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1. WO2007074437 - METHODS FOR PRODUCTION OF METAL OXIDE NANO PARTICLES, AND NANO PARTICLES AND PREPARATIONS PRODUCED THEREBY

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[ EN ]

WHAT IS CLAIMED IS:
1. A method for the formation of small-size metal oxide particles, comprising the steps of:
a) preparing a starting aqueous solution comprising at least one of metallic ion and complexes thereof, at a concentration of at least 0.1%
w/w of said metal component;
b) preparing a modifying aqueous solution having a temperature greater than 5O0C;
c) contacting the modifying aqueous solution with the starting aqueous
solution in a continuous mode in a mixing chamber to form a modified
system;
d) removing the modified system from the mixing chamber in a plug-flow
mode;
wherein said method is characterized in that:
i) the residence time in the mixing chamber is less than about 5 minutes;
and
ii) there are formed particles or aggregates thereof,
wherein the majority of the particles formed are between about 2nm and about 500nm in size.
2. A method according to Claim 1 , wherein the conditions in said system are adjusted by at least one of the steps of:
a) heating said starting aqueous solution by at least 10°C,
b) elevating the pH of said starting aqueous solution by at least 0.2 units;
and
c) diluting the starting aqueous solution by at least 20%
or a combination thereof, wherein said modified system is maintained at said adjusting conditions for at least 0.5 minutes.
3. A method according to Claim 2, wherein said adjustment of conditions is carried out for a period of less than 2 hours.
4. A method according to Claim 1 , further characterized in that the majority of the formed particles have a degree of crystallinity of more than 50%.

5. A method according to Claim 1 , further characterized in that the size ratio between the smallest and largest particle of the mean 50% by weigh of the formed particles is less than about 10
6. A method according to Claim 1 further characterized in that the size ratio between the smallest and largest particle of the mean 50% by weight of the formed particles is less than about 5.
7. A method according to Claim 1 , further characterized in that the majority of the formed particles are of a configuration other than elongated.
8. A method according to Claim 1 , further characterized in that the majority of the formed particles have a surface area of at least 30 m2/gr.
9. A method according to Claim 2, further comprising the step of calcination for dehydrating said formed particles at a temperature in a range between about 90°C and about 9000C to form dehydrated particles.
10. A method according to Claim 9, wherein said dehydrating is conducted under super-atmospheric pressure.
11. A method according to Claim 9, wherein said dehydrating step and said adjusting step are conducted simultaneously.
12. A method according to Claim 11 , wherein adjusting involves heating to the temperature of the calcination.
13. method according to Claim 9, further characterized in that the majority of the dehydrated particles are of a configuration other than elongated.
14. A method according to Claim 9, further characterized in that the majority of the dehydrated particles have a surface area of at least 30 m2/gr.
15. A method according to Claim 1 , wherein said metal is selected from the group consisting of tin, aluminum, silicon, zinc, cobalt, copper, nickel, magnesium, yttrium, vanadium, manganese, cadmium, zirconium, palladium, molybdenum, chromium ruthenium and a combination thereof.
16. A method according to Claim 1 , wherein said metal oxide is selected from the group consisting of metal oxides of the formula MetalxOy , metal hydroxy- oxides of the formula Metalp(OH)qOr] metallic acid, various hydration forms of those and compositions wherein those are major components, wherein x, y, p, q, r are each whole integers.

17. A method according to claim 1 wherein said metal oxides of the formula Metalχθy are selected from the group consisting of SnO, Snθ2, AI2O3, SiO2, ZnO, CoO, Co3O4, Cu2O, CuO, Ni2O3, NiO, MgO, Y2O3, VO, VO2, V2O3, V2O5, MnO MnO2, CdO, ZrO2, PdO, PdO2, MoO3, MoO2, Cr2O3, CrO3, and RuO2.

18. A method according to claim 16 wherein said metal hydroxy-oxide of the formula Metalp(OH)qOr is Sn(OH)2, Sn(OH)4, AI(OH)3, Si(OH)4, Zn(OH)2, Co(OH)2, Co(OH)3, CuOH, Cu(OH)2, Ni(OH)3, Ni(OH)2, Mg(OH)2, Y(OH)3, V(OH)2, V(OH)4, V(OH)3, Mn(OH)2 Mn(OH)4, Cd(OH)2, Zr(OH)4, Pd(OH)2, Pd(OH)4, Mo(OH)4, Cr(OH)3, and Ru(OH)4.
19. A method according to Claim 1 , wherein said preparation of said starting aqueous solution involves at least one of the following actions:
a) dissolution of a metal compound,
b) addition of a base; and
c) acidulation of a metal salt solution.
20. A method according to Claim 19, wherein said metal compound is selected from the group consisting of metal oxides, metal hydroxides, minerals containing the same said metal compound and mixtures thereof and wherein said compound is dissolved in an acidic solution comprising an acid selected from the group consisting of sulfuric acid, nitric acid, hydrochloric acid, phosphoric acid, an organic acid, their acidic salts and combinations thereof.

