Basf Aktiengesellschaft

Werner Biffar

Wolfgang Hoelderich

Michael Kroener

Franz-Josef Weiss

Matthias Irgang

Wolf D Mross

Erwin Thomas

Otto Hofstadt

Klaus Kartte

Werner Steigleiter

Eberhard Ambach

Peter Kroetzsch

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.

Preparation of hydroxylammonium salts

A novel fixed-bed catalyst structure obtained using honeycomb elements, for highly exothermic and endothermic chemical reactions, wherein the required heat exchange, both in the liquid phase and in the gas phase, is forcibly effected in the fixed catalyst bed by means of static mixing elements made of inert ceramic and/or metallic material or completely of catalyst material, between the individual honeycomb elements.

Fixed-bed catalyst structure obtained using honeycomb elements

A honeycomb catalyst consisting of from 30 to 95% by weight, calculated as Fe.sub.2 O.sub.3, of an iron compound and from 0.1 to 60% by weight, calculated as Al.sub.2 O.sub.3, CeO.sub.2 or Cr.sub.2 O.sub.3, of an aluminum, cerium and/or chromium compound and/or from 1 to 50% by weight of an alkali metal compound, in particular potassium, calculated as K.sub.2 O, and/or from 0.2 to 20% by weight, calculated as MeO.sub.3, of an element of sub-group 6, preferably MoO.sub.3 and WO.sub.3, and/or from 0.1 to 20% by weight, calculated as V.sub.2 O.sub.5, of a compound of vanadium and/or from 0.1 to 20% by weight, calculated as P.sub.2 O.sub.5, of a compound of phosphorus, a process for the preparation of the honeycomb catalyst, and the use of the catalyst for organic reactions.

Honeycomb catalyst and its preparation

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.

Regeneration of inactive and poisoned platinum catalysts

Growing community of inventors

Frankenthal, Germany

Werner Biffar