METHODS AND CATALYSTS FOR CONVERTING METHANE TO METHANOL

Abstract

The invention encompasses methods of directly converting methane- to methanol The invention further encompasses catalysts that efficiently afford this transformation at low temperatures. Exemplary embodiments encompassed by the invention include a gas stream containing methane gas and oxygen,which is passed over an oxygen-activated catalyst to directly form methanol

Claims

1. A catalyst comprising: i. a solid matrix; ii. at least one transition metal; iii. at least one ligand eovalently bound to the solid matrix; and iv. oxygen bound to the transition metal.

2. The catalyst of claim 1, wherein said ligand is bound to said transition metal.

3. The catalyst of claim 1 or 2, wherein said solid matrix is a silica matrix.

4. The catalyst of claim 3, wherein said silica matrix is mesoporous or nanoporous silica.

5. The catalyst of any one of claims 1 to 4, wherein said transition metal is selected from the group consisting of manganese, iron, cobalt, nickel, copper, and combinations thereof.

6. The catalyst of any one of claims 1 to 5, wherein said ligand comprises a moiety selected from an imidazole moiety, a triazole moiety, a pyrazole moiety, a pyridine moiety, and a tetrazole moiety.

7. The catalyst of claim 6, wherein said imidazole moiety, said triazole moiety, said pyrazole moiety, said pyridine moiety, and said tetrazole moiety are selected form those depicted within FIG. 4.

8. A method for synthesizing an oxygen-activated catalyst, the method comprising: (i) contacting a pre-catalyst with oxygen (calcination) in a gaseous environment, thereby forming said oxygen-activated catalyst, wherein the pre-catalyst comprises (a) a solid matrix; (b) at least one transition metal; and (c) at least one ligand covalently bound to said solid matrix.

9. The method of claim 8, wherein said ligand is bound to said transition metal.

10. The method of claim 8 or 9, wherein said contacting said pre-catalyst with said oxygen occurs at a temperature from about 370 C. to about 950 C.

11. The method of any one of claims 8 to 10, wherein said solid matrix is a silica matrix.

12. The method of claim 11, wherein said silica matrix is mesoporous or nanoporous silica.

13. The method of any one of claims 8 to 12 further comprising: (ii) reacting said solid matrix with a ligand precursor, thereby forming a ligand-grafted solid matrix.

14. The method of claim 13, wherein said solid matrix is a mesoporous silica template selected from SBA-15 and MCM-41.

15. The method of claim 13 or 14, wherein said ligand precursor comprises an imidazole moiety, a triazole moiety, a pyrazole moiety, a pyridine moiety, or a tetrazole moiety.

16. The method of claim 15, wherein said ligand precursor further comprises a silyl ether moiety.

17. The method of claim 16, wherein said ligand precursor has a structure according to Formula I, Formula II, Formula III, Formula IV, Formula V, Formula VI, Formula VII, Formula VIII, or Formula IX as shown in FIG. 4, wherein R.sub.1 to R.sub.23 are independently selected from H, amino, alkyl, substituted alkyl. heteroalkyl, substituted heteroalkyl, cycloalkyl, substituted cycloalkyl heterocycloalkyl, substituted heterocyloalkyl, aryl, substituted aryl, heteroaryl, substitute heteroaryl, aralkyl, substituted aralkyl, hydroxyl, alkoxy, alkenyl, substituted alkenyl, alkynyl, substitute alkynyl, amide, azo, benzyl, substituted benzyl, carbonate, acyl, carboxylate, amide, sulfonamide, cyanate, ether, ester, halide, imine, isocyanide, isocyanate, oxy, sulfonyl, nitrile, nitro, nitroso, thiol, and substituted thiol.

18. The method of claim 17, wherein said ligand precursor is selected from N-(3-propyltrimethoxysilane) imidazole and N-(3-propyltrimethoxysilane) 1,2,4,-triazole.

19. the method of any one of claims 13 to 18 further comprising: (iii) reacting said ligand-grafted solid matrix with a transition metal salt, thereby forming said pre-catalyst.

20. the method of claim 19, wherein said transition metal is selected from the group consisting of manganese, iron, cobalt, nickel, copper, and combinations thereof.

22. The method of claim 8 further comprising (ii) reacting a ligand precursor with tetraethyl orthosilate (TEOS) at a ratio of TEOS:ligand precursor from about 4 to 24; and optionally adding a structure-directing agent, thereby forming a ligand-grafted silica matrix.

23. The method of claim 22, wherein said structure-directing agent is an amine-based surfactant.

24. The method of claim 23, wherein said amine-based surfactant is selected from n-hexadecylamine and n-octadecylamine.

25. The method of any one of claims 22 to 24, wherein said ligand precursor comprises an imidazole moiety, a triazole moiety, a pyrazole moiety, a pyridine moiety, or a tetrazole moiety.

26. The method of claim 25, wherein said ligand precursor further comprises a silyl ether moiety.

27. The method of claim 26, wherein said ligand precursor has a structure according to Formula I, Formula II, Formula III, Formula IV, Formula V, Formula VI, Formula VII, Formula VIII, or Formula IX as shown in FIG. 4, wherein R.sub.1 to R.sub.23 are independently selected from H, amino, alkyl, substituted alkyl, heteroalkyl, substituted heteroalkyl, cycloalkyl, substituted cycloalkyl, heterocycloalkyl, substituted heterocycloalkyl, aryl, substituted aryl, heteroaryl, substituted heteroaryl, aralkyl, substituted aralkyl, hydroxyl, alkoxy, alkenyl, substituted alkenyl, alkynyl, substitute alkynyl, amide, azo, benzyl, substituted benzyl, carbonate, acyl, carboxylate, amide, sulfonamide, cyanate, ether, ester, halide, imine, isocyanide, isocyanate, oxy, sulfonyl, nitrile, nitro, nitroso, thiol, and substituted thiol.

28. The method of claim 27, wherein said ligand precursor is selected from N-(3-propytrimethoxysilane) imidazole and N-(3-propyltrimethoxysilane) 1,2,4-triazole.

29. The method of any one of claims 22-28 further comprising, reacting said ligand-grafted silica matrix with a transition metal salt, thereby forming said pre-catalyst.

30. The method of claim 29, wherein said transition metal is selected from the group consisting of manganese, iron, cobalt, nickel, copper, and combinations thereof.

31. The method of claim 30, wherein said transition metal is selected from the group consisting of manganese, copper, and combinations thereof.

32. The method of any one of claims 8 to 31, further comprising silylating said pre-catalyst or said oxygen-activated catalyst thereby forming a silylated pre-catalyst or a silylated oxygen-activated catalyst.

33. An oxygen-activated catalyst made according to the method of any one of claims 8 to 32.

34. A method for directly converting methane (CH.sub.4) to methanol (CH.sub.3OH) comprising, contacting a gas feed comprising methane with an oxygen-activated catalyst according to any one of claims 1 to 7 and 33, under conditions sufficient to form said methanol.

35. The method of claim 34, wherein said gas feed is contacted with said oxygen-activated catalyst at a temperature below about 750 C.

36. The method of claim 35, wherein said gas feed is contacted with said oxygen-activated catalyst at a temperature from about 150 C. to about 350 C.

37. The method of any one of claims 34 to 36, wherein said gas feed is contacted with said oxygen-activated catalyst at a pressure of less than about 50 atm.

38. The method of claim 37, wherein said gas feed is contacted with said oxygen-activated catalyst at a pressure of less than about 20 atm.

39. The method of claim 38, wherein said gas feed is contacted with said oxygen-activated catalyst at ambient (atmospheric) pressure.

40. The method of any one of claim 34 to 39 wherein said gas feed further comprises oxygen.

41. the method of any one of claim 34 to 40 wherein said gas feed further comprises a carrier gas.

42. The method of any one of claim 34 to 41 further comprising, collecting said methanol.

43. A method for directly converting methane to methanol at a temperature of less than 750 C., said method comprising: contacting a gas feed comprising methane with an oxygen-activated catalyst, thereby forming said methanol from said methane, wherein said oxygen-activated catalyst comprises: i. a solid matrix; ii. at least one transition metal; iii. at least one ligand covalently bound to said solid matrix; and iv. oxygen bound to said transition metal.

44. The method of claim 43, wherein said ligand is bound to said transition metal.

45. The method of claim 43 or 44, wherein said solid matrix is a silica matrix.

46. The method of claim 45, wherein said silica matrix is mesoporous or nanoporous silica.

47. The method of any one of claims 43 to 46, wherein said transition metal is selected from the group consisting of manganese, iron, cobalt, nickel, copper, and combinations thereof.

48. the method of claim 47, wherein said transition metal is selected from the group consisting of manganese, copper, and combinations thereof.

49. The method of any one of claims 43 to 48, wherein the ligand comprises a moiety selected from an imidazole moiety, a triazole moiety, a pyrazole moiety, a pyridine moiety, and a tetrazole moiety.

