Chemistry of inorganic compounds – Halogen or compound thereof
Patent
1990-09-18
1992-06-09
Niebling, John
Chemistry of inorganic compounds
Halogen or compound thereof
423468, 423556, C01B 1745, C01F 756
Patent
active
051205220
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a process for preparing basic aluminum compounds. More particularly, the present invention relates to the preparation of basic aluminum compounds having the general formula (1)
The present invention furthermore relates to the use of an apparatus which is specified hereinafter in greater detail and by means of which it is possible to prepare the compounds of formula (1) at temperatures lower than 100.degree. C. and at atmospheric pressure.
BACKGROUND ART
Basic compounds according to the invention are generally used in aqueous solution, but can also occur in the form of crystalline solids.
Said compounds are mainly used in the conditioning of water as flocculants and in the paper-sizing process. Bauxite, bayerite, gibbsite, hydrargillite etc. may be materials used as raw material, provided that they are hydrated oxides.
For the sake of simplicity, said compounds are hereinafter indicated by the generic term alumina.
Various methods, disclosed in patent and scientific literature, are known for obtaining basic compounds.
Ignoring electrochemical methods, the method most used industrially is the one which provides for the etching of alumina with a marked stoichiometric lack of hydrochloric acid. This etching must be performed at temperatures above 100.degree. C. and under pressure. This process, operating under pressure and with a large excess of alumina which must be recycled, requires technologically demanding systems.
DISCLOSURE OF THE INVENTION
The Applicant has now surprisingly found, and this constitutes one of the aspects of the present invention, that it is possible to obtain basic aluminum compounds having the general formula (1) by making alumina react with hydrochloric acid, optionally mixed with sulfuric acid, at temperatures below 100.degree. C., operating under given reaction conditions which are defined hereinafter.
One of the aspects of the present invention is therefore a process for preparing basic aluminum compounds having the general formula (1) mixed with sulfuric acid, under atmospheric pressure said process being characterized in that
(a) the alumina is caused to react with acid under stoichiometric conditions to obtain the compound of formula (I); and
(b) the reaction according to item (a) is performed by milling the alumina in a liquid phase under heavy agitation at a temperature comprised between 50.degree. C. and 95.degree. C., in a microsphere mill, the operative parameters of said mill being the following:
(a) microsphere filling bodies with a diameter of 0.6-2.5 mm,
(b) peripheral speed of stirring disks: 2.5 to 12 m/sec.
(c) degree of filling of the milling chamber with microspheres: 70% to 95% in apparent volume.
Preferably microspheres are formed of glass, ceramics, zirconia or similar materials.
The reaction temperature is preferably comprised between 75.degree. C. and 95.degree. C. and more preferably between 90.degree. C. and 95.degree. C.
Preferred operative parameters of said mill are the following: 0.8-1.2 mm,
(b) peripheral speed of stirring disks: 10.5 m/sec;
(c) degree of filling of the milling chamber with microspheres: about 75% in apparent volume.
The apparatus employed, according to the invention, is preferably a thermostat-controlled tubular reactor filled with microspheres subjected to heavy shearing stresses. Said reactor is more preferably constituted by a cylindrical container made of glass or metal with a jacket (interspace) inside which liquid is circulated to keep the temperature at the required level. A stirring means, constituted by a shaft coated with PTFE (polyester) or PVDF (polyvinylidene fluoride), rotates at the center, and adequately shaped stirring disks, again made of PTFE or PVDF, are keyed thereon.
A further aspect of the present invention is the use of an apparatus as described above to prepare basic aluminum compounds having the general formula (1) in compliance with the process according to the present invention.
The aluminas employed may have different granulometries, with a maximum upp
REFERENCES:
patent: 3894144 (1975-07-01), Becher et al.
patent: 3909439 (1975-09-01), Rivola et al.
patent: 3920406 (1975-11-01), Danner et al.
patent: 3920800 (1975-11-01), Harris
patent: 3957947 (1976-05-01), Yamada et al.
patent: 3989805 (1976-11-01), Notari et al.
patent: 4034067 (1977-07-01), Seigneurin et al.
patent: 4082685 (1978-04-01), Notari et al.
Chemical Abstract: 83:45400k--Aug. 11, 1975.
Donelli Giordano
Dore Fausto
Bolam Brian M.
Caffaro S.p.A.
Niebling John
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