APPLICATIONS OF A TUNGSTEN-CONTAINING MATERIAL

Abstract

This invention concerns a tungsten-containing material, the application thereof and a preparation method thereof. Tungsten-containing materials can be used as electrochemical energy storage materials, fuel cell electrolytes and chemical catalyst materials. Tungsten-containing materials include tungsten oxide and tungsten oxide hydrate, doped tungsten oxides and doped tungsten oxide hydrates, tungsten oxide composites, and tungsten oxide hydrate composites.

Claims

1-11. (canceled)

12. A method for producing a tungsten-containing material, the method comprising the steps of: 1) forming a solution or dispersion of tungsten-containing precursor material, wherein the concentration of the precursor material is from 0.1 wt. % to 20 wt. %; 2) adding acid, adjusting the pH value of the solution or the dispersion in step 1 to 1 to 3, and performing acidification to form an intermediate; and 3) transferring the intermediate to a hydrothermal reaction vessel and heating to 90-200 C. for 1 to 96 hours to dehydrate the intermediate to form the tungsten-containing material.

13. The method according to claim 12, wherein the tungsten-containing material comprises tungsten oxide (WO.sub.3) and/or tungsten oxide hydrate (WO.sub.3xH.sub.2O).

14. The method according to claim 13 further comprising immersing the tungsten oxide and/or the tungsten oxide hydrate in a solution of different dopant elements, separating by centrifuging, and then heating.

15. The method according to claim 14, wherein the tungsten-containing material comprises doped tungsten oxide (M.sub.xWO.sub.3), and doped tungsten oxide hydrate (M.sub.xWO.sub.3xH.sub.2O), or a composite of tungsten oxide and tungsten oxide hydrate.

16. The method according to claim 15, wherein the doped tungsten oxide has MLi, Na, K, Ca, Mg, Sr, Ba, the doped tungsten oxide hydrate has MLi, Na, K, Ca, Mg, Sr, and Ba, the tungsten oxide composite comprises tungsten oxide and metal, metal oxide, carbon material or polymer, and the tungsten oxide hydrate composite comprises tungsten oxide hydrate with metal, metal oxide, carbonaceous material, or polymer.

17. The method according to claim 14, wherein the solution is a solution of strontium oxide, a solution of calcium oxide, a solution of strontium chloride, a solution of calcium chloride, a chloroplatinic acid solution, a palladium chloride solution, or a copper acetate solution in a concentration of 0.1 to 6 moles per liter; and the heat treatment is performed for 4 to 8 hours at 200 to 800 C.

18. The method according to claim 12-17, wherein the tungsten-containing precursor material is sodium tungstate and/or ammonium tungstate.

19. The method according to claim 12-17, wherein the acid is sulfuric acid and/or hydrochloric acid.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0039] FIG. 1. shows the ionic conductivity of tungsten oxide materials, and temperature dependence of the proton conductivity of tungsten oxide material.

[0040] FIG. 2. shows the electronic conductivity of the doped tungsten oxide material, and the temperature dependence of the electronic conductivity of the doped tungsten oxide material at 400 degrees Celsius.

[0041] FIG. 3. Cyclic voltammogram of tungsten oxide material, and the high redox activity of the tungsten oxide material.

[0042] FIG. 4. X-ray spectra of tungsten oxide materials obtained (or treated) at different temperatures, more specially shows x-ray patterns of tungsten oxide materials at room temperature (bottom) and after 400 C. heat treatment.

[0043] FIG. 5. shows the cyclic lifetime of the tungsten oxide material as an electrode, and more specially FIG. 5 shows the stable charge and discharge cycle characteristics of the tungsten oxide material as an electrode.

[0044] FIG. 6. Results of producing product 9 in catalytic partial oxidation of methane.

[0045] FIG. 7. Results of producing product 10 in catalytic partial oxidation of methane.

[0046] FIG. 8. Results of producing product 11 in catalytic partial oxidation of methane.

