Monolithic VOCs catalyst as well as preparation method and application thereof

Abstract

The invention provides a monolithic VOCs catalyst as well as a preparation method and application thereof, and belongs to the technical field of catalysts. The preparation method provided by the invention comprises the following steps: carrying out acid etching treatment on cordierite to obtain a cordierite carrier with a reconstructed surface structure; under the ultrasonic condition, the cordierite carrier with the reconstructed surface structure is soaked in a precious metal precursor solution, then drying and calcination are conducted, and the monolithic catalyst is obtained. The surface structure of the cordierite carrier is improved through acid etching, the porosity and active sites of the carrier are increased, and efficient loading and good dispersion of precious metal are facilitated. The ultrasonic technology promotes the uniform dispersion of the noble metal precursor and ensures the high activity of the catalyst. The catalyst prepared by the method shows excellent catalytic oxidation performance under the condition of low noble metal loading.

Description

Technical Field

[0001] This invention relates to the field of catalyst technology, and in particular to an integral VOCs catalyst, its preparation method, and its application. Background Technology

[0002] Volatile organic compounds (VOCs) are pollutants emitted into the atmosphere from multiple industrial sources and are widely present in various industries such as coatings, solvents, building materials, and chemical manufacturing. VOCs cause serious harm to the environment and human health, especially some VOCs such as toluene, which are highly toxic, carcinogenic, and have a negative impact on air pollution. Therefore, developing efficient and low-cost catalysts for the catalytic oxidation of VOCs is of great significance for environmental protection.

[0003] Currently, noble metal catalysts such as platinum (Pt) are widely used in the catalytic oxidation of VOCs due to their high catalytic activity at low temperatures. However, existing noble metal catalysts suffer from problems such as high noble metal usage, high cost, and poor catalyst stability, which limit their widespread application. To address these issues, researchers have attempted to improve catalyst performance by modifying support materials and optimizing catalyst preparation processes. However, these processes are complex and often fail to significantly reduce the amount of noble metal used while ensuring a synergistic improvement in catalyst activity, stability, and feasibility for industrial-scale preparation. This is particularly true for applications like catalytic combustion, which require high activity and long lifespan. Summary of the Invention

[0004] In view of this, the present invention aims to provide an integral VOCs catalyst, its preparation method, and its application. The present invention prepares a catalyst for toluene purification using a noble metal supported dispersion process. This method is simple, has a low noble metal loading, and the prepared catalyst exhibits low-temperature purification performance for toluene (T90 < 220℃).

[0005] To achieve the above objectives, the present invention provides the following technical solution: One of the technical solutions of this invention is a method for preparing an integral catalyst, comprising the following steps: Cordierite was subjected to acid etching to obtain a cordierite carrier with reconstructed surface structure. Under ultrasonic conditions, the cordierite support with the reconstructed surface structure is impregnated in a noble metal precursor solution, and then dried and calcined to obtain the monolithic catalyst.

[0006] The second technical solution of the present invention is an integral catalyst prepared by the above preparation method.

[0007] The third technical solution of the present invention is the application of the above-mentioned monolithic catalyst in the catalytic oxidation of VOCs.

[0008] The present invention discloses the following technical effects: This invention improves the surface structure of the cordierite support through acid etching, increasing its porosity and active sites, which facilitates efficient loading and good dispersion of noble metals. Ultrasonic technology promotes the uniform dispersion of the noble metal precursor, ensuring high catalyst activity. The catalyst prepared using this method exhibits excellent catalytic oxidation performance and high stability under low noble metal loading conditions, making it particularly suitable for the catalytic oxidation and purification of volatile organic compounds such as toluene. Furthermore, the catalyst demonstrates good water resistance and stability during long-term use, maintaining high catalytic activity even after multiple uses, significantly reducing the amount of noble metal used and the production cost of the catalyst, thus showing promising practical application prospects.

[0009] The method provided by this invention has a simple preparation process and low cost, which can significantly reduce the consumption of precious metals and has good economic benefits and practical application value. Attached Figure Description

[0010] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0011] Figure 1 The images show SEM comparisons of the monolithic catalysts prepared in Example 1, Comparative Example 1, and Comparative Example 2 of this invention. (a), (b), and (c) are Comparative Example 1 at different magnifications, (d), (e), and (f) are Comparative Example 2 at different magnifications, and (g), (h), and (i) are Example 1 at different magnifications.

[0012] Figure 2 The XRD patterns of the monolithic catalysts prepared in Examples 1, 1, and 2 of this invention are shown.

[0013] Figure 3 The conversion curves (a) and CO2 selectivity (b) of the monolithic catalysts prepared in Examples 1, 1, and 2 of this invention at different temperatures for the oxidation of toluene.

