Synthesis of hierarchical nano-Y zeolite supported Pt catalyst for efficient hydrocracking of Fischer–Tropsch wax to jet fuel
The inherent diffusion constraints imposed by narrow micropores and elongated channels in Y zeolites severely limit jet fuel selectivity during Fischer-Tropsch wax hydrocracking. Advanced supports were synthesized via seed-directed crystallization (nano-Y-0P zeolite) and PDDA (polydiallydimethyl ammonium chloride)-mediated assembly (hierarchical nano-Y-xP zeolites, x = 0.1, 0.3, 0.6, 0.9). This dual-strategy synergistically addresses diffusion constraints in conventional Y-zeolite by optimizing nano structure of active sites and improving interfacial mass transfer (i.e., nano-crystal size and hierarchical porosity). Intelligent Gravimetric Analysis (IGA) directly validates hierarchical porosity and nanocrystalline advantages. Y-0.6P zeolite with optimal mesoporosity (0.75 cm 3 /g vs. 0.25 cm 3 /g in conventional Y-zeolite) and minimal crystallite size (131 nm vs. 1258 nm in conventional Y-zeolite) achieves intrinsic diffusion enhancement—the 5.36-fold higher diffusion rate than conventional S-Y zeolite. Zeolite crystallite size and hierarchical porosity critically govern metal–acid functionality balance by modulating acid site density (589.7 μmol/g vs. 812.4 μmol/g in conventional Y zeolite) and optimizing metal dispersion (40.5 %, vs. 18.26 % in conventional Y-zeolite). Pt/(Y-0.6P+ASA) catalyst achieves peak performance with 35.04 % C 9 –C 17 yield and 47.35 % selectivity in n-docosane hydrocracking. Notably, Fischer-Tropsch wax hydrocracking yields 26.83 % jet fuel (49.88 % selectivity) with ideal bell-shaped distribution. This work demonstrates Y-0.6P-supported catalyst has industrial potential for aviation fuel production from Fischer-Tropsch wax upgrading.
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