Preparation method, product and application of coating type cordierite catalyst

Abstract

The invention relates to the technical field of catalysts, in particular to a preparation method, a product and application of a coating type cordierite catalyst. The preparation method of the coating type cordierite catalyst comprises the following steps: step 1, mixing diaspore, water and concentrated nitric acid to prepare pseudo-boehmite slurry; step 2, adding honeycomb cordierite into the pseudo-boehmite slurry for ultrasonic treatment, and then drying and calcining to obtain calcined cordierite; and step 3, adding the calcined cordierite into the slurry A, carrying out ultrasonic treatment, drying and calcining in sequence, and repeating the steps of ultrasonic treatment, drying and calcining to obtain the coating type cordierite catalyst, the slurry A is prepared by adding an auxiliary agent and active powder into water. The VOCs purification performance of the coating type cordierite catalyst is compared with that of a commercial catalyst, and the result shows that the coating type cordierite catalyst has more excellent purification performance and stability.

Description

Technical Field

[0001] The present invention relates to the technical field of catalysts, and particularly to a preparation method, a product and an application of a coated cordierite catalyst. Background Art

[0002] Among various volatile organic compounds (VOCs), chlorinated volatile organic compounds (Cl-VOCs) have attracted wide attention from countries around the world due to their high environmental toxicity and persistent hazards. Cl-VOCs cannot be well degraded naturally, and most of them released into the environment will accumulate. Among them, chlorobenzene (CB) is a typical Cl-VOC commonly found in solid waste treatment, pharmaceutical and chemical industries. After chlorinated volatile organic compounds (Cl-VOCs) enter the atmosphere, they will form ozone, photochemical smog and secondary organic aerosols in the air, which are highly toxic. Therefore, controlling the pollution of volatile organic compounds is crucial for reducing environmental risks.

[0003] In the removal technologies of volatile organic compounds (VOCs), due to the obvious advantages of catalytic oxidation technology, people have widely devoted themselves to developing efficient catalysts for catalytic oxidation of VOCs. However, the existing catalysts for catalytic oxidation of VOCs generally have problems of insufficient low-temperature purification performance and low-temperature stability. Summary of the Invention

[0004] The purpose of the present invention is to provide a coated cordierite catalyst prepared by a simple coating process for the catalytic oxidation of chlorobenzene. The catalyst prepared by this method has low-temperature purification performance (T 90 = 370 °C) and low-temperature stability for chlorobenzene.

[0005] To achieve the above purpose, the present invention provides the following solutions:

[0006] One of the technical solutions of the present invention, a preparation method of a coated cordierite catalyst, includes the following steps:

[0007] Step 1, mixing boehmite, water and concentrated nitric acid to prepare a pseudo-boehmite slurry;

[0008] Step 2, adding honeycomb cordierite into the pseudo-boehmite slurry for ultrasonic treatment, then drying and calcining to obtain calcined cordierite;

[0009] Step 3, adding the calcined cordierite into slurry A for ultrasonic treatment, drying and calcining in sequence, and repeating the above steps of ultrasonic treatment, drying and calcining to obtain the coated cordierite catalyst;

[0010] The slurry A is prepared by adding an auxiliary agent and an active powder into water.

[0011] In a preferred embodiment of the present invention, the mass-volume ratio of boehmite, water and concentrated nitric acid is 150-250 g∶1500-2000 ml∶200-300 ml.

[0012] The present invention mainly appropriately strengthens the surface adhesiveness of the carrier through the boehmite slurry. Excessive or too low adhesiveness will cause the shedding of the active powder and the deterioration of dispersibility. Through repeated experiments, the present invention finds that the boehmite slurry prepared with the above-mentioned mass-volume ratio of boehmite, water and concentrated nitric acid can give the most appropriate surface adhesiveness strengthening to the carrier.

[0013] In a preferred embodiment of the present invention, in step 2, the power of ultrasonic is 60-120 W, and the time is 0.5-1 h; the drying temperature is 80-150 °C, and the time is 8-24 h; the calcination temperature is 400-800 °C, and the time is 2-5 h.

[0014] In a preferred embodiment of the present invention, in step 3, the power of ultrasonic is 60-120 W, and the time is 0.5-1 h; the drying temperature is 80-150 °C, and the time is 8-24 h; the calcination temperature is 400-800 °C, and the time is 2-5 h.

[0015] In step 2 and step 3, the heating rate during calcination is independently 5-10 °C / min.

[0016] In a preferred embodiment of the present invention, in step 3, the number of repetitions is 3-5 times.

[0017] In a preferred embodiment of the present invention, the additive is polyethylene glycol; the active powder is a supported Pt-TiO₂ catalyst.

[0018] In a preferred embodiment of the present invention, the content of the additive in slurry A is 30-70 g / L; the content of the active powder in slurry A is 30-85 g / L.

