Process for preparing mixed metal oxide powders
Process for preparing a mixed metal oxide powder, in which oxidizable starting materials are evaporated and oxidized, the reaction mixture is cooled after the reaction and the pulverulent solids are removed from gaseous substances, wherein as starting materials, at least one pulverulent metal and at least one metal compound, the metal and the metal component of the metal compound being different and the proportion of metal being at least 80% by weight based on the sum of metal and metal component from metal compound, together with one or more combustion gases, are fed to an evaporation zone of a reactor, where metal and metal compound are evaporated completely under nonoxidizing conditions, subsequently, the mixture flowing out of the evaporation zone is reacted in the oxidation zone of this reactor with a stream of a supplied oxygen-containing gas whose oxygen content is at least sufficient to oxidize the starting materials and combustion gases completely.
1. A process for preparing a mixed metal oxide powder, comprising:
evaporating oxidizable starting materials in an evaporation zone of a reactor;
oxidizing the starting materials in a vaporous state in an oxidation zone of the reactor to form a reaction mixture; and
cooling the reaction mixture after removing reaction and pulverulent solids from gaseous substances,
wherein the starting materials comprise:
at least one pulverulent metal; and
at least one metal compound comprising a metal component that is different from the at least one pulverulent metal,
the at least one puverulent metal is at least 80% by weight based on the sum of the at least one pulverulent metal and the metal component of the metal compound,
the evaporating comprises feeding the starting materials and at least one combustion gas to the evaporation zone of the reactor to completely evaporate the at least one pulverulent metal and the metal compound under nonoxidizing conditions,
the oxidizing comprises reacting a mixture flowing out of the evaporation zone with a stream of a supplied oxygen-containing gas in the oxidization zone of the reactor, and
the oxygen-containing gas has an oxygen content at least sufficient to oxidize the starting materials and the at least one combustion gas completely.
2. The process according to claim 1 , further comprising igniting the at least one combustion gas with an oxygenous gas to form a flame for evaporation, where a lambda value in the evaporation zone satisfies 0.5≦lambda≦1.
3. The process according to claim 1 , wherein the process is performed at a pressure is of 200 mbar to 1100 mbar in the reactor.
4. The process according to claim 1 , wherein the pulverulent metal introduced into the evaporation zone is selected from the group consisting of Ag, Al, Ba, Bi, Ca, Er, Eu, Ga, In, Li, K, Mg, Mn, Na, Pb, Sb, Sm, Sn, Sr, Te, Th, Yb and Zn.
5. The process according to claim 1 , wherein the metal compound is supplied to the evaporation zone in solid form, in dissolved or dispersed form in an aqueous phase, or in the form of vapor.
6. The process according to claim 1 , wherein the solid starting materials have a particle size of less than 1000 μm.
7. The process according to claim 1 , further comprising introducing one or more metal compounds into the oxidation zone.
8. The process according to claim 1 , wherein the at least one metal compound used is a chloride, a nitrate, a sulfate, a carbonate, a C 1 -C 12 -alkoxide, a C 1 -C 12 -carboxylate, an acetylacetonate and/or a carbonyl, and comprises the metal compound comprising Ag, Al, As, Au, B, Ba, Be, Bi, Ca, Cd, Ce, Co, Cr, Cs, Cu, Er, Eu, Fe, Ga, Gd, Ge, Hf, In, K, La, Li, Mg, Mn, Mo, Na, Nb, Nd, Ni, P, Pb, Pd, Pm, Pr, Pt, Rb, Ru, Sb, Sc, Sm, Sn, Sr, Ta, Tb, Ti, Tl, Tm, V, W, Y, Yb, Zn, and/or Zr.
9. The process according to claim 1 , wherein
the at least one pulverulent metal introduced into the evaporation zone is zinc,
the at least one metal compound introduced into the evaporation zone is an inorganic or organic metal compound, which has not more than 4 carbon atoms and comprises the metal component comprising one of aluminum, cerium and manganese,
zinc is at least 95% by weight, based on the sum of zinc and the metal component of the at least one metal compound,
lambda is 0.8 to 0.95 in the evaporation zone, and
lambda is 1.5 to 6 in the oxidation zone.
10. The process according to claim 1 , wherein
the pulverulent metal introduced into the evaporation zone is zinc,
a solution of the metal compound introduced into the evaporation zone is an aqueous solution of an inorganic or organic metal compound, which has not more than 4 carbon atoms and comprises the metal component comprising one of aluminum, cerium and manganese,
zinc is at least 95% by weight, based on the sum of zinc and the metal component of the at least one metal compound,
lambda is 0.8 to 0.95 in the evaporation zone, and
lambda is 1.5 to 6 in the oxidation zone.
11. The process according to claim 1 , wherein
the at least one pulverulent metal introduced into the evaporation zone is zinc,
a solution of the metal compound introduced into the evaporation zone is an aqueous solution of an inorganic or organic metal compound, which has not more than 4 carbon atoms and comprises the metal component comprising one of aluminum, cerium and manganese,
a solution of the metal compound introduced into the oxidation zone is a solution of a C 2 -C 8 -carboxylate or C 1 -C 4 -alkoxide of aluminum, cerium or manganese as the metal component in C 1 -C 4 -alcohols and/or C 2 -C 8 -carboxylic acids,
zinc is at least 95% by weight, based on the sum of zinc and the metal component of the at least one metal compound,
lambda is 0.8 to 0.95 in the evaporation zone, and
lambda is 1.3 to 6 in the oxidation zone.
12. The process according to claim 1 , wherein the at least one combustion gas is ignited with an oxygenous gas to form a flame for oxidation, where a lambda value in the oxidation zone satisfies 1<lambda≦10.
13. The process according to claim 1 , further comprising igniting the at least one combustion gas with an oxygenous gas to provide a temperature of 500° C. to 3000° C. in the evaporation zone.
14. The process according to claim 1 , further comprising igniting the at least one combustion gas with an oxygenous gas to provide a temperature of 500° C. to 3000° C. in the oxidation zone.