Combined CO/CH4 oxidation tests over Pd/Co3O4 monolithic catalyst: Effects of high reaction temperature and SO2 exposure on the deactivation process

CO and CH4 combined oxidation tests were performed over a Pd (70 g/ft3)/Co3O4 monolithic catalyst in conditions of GHSV = 100,000 h−1 and feed composition close to that of emission from bi-fuel vehicles. The effect of SO2 (5 ppm) on CO and CH4 oxidation activity under lean condition (λ = 2) was investigated. The presence of sulphur strongly deactivated the catalyst towards methane oxidation, while the poisoning effect was less drastic in the oxidation of CO. Saturation of the Pd/Co3O4 catalytic sites via chemisorbed SO3 and/or sulphates occurred upon exposure to SO2. A treatment of regeneration to remove sulphate species was attempted by performing a heating/cooling cycle up to 900 °C in oxidizing atmosphere. Decomposition of PdO and Co3O4 phases at high temperature, above 750 °C, was observed. Moreover, sintering of Pd0 and PdO particles along with of CoO crystallites takes place.