Preparation of hierarchical structure of Y zeolite with ultrasonic-assisted alkaline treatment method used in catalytic cracking of middle distillate cut: The effect of irradiation time

摘要

Hierarchical structure of NaY zeolite was synthesized with conventional and ultrasonic assisted alkaline treatment methods. Furthermore, their catalytic performance was evaluated in catalytic cracking process. The synthesized catalysts were characterized using XRD, FE-SEM, N-2 adsorption-desorption and NH3-TPD analysis. The amount and the type of coke, which formed on the catalysts have also been studied using TGA and FTIR analysis, respectively. The XRD, FE-SEM and BET results revealed that the ultrasonic assisted alkaline-treatment method created more mesopores and lower destruction at zeolite structure, compared to conventional alkaline-treatment method. Furthermore, the results demonstrated that ultrasonic irradiation performed facile creation of hierarchical structure for NaY zeolite. The obtained results from BET analysis showed that by increasing alkaline treatment time, mesoporosity increased gradually. Also, TPD analysis revealed that desilication led to increasing acidity amount. In comparison to the Parent Y catalyst, both the superior catalytic performance and efficient decrease in viscosity, density and molecular weight of liquid product were obtained over the modified Y catalyst which was alkaline-treated, in presence of ultrasound in 60 min. Also the maximum gasoline yield over this catalyst was 47%. Well mesopore structure and moderate acidity also led to decreased coke formation rate and increased catalytic stability and activity.