SAPO-11 with preferential growth along the a-direction as an improved active catalyst in long-alkane isomerization reaction

SAPO-11 zeolites with oriented crystals have been hydrothermally synthesized at a relatively high H₂O/Al₂O₃ ratio in raw materials, where the phenomenon of preferential growth could be explained by the change in the concentration of organic structure directing agents (OSDA). Showed with XRD and TEM, the AEL type zeolite crystals possessed preferred orientation along a-axis, in which [100] crystal face was thinner and larger. Meanwhile, the results of ICP, ²⁹Si MAS NMR, NH₃-TPD and BET showed that the orientation growth process did not cause significant changes in the composition, structure and acid properties of SAPO-11 zeolites. Therefore, adjusting the synthesis conditions is a rather simple way to decrease the crystallite size in the directions of the 10-ring channels [100] crystal face and increase the number of pores accessible. Moreover, the oriented SAPO-11 resulted in an improved accessibility of reactants to the catalytic active centers and enhanced product diffusion, which obtained a higher isomerization activity of the n-tetradecane and higher selectivity of multi-branched isomers.