Bayer Aktiengesellschaft

Wolfgang Bockelmann

Hans Niederprum

Jakob Rademachers

Johann-Nikolaus Meussdoerffer

Hans-Georg Nieder-Vahrenholz

Wilfried Burow

Johann Nikolaus Meussdoerffer

Kurt Schafer

Heinz Jonas

Hans-George Nieder-Vahrenholz

Klaus Gauler

Georg Uecker

A process is disclosed for preparing iron oxide black pigments obtained by the nitrobenzene reduction process, wherein the iron oxide black is heated to 400.degree.-800.degree. C. in a slightly oxidizing atmosphere with optional milling. The pigments are useful for coloring plastics, coatings and building materials.

Iron oxide black pigments, processes for their preparation and their use

A process is disclosed for preparing dispersant-free iron oxide pigment granules by spraying or atomizing an iron oxide black pigment suspension and heating the resulting granules at a temperature of 400.degree.-800.degree. C. The granules are useful for coloring building materials such as concrete.

Iron oxide black pigment granules, processes for their preparation and

In the disintegration of a chromite or chromium-containing residue, wherein the chromium-containing material is disintegrated with an alkaline compound in the presence of oxygen and a diluent at a temperature above about 800.degree. C. and thereafter leached, the improvement which comprises pre-roasting the chromium-containing material prior to addition of the alkaline compound. Pre-roasting can be effected at 400.degree. to 1200.degree. C. with addition of certain amounts of silica dioxide and/or aluminum oxide and such additives, depending on the chromium containing material, if still required, are added--prior to disintegration and leaching--in such a quantity to establish a ratio of SiO.sub.2 : AL.sub.2 O.sub.3 of about 2:1 and further a ratio, calculated on the basis of NaOH as the alkaline compound, of SiO.sub.2 : Na.sub.2 O of about 1:0.5 plus a Cr.sub.2 O.sub.3 : Na.sub.2 O ratio of about 1:2 to 1:4. Residues from previous leaching cycles can be present during disintegration as solid diluents but their contents of SiO.sub.2 and/or Al.sub.2 O.sub.3 are not taken into account in calculating the SiO.sub.2 :AL.sub.2 O.sub.3 ratios. The process gives excellent results even with starting materials relatively high in SiO.sub.2 which are difficult to disintegrate to materials of desirable properties by other methods.

Disintegration of chromites

A process for the preparation of a chrome-tanning agent and Glauber's salt from sodium bisulphate contaminated with chromium compounds obtained as by-product from the manufacture of chromic acid from solid sodium dichromate and sulphuric acid, comprising

Process for the preparation of a chrome tanning agent and Glauber's salt

In the recovery of chromium from a residue containing chromate and vanadate, by oxidative decomposition of a chromium and vanadium-containing ore in the presence of an alkali at temperatures of about 600 to 1200.degree. C., and leaching such residue with water, the improvement which comprises adding titanium dioxide to the residue and heating, whereby upon leaching the chromium enters the water while the vanadium is substantially left in the residue.

Producing chromate substantially free of vanadium

In the disintegration of at least one chromium source selected from the group consisting of a SiO.sub.2 -containing chromite and a chromium-containing residue with an alkali compound at a temperature above about 800.degree. C in the presence of atmospheric oxygen and a lime-free diluent, followed by leaching of the mixture with at least one of water and/or a chromium (VI)-containing aqueous solution, the improvement which comprises including in the mixture to be disintegrated an aluminum compound and at least sufficient alkali to form alkali chromate and to convert the SiO.sub.2 into an alkali-aluminum silicate corresponding to the formula nMe.sub.2 O . mSiO.sub.2 . Al.sub.2 O.sub.3, wherein Me is at least one of sodium and potassium, 0.8 .ltoreq. n .ltoreq. 1.2 and 1.3 .ltoreq. m .ltoreq. 4.3.

Disintegration of silica-rich chromite

In the alkaline-oxidative disintegration of chromites into chromates with an alkali comprising reacting a chromium ore in the presence of oxygen and a diluent, and leaching the reaction mixture with at least one of water and/or a chromate-containing aqueous solution, the improvement which comprises reacting the residue obtained after leaching with an excess of alkali, based on the chromium oxide content of the residue, in the presence of oxygen, grinding the reaction mixture and, without leaching, employing the ground reaction mixture as an alkali source in another chromite disintegration cycle. The alkali reacted with the leaching residue is preferably sodium and/or potassium hydroxide and/or carbonate and is employed in about 100 to 400%, and preferably about 150 to 330%, of the stoichiometric amount based on the chromium oxide content of the leaching residue.

Growing community of inventors

Leverkusen, Germany

Wolfgang Bockelmann