Study Of Catalysts Used In The Transesterification Of Dimethyl Carbonate And Ethanol To Diethyl Carbonate

Diethyl carbonate(DEC), a non-toxic and environmentally benign chemical, is an important chemical intermediate which is used as a safe substitute for diethyl sulfate ,ethyl halide, and phosgene. In addition, DEC is an excellent solvent, which is widely applied in lithium batteries. This dissertation is mainly focused on the study of catalysts that are used in the transesterification of DMC and ethanol to produce diethyl carbonate.Transesterification of DMC and ethanol for preparing diethyl carbonate was carried out in the presence of lanthanum nitrate for the first time and the reaction conditions were optimized. At 76-80 oC, 7 h, n(ethanol):n(DMC)=8:1, 0.7 mol % catalyst based on DMC, the conversion of DMC was 86.5 %, the yields of diethyl carbonate (DEC) and ethyl methyl carbonate (EMC) were 59 % and 26.5 %, respectively, the transesterification selectivity was 99.4 %. La(NO3)3 was reused 5 times for the transesterification of DMC with ethanol without loss of its catalytic activity.A variety of triflate compounds were tested for their catalytic activity in the transesterification of DMC and ethanol to produce diethyl carbonate. Earth metal triaflates showed good catalytic performance in this reaction. Among the catalysts, Y(OTf)3 was the most active catalyst under optimized reaction conditions, 76-80oC, 7 h, n(ethanol):n(DMC)=6:1, 0.35 mol % catalyst based on DMC, the conversion of DMC was 89.2 %, the yields of DEC was 75.9 %, and the selectivity of DEC was 85.1%.Hydrotalcites(HT) which is well known for its special pillared layered structure, was firstly introduced to catalyze the transesterification of DMC and ethanol, HT intercalated with t-BuO- anion(HT-OtBu) showed the best catalytic performance. HT-OtBu was characterized by XRD, FT-IR and TGA-DTA which indicated that t-BuO- anion was mostly incorporated into HT interlayer spaces .When the reaction was carried out over HT-OtBu ,at 76-80 oC, 7 h, molar ratio of ethanol to DMC was 5:1, mass fraction of catalyst =1%, the conversion of DMC was 86.4 %, the yield of DEC and the selectivity to DEC were 61.2 % and 70.8 % respectively.