[0047] FIG. 9. Concentrations of H.sub.2O and CO.sub.2 related to producing product 9 by catalyzing the complete oxidation of methane

[0048] FIG. 10. Concentrations of H.sub.2O and CO.sub.2 related to producing product 10 by catalyzing the complete oxidation of methane

[0049] FIG. 11. Concentrations of H.sub.2O and CO.sub.2 related to producing product 11 by catalyzing the complete oxidation of methane

[0050] FIG. 12. Conversion rate of methane oxidation at different temperatures for product 9-11 (Samples 1-3).

SUMMARY OF THE INVENTION

[0051] The advantages of the present invention will be further elucidated by way of specific examples, but the scope of the present invention is not limited to the following examples.

[0052] The reagents and starting materials used in the present invention are commercially available.

[0053] Firstly, tungsten oxide materials with above-mentioned special properties were synthesized by hydrothermal method, co-precipitation method, thermal decomposition method or spray drying method. For example, for the synthesis of tungsten oxide hydrate (WO.sub.3 xH.sub.2O), sodium tungstate or sodium tungstate hydrate is dissolved in deionized water to form a the homogeneous solution with concentration of 0.1% -20%, followed by adding sulfuric acid or hydrochloric acid; Then adding 1 to 10% of ammonium sulfate to form an intermediate; then the mixed solution is transferred into a reaction vessel to heat the reaction, reacting at a temperature of 90 to 200 degrees Celsius for 1 to 96 hours to obtain the product; after the reaction the reactor is cooled down, the product is washed and dried to obtain the tungsten oxide material.

Specific Example 1 (Electrochemical Energy Storage Material)

[0054] (1) Sodium tungstate was used as a tungsten precursor material and dissolved in deionized water to form a homogeneous solution at a concentration of 5% by mass. An appropriate amount of hydrochloric acid was added to make the pH of the solution=1.5. Then, 5% ammonium sulfate was added to form an intermediate, and the mixed solution was transferred to a reaction vessel for reaction at 160 C. for 72 hours to finally obtain a tungsten trioxide material. The proton conductivity of tungsten oxide material is shown in FIG. 1, and its charge/discharge current density property is shown in FIG. 3, and the X-ray measurement data of the tungsten oxide material is shown in FIG. 4.

[0055] In addition, the obtained tungsten oxide was made into electrodes to explore the application and performance as electrochemical energy storage materials. In this embodiment, for example, in the case of electrochemical capacitor application, the tungsten oxide material can be configured as an electrode paste or in combination with a conductive material to form an electrode. In the present embodiment, specifically, the above-mentioned tungsten oxide is uniformly mixed with the conductive agent, the binder and the dispersion solvent in a certain mass ratio (8:1:1) to obtain an electrode paste, which is coated on the current collector, and dried for 10 hours to form an electrode. The obtained electrode was combined with the positive electrode, the glass fiber separator and the electrolyte (2 mol sulfuric acid) to form the initial cell. The battery was activated to obtain tungsten-acid battery with excellent performance. The obtained electrode was paired with a lead oxide electrode, separated by a separator, an acidic electrolyte was added to form a single cell, and electrochemical test was performed. The results are shown in FIG. 5, which shows that the synthesized tungsten oxide has high electrochemical redox active.

[0056] Besides the above specific methods, the inventors of the present application also obtained different types of tungsten materials and electrodes by the following ratios, all achieving similar properties to those of Example 1 (except for the parameters listed in Table 1, all other parameters are the same):

TABLE-US-00001 TABLE 1 Preparation of tungsten oxide Content of ammonium Reaction Tungsten Content sulfate temperature precursor (wt %) pH (wt %) and time Product 1 ammonium 0.5 2 1 90 C., 5 hr tungstate Product 2 ammonium 10 1 1 130 C., 40 hr tungstate Product 3 sodium 2 1.5 2 200 C., 20 hr tungstate Product 4 sodium 15 3 5 150 C., 70 hr tungstate Product 5 sodium 20 3 4 200 C., 96 hr tungstate

[0057] It should be noted that the tungsten oxide prepared by the above method may contain a hydrated tungsten oxide which depends on the reaction temperature and time, but the present application does not make any restriction to the number of hydrated water molecules contained in the oxides. Any tungsten oxide and/or tungsten oxide hydrate obtained by the above process is within the scope of the present application.

