Preparation method, product and application of a cl-vocs catalyst

Abstract

The present application relates to the technical field of catalyst, in particular to a preparation method, product and application of Cl-VOCs catalyst. The preparation method of the Cl-VOCs catalyst comprises the following steps: dissolving a manganese source and a trimesic acid in a solvent, then adding a Pt source solution and an organic acid to obtain a homogeneous solution; centrifuging the homogeneous solution after a solvothermal reaction to obtain a precipitate; calcining the precipitate after drying to obtain the Cl-VOCs catalyst; and the organic acid is one of oxalic acid, citric acid or tartaric acid. The present application uses a process that is easy to operate and efficiently utilizes a noble metal precursor to prepare a Cl-VOCs catalyst with a stable combination and high dispersion of Pt on the surface of the carrier and multiple active sites, which is used for low-temperature stable catalytic oxidation of chlorobenzene. The Cl-VOCs catalyst of the present application exhibits excellent resistance to chlorine and water, can greatly reduce the operating cost of enterprises, and effectively reduces the economic cost of commercial catalysts.

Description

Technical Field

[0001] This invention relates to the field of catalyst technology, and in particular to a method for preparing a Cl-VOCs catalyst, a product thereof, and its application. Background Technology

[0002] Chlorobenzene (CB), a common volatile organic compound (Cl-VOC), has wide applications in industry, agriculture, and medicine. However, with rapid industrial development, Cl-VOC emissions have gradually increased, posing a persistent pollution and hazard to environmental safety and human health. Furthermore, Cl-VOCs readily condense with other organic pollutants at high temperatures, producing more toxic chlorine-containing byproducts such as polychlorinated dibenzofurans (PCDFs) and polychlorinated dibenzodioxins (PCDDs). Therefore, conducting research on core technologies for the efficient removal of Cl-VOCs and effectively controlling pollutants such as chlorobenzene is of great significance for improving the ecological environment and protecting human health.

[0003] VOCs removal technologies mainly include biodegradation, photocatalysis, catalytic oxidation, and plasma catalysis. Among these, catalytic oxidation technology, due to its significant advantages such as low cost, high efficiency, good stability, wide applicability, and no secondary pollution, can convert VOCs into CO2 and H2O without producing other harmful substances, and has broad application prospects in Cl-VOCs control. In the oxidation process of chlorobenzene, the active component Pt in noble metal Pt-based catalysts is easily affected by Cl poisoning and water molecule adsorption, leading to a decrease in catalyst activity. Traditional metal-support interaction (MSI) strategies have improved the resistance of Pt-based catalysts to chlorine and water poisoning to some extent by adjusting the binding form of Pt with the oxide support, constructing a second metal sacrificial site to protect Pt, and constructing a mixed interface. For example, Chen et al.'s study published in the Journal of Hazardous Materials, "Pt / CeO2 coated with polyoxometallate chainmail to regulate oxidation of chlorobenzene without hazardous by-products," showed that protecting Pt from exposure to Cl-containing atmospheres by using an HSiW chainmail coating can effectively protect the Pt active sites. A study published by Dai et al. in *Environmental Science & Technology*, titled *Pt and Mo Co-Decorated MnO2 Nanorods with Superior Resistance to H2O, Sintering, and HCl for Catalytic Oxidation of Chlorobenzene*, demonstrates that introducing Mo as a sacrificial site inhibits the adsorption of water molecules onto Pt, thereby protecting the Pt sites. While the capping layer strategy can stabilize metal active sites, the capped active sites can lead to a decrease in catalytic activity. Furthermore, the instability of the isolation layer in aqueous reactions can also cause metal sites to be capped, which in turn leads to a decrease in catalytic activity.

