Abstract: A hydrogenation catalyst, obtainable by carrying out essentially the following steps:(a) treatment of a platinum metal salt with finely divided sulfur followed by(b) reduction of the platinum metal salt to metallic platinum metal.

Abstract: A process of use of hydrogenation catalyst, obtainable by carrying out essentially the following steps:(a) treatment of a platinum metal salt with finely divided sulfur followed by(b) reduction of the platinum metal salt to metallic platinum metal.

Abstract: A hydrogenation catalyst, obtainable by carrying out essentially the following steps:(a) treatment of a platinum metal salt with finely divided sulfur followed by(b) reduction of the platinum metal salt to metallic platinum metal.

Abstract: A process for the preparation of hydroxylammonium salts by the reduction of nitrogen oxide (NO) with hydrogen in dilute aqueous mineral acid in the presence of a suspended platinum catalyst which is partially poisoned with arsenic, at elevated temperature, wherein the catalyst used is one which has been produced by precipitation of metallic platinum from an aqueous solution on to a suspended support in the presence of an oxidic arsenic compound, by means of a reducing agent.

Abstract: A platinum-on-graphite catalyst having a platinum content of from 0.01 to 5% w/w, wherein the graphite support has an apparent density of from 1.7 to 2.2 g/ml and the use thereof as a hydrogenation catalyst.

Abstract: A method of regenerating noble metal catalysyts used for the catalytic reduction of nitrogen oxide with hydrogen, wherein the noble metal catalyst is treated with an aqueous alkaline solution having a pH of more than 9.

Abstract: A platinum-on-graphite catalyst having a platinum content of from 0.01 to 5% w/w, wherein the graphite support has a particle size of from 1 to 600 .mu.m and the following particle size distribution:______________________________________ 183 to 600 .mu.m 15% v/v .+-. 15% absolute 68.3 to 183 .mu.m 30% v/v .+-. 20% 31.0 to 68.3 .mu.m 25% v/v .+-. 20% 17.1 to 31.0 .mu.m 15% v/v .+-. 10% 5.2 to 17.1 .mu.m 12% v/v .+-. 10% .sup. <5.2 .mu.m 5% v/v .+-. 5%.

Abstract: Crystalline hydroxylammonium sulfate is prepared by a process which comprises the following steps:(a) Bringing an aqueous solution which contains from 0.02 to 0.3 part by weight of ammonium sulfate and from 0.02 to 0.2 part by weight of sulfuric acid per part by weight of hydroxylammonium sulfate into contact with a basic ion exchanger and obtaining a solution which has a pH of from 3.0 to 4.0,(b) separating off the basic ion exchanger from the aqueous hydroxylammonium sulfate solution,(c) evaporating down the resulting aqueous hydroxylammonium sulfate solution under reduced pressure at <100.degree. C. and obtaining a concentrated hydroxylammonium sulfate solution,(d) crystallizing out not more than 70% by weight of the hydroxylammonium sulfate present in the aqueous solution to give crystalline hydroxylammonium sulfate and a mother liquor, and(e) isolating and crystalline hydroxylammonium sulfate from the mother liquor.

Abstract: Hydroxylammonium salts are prepared by catalytic reduction of nitrogen monoxide with hydrogen in dilute aqueous mineral acids at elevated temperature in the presence of suspended supported platinum catalysts obtainable by precipitating metallic platinum from aqueous solutions of platinum salts onto carriers suspended therein by means of reducing agents in the presence of one or more water-soluble substituted or unsubstituted thioureas.

Abstract: Hydroxylammonium salts are prepared by catalytic reduction of nitrogen monoxide with hydrogen at elevated temperature in a dilute aqueous solution of a mineral acid in the presence, in suspension, of a supported platinum catalyst obtainable by precipitating metallic platinum from an aqueous platinum solution onto a support by means of a reducing agent in the presence of an organic chelating agent and partially poisoned with sulfur.

