Study On The Coupling Technics Of Reaction-Adsorption For Dimethyl Adipate

Dimethyl adipate has played an important part in fine chemical industry, it has been used widely as fine chemical products and chemical raw materials. The synthesis method is a typical esterification process, generally uses the sulfuric acid, nitric acid and other inorganic acid as catalyst. The yield is higher method by the method, but equipment corrosion is severe, and a great deal of waste acid exist in this process, so that it is unable to meet the requirement of environmental protection. In order to solve the problems, a new kind of esterification technology was researched in the paper. The process choosed the solid strong acid cation exchange resin to replace the serious pollution of inorganic acid as catalyst, and used 4A molecular sieve as absorbent to prompt the esterification reaction and improve esterification rate.Esterification reaction is reversible, in general, the reaction is not complete. In accordance with equilibrium theory, it is necessary to require a kind of product isolated from the reaction system or an excess component of reactants added the reaction system in order to improve the yield of ester. In accordance with the theory of chemical reaction, the equilibrium of chemical reaction and the yield of the esterification reaction can be changed if one of the reactants forms binary or ternary azeotrope with the water produced and makes it leave the reaction system in time. Moreover,In this paper, we used reaction-absorption coupling process, the molecular sieve as absorbent which brought out constantly the reaction of water, and the methanol was greatly excessive in raw materials. Methanol vapour carried water vaporized unceasingly in a certain of temperature, they were enter adsorption device to remove the water produced after condensated in the condenser. Methanol was recycled. The advantages of the technology is manifest, such as clean process mild reaction conditions, high yield and easy product separation, are suitable for the production of fine chemicals.The reaction-adsorption coupled technics and the apparent reaction kinetics for dimethyl adipate produced were studied in this paper. Firstly, the coupled technics route of reaction-adsorption was proposed for dimethyl adipate produced using adipic acid and methanol as raw materials, the experimental mathod of which a single factor combined the orthogonal design methods was used, and esterification rate was used as assessment criteria of the reaction. The various factors on the influence of synthetic reaction were investigated, and better reaction conditions were optimized. In the conditions, the yield of dimethyl adipate was up to 96.3%.By comparison,732 strong acid cation exchange resin is superior to NKC-9 cation exchange resin, so 732 strong acid cation exchange resin was selected to used as catalyst of dimethyl adipate synthesized with methanol and adipate. The optimal technological conditions were obtained as follows:Mole ratio of alcohol to acid is 6:1; temperature is 70-75℃; reflux reaction time is 8h; the amount of catalyst is 14% based on the amount of adipic acid.Secondly, the apparent kinetics of dimethyl adipate synthesized was discussed according to the reaction theory in this paper, its apparent kinetics equation was written as follows: Where CA is the instantaneous molar concentration of adipic acid, mol·L-1; CB is the instantaneous molar concentration of methanol, mol·L-1.The result shows that the apparent activation energy Ea= 23.5583kJ·mol-1 for adipic acid dimethyl synthesized with adipic acid and methanol using the 732 strong acid cation exchange resin as catalyst and 4A molecular as sieve adsorption.In addition, in the paper a technical analysis method also was established by gas chromatography for reactants. The various components of the reaction system could be well separated by using first-order program warming.In summary, a better reaction conditions of dimethyl adipate synthesized were optimized by the single factor and the orthogonal experimental design method in this article, the apparent kinetics of the reaction was disscussed, and the analysis method was suggested for their components in the reaction system. A certain design parameters and theoretical basis were provided for engineering design and industrialized production stage.