Unveiling the Role of Zn/Zr Ratios in ZnO/ZrO Catalysts Prepared via Reverse Co-precipitation Method for Efficient CO to Methanol Conversion.

This study evaluates the catalytic performance of ZnO/ZrO catalysts, which were synthesized through reverse co-precipitation with Zn/(Zn + Zr) ratios varying from 0 to 100%, for converting CO into methanol (CHOH). The catalysts underwent systematic characterization using XRD, TEM-EDS mapping, N adsorption-desorption, XPS, and TPD-MS techniques, focusing on both H and CO interactions. Results showed that pure ZnO typically forms as aggregated needles, while pure ZrO manifests as clustered aggregates of significantly smaller nanoparticles. At lower Zn contents (20-30%), ZnO particles are small and evenly distributed among the ZrO nanoparticles, effectively inhibiting ZrO aggregation. Conversely, at higher Zn contents (40-80%), ZnO particles increase in size, while ZrO particles remain smaller and tend to accumulate predominantly on the surfaces of the larger ZnO particles. Catalysts with a predominance of ZnO contents exhibited greater H adsorption, whereas those with higher ZrO contents showed increased CO adsorption. The Zn60Zr40 (60 wt % Zn) catalyst was identified as optimal, achieving 11.8% CO conversion at 340 °C, with a peak CHOH selectivity of 74.0% at 320 °C and a CHOH yield of 6.1% at 340 °C, maintaining excellent stability over 100 h. Furthermore, the study found a direct correlation between catalytic activity and gas adsorption: higher H adsorption rates significantly improved CO conversion, while CHOH selectivity was more influenced by CO adsorption. These findings underscore the importance of adsorptive properties in determining product distribution and offer essential insights for designing ZnO/ZrO catalysts optimized for efficient CHOH production from CO hydrogenation.