パラジウム触媒によるメタン燃焼の特異性

概要

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This paper describes an anomalous behavior observed in combustion of methane on palladium catalysts. Lean methane / air mixtures were reacted in catalytic reactors composed of platinum and palladium catalyst elements. The combustion efficinecy was determined for two cell densities (15.5 and 30cells / cm^2) at inlet mixture temperatures of 600 and 700℃, inlet mixture velocities (8-16 m/s), and equivalence ratios (O.05-0.3) . The equivalence ratio was increased stepwise with other experimental conditions being fixed. With the platinum catalysts complete combustion was attained for richer mixtures. On the other hand, with the palladium catalysts high combustion efficiencies could not be sustained : The combustion efficiency was very high (greater than 99%) for a moment at first, but decreased with time to fairly low values at richer mixtures. The honeycomb temperature was also lowered and, in the final states, its maximum was found to be in the range from 750 to 800℃. The reaction seemed to be suppressed when the catalysts temperature was above this temperature range. The results of gravimetric analysis of palladium / alumina system showed that oxidized palladium was deoxidized at temperatures in the range from 820 to 870℃. This suggested the anomalous behavior was due to the change of oxidation state of palladium.
社団法人日本ガスタービン学会の論文
1990-09-10