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Catalytic structures are provided comprising octahedral tunnel lattice manganese oxides ion-exchanged with metal cations or mixtures thereof. The structures are useful as catalysts for the oxidation of alkanes and may be prepared by treating layered manganese oxide under highly acidic conditions, op

Catalytic structures are provided comprising octahedral tunnel lattice manganese oxides ion-exchanged with metal cations or mixtures thereof. The structures are useful as catalysts for the oxidation of alkanes and may be prepared by treating layered manganese oxide under highly acidic conditions, optionally drying the treated product, and subjecting it to ion exchange.

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1. A process for the oxidation of an alkane comprising contacting the alkane with oxygen in the presence of a catalyst system comprising a 2×2 octahedral manganese oxide structure ion-exchanged with one or more metal cations. 2. The process according to claim 1 wherein the contacting is performed at

1. A process for the oxidation of an alkane comprising contacting the alkane with oxygen in the presence of a catalyst system comprising a 2×2 octahedral manganese oxide structure ion-exchanged with one or more metal cations. 2. The process according to claim 1 wherein the contacting is performed at a pressure of from 1 to 50 bar, and/or a temperature of from 300° C. to 550° C., and/or a contact time between the reaction mixture and the catalyst of from 0.01 sec to 100 sec, and/or a space velocity of from 50 to 50,000 h−1. 3. The process according to claim 1 in which the alkane comprises ethane, propane or butane. 4. The process according to claim 1 in which the oxygen is provided solely by the lattice oxygen of the manganese oxide. 5. The process according to claim 1 in which oxygen is provided as molecular oxygen. 6. The process according to claim 1 in which the alkane is propane and the reaction mixture contains, per mole of propane, from 0.01 to 2.0 moles of additional molecular oxygen and from 0 to 4.0 moles of water in the form of steam. 7. The process according to claim 1 in which the metal cation is vanadium or molybdenum. 8. The process according to claim 1 in which the metal cation is a mixture of metal cations comprising as essential components, Mo, V, Te, and X wherein X is at least one element selected from the group consisting of niobium, tantalum, tungsten, titanium, aluminium, zirconium, chromium, manganese, iron, ruthenium, cobalt, rhodium, nickel, palladium, platinum, antimony, bismuth, boron, indium and cerium. 9. The process according to claim 1 in which the catalyst system comprises metal cations that are non-homogeneously ion-exchanged into the manganese oxide. 10. The process of claim 1 wherein the 2×2 octahedral manganese oxide structure is a 2×2 octahedral manganese oxide structure ion-exchanged with one or more metal cations in which the metal cation component comprises, as essential components, Mo, V, Te, and X wherein X is at least one element selected from the group consisting of niobium, tantalum, tungsten, titanium, aluminium, zirconium, chromium, manganese, iron, ruthenium, cobalt, rhodium, nickel, palladium, platinum, antimony, bismuth, boron, indium and cerium. 11. The process of claim 10 wherein the 2×2 octahedral manganese oxide structure has been calcined. 12. The process of claim 10 wherein the ion exchanged metal cations are non-homogeneously distributed in the manganese oxide. 13. The process of claim 10 wherein the metal cations are more concentrated in a surface zone of the manganese oxide than elsewhere in the structure. 14. The process of claim 1 wherein the 2×2 octahedral manganese oxide structure ion-exchanged with one or more metal cations has the general formula: [A16-aMaMn16-aO32]n  (I)in which:A represents a tunnel metal cation in oxidation state +1, +2, +3, +4 or +5, wherein the metal of the cation is selected from the transition metals (Groups 3-12) and metals of Group 1 and Group 2 of the IUPAC Periodic Table of the Elements (1 Nov. 2004);M represents a lattice metal cation in oxidation state +1, +2, +3, +4 or +5, wherein the metal of the cation is a transition metal (Group 3-12);Mn represents the transition metal, manganese;a is a number equal to or greater than zero and less than 16; andn is a number equal to or greater than 1. 15. The process of claim 14 where the 2×2 octahedral manganese oxide structure comprises K16+1 Mn16+3 O32, K8+1 Mn8+3 Mn8+4 O32, or Mn16+4 O32. 16. The process of claim 14 wherein the tunnel metal cations are non-homogeneously distributed in the manganese oxide. 17. The process of claim 14 wherein the tunnel metal cations are more concentrated in a surface zone of the manganese oxide than elsewhere in the structure. 18. The process of claim 1 wherein the 2×2 octahedral manganese oxide structure containing metal cations is produced by a process comprising treating a layered manganese oxide under highly acidic conditions comprising a pH not greater than 5, to rearrange the oxide to the 2×2 octahedral structure containing free protons, optionally drying the proton-containing structure, and ion exchanging the proton-containing structure with metal cations. 19. The process of claim 1 wherein the 2×2 octahedral manganese oxide structure containing metal cations is produced by a process comprising mixing a solution of basic hydrogen peroxide and a solution of manganese nitrate hydrate at a basic pH to form the layered manganese oxide, treating the layered manganese oxide with acid to reduce the pH to the range of from 0.1 to 3 and to rearrange the layered oxide to form the octahedral 2×2 structure, drying, and treating the resulting octahedral 2×2 manganese oxide structure with a solution of metal ions to perform an ion exchange reaction with protons in the 2×2 octahedral structure. 20. The process according to claim 1 in which the ion-exchanged product material is calcined to convert the ion-exchanged product material fully into the ion-exchanged product material's oxide form. 21. The process according to claim 1 in which the metal cations are redox active. 22. The process according to claim 1 in which the ion exchange reaction of the proton containing structure with metal cations is performed at a pH in the range of from 1 to 10. 23. The process according to claim 1 in which the ion exchange reaction is performed at a temperature of from 30 to 100° C. 24. The process according to claim 1 in which the metal of the metal cations is selected from the group consisting of molybdenum, vanadium, gallium and palladium. 25. The process according to claim 1 in which the metal cations comprise, as essential components, a mixture of metals comprising Mo, V, Te and X wherein X is at least one element selected from the group consisting of niobium, tantalum, tungsten, titanium, aluminium, zirconium, chromium, manganese, iron, ruthenium, cobalt, rhodium, nickel, palladium, platinum, antimony, bismuth, boron, indium and cerium. 26. The process according to claim 1 in which the metal cation is a mixture of metal cations comprising as essential components, Mo, V, Te, and X wherein X is at least one element selected from the group consisting of niobium, tantalum, tungsten, and titanium. 27. The process of claim 1 in which the pH is 2 or less. 28. The process of claim 1 in which the pH is 0.1 to 2. 29. The process of claim 1 in which the pH is 0.5 to 1.5. 30. The process of claim 1 in which the pH is 0.1 to 1.1. 31. A process for the oxidation of an alkane comprising contacting the alkane with oxygen in the presence of a catalyst system comprising a 2×2 octahedral manganese oxide structure ion-exchanged with one or more metal cations, in which the metal cations comprise, as essential components, a mixture of metals comprising Mo, V, Te, and X wherein X is at least one element selected from the group consisting of niobium, tantalum, tungsten, titanium, aluminium, zirconium, chromium, manganese, iron, ruthenium, cobalt, rhodium, nickel, palladium, platinum, antimony, bismuth, boron, indium, and cerium.