NANOSTRUCTURED BINARY OXIDE TiO2/Al2O3 WITH STABILIZED ACIDITY AS CATALYTIC SUPPORT AND ITS SYNTHESIS PROCESS

Abstract

The present invention is directed to a nanostructured binary oxide TiO.sub.2Al.sub.2O.sub.3 with high acidity and its synthesis process via the sol-gel method, hydrotreating and thermal activation. The nanostructured binary oxide TiO.sub.2Al.sub.2O.sub.3 with high acidity consists basically of titanium oxide and aluminum oxide with the special characteristic of being obtained as nanostructures, in their nanocrystal-nanotube evolution, which provides special physicochemical properties such as high specific area, purity and phase stability, acidity stability and different types of active acid sites, in addition to the capacity to disperse and stabilize active metal particles with high activity and selectivity mainly in catalytic processes.

Claims

1. A nanostructured binary oxide TiO.sub.2Al.sub.2O.sub.3 with high acidity obtained by a sol-gel method and hydrotreating and thermal activation, said nanostructured binary oxide TiO.sub.2Al.sub.2O.sub.3 having the following proportions and phase transitions: TABLE-US-00011 Proportion of the crystalline amorphous phases present in the nanostructured binary oxide TiO.sub.2Al.sub.2O.sub.3 Crystalline Amorphous Phase (%) Annealing Temperature General/(Preferable) ( C.) Titanates/Anatase Titanates/Anatase (100 C.) (350 C.) 100-350 95-5 70-30 (98-2) (75-25) (350 C.) (600 C.) 350-600 70-30 25-75 (75-25) (20-80)

2. A nanostructured binary oxide TiO.sub.2Al.sub.2O.sub.3 according to claim 1, characterized by the external and internal diameter and interlayer intervals shown as follows: TABLE-US-00012 Dimensions of external (D.sub.e) and internal (D.sub.i) diameters and interlayers (E.sub.i) of the nanostructured binary oxide TiO.sub.2Al.sub.2O.sub.3 Hydrogen Titanates Annealing (nm) Temperature General/(Preferable) ( C.) D.sub.e D.sub.i E.sub.i 100-350 10-9 3-5 0.7-0.8 (9-8) (3-4) (0.6-0.7) 350-600 6-7 1-2 0.1-0.2 (5-6) (1.5-2) (0.06-01)

3. A nanostructured binary oxide TiO.sub.2Al.sub.2O.sub.3 according to claim 1, characterized by the following textural properties: TABLE-US-00013 Textural properties of the nanostructured binary oxide TiO.sub.2Al.sub.2O.sub.3 Surface Average Pore Annealing Area Diameter Temperature (m.sup.2/g) () ( C.) General Preferable General Preferable 100-350 370-350 330-340 20-40 30-55 350-600 200-280 260-270 20-30 20-25

4. A nanostructured binary oxide TiO.sub.2Al.sub.2O.sub.3 according to claim 1, characterized by the following band gap energies: TABLE-US-00014 Band gap energy (Eg) data of the nanostructured binary oxide TiO.sub.2Al.sub.2O.sub.3 Annealing Band gap energy (Eg) Temperature (eV) ( C.) General Preferable 100-350 2.8-2.9 3.2-2.8 350-600 2.9-3.3 2.9-3.0

5. A nanostructured binary oxide TiO.sub.2Al.sub.2O.sub.3 according to claim 1, characterized by the following hydroxylation degrees: TABLE-US-00015 Hydroxylation degrees for the nanostructured binary oxide TiO.sub.2Al.sub.2O.sub.3 at different annealing temperatures Activation Temperature Hydroxylation Sample ( C.) Degree* TiO.sub.2Al.sub.2O.sub.3 300 9.5-12 TiO.sub.2Al.sub.2O.sub.3 600 7.5-8.5 CommercialTiO.sub.2** 600 0.99779 *Deconvolutions obtained at 300 C. **Commercial Titania Degussa P25.

