Manganese dioxide catalyst as well as preparation method and application thereof

Abstract

The invention discloses a manganese dioxide catalyst as well as a preparation method and application thereof, and belongs to the field of thermal catalysts. The manganese dioxide catalyst is of a nano polycrystalline structure, the nano polycrystalline structure is composed of nanoscale crystal particles, and alkali metal and / or precious metal are / is doped in crystal lattices of the nano polycrystalline structure of the manganese dioxide catalyst. Alkali metal and / or precious metal are / is doped into nano polycrystalline crystal lattices of the manganese dioxide catalyst, so that the catalyst obtains rich oxygen vacancies, high-activity adsorption catalysis is realized, a large amount of oxygen is adsorbed, the oxygen vacancies and the oxygen adsorption proportion of the catalyst are effectively increased, an oxygen source is provided for oxidative degradation of the manganese dioxide catalyst to oil fume grease, and the oil fume grease can be effectively degraded. And moreover, the catalytic oxidation degradation onset temperature of the cooking oil fume grease can be reduced to 100 DEG C or below.

Description

Technical Field

[0001] The present invention relates to the field of thermal catalysts, and particularly to a manganese dioxide catalyst, a preparation method thereof, and an application thereof. Background Art

[0002] With the improvement of people's living standards and the change of eating habits, the cooking industry has developed rapidly. However, the oil fumes and grease generated during the cooking process have become an environmental pollution problem that cannot be ignored. These oil fumes and grease will not only have a negative impact on people's health, but also pollute the surrounding environment.

[0003] Traditional oil fume purification technologies include methods such as mechanical filtration, electrostatic deposition, and activated carbon adsorption. These methods can reduce the emissions of oil fumes and grease to a certain extent, but there are some disadvantages, such as being prone to secondary pollution and having high operating costs. Therefore, it is particularly important to develop an efficient and environmentally friendly oil fume purification technology. Summary of the Invention

[0004] The main object of the present invention is to provide a manganese dioxide catalyst, a preparation method thereof, and an application thereof, which can oxidize and degrade the generated oil fumes and oil stains during the cooking process, solve the technical problems that oil fume and grease pollutants and harmful substances are easily generated during the cooking process, and it is difficult to clean the cooking utensils due to the easy accumulation of oil stains.

[0005] To achieve the above object, the present invention provides a manganese dioxide catalyst. The manganese dioxide catalyst has a nano-polycrystalline structure, and the nano-polycrystalline structure is composed of nano-scale crystal grains. Alkali metals and / or noble metals are doped in the crystal lattice of the nano-polycrystalline structure of the manganese dioxide catalyst.

[0006] In some embodiments of the present invention, the alkali metals include one or more of potassium, calcium, magnesium, aluminum, zinc, copper, iron, cerium, cobalt, titanium, zirconium, nickel, vanadium, lanthanum, and tungsten;

[0007] and / or, the noble metals include at least one of gold, platinum, palladium, rhodium, and ruthenium;

[0008] and / or, the length of a single crystal grain of the crystal grains of the manganese dioxide catalyst is 20 nm - 90 nm.

[0009] In some embodiments of the present invention, the crystal form of the manganese dioxide catalyst includes at least one of α-MnO 2 、β-MnO 2 、γ-MnO 2 、ε-MnO 2 、δ-MnO 2 、λ-MnO 2 。

[0010] In some embodiments of the present invention, the oxygen atoms in the manganese dioxide catalyst consist of adsorbed oxygen (O β ) and bound oxygen (O α ). Calculated by the area characterized by XPS, the adsorbed oxygen (O β ) accounts for 5%-50% of the total mass of the oxygen atoms.

[0011] In some embodiments of the present invention, the binding energy of the adsorbed oxygen (O β ) is at 531.9 eV, and the binding energy of the bound oxygen (O α ) is at 530 eV.

[0012] In some embodiments of the present invention, the shape of the manganese dioxide catalyst includes flake-like, needle-like, rod-like, strip-like, spherical or sea urchin-like.

[0013] In some embodiments of the present invention, the width of the manganese dioxide catalyst in the shape of flake is 10 nm - 100 μm, and the thickness is 2 nm - 1 μm;

[0014] and / or, the width of the manganese dioxide catalyst in the shape of needle is 10 nm - 100 μm, and the thickness is 2 nm - 1 μm;

[0015] and / or, the axial length of the manganese dioxide catalyst in the shape of rod or strip is 10 nm - 10 μm, and the radial length is 10 nm - 100 nm;

[0016] and / or, the diameter of the manganese dioxide catalyst in the shape of sphere or sea urchin is 200 nm - 800 nm.

[0017] In some embodiments of the present invention, the specific surface area range of the manganese dioxide catalyst is 30 m 2 / g - 500 m 2 / g;

[0018] and / or, the pore volume of the manganese dioxide catalyst is 0.1 cm 3 / g - 1.0 cm 3 / g;

[0019] and / or, the pore diameter range of the manganese dioxide catalyst is 5 nm - 50 nm.

[0020] In some embodiments of the present invention, the mass ratio of manganese element to metal element in the manganese dioxide catalyst is less than or equal to 70:100.

[0021] In some embodiments of the present invention, the mass ratio of manganese element to metal element in the manganese dioxide catalyst is (1 - 20):100.

[0022] The present invention also provides a method for preparing the manganese dioxide catalyst as described above, comprising the following steps:

[0023] Mix a reaction solution A containing divalent manganese ions and a solvent to form a mixed solution C;

[0024] Form a solid precipitate D from the mixed solution C;

[0025] Calcine the solid precipitate D to obtain a base catalyst;

[0026] Mix and ball-mill the base catalyst with an alkali metal source and / or a noble metal source to obtain the manganese dioxide catalyst.

[0027] In some embodiments of the present invention, the alkali metal source includes at least one of potassium hydroxide, calcium(II) oxide, magnesium(II) oxide, aluminum(III) oxide, zinc(II) oxide, copper(II) oxide, iron(III) oxide, cerium(III) dioxide, cobalt(III) oxide, titanium(IV) dioxide, zirconium acetate, vanadium(IV) oxide, nickel(II) oxide, lanthanum(III) oxide or tungstic acid;

[0028] And / or, the noble metal source includes at least one of chloroplatinic acid, ammonium tetrachloroaurate(II), palladium(III) chloride, rhodium(III) acetate, ruthenium(III) acetate, silver(II) nitrate.

[0029] The present invention also provides an application of the manganese-based thermal catalyst as described above in degrading cooking fume oil pollutants.

[0030] The beneficial effects that the present invention can achieve:

[0031] In the presence of oxygen in the air, the manganese dioxide catalyst of the present invention can react with the cooking fume oil generated during cooking, decompose the cooking fume oil into water and carbon dioxide, and at the same time inhibit the generation of harmful substances.

[0032] The manganese dioxide catalyst of the present invention has a nano-polycrystalline structure, which is composed of nano-scale crystal grains. Moreover, the lattice of the nano-polycrystalline structure is doped with alkali metals and / or noble metals, increasing the oxygen vacancies, improving the proportion of adsorbed oxygen of the manganese dioxide catalyst, continuously providing sufficient oxygen for the oxidative degradation of cooking fume oil by the manganese dioxide catalyst, making the degradation of cooking fume oil more thorough, improving the catalytic effect, and also reducing the activation temperature of the manganese dioxide catalyst, enabling catalytic degradation of cooking fume oil under the condition of less than 100 °C.

[0033] Apply the above manganese dioxide catalyst to cooking appliances. Coat the manganese dioxide catalyst on the surface of the cooking appliance that is prone to being stained with cooking fumes and grease to form a catalytic coating. The manganese dioxide catalyst of the present invention can achieve the catalytic degradation of cooking fumes and grease under relatively low temperature conditions below 100°C. Therefore, using the heat generated during cooking as the catalytic heat source, a large number of oxygen vacancies in the catalyst adsorb oxygen in the air to continuously provide a sufficient oxygen source, promoting the rapid oxidation degradation of the cooking fumes and grease generated during cooking, and finally being degraded into carbon dioxide and water. It can achieve the purpose of timely degrading cooking fumes and grease during the cooking process, ensuring that there is no grease deposition and residue in the cavity after cooking, avoiding the pain point of difficult cleaning inside the cavity, and without the need to increase additional energy consumption. It can not only reduce environmental pollution, reduce the harm to people's health, but also reduce the accumulation of oil stains, making the cooking appliance easy to clean. Especially for cooking appliances with a compact structure, a closed space, and extremely easy to form cleaning dead corners inside the cooking cavity, it can solve many troubles brought by difficult daily cleaning, and reduce the growth of bacteria and carcinogenic risks on the surface of the cooking appliance. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following briefly introduces the drawings required for use in the description of the embodiments or the prior art. Obviously, the following drawings are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on the structures shown in these drawings.

[0035] Figure 1 It is a morphology diagram of the manganese dioxide catalyst of Embodiment 1 of the present invention.

[0036] Figure 2 It is an XRD characterization diagram of the manganese dioxide catalyst of Embodiment 1 of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0037] It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0038] The following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the drawings in the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, rather than all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present invention.

[0039] In the present invention, descriptions such as "first", "second", etc. are for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the quantity of the indicated technical features. Thus, features defined with "first", "second" may explicitly or implicitly include at least one such feature. Additionally, the technical solutions between various embodiments may be combined with each other, but it must be based on the ability of those of ordinary skill in the art to implement. When the combination of technical solutions results in contradictions or cannot be implemented, it should be considered that such a combination of technical solutions does not exist and is not within the scope of protection required by the present invention.

[0040] The present invention provides a manganese dioxide catalyst. The manganese dioxide catalyst has a nano-polycrystalline structure, and the nano-polycrystalline structure is composed of nano-scale crystal grains. Alkali metals and / or noble metals are doped in the lattice of the nano-polycrystalline structure of the manganese dioxide catalyst.

[0041] The manganese dioxide catalyst of the present invention can undergo a catalytic oxidation degradation reaction with the cooking fume grease generated during cooking under the conditions of oxygen and a heat source, degrading the cooking fume grease into carbon dioxide and water, reducing the accumulation of cooking fume grease on the surface of the cooking appliance, and making the cooking appliance easier to clean.

[0042] Alkali metals and / or noble metals are doped in the lattice of the crystal grains of the manganese dioxide catalyst, increasing the oxygen vacancies, improving the proportion of oxygen adsorbed by the manganese dioxide catalyst, continuously providing sufficient oxygen for the oxidation degradation of the cooking fume grease by the manganese dioxide catalyst, making the cooking fume grease degrade more thoroughly, improving the catalytic effect, and also reducing the activation temperature of the manganese dioxide catalyst, enabling the catalytic degradation of the cooking fume grease at a temperature below 100°C.

[0043] In some embodiments, the activation temperature for the manganese dioxide catalyst to catalytically oxidize and degrade the cooking fume grease is 95°C - 800°C, and it can be any temperature value within the range of 95°C - 800°C such as 95°C, 100°C, 105°C, 110°C, 120°C, 150°C, 200°C, 250°C, 300°C, 400°C, 500°C, 600°C, 700°C, 750°C, 800°C, etc. At the above temperature range, the manganese dioxide catalyst can catalytically oxidize and degrade the cooking fume grease to form carbon dioxide and water. The above temperature range basically covers the daily cooking temperatures, enabling the oxidation degradation of the cooking fume grease generated during cooking during the cooking process.

[0044] In some embodiments, the alkali metals include one or more of potassium, calcium, magnesium, aluminum, zinc, copper, iron, cerium, cobalt, titanium, zirconium, nickel, vanadium, lanthanum, and tungsten; the above types of alkali metal elements can help the catalyst to reduce the effective temperature for catalytic oxidation and degradation of cooking fume grease to 95 °C, and can achieve catalytic oxidation and degradation of cooking fume grease under the conditions of 95 °C - 800 °C. Usually, the cooking temperature is also within the range of 95 °C - 800 °C, so that the purpose of catalytic oxidation and degradation of cooking fume grease generated during cooking can be achieved during the cooking process.

[0045] In some embodiments, the noble metals include at least one of gold, platinum, palladium, rhodium, and ruthenium. The above types of noble metal elements can reduce the effective temperature for the catalyst to catalytically oxidize and degrade cooking fume grease to 95 °C, and can achieve catalytic oxidation and degradation of cooking fume grease under the conditions of 95 °C - 800 °C. Usually, the cooking temperature is also within the range of 95 °C - 800 °C, so that the purpose of catalytic oxidation and degradation of cooking fume grease generated during cooking can be achieved during the cooking process.

[0046] The nanoscale crystal particles of the manganese dioxide catalyst have a large specific surface area, which can enhance the adsorption of oxygen and prolong the residence time of cooking fume oil stains on the catalyst surface, making the degradation of cooking fume grease more complete.

[0047] It should be noted that the number of the above nanoscale crystal particles is not limited and can be determined according to the particle size and shape of the manganese dioxide catalyst.

[0048] In some embodiments, the size of the crystal particles of the manganese dioxide catalyst is 20 nm - 90 nm. For example, it can be any size value within the range of 20 nm - 90 nm, such as 20 nm, 22 nm, 25 nm, 28 nm, 30 nm, 35 nm, 40 nm, 45 nm, 50 nm, 60 nm, 65 nm, 70 nm, 75 nm, 80 nm, 85 nm, 90 nm, etc. Under the size conditions within the above range, the manganese dioxide catalyst has a large specific surface area, which can enhance the adsorption of oxygen, provide a relatively sufficient oxygen source for the degradation of cooking fume grease, and can prolong the residence time of cooking fume grease on the catalyst surface, making the degradation of cooking fume grease more complete.

[0049] The present invention does not limit the crystal form of the manganese dioxide catalyst. In some embodiments, the crystal form of the manganese dioxide catalyst includes at least one of α-MnO 2 , β-MnO 2 , γ-MnO 2 , ε-MnO 2 , δ-MnO 2 , λ-MnO 2 ; where:

[0050] α-MnO 2The XRD characterization pattern of 2 is rod-shaped or strip-shaped, has a large specific surface area, exposes more crystal grains, prolongs the residence time of the reactant cooking fume grease on the catalyst surface, makes its catalytic oxidation degradation more thorough, reduces the residual accumulation of cooking fume grease after cooking, and makes the cooking utensils easier to clean.

[0051] β-MnO 2 The XRD characterization pattern of 2 is rod-shaped, has a large specific surface area, exposes more crystal grains, prolongs the residence time of the reactant cooking fume grease on the catalyst surface, makes its catalytic oxidation degradation more thorough, reduces the residual accumulation of cooking fume grease after cooking, and makes the cooking utensils easier to clean.

[0052] γ-MnO 2 The XRD characterization pattern of 2 is strip-shaped, has a large specific surface area, exposes more crystal grains, prolongs the residence time of the reactant cooking fume grease on the catalyst surface, makes its catalytic oxidation degradation more thorough, reduces the residual accumulation of cooking fume grease after cooking, and makes the cooking utensils easier to clean.

[0053] ε-MnO 2 The XRD characterization pattern of 2 is spherical, has a large specific surface area, exposes more crystal grains, prolongs the residence time of the reactant cooking fume grease on the catalyst surface, makes its catalytic oxidation degradation more thorough, reduces the residual accumulation of cooking fume grease after cooking, and makes the cooking utensils easier to clean.

[0054] δ-MnO 2 The XRD characterization pattern of 2 is sea urchin-shaped, has a large specific surface area, exposes more crystal grains, prolongs the residence time of the reactant cooking fume grease on the catalyst surface, makes its catalytic oxidation degradation more thorough, reduces the residual accumulation of cooking fume grease after cooking, and makes the cooking utensils easier to clean.

[0055] λ-MnO 2 The XRD characterization pattern of 2 2 λ-MnO has characteristic diffraction peaks at positions of 21.9±0.3°, 37.1±0.3°, and 56.4±0.3°. The morphology of β

[0056] λ-MnO is leaf-shaped or flaky, with a large specific surface area, exposing more crystal grains, increasing the residence time of the reactant cooking fume oil on the catalyst surface, making its catalytic oxidation degradation more thorough, reducing the residual accumulation of cooking fume oil after cooking, and making the cooking utensils easier to clean. β The oxygen atoms in the manganese dioxide catalyst exist in the form of adsorbed oxygen or bound oxygen, that is, the oxygen atoms are composed of adsorbed oxygen and bound oxygen. In some embodiments, calculated by the area characterized by XPS (X-ray photoelectron spectroscopy), the binding energy of adsorbed oxygen (O α ) is at 531.9 eV, and the binding energy of bound oxygen (O β ) is at 530 eV. The adsorbed oxygen (O

[0057] ) accounts for 5%-50% of the total mass of the oxygen atoms, further 5% - 45%, and can be any value in the range of 5%-50% such as 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, etc. The manganese dioxide catalyst of the present invention has a strong adsorption capacity for oxygen, can adsorb a large amount of oxygen for catalytic oxidation of cooking fume oil, and improves the catalytic oxidation degradation efficiency of cooking fume oil.

