Process for forming multi-component oxide complex catalysts

In a process for producing a molybdate or tungstate oxide complex catalyst in which compounds capable of yielding said catalyst are combined together so as to form a pre-catalyst solid and the pre-catalyst solid is calcined in air to activate said pre-catalyst and thereby form said catalyst, the improvement wherein the key catalytic phase of said catalyst comprising a molybdate and/or tungstate of Bi, Te, Sb, Sn, Cu or mixtures thereof is pre-formed prior to combining with the other elements in said catalyst;

• and further wherein none of the Group VIII elements in said catalyst, if any, is separately preformed into a molybdate or tungstate prior to combining with the key catalyst phase, said catalyst having a composition defined by the formula:
• [M.sub.m N.sub.n O.sub.x ].sub.q [A.sub.a C.sub.b D.sub.c E.sub.d F.sub.e N.sub.f O.sub.y ].sub.p
• wherein
• M=bi, Te, Sb, Sn and/or Cu
• N=mo and/or W
• A=alkali, Tl, and/or Sm
• C=ni, Co, Mn, Mg, Be, Ca, Sr, Ba, Zn, Cd and/or Hg
• D=fe, Cr, Ce, and/or V
• E=p, as, B, Sb
• F=rare earth, Ti, Zr, Nb, Ta, Re, Ru, Rh Ag, Au, Al, Ga, In, Si, Ge, Pb, Th, and/or U, and further
• wherein
• a=0-4
• b=0-20
• c=0.01-20
• d=0-4
• e=0-8
• f=8-16
• m=0.01-10
• n=0.1-30, and
• x and y are numbers such that the valence requirements of the other elements for oxygen in the key catalytic phase and the host-catalyst phase, respectively, are satisfied;
• and the ratio q/p is 0.1 to 10.