Stannosilicate molecular sieves

Chemistry of inorganic compounds – Zeolite – Isomorphic metal substitution

Reexamination Certificate

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Details

C423S326000, C423SDIG002, C568S028000, C568S385000, C568S403000, C568S909800, C568S910000, C568S716000, C549S531000, C502S242000, C502S060000, C502S064000

Reexamination Certificate

active

06306364

ABSTRACT:

FIELD OF THE INVENTION
This invention relates to molecular sieves which have the zeolite beta structure. The molecular sieves have SnO
2
and SiO
2
tetrahedral oxide units and have an empirical formula of:
(Sn
x
Ti
y
Si
1-x-y-z
Ge
z
)O
2
The invention also relates to a process for using the sieves.
BACKGROUND OF THE INVENTION
Zeolites are crystalline aluminosilicate molecular sieves which have a microporous three-dimensional framework structure. In general, the crystalline zeolites are formed from corner-sharing AlO
2
and SiO
2
tetrahedra and 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 crystal structure.
Zeolite beta, which is described in U.S. Pat. No. RE 28,341 and is incorporated by reference, is one particular zeolite which has recently received considerable attention for catalyzing various types of reactions. Zeolite beta is usually synthesized in a basic medium in the presence of tetraethylammonium and alkali cations and has a Si/Al mole ratio from about 5 to about 100. A molecular sieve with the zeolite beta structure but containing titanium in the framework is described in Spanish patent no. 2,037,596 which also discloses that the titanium containing material can be used as a catalyst in selective oxidation reactions of organic compounds using hydrogen peroxide, organic peroxides or hydroperoxides as the oxidizing agent.
WO97/33830 discloses the synthesis of zeolite beta using fluoride anions as the mineralizing agent at or near neutral pH. It is disclosed that these materials exhibit enhanced thermal stability and low concentration of SiO or SiOH defects over a wide chemical composition range. Finally, T. Blasco et al. in
J. Phys. Chem. B,
1998, 102, p. 75 disclose the incorporation of titanium into the beta structure by using the procedure in WO97/33830 again over a wide Si/Al range. These materials also have increased hydrophobicity.
There is also a number of reports where tin has been incorporated into the framework. U.S. Pat. No. 5,648,558 discloses a metallo-aluminosilicate having a skeletal structure of zeolite beta and having substituted in the aluminosilicate a metal species such as chromium, gallium, boron, tin, etc. Aluminum is always present in these molecular sieves. In U.S. Pat. No. 4,543,347 it is stated that compositions containing SiO
4
and MO
4
tetrahedra are known in the art. Tin is included in a list of 21 elements but no reference is given which provides synthesis conditions. In U.S. Pat. No. 5,399,336 a stannozeosilite is disclosed which has the MFI structure. U.S. Pat. No. 5,110,571 discloses stannosilicates in which tin is octahedrally coordinated and have diffraction patterns of other than that of zeolite beta. U.S. Pat. No. 4,933,161 discloses substituting Sn into an aluminosilicate zeolite. Some aluminum is always present. In U.S. Pat. No. 4,576,805 a process for increasing the total amount of lattice metal in a porous inorganic oxide is disclosed. The composition is represented by the formula: (1-x)SiO
2
:(x)MO
n/2
where M is at least one lattice metal selected from Groups IIIB, IVB, VB, VIB, VIIB, VIII, IIIA, IVA and VA. Although tin is one of the metals included in the list, again no reference or method is provided to prepare the initial porous oxide. U.S. Pat. No. 4,329,328 discloses a method of preparing zinco/stanno/titano-silicate with the structure of zeolite A, X and Y. U.S. Pat. No. 5,401,488 discloses a molecular sieve with an empirical formula of (Sn
w
Al
x
Si
y
)O
2
. Aluminum is always present in the formula. WO 88/01254 discloses a process for modifying the framework of a zeolite by replacing aluminum in the framework by elements such as tin. Finally, N. K. Mal and A. V. Ramaswanvy in
Chem. Commun.,