50. The method of claim 49, wherein said imidazole moiety, said triazole moiety, said pyrazole moiety, said pyridine moiety, and said tetrazole moiety are selected from those depicted in FIG. 4, wherein R.sub.1 and R.sub.23 are independently selected from H, amino, alkyl, substituted alkyl, heteroalkyl, substituted heteroalkyl, cycloalkyl, substituted cycloalkyl, heterocycloalkyl, substituted heteroalkyl, cycloalkyl, substituted aryl, heteroaryl, substituted heteroaryl, aralkyl, substituted aralkyl, hydroxyl, alkoxy, alkenyl, substituted alkenyl, alkynyl, substitute alkynyl, amide, azo, benzyl, substituted benzyl, carbonate, acyl, carboxylate, amide, sulfonamide, cyanate, ether, ester, halide, imine, isocyanide, isocyanate, oxy, sulfonyl, nitrile, nitro, nitroso, thiol, and substituted thiol.

51. The method of any one of claims 43 to 50, wherein said gas feed is contacted with said oxygen-activated catalyst at a pressure of less than about 50 atm.

52. The method of claim 51, wherein said gas feed is contacted with said oxygen-activated catalyst at a pressure of less than about 20 atm.

53. The method of claim 52, wherein said pressure is ambient (atmospheric) pressure.

54. An apparatus for the direct conversion of methane gas to methanol comprising: i. a storage unit for methane gas; ii. a contacting unit for passing a gas feed comprising methane gas and oxygen over an oxygen-activated catalyst according to claim 1.

55. The apparatus of claim 54 further comprising a collecting unit for removing methanol from said contacting unit.

56. The apparatus of claim 54 or 55, wherein the apparatus further comprises a heating unit for heating said oxygen-activated catalyst to a temperature of less than 750 C.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0080] FIG. 1 is an exemplary illustration of the process steps involved in the direct selective conversion of methane to methanol according to an embodiment of the invention.

[0081] FIG. 2 is an exemplary illustration of schematically the synthetic steps to produce an exemplary oxygen-activated post-synthetic grafter catalyst beginning with a mesoporous silica scaffold, e.g., SBA-15, MCM-41, etc.

[0082] FIG. 3 is an exemplary illustration of schematically synthetic steps to produce oxygen-activated self-assembled catalysts of the invention.

[0083] FIG. 4 illustrates exemplary ligands for both the post-synthetic grafted and self-assembled catalysts of the invention.

[0084] FIG. 5 illustrates exemplary metal salts that could be used to impregnate the pre-catalysts.

[0085] FIG. 6 illustrates exemplary post-synthetically grafted pre-catalysts comprising more than one metal.

[0086] FIG. 7 illustrates exemplary post-synthetically grafted pre-catalysts comprising more than one metal and more than one ligand type.

[0087] FIG. 8 illustrates exemplary self-assembled pre-catalysts comprising more than one metal and more than one ligand type.

[0088] FIG. 9 illustrates exemplary methods to silylate the surface of the catalysts.

DETAILED DESCRIPTION OF THE INVENTION

[0089] The invention generally encompasses methods of converting methane to one or more oxidative products, for example, but not limited to, methanol and/or dimethyl ether. In certain embodiments, the invention encompasses methods of directly converting methane to methanol. In certain embodiments, the invention encompasses methods of directly converting methane to dimethyl ether. In certain embodiments, the invention encompasses methods of directly converting methane to methanol and dimethyl ether. The following scheme illustrates the general nature of the reaction encompassed by the invention.

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[0090] In an exemplary embodiment, the invention encompasses a process for the direct and selective oxidation of methane to methanol at low temperature. FIG. 1 illustrates an exemplary process of the invention. The exemplary process involves the formation of a pre-catalyst, which is heated in an oxidizing atmosphere to form an oxygen-activated catalyst. This leads to the formation of an active site in the oxygen-activated catalyst, which facilitates the direct conversion of methane to methanol. Next, methane gas is contacted with or passed over the oxygen-activated catalyst to directly form methanol. The entire reaction (i.e., creation of the active site and passing methane gas) is carried out at temperatures, for example, below 750 degrees Celsius and at ambient pressure. Finally, methanol is collected from the reaction vessel.

[0091] In another example, a gas stream containing methane is contacted with or passed over the oxygen-activated catalyst to directly form methanol. The catalyst may be heated directly by an external source or by a heated stream of methane and the oxygen containing gas stream. In certain embodiments, the temperature of the reaction is less than 750 degrees Celsius. In other examples the temperature could be in a temperature range of about 150 degrees Celsius to about 350 degrees Celsius. In other examples the temperature range may be about 350 degrees Celsius to about 500 degrees Celsius. In further examples the temperature range may about 500 degrees Celsius to about 750 degrees Celsius. In certain embodiments, the total pressure of the gas feed in the reaction is typically less than 50 atm. This gas feed is composed of methane and oxygen and/or may contain air. In certain embodiments, the gas feed may also be partially composed of a carrier gas, examples of which may include, for example, helium and/or nitrogen.

[0092] In another exemplary embodiment, the invention encompasses a process for the direct and selective oxidation of methane to dimethyl ether at low temperatures. FIG. 1 illustrates an exemplary process of the invention. The exemplary process involves the formation of a pre-catalyst, which is heated in an oxidizing atmosphere to form a oxygen n-activated catalyst. This leads to the formation of an active site in the oxygen-activated catalyst, which facilitates the direct conversion of methane to dimethyl ether. Next, methane gas is contacted with or passed over the oxygen-activated catalyst to directly form dimethyl ether. The entire reaction (i.e., creation of the active site and passing methane gas) is carried out at temperatures, for example, below 750 degrees Celsius and at ambient pressure. Finally, dimethyl ether is collected from the reaction vessel.

[0093] In another example, a gas stream containing methane is contacted with or passed over the oxygen-activated catalyst to directly form dimethyl ether. The catalyst may be heated directly by an external source or by a heated stream of methane and the oxygen containing gas stream. In certain embodiments, the temperature of the reaction is less than 750 degrees Celsius. In other examples the temperature could be in a temperature range of about 150 degrees Celsius to about 350 degrees Celsius. In other examples the temperature range may be about 350 degrees Celsius to about 500 degrees Celsius. In further examples the temperature range may about 500 degrees Celsius to about 750 degrees Celsius. In certain embodiments, the total pressure of the gas feed in the reaction is typically less than 50 atm. This gas feed is composed of methane and oxygen and/or may contain air. In certain embodiments, the gas feed may also be partially composed of a carrier gas, examples of which may include, for example, helium and/or nitrogen.

Definitions

[0094] The definitions and explanations below are for the terms as used throughout this entire document including both the specification and the claims. Throughout the specification and the appended claims, a given formula or name shall encompass all isomers thereof, such as stereoisomers, geometrical isomers, optical isomers, tautomers, and mixtures thereof where such isomers exist.

[0095] The term director directly in the context of methane conversion to methanol refers to a process, in which no substantial amount of an intermediate (e.g., gaseous intermediate), such as hydrogen gas (H.sub.2) and/or carbon monoxide (CO) is formed and/or isolated. In some examples, the process does not involve the formation of syngas. In one example, the process is a one-step process. In certain exemplary embodiments, the process of directly converting methane to methanol doe snot involve substantial formation of oxygenated species other than methanol. For example, the direct process does not involve the substantial formation of carbon dioxide (CO.sub.2).

[0096] The terms oxidative product(s) or oxygenated species refers to any products that result from the oxidation of methane using the methods disclosed herein. Oxidative products as used therein include methanol, dimethyl ether, formaldehyde, formic acid, etc. Preferably, oxidative products as used herein include methanol and dimethyl ether. More preferably, oxidative product as used herein include only methanol.

[0097] The term bound or bound to (or any grammatical variation thereof) in the context of chemical structure refers to various types of chemical bonds, such as covalent bonds (e.g., non-polar and polar), coordinate covalent (i.e., dipolar bonds), ionic bonds, metallic bonds, bonds with covalent as well as ionic character, metallic coordination (i.e., coordination complex or metal complex). In certain illustrative embodiments, the term bound or bound to refers to a chemical bond forming a metal complex or coordination complex. In some examples, the transition metal contained in the catalysts of the invention is (e.g., reversibly or irrepressibly) coordinated to oxygen. In other examples, the transition metal can be coordinated to hydroxyl groups located on a solid matrix, such as a silica matrix. In other examples, ligands, which are covalently bound to the surface of a solid matrix (e.g., a silica matrix), are additionally bound to a transition metal forming a ligand-metal complex (coordination complex). In other illustrative embodiments, a multitude of bonds formed between oxygen and the transition metal (e.g., during calcination of the catalyst), or between oxygen, ligands, and the transition metal create catalytic sites capable of catalyzing the conversion of methane to methanol (e.g., under reaction conditions described herein).

