Effect of sodium promotion on zinc-ferrite catalysts for CO and CO2 co-conversion: Insights from in situ and theoretical studies

초록

This study investigates the influence of sodium (Na) on the co-conversion of CO and CO2 over Na-promoted zincferrite catalysts. Using a combination of H2-TPR, CO-TPR, in situ Raman spectroscopy, calorimetry, and density functional theory (DFT) calculations, we demonstrate that Na significantly modifies catalyst performance. Even at low Na levels (Na/Fe = 0.06), CO conversion is accelerated by up to 120 times compared to CO2, while methanation is suppressed and olefin production is enhanced. However, excess Na leads to graphite formation and coke deposition. In situ Raman analysis reveals the transformation of Fe oxides into Fe carbides in Na-doped catalysts, while calorimetry indicates a reduced strength in the exothermicity associated with suppressed methanation and enhanced C2+ hydrocarbon formation. DFT calculations further demonstrate that high Na content strengthens adsorption, particularly for CO2 and 1-hexene, increasing the likelihood of coke formation. These findings emphasize the key role of Na in modifying catalytic activity and offer valuable insights for optimizing CO/CO2 co-conversion processes.

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