WO2009082536A1

WO2009082536A1 - Process for epoxidizing olefins with hydrogen peroxide using supported oxo-diperoxo tunsgstate catalyst complex

Info

Publication number: WO2009082536A1
Application number: PCT/US2008/080433
Authority: WO
Inventors: Heiko Weiner
Original assignee: Dow Global Technologies Inc.
Priority date: 2007-10-22
Filing date: 2008-10-20
Publication date: 2009-07-02
Also published as: TW200930455A; WO2009082536A9

Abstract

A quaternary ammonium polyphosphatotungstate deposited on a titanium silicalite support is a useful catalyst for the reaction of an alkene and hydrogen peroxide to form the corresponding epoxide. The polyphosphatotungstate forms soluble, catalytically active species in the presence of hydrogen peroxide, and in this manner can enter the organic phase of an epoxidation reaction. When the hydrogen peroxide is consumed, the polyphosphatotungstate again becomes insoluble, and re-deposits onto the support.

Description

DENTAL IMPLANT ASSEMBLY

BACKGROUND OF THE INVENTION

This invention relates to a process for oxidizing olefins to epoxides with hydrogen peroxide.

Epoxide compounds are generally manufactured by oxidizing an olefin, introducing an atom of oxygen across the double bond to produce the epoxide functionality. Various types of oxidants are used in these reactions, including molecular oxygen, peracids such as peracetic acid, epichlorohydrin, and hydrogen peroxide. From an environmental standpoint, molecular oxygen is an ideal oxidant, as it in theory produces no reaction products. A problem with liquid-phase oxidations with molecular oxygen is that they are radical chain processes. Intermediate alkylperoxy and alkoxy radicals that form are largely indiscriminate in their reactivity. Molecular oxygen often will oxidize the substrate past the desired oxidation state, producing, for example, ketones, aldehydes or carboxylic acids rather than the desired epoxides. Therefore, oxidation reactions using molecular oxygen are usually operated at low conversions to protect against the over-oxidation of the substrate. Another limitation on molecular oxygen oxidation processes is that the oxidation is not selective, if the substrate contains more than one site that is susceptible to oxidation. These problems have limited molecular oxygen processes mainly to the oxidation of small molecules containing only one reactive group. Thus, although molecular oxygen is a relatively cheap oxidant with limited waste problems, its applicability has been largely limited to the oxidation of a small number of simple petrochemicals.

The economics of fine chemicals and pharmaceutical production, in contrast, allows a broader range of primary oxidants to be employed. Even though hydrogen peroxide is more expensive than oxygen, it can be the oxidant of choice because of its simplicity of operation. In fine chemical or pharmaceutical use, the total cost of equipment and raw material may be lower for oxidation employing hydrogen peroxide over oxygen. Hydrogen peroxide is a less vigorous oxidant than is molecular oxygen, which is beneficial in that the oxidation reaction is easier to control and a wider range of substrates can be oxidized. However, oxidation reactions of olefins with hydrogen peroxide to form epoxides usually require a catalyst to obtain reasonable efficiencies.

One catalyst that has shown some promise is a quaternary ammonium phosphatotung state complex, which is sometimes referred to as a Venturello catalyst or an Ishii- Venturello catalyst. Those catalysts are described, for example, in Venturello et al, J. Org. Chem. 1983,48, 3831; Venturello et al, J. Org. Chem. 1988, 53, 1553; Venturello et al., J. Org. Chem. 1991, 56, 5924, Venturello et al., J. Org. Chem. 1998,63,7190, Ishii et al., J. Org. Chem. 1988, 53, 3587 and Oguchi et al., Chem. Lett. 1989, 857. The active catalyst, which is actually a complex with hydrogen peroxide, is commonly said to correspond to the formula Q₃PW₄O₂₄ (variously written as Q₃[PO₄[W(O)(O₂)₂]₄]) the structure of which is represented as:

In the forgoing formulae and structure I, Q represents a hydrophobic cation, typically a quaternary ammonium ion. This active catalyst complex is believed to act as a transporter of peroxide to the substrate, such that the complex becomes reduced as the substrate is oxidized and some of the peroxide is removed from the complex. In the absence of additional hydrogen peroxide and, depending on the particular Q ion, this reduced species is believed to exist at least partially in the form of a material having the empirical formula Q₃PW₄O₁₆. This material is believed to exist at least partially in a polymeric form, and has little solubility in water and in many inorganic media.

