O3 catalyst comprising of 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 {TAIL ~ a Zn ZSM 5 zeolite} or {HEAD ~ a Zn ZSM 5 zeolite/asbestos} 
O3 catalyst comprising of 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 { TAIL ~ a Zn ZSM 5 zeolite } or { HEAD ~ a Zn ZSM 5 zeolite / asbestos }
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 TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD