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