Process for preparing crystalline mixed metal oxides
First Claim
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1. A process for preparing crystalline mixed metal oxides having simultaneously a narrow particle size distribution and low surface area of the formula:
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space="preserve" listing-type="equation">ABO.sub.3wherein,A is metal cation selected from Ba, Sr, Ca, Mg, Pb and Nd and mixtures thereof; and
B is metal cation selected from Ti, Zr, Nb, Hf, Zn and Sn and mixtures thereof which comprises the steps of;
(a) simultaneously and continuously mixing an organometallic compound, mixture of organometallic compounds or a hydrolyzable system, of the structure BLn, where B is as defined above, L is a hydrolyzable group, or a combination of such groups, selected from alkoxy, aryloxy, aminoalkoxy, acetoxy, acetoacetonyl, chlorides, nitrates, and acetates, and n is 2 or 4 with a solution of a compound, or a mixture of compounds, of the general structure AXy, where A is as defined above, X is an anion, or combination of anions, selected from hydroxide, chloride, nitrate and acetate, and y is 2 or 3 in an alkaline, high turbulence energy environment characterized by a turbulence intensity greater than 9×
106 cm/sec3 ;
(b) crystallizing the reaction product; and
(c) recovering crystals wherein 90% of particles are greater than 0.2 μ
m in size up to about 1.0 μ
m in size, the surface area is less than 15 m2 /g and the A/B mole ratio is from 0.990 to 1.020.
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Abstract
An improved process for preparing crystalline mixed metal oxides, such as barium titanate, in which an organometallic compound is reacted simultaneously and continuously with a solution of a divalent alkaline earth metal ion in an alkaline high turbulence energy environment, the reaction product is crystallized, and the crystals are isolated.
48 Citations
12 Claims
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1. A process for preparing crystalline mixed metal oxides having simultaneously a narrow particle size distribution and low surface area of the formula:
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space="preserve" listing-type="equation">ABO.sub.3wherein, A is metal cation selected from Ba, Sr, Ca, Mg, Pb and Nd and mixtures thereof; and
B is metal cation selected from Ti, Zr, Nb, Hf, Zn and Sn and mixtures thereof which comprises the steps of;(a) simultaneously and continuously mixing an organometallic compound, mixture of organometallic compounds or a hydrolyzable system, of the structure BLn, where B is as defined above, L is a hydrolyzable group, or a combination of such groups, selected from alkoxy, aryloxy, aminoalkoxy, acetoxy, acetoacetonyl, chlorides, nitrates, and acetates, and n is 2 or 4 with a solution of a compound, or a mixture of compounds, of the general structure AXy, where A is as defined above, X is an anion, or combination of anions, selected from hydroxide, chloride, nitrate and acetate, and y is 2 or 3 in an alkaline, high turbulence energy environment characterized by a turbulence intensity greater than 9×
106 cm/sec3 ;(b) crystallizing the reaction product; and (c) recovering crystals wherein 90% of particles are greater than 0.2 μ
m in size up to about 1.0 μ
m in size, the surface area is less than 15 m2 /g and the A/B mole ratio is from 0.990 to 1.020. - View Dependent Claims (2, 3, 4, 5, 6, 11)
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7. A process for preparing crystalline barium titanate having 90% of the particles greater than 0.2 μ
- m in size up to about 1.0 μ
m in size, and a surface area of less than about 15 m2 /g which comprises the steps of;(a) reacting tetrabutyl titanate as a first ingredient stream with a solution of barium hydroxide as a second ingredient stream at a temperature of 80°
-85°
C. in a high turbulence energy environment comprising pumping said ingredient streams simultaneously through a coaxial jet mixer, said environment characterized by a turbulence intensity greater than 9×
106 cm/sec3 to form a slurry and discharging said slurry into an alkaline heel of water;(b) crystallizing said slurry by heating under reflux with continuous agitation for at least about 6 hours to no more than 48 hours; and (c) recovering said crystals.
- m in size up to about 1.0 μ
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8. A chemically homogeneous crystalline mixed metal oxides having a narrow particle size distribution and low surface area of the formula:
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space="preserve" listing-type="equation">ABO.sub.3wherein, A is metal cation selected from Ba, Sr, Ca, Mg, Pb and Nd and mixtures thereof; and B is metal cation selected from Ti, Zr, Nb, Hf, Zn and Sn and mixtures thereof which are prepared by a process comprising the steps of; (a) simultaneously and continuously reacting an organometallic compound, or mixture of organometallic compounds, of the general structure BLn where B is as defined above, L is a hydrolyzable group, or combination of such groups, selected from alkoxy, aryloxy, aminoalkoxy, acetoxy, and acetoacetonyl, and n is 2, 4, or 5 as a first ingredient stream with a solution of a compound, or a mixture of compounds, of the general structure AXy, where A is as defined above, X is an anion, or a combination of anions, selected from hydroxide, chloride, nitrate and acetate, and y is 2 or 3 in an alkaline, high turbulence energy environment comprising pumping said ingredient streams simultaneously and continuously through a coaxial jet mixer characterized by a turbulence intensity greater than 9×
106 cm/sec3 ;(b) crystallizing the reaction product for at least 6 hours to no more than 48 hours; and (c) recovering crystals wherein 90% of particles are greater than 0.2 μ
m in size up to about 1.0 μ
m in size, a surface area of less than about 15 m2 /g and an A/B mole ratio in the range of about 0.990 to about 1.020. - View Dependent Claims (9, 10, 12)
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Specification