TW202112443A - Catalyst and method for manufacturing the same and method of removing vocs - Google Patents

Abstract

A method of manufacturing catalyst is provided, which includes providing a neutral aqueous solution of noble metal salt and transition metal salt, dispersing mesoporous templates into a non-polar solvent to form a dispersion, and mixing the neutral aqueous solution and the dispersion to form a mixture liquid. The mixing liquid is heated to remove water and the non-polar solvent thereof to form powders. The powders are calcined to form a catalyst in pores of the mesoporous template. The mesoporous template is removed to keep the catalyst. The catalyst includes a mesoporous transition metal oxide, and a single-atom of noble metal anchored on the mesoporous transition metal oxide.

Description

Catalyst and its forming method and method for removing volatile organic compounds

This disclosure relates to single-atom noble metal catalysts, their formation methods, and their applications.

In recent years, the air pollution caused by volatile organic compounds (VOCs) has attracted increasing attention. At present, the main methods for removing volatile organic compounds are adsorption, incineration, photocatalysis, and catalytic oxidation. Among them, catalytic oxidation is the most effective method to remove VOCs. The catalyst active ingredients used in the catalytic oxidation method are generally micron or nanometers, and few single-atom metals are anchored on the carrier. Therefore, it is urgent to develop a new single-atom catalyst and its formation method to be applied to the catalytic oxidation method for removing VOCs.

The catalyst provided by an embodiment of the present disclosure includes: a mesoporous transition metal oxide; and a single-atom noble metal anchored on the mesoporous transition metal oxide, wherein the transition metal includes Co, Mn, Fe, Ni, Ce, or In the above combination, the single-atom noble metal is Pt, Rh, Pd, or Ru; when the single-atom noble metal is Pt, the transition metal does not include Fe; when the single-atom noble metal is Ru, the transition metal does not include Ni or Ce.

In some embodiments, when the single-atom noble metal is Pt, the transition metal includes Co, Mn, Ni, Ce, or a combination thereof.

In some embodiments, when the single-atom noble metal is Rh, the transition metal includes Co, Mn, Fe, Ni, Ce, or a combination thereof.

In some embodiments, when the single-atom noble metal is Pd, the transition metal includes Co, Mn, Fe, Ni, Ce, or a combination thereof.

In some embodiments, when the single-atom noble metal is Ru, the transition metal includes Co, Mn, Fe, or a combination thereof.

In some embodiments, the weight ratio of the mesoporous transition metal oxide to the monoatomic noble metal is between 1:0.002 and 1:0.06.

The method for forming a catalyst provided by an embodiment of the present disclosure includes: providing a neutral aqueous solution of a salt of a precious metal and a salt of a transition metal; dispersing a mesoporous template in a non-polar solvent to form a dispersion; mixing neutral Aqueous solution and dispersion to form a mixed solution; heating the mixed solution to remove the non-polar solvent and water in the mixed solution and form a powder; sinter the powder to form a catalyst in the hole of the mesoporous template; and remove the mesoporous template to retain The catalyst, wherein the catalyst includes: a mesoporous transition metal oxide; and a single-atom noble metal, anchored on the mesoporous transition metal oxide.

In some embodiments, the single-atom noble metal is Pt, Rh, Pd, or Ru, and the transition metal includes Co, Mn, Fe, Ni, Ce, or a combination thereof.

In some embodiments, the weight ratio of the mesoporous transition metal oxide to the monoatomic noble metal is between 1:0.002 and 1:0.06.

In some embodiments, the temperature at which the mixed solution is heated to remove the non-polar solvent and water in the mixed solution and form a powder is between 55°C and 75°C.

In some embodiments, the temperature at which the powder is sintered to form the catalyst is between 280°C and 350°C.

In some embodiments, the step of removing the mesoporous template to retain the catalyst uses an aqueous solution of hydrofluoric acid or sodium hydroxide.

The method for removing volatile organic compounds provided by an embodiment of the present disclosure includes: passing a mixed gas containing volatile organic compounds into a catalyst reactor to oxidize the volatile organic compounds into water and carbon dioxide, wherein the catalyst includes: Porous transition metal oxides; and single-atom noble metals, anchored on the mesoporous transition metal oxides.

In some embodiments, the single-atom noble metal is Pt, Rh, Pd, or Ru, and the transition metal includes Co, Mn, Fe, Ni, Ce, or a combination thereof.

In some embodiments, the weight ratio of the mesoporous transition metal oxide to the monoatomic noble metal is between 1:0.002 and 1:0.06.

In some embodiments, the volatile organic compound includes propane, isopropanol, acetone, toluene, propylene glycol methyl ether, propylene glycol methyl ether acetate, or a combination thereof.

The catalyst provided by an embodiment of the present disclosure includes: a mesoporous transition metal oxide; and a single-atom noble metal anchored on the mesoporous transition metal oxide, that is, a strong metal-support function between the single atom and the carrier Force (Strong Metal Support Interaction). The mesopore is defined as the width of the hole greater than 2 nm and less than 50 nm, see IUPAC, Compendium of Chemical Terminology, 2 ^nd ed. (the "Gold Book"), Oxford (1997). In some embodiments, the transition metal of the mesoporous transition metal oxide includes Co, Mn, Fe, Ni, Ce, or a combination thereof, and the single-atom noble metal is Pt, Rh, Pd, or Ru. In some embodiments, when the single-atom noble metal is Pt, the transition metal does not include Fe. In some embodiments, when the single-atom noble metal is Ru, the transition metal does not include Ni or Ce. For example, when the single-atom noble metal is Pt, the transition metal includes Co, Mn, Ni, Ce, or a combination of the foregoing. When the single-atom noble metal is Rh, the transition metal is Co, Mn, Fe, Ni, Ce, or a combination of the above. When the single-atom noble metal is Pd, the transition metal is Co, Mn, Fe, Ni, Ce, or a combination of the above. When the single-atom noble metal is Ru, the transition metal is Co, Mn, Fe, or a combination of the above. In some embodiments, the weight ratio of the mesoporous transition metal oxide to the monoatomic noble metal is between 1:0.002 and 1:0.06. If the amount of monoatomic noble metal is too low, it cannot be anchored in a monoatomic form on the mesoporous transition metal oxide to form highly reactive active sites. If the amount of monoatomic noble metal is too high, large-sized particles such as metal clusters or nanoparticles will be produced, which will reduce the number of active sites and their activity. In some embodiments, the specific surface area of the catalyst is between 60 m ² /g and 200 m ² /g, and the average pore size of the catalyst is between 8 nm and 20 nm, which conforms to the alignment in the technical field. Definition of hole material. Since the amount of mesoporous transition metal oxide is much higher than the amount of monoatomic precious metal, the mesoporous transition metal oxide will form the framework of the catalyst. In other words, mesoporous transition metal oxides belong to mesoporous materials.

The method for forming a catalyst provided in an embodiment of the present disclosure includes: providing a neutral aqueous solution of a salt of a precious metal and a salt of a transition metal. For example, salts of transition metals such as cobalt salts (such as Co(NO ₃ ) ₂ •6H ₂ O, CoCl ₂ •6H ₂ O, CoSO ₄ •7H ₂ O, or other suitable cobalt salts), manganese salts can be used (Such as Mn(NO ₃ ) ₂ •4H ₂ O, MnCl ₂ •4H ₂ O, MnSO ₄ •xH ₂ O, or other suitable manganese salts), iron salts (such as Fe(NO ₃ ) ₃ •9H ₂ O, FeCl _3. FeSO ₄ •xH ₂ O, or other suitable iron salts), nickel salts (such as Ni(NO ₃ ) ₂ •6H ₂ O, NiCl ₂ •6H ₂ O, NiSO ₄ •7H ₂ O, or other suitable nickel salts) ), or cerium salt (such as Ce(NO ₃ ) ₃ •6H ₂ O, CeCl ₃ •7H ₂ O, Ce ₂ (SO ₄ ) ₃ •8H ₂ O, or other suitable cerium salt) dissolved in water to form a transition Aqueous metal salt solution. In one embodiment, the concentration of the transition metal salt aqueous solution is between 0.1M and 5.0M. If the concentration of the transition metal salt aqueous solution is too low, the subsequent formation of the mesoporous structure will be incomplete. If the concentration of the transition metal salt aqueous solution is too high, a metal oxide with a non-mesoporous structure will be formed.

