Chemistry of inorganic compounds – Zeolite – Structure defined x-ray diffraction pattern
Reexamination Certificate
2001-07-06
2003-04-29
Dang, Thuan D. (Department: 1764)
Chemistry of inorganic compounds
Zeolite
Structure defined x-ray diffraction pattern
C423S329100, C585S750000, C585S739000, C208S028000, C208S113000, C208S119000
Reexamination Certificate
active
06555090
ABSTRACT:
TECHNICAL FIELD
The present invention refers to the area of chemistry, in particular to materials of catalytic interest
BACKGROUND
The present invention deals with a pillared mixed oxide that maintains a separation between sheets, there being individual structural layers, that have microporous channels and cavities.
Laminar materials such as clays, phosphates, hydroxycarbonates, silicic acids (kanemite, magadiite, keniaite, etc.), transition metal sulfides, graphite, laminar hydroxides and others, are capable of swelling in the presence of water and/or suitable interlaminar cations. The individual sheets of these materials are kept together by means of weak hydrogen bond type forces and/or electrostatic interactions. These bonds break easily when the intercalation force or the solvation energy of the cations are greater than the interlaminar attraction forces.
The interest of swollen materials is to make the interlaminar space accessible to the reacting molecules, and consequently, the inside surface, considerably increasing the active surface accessible to the reagent. When the material intercalated between the sheets of the mixed oxide is eliminated by calcination, the swollen laminar compound collapses, recovering the original interlaminar distance.
In order to prevent the interlaminar collapse, intercalation of the “pillars” comprised of thermally stable inorganic oxyhydroxides in the swollen material has been proposed. These “pillars” are comprised of polymeric hydroxides of Al, Si, Cr, Ni, Zr, etc. . . . , which after calcination treatment give rise to columns of the corresponding oxide that are anchored in the surface of the sheets keeping them separated and stabilizing the final pillared product.
OBJECTS OF THE INVENTION
It is an object of the present invention to provide a pillared material consisting of a mixed oxide, which maintains a separation among sheets, appearing isolated structural layers with channels and microporous cavities, and which may be used as catalyst in acid catalyzed reactions.
It is an additional object of the present invention a method for preparing the laminar solid and the subsequent treatment thereof, until a highly accessible microporous pillared material with acid characteristics capable of being used as a catalyst is obtained.
It is an additional object of the invention the use of the pillared microporous material in acid catalyzed reactions, such as cracking and isomerization of organic compounds, and preferably of hydrocarbons, as well as in hydroisomerization and hydrocracking processes.
It is a further object of the invention to provide catalytic compounds which comprise the pillared micro- or mesoporous material and a matrix and their use in processes of dewaxing and isodewaxing.
Finally, it is an additional object of the invention catalytic compositions which comprise the pillared micro- or mesoporous material and a hydrogenating function.
DESCRIPTION OF THE INVENTION
The present invention refers to an oxide which is a pillared material, called ITQ-36, with a micro- and mesoporous structure and a high external surface area, capable of supporting Brönsted and Lewis acid centers and that is characterized by its X-ray diffractogram and its adsorption and catalytic properties.
The material ITQ-36 has a chemical composition represented by the formula
(XO
2
)
n
(Y
2
O
3
)
m
(H
2
O)
p
wherein X represents, at least, a tetravalent element and Y represents, at least, a trivalent element, the atomic ratio between X and Y being at least 5. In preferred embodiments the atomic ratio between X and Y is higher than 10, or even higher than 30. In a more preferred embodiment said atomic ratio is higher than 30, or even higher than 40. Suitable limits for said atomic ratio may be between 30 and 500.
Preferably, X in XO
2
represents, at least, a tetravalent element selected from among silicon, germanium and, more specifically silicon, in some cases it being able to also be titanium.
Preferably, Y in Y
2
O
3
represents, at least, a trivalent, element, selected from among aluminum, iron, chromium and gallium, and more specifically aluminum.
