Catalytic combustion over platinum group catalysts: fuel-lean versus fuel-rich operation

• Published in: Catalysis today Vol. 83; no. 1; pp. 71 - 84
• Main Authors: Lyubovsky, Maxim, Smith, Lance L., Castaldi, Marco, Karim, Hasan, Nentwick, Brian, Etemad, Shahrokh, LaPierre, Rene, Pfefferle, William C.
• Format: Journal Article Conference Proceeding
• Language: English
• Published: Amsterdam Elsevier B.V 15.08.2003; Elsevier Science
• Subjects: Catalysis; Catalytic combustion; Catalytic reactions; Chemistry; Exact sciences and technology; Gas turbine; General and physical chemistry; Methane oxidation; Reaction mechanism; Theory of reactions, general kinetics. Catalysis. Nomenclature, chemical documentation, computer chemistry; Reaction mechanism; Catalytic combustion; Gas turbine; Methane oxidation; Methane; Hydrocarbon; Catalytic reactor; Transition metal; Palladium; Supported catalyst; Heterogeneous catalysis; Aluminium Oxides; Rhodium; Platinum; Alkane; Oxidation; Platinoid
• ISSN: 0920-5861; 1873-4308
• DOI: 10.1016/S0920-5861(03)00217-7

Performance data are presented for methane oxidation on alumina-supported Pd, Pt, and Rh catalysts under both fuel-rich and fuel-lean conditions. Catalyst activity was measured in a micro-scale isothermal reactor at temperatures between 300 and 800 °C. Non-isothermal (near adiabatic) temperature and reaction data were obtained in a full-length (non-differential) sub-scale reactor operating at high pressure (0.9 MPa) and constant inlet temperature, simulating actual reactor operation in catalytic combustion applications. Under fuel-lean conditions, Pd catalyst was the most active, although deactivation occurred above 650 °C, with reactivation upon cooling. Rh catalyst also deactivated above 750 °C, but did not reactivate. Pt catalyst was active above 600 °C. Fuel-lean reaction products were CO 2 and H 2O for all three catalysts. The same catalysts tested under fuel-rich conditions demonstrated much higher activity. In addition, a ‘lightoff’ temperature was found (between 450 and 600 °C), where a stepwise increase in reaction rate was observed. Following ‘lightoff’ partial oxidation products (CO, H 2) appeared in the mixture, and their concentration increased with increasing temperature. All three catalysts exhibited this behavior. High-pressure (0.9 MPa) sub-scale reactor and combustor data are shown, demonstrating the benefits of fuel-rich operation over the catalyst for ultra-low emissions combustion.