Process for making, and use of, anionic clay materials

Details Process for making, and use of, anionic clay materials Process for making, and use of, anionic clay materials

1999-12-09

2002-11-12

Silverman, Stanley S. (Department: 1754)

Catalyst, solid sorbent, or support therefor: product or process

Zeolite or clay, including gallium analogs

Clay

C502S080000, C502S085000

Reexamination Certificate

active

06479421

ABSTRACT:

BACKGROUND OF THE INVENTION
This invention is generally concerned with methods of making anionic clays. Such clays are characterized by crystalline structures that consist of positively charged layers that are separated by interstitial anions and/or water molecules. The positively charged layers are often comprised of metal hydroxides of divalent metal cations (e.g., Mg
2+
, Ca
2+
, Zn
2+
, Mn
2+
, Co
2+
, Ni
2+
, Sr
2+
, Ba
2+
and Cu
+
) and trivalent metal cations (e.g., Al
3+
, Mn
3+
, Fe
3+
, Co
3+
, Ni
3+
, Cr
3+
, Ga
3+
, B
3+
, La
3+
and Gl
3+
). The interstitial anions are usually NO
3
—, OH—, Cl—, Cr—, I—, CO
3
2−
, SO
4
2−
, SIO
3
2−
, HPO
3
2−
, MnO
4
—, HGaO
3
2−
, HVO
4
2−
, ClO
4
—, BO
3
2−
, monocarboxylates (e.g., acetate) and dicarboxylates (e.g., oxalate), alkyl sulphonates (e.g., lauryl sulphonate) and various combinations thereof.
Therefore, anionic clays are further subdivided according to the identity of the atoms that make up their crystalline structures. For example, anionic clays in the pyroaurite-sjogrenite-hydrotalcite group are based upon brucite-like layers (wherein magnesium cations are octahedrally surrounded by hydroxyl groups) which alternate with interstitial layers of water molecules and/or various anions (e.g., carbonate ions). When some of the magnesium in a brucite-like layer is isomorphously replaced by a higher charged cation, e.g., Al
3+
, then the resulting Mg
2+
—Al
3+
—OH layer gains in positive charge. Hence, an appropriate number of interstitial anions, such as those noted above, are needed to render the overall compound electrically neutral.
The literature also teaches that as the concentration of Al
3+
increases in a Brucite-type lattice, a reduction of the lattice parameter known as “a”, takes place. The lattice parameter known as “c” also is reduced. The reduction in lattice parameter, a, is due to the smaller, plus three charged, Al
3+
ions substituting for the larger, plus two charged Mg
2+
ions. This higher charge causes increased coulombic forces of attraction between the positive charged Brucite-type layer and the negative interlayer ions—thus giving rise to a decrease in the size of the interlayer itself.
Natural minerals that exhibit such crystalline structures include, but by no means are limited to, pyroaurite, sjogrenite, hydrotalcite, stichtite, reevesite, eardleyite, mannaseite, barbertonite and hydrocalumite. The chemical formulas for some of the more common synthetic forms of anionic clays would include: [Mg
6
Fe
2
(OH)
16
]CO
3
. 4H
2
O, [Mg
6
Al
2
—(OH)
16
]CO
3
.4H
2
O, [Mg
6
Cr
2
(OH)
16
]CO
3
.4H
2
O, [Ni
6
—Fe
2
(OH)
16
]C
3
.4H
2
O, [Ni
6
Al
2
(OH)
16
]CO
3
.4H
2
O, [Fe
4
Fe
2
(OH)
12
]CO
3
.#H
2
O, [Ca
2
Al (OH)
6
](OH)
0.75
—(CO
3
)
0.125
2.5H
2
O
6
]OH.6H
2
O, [Ca
2
Al—(OH)
6
]OH.3H
2
O, [Ca
2
Al(OH)
6
]OH.2H
2
O, [Ca
2
Al—(OH)
6
]OH, [Ca
2
Al(OH)
6
]Cl
2
H
2
O, [Ca
2
Al(OH)
6
]0.5CO
3
2.5H
2
O, [Ca
2
Al(OH)
6
]0.5SO
4
.3H
2
O, [Ca
2
—Fe(OH)
6
]0.5SO
4
.3H
2
O, [(Ni, Zn)
6
Al
2
(OH)
16
]CO
3
.4H
2
O, [Mg
6
(Ni, Fe)
2
(OH)
16
](OH)
2
.2H
2
O, [Mg
6
Al
2
(OH)
16
—](OH)
2
.4H
2
O, [(Mg
3
Zn
3
)al
2
(OH)
16
]CO
3
.4H
2
O, [Mg
6
Al
2
(OH)
16
]SO
4
.xH
2
O, [Mg
6
Al
2
(OH)
16
](NO
3
)
2
.x—H
2
O, [Zn
6
Al
2
(OH)
16
]CO
3
.xH
2
O, [Cu
6
Al
2
(OH)
16−
]CO
3
.xH
2
O, [Cu
6
Al
2
(OH)
16
]SO
4
.xH
2
O and [Mn
6
Al
2−
(OH)
16
]CO
3
.xH
2
O, wherein x has a value of from 1 to 6.
Those skilled in this art also will appreciate that anionic clays are often referred to as “mixed metal hydroxides.” This expression derives from the fact that, as noted above, positively charged metal hydroxide sheets of anionic clays may contain two metal cations in different oxidation states (e.g., Mg
