Study On The Synthesis Process Of Dimethyl Phthalate From The Viewpoint Of Chemical Reaction Engineering

Dimethyl phthalate (DMP) is a common plasticizer with excellent dissolving capacity for many kinds of resins, which can be added to cellulose resins, acrylic resins and polyurethane resins, and also has a wide range of other industrial applications, such as building materials, paints, pesticides, cosmetics and so on. The most important production route of DMP is the catalytic synthesis of phthalic anhydride (PA) with methanol (MeOH) using the batch stirred tank in the presence of sulfuric acid, but the production scale and efficiency are not satisfactory, it is very urgent to upgrade the synthesis process.In comprehensive consideration of the excellent mixing performance of oscillatory flow reactor (OFR) and energy saving advantages of falling film evaporator (FFE), this paper proposed a serial multi-stage continuous synthesis process using a composition unit of OFR and FFE. An experiment taking the time series of composition unit of stirred tank reactor and vacuum distiller to simulate the space series of the continuous process was carried out. The result shows that acid value of final mixer reduces to the value which meets the requirements of industrial quality product by five or six stages series reaction. This proves that the new continuous process is feasible.Although the synthesis process of DMP catalyzed by sulfuric acid has been implemented in industrial scale production, the relative quantitative kinetics results of this reaction are not published. Due to lack of kinetic parameters for reactor design and process analysis, the continuous process design and optimization cannot be carried out either. This has become the key factor that influences the synthesis process development or optimization of DMP.Through a series of experiments, this paper measured components concentration data under different time and at the temperatures ranging from 353.15K to 383.15K and the concentration of sulfuric acid ranging from 0.2% to 0.9%, then got the numerical relations of reaction rate, components concentration, catalyst concentration and temperature by numerical method, and then derived the reasonable functional relationships of reaction order, equilibrium constant, reaction rate, preexponential factor, activation energy and catalyst concentration or temperature by statistical analysis method, at last, established quantitative expression of complete macrokinetics model.This paper applied serial muti-tank model with secondary flow and inter-cell back-mixing (SMTSIB) and the above macrokinetics model to numerically simulate the synthesis reaction of DMP in three step series combination unit, then at a certain temperature, a certain catalyst concentration and under the condition of oscillation frequency of 2.8Hz, amplitude of 3mm and total residence time of 364.25min, the conversion rate of monomethyl phthalate is 89.84%.