Investigation of the Effect of Crystallization Temperature and Time in Synthesis of SAPO-34 Catalyst for the Production of Light Olefins

Abstract

In this paper, the effect of variation of crystallization temperatures and times on the synthesis of SAPO-34 catalysts for conversion of methanol to light olefins has been investigated. These are two of the very effective parameters in the synthesis of SAPO-34 which affect phase purity, crystallinity, acidic properties, and finally the performance of catalysts. For this purpose, 9 samples have been synthesized by varying of temperature and time of crystallization in the range of 170–210°C, 12–36 h, respectively and the molar ratio of 1Al2O3 : 1P2O5 : 0.4 SiO2: 0.5 TEAOH : 1.5 MOR : 70 H2O and characterized by XRD, SEM, FTIR, BET, and NH3–TPD techniques. Finally, performance of catalysts was investigated in the process of conversion of methanol to light olefins in a fixed-bed reactor 410°C. The results show that crystallinity, phase purity, size, and distribution of particles, surface area, and acidic properties have great effects on performance and selectivity of ethylene and propylene and these properties themselves severely depend on Crystallization temperature and time. The results of characterized of catalysts show that high characterized temperature, reduces the phase purity and increases size in particles. The catalysts that have been synthesized at 190°C and 24 h have the highest crystallinity, suitable size, and distribution of particles, high surface area, and suitable acidic sites, so it has the highest selectivity of light olefins at MTO process.