Oscillatory behaviour of catalytic properties, structure and temperature during the catalytic partial oxidation of methane on Pd/Al2O3

Pd/Al2O3 catalysts showed an oscillatory behaviour during the catalytic partial oxidation (CPO) of methane, which was investigated simultaneously by IR-thermography, X-ray absorption spectroscopy, and online mass-spectrometry to correlate the temperature, state of the catalyst and catalytic performance. The following stages were observed: (i) build-up of a temperature maximum in the first half of the catalyst bed, (ii) reduction of palladium in the end zone of the catalyst bed with a front moving toward the entrance zone, (iii) strong hot spot formation accompanied by reduction of palladium due to self-reduction leading to extinction of the process. The latter was the key driver for the oscillations and thus gave additional insight into the mechanism of partial methane oxidation.