A catalyst for catalytic combustion of chlorinated vocs and its preparation method and application

Abstract

The application discloses a chlorine-containing VOCs catalytic combustion catalyst, a preparation method thereof and application of the catalyst in catalytic combustion of chlorine-containing VOCs. The chlorine-containing VOCs catalytic combustion catalyst comprises a carrier cerium-zirconium solid solution and active metals ruthenium, an assistant phosphorus and an assistant alkaline earth metal supported on the surface of the carrier; the alkaline earth metal comprises at least one of calcium, magnesium and barium. The preparation method comprises the following steps: loading the active metals ruthenium, the assistant phosphorus and the assistant alkaline earth metal on the surface of the carrier cerium-zirconium solid solution. The catalyst has high activity, is resistant to chlorine poisoning, resistant to loss of active elements and has high-temperature stability. In addition, the preparation method of the catalyst is simple, raw materials are widely sourced, no special requirements are needed for equipment, the catalyst is easy to be prepared on a large scale, and has certain industrial application prospect.

Description

Technical Field

[0001] This invention relates to the field of industrial exhaust gas treatment, specifically to a chlorine-containing VOCs catalytic combustion catalyst that combines high activity, resistance to chlorine poisoning, resistance to loss of active elements, and high-temperature stability, as well as its preparation method and application. Background Technology

[0002] Chlorinated volatile organic compounds (CVOCs) are a type of volatile organic compound (VOC). Compared to ordinary VOCs, chlorinated VOCs have stronger carcinogenic, teratogenic, and mutagenic effects. CVOCs emitted into the atmosphere pose a greater threat to human health and the environment. However, CVOCs are widely used in pharmaceuticals, chemicals, dyes, leather, electronics, and other fields, making them irreplaceable. Therefore, it is impossible to completely avoid the use of CVOCs at the source; exhaust gas treatment is a feasible solution to reduce the harm caused by CVOCs.

[0003] Catalytic combustion is one of the many feasible technologies for treating VOCs. However, under actual industrial conditions, CVOC catalysts face technical challenges such as low activity, chlorine poisoning, high-temperature deactivation, and loss of active elements, which to some extent inhibits the application of this technology.

[0004] Chinese patent CN116251619B discloses an integral catalyst for the catalytic combustion of chlorine-containing VOCs and its preparation method. Ruthenium (Ru) is used as the active element, and B and transition metals are loaded onto CeO2 modified with molecular sieve. The catalyst exhibits high activity, high stability and strong resistance to chlorine poisoning.

[0005] The patent document with publication number CN102200287A discloses a method for eliminating chlorinated aromatic hydrocarbons by catalytic combustion. It mainly uses cerium oxide nanorods, nanocubes, and nanooctahedrons as supports to support the noble metal ruthenium as a catalyst. The catalyst has high activity, no by-products are generated, no secondary pollution is caused, strong resistance to chlorine poisoning, and long catalyst life.

[0006] The catalysts mentioned in the aforementioned patent documents show promising industrial applications for chlorinated VOCs. However, fluctuations in the concentration of chlorinated VOCs in actual industrial waste gas lead to conditions such as high temperature, high moisture content, and high concentrations of acidic gases. Under these conditions, the catalysts may experience loss of active elements and sintering deactivation. Therefore, the elimination of chlorinated VOCs by catalytic combustion under actual industrial conditions still needs to overcome these unfavorable factors. Summary of the Invention

[0007] To address the aforementioned technical problems and shortcomings in this field, the present invention provides a chlorine-containing VOCs catalytic combustion catalyst, its preparation method, and its application.

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

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

[0010] The method for preparing the cerium-zirconium solid solution may include:

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

[0012] In the method for preparing the cerium-zirconium solid solution, both the cerium precursor and the zirconium precursor can 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 can 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 zirconium in the zirconium precursor to the molar number of citric acid can be 1:(0.5-2.5), preferably 1:(1-1.5).

[0015] In the preparation method of the cerium-zirconium solid solution, the calcination temperature can be 380-420℃, preferably 400℃.

[0016] In the method for preparing the cerium-zirconium solid solution, the calcination time can 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 can be 1:(0.1-0.4), preferably 1:(0.15-0.3), and more preferably 1:(0.2-0.3).

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

[0019] In the chlorine-containing VOCs catalytic combustion catalyst, the mass ratio of phosphorus to the cerium-zirconium solid solution can 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 preparation method of the chlorine-containing VOCs catalytic combustion catalyst according to [1] includes: loading active metal ruthenium, auxiliary phosphorus and auxiliary alkaline earth metal onto the surface of the support cerium zirconium solid solution.

