passing said reactants at a known preselected concentration through said bundle of parallel tubes wherein the inlet temperature is high enough to initiate said catalytic conversion throughout {HEAD ~ said volume} of {TAIL ~ catalyst} 
passing said reactants at a known preselected concentration through said bundle of parallel tubes wherein the inlet temperature is high enough to initiate said catalytic conversion throughout { HEAD ~ said volume } of { TAIL ~ catalyst }
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL