Classifications

• • C—CHEMISTRY; METALLURGY
  • C01—INORGANIC CHEMISTRY
  • C01F—COMPOUNDS OF THE METALS BERYLLIUM, MAGNESIUM, ALUMINIUM, CALCIUM, STRONTIUM, BARIUM, RADIUM, THORIUM, OR OF THE RARE-EARTH METALS
  • C01F7/00—Compounds of aluminium
  • C01F7/48—Halides, with or without other cations besides aluminium
  • C01F7/56—Chlorides
• • C—CHEMISTRY; METALLURGY
  • C01—INORGANIC CHEMISTRY
  • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
  • C01B15/00—Peroxides; Peroxyhydrates; Peroxyacids or salts thereof; Superoxides; Ozonides
  • C01B15/01—Hydrogen peroxide
  • C01B15/022—Preparation from organic compounds
  • C01B15/023—Preparation from organic compounds by the alkyl-anthraquinone process
• • C—CHEMISTRY; METALLURGY
  • C01—INORGANIC CHEMISTRY
  • C01F—COMPOUNDS OF THE METALS BERYLLIUM, MAGNESIUM, ALUMINIUM, CALCIUM, STRONTIUM, BARIUM, RADIUM, THORIUM, OR OF THE RARE-EARTH METALS
  • C01F7/00—Compounds of aluminium
  • C01F7/68—Aluminium compounds containing sulfur
  • C01F7/74—Sulfates

Definitions

• the invention relates to a method for purifying impure aluminium oxide and to the use of the aluminium salts produced with this method as a raw material in industrial applications.
• alurninium oxide is used to regenerate and remove organic secondary products formed in the working solution.
• the porosity of active aluminium oxide allows it to be used particularly in the anthraquinone process with a view to adsorb spent organic compounds.
• the impurities are mostly aromatic hydrocarbons. Having lost its activity, aluminium oxide is removed from the process and replaced with a new oxide.
• the spent aluminium oxide contains organic substances which restrict its utilization. At present, residual aluminium oxide is usually disposed of as a waste, or optionally stored in the scope of its eventual utilization.
• US patent specification 3 814 701 sets out removal of organic matter from spent aluminium oxide from an anthraquinone working solution by calcinating aluminium oxide at a temperature of 300-400 °C.
• the organic matter adsorbed into aluminium oxide will be removed by combustion during the calcination.
• the calcinated aluminium oxide is then subjected to caustic treatment and recalculated. Nevertheless, treated in this way, aluminium oxide is highly dusting if recycled in the H2O2 process.
• DE patent application 4 0127 159 describes purifying impure alurninium oxide with a method comprising dissolving aluminium oxide into mineral acids or lye. The component insoluble in acids or lye is separated, the purified aluminium oxide is filtered, dried and eventually calcinated.
• the patent application does not specify how the various steps of the invention can be performed. All the same, the aluminium oxide dissolved in acids or lye and the accompanying impurities constitute a diphase solution which is particularly hard to treat, containing a tar-like, sticky organic phase. Technically speaking, it is nearly impossible to perform additional treatments of great volumes of such a solution.
• the purpose of the present invention is to provide a method for removing organic substances from aluminium oxide waste deriving from the hydrogen peroxide process.
• the goal of the inventive method is to allow controlled, safe and environment-friendly purification of contaminated and impure aluminium oxide, allowing the aluminium salts obtained as a product to be used as a raw material in industrial applications.
• Another goal of the inventive method is not only to recycle the organic contaminant compounds but also to utilize them as a fuel.
• the invention relates to a new method for purifying impure aluminium oxide, which has been used in hydrogen peroxide preparation for the adsorption of organic components.
• the method of the invention makes it possible to obtain a perfectly pure alunrinium salt, such as aluminium sulphate or aluminium chloride, which is even purer than commercially available technical products.
• the alurninium salts prepared with this method are well-suited to be used as raw materials in industrial applications, particularly alurninium salts are suitable to be employed as water purification and retention chemicals.
• organic hydrocarbons present as impurities in aluminium oxide can be utilized as a fuel.
• part of the organic hydrocarbons can be dissolved into the solvent in prepurification, and the useful components can be recycled in the hydrogen peroxide process.
• the method allows the environmental hazards of hydro ⁇ carbons to be markedly reduced compared to most other purifying methods.
• Porous, active alurninium oxide is used to regenerate the working solution in the preparation of hydrogen peroxide with the anthraquinone method.
• Porous aluminium oxide adsorbs the organic hydrocarbons used as an anthraquinone solvent, working solution components and other degradation and oxidation products from the working solution.
• solvents used to dissolve anthraquinone s in the preparation of working solutions we cite among others secondary alcohols, trialkyl phosphates, alkyl benzenes, triacetyl benzene, alkyl cyclohexanones, naphtalenes, xylenes, anilines and quinones.
• the working solution may further contain many other potential substances used to dissolve anthraquinone.
• the inactive and impure un inium oxide removed from the process may thus contain different organic matters in varying amounts, depending on the manufacturing process of the hydrogen peroxide.
• the invention comprises thermal treatment of the impure aluminium oxide at 500- 900 °C, at which organic components present as impurities evaporate or burn.
• the invention recommends a sufficiently low calcinating temperature for aluminium oxide to remain soluble in acids, but also sufficiently high for the organic components present as impurities to be removed.
• the calcinating conditions affect the acid solubility of aluminium oxide.
• aluminium oxide was calcinated at higher temperatures, for instance 1,000 °C, its solubility in acids dropped markedly.
• aluminium salts were more slowly filtered, and unsolved precipitates remained to a larger extent than with aluminium oxide calcinated at lower temperatures.
• the calcinating time depends on the amount of organic component to be burnt, on the temperature, and on the calcinating equipment. Calcination may be carried out in any furnace suitable for calcination. Rotary and tubular furnaces were found to be particularly suitable. It is recommended to equip the furnace with a catalyst or a thermal afterburner. During calcination, evaporating or combustible organic exhaust gases are burnt catalytically or with a thermal afterburner. The gases may also be conducted to be burnt in the combustion chamber of a combustion plant. In this way, the method enables the caloric value of the impurities to be utilized.
• impure alurninium oxide can be prewashed before thermal treatment using an organic hydrocarbon solvent.
• the washing solvent may consist of any organic hydrocarbon capable of dissolving the organic impurity component from aluminium oxide.
• the solvent is Shellsol AB, which is a commercially available product containing mainly C10-C11 aromatic hydrocarbons.
• Preliminary washing allows such organic useful components, for instance quinone ⁇ , to be extracted and subsequently recycled directly into the hydrogen peroxide process.
• Prewashing also allows the amount of organic matter for combustion to be reduced, while organic compounds are recycled into the hydrogen peroxide process.
• the invention recommends pulverization of the thermally-treated aluminium oxide.
• impure, granular aluminium oxide may be finely ground before the thermal treatment.
