Diffusion-dependent upgrading of hydrocarbons synthesized by Co/zeolite bifunctional Fischer–Tropsch catalysts

[Display omitted] •One-step production of synthetic liquid fuels was achieved using Co/zeolite bifunctional catalysts.•Structural and chemical properties of zeolites did not affect the intrinsic activity of Co.•Diffusion characteristics of zeolite correlated with chain growth probability and iso-paraffin content in liquid products.•Catalysts with fast diffusion facilitated isomerization and cracking of paraffinic hydrocarbons. The design of efficient zeolite-supported Co catalysts is essential for the further development of the one-step production of liquid fuels via the low-temperature Fischer–Tropsch synthesis (FTS). Herein, Co/zeolite catalysts were prepared from zeolites SSZ-13, ZSM-22, ZSM-11, ZSM-5, Mordenite, and Y. Their textural and acidic properties, Co dispersion, and internal diffusion behaviors were comprehensively analyzed, along with their FTS product mixtures. Counterintuitively, the degree of isomerization and hydrocarbon decomposition did not correlate with the acidic properties of the zeolite support. Instead, catalysts with high characteristic diffusivity delivered product mixtures with high degree of isomerization and decomposition, suggesting that the access of paraffinic hydrocarbons to the internal acid sites of the zeolite determines the upgrading performance of the bifunctional Co/zeolite catalyst in the low-temperature FTS reaction. Hence, the present findings support upcoming efforts on the design of new and effective FTS catalysts.