Rapid synthesis of SAPO-34 nanocatalyst by dry gel conversion method templated with morphline: Investigating the effects of experimental parameters

Abstract

SAPO-34 nanoparticles were successfully synthesized by a dry gel conversion method using morpholine as a structure-directing agent. In this study, the effects of synthesis parameters, such as crystallization time, gel drying temperature and water content added in the crystallization stage, on crystallinity, shape and particle size of SAPO-34 are investigated and the advantages of the dry-gel conversion (DGC) method are described for the synthesis of SAPO-34 molecular sieves. The products were characterized by XRD, SEM, TEM, EDX, BET and NH3-TPD. The results show that the favorable phase of crystallinity has been improved by increasing the crystallization time, gel drying temperature and water content. Most of the particles have particle sizes lower than 500nm and it is an excellence of employing the DGC method despite using morpholine as a structure-directing agent. The high nucleation density and slow crystal growth after nucleation for SAPO-34 crystals in the dry gel conversion method result in the formation of nanoparticles. Contrary to the hydrothermal method in which at least 24h of the synthesis time is required to obtain crystalline SAPO-34, dry-gel conversion synthesis of samples leads to formation of fully crystalline SAPO-34 crystals taking only 6h. This has been observed as an important influence of dry-gel conversion synthesis on the activity and selectivity of the samples in the MTO reaction.