6. A nanostructured titania catalyst comprising the TiO.sub.2Al.sub.2O.sub.3 of claim 1, characterized by the following acidity characteristics: TABLE-US-00016 Pyridine acidity within the temperature interval from 300 to 500 C. of the binary oxide TiO.sub.2Al.sub.2O.sub.3 with and without active metals Micro-moles of Micro-moles of pyridine/m.sup.2 pyridine/m.sup.2 Lewis Sites Brnsted Sites Sample (1445 cm.sup.1) (1540 cm.sup.1) TiO.sub.2Al.sub.2O.sub.3 3.5 0.222 V/TiO.sub.2Al.sub.2O.sub.3 3.7 0.255

7. A synthesis process for producing the nanostructured binary oxide TiO.sub.2Al.sub.2O.sub.3 of claim 1, comprising: a first stage comprising the following steps; I) Preparation of an alcoholic solution, as a preparation of a feedstock, and consists of the addition of a titanium alkoxide with three or four branched or linear carbon atoms to an alcoholic solution with alcohols from three to four linear or branched carbon atoms; II) Solution in acid medium, comprising the addition of an acid to the alcoholic solution from stage I), controlling the pH from 1 to 5, where the acid is selected from hydrochloric acid, nitric acid, and acetic acid; III) Hydrolysis, comprising subjecting the acid solution from stage II) to conditions of constant stirring and reflux at temperatures from 70 to 80 C., stabilizing the medium and proceeding to the addition of bidistilled water dropwise in a water/alkoxide molar ratio of 1-2/0.100-0.150, keeping the reflux until the formation of a gel; IV) Aging, comprising subjecting the gel obtained in stage III) to an aging treatment under the same conditions of stirring and reflux of stage III) for 1 to 24 hours for the total formation of the nanostructured titania; V) Drying, comprising drying the nanostructured titania obtained in stage IV) at temperatures from 50 to 80 C., for 1 to 24 hours; VI) Annealing, comprising subjecting the dry nanostructured titania obtained in stage V) to an annealing stage with the option of using an oxidizing or reducing atmosphere at temperatures from 200 to 600 C. for 1 to 12 hours; and a second Stage comprising a Hydrothermal Process including the steps of; I) Normality of an alkaline solution (NaOH), including forming a mixture of nanostructured titania with a 5 to 10 N solution of sodium hydroxide (NaOH) with stirring from 100 to 200 rpm, temperatures from 130 to 180 C., with dried titania obtained during stage V), up to an annealing stage, with the option of using an oxidizing or reducing atmosphere, at temperatures from 200 to 600 C. for 1 to 12 hours, preferably at 300-500 C. for 3 to 9 hours; II) Reaction temperature, comprising subjecting the nanostructured titania mixed with a 5 to 10 N sodium hydroxide solution at temperatures from 130 to 180 C.; III) Stirring and reaction times, comprising subjecting the nanostructured titania mixed with a 5 to 10 N sodium hydroxide solution at temperatures from 130 to 180 C. for 12 to 24 hours with stirring from 100 to 200 rpm; IV) Washing, comprising subjecting the nanostructured titania, once stages I, II and III have been completed, to the washing step with hydrochloric acid (HCl) until reaching an acid pH between 1 and 3; afterwards, a second washing with deionized water is performed until reaching a pH of 6 or 7; V) Annealing, comprising subjecting the nanostructured titania, once stages I, II, III and IV have been completed, to a drying step from 70 to 80 C.; once this material is dry, it is submitted to an annealing process from 100 to 600 C., where the heating profile is 5 C. per minute; where the nanostructured titania is obtained with two annealing profiles (350 and 600 C.); when the corresponding temperatures are reached, they are kept constant for 1 to 4 hours.

8. The process of claim 7, wherein the titanium alkoxide in step I of the first stage has three or four branched or lineal carbon atoms.