• the choice of the grinding moment depends on the amount of organic component in the aluminium oxide, and the fact whether the alurninium oxide has been prewashed before the thermal treatment or not. It is a fact that grinding is complicated by considerable amounts of organic impurities.
• thermal treatment of ground, dusting aluminium oxide is awkward, but organic components burn more effectively in ground oxide than in granular oxide.
• Acid dissolving comprises dissolving ground alurriinium oxide in a concentrated acid solution. Any concentrated mineral acid is appropriate for dissolving, however, sulphuric and hydrochloric acid are recommended. Sulphuric acid used in a 50-60% concentration is considered particularly suitable.
• the dissolving is appropriately enhanced by heating. To ensure nearly complete dissolving of aluminium oxide, it is recommended to heat the mixture to a temperature of about 100-150 °C, while stirring for several hours. After the reaction, the reaction mixture is diluted with water to prevent aluminiiim salts from crystallizing, if a liquid product is desired, which can be filtered to separate the insoluble portion. The reaction mixture may also be directly crystallized by cooling in order to obtain a solid aluminium salt.
• the undissolved aluminium oxide precipitates in the acid can be removed by filtering or centrifugating, and the undissolved portion can be returned to the dissolving step.
• the filtrate, which contains aluminium salt can be used as such as an aqueous solution, or then can be solidified by crystallizing.
• the aqueous phase is purified by filtering in order to remove organic residues that may remain in the aqueous phase.
• Purification can be performed with an active carbon treatment.
• Other chemicals may also be used, for instance flocculating agents, instead of, or along with active carbon.
• flocculating agent allows a finely-divided dissolving residue, which contains undissolved oxide and possibly uncombusted carbon, to be bound in a form which makes it easier to separate from the solution.
• the perfectly pure aqueous solution of aluminium salt derived from the filtration with active carbon can be used as such, or supplied in a solid crystallized form for use say, as a water purification or retention chemical.
• Figure 1 shows a block diagram of the various steps of the invention.
• Figure 2 illustrates the solubility of aluminium oxide in sulphuric acid as a function of the calcinating temperature.
• impure aluminium oxide is subjected to thermal treatment at 500-900 ° C.
• Another option is to prewash aluminium oxide before the thermal treatment with an organic hydrocarbon solvent, and in that case the useful organic components extracted into the solvent can be returned to the hydrogen peroxide process.
• the thermally-treated aluminium oxide is ground before being dissolved in mineral acid, unless it has already been ground before the thermal treatment.
• uminium oxide precipitates undissolved in the acid can be removed by filtering or centrifugating.
• the purified alurninium salt can be industrially used as an aqueous solution or in solid form say, as a water purification or retention agent.
• Impure aluminium oxide was subjected to thermal treatment at 200 °C over a period of two hours. 100 g of treated aluminium oxide was dissolved in a mixture of sulphuric acid (264 g) and water (278 g). 93% of the aluminium oxide was dissolved in the acid solution. A tar-like layer of impurities was formed on the walls of the reaction vessel.
• Spent ali ⁇ minium oxide was prewashed before thermal treatment with an organic hydrocarbon solvent in order to recover the anthraquinones.
• the alurninium oxide had been normally evaporated to recover the solvent and the quinones.
• the aluminium oxide to be washed still had a 2.0% quinone content and a 2.2% solvent content (trialkyl phosphate).
• the column which contained 510 g of aluminium oxide, was filled with pure Shellsol AB solvent (200 ml.). The temperature was maintained at about 40 to 50 °C. The mixture was stored over a period of 7 hours. The solvent was evacuated. The thermal treatment was repeated two more times. In the first wash, the quinone content of the aluminium oxide dropped by about 80%. The second treatment yielded a 98-100% reduction. The solvent residues (trialkyl phosphate) decreased at a corresponding rate.
• Example 7 Spent aluminium oxide from a hydrogen peroxide plant was calcinated in a continuously operating circular furnace at 550 °C so as to provide a 1.5 hour delay. The product was nearly white and was analysed as follows: AI2O3 91%, Fe 0.11% and C 0.2%. The calcinated oxide (150 g) was admixed with water (307 g) in a 2 1 decanter, was heated to 60 °C, and after this 96% sulphuric acid was cautiously introduced into the vessel during about 15 minutes. The temperature then rose from 115 to 130 °C.
• Example 8 Spent aluminium oxide (137 g) containing organic matter was ground 20 s with a Schwing mill and was calcinated in a quarz basin in a 6 mm layer thickness for 1.5 h. The calcination loss was 21.3%. 100 g of the product (screened with a 250 ⁇ m screen, 99.3% passing through) was elutriated in 205 g of water, the reaction mixture was heated to 60 °C and sulphuric acid (96%, 273 g) was introduced into the reaction mixture during about half an hour. The temperature rose to 120 °C. The mixture was allowed to react for 3 hours at the boiling point (112 °C at the end), and was subsequently diluted with water (1078 g).
• Figure 2 illustrates the dissolving yield as a function of the calcinating temperature. All the tests were conducted in the same way as the above example, and thus they are mutually comparable.
• Figure 2 shows graphically the solubility of aluminium oxide in sulphuric acid, calcinated at various temperatures, as a function of the calcinating temperature. The results show that when aluminium oxide is calcinated at > 900 °C, the aluminium oxide dissolving yield drops below 90%. A dissolving yield below 90% is not considered acceptable. In this situation, the slow filtering of the undissolved substance is a further inconvenience.

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• Chemical & Material Sciences (AREA)
• Organic Chemistry (AREA)
• Inorganic Chemistry (AREA)
• Life Sciences & Earth Sciences (AREA)
• Geology (AREA)
• Compounds Of Alkaline-Earth Elements, Aluminum Or Rare-Earth Metals (AREA)

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• 1994
  • 1994-05-20 FI FI942339A patent/FI98509C/sv not_active IP Right Cessation
• 1995
  • 1995-05-19 EP EP95918630A patent/EP0764136A1/en not_active Withdrawn
  • 1995-05-19 JP JP7530076A patent/JPH10500389A/ja active Pending
  • 1995-05-19 WO PCT/FI1995/000273 patent/WO1995032153A1/en not_active Application Discontinuation

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