Li et al., in Org. Process Res. and Devel. 2006, 10, 876-880, have reported a scheme which takes advantage of the differing solubilities of the oxidized and reduced catalyst species to create a reversibly supported polyphosphatotungstate catalyst. In Li's method, the insoluble species, believed to be mainly Q₃PW₄O₁₆, is deposited onto an inorganic support. When the supported material is brought into contact with hydrogen peroxide and the substrate, the catalytically active and soluble complex(es) (mainly Q₃PW₄O₂₄) are formed, and the oxidation reaction proceeds. As long as hydrogen peroxide is available, the soluble, catalytically active complex(es) will be regenerated and remain in solution. When the hydrogen peroxide becomes depleted, the insoluble species re-form and precipitate back onto the carrier. A potential advantage of this approach is that the catalyst can be removed from the organic phase through simple solid-liquid separation techniques such as filtration.

Titanium silicalites represent another class of oxidation catalysts. These materials are zeolite or molecular sieves that can have one or more of several topologies. Their use in olefin epoxidation reactions is described, for example, in U. S. Patent Nos. 5,262,550 and 5,646,314. They have also been used in alkene oxidation reactions, as described by Huybrechts et al. in Nature 345, 240-242. One of the limitations of these small pore zeolytic materials is their low activity when larger substrates are to be oxidized. This is believed to be due to the geometric restraints of the zeolytic structure.

It would be desirable to provide a more efficient catalyst for oxidizing alkenes, particularly with hydrogen peroxide, to form epoxides. It would also be desirable to provide a more efficient and economical process for epoxidizing alkenes to form epoxides, particularly a process that uses hydrogen peroxide as an oxidant. Furthermore, the combination of a heterogeneous, active epoxidation catalyst with an active component that is homogeneous under reaction conditions would be desirable for the epoxidation of a wide range of smaller and larger substrates.

SUMMARY OF THE INVENTION

In one aspect, this invention is a polyphosphatotungstate complex deposited on a titanium silicalite support.

In a particular embodiment, the present invention is a polyphosphatotungstate complex deposited on a titanium silicalite support, wherein the polyphosphatotungstate complex is at least partially in the form of a material having the approximate empirical structure Q₃PW₄O₁₆, wherein Q represents a hydrophobic cation.

In another aspect, this invention is a method for oxidizing an alkene to form an epoxide. In the method, an alkene is contacted with a hydrogen peroxide source in the presence of a catalytically effective amount of a polyphosphatotungstate complex deposited on a titanium silicalite support, at a temperature sufficient to convert at least a portion of the alkene to an epoxide.

In a particular embodiment, the present invention is a method for oxidizing an alkene to form an epoxide, comprising the steps of: (a) contacting hydrogen peroxide with a supported catalyst that includes a quaternary ammonium polyphosphatotungstate complex deposited on a titanium silicalite support, such that at least a portion of the quaternary ammonium polyphosphatotungstate is converted to a catalytically active species that is soluble in the

5 alkene or any solvent for the alkene that may be present; and

(b) contacting the soluble, catalytically active species with the alkene in the presence of the support, at a temperature sufficient to convert at least a portion of the alkene to an epoxide, whereby at least a portion of the soluble species is reduced to an insoluble species which precipitates onto the support to regenerate the supported o catalyst.

In another particular embodiment, the present invention is a method for oxidizing an alkene to form an epoxide, comprising the steps of:

(a) contacting hydrogen peroxide with a supported catalyst that includes a quaternary ammonium polyphosphatotungstate deposited on a titanium silicalite support,5 wherein the supported quaternary ammonium polyphosphatotungstate is at least partially in a form having the approximate empirical formula Q₃PW₄O₁₆, wherein Q represents a hydrophobic quaternary ammonium ion, such that at least a portion of the quaternary ammonium polyphosphatotungstate is converted to a soluble species having the empirical formula Q₃PW₄O₂₄; and o (b) contacting the soluble species and the support with an alkene at a temperature sufficient to convert at least a portion of the alkene to an epoxide, whereby at least a portion of the soluble species is reduced to an insoluble species having the approximate empirical formula Q₃PW₄O₁₆, which precipitates onto the support to regenerate the supported catalyst. 5 In still another aspect, this invention is a process comprising contacting an alkene with molecular oxygen in the presence of a quaternary ammonium polyphosphatotungstate deposited on a titanium silicalite support, at a temperature sufficient to oxidize a carbon-carbon double bond of the alkene.