[0019] In the present invention, the use of the additive polyethylene glycol is beneficial to the uniform dispersion of the active powder in the slurry and the strengthening of the combination on the surface of the carrier, improving the combination of the powder and the carrier. Only when the content of the additive in slurry A is within the above concentration range, the dispersibility of the active powder and its combination with the carrier are the best.

[0020] The second technical solution of the present invention is a coated cordierite catalyst prepared by the above-mentioned preparation method.

[0021] The third technical solution of the present invention is the application of the above-mentioned coated cordierite catalyst in the catalytic oxidation of Cl-VOCs.

[0022] The Cl-VOCs is chlorobenzene.

[0023] The present invention discloses the following technical effects:

[0024] The present invention uses a coating process to load active powder (noble metal powder) on cordierite to prepare a coated cordierite catalyst with high-temperature stability. In the preparation process of the catalyst, first, the specific surface area of cordierite is expanded by nitric acid and pseudo-boehmite, and then the noble metal powder is coated on the honeycomb cordierite through the steps of repeated ultrasonic treatment, drying, and calcination, to obtain a coated cordierite catalyst with a relatively high specific surface area (35 m 2 / g, about twice as high as that of conventional cordierite) and high stability. The preparation process of the present invention is simple and has high practical application value.

[0025] The present invention uses cordierite as a carrier and prepares a coated cordierite catalyst (monolithic catalyst) loaded with noble metal powder by a simple and easy-to-operate process for the low-temperature stable catalytic oxidation of chlorobenzene. By testing the oxidation performance of chlorobenzene (1000 ppm) of the developed monolithic catalyst at reaction temperatures of 300, 350, and 400 °C, the developed monolithic catalyst can achieve complete oxidation of chlorobenzene within 120 minutes at a reaction temperature of 400 °C, showing excellent anti-chlorine performance, which can greatly reduce the operation cost of enterprises and effectively reduce the economic cost of commercial catalysts. Description of the Drawings

[0026] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the embodiments. Obviously, the drawings described below 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 these drawings.

[0027] Figure 1 It is the test result of the catalyst stability prepared in Example 2 of the present invention.

[0028] Figure 2 It is the test result of the catalyst stability in Comparative Examples 1-3 of the present invention.

[0029] Figure 3 It is the test result of the catalyst stability and water resistance stability prepared with different coating times in Example 1 of the present invention.

[0030] Figure 4 It is the test result of the catalyst stability and water resistance stability prepared with different coating times in Example 2 of the present invention. Detailed Embodiments

[0031] The various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be construed as a limitation on the present invention, but rather as a more detailed description of certain aspects, features, and implementation manners of the present invention.

[0032] It should be understood that the terms described in the present invention are only for describing particular embodiments and are not intended to limit the present invention. Additionally, for the numerical ranges in the present invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Any intermediate value within any stated value or stated range, as well as each smaller range between any other stated value or intermediate value within the stated range, is also included in the present invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0033] Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by those of ordinary skill in the art to which the present invention pertains. Although the present invention only describes preferred methods and materials, any methods and materials similar or equivalent to those described herein may also be used in the implementation or testing of the present invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials related to the documents. In case of conflict with any incorporated document, the content of this specification shall prevail.

[0034] Without departing from the scope or spirit of the present invention, various improvements and changes can be made to the specific embodiments of the present invention specification, which are obvious to those skilled in the art. Other embodiments obtained from the specification of the present invention are obvious to those skilled in the art. The specification and examples of the present invention are merely exemplary.

[0035] Regarding the use of "comprising", "including", "having", "containing", etc. in this article, they are all open-ended terms, meaning including but not limited to.

[0036] The "%" described in the present invention represents mass percentage unless otherwise specified.

[0037] Compared with traditional carriers (such as TiO2, Al2O3, etc.), cordierite, as a material with a low coefficient of thermal expansion and high temperature resistance, is suitable as a carrier for long-term high-temperature operation. Developing a coated cordierite catalyst has the advantages of high-temperature stability, low energy consumption, and long lifespan in the treatment of VOCs. The present invention is of great significance for developing catalysts with simple processes and high practicability.

[0038] The present invention provides a preparation method of a coated cordierite catalyst. By means of a cordierite coating process, a noble metal catalyst is loaded on the surface of a cordierite honeycomb carrier. The VOCs purification performance of the obtained coated cordierite catalyst is compared with that of a commercial catalyst, and the results show that the prepared coated cordierite catalyst has more excellent purification performance and stability.

[0039] The technical solutions described in the present invention are all conventional solutions in the art if not otherwise specified. The reagents or raw materials used are all purchased from commercial channels or are publicly available if not otherwise specified.

[0040] The honeycomb cordierite used in the examples of the present invention is purchased from Taizhou Zhongdu New Materials Co., Ltd., and the main parameter specifications are 10*10*5 cm.

[0041] The active powder used in the examples of the present invention is a supported Pt-TiO2 catalyst, purchased from Xuancheng Jingrui New Materials Co., Ltd., with a particle size of 10 nm and a Pt content of 0.5 wt% in the active powder.

[0042] The technical solutions provided by the present invention will be described in detail below in conjunction with the examples, but they should not be construed as limiting the protection scope of the present invention.

[0043] Example 1

[0044] (1) 200 g of boehmite and 1750 ml of water are stirred for 30 min, and then 250 ml of concentrated nitric acid solution is added until the slurry is stirred evenly to obtain a pseudo-boehmite slurry.

[0045] (2) The honeycomb cordierite is added to the pseudo-boehmite slurry in step (1) and sonicated for 0.75 h (0.5 - 1 h is acceptable), dried at 100 °C for 20 h, and then calcined in a muffle furnace at a rate of 5 °C / min to 500 °C for 5 h for standby. This step completes the first coating of the two-step coating process (pretreating the cordierite carrier with pseudo-boehmite).

[0046] (3) 3 L of aqueous solution is added to a 5 L beaker, and then polyethylene glycol and the active powder are added and sonicated until uniform to obtain a slurry with a polyethylene glycol content of 50 g / L and an active powder content of 50 g / L. Subsequently, the cordierite calcined in step (2) is added and sonicated for 0.75 h (0.5 - 1 h is acceptable), dried at 100 °C for 20 h, and then calcined in a muffle furnace at a rate of 5 °C / min to 500 °C for 4 h. The sonication, drying, and calcination steps in step (3) are repeated 5 times in total. This step completes the second coating of the two-step coating process (coating the active powder on the surface of the cordierite), and finally a two-step coated cordierite catalyst is obtained, marked as.

[0047] Example 2

[0048] (1) This step is the same as step (1) in Example 1.

[0049] (2) Add polyethylene glycol to the pseudo-boehmite slurry in step (1) so that the concentration of polyethylene glycol in the slurry precursor is 50 g / L. Add concentrated nitric acid to adjust the slurry to acidic (pH 3 - 5), and then add the active powder so that its concentration in the slurry is 50 g / L. This step completes the preparation of the slurry required for one-step coating.

[0050] (3) After the slurry in step (2) shows a homogeneous state, add cordierite and perform ultrasonic treatment, drying, and calcination (the parameter settings for ultrasonic treatment, drying, and calcination are the same as those in Example 1). Repeat the steps of ultrasonic treatment, drying, and calcination a total of 5 times to obtain a one-step coated cordierite catalyst.

[0051] Comparative Example 1

[0052] Pt-based - 5511, purchased from Shaanxi Kaida Co., Ltd., with the main parameter specifications of 10 * 10 * 5 cm and a Pt content of 0.5%.

[0053] Comparative Example 2

[0054] PtPd - 6551, purchased from Sino-Platinum Metals Co., Ltd., with the main parameter of 10 * 10 * 5 cm, a Pt content of 0.5%, and a Pd content of 0.3%.

[0055] Comparative Example 3

[0056] 7541 - non-noble metal, purchased from Shanghai Xifu New Materials Co., Ltd., with the main parameter specifications of 10 * 10 * 5 cm and an Mn content of about 15%.

[0057] Performance testing

[0058] Perform the catalytic oxidation activity test of chlorobenzene on the catalysts prepared in Examples 1 - 2 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 chlorobenzene into the reaction system. Among them, the chlorobenzene concentration is controlled at 500 ppm by air, the total gas flow rate is 50 ml / min, and the mass space velocity is 30000 ml / (g*h). Or adjust the experimental parameters to two experimental conditions of a chlorobenzene concentration of 1000 ppm, a total gas flow rate of 100 ml / min, and a mass space velocity of 60000 ml / (g*h) to conduct the chlorobenzene oxidation performance test, and monitor the chlorobenzene concentration in real time through on-line chromatography.

[0059] The T 90 (°C) and T 50 (°C) respectively represent the reaction temperatures when the CVOCs conversion rate is 50% and 90%.

[0060] Figure 1 The stability test results of the catalyst prepared in Example 1 of the present invention( Figure 1 The uncoated cordierite mentioned in () refers to the untreated honeycomb cordierite used in Example 1). Figure 2 These are the stability test results of the catalysts in Comparative Examples 1-3 of the present invention at a chlorobenzene concentration of 1000 ppm, a total gas flow rate of 100 ml / min, a mass space velocity of 60000 ml / (g*h), and a reaction temperature of 350 °C. From Figure 1 It can be found that in the stability experiments of the catalyst prepared in Example 1 at three reaction temperatures of 300, 350, and 400 °C, the catalyst prepared in Example 1 exhibits high stability and can achieve a purification effect of more than 98% for chlorobenzene at a reaction temperature of 400 °C. In addition, by horizontally comparing the chlorobenzene oxidation and stability performance of Comparative Examples 1-3, the performance of the catalyst prepared in Example 1 is superior to that of Comparative Examples 1-3.

