Simultaneous oxidation of carbon black and volatile organic compounds over Ru/CeO₂ catalysts

Ru/CeO₂ catalysts with Ru loading of 1-5 wt.% were prepared by wet impregnation from aqueous ruthenium (III) nitrosyl nitrate solution and activation with an air flow at 600 °C for 4 h. This activation resulted in a considerable reactivity for the catalytic oxidation of carbon black (CB) (T_50% ∼350 °C "tight contact" mixtures and T_50% ∼515 °C "loose contact" mixtures) and volatile organic compounds (VOCs) (T_50% = 175 °C for propene, T_50% = 215 °C for toluene). When carbon black oxidation was conducted under "propene (6000 ppm) + air" or "toluene (2000 ppm) + air" flow, the elimination of an important part of CB was observed at relatively low temperatures comparing to its elimination under pure air flow. These temperatures correspond to the total oxidation of the VOC present in the reactant gases. Carbon black total elimination was also investigated under isotherm conditions in the presence and in the absence of propene. Total elimination occurred during shorter times when combustion was performed under propene. TPR study showed that ruthenium species present in the catalysts after activation reduces at relatively low temperatures (<100 °C) and that from a Ru loading of 1.5 wt.%, agglomerated ruthenium oxide was formed and that this latter is more difficult to reduce (>100 °C).