[0004] Currently, the problems of chlorine poisoning resistance, water poisoning resistance, easy aggregation, and poor stability of precious metal catalysts have not been effectively solved. Numerous studies have improved the catalytic activity and poisoning resistance of precious metals by introducing multi-metal sites and constructing protective layers for active sites using additives; however, the dispersibility and aggregation problems of precious metals remain unresolved. Therefore, further improving the stability and chlorine and water resistance of the active component Pt in Pt-oxide supported catalysts in Cl-VOC atmospheres is of great significance for developing inexpensive and highly practical catalysts. Summary of the Invention

[0005] The purpose of this invention is to provide a simple and low-cost method for preparing a multi-active-site Cl-VOCs catalyst (i.e., a Pt-Mn2O3 catalyst) based on non-benzene ring carboxyl-coordinated Pt, for the catalytic oxidation of chlorobenzene. The catalyst prepared by this method exhibits low-temperature purification performance for chlorobenzene (T...). 90 =300℃) and resistance to chlorine and water poisoning. In addition, catalysts with low Pt content have greater potential for industrial applications.

[0006] To achieve the above objectives, the present invention provides the following solution:

[0007] One of the technical solutions of this invention is a method for preparing a Cl-VOCs catalyst, comprising the following steps:

[0008] Manganese source and pyromellitic acid are dissolved in a solvent, and then Pt source solution and organic acid (non-phenyl ring organic acid) are added to obtain a homogeneous solution;

[0009] The homogeneous solution was subjected to a solvothermal reaction and then centrifuged to obtain a precipitate;

[0010] The precipitate was dried and then calcined to obtain the Cl-VOCs catalyst;

[0011] The organic acid is one of oxalic acid, citric acid, or tartaric acid.

[0012] The second technical solution of the present invention is a Cl-VOCs catalyst (i.e., Pt-Mn2O3 catalyst) prepared according to the above preparation method.

[0013] The third technical solution of the present invention is the application of the above-mentioned Cl-VOCs catalyst in the catalytic oxidation of Cl-VOCs.

[0014] The present invention discloses the following technical effects:

[0015] This invention utilizes a strategy of strong coordination of Pt with non-benzene ring carboxyl groups and prepares a Pt-Mn2O3 catalyst with low Pt content and multiple active sites through pyrolysis and carbonization. In the catalyst preparation process, Pt is first stably dispersed on the precursor surface through strong coordination of the carboxyl groups of non-benzene ring organic acids, promoting stable bonding and high dispersion of Pt on the support surface. Further, high-temperature pyrolysis and carbonization generate abundant active sites on the catalyst surface, while the strong coordination of carboxyl groups prevents Pt surface agglomeration, thus stably dispersing Pt on the support surface, resulting in a Pt-Mn2O3 catalyst with highly dispersed Pt and multiple surface active sites.

[0016] This invention utilizes a highly efficient and easily operable process with a noble metal precursor to prepare a multi-active-site Pt-Mn2O3 catalyst with stable Pt binding and high dispersion on the support surface, for the low-temperature stable catalytic oxidation of chlorobenzene. This catalyst achieves complete chlorobenzene oxidation within 40 hours at 320℃, 1000 ppm chlorobenzene, and 5% H2O, exhibiting excellent resistance to chlorine and water, significantly reducing enterprise operating costs and effectively lowering the economic cost of commercial catalysts. Attached Figure Description

[0017] 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.

[0018] Figure 1 These are X-ray diffraction patterns of the catalysts prepared in Example 1 and Comparative Examples 1-2 of this invention.

[0019] Figure 2 These are scanning electron microscope (SEM) images of the catalysts prepared in Example 1 and Comparative Examples 1-2 of the present invention; wherein, a1 and a2 are SEM images of Comparative Example 1 at different magnifications, b1 and b2 are SEM images of Comparative Example 2 at different magnifications, and c1 and c2 are SEM images of Example 1 at different magnifications.

[0020] Figure 3 This is a graph showing the chlorobenzene oxidation performance of the catalysts prepared in Example 1 and Comparative Examples 1-2 of this invention.

[0021] Figure 4 This is a graph showing the chlorobenzene oxidation performance of the catalysts prepared in Examples 2-3 of this invention.

[0022] Figure 5 These are stability test graphs of the catalysts prepared in Example 1 and Comparative Examples 1-2 of this invention.

[0023] Figure 6 This is a high-concentration chlorobenzene stability test diagram of the catalyst prepared in Example 1 of this invention. Detailed Implementation

[0024] 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.

[0025] 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.

[0026] 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.

[0027] 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 apparent to those skilled in the art. This specification and embodiments are merely exemplary.

[0028] 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.