[0058] In some embodiments, the shape of the manganese dioxide catalyst includes flaky, needle-shaped, rod-shaped, strip-shaped, spherical or sea urchin-shaped. The above types of shapes are more conducive to increasing the specific surface area of the manganese dioxide catalyst, exposing more oxygen vacancies, increasing the adsorption rate of oxygen, and prolonging the residence time of cooking fume oil on the catalyst surface, making the degradation of cooking fume oil more thorough.

[0059] In some embodiments, the width of the flaky manganese dioxide catalyst is 10 nm - 100 μm, and the thickness is 2 nm - 1 μm.

[0060] In some embodiments, the axial length of the rod-shaped or strip-shaped manganese dioxide catalyst is 10 nm - 10 μm, and the radial length is 10 nm - 100 nm.

[0061] In some embodiments, the diameter of the spherical or sea urchin-shaped manganese dioxide catalyst is 200 nm - 800 nm.

[0062] In some embodiments, the specific surface area of the manganese dioxide catalyst ranges from 30 m 2 / g to 500 m 2 / g. For example, it can be 30 m 2 / g, 50 m 2 / g, 80 m 2 / g, 100 m 2 / g, 150 m 2 / g, 200 m 2 / g, 250 m 2 / g, 300 m 2 / g, 350 m 2 / g, 400 m 2 / g, 450 m 2 / g, 480 m 2 / g, 500 m 2 / g, etc., any specific surface area value within the range of 30 m 2 / g to 500 m 2 / g. Within the above range of specific surface areas, more oxygen vacancies can be exposed, the oxygen adsorption rate can be increased, and the residence time of cooking oil fumes on the catalyst surface can be extended, making the degradation of cooking oil fumes and oil stains more complete.

[0063] In some embodiments, the pore volume of the manganese dioxide catalyst is 0.1 cm 3 / g to 1.0 cm 3 / g. For example, it can be 0.1 cm 3 / g, 0.2 cm 3 / g, 0.5 cm 3 / g, 0.6 cm 3 / g, 0.7 cm 3 / g, 0.9 cm 3 / g, 1.0 cm 3 / g, etc., any pore volume value within the range of 0.1 cm 3 / g to 1.0 cm 3 / g.

[0064] In some embodiments, the pore diameter of the manganese dioxide catalyst ranges from 5 nm to 50 nm. For example, it can be 5 nm, 10 nm, 15 nm, 20 nm, 25 nm, 30 nm, 35 nm, 40 nm, 45 nm, 50 nm, etc., any pore diameter value within the range of 5 nm to 50 nm.

[0065] The manganese dioxide catalyst with the above pore volume and pore diameter has a mesoporous structure, and the mesoporous structure is more conducive to improving the oxygen adsorption effect, and can also improve the adhesion effect of the catalyst on cooking oil fumes and extend the residence time of cooking oil fumes and oil stains on the catalyst surface.

[0066] In some embodiments, the mass ratio of manganese element to metal element in the manganese dioxide catalyst is less than or equal to 70:100. Further, the mass ratio of metal element to manganese element in the manganese dioxide catalyst is (1 - 20):100. Still further, specifically, it is any ratio less than or equal to 70:100 such as 70:100, 65:100, 60:100, 55:100, 50:100, 45:100, 40:100, 35:100, 30:100, 25:100, 20:100, 15:100, 10:100, 5:100, 3:100, 2:100, 1:100, 0.5:100, 0.1:100, etc. Within the above ratio range, the purpose of catalytically oxidizing and degrading the cooking fume grease generated during cooking can be achieved, which can maintain the excellent catalytic characteristics of the manganese dioxide catalyst and increase the oxygen active sites of the catalyst.

[0067] The present invention also provides a preparation method of the manganese dioxide catalyst as described above, comprising the following steps:

[0068] Step S10: Mix a reaction solution A containing divalent manganese ions with a solvent to form a mixed solution C;

[0069] Step S20: Make the mixed solution C form a solid precipitate D;

[0070] Step S30: Calcinate the solid precipitate D to obtain a base catalyst;

[0071] Step S40: Mix and ball-mill the base catalyst with an alkali metal source and / or a noble metal source to obtain the manganese dioxide catalyst of the present invention.

[0072] In step S10, the divalent manganese ions are provided by a manganese salt, and the manganese salt can be dissolved in water to obtain a reaction solution A containing manganese ions. The present invention does not limit the type of the above manganese salt. In some embodiments, the manganese salt includes at least one of manganese nitrate, manganese sulfate, manganese chloride, and potassium permanganate. The above types of manganese salts can form divalent manganese ions in a solution state, which is beneficial to obtaining a manganese dioxide catalyst with a nano-polycrystalline structure in subsequent preparation.

[0073] In some embodiments of step S10, the solvent includes at least one of potassium permanganate, nitric acid, ammonium sulfite, ammonia water, and ethylene glycol. The above solvents are beneficial to helping the reactant solution A form a better-shaped nano-polycrystalline structure during calcination, obtaining more oxygen vacancies, and increasing the oxygen adsorption amount of the catalyst.

[0074] In some embodiments, the reaction solution A can be mixed with potassium permanganate and concentrated nitric acid to form a mixed solution C, which is beneficial to obtaining a manganese dioxide catalyst with a crystal form of α-MnO 2 2.

[0075] In some embodiments, reaction solution A can be mixed with ammonium sulfite and ammonia water, and the pH of the system can be adjusted to be alkaline to form mixed solution C. In one embodiment, the pH can be 8, 9, 10, 11, etc., which is beneficial to obtaining a crystal form of λ-MnO 2 .

[0076] In some embodiments, reaction solution A can be mixed with potassium permanganate to form mixed solution C, which is beneficial to obtaining a crystal form of δ-MnO 2 manganese dioxide catalyst.

[0077] In some embodiments, potassium permanganate can be dissolved and then added dropwise to reaction solution A to form mixed solution C, which is beneficial to obtaining a crystal form of β-MnO 2 manganese dioxide catalyst.

