Process for improving surface catalytic efficiency of catalyst substrate

Abstract

The present disclosure discloses a process for improving the surface catalytic efficiency of a catalyst substrate. In some embodiments, to use nano-catalyst particles more efficiently, a process uses a porous substrate as a stationary phase support and disperses the nano-catalyst particles uniformly in all the internal space of the porous substrate, such that reactants flow through the porous substrate to achieve a catalytic effect. In some embodiments, the process not only improves the use efficiency of nano-catalyst particles, but also enables easier and more convenient adjustment of various parameters of a catalytic reaction.

Claims

1. A process for preparing a supported catalyst, comprising: (1) adding an amount of a coagulant and an amount of ethylene glycol to an aqueous solution of a catalyst particle reagent, heating to 120-150° C. and stirring, continuing heating until 60-80% by weight of water of said aqueous solution of said catalyst particle reagent is removed and polymerization of the ethylene glycol occurs, making said aqueous solution become viscous, and immersing a porous support completely in said aqueous solution until said aqueous solution completely penetrates all pores in the porous support, and stopping the heating, wherein the aqueous solution of said catalyst particle reagent is prepared by a method comprising dissolving at least one metal compound in deionized water, adding citric acid in an amount of 2-2.5 times a total molar number of metal ions of the at least one metal compound, and continuously stirring to prepare a 0.1-1 mol/L aqueous solution of said catalyst particle reagent; (2) cooling the aqueous solution to room temperature to transform the aqueous solution of the catalyst particle reagent to a jelly, the jelly filling and coating all the pores of the porous support completely, to obtain a jelly-filled and coated support; and (3) pre-heating a furnace to a temperature of 1,000-1,400° C., directly putting a the jelly-filled and coated support thereinto so that a combustion reaction is conducted immediately on the jelly-filled and coated support, and maintaining the temperature in the furnace for 5-10 hours to obtain the supported catalyst.

2. The process of claim 1, wherein at least one of the following (a) to (c) is applied: (a) said at least one metal compound is one selected from the group consisting of a metal carbonate, a metal nitrate, and a metal ester compound; (b) the method in step (1) further comprises after dissolving said at least one metal compound in deionized water, adding an amount of concentrated nitric acid thereto; and (c) the method in step (1) further comprises adjusting the aqueous solution of said catalyst particle reagent to a pH value of 6-7 with ammonia water.

3. The process of claim 2, wherein after dissolving said at least one metal compound in deionized water, said amount of concentrated nitric acid is added thereto, and at least one of the following (a) and (b) is applied: (a) an amount of nitric acid in said amount of concentrated nitric acid is 10-20% of a total molar number of metal ions of said at least one metal compound put in the deionized water; and (b) the concentrated nitric acid has a concentration of 16 mol/L.

4. The process of claim 3, wherein in step (1), at least one of the following (a) and (b) is applied: (a) the porous support is completely immersed in said aqueous solution for 0.5-1 hour; and (b) a pore former is added, along with the coagulant and ethylene glycol, to the aqueous solution of the catalyst particle reagent.

5. The process of claim 3, wherein at least one of the following (a) to (c) is applied: (a) the amount of the coagulant is 1-5% of a mass of the at least one metal compound in the aqueous solution of the catalyst particle reagent; (b) the coagulant is one selected from the group consisting of agar powder and Kanten powder; and (c) the amount of the ethylene glycol is 2-2.5 times the total molar number of metal ions of said at least one metal compound put in the deionized water.

6. The process of claim 3, wherein in step (1), a flux is added, along with the coagulant and the ethylene glycol, to the aqueous solution of the catalyst particle reagent.

7. The process of claim 2, wherein in step (1), at least one of the following (a) and (b) is applied: (a) the porous support is completely immersed in said aqueous solution for 0.5-1 hour; and (b) a pore former is added, along with the coagulant and ethylene glycol, to the aqueous solution of the catalyst particle reagent.

8. The process of claim 2, wherein at least one of the following (a) to (c) is applied: (a) the amount of the coagulant is 1-5% of a mass of the at least one metal compound in the aqueous solution of the catalyst particle reagent; (b) the coagulant is one selected from the group consisting of agar powder and Kanten powder; and (c) the amount of the ethylene glycol is 2-2.5 times a total molar number of metal ions of said at least one metal compound put in the deionized water.

9. The process of claim 2, wherein in step (1), a flux is added, along with the coagulant and the ethylene glycol, to the aqueous solution of the catalyst particle reagent.

10. The process of claim 1, wherein in step (1), at least one of the following (a) and (b) is applied: (a) the porous support is completely immersed in said aqueous solution for 0.5-1 hour; and (b) an amount of a pore former is added, along with the coagulant and ethylene glycol, to the aqueous solution of the catalyst particle reagent.

11. The process of claim 10, wherein said amount of said pore former is added, along with the coagulant and ethylene glycol, to the aqueous solution of the catalyst particle reagent, and at least one of the following (a) and (b) is applied: (a) the amount of the pore former is 1-5% of a mass of the at least one metal compound in the aqueous solution of the catalyst particle reagent; and (b) the pore former is at least one selected from the group consisting of (NH.sub.4).sub.2SO.sub.4, NH.sub.4HC.sub.O3 and starch.

12. The process of claim 1, wherein at least one of the following (a) to (c) is applied: (a) the amount of the coagulant is 1-5% of a mass of the at least one metal compound in the aqueous solution of the catalyst particle reagent; (b) the coagulant is one selected from the group consisting of agar powder and Kanten powder; and (c) the amount of the ethylene glycol is 2-2.5 times a total molar number of metal ions of said at least one metal compound put in the deionized water.

13. The process of claim 1, wherein in step (1), an amount of a flux is added, along with the coagulant and the ethylene glycol, to the aqueous solution of the catalyst particle reagent.

14. The process of claim 13, wherein at least one of the following (a) to (b) is applied: (a) the amount of the flux is 0.5-3% of a mass of the at least one metal compound in the aqueous solution of the catalyst particle reagent, while reducing a reaction temperature of the furnace by 200-450° C. or shortening a maintaining time of the furnace to 0.5-2 hours; and (b) the flux is at least one selected from the group consisting of Li.sub.2CO.sub.3, B.sub.2O.sub.3, ZnO, Al.sub.2O.sub.3, PbO.sub.2, Bi.sub.2O.sub.3, and V.sub.2O.sub.5.

15. The process of claim 1, wherein in step (3), a reducing atmosphere is introduced to activate catalyst particles in the process of maintaining the temperature in the furnace.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 shows a magnified (1000×) SEM photograph of a catalyst substrate prepared in Example 1.

(2) FIG. 2 shows a magnified (5000×) SEM photograph of a catalyst substrate prepared in Example 1.

(3) FIG. 3 shows a magnified (20000×) SEM photograph of a catalyst substrate prepared in Example 6.

(4) FIG. 4 shows a magnified (20000×) SEM photograph of a catalyst substrate prepared in Example 7.

(5) FIG. 5 illustrates a comparison of ammonia-nitrogen conversion in a catalytic performance test for the catalyst substrates prepared in Examples 1, 6, and 7.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENT(S)

(6) The present disclosure is described in detail below with reference to the examples, but the implementation of the present disclosure is not limited thereto. Various substitutions and alterations made based on ordinary skills and conventional means in the art without departing from the above technical ideas of the present disclosure are included in the scope of the present disclosure.

(7) Chemicals used in the examples of the present disclosure are listed as follows:

(8) Chemical

(9) Al(NO.sub.3).sub.3.9H.sub.2O

(10) Li.sub.2O.sub.3Si

(11) Li.sub.2CO.sub.3

(12) AgNO.sub.3

(13) Ni(NO.sub.3).sub.2.6H.sub.2O

(14) Ti(OC.sub.4H.sub.9).sub.4

(15) Cu(NO.sub.3).sub.2.3H.sub.2O

(16) Zn(NO.sub.3).sub.2.6H.sub.2O

(17) HNO.sub.3(aq)

(18) CH.sub.3COCH.sub.3

(19) C.sub.6H.sub.8O.sub.7 (citric acid)

(20) Starch

(21) Kanten powder

(22) The examples of the present disclosure provide processes for improving the surface catalytic efficiency of a catalyst substrate, without adding a pore former and a flux. The processes can include the following steps:

