Improved high shear mixers enhance fast halogenation reactions of alcohols

Abstract

In the view of green and sustainable synthesis, there is still a broad space for improvement with respect to the halogenations of the alcohol, which is facing up with the problems of high input and low yield. Herein, high shear mixers (HSM) were exploited first to enhance the bromination of tert-butyl alcohol by improving the mixing performance. Notably, the baffle plate (BP) was first proposed to facilitate the in situ separation of the product from the reaction system, promoting the reversible reaction equilibrium to shift toward the right direction. The influences of the molar ratio of reactants, temperature, feed rate, rotor speed, and height of BP were investigated on the reaction performance, which provides a facile and cost-efficient intensified technology to prepare 2-bromo-2-methylpropane. The maximum yield is achieved as 94.8% using HSM, obviously higher than that using CST (82.6%) and HST-Impeller (87.6%), and the reaction time can be shortened by 75%. Furthermore, such HSM and BP-HSM can successfully improve the yields of some fast alcohol halogenations with shorter reaction time. This ingenious exploration of BP in HSM provides valuable guidance on design new technology to intensify some fast organic chemical reactions with the products immiscible to the reactants.