[0014] Figure 4 The stability curves of the catalysts prepared in Example 1 and Comparative Examples 1-2 of this invention are shown (test temperature is 320℃). Detailed Implementation

[0015] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0016] It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the invention. Furthermore, with respect to numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Any stated value or intermediate value within a stated range, as well as each smaller range between any other stated value or intermediate value within said range, is also included in this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0017] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials have been described herein, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of this invention. All references to this specification are incorporated by way of citation to disclose and describe methods and / or materials associated with those references. In the event of any conflict with any incorporated reference, the content of this specification shall prevail.

[0018] Various modifications and variations can be made to the specific embodiments described in this specification without departing from the scope or spirit of the invention, as will be apparent to those skilled in the art. Other embodiments derived from this specification will also be obvious to those skilled in the art. This specification and embodiments are merely exemplary.

[0019] The terms “include,” “including,” “have,” “contain,” etc., used in this article are all open-ended terms, meaning that they include but are not limited to.

[0020] In this invention, room temperature is defined as 20±5 °C.

[0021] Cordierite possesses good mechanical strength, thermal stability, and a high specific surface area, making it suitable as a support for noble metal catalysts. However, traditional noble metal loading techniques suffer from poor dispersion of the noble metal on the support surface and weak bonding between the support and the active component. Acid etching is an effective method to improve the surface properties of the support, enhancing the interfacial bonding between the noble metal and the support by altering the surface structure.

[0022] This invention proposes an acid etching-ultrasound-assisted loading method for noble metals. By acid etching the cordierite support to reconstruct its surface structure, and then using ultrasound technology to promote uniform loading of the noble metal, the noble metal achieves higher dispersion on the support surface, thereby improving the catalyst's activity and stability. Compared to traditional catalysts, the catalyst of this invention can still achieve high VOCs conversion efficiency even with low noble metal loading.

[0023] The first aspect of this invention provides a method for preparing a monolithic catalyst, comprising the following steps: Cordierite was subjected to acid etching to obtain a cordierite carrier with reconstructed surface structure. Under ultrasonic conditions, the cordierite support with the reconstructed surface structure is impregnated in a noble metal precursor solution, and then dried and calcined to obtain the monolithic catalyst.

[0024] In a preferred embodiment of the present invention, the cordierite has a honeycomb structure. 。 The cordierite is a monolithic cordierite that has not been crushed or ground.

[0025] In a preferred embodiment of the present invention, the acid reagent used for acid etching is nitric acid, hydrochloric acid or sulfuric acid, and the concentration of the acid reagent is 0.1~5.0 mol / L.

[0026] More preferably, the concentration of the acid reagent is 0.1 mol / L, 0.5 mol / L, 1 mol / L, 1.5 mol / L, 2 mol / L, 2.5 mol / L, 3 mol / L, 4 mol / L, or 5 mol / L.

[0027] In a preferred embodiment of the present invention, the acid etching treatment is performed at a temperature of room temperature to 80°C for a time of 0.5 to 5 hours.

[0028] More preferably, the acid etching treatment is performed at temperatures of 20 ℃, 30 ℃, 40 ℃, 50 ℃, 60 ℃, 70 ℃, and 80 ℃, and for times of 0.5 h, 1 h, 2 h, 3 h, 4 h, and 5 h.

[0029] In a preferred embodiment of the present invention, the power of the ultrasound is 20~60 kHz.

[0030] More preferably, the power of the ultrasound is 20 kHz, 30 kHz, 40 kHz, 50 kHz, or 60 kHz.

[0031] In a preferred embodiment of the present invention, the noble metal precursor in the noble metal precursor solution is a soluble salt of platinum.

[0032] More preferably, the noble metal precursor in the noble metal precursor solution is chloroplatinic acid.

[0033] In a preferred embodiment of the present invention, the immersion time is 10 to 60 minutes.

[0034] In a preferred embodiment of the present invention, after impregnation, the cordierite support with reconstructed surface structure is loaded with precious metal elements. After subsequent drying and calcination, the loading of precious metal elements in the monolithic catalyst is calculated to be 0.05wt%~1wt%.

[0035] In this invention, the loading amount = mass of precious metal element / (mass of precious metal element + mass of carrier) * 100%.

[0036] In a preferred embodiment of the present invention, the drying temperature is 80-120 °C and the time is 12-24 h.

[0037] More preferably, the drying temperature is 100 °C and the time is 12 h.

[0038] In a preferred embodiment of the present invention, the calcination temperature is 400~600 ℃ and the time is 1~5 h.

[0039] More preferably, the calcination temperature is 400 ℃, 450 ℃, 500 ℃, 550 ℃, or 600 ℃, and the time is 1 h, 2 h, 3 h, 4 h, or 5 h.

[0040] A second aspect of the present invention provides a monolithic catalyst prepared by the above-described preparation method.

[0041] A third aspect of this invention provides the application of the above-described monolithic catalyst in the catalytic oxidation of VOCs. In this invention, the VOCs are preferably toluene.

