Ni_5-xGa_3+x Catalyst for Selective CO₂ Hydrogenation to MeOH : Investigating the Activity at Ambient Pressure and Low Temperature with Microreactors

Methanol obtained from the direct hydrogenation of CO₂ at low pressures and temperatures can be used as a fuel/chemical feedstock and, if paired with renewable energy sources, could strongly contribute to reach a more sustainable society.

We have studied the catalytic performance of the intermetallic compound Ni_{5- x}Ga_3+x for methanol production. The catalyst shows outstanding activity and selectivity at low temperatures, outperforming the conventional Cu/ZnO. At higher T, the selectivity promptly shifts towards the production of methane and CO, leading to surface poisoning. Nevertheless, the experiments demonstrate the possibility of full regeneration of the catalyst by hydrogen reduction. Lastly, high stability over time under reaction conditions makes it an interesting candidate for scale-up and future industrial application. 

A variety of techniques are used to characterize the surface before and after reaction, including XPS, HR-SEM/STEM, XRD, etc., along with close collaboration with computational theoreticians for DFT calculations. All the experiments are performed in state-of-the-art equipment: microreactors of 256 nL are used for catalytic testing. The inlet flow rate is in the order of magnitude of nanomoles/min, making it possible for all the gases to enter directly the QMS, leading to extremely high product detection sensitivity. This, together with an almost immediate temperature control, makes our system ideal for further fundamental studies about CO₂ hydrogenation.