[0078] In some embodiments, the mixing of reaction solution A and the solvent can be promoted under stirring conditions, and the stirring speed can be 500 rpm - 1500 rpm.

[0079] In step S20, there is no limitation on the method of forming solid precipitate D from mixed solution C. When there is more liquid in mixed solution C, the drying method can be selected to obtain solid precipitate D. For example, mixed solution C can be dried at 90°C - 250°C to obtain solid precipitate D. In some embodiments, the drying temperature can be 90°C, 100°C, 120°C, 130°C, 150°C, 160°C, 180°C, 200°C, 230°C, 250°C, etc.

[0080] In some embodiments, when there is less liquid in mixed solution C, the static method can be selected to make mixed solution C form solid precipitate D, and the static time can be 12 h, 24 h, 48 h, etc.

[0081] Roasting solid precipitate D in step S30 can promote the reaction of divalent manganese ions to form a basic catalyst with a nano-polycrystalline structure, making the final product manganese dioxide catalyst have a nano-polycrystalline structure, providing a large specific surface area, thereby enhancing the adsorption of oxygen and prolonging the residence time of oil fume and oil stains on the catalyst surface, making the degradation of oil fume and grease more thorough.

[0082] In some embodiments, the calcination temperature of the precipitate D is 450°C - 650°C, and the calcination time is 2h - 6h. Specifically, the calcination temperature can be any value within the range of 450°C - 650°C, such as 450°C, 500°C, 550°C, 600°C, 650°C, etc.; the calcination time can be any value within the range of 2h - 6h, such as 2h, 3h, 3.5h, 4h, 4.5h, 5h, 5.5h, 6h, etc. Under the above calcination conditions, it can promote the formation of a manganese dioxide catalyst with a nano-polycrystalline structure from ionic reactants, increase the content of oxygen vacancies in the catalyst, and increase the oxygen adsorption capacity.

[0083] The manganese dioxide catalyst obtained by calcination can be in powder form, or in block or granular form, and then processed into powder form later. The powdered manganese dioxide catalyst is more conducive to spraying into a uniform thermal catalytic coating.

[0084] In step S40, by means of ball milling, the alkali metal elements in the alkali metal source and the noble metal elements in the noble metal source can be doped into the crystal lattice of the manganese dioxide catalyst without destroying the nano-polycrystalline structure of the manganese dioxide catalyst itself. The manganese dioxide catalyst retains the nano-polycrystalline structure, has a large specific surface area, and also has a large number of oxygen vacancies endowed by alkali metals and / or noble metals, which can increase the proportion of adsorbed oxygen in the catalyst, provide a sufficient oxygen source for the catalytic degradation of cooking oil fumes, improve the catalytic oxidation effect on cooking oil fumes, and reduce the effective temperature of catalytic oxidation degradation to 95°C, and has a good catalytic oxidation degradation effect at 95°C - 800°C, covering the conventional cooking temperature range, and can achieve the purpose of catalytically oxidizing and degrading the cooking fumes and oil stains generated during cooking into carbon dioxide and water, reducing the accumulation of oil stains after cooking, and making the cooking utensils easier to clean.

[0085] In some embodiments, the ball milling time is 6 - 10h, and can be any time value within 6 - 10h, such as 6h, 7h, 8h, 9h, 10h, etc. Within the above ball milling time, the success rate of doping noble metals and / or alkali metals into the crystal lattice of the manganese dioxide catalyst is relatively high, and it is not easy to destroy the nano-polycrystalline structure of the manganese dioxide catalyst.

[0086] In some embodiments, the alkali metal source includes at least one of potassium hydroxide, calcium(II) oxide, magnesium(II) oxide, aluminum(III) oxide, zinc(II) oxide, copper(II) oxide, iron(III) oxide, cerium(III) dioxide, cobalt(III) oxide, titanium(IV) dioxide, zirconium acetate, vanadium(IV) oxide, nickel(II) oxide, lanthanum(III) oxide or tungstic acid. The above types of alkali metal sources and manganese dioxide catalysts are prone to allowing alkali metal elements to enter the crystal lattice of the manganese dioxide catalyst under ball milling conditions.

[0087] In some embodiments, the noble metal source includes at least one of chloroplatinic acid, ammonium tetrachloroaurate (II), palladium(III) chloride, rhodium(III) acetate, ruthenium(III) acetate, and silver(II) nitrate. The noble metal sources of the above types and the manganese dioxide catalyst are liable to introduce alkali metal elements into the lattice of the manganese dioxide catalyst under ball milling conditions. It should be noted that when the metal source includes the above noble metal sources, after ball milling is completed, the final product manganese dioxide catalyst can be obtained by calcination at 600 °C - 900 °C.

[0088] The manganese dioxide catalyst of the present invention can also be applied to cooking utensils. The catalyst is coated on the surface of the cooking utensil that is liable to be stained with cooking fumes and oil stains to form a catalytic coating. Using the heat generated during cooking as the catalytic heat source, the oxygen vacancies of the catalyst adsorb oxygen in the air to provide an oxygen source, promoting the oxidative degradation of the cooking fumes and oils and fats, which are finally degraded into carbon dioxide and water. Moreover, the effective temperature of the catalyst can reach below 100 °C, and it can catalyze the degradation of cooking fumes and oils and fats at 95 °C, achieving the purpose of timely degrading cooking fumes and oils and fats during cooking, ensuring that there is no oil deposition and residue in the cavity after cooking, avoiding the pain point of difficult cleaning inside the cavity, and without additional energy consumption. It can not only reduce environmental pollution, reduce the harm to people's health, but also reduce the accumulation of oil stains, making the cooking utensil easy to clean. Especially for cooking utensils with a compact structure design, a closed space, and extremely easy to form cleaning dead corners inside the cooking cavity, it can solve many problems brought by difficult daily hygiene cleaning, and reduce the breeding of bacteria and carcinogenic risks on the surface of the cooking utensil.

