Role of Ce-Zn nanocatalyst and solvent impact in carbon dioxide-epoxide cycloaddition

Abstract

Carbon dioxide (CO₂) makes an appealing building block and has a crucial role in the environment. An arduous issue is turning the captured CO₂ into valuable compounds. This study outlines a CO₂ cycloaddition reaction with an epoxide using N,N-dimethylformamide (DMF) as a solvent, Ce-Zn mixed oxide catalysts, and tetrabutylammonium bromide (TBAB) as a co-catalyst. The prepared catalysts were characterized using XRD, SEM-EDX, BET, TGA, FTIR, and TPD measurements. Studies were performed in a high-pressure top-stirred batch reactor. As measured by the propylene oxide (PO) conversion and propylene carbonate (PC) yield, the catalytic activity has a strong association with medium and weak acid-base sites, showing that acidity and basicity are crucial components for this reaction. Adding DMF with a CeO₂ catalyst resulted in lower PO conversion and PC yield. Although TBAB alone acts as an excellent catalyst for this reaction, it was found that CeO₂ and TBAB combined as catalysts and co-catalysts can give exquisite results. All reaction parameters were optimized, and a maximum PO conversion of ≈92 % and PC yield of ≈84 % was achieved without any solvent or co-catalyst.