In still another aspect, this invention is a process comprising contacting an 0 alkene with an oxidant in the presence of a quaternary ammonium polyphosphatotungstate deposited on a titanium silicalite support, at a temperature sufficient to oxidize a carbon-carbon double bond of the alkene. The catalyst of the present invention is an active oxidation catalyst that is useful in conjunction with a variety of oxidants. The catalyst provides for commercially reasonable reaction rates at good conversions of both substrate and oxidant. Oxidations performed using the catalyst tend to be selective, so that high yields of the desired oxidation product are obtained, even when the substrate is susceptible to oxidation at multiple molecular sites. In addition, the catalyst of the invention is useful for oxidizing substrates that have a broad range of molecular weights.

DETAILED DESCRIPTION OF THE INVENTION In this invention, a phosphatotung state is deposited onto a titanium silicalite support. This is conveniently accomplished by a precipitation process as described more fully below. The phosphatotung state is a salt of a hydrophobic cation and a phosphatotung state ion.

Phosphatotung state ions can exist in several forms, which vary in the ratio of tungsten to phosphorus atoms, and also in the number of oxygens. Phosphatotungstate ions may exist in which the tungsten to phosphorus ratio is 1:1, 2:1, 3:1 and/or 4:1. For convenience, these ions are sometimes designated as PW₁, PW₂, PW₃ and PW₄, respectively. Other possible phosphatotungstate ions have higher tungsten to phosphorous ratios, including but not limited to 1:9 (PW₉), 1:10 (PW₁₀), 1:11 (PW₁₁), 1:12 (PW₁₂), 2:17 (P₂W₁₇), and 2:18 (P₂W₁₈). At least a portion of the supported quaternary ammonium phosphatotungstate is in the form of PW₄ species. It is believed that in the presence of hydrogen peroxide, the PW₄ species is the dominant form in the supported catalyst, although some quantities of PW₁, PW₂, PW₃, PW₉, PW₁₀, PW₁₁, PW₁₂, P₂W₁₇, P₂W₁₈ or even other species may be present. In the absence of hydrogen peroxide, the PW₄ species include those having the approximate empirical formula

Q₃PW₄O₁₆, where Q is a hydrophobic cation, preferably a hydrophobic quaternary ammonium ion. The Q₃PW₄O₁₆ species (as well as other PW species) may be at least partially in a polymeric form that has little solubility in water and many organic materials. In addition, a small amount of tungstates may also be present in the supported catalyst.

By "hydrophobic", it is meant that the Q ion forms a salt with a peroxophosphotungstate ion which exhibits little or no solubility in an aqueous environment, but which is soluble in the organic phase that is present in the epoxidation reaction. The organic phase may be constituted by the alkene itself, or by a solution of the alkene in some solvent. Q is suitably an N⁺R₄ structure, wherein each R group is a hydrocarbon, and at least one R group contains at least 4 carbon atoms, and the R groups together contain at least 8 carbon atoms. Preferably, at least one R group contains at least 8 carbon atoms and even more preferably at least one R group contains at least 12 carbon atoms. The R groups together preferably contain at least 12 carbons and more preferably at least 18 carbon atoms. By "hydrocarbon", it is meant that the group contains only carbon and hydrogen atoms. The R groups may be aliphatic, such as straight or branched-chain alkyl. The R groups may be cyclopentadienyl, phenyl, alkyl- substituted phenyl, benzyl or alkyl- substituted benzyl. Alternatively, Q may be a substituted pyridinium ion represented by

wherein R¹ is alkyl, alkenyl or phenyl- substituted alkyl having at least 4 carbon atoms. The R¹ group preferably has at least 8 carbon atoms and even more preferably has at least 12 carbon atoms.

Specific examples of Q groups include, but are not limited to tetra(n- butyl) ammonium, tetra(n-hexyl) ammonium, trimethylhexadecylammonium, trimethylocadecylammonium, trimethyldodecylammonium, methyltri(octyl)ammonium, dimethyldi(hexadecyl)ammonium, dimethyldi(octadecyl)ammonium, hexadecylpryidinium, octadecylpyridiniyum, dodecylpyridinium, and the like.

