Passivation of metal contaminants in cat cracking
AssigneeExxon Research & Engineering Co.
InventorsGordon F. Stuntz, Robert C. Schucker
Life of this patent
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Abstract
A method for passivating metal contaminants present in a hydrocarbon feedstock which become deposited on cracking catalyst is described. The method is directed at passing the cracking catalyst through a passivation zone having a reducing atmosphere maintained at an elevated temperature. The reducing atmosphere comprises a process reducing gas stream which has been passed through a guard bed adapted to selectively remove an unsaturated hydrocarbon prior to the process reducing gas being added to the passivation zone.
Claims25
In a cracking process, a method for reducing the adverse catalytic effects of metal contaminants selected from the group consisting of nickel, vanadium, iron and mixtures thereof present in a feedstock, said method comprising:
- A. contacting the feedstock containing the metal contaminant with cracking catalyst in a reaction zone under cracking conditions to produce cracked product and coke, coke and metal contaminant being deposited on cracking catalyst;
- B. passing coke and metal contaminated catalyst from the reaction zone to a regeneration zone maintained under regeneration conditions to remove coke from the catalyst;
- and,
- C. passing metal contaminated catalyst through a passivation zone maintained under reducing conditions at an elevated temperature prior to the catalyst being returned to the reaction zone, the improvement wherein the reducing conditions are maintained in the passivation zone by passing process reducing gas through a guard zone adapted to remove an unsaturated hydrocarbon compound from the reducing gas prior to the reducing gas entering the passivation zone.
A cracking process for decreasing the molecular weight of a hydrocarbon feedstock containing metal contaminant, said method comprising:
- A. contacting the feedstock containing the metal contaminant with cracking catalyst in a reaction zone under cracking conditions to produce cracked product and coke, coke and metal contaminant being deposited on cracking catalyst;
- B. passing coke and metal contaminated catalyst from the reaction zone to a regeneration zone maintained under regeneration conditions to remove coke from the catalyst;
- and,
- C. passing metal contaminated catalyst from the regneration zone through a passivation zone maintained under reducing conditions at an elevated temperature prior to the catalyst being returned to the reaction zone;
- D. passing process reducing gas having an unsaturated hydrocarbon therein through a guard bed adapted to remove unsaturated hydrocarbon from the process reducing gas;
- and
- E. passing the process reducing gas having a reduced unsaturated hydrocarbon content from the guard bed to the passivation zone.
Dependencies are inferred from the claim text.