9. The process of claim 7, wherein the acid medium in step II of the first stage has a pH from 2 to 3.

10. The process of claim 7, wherein the acid medium in step II of the first stage is obtained with nitric acid.

11. The process of claim 7, wherein the water/alkoxide molar ratio in step III of the first stage is 1-2/0.120-0.130.

12. The process of claim 7, wherein the drying step in step V of the first stage is performed at 60-70 C. for 4 to 12 h.

13. The process of claim 7, wherein the activation or annealing in step VI of the first stage is carried out at 300-500 C. for 3 to 9 h.

14. The process of claim 7, wherein the normality of the NaOH solution in step I of the second stage is from 5 to 10 N.

15. The process of claim 7, wherein the reaction temperature in step II of the second stage is from 130 to 180 C.

16. The process of claim 7, wherein the stirring time in step III of the second stage is for 12 to 24 h from 100 to 200 rpm.

17. The process of claim 7, wherein the washing in step IV of the second stage is carried out with HCl until reaching a pH from 1 to 3.

18. The process of claim 7, wherein the washing in step IV of the second step is carried out with deionized water until reaching a pH from 6 to 7.

19. The process of claim 7, the activation or annealing in step V of the second stage is carried out at 350-600 C. for 1 to 4 h.

20. The nanostructured binary oxide TiO.sub.2Al.sub.2O.sub.3 with high acidity identified as TiO.sub.2Al.sub.2O.sub.3, of claim 1, wherein said nanostructured binary oxide is a catalyst support for active metals, a catalyst in heterogeneous or homogeneous catalytic processes; a coating of catalytic matrices, a film on a substrate; or with the incorporation of active metals.

Description

BRIEF DESCRIPTION OF THE INVENTION FIGURES

[0128] FIG. 1 shows a flow chart of the stage-based synthesis process of the nanostructured binary oxide TiO.sub.2Al.sub.2O.sub.3 obtained by the process of the present invention.

[0129] FIG. 2 shows the transformation evolution of the nanocrystals-nanotubes of the nanostructured binary oxide TiO.sub.2Al.sub.2O.sub.3 according the preparation stages of the nanostructured TiO.sub.2Al.sub.2O.sub.3 binary oxides obtained by the process of the present invention.

[0130] FIG. 3 shows the XRD spectroscopy diffractogram of the nanostructured binary oxide TiO.sub.2Al.sub.2O.sub.3 , fresh and annealed at 400 and 600 C., where the phases and planes that contain the nanostructured binary oxide TiO.sub.2Al.sub.2O.sub.3 with respect to their corresponding thermal treatments, obtained by the process of the present invention, can be observed.

[0131] FIG. 4 shows an XRD spectroscopy graph of the nanostructured binary oxide TiO.sub.2Al.sub.2O.sub.3 , fresh and annealed at 400 and 600 C., where the phases and planes that contain the nanostructured binary oxide TiO.sub.2Al.sub.2O.sub.3 with respect to their corresponding thermal treatments, obtained by the process of the present invention, can be observed.

[0132] FIG. 5 shows high resolution transmission electron microscopy micrographs (HRTEM), where the morphological characteristics and dimensions of the nanotubes that form the nanostructured binary oxide TiO.sub.2Al.sub.2O.sub.3, annealed at 500 C., can be observed.

[0133] FIG. 6 shows the XRD spectroscopy graph of the nanostructured V/TiO.sub.2Al.sub.2O.sub.3 catalyst, fresh and annealed at 400 and 600 C., where the evolution of phases and planes and vanadium identification contained by this catalyst can be observed with respect to the corresponding thermal treatments obtained by means of the process of the present invention.

[0134] FIG. 7 shows the high resolution transmission electron microscopy micrographs (HRTEM) of the nanostructured V/TiO.sub.2Al.sub.2O.sub.3 catalyst, where the high and homogeneous dispersion of vanadium as active metal can be observed in the phase of the nanostructured binary oxide TiO.sub.2Al.sub.2O.sub.3 at 50 nm, and activated at high temperature (600 C., 5 nm), obtained by means of the process of the present invention.