[0029] The first aspect of this invention provides a method for preparing a Cl-VOCs catalyst. Firstly, Pt is stably dispersed on the surface of a precursor through strong coordination of the carboxyl groups of a non-benzene ring organic acid, promoting stable bonding and high dispersion of Pt on the support surface. Further, high-temperature pyrolysis and carbonization induce abundant active sites on the catalyst surface, while the strong carboxyl coordination prevents Pt surface agglomeration, thereby stably dispersing Pt on the support surface to obtain a Pt-Mn2O3 catalyst with high Pt dispersion and multiple surface active sites. Specifically, the method includes the following steps:

[0030] Manganese source and pyromellitic acid are dissolved in a solvent, and then Pt source solution and organic acid are added to obtain a homogeneous solution.

[0031] The homogeneous solution was subjected to a solvothermal reaction and then centrifuged to obtain a precipitate;

[0032] The precipitate was dried and then calcined to obtain the Cl-VOCs catalyst;

[0033] The organic acid is one of oxalic acid, citric acid, or tartaric acid. More preferably, the organic acid is oxalic acid.

[0034] In a preferred embodiment of the present invention, the manganese source is one of manganese nitrate, manganese chloride, or manganese sulfate; more preferably, the manganese source is manganese nitrate.

[0035] The mass ratio of the manganese source to the trimellitic acid is (0.5-1.5):(1.5-3.5). More preferably, the mass ratio of the manganese source to the trimellitic acid is (0.9-1):(2.5-2.6).

[0036] In a preferred embodiment of the present invention, the solvent is N,N-dimethylformamide and / or ethanol. More preferably, the solvent is a mixture of N,N-dimethylformamide and ethanol in a volume ratio of 3:1.

[0037] This invention does not impose any particular limitation on the amount of solvent used; the amount of solvent should be sufficient to fully dissolve the manganese source and pyromellitic acid.

[0038] In a preferred embodiment of the present invention, the Pt source in the Pt source solution is chloroplatinic acid or platinum chloride; more preferably, the Pt source is H2PtCl6·6H2O;

[0039] The mass ratio of the manganese source to the Pt element in the Pt source solution is (0.5-1.5):0.0095.

[0040] This invention does not impose any particular limitation on the amount of solvent used in the Pt source solution; the amount of solvent is sufficient to fully dissolve the Pt source.

[0041] In a preferred embodiment of the present invention, the mass ratio of the manganese source to the organic acid is (0.5-1.5):1.

[0042] In this invention, the mass ratio of manganese source to organic acid exceeds the parameter range described above. For example, increasing or decreasing the amount of organic acid will lead to a decrease in the effective utilization rate of the precious metal Pt (such as Pt agglomeration or uneven dispersion on the surface of the prepared catalyst). Therefore, this invention limits the mass ratio of manganese source to organic acid to the above parameter range.

[0043] In a preferred embodiment of the present invention, the temperature of the solvothermal reaction is 80-150°C and the time is 10-30h.

[0044] In a preferred embodiment of the present invention, the centrifugation is specifically performed as follows: centrifugation at a speed of 5000-8000 r / min, using deionized water and ethanol as solvents respectively, centrifuging for 2-5 min each time, for a total of six centrifugations, of which three centrifugations are performed using deionized water and three centrifugations are performed using ethanol.

[0045] In a preferred embodiment of the present invention, the drying is specifically drying at 80°C for 12-24 hours; the calcination is specifically heating to 400-800°C at a rate of 5-10°C / min and holding for 2-5 hours.

[0046] A second aspect of the present invention provides a Cl-VOCs catalyst (i.e., a Pt-Mn2O3 catalyst) prepared according to the above-described preparation method.

[0047] A third aspect of the present invention provides the application of the above-described Cl-VOCs catalyst in the catalytic oxidation of Cl-VOCs.

[0048] The Cl-VOCs are chlorobenzene.

[0049] 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.

[0050] The technical solutions provided by the present invention will be described in detail below with reference to the embodiments, but they should not be construed as limiting the scope of protection of the present invention.

