Molecular Process Simulation Of Transesterification Synthesis Of Carbonate Catalyzed By Ionic Liquids

Dimethyl carbonate and methyl ethyl carbonate are important green organic chemical products.Because of their high oxygen content,green environmental protection,safe and stable,they are widely used in the synthesis of chemical products such as glycerol carbonate,polyurethane and polycarbonate.In addition,dimethyl carbonate and methyl ethyl carbonate have high octane number and strong solubility.They are often used as gasoline additives and new electrolyte for lithium batteries.Transesterification is the main process for the synthesis of dimethyl carbonate and methyl ethyl carbonate,which conforms to the principle of"green and sustainable development"and is easy to realize industrialization.However,the traditional sodium alcohol catalysts in transesterification have some problems,such as low selectivity,catalyst deactivation and by-product blocking.In order to solve the above problems,ionic liquids catalysts have the advantages of energy saving,environmental protection and recycling,among which the transesterification catalyzed by basic ionic liquids is a new research direction.In this paper,three kinds of traditional ionic liquids[Bmim]OH,[Bmim]IM,[Bmim]PF₆ were synthesized and their chemical structures were characterized.The catalytic activity of three kinds of ionic liquids for the synthesis of dimethyl carbonate from ethylene carbonate and methanol was evaluated by the distillation integrated continuous reaction device.The interaction of ionic liquids,cocatalysts and reaction temperature on the catalytic performance was investigated by orthogonal experiment,and the influence of the proportion and amount of ionic liquid and cocatalyst on the transesterification reaction was explored.The results showed that[Bmim]PF₆/Cao was the best catalytic activity in the transesterification reaction.When the catalytic temperature was 130?,the mass ratio of[Bmim]PF₆ and Cao was 5:1,the catalytic system accounted for 4%of the total mass of the reaction system,and the molar ratio of methanol to ethylene carbonate was 10:1,the one-way conversion rate of ethylene carbonate was 65.23%,and the selectivity of dimethyl carbonate was 98.95%.The catalytic activity of the system remained basically unchanged after 7 times of recycling.A functionalized ionic liquid was synthesized and modified.Then,the ionic liquid catalyst was prepared by 3-chloropropyl triethoxysilane?CPTES?as coupling agent,molecular sieve MCM-22 as supporter to obtain immobilized functionalized ionic liquid catalyst.This catalytic system completed the high energy chemical bonding among the silane coupling agent,molecular sieves and ionic liquid.Meanwhile,the immobilized ionic liquid catalytic system wer e successfully prepared fromFT-IR,TG,XRD and SEM.The transesterification of dimethyl carbonate and ethanol to ethyl carbonate catalyzed by immobilized ionic liquid was investigated in a distillation integrated continuous reactor.The effects of reaction temperature,mass ratio of cocatalyst to ionic liquid and the number of catalytic cycles on transesterification were investigated.The results show that MCM-22-CPTES-MIL/Cao catalyst system has the best catalytic performance.When the catalytic temperature is 110?,the mass ratio of CM-22-CPTES-MIL to Cao is 3:1,the total amount of catalyst is 1.0%of total mass,the conversion rate of dimethyl carbonate is 86.3%,and the selectivity of Methyl ethyl carbonate is 91.9%.Under these conditions,the catalytic activity of the catalyst was still high after 7 cycles,but this catalyst also existed the phenomenon that the loss of active component ionic liquid.By using Gaussian 05 software,the molecular process simulation of the continuous catalytic transesterification of ionic liquids was completed,and the reaction mechanism was revealed.The results show that the relative energy of the transition state can be significantly reduced by the ionic liquid catalyst through the hydrogen bond network,which shows that the ionic liquid catalyst can effectively reduce the activation energy of the reaction and the continuous transesterification process was completed efficiently.