{TAIL ~ Propylene}, oxygen, and hydrogen are preferably fed to the reactor at or near the bottom of {HEAD ~ the reactor} 
{ TAIL ~ Propylene } , oxygen , and hydrogen are preferably fed to the reactor at or near the bottom of { HEAD ~ the reactor }
TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD