Preparation method and application of copper-manganese composite monolithic metal substrate catalyst

Abstract

The application belongs to the field of catalyst material preparation, and particularly relates to a preparation method of a metal oxide monolithic catalyst and application thereof. The metal oxide monolithic catalyst is prepared by hydrothermally loading copper-manganese composite oxides on a foam metal substrate. The surface of the catalyst prepared by the method can form an oxide heterojunction interface. The oxide heterojunction interface activates ozone by electron delocalization, generates high-activity oxygen species, and can reduce the activation energy required for the reaction under the condition of no high temperature and high pressure. Meanwhile, the monolithic composite metal oxide catalyst is pretreated by hydrogen peroxide, which can form a multi-level structure on the surface of the substrate, and the treatment of the surfactant can greatly promote the adsorption of organic pollutants.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of catalyst material preparation, in particular to a preparation method of copper-manganese composite monolithic metal substrate catalyst and application thereof. BACKGROUND

[0002] In a closed environment, monolithic catalysts can be designed to integrate various technologies for different gas pollutants. Although adsorption can reduce the concentration of pollutants to within the national regulations, it often takes a long time, and after saturation, some pollutants may be released to cause secondary pollution to the environment. The adsorbents on the market are mostly disposable goods, which are difficult to achieve long-term cyclic use. Chemical degradation is considered to be the most promising treatment technology due to its high efficiency, environmental friendliness, and versatility. Chemical degradation completely converts VOCs into water and carbon dioxide with less public health risk, usually uses heat, electricity, light, and other external energy to degrade pollutants in cooperation with metal catalysts, so the energy consumption is usually high. In order to reduce the cost of external energy in the chemical degradation process, it is necessary to improve the performance of the catalyst to achieve the removal of pollutants at low temperature. However, there are many difficulties in the low-temperature degradation of VOCs in a closed environment, especially the feature that the triplet oxygen as an oxidant is difficult to dissociate into active oxygen species at low temperature, which limits many reactions at low temperature.

[0003] Therefore, there is an urgent need for a catalyst that can deeply convert indoor pollutants at low temperature. SUMMARY

[0004] Therefore, the present application provides a preparation method of copper-manganese composite monolithic metal substrate catalyst, which comprises:

[0005] A. Potassium permanganate and glucose are dissolved in water to perform a redox reaction to obtain a precursor solution;

[0006] B. Copper salt is added to the precursor solution and stirred uniformly to obtain a precursor turbid solution;

[0007] C. Foam metal is placed in the precursor turbid solution in step B to perform a hydrothermal reaction to obtain a precursor material containing copper-manganese composite oxides;

[0008] D. The precursor material is soaked in a surfactant for hydrophobic treatment;

[0009] E. The precursor material after hydrophobic treatment in step D is subjected to air calcination treatment to obtain a copper-manganese composite monolithic metal substrate monolithic catalyst.

[0010] According to a specific embodiment of the present application, in step A, the mass ratio of the potassium permanganate to the glucose is (0.5-1):1, and the pH of the precursor solution is 6-8.

[0011] According to a specific embodiment of the present application, in step B, the copper salt comprises copper nitrate and / or copper sulfate.

[0012] According to a specific embodiment of the present application, the stirring time is 1-5h, the pH of the precursor turbid solution is 6-8, and the mass ratio of the potassium permanganate to the glucose, the copper salt is (0.5-1):1:(0.08-0.12).

[0013] According to a specific embodiment of the present application, in step C, the foamed metal is foamed metal pre-treated by hydrogen peroxide.

[0014] The foamed metal is selected from foamed nickel and / or foamed copper.

[0015] The hydrothermal reaction is carried out in a hydrothermal kettle, and the reaction temperature during the hydrothermal reaction is 120-170℃, and the reaction time is 8-12h.

[0016] After step C, further comprising sequentially filtering, washing, and drying the precursor material, and the drying temperature is 60-80℃, and the time is 10-12h.

[0017] According to a specific embodiment of the present application, in step D, the surfactant comprises at least one of hexadecyl trimethoxysilane toluene and sodium hexadecyl benzene sulfonate.

