(619d) Sintering of Copper-Based Catalysts for Methanol Synthesis From Carbon Dioxide

Hydrogenation of carbon dioxide to methanol over Cu-based catalysts has been considered a viable pathway to reduction of greenhouse gas emissions.  Under typical reaction conditions, catalyst deactivation is primarily attributed to loss of active surface area and is accelerated by water vapor byproduct.  Therefore, Cu sintering remains one of the most significant technical barriers to the effective use of these catalytic systems.

Our approach for enhancing sintering resistance is to add promoters that can help suppress the crystallization of active catalytic phases during thermal treatment.  We have examined the sintering of Cu-based catalysts designed specifically for methanol synthesis from CO₂ using various techniques including N₂O decomposition, X-ray diffraction (XRD), and transmission electron microscopy (TEM).  The incorporation of gallium and yttrium oxides into our catalyst formulations is effective in maintaining high Cu dispersion, therefore leading to significant improvement in the overall performance.  Interestingly, ZnO remains well-dispersed or XRD-amorphous in best-performing catalysts.  We have also attempted to fit sintering data to a model that can predict a limiting Cu dispersion at infinite time.  Kinetic parameters such as rate constant and deactivation order obtained from curve fitting provide new insight into possible sintering mechanisms.  These findings have important implications for the rational design of robust catalytic systems for CO₂ conversion to fuels and chemicals.