Characterization of Fresh and Regenerated Industrial Hydrocracking Catalysts; Study Causes of Deactivation

In this investigation, fresh and regenerated Ni-W-Alumina-Zeolite industrial hydrocracking catalysts characterized via several analyzing methods, including XRF, XRD, BET adsorption, FT-IR, FESEM-EDS, and TGA-DTA to understand the phenomena affecting trend towards their deactivation. The XRD patterns represented the presence of main phases of Al2O3/Y-zeolite as support and NiWO4/WO3 as active compounds. For the catalysts subjected to a three-year reactor operation/regeneration cycle, the XRF analysis revealed elemental enhancement of Fe, Na, V, Pb, Sb, and S, mostly from outsources environment. The BET and BJH analyses represented cylindrical shape mesoporosity for the samples, while the total pore specific surface area and volume were reduced from 287.73 m2/g and 0.46 cm3/g to 160.84 m2/g and 0.40 cm3/g for fresh and regenerated samples, respectively. The latter results indicated possibly filling the pores with impurities and/or sintering of pores. By considering FESEM images, the smooth surface of the fresh sample and indented/corroded characteristics of the regenerated one were seen. The variety of analyses portrayed the increasing trend of the poisoning factors and the structural malfunction of the catalysts towards irreversible deactivation.