Abstract: A method (100) is proposed for the preparation of a polyolefin from olefin monomers, wherein the olefin monomers are subjected to one or more polymerisation steps (13), in which a proportion of the olefin monomers are catalytically reacted to form the polyolefin, while the olefin monomers that are not reacted in the polymerisation step or steps (13) are at least partly transferred into one or more gaseous, monomer-containing purge streams (g, h), which additionally contain(s) one or more aluminium organic compounds, which comprise one or more co-catalysts used in the polymerisation step or steps (13) and/or one or more compounds formed from the co-catalyst(s).