Combining wet impregnation and dry sputtering to prepare highly-active CoPd/H-ZSM5 ternary catalysts applied for tandem catalytic synthesis of isoparaffins

Abstract

Tuning hydrocarbon distribution in Fischer–Tropsch synthesis is greatly challenging. By employing three different pathways to deposit trace palladium on Co/H-ZSM5 catalyst, tunable isoparaffin and olefin selectivity was successfully achieved. The impregnated Pd showed poor promotion of Co dispersion and reducibility, producing a slight enhancement of FTS activity and isoparaffin selectivity. The unique mechanical stir during Pd sputtering induced re-dispersion of impregnated Co/H-ZSM5 particles and Pd was deposited with an intimate distance to Co species and with a weak interaction combining zeolite, due to which complete hydrogenation of olefins was achieved. The surface enriched Pd on pre-sputtered Co catalyst was inclined to form Pd–Co nano-alloys, suppressing the chain growth activity by excessive hydrogenation process.