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