[0018] According to a specific embodiment of the present application, the surfactant is hexadecyl trimethoxysilane toluene, the concentration of the hexadecyl trimethoxysilane toluene is (45-60)g / L, and the hydrophobic treatment time is 1-3h.

[0019] According to a specific embodiment of the present application, in step E, the air calcination treatment temperature is 240-500℃, and the calcination time is 2-4h.

[0020] According to a specific embodiment of the present application, the mass percentage of copper atoms in the copper salt in the copper-manganese composite oxide is 4-7%.

[0021] According to a specific embodiment of the present application, the mass percentage of the copper-manganese composite oxide in the copper-manganese composite monolithic metal-based catalyst is 4.5-6.5%.

[0022] The second aspect of the present application provides a copper-manganese composite monolithic metal substrate catalyst prepared by the method of the first aspect, which is used for ozone-assisted catalytic oxidation reaction.

[0023] The third aspect of the present application provides the use of the copper-manganese composite monolithic metal substrate catalyst of the second aspect in the preparation of an air purifier.

[0024] The fourth aspect of the present application provides an air purifier containing the copper-manganese composite monolithic metal substrate catalyst of the second aspect.

[0025] According to a specific embodiment of the present application, the air purifier further comprises at least one of a filter screen, a fan, an adsorption plate, an ozone generator, an air duct, a catalytic cabin, a heat exchange plate, and an air outlet.

[0026] The fifth aspect of the present application provides the use of the copper-manganese composite monolithic metal substrate catalyst of the second aspect and the air purifier of the fourth aspect in the conversion of formaldehyde, propane, toluene, chloroform, acetone, or ozone.

[0027] The present application designs a monolithic composite metal oxide catalyst, which activates ozone by using the electron delocalization effect of oxide heterojunction, generates highly active oxygen species, and converts gaseous pollutants existing in a closed space at low temperature. Meanwhile, the multi-level pores and surface hydrophobic structure of the monolithic composite metal oxide catalyst can greatly promote the adsorption of organic pollutants and reduce the competitive adsorption of water vapor, the strong ozone activation capacity can avoid secondary pollution caused by ozone overflow, and the indoor pollutants can be converted with high efficiency and low cost. Considering the limited characteristics of the closed space, the monolithic catalyst has the characteristics of simple operation and easy replacement, and a closed space integrated air purification device is assembled based on the strategy of the composite metal oxide catalyst. In summary, the present application prepares a low-cost monolithic catalyst material that can truly realize air purification in a closed space, and assembles a closed space integrated air purification device that operates based on the catalytic technology.

[0028] In the prior art, the required activation energy is high when a catalyst is used for gaseous pollutant conversion, and the person skilled in the art usually reduces the required activation energy by heating or pressurizing. The surface of the catalyst prepared by the method of the present application can form an oxide heterojunction, which activates ozone by using the electron delocalization effect of the oxide heterojunction, generates highly active oxygen species, and reduces the required activation energy without high temperature and high pressure. Meanwhile, the monolithic composite metal oxide catalyst is pretreated with hydrogen peroxide to form a multi-level structure on the surface of the substrate, and the treatment of the surfactant can greatly promote the adsorption of organic pollutants. Therefore, the catalyst obtained by the present application has high catalytic activity for gaseous pollutants in a lower temperature range. Compared with the prior art, the present application has the following beneficial effects:

[0029] (1) CMO-MO-NF catalyst, in the presence of 5% water vapor, the conversion rates of formaldehyde, propane, toluene, chloroform and acetone at low temperature (60℃) are 100%, 96%, 98%, 90% and 97% respectively, and the stability is up to 100h or more;

[0030] (2) The oxidation effect of the monolithic catalyst provided in the application is better than that of the traditional powder catalyst, and the preparation process is simple, the operation is convenient, the cost is low, the conversion rate of gas pollutants is high, the operation stability is strong, and the monolithic catalyst has obvious industrial application value;

[0031] (3) The composite metal oxide catalyst in the application is used for catalytic oxidation reaction in cooperation with ozone, has strong ozone decomposition capacity, and the monolithic characteristic facilitates application in a closed space;

[0032] (4) The closed space air purification device in the application has low cost, easy assembly, light weight, environmental protection, small volume, does not produce secondary pollution, greatly meets the air purification demand of the closed space, and improves the comfort and health level of personnel. BRIEF DESCRIPTION OF DRAWINGS

[0033] In order to more clearly illustrate the technical solutions in the embodiments of the application or the prior art, the drawings needed to be used in the embodiment or the prior art description will be briefly introduced. Obviously, the drawings in the following description are only some embodiments of the application, and other drawings can be obtained by those skilled in the art without creative labor.

