Synthesis of SAPO-31 Nanorod in Ethylene Glycol-Water Medium and Its Catalytic Performance in the n-Hexadecane Hydroisomerization

Silicoaluminophosphates (SAPOs) molecular sieves with one-dimensional channels as acid component of bifunctional catalysts loading metal have been attracted attention in the field of clean fuel production due to their mild acidity and shape-selectivity. Herein, a series of novel SAPO-31 molecular sieve nanorod aggregations (S31-xEG) were synthesized in an ethylene glycol-water (EG-H2O) crystallization medium, and the morphology and acidity, as well as the location of Si atoms on the framework were adjusted by changing the EG/H2O ratio. The S31-xEG samples exhibit morphology of aggregation composed of nanorods with mean diameter of similar to 30 nm and length of 3 similar to 4 mu m, as well as reduced total Bronsted acid density, which is in good linear correlation with the amount of the framework Si atom with Si(1 similar to 4Al) chemical environment. The catalytic performances of 0.5Pd/S31 and 0.5Pd/S31-20EG bifunctional catalysts prepared by loading 0.5 wt % Pd on the SAPO-31 (S31) synthesized in the water as crystallization medium and S31-20EG (EG/H2O = 2 : 3) were tested in the n-hexadecane hydroisomerization, respectively, and both catalysts showed high iso-hexadecane yield (similar to 85.0%), while 0.5Pd/S31-20EG demonstrated larger turnover frequency (TOF) value and proportion of mono-branched iso-hexadecane in the thermodynamic control region (at n-hexadecane conversion of similar to 90%) due to a synergistic catalysis between metal and Bronsted acid sites.