Selective Iron Catalysts for Direct Fischer-Tropsch Synthesis to Light Olefins

Ethylene, propylene, and butylene may be directly produced through selective CO hydrogenation over Fischer-Tropsch to light olefins (FTO) catalysts. It is known that Fe-based catalysts promoted by S/Na synergistic effect may reach a C-2(=)-C-4(=) hydrocarbon selectivity of 53% at 20 bar. Herein, we report a zeolite-free, potassium-promoted iron FTO catalyst modulated by high-temperature annealed composite oxides, 15%Fe/2%K2O/83%ZnAl8O13, exhibiting a C-2(=)-C-4(=) hydrocarbon selectivity of 64.4% at a total pressure of ca. 20 bar, which is one of the best practicable hydrocarbon selectivity values for Fe-based FTO catalysts so far. Simultaneously, its contents of ethylene in C-2 (i.e., the C-2 olefin fraction), propylene in C-3 (i.e., the C-3 olefin fraction), and butylene in C-4 hydrocarbons (i.e., the C-4 olefin fraction) achieve 88, 92, and 89%, respectively.

Automated summary

A highly efficient potassium-promoted iron catalyst modulated by composite oxides exhibited a high selectivity of 64.4% for olefins at 20 bar, making it one of the best practical values for Fe-based FTO catalysts. Additionally, the catalyst showed exceptionally high contents of ethylene, propylene, and butylene.