[0098] The term ligand refers to a chemical moiety comprising at least one heteroatom. In some embodiments, a ligand comprises a heterocyclic or heteroaryl moiety. In other examples, the ligand is capable of forming a ligand transition metal complex.

[0099] The terms solid matrix, template, or substrate means a solid carrier material. In some examples, the solid matrix has a large surface area (e.g., is a porous material). In other examples, the solid matrix has functional groups (e.g., hydroxyl groups), which can be used to form a covalent bond to a ligand. In some examples, the solid matrix is a silica matrix (e.g., mesoporous or nanoporous silica).

[0100] The term transition metal is used within its art-recognized meaning. For example, a transition metal is an element is an element whose atom has a partially filled d sub-shell, or which can give rise to cations with an incomplete d sub-shell. In other examples, the transition metal is selected from elements found in groups 3 to 12 of the periodic table and f-block lanthanides and actinides.

[0101] The terms alkyl by itself for as part of another substituent, means, unless otherwise stated, a straight or branched chain hydrocarbon radical having the number of carbon atoms designated (e.g., C.sub.1-C.sub.10 means one to ten carbon atoms). Typically, an alkyl group will have from 1 to 24 carbon atoms, for example having from 1 to 10 carbon atoms, from 1 to 8 carbon atoms or from 1 to 6 carbon atoms. A lower alkyl group is an alkyl group having from 1 to 4 carbon atoms. The term alkyl includes di- and multivalent radicals. For example, the terms alkyl includes alkylene wherever appropriate, e.g., when the formula indicates that the alkyl group is divalent or when substituents are joined to form a ring. Examples of alkyl radicals include, but are not limited to, methyl, ethyl, n-propyl, iso-propyl, n-butyl, tert-butyl, iso-butyl, sec-butyl, as well as homologs and isomers of, for example, n-pentyl, n-hexyl, n-heptyl and n-octyl.

[0102] The term alkylene by itself or as part of another substituent means a divalent (diradical) alkyl group, wherein alkyl is defined herein. Alkyleneis exemplified, but not limited by CH.sub.2CH.sub.2CH.sub.2CH.sub.2. Typically, an alkylene group will have from 1 to 24 carbon atoms, for example, having 10 or fewer carbon atoms (e.g., 1 to 8 or 1 to 6 carbon atoms). A lower alkylene group is an alkylene group having from 1 to 4 carbon atoms.

[0103] The term alkenyl by itself or as part of another substituent refers to a straight or branched chain hydrocarbon radical having from 2 to 24 carbon atoms and at least one double bond. A typical alkenyl group has from 2 to 10 carbon atoms and at least one double bond. In one embodiment, alkenyl groups have from 2 to 8 carbon atoms or from 2 to 6 carbon atoms and from 1 to 3 double bonds. Exemplary alkenyl groups include vinyl, 2-propenyl, 1-but-3-enyl, crotyl, 2-(butadienyl), 2,4-pentadienyl, 3-(1,4-pentadienyl), 2-isopentenyl, 1-pent-3-enyl, 1-hex-5-enyl and the like.

[0104] The term alkynyl by itself or as part of another substituent refers to a straight or branched chain, unsaturated or polyunsaturated hydrocarbon radical having from 2 to 24 carbon atoms and at least one triple bond. A typical alkynyl group has from 2 to 10 carbon atoms and at least one triple bond. In one aspect of the disclosure, alkynyl groups have from 2 to 6 carbon atoms and at least one triple bond. Exemplary alkynyl groups include prop-1 ynyl, prop-2-ynyl (i.e., propargyl), ethynyl and 3-butynyl.

[0105] The terms alkoxy, alkylamino and alkylthio (or thioalkoxy) are used in their conventional sense, and refer to alkyl groups that are attached to the remainder of the molecule via an oxygen atom, an amino group, or a sulfur atom, respectively.

[0106] The term heteroalkyl, by itself or in combination with another term, means a stable, straight or branched chain hydrocarbon radical consisting of the stated number of carbon atoms (e.g., C.sub.2-C.sub.1, or C.sub.2-C.sub.8) and at least one heteroatom chosen, e.g., from N, O, S, Si, B and P (in one embodiment, N, O and S), wherein the nitrogen, sulfur and phosphorus atoms are optionally oxidized, and the nitrogen atoms(s) are optionally quaternized. The heteroatoms(s) is/are placed at any interior position of the heteroalkyl group. Examples of heteroalkyl groups include, but are not limited to, CH.sub.2CH.sub.2OCH.sub.3, CH.sub.2CH.sub.2NHCH.sub.3, CH.sub.2CH.sub.2N(CH.sub.3)CH.sub.3, CH.sub.2SCH.sub.2CH.sub.3, CH.sub.2CH.sub.2S(O)CH.sub.3, CH.sub.2-CH.sub.2S(O).sub.2CH.sub.3, CHCHOCH.sub.3, CH.sub.2Si(CH.sub.3).sub.3, CH.sub.2CHNOCH.sub.3, and CHCHN(CH.sub.3)CH.sub.3. Up to two heteroatoms can be consecutive, such as, for example, CH.sub.2NHOCH.sub.3 and CHOSi(CH.sub.3).sub.3. Similarly, the term heteroalkylene by itself or as part of another substituent means a divalent radical derived from heteroalkyl, as exemplified, but not limited by, CH.sub.2CH.sub.2SCH.sub.2CH.sub.2 and CH.sub.2SCH.sub.2CH.sub.2NHCH.sub.2. Typically, a heteroalkyl group will have from 3 to 24 atoms (carbon and heteroatoms, excluding hydrogen) (3- to 24-membered heteroalkyl). In another example, the heteroalkyl; group has a total of 3 to 10 atoms (3- to 10-membered heteroalkyl) or from 3 to 8 atoms (3- to 8-membered heteroalkyl). The heteroalkyl includes heteroalkylene wherever appropriate, e.g., when the formula indicates that the heteroalkyl group is divalent or when substituents are joined to form a ring.

[0107] The term cycloalkyl by itself or in combination with other terms, represents a saturated or unsaturated, non-aromatic carbocyclic radical having from 3 to 24 carbon atoms, for example, having from 3 to 12 carbon atoms (e.g., C.sub.3-C.sub.8 cycloalkyl or C.sub.3-C.sub.6 cycloalkyl). Examples of cycloalkyl include, but are not limited to, cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl, 1-cyclohexenyl, 3-cyclohexenyl, cycloheptyl and the like. The terms cycloalkyl also includes bridged, polycyclic (e.g., bicyclic) structures, such as norbornyl, adamantyl and bicyclo[2.2.1]heptyl. The cycloalkyl group can be fused to at least one (e.g., 1 to 3 ) other ring selected from aryl (e.g., phenyl), heteroaryl (e.g., pyridyl) and one-aromatic (e.g., carbocyclic or heterocyclic) rings. When the cycloalkyl group includes a fused aryl, heteroaryl or heterocyclic ring, then the cycloalkyl group is attached to the remainder of the molecule via the carbocyclic ring.

[0108] The terms heterocycloalkyl, heterocyclic, heterocycle, or heterocyclyl, by itself or in combination with other terms, represents a carbocyclic, non-aromatic ring (e.g., 3- to 8-membered ring and for example 4-, 5-, 6- or 7-membered ring) containing at least one and up to 5 heteroatoms selected from, e.g., N, O, S, Si, B and P (for example, N, O and S), wherein the nitrogen, sulfur and phosphorus atoms are optionally oxidized, and the nitrogen atom(s) are optionally quaternized (e.g., from 1 to 4 heteroatoms selected from nitrogen, oxygen and sulfur), or a fused ring system of 4- to 8-membered rings, containing at least one and up to 10 heteroatoms (e.g., from 1 to 5 heteroatoms selected from N, O and S) in stable combinations known to those of skill in the art. Exemplary heterocycloalkyl groups include a fused phenyl ring. When the heterocyclic group includes a fused aryl, heteroaryl or cycloalkyl ring, then the heterocyclic group is attached to the remainder of the molecule via a heterocycle. A heteroatom can occupy the position at which the heterocycle is attached to the remainder of the molecule. Exemplary heterocycloalkyl or heterocyclic groups of the present disclosure include morpholinyl, thiomorpholinyl, thiomorpholinyl S-oxide, thiomorpholinyl S,S-dioxide, piperazinyl, homopiperazinyl, pyrrolidinyl, pyrrolinyl, imidazolidinyl, tetrahydropyranyl, piperazinyl, homopiperazinyl, pyrrolidinyl, pyrrolinyl, imidazolidinyl, tetrahydropyranyl, piperidinyl, tetrahydrofuranyl, tetrahydrothienyl, piperindinyl, homopiperidinyl, homomorpholinyl, homothiomorpholinyl, homothiomorpholinyl S,S-dioxides, ozazolidinonyl, dihydropyrazolyl, dihydropyrrolyl, dihydropyrazolyl, dihydropyridyl, didhydropyrimidinyl, dihydrofuryl, dihydropyranyl, tetrahydrothienyl S-oxide, tetrahydrothienyl S,S-dioxide, homothiomorpholinyl S-oxide, 1-(1,2,5,6-tetrahydropyridyl), 1-piperidinyl, 2-piperidinyl, 3-piperidinyl, 4-morpholinyl, 3-morpholinyl, tetrahydrofuran-2-yl, tetrahydrofuran-3-yl, tetrahydrothien-2yl, tetrahydrothien-3-yl, 1-piperazinyl, 2-piperazinyl, and the like.

