Organic compounds -- part of the class 532-570 series – Organic compounds – Carboxylic acid esters
Reexamination Certificate
2000-04-25
2002-02-05
Killos, Paul J. (Department: 1623)
Organic compounds -- part of the class 532-570 series
Organic compounds
Carboxylic acid esters
C560S102000
Reexamination Certificate
active
06344583
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to a process for the oxidation of ketones to esters. The process involves contacting the ketone with hydrogen peroxide and a catalyst which comprises a tin substituted molecular sieve at oxidation conditions to form the corresponding ester.
BACKGROUND OF THE INVENTION
Esters and lactones (cyclic esters) have various uses in and of themselves and also can be intermediates in the synthesis of antibiotics, steroids, phermones, fragrances and monomers. In 1899 Adolph Baeyer and Victor Villiger first reported the oxidation of menthone and tetrahydrocarvone to the corresponding lactones. The reaction was carried out using monopersulfuric acid, which was the most powerful oxidant known at that time. There has been considerable interest in the Baeyer-Villiger reaction in academia and in industry with numerous papers being published. See, e.g., G. Strukul,
Angew. Chem. Int
. Ed., 37,11-98 (1998).
The reaction is usually carried out with organic per-acids. When the oxidant is hydrogen peroxide, there are reports of using transition metal catalysts for the Baeyer-Villiger reaction. For example, Jacobson et al.,
J.Chem. Soc. Chem. Comun
., 888, (1978) and in
Inorg. Chem
., 17, 3055 (1978), have disclosed the use of molybdenum(VI) peroxo-complexes as catalysts in combination with 98% hydrogen peroxide as the oxidant. W. A. Herrmann, et al., in
J. Mol. Catal
., 94, 213 (1994) have disclosed that the di-peroxo complex of methyl trioxorhenium is also active for the Baeyer-Villiger reaction. In his paper, Strukul also reports on the use of platinum complexes to carry out the oxidation of ketones in conjunction with 35% hydrogen peroxide. Finally, A. Bhaumik et al., in
Catal. Lett
., 40, 47 (1996) discloses the use of titanium silicalite (TS-1) as a catalyst for the oxidation of ketones in conjunction with hydrogen peroxide. However, the use of TS-1 gave selectivities to the ester of below 50% with hydroxycarboxylic acids being the major by-products.
In contrast to the work disclosed above, applicants have developed a process for converting ketones to esters or lactones, which uses as the catalyst a tin substituted molecular sieve in conjunction with hydrogen peroxide. The catalyst has an empirical formula on an anhydrous basis of:
(M
w
Sn
x
Ti
y
Si
1−x−y−z
Ge
z
)O
2
where M represents a metal having a +3 valence such as Al or B and “w” is the mole fraction of M and varies from 0 to about 2x. The value of “x” can be from about 0.001 to about 0.1 while “y” and “z” have, respectively, values of 0 to about 0.1 and 0 to about 0.08. The catalysts of this invention have been found to have higher conversions and virtually exclusive selectivity to the lactones.
SUMMARY OF THE INVENTION
An object of the present invention is the conversion of ketones and especially cyclic ketones to esters and especially lactones. Accordingly, one embodiment of the invention is a process for the oxidation of a ketone to an ester comprising contacting a ketone with hydrogen peroxide and a catalyst at oxidation conditions to provide the corresponding ester, the catalyst comprising a molecular sieve having an empirical formula on a calcined and anhydrous basis of:
(M
w
Sn
x
Ti
y
Si
1−x−y−z
Ge
z
)O
2
where M is a metal having a +3 valence, “w” is the mole fraction of M and varies from 0 to about 2x, “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 “z” is the mole fraction of germanium and varies from zero to less than about 0.08 and characterized in that the composition has the characteristic x-ray diffraction pattern of zeolite beta, and when “w”, “y” and “z” are all zero, then the molecular sieve is amorphous with short range order or has the characteristic x-ray diffraction pattern of zeolite beta.
This and other objects and embodiments of the invention will become more apparent after a detailed description of the invention.
DETAILED DESCRIPTION OF THE INVENTION
As stated, the present application deals with a process (known as the Baeyer-Villiger reaction) in which ketones are converted to esters. It is preferred to convert cyclic ketones to cyclic esters which are generally called lactones. One essential part of this process is a catalyst which comprises a tin containing molecular sieve having the characteristic x-ray diffraction pattern of zeolite beta and an empirical formula on a calcined and anhydrous basis of:
(M
w
Sn
x
Ti
y
Si
1−x−y−z
Ge
z
)O
2
“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 “z” is the mole fraction of germanium and varies from zero to less than about 0.08. However, when “w”, “y” and “z” are all zero, then the molecular sieve is either amorphous with short range order or has the zeolite beta structure. The M metals which can be used include but are not limited to aluminum, boron, gallium, and iron; and “w”is the mole fraction of M and varies from 0 to about 2x. These molecular sieves have a microporous three dimensional framework structure of at least SiO
2
and SnO
2
tetrahedral units, and a crystallographically regular pore system.
These molecular sieves are prepared using a hydrothermal crystallization process in which a reaction mixture is prepared by combining reactive sources of tin, silicon, an organic templating agent, optionally germanium, optionally titanium, optionally a M metal, a fluoride or hydroxide 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, without limitation, 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 oxides. Titanium sources include titanium alkoxides and titanium halides. Preferred titanium alkoxides are titanium tetraethoxide, titanium isopropoxide and titanium tetrabutoxide. When M is aluminum, the sources of aluminum include but are not limited to aluminum oxides, such as pesudo-boehmite, aluminum alkoxides such as aluminum isopropoxide, sodium aluminate and aluminum trichloride, with pseudo-boehmite and aluminum alkoxides being preferred. Sources of boron, gallium and iron include oxides, hydroxides, alkoxides, nitrates, sulfates, halides, carboxylates and mixtures thereof. Representative compounds include without limitation boron alkoxides, gallium alkoxides, iron (II) acetate, etc.
The reaction mixture will also contain either a fluoride source such as hydrofluoric acid or ammonium fluoride or a hydroxide source such as sodium hydroxide or potassium hydroxide. The hydroxide source may also be added by using the hydroxide compound of the templating agent. Water is also added to the mixture and optionally hydrogen peroxide.
Generally, the hydrothermal process used to prepare the tin containing molecular sieves involves forming a reaction mixture, using the sources stated above, which is expressed by the formula:
SiO
2
:kM
2
O
3
:aR
2
O:bSnO
2
:cGeO
2
:dTiO
2
:eF:fH
2
O
2
:gH
2
O
where “k” has a value from zero to about 0.1, “a” has a value from about 0.06 to about 0.5, “b” has a value from about 0.001 to about 0.1, “c” has a value from zero to about 0.08, “d” has a value from 0 to about 0.1, “e” has a value from about 0.1
Canos Avelino Corma
Moscoso Jaime G.
Nemeth Laszlo T.
Renz Michael
Molinaro Frank S.
Tolomei John G.
UOP LLC
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