Combinations of platinum and palladium on alumina supports as oxidation catalysts

The effects of the total content of Pd+Pt, the mol-% ratio of Pd to Pt, hydrothermal treatment of the catalyst wash-coat, and the oxygen concentration on the light-off temperature, T50, for the complete oxidation of xylene isomers, propene, and carbon monoxide were studied. The alumina wash-coats were thermally treated at 500°C for 2 h in air or after the thermal treatment, hydrothermslly treated at 814°C for 2 h in 100-% steam. The catalysts were impregnated with 5, 10, and 20 micromol of Pd+Pt per gram of catalyst. The mol-% ratio of Pd to Pt was varied in the range from 0:100 to 100:O. The light-off temperatures had a minimum at a Pd:Pt mol-% ratio of 80:20, and decreased with increasing total metals concentration, increasing oxygen concentration and hydrothermal treatment of the alumina wash-coat