Two stage system for catalytic conversion of olefins with distillate and gasoline modes

DETAILED DESCRIPTION What is claimed is: 1.
A continuous process for converting an olefinic feedstock containing ethylene and C.
sub.
3.
sup.
+ olefins by catalytic oligomerization to produce heavier hydrocarbons in the gasoline or distillate boiling range which comprises: (a) contacting the olefinic feedstock in a first catalyst reactor zone with a crystalline zeolite oligomerization catalyst at elevated pressure and moderate temperature under conditions favorable for conversion of C.
sub.
3.
sup.
+ olefins to a first reactor effluent stream rich in distillate range hydrocarbons; (b) flashing the distillate-rich stream and separating the first reactor effluent stream into a liquid stream rich in distillate and a vapor stream rich in ethylene; (c) contacting the ethylene-rich stream from step (b) in a second catalyst reactor zone with a crystalline zeolite oligomerization catalyst at moderate pressure and elevated temperature under conditions favorable for conversion of ethylene and other lower olefins to a second reactor effluent stream rich in olefinic gasoline range hydrocarbons; (d) reactionating effluent from the second reactor zone to recover a gasoline stream; and (e) recycling at least a portion of the gasoline stream to the first reactor zone.
2.
The process of claim 1 wherein reactor effluent is fractionated to provide a C.
sub.
3 -C.
sub.
4 rich stream for recycle to the second reactor zone.
3.
The process of claim 1 wherein the first and second reactor zones contain an acid ZSM-5 type catalyst.
4.
The process of claim 3 wherein the catalyst reactor zones comprise a fixed bed down flow pressurized reactor having a porous bed of ZSM-5 type catalyst particles with an acid activity of about 160 to 200.
5.
The process of claim 4 wherein the first reactor zone is maintained at a pressure of about 4200 to 7000 kPa and a temperature of about 190.
degree.
C.
to 315.
degree.
C.
; and wherein the second reactor zone is maintained at a pressure of about 400 to 3000 kPa and a temperature of about 285.
degree