The titanium silicalite support is one of a class of zeolite materials in which titanium is substituted for a portion of the silicon atoms in the lattice framework. The titanium silicalite support can have any of a number of topologies, including MFI, MEL, CAN, FAU, FER, TON, LTA, MTT, MTW or MAX topologies. In addition, mesoporous materials containing titanium are also suitable, such as, for example, the so- called MCM-41 zeolite material. However, those having an MFI topology (analogous to that of the ZSM-5 aluminosilicate zeolites) and those having a MEL topology are generally preferred. The titanium silicalite preferably contains at most only minor amounts of other elements, except for oxygen. The other elements preferably constitute no more than about 5 weight percent, more preferably no more than about 3 weight percent of the titanium silicalite support. The titanium silicalite support can be characterized in terms of the molar ratio of silicon to titanium atoms. A suitable titanium silicalite support may contain silicon to titanium atoms in a molar ratio of about 5 or more, preferably about 20 or more, even more preferably about 30 or more and still more preferably about 40 or more. The ratio may be as high as about 500, preferably up to about 200 and still more preferably up to about 50.

Methods for preparing the titanium silicalite catalyst are described, for example, in U. S. Patent No. 4,410,501 and by Thangaraj et al, Zeolites, 1992, 943-950; incorporated herein by reference. The phosphatotungstate may constitute about 1% or more, preferably at least about 5%, more preferably at least about 30% and even more preferably at least about 40% of the total weight of the supported catalyst. The phosphatotungstate may constitute as much as about 95%, preferably up to about 80%, more preferably up to about 60% and still more preferably up to about 50% of the total weight of the supported catalyst. The supported phosphatotungstate catalyst can be made by precipitating the phosphatotungstate onto a titanium silicalite support or other titanium-containing support. The phosphatotungstate can be synthesized and precipitated via at least two synthetic routes.

In the first route, phosphotungstic acid (molecular formula H₃PW₁₂O_4O) and optionally an alkali metal dihydrogenphosphate hydrate (such as NaH₂PO₄-H₂O) are reacted with aqueous hydrogen peroxide to form one or more soluble oxodiperoxophosphotungstate complexes, at least some of which have the molecular formula M₃[PO₄[W(O)(O₂)₂]₄], where M represents the alkali metal. The corresponding quaternary ammonium compound is formed and deposited on the support by contacting a solution of the oxodiperoxophosphotungstate complex with a solution of a compound of the form Q_aX, where Q is as defined before, a is the valence of X and X represents an anion such as halide, sulfate or hydroxyl. The Q_aX compound is generally dissolved in an organic solvent. The resulting mixture is then heated to drive off the organic solvent. The heating step also causes molecular oxygen to become eliminated from the oxodiperoxophosphotungstate complexes. Mild heating (30-50⁰C) is generally sufficient, although higher temperatures may be necessary if the organic solvent has a higher boiling temperature. Subatmospheric pressures may be employed to help remove the solvent and reduce the temperature that is needed. The elimination of oxygen from the complex, together with the removal of the solvent, causes the quaternary ammonium phosphatotungstate to become insoluble, and to precipitate onto the support. As mentioned before, the main species that is deposited onto the support is believed to have the approximate empirical formula Q₃PW₄O₁₆, although other quaternary ammonium phosphatotungstate species may be present, as may some tungstates.

The second route is similar, except that an alkali metal tungstate such as sodium or potassium tungstate is used in place of the polyoxotungstate. The reaction of the alkali metal tungstate and hydrogen peroxide is performed under acidic conditions (pH <2 is suitable), to produce the soluble oxodiperoxophosphotungstate complex(es), which include the M₃[PO₄[W(O)(O₂)I]₄] species. Subsequent steps to form the quaternary ammonium compounds and deposit them onto the support are as before.

