Patent ID: 7179366

Claim:
A catalyst containing at least one group VIII element and at least molybdenum and/or tungsten, said elements being present at least in part in the catalyst in the dry state in the form of at least one heteropolyanion having a structural formula M x AB 6 O 24 H 6 C (3-2x) .tH 2 O(I);M x AB 6 O 24 H 6 C (4-2x) .tH 2 O(I′); M x A 2 B 10 O 38 H 4 C (6-2x) .tH 2 O; M x A 2 B 10 O 38 H 4 C (8-2x) .tH 2 O(I′″); or M x A 2 B 10 O 38 H 4 C (7-2x) .tH 2 O(I″″); wherein M is cobalt, nickel, iron, copper, zinc, or mixtures thereof, A is an element of group VIII of the periodic table for formulae I and I′ or one or elements of group VIII of the periodic table for formulae I″, I′″, and I″″, B is molybdenum and/or tungsten and C is an H + ion and/or a (NR 1 R 2 R 3 R 4 ) + type ammonium ion, wherein R 1 , R 2 , R 3 and R 4 , may be identical or different, and correspond either to a hydrogen atom or to an alkyl group, cesium, potassium, sodium or mixtures thereof, t is a number from 0 to 15 and x is 0 to 3/2 in (I), 0 to 2 in (I′), 0 to 3 in (I″), 0 to 4 in (I′″) and 0 to 7/2 in (I″″) and wherein the number of bonds connecting the group VIII element or elements with the molybdenum and/or tungsten having a length of 3.6 angstroms or less is greater than 2.