Spectroscopic studies on the formation of coke on individual Fluid Catalytic Cracking particles: the effect of poisoning metal compounds

Abstract

The formation of coke on individual Fluid Catalytic Cracking (FCC) catalyst particles was studied using UV/Vis microspectroscopy and confocal fluorescence microscopy, with n-hexane cracking as a model reaction. Bulk information was obtained with thermogravimetric analysis (TGA) and elemental analysis. To study the effect of metal poisons, four different catalyst particles were used: fresh particles and three kinds of deactivated particles, of which two had been treated with metal poisons (Ni, V). The microscopic measurements were performed using a specially designed quartz cell, which enabled studying individual FCC particles during hexane cracking. UV/Vis absorbance was found to be linearly related to the concentration of coke in the catalyst particles determined with TGA. The coke concentration was approximately 3 times higher for the particles deactivated with metal compounds than for the fresh particles after 2 hours of cracking. The UV/Vis data were fitted with a simplified kinetic model, which was able to explain the observed differences in UV/Vis absorbance between the different particles based on their deactivation treatments. Confocal fluorescence microscopy revealed the location of coke molecules within individual FCC particles.