(618b) Understanding CO2 Conversion to Methanol on Cu/ZnO/Al2O3 Using Microkinetic Modelling

Technological improvements are crucial for CO₂ conversion since they can contribute to the efficient closure of the carbon loop and utilization of renewable energy sources with the focus to create a stable and safer future. Methanol synthesis from CO₂ is a young process compared to syn–gas transformation. Essential differences between these two processes need to be addressed and potentially used to gain an advantage for optimal production.

We previously found a correlation between the H₂O partial pressure, as a product of CO₂ hydrogenation, and a copper nanoparticle size increase at Cu/ZnO/Al₂O₃ and developed a deactivation model with pressure and temperature as input variables. We continued the study to determine the effects of structural changes on catalytic properties with the focus on identification and quantification of active sites. The brass was formed during H₂ reduction, evidenced by the Cu crystal unit cell size increase. However, during the reaction, coverage of the Zn phase over Cu nanoparticles increased, which promoted MeOH and CO synthesis. A thick overlayer was found as inactive, pointing to close interaction of Cu and Zn phases as optimal. A microkinetic model of MeOH synthesis was constructed, based on the determined structure and the corresponding density functional theory study. Using this model, we can select a number of Cu and Zn sites, which are the most influential structural parameters affecting activity for Cu/ZnO/Al₂O₃.

We can enhance the process by using a combination of perm–selective membranes and conventional methanol synthesis reactors. Additionally, we can largely remove steam from the reactor, which is the Achilles heel of current commercial catalysts and therefore increasing its lifetime. We applied the microkinetic model for the description of membrane–assisted methanol synthesis and found a good description of experiments and increased rate of methanol synthesis compared to a conventional packed bed reactor.