Kinetic Study And Reactive Distillation Simulation For Transesterification Of 1,4-Butanediol With Methyl Acetate

1,4-Butanediol monoacetate and 1,4-butanediol diacetate are important industrial relevant products.In the synthesis of polyvinyl alcohol(PVA),methyl acetate is a byproduct and its industrial application is limited.Hence,the transesterification of methyl acetate with 1,4-Butanediol is regarded as a promising approach to produce 1,4-Butanediol monoacetate and 1,4-butanediol diacetate.In this paper,the kinetics of transesterification of methyl acetate with 1,4-Butanediol catalyzed by the ion-exchnage resin is researched in detail.After the reaction kinetics equation is set up,a reactive disitilation process is devised and simulated by Aspen plus,which provides necessary data and theoretical guidance for the production of 1,4-butanediol acetate.The kinetic experiment is conducted in intermittent tank reactor.Comparisons of three different commercial ion-exchange resins are carried out.It is found that NCK-9 resin has a superior catalytic performance for this reaction.The variation of stirring speed and particle size has no appreciable impact on the reaction process,which implies that the masstransfer resistance can be negligible.In absence of mass transfer resistance,the effects of reaction temperature,catalyst loading and initial reactants molar ratio are studied.The temperature has a greater influence on the chemical reaction rate,and this transesterification is slightly exothermic and the equilibrium constants mildly change with the temperature.The experimental standard reaction enthalpies for reactions 1 and 2 are found to be-8.50 and-6.85 kJ/mol,which have an excellent agreement with the values computed from the standard formation enthalpy.Three kinetic models(PH,LH and ER)are used to correlate the experimental data,of which ER model with simple rate expression is found to be the most suitable model to represent the experimental data.The activation energies are calculated to be 38.53 and 51.06 kJ/mol,respectively.The high values of reaction activation energy demonstrate that the over-all reaction rates are controlled by the reaction on the surface of the catalyst.After the reaction kinetics equation is set up,a reaction disitilation process is devised and simulated by Aspen plus.NRTL model is selected for the description of the phase behavior.Operational and structural parameters(number of theoretical stages,feed location,reflux ratio,feed molar ratio of reactant)are researched in detail.We obtained optimization results: the number of rectifying stages(Nr),reactive stages(Nrxn)and stripping stages(Ns)in the RD are 3,30 and 3,respectively;the reflux ratio is 0.5;the feed ratio of methyl acetate to 1,4-Butanediol is 1,the heavier 1,4-Butanediol places at the upper of reaction section and the lighter methyl acetate feeds at bottom of reaction section.The purity of methanol at the top is 95 %,meanwhile,the conversion of 1,4-butanediol climbed to 75%,which reaches a compromise between the purity of methanol and the conversion of 1,4-butanediol.