Characterisation of BN-supported palladium oxide catalyst used for hydrocarbon oxidation
Résumé
Hexagonal boron nitride (BN), with a graphite-type structure and with surface area of 184 m2/g was used as a support for palladium oxide (PdO/BN). About 1 wt% of palladium was deposited on BN by incipient wetness method by using palladium nitrate as precursor. The support and the catalyst were characterized by BET, TEM, XRD, XPS, ICP, TG, TPD, in situ ac electrical conductivity and by ammonia adsorption microcalorimetry. Oxidation of propylene and methane were used as model reactions to study the catalytic properties of the PdO/BN catalyst. The BN support was practically inactive in propylene oxidation up to 400 8C, while the onset of the oxidation was detected around 200 8C on PdO/BN, which points out the role of the palladium in adsorption of the reactive hydrocarbon species. At the same time, this temperature is coincident with the increase of the electronic conductivity on both BN and PdO/BN samples, which is important for oxygen adsorption/activation as electrophilic species. The catalyst was inactive in methane oxidation below 400 8C. Only about 2% CH4 conversion was observed at 400 8C, increasing sharply up to 87% at 550 8C with methane transformation only to CO2 and water.