Catalyst – solid sorbent – or support therefor: product or process – Zeolite or clay – including gallium analogs – And group viii containing
Reexamination Certificate
2000-04-03
2002-06-25
Hendrickson, Stuart L. (Department: 1754)
Catalyst, solid sorbent, or support therefor: product or process
Zeolite or clay, including gallium analogs
And group viii containing
C423S277000, C423S326000, C423S705000
Reexamination Certificate
active
06410473
ABSTRACT:
BACKGROUND OF THE INVENTION
(1) Field of the Invention
This invention relates to new mesoporous quasi crystalline inorganic oxide compositions having regular worm hole shaped channels. In particular, the present invention relates to those compositions formed by a novel self-assembly method comprising steps of hydrogen bonding between a neutral amine template in water and a water miscible organic solvent with a substantial excess of the water or the solvent, and a neutral inorganic oxide precursor, followed by hydrolysis and crosslinking. This invention also relates to a route for facile recovery and recycling of the template by simple solvent extraction.
(2) Description of Related Art
Porous solids created by nature or by synthetic design have found great utility in all aspects of human activity. The pore structure of the solids is usually formed in the stages of crystallization or subsequent treatment. Depending on their predominant pore size, the solid materials are classified as: (i) microporous, having pore sizes <20 Å; (ii) macroporous, with pore sizes exceeding 500 Å; and (iii) mesoporous, with intermediate pore sizes between 20 and 500 Å. The use of macroporous solids as adsorbents and catalysts is relatively limited due to their low surface area and large non-uniform pores. Microporous and mesoporous solids, however, are widely used in adsorption, separation technology and catalysis. Owing to the need for higher accessible surface area and pore volume for efficient chemical processes, there is a growing demand for new highly stable mesoporous materials. Porous materials can be structurally amorphous, paracrystalline, or crystalline. Amorphous materials, such as silica gel or alumina gel, do not possess long range order, whereas paracrystalline solids, such as &ggr;- or &eegr;- A1
2
O
3
are quasiordered as evidenced by the broad peaks on their X-ray diffraction patterns. Both classes of materials exhibit a broad pore size distribution of pores predominantly in the mesoporous range. This wide pore size distribution limits the shape selectivity and the effectiveness of the adsorbents, ion-exchanges and catalysts prepared from amorphous and paracrystalline solids.
The only class of porous materials possessing rigorously uniform pore sizes is that of zeolites and related molecular sieves. Zeolites are microporous highly crystalline aluminosilicates. Their lattice is composed by IO
4
tetrahedra (I=A1 and Si) linked by sharing the apical oxygen atoms. Their pore network, which is confined by the spatially oriented IO
4
tetrahedra, consists of cavities and connecting windows of uniform size (Breck D. W.,
Zeolite Molecular Sieves: Structure, Chemistry and Use
; Wiley and Sons; London, 1974). Because of their aluminosilicate composition and ability to discriminate small molecules, zeolites are considered as a subclass of molecular sieves. Non-zeolitic molecular sieves are crystalline framework materials in which Si and/or A1 tetrahedral atoms of a zeolite lattice are entirely or in part substituted by other I atoms such as B, Ga, Ge, Ti, V, Fe, or P.
