A Diesel soot-simulating carbonizate containing C 78.64, H 1.34, and N 1.71%, producing (in air) a broad exothermic effect over 200-940degreesC (deconvolution of DTA curve disclosed 6 components), was heated with a 65% (Group IV transition) metal oxide catalyst, 1.29 w/w, over 20-950degreesC and DTA and TG thermograms were recorded. Three original components (characterized by DTA maxima at 450, 550 and 620degreesC) remained unoxidized The carbonizate weight loss was 66%. To simulate a flow-through (Diesel soot) oxidation catalyst, the metal oxide was deposited on Al(2)O(3). It failed to oxidize the carbonizate, converted the original components into other components and reduced their total number from 6 to 3. The impregnated catalysts were inferior. Sulfate added as (NH(4))(2)SO(4) to the carbonizate-catalyst/Al(2)O(3) system suppressed the oxidation activity by 32%.