Catalyst – solid sorbent – or support therefor: product or process – Zeolite or clay – including gallium analogs – Clay
Reexamination Certificate
2002-02-07
2004-03-23
Dunn, Tom (Department: 1725)
Catalyst, solid sorbent, or support therefor: product or process
Zeolite or clay, including gallium analogs
Clay
C502S080000, C423S593100, C423S600000
Reexamination Certificate
active
06710004
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a process for the preparation of anionic clay and boehmite-containing compositions. The invention also relates to the preparation of catalyst compositions comprising anionic clay and boehmite-containing compositions.
2. Prior Art
Anionic clays have a crystal structure which consists of positively charged layers built up of specific combinations of metal hydroxides between which there are anions and water molecules. Hydrotalcite is an example of a naturally occurring anionic clay, in which carbonate is the predominant anion present. Meixnerite is an anionic clay wherein hydroxyl is the predominant anion present.
In hydrotalcite-like anionic clays the brucite-like main layers are built up of octahedra alternating with interlayers in which water molecules and anions, more particularly carbonate ions, are distributed. The interlayers may contain anions such as NO
3
−
, OH
−
, Cl
−
, Br
−
, I
−
, SO
4
2−
, SiO
3
2−
, CrO
4
2−
, BO
3
2−
, MnO
4
−
, HGaO
3
2−
, HVO
4
2−
, CIO
4
−
, BO
3
2−
, pillaring anions such as V
10
O
28
6−
and Mo
7
O
24
6−
, monocarboxylates such as acetate, dicarboxylates such as oxalate, and alkyl sulphonates such as laurylsulphonate.
It should be noted that a variety of terms are used to describe the material that is referred to in this specification as an anionic clay. Hydrotalcite-like and layered double hydroxide are interchangeably used by those skilled in the art. In this specification we refer to these materials as anionic clays, comprising within that term hydrotalcite-like and layered double hydroxide materials.
These anionic clays can contain different divalent or trivalent metals. The most commonly described anionic clays are Mg—Al anionic clays. These anionic clays are suitable for many applications in the absorbent and catalyst field. Anionic clays from other divalent and/or trivalent metals have specific applications in these fields. Fe—Al anionic clays, for instance, are useful as hydrogenation catalysts; Zn—Cr anionic clays can be used as catalysts in oxidation reactions.
Anionic clays have been described in many prior art publications. Two major reviews of anionic clay chemistry were published in which the synthesis methods available for anionic clay synthesis have been summarised: F. Cavani et al “Hydrotalcite-type anionic clays: Preparation, Properties and Applications,”
Catalysis Today”,
11 (1991) Elsevier Science Publishers B. V. Amsterdam; and J P Besse and others
“Anionic clays: trends in pillary chemistry, its synthesis and microporous solids
” (1992), 2, 108, editors: M. I. Occelli, H. E. Robson, Van Nostrand Reinhold, N.Y.
In the above reviews basically two types of anionic clay preparation are described. The most conventional method is co-precipitation (in Besse this method is called the salt-base method) of a soluble divalent metal salt and a soluble trivalent metal salt, optionally followed by hydrothermal treatment or aging to increase the crystallite size. The second method is the salt-oxide method in which a divalent metal oxide is reacted at atmospheric pressure with a soluble trivalent metal salt, followed by aging under atmospheric pressure. This method has only been described for the use of ZnO and CuO in combination with soluble trivalent metal salts.
For work on anionic clays, reference is further made to the following articles:
Helv. Chim. Acta,
25, 106-137 and 555-569 (1942)
J. Am. Ceram. Soc.,
42, no. 3, 121 (1959)
Chemistry Letters
(
Japan
), 843 (1973)
Clays and Clay Minerals,
23, 369 (1975)
Clays and Clay Minerals,
28, 50 (1980)
Clays and Clay Minerals,
34, 507 (1996)
Materials Chemistry and Physics,
14, 569 (1986).
In addition there is an extensive amount of patent literature on the use of anionic clays and processes for their preparation.
Several patent applications relating to the production of anionic clays from inexpensive raw materials have been published. These materials include magnesium oxide, aluminum trihydrate, and boehmite.
WO 99/41198 relates to the production of anionic clay from two types of aluminum compounds and a magnesium source. One of the aluminum compounds is aluminum trihydrate or a thermally treated form thereof.
WO 99/41196 discloses the preparation of anionic clays with acetate as the charge balancing anion from magnesium acetate, another magnesium source, and aluminum trihydrate.
In WO 99/41195 a continuous process is described for the production of a Mg—Al anionic clay from a magnesium source and aluminum trihydrate.
WO 99/41197 discloses the production of an anionic clay-containing composition comprising a Mg—Al anionic clay and unreacted aluminum trihydrate.
WO 00/44672 discloses the production of anionic clays by hydrothermal treatment of a slurry of a magnesium source and boehmite, which has been peptised by an inorganic acid. By using an excess of boehmite, unreacted boehmite ends up in the composition.
WO 00/44671 relates to compositions comprising Mg—Al anionic clay and boehmite. These compositions are prepared from boehmite and a magnesium source not being hydromagnesite. The boehmite in the composition results from an excess of boehmite starting material, which ends up in the composition as unreacted boehmite.
There are many fields of use for anionic clays. These include but are not restricted to: catalysts, adsorbents, drilling muds, fillers for plastics, water treatment materials, catalyst supports and carriers, extenders and applications in the medical field. In particular Van Broekhoven (U.S. Pat Nos. 4,956,581 and 4,952,382) has described their use in SO
x
abatement chemistry.
SUMMARY OF THE INVENTION
In one embodiment, the present invention comprises a process for the preparation of anionic clay and boehmite-containing compositions. The process according to the invention comprises subjecting a precursor mixture comprising a divalent metal source and a trivalent metal source to at least two aging steps, wherein at least once between two aging steps an aluminum source is added. Optionally, these compositions may also contain unreacted trivalent metal source and/or divalent metal source.
In another embodiment, the present invention comprises the anionic clay and boehmite-containing composition obtained by the above process.
Other embodiments of the present invention include the use of specific reactants in the above precursor mixture, the use of the above anionic clay and boehmite-containing composition as a precursor in making other compositions, such as catalysts, and conditions employed in the making of the various compositions.
DETAILED DESCRIPTION OF THE INVENTION
One of the advantages of performing at least two aging steps with intermediate aluminum source addition is that it provides a way to tune the crystallinity of the boehmite in the composition. As the surface area, pore volume, pore size distribution, density, binding properties, and catalytic activity of boehmites depends on their crystallinity, tuning of their crystallinity is very desirable. This tuning can be achieved by using a different pH and/or temperature in each of the aging steps and/or by adding different aluminum sources in between aging steps.
Furthermore, this process offers a way to easily control the anionic clay to boehmite ratio. This can be especially useful for catalysis or adsorption purposes. Anionic clay mainly possesses basic sites; boehmite primarily consists of acidic sites. Therefore, by varying the anionic clay to boehmite ratio, the ratio of acidic to basic sites can be varied as well.
To obtain a catalyst composition comprising an anionic clay and boehmite-containing composition obtainable by the process according to the invention, the anionic clay and boehmite-containing composition is added to a slurry containing the other catalyst components or precursors thereof and finally shaped.
The present invention relates to a process for the preparation of anionic clay and boehmite-containing compositio
Jones William
O'Connor Paul
Stamires Dennis
Akzo Nobel nv
Dunn Tom
Ildebrando Christina
Morris Louis A.
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