Boreskov Institute of Catalysis of the Siberian Branch of Russian ...

OP-V-18dynamic saturation with additional oxygen pulses and immediately following pump-probeexperiments allowed defined investigations with oxidation profiles close to those present atatmospheric pressure in a short contact time reactor.Results and discussionImpacts of the oxidation state and co-presence of methane and oxygen clearly differ as afunction of dopants promoting the fluorite structured ceria/zirconia solid solution supportingPt as active metal. Employing Pr as dopant yields a catalyst capable to preserve a minimumselectivity in all studied cases using the «working state» of the catalyst as origin. A significantand fast hydrogen release was observed, which varied only slightly altering the oxidation stateof the sample by pre-injected oxygen. Furthermore, the co-presence of O 2 and CH 4 injectingboth reactants at short time offset did not lead to an entire loss of selectivity. The weakness ofthe Pr doped sample relates to the relative slow formation of CO. It is currently not entirelyclear if the low CO formation rate, i.e. the freeing of the catalyst surface from CH x species,leads to a build-up of carbonaceous species impacting under ambient pressure conditions onthe activity. However, the presence of CH x at «working state» is clearly confirmed for the Gddoped sample. The activity of the Pr doped catalyst is clearly lower than that of the Gd dopedcatalyst, which may be slightly observed in terms of hydrogen release, but it become muchmore obvious when focusing on the formation of carbon monoxide as primary carbon oxidesproduct. The Gd doped sample shows a complex behavior of performance as a function of thecatalyst’s oxidation state.The Gd-doped catalyst seems more selective towards synthesis gas at the «working state»established by reaction of oxygen with methane injected at 0.5 seconds offset at a ratio of 1:2.The Pr-doped catalyst reveals a more stable behavior showing no major loss in selectivitywhen the «working state» determined quantity of oxygen becomes altered or when oxygenand methane become injected with shorter time offset.Acknowledgement: Support by the joined European laboratory on catalysis betweenFrance and Russia (LFRC,LEA-313) and support by the RFBR-CNRS 05-03-34761 project isacknowledged.References:1. R.E. Kirk, D.F. Othmer (Eds.), third ed., Encyclopedia of Chemical Technology, vol. 12, Wiley Interscience,New York, 1980, p.952.2. R. Horn, K.A. Williams, N.J. Degenstein, A. Bitsch-Larsen, et al., J. Catal. 249 (2007), p.380.3. R. Horn, K.A. Williams, N.J. Degenstein, L.D. Schmidt, Chem. Eng. Sci. 62 (2007), p.1298.4. V.A. Sadykov, et al., Catalysis Today 117(2006), p.475.203