On the other hand, take precious metal salts such as platinum salts (such as H ₂ PtCl ₆ , Pt(NH ₃ ) ₂ Cl ₂ , Na ₂ PtCl ₆ •6H ₂ O, or other suitable platinum salts), palladium salts (such as H ₂ PdCl ₄ , Na ₂ PdCl ₄ , or other suitable palladium salt), rhodium salt (such as Na ₃ RhCl ₆ , Rh(NO ₃ ) ₃ or other suitable rhodium salt), or ruthenium salt (such as RuCl ₃ •xH ₂ O, [ Ru(NH ₃ ) ₆ Cl ₂ , or other suitable ruthenium salt) is dissolved in water to form an aqueous solution of a precious metal salt. In one embodiment, the concentration of the precious metal salt aqueous solution is between 0.001M and 0.05M. If the concentration of the noble metal salt aqueous solution is too low, monoatoms cannot be formed on the carrier. If the concentration of the aqueous solution of the noble metal salt is too high, large-sized particles such as metal clusters or nanoparticles are produced. Then mix the transition metal salt aqueous solution and the precious metal salt aqueous solution, and then adjust the above-mentioned salt aqueous solution to neutral (pH =7). In one embodiment, the neutral aqueous solution can be stirred at room temperature for 1 to 5 hours to ensure uniform mixing of ions in the aqueous solution. It can be understood that the concentration and the amount of the aqueous solution of the transition metal salt and the aqueous solution of the noble metal salt determine the weight ratio of the mesoporous transition metal oxide to the monoatomic noble metal in the subsequently formed catalyst.

On the other hand, the mesoporous template can be dispersed in a non-polar solvent to form a dispersion. The mesoporous template can be KIT-6, SBA-15, SBA-16, MCM-41, or a combination of the above, which is silicon dioxide with a network of pores. In one embodiment, the non-polar solvent is a solvent with a polarity between 0.05 and 4, such as toluene, n-hexane, or a combination of the foregoing. If the polarity of the non-polar solvent is too high, the metal ions will not easily diffuse into the mesoporous template. In one embodiment, the weight ratio of the mesoporous template to the non-polar solvent is between 1:5 and 1:20. If the amount of non-polar solvent is too low, the mesoporous template cannot be completely dispersed. If the amount of non-polar solvent is too high, it is not conducive to the diffusion of metal ions.

Next, the neutral aqueous solution and the dispersion liquid are mixed to form a mixed liquid. The above steps are an important key for single-atom precious metals. For example, if (1) the transition metal salt is dissolved in other polar solvents such as alcohols instead of water; and/or (2) the mesoporous template is not dispersed in the non-polar solvent first, but the mesoporous template is directly When added to a neutral salt aqueous solution, the final main catalyst formed is not a single-atom noble metal, and may be mainly nano particles or metal clusters.

Then the mixed solution is heated to remove the non-polar solvent and water in the mixed solution and form a powder. For example, the temperature of this heating step is between 55°C and 75°C. If the heating temperature is too low, the solvent cannot be effectively removed. If the heating temperature is too high, the solvent will be removed too quickly, which is not conducive to the uniform diffusion of metal ions. The powder is then sintered to form a catalyst in the holes of the mesoporous template. In some embodiments, the temperature for sintering the powder to form the catalyst is between 280° C. and 350° C., and the time for this sintering step is between 2 and 12 hours. If the sintering temperature is too low and/or the sintering time is too short, the mesoporous metal oxide structure is incomplete. If the sintering temperature is too high and/or the sintering time is too long, the structure will collapse.

Then remove the middle hole template to retain the catalyst. In some embodiments, the step of removing the mesoporous template to retain the catalyst uses an aqueous solution of hydrofluoric acid or sodium hydroxide. The aqueous solution of hydrofluoric acid or sodium hydroxide can remove the material of the mesoporous template such as silicon dioxide without damaging the catalyst. It is worth noting that the catalyst disclosed in the present disclosure is not limited to the above-mentioned forming method. Those skilled in the art can choose other suitable methods according to the equipment to form the above-mentioned catalyst.

An embodiment of the present disclosure provides a method for removing volatile organic compounds (VOCs), including: passing a mixed gas containing volatile organic compounds into a reactor filled with the above catalyst to oxidize the volatile organic compounds into water and carbon dioxide . In some embodiments, the volatile organic compound includes propane, isopropanol, acetone, toluene, propylene glycol methyl ether, propylene glycol methyl ether acetate, or a combination thereof. It can be seen from the following examples that, since the catalyst of the present disclosure has monoatomic noble metals anchored on the mesoporous transition metal oxide, it can effectively reduce the temperature at which VOCs are oxidized to carbon dioxide and water. In summary, the present disclosure provides novel catalyst morphology and composition and its formation method, which can be used to remove VOCs.

The above method of forming a catalyst can be shown in FIG. 1. In FIG. 1, the mesoporous template 11 is dispersed in a non-polar solvent, and the mesoporous template 11 has a mesoporous 13. After mixing the neutral aqueous solution of the noble metal salt and the transition metal salt and the dispersion liquid of the mesoporous template, the aqueous solution of the transition metal salt and the noble metal salt will fill the mesopore 13. The mixed solution is heated to remove water and non-polar solvents, so that the transition metal salts and noble metal salts in the mesoporous 13 form mesoporous transition metal oxides 15 and monoatomic noble metals 17, and the monoatomic noble metals 17 are anchored in the mesoporous transition Metal oxide 15 on. Then, the mesoporous template 11 is removed, and the mesoporous transition metal oxide 15 and the monoatomic precious metal 17 are retained, and the monoatomic precious metal 17 is anchored on the mesoporous transition metal oxide 15.

In order to make the above-mentioned content and other purposes, features, and advantages of this disclosure more obvious and understandable, the following examples are specially enumerated in conjunction with the accompanying drawings, and detailed descriptions are as follows: [ Examples ]

Example 1-1 (Pt ₁ /Mesoporous Cobalt Oxide) 6.02 g of Co(NO ₃ ) ₂ • 6H ₂ O was dissolved in 10.24 mL of water to form an aqueous solution of cobalt salt. Then H ₂ PtCl ₆ (50 mM, 2.6 mL) was added to the above-mentioned cobalt salt aqueous solution, and the solution was adjusted to neutral (pH=7) with 1M NaOH aqueous solution, and stirred at room temperature for two hours.

Take 5.12g of the middle hole template KIT-6 (see Chem. Mater. 2017, 29, 40−52.) and disperse it in 64 mL of toluene, stir and disperse sufficiently to form a KIT-6 dispersion. Next, after adding the dispersion of KIT-6 to the aforementioned aqueous solution, it was heated to 65° C. and stirred to slowly volatilize water and toluene until a powder was formed. Then, the powder was calcined at 300° C. for 3 hours to form a catalyst in the holes of the middle hole template KIT-6. Next, the medium hole template KIT-6 containing the catalyst in the hole was dispersed in 64 mL of toluene, and the dispersion was sufficiently stirred to form a dispersion liquid of the medium hole template KIT-6 containing the catalyst in the hole.

In addition, 4g of Co(NO ₃ ) ₂ •6H ₂ O was dissolved in 10 mL of water to form an aqueous solution of cobalt salt. Then H ₂ PtCl ₆ (50 mM, 1.73 mL) was added to the aqueous solution of the cobalt salt, the solution was adjusted to neutral (pH=7) with 1 M NaOH aqueous solution, and stirred at room temperature for two hours to form another aqueous solution.

Then, the dispersion liquid of the middle hole template KIT-6 containing the catalyst in the hole is added to another aqueous solution, heated to 65° C. and stirred to slowly volatilize the water and toluene until a powder is formed. Then, the powder was calcined at 300° C. for 3 hours to form a catalyst in the holes of the middle hole template KIT-6. Then, the medium hole template KIT-6 containing the catalyst in the hole was added to the 2M NaOH solution, heated to 65° C. and stirred to remove the medium hole template KIT-6. In this way, the resulting catalyst includes mesoporous cobalt oxide and monoatomic Pt anchored on the mesoporous cobalt oxide. The scanning transmission electron microscope photograph of the above-mentioned catalyst is shown in Figure 2. It can be seen from Figure 2 that the size of Pt (bright spot) is less than 1nm and is similar to the theoretical diameter of Pt (2Å~3Å). It should be proved that the Pt anchored on the mesoporous cobalt oxide is a single atom.

According to the teaching of Adsorption Isotherms. In: Gas Adsorption Equilibria. Springer, Boston, MA (2005), the constant temperature adsorption and desorption experiment of the above catalyst shows that it belongs to the mesoporous structure, and its specific surface area is 136.6m ² /g. The volume is 0.52 cm ³ /g, and the hole width is 15.2 nm.

Example 1-2 (Pt ₁ /Mesoporous manganese oxide) 5.19 g of Mn(NO ₃ ) ₂ •4H ₂ O was dissolved in 10.24 mL of water to form an aqueous solution of manganese salt. Then H ₂ PtCl ₆ (50 mM, 2.6 mL) was added to the above-mentioned aqueous solution of manganese salt, and the solution was adjusted to neutral (pH=7) with 1 M NaOH aqueous solution, and stirred at room temperature for two hours.

Disperse 5.12 g of the middle hole template KIT-6 in 64 mL of toluene, stir and disperse sufficiently to form a KIT-6 dispersion. Next, after adding the dispersion of KIT-6 to the aforementioned aqueous solution, it was heated to 65° C. and stirred to slowly volatilize water and toluene until a powder was formed. Then, the powder was calcined at 300° C. for 3 hours to form a catalyst in the holes of the middle hole template KIT-6. Next, the medium hole template KIT-6 containing the catalyst in the hole was dispersed in 64 mL of toluene, and the dispersion was sufficiently stirred to form a dispersion liquid of the medium hole template KIT-6 containing the catalyst in the hole.

In addition, 3.46 g of Mn(NO ₃ ) ₂ •4H ₂ O was dissolved in 10 mL of water to form an aqueous solution of manganese salt. Then H ₂ PtCl ₆ (50 mM, 1.73 mL) was added to the above-mentioned aqueous solution of manganese salt, the solution was adjusted to neutral (pH=7) with 1 M NaOH aqueous solution, and stirred at room temperature for two hours to form another aqueous solution.

Then, the dispersion liquid of the middle hole template KIT-6 containing the catalyst in the hole is added to another aqueous solution, heated to 65° C. and stirred to slowly volatilize the water and toluene until a powder is formed. Then, the powder was calcined at 300° C. for 3 hours to form a catalyst in the holes of the middle hole template KIT-6. Then, the medium hole template KIT-6 containing the catalyst in the hole was added to the 2M NaOH solution, heated to 65° C. and stirred to remove the medium hole template KIT-6. In this way, the resulting catalyst includes mesoporous manganese oxide and monoatomic Pt anchored on the mesoporous manganese oxide. The scanning transmission electron microscope photograph of the above catalyst is shown in Figure 3. It can be seen from Figure 3 that the size of Pt (bright spot) is less than 1nm and is similar to the theoretical diameter of Pt (2Å~3Å). It should prove that the Pt anchored on the mesoporous manganese oxide is a single atom. On the other hand, the analysis of the above-mentioned catalyst by the extended X-ray absorption fine structure (EXAFS) is shown in Figure 4. It does not have a Pt-Pt signal, which should prove that there is a certain gap between the Pt anchored on the manganese oxide in the middle hole. The distance belongs to a single atom without clustering.

According to the teaching of Adsorption Isotherms. In: Gas Adsorption Equilibria. Springer, Boston, MA (2005), the constant temperature adsorption and desorption experiment of the above catalyst shows that it belongs to a mesoporous structure with a specific surface area of 61.5m ² /g. The volume is 0.13 cm ³ /g, and the hole width is 8.7 nm.

Example 1-3 (Pt ₁ /Mesoporous Iron Oxide) Take 8.36 g of Fe(NO ₃ ) ₃ •9H ₂ O and dissolve it in 10.24 mL of water to form an aqueous solution of iron salt. Then H ₂ PtCl ₆ (50 mM, 2.6 mL) was added to the above-mentioned iron salt aqueous solution, and the solution was adjusted to neutral (pH=7) with 1 M NaOH aqueous solution, and stirred at room temperature for two hours.

Disperse 5.12 g of the middle hole template KIT-6 in 64 mL of toluene, stir and disperse sufficiently to form a KIT-6 dispersion. Next, after adding the dispersion of KIT-6 to the aforementioned aqueous solution, it was heated to 65° C. and stirred to slowly volatilize water and toluene until a powder was formed. Then, the powder was calcined at 300° C. for 3 hours to form a catalyst in the holes of the middle hole template KIT-6. Next, the medium hole template KIT-6 containing the catalyst in the hole was dispersed in 64 mL of toluene, and the dispersion was sufficiently stirred to form a dispersion liquid of the medium hole template KIT-6 containing the catalyst in the hole.

In addition, 5.57g of Fe(NO ₃ ) ₃ •9H ₂ O was dissolved in 10 mL of water to form an aqueous solution of iron salt. Then H ₂ PtCl ₆ (50 mM, 1.73 mL) was added to the above-mentioned iron salt aqueous solution, and the solution was adjusted to neutral (pH=7) with 1M NaOH aqueous solution, and stirred at room temperature for two hours to form another aqueous solution.

Then, the dispersion liquid of the middle hole template KIT-6 containing the catalyst in the hole is added to another aqueous solution, heated to 65° C. and stirred to slowly volatilize the water and toluene until a powder is formed. Then, the powder was calcined at 300° C. for 3 hours to form a catalyst in the holes of the middle hole template KIT-6. Then, the medium hole template KIT-6 containing the catalyst in the hole was added to the 2M NaOH solution, heated to 65° C. and stirred to remove the medium hole template KIT-6. In this way, the resulting catalyst includes mesoporous iron oxide and monoatomic Pt anchored on the mesoporous iron oxide. The scanning transmission electron microscope photograph of the above catalyst is shown in Figure 5. It can be seen from Fig. 5 that the size of Pt (bright spot) is less than 1nm and is similar to the theoretical diameter of Pt (2~3Å). It should be proved that the Pt anchored on the mesoporous iron oxide is a single atom.

According to the teaching of Adsorption Isotherms. In: Gas Adsorption Equilibria. Springer, Boston, MA (2005), the constant temperature adsorption and desorption experiment of the above catalyst shows that it is a mesoporous structure with a specific surface area of 194m ² /g and a pore volume. It is 0.47 cm ³ /g, and the hole width is 9.6 nm.

Example 1-4 (Pt ₁ /Mesoporous Nickel Oxide) 6.02 g of Ni(NO ₃ ) ₂ •6H ₂ O was dissolved in 10.24 mL of water to form an aqueous solution of nickel salt. Then H ₂ PtCl ₆ (50 mM, 2.6 mL) was added to the above-mentioned nickel salt aqueous solution, and the solution was adjusted to neutral (pH=7) with 1 M NaOH aqueous solution, and stirred at room temperature for two hours.

Disperse 5.12 g of the middle hole template KIT-6 in 64 mL of toluene, stir and disperse sufficiently to form a KIT-6 dispersion. Next, after adding the dispersion of KIT-6 to the aforementioned aqueous solution, it was heated to 65° C. and stirred to slowly volatilize water and toluene until a powder was formed. Then, the powder was calcined at 300° C. for 3 hours to form a catalyst in the holes of the middle hole template KIT-6. Next, the medium hole template KIT-6 containing the catalyst in the hole was dispersed in 64 mL of toluene, and the dispersion was sufficiently stirred to form a dispersion liquid of the medium hole template KIT-6 containing the catalyst in the hole.

In addition, 4.01 g of Ni(NO ₃ ) ₂ •6H ₂ O was dissolved in 10 mL of water to form an aqueous solution of nickel salt. Then H ₂ PtCl ₆ (50 mM, 1.73 mL) was added to the above-mentioned nickel salt aqueous solution, and the solution was adjusted to neutral (pH=7) with 1 M NaOH aqueous solution, and stirred at room temperature for two hours to form another aqueous solution.

Then, the dispersion liquid of the middle hole template KIT-6 containing the catalyst in the hole is added to another aqueous solution, heated to 65° C. and stirred to slowly volatilize the water and toluene until a powder is formed. Then, the powder was calcined at 300° C. for 3 hours to form a catalyst in the holes of the middle hole template KIT-6. Then, the medium hole template KIT-6 containing the catalyst in the hole was added to the 2M NaOH solution, heated to 65° C. and stirred to remove the medium hole template KIT-6. In this way, the resulting catalyst includes mesoporous nickel oxide and monoatomic Pt anchored on the mesoporous nickel oxide. The scanning transmission electron microscope photograph of the above catalyst is shown in Figure 6. It can be seen from Figure 6 that the size of Pt (bright spot) is less than 1nm and is similar to the theoretical diameter of Pt (2Å~3Å). It should prove that the Pt anchored on the mesoporous nickel oxide is a single atom.

According to the teaching of Adsorption Isotherms. In: Gas Adsorption Equilibria. Springer, Boston, MA (2005), the constant temperature adsorption and desorption experiment of the above catalyst shows that it belongs to a mesoporous structure with a specific surface area of 116m ² /g and a pore volume. It is 0.55 ^{cm 3} /g, and the hole width is 18.6 nm.

Example 1-5 (Pt ₁ /Mesoporous cerium oxide) 8.98 g of Ce(NO ₃ ) ₃ •6H ₂ O was dissolved in 10.24 mL of water to form an aqueous solution of cerium salt. Then H ₂ PtCl ₆ (50 mM, 2.6 mL) was added to the aqueous solution of the cerium salt, the solution was adjusted to neutral (pH=7) with 1 M NaOH aqueous solution, and stirred at room temperature for two hours.

