Reactive Distillation Preparation Of Triacetin From Glycerol And Acetic Acid Catalyzed By Pyridine Bisulfate Ionic Liquid

As an important fine chemical intermediate,triacetin?TAG?is widely used in perfume,paint,medicine,cigarette and other industries.The traditional production process of TAG usually uses the concentrated sulfuric acid as a catalyst,and the product is obtained after the esterification reaction between glycerin and acetic acid,and then separated and purified.But the concentrated sulfuric acid catalyst has the disadvantages of low conversion rate,poor selectivity,more by-products,equipment corrosion,and environmental pollution.As a new type of“green”liquid catalyst,ionic liquid has a good catalytic effect and is less corrosive,and has a prosperous application prospect in the field of esterification reaction.At the same time,as a means of strengthening chemical processes,reactive distillation technology has obvious advantages in esterification reactions.In this paper,the effects of reaction temperature,acid-alcohol molar ratio and catalyst dosage on the conversion rate of glycerol and the yield of product TAG were investigated through the kinetic experiment of the esterification reaction of glycerol and acetate catalyzed by pyridine bisulfate ionic liquid,and the optimal reaction conditions were determined.At the same time,a differential equation model was established according to the quasi-homogeneous first-order reaction mechanism,and the pre-finger factor and reaction activation energy were obtained through kinetic data fitting.The calculated value of the dynamic model was in good agreement with the experimental value.Compared with the reported Amberlyst-15 catalyst and heteropoly acid catalyst,the ionic liquid used in the experiment has milder reaction conditions,higher selectivity,lower reaction activation energy and better catalytic effect.In order to explore the catalytic performance of ionic liquids in reactive rectification,the experiment-scale reaction rectification experiment was conducted with a glass reactive distillation tower to investigate the effects of reflux ratio,glycerol feed position,acetic acid feed position and feed acid-alcohol molar ratio on the reactive distillation process.Under the best operating conditions:the feed rate of acetic acid was 30 mol·h^-1,the feed rate of glycerin was 10 mol·h^-1,that is the feed acid-alcohol molar ratio was 3:1;the mass flow rate of the catalyst was 27.627 g·h^-1.Molar reflux ratio was 2,the liquid holding capacity of the tower kettle was 1000 m L,when the glycerol feeding position is located in the third theoretical plate,and the acetic acid feeding position is located in the eleventh theoretical plate,the conversion rate of glycerin is up to 100%.The purity of TAG was as high as 91.77%.At the same time,in order to improve the purity of the product TAG,the purification method of vacuum distillation was used in this article,the purity of the TAG in the crude product was increased from 91.77%to 99.52%through exploratory experiments,which verified the feasibility of the process.Finally,the Aspen plus software was used to simulate the entire process in detail,and the simulation results were compared with the experimental results of the small test.The two results were highly consistent,which proved that the simulation results had good reliability.