Patent ID: 7589244

Claim:
A process for producing propylene and co-producing a desulphurized gasoline with a high octane number from a feed constituted by a C4/C5 cut from a steam cracking unit (A) and a FCC gasoline (B), said process comprising the following steps: a step for selective hydrogenation ( 20 ) of the FCC gasoline (B) (stream 2 ), producing an effluent ( 3 ) sent to a separation ( 21 ) which produces a light fraction ( 4 ) which is sent to a one-step oligocracking unit ( 40 ) and a mainly C6+ heavy fraction ( 5 ) which is sent to a hydrotreatment unit ( 30 ); in said one step oligocracking unit ( 40 ) treating a mixture of C4/C5 cut from the steam cracking unit (A) (stream 1 ), and the light fraction ( 4 ) from the separation unit ( 21 ), an effluent ( 17 ) from the oligocracking unit ( 40 ) being separated in one or more distillation columns ( 50 ) into at least 5 cuts: 1) an overhead cut ( 10 ) mainly constituted by ethylene; 2) an overhead cut ( 7 ) which constitutes the propylene production of the process; 3) a first intermediate cut ( 8 ) mainly constituted by C4 molecules, a portion ( 16 ) of which is recycled to the inlet to the one-step oligocracking unit ( 40 ), and a non-recycled portion ( 11 ) of which is upgraded to liquefied petroleum gas; 4) a second intermediate cut ( 18 ) mainly constituted by C5 and C6 molecules, a portion ( 15 ) of which is recycled to the inlet of the one step oligocracking unit ( 40 ), and a non-recycled portion ( 19 ) constituting a gasoline directed to the gasoline pool; 5) a bottom cut ( 9 a ) constituted by C9+ molecules which is sent to a hydrotreatment unit ( 30 ) mixed with the heavy fraction ( 5 ) from the separation unit ( 21 ), an effluent ( 31 ) from said hydrotreatment unit ( 30 ) constituting co-production of desulphurized gasoline with a high octane number.