[0051] Example 1

[0052] A method for preparing a Pt-Mn2O3 catalyst for chlorobenzene purification using non-benzene ring carboxyl-coordinated Pt is described below:

[0053] (1) Add 0.996g Mn(NO3)2·4H2O and 2.568g trimesic acid (BTC) to a mixed solvent of 75ml DMF and 25ml ethanol. After mixing and stirring evenly, add a Pt source solution with a Pt element content of 0.0095g (Pt source is chloroplatinic acid, solvent is water) and 1g oxalic acid to obtain a homogeneous solution.

[0054] (2) Transfer the homogeneous solution from step (1) to a reaction vessel and place it in an oven. Set the oven temperature to 105℃ and the reaction time to 20h. After the reaction vessel cools to room temperature, centrifuge it. Use deionized water and ethanol as centrifuge solvents to dissolve the unreacted manganese source and organic acid. Set the centrifuge speed to 8000r / min and the time to 5min. After six centrifugations, a white precipitate is obtained. Three centrifugations were performed using deionized water as the centrifuge solvent, and three centrifugations were performed using ethanol as the centrifuge solvent.

[0055] (3) Take out the white precipitate obtained in step (2) and place it in an oven at 80°C for 18 hours (12-24 hours is acceptable). After drying, place it in a muffle furnace and calcine it at 500°C for 3 hours at 5°C / min to obtain the Pt-Mn2O3 catalyst, which is denoted as Pt-MDs-A-1 catalyst.

[0056] Example 2

[0057] The only difference from Example 1 is that 1g of oxalic acid in step (1) is replaced with 1g of citric acid; the other steps and parameters are the same as in Example 1; the obtained Pt-Mn2O3 catalyst is denoted as Pt-MDs-B-1 catalyst.

[0058] Example 3

[0059] The only difference from Example 1 is that 1g of oxalic acid in step (1) is replaced with 1g of tartaric acid; the other steps and parameters are the same as in Example 1; the obtained Pt-Mn2O3 catalyst is denoted as Pt-MDs-C-1 catalyst.

[0060] Comparative Example 1

[0061] The only difference from Example 1 is that the addition of a Pt source solution with a Pt element content of 0.0095g (Pt source is chloroplatinic acid, solvent is water) and 1g of oxalic acid in step (1) is omitted. The other steps and parameters are the same as in Example 1. A Mn2O3 catalyst for chlorobenzene purification is obtained, denoted as MDs catalyst.

[0062] Comparative Example 2

[0063] The only difference from Example 1 is that the addition of 1g of oxalic acid in step (1) is omitted, and the other steps and parameters are the same as in Example 1; a Pt-Mn2O3 catalyst for chlorobenzene purification is obtained, which is denoted as Pt-MDs catalyst.

[0064] Performance testing

[0065] I. X-ray diffraction analysis was performed on the catalysts prepared in Example 1 and Comparative Examples 1-2. The results are as follows: Figure 1 As shown. By Figure 1 It can be seen that with the introduction of Pt, the characteristic peaks of the Mn2O3 support gradually weaken. The characteristic peaks of the support in the Pt-Mn2O3 catalyst (i.e., the Pt-MDs-A-1 catalyst) obtained by coordinating Pt with oxalic acid further weaken. This indicates that the Pt on the support surface is more uniformly dispersed. The highly dispersed active component Pt is beneficial to the improvement of catalytic activity, thereby promoting the improvement of the catalytic oxidation performance of chlorobenzene.

[0066] Scanning electron microscopy analysis was performed on the catalysts prepared in Example 1 and Comparative Examples 1-2, and the results are as follows: Figure 2 As shown. Figure 2 Figures c1 and c2 show that the catalyst prepared by Pt coordination with organic acids has finer particles, confirming that the organic acid coordination strategy for Pt can improve the surface properties of the support and promote the dispersion of Pt on the surface. This helps to alter the surface properties of the catalyst and effectively enhance its catalytic activity.

[0067] II. The catalytic oxidation activity of the catalysts prepared in Examples 1-3 and Comparative Examples 1-2 was tested. The test method is as follows: 0.1 g of catalyst (40-60 mesh) was placed in a fixed-bed reactor. Liquid chlorobenzene was bubbled into the reaction system using compressed air to simulate gas. The concentration of chlorobenzene was controlled at 500±50 ppm by air, the total gas flow rate was 50 ml / min, and the mass hourly space velocity was 30000 ml / (g*h). The concentrations of chlorobenzene and CO2 were monitored in real time by online chromatography.

