Provided is a method of producing polypropylene comprising contacting an oxygenate stream with a molecular sieve to form an olefin stream comprising propane, propylene and dimethylether; introducing the olefin stream into a propylene rectification tower possessing from less than 200 theoretical stages; withdrawing from the propylene rectification tower a bottom stream comprising dimethylether, a sidestream comprising propane, and an overhead stream comprising propane and propylene; introducing the overhead to a condenser to accumulate a propylene-rich stream; passing the propylene-rich stream to a splitter to produce (i) a first propylene stream that is introduced into a polypropylene reactor to contact a polyolefin catalyst, and (ii) a second propylene stream that is re-introduced into the rectification tower, the first and second propylene streams introduced at a desirable ratio; and recirculating the dimethylether stream to contact the molecular sieve.