CN113477246B - A manganese-containing monolithic electrically assisted metal honeycomb catalyst and its preparation method and application - Google Patents

Abstract

The invention belongs to the technical field of air purification, and discloses a manganese-containing integral electric auxiliary metal honeycomb catalyst and a preparation method and application thereof. The method comprises the following operation steps: the metal honeycomb substrate is subjected to surface pretreatment; mixing and stirring potassium permanganate, acetic acid and glucose solution to obtain manganese-containing precursor liquid; soaking the pretreated metal honeycomb substrate in manganese-containing precursor liquid, and carrying out hydrothermal reaction for 5-40h at 100-200 ℃; then taking out the mixture and ultrasonic treating the mixture in distilled water for 2 to 20 minutes; finally drying at 50-150 ℃ for 5-20 hours to obtain the manganese-containing integral electric auxiliary metal honeycomb catalyst, wherein the mass percentage of manganese elements is 10-70wt.%. The manganese-containing active component in the catalyst can be firmly loaded on the surface of the metal honeycomb substrate and uniformly dispersed; the catalyst has excellent conductivity, and can effectively improve the stability and water resistance of the catalyst in ozone decomposition reaction in a direct current auxiliary mode.

Description

A manganese-containing monolithic electrically assisted metal honeycomb catalyst and its preparation method and application

technical field

The invention belongs to the technical field of air purification, and in particular relates to a manganese-containing monolithic electric-assisted metal honeycomb catalyst, a preparation method thereof and an application in catalytic decomposition of ozone (O ₃ ).

Background technique

Ozone (O ₃ ) is widely used as a disinfectant, bactericide, and deodorant due to its strong oxidizing properties. However, the inefficient use of ozone during use will result in more residues. These untreated ozone is directly discharged into the atmosphere, which will cause harm to various living organisms and their living environment. Therefore, China's "Ambient Air Quality Standard" (GB3095-2012) clearly stipulates that the average value of ozone in ambient air for one hour is not more than 0.16mg /m ³ .

At present, the methods for treating ozone mainly include activated carbon method, pyrolysis method, plasma decomposition method and catalytic decomposition method. The activated carbon method removes ozone through adsorption, but it has the disadvantages of low adsorption capacity and frequent replacement. The pyrolysis method decomposes ozone by burning, but it is only suitable for high-concentration ozone treatment. The plasma decomposition method generates plasma to decompose ozone through high-voltage discharge, but there are disadvantages such as complicated operation and high power consumption. The catalytic decomposition method can better make up for the shortcomings of the above methods, and the removal rate of ozone is relatively high. It is currently the most researched and applied ozone treatment method.

Ozonolysis catalysts in the prior art are mainly classified into noble metal catalysts, transition metal oxide catalysts and manganese-containing catalysts. Among them, the high price of noble metal catalysts limits its large-scale industrial application; while the low-temperature ozone decomposition efficiency of catalysts containing transition metal oxides is not high enough. Relatively speaking, the manganese-containing catalyst can effectively enhance the low-temperature ozone decomposition efficiency of the catalyst by doping a single manganese dioxide system with noble metals, non-noble metal elements, and transition metal elements. However, manganese-containing catalysts have short service life and poor water resistance in practical applications. This is mainly because in the oxidizing atmosphere of the ozonolysis reaction, low chemical valence Mn ³⁺ in the catalyst is oxidized to high chemical valence Mn The rate of ⁴⁺ is relatively fast, while the rate of reduction of Mn ⁴⁺ back to Mn ³⁺ is relatively slow, which causes an imbalance in the mutual conversion rate of Mn ³⁺ and Mn ⁴⁺ in the catalyst, resulting in a continuous decrease in the number of active oxygen vacancies on the surface of the catalyst, and the catalyst gradually Inactivate. At present, researchers mainly increase the reduction reaction rate of Mn ⁴⁺ to Mn ³⁺ in the catalyst by doping and modifying the manganese-containing catalyst, so as to maintain the number of active oxygen vacancies on the surface and improve the service life of the catalyst. However, in the ozonolysis reaction, the service life and water resistance of manganese-containing catalysts are improved by a simple DC-assisted method, which has not been reported yet.

