Heat exchange technique for olefin fractionation and catalytic

Abstract

A heat balanced technique for converting an olefinic feedstock comprising ethylene and C.sub.3.sup.+ olefins to heavier liquid hydrocarbon product in a catalytic exothermic process. Methods and means are provided for prefractionating the olefinic feedstock to obtain a gaseous stream rich in ethylene and a liquid stream containing C.sub.3.sup.+ olefin, and contacting an olefinic feedstock stream from the prefractionating step with ZSM-5 type oligomerization catalyst in a series of exothermic catalytic reactors to provide a heavier hydrocarbon effluent stream comprising distillate, gasoline and lighter hydrocarbons. In a preferred embodiment a catalytic system is provided for making gasoline or diesel fuel from an olefinic feestock containing ethylene and C.sub.3.sup.+ lower olefins comprising a prefractionation system for separating and recovering ethylene and a liquid stream rich in C.sub.3.sup.+ olefins; a multi-stage adiabatic downflow reactor system operatively connected for serially contacting olefinic feedstock with a plurality of fixed shape selective oligomerization catalyst beds; means for thermally exchanging hot reactor effluent from at least one catalyst bed with at least a portion of a prefractionation liquid stream for reboiling the liquid stream; and means for recovering gasoline and diesel product from the catalytic system.