Catalytic cracking of resid feedstocks

Resid cracking, first industrialized at the beginning of the 1960s, only reached its full maturity in the 1980s thanks both to favorable economic factors and to important progress in process technology and catalysts. This article first discusses the main difficulties to be taken into account when residual feedstocks are to be processed; these difficulties are essentially linked to the presence of various contaminants such as heavy hydrocarbons with high boiling points, heavy metals (Ni + V), and nitrogen- and sulfur-containing-organic compounds. It then describes the principal zones of FCC unit where decisive progress has been made To overcome most difficulties. The four main industrial processes developed by different companies are presented and stress is laid on the specific solutions proposed for each zone of the FCC unit. Finally, the principal characteristics that resid cracking catalysts must possess are discussed in terms of porosity and acidity, and a number of useful catalyst additives are briefly presented.