Feasibility of reactive distillation for methanol synthesis

Abstract

The performance of reactive distillation (RD) for methanol synthesis from syngas in terms of reactant conversions and methanol productivity was studied in this simulation work. An inert, high boiling solvent (tetraglyme) was used to maintain sufficient liquid load in the column under the reaction conditions. A fully reactive column with four reactive stages was considered and the results were compared with a conventional packed bed reactor (PBR) and a slurry reactor (SR). Six different syngas feed compositions were considered by varying the proportions of CO, CO2 and H2. A power law kinetic model for methanol synthesis on conventional Cu-ZnO-Al2O3 catalyst was used to simulate the RD and the SR, and a Langmuir-Hinshelwood-Hougen-Watson (LHHW) model was employed in the PBR for the same type of catalyst. Despite the high pressure (50 atm) used in the RD column, the presence of non-condensables allowed for separation and also removed the necessity for a reboiler. The performance of the RD was found to be comparable with the SR. Though the PBR gave higher methanol productivities due to the absence of a separate liquid phase, it exhibited lower conversions than the SR and RD for syngas rich in CO2.