Experimental Investigation of Sorption-Enhanced CO2 Hydrogenation to Methanol

In this work, we investigate experimentally the use of zeolite 13X as an efficient water sorbent in the sorption-enhanced CO2 hydrogenation reaction over Cu/ZnO/Al2O3 under different operating conditions and over multiple reaction–regeneration cycles. Introduction of the solid sorbent along with the catalyst in the reactor leads to a prominent increase in the CO2 conversion and CH3OH yield. As the reaction proceeds, the sorbent gradually becomes saturated, the enhancement effect reduces, and the system eventually reaches the same steady state as with catalyst only. The CH3OH yield increase is higher than that of the CO2 conversion, indicating preferential enhancement of methanol production. This can be attributed to the partial co-adsorption of both methanol and water on zeolite 13X. The effects of reaction and regeneration temperature on the activity, product distribution, enhancement degree, and recyclability are also examined. The highest sorption enhancement occurs at 225 °C, with the methanol yield increasing by 115% compared to the conventional process. The cyclic stability is investigated by consecutive reaction–regeneration cycles. The correlation between activity reduction and textural properties of both the catalyst and sorbent as well as the zeolite’s ability to regenerate are explored. To that end, the effect of regeneration temperature on the products’ desorption is also examined.