Disperse 5.12 g of the middle hole template KIT-6 in 64 mL of toluene, stir and disperse sufficiently to form a KIT-6 dispersion. Next, after adding the dispersion of KIT-6 to the aforementioned aqueous solution, it was heated to 65° C. and stirred to slowly volatilize water and toluene until a powder was formed. Then, the powder was calcined at 300° C. for 3 hours to form a catalyst in the holes of the middle hole template KIT-6. Next, the medium hole template KIT-6 containing the catalyst in the hole was dispersed in 64 mL of toluene, and the dispersion was sufficiently stirred to form a dispersion liquid of the medium hole template KIT-6 containing the catalyst in the hole.

In addition, 5.99 g of Ce(NO ₃ ) ₃ •6H ₂ O was dissolved in 10 mL of water to form an aqueous solution of cerium salt. Then H ₂ PtCl ₆ (50 mM, 1.73 mL) was added to the aqueous solution of the cerium salt, the solution was adjusted to neutral (pH=7) with 1 M NaOH aqueous solution, and stirred at room temperature for two hours to form another aqueous solution.

Then, the dispersion liquid of the middle hole template KIT-6 containing the catalyst in the hole is added to another aqueous solution, heated to 65° C. and stirred to slowly volatilize the water and toluene until a powder is formed. Then, the powder was calcined at 300° C. for 3 hours to form a catalyst in the holes of the middle hole template KIT-6. Then, the medium hole template KIT-6 containing the catalyst in the hole was added to the 2M NaOH solution, heated to 65° C. and stirred to remove the medium hole template KIT-6. In this way, the resulting catalyst includes mesoporous cerium oxide and monoatomic Pt anchored on the mesoporous cerium oxide. The scanning transmission electron microscope photograph of the above-mentioned catalyst is shown in Fig. 7. It can be seen from Fig. 7 that the size of Pt (bright spot) is less than 1nm and is similar to the theoretical diameter of Pt (2Å~3Å). It should be proved that the Pt anchored on the mesoporous cerium oxide is a single atom.

According to the teaching of Adsorption Isotherms. In: Gas Adsorption Equilibria. Springer, Boston, MA (2005), the constant temperature adsorption and desorption experiment of the above catalyst shows that it is a mesoporous structure with a specific surface area of 135m ² /g and a pore volume. It is 0.43 cm ³ /g, and the hole width is 12.8 nm.

Example 2-1 (Rh ₁ /Mesoporous Cobalt Oxide) 6.02 g of Co(NO ₃ ) ₂ • 6H ₂ O was dissolved in 10.24 mL of water to form an aqueous solution of cobalt salt. Then Na ₃ RhCl ₆ (50 mM, 2.6 mL) was added to the aqueous solution of the cobalt salt, and the solution was adjusted to neutral (pH=7) with 1 M NaOH aqueous solution, and stirred at room temperature for two hours.

Disperse 5.12 g of the middle hole template KIT-6 in 64 mL of toluene, stir and disperse sufficiently to form a KIT-6 dispersion. Next, after adding the dispersion of KIT-6 to the aforementioned aqueous solution, it was heated to 65° C. and stirred to slowly volatilize water and toluene until a powder was formed. Then, the powder was calcined at 300° C. for 3 hours to form a catalyst in the holes of the middle hole template KIT-6. Next, the medium hole template KIT-6 containing the catalyst in the hole was dispersed in 64 mL of toluene, and the dispersion was sufficiently stirred to form a dispersion liquid of the medium hole template KIT-6 containing the catalyst in the hole.

In addition, 4g of Co(NO ₃ ) ₂ •6H ₂ O was dissolved in 10 mL of water to form an aqueous solution of cobalt salt. Then Na ₃ RhCl ₆ (50 mM, 1.73 mL) was added to the aqueous solution of the cobalt salt, the solution was adjusted to neutral (pH=7) with 1 M NaOH aqueous solution, and stirred at room temperature for two hours to form another aqueous solution.

Then, the dispersion liquid of the middle hole template KIT-6 containing the catalyst in the hole is added to another aqueous solution, heated to 65° C. and stirred to slowly volatilize the water and toluene until a powder is formed. Then, the powder was calcined at 300° C. for 3 hours to form a catalyst in the holes of the middle hole template KIT-6. Then, the medium hole template KIT-6 containing the catalyst in the hole was added to the 2M NaOH solution, heated to 65° C. and stirred to remove the medium hole template KIT-6. In this way, the resulting catalyst includes mesoporous cobalt oxide and monoatomic Rh anchored on the mesoporous cobalt oxide. The scanning transmission electron microscope photograph of the above catalyst is shown in Figure 8. It can be seen from Figure 8 that the size of Rh (bright spot) is less than 1nm and is similar to the theoretical diameter of Rh (2Å~3Å). It should be proved that the Rh anchored on the mesoporous cobalt oxide is a single atom.

Example 2-2 (Rh ₁ /Mesoporous manganese oxide) 5.19 g of Mn(NO ₃ ) ₂ •4H ₂ O was dissolved in 10.24 mL of water to form an aqueous solution of manganese salt. Then Na ₃ RhCl ₆ (50 mM, 2.6 mL) was added to the above-mentioned aqueous solution of manganese salt, and the solution was adjusted to neutral (pH=7) with 1 M NaOH aqueous solution, and stirred at room temperature for two hours.

Disperse 5.12 g of the middle hole template KIT-6 in 64 mL of toluene, stir and disperse sufficiently to form a KIT-6 dispersion. Next, after adding the dispersion of KIT-6 to the aforementioned aqueous solution, it was heated to 65° C. and stirred to slowly volatilize water and toluene until a powder was formed. Then, the powder was calcined at 300° C. for 3 hours to form a catalyst in the holes of the middle hole template KIT-6. Next, the medium hole template KIT-6 containing the catalyst in the hole was dispersed in 64 mL of toluene, and the dispersion was sufficiently stirred to form a dispersion liquid of the medium hole template KIT-6 containing the catalyst in the hole.

In addition, 3.46 g of Mn(NO ₃ ) ₂ •4H ₂ O was dissolved in 10 mL of water to form an aqueous solution of manganese salt. Then Na ₃ RhCl ₆ (50 mM, 1.73 mL) was added to the above-mentioned aqueous solution of manganese salt, and the solution was adjusted to neutral (pH=7) with 1 M NaOH aqueous solution, and stirred at room temperature for two hours to form another aqueous solution.

Then, the dispersion liquid of the middle hole template KIT-6 containing the catalyst in the hole is added to another aqueous solution, heated to 65° C. and stirred to slowly volatilize the water and toluene until a powder is formed. Then, the powder was calcined at 300° C. for 3 hours to form a catalyst in the holes of the middle hole template KIT-6. Then, the medium hole template KIT-6 containing the catalyst in the hole was added to the 2M NaOH solution, heated to 65° C. and stirred to remove the medium hole template KIT-6. In this way, the resulting catalyst includes mesoporous manganese oxide and monoatomic Rh anchored on the mesoporous manganese oxide.

Example 2-3 (Rh ₁ /Mesoporous Iron Oxide) Take 8.36 g of Fe(NO ₃ ) ₃ •9H ₂ O and dissolve it in 10.24 mL of water to form an aqueous solution of iron salt. Next, after adding Na ₃ RhCl ₆ (50 mM, 2.6 mL) to the above-mentioned iron salt aqueous solution, the solution was adjusted to neutral (pH=7) with 1 M NaOH aqueous solution, and stirred at room temperature for two hours.

Disperse 5.12 g of the middle hole template KIT-6 in 64 mL of toluene, stir and disperse sufficiently to form a KIT-6 dispersion. Next, after adding the dispersion of KIT-6 to the aforementioned aqueous solution, it was heated to 65° C. and stirred to slowly volatilize water and toluene until a powder was formed. Then, the powder was calcined at 300° C. for 3 hours to form a catalyst in the holes of the middle hole template KIT-6. Next, the medium hole template KIT-6 containing the catalyst in the hole was dispersed in 64 mL of toluene, and the dispersion was sufficiently stirred to form a dispersion liquid of the medium hole template KIT-6 containing the catalyst in the hole.

In addition, 5.57g of Fe(NO ₃ ) ₃ •9H ₂ O was dissolved in 10 mL of water to form an aqueous solution of iron salt. Then Na ₃ RhCl ₆ (50 mM, 1.73 mL) was added to the above-mentioned iron salt aqueous solution, and the solution was adjusted to neutral (pH=7) with 1 M NaOH aqueous solution, and stirred at room temperature for two hours to form another aqueous solution.

Then, the dispersion liquid of the middle hole template KIT-6 containing the catalyst in the hole is added to another aqueous solution, heated to 65° C. and stirred to slowly volatilize the water and toluene until a powder is formed. Then, the powder was calcined at 300° C. for 3 hours to form a catalyst in the holes of the middle hole template KIT-6. Then, the medium hole template KIT-6 containing the catalyst in the hole was added to the 2M NaOH solution, heated to 65° C. and stirred to remove the medium hole template KIT-6. In this way, the resulting catalyst includes mesoporous iron oxide and monoatomic Rh anchored on the mesoporous iron oxide.

Example 2-4 (Rh ₁ /Mesoporous Nickel Oxide) Take 6.02 g of Ni(NO ₃ ) ₂ •6H ₂ O and dissolve in 10.24 mL of water to form an aqueous solution of nickel salt. Then Na ₃ RhCl ₆ (50 mM, 2.6 mL) was added to the above-mentioned nickel salt aqueous solution, and the solution was adjusted to neutral (pH=7) with 1 M NaOH aqueous solution, and stirred at room temperature for two hours.

Disperse 5.12 g of the middle hole template KIT-6 in 64 mL of toluene, stir and disperse sufficiently to form a KIT-6 dispersion. Next, after adding the dispersion of KIT-6 to the aforementioned aqueous solution, it was heated to 65° C. and stirred to slowly volatilize water and toluene until a powder was formed. Then, the powder was calcined at 300° C. for 3 hours to form a catalyst in the holes of the middle hole template KIT-6. Next, the medium hole template KIT-6 containing the catalyst in the hole was dispersed in 64 mL of toluene, and the dispersion was sufficiently stirred to form a dispersion liquid of the medium hole template KIT-6 containing the catalyst in the hole.

In addition, 4.01 g of Ni(NO ₃ ) ₂ •6H ₂ O was dissolved in 10 mL of water to form an aqueous solution of nickel salt. Then Na ₃ RhCl ₆ (50 mM, 1.73 mL) was added to the above-mentioned nickel salt aqueous solution, and the solution was adjusted to neutral (pH=7) with 1 M NaOH aqueous solution, and stirred at room temperature for two hours to form another aqueous solution.

Then, the dispersion liquid of the middle hole template KIT-6 containing the catalyst in the hole is added to another aqueous solution, heated to 65° C. and stirred to slowly volatilize the water and toluene until a powder is formed. Then, the powder was calcined at 300° C. for 3 hours to form a catalyst in the holes of the middle hole template KIT-6. Then, the medium hole template KIT-6 containing the catalyst in the hole was added to the 2M NaOH solution, heated to 65° C. and stirred to remove the medium hole template KIT-6. In this way, the resulting catalyst includes mesoporous nickel oxide and monoatomic Rh anchored on the mesoporous nickel oxide.

Example 2-5 (Rh ₁ /Mesoporous Cerium Oxide) Take 8.98 g of Ce(NO ₃ ) ₃ •6H ₂ O and dissolve in 10.24 mL of water to form an aqueous solution of cerium salt. Then Na ₃ RhCl ₆ (50 mM, 2.6 mL) was added to the aqueous solution of the cerium salt, and the solution was adjusted to neutral (pH=7) with 1 M NaOH aqueous solution, and stirred at room temperature for two hours.

Disperse 5.12 g of the middle hole template KIT-6 in 64 mL of toluene, stir and disperse sufficiently to form a KIT-6 dispersion. Next, after adding the dispersion of KIT-6 to the aforementioned aqueous solution, it was heated to 65° C. and stirred to slowly volatilize water and toluene until a powder was formed. Then, the powder was calcined at 300° C. for 3 hours to form a catalyst in the holes of the middle hole template KIT-6. Next, the medium hole template KIT-6 containing the catalyst in the hole was dispersed in 64 mL of toluene, and the dispersion was sufficiently stirred to form a dispersion liquid of the medium hole template KIT-6 containing the catalyst in the hole.

In addition, 5.99 g of Ce(NO ₃ ) ₃ •6H ₂ O was dissolved in 10 mL of water to form an aqueous solution of cerium salt. Then Na ₃ RhCl ₆ (50 mM, 1.73 mL) was added to the aqueous solution of the cerium salt, the solution was adjusted to neutral (pH=7) with 1 M NaOH aqueous solution, and stirred at room temperature for two hours to form another aqueous solution.

Then, the dispersion liquid of the middle hole template KIT-6 containing the catalyst in the hole is added to another aqueous solution, heated to 65° C. and stirred to slowly volatilize the water and toluene until a powder is formed. Then, the powder was calcined at 300° C. for 3 hours to form a catalyst in the holes of the middle hole template KIT-6. Then, the medium hole template KIT-6 containing the catalyst in the hole was added to the 2M NaOH solution, heated to 65° C. and stirred to remove the medium hole template KIT-6. In this way, the resulting catalyst includes mesoporous cerium oxide and monoatomic Rh anchored on the mesoporous cerium oxide.

Example 3-1 (Pd ₁ /Mesoporous cobalt oxide) 6.02 g of Co(NO ₃ ) ₂ • 6H ₂ O was dissolved in 10.24 mL of water to form an aqueous solution of cobalt salt. Then H ₂ PdCl ₄ (50 mM, 2.6 mL) was added to the aqueous solution of the cobalt salt, and the solution was adjusted to neutral (pH=7) with 1 M NaOH aqueous solution, and stirred at room temperature for two hours.

Disperse 5.12 g of the middle hole template KIT-6 in 64 mL of toluene, stir and disperse sufficiently to form a KIT-6 dispersion. Next, after adding the dispersion of KIT-6 to the aforementioned aqueous solution, it was heated to 65° C. and stirred to slowly volatilize water and toluene until a powder was formed. Then, the powder was calcined at 300° C. for 3 hours to form a catalyst in the holes of the middle hole template KIT-6. Next, the medium hole template KIT-6 containing the catalyst in the hole was dispersed in 64 mL of toluene, and the dispersion was sufficiently stirred to form a dispersion liquid of the medium hole template KIT-6 containing the catalyst in the hole.

In addition, 4g of Co(NO ₃ ) ₂ •6H ₂ O was dissolved in 10 mL of water to form an aqueous solution of cobalt salt. Then H ₂ PdCl ₄ (50 mM, 1.73 mL) was added to the aqueous solution of the cobalt salt, the solution was adjusted to neutral (pH=7) with 1 M NaOH aqueous solution, and stirred at room temperature for two hours to form another aqueous solution.

Then, the dispersion liquid of the middle hole template KIT-6 containing the catalyst in the hole is added to another aqueous solution, heated to 65° C. and stirred to slowly volatilize the water and toluene until a powder is formed. Then, the powder was calcined at 300° C. for 3 hours to form a catalyst in the holes of the middle hole template KIT-6. Then, the medium hole template KIT-6 containing the catalyst in the hole was added to the 2M NaOH solution, heated to 65° C. and stirred to remove the medium hole template KIT-6. In this way, the resulting catalyst includes Co ₃ O ₄ with a mesoporous hole and a monoatomic _{Pd anchored on the Co 3} O ₄ with a mesoporous hole. The scanning transmission electron microscope photograph of the above-mentioned catalyst is shown in Fig. 9. It can be seen from Fig. 9 that the size of Pd (bright spot) is less than 1nm and is similar to the theoretical diameter of Pd (2Å~3Å). It should be proved that _{the Pd anchored on Co 3} O ₄ is a single atom.

Example 3-2 (Pd ₁ /Mesoporous Manganese Oxide) 5.19 g of Mn(NO _{3 ) 2} •4H ₂ O was dissolved in 10.24 mL of water to form an aqueous solution of manganese salt. Then H ₂ PdCl ₄ (50 mM, 2.6 mL) was added to the above-mentioned aqueous solution of manganese salt, and the solution was adjusted to neutral (pH=7) with 1 M NaOH aqueous solution, and stirred at room temperature for two hours.

Disperse 5.12 g of the middle hole template KIT-6 in 64 mL of toluene, stir and disperse sufficiently to form a KIT-6 dispersion. Next, after adding the dispersion of KIT-6 to the aforementioned aqueous solution, it was heated to 65° C. and stirred to slowly volatilize water and toluene until a powder was formed. Then, the powder was calcined at 300° C. for 3 hours to form a catalyst in the holes of the middle hole template KIT-6. Next, the medium hole template KIT-6 containing the catalyst in the hole was dispersed in 64 mL of toluene, and the dispersion was sufficiently stirred to form a dispersion liquid of the medium hole template KIT-6 containing the catalyst in the hole.

In addition, 3.46 g of Mn(NO ₃ ) ₂ •4H ₂ O was dissolved in 10 mL of water to form an aqueous solution of manganese salt. Then H ₂ PdCl ₄ (50 mM, 1.73 mL) was added to the above-mentioned aqueous solution of manganese salt, the solution was adjusted to neutral (pH=7) with 1M NaOH aqueous solution, and stirred at room temperature for two hours to form another aqueous solution.

