Synthesis of Al-Doped SBA-15, MCM-41, MCM-48 by Incorporation and Catalytic Performance in Propylene oligomerization

Aluminum-doped mesoporous silica materials SBA-15, MCM-41, and MCM-48 were synthesized by direct incorporation and then investigated for gas-phase oligomerization of propylene at temperatures 433-503K and 5 atm pressure. The synthesis method aimed to create aluminum-based active centers suitable for catalytic processes. The resulting samples were characterized using X-ray diffraction (XRD), nitrogen adsorption–desorption (BET), Fourier transform infrared spectroscopy (FTIR), and scanning electron microscopy (SEM). Results indicated that aluminum incorporated during synthesis is homogeneously distributed within the silica framework, and the synthesized materials possess unique structural characteristics, including a large specific surface area, high pore volume, and tunable pore sizes within the mesoporous range of 2 to 50 nm. Catalytic tests showed that propylene conversion and productivity increase with temperature following Arrhenius behavior (Ea, app = 39 – 55 kJ/mol), while flow rate experiments indicated negligible external diffusion limitations. Time-on-stream analysis revealed progressive deactivation due to pore blocking by heavier oligomers. Among the studied catalysts, Al-SBA-15 exhibited the highest conversion, superior selectivity toward heavier products (C10-C12+) and improved stability, highlighting the critical role of pore size and connectivity in controlling activity and selectivity during propylene oligomerization.