Unit Cell Volume as a Tool to Monitor the Deactivation of ZSM-5 in FCC Catalyst
In a fluid catalytic cracking (FCC) application, ZSM-5 containing catalysts are extensively used to boost gasoline octane, and maximize propylene yields to meet the demands for petrochemical feedstock. The severe hydrothermal conditions of a FCC unit gradually deactivate the ZSM-5 in the catalyst, by framework dealumination. The stability of the ZSM-5 with respect to surface area and framework dealumination, under FCC operating conditions, is important to maximize its effectiveness for propylene activity. The characterization of ZSM-5 in the commercial FCC catalyst has always been a challenge. The ability to determine its acidity is important to the successful development of new products and processes.
A simple and robust method based on unit cell volume (UCV) has been developed to characterize the ZSM-5 in the catalyst. The results show UCV is a powerful tool to monitor deactivation of ZSM-5 in a commercial unit. It can be measured by combining powder X-ray diffraction technique with Rietveld analysis. The measurement of UCV shows a good correlation with the acidity, and the catalytic properties of ZSM-5 catalyst. The data demonstrate that the technology can be applied to both laboratory and field deactivated ZSM-5 based catalysts.