The supported catalyst can be separated from the reaction mixture and dried if desired. The supported catalyst is useful in the oxidation of an alkene with hydrogen peroxide, particularly to form an epoxide. In a preferred oxidation reaction, the alkene is contacted with a hydrogen peroxide source in the presence of a catalytically effective amount of the supported catalyst. The oxidation in many cases proceeds under mild conditions, with good conversions and good selectivities. The alkene is a compound having one or more non-conjugated carbon-carbon double bonds that are susceptible to oxidation. The alkene may have a molecular weight from about 28 to about 10,000 or more. A preferred alkene has a molecular weight from about 28 to about 1000. Examples of suitable alkenes include, for example, linear alkenes such as 1-dodecene, 1-octene, 1-hexene, 1-pentene, propylene, ethylene and 1- butene; unsaturated fatty acids; unsaturated vegetable oils or animal fats, such as soybean, canola, corn or sunflower oil; cycloalkenes and compounds containing cycloalkenyl groups, such as cyclohexane, cyclooctene and 3-cyclohexene-l-carboxylic acid-3-cyclohexene-l-ylmethyl ester; allylic compounds such as allyl chloride, bisphenol A diallyl ether, bisphenol F diallyl ether as well as other allyl ethers and esters, and the like. Diene epoxidations are of particular interest because the products are often useful epoxy resins.

The oxidation reaction is conducted by contacting the alkene and a hydrogen peroxide source with the supported catalyst of the invention. Suitable reaction conditions are well-known and described, for example, in Li et al., Org. Process Res. and Devel. 2006, 10, 876-880 and by Maiti at al., New J. Chem., 2006, 30, 470-489; incorporated herein by reference. Generally, the alkene, hydrogen peroxide and the catalyst are brought together, at a temperature sufficient to convert at least a portion of the alkene to an epoxide. The reaction is continued until the desired conversion of alkene to product is obtained.

A suitable temperature for conducting the reaction is from about 20 to about

100⁰C, with from about 35 to about 80⁰C being a preferred temperature range, and from about 45 to about 75°C being especially preferred. Hydrogen peroxide is conveniently provided as an aqueous solution, although organic solutions of hydrogen peroxide, i.e., in methyl t-butyl ether (MTBE) can also be employed.

The alkene can be supplied neat or in the form of a solution in a suitable solvent.

If a solvent is used, the solvent is preferably one that is substantially immiscible with water or other solvent in which the hydrogen peroxide is supplied. This characteristic simplifies the separation of the product from the reaction mixture, as the phase that includes the product will phase separate and can be isolated easily. The solvent for the alkene is preferably a liquid at the reaction temperature. A solvent is often unnecessary if the alkene is a liquid having a reasonable viscosity at the reaction temperatures, and if the alkene and the oxidized product are immiscible in water. Suitable solvents will of course depend on the particular alkene, but in general hydrocarbon solvents such as alkenes, benzene, toluene, cyclohexane and the like, as well as halogenated hydrocarbons like 1,2-dichloroethane and the like are suitable.

The reaction mixture in most cases forms a multi-phase system that includes the solid catalyst support, an aqueous phase and an organic phase. Mixing is therefore needed in order to obtain transport of species between the phases and obtain reasonable reaction rates. The manner in which the reaction mixture is mixed is not critical. Simple stirring or a variety of active and/or static mixing methods can be used. High shear conditions are not normally necessary and can be detrimental, as those conditions can lead to the formation of emulsions and/or break down the support.

Although the present invention is not limited to any theory, it is believed that when the deposited quaternary ammonium polyphosphatotungstate is brought into contact with hydrogen peroxide, a complex is formed that is soluble in the alkene. The main components in solution are soluble catalytic complexes such as Q₃PW₄O₂₄ or Q₂W₂O₁₃H₂ (variously written as Q₃[PO₄[W(O)(O₂)₂]₄], (peroxophosphato-tungstate) and Q₂[W₂O₃(O₂)₄(H₂O)₂] (peroxotungstate), respectively). The idealized structure of the peroxophosphato-tungstate complex is represented as:

This complex is believed to be the primary catalytically active material, however, the Q₂[W₂O₃(O₂)₄(H₂O)₂] complex is also believed to act as a catalyst in these reactions. Because the active catalytic complexes are soluble in the organic phase, they are removed from the support and migrate to the organic phase, where they oxidize a o carbon-carbon double bond, in most cases to the corresponding epoxide. This reaction creates one or more reduced species, which can react in various ways to regenerate soluble, catalytically active complexes, as long as there is hydrogen peroxide available in the reaction mixture.

