1774 Korean J. Chem. Eng., 32(9), 1774-1783 (2015) DOI: 10.1007/s11814-015-0040-z INVITED REVIEW PAPER pISSN: 0256-1115 eISSN: 1975-7220 INVITED REVIEW PAPER † To whom correspondence should be addressed. E-mail: vimalcsr@yahoo.co.in, vimalfch@iitr.ac.in Copyright by The Korean Institute of Chemical Engineers. Dimethyl carbonate synthesis via transesterification of propylene carbonate with methanol by ceria-zinc catalysts: Role of catalyst support and reaction parameters Praveen Kumar, Vimal Chandra Srivastava † , and Indra Mani Mishra Department of Chemical Engineering, Indian Institute of Technology Roorkee, Roorkee 247667, Uttarakhand, India (Received 26 December 2014 • accepted 16 February 2015) Abstract-Ceria and zinc oxide catalyst were impregnated onto various oxide supports, namely Al 2 O 3 , TiO 2 and SiO 2 , individually by deposition-coprecipitation method. The synthesized catalysts (CZA, CZS and CZT having supports Al 2 O 3 , TiO 2 and SiO 2 , respectively) were characterized by X-ray diffraction (XRD), NH 3 - and CO 2 -temperature pro- grammed desorption (TPD) and N 2 adsorption. These catalysts were used for synthesis of dimethyl carbonate (DMC) from methanol and propylene carbonate in a batch reactor. CZS was found to have larger average grain size as com- pared to CZA and CZT. Composite oxides (catalysts) were found to contain individual phases of ZnO, CeO 2 and some spinel forms of Zn, Ce along with their supports. CZS having highest basicity and surface area showed better catalytic activity as compared to CZA and CZT. Effect of reaction temperature and methanol/PC molar ratio on DMC yield was studied and a reaction mechanism has been discussed. Maximum DMC yield of 77% was observed with CZS catalyst at 170 o C with methanol/PC molar ratio of 10. Keywords: DMC, Transesterification Catalysts, Propylene Carbonate, Methanol INTRODUCTION Dimethyl carbonate (DMC) is an environmentally benign build- ing block chemical compound that has diversified uses in the chemi- cal industry [1]. It has low eco-toxicity, and low persistence and bioaccumulation in life forms [2,3]. DMC is a non-toxic chemical widely used as a methylation agent for substituting the highly toxic dimethyl sulfate and dimethyl halides, and also as a carbonylation agent in various applications [1-3]. The high dielectric constant of DMC allows it to be used as an electrolyte too. It is also used in electrolytic lithium batteries [3]. DMC is used in the production of glycerol carbonate [4,5], O-methylation [6], diphenyl carbonate [7], and can be used as a substitute in place of many conventional solvents [4-8]. DMC is also an alternative oxygenate additive in gasoline-based fuels in place of toxic and poorly biodegradable methyl tert-butyl ether (MTBE). It has higher oxygen content on weight basis (53.3%) in comparison to methanol (50%), ethanol (34.89%) and MTBE (17.6%). The use of DMC in gasoline also reduces the emission of solid particulates (SPM) and NOx [1-3]. Traditionally, DMC was produced by using the phosgenation process, methanol oxycarbonylation process and methyl nitrite car- bonylation process. Phosgenation of methanol was considered to be hazardous, and therefore, this process of DMC production was abandoned by 1980. Currently, DMC is predominantly produced from methanol oxycarbonylation process [1-3]. These conventional DMC production processes are not considered to be safe, as they suffer from problems such as the production of carbon monox- ide, hydrogen chloride and nitric oxide through the complex reac- tion pathways [1-3]. Some other pathways used for the production of DMC such as the direct synthesis from CO 2 suffer from low con- version to DMC, and has thermodynamic limitations [9-12]. Urea methanolysis process suffers from low selectivity because of the formation of the byproducts such as methyl carbamate, N-methyl urea, N-methyl methyl carbamate [13-15]. Transesterification of pro- pylene carbonate (PC) with methanol is a promising method for the synthesis of DMC. The catalytic mechanism for transesterification Scheme 1. Proposed reaction mechanism of DMC synthesis.