Study On Rectifying Preparation Of Ethyl Acetate By Catalytic Esterification Reaction Of 1-sulphonic Acid Butyl-2-methylpyridine Hydrogen Sulfate Ionic Liquid

Ethyl acetate is a very common employed reagent for industry and plays an important role in coatings and other fields.As for the traditional process of preparing ethyl acetate in the current stage,the concentrated sulfuric acid as the traditional homogeneous catalyst,has the advantages such as low price and mature technology,but there also exists some other disadvantages like a lot of side reactions in the preparation,as well as strong corrosion for equipment.The solid acid catalyst,which has the advantages of convenient separation and recovery for the continuous operation in the chemical industry,however has the disadvantages such as a low activity at a lower reaction temperature,an easy deactivation and short life at a higher reaction temperature,as well as a subsequently complicated processing and so on.The ionic liquid,as a new type of liquid catalyst,has excellent catalytic performance and low corrosivity on equipment,which are of great potential in the field of esterification reaction.The 1-sulfonic acid butyl-2-methylpyridine hydrogensulfate ionic liquid was used as a catalyst here,this paper has systematically study its kinetics property for the synthesis of ethyl acetate by acetic acid and ethanol esterification.The impact of various factors on the reaction conversion rate was investigated under the condition:temperature of 313.15-333.15 K,catalyst concentration of 0.07-0.27 mol·L-1 and acid-alcohol molar ratio of 0.56-1.5.The non-ideal homogeneous(NIH)model of kinetics of esterification reaction was established on the basis of the two-stage reversible reaction mechanism,and the the NRTL activity equation was adopted to correlate the non-ideal properties of the mixed liquid.Parameters such as the kinetic constants,reaction activation energy and pre-exponential factors in the model were obtained by the fitting of kinetic data.With the rising of temperature and concentration of ionic liquid catalyst,the reaction rate of acetic acid increases gradually,but the equilibrium conversion rate stayed basically the same,and reach the highest conversion rate of esterification reaction with molar ratio of acid to alcohol is 1.The positive reaction activation energy is 49.48 kJ·mol-1,the negative reaction activation energy is 53.78 kJ·mol-1,the positive pre-factor is 7.25×105 L2·mol-2·min-1,and the negative pre-factor is 3.87×105L2·mol-2·min-1.The consistence of the predicted values of the model and the experimental values is shown,which indicate that the NIH model is suitable for the ionic liquid to catalyze the kinetic system of ethyl acetate reaction,can provide kinetic data for the subsequent simulation of reactive rectification.By comparison,it was found that the catalytic effect of ionic liquid under the same conditions was better than that of the ion exchange resin of Amberlyst 15 with a lower corrosivity than that of concentrated sulfuric acid.The catalytic activity of the ionic liquid 1-sulfonic acid butyl-2-methylpyridine hydrogensulfate did not show a significant decrease after 5 times recycling and reuse,which demonstrates that this ionic liquid is an esterification reaction catalyst with excellent performance.On the purpose of analyzing the role of ionic liquids in the reactive rectification process,the purity of ethyl ester was determined with a small glass rectification unit at different feed positions,feed amount(initial ratio of acid to alcohol),molar reflux ratio and the amount of liquid holdup.On the basis of the specific conditions of the equipment,there reaches a highest content of ethyl ester,which is of 86.7%when the reflux ratio is 3,the liquid holding capacity of the kettle is 1L,the mass of the catalyst accounts for 5%of the acetic acid mass,the molar ratio of the feed acid to alcohol is 1.3,where the acetic acid is fed from the third plate and the ethanol is fed from the 10th plate.The Aspen Plus simulation software was applied to conduct a simulating calculation on the experimental condition of rectifying reaction,which has an error less than 3%between the obtained ethyl acetate mass fraction and the experimental value.And the optimum conditions for analysis of simulating reaction rectification respectively are as follows:the reflux ratio was 2,the acid-alcohol molar ratio was 1.3,the acetic acid feed flow rate was 52 mol·h-1,and the ethanol feed flow rate was 41 mol·h-1.The ethanol was fed from 9th plates,acetic acid and catalyst were fed in the third plate,the amount of holding liquid in the plate was 0.025 L,and the content of ethyl ester obtained was 88.53%.