[0034] Figure 1 The monolithic composite metal oxide catalyst (CMO-MO-NF) and the manganese-based catalyst (MO-N) in the application comparative example 1 were tested for formaldehyde conversion durability at low temperature;

[0035] Figure 2 The monolithic composite metal oxide catalyst (CMO-MO-NF) and the manganese-based catalyst (MO-N) in the application comparative example 1 were tested for propane conversion durability at low temperature;

[0036] Figure 3 The monolithic composite metal oxide catalyst (CMO-MO-NF) and the manganese-based catalyst (MO-N) in the application comparative example 1 were tested for toluene conversion durability at low temperature;

[0037] Figure 4 The monolithic composite metal oxide catalyst (CMO-MO-NF) and the manganese-based catalyst (MO-N) in the application comparative example 1 were tested for chloroform conversion durability at low temperature;

[0038] Figure 5 The durability test of the monolithic composite metal oxide catalyst (CMO-MO-NF) and the manganese-based catalyst (MO-N) prepared in Comparative Example 1 of the present application at low temperature for the conversion of acetone;

[0039] Figure 6 The durability test of the monolithic composite metal oxide catalyst (CMO-MO-NF) and the manganese-based catalyst (MO-N) prepared in Comparative Example 1 of the present application at low temperature for the conversion of ozone;

[0040] Figure 7 The CMO-MO-NF prepared in Example 1 of the present application showed Cu 1.5 Mn 1.5 O4(PDF#35-1172) and Mn2O3(PDF#41-1442) characteristic diffraction;

[0041] Figure 8 The general transmission electron microscope images of the catalysts prepared in Example 1 and Comparative Example 1 of the present application, wherein a figure and c figure respectively represent the electron microscope structure images of the catalyst prepared in Comparative Example 1 at different magnifications; b figure and d figure respectively represent the electron microscope structure images of the catalyst prepared in Example 1 at different magnifications;

[0042] Figure 9 The Cu atomic mass ratio exploration result figure in Comparative Example 3 of the present application;

[0043] Figure 10 The cross-sectional schematic diagram of the air purifier assembled in Example 4 of the present application. DETAILED DESCRIPTION

[0044] The embodiments of the present application are described in detail below, examples of which are shown in the accompanying drawings. The embodiments described below by referring to the accompanying drawings are exemplary, and are intended to explain the present application, and cannot be understood as a limitation of the present application.

[0045] It should be noted that the terms "first", "second" are only used for the purpose of description, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined with "first", "second" can explicitly or implicitly include one or more of the features. Further, in the description of the present application, unless otherwise specified, the meaning of "a plurality of" is two or more.

[0046] In this document, the terms "containing", "including" or "comprising" are open expressions, i.e. including the contents indicated in the present application, but not excluding other aspects.

[0047] In this document, the terms "optionally," "optional," or "may" generally mean that the subsequently described event or circumstance can or can not occur, and the description includes instances where the event or circumstance occurs, and instances where it does not.

[0048] To make the technical means, creative features, purposes and effects realized by the present application easy to understand, the present application provides drawings which are part of the disclosure of the present application, mainly used to illustrate the embodiments, and can explain the operation principle of the embodiments in conjunction with the related description of the specification. By referring to these contents, those skilled in the art should be able to understand other possible implementation manners and advantages of the present application.

[0049] The technical solutions in the embodiments of the present application will be described clearly and completely below in conjunction with the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application.

[0050] Preparation of the monolithic catalyst of Example 1

[0051] 1. Pretreatment of the foam metal:

[0052] The cut foam metal piece was placed in a 30% hydrogen peroxide aqueous solution for 1-2 hours.

