Title of Invention	"NANOCRYSTALLINE AND MESOPOROUS TITANIUM DIOXIDE AND ITS PREPARATION FROM TITANIUM CARBONATE SOURCE"
Abstract	The present invention relates to preparation of nanocrystalline and mesoporous titanium dioxide powder with high surface area and a use of the prepared titanium dioxide as a photo-catalyst. The procedure provides highly crystalline titanium dioxide with narrow particle size / pore distributions and use of carbonate precursor instead of other titanium source provides an economical, greener, safe procedure. More particularly, discloses a method for the preparation of titanium dioxide powder comprises of the steps of 1) the synthesis of aqueous titanium peroxo-carbonate solution; an aqueous titanium precursor from bulk TiO2, titanium alkoxide, titanium tetrachloride or titanium sulphate; 2) adjustment of pH in the range of 2 - 14, 3) addition of aqueous solution of surfactant, 4) hydrothermal treatment of the resultant solution at 50-400°C for 30min -60h, 5) filtering, washing and drying the resultant precipitates 6) calcining the dried materials at 300-900°C for 2-8 h to give desired nanocrystalline TiO2 powder with a specific surface area of 30-375 m2/g. The synthesized TiO2 shows high photocatalytic activity, which can decompose environmental gaseous and organic pollutants by taking advantage of an advanced oxidation process (AOP) in which pollution-free energy, such as solar energy is utilized as a driving force. The procedure provides highly crystalline titanium dioxide with narrow particle size distributions and use of carbonate precursor instead of titanium chloride, organo-titanium precursor provides an economical, greener, safe procedure.

Title of Invention

"NANOCRYSTALLINE AND MESOPOROUS TITANIUM DIOXIDE AND ITS PREPARATION FROM TITANIUM CARBONATE SOURCE"

Abstract

The present invention relates to preparation of nanocrystalline and mesoporous titanium dioxide powder with high surface area and a use of the prepared titanium dioxide as a photo-catalyst. The procedure provides highly crystalline titanium dioxide with narrow particle size / pore distributions and use of carbonate precursor instead of other titanium source provides an economical, greener, safe procedure. More particularly, discloses a method for the preparation of titanium dioxide powder comprises of the steps of 1) the synthesis of aqueous titanium peroxo-carbonate solution; an aqueous titanium precursor from bulk TiO2, titanium alkoxide, titanium tetrachloride or titanium sulphate; 2) adjustment of pH in the range of 2 - 14, 3) addition of aqueous solution of surfactant, 4) hydrothermal treatment of the resultant solution at 50-400°C for 30min -60h, 5) filtering, washing and drying the resultant precipitates 6) calcining the dried materials at 300-900°C for 2-8 h to give desired nanocrystalline TiO2 powder with a specific surface area of 30-375 m2/g. The synthesized TiO2 shows high photocatalytic activity, which can decompose environmental gaseous and organic pollutants by taking advantage of an advanced oxidation process (AOP) in which pollution-free energy, such as solar energy is utilized as a driving force. The procedure provides highly crystalline titanium dioxide with narrow particle size distributions and use of carbonate precursor instead of titanium chloride, organo-titanium precursor provides an economical, greener, safe procedure.