[0135] FIG. 8 shows the FTIR spectrum of the nanostructured binary oxide TiO.sub.2Al.sub.2O.sub.3, where the preserved acid sites of Lewis and Brnsted types can be observed within a temperature interval from 100 to 400 C., obtained by means of the process of the present invention.

[0136] FIG. 9 shows the FTIR spectrum of the nanostructured V/TiO.sub.2Al.sub.2O.sub.3 catalyst with the incorporation of vanadium, where the preserved acid sites of Lewis and Brnsted types can be observed within a temperature interval from 100 to 400 C., obtained by means of the process of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

[0137] The present invention is directed to nanostructured binary oxides TiO.sub.2Al.sub.2O.sub.3, and their synthesis process via the sol-gel method, hydrotreating and thermal activation, which includes basically titanium oxide and aluminum oxide with the evolution of nanostructures to nanocrystals-nanotubes-nanocrytals as main characteristic. The TiO.sub.2Al.sub.2O.sub.3 binary oxides provide special physicochemical properties of texture and morphology such as high specific area, purity and crystal phase stability, which provides the capacity to disperse and stabilize metal particles with a special metal-support interaction, which results in a high activity and selectivity mainly in catalytic processes. In one embodiment the nanostructured binary oxides consist essentially of titanium oxide and aluminum oxide. The nanostructured binary oxides can have a nanocrystal-nanotube-nanocrystal structure.

[0138] The nanostructured binary oxides TiO.sub.2Al.sub.2O.sub.3 obtained by the process of the present invention show advantages with respect to the known catalytic supports of this type, mainly in the evolution of their nanostructures and size dimensions with respect to their thermal treatment and the relationship with their physicochemical properties. The physicochemical properties are defined by the type of interactions that exist between ions and electrons in these nanostructures, which provide specific textural (specific area and pore size distribution) and morphological (crystalline phases) properties, which in turn provide specific properties of dispersion and size of the active metal particles incorporated to the nanostructures, providing the catalyst high activity and selectivity mainly in catalytic processes.

[0139] Likewise, the nanostructured binary oxides TiO.sub.2Al.sub.2O.sub.3 as a catalytic support in the evolution of its nanostructures (nanocrystals-nanotubes-nanocrystals) shows fundamental specific acidity properties such as high stability at high temperature, based on acid sites of both types, Brnsted and Lewis, under the conditions described above. The process conditions also provide the catalytic support high activity and selectivity, mainly in catalytic processes.

[0140] The physicochemical properties of the nanostructured binary oxides TiO.sub.2Al.sub.2O.sub.3 as catalytic support depend on three stages. The first stage is relates to the particular or as a whole handling of the variables of the sol-gel method such as the types of titanium metal alkoxides, the characteristics of the solvents, the alkoxide/water ratio, and the medium in which the hydrolysis takes place, which can be acid or basic. The second stage corresponds to the hydrothermal process and the handling of variables such as the concentration of an alkaline solution, temperature, aging time and washing conditions. The third stage corresponds to the evolution of the nanostructures, which is the evolution from nanocrystal-nanotubes-nanocrystals, just by thermal effect with or without the incorporation of an active metal or metals. The process for producing the nanostructured binary oxide basically obtains TiO.sub.2Al.sub.2O.sub.3 by a sol-gel method, subjects the resulting binary oxide to a hydrothermal treatment and then subjects the hydrothermal-treated binary oxide to an activation process.

[0141] In order to provide a better understanding of the synthesis process of the nanostructured binary oxides TiO.sub.2Al.sub.2O.sub.3, FIG. 1 shows a flow chart of the different stages:

[0142] First Stage-Sol-Gel Method:

[0143] I). Preparation of an alcoholic solution;

[0144] II). Solution in acid medium;

[0145] III). Hydrolysis;

[0146] IV). Aging;

[0147] V). Drying, and;

[0148] VI). Activation or annealing.