Zeolite frameworks are usually negatively charged due to the replacement of Si
4+
by A1
3+
. In natural zeolites this charge is compensated by alkali or alkali earth cations such as Na
+
, K
+
or Ca
2+
. In synthetic zeolites the charge can also be balanced by quaternary ammonium cations or protons. Synthetic zeolites and molecular sieves are prepared usually under hydrothermal conditions from aluminosilicate or phosphate gels. Their crystallization, according to the hereafter discussed prior art, is accomplished through prolonged reaction in an autoclave for 1-50 days and, often times, in the presence of structure directing agents (templates). The proper selection of template is of extreme importance for the preparation of a particular framework and pore network. A large variety of organic molecules or assemblies of organic molecules with one or more functional groups are known in the prior art to give more than 85 different molecular sieve framework structures. (Meier et al.,
Atlas of Zeolite Structure Types
, Butterworth, London, 1992). Excellent up to date reviews of the use of various organic templates and their corresponding structures, as well as the mechanism of structure directing are given in Barrer et al.,
Zeolites
, vol. 1, 130-140 (1981); Lok et al.,
Zeolites
, vol. 3, 282-291 (1983); Davis et al.,
Chem. Mater
., vol. 4, 756-768 (1992) and Gies et al. ,
Zeolites
, vol. 12, 42-49 (1992). For example, U.S. Pat. No. 3,702,886 teaches that crystallization of aluminosilicate gel (high Si/A1 ratio) in the presence of quaternary tetrapropyl ammonium hydroxide template affords zeolite ZSM-5. Other publications teaching the use of various organic directing agents include, for example, U.S. Pat. No. 3,709,979, wherein quaternary cations, such as tetrabutyl ammonium or tetrabutyl phosphonium, are used to crystallize zeolite ZSM-11 and U.S. Pat. No. 4,391,785 demonstrating ZSM-12 preparation in the presence of tetraethyl ammonium cations. Another zeolite-ZSM-23 synthesis, directed by (CH
3
)
3
N
+
(CH
2
)
7
N
+
(CH
3
)
3
dications, is taught in U.S. Pat. No.4,619,820. The use of yet another dicationic template-N, N, N, N′, N′, N′, -hexamethyl-8,11-[4.3.3.0] dodecane diammonium diiodide, for the preparation of zeolite SSZ-26, is shown in U.S. Pat. No. 4,910,006.
Other prior art teaches that primary amines such as propylamine, i - propylamine (U.S. Pat. No. 4,151,189), and diamines, such as diaminopentane, diaminohexane and diaminododecane (U.S. Pat. No. 4,108,881) also direct the synthesis of the ZSM-5 type structure. However, as pointed out by Hearmon et al.,
Zeolites
, vol. 10, 608-611 (1990), it is the protonated form of these amines which most likely is responsible for the framework assembly.
In summary, most of the prior art zeolites and molecular sieve frameworks were assembled by using quaternary ammonium cations or protonated forms of amines or diamines as templates.
The search for new organic directing agents, as evident in the increasing number of prior art reports, is attributable to: (i) the need for new and attractive types of stable frameworks and (ii) to the need for expanding the uniform micropore size to mesopore region and thus allowing one to adsorb, process and discriminate among much larger molecules. However, the prior art molecular sieves typically possess uniform pore size in the microporous region. This pore size is predetermined by the thermodynamically favored formation of framework windows containing 8, 10 and 12 - I atom rings. Thus, the ability of the prior art zeolites and molecular sieves to adsorb, process and discriminate among molecules of certain shape and size is strictly limited by the size of these windows. During the last three decades considerable synthetic effort has been devoted to developing frameworks with pore sizes larger than that of the naturally occurring zeolite faujasite (pore size 7.4 Å). However, due to the above limitations, the synthetic faujasite analogs, zeolite X or Y, with 8 Å pore windows (Breck D. W.,
Zeolite Molecular Sieves: Structure, Chemistry and Use
; Wiley and Sons; London, 1974), maintained for decades their position as the largest pore molecular sieves. The replacement of aluminosilicate gels by alumino-and gallophosphate gels gave new direction to the synthesis of large uniform pore materials. Thus, a 18-membered ring aluminophosphate molecular sieve VPI-5 (Davis et al. ,
Nature
, vol. 331, 698-699 (1988)), was found to possess a structure with an hexagonal arrangement of one-dimensional channels (pores) of diameter ≈12 Å. The discovery of a 20-membered ring gallophosphate molecular sieve-cloverite, exhibiting a uniform pore size of 13 Å is disclosed in Estermann M. et al.,
Nature
, vol. 352, 320-323 (1991). Recently, Thomas et al.,
J. Chem. Soc., Chem. Commun.
, 875-876 (1992) reported a triethyl ammonium cation—directed synthes
Pauly Thomas R.
Pinnavaia Thomas J.
Tanev Peter T.
Zhang Wenzhong
Board of Trustees of Michigan State University
Hendrickson Stuart L.
McLeod Ian C.
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