Promotional role of methanol and CO2 in carbon dioxide-rich syngas hydrogenation over slurry reactor utilizing combustion induced Cu-based catalysts

Abstract

Converting CO₂ to methanol directly remains a hurdle due to catalyst and thermodynamic limitations. This study proposes a solution: using Cu–MgO–CeO₂ (CuMgCe) catalysts (synthesized by solvent combustion) in slurry reactors for methanol formation through methanol-assisted CO₂-rich syngas hydrogenation. The key innovation lies in the catalyst design by focusing on CO₂-rich syngas mixtures, we establish a crucial link between catalyst structure and its activity (structure-activity relationship). Our CuMgCe catalyst achieves a space-time yield of 646 g_MeOH/kg_cat-h⁻¹, exceeding lab-made industrial catalysts (608.5 g_MeOH/kg_cat-h⁻¹). This yield is further boosted by 5% through an ingenious method - adding initial methanol, which promotes formate intermediates for enhanced productivity. In-depth analysis reveals CO₂ formation during CO-TPD-MS and CO-TPR-MS, generating highly active surface species (CO₂^δ−) ideal for forming formate intermediates. In-situ DRIFTS confirms the dominance of this formate pathway on CuMgCe for selective methanol synthesis. A mechanistic study sheds light on the synergistic effect of MgO and CeO₂ in the lab-prepared CuMgCe catalyst. This synergy promotes methanol formation during CO₂-cofed syngas conversion. This research paves the way for highly efficient and selective catalysts for CO₂ utilization in slurry reactor technology, offering a significant step towards cleaner fuel production.