Study On The Aminolysis Of Esters And Its Pipeline Reaction Process

Amides are widely used organic compounds,generally sythetised by the following methods:aminolysis of acyl halides,aminolysis of anhydrides,aminolysis of carboxylic acids,dehydration of ammonium carboxylates,aminolysis of esters,nitrile hydration,aldehyde ammonification,alcohol catalytic ammonification,alkyne ammonification.This paper explored the pros and cons of those methods,and used aminolysis of esters to synthesize amides.In the experiments,The batch tank reactor and pipeline reactor were employed to prepare amides.Firstly,a series of experiments were conducted to investigate the catalytic effect of some basic catalysts on the reaction of ethyl acetate and liquid ammonia in the batch tank reactor.The experimental results showed that the catalytic effect of sodium metal was the best.Through the optimization of process conditions,the optimal reaction conditions are:ethyl acetate:ammonia(molar ratio)=1:2,catalyst 0.06 equivalent,reaction temperature 90℃,reaction time 6hr,the conversion of ethyl acetate was 97.8%.The product was preliminarily confirmed by GC-MS.Then the product is purified by recrystallization,and was further confirmed by1H NMR.The process was suitable for aminolysis of the other esters.After optimization of the process,the conversion rates of the selected esters were all above 85%without side reactions.The structures are characterized by1H NMR.Secondly,a pipeline reactor was used to research the reaction of ethyl acetate and N-propylamine without catalyst.At the temperature from 188℃ to 228℃,the conversion rate of the reaction could reach more than 93%.However,the lower the temperature was,the longer the residence time was needed,which mean a larger reactor volume is required,under the same capacity.The ratio of materials in the range of 1:0.667-1.50 had little effect on the residence time required for the complete reaction,and all could obtain high conversion rate.However,from the molar mass concentration of the product,the highest product concentration is obtained when the ester-ammonia ratio is 1:1.00.Increasing the proportion of a certain material could increase the conversion rate of another material,but the molar mass of the product decreased instead.Pressure did not affect the reaction results,when the pressure was greater than bubble point pressure.In this paper,the apparent kinetics of the reaction of ethyl acetate and N-propylamine was also calculated by combining the mechanism and the data of pipeline reaction.The conversion rate vs.residence time curve is like ’S’,which is similar to the autocatalytic reaction,and in the rapid reaction period,the conversion rate and residence time satisfy a linear function.Therefore it was proposed that the hydrogen abstraction step controlled the rate of the reaction.It was determined by the reaction temperature,which was independent of with the concentration of ester and amine.The apparent reaction kinetics of the reaction is zero-order reaction.The reaction rate constant of the zero-order reaction satisfied the Arrhenius equation,and the activation energy was 38489 J·mol-1 and the pre-exponential factor is 8.4709.The reaction process in this paper had a certain innovation.In these experiments,it was not needed to use solvent.Side effects were not detected,and the conversion rate was high.The catalytic effect of the catalyst was considerable,although with a small amount,which was of great interest to the industrialization of this process.The experimental results of pipeline reaction provide data supported for studying the kinetics of ester amination reaction and actual industrial process simulation.