[0149] I) Preparation of an alcoholic solution, which can be considered as the preparation of the feedstock, and includes the addition of a titanium alkoxide with three or four branched or linear carbon atoms to an alcoholic solution with alcohols from three to four linear or branched carbon atoms in a reflux system under constant stirring. In one embodiment, the alcoholic solution consists essentially of the titanium alkoxides in the solution containing the alcohol.

[0150] II) Solution in acid medium, which consists of the addition of an acid to the alcoholic solution from stage I), controlling the pH from 1 to 5, preferably from 2 to 3, where the employed acid is selected from hydrochloric acid, nitric acid, and acetic acid, preferring the nitric acid.

[0151] III) Hydrolysis, which includes subjecting the acid solution from stage II) to conditions of constant stirring and reflux at temperatures from 70 to 80 C., stabilizing the medium and proceeding to the addition of bidistilled water dropwise in a water/alkoxide molar ratio of 1-2/0.100-0.150, preferably 1-2/0.120-0.130, keeping the reflux until the formation of a gel.

[0152] IV) Aging, includes subjecting the gel obtained in stage III) to an aging treatment under the same conditions of stirring and reflux of stage III) for 1 to 24 hours, preferably for 4 to 12 hours, for the total formation of the nanostructured titania.

[0153] V) Drying, includes drying the nanostructured titania obtained in stage IV) at temperatures from 50 to 80 C., for 1 to 24 hours, preferably at 60-70 C. for 4 to 12 hours.

[0154] VI) Annealing, including subjecting the dry nanostructured titania obtained in stage V) to an annealing stage with the option of using an oxidizing or reducing atmosphere at temperatures from 200 to 600 C. for 1 to 12 hours, preferably at 300-500 C. for 3 to 9 hours.

[0155] FIG. 2 shows a scheme of how the evolution of the nanostructures nanocrystals-nanotubes-nanocrystals occurs by thermal effect once the nanotubes are obtained.

[0156] Second Stage-Hydrothermal Process

[0157] I). Normality of an alkaline solution (NaOH);

[0158] II). Reaction Temperature;

[0159] III). Stirring and reaction times;

[0160] IV). Washing, and;

[0161] V). Activation or annealing

[0162] I) Normality of an alkaline solution (NaOH), which forms a mixture of nanostructured titania with a 5 to 10 N solution of sodium hydroxide (NaOH) with stirring from 100 to 200 rpm, temperatures from 130 to 180 C., with dried titania obtained during stage V), up to an annealing stage, with the option of using an oxidizing or reducing atmosphere, at temperatures from 200 to 600 C. for 1 to 12 hours, preferably at 300-500 C. for 3 to 9 hours.

[0163] II) Reaction temperature, which includes subjecting the nanostructured titania mixed with a 5 to 10 N sodium hydroxide solution at temperatures from 130 to 180 C.

[0164] III) Stirring and reaction times, which includes subjecting the nanostructured titania mixed with a 5 to 10 N sodium hydroxide solution at temperatures from 130 to 180 C. for 12 to 24 hours with stirring from 100 to 200 rpm.

[0165] IV) Washing, which includes subjecting the nanostructured titania, once stages I, II and III have been completed, to the washing step with hydrochloric acid (HCl) until reaching an acid pH between 1 and 3; afterwards, a second washing with deionized water is performed until reaching a pH of 6 or 7.

[0166] V) Annealing, which includes subjecting the nanostructured titania, once stages I, II, III and IV have been completed, to a drying step from 70 to 80 C.; once this material is dry, it is submitted to an annealing process from 100 to 600 C., where the heating profile is 5 C. per minute. The nanostructured titania is obtained with two annealing profiles (350 and 600 C.); when the corresponding temperatures are reached, they are kept constant for 1 to 4 hours.

[0167] The nanostructured binary oxides TiO.sub.2Al.sub.2O.sub.3 obtained by means of the present invention shows the following main properties at different activation temperatures: [0168] The physicochemical properties, mainly those regarding the morphology, of the nanostructured binary oxides TiO.sub.2Al.sub.2O.sub.3 are shown in the following tables: [0169] Table 1 shows the nanostructured binary oxide TiO.sub.2Al.sub.2O.sub.3, which consists of proportions of amorphous crystalline phases: hydrogen titanates and the titanate/anatase combination.

