Nanostructured titanium oxide material and its synthesis procedure

• US 20060078726A1
• Filed: 05/04/2005
• Published: 04/13/2006
• Est. Priority Date: 10/10/2003
• Status: Active Grant

• Current Assignee: Instituto Mexicano Del Petrã³Leo (Gobierno Federal De Los Estados Unidos Mexicanos)
• Original Assignee: Instituto Mexicano Del Petrã³Leo (Gobierno Federal De Los Estados Unidos Mexicanos)
• Inventors: Morales, Yosadara Ruiz, Jacome, Maria Antonia Cortes, Chavez, Carlos Angeles, Ortiz, Luis Francisco Flores, Torres, Gerardo Ferrat, Salinas, Esteban Lopez, Cassou, Marcelo Lozada y, Ramirez, Fernando Alvarez, Antonio, Jose Antonio Toledo
• Granted Patent: US 7,645,439 B2
• Time in Patent Office: Days
• US Class Current: 428/328
• CPC Class Codes: B82Y 30/00 Nanotechnology for materials or surface science, e.g. nanocomposites
• CPC Class Codes: C01G 23/04 Oxides; Hydroxides
• CPC Class Codes: C01G 23/043 Titanium sub-oxides
• CPC Class Codes: C01G 23/047 Titanium dioxide
• CPC Class Codes: C01P 2002/76 by a space-group or by other symmetry indications
• CPC Class Codes: C01P 2002/77 by unit-cell parameters, atom positions or structure diagrams
• CPC Class Codes: C01P 2004/03 obtained by SEM
• CPC Class Codes: C01P 2004/04 obtained by TEM, STEM, STM or AFM
• CPC Class Codes: C01P 2004/13 Nanotubes
• CPC Class Codes: C01P 2004/16 Nanowires or nanorods, i.e. solid nanofibres with two nearly equal dimensions between 1-100 nanometer
• CPC Class Codes: Y10S 977/811 Of specified metal oxide composition, e.g. conducting or semiconducting compositions such as ITO, ZnOx
• CPC Class Codes: Y10T 428/256 Heavy metal or aluminum or compound thereof
• CPC Class Codes: Y10T 428/2975 Tubular or cellular
• CPC Class Codes: Y10T 428/298 Physical dimension
• CPC Class Codes: Y10T 428/2982 Particulate matter [e.g., sphere, flake, etc.]

Abstract

Nanomaterials of the JT phase of the titanium oxide TiO_2-x, where 0≦x≦1 having as a building block a crystalline structure with an orthorhombic symmetry and described by at least one of the space groups 59 Pmmn, 63 Amma, 71 Immm or 63 Bmmb. These nanomaterials are in the form of nanofibers, nanowires, nanorods, nanoscrolls and/or nanotubes. The nanomaterials are obtained from a hydrogen titanate and/or a mixed sodium and hydrogen titanate precursor compound that is isostructural to the JT crystalline structure. The titanates are the hydrogenated, the protonated, the hydrated and/or the alkalinized phases of the JT crystalline phase that are obtained from titanium compounds such as titanium oxide with an anatase crystalline structure, amorphous titanium oxide, and titanium oxide with a rutile crystalline structure, and/or directly from the rutile mineral and/or from ilmenite. The titanates are submitted to dynamic thermal treatment in an inert, oxidizing or reducing atmosphere to produce the JT phase of the TiO_2-x, where 0≦x≦1 with an orthorhombic structure.

Claims

1. A thermally stable nanomaterial of titanium oxide of the formula TiO_2-x, where 0≦

x≦

1, having an orthorhombic crystalline lattice which is described by at least one of the space groups 59 Pmmn, 63 Amma, 71 Immm or 63 Bmmb, and a nanofibrilar and/or nanotubular morphology constituted of piled structural layers, which are folded or rolled inwards into themselves, or formed from overlapped semitubes.

2. The titanium oxide nanomaterial of claim 1, wherein said orthorhombic crystalline lattice is described by the space group 59 Pmmn.

3. The titanium oxide nanomaterial of claim 1, wherein said orthorhombic crystalline lattice is described by the space group 63 Amma.

4. The titanium oxide nanomaterial of claim 1, wherein said orthorhombic crystalline lattice is described by the space group 71 Immm.

5. The titanium oxide nanomaterial of claim 1, wherein said orthorhombic crystalline lattice is described by the space group 63 Bmmb.

6. The titanium oxide nanomaterial of claim 1, wherein the cell parameters of the orthorhombic crystalline lattice are:

a=from 0.283 to 0.324 nm, b=from 0.354 to 0.395 nm and c=from 0.695 to 0.735 nm, for the space group 59 Pmmn and c=from 1.453 to 1.408 nm, for the space groups 63 Amma, 71 Immm and 63 Bmmb;

with α

=β

=γ

90°

.

7. The titanium oxide nanomaterial of claim 1, wherein x is from 0 to 1 with a high oxygen deficiency and an O/Ti ratio between 1.0 and 2.

8. The titanium oxide nanomaterial of claim 1, wherein x is between 0.1 and 0.95 with a high oxygen deficiency and an O/Ti ratio between 1.0 and 2.

9. The titanium oxide nanomaterial of claim 1, wherein x is between 0.1 and 0.95.

10. The titanium oxide nanomaterial of claim 1, wherein said nanofibers and/or nanotubes have a diameter of between 3 and 50 nm and a length from 0.01 μ

m and 100 μ

m.