Then, the dispersion liquid of the middle hole template KIT-6 containing the catalyst in the hole is added to another aqueous solution, heated to 65° C. and stirred to slowly volatilize the water and toluene until a powder is formed. Then, the powder was calcined at 300° C. for 3 hours to form a catalyst in the holes of the middle hole template KIT-6. Then, the medium hole template KIT-6 containing the catalyst in the hole was added to the 2M NaOH solution, heated to 65° C. and stirred to remove the medium hole template KIT-6. In this way, the resulting catalyst includes mesoporous manganese oxide and monoatomic Pd anchored on the mesoporous manganese oxide.

Example 3-3 (Pd ₁ /Mesoporous Iron Oxide) Take 8.36 g of Fe(NO ₃ ) ₃ •9H ₂ O and dissolve it in 10.24 mL of water to form an aqueous solution of iron salt. Then, H ₂ PdCl ₄ (50 mM, 2.6 mL) was added to the above-mentioned iron salt aqueous solution, and the solution was adjusted to neutral (pH=7) with 1 M NaOH aqueous solution, and stirred at room temperature for two hours.

Disperse 5.12 g of the middle hole template KIT-6 in 64 mL of toluene, stir and disperse sufficiently to form a KIT-6 dispersion. Next, after adding the dispersion of KIT-6 to the aforementioned aqueous solution, it was heated to 65° C. and stirred to slowly volatilize water and toluene until a powder was formed. Then, the powder was calcined at 300° C. for 3 hours to form a catalyst in the holes of the middle hole template KIT-6. Next, the medium hole template KIT-6 containing the catalyst in the hole was dispersed in 64 mL of toluene, and the dispersion was sufficiently stirred to form a dispersion liquid of the medium hole template KIT-6 containing the catalyst in the hole.

In addition, 5.57g of Fe(NO ₃ ) ₃ •9H ₂ O was dissolved in 10 mL of water to form an aqueous solution of iron salt. Then H ₂ PdCl ₄ (50 mM, 1.73 mL) was added to the above-mentioned iron salt aqueous solution, and the solution was adjusted to neutral (pH=7) with 1 M NaOH aqueous solution, and stirred at room temperature for two hours to form another aqueous solution.

Then, the dispersion liquid of the middle hole template KIT-6 containing the catalyst in the hole is added to another aqueous solution, heated to 65° C. and stirred to slowly volatilize the water and toluene until a powder is formed. Then, the powder was calcined at 300° C. for 3 hours to form a catalyst in the holes of the middle hole template KIT-6. Then, the medium hole template KIT-6 containing the catalyst in the hole was added to the 2M NaOH solution, heated to 65° C. and stirred to remove the medium hole template KIT-6. In this way, the resulting catalyst includes mesoporous iron oxide and monoatomic Pd anchored on the mesoporous iron oxide.

Example 3-4 (Pd ₁ /Mesoporous Nickel Oxide) 6.02 g of Ni(NO ₃ ) ₂ •6H ₂ O was dissolved in 10.24 mL of water to form an aqueous solution of nickel salt. Then H ₂ PdCl ₄ (50 mM, 2.6 mL) was added to the above-mentioned nickel salt aqueous solution, and the solution was adjusted to neutral (pH=7) with 1 M NaOH aqueous solution, and stirred at room temperature for two hours.

Disperse 5.12 g of the middle hole template KIT-6 in 64 mL of toluene, stir and disperse sufficiently to form a KIT-6 dispersion. Next, after adding the dispersion of KIT-6 to the aforementioned aqueous solution, it was heated to 65° C. and stirred to slowly volatilize water and toluene until a powder was formed. Then, the powder was calcined at 300° C. for 3 hours to form a catalyst in the holes of the middle hole template KIT-6. Next, the medium hole template KIT-6 containing the catalyst in the hole was dispersed in 64 mL of toluene, and the dispersion was sufficiently stirred to form a dispersion liquid of the medium hole template KIT-6 containing the catalyst in the hole.

In addition, 4.01 g of Ni(NO ₃ ) ₂ •6H ₂ O was dissolved in 10 mL of water to form an aqueous solution of nickel salt. Then H ₂ PdCl ₄ (50 mM, 1.73 mL) was added to the above-mentioned nickel salt aqueous solution, the solution was adjusted to neutral (pH=7) with 1M NaOH aqueous solution, and stirred at room temperature for two hours to form another aqueous solution.

Then, the dispersion liquid of the middle hole template KIT-6 containing the catalyst in the hole is added to another aqueous solution, heated to 65° C. and stirred to slowly volatilize the water and toluene until a powder is formed. Then, the powder was calcined at 300° C. for 3 hours to form a catalyst in the holes of the middle hole template KIT-6. Then, the medium hole template KIT-6 containing the catalyst in the hole was added to the 2M NaOH solution, heated to 65° C. and stirred to remove the medium hole template KIT-6. In this way, the resulting catalyst includes mesoporous nickel oxide and monoatomic Pd anchored on the mesoporous nickel oxide.

Example 3-5 (Pd ₁ /Mesoporous Cerium Oxide) 8.98g of Ce(NO ₃ ) ₃ •6H ₂ O was dissolved in 10.24 mL of water to form an aqueous solution of cerium salt. Then H ₂ PdCl ₄ (50 mM, 2.6 mL) was added to the aqueous solution of the cerium salt, and the solution was adjusted to neutral (pH=7) with 1 M NaOH aqueous solution, and stirred at room temperature for two hours.

Disperse 5.12 g of the middle hole template KIT-6 in 64 mL of toluene, stir and disperse sufficiently to form a KIT-6 dispersion. Next, after adding the dispersion of KIT-6 to the aforementioned aqueous solution, it was heated to 65° C. and stirred to slowly volatilize water and toluene until a powder was formed. Then, the powder was calcined at 300° C. for 3 hours to form a catalyst in the holes of the middle hole template KIT-6. Next, the medium hole template KIT-6 containing the catalyst in the hole was dispersed in 64 mL of toluene, and the dispersion was sufficiently stirred to form a dispersion liquid of the medium hole template KIT-6 containing the catalyst in the hole.

In addition, 5.99 g of Ce(NO ₃ ) ₃ •6H ₂ O was dissolved in 10 mL of water to form an aqueous solution of cerium salt. Then H ₂ PdCl ₄ (50 mM, 1.73 mL) was added to the aqueous solution of the cerium salt, the solution was adjusted to neutral (pH=7) with 1 M NaOH aqueous solution, and stirred at room temperature for two hours to form another aqueous solution.

Then, the dispersion liquid of the middle hole template KIT-6 containing the catalyst in the hole is added to another aqueous solution, heated to 65° C. and stirred to slowly volatilize the water and toluene until a powder is formed. Then, the powder was calcined at 300° C. for 3 hours to form a catalyst in the holes of the middle hole template KIT-6. Then, the medium hole template KIT-6 containing the catalyst in the hole was added to the 2M NaOH solution, heated to 65° C. and stirred to remove the medium hole template KIT-6. In this way, the resulting catalyst includes mesoporous cerium oxide and monoatomic Pd anchored on the mesoporous cerium oxide.

Example 4-1 (Ru ₁ /Mesoporous Cobalt Oxide) 6.02 g of Co(NO ₃ ) ₂ •6H ₂ O was dissolved in 10.24 mL of water to form an aqueous solution of cobalt salt. Next, RuCl ₃ (50 mM, 2.6 mL) was added to the aqueous solution of the cobalt salt, and the solution was adjusted to neutral (pH=7) with 1 M NaOH aqueous solution, and stirred at room temperature for two hours.

Disperse 5.12 g of the middle hole template KIT-6 in 64 mL of toluene, stir and disperse sufficiently to form a KIT-6 dispersion. Next, after adding the dispersion of KIT-6 to the aforementioned aqueous solution, it was heated to 65° C. and stirred to slowly volatilize water and toluene until a powder was formed. Then, the powder was calcined at 300° C. for 3 hours to form a catalyst in the holes of the middle hole template KIT-6. Next, the medium hole template KIT-6 containing the catalyst in the hole was dispersed in 64 mL of toluene, and the dispersion was sufficiently stirred to form a dispersion liquid of the medium hole template KIT-6 containing the catalyst in the hole.

In addition, 4g of Co(NO ₃ ) ₂ •6H ₂ O was dissolved in 10 mL of water to form an aqueous solution of cobalt salt. Then RuCl ₃ (50 mM, 1.73 mL) was added to the aqueous solution of the cobalt salt, the solution was adjusted to neutral (pH=7) with 1 M NaOH aqueous solution, and stirred at room temperature for two hours to form another aqueous solution.

