Abstract: On the basis of the conventional hydrothermal method, the small crystal SAPO-11 molecular sieves with sub-micron size were synthesized by controlling the aging conditions of the synthesis gel and without using other organic additives except for the template. The particles of the samples synthesized by this method possessed much smaller crystal dimension and were more uniform in size than conventionally synthesized samples. The crystal morphology of SAPO-11 samples synthesized by the improved hydrothermal method exhibited in cube shape with particle size in the range of 400-500 nm, whereas for the SAPO-11 samples synthesized by the conventional method, pseudo-spherical aggregates ranging from7 to10 μm were obtained. The sample synthesized by the improved method had larger BET surface area and larger external surface area than that of the samples prepared by the conventional hydrothermal method. The results of n-hexadecane hydroisomerization showed that the Pt/SAPO-11 catalysts synthesized by the improved method exhibited both higher catalytic activity and higher hydroisomerization selectivity than the catalysts synthesized by the conventional hydrothermal method.

Key words: SAPO-11 molecular sieve, aging treatment, static hydrothermal synthesis, n-hexadecane, hydroisomerization