CN115722225B - A monolithic catalyst and its preparation method and application - Google Patents

Abstract

The present invention provides a monolithic catalyst and a preparation method and application thereof. The monolithic catalyst comprises a catalyst carrier and an aluminum-based spinel. The preparation method comprises the following steps: (1) mixing a transition metal salt, an aluminum salt and water, and stirring in a water bath to obtain a mixed solution; (2) mixing a pH adjustment solution and the mixed solution obtained in step (1), and stirring in a water bath to obtain a precursor of the aluminum-based spinel; (3) dipping the catalyst carrier into the precursor of the aluminum-based spinel obtained in step (2), taking it out and standing it to obtain a catalyst precursor; (4) drying the catalyst precursor obtained in step (3) and calcining it under a protective atmosphere in sequence to obtain the monolithic catalyst. The monolithic catalyst comprises an aluminum-based spinel, and its precursor is a colloid. During the preparation process, the catalyst carrier can be directly immersed in the colloid without adding a binder or a thickener, and no waste liquid is generated during the production process, and the catalyst has good application prospects.

Description

A monolithic catalyst and its preparation method and application

Technical Field

The invention relates to the field of air pollution, and relates to a catalyst, and in particular to an integral catalyst and a preparation method and application thereof.

Background technique

Ozone in the stratosphere absorbs ultraviolet rays and protects the earth's animals and plants from harm by ultraviolet rays. However, low-altitude ozone is a harmful gas that kills organisms and is one of the main pollutants in the air when ultraviolet rays are strong in summer. Although ozone is thermodynamically unstable, it decomposes slowly below 250°C in the absence of ultraviolet radiation or catalysts. Therefore, it is necessary to develop ozone degradation catalysts to control ozone pollution in the air.

When applied in practice, powder catalysts usually need to be further made into particles or coated on porous carriers, which makes the preparation steps of monolithic catalysts cumbersome. Traditional granular catalysts have obvious disadvantages such as large pressure drop in the catalyst bed, uneven distribution of reactants on the surface of catalyst particles, and large temperature gradient at each point in the catalyst bed. Monolithic catalysts have more advantages in application than powder catalysts and granular catalysts due to their small size, low pressure drop, efficient mass and heat transfer, and small amplification effect.

At present, the preparation method of monolithic catalyst is usually to coat active components (usually including precious metals and metal oxides) on a honeycomb substrate. That is, with the honeycomb substrate as the carrier, the powder of the active component of the catalyst is mixed with a certain amount of water and a binder in a certain proportion to form a coating slurry, and then dip-coated to obtain a monolithic catalyst. This method is easy to operate, but it has the disadvantages of uneven coating of active components, easy coverage of active components by binders, and low firmness of the coating on the metal substrate due to the mismatch of thermal expansion coefficients between the catalyst ceramic coating and the substrate.

At present, the preparation of binder-free monolithic catalysts is mainly molecular sieve catalysts. CN 111111752A discloses a binder-free monolithic catalyst, the preparation method of which is mainly to add a certain mass ratio of silica sol and aluminum sol binders to the molded molecular sieve, and then convert the binder into the effective component of the molecular sieve through aging and crystallization. Although the binder content in the final catalyst is less than 5%, the binder still needs to be added during the preparation process, which makes the process complicated and the active components are easily covered.

CN 111672506A discloses a method for obtaining a metal-based integral catalyst by liquefying a precursor liquid, passing it through a flame field, and depositing it on a metal substrate by thermophoresis to form a coating. Although this method does not use an adhesive, it is necessary to atomize the precursor liquid and pass it through a flame field. The reaction temperature is as high as thousands of degrees Celsius, and the preparation conditions are harsh and the energy consumption is high.

CN 111774068A discloses an electrochemical deposition method, wherein the active component manganese is deposited onto a nickel foam connected to a working electrode by an electrochemical deposition method, and then dried and calcined to obtain a monolithic catalyst. This method allows for in-situ growth, resulting in better dispersion of the active component, but has certain requirements on the conductivity of the carrier and is difficult to achieve large-scale production.

CN 109107578A discloses a method for preparing a monolithic catalyst for catalytic oxidation of VOCs, wherein a Co/Al hydrotalcite precursor is ground and dispersed into a colloid prepared from water, ethylene glycol and citric acid, and cordierite is immersed in the colloid and then dried and calcined. However, this method requires grinding the precursor into uniform powder and preparing a colloid with a specific mass fraction, and the process flow is complicated.

At present, there are many methods for preparing monolithic catalysts, but their application in industrial environments is very challenging. For example, the electrochemical deposition method has high requirements on the conductivity of the carrier and cannot achieve large-scale industrial production; the sedimentation method process control is very delicate and cumbersome, and is often not guaranteed in an industrial environment; the hydrothermal synthesis process is time-consuming and requires the generation of a large amount of waste liquid.

Therefore, the development of an integrated catalyst with high ozone decomposition activity, simple process, environmental protection, easy operation, and industrial production is of great environmental significance.

Summary of the invention

The purpose of the present invention is to provide a monolithic catalyst and its preparation method and application. The precursor of the aluminum-based spinel of the monolithic catalyst provided by the present invention is a colloid, and the catalyst carrier can be directly immersed in the colloid without the need to add an additional binder or thickener, and no waste liquid is generated during the production process. The preparation process is simple, environmentally friendly and easy to operate, and has a good application prospect.

In order to achieve the purpose of the invention, the present invention adopts the following technical solutions:

In a first aspect, the present invention provides a monolithic catalyst, the monolithic catalyst comprising a catalyst carrier and an aluminum-based spinel;

The catalyst carrier has a porous structure;

The mass ratio of the aluminum-based spinel to the catalyst carrier is 1:(10-1000).

The active components of the monolithic catalyst of the present invention are derived from the metal oxides in the aluminum-based spinel. The monolithic catalyst provided by the present invention contains the aluminum-based spinel, and its precursor is a colloid. During the preparation process, the catalyst carrier can be directly immersed in the colloid without adding a binder or a thickener.

The active components of the monolithic catalyst of the present invention are derived from metal oxides in the aluminum-based spinel.

Preferably, the catalyst carrier comprises any one of honeycomb aluminum, cordierite, iron-chromium aluminum, copper foam or nickel foam, or a combination of at least two thereof. Typical but non-limiting combinations include a combination of honeycomb aluminum and cordierite, a combination of honeycomb aluminum, cordierite and iron-chromium aluminum, a combination of cordierite, iron-chromium aluminum and copper foam, a combination of iron-chromium aluminum, copper foam and nickel foam, or a combination of honeycomb aluminum, cordierite, copper foam and nickel foam.

Preferably, the aluminum-based spinel includes any one of cobalt aluminum spinel, manganese aluminum spinel, iron aluminum spinel, copper aluminum spinel or nickel aluminum spinel, or a combination of at least two of them. Typical but non-limiting combinations include a combination of cobalt aluminum spinel and manganese aluminum spinel, a combination of manganese aluminum spinel and iron aluminum spinel, a combination of iron aluminum spinel, copper aluminum spinel and nickel aluminum spinel, or a combination of cobalt aluminum spinel, manganese aluminum spinel and iron aluminum spinel.

In a second aspect, the present invention provides a method for preparing the monolithic catalyst as described in the first aspect, the preparation method comprising the following steps:

(1) mixing a transition metal salt, an aluminum salt and water, and stirring in a water bath to obtain a mixed solution;

(2) mixing the pH adjustment solution and the mixed solution obtained in step (1), and stirring in a water bath to obtain an aluminum-based spinel precursor;

(3) impregnating the catalyst carrier into the aluminum-based spinel precursor obtained in step (2), taking it out and letting it stand to obtain a catalyst precursor;

(4) The catalyst precursor of step (3) is dried and calcined in a protective atmosphere to obtain the monolithic catalyst.

