Effects of ionic liquid in the catalyst preparation of MgO-CeO 2 mixed oxide for dimethyl carbonate synthesis via transesterification Kye Sang Yoo, Haznan Abimanyu, Byoung-Sung Ahn, Honggon Kim Hydrogen Energy Research Center, KIST, Korea Introduction The synthesis and application of dimethyl carbonate (DMC) are achieving increasing importance due to its low toxicity and versatile reactivity. DMC can be used as environment- friendly intermediate and starting material for organic synthesis via carbonylation and it can replace methylating agents such as dimethyl sulphate and methyl halides [1–3]. DMC is also being considered as a component for replacing methyl tert-butyl ether (MTBE) as an oxygen- containing additive for gasoline, owing to its high oxygen content, good blending octane and quick biodegradation [4]. Moreover, DMC can be used in lithium batteries as an electrolyte due to its high dielectric constant [5]. With the exception of phosgenation-route, there are three main production technologies for DMC synthesis, methanol oxy-carbonylation, carbonylation of methylnitrite and transesterification of ethylene carbonate (EC) or urea [2,5,6]. The phosgenation-route has been losing attraction recently due to the use of virulent phosgene [5]. In transesterification process, DMC is co-generated with ethylene glycol (EG). This reaction takes place in the presence of a catalyst at about 100–150 ºC at moderate pressure [7]. Numerous homogeneous and heterogeneous, acid or base catalysts have been reported as being useful for this reaction. However, the base catalyzed reaction appears generally to be the most effective for the synthesis of DMC [8,9]. Various heterogeneous catalysts such as alkali-treated zeolite [10,11], basic metal oxides [12–14], and hydrotalcite [15] were used for the transesterification. In our previous work, MgO–CeO 2 catalyst systems, which were prepared via co- precipitation of magnesium chloride and cerium (III) nitrate, were found to have attractive catalytic performance without decay of activity and had excellent selectivity to the sum of dimethyl carbonate at a temperature of 150 ºC and pressure of 0.2 MPa. The modification presented in this study is to apply ionic liquid as a templating material. Ionic liquids (ILs) are an exceptional type of solvent consisting virtually only of ions. They have practically no vapor pressure and possess tunable solvent properties [16,17]. In this study, various ionic liquids