The Study On Reaction Process Of Methanol With Mixed Dibasic Acid

Mixed dibasic acid(DBA)were composed of adipic acid, glutaric acid, succinic acid, which come from the oxidation of cyclohexane and producing process of adipic acid from KA oil.The recycle of mixed dibasic acid has attracted much attention for they were important chemical raw materials and had high economic value. The existing studies suggest that how to obtain monomer acid from the mixed dibasic acid with high purity exists a lot of technical barriers, however the esterification of DBA is a feasible method. Among them, the reaction of methanol with mixed dibasic acid to mixed dibasic esters(DBE) is green feasible process. The technology will have broad prospect of industrial application, and be in line with the green chemistry development thought. However, the existing research have little correction on the study of reaction process of methanol with mixed dibasic acid, including the study of series multi-step complex kinetic network with onsidering both esterification and hydrolysis at the same time. There was also lack of the study on the solid liquid equilibrium of mixed dibasic acid in the reaction system.Based on the above problems, the reaction process of mixed dibasic acid with methanol were studied in this paper, a feasible analysis method has been set up, the appropriate catalyst was selected, the process conditions were optimizied, ester hydrolysis reaction kinetics model was established, the kinetic parameters was obtained. At the same time, the solubility of three dibasic acid in the relevant system were measured, and the thermodynamic model of solid liquid equilibrium was established which can provide the basis data for industrial design about the reaction of DBA with methanol. Concrete research content was as follows:Firstly, the products of the reaction were analyzed qualitatively by GC-MS, further dimethyl adipate, dimethyl glutarate and dimethyl succinate were analyzed quantitatively by gas chromatography, adipic acid, glutaric acid, succinic acid, mono-methyl succinate, mono-methyl glutarate, mono-methyl adipate were analyzed quantitatively by HPLC. The mass fraction of water was determined by Karl Fischer AKF-1B.Their own standard curves were got, and the method of quantitative analysis was established.Secondly, the influences of different catalysts and dehydrant for the ester reaction of mixed dibasic acid with methanol have been examined, thus under the condition of sodium hydrogen sulfate as catalyst, factors of esterfication such as the temperature j the ratio of acid to alcohol, reaction time, catalyst content were investigate by orthogonal experiment. Base on the yield of DBE, the best conditions were temperature 65 T, the ratio of acid to alcohol was 1:8, catalyst dosage was 8%, the reaction time was 1.5 h. Under the best experimental conditions, the experiment was repeated three times, the yield of dimethyl adipate, dimethyl glutarate and dimethyl succinate can reach 83.5%, 87.0% and 90.0% respectively.Thirdly, kinetics model that condiderding esterification and hydrolysis were established. The data was disposed by the function of ode45(F) in MATLAB.The calculated data and experimental data can be a very good match. A total of 24 kinetic parameters were obtained. The influence of temperature on reaction rate of esterification and hydrolysis has been analysed. The results show that temperature has little impact on the first step in dibasic acid to generate monoester, and the second step that monoester to DBE was the control of the whole reaction,what's more, the generation rate of dimethyl succinate was affected more easily.Forthly, A set of laser device for solid liquid balance was established to measure solubilities of the three dibasic acid in methanol and dimethyl adipate mixed solvent at 283.15 K ~333.15 K. Apelblat model, the NRTL model and $h model were adopted to correlate the solid-liquid equilibrium data, and corresponding model parameters were obtained.Results showed that Apelblat model and NRTL model can be very good correlated the solubilities of these three dibasic acid,the average relative error was within 3%.However the $h model for the correlations of solubilities of adipic acid and succinic acid in methanol and dimethyl adipate mixed solvent were bad when the mass fraction of dimethyl adipate was less than 10%. the average relative error was as high as 20%.