TABLE-US-00001 TABLE 1 Proportion of the crystalline amorphous phases present in the nanostructures of the nanostructured binary oxide TiO.sub.2Al.sub.2O.sub.3 Crystalline Amorphous Phase (%) General/(Preferable) Annealing Temperature Titanates/Anatase Titanates/Anatase ( C.) (100 C.) (350 C.) 100-350 95-5 70-30 (98-2) (75-25) (350 C.) (600 C.) 350-600 70-30 25-75 (75-25) (20-80)

[0170] The morphological properties related to the purity and stability of the nanostructured binary oxide TiO.sub.2Al.sub.2O.sub.3 give this material special characteristics to support, distribute and interact with the incorporated active metals.

[0171] The nanostructured binary oxide TiO.sub.2Al.sub.2O.sub.3 shows characteristics of 1D (>100 nm), structures with external and internal diameter and interlayer intervals that are shown in Table 2.

TABLE-US-00002 TABLE 2 Dimensions of external (D.sub.e) and internal (D.sub.i) diameters and interlayers (E.sub.i) of the nanostructured binary oxide TiO.sub.2Al.sub.2O.sub.3 catalysts Hydrogen Titanates (nm) Activation Temperature General/(Preferable) ( C.) D.sub.e D.sub.i E.sub.i 100-350 10-9 3-5 0.7-0.8 (9-8) (3-4) (0.6-0.7) 350-600 6-7 1-2 0.1-0.2 (5-6) (1.5-2) (0.05-01)

[0172] As for the evolution from nanotubes to nanocrystals of the nanostructured binary oxide TiO.sub.2Al.sub.2O.sub.3, its dimension characteristics are shown in Table 3.

TABLE-US-00003 TABLE 3 Dimensions of the nanostructure crystals of the nanostructured binary oxide TiO.sub.2Al.sub.2O.sub.3 Annealing Crystal Dimensions Temperature (nm) ( C.) General Preferable 350-600 7-15 11-14

[0173] The textural properties related to the surface area, distributions of volume and pore diameter of the nanostructured binary oxide TiO.sub.2Al.sub.2O.sub.3, which also exert an special effect on its catalytic properties are shown in Table 4.

TABLE-US-00004 TABLE 4 Textural properties of the nanostructured binary oxide TiO.sub.2Al.sub.2O.sub.3 Surface Average Pore Annealing Area Diameter Temperature (m.sup.2/g) () ( C.) General Preferable General Preferable 100-350 370-350 330-340 20-40 30-55 350-600 200-280 260-270 20-30 20-25

[0174] The textural properties shown in Table 4 related to the surface area and pore diameter of the nanostructured binary oxide TiO.sub.2Al.sub.2O.sub.3 give this material special characteristic to support and distribute active metals.

[0175] The Quantum Size Effect.

[0176] The size dimension of the nanostructures in the evolution of the binary oxide TiO.sub.2Al.sub.2O.sub.3 exerts an effect on its physicochemical properties and particularly on the effect known as quantum size effect, which is related to its electronic properties, mainly to the band gap energy (Eg), which specially in semiconductor materials, is the one that drives the formation dynamics of the electron-hole pair, from which the efficiency of the redox processes depend on.

[0177] Commonly, in semiconductor materials, the goal is to reduce the Eg, but in the case of the binary oxide TiO.sub.2Al.sub.2O.sub.3, this energy value is special because it is associated with a structure change from nanocrystal to nanotube and the concomitant effect of this type of nanometric structures on the Eg.

[0178] Based on the aforementioned about the nanostructured binary oxide TiO.sub.2Al.sub.2O.sub.3, Table 5 shows the Eg values per structure type.

