Basf Aktiengesellschaft

Basf Aktiengsellschaft

Peter Thoma

Wolfgang Habermann

Peter Hammes

Franz-Josef Weiss

Erwin Thomas

Joachim Kranz

Klaus Wintermantel

Hugo Fuchs

Josef Ritz

Rolf Schneider

Elmar Frommer

Helmut Knittel

Eckhard Hetzel

Klaus Borho

Karl K Mayer

Dieter Stockburger

Karl-Heinz Sartor

Wolfgang Mach

Gotthard Csizi

Bernhard Holzknecht

Karl-Ludwig Hock

Friedrich Brunnmueller

Zafirios Grammatis

Ewald Vollmerhaus

Wolf D Stege

Joachim Felger

Karl-Heinz Hennicke

A continuous closed-system process for the environmentally friendly drying and purification of benzanthrone which comprises the steps of charging a benzanthrone-containing paste of pumpable consistency onto a melt held in a stirred kettle, dewatering and melting the paste by means of steam, condensing the water vapor emerging from the stirred kettle, flaking the melt from the stirred kettle by means of a rotating drum, and packaging the flaked solids.

Drying and purification of benzanthrone

Frozen crystal layers are purified by a process in which these crystal layers, after they have been frozen out from a melt or solution on a cooling surface, are brought into contact with a purifying liquid and thus purified over their entire thickness, after which the said layers are separated from the purifying liquid and then melted, wherein the temperature of the crystal layers and of the purifying liquid is close to the melting point or solubility temperature, mass transfer at the phase boundary is intensified by forced convection, and this purification is carried out in the course of from 1 to 60 minutes on layers having a thickness of from 0.2 to 10 mm.

Purification of frozen crystal layers

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.

Preparation of aqueous hydroxylamine solutions

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.

Preparation of aqueous solutions of hydroxylammonium carbonate

Blue iron hexacyanoferrate-III pigments are produced by a process wherein complex iron-II hexacyanoferrate-II (Berlin white) is prepared by electrolysis of an aqueous catholyte solution containing (a) an iron-II salt, (b) an alkali metal salt, an ammonium salt or a mixture of these, and (c) hydrogen cyanide, in an electrolysis cell in which the anode chamber and cathode chamber are separated by an ion exchange membrane, using an electrically conductive aqueous liquid in the anode chamber, and the iron-II hexacyanoferrate-II obtained is then converted to the blue pigment. The process gives Berlin white, which is substantially free from salt, in high yield and high purity. Pollution caused by the process is very low, since only a small amount of salt is produced. Compared with the corresponding blue pigments produced by prior art processes, the pigments obtained give purer colorations with better gloss, and are of higher color strength.

Production of blue iron hexacyanoferrate-III pigments

An electrode for electrolysis purposes, which may in particular be used as an anode for the electrolysis of alkali metal chlorides, contains, in addition to an alloy of niobium with a metal of the iron group, tantalum, tantalum carbide or an alloy of tantalum with metals of the iron group, individually or as mixtures. The surface of the electrode is modified with a metal of the platinum group, especially with rhodium.

Electrodes for electrolysis purposes

Metal-free phthalocyanines (PC) are prepared by electrolysis, at inert electrodes, of aromatic o-dinitriles in organic liquids which contain small amounts of dissolved electrolytically conductive compounds, in the presence of hydrogen or of a compound which eliminates hydrogen under the reaction conditions and in the presence of alkaline compounds (as activators). The PC formed may be isolated in the pure form by filtration. The product contains from 90 to 99% of PC. It is used for the preparation of PC-based pigments.

Preparation of metal-free phthalocyanines

In a process for the removal of mercury by treatment with elementary nickel an external voltage is applied to maintain the potential of the nickel at a value which differs from the potential of the reversible hydrogen electrode in the liquid concerned by not more than from -250 mV to +50 mV. The treatment is carried out at temperatures of from 80.degree. to 230.degree. C.

Removal of mercury from liquids

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Frankenthal, Germany

Peter Thoma