Process development aspects of production of dibenzyl ether

Abstract

To develop an economically viable process for the synthesis of dibenzyl ether, the reaction of benzyl chloride with aqueous sodium hydroxide in the presence of phase-transfer catalysts has been investigated. The effects of agitation speed, catalyst type and concentration, reaction temperature, mole ratio of reactants, concentration of aqueous sodium hydroxide on the conversion of benzyl chloride, and yield of dibenzyl ether have been evaluated. Tributylamine is found to be a suitable catalyst. The reaction is favored by high molar ratio of sodium hydroxide to benzyl chloride. Conversion of benzyl chloride to benzyl alcohol is found to be the rate-controlling step at high sodium hydroxide concentration. Deprotonation of benzyl alcohol at the interphase by aqueous sodium hydroxide is a key step in the formation of dibenzyl ether. The yield of dibenzyl ether is dependent on the concentration of sodium hydroxide in the aqueous phase, the yield being almost 100% at high concentrations of sodium hydroxide. The successful recycle of excess NaOH in the aqueous phase in subsequent batches, without affecting the progress of the reaction, has been demonstrated.