Fabrication of ZSM-5 and its ion exchange for naphtha cracking

Abstract

Light olefins are the backbone of modern industrialization. For more than a half century, steam/thermal hydrocarbon cracking is considered as the main route and conventional process for light olefins yield. Few drawbacks of conventional steam cracking such as extensive energy consumption, high temperature requirement and excess emission of CO2 relate to this technology, which cannot accommodate further needs regarding the chemical process industry. Catalytic cracking of hydrocarbons is a less energy consuming and an environmentally-friendly process for light olefins production. Nowadays petroleum-extracted naphtha catalytic cracking is mainly used process. In this study, ZSM-5 is synthesized via hydrothermal crystallization method using structural directing agents (TPABr and TPAOH). The physiochemical characteristics of calcined and ion-exchanged ZSM-5 samples are well characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), differential thermogravimetric analysis (TG-DTA) and temperature programmed desorption (TPD). Kinetic study of n-hexane over ZSM-5 catalysts is observed at temperatures of 500°C and 600°C under atmospheric pressure, mainly focusing the related reaction rate constants and activation energies. The n-hexane catalytic cracking was found to be first order regarding n-hexane concentration. The activation energies of 21.867 KJ/mol and 32.018 KJ/mol were evaluated for n-hexane over calcined and ion-exchanged samples. The application of ZSM-5 to the cracking of model naphtha is quite effective.