CATALYTIC-OXIDATION OF CARBON-BLACK - I - ACTIVITY OF CATALYSTS AND CLASSIFICATION OF OXIDATION PROFILES

The oxidation of carbon black in the presence of catalytically active compounds has been studied under isothermal conditions in a flow react or. In the presence of metal oxides, oxidation rates of the carbon bla ck are found to be up to a few hundred times higher compared with the non-catalysed oxidation. Alkali metal carbonates increase this oxidati on rate even up to a factor of over 100 000. The combustion curves (re action rate as a function of carbon conversion) of isothermal, catalyt ic oxidation of carbon black can be classified in four distinct profil e types. From these combustion curves, it can be concluded that a rela tive ranking of catalysts depends on the carbon conversion level and o n the catalyst-to-carbon black ratio. The contact between catalyst and carbon black is an essential parameter in the catalysed oxidation of carbon black. When this contact is poor, the catalytic effect of the m etal oxides and alkali metal carbonates is low or even absent. For alk ali carbonate catalysts, the very high reaction rates were attributed to redistribution of the catalyst during reaction. Also for some of th e metal oxides (i.e., Ag2O, CuO, MoO3, PbO, Sb2O3) it is suggested tha t mobility of the catalyst can increase the contact between the cataly st and the carbon black, resulting in higher oxidation rates. (C) 1998 Elsevier Science Ltd.