Residue fluid catalytic cracking: A review on the mitigation strategies of metal poisoning of RFCC catalyst using metal passivators/traps.

[Display omitted] • Residue fluid catalytic cracking (RFCC) processes heavy and contaminated feedstocks. • Mechanism of catalyst contamination and passivation have been discussed. • Nickel and vanadium are the most harmful contaminants of RFCC catalyst. • Antimony, bismuth and boron have been identified as nickel passivators. • Tin, alkaline earth and rare earth compounds are the major vanadium passivators. The catalysts used for residue fluid catalytic cracking must have good catalyst activity, selectivity, hydrothermal stability, coke selectivity and metals tolerance to high concentrations of heteroatoms such as N, S, Fe, Na, Ni, and V. Recent increase in energy demand leads to the processing of heavy feedstocks such as atmospheric residue that hitherto have been disfavoured. Processing these feedstocks comes with several challenges due to the presence of these heteroatom poisons that are detrimental to catalysts as they either permanently or temporarily deactivate or poison the catalysts, thereby promoting undesirable reactions such as dehydrogenation and coke production. To give perspective on these challenges, RFCC technologies, catalysts, and catalyst deactivation are discussed. The differences and limitations of conventional fluid catalytic cracking and contemporary residue fluid catalytic cracking are also highlighted. This study emphasises the passivation of Ni using antimony, rare earth metals, bismuth and boron compounds and passivation of V using tin, rare earth metals, and basic alkaline earth compounds such as Mg. The work also presents new illustrations of nickel and vanadium poisoning mechanisms. While antimony successfully mitigates nickel's deleterious effects; it leads to NOx emissions and increased bottom fouling. Boron does not exhibit such a problem and has been shown to be a good substitute for antimony in mitigating the harmful effect of nickel. [ABSTRACT FROM AUTHOR]