The present invention directly immerses the catalyst carrier into the aluminum-based spinel precursor so that the pores of the catalyst carrier are filled with the aluminum-based spinel precursor. Compared with the traditional powder coating method, there is no need to disperse the powder of the active component into the binder, which effectively avoids the problems of uneven dispersion and agglomeration of the active component. In addition, the preparation method of the present invention is simple to operate, does not generate waste liquid, has a simple process flow, and has good application prospects.

Preferably, the transition metal salt in step (1) comprises any one of manganese salts, cobalt salts, copper salts, iron salts or nickel salts, or a combination of at least two thereof. Typical but non-limiting combinations include a combination of manganese salts and cobalt salts, a combination of manganese salts and copper salts, a combination of cobalt salts and iron salts, a combination of iron salts and copper salts, or a combination of manganese salts, cobalt salts and nickel salts.

The manganese salt includes any one of manganese nitrate, manganese chloride, manganese sulfate or manganese acetate, or a combination of at least two thereof. Typical but non-limiting combinations include a combination of manganese nitrate and manganese chloride, a combination of manganese chloride and manganese sulfate, a combination of manganese nitrate, manganese chloride and manganese sulfate, or a combination of manganese nitrate, manganese chloride, manganese sulfate and manganese acetate.

The cobalt salt includes any one of cobalt nitrate, cobalt chloride, cobalt sulfate or cobalt acetate, or a combination of at least two thereof. Typical but non-limiting combinations include a combination of cobalt nitrate and cobalt chloride, a combination of cobalt chloride and cobalt sulfate, a combination of cobalt nitrate, cobalt chloride and cobalt sulfate, or a combination of cobalt nitrate, cobalt chloride, cobalt sulfate and cobalt acetate.

The copper salt includes any one of copper nitrate, copper chloride, and copper sulfate, or a combination of at least two thereof. Typical but non-limiting combinations include a combination of copper nitrate and copper chloride, a combination of copper nitrate and copper sulfate, a combination of copper chloride and copper sulfate, or a combination of copper nitrate, copper chloride, and copper sulfate.

The iron salt includes any one of ferric nitrate, ferric chloride, and ferric sulfate, or a combination of at least two thereof. Typical but non-limiting combinations include a combination of copper nitrate and copper chloride, a combination of ferric nitrate and ferric sulfate, a combination of ferric chloride and ferric sulfate, or a combination of ferric nitrate, ferric chloride, and ferric sulfate.

The nickel salt includes any one of nickel acid, nickel chloride, and nickel sulfate, or a combination of at least two of them. Typical but non-limiting combinations include a combination of copper nitrate and copper chloride, a combination of nickel nitrate and nickel sulfate, a combination of nickel chloride and nickel sulfate, or a combination of nickel nitrate, nickel chloride and nickel sulfate.

Preferably, the aluminum salt in step (1) comprises any one of aluminum chloride, aluminum nitrate, aluminum acetate or aluminum sulfate, or a combination of at least two thereof. Typical but non-limiting combinations include a combination of aluminum nitrate and aluminum chloride, a combination of aluminum chloride and aluminum sulfate, a combination of aluminum nitrate, aluminum chloride and aluminum sulfate, or a combination of aluminum nitrate, aluminum chloride, aluminum sulfate and aluminum acetate.

Preferably, the temperature of the water bath stirring in step (1) is 20-70°C, for example, it can be 20°C, 25°C, 30°C, 35°C, 40°C, 45°C, 50°C, 55°C, 60°C, 65°C or 70°C, but is not limited to the listed values. Other values not listed within the numerical range are also applicable, preferably 40-60°C.

Preferably, the stirring time in the water bath in step (1) is 15-60 min, for example, 15 min, 20 min, 25 min, 30 min, 35 min, 40 min, 45 min, 50 min, 55 min or 60 min, but is not limited to the listed values, and other values not listed within the numerical range are also applicable.

Preferably, the ratio of the transition metal salt, the aluminum salt and the water in step (1) is 0.1 mol: (0.2-0.4) mol: (10-30) mL, for example, it can be 0.1 mol: 0.2 mol: 10 mL, 0.1 mol: 0.3 mol: 20 mL, 0.1 mol: 0.4 mol: 15 mL, 0.1 mol: 0.2 mol: 30 mL, 0.1 mol: 0.3 mol: 30 mL, or 0.1 mol: 0.4 mol: 20 mL, but is not limited to the listed values, and other values not listed within the numerical range are equally applicable.