pp. 425-426, 1977, discloses the synthesis of an alumina free tin containing zeolite beta.
In contrast to this art, applicants have synthesized a series of molecular sieves having SnO
2
and SiO
2
tetrahedral oxide units and at least one of TiO
2
or GeO
2
tetrahedral oxide units and have an empirical formula of:
(Sn
x
TI
y
Si
1-x-y-z
Ge
z
)O
2
where “x”, “y” and “z” are the mole fractions of tin, titanium and germanium.
These metallo-stannosilicate molecular sieves are useful as catalysts in selective oxidation processes such as olefin epoxidation and hydroxylation of aromatic compounds.
SUMMARY OF THE INVENTION
The present invention relates to a new series of crystalline metallo-stannosilicate molecular sieves and a process using them. Accordingly, one embodiment of the invention is a crystalline metallo-stannosilicate molecular sieve having a microporous three dimensional structure containing SiO
2
and SnO
2
tetrahedral oxide units and at least one of TiO
2
or GeO
2
tetrahedral oxide units, a crystallographically regular pore system, and an empirical formula on a calcined and anhydrous basis of:
(Sn
x
Ti
y
Si
1-x-y-z
Ge
z
)O
2
where “x” is the mole fraction of tin and varies from about 0.001 to about 0.1, “y” is the mole fraction of titanium and varies from zero to about 0.1 and “y” and “z” are not simultaneously both zero, and “z” is the mole fraction of germanium and varies from zero to less than about 0.08 and is characterized in that the composition has the characteristic x-ray diffraction pattern of zeolite beta.
Another embodiment is a process for the selective oxidation of organic compounds comprising reacting an organic compound with a peroxide in the presence of a catalyst under oxidation conditions to give an oxidized product, the catalyst comprising the molecular sieves described above.
These and other objects and embodiments will become more apparent after a detailed description of the invention.
DETAILED DESCRIPTION OF THE INVENTION
The crystalline molecular sieves of the present invention have a microporous three dimensional framework structure containing SiO
2
and SnO
2
tetrahedral oxide units, and at least one of TiO
2
or GeO
2
tetrahedral oxide units, a crystallographically regular pore system and an empirical formula on a calcined and anhydrous basis of:
(Sn
x
Ti
y
Si
1-x-y-z
Ge
z
)O
2
where “x” is the mole fraction of tin and varies from about 0.001 to about 0.1, “y” is the mole fraction of titanium and varies from zero to about 0.1, “z” is the mole fraction of germanium and varies from zero to less than about 0.08 and “y” and “z” are not both simultaneously zero. Finally, the molecular sieves have the structure of zeolite beta.
These molecular sieves are prepared using a hydrothermal crystallization process in which a reaction mixture prepared by combining reactive sources of tin, silicon, an organic templating agent, optionally germanium, and/or titanium, a fluoride source, optionally hydrogen peroxide and water. The sources of silicon include but are not limited to colloidal silica, amorphous silica, fumed silica, silica gel and tetraalkylorthosilicate. Sources of tin include but are not limited to tin halides, tin alkoxides, tin oxide, metallic tin, alkaline and alkaline earth stannates and alkyl tin compounds. A preferred source is tin tetrachloride. Examples of tin alkoxides include tin butoxide, tin ethoxide and tin propoxide. The organic templating agents include tetraalkylammonium ions such as tetraethylammonium ions, aza-polycyclic compounds such as 1,4-diazabicyclo 2,2,2, octane; dialkyldibenzylammonium ions such as dimethyldibenzyl ammonium ion and bis-piperidinium ions such as 4,4′ trimethylene bis (N-benzyl N-methyl piperidinium) ion. These ions may be added as the hydroxide or halide compounds. Germanium sources include germanium halides, germanium alkoxides and germanium oxide. Finally, titanium sources include titanium alkoxides and titanium halides. Preferred titanium alkoxides are titanium tetraethoxide, titanium isopropoxide and titanium tetrabutoxide.
The reaction mixture will also contain a fluoride sou

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