Multimetal oxides

A process for preparing a mixture, comprising:

• mixing a first multimetal oxide together with a second multimetal oxide, wherein said first multimetal oxide is a mulitmetal oxide of the formula I
• Mo12−a−b−cVaM1bM2cOx (I),
• where
• M1 is W and/or Nb,
• M2 is Ti, Zr, Hf, Ta, Cr, Si and/or Ge,
• a is from 0.1 to 6,
• b is from 0 to 6,
• c is from 0 to 6,
• with the proviso that a+b+c is from 0.1 to 6, and
• x is a number which is determined by the valency and frequency of the elements in I other than oxygen,
• whose three-dimensional atomic arrangement obtained using CuKα radiation (λ=1.54178 Å) gives all X-ray powder diffraction spectrum (the intensity A of the diffracted X-rays plotted as a function of twice the diffraction angle (2⊖)) which contains, in the 2⊖ range from 5 to 50°, at least the following characteristic diffraction lines A1, A3, A5, A9 and A10, but at most the following diffraction lines A1 to A10:
• X-ray diffraction line 2θ(°) A1 8.3 ± 0.7 A2 14.4 ± 0.7 A3 22.3 ± 0.2 A4 23.5 ± 0.7 A5 27.2 ± 0.4 A6 32.0 ± 0.8 A7 34.8 ± 0.6 A8 38.7 ± 0.5 A9 45.4 ± 0.4 A10 48.8 ± 0.4
• and wherein said second multimetal oxide is a multimetal oxide of the formula II
• M312CudHeOy (II),
• where
• M3 is Mo, W, V, Nb or Ta,
• d is from 4 to 30,
• e is from 0 to 20 and
• y is a number which is determined by the valency and frequency of the elements in II other than oxygen.

A mixture comprising a first multimetal oxide I and a second multimetal oxide II, wherein said first multimetal oxide is a mulitmetal oxide of the formula I

• Mo12−a−b−cVaM1bM2cOx (I),
• where
• M1 is W and/or Nb,
• M2 is Ti, Zr, Hf, Ta, Cr, Si and/or Ge,
• a is from 0.1 to 6,
• b is from 0 to 6,
• c is from 0 to 6,
• with the proviso that a+b+c is from 0.1 to 6, and
• x is a number which is determined by the valency and frequency of the elements in I other than oxygen,
• whose
• three-dimensional atomic arrangement obtained using CuKα radiation (λ=1.54178 Å) gives an X-ray powder diffraction spectrum (the intensity A of the diffiacted X-rays plotted as a function of twice the diffraction angle (2⊖)) which contains, in the 2⊖ range from 5 to 50°, at least the following characteristic diffraction lines A1, A3, A5, A9 and A10, but at most the following diffraction lines A1 to A10:
• X-ray diffraction line 2⊖ (°) A1 8.3 ± 0.7 A2 14.4 ± 0.7 A3 22.3 ± 0.2 A4 23.5 ± 0.7 A5 27.2 ± 0.4 A6 32.0 ± 0.8 A7 34.8 ± 0.6 A8 38.7 ± 0.5 A9 45.4 ± 0.4 A10 48.8 ± 0.4
• and said second multimetal oxide is a multimetal oxide of the formula II
• M312CudHeOy (II),
• where
• M3 is Mo, W, V, Nb or Ta,
• d is from 4 to 30,
• e is from 0 to 20 and
• y is a number which is determined by the valency and frequency of the elements in II other than oxygen.

A multimetal oxide material having at least two phases and of the formula III

• {A}p{B}q (III),
• wherein
• A=(Mo12−a−b−cVaM1bM2cOx)·(12/(12−a−b−c)) (active phase),
• B=M312CudHeOy (promoter phase),
• M1 is W or Nb,
• M2 is Ti, Zr, Hf, Ta, Cr, Si or Ge,
• a is from 0.1 to 6,
• b is from 0 to 6,
• c is from 0 to 6,
• with the proviso that a+b+c is from 0.1 to 6.
• x is a number which is determined by the valency and frequency of the elements in A other than oxygen,
• M3 is Mo, W, V, Nb or Ta,
• d is from 4 to 30,
• e is from 0 to 20,
• y is a number which is determined by the valency and frequency of the elements in B other than oxygen,
• p and q are numbers other than zero, whose ratio p/q is from 160:1 to 1:1,
• which contains the moiety {A}p in the form of three-dimensional regions A which are delimited from their local environment owing to their chemical composition differing from their local environment and are of the chemical composition
• Mo12−a−b−cVaM1bM2cOx A
• and the moiety {B}q in the form of three dimensional regions B which are delimited from their local environment owing to their chemical composition differing from their local environment and are of the chemical composition
• M312CudHeOy B
• where the regions A and B are distributed relative to one another as in a mixture of finely divided A and finely divided B and a three-dimensional atomic arrangement of the regions A is that of the multimetal oxide Mo8.54V2.47W0.99O33.35 which is obtained as follows:
• 33.746 kg of ammonium heptamolybdate hydrate (MoO3 content:
• 81.8% by weight, ideal composition:
• (NH4)6Mo7O24.4 H2O), 6.576 kg of ammonium metavanadate (V2O5 content:
• 76.5% by weight, ideal composition:
• NH4VO3), 5.764 kg of ammonium paratungstate hydrate (WO3 content:
• 89.0% by weight, ideal composition:
• (NH4)10W12O41.7 H2O) and 7.033 kg of ammonium acetate (CH3COONH4 content:
• 97.0% by weight, ideal composition:
• CH3COONH4) are dissolved in succession in the stated order in 250 l of water at 90° C. while stirring;
• the resulting yellow to orange solution is cooled to 80° C. and spray-dried at an inlet temperature of 300° C. and an outlet temperature of 110° C.;
• 800 g of the spray powder obtained are kneaded in a kneader (type LUK 2.5 from Werner and Pfleiderer, 7000 Stuttgart, Germany) having an effective volume of 2.5 l, with the addition of 250 g of water, for 1 hour;
• of the 250 g of water, 180 g are added within the first 10 minutes of kneading and 70 g within the remaining 50 minutes of kneading;
• the resulting kneaded product is dried for 15 hours at 110° C. and then forced through a sieve having a mesh size of 5 mm;
• 100 g of the resulting granules are then calcined in a horizontal rotary kiln with an isothermally heated quartz bulb volume of 1 l and a rotary speed of 12 revolutions per minute, the calcination conditions being as follows:
• 1st step:
• the granules used are continuously heated from 25 to 275° C. within 50 minutes;
• 2nd step:
• the granules used are continuously heated from 275 to 325° C. within 30 minutes;
• 3rd step:
• the granules used are kept at 325° C. for 4 hours;
• 4th step:
• the granules used are continuously heated from 325 to 400° C. within 30 minutes;
• 5th step:
• the granules used are kept at 400° C. for 10 minutes;
• the external heating of the rotary kiln is then switched off and the latter is cooled by blowing on surrounding air from the outside;
• the granules used cool to 25° C. in the course of 5 hours;
• during the individual calcination steps, gas mixtures which have the following compositions (standard temperature and pressure conditions (S.T.P.) 1 atm, 25° C.) flow through the interior of the rotary kiln, parallel to the axis of rotation:
• 1st step, 2nd step and 3rd step:
• 3.6 l (S.T.P.)/h or air, 1.5 l (S.T.P.)/h of NH3 and 44.9 l (S.T.P.)/h of N2 (total gas flow:
• 50 l (S.T.P.)/h);
• 4th step, 5th step and cooling phase:
• 3.6 l (S.T.P.)/h of air and 44.9 l (S.T.P.)/h of N2 (total gas flow:
• 48.5 l (S.T.P.)/h).

A multiphase composition, comprising homogeneously distributed regions having a maximum diameter of from >0 to 300 μm of a mulitmetal oxide of the formula I

• Mo12−a−b−cVaM1bM2cOx (I),
• where
• M1 is W and/or Nb,
• M2 is Ti, Zr, Hf, Ta, Cr, Si and/or Ge,
• a is from 0.1 to 6,
• b is from 0 to 6,
• c is from 0 to 6,
• with the proviso that a+b+c is from 0.1 to 6, and
• x is a number which is determined by the valency and frequency of the elements in I other than oxygen,
• whose three-dimensional atomic arrangement obtained using CuKα radiation (λ=1.54178 Å) gives an X-ray powder diffraction spectrum (the intensity A of the diffracted X-rays plotted as a function of twice the diffraction angle (2⊖)) which contains, in the 2⊖ range from 5 to 50°, at least the following characteristic diffraction lines A1, A3, A5, A9 and A10, but at most the following diffraction lines A1 to A10.
• X-ray diffraction line 2θ(°) A1 8.3 ± 0.7 A2 14.4 ± 0.7 A3 22.3 ± 0.2 A4 23.5 ± 0.7 A5 27.2 ± 0.4 A6 32.0 ± 0.8 A7 34.8 ± 0.6 A8 38.7 ± 0.5 A9 45.4 ± 0.4 A10 48.8 ± 0.4