Chemistry of inorganic compounds – Oxygen or compound thereof – Metal containing
Patent
1996-06-07
1998-09-01
Langel, Wayne
Chemistry of inorganic compounds
Oxygen or compound thereof
Metal containing
422225, 422234, 423626, 423628, C01F 702, B01J 800
Patent
active
058007970
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a process for producing alumina. More particularly, it is concerned with a process for producing a porous alumina having its pore volume, size and surface area controlled so that the porous alumina can suitably be used as, for example, a catalyst support or an adsorbent.
BACKGROUND ART
A porous alumina now finds wide industrial application as, for example, a catalyst support or an adsorbent. The requisite ranges of a pore volume, size and a surface area of a porous alumina vary depending on the intended use of the porous alumina. Thus, control of the pore distribution in such aspects is inevitable. With respect to a molding of the porous alumina, being excellent in mechanical strength and other properties is required.
Methods in which aging or other treatment is effected of an alumina hydrate obtained by, for example, a neutralization reaction and methods in which alumina hydrate precipitation conditions are controlled have been proposed as methods suitable for achieving control of the pore distributions, e.g., the pore volume and pore size distributions of the porous alumina.
An example of the former methods is described in Japanese Patent Publication No. 53(1978)-19000 in which, for example, an amorphous alumina hydrate is heated at 50.degree. C. or above under agitation in weakly alkali conditions (pH 8 to 12) to thereby carry out aging thereof, so that a pseudoboehmite alumina particle size is grown with the result that, in an alumina product, the volume of pores each having a size of smaller than 600 .ANG. is larger than 0.6 ml/g.
Examples of the latter methods are described in Japanese Patent Publication No. 57(1982)-44605 and Japanese Patent Laid-open Publication No. 58(1983)-190823.
Illustratively, Japanese Patent Publication No. 57(1982)-44605 describes a method comprising adding an aluminum salt to a slurry containing aluminum hydroxide which has its pH value adjusted to 6-10 and is held at 50.degree. C. or higher temperatures to thereby cause the slurry to have a pH value of not greater than 5 or at least 11, adding a neutralizer to return the pH value to 6-10 and repeating these a plurality of times, so that the pore distribution, e.g., the pore volume distribution of the alumina product is controlled.
Japanese Patent Laid-open Publication No. 58(1983)-190823 discloses a process for producing an alumina support which comprises a step of adding to a slurry containing aluminum hydroxide an aluminum salt at a rate of 20 to 500%/hr, provided that the amount of the aluminum hydroxide contained in the slurry is regarded as being 100% in terms of molar ratio of aluminum, together with a pH controller while maintaining a hydrogen icon concentration and temperature of the slurry at 6 to 11 in pH and 50.degree. C. or higher, respectively, to thereby form an alumina gel and a step of converting the alumina gel to alumina. At least one of the above aluminum salt and the pH controller substantially contains sulfate ions.
In any of the conventional processes for producing a porous alumina as described in, for example, the above Japanese Patent Publication No. 57(1982)-44605 and Japanese Patent Laid-open Publication No. 58(1983)-190823, an aluminum salt and a neutralizer are in sequence or simultaneously added to a slurry containing aluminum hydroxide (corresponding to a seed alumina hydrate) to thereby effect reaction, so that the desired porous alumina is batchwise obtained.
However, the production of the porous alumina according to the above processes has been accompanied by an undesirable phenomenon that not only does precipitation of alumina hydrate occur in the slurry containing a large quantity of alumina hydrate to thereby render the state of mixing of alumina hydrate ununiform but also fine particles of alumina hydrate are newly formed with the result that the finally obtained alumina hydrate particles would have a size distribution to thereby disenable satisfactory control of the pore distribution of tie porous alumina.
Further, the conventional c
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Arao Hiroki
Fukuda Morio
Matsumoto Hiroshi
Catalysts & Chemicals Industries Co. Ltd.
Langel Wayne
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