[0058] (2) Doped tungsten oxide can be obtained by soaking tungsten oxide in a salt solution of different doping elements, followed by centrifugation separation and heat treatment for a certain time.

[0059] Wherein, the salt solution is 0.1 to 6 mol per liter of the strontium chloride solution, or the calcium chloride solution; the time of heat treatment is 4-8 hours, and the temperature of the heat treatment is 200-800 degrees Celsius. Specific ratios are shown in Table 2:

TABLE-US-00002 TABLE 2 Preparation of doped tungsten oxide Heat treatment Dopant temperature Tungsten oxide oxide content and time Product 6 The tungsten Strontium 1 mol/L 400 C., (Strontium doped oxide described oxide 6 hr tungsten oxide) in detail in Example 1, 1 g Product 7 The tungsten Calcium 6 mol/L 400 C., (Calcium doped oxide described Oxide 6 hr tungsten oxide) in detail in Example 1, 3g Product 8 The tungsten Sodium 4 mol/L 400 C., (Sodium doped oxide described chloride 6 hr tungsten oxide) in detail in Example 1, 2g

[0060] Among them, the electronic conductivity of the product 6 is measured, and the performance data is shown in FIG. 2.

Specific Example 2 (Fuel Cell Electrolyte and Chemical Catalyst Material)

[0061] (1) First, a tungsten oxide material (specifically, a tungsten oxide hydrate (WO.sub.3 xH.sub.2O)) was synthesized by dissolving sodium tungstate or sodium tungstate hydrate in deionized water to form a homogeneous solution having a concentration of 0.1 wt % 20 wt. % of tungsten salt, followed by adding the appropriate amount of sulfuric acid or hydrochloric acid to adjust the pH value to 1 to 3, so that the solution acidification; then adding 1 wt. %-10 wt. % of ammonium sulfate to form intermediates; the resulting mixed solution was transferred to a reactor. The reaction product is obtained at a temperature of 90 to 200 C. for 1 to 96 hours. After the completion of the reaction, the product is cooled down, washed and dried to obtain a tungsten oxide material. In Table 3, the specific tungsten oxide material is the one described in specific example 1.

[0062] (2) Doped tungsten oxide can be obtained by reacting tungsten oxide with a salt solution of different dopant elements. In the specific examples, the ratios of chloroplatinic acid (H.sub.2PtCl.sub.66H.sub.2O), palladium chloride, copper acetate (monohydrate) (all these materials are commercially available), tungsten oxide, the above materials, and water are shown in Table 3:

TABLE-US-00003 TABLE 3 Preparation of doped tungsten oxide Heat treatment temperature Tungsten oxide Dopant salt content and time Product 9 The tungsten H.sub.2PtCl.sub.66H.sub.2O 4 mol/L 250 C., (Platinum oxide described 3 hr doped tungsten in detail in oxide) Example 4g, Product 10 The tungsten PdCl.sub.2 4 mol/L 250 C., (Palladium oxide described 6 hr doped tungsten in detail in oxide) Example 4g, Product 11 The tungsten Cu.sub.2(OAc).sub.4(H.sub.2O).sub.2 4 mol/L 300 C., (Copper oxide described 2 hr doped tungsten in detail in oxide) Example 4g,

[0063] (3) Test conditions of the catalyst:

[0064] Test Condition 1:0.1 g of product 9-11 was homogeneously mixed with 0.9 g of quartz sand and placed in a tubular reactor. Before the test, the sample was activated for 30 min at 250 C. in a 5% H.sub.2 atmosphere. The total flow rate of the raw reaction gas was 500 mL/min; nitrogen was the balance gas; the methane content was 2% and the oxygen content was 0.5%. The heating rate was controlled at 10 C./min, and the reaction temperature was raised from 250 C. to 450 C. The products concentration of methane partial oxidation was monitored.

