Epoxidation of propylene to propylene oxide with molecular oxygen over Sb2O3–CuO–NaCl/SiO2 catalysts

• The direct propylene epoxidation catalysis of Sb2O3–CuO–NaCl/SiO2 was investigated.
• A propylene oxide selectivity of 43% with 0.7% propylene conversion is achievable.
• A total metal loading of 18 wt% and a 500 °C calcination temperature maximizes yield.
• The optimal Sb:Cu:Na metal weight ratio is 2:3:1.
• Epoxidation requires the presence of both Sb2O3 and CuO crystals.

Co-impregnated Sb2O3–CuO–NaCl/SiO2 catalysts were investigated for the direct gas-phase synthesis of propylene oxide (PO) from propylene and molecular oxygen at atmospheric pressure. The trimetallic system was optimized for PO formation by varying the Sb:Cu:Na ratios, total metal loadings and calcination temperatures. At a reaction temperature of 250 °C and propylene/oxygen molar ratio = 1:4, the highest performing catalyst achieved 40–45% PO selectivity with 0.4–0.7% propylene conversion without a co-feeding gas. The coexistence of Sb2O3 and CuO crystals was determined to play a vital role in propylene epoxidation, while NaCl helped to suppress combustion.

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