Full Text	FIELD OF THE INVENTION The present invention relates to a process for the preparation of nanocrystalline and mesoporous titanium dioxide (Titania) powder using a new titanium source titanium peroxo carbonate, with a large specific surface area, useful as photo catalyst. The present invention further relates to a method for the preparation of titanium dioxide powder which can be used as a catalyst for the removal of different toxic gases, pollutant organic substances and the like. BACKGROUND OF THE INVENTION Titanium dioxide is used as a photocatalyst. Particularly, titanium dioxide with anatase phase has been known to be highly stable and show excellent photo catalytic activity by absorbing light and reacting with toxic materials. P-25, a brand name of titanium dioxide, manufactured by M/s Degussa Germany, which has been evaluated as being the most active among the presently available photocatalysts, shows insufficient photo activity under a practically employed light intensity of tens of watts, which has limited its practical application. Titania is also an important material used as white pigment, solar-cell device etc. Titanium dioxide powders have been conventionally prepared by a sol-gel method and a chloride process. The sol-gel method is, however, difficult to perform continuously and incurs a high production cost because additional heat treatments must be adopted and alkoxide, the raw material used is moisture sensitive and very expensive. The chloride process, which is at present commonly used, also suffers from disadvantages: it needs a sophisticated experimental setup owing to its high temperature and pressure reaction. This process requires an additional protective facility because of the corrosive gases (Cl2, HC1) produced during the reaction, leading to higher production costs. In addition, special devices are employed for applying electric fields or controlling the reactant mixing ratio to control the shape and size of TiO2 particles. Titanium dioxide P-25, manufactured by Degussa Co., Germany, is well known to be produced using the chloride process and not desirable in terms of production cost and photocatalytic properties. References may be made to patent 6,517,804, wherein the synthesis of Titania ultrafine powder from pure titanium tetrachloride is reported. The process contains the following steps; addition of ice pieces or icy distilled water to pure titanium tetrachloride (TiCl4) to give an aqueous titanylchloride, controlled addition of distilled water to the aqueous titanylchloride solution with heating from controlled hydrolysis is disclosed. Filtering and washing gave the Titania ultrafine powder. In the above process requires an additional protective facility because of the corrosive gases (Cl2, HC1) produced during the reaction, leading to higher production costs and risky. Again, it demands special care during the dilution and hydrolysis steps, which makes the procedure too complicated. The present process overcomes the above drawbacks. References may be made to patent application WO2008036176-A1, wherein the synthesis of nanosized Titania using titanium peroxo precursor is disclosed. To titanium compound solution (titanium tetrachloride, titanium oxychloride, titanium trichloride, titanium tetrabromide, hydrated titanium sulfate, or hydrated titanium oxysulfate) excess hydrogen peroxide was added and mixed with an alkali; and/or compound containing sulfate, nitrate, and fluorine ions to accelerate formation of anatase titanium dioxide (TiO2). Then the solution was heated to get the nanosized Titania. Presence of large amount of H2O2 makes the procedure more risky and complicated. Again the used titanium source is moisture sensitive, corrosive and costly. In the present procedure, we are able to avoid the difficulty by using very small amount of H2O2 and the use of bulk TiO2 as titania source avoids other problems. References may be made to patent applications WO2007085911-A2 and WO2007085911-A3, wherein the synthesis of size homogenous composition of titanium (IV) oxide nanoparticles using alkoxide through a sol-gel process is disclosed. In a detail procedure, a solution of titanium alkoxide precursor was added to an aqueous acidic aqueous solution (below pH 4). The dispersed mixture was constantly stirred for 4 hours, resulting in the formation of a colloidal solution. Only after the solution was refined, a second solution containing the complexing agent was added, and the color of the final solution turned to yellow-orange. Under continuous stirring, to the final sol, an amount of a modifier-stabilizer was added. The preparation of nanostructured titania powders included solvent evaporation followed by thermal treatment of the solid residue at 400-550°C. However, the method is quite complicated and difficult to perform. The used titanium source titanium alkoxide is moisture sensitive and very expensive. Present developed procedure is simple and it is possible to overcome the moisture sensitivity and cost problem by using the titanium peroxo carbonate complex. References may be made to patent applications CN1398665-A and CN1132679-C for the synthesis of mesoporous TiO2-SiO2. The synthetic procedure contains the following steps: the preparation of an isopropanol titanium-acetone solution; the preparation of a titanium polymerized sol; and the preparation of a titania membrane, soaking the mesoporous Ti-Si support body in titanium polymerized sol with 1.9-2.5 x 10" Pa.s viscosity for 0.5-2 minutes before taking out and drying naturally for 44-52 hours to form a gel layer, then drying in a vacuum drier, calcining to 630-670°C. The main drawbacks of the procedure are the use of moisture sensitive and costly alkoxide and hazards organic solvent isopropanol. Again the photocatalytic activituy of the synthesized material is not upto the mark. Using the developed procedure it is possible to overcome the above drawbacks. References may be made to patent JP-A-5-184923, wherein titania catalyst can be obtained by heat-treating amorphous fibers to deposit a crystal of an anatase-form titanium oxide and a vanadium oxide, in which amorphous fibers is produced by the sol-gel method of hydrolyzing a alkoxide in a mixed solution of a titanium alkoxide, a vanadium compound and other alkoxide, successively gelling is disclosed. Used precursor titanium alkoxide is moisture sensitive and costly. Moreover, Titania catalyst described has problems in that the activity is low and the performance of removal of nitrogen oxides is low. The present process overcomes the above drawbacks of moisture sensitive and costly reagent. The synthesized titanium dioxide is catalytically highly active. References may be made to patent US6444608, wherein the synthesis of mesoporous TiO2 by dissolving a titanium alkoxide in a solvent to give a titanium alkoxide solution; adding a mixed solution containing water and a solvent to the titanium alkoxide solution to perform hydrolysis as well as simultaneous polymerization of titania to give a polymer solution; adding a fatty acid; separating a polymer containing the fatty acid from the polymer solution and calcinations is disclosed. The main drawbacks of the procedure are the use of moisture sensitive, costly alkoxide and hazards organic solvent. It is a complicated procedure. Catalytic activity of the TiO2 towards removal of nitrogen oxides, oxidation of organic substances, decomposition of dioxine compounds, as well as decomposition and removal of organic solvents, agricultural chemical and surfactant is low. Using the developed procedure it is possible to overcome the above drawbacks In all the above stated prior arts, it is evident that selection of titanium source is a crucial step for the synthesis of above mentioned titanium based materials with respect to the moisture sensitivity, risk factor to handle and cost factor. In all the synthetic procedures described above use of titanium epoxide and chloride makes the procedure more complicated costly and risky. Moreover, Titania synthesized by these procedures has problems, in that the catalytic activity is low. The present invention is directed to a novel approach for the synthesis of nanocrystalline and mesoporous titania using a new titanium source "titanium preoxy-carbonate" which is cost effective, easy to handle to avoid the existing titanium sources which are costly, moisture sensitive and corrosive. The "titanium preoxy-carbonate" is synthesized from bulk titania and the required amount of peroxide is very low which is catalytic amount. OBJECTIVE OF THE INVENTION The main objective of the present invention is to provide a process to prepare nanocrystalline and mesoporous titanium dioxide powder from an aqueous titanium peroxy-carbonate solution from bulk titanium dioxide which obviates the drawback as detailed above. Another objective of the present invention is to prepare an aqueous titanium peroxy-carbonate solution from other titanium source viz. titanium alkoxide, titanium tetrachloride and titanium sulphate. Still another objective of the present invention is to provide a method of producing the mesoporous, nanocrystalline titanium dioxide with high specific surface area, narrow pore size distribution and having anatase crystalinity, using the aqueous titanium peroxy-carbonate solution. Yet another objective of the present invention is to synthesize mesoporous and nano-cryatalline titanium dioxide catalyst and at least one catalyst component selected from the group consisting of V, W, Al, As, Ni, Zr, Mo, Ru, Mg, Mn, Cu, Cs, Ca, Fe, Cr and Pt. Yet another objective of the present invention is the synthesize mesoporous and nano-cryatalline titanium dioxide based mixed metal oxides catalyst like TiO2-ZrO2, TiO2-SiO2, TiO2-Al2O3, TiO2-SiO2-ZrO2, TiO2-SiO2-Al2O3 using the precursor. Yet another objective of the present invention is to use the above mesoporous and nano-cryatalline titanium dioxide powder as a photo catalyst. SUMMARY OF THE INVENTION Accordingly, present invention provides a process for the preparation of nanocrystalline and mesoporous titanium dioxide from titanium peroxo carbonate and the said process comprising the steps of: i. digesting titanium source using ammonium fluoride, hydrofluoric acid and water with a molar ratio in the range of 1: 3.25: 3.06: 111.02 to 1: 1.5: 2.45: 44.4 at a temperature in the range of 25-70°C for a period of 20-40 h; ii. adjusting pH of the solution as obtained in step (i) in the range of 8 to 14 by adding base followed by filtering and washing with ammonium chloride and water till free from fluoride ions to obtain titanium hydroxide precipitate; iii. stirring the titanium hydroxide precipitate as obtained in step (ii) in a solution containing water, H2O2, ammonium carbonate with a molar ratio range of 53.5: 0.8:1 to 26.7: 0.338: 1 for a period in the range of 10-45 min at a temperature in the range of 20-35°C at the rate of 100-700 rpm to obtain titanium peroxo-carbonate solution; iv. adjusting the pH of the titanium peroxo-carbonate solution as obtained in step (iii) in the range of 2-14 by adding acid or base; v. adding 5-30 % w/v aqueous solution surfactant in a range of 2.18 x10-2 -8.72 mole % with respect to titanium source to the pH adjusted solution as obtained in the step (iv) with constant stirring at the rate of 100-700 rpm for a period in the range of 10-30 min at temperature in the range of 25-35°C; vi. dopping 0.001-10 mole % metal salt with respect to titania to the solution as obtained in the step (v) with constant stirring at the rate of 100-700 rpm for a period in the range of 10-20 min; vii. autoclaving for hydrothermal treatment of the solution as obtained in the step (vi) at a temperature range of 50-400°C for a period in the range of 30 min to 60 h; viii. filtering and drying of the precipitate as obtained in step (vii) at a temperature in the range of 25-90°C; ix. calcining the dried precipitate as obtained in step (viii) at a temperature in the range 300-900°C for a period in the range of 2-8 h to get nano-crystalline and mesoporous titanium dioxide. In an embodiment of the present invention, titanium source used is selected from the group consisting of bulk titanium dioxide, titanium alkoxide, titanium tetrachloride or titanium sulphate more preferably bulk titanium dioxide. In another embodiment of the present invention, yield of the said nano-crystalline, mesoporous and doped titanium dioxide is ranging between 78-92%. In still another embodiment of the present invention, pore size of the nanocrystalline, mesoporous and doped titanium dioxide is ranging between 6 to 30 nm. In still another embodiment of the present invention, BET surface area of the nanocrystalline, mesoporous and doped titanium dioxide is ranging between 30-375 m2/g. In still another embodiment of the present invention, base used is selected from the group consisting of ammonium hydroxide, sodium hydroxide or potassium hydroxide more preferably ammonium hydroxide. In yet another embodiment of the present invention, acid used is selected from the group consisting of acetic acid, propanoic acid, tartaric acid, citric acid and oxalic acid. In yet another embodiment of the present invention, surfactant used is selected from the group consisting of Cetyltrimethylammonium bromide (CTAB), tetradecyltrimethylammonium bromide (TTAB), Decyltnmethylammonium bromide (DTAB) or hexadecyltrimethylammonium bromide (HTAB). In yet another embodiment of the present invention, metal salt used is selected from the group consisting of alkali metal, alkali earth metal or transition metal salts more preferably copper nitrate, iron nitrate, copper chloride, cerium nitrate and magnesium nitrate. DETAIL DESCRIPTION OF THE INVENTION Present invention provides a process for the synthesis of aqueous titanium peroxo carbonate, an aqueous titanium precursor from bulk TiO2 In the present invention much intensive efforts have been given to synthesis and improving catalytic activity of titania using freshly prepared titanium peroxo carbonate solution as titanium source. As a result, in the present invention produced nanocrystalline and porous titania having a high degree of anatase crystallinity, a large specific surface area and a narrow pore size / particle size distribution, which is obtainable by hydrothermal treatment of titanium peroxo carbonate solution in the presence or absence of surfactant, which exhibits an excellent catalytic activity. The present invention also provides a titania catalyst comprising the nanocrystalline or porous titania described above and at least one catalyst component selected from the group consisting of alkali metals, alkali-earth metals or transition metals. The present invention provides a method for the synthesis of highly active nanocrystalline and mesoporous titania catalyst from freshly prepared aqueous titanium peroxo carbonate solution which comprises of the following steps; (i) digesting 2-10g bulk TiO2 in 50-100ml of