Tunable isoparaffin and olefin synthesis in Fischer–Tropsch synthesis achieved by composite catalyst

• A hierarchical HZSM-5 was developed by using dual templates.
• Facilely realizing the direct middle isoparaffin synthesis via FTS reaction
• An anti-ASF product distribution was realized over the mesoporous Co/HZSM-5 catalyst.
• The shape-selective catalysis was offered by the mesoporous HZSM-5 zeolite.

Hierarchical HZSM-5 zeolite with combined micropores and mesopores was synthesized by one-step approach with TPAOH and F127 as dual templates. The physical and acidic properties of the hierarchical HZSM-5 zeolite were characterized by XRD, N2 adsorption–desorption isotherm, SEM, TEM, and NH3-TPD techniques. The hierarchical HZSM-5 zeolite exhibited a significantly higher mesopore surface area and larger mesopore volume than that of the conventional HZSM-5. The prepared hierarchical HZSM-5 and conventional HZSM-5 zeolite supported cobalt catalysts were evaluated via Fischer–Tropsch synthesis (FTS) reaction to tune product selectivity. Compared with the conventional catalyst, the CO conversion of FTS reaction on the present catalyst increased significantly. Meanwhile, the C5 + selectivity and isoparaffin selectivity also increased. The C5–11 hydrocarbons with a lot of isoparaffin and olefin had become the main FTS products due to the optimized hydrocracking and isomerization afforded by the hierarchical pore structure, different from the conventional FTS hydrocarbons which were mainly composed of normal paraffin.

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