Study On The Acidic Ionic Liquid Catalyst And The Esterification-Separation Coupling Process

Ionic liquids are a green and highly efficient reaction catalyst and solvent that have been widely used in various fields of chemistry and chemical engineering.In particular,ionic liquids are used as catalysts in the coupling process of esterification reaction and extraction separation,which could solve the problems of low efficiency,excessive energy consumption and serious secondary pollution caused by traditional proton acid catalyzed esterification reaction.In view of the excellent performance of ionic liquids in esterification,four kinds of Br(?)nsted acidic ionic liquids were designed and their catalytic-separation properties in the synthesis of ethyl acetate from acetic acid and ethanol were investigated.At the same time,these ionic liquids were also mixed to study their eultectic behavior.Beside,the reactive distillation promoted by these ILs was tested.Firstly,four binary Br(?)nsted acidic ionic liquids were designed and synthesized,including tow-concentration acidic ionic liquid 1,3-dimethyl-2-im idazo lid i no ne hydrogen sulfate([DMI][HSO4])and high-concentration non-corrosive ionic liquids 1-methylimidazo lium hydrogensulfate([mim][HSO4])or 1-ethylimid azo lium hydrogensulfate([eim][HSO4]).This paper studied their catalytic performance for the synthesis of ethyl acetate.It has been found that the binary Br(?)nsted ionic liquid catalysts have lower corrosivity and higher catalytic activity compared with pure Br(?)nsted acidic ionic liquid.In particular,the reaction of the binary Br(?)onsted ionic liquid as a catalyst also achieves the phase separation of ethyl acetate,and the coupling of reaction and separation is realized.Promoting by phase transfer of ethyl acetate,the reaction equilibrium is broken.Consequently the reaction moves to the positive reaction direction,and the acetic acid reaches a conversion rate greater than 90%.In addition,this paper utilized the reaction kinetics model to fit the experimental data and calculate the kinetic parameters,which provided valuable basic data for later industrial applicatio ns.Secondly,based on the above research,this paper designed and synthesized six sets of binary Br(?)nsted ionic liquids,studied their eutectic behavior,measured the melting temperature of different molar content.The results show that all the six mixed ionic liquids have the lowest eutectic temperature at a certain molar content,and the temperature is lower than the melting point of pure ionic liquids.In addition,the solid-liquid equilibrium equation was used to fit the experimental data of the melting temperature of six binary Br(?)nsted ionic liquids.It is found that the equation could correlate the data at a satisfied stage,which can be used to predict the lowest eutectic temperature.Finally,combined with the results of the above two studies,this paper designed and synthesized a formulation ionic liquid which was liquid at normal temperature,and used the formulated ionic liquid as a catalyst to carry out continuous ethyl acetate reaction in a laboratory-scale rectification column.At the same time,the conditions of the distillation column were optimized,and the catalytic performance of the catalyst was examined.It is shown that the catalyst has high catalytic ability.Under the rectification conditions of this paper,the purity of the product ester can reach 98%.In addition,this paper presented a concept of a reaction-extraction rectification process with a formulated ionic iquid as catalyst,and used PRO/II software to simulate the calculation of the data of the rectification column.In short,the research is based on Br(?)nsted ionic liquids to explore the catalytic performance of mixed ionic liquids in the esterification process.It provides some key basic data for designing ionic liquid catalysts for industrial applications,and finally achieves a clean and efficient production process.