21. A method according to Claim 1 , wherein said prepared starting aqueous solution comprises an anion selected from the group consisting of sulfate, chloride, nitrate, phosphate, an organic acid and mixtures thereof.
22. A method according to Claim 1 , wherein the majority of the anions in said prepared starting aqueous solution are sulfate anions.
23. A method according to Claim 1 , wherein the metal concentration in the prepared solution is greater than about 5wt%
24. A method according to Claim 19, wherein said acidulation of said metal salt solution is preformed by the addition of an acid selected from the group consisting of: the acid of the anion present in said metal salt, another acid and combinations thereof.
25. A method according to Claim 2,- comprising at least two heating steps.

26. A method according to Claim 1 further comprising at least one the following steps of a) grinding said formed particles; and b)screening said formed particles.
27. A method according to Claim 1 , wherein a solution containing a compound selected from the group consisting of an acid and a base is added to at least one of the solutions selected from the group consisting of said starting solution, said modifying solution and said modified system.
28. A method according to Claim 1 , wherein said starting solution is treated by at least one of the following operations: a) ultrasound, and
b) microwaving.
29. Metal oxide particles whenever formed according to the method of
Claim 1 and products of their conversion.
30. The metal oxide particles of Claim 29, characterized in that the purity of the metal oxide particles with regard to other metals intermixed therewith is of at least 95%.
31. The metal oxide particles of Claim 29, characterized by having a shape selected from the group consisting of spherical shape, rod shape needle shape and raft shape.
32. The metal oxide particles of Claim 29, characterized in that said particles are doped with atoms of other compounds.
33. A preparation comprising said metal oxide particles whenever prepared according to the method of claim 1.
34. A preparation according to Claim 33, wherein said particles are dispersed in a liquid, supported on a solid compound, agglomerated to larger particles, partially fused, coated or any combination thereof.
35. A method for the production of a preparation of Claim 33 comprising steps selected from a group consisting of dispersing said particles, addition of a support, heat treatment, mixing, water evaporation spray drying, thermal spraying and a combination thereof.
36. A method comprising using at least one of said particles according to claim 29 and said preparations according to claim 33 as a pigment.
37. A method comprising using at least one of said particles according to claim 29 and said preparations according to claim 33 in a catalyst.

38. A method comprising using at least one of said particles according to claim 29 and said preparations according to claim 33 in a coating.
39. Industrial production of particles according to any of the above claims, wherein particles are formed at a rate of at least 50Kg/hour.
40. A method for the formation of a pigment, comprising the steps of Claim 1.
41. A method for the formation of a catalyst, comprising the steps of Claim 1.
42. A method according to Claim 1, wherein solution containing a compound selected from the group consisting of an acid and a base is added to at least one of the solutions selected from the group consisting of said starting solution, modifying solution and modified system.
43. A method according to Claim 42, wherein said basic compound is selected from a group consisting of ammonia, ammonium carbonate, ammonium bicarbonate and urea.
44. A method according to Claim 42, wherein the OH/metal molar ratio in the solution of said modified system is less than 4.
45. A method according to Claim 1 , wherein the temperature of the modifying solution is in the range between 1000C and 3000C.
46. A method according to Claim 1 , wherein said modified system is retained at a pressure of less than 100 atmospheres.
47. A method according to Claim 1 , wherein the modified system is retained for duration of between 1 and 30 minutes.
48. A method according to Claim 47 wherein during said retaining the temperature is maintained within less than 2O0C change in either direction from the temperature of the modified system.
49. A method according to Claim 1 , where the residence time in the mixing chamber is less than about 5 seconds.
50. A method according to Claim 1 , where the residence time in the mixing chamber is less than about 0.5 seconds.
51. A method according to Claim 1 , wherein the removed modified system is maintained for at least 0.5 minutes.
52. A method according to Claim 1 , wherein the removed modified system is introduced into a crystallizer.

53. A method according to Claim 52, wherein the temperature inside the crystallizer is kept in the range of 100-3000C.
54. A method according to Claim 52, wherein a metal salt solution is also introduced into a crystallizer.
55. A method according to Claims 1 , and 52 wherein a reagent selected from a group consisting of a dispersant and basic compound is present in at least one step of a group consisting of preparing, maintaining, adjusting, crystallizing in said crystallizer, flowing in said plug-flow mode.
56. A method according to Claim 55, wherein said dispersant is selected from a group consisting of cationic polymers, anionic polymers, nonionic polymers, surfactants, and mixtures thereof.
57. A method according to Claim 55, further comprising the step of changing the amount of said dispersant.