Nitrogen Oxide Reduction Using Methane or Methanol over Well-Characterized Dispersed Rare Earth Oxide Catalysts

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ABSTRACT CTS-9633752 This is an extension of studies on reduction of nitrogen oxides by methane. It has been established that certain rare-earth oxides, with or without promotion by strontium, have high specific activities for this reaction and activity is enhanced by excess oxygen. In this work, lanthana and neodymia (excellent catalysts in the bulk form) both with and without strontium promoter, are dispersed on high-surface-area supports such as alumina, silica, or zirconia. Catalytic behavior and rate expressions over a range of oxygen partial pressures are determined using a variety of reductants including methane, methanol, hydrogen, and carbon monoxide. The supported rare-earth-oxide catalysts are characterization by BET measurements, chemisorption of nitric oxide and other gases, X-ray diffraction, diffuse reflectance Fourier-transform infrared spectroscopy (DRIFTS), electron-spin resonance, thermal analysis, and isotopic kinetic studies. This work is directly relevant to the current efforts to control emissions of nitrogen oxides and reduce occurrence of acid rain. This technology is suitable for emission control in both stationary boiler (power plant) sources and lean-burn mobile (automotive) sources.