Synthesis of SAPO-34 catalyst with varying molar ratios of SiO2/Al2O3 and H2O/Al2O3

Silicoaluminophosphate, SAPO-34, is known as promising molecular sieve, which is widely used in catalysis, separation processes, and is being developed for new applications, especially in the methanol-to-olefin (MTO) process. In order to examine the influence of silicon and water contents on the morphology of SAPO-34 crystal, different SiO2/Al2O3 and H2O/Al2O3 ratios of synthesis gel were prepared hydrothermally at crystallization temperature of 190 C. The sources of Al, Si, and P were aluminum isopropoxide, silica gel, and phosphoric acid, respectively. The templates used were the mixture of 75 % morpholine and 25 % tetraethyl ammonium hydroxide. The samples were characterized by XRD, FTIR and SEM techniques. XRD showed that the crystallinity of samples increased with SiO2/Al2O3 ratio. The samples with low silicon content had impurities of SAPO-5 and ALPO-5. SEM images showed the sample synthesized by SiO2/Al2O3 = 0.17, H2O/Al2O3=109.75 ratios had the smallest crystal size. The FTIR results showed that there was no considerable increase in the concentration of strong acidic hydroxyl groups with increasing of SiO2/Al2O3 ratio.

Keywords:

Synthesis , hydrothermal , SAPO-34 , crytallinity , Morphology , strong acidic site