(23) (1) Dissolving Al(NO.sub.3).sub.3.9H.sub.2O (0-0.3 g), Li.sub.2O.sub.3Si (0-0.3 g), Ni(NO.sub.3).sub.2.6H.sub.2O (0-0.3 g), Cu(NO.sub.3).sub.2.3H.sub.2O (0-0.3 g), AgNO.sub.3 (0-0.3 g), Zn(NO.sub.3).sub.2.6H.sub.2O (0-0.3 g), and Ti(OC.sub.4H.sub.9).sub.4 (0-0.3 g) in 100 mL of deionized water, mixed with 2-2.5 times the total number of moles of metal ions of citric acid chelating agent, and continuously stirred. If any catalyst compound is not easily dissolve, adding an additional 16 mol/L of concentrated nitric acid (10-20% of the total number of moles of metal ions of the metal compound put in the deionized water) to help dissolve and prepare a 0.1-1 mol/L aqueous solution of catalyst particle reagent (optional selection, mixing and combination of the foregoing metal compounds can achieve the preparation of the 0.1-1 mol/L catalyst particle reagent aqueous solution and obtain similar effects, and the amount of each metal compound used is within the above range; the nitric acid is used when the metal compound is difficult to dissolve; in case of preparation with 100 mL of deionized water, 5 mL of nitric acid can be added to the solution each time to indicate that the metal compound is completely dissolved; the specific amount depends on the combination of the metal compounds, and the amount ranges from 10% to 20% of the total number of moles of metal ions).

(24) (2) After the added reagent is completely dissolved, the pH is adjusted to 6-7 with ammonia water. If the pH is too low, citric acid will not easily deprotonate to chelate the metal ions; if the pH is too high, the metal ions will easily form colloidal hydroxides. If Li.sub.2O.sub.3Si is added, it should be added after the pH of the solution is neutral, avoiding colloidization of Li.sub.2O.sub.3Si in acidic solution.

(25) (3) After adjusting the pH value, 2.5 times the moles of the sample of C.sub.2H.sub.4(OH).sub.2 (ethylene glycol) can be added along with 1% of the total solute weight of agar powder or Kanten powder, heated on a heater plate to remove excess water until 60-80% by weight of the water is removed and the solution forms a slightly viscous polymer.

(26) (4) The porous alumina substrate can be placed and immersed completely in the solution for 0.5-1 h, until the solution completely penetrates most, if not all, the pores inside the substrate.

(27) (5) The heating is stopped, and when the solution drops to room temperature, the catalyst solution becomes jelly-like and completely covers most, if not all, the voids of the porous alumina substrate. The substrate is taken out and the jelly-like catalyst is removed from the surface of the substrate.

(28) (6) A high temperature furnace is preheated to 800-1,400° C.

(29) (7) A catalyst-coated porous substrate is placed into the high temperature furnace to immediately undergo a combustion reaction and the temperature of the high temperature furnace can be held for 10 h. A reducing hydrogen atmosphere can be introduced to activate catalyst particles in the holding process. After ignition and combustion, a fluffy porous structure with finer pores is formed and completely fills in the pores of the porous substrate.

(30) The process of the nano-catalyst substrate is further described in detail below with reference to Examples 1 to 6.

EXAMPLE 1

(31) A process for improving the surface catalytic efficiency of a catalyst substrate without adding a pore former and a flux, can include the following steps:

(32) (1) Dissolving Al(NO.sub.3).sub.3.9H.sub.2O (0-0.3 g), Li.sub.2O.sub.3Si (0-0.3 g), Ni(NO.sub.3).sub.2.6H.sub.2O (0-0.3 g), Cu(NO.sub.3).sub.2.3H.sub.2O (0-0.3 g), AgNO.sub.3 (0-0.3 g), Zn(NO.sub.3).sub.2.6H.sub.2O (0-0.3 g), and Ti(OC.sub.4H.sub.9).sub.4 (0-0.3 g) in 100 mL of deionized water, mixed with 2 times the total number of moles of metal ions of citric acid chelating agent, and continuously stirred. If any catalyst compound is not easily dissolved, adding additional 16 mol/L concentrated nitric acid (10-20% of the total number of moles of metal ions of the metal compound put in the deionized water) to help dissolve and prepare a 0.5 mol/L aqueous solution of catalyst particle reagent.

(33) (2) After the added reagent is completely dissolved, the pH is adjusted to 6-7 with ammonia water. If the pH is too low, citric acid will not easily deprotonate to chelate the metal ions; if the pH is too high, the metal ions will easily form colloidal hydroxides. If Li.sub.2O.sub.3Si is added, it should be added after the pH of the solution is neutral, avoiding colloidization of Li.sub.2O.sub.3Si in acidic solution.