[0089] Using the catalyst of the present invention to catalytically degrade cooking fumes and oil stains for cleaning purposes, compared with traditional adsorption methods, the catalyst can be reused without increasing the cost of replacing consumables, greatly reducing the use cost. In addition, the preparation process of the catalyst of the present invention is simple, easy to operate, and has a low cost, with broad application prospects. During the process of using the catalyst of the present invention to purify cooking fumes and oils and fats, the catalyst can effectively decompose cooking fumes and oils and fats, making the surface of the cooking utensil free from cleaning, reducing the cleaning cost, and at the same time reducing the environmental pollution caused by cleaning. Therefore, the present invention has important practical significance and application value, and can be widely applied in the cooking industry to contribute to people's health and quality of life.

[0090] The technical solutions of the present invention will be further described in detail below in conjunction with specific embodiments. It should be understood that the following specific embodiments are only used to explain the present invention and are not used to limit the present invention.

[0091] Example 1

[0092] Step S10: Dissolve the manganese salt in water to form reaction solution A containing divalent manganese ions. Under the stirring condition of 500 rpm - 1500 rpm, add potassium permanganate and concentrated nitric acid to reaction solution A to form mixed solution C.

[0093] Step S20: Place mixed solution C in an oven and dry it at 90 - 130 °C to obtain solid precipitate D.

[0094] Step S30: Place solid precipitate D in a muffle furnace and calcine it at 450 °C - 650 °C to obtain an α-MnO 2 crystal form basic catalyst.

[0095] Step S40: Mix the basic catalyst with a noble metal and / or an alkali metal source, and perform ball milling for 6 h - 10 h to obtain a manganese dioxide catalyst. The types and doping amounts of the doped metal elements are shown in Table 2. When the doped metal source includes a noble metal, after ball milling for 6 h - 10 h, continue to calcine it at 600 °C - 900 °C to obtain a manganese dioxide catalyst with a crystal form of α-MnO 2 。

[0096] Comparative Example 1

[0097] Comparative Example 1 prepares an α-MnO 2 crystal form basic catalyst with no metal element doping.

[0098] Example 2

[0099] Step S10: Dissolve the manganese salt in water to form reaction solution A1 containing divalent manganese ions. Under the stirring condition of 500 rpm - 1500 rpm, add potassium permanganate and concentrated nitric acid to reaction solution A to form mixed solution C.

[0100] Step S20: Place mixed solution C in an oven and dry it at 90 - 130 °C to obtain solid precipitate D.

[0101] Step S30: Place solid precipitate D in a muffle furnace and calcine it at 450 °C - 650 °C to obtain a β-MnO 2 crystal form basic catalyst.

[0102] Step S40: Mix the basic catalyst with a noble metal and / or an alkali metal source, and perform ball milling for 6 h - 10 h to obtain a manganese dioxide catalyst. The types and doping amounts of the doped metal elements are shown in Table 1. When the doped metal source includes a noble metal, after ball milling for 6 h - 10 h, continue to calcine it at 600 °C - 900 °C to obtain a manganese dioxide catalyst with a crystal form of β-MnO 2 。

[0103] Comparative Example 2

[0104] Comparative Example 2: Referring to Example 2, β-MnO 2 crystalline basic catalyst was prepared without doping with metal elements.

[0105] Example 3

[0106] Step S10: Dissolve the manganese salt in water to form a reaction solution A containing divalent manganese ions, and add potassium permanganate and concentrated nitric acid to the reaction solution A under stirring conditions of 500 rpm - 1500 rpm to form a mixed solution C.

[0107] Step S20: Place the mixed solution C in an oven and dry it at 90 - 130 °C to obtain a solid precipitate D.

[0108] Step S30: Place the solid precipitate D in a muffle furnace and calcine it at 450 °C - 650 °C to obtain γ-MnO 2 crystalline manganese dioxide catalyst.

[0109] Step S40: Mix the basic catalyst with the noble metal and / or alkali metal source, and perform ball milling for 6 h - 10 h to obtain a manganese dioxide catalyst. The types and amounts of the doped metal elements are shown in Table 2. When the doped metal source includes a noble metal, after ball milling for 6 h - 10 h, continue to calcine it at 600 °C - 900 °C to obtain a manganese dioxide catalyst with a crystal form of γ-MnO 2 .

[0110] Comparative Example 3

[0111] Comparative Example 3: Referring to Example 3, γ-MnO 2 crystalline basic catalyst was prepared without doping with metal elements.

[0112] Example 4

[0113] Step S10: Dissolve the manganese salt in water to form a reaction solution A containing divalent manganese ions, and add potassium permanganate and concentrated nitric acid to the reaction solution A under stirring conditions of 500 rpm - 1500 rpm to form a mixed solution C.

[0114] Step S20: Place the mixed solution C in an oven and dry it at 90 - 130 °C to obtain a solid precipitate D.

[0115] Step S30: Place the solid precipitate D1 in a muffle furnace and calcine it at 450 °C - 650 °C to obtain ε-MnO 2 crystalline manganese dioxide catalyst.

[0116] Step S40: The base catalyst is mixed with a noble metal and / or an alkali metal source, and a manganese dioxide catalyst is obtained through ball milling for 6 h - 10 h. The types and amounts of the doped metal elements are shown in Table 2. When the doped metal source includes a noble metal, after ball milling for 6 h - 10 h, it is further calcined at 600°C - 900°C to obtain a manganese dioxide catalyst with a crystal form of ε-MnO 2 。

[0117] Comparative Example 4

[0118] Comparative Example 4 was prepared by referring to Example 4 to obtain an ε-MnO 2 crystal form base catalyst without doping metal elements.

