Insights into a New Formation Mechanism of Robust Cu/SiO2 Catalysts for Low-Temperature Dimethyl Oxalate Hydrogenation Induced by a Chelating Ligand of EDTA

Tianyou Li,Long Huang,Jiankai Cheng,Ling Lin,Jinxia Yang,Runping Ye,Yuangen Yao,Yeyan Qin,Peng Zhang,Chongchong Chen

doi:10.3390/catal12030320

Abstract

The Cu/SiO2 catalyst has been widely used in dimethyl oxalate (DMO) hydrogenation due to its low cost and high efficiency. However, the reaction temperature of DMO hydrogenation is higher than the Hüttig temperature of Cu, and the smaller Cu particles are easier to agglomerate. Therefore, there is much interest in constructing a catalyst with a small particle size and strong stability. In the present work, the effect of introducing EDTA on Cu/SiO2 catalysts is systematically investigated. It not only was beneficial to form smaller copper nanoparticles (CuNPs) but also to enhance the stability of Cu species by introducing a suitable amount of EDTA. Furthermore, the surface Cu species were more evenly dispersed, and the number of active sites was increased with the introduction of EDTA; subsequently, the synergistic effect between Cu+ and Cu0 was enhanced. The best performance of 0.08E-Cu/SiO2 had been achieved in the DMO hydrogenation to ethylene glycol (EG), and the DMO conversion and EG selectivity reached 99.9% and 97.7%, respectively. Above all, the 0.08E-Cu/SiO2 catalyst exhibited a high level of stability during the 1200 h life test at 180 °C.

Highlights

Publisher’s Note: MDPI stays neutralEthylene glycol (EG) is an important organic chemical raw material, which is widely used in the production of antifreeze, polyester fiber, explosives, lubricants, plasticizers, surfactants and so on [1]
The results of N2 O titration indicated that the surface area of active copper (SCu ) increased firstly and decreased with the increase of Ethylenediaminetetraacetic acid (EDTA) dosage and reached the maximum (12.8 m2 g−1 ) as EDTA/Cu = 0.08, which indicated that the appropriate amount of EDTA was beneficial to improve the surface area of active copper
Based on the above findings, the following conclusions could be summarized: (1) The chelation of EDTA and Cu2+ ions affected the formation of Cu species by changing the concentration of Cu(NH3 )4 2+ ions

Summary

Introduction

Ethylene glycol (EG) is an important organic chemical raw material, which is widely used in the production of antifreeze, polyester fiber, explosives, lubricants, plasticizers, surfactants and so on [1]. The majority of its consumption is in the field of polyester fiber [2–4]. The traditional route of ethylene glycol production is the petroleum route, which is subject to large fluctuations in oil prices and high energy consumption, so other emerging routes have appeared [5]. The technology of coal to ethylene glycol with coal (or natural gas) as the raw material has attracted great attention because of its advantages including short process, low cost and abundant raw material sources. The hydrogenation of dimethyl oxalate (DMO) to ethylene glycol is a key step in this technology

Results

Discussion

Conclusion