(34) (3) After adjusting the pH value, 2.5 times the moles of the sample of C.sub.2H.sub.4(OH).sub.2 (ethylene glycol) is added along with 1% of the total solute weight of agar powder, heated up to 120-150° C. and stirred on a heater plate; excess water is removed until 60-80% by weight of the water is removed and the solution forms a slightly viscous polymer.

(35) (4) A porous alumina substrate is placed and immersed completely in the solution for 0.5 h, until the solution completely penetrates most, if not all, pores inside the substrate.

(36) (5) The heating is stopped, and when the solution drops to room temperature, the catalyst solution becomes jelly-like and completely covers most, if not all, the voids of the porous alumina substrate. The substrate is taken out and the jelly-like catalyst is removed from the surface of the substrate.

(37) (6) A high temperature furnace is preheated to 1,400° C.

(38) (7) A catalyst-coated porous substrate is placed into the high temperature furnace to immediately undergo a combustion reaction and the temperature of the high temperature furnace is held for 10 h. A reducing hydrogen atmosphere is introduced to activate catalyst particles in the holding process. After ignition and combustion, a fluffy porous structure with finer pores is formed and completely filled in the pores of the porous substrate, and the obtained nanometer scale is about 200 nm to 1 μm, as shown in FIG. 1 and FIG. 2.

EXAMPLES 2 TO 5

(39) The process is the same as that in Example 1, except for the concentration of the prepared aqueous solution of catalyst particle reagent. Specific methods for preparing the aqueous solution of catalyst particle reagent are listed in the following table:

(40) TABLE-US-00001 Preparation Method Example Al(NO.sub.3).sub.3•9H.sub.2O (0-0.3 g), Li.sub.2O.sub.3Si (0-0.3 g), Ni(NO.sub.3).sub.2•6H.sub.2O 2 (0-0.3 g), Cu(NO.sub.3).sub.2•3H.sub.2O (0-0.3 g), AgNO.sub.3 (0-0.3 g), Zn(NO.sub.3).sub.2•6H.sub.2O (0-0.3 g), and Ti(OC.sub.4H.sub.9).sub.4 (0-0.3 g) are dissolved in 100 mL of deionized water, mixed with 2 times the total number of moles of metal ions of citric acid chelating agent, and continuously stirred. If any catalyst compound is not easily dissolved, add additional 16 mol/L concentrated nitric acid (10-20% of the total number of moles of metal ions of the metal compound put in the deionized water) to help dissolve and prepare a 0.1 mol/L aqueous solution of catalyst particle reagent. Example Al(NO.sub.3).sub.3•9H.sub.2O (0-0.3 g), Li.sub.2O.sub.3Si (0-0.3 g), Ni(NO.sub.3).sub.2•6H.sub.2O 3 (0-0.3 g), Cu(NO.sub.3).sub.2•3H.sub.2O (0-0.3 g), AgNO.sub.3 (0-0.3 g), Zn(NO.sub.3).sub.2•6H.sub.2O (0-0.3 g), and Ti(OC.sub.4H.sub.9).sub.4 (0-0.3 g) are dissolved in 100 mL of deionized water, mixed with 2 times the total number of moles of metal ions of citric acid chelating agent, and continuously stirred. If any catalyst compound is not easily dissolved, add additional 16 mol/L concentrated nitric acid (10-20% of the total number of moles of metal ions of the metal compound put in the deionized water) to help dissolve and prepare a 0.3 mol/L aqueous solution of catalyst particle reagent. Example Al(NO.sub.3).sub.3•9H.sub.2O (0-0.3 g), Li.sub.2O.sub.3Si (0-0.3 g), Ni(NO.sub.3).sub.2•6H.sub.2O 4 (0-0.3 g), Cu(NO.sub.3).sub.2•3H.sub.2O (0-0.3 g), AgNO.sub.3 (0-0.3 g), Zn(NO.sub.3).sub.2•6H.sub.2O (0-0.3 g), and Ti(OC.sub.4H.sub.9).sub.4 (0-0.3 g) are dissolved in 100 mL of deionized water, mixed with 2.5 times the total number of moles of metal ions of citric acid chelating agent, and continuously stirred. If any catalyst compound is not easily dissolved, add additional 16 mol/L concentrated nitric acid (10-20% of the total number of moles of metal ions of the metal compound put in the deionized water) to help dissolve and prepare a 0.8 mol/L aqueous solution of catalyst particle reagent. Example Al(NO.sub.3).sub.3•9H.sub.2O (0-0.3 g), Li.sub.2O.sub.3Si (0-0.3 g), Ni(NO.sub.3).sub.2•6H.sub.2O 5 (0-0.3 g), Cu(NO.sub.3).sub.2•3H.sub.2O (0-0.3 g), AgNO.sub.3 (0-0.3 g), Zn(NO.sub.3).sub.2•6H.sub.2O (0-0.3 g), and Ti(OC.sub.4H.sub.9).sub.4 (0-0.3 g) are dissolved in 100 mL of deionized water, mixed with 2.5 times the total number of moles of metal ions of citric acid chelating agent, and continuously stirred. If any catalyst compound is not easily dissolved, add additional 16 mol/L concentrated nitric acid (10-20% of the total number of moles of metal ions of the metal compound put in the deionized water) to help dissolve and prepare a 1 mol/L aqueous solution of catalyst particle reagent.

