CO and CH4 combined oxidation tests were performed over a Pd (70 g/ft(3))/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 (lambda = 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 degrees C in oxidizing atmosphere. Decomposition of PdO and Co3O4 phases at high temperature, above 750 degrees C, was observed. Moreover, sintering of Pd-0 and PdO particles along with of CoO crystallites takes place. (c) 2007 Elsevier B.V. All rights reserved.