New insight into the activity of ZSM-5 supported Co and CoRu bifunctional Fischer–Tropsch synthesis catalyst

• PEG-additive method can deposit almost Co3O4 particles on exterior surface of ZSM-5.
• PEG additive method improves the reduction and CO conversion of Co/ZSM-5 catalyst.
• ZSM-5 supported Co catalyst adsorbs H stronger than SiO2 supported Co catalyst.
• CoRu synergistic effect weakens H–catalyst interaction.
• CoRu/ZSM-5 catalyst produce more gasoline hydrocarbons than Co/ZSM-5 catalyst.

The PEG-additive method was used to prepare the ZSM-5 supported Co- and CoRu-based bifunctional Fischer–Tropsch synthesis (FTS) catalysts. This method facilitated the deposition of Co3O4 particles on the exterior surface of ZSM-5 support. The resultant catalyst had better reducibility than the conventional impregnation method derived catalyst. Although the PEG-additive protocol could improve the CO conversion on Co/ZSM-5 catalyst, the ZSM-5 supported Co catalyst adsorbed H species stronger than the SiO2 supported Co catalyst. As a result, the Co/ZSM-5 catalyst had lower turnover frequency (TOF) than Co/SiO2 catalyst. The presence of trace Ru promoter by the PEG-additive method could form bimetallic CoRu particles on CoRu/ZSM-5 catalyst. The Co–Ru synergistic effect improved the TOF value and the C5+ selectivity of CoRu/ZSM-5 catalyst by weakening the interaction between the H species and catalyst instead of altering the nature of Co0 sites. This effect allowed the CoRu/ZSM-5 catalyst produce more gasoline-range hydrocarbons than Co/ZSM-5 catalyst in the FTS reaction.