The sintering of supported metal catalystsI. Redispersion of supported platinum in oxygen

The effects of treatment in oxygen at elevated temperatures on the dispersion of five Pt/MAl2O3 catalysts (0.5 to 4.0 wt% Pt) were determined. Treatment temperatures of 300 to 700 °C and treatment periods of 1 to 128 hr were studied. Significant increases in dispersion (at times a two- to threefold increase) were observed at ≤600 °C. At 500 and 550 °C the increases in dispersion were relatively independent of the treatment time. At higher temperatures, rapid, time-dependent decreases in dispersion occurred. The results are in agreement with a molecular migration mechanism.