The material ITQ-36 has an X-ray diffraction diagram with basal spacings and relative intensities summarized in Table 1.
TABLE 1
d
(Å)
I/I
O
* 100
37.01
Vs
18.77
W
7.01
W
6.51
W
3.95
W
3.50
W
2.62
W
2.35
W
In this description, and unless it is specified otherwise, the relative intensities of the X-ray diffraction peaks will be represented with the symbols and meaning established hereinafter:
w
weak
0-20%
relative intensity
m
medium
20-40%
s
strong
40-60%
vs
very strong
60-100%
The preparation process of the pillared oxide ITQ-36 consists of:
a first step comprising the synthesis of a precursor which is a laminar material that can be swollen,
a second step wherein the laminar material obtained is swollen by mixing the same with a swelling solution resulting in a swollen laminar material, which is a swollen laminar mixed oxide,
a third step wherein the swollen laminar material is washed and dried giving rise to a swollen dried laminar material, and
a fourth step wherein the swollen dried laminar material is pillared, washed, dried and calcined, to obtain the pillared mixed oxide, ITQ-36, of the invention.
In the first step the synthesis of a solid which is a laminar material, is carried out by mixing in an autoclave a source of a tetravalent element, which in the case of silicon may be for example a silica source such as AEROSIL, LUDOX, CABOSIL, tetraethylorthosilicate (TEOS) or any other known; a source of a trivalent element, which in the case of aluminum may be a source selected among boehmite, pseudoboehmite, Al
2
(SO
4
)
3
, AlCl
3
, Al(NO
3
) or any other one; a fluoride salt and a fluoride acid such as for example ammonium fluoride and hydrogen fluoride; an organic compound such as 1,4-diaminobutane, ethylendiamine, 1,4-dimethylpiperazine, 1,4-diaminocyclohexane, hexamethylenimine and pyrrolidine, preferably, 4-amino-2,2,6,6-tetramethylpiperidine; and water in suitable proportions.
Synthesis of said solid material takes place at temperatures between 100 and 200° C., with permanent stirring of the gel and a duration between 1 and 30 days and, preferably between 1 and 18 days, and more preferably between 2 and 12 days. After this time the reaction product, a white solid with a pH between 9 and 10 is washed with distilled water, filtered and dried.
During the second step swelling of the obtained solid material takes place by preparing a suspension thereof in a solution that we will call the “swelling” solution, formed by an organic compound of a long hydrocarbonated chain that has a proton acceptor group, such as for example a quaternary alkylammonium, an amine, or an alcohol with more than three carbons in the chain, to which a controlled amount of a compound capable of providing OH
−
to the reaction medium, such as for example, a quaternary alkylammonium hydroxide is added, until a pH higher than 10 is obtained. The organic compound used as a OH
−
source may be any amine or quaternary alkylammonium compound, preferably cetyltrimethylammonium hydroxide (CTMA
+
OH
−
).
The swelling solution prepared is mixed with the previously described solid material of the first step in a weight ratio of swelling solution to solid laminar material between 4 and 200. The resulting suspension is kept under reflux and permanent stirring between 20 and 200° C., and preferably between 40 and 120° C., for a time no less than 1 hour until the swollen laminar material is obtained.
During the third step the swollen laminar material is thoroughly washed with distilled water and dried at temperatures lower than 300° C. and preferably lower than 150° C. A swollen dried laminar material is thus obtained.
Once washed and dried, the swollen dried material has a characteristic X-ray diffraction diagram whose basal spacings and relative intensities are summarized in Table 2.
TABLE 2
d
(Å)
I/I
O
* 100
28.20
Vs
14.45
S
9.81
W
6.46
W
4.31
M
4.10
M
3.93
M
3.65
W
3.49
M
2.87
W
2.62
W
Th
Canós Avelino Corma
Chica Lara Antonio
Díaz Morales Urbano
Fornés Segúi Vicente
Consejo Superior de Investigaciones Cientificas
Dang Thuan D.
Klauber & Jackson
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