Chemistry of inorganic compounds – Zeolite – Isomorphic metal substitution
Reexamination Certificate
2002-05-09
2004-08-17
Sample, David (Department: 1755)
Chemistry of inorganic compounds
Zeolite
Isomorphic metal substitution
C423S718000, C502S085000, C208S046000
Reexamination Certificate
active
06776975
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to an aluminosilicate zeolite (UZM4M) derived from an as synthesized zeolite designated UZM-4. The UZM-4 composition is structurally related to zeolite Q (BPH topology), but is often thermally stable up to a temperature of 600° C. and has a higher Si/Al ratio in the range of about 1.5 to about 4.0.
BACKGROUND OF THE INVENTION
Zeolites are crystalline aluminosilicate compositions which are microporous and which are formed from corner sharing AlO
2
and SiO
2
tetrahedra. Numerous zeolites, both naturally occurring and synthetically prepared are used in various industrial processes. Zeolites are characterized by having pore openings of uniform dimensions, having a significant ion exchange capacity, and being capable of reversibly desorbing an adsorbed phase which is dispersed throughout the internal voids of the crystal without significantly displacing any atoms which make up the permanent zeolite crystal structure.
One particular zeolite, designated zeolite Q, was first disclosed in U.S. Pat. No. 2,991,151. The general formula for zeolite Q is represented in terms of mole ratio of the oxides by the following:
0.95±0.05 M
2
O:Al
2
O
3
:2.2±0.05 SiO
2
:x
H
2
O
where M designates at least one exchangeable cation, n represents the valence of M and x has a value from 0 to about 5. The examples in the patent are prepared with M being potassium. Synthesis of zeolite Q was conducted at 25° C. to 50° C. After activation at about 130° C., zeolite Q was found to adsorb small polar molecules.
In a paper by John D. Sherman entitled, “Identification and Characterization of Zeolites Synthesized in the K
2
O—Al
2
O
3
—SiO
2
—H
2
O System,”
Molecular Sieves
—II(102) 30, 1974, he reports that the zeolite Q of the '151 patent is the same zeolite as zeolite K-I reported by other researchers. Zeolite K-I was first reported by S. P. Zhdanov and M. E. Ovsepyon in
Doklady Chemistry. Proc. Acad. Sci. USSR,
156, 756 (1964). M. E. Ovsepyan and S. P. Zhdanov further reported on K-I zeolite in
Bull. Acad. Sci. USSR, Chem. Sci.
1, 8 (1965). R. M. Barrer et al. in J. Chem. Soc. (A) 2475 (1968) showed that K-I decomposed at 168° C. It is also reported by Sherman and other researchers that zeolite Q is unstable above 130° C. and is totally disintegrated at 200° C. Owing to this thermal instability, zeolite Q has received little industrial interest. K. J. Andries et al., in
Zeolites,
11, 124 (1991) proposed the BPH topology for zeolite Q. Synthesis of a pure form of zeolite Q was reported by K. J. Andries et al., in Zeolites, 11, 116 (1991). Finally, U.S. Pat. No. 5,382,420 discloses a composition designated ECR-33, which is a partially rare earth (La) exchanged zeolite Q. In all of the above reports, the Si/Al ratio is 1.
Copending application Ser. No. 09/705,653 filed Nov. 3, 2000 discloses the synthesis of a zeolite designated UZM-4, which appears to have a similar topology to that of zeolite Q, i.e., BPH, but has considerably different characteristics. The biggest difference is that UZM-4 has been synthesized with higher Si/Al ratios than zeolite Q, starting from a low of about 1.5 and going higher. The most important characteristic of UZM-4 is the greater thermal stability associated with the higher Si/Al ratios. UZM-4 in its various forms is stable to at least 400° C. and often up to greater than 600° C. The x-ray diffraction pattern of UZM-4 is noticeably different from that of zeolite-Q; and UZM-4 has smaller cell dimensions than that of zeolite Q, consistent with its higher Si/Al ratio.