[0065] Test Condition 2:0.1 g of product 9-11 was homogeneously mixed with 0.9 g of quartz sand and placed in a tubular reactor (internal diameter of about 4 mm). The sample was activated for 30 min at 250 C. in a 5% H.sub.2 atmosphere. The total flow rate of the feed gas was 210 mL/min, consisting of 200 mL/min of methane/nitrogen mixture with a methane content of 20% pre-mixed with 10 mL/min of pure oxygen. The temperature of the feed gas was maintained for 30 min at 250, 300, 350 and 400 C. while flowing the raw reaction gas. The conversion rate of full methane oxidation reaction and amount of H.sub.2O and CO.sub.2 production were monitored.

[0066] (4) Comparison of catalytic performance

[0067] The catalytic oxidation of methane on the surface of the prepared catalyst was investigated. First, the methane molecules are adsorbed onto the active sites of the precious metal; then the electron and proton are transferred to the tungsten oxide carrier (WO.sub.3) to form HWO.sub.3 bronze; finally, the gas phase oxygen oxidizes HWO.sub.3 bronze to produce WO.sub.3 and water, and the methane can be partially oxidized and converted to methanol. By continuing to increase the amount of oxygen supply, methanol can be further oxidized, which is the complete oxidation of methane to generate CO.sub.2 and water.

[0068] The conversion efficiency of methane partial oxidation was tested under test condition 1, and the catalytic performance of partial oxidation of methane can be quantitatively evaluated by comparing product 9, 10 and 11. Product 9-10 can catalyze partial oxidation of methane at 250 C. to efficiently convert methane to methanol and water, and maintain high methanol yield at low temperature (250 C. to 400 C.), showing excellent low temperature catalytic performance, while the product 10 exhibits only a limited catalytic activity at 300 C. or higher. When the temperature rose to above 400 C., the main oxidation reaction of methane occurred on the product 9, 10 and 11 is full oxidation, which forms CO.sub.2 and water as the products.

[0069] The conversion efficiencies of complete oxidation of methane were measured under test conditions 2 for product 9, 10 and 11, and the difference between CO.sub.2 and water production was compared to quantify their efficiency difference. Product 9 can be highly efficiently catalytize oxidation reaction at 250 C., all of the methane gases were completely oxidized to CO.sub.2 and water. The product 10 only showed some complete oxidation catalytic activity at temperatures above 350 C., and all methane can be completely oxidized at temperatures up to 400 C., while product 11 did not show catalytic activity over the entire test temperature range, without CO.sub.2 and water formation.

[0070] The oxidation conversion of methane at different temperatures was directly compared for the catalytic efficiency of products 9, 10 and 11. Product 9 can achieve 14% conversion rate at 250 C., i.e. more than 70% of methane is effectively converted, and the conversion rate did not change significantly with the increase of reaction temperature. Product 10 did not undergo significant catalytic oxidation of methane below 350 C. until the temperature rose to 400 C. to achieve a similar conversion to product 9. Product 11 did not show an effective catalytic oxidation activity in the temperature range of 250-400 C. It can be seen that using tungsten oxide as the support, an active metal components can be rationally chosen to prepare effective methane oxidation catalyst, and it can be also used for solid oxide fuel cell.

[0071] While specific embodiments of the present invention have been described in detail above, they are provided by way of example only and are not intended to limit the invention to the specific embodiments described above. It will be apparent to those skilled in the art that any equivalents and alternatives to the present invention are within the scope of the present invention. Accordingly, equivalents and modifications may be made without departing from the spirit and scope of the invention, which is intended to be within the scope of the invention.