Abstract: Polymerization processes having as constituent parts high conversion membrane reactors, that provide a source of monomer, and subsequent polymerization of the monomer, without passing products of the conversion through an alkane/alkene splitter, are disclosed. Polymers of light alkene hydrocarbons, such as ethylene, propylene and alkenes consisting of up to 6 carbon atoms, are prepared from gaseous feedstreams consisting predominantly of volatile alkane compounds substantially free of dihydrogen and/or dioxygen. Equipment required for separation of alkene products from unreacted alkanes in conventional plants is eliminated because of the high alkane conversions provided in the membrane reactors. Particularly useful are flow reactors comprising dense membranes of multiphasic materials that provide independent, controllable, counter-current transport of hydrogen, electrons and oxygen.