Preferably, the pH adjusting solution in step (2) comprises any one of urea, sodium carbonate, aqueous ammonia, sodium hydroxide or potassium carbonate, or a combination of at least two thereof. Typical but non-limiting combinations include a combination of urea and sodium carbonate, a combination of aqueous ammonia and sodium hydroxide, a combination of sodium carbonate, aqueous ammonia and sodium hydroxide, a combination of aqueous ammonia, sodium hydroxide and potassium carbonate, or a combination of sodium carbonate, aqueous ammonia, sodium hydroxide and potassium carbonate, preferably any one of urea, aqueous ammonia or sodium carbonate.

Preferably, the molar concentration of the pH adjusting solution in step (2) is 0.001-0.006 mol/mL, for example, 0.001 mol/mL, 0.002 mol/mL, 0.003 mol/mL, 0.004 mol/mL, 0.005 mol/mL or 0.006 mol/mL, but is not limited to the listed values, and other values not listed within the numerical range are also applicable.

Preferably, the volume ratio of the pH adjusting solution to the mixed solution in step (2) is 1:(1.5-3), for example, it can be 1:1.5, 1:2, 1:2.5 or 1:3, but is not limited to the listed values, and other values not listed within the numerical range are also applicable.

Preferably, the temperature of the water bath stirring in step (2) is 40-95°C, for example, it can be 40°C, 45°C, 50°C, 55°C, 60°C, 65°C, 70°C, 75°C, 80°C, 85°C, 90°C or 95°C, but is not limited to the listed values. Other values not listed within the numerical range are also applicable, preferably 60-90°C.

Preferably, the stirring time in the water bath in step (2) is 0.5-24 h, for example, 0.5 h, 1 h, 4 h, 8 h, 12 h, 16 h, 20 h or 24 h, but is not limited to the listed values, and other values not listed within the numerical range are also applicable, preferably 2-12 h.

Preferably, the aluminum-based spinel precursor in step (2) is a colloid.

Preferably, the end point of the impregnation in step (3) is that no bubbles are generated on the surface of the catalyst carrier.

Preferably, the standing time in step (3) is 3-5 h, for example, 3 h, 3.5 h, 4 h, 4.5 h or 5 h, but is not limited to the listed values, and other values not listed within the numerical range are also applicable.

Preferably, the drying temperature in step (4) is 60-100°C, for example, it can be 60°C, 65°C, 70°C, 75°C, 80°C, 85°C, 90°C, 95°C or 100°C, but is not limited to the listed values. Other values not listed within the numerical range are also applicable, preferably 70-90°C.

Preferably, the drying time in step (4) is 6-18 h, for example, 6 h, 8 h, 10 h, 12 h, 14 h, 16 h or 18 h, but is not limited to the listed values, and other values not listed within the numerical range are also applicable, preferably 8-15 h.

Preferably, the calcination temperature in step (4) is 200-800°C, for example, it can be 200°C, 300°C, 400°C, 500°C, 600°C, 700°C or 800°C, but is not limited to the listed values. Other values not listed within the numerical range are also applicable, preferably 350-550°C.

Preferably, the calcination time in step (4) is 1-12 h, for example, 1 h, 2 h, 3 h, 4 h, 5 h, 6 h, 7 h, 8 h, 9 h, 10 h, 11 h or 12 h, but is not limited to the listed values, and other values not listed within the numerical range are also applicable, preferably 2-6 h.

Preferably, the protective atmosphere includes any one of argon atmosphere, nitrogen atmosphere or helium atmosphere, preferably argon atmosphere.