[0068] The T used in the activity test 90 (°C) and T 50 (°C) represents the reaction temperature when the CVOCs conversion rate is 50% and 90%, respectively.

[0069] Figure 3 and Figure 4 The chlorobenzene oxidation performance of the catalysts prepared in Examples 1-3 and Comparative Examples 1-2 of this invention is examined. Figure 3 As can be seen, the catalyst prepared in Example 1 exhibits excellent catalytic activity at high temperatures and resistance to chlorine poisoning, demonstrating the high efficiency of the developed catalyst in purifying chlorobenzene and its potential for practical application. Figure 4 It can be seen that changing the type of non-benzene ring organic acid has a small impact on the chlorobenzene oxidation performance of the prepared catalyst, indicating that the developed catalyst can be obtained with high efficiency in chlorobenzene oxidation in different types of non-benzene ring organic acids.

[0070] Figure 5 The long-term stability and water resistance of the catalysts prepared in Example 1 and Comparative Examples 1-2 were tested. The fixed-bed reactor temperature was controlled at 300°C, and the liquid water temperature was controlled by introducing air to remove 5% water vapor from the liquid water into the reaction gas path. The removal of water vapor was used as the research variable to investigate the catalyst's resistance to water poisoning. Figure 5 It can be seen that, in the stability experiment, the catalyst prepared in Example 1 exhibited stable chlorobenzene oxidation ability and water resistance, further demonstrating that the developed catalyst has low-temperature oxidation ability and anti-poisoning performance for chlorobenzene.

[0071] Figure 6 This is a high-concentration chlorobenzene stability test chart of the catalyst prepared in Example 1 of this invention; the experimental conditions are 100mg catalyst, gas mass flow rate of 50ml / min, chlorobenzene concentration of 1000ppm, water vapor content of 5%, mass hourly space velocity of 30000ml / (g*h), and reaction temperature of 320℃.

[0072] Depend on Figure 6It can be seen that the catalyst prepared in Example 1 achieved complete chlorobenzene oxidation within 40 hours at 320°C, a mass hourly space velocity of 30000 ml / (g*h), 1000 ppm of chlorobenzene, and 5% H2O.

[0073] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made by those skilled in the art to the technical solutions of the present invention without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.

Claims

1. The application of a Cl-VOCs catalyst in the catalytic oxidation of Cl-VOCs, characterized in that, The preparation method of the Cl-VOCs catalyst includes the following steps: Manganese source and pyromellitic acid are dissolved in a solvent, and then Pt source solution and organic acid are added to obtain a homogeneous solution. The homogeneous solution was subjected to a solvothermal reaction and then centrifuged to obtain a precipitate; The precipitate was dried and then calcined to obtain the Cl-VOCs catalyst; The organic acid is one of oxalic acid, citric acid or tartaric acid; The mass ratio of the manganese source to the organic acid is (0.5-1.5):1; The solvothermal reaction is carried out at a temperature of 80-150℃ for a duration of 10-30 hours.

2. The application according to claim 1, characterized in that, The manganese source is one of manganese nitrate, manganese chloride, or manganese sulfate; The mass ratio of the manganese source to the trimesic acid is (0.5-1.5):(1.5-3.5).

3. The application according to claim 1, characterized in that, The solvent is N,N-dimethylformamide and / or ethanol.

4. The application according to claim 1, characterized in that, The Pt source in the Pt source solution is chloroplatinic acid or platinum chloride. The mass ratio of the manganese source to the Pt element in the Pt source solution is (0.5-1.5):0.0095.

5. The application according to claim 1, characterized in that, The centrifugation process specifically involves centrifuging at a speed of 5000-8000 r / min, using deionized water and ethanol as solvents respectively, centrifuging for 2-5 min each time, for a total of six centrifugations, including three centrifugations using deionized water and three centrifugations using ethanol.

6. The application according to claim 1, characterized in that, The drying process specifically involves drying at 80℃ for 12-24 hours; the calcination process specifically involves heating to 400-800℃ at a rate of 5-10℃ / min and holding at that temperature for 2-5 hours.

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