A co processing combining {HEAD ~ a first selective catalytic bed} consisting of only one metal element selected from group VIB metals and of {TAIL ~ at least one conventional hydrotreating bimetallic catalytic bed} 
consisting of
A co processing combining { HEAD ~ a first selective catalytic bed } consisting of only one metal element selected from group VIB metals and of { TAIL ~ at least one conventional hydrotreating bimetallic catalytic bed }
OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL