Enhancement effect of gold and silver on nitric oxide decomposition over Pd/Al2O3 catalysts

• Published in: Applied catalysis. B, Environmental Environmental, 1995-07, Vol.6 (2), p.105-116
• Main Authors: Wu, R.J., Chou, T.Y., Yeh, C.T.
• Format: Article
• Language: English
• Subjects: Alloy; Catalysis; Catalysts: preparations and properties; Chemistry; Decomposition of nitric oxide; Exact sciences and technology; General and physical chemistry; Palladium; Temperature-programmed oxidation; Temperature-programmed reduction; Theory of reactions, general kinetics. Catalysis. Nomenclature, chemical documentation, computer chemistry
• ISSN: 0926-3373; 1873-3883
• DOI: 10.1016/0926-3373(95)00005-4

The effect of alloying palladium supported on alumina with Group 1B metals was studied with the catalytic decomposition of nitric oxide into nitrogen and oxygen. Pd/Al2O3 was inactive for the decomposition at low temperatures, but the activity increased rapidly when the system temperature was raised to 1023 K. TPO studies revealed that supported PdO became unstable at elevated temperatures and started to decompose to metallic palladium by desorbing oxygen also around 1023 K. Therefore, the desorption of oxygen is regarded as the rate determining step for the catalytic decomposition at T < 1023K. An addition of gold or silver to Pd/Al2O3 increased its catalytic activity towards the decomposition. TPR and hydrogen chemisorption studies confirmed that added gold and silver alloyed with palladium on the surface of Al2O3. TPO studies also demonstrated that the enhanced activity on alloying palladium with gold and silver can be correlated with a decrease in the temperature required for the desorption of oxygen.