Methods of producing titanium dioxide nanoparticles
View Patent ↗A method is provided for producing TiO 2 nanoparticles. The nanoparticles can be further processed by neutralization, calcination, and/or micronization. The TiO 2 nanoparticle size is controlled by controlling synthetic and process conditions. TiO 2 nanoparticles produced are of the anatase polymorph, of the rutile polymorph, or a mixture thereof, and have particle sizes in the range of from 10 nm to 100 nm.
1. A method for manufacturing titanium dioxide crystalline powders, comprising:
thermally hydrolyzing an aqueous titanium oxychloride solution free of titanium dioxide nucleating agents, to form a resultant suspension;
neutralizing the resultant suspension to form a neutralized product;
filtering the neutralized product to form a filtered neutralized product; and
calcining the filtered neutralized product at a temperature of from 300° C. to 700° C., or 800° C. or higher, to form a calcined product.
2. The method of claim 1 , wherein the titanium oxychloride solution comprises from 0.687 to 2.5 moles of titanium ions per liter of solution.
3. The method of claim 2 , wherein the calcined product exhibits a specific surface area of from 50 m 2 /g to 300 m 2 /g.
4. The method of claim 2 , wherein the calcined product comprises more than 99% titanium dioxide of the anatase polymorph.
5. The method of claim 1 , wherein the titanium oxychloride solution comprises from 2.5 to 3.5 moles of titanium ions per liter of solution.
6. The method of claim 5 , wherein the calcined product exhibits a BET specific surface area of from 30 m 2 /g to 100 m 2 /g.
7. The method of claim 5 , wherein the calcined product comprises more than 99.5% by weight titanium dioxide of the rutile polymorph.
8. The method of claim 1 , wherein sulphate ions are added to the aqueous titanium oxychloride solution prior to the thermally hydrolyzing to form a resultant aqueous titanium oxychloride solution, and the calcined product comprises more than 50% by weight titanium dioxide of the anatase polymorph.
9. The method of claim 8 , wherein the sulphate ions are added in an amount to result in a concentration of sulphate ions in a range of from 0.01 mole to 1.0 mole per liter based on the volume of the resultant aqueous titanium oxychloride solution.
10. The method of claim 1 , wherein aluminum ions are added to the aqueous titanium oxychloride solution prior to the thermally hydrolyzing to form a resultant aqueous titanium oxychloride solution, and the calcined product comprises more than 50% by weight titanium dioxide of the rutile polymorph.
11. The method of claim 10 , wherein the aluminum ions are added in an amount to result in a concentration of aluminum ions in a range of from 0.045 mole to 0.15 mole per liter based on the volume of the resultant aqueous titanium oxychloride solution.
12. The method of claim 1 , wherein the thermally hydrolyzing is carried out at a temperature of from 95° C. to 105° C.
13. The method of claim 1 , wherein the thermally hydrolyzing is carried out at atmospheric pressure.
14. The method of claim 1 , wherein the thermally hydrolyzing is carried out for a time of from one hour to two hours.
15. The method of claim 1 , further comprising drying the filtered neutralized product at a temperature of from 80° C. to 130° C. prior to said calcining, for a period of time of from one hour to six hours.
16. The method of claim 1 , wherein the calcining is carried out at a temperature of from 300° C. to 700° C., after drying.
17. The method of claim 1 , wherein the calcining is carried out for a period of time of from one hour to four hours.
18. The method of claim 1 , wherein the calcining is carried out at a temperature of 800° C. or higher, and the calcined product comprises greater than 50% by weight the rutile polymorph.
19. The method of claim 1 , further comprising milling the calcined product in a fluid energy mill driven by air.
20. The method of claim 1 , wherein the calcined product has an average particle diameter of less than 40 nm.