Bayer Aktiengesellschaft

Bayer Akteingesellschaft

Karl-Heinz Schultz

Gunter Lailach

Rudolf Gerken

Peter Woditsch

Hans L Kuhnlein

Walter Bockmann

Joachim Maas

Klaus Kohler

Hans R Kung

Wolfgang Larbig

Walter Deissmann

Wolfgang Dietz

Jurgen Groening

Hansruedi Forter

Rudolf Hornung

A process for the preparation of titanium dioxide by the sulphate process in which titanium raw materials are decomposed with sulphuric acid, the resulting titanyl sulphate is hydrolyzed, the waste acid is separated from the hydrolyzate and evaporated to a concentration of 60 to 70%, sulphuric acid is separated from the solid metal sulphates, and the sulphuric acid which has been concentrated by evaporation is used again for the decomposition of the titanium raw material, the improvement wherein the 60 to 70% sulphuric acid is concentrated to 70 to 80% H.sub.2 SO.sub.4 in a further evaporation stage and the concentration of a part of this sulphuric acid is raised to a concentration of 98 to 99% H.sub.2 SO.sub.4 by the absorption of SO.sub.3 and then used together with the remainder of the above-mentioned 70 to 80% sulphuric acid for the decomposition of titanium raw materials.

Process for the preparation of titanium dioxide

Energy required for the calcining or drying operations in the production of titanium dioxide by the sulfate process and the chloride process is at least in part provided by burning by-product offgases containing carbon monoxide obtained in the chlorination of titanium-containing raw materials under reducing conditions.

Process for the production of titanium dioxide pigments

In the production of nitrobenzene by subjecting benzene to nitration with a mixture of nitric acid and sulfuric acid, separating off the nitrobenzene formed, concentrating the sulfuric acid by evaporation and returning the concentrated sulfuric acid to the bezene nitration stage, the improvement which comprises concentrating sulfuric acid to a concentration of from 75 to 92% by evaporation in vacuo at temperatures in the range from 130.degree. to 195.degree. C. Thereby the energy per kg of water evaporated is drastically reduced compared to processes wherein the sulfuric acid is concentrated to a higher level, without a corresponding loss in efficiency or capacity.

Process for the production of nitrobenzene

An improved process for the preparation of TiCl.sub.4 comprising

Process for the preparation of TiCl.sub.4

In the desulphurizing of SO.sub.2 - and hydrogen halide-containing flue gases by catalytically oxidizing the sulphur dioxide on moist active carbon at a temperature of from 45.degree. to 70.degree. C. with the formation of 3 to 20% dilute sulphuric acid, the improvement which comprises contacting the dilute sulphuric acid with the hot flue gases to be desulphurized so as to evaporate water resulting sulphuric acid of a concentration of from 60 to 85%, and removing by evaporation the hydrogen chloride and hydrogen fluoride dissolved in the dilute sulphuric acid. Advantageously evaporation is carried out in two scrubbing stages, the hydrogen chloride and hydrogen fluoride being removed, by vacuum evaporation or by stripping with air or flue gas, from a mixture of the dilute sulphuric acid from the second scrubbing stage with the concentrated sulphuric acid from the first scrubbing stage, the mixture having the H.sub.2 SO.sub.4 concentration of from 40 to 70%.

Process for desulphurizing flue gases

The invention procides a circulation evaporator for concentrating mineral acid, particularly sulphuric acid, comprising parts of, or at least coated with, enamel, characterized by a heat exchanger for heating the acid comprising at least one acid feed pipe provided with an enamel layer, means being provided to maintain the compressive stress in the enamel layer under all working conditions, said acid feed pipe being connected at its inlet end to a circulation pump and at its outlet end to a flash evaporator for concentrating the heated acid, this evaporator being connected by a circulation pipe to the pump inlet and to means for introducing the crude acid, for discharging the concentrate and for carrying away the vapors.

Evaporator for concentrating mineral acid, particularly sulphuric acid

A metallic iron-containing starting material such as iron filings, iron powder or a reduced ore such as ilmenite is oxidized with air in the presence of 5 to 40% of iron oxide and/or iron oxide hydroxide nuclei and about 2.5 to 200% of an electrolyte, percentages being based on metallic iron by weight. The oxidation is effected in aqueous suspension at 75.degree. to 100.degree. C and a pH of 4 to 6.5. If the nuclei are magnetite-free, at least the first quarter of the oxidation should be at pH 5 to 6.5. Preferred electrolytes are transition metal salts. The pigments are more intense in color and have a more pronounced blue tinge.

Growing community of inventors

Krefeld, Germany

Karl-Heinz Schultz