Method for the hydrothermal preparation of molybdenum-bismuth-cobalt-iron-based mixed oxide catalysts

A process for preparing a multielement oxide catalyst, the process comprising:

• providing a mixture of an aqueous solution and/or an aqueous suspension of precursor compounds of elements present in the multielement oxide catalyst in an amount to achieve stoichiometry thereof,
• setting a pH of the mixture obtained from the providing to a value between 5.5 and 8.5,
• reacting the mixture comprising the precursor compounds obtained from the setting under solvothermal reaction conditions in an autoclave at a temperature of from 100° C. to 600° C. to form the multielement oxide catalyst, and
• separating the multielement oxide catalyst from the aqueous solution and/or suspension,
• wherein the multielement oxide catalyst is of formula (I):
• MoaBibCocFedNigXfX′gX″hX′″iX″″jOx (I),
• wherein
• X is W or P,
• X′ is Li, K, Na, Rb, Cs, Mg, Ca, Ba or Sr,
• X″ is Ce, Mn, Cr or V,
• X″′ is Nb, Se, Te, Sm, Gd, La, Y, Pd, Pt, Ru, Ag or Au,
• X″″ is Si, Al, Ti or Zr,
• a is 12,
• b is 1 to 4,
• c is 4 to 10,
• d is 1 to 4,
• e is 0 to 4,
• f is 0 to 5,
• g is 0 to 2,
• h is 0 to 5,
• i is 0 to 2,
• j is 0 to 800, and
• x is a number which is determined by a valency and frequency of the elements other than oxygen.