de-ionized water containing ammonium fluoride in the range 3-7g, hydrofluoric acid in the range of 3-12 ml at a temperature range of 25-70°C for a period of 20-40h; (ii) treating the solution obtained in step (i) with 2N ammonium hydroxide solution in the range of 10-75 ml, filtering and washing with water till free from fluoride ions; (iii) stirring the freshly prepared titanium hydroxide obtained in step (ii) in de-ionized water in the range of 20-100 ml, H2O2 in the range of 2-8ml, ammonium carbonate in the range of 2-20 g for a period in the range of 10-45 min at a temperature in the range of 20-35°C; (iv) adjusting the pH of the clear titanium peroxo-carbonate solution obtained in step (iii) in the range of 2-14 by adding NaOH or NH4OH or acetic acid in the range of 1-25 ml solution; (v) adding Cetyltrimethylammonium bromide in the range of 0-4 g to the pH adjusted solution obtained in the step (iv) with constant stirring for a period in the range of 10-30 min; (vi) adding 0.001-10 mole % transition/alkaline/alkaline-earth metal salt with respect to titania to the solution obtained in the step (v) with constant stirring for a period in the range of 10-20 min at a temperature in the range of 25-35°C; (vii) autoclaving the solution obtained in the step (vi) at a temperature range of 50- 400°C for a period in the range of 30min-60 h; (viii) filtering and drying of the precipitate obtained in step (vii) at a temperature in the range of 25-90°C; (ix) calcining the dried sample as obtained in step (xii) at a temperature in the range 300-900°C for a period in the range of 2-8 h to get nano-crystalline, mesoporous and doped titanium dioxide. Present invention provides a process for the preparation of nanocrystalline and mesoporous titanium di-oxide from bulk titanium dioxide. Here solid titanium dioxide is initially reacted with ammonium fluoride and hydrofluoric acid to obtain a soluble titanium solution to which ammonia is added to precipitate titanium hydroxide. The latter is reacted with hydrogen peroxide and ammonium carbonate, to obtain a clear solution of titanium peroxo-carbonate solution. The hydrothermal treatment of the titanium peroxo-carbonate solution with / without surfactant gives highly crystalline titanium dioxide with high surface area, porous with narrow pore size / particle size distribution. This titanium dioxide shows very high photo-catalytic activity. We are reporting for the first time the initial preparation of titanium peroxo-carbonate to obtain highly crystalline and porous titanium dioxide. The prior act neither teaches nor reveals how titanium peroxo-carbonate solution as a source of titanium can be used to prepare crystalline and porous titanium dioxide which exhibits high photo-catalytic activity. The inventive steps adopted in the present invention are (i) it obviates the need of having a starting material which are sensitive to moisture or corrosive, (ii) hydrothermal treatment of titanium peroxo-carbonate in presence of surfactant and peroxide as oxidizing agent decompose carbonate into carbon dioxide and water and thereby facilities formation of porous and material with high crystalline. BRIEF DISCRETION OF THE DRAWING Figure-1. Represents Transmission Electron Micrograph (TEM) of the synthesized copper doped mesoporous titanium dioxide by the process described in Example 1. Figure-2 Represents XRD patterns of copper doped mesoporous titanium dioxide synthesized by the process described in Example 1. Figure-3 Represents N2 sorption isotherm of the synthesized copper doped mesoporous titanium dioxide by the process described in Example 1. Figure-4. Represents transmission electron micrograph (TEM) of the synthesized copper doped mesoporous titanium dioxide by the process described in Example 5. Figure-5.Represents N2 sorption isotherm of the synthesized copper doped mesoporous titanium dioxide by the process described in Example 11. Figure-6. Represents Transmission Electron Micrograph (TEM) of the synthesized nanocrystalline titanium dioxide Cubes by the process described in Example 12. Figure-7. Represents XRD patterns of pure anatase TiO2 nano cubes synthesized by the process described in Example 12. Figure-8 Represents N2 sorption isotherm of the synthesized titanium dioxide cubes synthesized by the process described in Example 12. Figure-9 Represents transmission electron micrograph (TEM) of the synthesized copper doped nanocrystalline titanium dioxide Cubes by the process described in Example 13. Figure-10.Represents XRD patterns of copper doped anatase TiO2 nano cubes synthesized by the process described in Example 13 EXAMPLES The following examples are given by way of illustration and therefore should not be construed to limit the scope of the present invention. Example-1 5 g bulk TiO2 and 6 g ammonium fluoride was taken In a 250 ml plastic beaker and to it 8 ml hydrofluoric acid and 75 ml water was added and heated at 70°C temperature for 30 hrs. After the digestion period, 50 ml 2N ammonium hydroxide was slowly added to adjust the pH of the solution mixture to 11.5. After pH adjustment white precipitate appeared and were filtered, washed initially with ammonium hydroxide followed by distilled water. The titanium hydroxide precipitates were dispersed in 50ml water to which 20 ml solution containing 6 gms ammonium carbonate was added under continuous stirring. To this reaction mixture 2 ml 30% concentration hydrogen peroxide was slowly added at 30°C and the stirring was continued for another 30 minutes. This resulted in the formation of titanium peroxo carbonate solution, which was further diluted by adding 25 ml water. The pH of this solution was adjusted from 9 by adding 2 ml of 1N acetic acid. From the total reaction mixture, 125ml of titanium peroxo carbonate was added at a rate of 2 ml/ minute to a separately prepared 25 ml of 8% (w/v) CTAB solution under stirring at 30°C. The stirring was continued for another 10 minutes and then 20 ml of 1.1% (w/v) solution of copper (II) nitrate was added at 30°C under stirring. 53 ml from the total mixture was taken in an 80 ml Teflon lined bomb and initially heated to 80°C for 24 hrs and then at 100°C for another 24hrs. The product was filtered, washed, dried and calcined at 550°C for 6 hrs. The yield was 88%. The product has BET surface area 180 m /g and X-ray diffraction pattern of metal ion incorporated TiO2 evidences pure anatase phase. Example-2 In a 250 ml plastic beaker, 5 g bulk TiO2, 6 gms ammonium fluoride was taken and to it 8ml hydrofluoric acid and 75 ml water was added and heated at 60°C for 40 hrs. After the digestion period, 35 ml 2N ammonium hydroxide was slowly added to adjust the pH of the solution mixture to 8.5. After pH adjustment white precipitate appeared and were filtered, washed initially with ammonium hydroxide followed by distilled water. The titanium hydroxide precipitates were dispersed in 50ml water to which 20 ml solution containing 6 gms ammonium carbonate was added under continuous stirring. To this reaction mixture 2 ml 30% concentration hydrogen peroxide was slowly added at 30°C and the stirring was continued for another 30 minutes. This resulted in the formation of titanium peroxo carbonate solution, which was further diluted by adding 25 ml water. The pH of this solution was adjusted to 9 by adding 2 ml of 1N acetic acid. From the total reaction mixture, 125ml of titanium peroxo carbonate was added at a rate of 2 ml/ minute to a separately prepared 25 ml of 8% (w/v) CTAB solution under stirring at 30°C. The stirring was continued for another 10 minutes and then 20 ml of 1.1% (w/v) solution of copper (II) nitrate was added at 30°C under stirring. 53 ml from the total mixture was taken in an 80 ml Teflon lined bomb and initially heated to 80°C for 24 hrs and then at 100°C for another 24hrs. The product was filtered, washed, dried and calcined at 550°C for 6 hrs. The yield was 85%. The product has BET surface area 174 m2/g and X-ray diffraction pattern of metal ion incorporated TiO2 evidences pure anatase phase. Example-3 In a 250 ml plastic beaker, 5 g bulk TiO2, 6 gms ammonium fluoride was taken and to it 8ml hydrofluoric acid and 75 ml water was added and heated at 70°C for 30 hrs. After the digestion period, 50 ml 2N ammonium hydroxide was slowly added to adjust the pH of the solution mixture to 11.5. After pH adjustment white precipitate appeared and were filtered, washed initially with ammonium hydroxide followed by distilled water. The titanium hydroxide precipitates were dispersed in 50ml water to which 20 ml solution containing 8 gms ammonium carbonate was added under continuous stirring. To this reaction mixture 2 ml 30% concentration hydrogen peroxide was slowly added at 30°C and the stirring was continued for another 30 minutes. This resulted in the formation of titanium peroxo carbonate solution, which was further diluted by adding 25 ml water. The pH of this solution was adjusted to 9 by adding 2.5 ml of 1N acetic acid. From the total reaction mixture, 125ml of titanium peroxo carbonate was added at a rate of 2 ml/ minute to a separately prepared 25 ml of 8% (w/v) CTAB solution under stirring at 30°C. The stirring was continued for another 10 minutes and then 20 ml of 1.1 % (w/v) solution of copper (II) chloride was added at 30°C under stirring. 53 ml from the total mixture was taken in an 80 ml Teflon lined bomb and initially heated to 80°C for 24 hrs and then at 100°C for another 24hrs. The product was filtered, washed, dried and calcined at 550°C for 6 hrs. The yield was 87%. The product has BET surface area 185 m2/g and X-ray diffraction pattern of metal ion incorporated TiO2 evidences pure anatase phase. Example-4 In a 250 ml plastic beaker, 5 g bulk TiO2, 6 gms ammonium fluoride was taken and to it 8ml hydrofluoric acid and 75 ml water was added and heated at 70°C for 30 hrs. After the digestion period, 50 ml 2N ammonium hydroxide was slowly added to adjust the pH of the solution mixture to 11.5. After pH adjustment white precipitate appeared and were filtered, washed initially with ammonium hydroxide followed by distilled water. The titanium hydroxide precipitates were dispersed in 50ml water to which 20 ml solution containing 6 gms ammonium carbonate was added under continuous stirring. To this reaction mixture 2 ml 30% concentration hydrogen peroxide was slowly added at 30°C and the stirring was continued for another 30 minutes. This resulted in the formation of titanium peroxo carbonate solution, which was further diluted by adding 25 ml water. The pH of this solution was adjusted to 6 by adding 7 ml of 1N acetic acid. From the total reaction mixture, 125ml of titanium peroxo carbonate was added at a rate of 2 ml/ minute to a separately prepared 25 ml of 8% (w/v) CTAB solution under stirring at 30°C. The stirring was continued for another 10 minutes and then 20 ml of 1.1 % (w/v) solution of copper (II) chloride was added at 30°C under stirring. 53 ml from the total mixture was taken in an 80 ml Teflon lined bomb and initially heated to 80°C for 24 hrs and then at 100°C for another 24hrs. The product was filtered, washed, dried and calcined at 550°C for 6 hrs. The yield was 78%. The product has BET surface area 142 m2/g and X-ray diffraction pattern of metal ion incorporated TiO2 evidences pure anatase phase. Example-5 In a 250 ml plastic beaker, 5 g bulk TiO2, 6 gms ammonium fluoride was taken and to it 8ml hydrofluoric acid and 75 ml water was added and heated at 60°C for 40 hrs. After the digestion period, 35 ml 2N ammonium hydroxide was slowly added to adjust the pH of the solution mixture to 8.5. After pH adjustment white precipitate appeared and were filtered, washed initially with ammonium hydroxide followed by distilled water. The titanium hydroxide precipitates were dispersed in 50ml water to which 20 ml solution containing 6 gms ammonium carbonate was added under continuous stirring. To this reaction mixture 2 ml 30% concentration hydrogen peroxide was slowly added at 30°C and the stirring was continued for another 30 minutes. This resulted in the formation of titanium peroxo carbonate solution, which was further diluted by adding 25 ml water. The pH of this solution was adjusted to 9 by adding 2 ml of 1N acetic acid. From the total reaction mixture, 125ml of titanium peroxo carbonate was added at a rate of 2 ml/ minute to a separately prepared 25 ml of 3% (w/v) CTAB solution under stirring at 30°C. The stirring was continued for another 10 minutes and then 20 ml of 1.1% (w/v) solution of copper (II) nitrate was added at 30°C under stirring. 53 ml from the total mixture was taken in an 80 ml Teflon lined bomb and initially heated to 80°C for 24 hrs and then at 100°C for another 24hrs. The product was filtered, washed, dried and calcined at 550°C for 6 hrs. The yield was 92%. The product has BET surface area 134 m2/g and X-ray diffraction pattern of metal ion incorporated TiO2 evidences pure anatase phase. Example-6 In a 250 ml plastic beaker, 5 g bulk TiO2, 6 gms ammonium fluoride was taken and to it 8ml hydrofluoric acid and 75 ml water was added and heated at 70°C for 30 hrs. After the digestion period, 50 ml 2N ammonium hydroxide was slowly added to adjust the pH of the solution mixture to 11.5. After pH adjustment white precipitate appeared and were filtered, washed initially with ammonium hydroxide followed by distilled water. The titanium hydroxide precipitates were dispersed in 50ml water to which 20 ml solution containing 6 gms ammonium carbonate was added under continuous stirring. To this reaction mixture 2 ml 30% concentration hydrogen peroxide was slowly added at 30°C and the stirring was continued for another 30 minutes. This resulted in the formation of titanium peroxo carbonate solution, which was further diluted by adding 25 ml water. The pH of this solution was adjusted from 9 by adding 2 ml of 1N acetic acid. From the total reaction mixture, 125ml of titanium peroxo carbonate was added at a rate of 2 ml/ minute to a separately prepared 25 ml of 8% (w/v) CTAB solution under stirring at 30°C. The stirring was continued for another 10 minutes and then 20 ml of 0.75% (w/v) solution of copper (II) nitrate was added at 30°C under stirring. 