[0109] By aryl is meant a 5-, 6- or 7-membered, aromatic carbocyclic group having a single ring (e.g., phenyl) or being fused to other aromatic or non-aromatic rings (e.g., from 1 to 3 other rings). When the aryl group includes a non-aromatic ring (such as in 1,2,3,4-tetrahydronaphthyl) or heteroaryl group then the aryl group is bonded to the remainder of the molecule via an aryl ring (e.g., a phenyl ring). The aryl group is optionally substituted (e.g., with 1 to 5 substituents described herein). In one example, the aryl group has from 6 to 10 carbon atoms. Non-limiting examples of aryl groups include phenyl, 1-naphthyl, 2-naphthyl, quinoline, indanyl, indenyl, dihydronaphthyl, fluorenyl, tetralinyl, benzo[d][1,3]dioxolyl or 6,7,8,9-tetrahydro-5H benzo[a]cycloehptenyl. In one embodiment, the aryl group is selected from phenyl, benzo[d][1,3]dioxolyl and naphthyl. The aryl group, in yet another embodiment, is phenyl.

[0110] The term arylalkyl is meant to include those radicals in which an aryl group or heteroaryl group is attached to an alkyl group to create the radicals -alkyl-aryl and -alkyl-heteroaryl, wherein alkyl, aryl and heteroaryl are defined herein. Exemplary arylalkyl groups include benzyl, phenethyl, pryidylmethyl and the like.

[0111] By aryloxy is meant the group O-aryl, where aryl is as defined herein. In one example, the aryl portion of the aryloxy group is phenyl or naphthyl. The aryl portion of the aryloxy group, in one embodiment, is phenyl.

[0112] The term heteroaryl or heteroaromatic refers to a polyunsaturated, 5-, 6- or 7-membered aromatic moiety containing at least one heteroatom (e.g., 1 to 5 heteroatoms, such as 1-3 heteroatoms) selected from N, O, S, Si and B (for example, N, O and S), wherein the nitrogen and sulfur atoms are optionally oxidized, and the nitrogen atoms(s) are optionally quaternized. The heteroaryl group can be a single ring or be fused to other aryl, heteroaryl, cycloalkyl or heterocycloakyl rings (e.g., from 1 to 3 other rings). When the heteroaryl group includes a fused aryl, cycloalkyl or heterocycloalkyl ring, then the heteroaryl group is attached to the remainder of the molecule via the heteroaryl ring. A heteroaryl group can be attached to the remainder of the molecule through a carbon- or heteroatom. In one example, the heteroaryl group has from 4 to 10 carbon atoms and from 1 to 5 heteroatoms selected from O, S and N. Non-limiting examples of heteroaryl groups include pyridyl, pyrimidine, quinolinyl, benzothienyl, indolyl, indolinyl, pyridazinyl, pyrazinyl, isoindolyl, isoquinolyl, quinazolinyl, quinoxalinyl, phthalazinyl, imidazolyl, isoxazolyl, pyrazolyl, oxazolyl, thiazolyl, indolizinyl, indazolyl, benzothiazolyl, benzimindazolyl, benzofuranyl, furanyl, thienyl, pyrrolyl, oxadiazolyl, thiadiazolyl, triazolyl, tetrazolyl, isothiazolyl, naphthyridinyl, isochromanyl, chromanyl, tetrahydroisoquinolinyl, isoindolinyl, isobenzotetrahydrofuranyl, isobenzotetrahydrothienyl, isobenzothienyl, benzoxazolyl, pyridopyridyl, benzotetrahydrofuranyl, benzotetrahydrothienyl, purinyl, benzodioxolyl, triazinyl, pteridinyl, benzothiazolyl, imidazopyridyl, imidazothiazolyl, dihydorbenzisoxazinyl, benzisoxazinyl, benzoxazinyl, dihydrobenzisothiazinyl, benzopyranyl, benzothiopyranyl, chromonyl, chromanonyl, pyridyl-N-oxide, tetrahydroquinolinyl, dihydroquinolinyl, dihydroquinolinonyl, dihydroisoquinolinonyl, dihydrocoumarinyl, dihydrosiocoumarinyl, isoindolinonyl, benzodioxanyl, benzoxazolinonyl, pyrrolyl N-oxide, pyrimidinyl N-oxide, pyridazinyl N-oxide, pyridazinyl N-oxide, quniolinyl N-oxide, indolyl N-oxide, indolinyl N-oxide, isoquinolyl N-oxide, quinazolinyl N-oxide, quinoxalinyl N-oxide, phthalazinyl N-oxide, imidazolyl N-oxide, isoxazolyl N-oxide, oxazolyl N-oxide, thiazolyl N-oxide, indolizinyl N-oxide, indazolyl N-oxide, benzothiazolyl N-oxide, benzimidazolyl N-oxide, pyrrolyl N-oxide, oxadiazolyl N-oxide, thiadiazolyl N-oxide, triazolyl N-oxide, tetrazolyl N-oxide, benzothiopyranyl S-oxide, benzothiopyranyl S,S-dioxide. Exemplary heteroaryl groups include imidazolyl, pyrazolyl, thiadiazolyl, triazolyl, isoxazolyl, isothiazolyl, imidazolyl, thiazolyl, oxadiazolyl, and pyridyl. Other exemplary heteroaryl groups include 1-pyrrolyl, 2-pyrrolyl, 3-pyrrolyl, 3-pyrazolyl, 2-imidazolyl, 4-imidazolyl, pyrazinyl, 2-oxazolyl, 4-oxazolyl, 2-phenyl-4-oxazolyl, 5-heteroaryl oxazolyl, 3-isoxazolyl, 4-isoxazolyl, 5-isoxazolyl, 2-thiazolyl, 4-thiazolyl, 5-thiazolyl, 2-furyl, 3-furyl 2-thienyl, 3-thienyl, 2-pyridyl, 3-pyridyl, pyridin-4-yl, 2-pyrimidyl, 4-pyrimidyl, 5-benzothiazolyl, purinyl, 2-benzimidazolyl, 5-indolyl, 1-isoquinolyl, 5- isoquinolyl, 2-quinoxalinyl, 5-quinoxalinyl, 3-quinolyl, and 6-quinolyl. Substituents for each of the above noted aryl and heteroaryl ring systems are selected from the group of acceptable aryl group substituents described below.

[0113] For brevity, the terms aryl when used in combination with other terms (e.g., aryloxy, arylthioxy, arylalkyl) includes both aryl and heteroaryl rings as defined above.

[0114] Each of the above terms (e.g., alkyl, cycloalkyl, heteroalkyl, heterocycloalkyl, aryl and heteroaryl) are meant to include both substituted and unsubstituted forms of the indicated radical. The term substituted for each type of radical is explained below. When a compound of the present disclosure includes more than one substituent, then each of the substituents is independently chosen.

[0115] The term substituted in connection with alkyl, alkenyl, alkynyl, cycloalkyl, heteroalkyl and heterocycloalkyl radicals (including those groups referred to as alkylene, heteroalkylene, heteroalkenyl, cycloalkenyl, heterocycloalkenyl, and the like) refers to one or more substituents, wherein each substituent is independently selected from, but not limited to, 3- to 10-membered heteroalkyl, C.sub.3-C.sub.10 cycloalkyl, 3- to 10-membered heterocycloalkyl, aryl, heteroaryl, OR.sup.a, SR.sup.a, O, NR.sup.a, NOR.sup.a, NR.sup.aR.sup.b, -halogen, SiR.sup.aR.sup.bR.sup.c, OC(O)R.sup.a, C(O)R.sup.c, C(O)OR.sup.a, C(O)NR.sup.aR.sup.b, OC(O)NR.sup.aR.sup.b, NR.sup.cC(O)R.sup.c, NR.sup.cC(O)NR.sup.aR.sup.b, NR.sup.cC(S)NR.sup.aR.sup.b, NR.sup.cC(O)OR.sup.a, NR.sup.cC(NR.sup.aR.sup.b)NR.sup.d, S(O)R.sup.c, S(O).sub.2R.sup.c, S(O).sub.2NR.sup.aR.sup.b, NR.sup.cS(O).sub.2R.sup.a, CN and NO.sub.2, R.sup.a, R.sup.b, R.sup.c, R.sup.d and R.sup.2 each indepenently refer to hydrogen, C.sub.1-C.sub.24 alkyl (e.g., C.sub.1-C.sub.10 alkyl or C.sub.1-C.sub.6 alkyl), C.sub.3-C.sub.10 cycloalkyl, C.sub.1-C.sub.24 heteroalkyl (e.g., C.sub.1-C.sub.10 heteroalkyl or C.sub.1-C.sub.6 heteroalkyl). C.sub.3-C.sub.10 heterocycloakyl, aryl, heteroaryl, arylalkyl and heteroarylalkyl, wherein, in one embodiment, R.sup.c is not hydrogen. When two of the above R groups (e.g., R.sup.a and R.sup.b) are attached to the same nitrogen atom, they can be combined with the nitrogen atom to form a 5-, 6-, or 7-membered ring. For example, NR.sup.aR.sup.b is meant to include pyrrolidinyl, N -alkyl-piperidinyl and morpholinyl.