At present, there are mainly two types of manganese-containing catalysts in terms of macroscopic morphology: granular catalysts and monolithic catalysts. Among them, the pressure drop of the granular catalyst bed is high, which is not suitable for treating ozone gas with high space velocity. For monolithic catalysts, active carbon honeycombs, ceramic honeycombs and metal honeycombs are often used as regular carriers. For example, Chinese patents CN102600861B and CN109261164A prepare catalyst powder first, then prepare catalyst slurry, and finally load it on the honeycomb carrier by soaking-coating process. It is made into a shaped monolithic catalyst, which can effectively reduce the pressure drop of the bed during use, and achieve effective ozone removal under the conditions of low temperature, high space velocity and high humidity. Compared with activated carbon honeycomb and ceramic honeycomb, the surface of metal honeycomb carrier is generally smooth and non-porous, and the specific surface area is very low. It is difficult to uniformly and firmly support manganese-containing catalytic active components by traditional soaking-coating process. However, the metal substrate has the advantages of higher processability and stronger shock resistance, and the metal honeycomb has excellent electrical conductivity, and is more suitable for the DC-assisted method to enhance the stability and water resistance of the manganese-containing catalyst.

Contents of the invention

In order to overcome the shortcomings and deficiencies in the prior art, the primary purpose of the present invention is to provide a method for preparing a monolithic electric-assisted metal honeycomb catalyst containing manganese. The preparation method is simple to operate and is applicable to metal substrates of any shape. The manganese-containing active component in the obtained catalyst is firmly loaded and evenly dispersed on the metal substrate, and has the characteristics of high activity, good conductivity and easy industrial application.

Another object of the present invention is to provide a monolithic electro-assisted metal honeycomb catalyst containing manganese prepared by the above preparation method.

Another object of the present invention is to provide the application of the manganese-containing monolithic electro-assisted metal honeycomb catalyst to catalyze, oxidize, and decompose ozone under the condition of direct current assistance, which has the characteristics of high reaction stability and strong water resistance.

The object of the present invention is achieved through the following technical solutions:

A method for preparing a manganese-containing monolithic electrically assisted metal honeycomb catalyst, comprising the following steps:

(1) Surface pretreatment of the metal substrate: Soak the metal honeycomb substrate in 0.5-2.0mol/L hydrochloric acid solution for 3-20min to remove surface oxides, then rinse with water;

(2) Preparation of manganese-containing precursor body fluid: mix potassium permanganate, acetic acid and glucose solution, and continue stirring for 0.5-4h to obtain manganese-containing precursor body fluid, which is placed in a hydrothermal reaction kettle; potassium permanganate, The concentrations of acetic acid and glucose in the manganese-containing precursor liquid are 0.05-0.30mol/L, 0.05-1.20mol/L and 0.01-0.10mol/L, respectively;

(3) Soak the metal honeycomb substrate pretreated in step (1) in the manganese-containing precursor liquid obtained in step (2), and conduct a hydrothermal reaction at 100-200°C for 5-40h; then take it out and ultrasonicate it in distilled water for 2-20min ; Finally, dry at 50-150° C. for 5-20 hours to obtain a manganese-containing monolithic electric-assisted metal honeycomb catalyst, wherein the mass percentage of manganese element is 10-70wt.%.

The material of the metal honeycomb base is stainless steel, iron-chromium-aluminum alloy, nickel-chromium alloy, metal aluminum or aluminum alloy.

The concentration of the hydrochloric acid solution in step (1) is 0.8-1.3mol/L, and the ultrasonic time is 8-15min.

The rotating speed of stirring described in step (2) is 600-1500r/min, and the time of stirring is 1.5-2h.

The hydrothermal reaction temperature in step (3) is 120-160°C, and the hydrothermal time is 10-24h.

The ultrasonic time in step (3) is 5-10 min, and the drying temperature is 80-120°C.

A manganese-containing monolithic electrically assisted metal honeycomb catalyst prepared by the above-mentioned preparation method is characterized in that the mass percentage of manganese element in the catalyst is 10-70%.

Application of the above manganese-containing monolithic electrically assisted metal honeycomb catalyst in the catalytic decomposition of ozone.