53 ml from the total mixture was taken in an 80 ml Teflon lined bomb and initially heated to 80°C for 24 hrs and then at 100°C for another 24hrs. The product was filtered, washed, dried and calcined at 550°C for 6 hrs. The yield was 89%. The product has BET surface area 203 m2/g and X-ray diffraction pattern of metal ion incorporated TiO2 evidences pure anatase phase. Example-7 In a 250 ml plastic beaker, 5 g bulk TiO2, 6 gms ammonium fluoride was taken and to it 8ml hydrofluoric acid and 75 ml water was added and heated at 70°C for 30 hrs. After the digestion period, 50 ml 2N ammonium hydroxide was slowly added to adjust the pH of the solution mixture toll.5. After pH adjustment white precipitate appeared and were filtered, washed initially with ammonium hydroxide followed by distilled water. The titanium hydroxide precipitates were dispersed in 50ml water to which 20 ml solution containing 6 gms ammonium carbonate was added under continuous stirring. To this reaction mixture 2 ml 30% concentration hydrogen peroxide was slowly added at 30°C and the stirring was continued for another 30 minutes. This resulted in the formation of titanium peroxo carbonate solution, which was further diluted by adding 25 ml water. The pH of this solution was adjusted from 9 by adding 2 ml of 1N acetic acid. From the total reaction mixture, 125ml of titanium peroxo carbonate was added at a rate of 2 ml/ minute to a separately prepared 25 ml of 8% (w/v) CTAB solution under stirring at 30°C. The stirring was continued for another 10 minutes and then 20 ml of 1.5 % (w/v) solution of Iron (III) nitrate was added at 30°C under stirring. 53 ml from the total mixture was taken in an 80 ml Teflon lined bomb and initially heated to 80°C for 24 hrs and then at 100°C for another 24hrs. The product was filtered, washed, dried and calcined at 550°C for 6 hrs. The yield was 89%. The product has BET surface area 194 m /g and X-ray diffraction pattern of metal ion incorporated TiO2 evidences pure anatase phase. Example-8 In a 250 ml plastic beaker, 5 g bulk TiO2, 6 gms ammonium fluoride was taken and to it 8ml hydrofluoric acid and 75 ml water was added and heated at 70°C for 30 hrs. After the digestion period, 50 ml 2N ammonium hydroxide was slowly added to adjust the pH of the solution mixture to 11.5. After pH adjustment white precipitate appeared and were filtered, washed initially with ammonium hydroxide followed by distilled water. The titanium hydroxide precipitates were dispersed in 50ml water to which 20 ml solution containing 6 gms ammonium carbonate was added under continuous stirring. To this reaction mixture 2 ml 30% concentration hydrogen peroxide was slowly added at 30°C and the stirring was continued for another 30 minutes. This resulted in the formation of titanium peroxo carbonate solution, which was further diluted by adding 25 ml water. The pH of this solution was adjusted from 9 by adding 2 ml of 1N acetic acid. From the total reaction mixture, 125ml of titanium peroxo carbonate was added at a rate of 2 ml/ minute to a separately prepared 25 ml of 8% (w/v) CTAB solution under stirring at 30°C. The stirring was continued for another 10 minutes and then 20 ml of 1 % (w/v) solution of cesium (III) nitrate was added at 30°C under stirring. 53 ml from the total mixture was taken in an 80 ml Teflon lined bomb and initially heated to 80°C for 24 hrs and then at 100°C for another 24hrs. The product was filtered, washed, dried and calcined at 550°C for 6 hrs. The yield was 89%. The product has BET surface area 184 m2/g and X-ray diffraction pattern of metal ion incorporated TiO2 evidences pure anatase phase. Example-9 In a 250 ml plastic beaker, 5 g bulk TiO2, 6 gms ammonium fluoride was taken and to it 8ml hydrofluoric acid and 75 ml water was added and heated at 70°C for 30 hrs. After the digestion period, 50 ml 2N ammonium hydroxide was slowly added to adjust the pH of the solution mixture to 11.5. After pH adjustment white precipitate appeared and were filtered, washed initially with ammonium hydroxide followed by distilled water. The titanium hydroxide precipitates were dispersed in 50ml water to which 20 ml solution containing 6 gms ammonium carbonate was added under continuous stirring. To this reaction mixture 2 ml 30% concentration hydrogen peroxide was slowly added at 30°C and the stirring was continued for another 30 minutes. This resulted in the formation of titanium peroxo carbonate solution, which was further diluted by adding 25 ml water. The pH of this solution was adjusted from 9 by adding 2 ml of 1N acetic acid. From the total reaction mixture, 125ml of titanium peroxo carbonate was added at a rate of 2 ml/ minute to a separately prepared 25 ml of 8% (w/v) CTAB solution under stirring at 30°C. The stirring was continued for another 10 minutes and then 20 ml of 1 % (w/v) solution of magnesium (III) nitrate was added at 30°C under stirring. 53 ml from the total mixture was taken in an 80 ml Teflon lined bomb and initially heated to 80°C for 24 hrs and then at 100°C for another 24hrs. The product was filtered, washed, dried and calcined at 550°C for 6 hrs. The yield was 90%. The product has BET surface area 184m2/gand X-ray diffraction pattern of metal ion incorporated TiO2 evidences pure anatase phase. Example-10 In a 250 ml plastic beaker, 5 g bulk TiO2, 6 gms ammonium fluoride was taken and to it 8ml hydrofluoric acid and 75 ml water was added and heated at 70°C for 30 hrs. After the digestion period, 50 ml 2N ammonium hydroxide was slowly added to adjust the pH of the solution mixture to 11.5. After pH adjustment white precipitate appeared and were filtered, washed initially with ammonium hydroxide followed by distilled water. The titanium hydroxide precipitates were dispersed in 50ml water to which 20 ml solution containing 6 gms ammonium carbonate was added under continuous stirring. To this reaction mixture 2 ml 30% concentration hydrogen peroxide was slowly added at 30°C and the stirring was continued for another 30 minutes. This resulted in the formation of titanium peroxo carbonate solution, which was further diluted by adding 25 ml water. The pH of this solution was adjusted from 9 by adding 2 ml of 1N acetic acid. From the total reaction mixture, 125ml of titanium peroxo carbonate was added at a rate of 2 ml/ minute to a separately prepared 25 ml of 8% (w/v) CTAB solution under stirring at 30°C. The stirring was continued for another 10 minutes and then 20 ml of 1.1 % (w/v) solution of copper (III) nitrate was added at 30°C under stirring. 53 ml from the total mixture was taken in an 80 ml Teflon lined bomb and initially heated to 300°C for 12 hrs. The product was filtered, washed, dried and calcined at 550°C for 6 hrs. The yield was 90%. The product has BET surface area 80 m2/g and X-ray diffraction pattern of metal ion incorporated TiO2 evidences pure anatase phase. Example-11 In a 250 ml plastic beaker. 5 g bulk TiO2, 6 gms ammonium fluoride was taken and to it 8ml hydrofluoric acid and 75 ml water was added and heated at 60°C for 40 hrs. After the digestion period, 35 ml 2N ammonium hydroxide was slowly added to adjust the pH of the solution mixture to 8.5. After pH adjustment white precipitate appeared and were filtered, washed initially with ammonium hydroxide followed by distilled water. The titanium hydroxide precipitates were dispersed in 50ml water to which 20 ml solution containing 6 gms ammonium carbonate was added under continuous stirring. To this reaction mixture 2 ml 30% concentration hydrogen peroxide was slowly added at 30°C and the stirring was continued for another 30 minutes. This resulted in the formation of titanium peroxo carbonate solution, which was further diluted by adding 25 ml water. The pH of this solution was adjusted to 9 by adding 2 ml of 1N acetic acid. From the total reaction mixture, 53 ml from the total mixture was taken in an 80 ml Teflon lined bomb and initially heated to 80°C for 24 hrs and then at 100°C for another 24hrs. The product was filtered, washed, dried for 12 h at 90°C. The yield was 85%. The product has BET surface area 370 m2 g-1 and X-ray diffraction pattern of metal ion incorporated TiO2 evidences pure anatase phase. Example-12 In a 250 ml plastic beaker, 5 g bulk TiO2, 6 gms ammonium fluoride was taken and to it 8ml hydrofluoric acid and 75 ml water was added and heated at 60°C for 40 hrs. After the digestion period, 35 ml 2N ammonium hydroxide was slowly added to adjust the pH of the solution mixture to 8.5. After pH adjustment white precipitate appeared and were filtered, washed initially with ammonium hydroxide followed by distilled water. The titanium hydroxide precipitates were dispersed in 50ml water to which 20 ml solution containing 6 gms ammonium carbonate was added under continuous stirring. To this reaction mixture 2 ml 30% concentration hydrogen peroxide was slowly added at 30°C and the stirring was continued for another 30 minutes. This resulted in the formation of titanium peroxo carbonate solution, which was further diluted by adding 25 ml water. The pH of this solution was adjusted to 9 by adding 2 ml of 1N acetic acid. The stirring was continued for another 10 minutes and then 20 ml of 1.1 % (w/v) solution of copper (II) chloride was added at 30°C under stirring. From the total reaction mixture, 53 ml from the total mixture was taken in an 80 ml Teflon lined bomb and initially heated to 80°C for 24 hrs and then at 100°C for another 24hrs. The product was filtered, washed, dried for 12 h at 90°C. The yield was 85%. The product has BET surface area 337 m2g-1 and X-ray diffraction pattern of metal ion incorporated TiO2 evidences pure anatase phase. Example-13 In a 250 ml plastic beaker, 5 g bulk TiO2, 6 gms ammonium fluoride was taken and to it 8ml hydrofluoric acid and 75 ml water was added and heated at 70°C for 30 hrs. After the digestion period, 50 ml 2N ammonium hydroxide was slowly added to adjust the pH of the solution mixture to 11.5. After pH adjustment white precipitate appeared and were filtered, washed initially with ammonium hydroxide followed by distilled water. The titanium hydroxide precipitates were dispersed in 50ml water to which 20 ml solution containing 6 gms ammonium carbonate was added under continuous stirring. To this reaction mixture 0.5 ml 30% concentration hydrogen peroxide was slowly added at 30°C and the stirring was continued for another 30 minutes, which was further diluted by adding 25 ml water. The pH of this solution was adjusted from 9 by adding 2 ml of 1N acetic acid. From the total reaction mixture, 125ml of was added at a rate of 2 ml/ minute to a separately prepared 0.5 ml of 5% (w/v) CTAB solution under stirring at 30°C. The stirring was continued for another 10 minutes and then 20 ml of 1.1 % (w/v) solution of copper (III) nitrate was added at 30°C under stirring. 53 ml from the total mixture was taken in an 80 ml Teflon lined bomb and initially heated to 300°C for 12 hrs. The product was filtered, washed, dried and calcined at 700°C for 6 hrs. The yield was 94%. The product has BET surface area 30 m2/g and X-ray diffraction pattern of metal ion incorporated TiO2 evidences pure anatase phase. ADVANTAGES OF THE INVENTION i. The main advantage of the procedure is to use an aqueous solution of freshly prepared titanium peroxo-carbonate solution, which is easy to handle, non corrosive, no special care need to be taken and is less moisture sensitive, ii. Another advantage of the procedure is to synthesis nano-crystalline and meso-porous TiO2 from bulk TiO2 through titanium peroxo-carbonate solution, which makes the procedure cheaper, iii. Another advantage is that the catalytic activity of TiO2 obtained from the present invention is high, iv. The incorporation of metal ions from the group of alkali metals, alkali-earth metals or transition metals in titania helps to improve the photo-catalytic activity. We Claim 1. A process for the preparation of nanocrystalline and mesoporous titanium dioxide from titanium peroxo carbonate and the said process comprising the steps of: i. digesting titanium source using ammonium fluoride, hydrofluoric acid and water with a molar ratio in the range of 1: 3.25: 3.06: 111.02 to 1: 1.5: 2.45: 44.4 at a temperature in the range of 25-70°C for a period of 20-40 h; ii. adjusting pH of the solution as obtained in step (i) in the range of 8 to 14 by adding base followed by filtering and washing with ammonium chloride and water till free from fluoride ions to obtain titanium hydroxide precipitate; iii. stirring the titanium hydroxide precipitate as obtained in step (ii) in a solution containing water, H2O2, ammonium carbonate with a molar ratio range of 53.5: 0.8:1 to 26.7: 0.338: 1 for a period in the range of 10-45 min at a temperature in the range of 20-35°C at the rate of 100-700 rpm to obtain titanium peroxo-carbonate solution; iv. adjusting the pH of the titanium peroxo-carbonate solution as obtained in step (iii) in the range of 2-14 by adding acid or base; v. adding 5-30 % w/v aqueous solution surfactant in a range of 2.18 x10-2 8.72 mole % with respect to titanium source to the pH adjusted solution as obtained in the step (iv) with constant stirring at the rate of 100-700 rpm for a period in the range of 10-30 min at temperature in the range of 25- 35°C; vi. dopping 0.001-10 mole % metal salt with respect to titania to the solution as obtained in the step (v) with constant stirring at the rate of 100-700 rpm for a period in the range of 10-20 min; vii. autoclaving for hydrothermal treatment of the solution as obtained in the step (vi) at a temperature range of 50-400°C for a period in the range of 30 min to 60 h; viii. filtering and drying of the precipitate as obtained in step (vii) at a temperature in the range of 25-90°C; ix. calcining the dried precipitate as obtained in step (viii) at a temperature in the range 300-900°C for a period in the range of 2-8 h to get nano- crystalline and mesoporous titanium dioxide. 2. A process as claimed in claim 1, wherein titanium source used is selected from the group consisting of bulk titanium dioxide, titanium alkoxide, titanium tetrachloride or titanium sulphate more preferably bulk titanium dioxide. 3. A process as claimed in claim 1, wherein yield of the said nano-crystalline, mesoporous and doped titanium dioxide is ranging between 78-92%. 4. A process as claimed in claim 1, wherein pore size of the nanocrystalline, mesoporous and doped titanium dioxide is ranging between 6 to 30 nm. 5. A process as claimed in claim 1, wherein BET surface area of the nanocrystalline, mesoporous and doped titanium dioxide is ranging between 30-375 m2/g. 6. A process as claimed in step (ii) and step (v) of claim 1, wherein base used is selected from the group consisting of ammonium hydroxide, sodium hydroxide or potassium hydroxide more preferably ammonium hydroxide. 7. A process as claimed in step (v) of claim 1, wherein acid used is selected from the group consisting of acetic acid, propanoic acid, tartaric acid, citric acid and oxalic acid. 8. A process as claimed in step (vi) of claim 1, wherein surfactant used is selected from the group consisting of Cetyltrimethylammonium bromide (CTAB), tetradecyltrimethylammonium bromide (TTAB), Decyltrimethylammonium bromide (DTAB) or hexadecyltrimethylammonium bromide (HTAB). 9. A process as claimed in step (vi) of claim 1, wherein metal salt used is selected from the group consisting of alkali metal, alkali earth metal or transition metal salts more preferably copper nitrate, iron nitrate, copper chloride, cerium nitrate and magnesium nitrate. 10. A process for the preparation of nanocrystalline, mesoporous and doped titanium dioxide, substantially as herein described with reference to the examples and drawing accompanying this specification.

Full Text

FIELD OF THE INVENTION
The present invention relates to a process for the preparation of nanocrystalline and mesoporous titanium dioxide (Titania) powder using a new titanium source titanium peroxo carbonate, with a large specific surface area, useful as photo catalyst. The present invention further relates to a method for the preparation of titanium dioxide powder which can be used as a catalyst for the removal of different toxic gases, pollutant organic substances and the like.
BACKGROUND OF THE INVENTION
Titanium dioxide is used as a photocatalyst. Particularly, titanium dioxide with anatase phase has been known to be highly stable and show excellent photo catalytic activity by absorbing light and reacting with toxic materials. P-25, a brand name of titanium dioxide, manufactured by M/s Degussa Germany, which has been evaluated as being the most active among the presently available photocatalysts, shows insufficient photo activity under a practically employed light intensity of tens of watts, which has limited its practical application. Titania is also an important material used as white pigment, solar-cell device etc. Titanium dioxide powders have been conventionally prepared by a sol-gel method and a chloride process. The sol-gel method is, however, difficult to perform continuously and incurs a high production cost because additional heat treatments must be adopted and alkoxide, the raw material used is moisture sensitive and very expensive. The chloride process, which is at present commonly used, also suffers from disadvantages: it needs a sophisticated experimental setup owing to its high temperature and pressure reaction. This process requires an additional protective facility because of the corrosive gases (Cl2, HC1) produced during the reaction, leading to higher production costs. In addition, special devices are employed for applying electric fields or controlling the reactant mixing ratio to control the shape and size of TiO2 particles. Titanium dioxide P-25, manufactured by Degussa Co., Germany, is well known to be produced using the chloride process and not desirable in terms of production cost and photocatalytic properties.
References may be made to patent 6,517,804, wherein the synthesis of Titania ultrafine powder from pure titanium tetrachloride is reported. The process contains the following steps; addition of ice pieces or icy distilled water to pure titanium tetrachloride (TiCl4) to give an aqueous titanylchloride, controlled addition of distilled water to the aqueous titanylchloride solution with heating from controlled hydrolysis is disclosed. Filtering and
washing gave the Titania ultrafine powder. In the above process requires an additional protective facility because of the corrosive gases (Cl2, HC1) produced during the reaction, leading to higher production costs and risky. Again, it demands special care during the dilution and hydrolysis steps, which makes the procedure too complicated. The present process overcomes the above drawbacks.
References may be made to patent application WO2008036176-A1, wherein the synthesis of nanosized Titania using titanium peroxo precursor is disclosed. To titanium compound solution (titanium tetrachloride, titanium oxychloride, titanium trichloride, titanium tetrabromide, hydrated titanium sulfate, or hydrated titanium oxysulfate) excess hydrogen peroxide was added and mixed with an alkali; and/or compound containing sulfate, nitrate, and fluorine ions to accelerate formation of anatase titanium dioxide (TiO2). Then the solution was heated to get the nanosized Titania. Presence of large amount of H2O2 makes the procedure more risky and complicated. Again the used titanium source is moisture sensitive, corrosive and costly. In the present procedure, we are able to avoid the difficulty by using very small amount of H2O2 and the use of bulk TiO2 as titania source avoids other problems.
References may be made to patent applications WO2007085911-A2 and WO2007085911-A3, wherein the synthesis of size homogenous composition of titanium (IV) oxide nanoparticles using alkoxide through a sol-gel process is disclosed. In a detail procedure, a solution of titanium alkoxide precursor was added to an aqueous acidic aqueous solution (below pH 4). The dispersed mixture was constantly stirred for 4 hours, resulting in the formation of a colloidal solution. Only after the solution was refined, a second solution containing the complexing agent was added, and the color of the final solution turned to yellow-orange. Under continuous stirring, to the final sol, an amount of a modifier-stabilizer was added. The preparation of nanostructured titania powders included solvent evaporation followed by thermal treatment of the solid residue at 400-550°C. However, the method is quite complicated and difficult to perform. The used titanium source titanium alkoxide is moisture sensitive and very expensive. Present developed procedure is simple and it is possible to overcome the moisture sensitivity and cost problem by using the titanium peroxo carbonate complex.
References may be made to patent applications CN1398665-A and CN1132679-C for the synthesis of mesoporous TiO2-SiO2. The synthetic procedure contains the following steps: the preparation of an isopropanol titanium-acetone solution; the preparation of a titanium polymerized sol; and the preparation of a titania membrane, soaking the
mesoporous Ti-Si support body in titanium polymerized sol with 1.9-2.5 x 10" Pa.s viscosity for 0.5-2 minutes before taking out and drying naturally for 44-52 hours to form a gel layer, then drying in a vacuum drier, calcining to 630-670°C. The main drawbacks of the procedure are the use of moisture sensitive and costly alkoxide and hazards organic solvent isopropanol. Again the photocatalytic activituy of the synthesized material is not upto the mark. Using the developed procedure it is possible to overcome the above drawbacks.
References may be made to patent JP-A-5-184923, wherein titania catalyst can be obtained by heat-treating amorphous fibers to deposit a crystal of an anatase-form titanium oxide and a vanadium oxide, in which amorphous fibers is produced by the sol-gel method of hydrolyzing a alkoxide in a mixed solution of a titanium alkoxide, a vanadium compound and other alkoxide, successively gelling is disclosed. Used precursor titanium alkoxide is moisture sensitive and costly. Moreover, Titania catalyst described has problems in that the activity is low and the performance of removal of nitrogen oxides is low. The present process overcomes the above drawbacks of moisture sensitive and costly reagent. The synthesized titanium dioxide is catalytically highly active.
References may be made to patent US6444608, wherein the synthesis of mesoporous TiO2 by dissolving a titanium alkoxide in a solvent to give a titanium alkoxide solution; adding a mixed solution containing water and a solvent to the titanium alkoxide solution to perform hydrolysis as well as simultaneous polymerization of titania to give a polymer solution; adding a fatty acid; separating a polymer containing the fatty acid from the polymer solution and calcinations is disclosed. The main drawbacks of the procedure are the use of moisture sensitive, costly alkoxide and hazards organic solvent. It is a complicated procedure. Catalytic activity of the TiO2 towards removal of nitrogen oxides, oxidation of organic substances, decomposition of dioxine compounds, as well as decomposition and removal of organic solvents, agricultural chemical and surfactant is low. Using the developed procedure it is possible to overcome the above drawbacks In all the above stated prior arts, it is evident that selection of titanium source is a crucial step for the synthesis of above mentioned titanium based materials with respect to the moisture sensitivity, risk factor to handle and cost factor. In all the synthetic procedures described above use of titanium epoxide and chloride makes the procedure more complicated costly and risky. Moreover, Titania synthesized by these procedures has problems, in that the catalytic activity is low.
The present invention is directed to a novel approach for the synthesis of nanocrystalline and mesoporous titania using a new titanium source "titanium preoxy-carbonate" which is cost effective, easy to handle to avoid the existing titanium sources which are costly, moisture sensitive and corrosive. The "titanium preoxy-carbonate" is synthesized from bulk titania and the required amount of peroxide is very low which is catalytic amount.
OBJECTIVE OF THE INVENTION
The main objective of the present invention is to provide a process to prepare nanocrystalline and mesoporous titanium dioxide powder from an aqueous titanium peroxy-carbonate solution from bulk titanium dioxide which obviates the drawback as detailed above.
Another objective of the present invention is to prepare an aqueous titanium peroxy-carbonate solution from other titanium source viz. titanium alkoxide, titanium tetrachloride and titanium sulphate.
Still another objective of the present invention is to provide a method of producing the mesoporous, nanocrystalline titanium dioxide with high specific surface area, narrow pore size distribution and having anatase crystalinity, using the aqueous titanium peroxy-carbonate solution.
Yet another objective of the present invention is to synthesize mesoporous and nano-cryatalline titanium dioxide catalyst and at least one catalyst component selected from the group consisting of V, W, Al, As, Ni, Zr, Mo, Ru, Mg, Mn, Cu, Cs, Ca, Fe, Cr and Pt. Yet another objective of the present invention is the synthesize mesoporous and nano-cryatalline titanium dioxide based mixed metal oxides catalyst like TiO2-ZrO2, TiO2-SiO2, TiO2-Al2O3, TiO2-SiO2-ZrO2, TiO2-SiO2-Al2O3 using the precursor. Yet another objective of the present invention is to use the above mesoporous and nano-cryatalline titanium dioxide powder as a photo catalyst.
SUMMARY OF THE INVENTION
Accordingly, present invention provides a process for the preparation of nanocrystalline and mesoporous titanium dioxide from titanium peroxo carbonate and the said process comprising the steps of:
i. digesting titanium source using ammonium fluoride, hydrofluoric acid and water with a molar ratio in the range of 1: 3.25: 3.06: 111.02 to 1: 1.5:
2.45: 44.4 at a temperature in the range of 25-70°C for a period of 20-40 h;
ii. adjusting pH of the solution as obtained in step (i) in the range of 8 to 14 by adding base followed by filtering and washing with ammonium chloride and water till free from fluoride ions to obtain titanium hydroxide precipitate;
iii. stirring the titanium hydroxide precipitate as obtained in step (ii) in a solution containing water, H2O2, ammonium carbonate with a molar ratio range of 53.5: 0.8:1 to 26.7: 0.338: 1 for a period in the range of 10-45 min at a temperature in the range of 20-35°C at the rate of 100-700 rpm to obtain titanium peroxo-carbonate solution;
iv. adjusting the pH of the titanium peroxo-carbonate solution as obtained in step (iii) in the range of 2-14 by adding acid or base;
v. adding 5-30 % w/v aqueous solution surfactant in a range of 2.18 x10-2 -8.72 mole % with respect to titanium source to the pH adjusted solution as obtained in the step (iv) with constant stirring at the rate of 100-700 rpm for a period in the range of 10-30 min at temperature in the range of 25-35°C;
vi. dopping 0.001-10 mole % metal salt with respect to titania to the solution as obtained in the step (v) with constant stirring at the rate of 100-700 rpm for a period in the range of 10-20 min;
vii. autoclaving for hydrothermal treatment of the solution as obtained in the step (vi) at a temperature range of 50-400°C for a period in the range of 30 min to 60 h;
viii. filtering and drying of the precipitate as obtained in step (vii) at a
temperature in the range of 25-90°C;
ix. calcining the dried precipitate as obtained in step (viii) at a temperature in the range 300-900°C for a period in the range of 2-8 h to get nano-crystalline and mesoporous titanium dioxide. In an embodiment of the present invention, titanium source used is selected from the group consisting of bulk titanium dioxide, titanium alkoxide, titanium tetrachloride or titanium sulphate more preferably bulk titanium dioxide.
In another embodiment of the present invention, yield of the said nano-crystalline, mesoporous and doped titanium dioxide is ranging between 78-92%.
In still another embodiment of the present invention, pore size of the nanocrystalline,
mesoporous and doped titanium dioxide is ranging between 6 to 30 nm.
In still another embodiment of the present invention, BET surface area of the
nanocrystalline, mesoporous and doped titanium dioxide is ranging between 30-375 m2/g.
In still another embodiment of the present invention, base used is selected from the group
consisting of ammonium hydroxide, sodium hydroxide or potassium hydroxide more
preferably ammonium hydroxide.
In yet another embodiment of the present invention, acid used is selected from the group
consisting of acetic acid, propanoic acid, tartaric acid, citric acid and oxalic acid.
In yet another embodiment of the present invention, surfactant used is selected from the
group consisting of Cetyltrimethylammonium bromide (CTAB),
tetradecyltrimethylammonium bromide (TTAB), Decyltnmethylammonium bromide
(DTAB) or hexadecyltrimethylammonium bromide (HTAB).
In yet another embodiment of the present invention, metal salt used is selected from the
group consisting of alkali metal, alkali earth metal or transition metal salts more
preferably copper nitrate, iron nitrate, copper chloride, cerium nitrate and magnesium
nitrate.
DETAIL DESCRIPTION OF THE INVENTION
Present invention provides a process for the synthesis of aqueous titanium peroxo carbonate, an aqueous titanium precursor from bulk TiO2 In the present invention much intensive efforts have been given to synthesis and improving catalytic activity of titania using freshly prepared titanium peroxo carbonate solution as titanium source. As a result, in the present invention produced nanocrystalline and porous titania having a high degree of anatase crystallinity, a large specific surface area and a narrow pore size / particle size distribution, which is obtainable by hydrothermal treatment of titanium peroxo carbonate solution in the presence or absence of surfactant, which exhibits an excellent catalytic activity.
The present invention also provides a titania catalyst comprising the nanocrystalline or porous titania described above and at least one catalyst component selected from the group consisting of alkali metals, alkali-earth metals or transition metals. The present invention provides a method for the synthesis of highly active nanocrystalline and mesoporous titania catalyst from freshly prepared aqueous titanium peroxo carbonate solution which comprises of the following steps;
(i) digesting 2-10g bulk TiO2 in 50-100ml of de-ionized water containing ammonium
fluoride in the range 3-7g, hydrofluoric acid in the range of 3-12 ml at a
temperature range of 25-70°C for a period of 20-40h; (ii) treating the solution obtained in step (i) with 2N ammonium hydroxide solution in
the range of 10-75 ml, filtering and washing with water till free from fluoride
ions; (iii) stirring the freshly prepared titanium hydroxide obtained in step (ii) in de-ionized
water in the range of 20-100 ml, H2O2 in the range of 2-8ml, ammonium
carbonate in the range of 2-20 g for a period in the range of 10-45 min at a
temperature in the range of 20-35°C; (iv) adjusting the pH of the clear titanium peroxo-carbonate solution obtained in step
(iii) in the range of 2-14 by adding NaOH or NH4OH or acetic acid in the range of
1-25 ml solution; (v) adding Cetyltrimethylammonium bromide in the range of 0-4 g to the pH adjusted
solution obtained in the step (iv) with constant stirring for a period in the range of
10-30 min; (vi) adding 0.001-10 mole % transition/alkaline/alkaline-earth metal salt with respect
to titania to the solution obtained in the step (v) with constant stirring for a period
in the range of 10-20 min at a temperature in the range of 25-35°C; (vii) autoclaving the solution obtained in the step (vi) at a temperature range of 50-
400°C for a period in the range of 30min-60 h; (viii) filtering and drying of the precipitate obtained in step (vii) at a temperature in the
range of 25-90°C; (ix) calcining the dried sample as obtained in step (xii) at a temperature in the range
300-900°C for a period in the range of 2-8 h to get nano-crystalline, mesoporous
and doped titanium dioxide. Present invention provides a process for the preparation of nanocrystalline and mesoporous titanium di-oxide from bulk titanium dioxide. Here solid titanium dioxide is initially reacted with ammonium fluoride and hydrofluoric acid to obtain a soluble titanium solution to which ammonia is added to precipitate titanium hydroxide. The latter is reacted with hydrogen peroxide and ammonium carbonate, to obtain a clear solution of titanium peroxo-carbonate solution. The hydrothermal treatment of the titanium peroxo-carbonate solution with / without surfactant gives highly crystalline titanium dioxide with high surface area, porous with narrow pore size / particle size distribution. This titanium
dioxide shows very high photo-catalytic activity. We are reporting for the first time the initial preparation of titanium peroxo-carbonate to obtain highly crystalline and porous titanium dioxide. The prior act neither teaches nor reveals how titanium peroxo-carbonate solution as a source of titanium can be used to prepare crystalline and porous titanium dioxide which exhibits high photo-catalytic activity. The inventive steps adopted in the present invention are (i) it obviates the need of having a starting material which are sensitive to moisture or corrosive, (ii) hydrothermal treatment of titanium peroxo-carbonate in presence of surfactant and peroxide as oxidizing agent decompose carbonate into carbon dioxide and water and thereby facilities formation of porous and material with high crystalline.
BRIEF DISCRETION OF THE DRAWING
Figure-1. Represents Transmission Electron Micrograph (TEM) of the synthesized
copper doped mesoporous titanium dioxide by the process described in Example
1. Figure-2 Represents XRD patterns of copper doped mesoporous titanium dioxide
synthesized by the process described in Example 1. Figure-3 Represents N2 sorption isotherm of the synthesized copper doped mesoporous
titanium dioxide by the process described in Example 1. Figure-4. Represents transmission electron micrograph (TEM) of the synthesized copper
doped mesoporous titanium dioxide by the process described in Example 5. Figure-5.Represents N2 sorption isotherm of the synthesized copper doped mesoporous
titanium dioxide by the process described in Example 11. Figure-6. Represents Transmission Electron Micrograph (TEM) of the synthesized
nanocrystalline titanium dioxide Cubes by the process described in Example 12. Figure-7. Represents XRD patterns of pure anatase TiO2 nano cubes synthesized by the
process described in Example 12. Figure-8 Represents N2 sorption isotherm of the synthesized titanium dioxide cubes
synthesized by the process described in Example 12. Figure-9 Represents transmission electron micrograph (TEM) of the synthesized copper
doped nanocrystalline titanium dioxide Cubes by the process described in
Example 13. Figure-10.Represents XRD patterns of copper doped anatase TiO2 nano cubes
synthesized by the process described in Example 13
EXAMPLES
The following examples are given by way of illustration and therefore should not be construed to limit the scope of the present invention.
Example-1
