Catalyst based on a group VI metal and a group VIII metal at least partially present in the form of heteropolyanions in the oxide precursor

摘要

A catalyst contains 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 with formula M_xAB₆O₂₄H₆C_(3-2x), tH₂O; M_xAB₆O₂₄H₆C_(4-2x), tH₂O; M_xA₂B₁₀O₃₈H₄C_(6-2x), tH₂O; M_xA₂B₁₀O₃₈H₄C_(8-2x), tH₂O; or M_xA₂B₁₀O₃₈H₄C_(7-2x), tH₂O, in which M is cobalt and/or nickel and/or iron and/or copper and/or zinc, A is one or two elements from group VIII of the periodic table, B is molybdenum and/or tungsten and C is an H⁺ ion and/or a (NR₁R₂R₃R₄)⁺ type ammonium ion, in which R₁, R₂, R₃ and R₄, which may be identical or different, correspond either to a hydrogen atom or to an alkyl group and/or caesium and/or potassium and/or sodium, t is a number between 0 and 15 and x takes a value in the range 0 to 4 depending on the formula.