[0053] 2. Preparation of the precursor:

[0054] (1) 0.79 g of potassium permanganate and 1.00 g of glucose were dissolved in 50 mL of deionized water, and stirred for 1-2 hours;

[0055] (2) The solution obtained in step (1) was added to 0.1 g of copper nitrate solid, and stirred for 3-4 hours to obtain a precursor turbid solution;

[0056] (3) The foam metal carrier obtained by pretreatment was placed in the solution obtained in (2) and transferred to the oven of an autoclave, and kept at 150°C for 10 hours, and then filtered, washed, and dried;

[0057] (4) 0.4 g of the precursor material obtained in step (3) was immersed in a 50 g / L hexadecyltrimethoxysilane toluene solution and stirred for 1-2 hours, and then centrifuged, washed, and dried.

[0058] 3. Calcination:

[0059] The prepared precursor was calcined at 250°C in air for 3 hours to obtain a monolithic catalyst named CMO-MO-NF.

[0060] Comparative Example 1

[0061] The difference from Example 1 is that the Mn2O3 solution obtained in step (1) is directly subjected to hydrothermal reaction with the foam metal carrier in the preparation of the precursor, i.e., pure Mn2O3 without copper doping modification is loaded on the foam metal to prepare (step 2 is removed), and the final monolithic catalyst is named MO-NF.

[0062] The conversion rates of pollutants at low temperature conditions of Example 1 and Comparative Example 1 are determined:

[0063] The packing volume of CMO-MO-NF and MO-NF is 10*10 cm -3 , the initial gas concentration is 100 ppb of formaldehyde, 10 ppm of ozone, 20 vol% of oxygen, 5% of water content, nitrogen as the carrier gas, and the volume space velocity is 10,000 h -1 ; the initial gas concentration is 120 ppb of propane, 10 ppm of ozone, 20 vol% of oxygen, 5% of water content, nitrogen as the carrier gas, and the volume space velocity is 10,000 h -1 ; the initial gas concentration is 200 ppb of toluene, 10 ppm of ozone, 20 vol% of oxygen, 5% of water content, nitrogen as the carrier gas, and the volume space velocity is 10,000 h -1 ; the initial gas concentration is 80 ppb of chloroform, 10 ppm of ozone, 20 vol% of oxygen, 5% of water content, nitrogen as the carrier gas, and the volume space velocity is 10,000 h -1 ; the initial gas concentration is 80 ppb of acetone, 10 ppm of ozone, 20 vol% of oxygen, 5% of water content, nitrogen as the carrier gas, and the volume space velocity is 10,000 h -1 , and the test temperature of each pollutant is 60℃, and the results are shown in Figures 1-6 .

[0064] As can be seen from Figure 1 , the catalyst prepared in Example 1 can achieve 100% conversion rate of formaldehyde at 60℃, and continuously maintain for 10h;

[0065] As can be seen from Figure 2 , the catalyst prepared in Example 1 can achieve 96% conversion rate of propane at 60℃, and continuously maintain for 10h;

[0066] As can be seen from Figure 3 , the catalyst prepared in Example 1 can achieve 98% conversion rate of toluene at 60℃, and continuously maintain for 10h;

[0067] As can be seen from Figure 4 , the catalyst prepared in Example 1 can achieve 90% conversion rate of chloroform at 60℃, and continuously maintain for 10h;

[0068] From Figure 5 It can be seen that the catalyst prepared in Example 1 can achieve 97% conversion of acetone at 60°C and continuously maintain for 10h;

[0069] From Figure 6 It can be seen that the catalyst prepared in Example 1 can achieve complete conversion of ozone at 60°C and continuously maintain for 10h.

[0070] The inventors conducted XRD tests on MO-NF and CMO-MO-NF, and the results are shown in Figure 7 As shown, the CMO-MO-NF prepared in Example 1 shows Cu 1.5 Mn 1.5 O4(PDF#35-1172) and Mn2O3(PDF#41-1442), indicating that it is composed of two metal oxides.

[0071] The inventors conducted microscopic observation on MO-NF and CMO-MO-NF, and the results are shown in Figure 8 As shown, Figure 8 The left side of the figure shows pure Mn2O3 without copper doping modification, which presents a spindle structure (a figure), and after magnification, it can be seen that there is a clear boundary between particles and particles (c figure); Figure 8 The right side of the figure shows the catalyst prepared in Example 1, which presents a micro-morphology composed of spindle-shaped Mn2O3 and nano-sheet-shaped Cu 1.5 Mn 1.5 O4(b figure), and after magnification, it can be seen that a clear heterojunction can be formed between the two phases (d figure).

[0072] Comparative Example 2

[0073] The difference from Example 1 is that in the preparation process of the precursor, no glucose is added in step (1), and the potassium permanganate is directly dissolved in deionized water, and the obtained potassium permanganate aqueous solution is used for the following reaction, and the finally obtained monolithic catalyst is named as CMO-NF.

[0074] The conversion rate of pollutants at low temperature of the finally obtained monolithic catalyst CMO-NF was determined, and the determination method is as described in Comparative Example 1.

[0075] The results show that the catalyst prepared in Comparative Example 2 can achieve 80% conversion of formaldehyde at 60°C and continuously maintain for 10h;

[0076] The catalyst prepared in Comparative Example 2 can achieve 70% conversion of propane at 60°C and continuously maintain for 10h;

[0077] The catalyst prepared in Comparative Example 2 can achieve 67% conversion of toluene at 60°C and continuously maintain for 10h;

[0078] The catalyst prepared in Comparative Example 2 can achieve 60% conversion of chloroform at 60°C and continuously maintain for 10h;

[0079] The catalyst prepared in Comparative Example 2 can achieve 68% conversion of acetone at 60°C and continuously maintain for 10h;

[0080] The catalyst prepared in Comparative Example 2 can achieve 73% conversion of ozone at 60°C and continuously maintain for 10h.

[0081] The inventors speculate that without glucose in step (1), high-valence manganese cannot be generated, and thus the oxide heterojunction interface cannot be formed, affecting the conversion rate of pollutants.

[0082] Comparative Example 3

[0083] The difference from Example 1 is that the content of copper nitrate added in step (2) during the preparation of the precursor is different.

[0084] The inventors set up 5 experimental groups according to the different content of copper nitrate, and measured the conversion rates of formaldehyde, propane, toluene, chloroform, acetone, and ozone at 60°C in different experimental groups. The results are shown in Table 1.

[0085] Table 1

[0086]

[0087] The inventors explored the Cu atomic mass ratio by ICO-OES method, and the results are shown in Table 2, which shows that the content of Cu atoms in copper-manganese composite oxide should be between 4-7% to form a two-phase heterojunction. Figure 9

[0088] Assembly of the air purification device in a closed space in Example 2

[0089] Considering the air flow path, material strength, durability, sealing, and safety, the shell was designed using Solidworks software, and the plastic and metal parts of the shell were made using injection molding and die casting processes. In order to ensure the lightness of the shell, glass fiber reinforced plastic was used as the raw material for the plastic part.

[0090] During assembly, a small ozone generator, a fan, and a catalytic chamber were installed, and the monolithic catalyst prepared in Example 3 was filled in the chamber to achieve effective air purification effect. At the same time, the circuit board, sensor, controller, and power module were assembled to ensure the normal operation and intelligent control function of the air purification device.

[0091] ​Finally, the internal components are assembled with the housing to complete the production of the enclosed space air purification device. The design and manufacturing process aims to provide an efficient and reliable enclosed space air purification device that meets performance requirements and ensures product safety and reliability. Figure 10 It is a cross-sectional view of the enclosed space air purification device, wherein 1 is the primary filter screen, 2 is the fan, 3 is the adsorption plate, 4 is the strong adsorption plate, 5 is the ozone generator, 6 is the air duct, 7 is the catalytic chamber, 8 is the integral catalyst, 9 is the heat exchange plate, and 10 is the air outlet. The improved enclosed space air purification device of the present application is low in cost, easy to assemble, light in weight, environmentally friendly, small in size, does not produce secondary pollution, greatly meets the air purification needs of enclosed spaces, and improves the comfort and health level of personnel.

[0092] In summary, the present application provides an integral catalyst material for efficient degradation of low-concentration pollutants in an enclosed space, and an integrated air purification device. The catalyst is prepared by hydrothermally loading copper-manganese composite oxides on a foam metal substrate. The manganese-based catalyst itself has good performance for indoor volatile organic pollutants, and after copper doping by the hydrothermal method, an oxide-oxide heterojunction interface is formed. Due to the interface electron delocalization effect, it has the ability to activate ozone at low temperature, and can realize catalyst synergistic ozone activation. The active oxygen species generated by ozone can exhibit good pollutant oxidation performance at low temperature. The integral catalyst can completely mineralize more than 90% of gaseous pollutants at low temperature, exhibiting good catalytic activity. This excellent oxidation performance also comes from the material's good ozone decomposition ability at low temperature, which can achieve 100% ozone activation at low temperature. The catalytic combustion performance of the catalyst provided by the present application is better than that of traditional powder catalysts, and its preparation process is simple, easy to operate, low in cost, strong in gaseous pollutant conversion rate, and strong in poison resistance and water resistance. The integrated air purification device provided by the present application is easy to install and low in cost. Tests have found that the total pollutant purification rate of the enclosed space air through one pass is 90%, which has good application prospect and greatly improves the air environment in the enclosed space.

[0093] The above only describes the preferred embodiments of the present application and is not intended to limit the present application. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present application shall be included in the protection scope of the present application.​

Claims

1. A method for preparing a copper-manganese composite monolithic metal substrate catalyst, characterized in that: include: A. Dissolve potassium permanganate and glucose in water to perform redox reaction to obtain a precursor solution; B. adding copper salt to the precursor solution and stirring uniformly to obtain a turbid precursor solution; C. placing the metal foam in the precursor turbid solution described in step B to undergo a hydrothermal reaction to obtain a precursor material comprising a copper-manganese composite oxide; D. soaking the precursor material in a hexadecyltrimethoxysilane toluene solution for hydrophobic treatment; E. calcining the precursor material after the hydrophobic treatment in step D in air to obtain a copper-manganese composite monolithic metal substrate catalyst; In step B, the copper salt includes copper nitrate and / or copper sulfate; The mass percentage of copper atoms in the copper salt to the copper-manganese composite oxide is 4-7%; The mass percentage of the copper-manganese composite oxide to the copper-manganese composite monolithic metal substrate catalyst is 4.5-6.5%; In step B, the stirring time is 1-5 hours, the pH of the precursor turbid solution is 6-8, and the mass ratio of the potassium permanganate to the glucose and the copper salt is (0.5-1):1:(0.08-0.12); In step C, the foam metal is a foam metal that has been pretreated with hydrogen oxide; the foam metal is selected from foam nickel; the hydrothermal reaction is carried out in a hydrothermal reactor, the reaction temperature during the hydrothermal reaction is 150° C., and the reaction time is 8-12 hours; In step E, the temperature of the air calcination treatment is 250° C., and the calcination time is 2-4 hours.

2. The method according to claim 1, characterized in that In step A, the mass ratio of the potassium permanganate to the glucose is (0.5-1):1, and the pH of the precursor solution is 6-8.

3. The method according to claim 1, characterized in that After step C, the process further includes filtering, washing, and drying the precursor material in sequence. The drying temperature is 60-80° C. and the drying time is 10-12 hours.

4. A copper-manganese composite monolithic metal substrate catalyst, characterized in that: Prepared by the method according to any one of claims 1 to 3, the copper-manganese composite monolithic metal substrate catalyst is used for ozone-synergistic catalytic oxidation reactions.

5. The role of the copper-manganese composite monolithic metal substrate catalyst according to claim 4 in the preparation of an air purifier.

6. An air purifier, characterized in that: Contains the copper-manganese composite monolithic metal substrate catalyst according to claim 4.

7. The air purifier according to claim 6, characterized in that Also includes: Filter, fan, adsorption plate, ozone generator, air duct, catalytic chamber, heat exchange plate, and air outlet.

8. Use of the copper-manganese composite monolithic metal substrate catalyst according to claim 4 or the air purifier according to claim 6 or 7 in converting formaldehyde, propane, toluene, chloroform, acetone or ozone.

Images