Comparative simulation study of methanol production by CO2 hydrogenation with 3A, 4A and 5A zeolites as adsorbents in a PSA reactor

Abstract

In this work, the performance of 3A, 4A and 5A zeolites in a PSA reactor to obtain methanol by CO2 hydrogenation has been compared by numerical simulation. Henry's constants of adsorption and the reciprocal diffusion time constants of water and methanol in these adsorbents have been measured in the reaction temperature range (200–350 °C) to simulate their performance using a zeolite/Cu-ZnO-Al2O3 catalyst mixture. A new cycle has been proposed for PSA reactors including a complete recirculation of heavy product, without using a purge. The best performance is obtained with 3A zeolite, having the lower water and methanol affinities facilitating bed regeneration. With the proposed process, methanol can be produced from CO2 hydrogenation at 250 °C and 50 bar with a conversion of 99.6% in one step, a selectivity of 83–96%, and productivities of 0.023–0.13 mol m3 s−1. The process has minimal loss of H2 in the form of water (1 mol H2O/mole converted CO2).