Calcium Stearate as an Acid Scavenger for Synthesizing High Concentrations of Bromobutyl Rubber in a Microreactor System

The preparation of bromobutyl rubber (BIIR) faces two challenges, the high viscosity of the reaction system and the accumulation of generated HBr during the reaction, which result in lower productivity, higher energy consumption, and lower selectivity for BIIR-1. In this work, we developed an efficiently intensified technology using calcium stearate as the acid scavenger and a microreactor as the reaction platform. We successfully realized both high productivity and high selectivity for synthesizing high concentrations of bromobutyl rubber. The optimized results indicate that using predispersed calcium stearate in a butyl rubber (IIR) solution (x_Ca of about 0.8 wt %) as the acid scavenger could guarantee sufficiently high selectivity for BIIR-1 (w of almost 95%). A T-junction microreactor with slitlike microchannels is suitable for mixing a high-viscosity IIR solution and a Br₂ solution. As the concentration of IIR increases from 10 wt % to 15 wt %, the conversion of IIR could increase by 13%, and the residence time could be shortened to less than 1 min. The utility of the reactants and the reaction efficiency have both been largely improved.