| Popis: |
The effects of La[sup 3+] incorporation into Rh/[gamma]-Al[sub 2]O[sub 3] were investigated by a combination of temperature-programmed reduction, X-ray photoelectron spectroscopy, CO chemisorption, and reactivity measurements. The reduction of Rh[sup 3+] following high-temperature (> 600 C) oxidation was more facile and the dispersion of Rh was higher with La[sup 3+] present. Notwithstanding, the catalytic activity, as manifested by the HC[sub 2]CO[sub 3] and NO[sub x] conversion efficiencies, was lower in the presence of La[sup 3+]. This is attributed to a combination of Rh particle-size effects and possible La-Rh compound formation under oxidizing conditions. Changes brought about by high-temperature oxidation in catalysts both with and without La[sup 3+] were completely reversed by high-temperature reduction. |
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