Study On The Dehydration Of Methyl Chioride Gas In The Production Process Of Butyl Rubber Based On Ionic Liquid

Butyl rubber is being applied to more fields because of its excellent properties,so the demand of butyl rubber is increasing day by day.The polymerization reaction in the production of butyl rubber uses methyl chloride as the solvent.The excessive water content of methyl chloride directly affects the polymerization reaction result and causes the problem of shutdown of the whole line.Therefore,the water content of methyl chloride is strictly controlled in the recovery stage.At present,the most methyl chloride is dried by activated alumina in the recycling process,it basically meets the production requirements.The coupling process of triethylene glycol and activated alumina proposed in recent years is used for the dehydration of methyl chloride.Although the dehydration cycle of activated alumina can be extended to a certain extent,the problems of the triethylene glycol that is easy to foam,easy to oxidize,and has a low decomposition temperature,high energy consumption in the recycling process are exposed.In this paper,green solvent ionic liquids are used as absorbents to study the dehydration process of methyl chloride,which mainly includes studying the dehydration mechanism of ionic liquids from a molecular perspective,and the dehydration performance and law of ionic liquids through gas-liquid equilibrium and dehydration experiments.The application prospects of ionic liquids in the dehydration of methyl chloride are analyzed in the industrial-scale process simulation at the end.Firstly,some suitable ionic liquids were screened from 210 kinds of ionic liquids for the dehydration of methyl chloride based on the COSMO-RS model.At the same time,considering the physical and chemical properties of the ionic liquid,[EMIM][BF4]was finally selected as the absorbent of methyl chloride.Compared with TEG,thermal stability of[EMIM][BF4]shows better performance.Secondly,the vapor-liquid equilibrium experiment of methyl chloride in ionic liquid or triethylene glycol was completed by static phase equilibrium method,and law solubility of methyl chloride is studied.Using the missing interaction parameters in the UNIFAC model were obtained by correlating between this experiment and the experimental data in the literature,and the accuracy of the model to predict the gas-liquid equilibrium was verified.Furthermore,by analyzing the surface charge density distribution probability σ-profiles of[EMIM]+,[BF4]-,CH3Cl and H2O;and the molecular surface polar and binary mixing enthalpy of[EMIM][BF4],CH3Cl and H2O,respectively predicted by the COSMO-RS initially revealed that the dehydration mechanism of ionic liquid gas is mainly hydrogen bonding.The binding energy and bond length for the binary mixed system are calculated by quantum chemistry,and the type of weak interaction and the site of action between the systems are calculated and analyzed by Multiwfn,which further reveals the mechanism of methyl chloride gas dehydration of ionic liquids from a molecular perspective.Finally,through the dehydration experiment of methyl chloride with[EMIM][BF4]as the absorbent,the influence of ionic liquid flow rate,methyl chloride feed the tower pressure and regeneration times of ionic liquid on the dehydration effect was explored.By comparing methyl chloride dehydration experiment results of[EMIM][BF4]and triethylene glycol,it is found that[EMIM][BF4]has better dehydration effect than triethylene glycol.At the same time,industrial-scale simulation and optimization of the methyl chloride dehydration process with[EMIM][BF4]or triethylene glycol as absorbents are carried out.Finally,from the product quality methyl chloride and energy recovery of absorbent and recycling process results,it is further demonstrated that the advantages of[EMIM][BF4]used in methyl chloride gas dehydration.