The Application Of Catalytic Distillation In The Production Of Maleic Acid Ester

Dimethyl maleate has been catalytically synthesized in a kettle reactor with liquid acid catalysts, such as vitriol, sulphur acid etc.. With high investment and operation cost, the traditional production process has a long flow and waste acid is hard to treat properly. A low recovery rate lessens its commercial attraction in addition.The emergence of cationic exchange resins mitigates the conditions required by reactions catalyzed with acid. It substitutes the role of liquid acid in some chemical industries. The successful application of exchange resin has made heterogeneous synthesization of dimethyl maleate possible. The new method reduces investment and energy expense, eliminates the tough problem of waste acid treatment. But because of the reversibility of this reaction, the conversion is limited by reaction equilibrium. Water formed during the process must be removed from the reaction zone in order to increase the conversion of maleic acid through continually breaking the balance. Catalytic distillation, integrating a reaction unit and a separation unit into one column, meets the requirement well. It not only shortens the production scheme, but also utilizes the reaction heat as it makes a quantity of reactants vaporize. Water moves upward and dimethyl maleate moves downward due to the fractionating effect, which decreases the contents of products and impells the balance toward favorable side, thus increases the conversion.Taking methanol and maleic anhydride as feed, several catalysts were tested under a given condition to determine the best one according to the selectivity of dimethyl maleate. The influence was studied of temperature, space velocity and methanol/meleic anhydride mole ratio on the process. Kinetic equation was obtained under the flowing assumptions:1. the reaction of methanol and maleic anhydride to monomethyl maleate is unreversible ,2. the reaction of methanol and monomethyl maleate to dimethyl maleate is reversible ,thus another rate equation should be defined.Calculated data using the equation mentioned above agrees well with the experimental data.A flow scheme was presented for the production of dimethyl maleate in which a pre-reactor was applied that was followed by a catalytic distillation column. Almost all maleic anhydride could be converted to dimethyl maleate. A simulation model was developed on the platform of commercial software ASPEN PLUS. The parameters of kinetic equation acquired from experimental data was integrated into the model. The simulated results agrees satisfactorily with the experimental ones, which indicates the model set up hereby can be relied on. A further research was done utilizing the model. The results thus derived manifests the influence of the number of stages, the flow of feed ,reflux ratio, pressure on the process. A preferential condition was sifted out. The success of synthesization of dimethyl maleate widens the application of catalytic distillation technology.