A combined theoretical and experimental study of NO decomposition on Pd and Pd-Mo catalysts

• Published in: Journal of molecular catalysis. A, Chemical Vol. 193; no. 1; pp. 121 - 137
• Main Authors: Tonetto, G.M., Ferreira, M.L., Damiani, D.E.
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 17.02.2003; Elsevier
• Subjects: Catalysis; Catalytic reactions; Chemistry; Exact sciences and technology; General and physical chemistry; NO decomposition; Pd catalyst; Pd-Mo catalyst; Theory of reactions, general kinetics. Catalysis. Nomenclature, chemical documentation, computer chemistry; Pd-Mo catalyst; NO decomposition; Pd catalyst; Mixed catalyst; Molecular orbital; Catalytic reaction; Transition metal; Palladium; Experimental study; Modeling; Molybdenum; Supported catalyst; Molecular dissociation; Gas solid adsorption; Heterogeneous catalysis; Aluminium Oxides; Hueckel method; Nitric oxide; Chemical decomposition; Platinoid
• ISSN: 1381-1169; 1873-314X
• DOI: 10.1016/S1381-1169(02)00444-2

NO decomposition reaction was studied on Pd/γ-Al 2O 3, Mo/γ-Al 2O 3 and Pd-Mo/γ-Al 2O 3 catalysts. The catalytic tests have revealed that the binary catalyst presents a longer steady-state activity. Adsorption and dissociation of NO, O 2 and N 2 over models of the catalyst surfaces have been investigated using a using a molecular orbital approach of the extended Hückel (EHMO) type. Experimental and theoretical results showed an effective interaction between the metals. Studies of NO decomposition on Pd/γ-Al 2O 3, Mo/γ-Al 2O 3 and Pd-Mo/γ-Al 2O 3 catalysts were made. The reaction was investigated at 400 °C using a reactant mixture of 1100 ppm NO in He. Adsorption and dissociation of NO, O 2 and N 2 on Pd(1 1 1), MoO x -Pd(1 1 1) and MoO x -γAl 2O 3 surfaces have been investigated using a molecular orbital approach of the extended Hückel (EHMO) type, including repulsion terms. The catalytic tests have revealed that the binary catalyst present a different behavior for the NO decomposition, the main difference being a longer steady-state activity at low temperature. Characterization results by TPR and hydrogen chemisorption have indicated that palladium physicochemical properties are altered by an effective interaction with molybdenum. This interaction appears to be responsible for the observed modification in NO activity. Our results of EHMO have showed that the NO adsorption energy on MoO x -Pd(1 1 1) model is lower than the one for Pd(1 1 1) or MoO x -γAl 2O 3. Also, adsorption and dissociation of N 2 and O 2 are notoriously modified when an interaction between the two metals exists. Those results would indicate the existence of a Pd–Mo interface with catalytic properties different to the metals.