Chapter 9 - Catalytic Cracking Processes

Abstract

Typically, the feedstocks for catalytic cracking can be any one (or blends) of the following: straight-run gas oil, vacuum gas oil, and heavy feedstocks. However, if blends of the above feedstocks are employed, compatibility of the constituents of the blends must be assured under certain conditions, or excessive coke will be laid down onto the catalyst. In addition, there are several pretreatment options for the feedstocks for catalytic cracking units, and these are (i) deasphalting to prevent excessive coking on catalyst surfaces; (ii) demetallization, that is, removal of nickel, vanadium, and iron to prevent catalyst deactivation; (iii) the use of a short residence time as a means of preparing the feedstock; and (iv) hydrotreating or mild hydrocracking to prevent excessive coking in the fluid catalytic cracking unit.