[0116] The terms substitutedin connection with aryl and heteroaryl groups, refers to one or more substituents, wherein each substituent is independently selected from, but not limited to, alkyl (e.g., C.sub.1-C.sub.24 alkyl, C.sub.1-C.sub.10 alkyl or C.sub.1-C.sub.6 alkyl), cycloalkyl (e.g., C.sub.3-C.sub.10 cycloalkyl, or C.sub.3-C.sub.8 cycloalkyl), alkenyl (e.g., C.sub.1-C.sub.10 alkenyl or C.sub.1-C.sub.6 alkenyl), alkynyl (e.g., C.sub.1-C.sub.10 alkynyl or C.sub.1-C.sub.6 alkynyl), heteroalkyl (e.g., 3- to 10-membered heteroalkyl), heterocycloalkyl (e.g., C.sub.3-C.sub.8 heterocycloalkyl), aryl, heteroaryl, R.sup.a, OR.sup.a, SR.sup.a, O, NR.sup.a, NOR.sup.a, NR.sup.aR.sup.b, -halogen, SiR.sup.aR.sup.bR.sup.c, OC(O)R.sup.a, C(O)R.sup.c, C(O)OR.sup.a, C(O)NR.sup.aR.sup.b, OC(O)NR.sup.aR.sup.b, NR.sup.cC(O)R.sup.a, NR.sup.cC(O)NR.sup.aR.sup.b, NR.sup.cC(S)NR.sup.aR.sup.b, NR.sup.cC(O)OR.sup.a, NR.sup.cC(NR.sup.aR.sup.b)NR.sup.d, S(O)R.sup.a, S(O).sub.2R.sup.c, S(O).sub.2NR.sup.aR.sup.b, NR.sup.cS(O).sub.2R.sup.a, CN, NO.sub.2-N.sub.3, CH(Ph).sub.2, fluoro(C.sub.1-C.sub.4)alkoxy, and fluoro(C.sub.1-C.sub.4)alkyl, in a number ranging from zero to the total number of open valences on the aromatic ring system, wherein R.sup.a, R.sup.b, R.sup.c, R.sup.d and R.sup.c each independently refer to hydrogen, C.sub.1-C.sub.24 alkyl (e.g., C.sub.1-C.sub.10 alkyl or C.sub.1-C.sub.6 alkyl), C.sub.3-C.sub.10 cycloalkyl, C.sub.1 -C.sub.24 heteroalkyl (e.g., C.sub.1-C.sub.10 heteroalkyl or C.sub.1-C.sub.6 heteroalkyl), C.sub.3-C.sub.10 heterocycloalkyl, aryl, heteroaryl, arylalkyl and heteroarylalkyl, wherein, in one embodiment, R.sup.c is not hydrogen. When two R groups (e.g., R.sup.a and R.sup.b) are attached to the same nitrogen atom, they can be combined with the nitrogen atom to form a 5-, 6-, or 7-membered ring. For example, NR.sup.aR.sup.b is meant to include pyrrolidinyl, N-alkyl-piperidinyl and moropholinyl.

[0117] The terms substituted in connection with aryl and heteroaryl groups also refers to one or more fused ring(s), in which two hydrogen atoms on adjacent atoms of the aryl or heteroaryl ring are optionally replaced with a substituent of the formula T-C(O) (CRR).sub.qU, wherein T and U are independently NR, O, CRRor a single bond, and q is an integer from 0 to 3. Alternatively, two of the hydrogen atoms on adjacent atoms of the aryl or heteroaryl ring can optionally be replaced with a substituent of the formula A-(CH.sub.2).sub.rB, wherein A and B are independently CRR, O, NR, S, (O), S(O).sub.2), S(O).sub.2NR or a single bond, and r is an integer from 1 to 4. One of the single bonds of the ring so formed can optionally be replaced with a double bond. Alternatively, two of the hydrogen atoms on adjacent atoms of the aryl or heteroaryl ring can optionally be replaced with a substituent of the formula (CRR).sub.sX(CRR).sub.d, where s and d are independently integers from 0 to 3, and X is O, NR, S, S(O), S(O).sub.2, or S(O).sub.2NR, wherein the substituents R R, R and R in each of the formulas above are independently selected from hydrogen and (C.sub.1-C.sub.6)alkyl.

[0118] The terms halo or halogen, by themselves or as part of another substituent, mean at least one of fluorine, chlorine, bromine and iodine.

[0119] By haloalkylis meant an alkyl radical, wherein alkyl is as defined above and wherein at least one hydrogen atom is replaced by a halogen atom. The term haloalkyl, is meant to include monohaloalkyl and polyhaloalkyl. For example, the terms halo(C.sub.1-C.sub.4)alkyl or (C.sub.1-C.sub.4)haloalkyl is mean to include, but not limited to, chloromethyl, 1-bromomethyl, fluoromethyl, difluoromethyl, trifluoromethyl, 1,1,1-trifluoromethyl and 4-chlorobutyl, 3-bromopropyl.

[0120] As used herein, the term acyl described the group C(O)R.sup.c, wherein R.sup.c is selected from hydrogen, C.sub.1-C.sub.24 alkyl (e.g., C.sub.1-C.sub.10 alkyl or C.sub.1-C.sub.6 alkyl), C.sub.1-C.sub.24 alkenyl (e.g., C.sub.1-C.sub.10 alkenyl or C.sub.1-C.sub.6 alkenyl), C.sub.1-C.sub.24 alkynyl (e.g., C.sub.1-C.sub.10 alkynyl or C.sub.1-C.sub.6 alkynyl), C.sub.3-C.sub.10 cycloalkyl, C.sub.1-C.sub.24 heteroalkyl (e.g., C.sub.1-C.sub.10 heteroalkyl or C.sub.1-C.sub.6 heteroalkyl), C.sub.3-C.sub.10 heterocycloalkyl, aryl, heteroaryl, arylalkyl and heteroarylalkyl. In one embodiment, R.sup.c is not hydrogen.

[0121] By alkanoyl is meant an acyl radical C(O)Alk-, wherein Alk is an alkyl radical as defined herein. Examples of alkanoyl include acetyl, propionyl, butyryl, isobutyryl, valeryl, isovaleryl, 2- methyl-butyryl, 2,2-dimethylpropinyl, hexanoyl, heptanol, octanoyl and the like.

[0122] As used herein, the term heteroatom includes oxygen (O), nitrogen (N), sulfur (S), silicon (Si) boron (B) and phosphorus (P). In one embodiment, heteroatoms are O, S and N.

[0123] By oxo is meant the group O.

[0124] By sulfonyl or sulfonyl group is meant a group that is connected to the remainder of a molecule via a S(O).sub.2 moiety. Hence sulfonyl can be S(O).sub.2R, wherein R is e.g., NHR, substituted or unsubstituted alkyl, substituted or unsubstituted heteroalkyl, substituted or unsubstituted cycloalkyl, substituted or unsubstituted heterocycloalkyl, substituted or unsubstituted aryl or substituted or unsubstituted heteroaryl. An exemplary sulfonyl group is S(O).sub.2-Cy, wherein Cy is, e.g., substituted or unsubstituted aryl or substituted or unsubstituted heteroaryl.

[0125] By sulfinyl or sulfinyl group is meant a group that is connected to the remainder of the molecule via a S(O) moiety. Hence, sulfinyl can be S(O)R, wherein R is as defined for sulfonyl group.

[0126] By sulfonamide is meant a group having the formula S(O).sub.2NRR, where each of the R variables are independently selected from the variables listed above for R.

[0127] The symbol R is a general abbreviation that represents a substituent group as described herein. Exemplary substituent groups include alkyl, alkenyl, alkynyl, cycloalkyl, heteroalkyl, aryl, heteroaryl and heterocycloalkyl groups, each as defined herein.

