Process for reducing coke formation in heavy feed catalytic cracking

Claim 1

A method for decreasing the rate of coke production from a hydrocarbon feedstock cracked to lower molecular weight products in a reaction zone containing cracking catalyst where the feedstock contains at least two metal contaminants selected from the class consisting of nickel, vanadium and iron and where at least some of the metal contaminants and coke become deposited on the catalyst, said method comprising: (a) passing the coke and metal contaminated catalyst from the reaction zone to a regeneration zone maintained at regeneration conditions having a regeneration gas passing therethrough whereby at least a portion of the coke is removed from the catalyst and thereafter the catalyst is passed through a reduction zone maintained at a temperature above about 600° C. for a time sufficient to at least partially passivate the metal contaminants on the catalyst, a reducing environment maintained in the reduction zone by the addition to the reduction zone of a material selected from the class consisting of hydrogen, carbon monoxide and mixtures thereof, said passivated catalyst thereafter passing to the reaction zone without further processing; and (b) adding a hydrogen donor material to the reaction zone whereby at least a portion of the hydrogen donor material transfers hydrogen to the hydrocarbon feedstock and/or to the cracked lower molecular weight products.

Claim 2

A method for decreasing the rate of coke production from a hydrocarbon feedstock cracked to lower molecular weight products in a reaction zone containing cracking catalyst where the feedstock contains at least two metal contaminants selected from the class consisting of nickel, vanadium and iron and where at least some of the metal contaminants and coke become deposited on the catalyst, said method comprising: (a) passing the coke and metal contaminated catalyst from the reaction zone to a regeneration zone maintained at regeneration conditions having a regeneration gas passing therethrough whereby at least a portion of the coke is removed from the catalyst and thereafter the catalyst is passed through a reduction zone maintained at a temperature above about 600° C. for a time sufficient to at least partially passivate the metal contaminants on the catalyst, a reducing environment maintained in the reduction zone by the addition to the reduction zone of a material selected from the class consisting of hydrogen, carbon monoxide and mixtures thereof, said passivated catalyst thereafter passing to the reaction zone without further processing; and (b) adding a hydrogen donor material to the reaction zone whereby at least a portion of the hydrogen donor material transfers hydrogen to the hydrocarbon feedstock and/or to the cracked lower molecular weight products.