Study On Synthesis Technology Of Benzyl Alcohol By Two-step Method

Benzyl alcohol is the most important aromatic alcohol. Nowadays benzyl alcohol is synthesized by the hydrolysis of benzyl chloride in the presence of alkali, but with almost 10-20% benzyl ether, the by-product. So we try to develop a new method of synthesizing benzyl alcohol from benzyl chloride with high selectivity and yield.Benzyl ether is easy to condensed from benzyl chloride in the presence of alkali. In order to prevent production of benzyl ether, benzyl chloride must not contact with alkali. New way, two-step synthesis of benzyl alcohol from benzyl chloride, was proposed, and the process consists of esterification reaction between benzyl chloride and sodium formate in the presence of PTC (phase-transfer catalyst) and esterolysis reaction of esterification mixture was deeply studied, and a kinetics model of esterification was developed. These are the guiding to plant design of benzyl alcohol.In the stirred vessel, some factors are observed and studied, including the reaction temperature, the initial mole ratio of benzyl chloride to sodium formate, the volume ratio of water to benzyl chloride, and the catalyst amount during esterification, and the esterolysis temperature, the speed of feed-in alkali and the volume ratio of water to esterication mixture during hydrolysis. The optimal esterfication reaction conditions as following, the esterification temperature is 115℃, the initial mole ratio of benzyl chloride to sodium formate is 1:1, the volume ratio of water to benzyl chloride is 1:1, and the catalyst amount is 2% according to the quantity of benzyl chloride. And the optimal esterolysis reaction conditions as following, the reaction temperature is 100℃, the speed of feed-in alkali is 5mL/h and the initial volume ratio water to esterification mixture is 1:1. Under the optimal conditions, the conversion of benzyl chloride is nearly 100% during esterification, and the total yield of benzyl alcohol is higher than 98%, the percent of benzyl ether is lower than 2%. The mother solution of esterification and esterolysis were recycled to prevent the discharging and made it to a cleanness process. On the basis of data of esterification between benzyl chloride and sodium formate with phase-transfer catalyst, three kinetics models were investigated, using the experimental data to validate the model, and the parallel-consecutive-reversible reaction network is determined. This network is:The rate constants are fitted according to the Marquardt method. The experimental data and the fitted data are identical, the kinetics parameters were obtained from the Arrhenius equation, was 83.768KJ/mol, was 69.998 KJ/mol, was 33.666 KJ/mol, was 166.030 KJ/mol。During esterification of benzyl chloride and sodium formate, benzyl formate is esterilysis which is a reversible reaction, and the mole ratio of benzyl formate to benzyl alcohol is 3:7 because of the chemical equilibrium.The study of this article has value for develop of high-yield synthesis of benzyl alcohol and the enlargement of reaction vessel.