Patent GB-775550-A (GB)
Title: Improvements in or relating to catalytic elements
IPC: B01D53/86
Filed: 1953-09-21
Abstract: Catalytic elements comprising a metallic base coated with a metal of the platinum group are prepared by cleaning the base, depositing the coating, and then heating to a temperature of approximately 600 DEG F. in an air stream containing volatile hydrocarbons.  The metallic base is formed from an alloy which can withstand high temperatures without scaling and which has substantial resistance to the passage of electric current.  The platinum group metal may be platinum, palladium, osmium, rhodium, iridium, or mixtures thereof.  In examples (1) nickel-chromium or nickel-chromium-iron alloy in the form of a wire, screen, or assembly of the type described in Specification 775,549 is cleaned by immersion in a hot solution of sodium orthosilicate and a surface actve agent, e.g. sodium stearate, palmitate, or oleate, or the sodium salt of dodecyl benzene sulphonic acid.  After rinsing it is electro-plated with palladium using a bath containing palladium chloride and hydrochloric acid at a temperature of 160 DEG -170 DEG  F., and graphite or palladium anodes; when a coating of about 0.5 mm. thickness has been formed, the catalyst is rinsed and heated to about 600 DEG  F. in an air stream containing hexane or other hydrocarbon fraction to condition the palladium and increase its tenactiy to the base metal.  (2) the base metal after cleaning is immersed and agitated at 108 DEG F. in a similar solution of palladium chloride without the application of an electric current and the catalyst is finished as in example (1).  The elements are intended for use in the combustion of combustible vapours in the exhaust gases from industrial ovens or from other operations for the elimination of air pollution or utilization of heat of combustion.ALSO:Catalytic elements comprising a metallic base coated with a metal of the platinum group are prepared by cleaning the base, depositing the coating, and then heating to a temperature of approximately 600 DEG F. in an air stream containing volatile hydrocarbons.  The metallic base is formed from an alloy which can withstand high temperatures without scaling and which has substantial resistance to the passage of electric current.  The platinum group metal may be platinum, palladium, osmium, rhodium, iridium, or mixtures thereof.  In an example nickel-chromium or nickel-chromium-iron alloy in the form of a wire, screen, or assembly of the type described in Specification 775,549 is cleaned by immersion in a hot solution of sodium orthosilicate and a surface active agent, e.g. sodium stearate, palmitate, or oleate, or the sodium salt of dodecyl benzene sulphonic acid.  After rinsing it is immersed and agitated at 180 DEG F. in a bath containing palladium chloride and hydrochloric acid until uniformly coated with amorphous palladium; the catalyst is rinsed and heated to about 600 DEG F. in an air stream containing hexane or other hydrocarbon fraction to condition the palladium and increase its tenacity to the base metal. The elements are intended for use in the combustion of combustible vapours in the exhaust gases from industrial ovens or from other operations for the elimination of air pollution or utilization of heat of combustion.