Methanol and dimethyl ether are highly efficient hydrogen carriers due to their impressive energy density, compatibility with existing energy infrastructure, and both are crucial precursors in various industrial applications. Importantly, both methanol and dimethyl ether can be synthesised from carbon dioxide and hence represent potential carbon utilisation strategies for clean fuel generation. However, the CO2 hydrogenation to methanol and subsequent dehydration to dimethyl ether encounters significant obstacles, attributed to both thermodynamic constraints and catalyst deactivation caused by the presence of by-product water. To overcome these challenges, this investigation focuses on the development of innovative hybrid catalytic membrane reactors, utilising high temperature resistant polymeric membranes, such as flexible polybenzimidazole (PBI) and polyimides. Conventional CuO/ZrO2 catalysts were deposited and embedded directly onto the membranes’ polymeric surface in a one-step process by direct flame spray pyrolysis. The precursor catalytic solution was introduced into the flame spray pyrolysis reactor at various flow rates and atomized into a fine spray using a dispersion, resulting in nano-catalyst adhering to the membrane surface in a highly porous layer, ideal for the CO2 hydrogenation reaction.
At 200°C and 20 bar, the catalytic membrane reactor exhibited exceptional performance, achieving at least a 9% improvement in CO2 conversion and a 30% increase in methanol production rate compared to a conventional fixed bed reactor. The subsequent dehydration of methanol to dimethyl ether took advantage of the high permeance of the membranes to water. This achieved a pressurized concentrated dimethyl ether product stream that was above the thermodynamic limitation in methanol dehydration. Hence, this investigation will demonstrate the potential of catalytic membrane reactors for methanol and dimethyl ether synthesis from CO2 hydrogenation.