The catalytic decomposition of ozone is carried out on a gas-solid phase reaction device: the manganese-containing monolithic electric-assisted metal honeycomb catalyst is placed in the reaction tube, and the two ends of the catalyst are connected to a direct current power supply; when the ozone gas is fed into the reaction, Apply a stable current to the catalyst through a DC power supply to assist in regulating the rate of electron gain and loss in the oxidation-reduction reaction in the catalyst, and then control the mutual conversion rate of Mn ³⁺ and Mn ⁴⁺ in the catalyst to achieve a dynamic balance, maintain the number of active oxygen vacancies on the surface, and increase the ozone of the catalyst Decomposition reaction stability and water resistance.

The present invention is essentially different from the preparation of the monolithic manganese-containing catalyst by the traditional soaking-coating process. The preparation of monolithic manganese-containing catalysts by the traditional soaking-coating process generally requires the preparation of manganese-containing active component powders in advance, and then the powders are loaded onto the honeycomb carrier by coating. However, the present invention does not need to pre-prepare the manganese-containing active component powder, and only needs to directly place the metal honeycomb in the manganese-containing precursor liquid, and use the reducibility of the metal substrate itself as an inducer to make the manganese-containing precursor preferentially on the surface of the metal substrate Manganese oxide crystal nuclei are formed by reduction and precipitation, and then gradually grow around the manganese oxide crystal nuclei under the guidance of the soft template agent in the solution, and finally form manganese-containing active component particles with specific crystal form and morphology on the surface of the metal substrate. By using these manganese oxide crystal nuclei preferentially formed on the surface of the metal substrate as the starting point for subsequent growth, the newly formed manganese-containing active component particles can not only be uniformly dispersed on the surface of the metal substrate, but also firmly bonded to the surface of the metal substrate.

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

(1) The manganese-containing active component in the catalyst of the present invention can be firmly supported and uniformly dispersed on the surface of the metal honeycomb substrate;

(2) The prepared catalyst has excellent electrical conductivity, and the stability and water resistance of the catalyst's ozonolysis reaction can be effectively improved by means of direct current assistance;

(3) The preparation method of the catalyst of the present invention is simple, the operation is convenient, there is no requirement on the shape of metal components, and the applicability to various metal substrates is strong.

Detailed ways

The present invention will be further described in detail below in conjunction with examples, but the embodiments of the present invention are not limited thereto.

Example 1

Soak a metal aluminum honeycomb substrate with a length, width, and height of about 0.23g in 0.8mol/L hydrochloric acid solution for 15 minutes to remove surface oxides, and then rinse with water; potassium permanganate, acetic acid and glucose solution Mixing, after 1.5h of continuous stirring at 1000r/min, obtain manganese-containing precursor liquid (concentrations of potassium permanganate, acetic acid and glucose in manganese-containing precursor liquid are respectively 0.14mol/L, 0.56mol/L and 0.04mol/L ), put it in a hydrothermal reaction kettle; soak the pretreated metal honeycomb in the manganese-containing precursor liquid, and conduct a hydrothermal reaction at 140°C for 24h; then take it out and ultrasonicate it in distilled water for 5min; finally dry it at 100°C for 10h, A manganese-containing monolithic electro-assisted metal honeycomb catalyst with a manganese content of 52% by mass is obtained.

The catalyst sample obtained in this example is placed in a reaction tube, and the two ends are connected to a DC power supply. When the ozone gas is fed into the reaction, a stable current is applied to the catalyst through the DC power supply, thereby realizing the DC-assisted reaction mode. In the ozone catalytic decomposition activity test.

Example 2

Soak an aluminum alloy honeycomb substrate with a length, width, and height of about 0.25g in 1.3mol/L hydrochloric acid solution for 8 minutes to remove surface oxides, and then rinse with water; potassium permanganate, acetic acid and glucose solution Mix, and continue stirring at 1500r/min for 1 hour to obtain a manganese-containing precursor liquid (concentrations of potassium permanganate, acetic acid and glucose in the manganese-containing precursor liquid are 0.30mol/L, 1.20mol/L and 0.10mol/L, respectively) , put it in a hydrothermal reaction kettle; soak the pretreated metal honeycomb in the manganese-containing precursor liquid, and conduct a hydrothermal reaction at 120°C for 24h; then take it out and ultrasonicate it in distilled water for 5min; finally dry it at 80°C for 20h to obtain Manganese-containing monolithic electric-assisted metal honeycomb catalyst with a mass percentage of manganese element of 67%.