2+
and Al
3+
). Moreover, because the XRD patterns for so many anionic clays are similar to that of the mineral known as Hydrotalcite, Mg
6
Al
2
(OH)
16
(CO
3
).4H
2
O, anionic clays also are very commonly referred to as “hydrotalcite-like compounds.” This term has been widely used throughout the literature for many years (see for example: Pausch, “Synthesis of Disordered and Al-Rich Hydrotalcite-Like Compounds,”
Clay and Clay Minerals
, Vol. 14, No. 5, 507-510 (1986). Such compounds also are often referred to as “anionic clays.” Indeed, the expressions “anionic clay,” “mixed metal hydroxides” and “hydrotalcite-like compounds” are often found very closely linked together. For example, in: Reichle, “Synthesis of Anionic Clay Minerals (Mixed Metal Hydroxides, Hydrotalcite),” Solid State Ionics, 22, 135-141 (1986) (at Paragraph 1, page 135) the author states: “The anionic clays are also called mixed metal hydroxides since the positively charged metal hydroxide sheets must contain two metals in different oxidation states. Crystallographically they have diffraction patterns which are very similar or identical to that of hydrotalcite (Mg
6
Al
2
(OH)
16
(CO
3
).4H
2
O); hence they have also been referred to as hydrotalcites or hydrotalcite-like.” (emphasis added). U.S. Pat. No. 5,399,329 (see col.1, lines 60-63) contains the statement: “The term ‘hydrotalcite-like’ is recognized in this art. It is defined and used in a manner consistent with usage herein in the comprehensive literature survey of the above-referenced Cavani et al. article.” Hence, for the purposes of the present patent disclosure, applicant will (unless otherwise stated) use the term “hydrotalcite-like” compound(s) with the understanding that this term should be taken to include anionic clays, hydrotalcite itself as well as any member of that class of materials generally known as “hydrotalcite-like compounds.” Moreover, because of its frequent use herein, applicant will often abbreviate the term “hydrotalcite-like” with
The methods by which HTL compounds have been made are found throughout the academic and the patent literature. For example, such methods have been reviewed by Reichle, “Synthesis of Anionic Clay Minerals (Mixed Metal Hydroxides, Hydrotalcite),” Solid States Ionics, 22 (1986), 135-141, and by Cavani et al., CATALYSIS TODAY, Vol. 11, No. 2, (1991). In the case of hydrotalcite-like compounds, the most commonly used production methods usually involve use of concentrated solutions of magnesium and aluminum which are often reacted with each other through use of strong reagents such as sodium hydroxide, and various acetates and carbonates. Such chemical reactions produce hydrotalcite or hydrotalcite-like compounds which are then filtered, washed, and dried. The resulting HTL compounds have been used in many ways—but their use as hydrocarbon cracking catalysts, sorbents, binder materials for catalysts and water softener agents is of particular relevance to this patent disclosure.
It also is well known that HTL compounds will decompose in a predictable manner upon heating and that, if the heating does not exceed certain hereinafter more fully discussed temperatures, the resulting decomposed materials can be rehydrated (and, optionally, resupplied with various anions, e.g., CO
3
=
, that were driven off by the heating process) and thereby reproduce the original, or a very similar, HTL compound. The decomposition products of such heating are often referred to as “collapsed,” or “metastable,” hydrotalcite-like compounds. If, however, these collapsed or metastable materials are heated beyond certain temperatures (e.g., 900° C.), then the resulting decomposition products of such hydrotalcite-like compounds can no longer be rehydrated and, hence, are no longer capable of forming the original hydrotalcite-like compound.
Such thermal decomposition of hydrotalcite-like compounds has been carefully studied and fully described in the academic

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