Therefore, during the course of the reaction, the quaternary ammonium5 polyphosphatotungstate will repeatedly cycle between the active catalyst complex and various reduced forms, until such time as hydrogen peroxide is no longer available to regenerate the soluble active catalyst species. At such time, the reduced quaternary ammonium polyphosphatotungstate species again form insoluble materials, believed to be mainly species having the empirical structure Q₃PW₄O₁₆ (which may be of a o polymeric nature). The insoluble complexes precipitate from the reaction mixture. If the titanium silicate support is present, the insoluble materials will deposit on the support and regenerate the supported catalyst. The regenerated supported catalyst is then easily removed from the liquid phases by any convenient solid-liquid separation method, such as decanting, filtering or centrifugation. 5 Because the redeposition of the catalyst depends on the consumption of peroxide from the active catalyst species, the reaction is preferably conducted such that hydrogen peroxide is the limiting reagent. In most cases, a small portion of the hydrogen peroxide will be lost to side-reactions, mainly decomposition into water, oxygen or hydrogen. Because of this, the oxidation is most typically performed using a small excess (up to about 25%, preferably up to about 5%) of hydrogen peroxide, to account for the loss of material due to the side reactions. This allows for the available hydrogen peroxide to become depleted at the end of the reaction, causing the catalyst to re-precipitate onto the support.

The oxidation process is often characterized by high conversions of alkene to epoxide, and high hydrogen peroxide conversions and efficiencies. Alkene conversions are often at least about 80% and can be at least about 90% or at least about 95%. Hydrogen peroxide conversions are often at least about 80% and can be about 85% or more. Hydrogen peroxide efficiencies are often at least about 70% and can be about 80% or more or even about 85% or more.

The catalyst of the present invention is also useful in other oxidation reactions. For example, the catalyst is useful in the oxidation of alkenes with molecular oxygen to form epoxides or other oxidized species. Processes for performing such a reaction are described, for example, by Sun et al. in J. Molecular Catalysis A: Chemical 166 (2001) 219-224; incorporated herein by reference. The catalyst is also useful in the oxidation of alkene with organic peroxy compounds such as organic peracids, hydroperoxides, peroxides, peroxyesters, peroxycarbonates and the like. The process of the present invention is particularly useful for manufacturing di- and polyepoxides that are useful raw materials for epoxy resins.

The following examples are provided to illustrate the present invention, but are not intended to limit the scope thereof. All parts and percentages are by weight unless otherwise indicated.

Example 1

Phosphotungstic acid (H₃PW₁₂O₄₀) hydrate (3.60 g, 1.25 mmol) is added to 40 mL of deionized water with stirring at room temperature. Then, 0.34 g (2.5 mmol) of solid sodium dihydrogenphosphate hydrate is added and dissolved. Next, 10.5 mL of a 30% solution of hydrogen peroxide in water is added, and the solution is stirred for 30 minutes at room temperature. Then, 4.0 grams of a commercially available titanium silicalite (Si/Ti ratio of 50) is added and stirred in for 30 minutes, and the suspension is then diluted with 50 mL of deionized water. A solution of 2.85 g (7.96 mmol) of cetylpyridinium chloride in 40 rnL of dichloromethane is then added to the suspension. The mixture is then heated to 35°C over 30 minutes and stirred at this temperature for another two hours. During this time, the dichloromethane evaporates, oxygen evolves and a light yellow precipitate forms on the titanium silicalite carrier. The mixture is cooled to room temperature, stirred another 30 minutes, and the solids are collected by vacuum filtration. The solids are dried under vacuum overnight at room temperature. 8.78 g of supported catalyst are obtained. The quaternary ammonium polyphosphatotungstate, mainly in the form of complexes having the empirical formula Q₃PW₄O₁O, constitutes about 54% by weight of the supported catalyst. The material is found to contain no active oxygen by IR spectroscopy and redox titration with Ce⁴⁺ vs. Ferroin indicator.

Examples 2-5

A supported quaternary ammonium polyphosphatotungstate catalyst as prepared in Example 1 is used in a series of epoxidations. In the first of these (Example 2), 0.24 g of the supported catalyst, 4.92 g (0.0223 moles) of 3-cyclohexene-l-carboxylic acid 3- cyclohexen-1-yl methyl ester, and 5.0 mL (0.049 mol) of a 30% solution of hydrogen peroxide in water are charged to a stirred batch reactor. The reaction mixture is heated to 60⁰C at atmospheric pressure and maintained at that temperature for 5 hours, with stirring. The stirring is then discontinued and the reactor contents cooled to room temperature. After cooling, the catalyst support is coated with a light yellow material, indicating that the quaternary ammonium polyphosphatotungstate has re-deposited on the carrier.