As a preferred technical solution, the method for preparing the monolithic catalyst according to the second aspect of the present invention comprises the following steps:

(1) mixing a transition metal salt, an aluminum salt and water, stirring in a water bath at 20-70° C. for 15-60 min to obtain a mixed solution, wherein the ratio of the transition metal salt, the aluminum salt and the water is 0.1 mol: (0.2-0.4) mol: (10-30) mL;

(2) mixing a pH adjusting solution and the mixed solution obtained in step (1) in a volume ratio of 1:(1.5-3), stirring in a water bath at 40-95° C. for 0.5-24 h to obtain an aluminum-based spinel precursor, wherein the molar concentration of the pH adjusting solution is 0.001-0.006 mol/mL, and the aluminum-based spinel precursor is a colloid;

(3) impregnating the catalyst support into the aluminum-based spinel precursor obtained in step (2), taking out the catalyst support when no bubbles are generated on the surface of the catalyst support, and leaving it to stand for 3-5 hours to obtain a catalyst precursor;

(4) The catalyst precursor of step (3) is dried at 60-100° C. for 6-18 h and calcined at 200-800° C. in a protective atmosphere for 1-12 h to obtain the monolithic catalyst.

In a third aspect, the present invention provides a use of the integral catalyst as described in the first aspect, wherein the integral catalyst is used for purifying ozone pollution.

Compared with the prior art, the present invention has the following beneficial effects:

(1) The precursor of the active component of the monolithic catalyst provided by the present invention is a colloid, which can be uniformly adhered to the pore wall of the catalyst carrier without the need for additional binders or thickeners;

(2) The monolithic catalyst provided by the present invention has high activity for ozone decomposition at room temperature and is suitable for eliminating ozone pollution;

(3) No waste liquid is generated during the preparation process of the monolithic catalyst provided by the present invention, the process is simple and easy to operate, and has good application prospects.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG1 is a time-ozone conversion diagram of the catalytic decomposition of ozone by the monolithic catalyst provided in Example 1 of the present invention;

FIG2 is an XRD pattern of the cobalt aluminum spinel provided in Example 1 of the present invention;

FIG3 is a process flow chart of preparing a monolithic catalyst provided in Example 1 of the present invention;

FIG. 4 is a process flow chart of preparing a monolithic catalyst by a conventional coating method.

Detailed ways

The technical solution of the present invention is further described below by specific implementation methods. It should be understood by those skilled in the art that the embodiments are only used to help understand the present invention and should not be regarded as specific limitations of the present invention.

Example 1

This embodiment provides a monolithic catalyst, which includes honeycomb aluminum and cobalt aluminum spinel. The mass ratio of the cobalt aluminum spinel to the honeycomb aluminum is 1:20.

The preparation method of the monolithic catalyst is shown in FIG3 , and comprises the following steps:

(1) mixing cobalt nitrate, aluminum nitrate and water, stirring in a water bath at 50° C. for 30 min to obtain a mixed solution, wherein the amount ratio of the cobalt nitrate, aluminum nitrate and water is 0.1 mol:0.2 mol:20 mL;

(2) mixing urea and the mixed solution obtained in step (1) in a volume ratio of 1:2, stirring in a water bath at 80° C. for 4 h to obtain a cobalt aluminum spinel precursor, wherein the molar concentration of the urea is 0.006 mol/mL, and the cobalt aluminum spinel precursor is a colloid;

(3) dipping the honeycomb aluminum into the cobalt aluminum spinel precursor obtained in step (2), taking out the honeycomb aluminum when no bubbles are generated on the surface of the honeycomb aluminum, and leaving it to stand for 3 hours to obtain a catalyst precursor;

(4) The catalyst precursor of step (3) is dried at 80° C. for 12 h, placed in an argon atmosphere, and calcined at 400° C. for 3 h to obtain the monolithic catalyst.

The time-ozone conversion rate graph of the catalytic decomposition of ozone by the monolithic catalyst obtained in this example is shown in FIG1 ; and the XRD spectrum of the cobalt aluminum spinel contained in the monolithic catalyst is shown in FIG2 .

Compared with the process flow of preparing monolithic catalysts by the traditional coating method shown in FIG4 , the preparation method described in this embodiment does not need to disperse the powder of the active component into the binder, which effectively avoids problems such as uneven dispersion and agglomeration of the active component.