5 g bulk TiO2 and 6 g ammonium fluoride was taken In a 250 ml plastic beaker and to it 8 ml hydrofluoric acid and 75 ml water was added and heated at 70°C temperature for 30 hrs. After the digestion period, 50 ml 2N ammonium hydroxide was slowly added to adjust the pH of the solution mixture to 11.5. After pH adjustment white precipitate appeared and were filtered, washed initially with ammonium hydroxide followed by distilled water. The titanium hydroxide precipitates were dispersed in 50ml water to which 20 ml solution containing 6 gms ammonium carbonate was added under continuous stirring. To this reaction mixture 2 ml 30% concentration hydrogen peroxide was slowly added at 30°C and the stirring was continued for another 30 minutes. This resulted in the formation of titanium peroxo carbonate solution, which was further diluted by adding 25 ml water. The pH of this solution was adjusted from 9 by adding 2 ml of 1N acetic acid. From the total reaction mixture, 125ml of titanium peroxo carbonate was added at a rate of 2 ml/ minute to a separately prepared 25 ml of 8% (w/v) CTAB solution under stirring at 30°C. The stirring was continued for another 10 minutes and then 20 ml of 1.1% (w/v) solution of copper (II) nitrate was added at 30°C under stirring. 53 ml from the total mixture was taken in an 80 ml Teflon lined bomb and initially heated to 80°C for 24 hrs and then at 100°C for another 24hrs. The product was filtered, washed, dried and calcined at 550°C for 6 hrs. The yield was 88%. The product has BET surface area 180 m /g and X-ray diffraction pattern of metal ion incorporated TiO2 evidences pure anatase phase.
Example-2
In a 250 ml plastic beaker, 5 g bulk TiO2, 6 gms ammonium fluoride was taken and to it 8ml hydrofluoric acid and 75 ml water was added and heated at 60°C for 40 hrs. After the digestion period, 35 ml 2N ammonium hydroxide was slowly added to adjust the pH of the solution mixture to 8.5. After pH adjustment white precipitate appeared and were filtered, washed initially with ammonium hydroxide followed by distilled water. The titanium hydroxide precipitates were dispersed in 50ml water to which 20 ml solution containing 6 gms ammonium carbonate was added under continuous stirring. To this reaction mixture 2 ml 30% concentration hydrogen peroxide was slowly added at 30°C
and the stirring was continued for another 30 minutes. This resulted in the formation of titanium peroxo carbonate solution, which was further diluted by adding 25 ml water. The pH of this solution was adjusted to 9 by adding 2 ml of 1N acetic acid. From the total reaction mixture, 125ml of titanium peroxo carbonate was added at a rate of 2 ml/ minute to a separately prepared 25 ml of 8% (w/v) CTAB solution under stirring at 30°C. The stirring was continued for another 10 minutes and then 20 ml of 1.1% (w/v) solution of copper (II) nitrate was added at 30°C under stirring. 53 ml from the total mixture was taken in an 80 ml Teflon lined bomb and initially heated to 80°C for 24 hrs and then at 100°C for another 24hrs. The product was filtered, washed, dried and calcined at 550°C for 6 hrs. The yield was 85%. The product has BET surface area 174 m2/g and X-ray diffraction pattern of metal ion incorporated TiO2 evidences pure anatase phase.
Example-3
In a 250 ml plastic beaker, 5 g bulk TiO2, 6 gms ammonium fluoride was taken and to it 8ml hydrofluoric acid and 75 ml water was added and heated at 70°C for 30 hrs. After the digestion period, 50 ml 2N ammonium hydroxide was slowly added to adjust the pH of the solution mixture to 11.5. After pH adjustment white precipitate appeared and were filtered, washed initially with ammonium hydroxide followed by distilled water. The titanium hydroxide precipitates were dispersed in 50ml water to which 20 ml solution containing 8 gms ammonium carbonate was added under continuous stirring. To this reaction mixture 2 ml 30% concentration hydrogen peroxide was slowly added at 30°C and the stirring was continued for another 30 minutes. This resulted in the formation of titanium peroxo carbonate solution, which was further diluted by adding 25 ml water. The pH of this solution was adjusted to 9 by adding 2.5 ml of 1N acetic acid. From the total reaction mixture, 125ml of titanium peroxo carbonate was added at a rate of 2 ml/ minute to a separately prepared 25 ml of 8% (w/v) CTAB solution under stirring at 30°C. The stirring was continued for another 10 minutes and then 20 ml of 1.1 % (w/v) solution of copper (II) chloride was added at 30°C under stirring. 53 ml from the total mixture was taken in an 80 ml Teflon lined bomb and initially heated to 80°C for 24 hrs and then at 100°C for another 24hrs. The product was filtered, washed, dried and calcined at 550°C for 6 hrs. The yield was 87%. The product has BET surface area 185 m2/g and X-ray diffraction pattern of metal ion incorporated TiO2 evidences pure anatase phase.
Example-4
In a 250 ml plastic beaker, 5 g bulk TiO2, 6 gms ammonium fluoride was taken and to it 8ml hydrofluoric acid and 75 ml water was added and heated at 70°C for 30 hrs. After the
digestion period, 50 ml 2N ammonium hydroxide was slowly added to adjust the pH of the solution mixture to 11.5. After pH adjustment white precipitate appeared and were filtered, washed initially with ammonium hydroxide followed by distilled water. The titanium hydroxide precipitates were dispersed in 50ml water to which 20 ml solution containing 6 gms ammonium carbonate was added under continuous stirring. To this reaction mixture 2 ml 30% concentration hydrogen peroxide was slowly added at 30°C and the stirring was continued for another 30 minutes. This resulted in the formation of titanium peroxo carbonate solution, which was further diluted by adding 25 ml water. The pH of this solution was adjusted to 6 by adding 7 ml of 1N acetic acid. From the total reaction mixture, 125ml of titanium peroxo carbonate was added at a rate of 2 ml/ minute to a separately prepared 25 ml of 8% (w/v) CTAB solution under stirring at 30°C. The stirring was continued for another 10 minutes and then 20 ml of 1.1 % (w/v) solution of copper (II) chloride was added at 30°C under stirring. 53 ml from the total mixture was taken in an 80 ml Teflon lined bomb and initially heated to 80°C for 24 hrs and then at 100°C for another 24hrs. The product was filtered, washed, dried and calcined at 550°C for 6 hrs. The yield was 78%. The product has BET surface area 142 m2/g and X-ray diffraction pattern of metal ion incorporated TiO2 evidences pure anatase phase.
Example-5
In a 250 ml plastic beaker, 5 g bulk TiO2, 6 gms ammonium fluoride was taken and to it 8ml hydrofluoric acid and 75 ml water was added and heated at 60°C for 40 hrs. After the digestion period, 35 ml 2N ammonium hydroxide was slowly added to adjust the pH of the solution mixture to 8.5. After pH adjustment white precipitate appeared and were filtered, washed initially with ammonium hydroxide followed by distilled water. The titanium hydroxide precipitates were dispersed in 50ml water to which 20 ml solution containing 6 gms ammonium carbonate was added under continuous stirring. To this reaction mixture 2 ml 30% concentration hydrogen peroxide was slowly added at 30°C and the stirring was continued for another 30 minutes. This resulted in the formation of titanium peroxo carbonate solution, which was further diluted by adding 25 ml water. The pH of this solution was adjusted to 9 by adding 2 ml of 1N acetic acid. From the total reaction mixture, 125ml of titanium peroxo carbonate was added at a rate of 2 ml/ minute to a separately prepared 25 ml of 3% (w/v) CTAB solution under stirring at 30°C. The stirring was continued for another 10 minutes and then 20 ml of 1.1% (w/v) solution of copper (II) nitrate was added at 30°C under stirring. 53 ml from the total mixture was taken in an 80 ml Teflon lined bomb and initially heated to 80°C for 24 hrs and then at
100°C for another 24hrs. The product was filtered, washed, dried and calcined at 550°C for 6 hrs. The yield was 92%. The product has BET surface area 134 m2/g and X-ray diffraction pattern of metal ion incorporated TiO2 evidences pure anatase phase.
Example-6
In a 250 ml plastic beaker, 5 g bulk TiO2, 6 gms ammonium fluoride was taken and to it 8ml hydrofluoric acid and 75 ml water was added and heated at 70°C for 30 hrs. After the digestion period, 50 ml 2N ammonium hydroxide was slowly added to adjust the pH of the solution mixture to 11.5. After pH adjustment white precipitate appeared and were filtered, washed initially with ammonium hydroxide followed by distilled water. The titanium hydroxide precipitates were dispersed in 50ml water to which 20 ml solution containing 6 gms ammonium carbonate was added under continuous stirring. To this reaction mixture 2 ml 30% concentration hydrogen peroxide was slowly added at 30°C and the stirring was continued for another 30 minutes. This resulted in the formation of titanium peroxo carbonate solution, which was further diluted by adding 25 ml water. The pH of this solution was adjusted from 9 by adding 2 ml of 1N acetic acid. From the total reaction mixture, 125ml of titanium peroxo carbonate was added at a rate of 2 ml/ minute to a separately prepared 25 ml of 8% (w/v) CTAB solution under stirring at 30°C. The stirring was continued for another 10 minutes and then 20 ml of 0.75% (w/v) solution of copper (II) nitrate was added at 30°C under stirring. 53 ml from the total mixture was taken in an 80 ml Teflon lined bomb and initially heated to 80°C for 24 hrs and then at 100°C for another 24hrs. The product was filtered, washed, dried and calcined at 550°C for 6 hrs. The yield was 89%. The product has BET surface area 203 m2/g and X-ray diffraction pattern of metal ion incorporated TiO2 evidences pure anatase phase.
Example-7
In a 250 ml plastic beaker, 5 g bulk TiO2, 6 gms ammonium fluoride was taken and to it 8ml hydrofluoric acid and 75 ml water was added and heated at 70°C for 30 hrs. After the digestion period, 50 ml 2N ammonium hydroxide was slowly added to adjust the pH of the solution mixture toll.5. After pH adjustment white precipitate appeared and were filtered, washed initially with ammonium hydroxide followed by distilled water. The titanium hydroxide precipitates were dispersed in 50ml water to which 20 ml solution containing 6 gms ammonium carbonate was added under continuous stirring. To this reaction mixture 2 ml 30% concentration hydrogen peroxide was slowly added at 30°C and the stirring was continued for another 30 minutes. This resulted in the formation of titanium peroxo carbonate solution, which was further diluted by adding 25 ml water.
The pH of this solution was adjusted from 9 by adding 2 ml of 1N acetic acid. From the total reaction mixture, 125ml of titanium peroxo carbonate was added at a rate of 2 ml/ minute to a separately prepared 25 ml of 8% (w/v) CTAB solution under stirring at 30°C. The stirring was continued for another 10 minutes and then 20 ml of 1.5 % (w/v) solution of Iron (III) nitrate was added at 30°C under stirring. 53 ml from the total mixture was taken in an 80 ml Teflon lined bomb and initially heated to 80°C for 24 hrs and then at 100°C for another 24hrs. The product was filtered, washed, dried and calcined at 550°C for 6 hrs. The yield was 89%. The product has BET surface area 194 m /g and X-ray diffraction pattern of metal ion incorporated TiO2 evidences pure anatase phase.
Example-8
In a 250 ml plastic beaker, 5 g bulk TiO2, 6 gms ammonium fluoride was taken and to it 8ml hydrofluoric acid and 75 ml water was added and heated at 70°C for 30 hrs. After the digestion period, 50 ml 2N ammonium hydroxide was slowly added to adjust the pH of the solution mixture to 11.5. After pH adjustment white precipitate appeared and were filtered, washed initially with ammonium hydroxide followed by distilled water. The titanium hydroxide precipitates were dispersed in 50ml water to which 20 ml solution containing 6 gms ammonium carbonate was added under continuous stirring. To this reaction mixture 2 ml 30% concentration hydrogen peroxide was slowly added at 30°C and the stirring was continued for another 30 minutes. This resulted in the formation of titanium peroxo carbonate solution, which was further diluted by adding 25 ml water. The pH of this solution was adjusted from 9 by adding 2 ml of 1N acetic acid. From the total reaction mixture, 125ml of titanium peroxo carbonate was added at a rate of 2 ml/ minute to a separately prepared 25 ml of 8% (w/v) CTAB solution under stirring at 30°C. The stirring was continued for another 10 minutes and then 20 ml of 1 % (w/v) solution of cesium (III) nitrate was added at 30°C under stirring. 53 ml from the total mixture was taken in an 80 ml Teflon lined bomb and initially heated to 80°C for 24 hrs and then at 100°C for another 24hrs. The product was filtered, washed, dried and calcined at 550°C for 6 hrs. The yield was 89%. The product has BET surface area 184 m2/g and X-ray diffraction pattern of metal ion incorporated TiO2 evidences pure anatase phase.
Example-9
In a 250 ml plastic beaker, 5 g bulk TiO2, 6 gms ammonium fluoride was taken and to it 8ml hydrofluoric acid and 75 ml water was added and heated at 70°C for 30 hrs. After the digestion period, 50 ml 2N ammonium hydroxide was slowly added to adjust the pH of the solution mixture to 11.5. After pH adjustment white precipitate appeared and were
filtered, washed initially with ammonium hydroxide followed by distilled water. The titanium hydroxide precipitates were dispersed in 50ml water to which 20 ml solution containing 6 gms ammonium carbonate was added under continuous stirring. To this reaction mixture 2 ml 30% concentration hydrogen peroxide was slowly added at 30°C and the stirring was continued for another 30 minutes. This resulted in the formation of titanium peroxo carbonate solution, which was further diluted by adding 25 ml water. The pH of this solution was adjusted from 9 by adding 2 ml of 1N acetic acid. From the total reaction mixture, 125ml of titanium peroxo carbonate was added at a rate of 2 ml/ minute to a separately prepared 25 ml of 8% (w/v) CTAB solution under stirring at 30°C. The stirring was continued for another 10 minutes and then 20 ml of 1 % (w/v) solution of magnesium (III) nitrate was added at 30°C under stirring. 53 ml from the total mixture was taken in an 80 ml Teflon lined bomb and initially heated to 80°C for 24 hrs and then at 100°C for another 24hrs. The product was filtered, washed, dried and calcined at 550°C for 6 hrs. The yield was 90%. The product has BET surface area 184m2/gand X-ray diffraction pattern of metal ion incorporated TiO2 evidences pure anatase phase.
Example-10
In a 250 ml plastic beaker, 5 g bulk TiO2, 6 gms ammonium fluoride was taken and to it 8ml hydrofluoric acid and 75 ml water was added and heated at 70°C for 30 hrs. After the digestion period, 50 ml 2N ammonium hydroxide was slowly added to adjust the pH of the solution mixture to 11.5. After pH adjustment white precipitate appeared and were filtered, washed initially with ammonium hydroxide followed by distilled water. The titanium hydroxide precipitates were dispersed in 50ml water to which 20 ml solution containing 6 gms ammonium carbonate was added under continuous stirring. To this reaction mixture 2 ml 30% concentration hydrogen peroxide was slowly added at 30°C and the stirring was continued for another 30 minutes. This resulted in the formation of titanium peroxo carbonate solution, which was further diluted by adding 25 ml water. The pH of this solution was adjusted from 9 by adding 2 ml of 1N acetic acid. From the total reaction mixture, 125ml of titanium peroxo carbonate was added at a rate of 2 ml/ minute to a separately prepared 25 ml of 8% (w/v) CTAB solution under stirring at 30°C. The stirring was continued for another 10 minutes and then 20 ml of 1.1 % (w/v) solution of copper (III) nitrate was added at 30°C under stirring. 53 ml from the total mixture was taken in an 80 ml Teflon lined bomb and initially heated to 300°C for 12 hrs. The product was filtered, washed, dried and calcined at 550°C for 6 hrs. The yield was 90%. The
product has BET surface area 80 m2/g and X-ray diffraction pattern of metal ion incorporated TiO2 evidences pure anatase phase.
Example-11
In a 250 ml plastic beaker. 5 g bulk TiO2, 6 gms ammonium fluoride was taken and to it 8ml hydrofluoric acid and 75 ml water was added and heated at 60°C for 40 hrs. After the digestion period, 35 ml 2N ammonium hydroxide was slowly added to adjust the pH of the solution mixture to 8.5. After pH adjustment white precipitate appeared and were filtered, washed initially with ammonium hydroxide followed by distilled water. The titanium hydroxide precipitates were dispersed in 50ml water to which 20 ml solution containing 6 gms ammonium carbonate was added under continuous stirring. To this reaction mixture 2 ml 30% concentration hydrogen peroxide was slowly added at 30°C and the stirring was continued for another 30 minutes. This resulted in the formation of titanium peroxo carbonate solution, which was further diluted by adding 25 ml water. The pH of this solution was adjusted to 9 by adding 2 ml of 1N acetic acid. From the total reaction mixture, 53 ml from the total mixture was taken in an 80 ml Teflon lined bomb and initially heated to 80°C for 24 hrs and then at 100°C for another 24hrs. The product was filtered, washed, dried for 12 h at 90°C. The yield was 85%. The product has BET surface area 370 m2 g-1 and X-ray diffraction pattern of metal ion incorporated TiO2 evidences pure anatase phase.
Example-12
In a 250 ml plastic beaker, 5 g bulk TiO2, 6 gms ammonium fluoride was taken and to it 8ml hydrofluoric acid and 75 ml water was added and heated at 60°C for 40 hrs. After the digestion period, 35 ml 2N ammonium hydroxide was slowly added to adjust the pH of the solution mixture to 8.5. After pH adjustment white precipitate appeared and were filtered, washed initially with ammonium hydroxide followed by distilled water. The titanium hydroxide precipitates were dispersed in 50ml water to which 20 ml solution containing 6 gms ammonium carbonate was added under continuous stirring. To this reaction mixture 2 ml 30% concentration hydrogen peroxide was slowly added at 30°C and the stirring was continued for another 30 minutes. This resulted in the formation of titanium peroxo carbonate solution, which was further diluted by adding 25 ml water. The pH of this solution was adjusted to 9 by adding 2 ml of 1N acetic acid. The stirring was continued for another 10 minutes and then 20 ml of 1.1 % (w/v) solution of copper (II) chloride was added at 30°C under stirring. From the total reaction mixture, 53 ml from the total mixture was taken in an 80 ml Teflon lined bomb and initially heated to
80°C for 24 hrs and then at 100°C for another 24hrs. The product was filtered, washed, dried for 12 h at 90°C. The yield was 85%. The product has BET surface area 337 m2g-1 and X-ray diffraction pattern of metal ion incorporated TiO2 evidences pure anatase phase.
Example-13
In a 250 ml plastic beaker, 5 g bulk TiO2, 6 gms ammonium fluoride was taken and to it 8ml hydrofluoric acid and 75 ml water was added and heated at 70°C for 30 hrs. After the digestion period, 50 ml 2N ammonium hydroxide was slowly added to adjust the pH of the solution mixture to 11.5. After pH adjustment white precipitate appeared and were filtered, washed initially with ammonium hydroxide followed by distilled water. The titanium hydroxide precipitates were dispersed in 50ml water to which 20 ml solution containing 6 gms ammonium carbonate was added under continuous stirring. To this reaction mixture 0.5 ml 30% concentration hydrogen peroxide was slowly added at 30°C and the stirring was continued for another 30 minutes, which was further diluted by adding 25 ml water. The pH of this solution was adjusted from 9 by adding 2 ml of 1N acetic acid. From the total reaction mixture, 125ml of was added at a rate of 2 ml/ minute to a separately prepared 0.5 ml of 5% (w/v) CTAB solution under stirring at 30°C. The stirring was continued for another 10 minutes and then 20 ml of 1.1 % (w/v) solution of copper (III) nitrate was added at 30°C under stirring. 53 ml from the total mixture was taken in an 80 ml Teflon lined bomb and initially heated to 300°C for 12 hrs. The product was filtered, washed, dried and calcined at 700°C for 6 hrs. The yield was 94%. The product has BET surface area 30 m2/g and X-ray diffraction pattern of metal ion incorporated TiO2 evidences pure anatase phase. ADVANTAGES OF THE INVENTION
i. The main advantage of the procedure is to use an aqueous solution of freshly prepared
titanium peroxo-carbonate solution, which is easy to handle, non corrosive, no special
care need to be taken and is less moisture sensitive, ii. Another advantage of the procedure is to synthesis nano-crystalline and meso-porous
TiO2 from bulk TiO2 through titanium peroxo-carbonate solution, which makes the
procedure cheaper, iii. Another advantage is that the catalytic activity of TiO2 obtained from the present
invention is high, iv. The incorporation of metal ions from the group of alkali metals, alkali-earth metals or
transition metals in titania helps to improve the photo-catalytic activity.