By gas chromatography, 100% of the starting diene is converted to epoxides, with a yield to diepoxide of 84%. Hydrogen peroxide conversion is determined by titration with Ce⁴⁺ ions vs. Ferroin indicator. Peroxide conversion is 88% and peroxide efficiency is 86%. Examples 3, 4 and 5 are conducted in the same manner, except in these cases the diene is dissolved in 8 mL of toluene (Ex. 3), 1,2-dichloroethane (Ex. 4) or cyclohexane (Ex. 5). Results are indicated in the following table.

Claims

WHAT IS CLAIMED IS:

1. A supported catalyst comprising a polyphosphatotungstate deposited on a titanium silicalite support.

5

2. The supported catalyst of claim 1 wherein the polyphosphatotungstate is a quaternary ammonium polyphosphatotungstate.

3. The supported catalyst of claim 1 or 2 wherein the polyphosphatotungstate o constitutes from about 5 to about 60% of the total weight of the supported catalyst.

4. The supported catalyst of any of claims 1-3 wherein the molar ratio of silicon to titanium atoms in the titanium silicalite support is from about 30 to about 200.

5 5. The supported catalyst of claim 2, wherein the quaternary ammonium polyphosphatotungstate is at least partially in the form of a material having the approximate empirical formula Q₃PW₄O_1O, wherein Q represents a hydrophobic quaternary ammonium ion.

0 6. The supported catalyst of claim 5 wherein the quaternary ammonium polyphosphatotungstate constitutes from about 5 to about 60% of the total weight of the supported catalyst.

7. The supported catalyst of claim 5 or 6 wherein the molar ratio of silicon to titanium 5 atoms in the titanium silicalite support is from about 30 to about 200.

8. The supported catalyst of claim 5, 6 or 7 wherein Q is tetra(n-butyl) ammonium, tetra (n-hexyl)ammonium, trimethylhexadecylammonium, trimethyloctadecylammonium, trimethyldodecylammonium, methyltri(octyl) ammonium, 0 dimethyldi(hexadecyl)ammonium, dimethyldi(octadecyl)ammonium, hexadecylpyridinium, octadecylpyridinium or dodecylpyridinium.

9. A method comprising contacting an alkene with an oxidant in the presence of the supported catalyst of claim 1, at a temperature sufficient to oxide a carbon-carbon double bond of the alkene.

5 10. The method of claim 9, wherein the oxidant is hydrogen peroxide.

11. The method of claim 9 or 10, wherein the alkene has a molecular weight of from about 28 to about 10,000.

o 12. The method of claim 9, 10 or 11, wherein the alkene is a diene, and at least a portion of the diene is converted to a diepoxide.

13. The method of any of claims 9-12, wherein the quaternary ammonium polyphosphatotungstate is at least partially in the form of a material having the approximate5 empirical formula Q₃PW₄O₁O, wherein Q represents a hydrophobic quaternary ammonium ion.

14. The method of any of claims 9-13, wherein the quaternary ammonium polyphosphatotungstate constitutes from about 5 to about 60% of the total weight of the o supported catalyst.

15. The method of any of claims 9-14, wherein the molar ratio of silicon to titanium atoms in the titanium silicalite support is from about 30 to about 200.

5 16. The method of claim 9, wherein the oxidant is molecular oxygen.

17. The method of claim 9, wherein the oxidant is an organic peracid, hydroperoxide, peroxide, perester or percarbonate.

0 18. The method of any of claims 9-17, wherein at least a portion of the alkene is converted to an epoxide.

19. A method for oxidizing an alkene to form an epoxide, comprising the steps of:

(a) contacting hydrogen peroxide with a supported catalyst that includes a quaternary ammonium polyphosphatotungstate complex deposited on a titanium silicalite support, such that at least a portion of the quaternary ammonium polyphosphatotungstate is converted to a

5 catalytically active species that is soluble in the alkene or any solvent for the alkene that may be present; and

(b) contacting the soluble, catalytically active species with the alkene in the presence of the support, at a temperature sufficient to convert at least a portion of the alkene to an epoxide, whereby at least a portion of the soluble species is reduced to an insoluble species i o which precipitates onto the support to regenerate the supported catalyst.

20. The method of claim 19, wherein the catalytically active species include Q₃PW₄O₂₄ and Q₂W₂O₁₃H₂ species, and at least a portion of the insoluble species have the empirical formula Q₃PW₄O₁₆.

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