A process for the preparation of a catalyst comprises abrading a solid metallic material selected from platinum, palladium, platinum-palladium alloys and mixtures thereof, in the presence of an aqueous alumina suspension to obtain a suspension which contains finely divided particles of the metallic material and the alumina uniformly dispersed throughout, applying the thus obtained suspension to a support, and then removing the water therefrom to obtain the desired catalyst.
A gas sensor element for detecting the presence of a flammable gas comprises an electrical resistance filament surrounded by a bead which is formed by an array of alumina particles interspersed between and bound together only by particles of a catalyst for inducing catalytic oxidation of flammable gases to form an open porous gas diffusive skeletal matrix having a mean particle size of less than 20 nm. When the bead includes such a matrix, the number of active sites at which catalytic oxidation of flammable gases can take place is greatly increased with the result that the sensor element is very resistant to poisoning by atmospheric contaminants such as traces of silicone and sulphur compounds. The sensor thus has a very much longer life and does not require such frequent recalibration.
A gas sensor element for detecting the presence of a flammable gas comprises an electrical resistance filament surrounded by a bead which is formed by an array of alumina particles interspersed between and bound together only by particles of a catalyst to form an open porous gas diffusive skeletal matrix having a mean particle size of less than 20 nm. When the bead includes such a matrix, the number of active sites at which catalytic oxidation of flammable gases can take place is greatly increased with the result that the sensor element is very resistant to poisoning by atmospheric contaminants such as traces of silicone and sulphur compounds. The sensor thus has a very much longer life and does not require such frequent recalibration.
Catalysts for the fluid-bed hydrodechlorination of carbon tetrachloride to chloroform having high catalytic stability and comprising platinum supported on microspheroidal gamma alumina, characterized in that the platinum is in the form of particles dispersed throughout the mass of the support.