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

[0023] In some embodiments, the preparation method of the chlorine-containing VOCs catalytic combustion catalyst involves equal-volume impregnation, adding a solution containing ruthenium precursor, phosphorus precursor and alkaline earth metal precursor dropwise to a cerium-zirconium solid solution support, followed by drying and calcination 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 can be 380–420°C, preferably 400°C.

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

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

[0030] Compared with the prior art, the beneficial effects of this invention are as follows:

[0031] This invention uses the noble metal Ru as the active element in the catalyst, and prepares a cerium-zirconium solid solution using a 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 significantly improve the high-temperature stability of the support. The promoter P increases the acidity of the support surface, which can improve the catalyst's resistance to chlorine poisoning.

[0032] In actual waste gas conditions, the precious metal Ru is prone to chlorination during the reaction process. Under long-term and instantaneous high-temperature conditions, Ru volatilizes, leading to the loss of active components. Calcium, magnesium, and barium alkaline earth metals have electron-donating effects in the catalyst system of this invention. Their introduction can protect the precious metal Ru, keeping Ru in a low valence state, effectively inhibiting Ru chlorination, and significantly reducing Ru loss.

[0033] The catalyst of this invention combines high activity, resistance to chlorine poisoning, resistance to loss of active elements, and high-temperature stability. Furthermore, the catalyst preparation method involved in this invention is simple, the raw materials are widely available, no special equipment requirements are needed, it is easy to prepare on a large scale, and it has certain prospects for industrial application. Detailed Implementation

[0034] The present invention will be further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention.

[0035] Example 1:

[0036] 8.682 g of cerium nitrate hexahydrate and 1.357 g of zirconium nitrate were weighed and dissolved in 100 mL of deionized water. After stirring for 30 min, 4.611 g of citric acid was added. Stirring was continued for 60 min, and the mixture was dried in an oven at 120 °C for 6 h. Subsequently, it was calcined in a muffle furnace at 400 °C for 4 h. After cooling, the mixture was ground to obtain the cerium-zirconium support.

[0037] Example 2:

[0038] 8.682 g of cerium nitrate hexahydrate and 2.035 g of zirconium nitrate were weighed and dissolved in 100 mL of deionized water. After stirring for 30 min, 4.995 g of citric acid was added. Stirring continued for 60 min, and the mixture was then dried in an oven at 120 °C for 6 h. Subsequently, it was calcined in a muffle furnace at 400 °C for 4 h. After cooling, the mixture was ground to obtain the cerium-zirconium support.

[0039] Example 3:

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

[0041] Example 4:

[0042] The only difference from Example 3 is that the amount of magnesium chloride used is changed to 0.596g, and everything else is the same.

[0043] Example 5:

[0044] The only difference from Example 3 is that the amount of magnesium chloride is reduced to 0; all other aspects are the same.

[0045] Example 6:

[0046] The only difference from Example 3 is that the amount of trimethyl phosphate is reduced to 0; all other aspects are the same.

[0047] Example 7:

[0048] The only difference from Example 3 is that 0.694g of calcium chloride is used instead of 0.396g of magnesium chloride; all other aspects are the same.

[0049] Comparative Example 1:

[0050] 8.682 g of cerium nitrate hexahydrate was dissolved in 100 mL of deionized water. After stirring for 30 min, 3.842 g of citric acid was added. Stirring continued for 60 min, and the mixture was then dried in an oven at 120 °C for 6 h. Subsequently, it was calcined in a muffle furnace at 400 °C for 4 h. After cooling, the mixture was ground to obtain the cerium oxide support.

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

[0052] Comparative Example 2:

[0053] The only difference from Example 3 is that the amounts of trimethyl phosphate and magnesium chloride are both reduced to 0; all other aspects are the same.

[0054] Powder catalyst activity evaluation:

[0055] The activity of the powdered catalysts involved in Examples 3-6 and Comparative Examples 1-2 for the catalytic combustion of dichloromethane was evaluated in a fixed-bed reactor. 200 mg of 40-60 mesh powdered catalyst was weighed into the fixed-bed reactor, and air was introduced into the reactor at a rate of 83.3 mL / min, wherein the concentration of dichloromethane in the air was 3000 mg / m³. 3 The total mass hourly space velocity (MHSV) was 25000 mL / (h·g), where g is the mass of the catalyst. The concentration of dichloromethane in the reactor tail gas was determined by programmed temperature rise under different temperature conditions. The conversion rate of dichloromethane was calculated, and the temperatures at which the dichloromethane conversion rate was 50% and 90% were recorded, denoted 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 powdered catalysts involved in Examples 3-6 and Comparative Examples 1-2 were calcined in a muffle furnace at 650°C for 10 hours, and then removed and evaluated for their catalytic activity against dichloromethane under the same conditions described above. The catalyst activities after high-temperature treatment are 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 loss resistance test:

[0064] The powder catalysts involved in Examples 3-6 and Comparative Examples 1-2 were treated at 600°C for 10 hours in an atmosphere of 15 vol% H2O, 5 vol% HCl, and the remainder air. Their catalytic activity against dichloromethane was then tested under the same conditions described above. Simultaneously, the Ru content in the catalysts was determined by ICP. 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] Weigh 200 mg of the 40-60 mesh powder catalyst from Example 3 into a fixed-bed reactor, and introduce air into the reactor at a rate of 83.3 mL / min, wherein the concentration of dichloromethane in the air is 3000 mg / m³. 3 The total mass hourly space velocity (MHSV) was 25000 ml / (h·g), where g represents the mass of the catalyst. The reaction was carried out continuously 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] As can be seen from Table 1, the catalyst involved in this invention exhibits higher activity compared to the comparative example. Combined with Table 2, it can be seen that the cerium-zirconium solid solution supported in Comparative Example 2 has relatively better high-temperature stability compared to the cerium oxide supported in Comparative Example 1.

[0072] Referring to Tables 1 and 2, it can be seen that the catalysts involved in this invention maintain essentially no change in catalytic activity after high-temperature treatment at 650℃. The catalyst in Example 5 is free of alkaline earth metals, and the catalyst in Example 6 is free of phosphorus; both catalysts exhibit significantly reduced high-temperature stability.

[0073] Table 3 shows that the catalyst involved in this invention exhibits no significant deactivation after treatment with high water vapor, high temperature, and high concentration of HCl, and there is also no significant loss of active elements. In Example 5, the catalyst lacks alkaline earth metals, and there is a significant loss of the active metal ruthenium. Comparing Comparative Examples 1 and 2 reveals that using a cerium-zirconium solid solution as a support is more helpful in suppressing the loss of active metal ruthenium compared to using cerium oxide as a support. Comparing Example 5 and Comparative Example 2 shows that the introduction of phosphorus can also suppress the loss of active metal ruthenium to some extent. A comparison of Examples 5 and 6 with Comparative Example 2 shows that alkaline earth metals have a greater effect on suppressing the loss of active metal ruthenium compared to phosphorus.

[0074] Table 4 illustrates that the catalyst involved in this invention has high stability.

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

[0076] Furthermore, it should be understood that after reading the above description of the present invention, those skilled in the art can make various alterations or modifications to the present invention, and these equivalent forms also fall within the scope defined by the appended claims.

Claims

1. Use of a chlorine-containing VOCs catalytic combustion catalyst for catalytic combustion of chlorine-containing VOCs, characterized in that, The chlorine-containing VOCs catalytic combustion catalyst comprises a cerium-zirconium solid solution carrier and active metal ruthenium, an auxiliary agent phosphorus and an auxiliary agent alkaline earth metal loaded on the surface of the carrier; The alkaline earth metal is at least one of calcium and magnesium; The preparation method of the chlorine-containing VOCs catalytic combustion catalyst comprises loading active metal ruthenium, an auxiliary agent phosphorus and an auxiliary agent alkaline earth metal on the surface of a cerium-zirconium solid solution carrier; An equal-volume impregnation method is adopted, a solution containing a ruthenium precursor, a phosphorus precursor and an alkaline earth metal precursor is dropped into the carrier cerium-zirconium solid solution, and then drying and calcination are performed to obtain the chlorine-containing VOCs catalytic combustion catalyst; the alkaline earth metal precursor is a chloride; the calcination temperature is 380-420 DEG C.

2. Use according to claim 1, characterized in that, The preparation method of the cerium-zirconium solid solution comprises adding citric acid to a solution containing a cerium precursor and a zirconium precursor, stirring, drying and calcining to obtain the cerium-zirconium solid solution.

3. Use 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 nitrate; The molar ratio of cerium in the cerium precursor to zirconium in the zirconium precursor is 1:(0.1-0.4); The ratio of the total moles of cerium in the cerium precursor and zirconium in the zirconium precursor to the moles of citric acid is 1:(0.5-2.5); The calcination temperature is 380-420 DEG C; The calcination time is 3-5 h.

4. Use 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); The mass ratio of the ruthenium to the cerium-zirconium solid solution is (0.4-2):100; The mass ratio of the phosphorus to the cerium-zirconium solid solution is (1-5):100; The mass ratio of the alkaline earth metal to the cerium-zirconium solid solution is (1-10):

100.

5. The use according to claim 1, characterized in that, The ruthenium precursor comprises at least one of ruthenium nitrate and ruthenium chloride; The phosphorus precursor comprises at least one of trimethyl phosphate and phosphoric acid; The calcination time is 3-5 h.

6. The use according to claim 1, characterized in that, The chlorine-containing VOCs comprise at least one of dichloromethane, chlorobenzene and dichloroethylene.