EXAMPLE 6

(41) The process is the same as that in Example 1, except for the heat treatment temperature. In this example, the high temperature furnace is heated to 800° C. The nanometer scale obtained in this example is smaller, about 20-80 nm, as shown in FIG. 3.

(42) The examples of the present disclosure provide a process for improving the surface catalytic efficiency of a catalyst substrate, with adding a pore former and a flux and reducing the heat treatment temperature and holding time, including the following steps:

(43) (1) Dissolving Al(NO.sub.3).sub.3.9H.sub.2O (0-0.3 g), Li.sub.2O.sub.3Si (0-0.3 g), Ni(NO.sub.3).sub.2.6H.sub.2O (0-0.3 g), Cu(NO.sub.3).sub.2.3H.sub.2O (0-0.3 g), AgNO.sub.3 (0-0.3 g), Zn(NO.sub.3).sub.2.6H.sub.2O (0-0.3 g), and Ti(OC.sub.4H.sub.9).sub.4 (0-0.3 g) in 100 mL of deionized water, mixed with 2-2.5 times the total number of moles of metal ions of citric acid chelating agent, and continuously stirred. If any catalyst compound is not easily dissolved, add additional 16 mol/L concentrated nitric acid (10-20% of the total number of moles of metal ions of the metal compound put in the deionized water) to help dissolve and prepare a 0.1-1 mol/L aqueous solution of catalyst particle reagent (optional selection, mixing and combination of the foregoing metal compounds can achieve the preparation of the 0.1-1 mol/L catalyst particle reagent aqueous solution and obtain similar effects, and the amount of each metal compound used is within the above range; the nitric acid is used when the metal compound is difficult to dissolve; in case of preparation with 100 mL of deionized water, 5 mL of nitric acid is usually added to the solution each time to indicate that the metal compound is completely dissolved; the specific amount depends on the combination of the metal compounds, and the amount ranges from 10% to 20% of the total number of moles of metal ions).

(44) (2) After the added reagent is completely dissolved, the pH is adjusted to 6-7 with ammonia water. If the pH is too low, citric acid will not easily deprotonate to chelate the metal ions; if the pH is too high, the metal ions will easily form colloidal hydroxides. If Li.sub.2O.sub.3Si is added, it should be added after the pH of the solution is neutral, avoiding colloidization of Li.sub.2O.sub.3Si in acidic solution.

(45) (3) After adjusting the pH value, 2.5 times the moles of the sample of C.sub.2H.sub.4(OH).sub.2 (ethylene glycol) is added along with 1% of the total solute weight of agar powder or Kanten powder, 3% starch and 0.5% Li.sub.2CO.sub.3, and heated on a heater plate until completely dissolved; excess water is removed until 60-80% by weight of the water is removed and the solution forms a slightly viscous polymer.

(46) (4) The porous alumina substrate is placed and immersed completely in the solution for 0.5-1 h, until the solution completely penetrates most, if not all, the pores inside the substrate.

(47) (5) The heating is stopped, and when the solution drops to room temperature, the catalyst solution becomes jelly-like and completely covers all the voids of the porous alumina substrate. The substrate is taken out and the jelly-like catalyst is removed from the surface of the substrate.

(48) (6) A high temperature furnace is preheated to 1,000° C.

(49) (7) A catalyst-coated porous substrate is placed into the high temperature furnace to immediately undergo a combustion reaction and the temperature of the high temperature furnace is held for 2 h. A reducing hydrogen atmosphere is introduced to activate catalyst particles in the holding process.

