Study On Two-step Preparation Of Neopentyl Glycol From 2,2-dimethyl-3-chloro-propanol

Neopentyl glycol has wide range of uses, not only in the production of polyester and aromatics, cycloalkanes choice of separation, but also in the field of pharmaceutical applications. As a condensing agent, a large amount of neopentyl glycol was consumed in the preparation of ibuprofen, at the same time, by-product waste contained 2,2-dimethyl-3-chloro-propanol. It would severely restrict the economic production process and environmental indicators, if not effective recovery and treatment. This article studied the preparation process of neopentyl glycol by cycliazation reaction and hydrolysis reaction from 2,2-dimethyl-3-chloro-propanol.In this paper, 2,2-dimethyl-1,3-epoxy propane was prepared from 2,2-dimethyl-3-chloro-propanol by cycliazation under different catalysts; neopentyl glycol was generated from 2,2-dimethyl-1,3-epoxy propane by hydrolysis under different catalyst. The optimized cycliazation process conditions were obtained by studying the effects of different phase transfer catalysts and their dosage, different alkali, alkali dosage, alkali concentration. The optimized hydrolysis process conditions were also obtained by studying the effects of different hydrolysis catalyst, catalyst amount, stirring speed, reaction temperature, and phase transfer catalyst. The kinetic model of cycliazation reaction under the optimized cycliazation process conditions was established, the kinetic parameters and cycliazation reaction activation energy were obtained by fitting the kinetic experiments to the model.The results of experimental show that the optimum conditions of the preaparation of 2,2 - dimethyl -1,3 - epoxy propane by the cycliazation of 2,2 - dimethyl -3 - chloro-propanol under phase transfer catalyst are: surfactant S1 as the phase transfer catalyst and the dosage of it is 3% of 2,2-dimethyl-3-chloro-propanol volume, the molar ratio of sodium hydroxide to 2,2 - dimethyl -3 - chloro-propanol = 1.4:1, the concentration of sodium hydroxide is 45%(wt).The cycliazation yield is 91.16% under this optimized cycliazation process conditions.It was shown that the kinetics of cycliazation reaction under phase transfer catalysts is a pseudo first-order reaction, the activation energies evaluated is 0.99×104J/mol, the pre-exponential factor is 1.44×106min-1. Mass transfer of two phases is the controlling step for the reaction and the reaction mechanism is intramolecular SN2 nucleophilic substitution reaction.The method for quantitative analysis of neopentyl glycol in water -based multicomponent system by gas chromatography internal standard curve using 1,3-propanediol as internal standard has been developed. The linear regression equation is y = 0.02786 x? 0.00627; regression coefficient is 0.9989; the relative standard deviation is 1.88% and the detection limit of this method is 2.0×10-6g/ml. The mechanism of 2,2 - dimethyl -1,3 - epoxy propane hydrolysis to generate neopentyl glycol is acid hydrolysis reaction mechanisms. The optimum conditions of the preparation of neopentyl glycol by the hydrolysis of 2,2 - dimethyl -1,3 - epoxy propane is: surfactant S2 as phase transfer catalyst and the dosage of it is 1% of 2,2 - dimethyl -1,3 - propylene of the amount; the concentration of sulfuric acid is 3.5%; the volume ratio of 2-2 Methyl-1,3-epoxy propylene to water is 1:7; the reaction temperature is 55℃and stirring speed is more than 40r/min. The average yield of hydrolysis reaction is 95.47% under the optimum conditions.According to the above researching results,neopentyl glycol recovery process by the two-step reaction from waste contained 2,2 - dimethyl -3 - chloro-propanol in ibuprofen was designed. The sizes and materials of various equipments were determined as well.This design host great value of industrial guidance and industrial applications show that the process is reasonable and technology is feasible.