Then, the dispersion liquid of the middle hole template KIT-6 containing the catalyst in the hole is added to another aqueous solution, heated to 65° C. and stirred to slowly volatilize the water and toluene until a powder is formed. Then, the powder was calcined at 300° C. for 3 hours to form a catalyst in the holes of the middle hole template KIT-6. Then, the medium hole template KIT-6 containing the catalyst in the hole was added to the 2M NaOH solution, heated to 65° C. and stirred to remove the medium hole template KIT-6. In this way, the resultant catalyst includes Co ₃ O ₄ with a mesoporous hole and a monoatomic _{Ru anchored on the Co 3} O ₄ with a mesoporous hole. The scanning transmission electron microscope photograph of the above catalyst is shown in Figure 10. It can be seen from Fig. 10 that the size of Ru (bright spot) is less than 1nm and is similar to the theoretical diameter of Ru (2Å~3Å). It should be proved that _{Ru anchored on Co 3} O ₄ is a single atom.

Example 4-2 (Ru ₁ /Mesoporous Manganese Oxide) 5.19 g of Mn(NO _{3 ) 2} •4H ₂ O was dissolved in 10.24 mL of water to form an aqueous solution of manganese salt. Next, RuCl ₃ (50 mM, 2.6 mL) was added to the above-mentioned manganese salt aqueous solution, and the solution was adjusted to neutral (pH=7) with 1 M NaOH aqueous solution, and stirred at room temperature for two hours.

Disperse 5.12 g of the middle hole template KIT-6 in 64 mL of toluene, stir and disperse sufficiently to form a KIT-6 dispersion. Next, after adding the dispersion of KIT-6 to the aforementioned aqueous solution, it was heated to 65° C. and stirred to slowly volatilize water and toluene until a powder was formed. Then, the powder was calcined at 300° C. for 3 hours to form a catalyst in the holes of the middle hole template KIT-6. Next, the medium hole template KIT-6 containing the catalyst in the hole was dispersed in 64 mL of toluene, and the dispersion was sufficiently stirred to form a dispersion liquid of the medium hole template KIT-6 containing the catalyst in the hole.

In addition, 3.46 g of Mn(NO ₃ ) ₂ •4H ₂ O was dissolved in 10 mL of water to form an aqueous solution of manganese salt. Next, after adding RuCl ₃ (50 mM, 1.73 mL) to the above-mentioned aqueous solution of manganese salt, the solution was adjusted to neutral (pH=7) with 1 M NaOH aqueous solution, and stirred at room temperature for two hours to form another aqueous solution.

Then, the dispersion liquid of the middle hole template KIT-6 containing the catalyst in the hole is added to another aqueous solution, heated to 65° C. and stirred to slowly volatilize the water and toluene until a powder is formed. Then, the powder was calcined at 300° C. for 3 hours to form a catalyst in the holes of the middle hole template KIT-6. Then, the medium hole template KIT-6 containing the catalyst in the hole was added to the 2M NaOH solution, heated to 65° C. and stirred to remove the medium hole template KIT-6. In this way, the resulting catalyst includes mesoporous manganese oxide and monoatomic Ru anchored on the mesoporous manganese oxide.

Example 4-3 (Ru ₁ /Mesoporous Iron Oxide) Take 8.36 g of Fe(NO ₃ ) ₃ •9H ₂ O and dissolve it in 10.24 mL of water to form an aqueous solution of iron salt. Next, after adding RuCl ₃ (50 mM, 2.6 mL) to the above-mentioned iron salt aqueous solution, the solution was adjusted to neutral (pH=7) with 1 M NaOH aqueous solution, and stirred at room temperature for two hours.

Disperse 5.12 g of the middle hole template KIT-6 in 64 mL of toluene, stir and disperse sufficiently to form a KIT-6 dispersion. Next, after adding the dispersion of KIT-6 to the aforementioned aqueous solution, it was heated to 65° C. and stirred to slowly volatilize water and toluene until a powder was formed. Then, the powder was calcined at 300° C. for 3 hours to form a catalyst in the holes of the middle hole template KIT-6. Next, the medium hole template KIT-6 containing the catalyst in the hole was dispersed in 64 mL of toluene, and the dispersion was sufficiently stirred to form a dispersion liquid of the medium hole template KIT-6 containing the catalyst in the hole.

In addition, 5.57g of Fe(NO ₃ ) ₃ •9H ₂ O was dissolved in 10 mL of water to form an aqueous solution of iron salt. Next, RuCl ₃ (50 mM, 1.73 mL) was added to the above-mentioned iron salt aqueous solution, and the solution was adjusted to neutral (pH=7) with 1 M NaOH aqueous solution, and stirred at room temperature for two hours to form another aqueous solution.

Then, the dispersion liquid of the middle hole template KIT-6 containing the catalyst in the hole is added to another aqueous solution, heated to 65° C. and stirred to slowly volatilize the water and toluene until a powder is formed. Then, the powder was calcined at 300° C. for 3 hours to form a catalyst in the holes of the middle hole template KIT-6. Then, the medium hole template KIT-6 containing the catalyst in the hole was added to the 2M NaOH solution, heated to 65° C. and stirred to remove the medium hole template KIT-6. In this way, the resulting catalyst includes mesoporous iron oxide and monoatomic Ru anchored on the mesoporous iron oxide.

Comparative Example 1 (Mesoporous cobalt oxide) 6.02 g of Co(NO ₃ ) ₂ • 6H ₂ O was dissolved in 10.24 mL of water to form an aqueous solution of cobalt salt. Take 5.12g of the middle hole template KIT-6 (see Chem. Mater. 2017, 29, 40−52.) and disperse it in 64 mL of toluene, stir and disperse sufficiently to form a KIT-6 dispersion. Next, after adding the dispersion of KIT-6 to the aforementioned aqueous solution, it was heated to 65°C and stirred to slowly volatilize water and toluene until a powder was formed. Then the powder was calcined at 300° C. for 3 hours to form Co ₃ O ₄ in the holes of the mesoporous template KIT-6.

Then, the medium hole template KIT-6 containing Co ₃ O ₄ in the hole was added to the 2M NaOH solution, heated to 65° C. and stirred to remove the medium hole template KIT-6. In this way, the cobalt oxide with middle pores is obtained.

Take the mesoporous cobalt oxide of Comparative Example 1, the Pt ₁ /mesoporous cobalt oxide of _{Example 1-1, and the Rh 1} /mesoporous cobalt oxide of Example 2-1. After heating to 700°C and calcining for 10 hours, measure them. XRD pattern. Comparing the graphs before and after calcination, it can be seen that the mesoporous cobalt oxide of Comparative Example 1, the Pt ₁ / mesoporous cobalt oxide of _{Example 1-1, and the Rh 1} / mesoporous cobalt oxide of Example 2-1 Both can withstand high temperature.

Example 5 (Removal of Propane) Take the Rh ₁ /medium-porous cobalt oxide of Example 2-1 and the Pt ₁ /medium-porous cobalt oxide of Example 1-1, respectively, after rolling, sieving and filling into the reaction tube, proceed differently Propane oxidation reaction test at temperature. The concentration of propane at the inlet of the reaction tube was 388 ppm (corresponding to a single Rh atom) and 374 ppm (corresponding to a single Pt atom), and the GHSV of propane was both 6250h ^-1 . Pass propane into reaction tubes at different temperatures, and measure the propane concentration at the outlet of the reaction tube to confirm the efficiency of the catalyst at different temperatures in removing propane. _{The T 50 of the} single atom of Pt (ie, the reaction temperature at which the propane removal efficiency reaches 50%) of Example 1-1 is 147°C, and the T ₅₀ of the single atom of Rh of Example 2-1 is 144°C, that is, the single atom of Rh The oxidation catalytic activity is slightly higher than that of Pt single atom. The removal efficiency of Rh single atom at 175℃ is more than 99%, while the removal efficiency of Pt single atom at 180℃ is more than 99%. _{It is worth noting that the T 50 of} conventional catalysts (such as Pt/Al ₂ O ₃ ) to propane is greater than or equal to 190°C. Compared with the conventional catalyst, the catalyst of the above embodiment can greatly reduce the T ₅₀ for propane to less than 150°C.

Comparative Example 2 (Mesoporous manganese oxide) 5.19 g of Mn(NO ₃ ) ₂ •4H ₂ O was dissolved in 10.24 mL of water to form an aqueous solution of manganese salt. Take 5.12g of the middle hole template KIT-6 (see Chem. Mater. 2017, 29, 40−52.) and disperse it in 64 mL of toluene, stir and disperse sufficiently to form a KIT-6 dispersion. Next, after adding the dispersion of KIT-6 to the aforementioned aqueous solution, it was heated to 65°C and stirred to slowly volatilize water and toluene until a powder was formed. Then, the powder was calcined at 300° C. for 3 hours to form MnO ₂ in the holes of the middle hole template KIT-6.

Then, the medium hole template KIT-6 containing MnO ₂ in the hole was added to a 2M NaOH solution, heated to 65° C. and stirred to remove the medium hole template KIT-6. In this way, manganese oxide with middle holes is obtained.

