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We claim: 1. A process for preparing an annular unsupported catalyst having at least one member selected from the group consisting of a curved and uncurved top surface thereof, whose active composition has a stoichiometry of the general formula I Mo12BiaFebX1cX2dX3eX4fOn (I) where X1=at least one element selected from the group consisting of nickel and cobalt, X2=at least one element selected from the group consisting of thallium, an alkali metal and an alkaline earth metal, X3=at least one element selected from the group consisting of...
We claim: 1. A process for preparing an annular unsupported catalyst having at least one member selected from the group consisting of a curved and uncurved top surface thereof, whose active composition has a stoichiometry of the general formula I Mo12BiaFebX1cX2dX3eX4fOn (I) where X1=at least one element selected from the group consisting of nickel and cobalt, X2=at least one element selected from the group consisting of thallium, an alkali metal and an alkaline earth metal, X3=at least one element selected from the group consisting of zinc, phosphorus, arsenic, boron, antimony, tin, cerium, lead and tungsten, X4=at least one element selected from the group consisting of silicon, aluminum, titanium and zirconium, a=from 0.2 to 5, b=from 0.01 to 5, c=from 0 to 10, d=from 0 to 2, e=from 0 to 8, f=from 0 to 10 and n=a number which is determined by the valency and frequency of the elements in I other than oxygen, or a stoichiometry of the general formula II [Y1a′Y2b′Ox′]p[Y3c′Y4d′Y5e′Y6f′Y7g′Y2h′Oy′]q (II) where Y1=only bismuth or bismuth and at least one element selected from the group consisting of tellurium, antimony, tin and copper, Y2=molybdenum or molybdenum and tungsten, Y3=at least one element selected from the group consisting of an alkali metal, thallium and samarium, Y4=at least one element selected from the group consisting of an alkaline earth metal, nickel, cobalt, copper, manganese, zinc, tin, cadmium and mercury, Y5=iron or iron and at least one element selected from the group consisting of vanadium, chromium and cerium, Y6=at least one element selected from the group consisting of phosphorus, arsenic, boron and antimony, Y7=at least one element selected from the group consisting of a rare earth metal, titanium, zirconium, niobium, tantalum, rhenium, ruthenium, rhodium, silver, gold, aluminum, gallium, indium, silicon, germanium, lead, thorium and uranium, a′=from 0.01 to 8, b′=from 0.1 to 30, c′=from 0 to 4, d′=from 0 to 20, e′ is from >0 to 20, f′=from 0 to 6, g′=from 0 to 15, h′=from 8 to 16, x′, y′=numbers which are determined by the valency and frequency of the elements in II other than oxygen and p, q=numbers whose p/q ratio is from 0.1 to 10, and whose annular geometry, without taking into account any existing curvature of the top surface, has a length L of from 2 to 11 mm, an external diameter E of from 2 to 11 mm and a wall thickness W of from 0.75 mm to 1.75 mm, comprising generating a finely divided shapeable mixture from sources of the elemental constituents of the active composition and, optionally after adding at least one member selected from the group consisting of shaping and reinforcing assistants, compressing this mixture to form annular shaped unsupported catalyst precursor bodies whose top surfaces are at least one member selected from the group consisting of curved and uncurved, and converting these to the annular unsupported catalysts by thermally treating at elevated temperature, wherein the side crushing strength of the annular shaped unsupported catalyst precursor bodies is ≧12 N and ≦23 N, and wherein the annular geometry additionally fulfills the condition L/E=from 0.3 to 0.7. 2. A process as claimed in claim 1, wherein the side crushing strength of the annular shaped unsupported catalyst precursor bodies is from ≧13 N to ≦22 N. 3. A process as claimed in claim 1, wherein the side crushing strength of the annular shaped unsupported catalyst precursor bodies is from ≧15 N to ≦20 N. 4. A process as claimed in any of claims 1 to 3, wherein the annular geometry additionally fulfills the condition L/E=from 0.4 to 0.6. 5. A process as claimed in any of claims 1 to 3, wherein the annular geometry additionally fulfills the internal diameter I/external diameter E ratio=from 0.5 to 0.8. 6. A process as claimed in any of claims 1 to 3, wherein the annular geometry additionally fulfills the internal diameter I/external diameter E ratio=from 0.6 to 0.7. 7. A process as claimed in any of claims 1 to 3, wherein L=from 2 to 6 mm. 8. A process as claimed in any of claims 1 to 3, wherein L=from 2 to 4 mm. 9. A process as claimed in any of claims 1 to 3, wherein E=from 4 to 8 mm. 10. A process as claimed in any of claims 1 to 3, wherein E=from 5 to 7 mm. 11. A process as claimed in any of claims 1 to 3, wherein the wall thickness of the annular geometry is from 1 to 1.5 mm. 12. A process as claimed in any of claims 1 to 3, wherein the annular geometry, expressed as E×L×I, is an annular geometry from the group consisting of a) 5 mm×3 mm×2 mm, b) 5 mm×3 mm×3 mm, c) 5.5 mm×3 mm×3.5 mm, d) 6 mm×3 mm×4 mm, e) 6.5 mm×3 mm×4.5 mm and f) 7 mm×3 mm×5 mm. 13. A process as claimed in any of claims 1 to 3, wherein the active composition has a stoichiometry of the general formula I wherein a=from 0.4 to 2; b=from 2 to 4; c=from 3 to 10; d=from 0.02 to 2; e=from 0 to 5 and f=from 0.5 to 10. 