Synthesis of hierarchical SAPO-11-based catalysts with Al-based metal-organic framework derivative as mesoporogen to improve n-decane branched isomerization

Hierarchical SAPO-11 molecular sieve (ACS-11) was successfully synthesized employing the Al2O3/carbon (Al2O3/C) composite obtained through the pyrolysis of Al-based metal-organic framework (Al-MOF-96) as mesoporogen. Unlike other carbon-based mesoporogens with strong hydrophobicity, the Al2O3/C interacts with phosphoric acid and generates the AlPO4/C structure, which promotes the Al2O3/C dispersion in the synthesis gel of SAPO-11 and avoids the phase separation between them. The Al2O3/C as mesoporogen decreases the crystallite size of SAPO-11 via preventing the aggregation of SAPO-11 crystals. Additionally, the addition of Al2O3/C improves the Si distribution in the ACS-11 framework. Consequently, ACS-11 has smaller crystallites, more mesopores, and a greater amount of medium Brønsted acid centers than the conventional microporous SAPO-11 and the SAPO-11 synthesized using activated carbon as mesoporogen. The corresponding Pt/ACS-11 catalyst exhibits the maximal selectivity to multi-branched C10 isomers (23.28%) and the minimal cracking selectivity (15.83%) in n-decane hydroisomerization among these catalysts. This research provides a new approach for preparing hierarchical silicoaluminophosphate molecular sieve-based catalysts to produce high-quality fuels.