Synthesis of linear alkyl benzene sulfonic acid by gas–liquid sulfonation under annular flow pattern in the cross-shaped microreactor: Mass transfer model and reaction kinetics

The synthesis of linear alkyl benzene sulfonic acid (LABSA) by gaseous SO3-sulfonated linear alkyl benzene (LAB) under annular flow in microreactors is limited by the lack of sufficient mass transfer model and reaction kinetics support, which hinders the understanding of gas–liquid micro-sulfonation process and the enhancement of LABSA yield. Therefore, the mass transfer model with chemical reaction is established to overcome this difficulty. First, the gas–liquid physical mass transfer mechanism is proposed in the cross-shaped microreactor based on the stretching deformation of liquid elements at the phase interface and small-scale eddies, and the gas–liquid physical mass transfer model is obtained by computational fluid dynamics. Then, the macroscopic reaction kinetics model of gas–liquid micro-sulfonation process is established, and the kinetic parameters are obtained combined with the experimental results. Finally, the chemical mass transfer model is constructed by integrating the physical mass transfer model with the reaction kinetic parameters. Studies show that SO3 absorption rate can reach 97% at 602.4–1168.5 mm of the microreactor. This study can guide SO3 concentration distribution in the microreactor and provide a theoretical basis for the length design of microreactors and the optimization of gas–liquid velocity conditions.