Example 2

This embodiment provides a monolithic catalyst, which includes cordierite and manganese aluminum spinel. The mass ratio of the manganese aluminum spinel to the cordierite is 1:50.

The preparation method of the monolithic catalyst comprises the following steps:

(1) mixing manganese chloride, aluminum chloride and water, stirring in a water bath at 20° C. for 60 min to obtain a mixed solution, wherein the amount ratio of manganese chloride, aluminum chloride and water is 0.1 mol:0.3 mol:30 mL;

(2) mixing sodium carbonate and the mixed solution obtained in step (1) in a volume ratio of 1:3, stirring in a water bath at 40° C. for 24 h to obtain a manganese aluminum spinel precursor, wherein the molar concentration of the sodium carbonate is 0.004 mol/mL, and the manganese aluminum spinel precursor is a colloid;

(3) impregnating cordierite into the manganese aluminum spinel precursor obtained in step (2), taking out the cordierite when no bubbles are generated on the surface of the cordierite, and leaving it to stand for 5 hours to obtain a catalyst precursor;

(4) The catalyst precursor of step (3) is dried at 60° C. for 18 h, placed in a helium atmosphere, and calcined at 200° C. for 12 h to obtain the monolithic catalyst.

Example 3

This embodiment provides a monolithic catalyst, which includes copper foam and copper aluminum spinel. The mass ratio of the copper aluminum spinel to the copper foam is 1:80.

The preparation method of the monolithic catalyst comprises the following steps:

(1) mixing copper sulfate, aluminum nitrate and water, stirring in a water bath at 70° C. for 15 min to obtain a mixed solution, wherein the amount ratio of copper sulfate, aluminum nitrate and water is 0.1 mol:0.2 mol:15 mL;

(2) mixing sodium hydroxide and the mixed solution obtained in step (1) in a volume ratio of 1:1.5, stirring in a water bath at 95° C. for 0.5 h to obtain a copper aluminum spinel precursor, wherein the molar concentration of the sodium hydroxide is 0.001 mol/mL, and the copper aluminum spinel precursor is a colloid;

(3) impregnating the copper foam into the copper-aluminum spinel precursor obtained in step (2), taking out the copper foam when no bubbles are generated on the surface of the copper foam, and leaving it to stand for 5 hours to obtain a catalyst precursor;

(4) The catalyst precursor of step (3) is dried at 100° C. for 6 h and calcined at 800° C. in a nitrogen atmosphere for 1 h to obtain the monolithic catalyst.

Example 4

This embodiment provides a monolithic catalyst, which includes nickel foam and nickel aluminum spinel. The mass ratio of the nickel aluminum spinel to the nickel foam is 1:25.

The preparation method of the monolithic catalyst described in this embodiment comprises the following steps:

(1) mixing nickel nitrate, aluminum acetate and water, stirring in a water bath at 50° C. for 20 min to obtain a mixed solution, wherein the amount ratio of the nickel nitrate, aluminum acetate and water is 0.1 mol:0.1 mol:10 mL;

(2) mixing ammonia water and the mixed solution obtained in step (1) in a volume ratio of 1:1.5, stirring in a water bath at 80° C. for 8 h to obtain an aluminum-based spinel precursor, wherein the molar concentration of the ammonia water is 0.003 mol/mL, and the nickel aluminum spinel precursor is a colloid;

(3) impregnating the nickel foam into the nickel aluminum spinel precursor obtained in step (2), taking out the nickel foam when no bubbles are generated on the surface of the nickel foam, and leaving it to stand for 3.8 hours to obtain a catalyst precursor;

(4) The catalyst precursor of step (3) is dried at 80° C. for 12 h and calcined at 450° C. for 4.5 h in an argon atmosphere to obtain the monolithic catalyst.

Example 5

This embodiment provides a monolithic catalyst, which includes honeycomb aluminum and cobalt aluminum spinel. The mass ratio of the cobalt aluminum spinel to the honeycomb aluminum is 1:20.

The preparation method of the monolithic catalyst is the same as that of Example 1 except that the calcination temperature in step (4) is changed to 900°C.

