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