Enhancing CO2 hydrogenation to methanol in fixed and fluidized bed reactors by selective in-situ adsorption of water

Methanol synthesis offers a significant pathway for carbon dioxide valorization and hydrogen storage. However, carbon dioxide hydrogenation to methanol is thermodynamically limited. To couple the process with biogenic carbon dioxide supply from organic wastes and green hydrogen, a way to shift the equilibrium by other means than the pressure must be found. This work investigates the underlying aspects of sorption-enhanced methanol synthesis by selective steam removal in fixed and bubbling fluidized bed configurations. Zeolite 3 A is chosen as a suitable sorbent based on its selectivity towards water and retention of sorption capacity between 220 and 280 °C. A dynamic model for simulation of the fixed-bed sorption-enhanced methanol synthesis shows reactor performance at the targeted application pressure of 20–30 bar. Enhanced product yields beyond thermodynamic equilibrium limits are obtained in a lab-scale reactor at 3 bar and 220–250 °C via over-stochiometric water adsorption. In both reactor configurations, low-pressure enhancement primarily promotes carbon monoxide yield. Predicted methanol yields at higher pressures reach similar values, which suggests implementing a two-stage process. The additional production relative to the total output expected under full equilibrium limitation results in a 14–23 % integrated enhancement for methanol and 17–20 % for carbon monoxide, depending on temperature and reactor configuration. During the sorption-enhancement peak, the maximum achievable yields reach 130–175 % and 160–185 %, respectively. The transient nature of sorption enhancement is highlighted, suggesting a fluidized reactor design for continuous regeneration in a separate vessel, promoted by a sharper water breakthrough than in a fixed bed, a more compact reactor volume, and improved temperature distribution. • Product yields are enhanced by selective in-situ water adsorption using zeolite 3A. • Comparable sorption-enhanced methanol synthesis in fixed and fluidized bed reactors. • Fluidized beds can facilitate continuous operation and uniform temperature profiles. • Fixed-bed dynamic simulations with estimated adsorption parameters guide scale-up. • Methanol synthesis as sustainable pathway for CO 2 upcycling and hydrogen storage.