Patent ID: 8957267
Filing Date: 2015-02-17
Classification: C10G

Abstract:
1. A process for producing gasoline and for the co-production of propylene in a catalytic cracking unit comprising a one- or two-stage catalyst regeneration zone and a reaction zone having two risers, one termed the principal riser, the other termed the secondary riser, said process comprising operating the risers in parallel under different severity conditions, with a catalyst to feed ratio (C/O ratio) of the principal riser being in the range of 7 to 12, and a catalyst to feed ratio (C/O ratio) of the secondary riser being in the range of 14 to 25, the principal riser outlet temperature being in the range of 520° C. to 570° C., the secondary riser outlet temperature being in the range of 580° C. to 610° C., and a contact time in the secondary riser being in the range of 50 to 500 ms with a solids flow rate in the range of 150 to 600 kg/s·m the principal riser being supplied by a feed having a hydrogen content in the range of 11.5% to 14.5% by weight, and the secondary riser being supplied by a gasoline cut comprising C5, C6, C7 and C8 oligomers wherein the feed to the secondary riser is, at least in part, a portion of the gasoline produced by the catalytic cracking unit, circulating the catalyst between the catalyst regeneration zone and the reaction zone in two parallel circuits, a circuit termed the principal circuit comprising the principal riser and a first external catalyst cooling system termed the principal cat cooler and a circuit termed the secondary circuit comprising the secondary riser and a second external catalyst cooling system termed the secondary cat cooler, the first external catalyst cooling system being supplied with catalyst removed from the catalyst regeneration zone and delivering the resultant cooled catalyst directly to the base of the principal riser, and the second external catalyst cooling system being supplied with catalyst removed from the regeneration zone and delivering resultant cooled catalyst directly to the base of the secondary riser.