11. The titanium oxide nanomaterial of claim 1, wherein said nanofibers and mesoporous nanotubes have a homogeneous distribution of pores between 2 and 30 nm and a specific area between 5 and 500 m²/g.

12. The titanium oxide nanomaterial of claim 1, wherein said nanomaterial comprises a stable specific area between 100 and 400 m²/g.

13. The titanium oxide nanomaterial of claim 1, wherein said nanotubular and/or nanofibrilar morphology is constituted of 1 to 50 structural layers with an inter-layer spacing between 0.695 and 0.735 nm, for the space group 59 Pmmn and from 0.704 to 0.727 nm, for the space groups 63 Amma, 71 Immm and 63 Bmmb.

14. The titanium oxide nanomaterial of claim 1, wherein said nanomaterial has a stable thermal nanotubular morphology at temperatures between 200°

C. and 500°

C.

15. Nanomaterial of hydrogen titanate and/or mixed sodium and hydrogen titanate, having the formula HTiO₂ and/or Na_xH_1-xTiO₂, wherein x is from 0 to less than 1, the hydrogen and sodium atoms are in the interlayer regions of the orthorhombic structure and said nanomaterial has nanofibrilar and/or nanotubular morphology constituted of piled structural layers that are folded or rolled inwards into themselves, or formed by overlapped semitubes.

16. The nanomaterial of claim 15, wherein said nanomaterial has an orthorhombic structure, which is isostructural with TiO_2-x, where 0≦

x≦

1, and whose unit cell is described by at least one of the space groups 59 Pmmn, 63 Amma, 71 Immm or 63 Bmmb.

17. The nanomaterial of claim 15, wherein the cell parameters of the crystalline lattice which is orthorhombic are:

a from 0.263 nm to 0.331 nm;

b from 0.332 nm to 0.448 nm, and c from 0.635 nm to 0.902 nm, for the case of the 59 Pmmn space group, and from 1.368 nm to 1.905, for the case of the 63 Amma, 71 Immm, and 63 Bmmb space groups;

with α

=β

=γ

=90°

18. The nanomaterial of claim 15, wherein said nanomaterial has a disordered mesoporosity with an average pore diameter between 3 and 25 nm and a specific area between 100 and 600 m²/g.

19. The nanomaterial of claim 15, wherein said nanomaterial has a nanofibrilar and/or a nanotubular morphology with dimensions of 3 to 50 nm in diameter and lengths from 0.1 to 100 μ

m.

20. The nanomaterial of claim 15, wherein said nanomaterial has a nanotubular morphology constituted by 1 to 50 structural layers with an inter-layer spacing in the range of 0.635 nm to 0.902 nm for the 59 Pmmn space group, and from 0.684 nm to 0.953 for the 63 Amma, 71 Immm, and 63 Bmmb space groups.

21. A method for the synthesis of titanium oxide with orthorhombic nanostructure of TiO_2-x JT phase, where 0≦

x≦

1, comprising heating a hydrogen titanate and/or a mixed sodium and hydrogen titanate under dynamic thermal treatment to produce a stable nanomaterial.

22. The method of claim 21, wherein said hydrogen titanate and/or mixed sodium and hydrogen titanate are obtained by mixing a titanium oxide compound with an alkaline solution under hydrothermal conditions in a closed system or under thermal conditions at atmospheric pressure in reflux conditions, followed by an ionic exchange treatment.

23. The method of claim 22, wherein said method is conducted under hydrothermal conditions in said closed system and with an autogenous pressure in the range of from 1 to 150 atm, a temperature in the range of from 80°

C. to 160°

C., and a reaction time in the range of 1 to 80 hours.

24. The method of claim 22, wherein said method is conducted under atmospheric pressure in reflux conditions at a temperature in the range of from 80°

C. to 160°

C., and a reaction time in the range of from 1 to 80 hours.

25. The method of claim 21, wherein said dynamic thermal treatment is conducted by flowing an oxidizing or inert gas or a mixture of an inert gas with a reducing gas through said hydrogen titanate and/or mixed sodium and hydrogen titanate at a temperature between 200°

C. and 500°

C.

26. The method of claim 25, wherein said thermal treatment is performed with flowing air or O₂ to achieve an oxidizing atmosphere or in flowing nitrogen, He or Ar to achieve an inert atmosphere or a mixture of flowing inert gas with H₂ at a concentration of 5% to 30% by volume of H₂ based on the total volume of gas.

27. The method of claim 25, wherein said dynamic thermal treatment is conducted at a temperature between 200°

C. and 450°

C.

28. The method of claim 25, wherein said dynamic thermal treatment is conducted at a temperature between 200°

C. and 400°

C.

29. The method of claim 25, wherein said dynamic thermal treatment is at a flowing gas rate of 0.1 liter per minute to 1.0 liter per minute.

30. The method of claim 25, wherein said dynamic thermal treatment is at a flowing gas rate of 0.3 liter per minute to 0.5 liter per minute

31. The method of claim 22, wherein said titanium oxide compound is anatase having a crystal size between 5 nm and 10 nm.

32. The method of claim 22, wherein said titanium oxide compound is amorphous titania having a crystal size between 0.1 nm to 5 nm.

33. The method of claim 22, wherein said titanium oxide compound is amorphous titania having a crystal size between 1 to 3 mm.

34. The method of claim 22, wherein said ionic exchange treatment is in alcoholic, acidic aqueous media or aqueous media.