A computationally efficient multi-scale simulation of a multi-stage fixed-bed reactor for methanol to propylene reactions

•A heterogeneous model was solved efficiently by hybrid of Matlab and Comsol.•Recycling the undesirable olefins into reactor inlet promotes propylene yield.•The simulated reactor agrees well with an industrial reactor of 500 KTY.•Low propylene selectivity is due to large catalyst diameter and long contact time.

A multi-scale model incorporating interphase and intraparticle mass and heat transfer was established for a multi-stage fixed-bed reactor for methanol to propylene (MTP) process with recycle of the undesired olefins other than propylene. By converting the catalyst dimension and reactor dimension into a pseudo two-dimension and solving the resulting model by a hybrid method of Matlab and Comsol, the computation efficiency is 5 times higher than the conventional one that solves separately the single catalyst dimension at different reactor position. The model was validated by experimental data obtained from a lab-scale isothermal fixed-bed reactor. The calculated results show that propylene selectivity and methanol conversion achieve 62.6% and 99.99%, respectively, with space velocity of 0.741 gMeOH/gcat/h, which agree well with the practical data from a commercial six-stage Lurgi reactor with a capacity of 500 KTY propylene. It was found furthermore that the intraparticle diffusion resistance is notable and the contact time of reactant fluid is too long, resulting in a low propylene selectivity of the present commercialized MTP reactor, thus decreasing catalyst size, stage number and contact time will effectively promote propylene selectivity.