Applicants have now modified the UZM-4 to give UZM-4M by treating it with a fluorosilicate salt and optionally following with a steaming, calcination, acid extraction, ion-exchange step, or a combination thereof. Skeels and Breck have disclosed in U.S. Pat. No. 4,610,856 a method for producing higher Si/Al ratio zeolites via silicon substitution for aluminum using an ammonium hexafluorosilicate post treatment. The method involves extraction of the Al from the zeolite framework, forming a defect that can be subsequently filled by Si, and producing (NH
4
)
3
AlF
6
as a soluble by-product. The process is a delicate one since it is disclosed that the extraction of Al from the framework tends to be faster than the insertion of Si into the resulting defects, thereby putting the zeolite structure at risk if the number of defects gets too high. In this regard, the composition of the initial zeolite is very important. K. J. Andries et al. in Zeolites, 11, 116 (1991), applied the techniques of Skeels and Breck to Zeolite Q, attempting to raise the Si/Al ratio from 1 in Zeolite Q to targeted values of 1.35, 1.67, and 3. However, the experimentally obtained values were 1.26, 1.32, and destruction of the framework, respectively. Their conclusion was that the zeolite Q framework is very susceptible to destruction.
Starting with UZM4, applicants have successfully used fluorosilicate treatments and optionally steaming, calcination and ion-exchange steps or combinations of these, to generate a family of stable materials with a variety of pore and catalytic properties and with Si/Al ratios that range from about 1.75 to about 500 while retaining the BPH topology, all of which are designated UZM-4M.
SUMMARY OF THE INVENTION
As stated, the present invention relates to a new aluminosilicate zeolite designated UZM-4M. Accordingly, one embodiment of the invention is a microporous crystalline zeolite having a three-dimensional framework of at least AlO
2
and SiO
2
tetrahedral units and an empirical composition on an anhydrous basis expressed by an empirical formula of:
M1
a
n+
Al
1-x
E
x
Si
y
O
z
(I)
where M1 is at least one exchangeable cation selected from the group consisting of alkali metals, alkaline earth metals, rare earth metals, hydronium ion, ammonium ion and mixtures thereof, “a” is the mole ratio of M1 to (Al+E) and varies from about 0.15 to about 1.5, “n” is the weighted average valence of M1 and has a value of about 1 to about 3, E is an element selected from the group consisting of gallium, iron, boron, chromium, indium and mixtures thereof, “x” is the mole fraction of E and has a value from 0 to about 0.5, “y” is the mole ratio of Si to (Al+E) and varies from about 1.75 to about 500 and “z” is the mole ratio of O to (Al+E) and has a value determined by the equation:
z=
(
a·n+
3+(4·
y
))/2
and is characterized in that it has the x-ray diffraction pattern having at least the d-spacings and intensities set forth in Table A:
TABLE A
2&thgr;
d(Å)
I/I
0
%
6.55-6.83
13.49-12.93
m
7.63-7.91
11.58-11.17
vs
13.27-13.65
6.67-6.48
m-s
14.87-15.25
5.95-5.81
m-vs
15.35-15.74
5.77-5.63
m
18.89-19.31
4.69-4.59
m
20.17-20.50
4.40-4.33
w-m
20.43-20.85
4.34-4.26
m
21.51-21.97
4.13-4.04
m-vs
24.14-24.67
3.68-3.60
m-s
24.47-24.98
3.63-3.56
m-s
27.73-28.27
3.21-3.15
w-m
30.11-30.73
2.97-2.90
m-s
31.13-31.75
2.87-2.81
w-m
Another embodiment of the invention is a process for preparing the crystalline microporous zeolite described above. The process comprises treating a starting microporous crystalline zeolite with a fluorosilicate solution or slurry at a pH of about 3 to about 7, whereby framework aluminum atoms of the starting zeolite are removed and replaced by extraneous silicon atoms to give the modified zeolite; the starting zeolite having an empirical formula on an anhydrous basis of:
M′
m′
n+
R
r′
p+
Al
1-x
E
x
Si
y
O
z
(III)
where “m′” is the mole ratio of M to (Al+E) and varies from 0 to about 1.5, M′ is at least one exchangeable cation selected from the group consisting of alkali metals, alkaline earth metals, rare earth metals, hydrogen ion, ammonium ion and mixtures thereof, R is at least one organic cation selected from the group consisting of protonated amines, quaternary ammonium ions, diquaternary ammonium ions, protonated alkanolamines and quaternized alkanolammonium ions, “r′” is the mole ratio of R to (Al+E) and has a v
Jan Deng-Yang
Lewis Gregory J.
Patton R. Lyle
Wilson Ben A.
Wilson Stephen T.
Molinaro Frank S.
Sample David
Tolomei John G.
UOP LLC
LandOfFree
Crystalline aluminosilicate zeolitic composition: UZM-4M does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Crystalline aluminosilicate zeolitic composition: UZM-4M, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Crystalline aluminosilicate zeolitic composition: UZM-4M will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3288433