Abstract: Pure hydroxylammonium salts of fatty acids of 1 to 4 carbon atoms are prepared by reacting hydroxylammonium sulfate and alkali metal salts of fatty acids with 1 to 4 carbon atoms in solution at elevated temperatures and separating off the hydroxylammonium salts of fatty acids of 1 to 4 carbon atoms by(a) reacting hydroxylammonium sulfate and alkali metal salts of fatty acids of 1 to 4 carbon atoms in solution in water or alkanols of 1 to 3 carbon atoms or mixtures thereof at 20.degree.-70.degree. C.,(b) evaporating the solvent out of the reaction mixture to obtain a dry residue,(c) isolating the hydroxlammonium salts of fatty acids of 1 to 4 carbon atoms from the dry residue thus obtained by sublimation under reduced pressure.

Abstract: Aqueous solutions of free hydroxylamine are prepared by a process in which(a) hydroxylammonium sulfate is reacted with ammonia in a lower alkanol as solvent, and a solution of free hydroxylamine and solid ammonium sulfate with residues of hydroxylammonium sulfate is obtained,(b) solid ammonium sulfate and hydroxylammonium sulfate are separated off from the resulting reaction mixture, and an alcoholic solution of free hydroxylamine is obtained as the filtrate,(c) a stabilizer and water are added to the resulting alcoholic solution of free hydroxylamine, and(d) the alkanol is distilled off from the alcoholic solution containing free hydroxylamine, the stabilizer and water.

Abstract: Hydroxylamine-O-sulfonic acid is prepared by(a) reacting hydroxylammonium sulfate with oleum at elevated temperatures,(b) isolating sulfuric acid from the hydroxylamine-O-sulfonic acid formed,(c) diluting the sulfuric acid which was obtained in stage (b) and which still contains hydroxylamino-O-sulfonic acid with water to 2-6N and heating it to 30.degree.-80.degree. C. for 1-10 hours,(d) preparing hydroxylamine by catalytic reduction of nitrogen monoxide with hydrogen using the dilute sulfuric acid from stage (c) in the presence of a noble metal catalyst at elevated temperatures.

Abstract: Wastewaters containing hydroxylamine or its salts are worked up by a process in which the said wastewaters are passed over a strongly acidic ion exchanger, after which a 5-15% strength by weight aqueous sulfuric acid is passed over the said ion exchanger and a solution of hydroxylammonium sulfate in aqueous sulfuric acid is obtained.

Abstract: Noble metal catalyst, in particular platinum catalysts, which are applied on carriers and have become poisoned by metals as a result of being used for many years in the preparation of hydroxyl-ammonium salts by catalytic reduction of nitric oxide with hydrogen in an aqueous mineral acid are regenerated by a process in which the metallic impurities are dissolved using nitric acid or aqua regia, the solution is neutralized, the troublesome metals are precipitated from the neutralized solution by means of a selective precipitating reagent, and the purified platinum solution is reused for the preparation of the catalyst. Organic complexing agents which form insoluble or sparingly soluble complexes with the metallic impurities are preferably used as precipitating reagents.

Abstract: Aqueous solutions of hydroxylamine are prepared from aqueous hydroxylammonium salt solutions by electrodialysis by a method in which the aqueous hydroxylammonium salt solution is fed into the middle zone of an electrolysis cell, which is divided into a cathode zone, an anode zone and a middle zone by means of semipermeable membranes, and is electrolyzed, and the catholyte used is an alkali metal hydroxide solution containing ammonia and/or amines.

Abstract: Stabilized solutions of hydroxylamine or its salts in water or alcohols, containing the lactone of the formula ##STR1## and their preparation.

Abstract: Stabilized solutions of hydroxylamine or its salts in water or alcohols, containing 8-hydroxyquinaldines, and their preparation.

Abstract: Aqueous solutions of hydroxylammonium carbonate are prepared from aqueous hydroxylammonium salt solutions by electrodialysis by a method in which the aqueous hydroxylammonium salt solution is fed into the middle zone of an electrolysis cell, which is divided into a cathode zone, an anode zone and a middle zone by means of semipermeable membranes, and is electrolyzed, and the catholyte used is an aqueous solution of an ammonium carbonate or an alkali metal carbonate or of one of the corresponding bicarbonates.

Abstract: Stabilized solutions of hydroxylamine or its salts in water or alcohols, containing hydroxyanthraquinones, and their preparation.