Effects of Ionic Liquid in the Catalyst Preparation of Mgo-Ceo2 Mixed Oxide for Dimethyl Carbonate Synthesis Via Transesterification
Kye Sang Yoo, Haznan Abimanyu, Byoung Sung Ahn, and Hoggon Kim. Environment and Process Tehcnology Division, Korea Institute of Science and Technology, Hawolgokdong 39-1, Seongbukgu, Seoul, 139-791, South Korea
Dimethyl carbonate (DMC) is very attractive due to its versatile chemical reactivity and unique physical properties. As a nontoxic intermediate, DMC is being touted for replacement of toxic intermediate, phosgene and dimethyl sulfate. It can also be used as a potential gasoline octane enhancer owing to its very high oxygen content, good blending octane and rapid biodegradability. Since the route of DMC synthesis using phosgene was eliminated in recent years, there have mainly been several environmentally benign routes developed and commercialized. DMC can be prepared by oxidative carbonylation of methanol and carbonylation of methyl nitrite. However, both routes bear a potential explosion hazard. The transesterification method is a potentially clean route to this valuable chemical. In this route a cyclic carbonate is transesterified with methanol to produce DMC cocurrently with alkylene glycol, very useful agents for synthesis of polyester. In this study, transesterification of ethylene carbonate with methanol to produce dimethyl carbonate was investigated over MgO-CeO2 mixed oxides. The co-precipitation was taken as the standard method of the catalysts preparation and the effects brought by the introduction of ionic liquid in the catalyst preparation were analyzed. The initial Ce contents in the mixed-oxide catalysts were 0, 19.4, 24.4, 35.4, 44.9, 55.9 and 100 mol%. It has been found that the catalyst with Ce content of 24.4 mol% had the best activity. The obtained DMC yield and selectivity by this catalyst were 65% and 95%, respectively. To improve activity of the catalyst for this reaction, ionic liquid [Bmim][PF6] has been introduced in the coprecipitation process. The surface area and pore volume of the modified catalyst increased significantly due to effect of the ionic liquid. The low vapor pressure of the IL could assist in reducing the problem of gel shrinkage during sol ageing and gel drying, which could prevent reduction of surface area and pore volume. With this modified coprecipitation method, it has been revealed that the activity of catalyst enhanced significantly, especially at high LHVS condition. The catalysts were characterized using X-ray diffraction (XRD), Fourier transformed infra red (FTIR) and BET for morphology, basicity and surface area of the catalysts, respectively.