Abstract: The deactivation of catalytic cracking catalyst is one of the important factors that affect the product quality and economic benefit of catalytic cracking units. The analysis of the reasons for the catalyst deactivation is of great theoretical significance to slow down or restrain the catalyst deactivation. In the present work, the deactivated catalytic cracking catalyst in a petrochemical plant was characterized by N2 physical adsorption, XRD, pyridine adsorption infrared (Py-IR) and X-ray fluorescence (XRF). The results showed that the structure of the molecular sieve in the deactivated catalyst collapsed seriously, the surface area decreased greatly, and the acid center decreased sharply. A large amount of V, Ni, Ca and other elements deposited on the deactivated catalyst. The continuous regeneration of the catalyst made the catalyst constantly subject to high temperature hydrothermal process, which could be one of the main factors of molecular sieve structure collapse. Secondly, the deposition of V, Ni and Ca could reacts with the molecular sieve and alumina on the catalyst at high temperatures, which was another reason for the catalyst structure damage. In addition, the deposition of metals also could poison the acid sites on the catalyst. These factors led to a significant decrease in catalyst acidity and to a permanent deactivation of the catalyst.

Key words: catalytic cracking, catalyst, deactivation