We Claim
1. A process for the preparation of nanocrystalline and mesoporous titanium dioxide from titanium peroxo carbonate and the said process comprising the steps of: i. digesting titanium source using ammonium fluoride, hydrofluoric acid
and water with a molar ratio in the range of 1: 3.25: 3.06: 111.02 to 1: 1.5:
2.45: 44.4 at a temperature in the range of 25-70°C for a period of 20-40
h; ii. adjusting pH of the solution as obtained in step (i) in the range of 8 to 14
by adding base followed by filtering and washing with ammonium
chloride and water till free from fluoride ions to obtain titanium hydroxide
precipitate; iii. stirring the titanium hydroxide precipitate as obtained in step (ii) in a
solution containing water, H2O2, ammonium carbonate with a molar ratio
range of 53.5: 0.8:1 to 26.7: 0.338: 1 for a period in the range of 10-45
min at a temperature in the range of 20-35°C at the rate of 100-700 rpm to
obtain titanium peroxo-carbonate solution; iv. adjusting the pH of the titanium peroxo-carbonate solution as obtained in
step (iii) in the range of 2-14 by adding acid or base; v. adding 5-30 % w/v aqueous solution surfactant in a range of 2.18 x10-2
8.72 mole % with respect to titanium source to the pH adjusted solution as
obtained in the step (iv) with constant stirring at the rate of 100-700 rpm
for a period in the range of 10-30 min at temperature in the range of 25-
35°C; vi. dopping 0.001-10 mole % metal salt with respect to titania to the solution
as obtained in the step (v) with constant stirring at the rate of 100-700 rpm
for a period in the range of 10-20 min; vii. autoclaving for hydrothermal treatment of the solution as obtained in the
step (vi) at a temperature range of 50-400°C for a period in the range of 30
min to 60 h;
viii. filtering and drying of the precipitate as obtained in step (vii) at a
temperature in the range of 25-90°C; ix. calcining the dried precipitate as obtained in step (viii) at a temperature in
the range 300-900°C for a period in the range of 2-8 h to get nano-
crystalline and mesoporous titanium dioxide.
2. A process as claimed in claim 1, wherein titanium source used is selected from the group consisting of bulk titanium dioxide, titanium alkoxide, titanium tetrachloride or titanium sulphate more preferably bulk titanium dioxide.
3. A process as claimed in claim 1, wherein yield of the said nano-crystalline, mesoporous and doped titanium dioxide is ranging between 78-92%.
4. A process as claimed in claim 1, wherein pore size of the nanocrystalline, mesoporous and doped titanium dioxide is ranging between 6 to 30 nm.
5. A process as claimed in claim 1, wherein BET surface area of the nanocrystalline, mesoporous and doped titanium dioxide is ranging between 30-375 m2/g.
6. A process as claimed in step (ii) and step (v) of claim 1, wherein base used is selected from the group consisting of ammonium hydroxide, sodium hydroxide or potassium hydroxide more preferably ammonium hydroxide.
7. A process as claimed in step (v) of claim 1, wherein acid used is selected from the group consisting of acetic acid, propanoic acid, tartaric acid, citric acid and oxalic acid.
8. A process as claimed in step (vi) of claim 1, wherein surfactant used is selected from the group consisting of Cetyltrimethylammonium bromide (CTAB), tetradecyltrimethylammonium bromide (TTAB), Decyltrimethylammonium bromide (DTAB) or hexadecyltrimethylammonium bromide (HTAB).
9. A process as claimed in step (vi) of claim 1, wherein metal salt used is selected from the group consisting of alkali metal, alkali earth metal or transition metal salts more preferably copper nitrate, iron nitrate, copper chloride, cerium nitrate and magnesium nitrate.
10. A process for the preparation of nanocrystalline, mesoporous and doped titanium dioxide, substantially as herein described with reference to the examples and drawing accompanying this specification.