14. A process as claimed in any of claims 1 to 3, wherein the active composition has a stoichiometry of the general formula I wherein X1=Co; X2=at least one element selected from the group consisting of K, Cs and Sr; X3=at least one element selected from the group consisting of Zn and P and X4=Si. 15. A process as claimed in any of claims 1 to 3, wherein the active composition has a stoichiometry of the general formula II and has three-dimensional regions of the chemical composition Y1a′Y2b′Ox′ which are delimited from their local environment owing to their different composition from their local environment and whose largest diameter is from 1 nm to 100 μm. 16. A process as claimed in any of claims 1 to 3, wherein Y1=Bi. 17. A process as claimed in any of claims 1 to 3, wherein the annular shaped unsupported catalyst precursor body is thermally treated at temperatures which exceed the temperature of 350° C. and do not exceed the temperature of 650° C. 18. A process as claimed in any of claims 1 to 3, wherein the thermal treatment is effected on a belt calciner. 19. A process as claimed in any of claims 1 to 3, wherein said compressing is carried out with a tableting machine or an extrusion reshaping machine. 20. An annular unsupported catalyst having at least one member selected from the group consisting of a curved and uncurved top surface thereof, whose active composition has a stoichiometry of the general formula I Mo12BiaFebX1cX2dX3eX4fOn (I) where X1=at least one element selected from the group consisting of nickel and cobalt, X2=at least one element selected from the group consisting of thallium, an alkali metal and an alkaline earth metal, X3=at least one element selected from the group consisting of zinc, phosphorus, arsenic, boron, antimony, tin, cerium, lead and tungsten, X4=at least one element selected from the group consisting of silicon, aluminum, titanium and zirconium, a=from 0.2 to 5, b=from 0.001 to 5, c=from 0 to 10, d=from 0 to 2, e=from 0 to 8, f=from 0 to 10 and n=a number which is determined by the valency and frequency of the elements in I other than oxygen, or a stoichiometry of the general formula II [Y1a′Y2b′Ox′]p[Y3c′Y4d′Y5e′Y6f′Y7g′Y2h′Oy′]q (II) where Y1=only bismuth or bismuth and at least one element selected from the group consisting of tellurium, antimony, tin and copper, Y2=molybdenum or molybdenum and tungsten, Y3=at least one element selected from the group consisting of an alkali metal, thallium and samarium, Y4=at least one element selected from the group consisting of an alkaline earth metal, nickel, cobalt, copper, manganese, zinc, tin, cadmium and mercury, Y5=iron or iron and at least one element selected from the group consisting of vanadium, chromium and cerium, Y6=at least one element selected from the group consisting of phosphorus, arsenic, boron and antimony, Y7=at least one element selected from the group consisting of a rare earth metal, titanium, zirconium, niobium, tantalum, rhenium, ruthenium, rhodium, silver, gold, aluminum, gallium, indium, silicon, germanium, lead, thorium and uranium, a′=from 0.01 to 8, b′=from 0.1 to 30, c′=from 0 to 4, d′=from 0 to 20, e′ is from >0 to 20, f′=from 0 to 6, g′=from 0 to 15, h′=from 8 to 16, x′, y′=numbers which are determined by the valency and frequency of the elements in II other than oxygen and p, q=numbers whose p/q ratio is from 0.1 to 10, and whose annular geometry, without taking into account any existing curvature of the top surface, has a length L of from 2 to 11 mm, an external diameter E of from 2 to 11 mm and a wall thickness W of from 0.75 mm to 1.75 mm, and wherein the specific surface area S is from 5 to 20 m2/g and the total pore volume V is from 0.1 to 1 cm3/g, the different pore diameters contributing to V as follows: pores having a diameter in the range from <0.03 μM: ≦5% by volume; pores having a diameter in the range from 0.03 to <0.1 μm: ≦25% by volume; pores having a diameter in the range from >0.1 to <1 μm: ≧70% by volume and pores having a diameter in the range from ≧1 to ≦10 μm: ≦10% by volume, and wherein the annular geometry additionally fulfills the condition L/E=from 0.3 to 0.7. 21. An annular unsupported catalyst as claimed in claim 20 where S=from 5 to 10 m2/g. 22. An annular unsupported catalyst as claimed in claim 20 or 21 where V=from 0.2 to 0.4 cm3/g. 23. An annular unsupported catalyst as claimed in claim 20 or 21, wherein the different pore diameters contribute to V as follows: pores having a diameter in the range <0.03 μm: ≧0% by volume and ≦5% by volume; pores having a diameter in the range ≧0.03 to ≦0.1 μm: ≧3 and ≦20% by volume; pores having a diameter in the range >0.1 to <1 μm: ≧75 and ≦95% by volume and pores having a diameter in the range ≧1 to ≦10 μm: ≧0 and ≦5% by volume. 