TABLE-US-00005 TABLE 5 Band gap energy (Eg) values of the nanostructured binary oxide TiO.sub.2Al.sub.2O.sub.3 Annealing Band gap energy (Eg) Temperature (eV) ( C.) General Preferable 100-350 2.8-2.9 3.2-2.8 350-600 2.9-3.3 2.9-3.0

[0179] The property related to the band gap energy (Eg) of the nanostructured binary oxide TiO.sub.2Al.sub.2O.sub.3 gives it special redox properties for its use as a support or catalyst in catalytic processes.

[0180] Hydroxylation Degree

[0181] The structure type and nanometric dimension of the nanostructured binary oxide TiO.sub.2Al.sub.2O.sub.3 exerts a special effect on the hydroxylation degree as morphological property as shown in Tables 6 to 9.

TABLE-US-00006 TABLE 6 Refined deconvolution of the zone of hydroxyl (OH) groups obtained at 300 C. for the nanostructured binary oxide TiO.sub.2Al.sub.2O.sub.3. Peak Area 1 6.90 2 2.79 3 1.53 Total area: 11.22

TABLE-US-00007 TABLE 7 Refined deconvolution of the zone of hydroxyl (OH) groups obtained at 600 C. for the nanostructured binary oxide TiO.sub.2Al.sub.2O.sub.3. Peak Area 1 3.86 2 2.15 3 1.27 4 1.21 Total area: 8.49

[0182] As a reference, Table 8 shows the deconvolution data of the zone of hydroxyl (OH) groups obtained at 300 C. for the commercial titania Degussa P25 activated at 600 C.

TABLE-US-00008 TABLE 8 Refined deconvolution of the zone of hydroxyl (OH) groups obtained at 300 C. for the commercial titania Degussa P25 activated at 600 C. Peak Area 1 0.12597 2 0.40968 3 0.40857 4 0.05357 Total area: 0.99779

[0183] The aforementioned properties provide that the nanostructured binary oxide of the present invention improves considerably the interaction degree of the OH groups on the surface (hydroxylation degree), which is a very important characteristic of its catalytic properties within the hydroxylation degree intervals shown in Table 9.

TABLE-US-00009 TABLE 9 Hydroxylation degrees for the nanostructured binary oxide TiO.sub.2Al.sub.2O.sub.3 at different activation temperatures Annealing Temperature Hydroxylation Sample ( C.) Degree* TNT-IMP 300 9.5-12 TNT-IMP 600 7.5-8.5 CommercialTiO.sub.2** 600 0.99779 *Deconvolutions obtained at 300 C. **Commercial titania Degussa P25. TNT-IMP corresponds to TiO.sub.2Al.sub.2O.sub.3.

[0184] The nanostructured binary oxide TiO.sub.2Al.sub.2O.sub.3 can be used mainly as: [0185] a) As a support of active metals or as a catalyst; [0186] b) In heterogeneous or homogeneous catalytic processes for the reduction of pollutants present in gaseous and/or aqueous emissions by means of thermal or photoassisted processes; [0187] c) As coatings of catalytic matrices such as ceramic and/or metallic monoliths made with different materials like catalytic matrices that can have different geometric bodies and different types and arrangements of cells or channels in order to make efficient both the contact and contact times; [0188] d) As a film on different types of substrates such as glass, metals, polymers, etc., and; [0189] e) Alone or with the incorporation of active metals, in order to control pollutants present in gaseous or aqueous emissions using heterogeneous or homogeneous catalytic processes.

[0190] In one embodiment the nanostructured titania catalyst having the formula TiO.sub.2Al.sub.2O.sub.3 is characterized by the following acidity characteristics:

TABLE-US-00010 Pyridine acidity within the temperature interval from 300 to 500 C. of the binary oxide TiO.sub.2Al.sub.2O.sub.3 with and without active metals Micro-moles of Micro-moles of pyridine/m.sup.2 pyridine/m.sup.2 Lewis Sites Brnsted Sites Sample (1445 cm.sup.1) (1540 cm.sup.1) TiO.sub.2Al.sub.2O.sub.3 3.5 0.222 V/TiO.sub.2Al.sub.2O.sub.3 3.7 0.255

EXAMPLES

[0191] What follows is the description of some practical examples to provide a better understanding of the present invention without limiting its scope.

