Basic Ionic Liquids Application For Catalyzing Transesterification

Base catalysis is an important part of modern chemistry. However, most of the traditional alkaline catalysts have high toxic and low catalytic efficiency. In orer to protect human health and promote sustainable development of society, it is necessary to develop a series of green, efficient, potential basic catalysts. Basic ionic liquids have been developed under the background of green chemistry, which can be used as solvent and alkaline catalysts. Basic ionic liquids have good application prospect in the future beause of its high catalytic activity, repeatability, non-volatility, non-inflammability.Dimethyl carbonate is a green chemical raw material. However, it is abundant in chemical industry. It is worth looking forward to develop its high value-added chemicals. It has an important application value to combine alkaline ionic liquid and dimethyl carbonate.According the above information, this paper attempts to preparation a series of alkaline ionic liquid catalysts and were used to the transesterification of dimethyl carbonate. The main research contents and results are as follows:Ten kinds alkaline ionic liquids such as 1-butyl-3-methylimidazolium benzoate, 1-butyl-3-methy-limidazolium nitrate, 1-butyl-3-methylimidazolium bicarbonate,l-butyl-3-methylimidazoium tetrafluorob-orate, 1-butyl-3-methylimidazoium lactate, 1-butyl-3-methylimidaizolium dicyanamide, 1-butyl-3-methy-limidazolium butyrate, l-butyl-3-methylimidazolium actate, 1-butyl-3-methylimidazolium propionate, 1-butyl-3-methylimidazoium formate were synthesized by exchange resin method and salt method. The chemical structure of ten kinds of ionic liquids were identified by IR and 1HNMR.Eight alkaline ionic liquids were used to catalyze the transesterification reaction of dimethy1 carbonate and isooctyl alcohol.Among all these catalysts, [C4mim][(C6Hs)COO] was choosed due to its good catalytic performance. The effect on the conversion of dimethyl carbonate and the selectivity and yield of di-2-ethyl-hexyl carbonate were studied in detail. The optimum operation conditions for [C4mim][(C6H5)COO] were as follows:reaction temperature 130℃,catalyst loading 2%(based on the mass of all reactants), n (DMC):n (EHOH) was 1:4, reaction time 6 h. Under this experimental condition,the conversion of dimethyl carbonate attained 99.97%, and the selectivity and yield of di-2-ethyl-hexyl carbonate was 86.35% and 86.32% respectively.Meanwhile, a appropriate elementary reaction sequence of transesteriflcation was proposed.The synthesis of ethyl methyl carbonate by transesterification of dimethyl carbonate and diethyl carbonate in the presence of four carboxylic ionic liquids as catalysts was studied.in which [C4mim][CH3(CH2)2COO] was selected due to its good catalytic performance compared with other alkaline ionic liquids. The effect on the conversion of diethyl carbonate was studied such as temperature, catalyst dosage, the reactant ration and so on. A pseudo homogeneous kinetic model was established to relate experimental data and the kinetics parameters were estimated. It has been found that the calculated results based on kinetic model were agreed well with the experimental results.FinaIly,[C4mim][CH3(CH2)2COO] was repeated use of five times, however, the conversion of dimethyl carbonate has no obvious decline, showing that the [G4mim][CH3 (CH2)2COO] have a good repeated performance.