(50) (8) After ignition and combustion, a fluffy porous structure with finer pores is formed and completely filled in the pores of the porous substrate.

(51) The process of the nano-catalyst substrate will be further described in detail below with reference to Examples 7 to 11.

EXAMPLE 7

(52) Provided is a process for improving the surface catalytic efficiency of a catalyst substrate, with adding a pore former and a flux and reducing the heat treatment temperature and holding time, including the following steps:

(53) (1) Dissolving Al(NO.sub.3).sub.3.9H.sub.2O (0-0.3 g), Li.sub.2O.sub.3Si (0-0.3 g), Ni(NO.sub.3).sub.2.6H.sub.2O (0-0.3 g), Cu(NO.sub.3).sub.2.3H.sub.2O (0-0.3 g), AgNO.sub.3 (0-0.3 g), Zn(NO.sub.3).sub.2.6H.sub.2O (0-0.3 g), and Ti(OC.sub.4H.sub.9).sub.4 (0-0.3 g) in 100 mL of deionized water, mixed with 2 times the total number of moles of metal ions of citric acid chelating agent, and continuously stirred. If any catalyst compound is not easily dissolved, add additional 16 mol/L concentrated nitric acid (10-20% of the total number of moles of metal ions of the metal compound put in the deionized water) to help dissolve and prepare a 0.5 mol/L aqueous solution of catalyst particle reagent.

(54) (2) After the added reagent is completely dissolved, the pH is adjusted to 6-7 with ammonia water. If the pH is too low, citric acid will not easily deprotonate to chelate the metal ions; if the pH is too high, the metal ions will easily form colloidal hydroxides. If Li.sub.2O.sub.3Si is added, it should be added after the pH of the solution is neutral, avoiding colloidization of Li.sub.2O.sub.3Si in acidic solution.

(55) (3) After adjusting the pH value, 2.5 times the moles of the sample of C.sub.2H.sub.4(OH).sub.2 (ethylene glycol) is added along with 1% of the total solute weight of agar powder or Kanten powder, 3% starch and 0.5% Li.sub.2CO.sub.3, and heated up to 120-150° C. and stirred on a heater plate until completely dissolved; excess water is removed until 60-80% by weight of the water is removed and the solution forms a slightly viscous polymer.

(56) (4) A porous alumina substrate is placed and immersed completely in the solution for 1 h, until the solution completely penetrates most, if not all, the pores inside the substrate.

(57) (5) The heating is stopped, and when the solution drops to room temperature, the catalyst solution becomes jelly-like and completely covered all the voids of the porous alumina substrate. The substrate is taken out and the jelly-like catalyst is removed from the surface of the substrate.

(58) (6) A high temperature furnace is preheated to 1,000° C.

(59) (7) A catalyst-coated porous substrate is placed into the high temperature furnace to immediately undergo a combustion reaction and the temperature of the high temperature furnace is held for 2 h. A reducing hydrogen atmosphere is introduced to activate catalyst particles in the holding process.

(60) (8) After ignition and combustion, a fluffy porous structure with finer pores is formed and completely fills in the pores of the porous substrate, and the obtained nanometer scale is about 50-200 nm. The apparent structure is relatively solid with higher crystallinity, as shown in FIG. 4.

EXAMPLES 8 TO 11

(61) The process is the same as that in Example 1, except for the concentration of the prepared aqueous solution of catalyst particle reagent. Specific methods for preparing the aqueous solution of catalyst particle reagent are listed in the following table:

