Study of supported heteropolyacid catalysts for one-step DME synthesis from CO₂ and H₂

Dimethyl ether (DME) is a versatile molecule, gaining increasing interest as a viable hydrogen and energy storage solution, pivotal for the transitioning from fossil fuels to environmentally friendly and sustainable energy supply. This research explores a novel approach for the direct conversion of CO₂ to DME in a fixed-bed reactor, combining the Cu/ZnO/Al₂O₃ methanol synthesis catalyst with supported heteropolyacids (HPAs). First, various HPAs, both commercially available and custom-synthesized, were immobilized on Montmorillonite K10. Using a wet impregnation procedure an almost ideal mono-layer of HPA on the support was achieved. The catalysts were further evaluated for their efficiency in direct synthesis of DME from CO₂/H₂ in combination with the Cu/ZnO/Al₂O₃ catalyst. Among the catalysts tested, tungstosilicic acid (HSiW) supported on K10 exhibited the most promising performance, achieving a DME yield (Y _DME) of 7.06% and a molar productivity (P _mol) of 77.84 mol_DME mol_HPA ^-1 h^-1. In a subsequent step, further tests using HSiW on various support materials identified ZrO₂ as the most effective support, increasing the molar productivity to 125.44 mol_DME mol_HPA ^-1 h^-1, while maintaining the DME yield. The results highlight the potential of applying HPA-based catalysts for sustainable DME synthesis directly from CO₂, emphasizing the critical role of the catalyst support for optimizing catalytic performance.