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The influence of the catalyst support on the oxidation of methane over palladium has been studied using a microcalorimetric bead reactor. The nature of the support had no detectable influence on the catalytic activity during a given experiment, but was found to affect the long-term stability of the catalyst.Investigations have been made of the kinetics of the oxidation of methane over a palladiumlthoria catalyst both in the absence and in the presence of the reaction products. Oxidation was found to be strongly inhibited by the water formed, which tended to cause permanent deactivation of the catalyst; there was also very slight inhibition by carbon dioxide. Measurements of the rates of co-oxidation of methane with other compounds showed that methanol reacted independently, whereas formaldehyde and carbon monoxide were both oxidized competitively.It has been shown that the reactivity of water towards the catalyst support is an important factor governing the deterioration of catalytic activity. In accordance with this there was no evidence of catalyst deactivation when methane was co-oxidized with methanol, which would be expected to displace water.Among the many previous investigations of the oxidation of methane over palladium catalysts, only rarely has the possibility been considered that the support may play an important part in catalysis. Furthermore, although it is generally agreed that the reaction is zero order in oxygen as a result of the strong adsorption of this gas on palladium, the other kinetic relationships obtained in various systems are not always in agreement. One possible reason for the observed differences in behaviour is the use of different catalyst supports, studies having been made with palladium supported on a l~m i n a ,~'~ silica gel and Linde 4A molecular sieve.7The present studies have been designed to elucidate the influence of the catalyst support on the general characteristics of the reaction. Use has been made of a recently developed technique in which the catalyst is in the form of a " bead " which can be used to give a calorimetric measure of the rate of reaction. Previous experiments 7-9 have shown that in this way it is possible to make kinetic measurements with a minimum amount of catalyst material. EXPERIMENTAL MATERIALSEach catalyst was deposited on an alumina bead, which was made by first dipping a small coil of platinum wire (0.005 cm diameter) into a concentrated solution of aluminium nitrate and then heating the wire electrically to ca. 7Oo0C in air. The process was repeated ten times to give a bead of alumina of about 1 mm diameter. The catalyst and support were then co-deposited on this bead from solutions of '' Specpure '' materials (Johnson-Matthey and Co.). Palladium was deposited from an aqueous solution of ammonium chloropalladite, * present address : 1407 thorium and uranium oxides were deposited from aqueous solutions of thorium nitrate and uranyl nitrate respectively, and each of the other rare earth oxides was deposited from a solution of the oxide in A.R. nit...