Dichromate Patents (Class 423/597)
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Publication number: 20130129604Abstract: Process for preparing ammonium dichromate, comprising the steps of c) thermally decomposing an alkali metal ammonium chromate double salt, especially a sodium ammonium chromate double salt or hydrates thereof, at a temperature up to 200° C., especially of 75 to 190° C., to form ammonium dichromate and d) removing the ammonium dichromate from the decomposition product obtained after step c), by crystallization, characterized in that the alkali metal ammonium chromate double salt corresponds to the formula Mx(NH4)yCrO4 or hydrates thereof, in which M is Na or K, particular preference being given to Na, x is from 0.1 to 0.9, preferably from 0.4 to 0.7, y is from 1.1 to 1.9, preferably from 1.3 to 1.6, and the sum of x and y is 2.Type: ApplicationFiled: December 8, 2010Publication date: May 23, 2013Applicant: LANXESS DEUTSCHLAND GMBHInventors: Holger Friedrich, Rainer Ortmann, Matthias Stenger, Matthias Boll, Daniel Van Rooyen, Naveen Kalideen
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Patent number: 6616744Abstract: The present invention provides a method of forming inorganic pigments using one or more metal alloys. Metal alloys used in the method of the invention are preferably milled to a mean particle size of less than about 10 microns, may be mixed with other metal oxides, and calcined in the presence of oxygen in a rotary kiln. Inorganic pigments formed in accordance with the method of the invention can be used in a wide variety of applications, including the coloration of glass matrixes, ceramic bodies, polymers, and paints.Type: GrantFiled: April 17, 2002Date of Patent: September 9, 2003Assignee: Ferro CorporationInventors: Javier Garcia Sainz, Rosario Blanch Castello, Rafael Mena Pla, Juan Carlos Gallart
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Patent number: 6482387Abstract: Described are preferred polymerized organic-inorganic processes for producing mixed metal oxide powders suitable for use in the ceramics and related industries. The preferred processes employ a non-chelating polymer such as polyvinyl alcohol or polyalkylene glycol as a carrier and can provide single-phase, mixed oxide powders in high yields at relatively low temperatures.Type: GrantFiled: June 16, 1999Date of Patent: November 19, 2002Inventors: Mehmet Ali Gülgün, Waltraud M. Kriven, My Hoang Nguyen
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Patent number: 5630994Abstract: A method for generation of phase-pure doped and undoped Li.sub.x Mn.sub.y O.sub.z precursors. The method of this invention uses organic solutions instead of aqueous solutions or nonsolution ball milling of dry powders to produce phase-pure precursors. These precursors can be used as cathodes for lithium-polymer electrolyte batteries. Dopants may be homogeneously incorporated to alter the characteristics of the powder.Type: GrantFiled: August 1, 1995Date of Patent: May 20, 1997Inventors: Timothy J. Boyle, James A. Voigt
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Patent number: 5571489Abstract: A process for recovery of chromium in an aqueous solution comprising converting the chromium to chromyl chloride, separating the chromyl chloride from the aqueous solution, either as a heavy underlayer, or by extraction into a solvent, purifying the chromyl chloride, hydrolyzing the purified chromyl chloride to form a solution, and drying or precipitating the solution to form chromium, either as chromic acid or a chromate salt.Type: GrantFiled: January 27, 1995Date of Patent: November 5, 1996Assignee: Illinois Institute of TechnologyInventors: Thomas M. Holsen, Jan R. Selman, Subbarao L. Guddati
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Patent number: 5482690Abstract: The invention relates to a process for the low-waste production of sodium dichromate from the mineral chromite with simultaneous recovery of low-carbon ferrochromium.Type: GrantFiled: January 6, 1995Date of Patent: January 9, 1996Assignee: Bayer AktiengesellschaftInventor: Karl-Christoph Scherhag
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Patent number: 5393503Abstract: Disclosed is an improvement on a process in which sodium chromate is reacted with sulfuric acid to produce sodium bichromate and sodium sulfate, and the sodium bichromate is reacted with sulfuric acid to produce chromic acid and sodium bisulfate. In the improvement, the sodium sulfate and sodium bisulfate are reacted with hydrogen chloride to produce sulfuric acid, which is recycled, and sodium chloride.Type: GrantFiled: September 9, 1991Date of Patent: February 28, 1995Assignee: Occidental Chemical CorporationInventors: Harry F. Buckholtz, Daniel J. Jaszka