24. An annular unsupported catalyst as claimed in claim 20 or 21, wherein the pore diameter dmax making the greatest contribution to the total pore volume V is from 0.3 to 0.8 μM. 25. An annular unsupported catalyst as claimed in claim 20 or 21 whose side crushing strength is from 5 to 13 N. 26. An annular unsupported catalyst as claimed in claim 20 or 21 whose ratio of apparent mass density to true mass density is >0.55. 27. An annular unsupported catalyst as claimed in claim 22, wherein the different pore diameters contribute to V as follows: pores having a diameter in the range <0.03 μm: ≧0% by volume and ≦5% by volume; pores having a diameter in the range ≧0.03 to ≦0.1 μm: ≧3 and ≦20% by volume; pores having a diameter in the range >0.1 to <1 μm: ≧75 and ≦95% by volume and pores having a diameter in the range ≧1 to ≦10 μm: ≧0 and ≦5% by volume. 28. An annular unsupported catalyst as claimed in claim 22, wherein the pore diameter dmax making the greatest contribution to the total pore volume V is from 0.3 to 0.8 μm. 29. An annular unsupported catalyst as claimed in claim 22 whose side crushing strength is from 5 to 13 N. 30. An annular unsupported catalyst as claimed in claim 22 whose ratio of apparent mass density to true mass density is >0.55. 31. An annular shaped unsupported catalyst precursor body which can be converted by thermal treatment at elevated temperature to an annular unsupported catalyst having at least one member selected from the group consisting of a curved and uncurved top surface thereof, whose active composition has a stoichiometry of the general formula I Mo12BiaFebX1cX2dX3eX4fOn (I) where X1=at least one element selected from the group consisting of nickel and cobalt, X2=at least one element selected from the group consisting of thallium, an alkali metal and an alkaline earth metal, X3=at least one element selected from the group consisting of zinc, phosphorus, arsenic, boron, antimony, tin, cerium, lead and tungsten, X4=at least one element selected from the group consisting of silicon, aluminum, titanium and zirconium, a=from 0.2 to 5, b=from 0.01 to 5, c=from 0 to 10, d=from 0 to 2, e=from 0 to 8, f=from 0 to 10 and n=a number which is determined by the valency and frequency of the elements in I other than oxygen, or a stoichiometry of the general formula II [Y1a′Y2b′Ox′]p[Y3c′Y4d′Y5e′Y6f′Y7g′Y2h′Oy′]q (II) where Y1=only bismuth or bismuth and at least one element selected from the group consisting of tellurium, antimony, tin and copper, Y2=molybdenum or molybdenum and tungsten, Y3=at least one element selected from the group consisting of an alkali metal, thallium and samarium, Y4=at least one element selected from the group consisting of an alkaline earth metal, nickel, cobalt, copper, manganese, zinc, tin, cadmium and mercury, Y5=iron or iron and at least one element selected from the group consisting of vanadium, chromium and cerium, Y6=at least one element selected from the group consisting of phosphorus, arsenic, boron and antimony, Y7=at least one element selected from the group consisting of a rare earth metal, titanium, zirconium, niobium, tantalum, rhenium, ruthenium, rhodium, silver, gold, aluminum, gallium, indium, silicon, germanium, lead, thorium and uranium, a′=from 0.01 to 8, b′=from 0.1 to 30, c′=from 0 to 4, d′=from 0 to 20, e′ is from >0 to 20, f′=from 0 to 6, g′=from 0 to 15, h′=from 8 to 16, x′, y′=numbers which are determined by the valency and frequency of the elements in II other than oxygen and p, q=numbers whose p/q ratio is from 0.1 to 10, and whose annular geometry, without taking into account any existing curvature of the top surface, has a length L of from 2 to 11 mm, an external diameter E of from 2 to 11 mm and a wall thickness W of from 0.75 mm to 1.75 mm, and which can be obtained by generating a finely divided, shapeable mixture from sources of the elemental constituents of the active composition and, optionally after adding at least one member selected from the group consisting of shaping and reinforcing assistants, compressing this mixture to form an annular shaped unsupported catalyst precursor body whose top surfaces are at least one of curved and uncurved in such a way that its side crushing strength is ≧12 N ands ≦23 N, and wherein the annular geometry additional fulfills the condition L/E=from 0.3 to 0.7. 32. A process for preparing acrolein and/or methacrolein by heterogeneously catalyzed partial gas phase oxidation of propene, isobutene and/or tertbutanol, wherein the catalyst for the gas phase oxidation is an annular unsupported catalyst as claimed in claim 20. 33. A process for preparing acrolein and/or methacrolein by heterogeneously catalyzed partial gas phase oxidation of propene, isobutene and/or tertbutanol, wherein the catalyst for the gas phase oxidation is an annular unsupported catalyst obtained by a process as claimed in claim 1.
