Synthesis of free template ZSM-5 catalyst from rice husk ash and co-modified with lanthanum and phosphorous for catalytic cracking of naphtha

Abstract

ZSM-5 catalysts were synthesized from rice husk ash without using template and their catalytic activity has been investigated in catalytic cracking of light naphtha. Effect of hydrothermal temperature (170, 180 and 190 °C) on physicochemical properties of catalysts was investigated by BET, FE-SEM, FTIR, XRD and TGA-DTG analyses. The XRD analysis showed that hydrothermal temperature had great influence on crystalline structure of ZSM-5. Sample which was synthesized at 180 °C showed high crystllinity without any undesired alumina-silicate phases. The FE-SEM analysis showed that synthesis of ZSM-5 at 180 °C led to showed micro-scale hexagonal-shaped morphology. Furthermore, the textural properties of synthesized samples depend on the synthesis temperature drastically. Results of catalytic activity test showed that the synthesis temperature has great influence on the activity of ZSM-5 and the sample which synthesized with at 180 °C showed the highest catalytic activity. Furthermore, in order to improve the catalyst performance and the stability, both of Lanthanum and Phosphorus were used in catalytic cracking of naphtha. 2.5La–3P/ZSM-5 produced the highest light olefins yield. Catalyst modification of ZSM-5 by La and P, increased the ratio of propylene/ethylene from 1 to 2.