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Patent number: 5279804Abstract: Disclosed is a method of removing soluble vanadium from an aqueous stream containing sodium chromate or sodium bichromate. The liquor is passed over a water-insoluble trivalent chromium compound, and the vanadium in the liquor is extracted from the liquor onto the trivalent chromium compound. The process is especially useful in removing vanadium from a recycled concentrated sodium bichromate liquor to prevent the buildup of vanadium therein.Type: GrantFiled: August 27, 1992Date of Patent: January 18, 1994Assignee: Occidental Chemical CorporationInventors: Robert L. Zeller, III, Russell J. Morgan, Ursula I. Keller
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Patent number: 5250274Abstract: The invention relates to a process for the production of sodium dichromate and sodium dichromate solutions by oxidative roasting of chrome ores under alkaline conditions, leaching of the furnace clinker obtained with water or an aqueous chromate-containing solution, adjustment of the pH to from 7 to 9.5, removal of the insoluble constituents by filtration, a sodium monochromate solution being obtained, conversion of the monochromate ions of this solution into dichromate ions by acidification and crystallization of sodium dichromate by concentration of this solution, characterized in that the acidification is carried out with carbon dioxide under pressure with removal of sodium hydrogen carbonate, the remaining solution is then very largely freed from sodium monochromate by cooling to a temperature below 10.degree. C.Type: GrantFiled: January 21, 1992Date of Patent: October 5, 1993Assignee: Bayer AktiengesellschaftInventors: Norbert Lonhoff, Bernhard Spreckelmeyer, Hans-Dieter Block, Rainer Weber, Jost Halstenberg, Bernd Rosenow
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Patent number: 4968503Abstract: A process for the production of sodium dichromate comprising reacting sodium chromate with acids, the acids being sulfuric acid and NaHSO.sub.4 formed as a waste product in the production of CrO.sub.3 and thus being contaminated with chromium compounds, adding PO.sub.4 ions in excess to the NaHSO.sub.4 contaminated with chromium compounds and precipitating the Cr(III) present therein as CrPO.sub.4 at a temperature of 50.degree. to 100.degree. C. and at a pH value of 3 to 6.Type: GrantFiled: April 24, 1989Date of Patent: November 6, 1990Assignee: Bayer AktiengesellschaftInventor: Albert E. B. Glissmann
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Patent number: 4773974Abstract: By-product hypochlorite from the electrolytic production of chlorates, notably sodium chlorate, is used to form hexavalent chromium for use in the electrolysis process by oxidation of trivalent chromium compounds by the hypochlorite. The hypochlorite may be the condensate produced by treatment of the chlorate cell by-product gas stream and/or present in the cell liquor.Type: GrantFiled: October 29, 1986Date of Patent: September 27, 1988Assignee: Tenneco Canada Inc.Inventor: Leszek M. Dobosz
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Patent number: 4759922Abstract: A new anhydrous sodium dichromate in flakes, Na.sub.2 Cr.sub.2 O.sub.7, m.p. 356.degree. C. (dec. 400.degree. C.) is described, characterized in that it comes in flakes with an area of approx. 1 cm.sup.2, thickness 0.5 mm and apparent specific gravity 1.10 (absolute 2.748) at 25.degree. C.; it is not deliquescent, nor does it become powdery. It is prepared from dihydrate sodium dichromate or aqueous solutions thereof using a new process in two stages, namely (a) evaporation-melting of the dihydrate salt or concentrated aqueous solution at a strictly controlled temperature of around 380.degree. C. and no higher, and (b) flaking of the melted mass obtained thereby, as it is being rapidly cooled to 150.degree.-160.degree. C. The apparatus for carrying out the process is also claimed; said apparatus consisting essentially of a dehydrator-melter oven, a flaker rotating at 10-20 revs per minute and a heat recovery system.Type: GrantFiled: October 16, 1985Date of Patent: July 26, 1988Assignee: Luigi Stoppani S.p.A.Inventor: Diego Perrone
