Effect of zeolite type in sorption-enhanced CO2 hydrogenation to methanol

The use of solid adsorbents for in-situ water removal can overcome thermodynamic constraints that limit CO2-derived methanol production to low levels. In this work, the water and methanol adsorption/desorption capacity and kinetics of four different zeolites (LTA-3A, LTA-4A, LTA-5A and FAU-13X) are investigated in a thermogravimetric setup equipped with a mass spectrometer. When water is replaced with methanol, the sorption kinetics are faster, the capacity is larger and the differences between the sorbents are more prominent. Co-adsorption is also evidenced on all zeolites. Use of the sorbents as admixtures with a commercial CuO/ZnO/Al2O3 catalyst in sorption-enhanced CO2 hydrogenation experiments at 250 °C and 70 bar increases CO2 conversion by 48–56 % and CH3OH yield by 63–70 %. Zeolites 4A and 13X demonstrate the highest performance improvement and 3A the lowest, while zeolite 5A leads to significant enhancement in methanol selectivity in agreement with the adsorption studies. Preferential methanol enhancement occurs due to the simultaneous sorption of methanol along with water. The stability, evaluated over consecutive cycles at the employed reaction-regeneration conditions, showcases zeolite 4A as the most stable adsorbent and zeolite 13X the least, in line with N2 adsorption/desorption and XRD observations. © 2024 Elsevier B.V.