Example 6

This embodiment provides a monolithic catalyst, which includes honeycomb aluminum and cobalt aluminum spinel. The mass ratio of the cobalt aluminum spinel to the honeycomb aluminum is 1:15.

The preparation method of the monolithic catalyst is the same as that of Example 1 except that the calcination temperature in step (4) is changed to 150°C.

Example 7

This embodiment provides a monolithic catalyst, which includes honeycomb aluminum and cobalt aluminum spinel. The mass ratio of the cobalt aluminum spinel to the honeycomb aluminum is 1:10.

The preparation method of the monolithic catalyst is the same as that of Example 1 except that the ratio of cobalt nitrate, aluminum nitrate and water in step (1) is changed to 0.1 mol:0.5 mol:10 mL.

Example 8

This embodiment provides a monolithic catalyst, which includes honeycomb aluminum and cobalt aluminum spinel. The mass ratio of the cobalt aluminum spinel to the honeycomb aluminum is 1:20.

The preparation method of the monolithic catalyst is the same as that of Example 1 except that the volume ratio of urea to the mixed solution in step (2) is changed to 1:1.

Example 9

This embodiment provides a monolithic catalyst, which includes honeycomb aluminum and cobalt aluminum spinel. The mass ratio of the cobalt aluminum spinel to the honeycomb aluminum is 1:20.

The preparation method of the monolithic catalyst is the same as that of Example 1 except that the volume ratio of urea to the mixed solution in step (2) is changed to 1:4.

The monolithic catalysts prepared in Examples 1 to 9 were subjected to an ozone purification experiment. The monolithic catalysts used in the experiment had a diameter of 25 mm, a height of 20 mm, and an inner hole side length of 1 mm.

During the ozone purification experiment, the ozone concentration was 50 ppm, the gas flow rate was 1000 mL/min, and the test temperature was 20° C. The ozone purification efficiency is shown in Table 1.

Table 1

By analyzing Example 1 and Examples 8-9, it can be seen that the amount of pH adjustment solution added will affect the stability of the colloid, and further affect the catalytic effect of the monolithic catalyst.

In summary, the integral catalyst provided by the present invention contains aluminum-based spinel, and its precursor is a colloid. During the preparation process, the catalyst carrier can be directly immersed in the colloid without adding a binder or thickener, and no waste liquid is generated during the production process. The preparation process is simple, environmentally friendly, and easy to operate, and has good application prospects.

The applicant declares that the above is only a specific implementation mode of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention are within the protection scope and disclosure scope of the present invention.

Claims (26)

1. Use of a monolithic catalyst for purifying ozone pollution, the monolithic catalyst comprising a catalyst support and an aluminum-based spinel;

the catalyst carrier has a porous structure;

the mass ratio of the aluminum-based spinel to the catalyst carrier is 1 (10-1000);

The preparation method of the monolithic catalyst comprises the following steps:

(1) Mixing transition metal salt, aluminum salt and water, and stirring in a water bath to obtain a mixed solution;

(2) Mixing the pH adjusting solution with the mixed solution obtained in the step (1), and stirring in a water bath to obtain an aluminum-based spinel precursor; the aluminum-based spinel precursor is colloid;

(3) Immersing a catalyst carrier into the aluminum-based spinel precursor colloid obtained in the step (2), and taking out and standing to obtain a catalyst precursor;

(4) Drying the catalyst precursor in the step (3) in sequence and calcining the catalyst precursor in a protective atmosphere to obtain the integral catalyst;

the pH adjusting solution in the step (2) comprises any one or a combination of at least two of urea, sodium carbonate, ammonia water, sodium hydroxide or potassium carbonate;

The molar concentration of the pH adjusting solution in the step (2) is 0.001-0.006mol/mL;

the volume ratio of the pH adjusting solution to the mixed solution in the step (2) is 1 (1.5-3);

The end point of the impregnation in the step (3) is that no bubbles are generated on the surface of the catalyst carrier.

2. The use of claim 1, wherein the catalyst support comprises any one or a combination of at least two of aluminum honeycomb, cordierite, iron-chromium-aluminum, copper foam, or nickel foam.

