Abstract: AlPO₄-31 molecular sieve was synthesized by microwave irradiation using aluminum isopropoxide, orthophosphoric acid, and di-n-butylamine as sources of aluminum, phosphorus, and template, respectively. The crystallization conditions of AlPO₄-31 were optimized. SAPO-31 molecular sieve samples with different silicon contents were synthesized at the optimal conditions. The structure and acidity of the samples were characterized by X-ray diffraction, N₂ physical adsorption, scanning electron microscopy, ²⁹Si MAS NMR, NH₃ temperature-programmed desorption, FT-IR of adsorbed pyridine. The catalytic performance of Pd/SAPO-31 bifunctional catalyst for hydroisomerization of n-decane was investigated. The results indicated that the AlPO₄-31 and SAPO-31 molecular sieves with pure crystal phase and higher crystallinity assigned to ATO topology structure were obtained at 170 ^oC for 2 h by microwave irradiation. The BET surface area and micropore volume were increased because of the introduction of Si to the framework of AlPO₄-31. The distribution of Si in the framework and the acidity of the SAPO-31 molecular sieve were varied by changing the composition of the reaction mixture. The bifunctional catalyst Pd/SAPO-31 with suitable acidity showed high activity and selectivity for hydroisomerization of n-decane.

Key words: microwave irradiation, SAPO-31 molecular sieve, di-n-butylamine, decane, hydroisomerization