[0128] As used herein, the term aromatic ring or non-aromatic ring is consistent with the definition commonly used in the art. For example, aromatic rings include phenyl and pyridyl. Non-aromatic rings include cyclohexanes.

[0129] As used herein, the term fused ring system means at least two rings, wherein each ring has at least 2 atoms in common with another ring. Fused ring systems can include aromatic as well as non-aromatic rings. Examples of fused ring systems are naphthlenes, indoles, quinolines, chromenes and the like. Likewise, the term fused ring refers to a ring that has at least two atoms in common with the ring to which it is fused.

[0130] Where multiple substituents are indicated as being attached to a structure, those substituents are independently chosen. For example ring A is optionally substituted with 1, 2 or 3 R.sub.q groups indicates that ring A is substituted with 1, 2 or 3 R.sub.q groups, wherein the R.sub.q groups are independently chosen (i.e., can be the same or different).

[0131] Where substituent groups are specified by their conventional chemical formulae, written from left to right, they equally encompass the chemically identical substituents, which would result from writing the structure from right to left. For example CH.sub.2O is intended to also recite OCH.sub.2.

Catalysts

[0132] In certain embodiments, the catalyst synthesis takes place in several steps. FIG. 2 illustrates an exemplar post-synthetic grafting route and FIG. 3 illustrates an exemplary self-assembly route.

[0133] Post-synthetic grafted catalysts can be synthesized by first using a mesoporous silica template such as, but not limited to SBA-15 or MCM-41. The mesoporous silica is then reacted, e.g., as shown in FIG. 2, with an alkyl silyl ether containing a ligand precursor. Exemplary ligand precursors are shown in FIG. 4. This forms a ligand grafted mesoporous silica material that is then impregnated with a transition metal M, for example by coordination with a metal salt, MX.sub.n, forming the pre-catalyst, where M is, for example, Mn, Fe, Co, Ni, or Cu; X is F, Cl, Br, I, NO.sub.3, CN, OH, CH.sub.3COO, etc.; and n is, for example, 1-3. In certain illustrative embodiments, the metal salt can also have the formula, M.sub.yX.sub.n, where M is, for example, Mn, Fe, Co, Ni, or Cu; X is F, Cl, Br, I, NO.sub.3, CN, OH, CH.sub.3COO, etc.; and n is, for example, 1-3, and Y is 1-2 Exemplary metal salts are shown in FIG. 5. The pre-catalyst is heated in an oxidizing environment. In an exemplary method, a catalyst is pre-treated by heating the catalyst in a gaseous environment with continuous gas flow and at a pre-treatment temperature range of about 370 degrees Celsius to about 950 degrees Celsius. This forms the oxygen-activated catalyst. The oxygen-activated catalyst may then be silylated, for example, using methods outlined in FIG. 9 to form a silylated oxygen-activated catalyst.

[0134] In certain illustrative embodiments, self-assembled catalysts can be synthesized, for example, as illustrated in FIG. 3. In one embodiment, an alkyl silyl ether containing the ligand precursor is reacted with a stoichiometric amount of TEOS (tetraethyl orthosilicate) where x=424 and x is chosen to influence both the pore structure and size in the mesoporous silica material. A structure-direction agent, for example, an amine-based surfactant is added. Exemplary amine-based surfactants include n-alkyl amines, such as C.sub.6-C.sub.20 n-alkyl amines. In some illustrative embodiments, the amine-based surfactant is n-hexadecylamine and n-octadecylamine. Exemplary ligand precursors are shown in FIG. 4. This forms a ligand grafted mesoporous silica material that is then impregnated with metal M, for example, by coordination with a metal salt, for example, MX.sub.n, forming the pre-catalyst. Exemplary metal salts are shown in FIG. 5. The pre-catalyst is then heated in an oxidizing environment. In this method a catalyst is pre-treated by heating the catalyst in a gaseous environment with continuous gas flow and at a pre-treatment temperature range of about 370 degrees Celsius to about 950 degrees Celsius. This forms the oxygen-activated catalyst. The oxygen-activated catalyst may then be silylated, for example, using methods outlined in FIG. 9 to form a silylated oxygen-activated catalyst.

[0135] The catalysts of the invention comprise at least one ligand, for example, covalently linked to the silica matrix, at least one transition metal, and oxygen. In some embodiments, the ligand is capable of binding (e.g., complexing/coordinating) a transition metal. In some embodiments, the transition metal is bound (e.g., coordinated) to oxygen. The catalysts can include more than one ligand and/or more than one transition metal. In some embodiments, the ligand comprises a moiety selected from an imidazole moiety, a triazole moiety (e.g., a 1,2,3-triazole moiety, or a 1,2,4-triazole moiety), a pyrazole moiety, a pyridine moiety (e.g., a 2-pyridine, 3-pyridine, or 4-pyridine moiety), an a tetrazole moiety.

Ligand Precursors

[0136] One or more ligand precursor can be used to form the catalyst. In some embodiments, the ligand precursor comprises a moiety selected from an imidazole moiety, a triazole moiety (e.g., a 1,2,3-triazole moiety, or a 1,2,4-triazole moiety), a pyrazole moiety, a pyridine moiety (e.g., a 2-pyridine, 3-pyridine, or 4-pyridine moiety), and a tetrazole moiety.

[0137] In FIG. 4, exemplary ligand precursors having Formulae I-IX are illustrated. In some embodiments in formulae I-IX, R.sub.1 is selected from C.sub.1-C.sub.6 alkyl. In other embodiments, R.sub.1 is methyl or ethyl. In some embodiments, in Formulae I-IX, n=0-6. In other embodiments in Formulae I-IX, R.sub.1 is selected from methyl and ethyl and n is 0-6.

[0138] In some embodiments, the ligand precursor comprises an imidazole moiety and has a structure according to Formula I, wherein R.sub.2, R.sub.3, and R.sub.4 are independently selected from the group consisting of H, amino (e.g., alkyl amino), alkyl, substituted alkyl, heteroalkyl, substituted heteroalkyl, cycloalkyl, substituted cycloalkyl, heterocycloalkyl, substituted heterocyloalkyl, aryl, substituted aryl, heteroaryl, substituted heteroaryl, aralkyl, substituted aralkyl, hydroxyl, alkoxy, alkenyl, substituted alkenyl, alkynyl, substitute alkynyl, amide, azo, benzyl, substituted benzyl, carbonate, acyl, carboxylate, amide, sulfonamide, cyanate, ether, ester, halide, imine, isocyanide, isocyanate, ketone (oxy), sulfonyl, nitrile, nitro, nitroso, thiol, and substituted thiol (e.g., alkyl thiol).

[0139] In other embodiments, the ligand precursor includes a substituted 1,2,4-triazoles (4-N) moiety and has a structure according to Formula II, wherein R.sub.5 and R.sub.6 are independently selected from the group consisting of H, amino (e.g., alkyl amino), alkyl, substituted alkyl, heteroalkyl, substituted heteroalkyl, cycloalkyl, substituted cycloalkyl, heterocycloalkyl, substituted heterocyloalkyl, aryl, substituted aryl, heteroaryl, substituted heteroaryl, aralkyl, substituted aralkyl, hydroxyl, alkoxy, alkenyl, substituted alkenyl, alkynyl, substitute alkynyl, amide, azo, benzyl, substituted benzyl, carbonate, acyl, carboxylate, amide, sulfonamide, cyanate, ether, ester, halide, imine, isocyanide, isocyanate, ketone (oxy), sulfonyl, nitrile, nitro, nitroso, thiol, and substituted thiol (e.g., alkyl thiol).

[0140] In other embodiments, the ligand precursor includes a substituted pyrazole moiety and has a structure according to Formula III, wherein R.sub.7 and R.sub.8 are independently selected from the group consisting of H. amino (e.g., alkyl amino), alkyl, substituted alkyl, heteroalkyl, substituted heteroalkyl, cycloalkyl, substituted cycloalkyl, heterocycloalkyl, substituted heterocyloalkyl, aryl, substituted aryl, heteroaryl, substituted heteroaryl, aralkyl, substituted aralkyl, hydroxyl, alkoxy, alkenyl, substituted alkenyl, alkynyl, substitute alkynyl, amide, azo, benzyl, substituted benzyl, carbonate, acyl, carboxylate, amide, sulfonamide, cyanate, ether, ester, halide, imine, isocyanide, isocyanate, ketone (oxy), sulfonyl, nitrile, nitro, nitroso, thiol, and substituted thiol (e.g., alkyl thiol).