3. The use according to claim 1, wherein the aluminium-based spinel comprises any one or a combination of at least two of cobalt-aluminium spinel, manganese-aluminium spinel, iron-aluminium spinel, copper-aluminium spinel or nickel-aluminium spinel.

4. The use according to claim 1, wherein the transition metal salt of step (1) comprises any one or a combination of at least two of a manganese salt, a cobalt salt, a copper salt, an iron salt or a nickel salt.

5. The use according to claim 1, wherein the aluminium salt of step (1) comprises any one or a combination of at least two of aluminium chloride, aluminium nitrate, aluminium acetate or aluminium sulphate.

6. The use according to claim 1, wherein the temperature of the water bath agitation in step (1) is 20-70 ℃.

7. The use according to claim 6, wherein the temperature of the water bath agitation in step (1) is 40-60 ℃.

8. The use according to claim 1, wherein the water bath is stirred for a period of 15-60min in step (1).

9. The use according to claim 1, wherein the transition metal salt, aluminum salt and water in step (1) are used in an amount ratio of 0.1mol (0.2-0.4) mol (10-30) mL.

10. The use according to claim 1, wherein the pH adjusting solution of step (2) is any one of urea, ammonia or sodium carbonate.

11. The use according to claim 1, wherein the temperature of the water bath agitation in step (2) is 40-95 ℃.

12. The use according to claim 11, wherein the temperature of the water bath agitation in step (2) is 60-90 ℃.

13. The use according to claim 1, wherein the water bath is stirred for a period of 0.5-24 hours in step (2).

14. The use according to claim 13, wherein the water bath is stirred for a period of 2-12 hours in step (2).

15. The use according to claim 1, wherein the time of the resting in step (3) is 3-5 hours.

16. The use according to claim 1, wherein the drying temperature in step (4) is 60-100 ℃.

17. The use according to claim 16, wherein the drying in step (4) is at a temperature of 70-90 ℃.

18. The use according to claim 1, wherein the drying in step (4) takes from 6 to 18 hours.

19. The use according to claim 18, wherein the drying in step (4) takes 8-15 hours.

20. The use according to claim 1, wherein the calcination in step (4) is carried out at a temperature of 200-800 ℃.

21. The use according to claim 20, wherein the calcination in step (4) is carried out at a temperature of 350-550 ℃.

22. The use according to claim 1, wherein the calcination in step (4) takes from 1 to 12 hours.

23. The use according to claim 22, wherein the calcination in step (4) is for a period of 2-6 hours.

24. The use according to claim 1, wherein the protective atmosphere of step (4) comprises any one of an argon atmosphere, a nitrogen atmosphere or a helium atmosphere.

25. The use of claim 24, wherein the protective atmosphere of step (4) is an argon atmosphere.

26. The use according to claim 1, wherein the method for preparing the monolithic catalyst comprises the steps of:

(1) Mixing transition metal salt, aluminum salt and water, and stirring in a water bath at 20-70 ℃ for 15-60min to obtain a mixed solution, wherein the dosage ratio of the transition metal salt to the aluminum salt to the water is 0.1mol (0.2-0.4 mol) (10-30 mL;

(2) Mixing the pH adjusting solution and the mixed solution obtained in the step (1) according to the volume ratio of 1 (1.5-3), and stirring in a water bath at 40-95 ℃ for 0.5-24 hours to obtain an aluminum-based spinel precursor, wherein the molar concentration of the pH adjusting solution is 0.001-0.006mol/mL, and the aluminum-based spinel precursor is colloid;

(3) Immersing the catalyst carrier into the aluminum-based spinel precursor obtained in the step (2), taking out the catalyst carrier when no bubbles are generated on the surface of the catalyst carrier, and standing the catalyst carrier for 3 to 5 hours to obtain the catalyst precursor;

(4) And (3) drying the catalyst precursor in the step (3) at 60-100 ℃ for 6-18h, and calcining at 200-800 ℃ in a protective atmosphere for 1-12h to obtain the monolithic catalyst.