Abstract: The present invention relates to a method for the isolation of olefins from a gas mixture comprising one or more olefins, inert gas and catalyst poison, where the gas mixture is fed to a separation unit (18) and separated into olefin and inert gas. The method according to the invention has the special feature that an apparatus (17) is installed upstream or downstream of the separation unit (18) and that i) in the case of an upstream apparatus (17), the catalyst poison is at least partially removed from the gas mixture, and ii) in the case of a downstream apparatus (17), the catalyst poison is at least partially removed from the separated-off olefin. The olefins here are preferably isolated from a gas mixture formed as offgas in catalytic gas-phase polymerization for the preparation of polyolefins. The recovery of the olefins from the offgas is of economic importance.

Abstract: In a continuous gas-phase polymerization process for preparing ethylene and propene homopolymers and copolymers, in which ethylene, propene or a mixture of ethylene or propene and C3-C8-&agr;-monoolefins is polymerized in the polymerization zone of a gas-phase polymerization reactor at from 30 to 125° C. and a pressure of from 1 to 100 bar in the gas phase in a bed of finely divided polymer in the presence of a catalyst, where the reactor gas is circulated to remove the heat of polymerization, polymer deposits in the circulating gas line are prevented by metering a catalyst poison having a boiling point above the maximum temperature within the circulating gas line into this circulating gas line in at most such an amount that it does not significantly impair the productivity of the catalyst in the reactor.