[0042] Unless otherwise specified, the technical solutions described in this invention are all conventional solutions in the field, and the reagents or raw materials used are all purchased from commercial channels or are publicly available unless otherwise specified.

[0043] To better understand the present invention, the following embodiments further illustrate the content of the present invention, but the content of the present invention is not limited to the following embodiments.

[0044] Example 1 (1) Immerse a cordierite carrier with a size of 10×10×5mm in a 1.5 mol / L nitric acid solution and perform acid etching treatment for 1 hour at room temperature; (2) The acid-etched cordierite carrier was washed with deionized water and dried to constant weight; (3) Add the support obtained in step (2) to 25 mL of chloroplatinic acid solution with a concentration of 1 mg / ml. Using ultrasonic-assisted impregnation method, the ultrasonic power is 20 kHz and the time is 30 minutes. Then dry at 100 °C for 12 hours, and calcine in a muffle furnace at 450 °C for 3 hours to obtain the monolithic catalyst. After calculation, the Pt loading in the obtained monolithic catalyst is 0.5 wt%.

[0045] Comparative Example 1 Cordierite with dimensions of 10×10×5 mm without any treatment.

[0046] Comparative Example 2 The difference from Example 1 is only that the step of acid etching treatment is omitted, and other steps and parameters are the same as those in Example 1. Since the cordierite is not acid-etched, the Pt loading is uneven and easy to fall off, and the Pt loading in the obtained monolithic catalyst is less than 0.5 wt%.

[0047] Performance test: Perform the catalytic oxidation activity test of toluene on the catalysts prepared in Example 1 and Comparative Examples 1-2. The test method is as follows: Place 0.1 g of the catalyst (40-60 mesh) in a fixed-bed reactor. The simulated gas uses compressed air to bubble liquid toluene into the reaction system. Among them, the toluene concentration is controlled at 500±50 ppm by air, the total gas flow rate is 50 ml / min, and the space velocity of the reaction gas is 30000 mL·g -1 ·h -1 , and the concentrations of toluene and CO2 are monitored in real time by on-line chromatography.

[0048] Figure 1 It shows the SEM comparison diagram of the monolithic catalysts prepared in Example 1 and Comparative Examples 1-2 of the present invention; from Figure 1 It can be seen that the surface porosity of Example 1 increases significantly, and many fine particles appear. It can be seen that the active component is deeply combined and highly dispersed with the acid-etched cordierite support.

[0049] Figure 2 It shows the XRD patterns of the monolithic catalysts prepared in Example 1 and Comparative Examples 1-2 of the present invention. From Figure 2 It can be seen that the characteristic peaks of cordierite are mainly exposed in all samples, indicating that the samples are successfully prepared.

[0050] Figure 3 It shows the catalytic oxidation toluene conversion rate curve and CO2 selectivity of the monolithic catalysts prepared in Example 1 and Comparative Examples 1-2 of the present invention at different temperatures; from Figure 3 It can be seen that the catalyst prepared in Example 1 shows excellent toluene oxidation ability compared with Comparative Examples 1-2.

[0051] Figure 4 The stability curves (test temperature 320℃) of the catalysts prepared in Example 1 and Comparative Examples 1-2 of this invention are shown. Figure 4 As can be seen, the catalyst prepared in Example 1 exhibits superior stability compared to Comparative Examples 1 and 2. Even after 2 hours of continuous operation, the chlorobenzene conversion rate still reaches 90%.

[0052] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing an integral catalyst, characterized in that, Includes the following steps: Cordierite was subjected to acid etching to obtain a cordierite carrier with reconstructed surface structure. Under ultrasonic conditions, the cordierite support with the reconstructed surface structure is impregnated in a noble metal precursor solution, and then dried and calcined to obtain the monolithic catalyst.

2. The preparation method according to claim 1, characterized in that, The acid reagent used for acid etching is nitric acid, hydrochloric acid, or sulfuric acid, and the concentration of the acid reagent is 0.1~5.0 mol / L.

3. The preparation method according to claim 1, characterized in that, The acid etching process is performed at a temperature of room temperature to 80°C for a duration of 0.5 to 5 hours.

4. The preparation method according to claim 1, characterized in that, The power of the ultrasound is 20~60 kHz.

5. The preparation method according to claim 1, characterized in that, The noble metal precursor in the noble metal precursor solution is a soluble salt of platinum.

6. The preparation method according to claim 1, characterized in that, The immersion time is 10-60 minutes.

7. The preparation method according to claim 1, characterized in that, The calcination temperature is 400~600 ℃, and the time is 1~5 h.

8. The preparation method according to claim 1, characterized in that, After calcination, the loading of noble metal elements in the obtained monolithic catalyst is 0.05wt%~1wt%.

9. The monolithic catalyst prepared by the preparation method according to any one of claims 1 to 8.

10. The application of the monolithic catalyst of claim 9 in the catalytic oxidation of VOCs.

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