[0061] Figure 3 These are the stability and anti-poisoning test results of the catalysts prepared in Example 1 with different coating times (that is, on the basis of Example 1, the steps of repeating ultrasonic treatment, drying, and calcination in Step 3 are adjusted from 5 times to 1 time, 2 times, 3 times, and 4 times respectively, and the other steps and parameters are the same as those in Example 1). By conducting chlorobenzene oxidation performance experiments on the catalyst under the experimental parameter conditions of a lower reaction temperature of 320 °C, 500 ppm chlorobenzene, and introducing 5% water vapor, with a total gas flow rate of 50 ml / min and a mass space velocity of 30000 ml / (g*h), the anti-poisoning performance of the catalyst is investigated. The results show that the catalyst prepared in Example 1 exhibits high anti-poisoning performance. From Figure 4 ( Figure 4 The different coating times mentioned in () refer to: on the basis of Example 2, the steps of repeating ultrasonic treatment, drying, and calcination in Step 3 are adjusted from 5 times to 1 time, 2 times, 3 times, and 4 times respectively, and the other steps and parameters are the same as those in Example 2) it can be seen that the catalyst prepared in Example 2 exhibits lower chlorobenzene oxidation ability under the same test conditions as Figure 3 Example 1, which indicates that the uniformity and coating rate of the surface active components of the one-step coated cordierite are low, resulting in a lower activity of the monolithic catalyst.

[0062] Table 1 shows the specific surface area data of the catalysts in Example 1 and Comparative Examples 1-2 of the present invention.

[0063] Table 1

[0064] Sample <![CDATA[Specific surface area (m 2 / g)]]> <![CDATA[Pore volume (cm 3 / g)]]> Pore volume (nm) Example 1 35.1 0.013 2.780 Comparative Example 1 13.4 0.010 2.147 Comparative Example 2 15.7 0.009 3.409

[0065] The embodiments described above are only descriptions of the preferred embodiments of the present invention, and do not limit the scope of the present invention. Without departing from the design spirit of the present invention, various deformations and improvements made by those of ordinary skill in the art to the technical solutions of the present invention shall fall within the protection scope determined by the claims of the present invention.

Claims

1. A preparation method of a coated cordierite catalyst, characterized in that, It includes the following steps: Step 1: Mix boehmite, water and concentrated nitric acid to prepare a pseudoboehmite slurry. Step 2: Add honeycomb cordierite into the pseudoboehmite slurry and ultrasonicate, then dry and calcine to obtain calcined cordierite. Step 3: Add the calcined cordierite into Slurry A, ultrasonicate, dry and calcine in sequence, and repeat the steps of ultrasonication, drying and calcination above to obtain the coated cordierite catalyst. Slurry A is prepared by adding an auxiliary agent and an active powder into water.

2. The preparation method of the coated cordierite catalyst according to claim 1, characterized in that, The mass-volume ratio of the boehmite, water and concentrated nitric acid is 150 - 250 g∶1500 ml - 2000 ml∶200 - 300 ml.

3. The preparation method of the coated cordierite catalyst according to claim 1, characterized in that, In Step 2, the power of ultrasonication is 60 - 120 W, and the time is 0.5 - 1 h; the drying temperature is 80 - 150 °C, and the time is 8 - 24 h; the calcination temperature is 400 - 800 °C, and the time is 2 - 5 h.

4. The preparation method of the coated cordierite catalyst according to claim 1, characterized in that, In Step 3, the power of ultrasonication is 60 - 120 W, and the time is 0.5 - 1 h; the drying temperature is 80 - 150 °C, and the time is 8 - 24 h; the calcination temperature is 400 - 800 °C, and the time is 2 - 5 h.

5. The preparation method of the coated cordierite catalyst according to claim 1, characterized in that, In Step 3, the number of repetitions is 3 - 5 times.

6. The preparation method of the coated cordierite catalyst according to claim 1, characterized in that, The auxiliary agent is polyethylene glycol; the active powder is a supported Pt-TiO₂ catalyst.

7. The preparation method of the coated cordierite catalyst according to claim 1, characterized in that, The content of the auxiliary agent in Slurry A is 30 - 70 g / L; the content of the active powder in Slurry A is 30 - 85 g / L.

8. A coated cordierite catalyst prepared by the preparation method according to any one of claims 1 - 7.

9. The application of the coated cordierite catalyst as claimed in claim 8 in the catalytic oxidation of Cl-VOCs.

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