Research On Plasma Technology For The Preparation Of Pd/Al₂O₃for Removing Carbon Monoxide

Plasma technology, as a kind of new technology has been widely used in the preparationof catalysts, which is green, environmental protection, high efficient and fast, and especiallyhas an important application in the modification of catalysts. The catalysts prepared byplasma, have the active smaller particles, higher dispersion, better stability, and longer life.Carbon monoxide oxidation is a structure-sensitive reaction，therefore,different preparationconditions,especially the reduction methods,could result in variation in particle morphologyand size, and then impacted on the catalytic behaviors. In this paper, supported palladiumcatalysts prepared by glow discharge plasma were used in carbon monoxide oxidation.In the paper, the powder supported palladium catalysts （φ0.15⁰.2mm） and the sphericalsupported palladium catalyst （φ2.2mm） were prepared by plasma technology. Thephenomenon in the process of catalysts treated by plasma was discussed.At first, the powder supported palladium catalysts were characterized by means of X-raydiffraction （XRD） and transmission electron microscope （TEM）, pressed, molded and used tocarbon monoxide oxidation. The results of characterizations showed that Pd²⁺was changed toPd during the process of the catalysts treated by plasma technology. The palladium particleswere5-8nm. The carbon monoxide conversion reached81.5%by the catalysts prepared byplasma method under the conditions of temperature20℃and high velocity of15000h^-1,which was higher than conventional catalysts by18.5%.On the basis of above results, the spherical supported palladium catalysts were studied indetail and characterized by means of SEM and EDX, TEM, XRD. The results showed that thecatalysts were eggshell catalysts, the palladium thickness of the shells was6.1, the size ofpalladium particles was4to10nm, and the relative content of Pd （111） crystal wassignificantly increased. Comparing with the catalysts prepared by conventional impregnation,the carbon monoxide conversion was increased20.5%by the catalysts prepared by plasmamethod under the conditions of temperature20℃and high velocity of18000h-1. In addition,the loading of palladium, the temperature of calcinations on the influence of the catalyticactivity was discussed.