate (DEC). The Co to Zn molar ratio and calcination temperature were varied to study the physical and chemical properties of Zn-Co@N-doped carbon materials identified by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), Brunauer-Emmett-Teller (BET), inductively coupled plasma (ICP), thermogravimetric analysis (TG) and temperature programmed desorption (TPD) analysis. It was deduced that the formation of a ZnO crystalline structure and the interaction between zinc and cobalt providing weak basic sites and strong basic sites, respectively, in different samples significantly affected their catalytic performance. The catalyst activated the reaction most effectively when the Co to Zn molar ratio was 1.0 and calcination temperature was 600 °C. With the DMC to DEC molar ratio controlled at 1:1, a superior yield of around 51.50% of product EMC can be gained over catalyst ZnCo/NC-600 at 100 °C with 1 wt% catalyst loading in 7 h.

Highlights

Ethyl methyl carbonate (EMC) is the simplest asymmetric ester and an important intermediate in organic synthesis
Zn-Co@N-doped carbon materials labeled as ZnCox /NC-T (x represents the molar ratio, T is the mark of calcined temperature) were synthesized at room temperature using a simple method, as shown in Scheme 1
Represents the molar ratio of Co to Zn ranging from 0.6 to 1.4 and T is the mark of calcined temperature between 550 ◦ C and 700 ◦ C

Summary

Introduction

Ethyl methyl carbonate (EMC) is the simplest asymmetric ester and an important intermediate in organic synthesis. Considering security and environmental issues, the traditional method of producing EMC by methyl chloroformate and ethanol was abandoned. Transesterification between dimethyl carbonate (DMC) and ethanol with mild reaction conditions and a high utilization rate of atoms is the most common method for the preparation of EMC [6,7,8]. The disadvantages of the above route have contributed to the development of alternative methods, such as the transesterification reaction between dimethyl carbonate and diethyl carbonate (DEC), which is environmentally-friendly, with high atom utilization and mild reaction conditions. In the transesterification system, reactants and products can be directly used as co-solvents in the electrolyte without further separation [10,11]

Methods

Results

Conclusion