Surface Reduced CeO2 Nanowires for Direct Conversion of CO2 and Methanol to Dimethyl Carbonate: Catalytic Performance and Role of Oxygen Vacancy

Zhongwei Fu,Zhen Li,Min Xiao,Shuanjin Wang,Yuehong Yu,Yuezhong Meng,Dongmei Han

doi:10.3390/catal8040164

Abstract

Ultralong 1D CeO2 nanowires were synthesized via an advanced solvothermal method, surface reduced under H2 atmosphere, and first applied in direct synthesis of dimethyl carbonate (DMC) from CO2 and CH3OH. The micro morphologies, physical parameters of nanowires were fully investigated by transmission electron microscopy (TEM), X-ray diffraction (XRD), N2 adsorption, X-ray photoelectron spectrum (XPS), and temperature-programmed desorption of ammonia/carbon dioxide (NH3-TPD/CO2-TPD). The effects of surface oxygen vacancy and acidic/alkaline sites on the catalytic activity was explored. After reduction, the acidic/alkaline sites of CeO2 nanowires can be dramatically improved and evidently raised the catalytic performance. CeO2 nanowires reduced at 500 °C (CeO2_NW_500) exhibited notably superior activity with DMC yield of 16.85 mmol gcat−1. Furthermore, kinetic insights of initial rate were carried out and the apparent activation energy barrier of CeO2_NW_500 catalyst was found to be 41.9 kJ/mol, much tiny than that of CeO2_NW catalyst (74.7 KJ/mol).

Highlights

As an environmentally benign compound and unique intermediate of versatile chemical products, dimethyl carbonate (DMC) is widely applied in polymer industry and pharmaceutical as well as detergent, surfactant, and softener additives [1,2]
CeO2 nanowires catalyst was prepared using a solvothermal method in a mixed water/ethanol solvents (v/v = 1:1)
Ultralong 1D CeO2 nanowires were synthesized via an advanced solvothermal method, surface reduced under H2 atmosphere, and firstly applied in direct synthesis of dimethyl carbonate (DMC)

Summary

Introduction

As an environmentally benign compound and unique intermediate of versatile chemical products, dimethyl carbonate (DMC) is widely applied in polymer industry and pharmaceutical as well as detergent, surfactant, and softener additives [1,2]. DMC is important raw material when serving as a non-toxic substitute for poisonous phosgene and dimethyl sulfate in sustainable chemistry of carbonylation, methylation, and polymer synthesis [3,4]. Considering the wide applications, DMC is known as the “new cornerstone” for synthesis chemistry nowadays and lots of efforts have been made in finding appropriate routes to meet the demand of DMC industrial production since it is far from satisfaction until now. Several approaches including the methanolysis of phosgene [6], the oxidative carbonylation of methanol [7], the transesterification of alkene carbonates [8], and the alcoholysis of urea [3], have been developed, but it is still limited with strict operation conditions, highly toxicity, and corrosivity up to now

Methods

Results

Conclusion