Modeling and simulation analysis of methanol conversion to olefins (MTO): A critical comparison of a honeycomb monolith and a fixed-bed of cylindrical extruded HZSM-5 catalyst

Abstract

The performance of a honeycomb monolith and a fixed-bed of cylindrical extruded HZSM-5 catalyst for the methanol to olefins process (MTO) are evaluated and compared using two-scale two-dimensional heterogeneous models in adiabatic and diabatic operations considering two approaches of “restricted comparison” and “free comparison”. The 53-step elementary reaction mechanism of Mihail and coworkers is used to model the MTO reactions. The effects of space-time (0.1–5 s), feed water content (up to 60 mol%), and monolith cell density (200–600 cpsi) on the catalyst temperature, feed conversion, and selectivity and yield of olefins are investigated. “Restricted comparison” indicates that the feed conversion and selectivity and yield of the total olefins in the monolithic reactor are greater than the fixed-bed with a maximum discrepancy of 5%. There is an optimum space-time of ~ 0.3 s at which the yield of total light olefins in the monolith and fixed-bed reactors achieves the maximum values of 0.45 and 0.43, respectively. The results of “free comparison” reveal that a 600 cpsi monolith can produce ~ 43% more light olefins using ~ 75% less catalyst mass at the optimal space-time of 0.3 s compare with a fixed-bed reactor at an identical specific surface area.