Chlorine-containing VOCs catalytic combustion catalyst as well as preparation method and application thereof

Abstract

The invention discloses a chlorine-containing VOCs catalytic combustion catalyst, a preparation method of the chlorine-containing VOCs catalytic combustion catalyst and application of the chlorine-containing VOCs catalytic combustion catalyst in catalytic combustion of chlorine-containing VOCs. The chlorine-containing VOCs catalytic combustion catalyst comprises a carrier cerium-zirconium solid solution, and an active metal ruthenium, an auxiliary agent phosphorus and an auxiliary agent alkaline earth metal which are loaded on the surface of the carrier, the alkaline earth metal comprises at least one of calcium, magnesium and barium. The preparation method comprises the step of loading the active metal ruthenium, the assistant phosphorus and the assistant alkaline earth metal onto the surface of the carrier cerium-zirconium solid solution. The catalyst has high activity, chlorine poisoning resistance, active element loss resistance and high-temperature stability. In addition, the catalyst provided by the invention is simple in preparation method, wide in raw material source, free of special requirements on equipment and easy for large-scale preparation, and has certain industrial application prospects.

Description

Technical Field

[0001] The present invention relates to the field of industrial tail gas treatment, and in particular to a chlorine-containing VOCs catalytic combustion catalyst having high activity, resistance to chlorine poisoning, resistance to loss of active elements and high-temperature stability, and a preparation method and application thereof. Background Art

[0002] Chlorinated volatile organic compounds (CVOCs) are a type of volatile organic compounds (VOCs). Compared with ordinary VOCs, chlorinated VOCs have stronger carcinogenic, teratogenic and mutagenic abilities. When CVOCs are discharged into the atmosphere, they cause greater harm to human health and the environment. However, CVOCs are widely used in the fields of pharmaceuticals, chemicals, dyes, leather, electronics, etc., and they are irreplaceable. Therefore, it is impossible to completely avoid the use of CVOCs from the source. Tail gas treatment is a feasible solution to reduce the harm of CVOCs.

[0003] Catalytic combustion is one of the feasible technologies for treating VOCs. Under actual industrial conditions, CVOCs catalysts face technical difficulties such as low activity, chlorine poisoning, high temperature deactivation, and loss of active elements, which to some extent inhibit the application of this technology.

[0004] Chinese patent CN116251619B discloses an integral catalyst for catalytic combustion of chlorine-containing VOCs and its preparation method, which uses ruthenium (Ru) as an active element and simultaneously loads B and transition metals on molecular sieve-modified CeO2. The catalyst exhibits high activity, high stability, and strong resistance to chlorine poisoning.

[0005] A patent document with publication number CN102200287A discloses a method for eliminating chlorinated aromatic hydrocarbons by catalytic combustion, which mainly uses cerium oxide nanorods, nanocubes, and nanooctahedra as carriers to load precious metal ruthenium as a catalyst. The catalyst has high activity, generates no by-products, does not cause secondary pollution, has strong resistance to chlorine poisoning, and has a long catalyst life.

[0006] The catalysts mentioned in the above patent documents show certain industrial application prospects for chlorine-containing VOCs, but the concentration fluctuations of chlorine-containing VOCs in actual industrial waste gas lead to high temperature, high water vapor, and high concentration of acidic gas conditions. Under these conditions, the catalyst will also experience loss of active elements and sintering deactivation of the catalyst. Therefore, the catalytic combustion method to eliminate chlorine VOCs under actual industrial conditions still needs to overcome the above unfavorable factors. Summary of the invention

[0007] In view of the above technical problems and the deficiencies in the art, the present invention provides a chlorine-containing VOCs catalytic combustion catalyst and a preparation method and application thereof.

[0008] [1] A chlorine-containing VOCs catalytic combustion catalyst, comprising a carrier cerium-zirconium solid solution and an active metal ruthenium, a promoter phosphorus and a promoter alkaline earth metal supported on the surface of the carrier;

[0009] The alkaline earth metal includes at least one of calcium, magnesium and barium.

[0010] The preparation method of the cerium-zirconium solid solution may include:

[0011] Citric acid is added to a solution containing a cerium precursor and a zirconium precursor, and the mixture is stirred, dried and calcined to obtain the cerium-zirconium solid solution.

[0012] In the method for preparing the cerium-zirconium solid solution, the cerium precursor and the zirconium precursor may both be nitrates.

[0013] In the method for preparing the cerium-zirconium solid solution, the molar ratio of cerium in the cerium precursor to zirconium in the zirconium precursor may be 1:(0.1-0.4), preferably 1:(0.15-0.3), and more preferably 1:(0.2-0.3).

[0014] In the method for preparing the cerium-zirconium solid solution, the ratio of the total molar number of cerium in the cerium precursor and the total molar number of zirconium in the zirconium precursor to the molar number of citric acid may be 1:(0.5-2.5), preferably 1:(1-1.5).

[0015] In the method for preparing the cerium-zirconium solid solution, the calcination temperature may be 380-420°C, preferably 400°C.

[0016] In the method for preparing the cerium-zirconium solid solution, the calcination time may be 3 to 5 hours, preferably 4 hours.

[0017] In the chlorine-containing VOCs catalytic combustion catalyst, the molar ratio of cerium to zirconium in the cerium-zirconium solid solution may be 1:(0.1-0.4), preferably 1:(0.15-0.3), and further preferably 1:(0.2-0.3).

[0018] In the chlorine-containing VOCs catalytic combustion catalyst, the mass ratio of the ruthenium to the cerium-zirconium solid solution may be (0.4-2):100, preferably 1.5:100.

[0019] In the chlorine-containing VOCs catalytic combustion catalyst, the mass ratio of the phosphorus to the cerium-zirconium solid solution may be 1 to 5:100, preferably 1.5 to 3:100, and more preferably 2:100.

[0020] In the chlorine-containing VOCs catalytic combustion catalyst, the mass ratio of the alkaline earth metal to the cerium-zirconium solid solution can be (1-10):100, preferably (2-5):100, for example, 2:100, 3:100, 5:100, etc.

[0021] [2] The method for preparing a chlorine-containing VOCs catalytic combustion catalyst according to [1] comprises: loading active metal ruthenium, auxiliary phosphorus and auxiliary alkaline earth metal onto the surface of a carrier cerium-zirconium solid solution.

[0022] The preparation method of the chlorine-containing VOCs catalytic combustion catalyst can load the active metal ruthenium, the auxiliary phosphorus and the auxiliary alkaline earth metal onto the surface of the carrier cerium zirconium solid solution by co-impregnation or step-by-step impregnation.

[0023] In some embodiments, the preparation method of the chlorine-containing VOCs catalytic combustion catalyst adopts equal volume impregnation, and a solution containing a ruthenium precursor, a phosphorus precursor and an alkaline earth metal precursor is added to the carrier cerium zirconium solid solution, and then dried and calcined to obtain the chlorine-containing VOCs catalytic combustion catalyst.

[0024] The ruthenium precursor may include at least one of ruthenium nitrate and ruthenium chloride.

[0025] The phosphorus precursor may include at least one of trimethyl phosphate and phosphoric acid.

[0026] The alkaline earth metal precursor may be a chloride.

[0027] The calcination temperature may be 380-420°C, preferably 400°C.

[0028] The calcination time may be 3 to 5 hours, preferably 4 hours.

[0029] [3] Use of the chlorinated VOCs catalytic combustion catalyst according to [1] in catalytic combustion of chlorinated VOCs. Further, the chlorinated VOCs may include at least one of dichloromethane, chlorobenzene, and dichloroethylene. The chlorinated VOCs catalytic combustion catalyst can maintain high activity and stability under high water vapor, high temperature, and high concentration of chlorinated VOCs.

[0030] Compared with the prior art, the present invention has the following beneficial effects:

[0031] The catalyst of the present invention uses the noble metal Ru as an active element, and the cerium-zirconium solid solution is prepared by the citric acid complexation method. The cerium oxide surface in the cerium-zirconium solid solution has abundant lattice oxygen, and the introduction of zirconium oxide can greatly improve the high-temperature stability of the carrier. The additive P increases the acidity of the carrier surface and can improve the catalyst's anti-chlorine poisoning stability.

[0032] In actual exhaust gas conditions, the precious metal Ru is easily chlorinated during the reaction process, and the Ru element volatilizes under long-term and instantaneous high-temperature conditions, resulting in the loss of active components. Calcium, magnesium, and barium alkaline earth metals have electron-donating effects in the catalyst system of the present invention. Their introduction can protect the precious metal Ru, keep the precious metal Ru in a low-valent state, effectively inhibit the chlorination of the Ru element, and greatly reduce the loss of Ru.

[0033] The catalyst of the present invention has high activity, resistance to chlorine poisoning, resistance to loss of active elements and high temperature stability. In addition, the catalyst preparation method of the present invention is simple, the raw material source is wide, there is no special requirement for equipment, it is easy to prepare on a large scale, and has certain industrial application prospects. DETAILED DESCRIPTION

[0034] The present invention will be further described below in conjunction with specific examples. It should be understood that these examples are only used to illustrate the present invention and are not intended to limit the scope of the present invention.

[0035] Embodiment 1:

[0036] Weigh 8.682g of cerium nitrate hexahydrate and 1.357g of zirconium nitrate and dissolve them in 100mL of deionized water. Stir for 30min and then add 4.611g of citric acid. Continue stirring for 60min and then put it in an oven and dry it at 120℃ for 6h. Then put it in a muffle furnace and calcine it at 400℃ for 4h. After cooling, grind it to obtain a cerium-zirconium carrier.

[0037] Embodiment 2:

[0038] Weigh 8.682g of cerium nitrate hexahydrate and 2.035g of zirconium nitrate and dissolve them in 100mL of deionized water. Stir for 30min and then add 4.995g of citric acid. Continue stirring for 60min and then put it in an oven to dry at 120℃ for 6h. Then put it in a muffle furnace and calcine it at 400℃ for 4h. After cooling, grind it to obtain a cerium-zirconium carrier.

[0039] Embodiment 3:

[0040] Weigh 5 g of the carrier in Example 1. Weigh 0.536 g of ruthenium nitrate solution with a ruthenium concentration of 14 wt%, 0.452 g of trimethyl phosphate, and 0.396 g of magnesium chloride, dissolve them in 2.25 g of deionized water, and stir for 30 minutes to obtain an impregnation solution. Add the impregnation solution to the carrier while stirring. After the addition is completed, let it stand for 4 hours. Then dry it at 100°C for 8 hours, and finally calcine it at 400°C for 4 hours to obtain a chlorine-containing VOCs catalytic combustion catalyst.

[0041] Embodiment 4:

[0042] The difference from Example 3 is only that the magnesium chloride consumption is changed to 0.596g, and all the other are the same.

[0043] Embodiment 5:

[0044] The difference from Example 3 is only that the magnesium chloride consumption becomes 0, and all the other are the same.

[0045] Embodiment 6:

[0046] The difference from Example 3 is that the amount of trimethyl phosphate is changed to 0, and the rest is the same.

[0047] Embodiment 7:

[0048] The difference from Example 3 is only that 0.694g of calcium chloride is used to replace 0.396g of magnesium chloride, and the rest is the same.

[0049] Comparative Example 1:

[0050] Weigh 8.682g of cerium nitrate hexahydrate and dissolve it in 100mL of deionized water. After stirring for 30min, add 3.842g of citric acid. Continue stirring for 60min and then put it in an oven to dry at 120℃ for 6h. Then put it in a muffle furnace and roast it at 400℃ for 4h. After cooling, grind it to obtain a cerium oxide carrier.

[0051] Weigh 5g of the cerium oxide carrier mentioned above. Weigh 0.536g of ruthenium nitrate solution with a ruthenium concentration of 14wt%, dissolve it in 2.25g of deionized water, and stir for 30min to obtain an impregnation solution. Add the impregnation solution to the carrier dropwise while stirring. After the addition is completed, let it stand for 4h. Then dry it at 100℃ for 8h, and finally calcine it at 400℃ for 4h to obtain a catalyst.

[0052] Comparative Example 2:

[0053] The difference from Example 3 is only that the amounts of trimethyl phosphate and magnesium chloride are changed to 0, and the rest are the same.

[0054] Evaluation of powder catalyst activity:

[0055] The powder catalysts involved in Examples 3 to 6 and Comparative Examples 1 to 2 were evaluated for their activity in catalytic combustion of dichloromethane in a fixed bed reactor. 200 mg of a 40-60 mesh powder catalyst was weighed into a fixed bed reactor, and 83.3 mL / min of air was introduced into the reactor, wherein the dichloromethane concentration in the air was 3000 mg / m 3 , the total mass space velocity is 25000mL / (h·g), where g is the mass of the catalyst. The concentration of dichloromethane in the tail gas of the reactor under different temperature conditions is measured by temperature programming, the conversion rate of dichloromethane is calculated, and the temperature at which the conversion rate of dichloromethane is 50% and 90% is recorded, which are recorded as T 50 , T 90 .

[0056] The evaluation results of the catalyst are shown in Table 1.

[0057] Table 1

[0058] catalyst <![CDATA[T 50 (℃)]]> <![CDATA[T 90 (℃)]]> Example 3 243.4 275.3 Example 4 255.2 280.5 Example 5 240.2 270.3 Example 6 260.2 288.5 Example 7 248.5 279.4 Comparative Example 1 270.3 310.5 Comparative Example 2 283.4 330.4

[0059] Catalyst thermal stability test:

[0060] The powder catalysts involved in Examples 3 to 6 and Comparative Examples 1 to 2 were placed in a muffle furnace and calcined at 650°C for 10 hours, and then taken out, and the catalytic activity of the catalysts to dichloromethane was evaluated under the same conditions as described above. The catalyst activity after high temperature treatment is shown in Table 2.

[0061] Table 2

[0062] catalyst <![CDATA[T 50 (℃)]]> <![CDATA[T 90 (℃)]]> Example 3 245.2 279.3 Example 4 257.3 282.3 Example 5 245.6 295.3 Example 6 285.2 305.6 Example 7 251.2 282.1 Comparative Example 1 320.5 387.4 Comparative Example 2 310.4 370.5

[0063] Catalyst active element anti-loss test:

[0064] The powder catalysts involved in Examples 3 to 6 and Comparative Examples 1 to 2 were placed in an atmosphere of 15 vol% H2O, 5 vol% HCl, and the rest was air at 600°C for 10 hours, and then the catalytic activity of the catalysts to dichloromethane was tested under the same conditions as described above. At the same time, the Ru content in the catalyst was tested by ICP method. The test results and ICP analysis results are shown in Table 3.

[0065] Table 3

[0066] catalyst <![CDATA[T 50 (℃)]]> <![CDATA[T 90 (℃)]]> Ru content (wt%) Example 3 246.3 280.5 1.45 Example 4 258.3 285.4 1.48 Example 5 277.5 340.5 1.12 Example 6 270.3 291.3 1.43 Example 7 249.2 295.4 1.45 Comparative Example 1 340.3 410.5 0.56 Comparative Example 2 320.4 393.3 0.82

[0067] Catalyst stability test:

[0068] 200 mg of the powder catalyst in Example 3 of 40-60 mesh was weighed and placed in a fixed bed reactor. Air at a flow rate of 83.3 mL / min was introduced into the reactor, wherein the concentration of dichloromethane in the air was 3000 mg / min. 3 , the total mass space velocity is 25000 ml / (h·g), where g is the mass of the catalyst. The reaction was continued at 300°C for 100 h. The catalyst activity at different reaction times was recorded, and the corresponding results are shown in Table 4.

[0069] Table 4

[0070] Reaction time (h) Dichloromethane conversion rate (%) 10 99.2 20 99.2 30 99.2 40 99.1 50 99.1 60 99.0 70 99.1 80 99.0 90 99.1 100 99.0

[0071] It can be seen from Table 1 that the catalyst involved in the present invention shows higher activity than the comparative example. Combined with Table 2, it can be seen that the cerium-zirconium solid solution carrier of Comparative Example 2 has relatively better high-temperature stability than the cerium oxide carrier of Comparative Example 1.

[0072] Combining Table 1 and Table 2, it can be found that the catalytic activity of the catalyst of the present invention remains basically unchanged after high temperature treatment at 650° C. The catalyst of Example 5 contains no alkaline earth metal, and the catalyst of Example 6 contains no phosphorus, and the high temperature stability of these two catalysts is significantly reduced.

[0073] It can be found from Table 3 that the catalyst involved in the present invention has no obvious deactivation of catalyst activity after being treated with high water vapor, high temperature and high concentration of HCl, and there is also no obvious loss of active elements. The catalyst of Example 5 has no alkaline earth metal, and the active metal ruthenium has obvious loss. Comparing Comparative Examples 1 and 2, it can be found that the use of a carrier cerium-zirconium solid solution is also helpful for the inhibition of active metal ruthenium compared to the carrier cerium oxide. Comparing Example 5 and Comparative Example 2, it can be found that the introduction of phosphorus can also inhibit the loss of active metal ruthenium to a certain extent. From the comparison of Examples 5, 6 and Comparative Example 2, it can be found that compared with phosphorus, alkaline earth metals have a greater effect in inhibiting the loss of active metal ruthenium.

[0074] Table 4 shows that the catalyst involved in the present invention has higher stability.

[0075] In summary, the catalyst involved in the present invention has high activity, resistance to chlorine poisoning, resistance to loss of active elements and high temperature stability.

[0076] In addition, it should be understood that after reading the above description of the present invention, those skilled in the art may make various changes or modifications to the present invention, and these equivalent forms also fall within the scope defined by the claims attached to this application.

Claims

1. A chlorine-containing VOCs catalytic combustion catalyst, characterized in that: The invention comprises a carrier cerium-zirconium solid solution and active metal ruthenium, auxiliary phosphorus and auxiliary alkaline earth metal loaded on the surface of the carrier; The alkaline earth metal includes at least one of calcium, magnesium and barium.

2. The chlorine-containing VOCs catalytic combustion catalyst according to claim 1, characterized in that: The preparation method of the cerium-zirconium solid solution comprises: Citric acid is added to a solution containing a cerium precursor and a zirconium precursor, and the mixture is stirred, dried and calcined to obtain the cerium-zirconium solid solution.

3. The chlorine-containing VOCs catalytic combustion catalyst according to claim 2, characterized in that: In the preparation method of the cerium-zirconium solid solution: The cerium precursor and the zirconium precursor are both nitrates; The molar ratio of cerium in the cerium precursor to zirconium in the zirconium precursor is 1:(0.1-0.4), preferably 1:(0.15-0.3), and more preferably 1:(0.2-0.3); The ratio of the total molar number of cerium in the cerium precursor and the total molar number of zirconium in the zirconium precursor to the molar number of citric acid is 1:(0.5-2.5), preferably 1:(1-1.5); The calcination temperature is 380-420°C, preferably 400°C; The calcination time is 3 to 5 hours, preferably 4 hours.

4. The chlorine-containing VOCs catalytic combustion catalyst according to claim 1, characterized in that: The molar ratio of cerium to zirconium in the cerium-zirconium solid solution is 1:(0.1-0.4), preferably 1:(0.15-0.3), and more preferably 1:(0.2-0.3); The mass ratio of the ruthenium to the cerium-zirconium solid solution is (0.4-2):100, preferably 1.5:100; The mass ratio of the phosphorus to the cerium-zirconium solid solution is (1-5):100, preferably (1.5-3):100, and more preferably 2:100; The mass ratio of the alkaline earth metal to the cerium-zirconium solid solution is (1-10):100, preferably (2-5):

100.

5. The method for preparing a chlorine-containing VOCs catalytic combustion catalyst according to any one of claims 1 to 4, characterized in that: include: Active metal ruthenium, auxiliary phosphorus and auxiliary alkaline earth metal are loaded onto the surface of the carrier cerium-zirconium solid solution.

6. The preparation method according to claim 5, characterized in that: The active metal ruthenium, the auxiliary phosphorus and the auxiliary alkaline earth metal are loaded onto the surface of the carrier cerium-zirconium solid solution by co-impregnation or step-by-step impregnation.

7. The preparation method according to claim 5, characterized in that: By adopting equal volume impregnation, a solution containing a ruthenium precursor, a phosphorus precursor and an alkaline earth metal precursor is added dropwise to a carrier cerium-zirconium solid solution, followed by drying and calcination to obtain the chlorine-containing VOCs catalytic combustion catalyst.

8. The preparation method according to claim 7, characterized in that: The ruthenium precursor includes at least one of ruthenium nitrate and ruthenium chloride; The phosphorus precursor includes at least one of trimethyl phosphate and phosphoric acid; The alkaline earth metal precursor is a chloride; The calcination temperature is 380-420°C, preferably 400°C; The calcination time is 3 to 5 hours, preferably 4 hours.

9. Use of the catalyst for catalytic combustion of chlorine-containing VOCs according to any one of claims 1 to 4 in catalytic combustion of chlorine-containing VOCs.

10. The use according to claim 9, characterized in that: The chlorine-containing VOCs include at least one of dichloromethane, chlorobenzene and dichloroethylene.