PtSn supported on hierarchical mesoporous SAPO-11: Synthesis, characterization and catalytic evaluation in n-heptane hydroisomerization

Abstract

Traditional microporous SAPO-11 molecular sieve was synthesized in Al2O3-P2O5-Dipropylamine-H2O system. To improve the mesoporosity aiming to overcome the diffusion limitations of zeolite, Hierarchical mesoporous SAPO-11 molecular sieve was synthesized via adding SAPO-11 seed into the Al2O3-P2O5-Dipropylamine-H2O system. Nitrogen physisorption analysis indicated that the synthesized SAPO-11 via seeding approach has additional mesoporosity with a mesopore volume of 0.11 cm3/g and average pore diameter ∼ 4 nm. Also, HR-TEM analysis proofed the formation of hierarchical mesoporous SAPO-11 as spherical aggregate particles in contrast to rectangular block crystals in the form of large particle aggregates showed by traditional micro-SAPO-11. To investigate the effect of the created mesoporosity on the catalytic performance toward n-heptane hydroisomerization, Hierarchical mesoporous SAPO-11support was employed to prepare PtSn (x) bimetallic bifunctional catalysts. Compared to PtSn(2)/micro-SAPO-11 catalyst, the PtSn(2)/meso‑ SAPO-11 catalyst exhibited higher isomerization selectivity, attributed to their excellent diffusion properties resulting from the hierarchical pore network, which is beneficial for catalytic reactions.