[0119] Example 5

[0120] Step S10: Dissolve the manganese salt in water to form a reaction solution A containing divalent manganese ions. Under the stirring condition of 500 rpm - 1500 rpm, add potassium permanganate and concentrated nitric acid to the reaction solution A to form a mixed solution C.

[0121] Step S20: Place the mixed solution C in an oven and dry it at 90 - 130°C to obtain a solid precipitate D.

[0122] Step S30: Place the solid precipitate D in a muffle furnace and calcine it at 450°C - 650°C to obtain a δ-MnO 2 crystal form base catalyst.

[0123] Step S40: The base catalyst is mixed with a noble metal and / or an alkali metal source, and a manganese dioxide catalyst is obtained through ball milling for 6 h - 10 h. The types and amounts of the doped metal elements are shown in Table 2. The manganese dioxide catalyst is obtained by calcination under the given conditions, and the crystal form is δ-MnO 2 。

[0124] Comparative Example 5 was prepared by referring to Example 4 to obtain a δ-MnO 2 crystal form base catalyst without doping metal elements.

[0125] Example 6

[0126] Step S10: Dissolve the manganese salt in water to form a reaction solution A containing divalent manganese ions. Under the stirring condition of 500 rpm - 1500 rpm, add potassium permanganate and concentrated nitric acid to the reaction solution A to form a mixed solution C.

[0127] Step S20: Place the mixed solution C in an oven and dry it at 90 - 130°C to obtain a solid precipitate D.

[0128] Step S30: Place the solid precipitate D in a muffle furnace and calcine it at 450°C - 650°C to obtain a λ-MnO 2 crystalline form-based catalyst.

[0129] Step S40: Mix the base catalyst with a noble metal and / or an alkali metal source, and perform ball milling for 6 h - 10 h to obtain a manganese dioxide catalyst. The types and doping amounts of the doped metal elements are shown in Table 2. When the doped metal source includes a noble metal, after ball milling for 6 h - 10 h, continue to calcine it at 600°C - 900°C to obtain a manganese dioxide catalyst with a crystalline form of λ-MnO 2 .

[0130] Comparative Example 6

[0131] Comparative Example 6 was prepared by referring to Example 6 to obtain a λ-MnO 2 crystalline form-based catalyst without doping metal elements.

[0132] Example 7

[0133] Prepare a composite manganese dioxide catalyst

[0134] Mix 1 g of the γ-MnO 2 crystalline form-based catalyst in Example 3 and 1 g of the λ-MnO 2 crystalline form-based catalyst in Example 6 evenly to form a composite base catalyst. Mix the composite base catalyst with a noble metal and / or an alkali metal source, and perform ball milling to obtain a composite manganese dioxide catalyst. The types and doping amounts of the doped metal elements are shown in Table 2.

[0135] Comparative Example 7 was prepared by referring to Example 7 to obtain a composite γ-MnO 2 crystalline form-based catalyst without doping metal elements.

[0136] Performance test

[0137] 1. Characterize the manganese dioxide catalyst in Example 3 using a scanning electron microscope to observe its morphology. Among them, the characterization diagram of Example 3 is shown in Figure 1 .

[0138] It can be seen from Figure 1 that the manganese dioxide catalyst in Example 3 has nano-crystalline particles with two morphologies of sheet-like and leaf-like. The catalyst particles with sheet-like and leaf-like morphologies have a large specific surface area. A catalyst with a large specific surface area can increase the residence time of the reactant cooking oil fumes on the catalyst surface, making its reaction degradation more complete and reducing the accumulation of cooking oil fumes on the cooking utensils after cooking.

[0139] 2. Measure the average particle size and specific surface area of the crystal grains of the manganese dioxide catalysts obtained in Examples 1 to 6. The results are shown in Table 2.

[0140] 3. The manganese dioxide catalysts of Examples 1 to 7 were characterized by an XPS diffractometer, and the adsorbed oxygen content of the catalysts was measured by area. The results are shown in Table 3. Among them, the characterization diagram of the manganese dioxide catalyst of Example 3 is shown in Figure 2 .

[0141] It can be seen from Figure 2 that for the manganese dioxide catalyst of Example 3, the adsorbed oxygen is at 529.9 ± 0.5 eV, and the combined oxygen is at 531.9 ± 0.5 eV. The content of adsorbed oxygen can reflect the number of oxygen vacancies on the catalyst surface.

[0142] 4. The catalytic oxidation degradation onset temperatures of the manganese dioxide catalysts obtained in Examples 1 to 7 were measured. The results are shown in Table 3. The components of cooking fume grease include alkanes, ketones, aromatic hydrocarbons, polycyclic aromatic hydrocarbons, aromatic amines, nitro polycyclic aromatic hydrocarbons, etc. In this test item, toluene was taken as an example. 0.2 g of different manganese dioxide catalysts were placed in 1000 ppm of toluene, and the concentration of toluene before and after the reaction was detected by a gas chromatograph. The ignition temperature is the temperature at which toluene starts to react.

[0143] Table 1

[0144] Experimental group Crystal form Catalyst morphology Average grain size (nm) <![CDATA[Specific surface area (m 3 / g)]]> Example 1 <![CDATA[λ-MnO 2 > Leaf-like, flaky 60 296 Example 2 <![CDATA[α-MnO 2 > Striped 86 107 Example 3 <![CDATA[β-MnO 2 > Rod-shaped 55 211 Example 4 <![CDATA[γ-MnO 2 > Striped 14 165 Example 5 <![CDATA[ε-MnO 2 > Spherical 3 84 Example 6 <![CDATA[δ-MnO 2 > Sea urchin-like 12 251

[0145] Table 2

[0146]

[0147]

[0148] It can be seen from Table 1 that the average sizes of the crystal grains of the manganese dioxide catalysts obtained in Examples 1 to 6 are all at the nanometer level, and the specific surface area is small.

[0149] It can be seen from Table 3 that the manganese dioxide catalysts of this example are doped with alkali metals and / or noble metal elements in the crystal lattice, have abundant highly active oxygen vacancies, strong oxygen adsorption capacity, improve the proportion of adsorbed oxygen in the catalyst, continuously provide sufficient oxygen sources for the catalytic oxidation degradation of cooking fume grease, and can catalyze and oxidize and degrade cooking fume grease at a relatively low temperature condition, enabling the oxidation degradation of cooking fume grease generated during cooking, making the cooking utensils easier to clean. Moreover, the manganese dioxide catalyst obtained by doping noble metals and / or alkali metal elements in the crystal lattice of the manganese dioxide catalyst also obtains a large number of oxygen vacancies with abundant activity, and the onset temperature for the catalytic oxidation degradation of cooking fume grease can be reduced to 95 °C.

[0150] The base catalysts of Comparative Examples 1 to 7 were not doped with alkali metals and / or noble metal elements, failed to provide a large number of oxygen vacancies with high activity, had relatively weak oxygen adsorption ability, a relatively low proportion of adsorbed oxygen in the catalyst, a relatively high light-off temperature, and relatively poor catalytic effects.

[0151] The above are only the preferred embodiments of the present invention, and do not limit the patent scope of the present invention accordingly. Any equivalent structural or equivalent process transformation made by using the content of the specification and drawings of the present invention, or directly or indirectly applied in other related technical fields, shall be equally included in the patent protection scope of the present invention.

Claims

1. A manganese dioxide catalyst, characterized in that, the manganese dioxide catalyst has a nano-polycrystalline structure, the nano-polycrystalline structure is composed of nano-scale crystal grains, and alkali metals and / or noble metals are doped in the lattice of the nano-polycrystalline structure of the manganese dioxide catalyst.

2. The manganese dioxide catalyst according to claim 1, characterized in that, the alkali metals include one or more of potassium, calcium, magnesium, aluminum, zinc, copper, iron, cerium, cobalt, titanium, zirconium, nickel, vanadium, lanthanum, tungsten; and / or, the noble metals include at least one of gold, platinum, palladium, rhodium, ruthenium; and / or, the length of a single crystal grain of the crystal grains of the manganese dioxide catalyst is 20 nm - 90 nm.

3. The manganese dioxide catalyst according to claim 1, characterized in that, The crystal forms of the manganese dioxide catalyst include α-MnO 2 , β-MnO 2 , γ-MnO 2 , ε-MnO 2 , δ-MnO 2 , λ-MnO 2 and at least one of them.

4. The manganese dioxide catalyst according to claim 1, characterized in that, In the manganese dioxide catalyst, the oxygen atoms consist of adsorbed oxygen (O β ) and bound oxygen (O α ). Calculated by the area characterized by XPS, the adsorbed oxygen (O β ) accounts for 5% - 50% of the total mass of the oxygen atoms.

5. The manganese dioxide catalyst according to claim 4, characterized in that, The binding energy of the adsorbed oxygen (O β ) is at 531.9 eV, and the binding energy of the combined oxygen (O α ) is at 530 eV.

6. The manganese dioxide catalyst according to claim 1, characterized in that, the shape of the manganese dioxide catalyst includes one or a combination of several of sheet-like, needle-like, rod-like, strip-like, spherical or sea urchin-like.

7. The manganese dioxide catalyst according to claim 6, characterized in that, the width of the sheet-like manganese dioxide catalyst is 10 nm - 100 μm, and the thickness is 2 nm - 1 μm; and / or, the width of the needle-like manganese dioxide catalyst is 10 nm - 100 μm, and the thickness is 2 nm - 1 μm; and / or, the axial length of the rod-like or strip-like manganese dioxide catalyst is 10 nm - 10 μm, and the radial length is 10 nm - 100 nm; and / or, the diameter of the spherical or sea urchin-like manganese dioxide catalyst is 200 nm - 800 nm.

8. The manganese dioxide catalyst according to claim 1, characterized in that, The specific surface area of the manganese dioxide catalyst ranges from 30 m 2 / g to 500 m 2 / g; and / or, the pore volume of the manganese dioxide catalyst is 0.1 cm 3 / g - 1.0 cm 3 / g; and / or, the pore size range of the manganese dioxide catalyst is 5 nm - 50 nm.

9. The manganese dioxide catalyst according to claim 1, characterized in that, the mass ratio of manganese element to metal element in the manganese dioxide catalyst is less than or equal to 70:

100.

10. The manganese dioxide catalyst according to claim 1, characterized in that, the mass ratio of manganese element to metal element in the manganese dioxide catalyst is (1 - 20):

100.

11. A preparation method of the manganese dioxide catalyst according to any one of claims 1 to 10, characterized in that, comprises the following steps: Mixing a reaction solution A containing divalent manganese ions and a solvent to form a mixed solution C; Making the mixed solution C form a solid precipitate D; Roasting the solid precipitate D to obtain a base catalyst; Mixing and ball-milling the base catalyst with an alkali metal source and / or a noble metal source to obtain the manganese dioxide catalyst.

12. The preparation method of the manganese dioxide catalyst according to claim 11, characterized in that, The alkali metal source includes at least one of potassium hydroxide, calcium(II) oxide, magnesium(II) oxide, aluminum(III) oxide, zinc(II) oxide, copper(II) oxide, iron(III) oxide, cerium(III) dioxide, cobalt(III) oxide, titanium(IV) dioxide, zirconium acetate, vanadium(IV) oxide, nickel(II) oxide, lanthanum(III) oxide or tungstic acid; And / or, the noble metal source includes at least one of chloroplatinic acid, ammonium tetrachloroaurate(II), palladium(III) chloride, rhodium(III) acetate, ruthenium(III) acetate, silver(II) nitrate.

13. Use of the manganese-based thermal catalyst according to any one of claims 1 to 10 in degrading cooking fume oil pollutants.

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