DEPENDENCE OF THE NATURE AND CATALYTIC PERFORMANCE ON THE SYNTHESIS FACTORS OF SAPO-5 MOLECULAR-SIEVE

A series of SAPO-5 molecular sieves have been synthesized by varying t he silicon source, template and crystallization time. X-ray diffractio n (XRD), SEM-EDAX, IR and TPD of ammonia have been employed to charact erize their structure and acidity. The results show that the type and the amount of the template has a great effect on the yield of SAPO-5. The silicon source also exerts influence on the morphology of SAPO-5 a nd its acidity. Prolonging the aging time not only increases the silic on content in SAPO-5, but also decomposes the large crystal into small one and alters the acidity. However, when the aging time is over 48 h , the crystallinity of the molecular sieve decreases and some SAPO-34 intergrows in the product. Bronsted acid sites with medium strength ar e predominant on the SAPO-5 samples prepared, with which the n-hexane cracking activity at 450 degrees C runs parallel.