Improving the performance of hydroisomerization catalysts for jet fuel production remains a considerable challenge, due to the difficulty in precisely controlling the balance between metal and acid functions. Although zinc modification offers a promising strategy to enhance the synergy, the underlying mechanistic understanding of Zn-induced framework repair and reconstruction remains unclear, blocking the rational design of bifunctional catalysts. In this work, A series of Zn-modified SAPO-11 zeolites with tunable ZnO/Al 2 O 3 ratios were synthesized via in-situ doping technique. Characterization results revealed that Zn substitution for Al altered the silicon incorporation environment. The formation of Si-O-Zn bonds (NH 3 adsorption energy = -0.99 eV) indicated weaker acidity than Si-O-Al bonds (−1.44 eV). At ZnO/Al 2 O 3 = 0.5% doping, isolated P-O-Zn bonds promoted the dispersion and dissolution of large silicon islands (Si(4Si)), increasing weak Brønsted acid sites. At higher Zn doping, the mechanism shifted inducing Si redistribution and forming medium-strong Brønsted acid sites. Namely, a dual role of Zn was identified as framework repair at low loading and framework reconstruction at high loading. The weakened and dispersed acidity enhanced Pt dispersion and reducibility, enabling Pt/(0.75ZnSAPO-11 + ASA) catalyst to deliver the highest iso-C 22 yield (30.9%) and selectivity (58.7%), with double-branched isomer yield (10.8%) and selectivity (20.6%). This work highlights the underlying mechanism of Zn modification in catalyst framework, and demonstrates its implications for enhancing the industrial application of Zn-modified catalysts in Fischer-Tropsch wax upgrading and jet fuel cold-flow performance.
The synthesis of SAPO-34 hollow fiber membranes employs the ball-milling assistant method to enhance membrane yield and quality. These membranes are then combined with CrO x /Al 2 O 3 catalyst to create a packed bed membrane reactor (PBMR) for propane dehydrogenation (PDH). The study investigates the impact of operating temperatures, weight hourly space velocities (WHSV), and sweep gas flow rates on the SAPO-34 zeolite membrane reactor's performance, comparing it to a traditional packed bed reactor (PBR). The removal of hydrogen from the reaction side significantly improves propane conversion, surpassing thermodynamic equilibrium. In PBMR, propylene selectivity slightly exceeds that in PBR, influenced by side reactions like hydrogenolysis and cracking after hydrogen removal. Furthermore, the SAPO-34 zeolite membrane reactor undergoes a prolonged stability test with frequent regeneration using pure propane as feedstock to simulate industrial conditions. It exhibits consistent performance over 120 regeneration cycles within 240 h, maintaining similar H 2 permeability and H 2 /C 3 H 8 selectivity as the fresh membrane post long-term testing.
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