GB606348A - Platinum group metal catalysts - Google Patents

Abstract

A platinum group metal catalyst is prepared by alloying a platinum group metal with at least one base metal capable of forming a chemical combination with it, and removing the base metal at least in part by means of a chemical treatment embodying at least in its final state the employment of acid. Specified base metals are zinc, cadmium, beryllium, bismuth, aluminium, magnesium, tellurium, selenium or lead. Metals such as iron, nickel, cobalt, manganese and copper form only solid solutions with platinum group metals, but can be used as one component of an alloy if one or more of the compound-forming metals are also present. The base metal in the alloy may be in excess of that necessary to combine chemically with the platinum group metal. The alloy is broken into small pieces or powder and subjected to the chemical treatment which may be by means of hydrochloric acid, or, when the base metals are zinc or aluminium, strong alkali hydroxide in the initial stages, followed and ended by a hydrochloric acid treatment. According to examples: (1) small packages of platinum wrapped in aluminium foil are dropped into aluminium fused under a reducing atmosphere and the resulting alloy is dissolved in excess of dilute hydrochloric acid, the remaining black residue being treated with further hydrochloric acid and washed with distilled water to produce a platinum - aluminium catalyst; (2) palladium sponge is fused with zinc under a reducing atmosphere, the resulting alloy being treated as in example (1) to produce a palladium-zinc catalyst; (3) platinum foil is dissolved in aqua regia, zinc nitrate and kieselguhr are added, the resulting mass is dried and ignited in the presence of air at 500 DEG C., the resulting product is reduced by hydrogen at 350-480 DEG C., the reduced product being treated with dilute hydrochloric acid and washed by decantation with distilled water to produce a platinum-zinc catalyst deposited on kieselguhr; (4) an alloy of copper with aluminium is fused under a salt cover, small packages of platinum foil wrapped in aluminium foil are added, and the resulting alloy is poured out, crushed and dissolved in hydrochloric acid as described in example (1) to produce a platinum catalyst containing minor amounts of copper and aluminium. These catalysts should be kept submerged in an aqueous or organic liquid when not in use. After exposure to air they may be reactivated by heating in hydrogen or nitrogen at 300-500 DEG C. followed by realloying the residues and treating the thus obtained alloys with hydrochloric acid as previously described.ALSO:A platinum group metal catalyst is prepared by alloying a platinum group metal with at least one base metal capable of forming a chemical combination with it, and removing the base metal at least in part by means of a chemical treatment embodying at least in its final stage the employment of acid. Specified base metals are zinc, cadmium, beryllium, bismuth, aluminium, magnesium, tellurium, selenium or lead. Metals such as iron, nickel, cobalt, manganese and copper form only solid solutions with platinum group metals but can be used as one component of an alloy if one or more of the compound-forming metals are also present. The base metal in the alloy may be in excess of that necessary to combine chemically with the platinum group metal. The alloy is broken into small pieces or powder and subjected to the chemical treatment which may be by means of hydrochloric acid, or, when the base metals are zinc or aluminium, strong alkali hydroxide in the initial stages, followed and ended by a hydrochloric acid treatment. According to examples (1) small packages of platinum wrapped in aluminium foil are dropped into aluminium fused under a reducing atmosphere and the resulting alloy is dissolved in excess of dilute hydrochloric acid, the remaining black residue being treated with further hydrochloric acid and washed with distilled water to produce a platinum-aluminium catalyst; (2) palladium sponge is fused with zinc under a reducing atmosphere, the resuting alloy being treated as in example (1) to produce a palladium zinc catalyst; (3) platinum foil is dissolved in aqua regia, zinc nitrate and kreselguhr are added, the resulting mass is dried and ignited in the presence of air at 500 DEG C. the resulting product is reduced by hydrogen at 350-480 DEG C., the reduced product being treated with dilute hydrochloric acid and washed by decantation with distilled water to produce a platinum-zinc catalyst deposited on kreselguhr; (4) an alloy of copper with aluminium is fused under a salt cover, small packages of platinum foil wrapped in aluminium foil are added, and the resulting alloy is poured out, crushed and dissolved in hydrochloric acid as described in example (1) to produce a platinum catalyst containing minor amounts of copper and aluminium.