CO 2 hydrogenation to high-value-added light olefins over bifunctional catalysts is a promising pathway toward achieving net zero emissions. Herein, a series of SAPO-34 zeolites (bio-SAPO-34) with consistent acid properties but different particle sizes ( e.g. , 170 nm, 610 nm, and 7.50 μm) were synthesized using rice husk as the sole silicon source. Meanwhile, the rice husk derived SiO 2 (bio-SiO 2 ) could serve as a platform to assemble SAPO-34 and ZnZrO x into a bifunctional catalyst. It was found that the bio-SAPO-34 with the smaller particle size resulted in higher selectivity of light olefins and better long-term stability. Especially, after integration with ZnZrO x , the bio-SAPO-34 with a particle size of 170 nm exhibited higher light olefins selectivity (89.6 vs. 58.5 %) and longer catalytic lifetime (1000 vs. 59 min), as compared to a particle size of 26.0 μm. Notably, the zero length column (ZLC) technique, N 2 physisorption, and thermogravimetric analyses revealed that reducing the particle size of bio-SAPO-34 significantly decreases the diffusion resistance of light olefins in zeolites by shortening the diffusion paths, thereby inhibiting the formation of coke and enhancing the catalytic stability. Moreover, the bio-SiO 2 platform acts as a light olefins diffusion promoter by decreasing the surface diffusion resistance between zeolite particles and significantly alleviating the coke formation.
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.
危险品化学品经营许可证（带存储）