[0141] In other embodiments, the ligand precursor includes a substituted 4-pyridine moiety and has a structure according to Formula IV, wherein R.sub.9, R.sub.10, R.sub.11, and R.sub.12 are independently selected from the group consisting of H, amino (e.g., alkyl amino), alkyl, substituted alkyl, heteroalkyl, substituted heteroalkyl, cycloalkyl, substituted cycloalkyl, heterocycloalkyl, substituted heterocycloalkyl, aryl, substituted aryl, heteroaryl, substituted heteroaryl, aralkyl, substituted aralkyl, hydroxyl, alkoxy, alkenyl, substituted alkenyl, alkynyl, substitute alkynyl, amide, azo, benzyl, substituted benzyl, carbonate, acyl, carboxylate, amide, sulfonamide, cyanate, ether, ester, halide, imine, isocyanide, isocyanate, ketone (oxy), sulfonyl, nitrile, nitro, nitroso, thiol, and substitute thiol (e.g., alkyl thiol).

[0142] In other embodiments, the ligand precursor includes a substituted 3-pyridine moiety and has a structure according to Formula V, wherein R.sub.13, R.sub.14, R.sub.15, and R.sub.16 are independently selected from the group consisting of H, amino (e.g., alkyl amino), alkyl, substituted alkyl, heteroalkyl, substituted heteroalkyl, cycloalkyl, substituted cycloalkyl, heterocycloalkyl, substituted heterocyloalkyl, aryl, substituted aryl, heteroaryl, substituted heteroaryl, aralkyl, substituted aralkyl, hydroxyl, alkoxy, alkenyl, substituted alkenyl, alkynyl, substitute alkynyl, amide, azo, benzyl, substituted benzyl, carbonate, acyl, carboxylate, amide, sulfonamide, cyanate, ether, ester, halide, imine, isocyanide, isocyanate, ketone (oxy), sulfonyl, nitrile, nitro, nitroso, thiol, and substituted thiol (e.g., alkyl thiol).

[0143] In other embodiments, the ligand precursor includes a substituted 2-pyridine moiety and has a structure according to Formula VI, wherein R.sub.17, R.sub.18, R.sub.19, and R.sub.20 are independently selected from the group consisting of H, amino (e.g., alkyl amino), alkyl, substituted alkyl, heteroalkyl, substituted heteroalkyl, cycloalklyl, substituted cycloalkyl, heterocycloalkyl, substituted heterocycloalkyl, aryl, substituted aryl, heteroaryl, substituted heteroaryl, aralkyl, substituted aralkyl, hydroxyl, alkoxy, alkenyl, substituted alkenyl, alkynyl, substitute alkynyl, amide, azo, benzyl, substituted benzyl, carbonate, acyl, carboxylate, amide, sulfonamide, cyanate, ether, ester, halide, imine, isocyanide, isocyanate, ketone (oxy), sulfonyl, nitrile, nitro, nitroso, thiol, and substituted thiol (e.g., alkyl thiol).

[0144] In other embodiments, the ligand precursor includes a substituted tetrazole moiety and has a structure according to Formula VII, wherein R.sub.21 is independently selected from the group consisting of H, amino (e.g., alkyl amino), alkyl, substituted alkyl, heteroalkyl, substituted heteroalkyl, cycloalkyl, substituted cycloalkyl, heterocycloalkyl, substituted heterocyloalkyl, aryl, substituted aryl, heteroaryl, substituted heteroaryl, aralkyl, substituted aralkyl, hydroxyl, alkoxy, alkenyl, substituted alkenyl, alkynyl, substitute alkynyl, amide, azo, benzyl, substituted benzyl, carbonate, acyl, carboxylate, amide, sulfonamide, cyanate, ether, ester, halide, imine, isocyanide, isocyanate, ketone (oxy), sulfonyl, nitrile, nitro, nitroso, thiol, and substituted thiol (e.g., alkyl thiol).

[0145] In other embodiments, the ligand precursor includes a substituted 1,2,3-triazole moiety and has a structure according to Formula VIII, wherein R.sub.22 is independently selected from the group consisting of H, amino (e.g., alkyl amino), alkyl, substituted alkyl, heteroalkyl, substituted heteroalkyl, cycloalkyl, substituted cycloalkyl, heterocycloalkyl, substituted heterocyloalkyl, aryl, substituted aryl, heteroaryl, substituted heteroaryl, aralkyl, substituted aralkyl, hydroxyl, alkoxy, alkenyl, substituted alkenyl, alkynyl, substitute alkynyl, amide, azo, benzyl, substituted benzyl, carbonate, acyl, carboxylate, amide, sulfonamide, cyanate, ether, ester, halide, imine, isocyanide, isocyanate, ketone (oxy), sulfonyl, nitrile, nitro, nitroso, thiol, and substituted thiol (e.g., alkyl thiol).

[0146] In other embodiments, the ligand precursor includes a substituted 1,2,4-triazole (1-N) moiety and has a structure according to Formula IX, wherein R.sub.22 and R.sub.23 are independently selected from the group consisting of H, amino (e.g., alkyl amino), alkyl substituted alkyl, heteroalkyl substituted heteroalkyl, cycloalkyl, substituted, cycloalkyl, heterocycloalkyl, substituted heterocyloalkyl, aryl, substituted aryl, heteroaryl, substituted heteroaryl aralkyl, substituted aralkyl hydroxyl, alkoxy, alkenyl, substituted alkenyl, alkynyl, substitute alkynyl, amide, azo, benzyl substituted benzyl, carbonate, acyl, carboxylate, amide, sulfonamide, cyanate, ether, ester, halide, imine, isocyanide, isocyanate, ketone (oxy), sulfonyl, nitrite, nitro, nitroso, thiol, and substituted thiol (e.g., alkyl thiol).

Transition Metals

[0147] The catalysts of the invention include at least one transition metal. In FIG. 5, exemplary transition metal salts that can be used to synthesize the pre-catalyst are presented. Exemplary transition metals include, but are not limited to, manganese, iron, cobalt, nickel, copper, and combinations thereof. In certain embodiments, metal salts are used in the formation of the pre-catalyst and may include a counteranion that may influence the eventual oxygen-activated catalyst structure and activity. Exemplary counteranions for the transition metal salts include, but are not limited to, fluoride, chloride, bromide, iodide, perchlorate, nitrate, sulfate, cyanide, thiocyanate, hydroxide, carboxylate, acetate, or acetylacetonate. Where appropriate, the transition metal salts used to synthesize the pre-catalysts may also contain waters of hydration.

[0148] In certain embodiments, the catalysts of the invention can contain more than one transition metal. FIG. 6 illustrates an alternative exemplary configuration of the post-synthetic grafted pre-catalyst illustrated in FIG. 2. In this example, more than one metal salt may be used yielding bi-metallic catalytic species.

[0149] A further illustrative example of the post-synthetic grafted pre-catalyst is shown in FIG. 7. In this example, more than one ligand precursor is used to synthesize the post-synthetic grafted pre-catalysts. Therefore, mono-functional, bi-functional, and tri-functional post-synthetic grafted catalysts are possible.

[0150] FIG. 8 illustrates an exemplary synthetic route to another example of self-assembled catalysts. In this example more than one ligand precursor is used to synthesize the self-assembled pre-catalysts. Therefore, mono-functional, bi-functional, and tri-functional self-assembled catalysts are possible. This example also illustrates that more than one metal salt may be used to synthesize the self-assembled pre-catalysts.

[0151] FIG. 9 illustrates two exemplary synthetic routes to silylate the surface of the oxygen-activated catalysts. Reagents used to silylate surfaces include, but are not limited to, hexamethyldisilazane. In one example, the hexamethyldisilazane reacts with the pre-catalyst prior to calcination. In another example, the silylation step occurs after calcination. Silylation of the surface may affect and enhance the oxygen-activated catalyst activity and selectivity. This class of catalysts is referred to as silylated oxygen-activated catalysts.

EXAMPLES

Example 1

Preparation of Catalysts by Post-Synthetic Grafting

A. Synthesis of Ligand Precursors

[0152] Ligand precursors can be synthesized using art recognized procedures, or using the procedures outlined below. It will be within the capabilities of a person of ordinary skill in the art to adapt the below procedures to prepare additional ligands, for example, those exemplary embodiments illustrated in FIG. 4.

(a) Synthesis of N-(3-propyltrimethoxysilane) imidazole (Ligand Precursor A)

[0153] To a solution of imidazole in dry toluene, 3-chloropropyltriethoxysilane was added and the mixture was refluxed overnight under a nitrogen atmosphere. The solvent was removed by rotatory evaporation under reduced pressure, and the product N-(3-propyltrimethoxysliane) imidazole was obtained as a transparent liquid after neutral column chromatography, eluting with hexane and ethyl ether (5:1). .sup.1H NMR(400 MHz, CDCl.sub.3): 7.53 (s, 1H), 7.07 (s, 1H), 6.93 (s, 1H), 3.96 (t, J=7.5 Hz, 2H), 3.82 (q, J=7.0 Hz, 6H), 1.90 (m, 2H), 1.23 (t, J=7.0 Hz, 9H), 0.57 (t, J=8.0 Hz, 2H); .sup.13C NMR (125 MHz, CDCl.sub.3): 7.2, 18.1, 24.8, 48.9, 58.2, 118.6, 129.0, 137.0.

