The catalyst, water and {TAIL ~ unreacted methanol} can be recovered and recycled back to {HEAD ~ the reaction zones} 
The catalyst , water and { TAIL ~ unreacted methanol } can be recovered and recycled back to { HEAD ~ the reaction zones }
OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD