Chemical and catalytic activation of methane by metal oxide surfaces. Annual report, September 1, 1987-August 31, 1988
New stable catalysts composed of alkaline earth (SrZrO{sub 3}) and rare earth (LaAlO{sub 3}) refractory oxides showed promising experimental results for methane coupling with premixed oxygen. Unlike the alkali-promoted catalysts, these highly active catalysts were run for 20 hours at 900 deg without loss of activity and without apparent evaporation or corrosive attack on the quartz reactors. The homogeneous and heterogeneous chemistry involved in the selective oxidation of methane and light alkanes and the construction of a self-consistent predictive kinetic model is described. The higher hydrocarbon yield appears to be limited by the homogeneous oxidation of methyl and ethyl radical intermediates. The kinetic model predicts significant yields of CO, H{sub 2}, CH{sub 2}O, and CH{sub 3}OH in addition to the commonly reported C{sub 2}H{sub 6} and C{sub 2}H{sub 4} primary products; absence of these by products and the predominance of by-product CO{sub 2} is attributed to heterogeneous reactions. The mechanism of co-oxidative methane coupling by basic Na/CaO and complex oxide catalysts continued to be investigated by a variety of dynamic methods including postreaction temperature programmed desorption (TPD) of stable adsorbed intermediates and pulsed flow H-D isotopic exchange between CH{sub 4} and CD{sub 4}. Inhibition of the methane conversion for coupling and for H-D exchange by CO{sub 2} suggests that by-product CO{sub 2} can displace the reactive oxygen centers on the surfaces of base oxide catalysts.
- Research Organization:
- SRI International, Menlo Park, CA (USA)
- OSTI ID:
- 5532599
- Report Number(s):
- PB-89-178776/XAB
- Country of Publication:
- United States
- Language:
- English
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