Monitoring the Fate of Zn in the Cu/ZnO/ZrO2 Catalyst During CO2-to-Methanol Synthesis at High Conversions by Operando Spectroscopy.

In the frame of developing a sustainable chemical industry, heterogeneously catalyzed CO2 hydrogenation to methanol has attracted considerable interest. However, the Cu-Zn based catalyst system employed in this process is very dynamic, especially in the presence of the products methanol and water. Deactivation needs to be prevented, but its origin and mechanism are hardly investigated at high conversion where product condensation is possible. Here, we report on the structural dynamics of a Cu/ZnO/ZrO2 catalyst at 90 bar and 40 % CO2 conversion (at equilibrium conditions), investigated in a dedicated metal-based spectroscopic cell specially fabricated using additive manufacturing. This particular reactor configuration aims to mimic the high CO2 conversion part of the catalyst bed and can induce product condensation, which is monitored by operando X-ray absorption spectroscopy. While Cu remained mostly stable throughout the experiment, Zn underwent strong restructuring. The chosen reaction conditions, including the use of CO2 as carbon source and in situ product condensation, were selected to provide insights under industrial conditions. This work is highlighting the importance of spectroscopic investigations at high conversion levels, offering insights into chemical transformations during deactivation, extending the concept of spatially resolved studies, and thus providing guidance for the design of more stable catalysts.