Total combustion of m-xylene over palladium catalysts supported by stainless steel flakes Original Research Article

Total combustion of m-xylene over Pd/stainless steel flakes has been investigated. Ignition temperature of the catalytic combustion of m-xylene mixtures over palladium catalysts is lowered by about 330°C compared to that of thermal oxidation. Hysteresis in the conversion-temperature curves recorded in temperature programmed modes is controlled not only by the operating conditions (the temperature ramp, concentration of the reactants, contact time) but also by catalyst pretreatments. High and low activity states have been observed with typical ignition temperatures of 200–250°C and about 400°C, respectively. In high activity state the combustion is likely initiated by the catalyst followed by a chain reaction which propagates into the gas phase. This is strongly supported by the abrupt increase in the conversion profile. During the induction period preceding the combustion, active species are accumulated on the surface which are responsible for this process.