Study On Synthesis And Properties Of Asymmetric Carbonate

Asymmetric carbonate is a new type of carbonates.The asymmetric carbonate molecules contain the active groups of methyl,methoxy and carbonyl groups,which can be used as methylation carbonylation reagents and organic synthesis intermediates,as well as oil additives.Asymmetric carbonate with the boiling point of medium,low melting point,low viscosity,good low temperature performance,no corrosion,self-cleaning,dissolving ability and other characteristics,so it can be used as lithium ion battery electrolyte,lube base oil,special coating solvents,special flavor,etc.,broad application prospect.The asymmetric carbonate is obtained from the exchange reaction of dimethyl carbonate with alcohols,and dimethyl carbonate is converted from carbon dioxide.It is one of the most effective ways to realize carbon dioxide resource and chemical utilization,which can reduce the negative effect of greenhouse effect.The preparation of new catalysts and the catalytic synthesis of asymmetric carbonates have important theoretical and practical values.In this paper,dimethyl carbonate and alcohol were used as raw materials to synthesize asymmetric carbonates under the action of alkaline catalyst.The thermodynamic feasibility of the transesterification reaction was analyzed and discussed;a single-component alkaline catalyst with high catalytic efficiency was selected;a supported alkaline catalyst was prepared and the catalytic performance of the catalyst was investigated;the process technology of continuous synthesis of asymmetric carbonate in fixed bed tubular reactor was studied;the properties of the synthesized methyl isooctyl carbonate and methyl octyl carbonate were measured.The synthesis of methyl isooctyl carbonate from dimethyl carbonate and isoctyl carbonate was studied by Benson group plus method.The results show that,under normal conditions,the ester exchange reaction can be spontaneous,the ester exchange reaction is feasible in thermodynamics,and the ester exchange reaction is exothermic reaction.The equilibrium constant of ester exchange reaction is large,and the equilibrium conversion rate is high and has practical significance.With dimethyl carbonate and ethanol as raw material,the synthesis of methyl ethyl carbonate ester exchange method,adopting inorganic potassium carbonate as catalyst,the suitable reaction conditions as follows:the reactant molar ratio of 3:1,1%of catalyst dosage,reaction time 4h,methyl ethyl carbonate yield was 76%.Using J base as the catalyst,the ideal reaction conditions were:reaction molar ratio 2:1,1%of catalyst dosage,reaction time 3h,and the yield of methyl carbonate was 93%.As the catalyst,organic J base is completely dissolved in the reaction system,with high catalytic activity and high yield of methyl carbonate.Using J base as a catalyst,dimethyl carbonate was transesterified with n-octanol and iso-octanol respectively to synthesize methyl?iso?octyl carbonate.The suitable reaction conditions as follows:raw material molar ratio 3:1,1.5%of catalyst dosage,reaction time 4h,methyl loctyl carbonate yield reached 92%and the yield of methyl isooctyl carbonate reached93%.Using?-alumina load potassium hydroxide as catalyst,dimethyl carbonate and is?iso?octyl alcohol as raw materials,easy synthesis of methyl?different?octyl carbonate,reaction products with the separation of catalyst is convenient.In the batch reactor,the suitable reaction conditions as follows:raw material mole ratio of 3:1,1%of catalyst dosage,reaction time,6h,methyl octyl carbonate yield was 91%,methyl isooctyl carbonate yield was 92%;In tubular fixed bed reactor,the ideal reaction conditions as follows:raw material mole ratio of3:1,reaction temperature 140?,pressure is 1.2MPa,airspeed 1.1h^-1,methyl octyl carbonate yield was 74%,the yield of methyl isooctyl carbonate was 76%.