{HEAD ~ O3 catalyst comprising} of {TAIL ~ a mixture} of from 2.5 to 7.5% wt of Cr2 O3, 5 to 17.5% wt of Al2 O3 and 75 to 85% wt of a Zn ZSM 5 zeolite or a Zn ZSM 5 zeolite/asbestos 
of
{ HEAD ~ O3 catalyst comprising } of { TAIL ~ a mixture } of from 2.5 to 7.5 % wt of Cr2 O3 , 5 to 17.5 % wt of Al2 O3 and 75 to 85 % wt of a Zn ZSM 5 zeolite or a Zn ZSM 5 zeolite / asbestos
HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL 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 OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH