Preparation method, product and application of Cl-VOCs catalyst

Abstract

The invention relates to the technical field of catalysts, in particular to a preparation method, a product and application of a Cl-VOCs catalyst. The preparation method of the Cl-VOCs catalyst comprises the following steps: dissolving a manganese source and trimesic acid in a solvent, and then adding a Pt source solution and organic acid to obtain a homogeneous solution; performing solvothermal reaction on the homogeneous solution, and centrifuging to obtain a precipitate; the precipitate is dried and then calcined, and the Cl-VOCs catalyst is obtained. The organic acid is one of oxalic acid, citric acid or tartaric acid. According to the present invention, the noble metal precursor is efficiently utilized, and the easily-operated process is adopted to prepare the highly-dispersed multi-active-site Cl-VOCs catalyst with the stably-combined Pt on the carrier surface, and the catalyst is used for the low-temperature stable catalytic oxidation of chlorobenzene. The Cl-VOCs catalyst disclosed by the invention shows excellent chlorine resistance and water resistance, the operation cost of an enterprise can be greatly reduced, and the economic cost of a commercial catalyst is effectively reduced.

Description

Technical Field

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

[0002] As a common volatile organic compound (Cl-VOCs), chlorobenzene (CB) has a wide range of applications in the fields of industry, agriculture, medicine, etc. However, with the rapid development of industry, the emissions of Cl-VOCs are gradually increasing, posing a persistent pollution and harm to environmental safety and human health. In addition, Cl-VOCs are prone to condense with other organic pollutants at high temperatures, generating more toxic chlorine-containing by-products such as PCDFs (polychlorinated dibenzofurans) and PCDDs (polychlorinated dibenzo-p-dioxins). Conducting research on the core technology for efficient removal of Cl-VOCs and effectively controlling pollutants represented by chlorobenzene is of great significance for improving the ecological environment and protecting human health.

[0003] The removal technologies of VOCs mainly include biodegradation, photocatalysis, catalytic oxidation, plasma catalysis, etc. Among them, the catalytic oxidation technology has broad application prospects in the control of Cl-VOCs due to its significant advantages such as low cost, high efficiency, good stability, wide application range and no secondary pollution. It can convert VOCs into CO2 and H2O without generating other harmful substances. During the oxidation of chlorobenzene, the active component Pt in the noble metal Pt-based catalyst is easily poisoned by Cl and interfered by the adsorption of water molecules, resulting in a decrease in the catalyst activity. The traditional metal-support interaction (MSI) strategy has improved the anti-chlorine and anti-water poisoning ability of Pt-based catalysts to a certain extent by adjusting the binding form of Pt and the oxide support, constructing a second metal sacrificial site to protect Pt, and building a mixed interface. For example, the study of Pt / CeO2 coated with polyoxometallate chainmail to regulate oxidation of chlorobenzene without hazardous by-products published by Chen et al. in the Journal of Hazardous Materials showed that the Pt active sites could be effectively protected by coating with HSiW chainmail to prevent Pt from being exposed to Cl-containing atmospheres. The study of Pt and Mo Co-Decorated MnO2 Nanorods with Superior Resistance to H2O, Sintering, and HCl for Catalytic Oxidation of Chlorobenzene published by Dai et al. in the Environmental Science & Technology showed that the introduction of Mo as a sacrificial site could inhibit the adsorption of water molecules on Pt, thereby protecting the Pt sites. The introduction of the coating protection strategy can stabilize the metal active sites, but the covered active sites will lead to a decrease in catalytic activity. In addition, the instability of the isolation layer in the aqueous reaction will also cause the metal sites to be covered, and the covered active sites will also lead to a decrease in catalytic activity.

[0004] At present, the problems of noble metal catalysts such as anti-chlorine poisoning, anti-water poisoning, easy agglomeration, and poor stability have not been effectively solved. A large number of studies have been able to improve the catalytic activity and anti-poisoning ability of noble metals by introducing multi-metal sites and using promoters to construct active site protection layers. However, the dispersion and agglomeration problems of noble metals have not been effectively solved. Therefore, it is of great significance to deeply improve the stability of the active component Pt in the Pt-oxide support catalyst in the Cl-VOCs atmosphere and its anti-chlorine and anti-water performance for the development of low-cost and highly practical catalysts. Summary of the Invention

[0005] The object of the present invention is to provide a preparation method of a multi-active site Cl-VOCs catalyst (i.e., Pt-Mn2O3 catalyst) based on non-benzenoid carboxyl coordinated Pt with simple preparation process and low cost, which is used for the catalytic oxidation of chlorobenzene. The catalyst prepared by this method has low-temperature purification performance for chlorobenzene (T 90 = 300 °C) and anti-chlorine and anti-water poisoning performance. In addition, the catalyst with low Pt content can provide greater potential for industrial applications.

[0006] To achieve the above object, the present invention provides the following solutions:

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

[0008] Dissolve a manganese source and trimesic acid in a solvent, and then add a Pt source solution and an organic acid (non-benzenoid organic acid) to obtain a homogeneous solution;

[0009] Perform a solvothermal reaction on the homogeneous solution and then centrifuge to obtain a precipitate;

[0010] The precipitate is 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] Another technical solution of the present invention is a Cl-VOCs catalyst (i.e., Pt-Mn2O3 catalyst) prepared according to the above preparation method.

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

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

[0015] The present invention utilizes the strategy of strong coordination of non-benzenoid carboxyl to Pt, and prepares a Pt-Mn2O3 catalyst with low Pt content and multi-active sites by pyrolytic carbonization. In the process of catalyst preparation, first, Pt is stably dispersed on the surface of the precursor by the strong coordination of the carboxyl group of the non-benzenoid organic acid, which promotes the stable binding and high dispersion of Pt on the surface of the carrier. Further, high-temperature pyrolytic carbonization is used to promote the generation of abundant active sites on the surface of the catalyst. At the same time, the strong coordination of the carboxyl group is used to prevent the surface agglomeration of Pt, and then Pt is stably dispersed on the surface of the carrier, obtaining a Pt-Mn2O3 catalyst with highly dispersed Pt and multi-surface active sites.

[0016] The present invention prepares a multi-active site Pt-Mn2O3 catalyst with stable binding and high dispersion of Pt on the surface of the carrier by efficiently utilizing noble metal precursors and an easy-to-operate process, which is used for the low-temperature stable catalytic oxidation of chlorobenzene. This catalyst achieves complete chlorobenzene oxidation within 40 hours at 320 °C, with 1000 ppm of chlorobenzene and 5% of H2O, showing excellent chlorine and water resistance, which can greatly reduce the operating costs of enterprises and effectively reduce the economic costs of commercial catalysts. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] 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 in the following description 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.

[0018] Figure 1 It is the X-ray diffraction pattern of the catalysts prepared in Example 1 and Comparative Examples 1-2 of the present invention.

[0019] Figure 2 It is the scanning electron microscope image of the catalysts prepared in Example 1 and Comparative Examples 1-2 of the present invention; among them, a1 and a2 are the scanning electron microscope images of Comparative Example 1 at different magnifications, b1 and b2 are the scanning electron microscope images of Comparative Example 2 at different magnifications, and c1 and c2 are the scanning electron microscope images of Example 1 at different magnifications.

[0020] Figure 3 It is the chlorobenzene oxidation performance diagram of the catalysts prepared in Example 1 and Comparative Examples 1-2 of the present invention.

[0021] Figure 4 It is the chlorobenzene oxidation performance diagram of the catalysts prepared in Examples 2-3 of the present invention.

[0022] Figure 5 It is the stability test diagram of the catalysts prepared in Example 1 and Comparative Examples 1-2 of the present invention.

[0023] Figure 6 It is the high-concentration chlorobenzene stability test diagram of the catalyst prepared in Example 1 of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0024] Now, various exemplary embodiments of the present invention will 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, characteristics, and implementation schemes of the present invention.

[0025] It should be understood that the terms used 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.

[0026] Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. Although the present invention only describes preferred methods and materials, any methods and materials similar or equivalent to those described herein can 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.

[0027] Without departing from the scope or spirit of the present invention, various improvements and variations 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.

[0028] Regarding the use of "comprising", "including", "having", "containing", etc. herein, they are all open-ended terms, meaning including but not limited to.

[0029] In a first aspect of the present invention, a method for preparing a Cl-VOCs catalyst is provided. First, Pt is stably dispersed on the surface of the precursor through strong coordination of the carboxyl group of non-aromatic ring organic acids, promoting the stable binding and highly dispersed of Pt on the surface of the carrier. Further, through high-temperature pyrolysis carbonization, rich active sites are generated on the surface of the catalyst. At the same time, the strong coordination of the carboxyl group is used to prevent the surface aggregation of Pt, and then Pt is stably dispersed on the surface of the carrier to obtain a Pt-Mn2O3 catalyst with highly dispersed Pt and multiple surface active sites. Specifically, it includes the following steps:

[0030] Dissolve a manganese source and trimesic acid in a solvent, and then add a Pt source solution and an organic acid to obtain a homogeneous solution;

[0031] After the homogeneous solution undergoes a solvothermal reaction, it is centrifuged to obtain a precipitate;

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

[0033] The organic acid is one of oxalic acid, citric acid or tartaric acid. Further 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 trimesic acid is (0.5 - 1.5)∶(1.5 - 3.5). More preferably, the mass ratio of the manganese source to the trimesic 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∶ethanol with a volume ratio of 3:1.

[0037] The present invention does not make a special limitation on the amount of the solvent, and the amount of the solvent only needs to be able to fully dissolve the manganese source and the trimesic 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] The present invention does not make a special limitation on the amount of the solvent in the Pt source solution, and the amount of the solvent only needs to be able 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 the present invention, if the mass ratio of the manganese source to the organic acid exceeds the above-mentioned parameter range, for example, increasing or decreasing the amount of the organic acid will result in a decrease in the effective utilization rate of the noble metal Pt (such as Pt agglomeration or uneven dispersion on the surface of the prepared catalyst). Therefore, the present invention limits the mass ratio of the manganese source to the organic acid to the above-mentioned 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 - 30 h.

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

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

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

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

[0048] The Cl-VOCs is chlorobenzene.

[0049] The technical solutions of the present invention, unless otherwise specified, are all conventional solutions in the art. The reagents or raw materials used, unless otherwise specified, are all purchased from commercial channels or are publicly available.

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

[0051] Example 1

[0052] A preparation method of a Pt-Mn2O3 catalyst for chlorobenzene purification with non-benzenecarboxyl coordinated Pt, the specific steps are as follows:

[0053] (1) Add 0.996 g of Mn(NO3)2·4H2O and 2.568 g of benzene-1,3,5-tricarboxylic acid (BTC) to a mixed solvent of 75 ml of DMF and 25 ml of ethanol. After mixing and stirring evenly, add a Pt source solution with a Pt element content of 0.0095 g (the Pt source is chloroplatinic acid and the solvent is water) and 1 g of oxalic acid to obtain a homogeneous solution.

[0054] (2) Transfer the homogeneous solution in step (1) to a reaction kettle and place it in an oven. Set the oven temperature to 105 °C and the reaction time to 20 h. After the reaction kettle cools to room temperature, centrifuge it. Use deionized water and ethanol as centrifugation solvents respectively to dissolve the unreacted manganese source and organic acid. Set the centrifuge speed to 8000 r / min and the time to 5 min. After six centrifugations, a white precipitate is obtained. Among them, centrifuge three times with deionized water as the centrifugation solvent and three times with ethanol as the centrifugation solvent.

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

[0056] Example 2

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

[0058] Example 3

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

[0060] Comparative Example 1

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

[0062] Comparative Example 2

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

[0064] Performance Detection

[0065] I. X-ray diffraction analysis was carried out on the catalysts prepared in Example 1 and Comparative Examples 1-2, and the results are as Figure 1 shown. It can be seen from Figure 1 that with the introduction of Pt, the characteristic peaks of the Mn2O3 support gradually become weaker. In the Pt-Mn2O3 catalyst (i.e., Pt-MDs-A-1 catalyst) obtained by coordinating Pt with oxalic acid, the characteristic peaks of the support further weaken, indicating that 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 chlorobenzene catalytic oxidation performance.

[0066] Scanning electron microscopy analysis was carried out on the catalysts prepared in Example 1 and Comparative Examples 1-2, and the results are as Figure 2 shown. Figure 2 c1 and c2 in it show that the catalysts prepared by coordinating Pt with organic acids have finer particles, confirming that the strategy of coordinating Pt with organic acids can improve the surface properties of the support and at the same time promote the dispersibility of Pt on the surface. Thus, it helps to change the surface properties of the catalyst and effectively improve the catalytic activity of the catalyst.

[0067] II. The catalytic oxidation activity of the catalysts prepared in Examples 1-3 and Comparative Examples 1-2 was tested. The test method was as follows: 0.1 g of the catalyst (40-60 mesh) was placed in a fixed-bed reactor, and the simulated gas bubbled liquid chlorobenzene into the reaction system through compressed air. Among them, the chlorobenzene concentration was controlled at 500 ± 50 ppm by air, the total gas flow rate was 50 ml / min, the mass space velocity was 30,000 ml / (g·h), and the chlorobenzene and CO2 concentrations were monitored in real time by on-line chromatography:

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

[0069] Figure 3 and Figure 4 are the chlorobenzene oxidation performance of the catalysts prepared in Examples 1-3 and Comparative Examples 1-2 of the present invention. It can be seen from Figure 3 that the catalyst prepared in Example 1 can exhibit excellent catalytic activity at high temperatures and show resistance to chlorine poisoning, indicating the high-efficiency purification ability and practical application potential of the developed catalyst for chlorobenzene. It can be seen from Figure 4 that changing the type of non-aromatic ring organic acid has a small impact on the chlorobenzene oxidation performance of the prepared catalyst, indicating that the developed catalyst can obtain a catalyst with high-efficiency oxidation performance for chlorobenzene in different types of non-aromatic ring organic acids.

[0070] Figure 5 The long-term stability and water resistance stability of the catalysts prepared in Example 1 and Comparative Examples 1-2 were tested in Figure 5 It can be seen from that in the stability experiment, the catalyst prepared in Example 1 showed stable chlorobenzene oxidation ability and water resistance stability, further indicating that the developed catalyst has low-temperature oxidation ability and anti-poisoning performance for chlorobenzene.

[0071] Figure 6 is the high-concentration chlorobenzene stability test chart of the catalyst prepared in Example 1 of the present invention; the experimental conditions were 100 mg of the catalyst, the gas mass flow rate was 50 ml / min, the chlorobenzene concentration was 1000 ppm, the water vapor content was 5%, the mass space velocity was 30,000 ml / (g·h), and the reaction temperature was 320 °C.

[0072] It can be seen from Figure 6It can be seen that the catalyst prepared in Example 1 achieved complete chlorobenzene oxidation within 40 hours at 320 °C, a mass space velocity of 30,000 ml / (g·h), 1000 ppm of chlorobenzene, and 5% H2O.

[0073] The above-described embodiments 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 Cl-VOCs catalyst, characterized in that, It includes the following steps: Dissolve the manganese source and trimesic acid in a solvent, and then add the Pt source solution and organic acid to obtain a homogeneous solution; After the homogeneous solution undergoes a solvothermal reaction, centrifuge it to obtain a precipitate; The precipitate is calcined after drying to obtain the Cl-VOCs catalyst; The organic acid is one of oxalic acid, citric acid or tartaric acid.

2. The preparation method of the Cl-VOCs catalyst 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 preparation method of the Cl-VOCs catalyst according to claim 1, characterized in that, The solvent is N,N-dimethylformamide and / or ethanol.

4. The preparation method of the Cl-VOCs catalyst 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 preparation method of the Cl-VOCs catalyst according to claim 1, wherein, The mass ratio of the manganese source to the organic acid is (0.5 - 1.5)∶1.

6. The preparation method of the Cl-VOCs catalyst according to claim 1, characterized in that, The temperature of the solvothermal reaction is 80 - 150 °C, and the time is 10 - 30 h.

7. The preparation method of the Cl-VOCs catalyst according to claim 1, characterized in that, The specific centrifugation is as follows: Centrifuge at a rotational speed of 5000 - 8000 r / min. Use deionized water and ethanol as solvents respectively. Centrifuge for 2 - 5 min each time, and centrifuge six times in total, including three times with deionized water and three times with ethanol.

8. The preparation method of the Cl-VOCs catalyst according to claim 1, characterized in that, The specific drying is drying at 80 °C for 12 - 24 h; the specific calcination is heating to 400 - 800 °C at a rate of 5 - 10 °C / min and holding for 2 - 5 h.

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

10. The application of the Cl-VOCs catalyst according to claim 9 in the catalytic oxidation of Cl-VOCs.

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