Process for the polymerization of olefins

Abstract

The present invention relates to a process for the continuous preparation of polypropylene in a reactor from propylene and optionally ethylene and/or at least one other oolefin monomer, wherein the reactor comprises a fluidized bed, an expanded section located at or near the top of the reactor, a distribution plate located at the lower part of the reactor and an inlet for a recycle stream located under the distribution plate, wherein the process comprises—feeding a polymerization catalyst to the fluidized bed in the area above the distribution plate—feeding the propylene and the optional at least one other oolefin monomer to the reactor—withdrawing the polypropylene from the reactor—circulating fluids from the top of the reactor to the bottom of the reactor, wherein the circulating fluids are compressed using a compressor and cooled using a heat exchanger, resulting in a cooled recycle stream comprising liquid, and wherein the cooled recycle stream is introduced into the reactor using the inlet for the recycle stream wherein an alkane chosen from the group of iso-butane, n-butane, cyclopropane and mixtures thereof is added to the reactor and wherein the molar composition of the components in the recycle stream is chosen such that the dew temperature of the recycle stream at the reactor pressure is at least 0.10° C. below the temperature of the reactor.