Example 6-1 (Removal of isopropanol) Take the mesoporous manganese oxide of Comparative Example 2 and the Pt ₁ /medium pore manganese oxide of Example 1-2, after rolling, sieving and filling the reaction tube, and performing different temperatures Isopropanol oxidation reaction test. The isopropanol concentration at the inlet of the reaction tube was 224 ppm, and the GHSV was 17,300 h ^-1 . Pour isopropanol into reaction tubes at different temperatures, and measure the concentration of isopropanol and by-product acetone at the outlet of the reaction tube to confirm the efficiency of the catalyst at different temperatures to completely remove isopropanol. _{The T 90} of the Pt single atom of Example 1-2 (ie, the reaction temperature at which the isopropanol removal efficiency reaches 90%) is about 120°C, while the T ₉₀ of the porous manganese oxide in Comparative Example 2 is about 155°C. _{It is worth noting that the T 90 of} conventional catalysts (such as Pt/Al ₂ O ₃ ) for isopropanol is greater than or equal to 150°C, even greater than 200°C. Compared with the conventional catalyst, the catalyst of the above embodiment can lower the T ₉₀ to isopropanol to less than 120°C.

Example 6-2 (Removal of isopropanol) Take the Pt/medium-porous cobalt oxide of Example 1-1, the Pt/medium-porous manganese oxide of Example 1-2, and the Pt/medium-porous iron oxide of Example 1-3 , And the Pt/medium-hole nickel oxide of Examples 1-4, sieved after rolling and filled into the reaction tube, and tested the isopropanol oxidation reaction at different temperatures. The isopropanol concentration at the inlet of the reaction tube was 234 ppm (Pt/medium-porous cobalt oxide in Example 1-1), 224 ppm (Pt/medium-porous manganese oxide in Example 1-2), and 274 ppm (Pt/medium-porous manganese oxide in Example 1-2). Pt/medium-porous iron oxide), and 248 ppm (Pt/medium-porous nickel oxide of Examples 1-4), and GHSV are both 17300h ^-1 . Pour isopropanol into reaction tubes at different temperatures, and measure the concentration of isopropanol and by-product acetone at the outlet of the reaction tube to confirm the efficiency of the catalyst at different temperatures to completely remove isopropanol. _{The T 90} of the Pt single atom of Example 1-1 (ie, the reaction temperature at which the isopropanol removal efficiency reaches 90%) is about 130°C, and the T ₉₀ of the Pt single atom of Example 1-2 is about 120°C. _{The T 90} of the single Pt atom of 1-3 is about 182°C, while the T ₉₀ of the single Pt atom of Example 1-4 is about 163°C. It can be seen from the above that the effect of monoatomic Pt anchoring to mesoporous cobalt oxide, mesoporous manganese oxide, and mesoporous nickel oxide are better than the effect of monoatomic Pt anchoring to mesoporous iron oxide.

Although this disclosure has been disclosed in several preferred embodiments as described above, it is not intended to limit the disclosure. Anyone with ordinary knowledge in the relevant technical field can make any changes without departing from the spirit and scope of this disclosure. Therefore, the scope of protection of this disclosure shall be subject to the scope of the attached patent application.

11: Middle hole template 13: Middle hole 15: Mesoporous transition metal oxide 17: Monoatomic precious metals

Fig. 1 is a schematic diagram of a method of forming a catalyst in an embodiment of the present invention. Fig. 2 is a scanning transmission electron microscope photograph of _{catalyst Pt 1} /cobalt oxide with mesoporous holes in an embodiment of the present invention. Fig. 3 is a scanning transmission electron micrograph of the _{catalyst Pt 1} /mesoporous manganese oxide in an embodiment of the present invention. Fig. 4 is an extended X-ray absorption microstructure spectrum of _{Pt foil and Pt 1} /Mesoporous manganese oxide in an embodiment of the present invention. Fig. 5 is a scanning transmission electron micrograph of the _{catalyst Pt 1} /Mesoporous iron oxide in an embodiment of the present invention. Fig. 6 is a scanning transmission electron micrograph of the _{catalyst Pt 1} /mesoporous nickel oxide in an embodiment of the present invention. Fig. 7 is a scanning transmission electron micrograph of the _{catalyst Pt 1} / mesoporous cerium oxide in an embodiment of the present invention. FIG. 8 is a scanning transmission electron micrograph of the _{catalyst Rh 1} /cobalt oxide with mesoporous holes in an embodiment of the present invention. Fig. 9 is a scanning transmission electron microscope photograph of the _{catalyst Pd 1} /cobalt oxide with mesoporous holes in an embodiment of the present invention. Fig. 10 is a scanning transmission electron micrograph of the _{catalyst Ru 1} /mesoporous cobalt oxide in an embodiment of the present invention.

11: Middle hole template

13: Middle hole

15: Mesoporous transition metal oxide

17: Monoatomic precious metals

Claims (18)

A catalyst including: A transition metal oxide with a medium void; and A single-atom noble metal anchored on the mesoporous transition metal oxide; Wherein the transition metal includes Co, Mn, Fe, Ni, Ce, or a combination of the foregoing, the single-atom noble metal is Pt, Rh, Pd, or Ru; when the single-atom noble metal is Pt, the transition metal does not include Fe; When the single-atom noble metal is Ru, the transition metal does not include Ni or Ce. The catalyst described in item 1 of the scope of patent application, wherein when the single-atom noble metal is Pt, the transition metal includes Co, Mn, Ni, Ce, or a combination of the foregoing. The catalyst described in item 1 of the scope of patent application, wherein when the single-atom noble metal is Rh, the transition metal includes Co, Mn, Fe, Ni, Ce, or a combination of the foregoing. The catalyst described in item 1 of the scope of patent application, wherein when the single-atom noble metal is Pd, the transition metal includes Co, Mn, Fe, Ni, Ce, or a combination of the foregoing. The catalyst described in item 1 of the scope of patent application, wherein when the single-atom noble metal is Ru, and the transition metal includes Co, Mn, Fe, or a combination of the foregoing. The catalyst described in item 1 of the scope of patent application, wherein the weight ratio of the mesoporous transition metal oxide to the monoatomic noble metal is between 1:0.002 and 1:0.06. The catalyst described in item 1 of the scope of patent application, wherein the specific surface area of the catalyst is between 60 m ² /g and 200 m ² /g. The catalyst described in item 1 of the scope of patent application, wherein the average pore size of the catalyst is between 8 nm and 20 nm. A method for forming a catalyst includes: Provide a neutral aqueous solution of precious metal salts and transition metal salts; Disperse a mesoporous template in a non-polar solvent to form a dispersion; Mixing the neutral aqueous solution and the dispersion liquid to form a mixed liquid; Heating the mixed liquid to remove the non-polar solvent and water in the mixed liquid and form a powder; Sintering the powder to form a catalyst in the hole of the middle hole template; and Remove the middle hole template to retain the catalyst, Among them, the catalyst includes: A transition metal oxide with a medium void; and A single-atom noble metal is anchored on the mesoporous transition metal oxide. The method for forming a catalyst as described in item 9 of the scope of patent application, wherein when the single-atom noble metal is Pt, Rh, Pd, or Ru, the transition metal includes Co, Mn, Fe, Ni, Ce, or a combination of the above . According to the method for forming a catalyst described in item 9 of the scope of the patent application, the weight ratio of the mesoporous transition metal oxide to the monoatomic noble metal is between 1:0.002 and 1:0.06. According to the method for forming a catalyst according to claim 9, wherein the temperature at which the mixed solution is heated to remove the non-polar solvent and water in the mixed solution and form a powder is between 55°C and 75°C. According to the method for forming a catalyst described in claim 9, wherein the temperature of sintering powder to form the catalyst in the hole of the middle hole template is between 280°C and 350°C. According to the method for forming a catalyst described in item 9 of the scope of patent application, the step of removing the mesoporous template to retain the catalyst uses an aqueous solution of hydrofluoric acid or sodium hydroxide. A method for removing volatile organic compounds, including: A volatile organic compound is passed into a catalyst to oxidize the volatile organic compound into water and carbon dioxide, wherein the catalyst includes: A transition metal oxide with a medium void; and A single-atom noble metal is anchored on the mesoporous transition metal oxide. The method for removing volatile organic compounds as described in item 15 of the scope of patent application, wherein the single-atom noble metal is Pt, Rh, Pd, or Ru, and the transition metal includes Co, Mn, Fe, Ni, Ce, or the above combination. According to the method for removing volatile organic compounds as described in item 15 of the scope of the patent application, the weight ratio of the mesoporous transition metal oxide to the monoatomic noble metal is between 1:0.002 and 1:0.06. The method for removing volatile organic compounds as described in item 15 of the scope of patent application, wherein the volatile organic compounds include propane, isopropanol, acetone, toluene, propylene glycol methyl ether, propylene glycol methyl ether acetate, or a combination of the above.

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