(62) TABLE-US-00002 Preparation method Example Al(NO.sub.3).sub.3•9H.sub.2O (0-0.3 g), Li.sub.2O.sub.3Si (0-0.3 g), Ni(NO.sub.3).sub.2•6H.sub.2O 8 (0-0.3 g), Cu(NO.sub.3).sub.2•3H.sub.2O (0-0.3 g), AgNO.sub.3 (0-0.3 g), Zn(NO.sub.3).sub.2•6H.sub.2O (0-0.3 g), and Ti(OC.sub.4H.sub.9).sub.4 (0-0.3 g) are dissolved in 100 mL of deionized water, mixed with 2 times the total number of moles of metal ions of citric acid chelating agent, and continuously stirred If any catalyst compound is not easily dissolved, add additional 16 mol/L concentrated nitric acid (10-20% of the total number of moles of metal ions of the metal compound put in the deionized water) to help dissolve and prepare a 0.1 mol/L aqueous solution of catalyst particle reagent. Example Al(NO.sub.3).sub.3•9H.sub.2O (0-0.3 g), Li.sub.2O.sub.3Si (0-0.3 g), Ni(NO.sub.3).sub.2•6H.sub.2O 9 (0-0.3 g), Cu(NO.sub.3).sub.2•3H.sub.2O (0-0.3 g), AgNO.sub.3 (0-0.3 g), Zn(NO.sub.3).sub.2•6H.sub.2O (0-0.3 g), and Ti(OC.sub.4H.sub.9).sub.4 (0-0.3 g) are dissolved in 100 mL of deionized water, mixed with 2 times the total number of moles of metal ions of citric acid chelating agent, and continuously stirred. If any catalyst compound is not easily dissolved, add additional 16 mol/L concentrated nitric acid (10-20% of the total number of moles of metal ions of the metal compound put in the deionized water) to help dissolve and prepare a 0.3 mol/L aqueous solution of catalyst particle reagent. Example Al(NO.sub.3).sub.3•9H.sub.2O (0-0.3 g), Li.sub.2O.sub.3Si (0-0.3 g), Ni(NO.sub.3).sub.2•6H.sub.2O 10 (0-0.3 g), Cu(NO.sub.3).sub.2•3H.sub.2O (0-0.3 g), AgNO.sub.3 (0-0.3 g), Zn(NO.sub.3).sub.2•6H.sub.2O (0-0.3 g), and Ti(OC.sub.4H.sub.9).sub.4 (0-0.3 g) are dissolved in 100 mL of deionized water, mixed with 2.5 times the total number of moles of metal ions of citric acid chelating agent, and continuously stirred. If any catalyst compound is not easily dissolved, add additional 16 mol/L concentrated nitric acid (10-20% of the total number of moles of metal ions of the metal compound put in the deionized water) to help dissolve and prepare a 0.8 mol/L aqueous solution of catalyst particle reagent. Example Al(NO.sub.3).sub.3•9H.sub.2O (0-0.3 g), Li.sub.2O.sub.3Si (0-0.3 g), Ni(NO.sub.3).sub.2•6H.sub.2O 11 (0-0.3 g), Cu(NO.sub.3).sub.2•3H.sub.2O (0-0.3 g), AgNO.sub.3 (0-0.3 g), Zn(NO.sub.3).sub.2•6H.sub.2O (0-0.3 g), and Ti(OC.sub.4H.sub.9).sub.4 (0-0.3 g) are dissolved in 100 mL of deionized water, mixed with 2.5 times the total number of moles of metal ions of citric acid chelating agent, and continuously stirred. If any catalyst compound is not easily dissolved, add additional 16 mol/L concentrated nitric acid (10-20% of the total number of moles of metal ions of the metal compound put in the deionized water) to help dissolve and prepare a 1 mol/L aqueous solution of catalyst particle reagent.

(63) In a test, the nano-catalyst substrates completed in Examples 1, 6, and 7 were put into a catalytic performance testing device, respectively; ammonia gas was pass through the catalyst, while circulating continuously for 60-70 min and finally introducing into the aqueous solution to collect. NO.sub.3.sup.− concentrations were determined by IC to observe the catalyst conversion ability, as shown in FIG. 5, and it was found that Examples 1, 6, and 7 were all effective. Moreover, Example 7 had a better structure and the optimal effect.

(64) It should be noted that relational terms herein such as first and second are only used to distinguish one entity or operation from another entity or operation without necessarily requiring or implying any actual such relationship or order between such entities or operations. Moreover, the terms “include”, “including” or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or terminal device including a series of elements not only includes those elements, but also includes those elements that are not explicitly listed, or also includes elements inherent to this process, method, article or terminal device. Without more limitations, the elements defined by the sentence “include . . . ” or “including . . . ” do not exclude the existence of other elements in the process, method, article, or terminal device that includes the elements. In addition, herein, “greater than”, “less than”, “more than”, etc. are understood as not including the number; “above”, “below”, “within”, etc. are understood as including the number.

(65) Although the foregoing examples have been described, those skilled in the art can make additional alterations and modifications to these examples once they learn the basic creative concept. Therefore, the above are only the examples of the present disclosure, but not intended to limit the scope of the present disclosure. Any equivalent structure or equivalent process transformation made by using the content of the description and drawings of the present disclosure, or directly or indirectly applied to other related technical fields, are included in the scope of the present disclosure.