TWO STAGE SYSTEM FOR CATALYTIC CONVERSION OF OLEFINS WITH DISTILLATE AND GASOLINE MODES

An improved process for converting an olefinic feedstock containing ethene and C3+ alkenes to produce a heavy hydrocarbon product rich in distillate by contacting the feedstock with an oligomerization catalyst bed, at elevated pressure and temperature conditions in operating mode favorable to formation of heavy distillate product by selective conversion of C3+ alkenes. The improvement comprises providing a distillate mode effluent stream containing substantially unconverted ethene in vapor phase and condensed distillate, and recovering unconverted ethene-rich hydrocarbon vapor from the distillate mode effluent stream and further converting such to olefinic gasoline in a second oligomerization catalyst bed at reduced moderate pressure and elevated temperature conditions in operating mode favorable to formation of C6+ olefinic gasoline. At least a portion of the olefinic gasoline is recycled for conversion with the feedstock in the distillate mode catalyst bed. Gasoline and distillate mode effluent streams may be fractionated to recover a light hydrocarbon stream rich in C3+ aliphatic hydrocarbons for recycling at least a portion of the light hydrocarbon stream to dilute the ethene-rich vapor in the second gasoline mode catalyst bed.