Heraeus Deutschland Gmbh & Co. KG

A method for breaking down a mixture, which is present in the form of solid particles, consisting of: (A) 0 to 99% by weight of metallic ruthenium, (B) 0 to 50% by weight of at least one element other than ruthenium, which is present in elementary form, selected from the group of elements of the atomic numbers 13, 21-30, 39-42, 45-52, and 72-83, (C) 0 to 99% by weight of ruthenium oxide, (D) 0 to 70% by weight of at least one solid element oxide other than ruthenium, (E) 0 to 30% by weight of at least one inorganic substance other than (A) to (D), and (F) 0 to 3% by weight of at least one organic substance, wherein the sum of the % by weight of the compounds (A) to (F) is 100% by weight and the ruthenium content of the mixture is 2 to 99% by weight, and wherein the method comprises the steps of: (1) optionally mixing said mixture with alkali carbonate by forming a blend, (2) alkaline oxidizing breakdown of the mixture or of the blend, respectively, formed in optional step (1) into molten potassium hydroxide using a gaseous oxidizing agent selected from the group consisting of air, oxygen, and air/oxygen mixtures, and without use of nitrate, and (3) cooling down the breakdown material formed in step (2) to a temperature below its solidification temperature, wherein the gaseous oxidizing agent is introduced into the melt in step (2).

The invention relates to a sintering paste consisting of: (A) 30 to 40 wt. % of silver flakes with an average particle size ranging from 1 to 20 μm, (B) 8 to 20 wt. % of silver particles with an average particle size ranging from 20 to 100 nm, (C) 30 to 45 wt. % of silver(I) oxide particles, (D) 12 to 20 wt. % of at least one organic solvent, (E) 0 to 1 wt. % of at least one polymer binder, and (F) 0 to 0.5 wt. % of at least one additive differing from constituents (A) to (E).

A preparation containing: (A) 30 to 90 wt. % of at least one organic solvent, (B) 10 to 70 wt. % of at least one noble metal complex comprising diolefin and C6-C18 monocarboxylate ligands selected from the group consisting of noble metal complexes of the type [LPd[O(CO)R1]X] n , [LRh[O(CO)R1]] m , and [LIr[O(CO)R1]] m , wherein L represents a compound acting as diolefin ligand, wherein X is selected among bromide, chloride, iodide, and —O(CO)R2, wherein —O(CO)R1 and —O(CO)R2 represent identical or different non-aromatic C6-C18 monocarboxylic acid residues, and wherein n is an integral number 1, and m is an integral number ≥2, and (C) 0 to 10 wt. % of at least one additive.

Methods of making dispersion-hardened platinum compositions include A) producing a melt having at least 70 wt. % platinum, up to 29.95 wt. % of one or more of rhodium, gold, iridium and palladium, between 0.05 wt. % and 1 wt. % of oxidizable non-precious metals in the form of zirconium, yttrium and scandium, and, as the remainder, platinum including impurities, wherein the ratio of zirconium to yttrium in the melt is in a range of from 5.9:1 to 4.3:1 and the ratio of zirconium to scandium in the melt is at least 17.5:1, B) hardening the melt to form a solid body, C) processing the solid body to form a volume body, and D) oxidizing the non-precious metals contained in the volume body by a heat treatment in an oxidizing medium over a time period of at least 48 hours at a temperature of at least 750° C.

A method for preparing a colloidal dispersion of precious metal nanoparticles free of organic adsorbates that have a molar weight above 100 g/mol, the colloidal dispersion of the precious metal nanoparticles obtained by the method according to the invention, solid and re-dispersed precious metal nanoparticles and products comprising colloidally dispersed or solid precious metal nanoparticles.

Platinum complex of the type [L1L2Pt[O(CO)R1]X] n , wherein L1 and L2 are the same or different monoolefin ligands or together represent a compound L1L2 acting as a diolefin ligand, wherein X is selected from bromide, chloride, iodide, and —O(CO)R2, wherein —O(CO)R1 and —O(CO)R2 are the same or different C6-C18 or C8-C18 non-aromatic monocarboxylic acid groups with the exception of a phenylacetic acid group, or together represent a C8-C18 non-aromatic dicarboxylic acid group —O(CO)R1R2(CO)O—, wherein it is a mononuclear platinum complex where n=1, or wherein, in the event of the presence of L1L2 and/or of —O(CO)R1R2(CO)O—, it may be a polynuclear platinum complex with a whole number n>1.

Known catalyst systems for the catalytic combustion of ammonia to form nitrogen oxides consist of a plurality of single- or multilayer catalyst gauzes warp-knitted, weft-knitted or woven from platinum-based noble metal wire, which, when arranged one behind the other in a fresh gas flow direction, form a front group of gauze layers and at least one downstream group of gauze layers arranged after the front group. To provide from this starting point a catalyst system for use in a medium-pressure plant for ammonia oxidation, with which a high service life and a high yield of the main product NO can be achieved, it is proposed that the front group comprises a gauze layer or a plurality of gauze layers made of a first, rhodium-rich noble metal wire, wherein the gauze layer or one of the gauze layers made of the rhodium-rich noble metal wire is a front gauze layer facing the fresh gas, and that the downstream group comprises gauze layers made of a second, rhodium-poor noble metal wire, wherein the rhodium content in the rhodium-rich noble metal wire is at least 7 wt. % and no more than 9 wt. % and is at least 1 percentage point higher than the rhodium content in the rhodium-poor noble metal wire.

A method for producing a collector alloy comprising 25 to 100 wt % precious metal in total, comprising 0 to <97 wt % of the precious metal silver, 0 to 75 wt % of at least one precious metal selected from gold, platinum, rhodium and palladium, and 0 to 75 wt % of at least one non-precious metal selected from copper, iron, tin and nickel, or for producing pure silver, comprising the steps of: (1) providing precious metal sweeps; (2) providing a flux which, during collective melting with the refractory inorganic material from the precious metal sweeps provided in step (1); (3) collective melting of the materials provided in steps (1) and (2) at a temperature in the range of from 1300 to 1600° C., forming a melt comprising at least two phases of different densities arranged one above the other; and, (4) separating the upper phase and the lower phase.

A method for producing a catalyst system for gas reactions comprising at least one planar structure of noble metal having gas-permeable openings, comprising the steps of: (1) providing at least one noble metal powder consisting of at least substantially spherical noble metal particles, and (2) repeatedly applying the noble metal powder or powders provided in step (1) in layers to a substrate in a build chamber, respectively followed by an at least partial melting of the respective noble metal powder applied as a layer with high-energy radiation, and allowing the melted noble metal powder to solidify within the scope of additive manufacturing.

A method for recovering precious metal from an acidic aqueous solution containing dissolved precious metal and free chlorine, comprising the following successive steps: (1) combining a salt of a non-precious metal present in a low oxidation state as a solid or as an aqueous solution with the acidic aqueous solution to consume the free chlorine and form an acidic aqueous mixture, and (2) adding non-precious metal to the acidic aqueous mixture formed in step (1) to precipitate elementary precious metal.