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Patent Number

277962

Indian Patent Application Number

772/DEL/2010

PG Journal Number

51/2016

Publication Date

09-Dec-2016

Grant Date

07-Dec-2016

Date of Filing

31-Mar-2010

Name of Patentee

COUNCIL OF SCIENTIFIC & INDUSTRIAL RESEARCH

Applicant Address

ANUSANDHAN BHAWAN, 2, RAFI MARG, NEW DELHI-110 001

Inventors:

#	Inventor's Name	Inventor's Address
1	ASIT BARAN PANDA	CENTRAL SALT & MARINE CHEMICALS RESEARCH INSTITUTE, GIJUBHAI BADHEKA MARG, BHAVNAGAR 364 002 GUJARAT. INDIA.
2	HARI CHAND BAJAJ	CENTRAL SALT & MARINE CHEMICALS RESEARCH INSTITUTE, GIJUBHAI BADHEKA MARG, BHAVNAGAR 364 002 GUJARAT. INDIA.
3	NAROTAM SUTRADHAR	CENTRAL SALT & MARINE CHEMICALS RESEARCH INSTITUTE, GIJUBHAI BADHEKA MARG, BHAVNAGAR 364 002 GUJARAT. INDIA.
4	APURBA SINHAMAHAPATRA	CENTRAL SALT & MARINE CHEMICALS RESEARCH INSTITUTE, GIJUBHAI BADHEKA MARG, BHAVNAGAR 364 002 GUJARAT. INDIA.

PCT International Classification Number

C07D36/00

PCT International Application Number

N/A

PCT International Filing date

PCT Conventions:

#	PCT Application Number	Date of Convention	Priority Country
1			NA