Patent ID: 8207387

Claim:
A method of producing polypropylene comprising: (a) contacting an oxygenate stream with a molecular sieve to form an olefin stream comprising propane, propylene and dimethylether; (b) introducing the olefin stream into a propylene rectification tower possessing from less than 200 theoretical stages; (c) withdrawing from the propylene rectification tower a bottom stream comprising dimethylether, a sidestream comprising propane, and an overhead stream comprising propane and propylene; (d) introducing the overhead to a condenser to accumulate a propylene-rich stream; (e) 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 ratio within the range from 1:2 to 1:30; and (f) recirculating the dimethylether stream to contact the molecular sieve.