Multimetal oxide compositions and process of preparing same

A composition of the formula I

• (X.sup.1.sub.a X.sup.2.sub.b O.sub.x).sub.p (X.sup.3.sub.c X.sup.4.sub.d X.sup.5.sub.e X.sup.6.sub.f X.sup.7.sub.g X.sup.2.sub.h O.sub.y).sub.q(I)
• where
• X.sup.1 is bismuth, tellurium, antimony, tin and/or copper;
• X.sup.2 is molybdenum and/or tungsten;
• X.sup.3 is an alkali metal, thallium and/or samarium;
• X.sup.4 is an alkaline earth metal, nickel, cobalt, copper, manganese, zinc, tin, cadmium, and/or mercury;
• X.sup.5 is iron, chromium, cerium and/or vanadium;
• X.sup.6 is phosphorus, arsenic, boron and/or antimony;
• X.sup.7 is a rare-earth metal, titanium, zirconium, niobium, tantalum, rhenium, ruthenium, rhodium, silver, gold, aluminum, gallium, indium, silicon, germanium, lead, thorium and/or uranium;
• a is from 0.01 to 8;
• b is from 0.1 to 30;
• c is from 0 to 4;
• d is from 0 to 20;
• e is from 0 to 20;
• f is from 0 to 6;
• g is from 0 to 15;
• h is from 8 to 16;
• x and y are numbers determined by the valency and frequency of the elements in formula I other than oxygen, and p and q are numbers whose ratio p/q is from 0.1 to 10, synthesized by
• preparing a first finely divided powder from a calcined mixed oxide X.sup.1.sub.a X.sup.2.sub.b O.sub.x, wherein said mixed oxide has a maximum particle diameter in the range from 1 to 25 .mu.m,
• preparing a second finely divided powder containing X.sup.3, X.sup.4, X.sup.5, X.sup.6, X.sup.7 and X.sup.2, wherein said second powder is in a form which is already oxidic and/or can be converted into oxidic form by calcination,
• mixing said first and said second powder to form a mixture, and
• calcining said mixture.

A process for the preparation of a composition of the formula I

• (X.sup.1.sub.a X.sup.2.sub.b O.sub.x).sub.p (X.sup.3.sub.c X.sup.4.sub.d X.sup.5.sub.e X.sup.6.sub.f X.sup.7.sub.g X.sup.2.sub.h O.sub.y).sub.q(I)
• where
• X.sup.1 is bismuth, tellurium, antimony, tin and/or copper;
• X.sup.2 is molybdenum and/or tungsten;
• X.sup.3 is an alkali metal, thallium and/or samarium;
• X.sup.4 is an alkaline earth metal, nickel, cobalt, copper, manganese, zinc, tin, cadmium, and/or mercury;
• X.sup.5 is iron, chromium, cerium and/or vanadium;
• X.sup.6 is phosphorus, arsenic, boron and/or antimony;
• X.sup.7 is a rare-earth metal, titanium, zirconium, niobium, tantalum, rhenium, ruthenium, rhodium, silver, gold, aluminum, gallium, indium, silicon, germanium, lead, thorium and/or uranium;
• a is from 0.01 to 8;
• b is from 0.1 to 30;
• c is from 0 to 4;
• d is from 0 to 20;
• e is from 0 to 20;
• f is from 0 to 6;
• g is from 0 to 15;
• h is from 8 to 16;
• x and y are numbers determined by the valency and frequency of the elements in formula I other than oxygen, and p and q are numbers whose ratio p/q is from 0.1 to 10, comprising
• preparing a first finely divided powder from a calcined mixed oxide X.sup.1.sub.a X.sup.2.sub.b O.sub.x, wherein said mixed oxide has a maximum particle diameter in the range from 1 to 25 .mu.m,
• preparing a second finely divided powder containing X.sup.3, X.sup.4, X.sup.5, X.sup.6, X.sup.7 and X.sup.2, wherein said second powder is in a form which is already oxidic and/or can be converted into oxidic form by calcination,
• mixing said first and said second powder to form a mixture, and
• calcining said mixture.