The catalyst sample obtained in this example is placed in a reaction tube, and the two ends are connected to a DC power supply. When the ozone gas is fed into the reaction, a stable current is applied to the catalyst through the DC power supply, thereby realizing the DC-assisted reaction mode. In the ozone catalytic decomposition activity test.

Example 3

Soak a metal aluminum honeycomb substrate with a length, width and height of about 0.23g in 1.0mol/L hydrochloric acid solution for 10 minutes to remove surface oxides, and then rinse with water; potassium permanganate, acetic acid and glucose solution Mixing, after continuous stirring at 600r/min for 2h, a manganese-containing precursor liquid was obtained (concentrations of potassium permanganate, acetic acid and glucose in the manganese-containing precursor liquid were 0.05mol/L, 0.05mol/L and 0.01mol/L respectively) , put it in a hydrothermal reaction kettle; soak the pretreated metal honeycomb in the manganese-containing precursor liquid, and conduct a hydrothermal reaction at 160°C for 30h; then take it out and ultrasonicate it in distilled water for 10min; finally dry it at 120°C for 5h to obtain A manganese-containing monolithic electro-assisted metal honeycomb catalyst with a mass percentage of manganese element of 23%.

The catalyst sample obtained in this example is placed in a reaction tube, and the two ends are connected to a DC power supply. When the ozone gas is fed into the reaction, a stable current is applied to the catalyst through the DC power supply, thereby realizing the DC-assisted reaction mode. In the ozone catalytic decomposition activity test.

Example 4

Soak a cylindrical iron-chromium-aluminum honeycomb substrate with a diameter of 14mm and a height of about 2.40g in a 1.2mol/L hydrochloric acid solution for 10 minutes to remove surface oxides, and then rinse with water; mix potassium permanganate, acetic acid and glucose solution, After stirring continuously at 1200r/min for 3h, the manganese-containing precursor liquid (concentrations of potassium permanganate, acetic acid and glucose in the manganese-containing precursor liquid were respectively 0.25mol/L, 1.00mol/L and 0.05mol/L) was obtained. It is placed in a hydrothermal reaction kettle; the pretreated metal honeycomb is soaked in the manganese-containing precursor liquid, and hydrothermally reacted at 140°C for 12h; then taken out and ultrasonicated in distilled water for 5min; finally dried at 100°C for 10h to obtain manganese element A manganese-containing monolithic electric-assisted metal honeycomb catalyst with a mass percentage of 15%.

The catalyst sample obtained in this example is placed in a reaction tube, and the two ends are connected to a DC power supply. When the ozone gas is fed into the reaction, a stable current is applied to the catalyst through the DC power supply, thereby realizing the DC-assisted reaction mode. In the ozone catalytic decomposition activity test.

Application Example 1 (when there is no direct current auxiliary reaction)

The catalyst obtained in Example 1 was tested on the ozone catalytic decomposition activity without direct current assistance on a self-made gas-solid phase reaction device. The reaction was carried out at normal pressure and room temperature, the inlet concentration of ozone was 20ppm, the relative humidity was 90%, the space velocity was 50000h ^-1 , and the ozone concentration at the outlet was detected by an ozone detector.

The result shows: the ozonolysis catalyst prepared in embodiment 1, when there is no direct current assistance, the ozone conversion efficiency drops rapidly from 95% to 45% within 0.5h under high humidity reaction conditions. It can be seen that the catalyst prepared by the present invention has poor service life and water resistance when there is no direct current auxiliary reaction.

Application example 2 (when there is direct current auxiliary reaction)

With the catalyst obtained in Example 1, on the self-made gas-solid phase reaction device, carry out the ozone catalytic decomposition activity investigation with direct current assistance, be about to place the integrated metal honeycomb catalyst in the reaction tube, and connect the two ends of the catalyst to the direct current power supply , when the ozone gas is fed into the reaction, a stable current is applied to the catalyst through the DC power supply, so as to realize the DC-assisted reaction method. The reaction was carried out at normal pressure and room temperature, the inlet concentration of ozone was 20ppm, the relative humidity was 90%, the space velocity was 50000h ^-1 , and the ozone concentration at the outlet was detected by an ozone detector.