Example 1

[0192] To synthesize the nanostructured binary oxide TiO.sub.2Al.sub.2O.sub.3, 3.0 g of TiO.sub.2Al.sub.2O.sub.3 nanocrystals previously synthesized by the sol-gel method with anatase phase crystal size of 5 nm, specific area of 220 m.sup.2/g, pore volume of 0.17 cm.sup.3/g and pore diameter of 36 are mixed in an autoclave Parr. By means of the hydrothermal method, a mixing process takes place using a sodium hydroxide (NaOH) solution with normality of 5 and 10 N at temperatures ranging from 130 to 180 C. for 24 h at 200 rpm with autogenous pressure. After 24 h, the product is washed with HCl until reaching an acid pH from 2 to 3; afterwards, the material is washed abundantly with deionized water until eliminating the chloride ions and reaching a pH from 6 to 7. The obtained materials are dried for 12 h at 80 C. The obtained nanostructured binary oxide was identified as TiO.sub.2Al.sub.2O.sub.3.

Example 2

[0193] From the nanostructured binary oxide TiO.sub.2Al.sub.2O.sub.3 prepared as in Example 1, the activation or annealing process took place at 350 C. for 4 h under oxidizing atmosphere. A second annealing stage was carried out from 350 to 600 C. The obtained nanostructured binary oxide was identified as TiO.sub.2Al.sub.2O.sub.3 and its textural and morphological properties are shown in Tables 1 to 9 and in FIGS. 1 to 5.

Example 3

[0194] To synthesize the nanostructured binary oxide TiO.sub.2Al.sub.2O.sub.3, 3.0 g of TiO.sub.2Al.sub.2O.sub.3 nanocrystals previously synthesized by the sol-gel method with crystal size of 7 nm, specific area of 190 m.sup.2/g, pore volume of 0.15 cm.sup.3/g and pore diameter of 40 are mixed in an autoclave Parr. By means of the hydrothermal method, a mixing process takes place using a sodium hydroxide (NaOH) solution with normality of 5 and 10 N at temperatures ranging from 130 to 180 C. for 24 h at 200 rpm with autogenous pressure. After 24 h, the product is washed with HCl until reaching an acid pH from 2 to 3; afterwards, the material is washed abundantly with deionized water until eliminating the chloride ions and reaching a pH from 6 to 7. The obtained materials are dried for 12 h at 80 C.

Example 4

[0195] From the nanostructured binary oxide TiO.sub.2Al.sub.2O.sub.3 prepared as in Example 3, the annealing process was carried out at 500 C. for 4 h under oxidizing atmosphere. The obtained nanostructured binary oxide TiO.sub.2Al.sub.2O.sub.3 and its textural and morphological properties are shown in Tables 1 to 9 and in FIGS. 1 to 5.

Example 5

[0196] To the nanostructured binary oxide TiO.sub.2Al.sub.2O.sub.3 obtained according to the procedure described in Example 1, vanadium is incorporated as an active metal. The procedure includes placing in a glass reactor 1 to 5 g of the nanostructured binary oxide TiO.sub.2Al.sub.2O.sub.3, adding 80 to 400 ml of an ammonium metavanadate solution to obtain percentages of 3, 5 and 10 wt. % of vanadium in the catalyst. After the catalyst impregnation, a washing step with deionized water takes place in order to reach a pH between 6 and 8. The obtained catalysts are dried for 12 h at 80 C. The obtained catalyst was identified as V/TiO.sub.2Al.sub.2O.sub.3.

Example 6

[0197] From the V/TiO.sub.2Al.sub.2O.sub.3 catalyst prepared as in Example 5, the annealing process was carried out at 500 C. for 4 h under oxidizing atmosphere. The obtained catalyst was identified as V/TiO.sub.2Al.sub.2O.sub.3-5 and its textural and morphological properties are shown in Table 10 and in FIGS. 6 to 9.