(b) Synthesis of N-(3-propyltrimethoxysilane)-1,2,4triazole (Ligand Precursor B)

[0154] SOCl.sub.2 was added with stirring to DMF below ambient temperature. After stirring, to the solution of this mixture, was added slowly aqueous hydrazine hydrate in DMF. The mixture was stirred at ambient temperature for two days and a white precipitate of dimethylformamide azine dihydrochloride was collected by filtration and washed with DMF and Et.sub.2O.

[0155] To a solution of (3-triethoxysilyl)-propan-1-amine) in benzene was added the above dimethylformanhde-axine-dihydrochloride and TsOH and the mixture was heated. The product precipitated from solution. The supernatant was tritirated with diethyl ether affording further precipitate. The solids were collected and washed with hexanes and dried under vacuum to yield a waxy off white solid.

B. Preparation of Silica Matrix/Templates/Substrates

[0156] Silica substrates can be synthesized using art recognized methods, or using the procedures outlined below. It will be within the capabilities of a person of ordinary skill in the art to adapt the below procedures to prepare additional substrates.

(a) Preparation of SBA-15

[0157] P123 (commercially available) was dissolved in an aqueous solution of HCl. The resulting clear solution was then added to TEOS. The mixture was stirred at room temperature until a transparent solution appeared. After gently heating the solution, NaF was added. After stirring above ambient temperature for several days, the resulting powder was filtered off and the surfactant was removed by Soxhlet extraction over ethanol for 24 hours. After drying with heating under vacuum, SBA-15 was obtained.

C. Post-Synthetic Grafting of Silica Templates

[0158] To a suspension of SBA-15 in a suitable solvent (e.g., toluene) one or more ligand precursor was added. The mixture was typically refluxed and stirred (e.g., for about 24 hours). After filtration, the solid was washed with a suitable solvent (e.g., acetone and/or diethyl ether) and dried (e.g., at 120 C.) under vacuum to give a ligand-grafted silica template.

(a) Post-Synthetic Grafting of SBA With Ligand Precursors A and B

[0159] To a suspension of SBA in toluene, ligand precursor A and ligand precursor B were added. The mixture was refluxed and stirred. After filtration, the solid was washed and then dried with heating under vacuum to give a white powder.

(b) Post-Synthetic Grafting of SBA With Ligand Precursor A

[0160] To a suspension of SBA in toluene, ligand precursor A was added. The mixture was refluxed and stirred. After nitration, the solid was washed and then dried with heating under vacuum to give a white powder.

(b) Post-Synthetic Grafting of SBA With Ligand Precursor B

[0161] To a suspension of SBA in toluene, ligand precursor B was added. The mixture was refluxed and stirred. After filtration, the solid was washed and then dried with heating under vacuum to give a white powder.

D. Metal Impregnation

[0162] Grafted mesoporous silica and a transition metal salt (i.e., MX.sub.n) were combined in THF and heated to reflux. The solid was collected by filtration, washed with THF and water, and dried with heating under vacuum overnight.

E. Preparation of Oxygen-Activated Catalysts (Calcination)

[0163] The materials were calcinated at 700 C. for several hours under oxygen atmosphere in a tube furnace (Thermo Scientific).

F. Methane to Methanol Conversion and Testing

[0164] Catalytic reactions were carried out using a high pressure reactor. Catalyst was added to a borosilicate glass vial. A mixture of methane and oxygen in a ratio of 1:1 under a total pressure of 2-12 atm was passed through the high pressure reactor. The reactor was heated to 260 C. for 1-24 hours.

[0165] To rigorously demonstrate that the systems produced methanol and were in fact catalytic, detailed spectroscopic experiments were conducted including .sup.1H NMR of the reaction products as well as calibration of the product distribution, mass balance, and methane and oxygen consumption by GC-MS that was internally calibrated using internal standards and constructing calibration curves. .sup.1H NMR alone can be insufficient to make this determination as paramagnetic impurities may be present which would cause a shift in the observed resonance frequencies.

[0166] For NMR-analysis, after cooling down the reaction, the vial was rinsed with D.sub.2O and the solution was analyzed by .sup.1H NMR. For GC analysis, the reactor was coupled to a GC and the gas phase mixture was analyzed, and the retention times were compared to runs with pure standards. The yields and selectivity were calculated by integrating the GC peak areas and quantifying them against calibration curves constructed from pure standards.

[0167] Using the above procedures, the following exemplary catalysts were prepared and tested, and were found to be active:

[0168] 1. Post-synthetic grafted triazole silica impregnated with copper

[0169] 2. Post-synthetic grafted triazole silica impregnated with manganese

[0170] 3. Post-synthetic grafted triazole silica impregnated with copper and manganese

[0171] 4. Post-synthetic grafted imidazole silica impregnated with copper

[0172] 5. Post-synthetic grafted imidazole silica impregnated with manganese

[0173] 6. Post-synthetic grafted imidazole silica impregnated with copper and manganese

[0174] 7. Post-synthetic grafted imidazole-triazole silica impregnated with copper

[0175] 8. Post-synthetic grafted imidazole-triazole silica impregnated with manganese

[0176] 9. Post-synthetic grafted imidazole-triazole silica impregnated with copper and manganese

[0177] The following additional exemplary catalysts can be prepared using the above procedures:

[0178] 1. Post-synthetic grafted tetrazole silica impregnated with copper

[0179] 2. Post-synthetic grafted tetrazole silica impregnated with manganese

[0180] 3. Post-synthetic grafted tetrazole silica impregnated with copper and manganese

[0181] 4. Post-synthetic grafted pyrazole silica impregnated with copper

[0182] 5. Post-synthetic grafted pyrazole silica impregnated with manganese

[0183] 6. Post-synthetic grafted pyrazole silica impregnated with copper and manganese

[0184] 7. Post-synthetic grafted pyridine silica impregnated with copper

[0185] 8. Post-synthetic grafted pyridine silica impregnated with manganese

[0186] 9. Post-synthetic grafted pyridine silica impregnated with copper and manganese

[0187] Additional catalysts may be prepared by incorporating a transition metal other than copper or manganese (e.g., iron, cobalt, or nickel) into each of the above catalysts, e.g., instead of or in addition to copper or manganese.

Example 2

Preparation of Self-Assembled Silica Catalysis

A. Preparation of Self-Assembled Silica

[0188] In a typical preparation, a mixture of silylated ligand and tetraethyl orthosilate (TEOS) was added under stirring to a solution of n-hexadecylamine in a 55:45 EtOH (95%)-H.sub.2O mixture at 35 C. A white precipitate appears within some minutes. The reaction mixture was kept at slightly above ambient temperature for several hours. The solid was then filtered and n-hexadecylamine was removed by Soxhlet extraction. After drying with heating under vacuum, the self-assembly mesoporous silica material was isolated.

D. Metal Impregnation, Calcination and Testing

[0189] Self-assembled silica and a transition metal salt (e.g., MX.sub.n) were combined in THF and heated to reflux for several hours. The solid was collected by filtration and washed, and dried with heating under vacuum overnight. Calcination and testing was performed as outlined in Example 1.

[0190] The following catalysts were synthesized using the above procedures and were found to be active:

[0191] 1. Self-assembled imidazole silica impregnated with copper

[0192] 2. Self-assembled imidazole silica impregnated with manganese

[0193] 3. Self-assembled imidazole silica impregnated with copper and manganese

[0194] The following additional catalysts can be prepared using the above procedures:

[0195] 1. Self-assembled tetrazole silica impregnated with copper

[0196] 2. Self-assembled tetrazole silica impregnated with manganese

[0197] 3. Self-assembled tetrazole silica impregnated with copper and manganese

[0198] 4. Self-assembled pyrazole silica impregnated with copper

[0199] 5. Self-assembled pyrazole silica impregnated with manganese

[0200] 6. Self-assembled pyrazole silica impregnated with copper and manganese

[0201] 7. Self-assembled pyridine silica impregnated with copper

[0202] 8. Self-assembled pyridine silica impregnated with manganese

[0203] 9. Self-assembled pyridine silica impregnated with copper and manganese

[0204] 10. Self-assembled triazole silica impregnated with copper

[0205] 11. Self-assembled triazole silica impregnated with manganese

[0206] 12. Self-assembled triazole silica impregnated with copper and manganese

[0207] Additional catalysts may be prepared by incorporating a transition metal other than copper or manganese (e.g., iron, cobalt or nickel) into each of the above catalysts, e.g., instead of or in addition to copper or manganese.

[0208] As one of ordinary skill in the art will appreciate, various changes, substitutions and alterations could be made or otherwise implemented without departing from the principles of the invention. Accordingly, the scope of the invention should be determined by the following claims and their legal equivalents.