The results show that: the ozonolysis catalyst prepared in Example 1, when assisted by direct current, continues to react for 10 hours under high humidity conditions, the ozone conversion efficiency fluctuates between 92-95%, and basically remains unchanged. It can be seen that the catalyst prepared by the present invention still has excellent reaction stability and water resistance even under high-humidity reaction conditions when direct current is assisted in the reaction.

The ozonolysis catalyst prepared in Examples 2-4 is also tested for ozone catalytic decomposition with and without direct current assisted reaction, and the activity test result similar to that of Example 1 can be obtained: that is, when there is direct current assisted reaction, the present invention prepares The catalysts all have superior reaction stability and water resistance.

The above-mentioned embodiment is a preferred embodiment of the present invention, but the embodiment of the present invention is not limited by the above-mentioned embodiment, and any other changes, modifications, substitutions, combinations, Simplifications should be equivalent replacement methods, and all are included in the protection scope of the present invention.

Claims (9)

1. A method for preparing a manganese monolithic electrically assisted metal honeycomb catalyst, characterized in that it comprises the following steps: (1) Surface pretreatment of the metal substrate: Soak the metal honeycomb substrate in 0.5-2.0mol/L hydrochloric acid solution for 3-20min to remove surface oxides, then rinse with water; (2) Preparation of manganese-containing precursor body fluid: mix potassium permanganate, acetic acid and glucose solution, and continue stirring for 0.5-4h to obtain manganese-containing precursor body fluid, which is placed in a hydrothermal reaction kettle; potassium permanganate, The concentrations of acetic acid and glucose in the manganese-containing precursor liquid are 0.05-0.30mol/L, 0.05-1.20mol/L and 0.01-0.10mol/L, respectively; (3) Soak the metal honeycomb substrate pretreated in step (1) in the manganese-containing precursor liquid obtained in step (2), and conduct a hydrothermal reaction at 100-200°C for 5-40h; then take it out and ultrasonicate it in distilled water for 2-20min ; Finally, dry at 50-150° C. for 5-20 hours to obtain a manganese-containing monolithic electric-assisted metal honeycomb catalyst, wherein the mass percentage of manganese element is 10-70wt.%. 2. The preparation method according to claim 1, characterized in that: the metal honeycomb substrate is made of stainless steel, iron-chromium-aluminum alloy, nickel-chromium alloy, metal aluminum or aluminum alloy. 3. The preparation method according to claim 1, characterized in that: the concentration of the hydrochloric acid solution in step (1) is 0.8-1.3mol/L, and the ultrasonic time is 8-15min. 4. The preparation method according to claim 1, characterized in that: the stirring speed in step (2) is 600-1500r/min, and the stirring time is 1.5-2h. 5. The preparation method according to claim 1, characterized in that: the hydrothermal reaction temperature in step (3) is 120-160°C, and the hydrothermal time is 10-24h. 6. The preparation method according to claim 1, characterized in that: the ultrasonic time in step (3) is 5-10 min, and the drying temperature is 80-120°C. 7. A manganese-containing monolithic electric-assisted metal honeycomb catalyst prepared by the preparation method described in any one of claims 1-6, characterized in that: the mass percentage of manganese in the catalyst is 10-70 %. 8. The application of the manganese-containing monolithic electric-assisted metal honeycomb catalyst in the catalytic decomposition of ozone according to claim 7. 9. The application according to claim 8, characterized in that: the catalytic decomposition of ozone is carried out on a gas-solid phase reaction device: the manganese-containing monolithic electric-assisted metal honeycomb catalyst is placed in the reaction tube, and the two ends of the catalyst are connected The lead wire is connected to the DC power supply; when the ozone gas is fed into the reaction, a stable current is applied to the catalyst through the DC power supply to assist in regulating the rate of electron gain and loss in the oxidation-reduction reaction in the catalyst, thereby controlling the mutual transformation of Mn ³⁺ and Mn ⁴⁺ in the catalyst The rate reaches a dynamic balance, which improves the reaction stability and water resistance of the catalyst for ozonolysis.