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Patent number: 4704259Abstract: Soluble hexavalent chromium values are removed from aqueous chlorate solutions by employing a critical effective ratio of OH.sup.- :Cr.sub.2 O.sub.7.sup.= ions of at least 3:1 in the aqueous chlorate solution and by employing a dithionite to reduce the hexavalent chromium to trivalent chromium, preferably in the mole ratio of S.sub.2 O.sub.4.sup.= :Cr.sub.2 O.sub.7.sup.= of at least 3:1. The trivalent chromium forms chromic hydroxide (Cr(OH).sub.3) with the hydroxyl ions and precipitates from the aqueous chlorate solution. The process is rapid and effective in quantitative removal of hexavalent chromium from the aqueous chlorate solutions and is especially useful for the removal of sodium dichromate from cell liquor which is intended to be employed in chlorine dioxide production and which is produced by diaphragmless electrolysis of sodium chloride.Type: GrantFiled: May 27, 1986Date of Patent: November 3, 1987Assignee: Tenneco Canada Inc.Inventor: Marek Lipsztajn
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Patent number: 4108596Abstract: A process and a product formed thereby for the recovery of chromium values from aqueous solutions (e.g., waste liquors) comprises contacting an acidic solution containing sulfate ion and trivalent chromium ion with at least about 4 molar equivalents of MgO or Mg(OH).sub.2 per 3 molar equivalents of trivalent chromium in addition to the amount required to neutralize the free acid to a pH of about 4 to form an amorphous, dense solid, grainy, easily settleable, trivalent chromium-containing precipitate in an alkaline solution according to the equation: 3Cr.sub.2 (SO.sub.4) + 8 MgO .fwdarw.Cr.sub.2 (OH).sub.4 SO.sub.4 .multidot. 4Cr(OH).sub.3 .multidot. 4H.sub.2 O + 8 MgSO.sub.4. The trivalent chromium-containing product can be readily separated from the water and is a useful source of chromium for subsequent processing. The water remaining after separation of the precipitate contains less than 0.5 mg/l chromium.Type: GrantFiled: April 18, 1977Date of Patent: August 22, 1978Assignee: Revere Copper and Brass, IncorporatedInventors: Donald C. Hemming, Robert E. Hahn, John W. Robinson, Jr.
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Patent number: 4086319Abstract: A process is disclosed for incinerating tannery waste solids containing organic material and chromium which comprises burning at least one ton per day of said waste in the combustion zone of an industrial furnace at a low temperature, preferably between about 800.degree. F. and 1200.degree. F., to convert at least a portion of the organic material to gases and the chromium to ash, removing the gases from the combustion zone and subjecting them to further oxidation, and removing the ash from the furnace. The waste solids include sludge separated from liquid waste, leather scrap, or preferably both. By controlling temperature, waste composition, or both, the chromium in the ash can be obtained in either trivalent or hexavalent form. The hexavalent chromium can be extracted with solvent for reuse in the tanning process. Trivalent chromium, with or without carbon, can be recovered as chromic oxide in an improved stable form for landfill, storage or shipment to a reprocessing center.Type: GrantFiled: November 8, 1976Date of Patent: April 25, 1978Inventor: Bradford H. Jones
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Patent number: 3981973Abstract: Metal salts which are crystallizable from a saturated aqueous solution of the salt in the presence of a dispersion of polytetrafluoroethylene (hereinafter referred to as PTFE) resin are grown as geometrically better defined and larger crystals than those grown from an unseeded saturated solution.Type: GrantFiled: December 17, 1973Date of Patent: September 21, 1976Assignee: The Harshaw Chemical CompanyInventor: John G. Richardson
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Patent number: 3933972Abstract: Processes for preparing vanadium- and chlorine-free sodium bichromate which comprises concentration of a sodium chromate liquor so as to cause formation of crystals of neutral sodium chromate tetrahydrate, separation of these crystals from their mother liquor, treatment thereof with sulfuric acid, concentration of the acid solution obtained, and after separation of insoluble sodium sulfate so formed, crystallization of sodium bichromate.Type: GrantFiled: February 11, 1974Date of Patent: January 20, 1976Assignee: Products Chimiques Ugine KuhlmannInventors: Robert Bauwens, Robert Lefrancois, Michel Gabriel
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Patent number: 3932598Abstract: An improved process for producing alkali metal chromates and dichromates wherein ferrochrome alloy containing at least 1% carbon by weight is reacted with a molten mixture of an alkali metal nitrate and an alkali metal carbonate at a temperature of at least 350.degree.C. The ferrochrome alloy can be prepared by smelting chromite ore in the presence of carbon.Type: GrantFiled: April 24, 1970Date of Patent: January 13, 1976Inventors: Hugh S. Cooper, deceased, Henry J. Rand, executor