Preparation method of ruthenium-based catalyst and application of ruthenium-based catalyst in catalytic combustion of chlorine-containing VOCs (Volatile Organic Compounds)

Abstract

The invention discloses a preparation method of a ruthenium-based catalyst and application of the ruthenium-based catalyst in catalytic combustion of chlorine-containing VOCs (Volatile Organic Compounds). The ruthenium-based catalyst comprises a ZSM-5 molecular sieve carrier, and an active metal ruthenium, a synergistic metal molybdenum and an auxiliary agent phosphorus which are loaded on the surface of the carrier. The preparation method adopts an equivalent-volume impregnation method and comprises the following steps: dropwise adding a solution containing a ruthenium precursor, a phosphorus precursor and a molybdenum precursor into the ZSM-5 molecular sieve carrier, and then standing, drying and calcining to obtain the ruthenium-based catalyst. The catalyst shows high catalytic activity, excellent chlorine poisoning resistance, excellent high-temperature thermal stability and strong active component loss resistance in a catalytic combustion reaction of chlorine-containing VOCs, is especially suitable for high-temperature, high-humidity, high-corrosion and other complex industrial waste gas environments, and has a remarkable industrial application prospect.

Description

Technical Field

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

[0002] Chlorine-containing volatile organic compounds (Cl-VOCs or CVOCs), such as chlorobenzene, dichloromethane, and trichloroethylene, are typical and difficult-to-treat pollutants emitted from industries such as chemical, pharmaceutical, pesticide production, and waste incineration. They not only have carcinogenic, teratogenic, and mutagenic effects on humans, but also readily generate more toxic dioxins during heat treatment, posing a serious threat to the environment and public health.

[0003] Catalytic combustion is one of the effective technologies for treating volatile organic compounds (VOCs). However, in practical industrial applications, catalysts used for the purification of chlorine-containing VOCs (CVOCs) generally face problems such as insufficient activity, easy chlorine poisoning, high-temperature sintering, and loss of active components, which restricts the promotion of this technology.

[0004] In existing research, ruthenium (Ru)-based catalysts have shown promising application potential. For example, patent CN116251619B discloses a monolithic catalyst that achieves high activity, high stability, and strong resistance to chlorine poisoning by loading Ru, B, and transition metals onto CeO2 modified with molecular sieves. Another patent document, CN102200287A, reports the use of Ru loaded onto cerium oxide nanomaterials with different morphologies for the catalytic combustion of chlorinated aromatics. This catalyst exhibits high activity, few byproducts, long lifetime, and excellent resistance to chlorine poisoning.

[0005] Although the aforementioned catalysts perform well under laboratory conditions, in actual industrial waste gas environments, the concentration of chlorine-containing VOCs fluctuates greatly, often accompanied by complex conditions such as high temperature, high humidity, and high concentrations of acidic gases. This can easily lead to the loss of active components and catalyst sintering, resulting in a decline in performance. Therefore, developing CVOCs catalysts that can adapt to harsh industrial conditions and possess both high activity and high stability remains a key technical challenge that needs to be addressed. Summary of the Invention

[0006] In view of the above-mentioned technical problems and the shortcomings in the field, the present invention provides a method for preparing a ruthenium-based catalyst and its application in the catalytic combustion of chlorine-containing VOCs.

[0007] The specific technical solution is as follows: In a first aspect, the present invention provides a ruthenium-based catalyst comprising a ZSM-5 molecular sieve support and active metal ruthenium, synergistic metal molybdenum, and auxiliary phosphorus supported on the surface of the support.

[0008] Furthermore, the ZSM-5 molecular sieve support has a silicon-to-aluminum ratio of 70 and a pore size of 0.53~0.58 nm.

[0009] Furthermore, the mass ratio of the active metal ruthenium to the ZSM-5 molecular sieve support is (0.5~2):100, and even more specifically (1~2):100, for example 1.1:100, 1.2:100, 1.8:100, etc.

[0010] Furthermore, the mass ratio of the auxiliary phosphorus to the ZSM-5 molecular sieve carrier is (1~4):100, and even more so (2~3.5):100, for example 2.1:100, 2.2:100, 3.2:100, etc.

[0011] Furthermore, the mass ratio of the synergistic molybdenum metal to the ZSM-5 molecular sieve support is (0.5~5):100, and even more specifically (2~4.5):100, such as 2.1:100, 2.5:100, 3:100, 4:100, etc.

[0012] In a second aspect, the present invention provides a method for preparing the ruthenium-based catalyst described in the first aspect, which employs an equal-volume impregnation method, comprising: adding a solution containing a ruthenium precursor, a phosphorus precursor and a molybdenum precursor dropwise to a ZSM-5 molecular sieve support, and then allowing it to stand, dry and calcining to obtain the ruthenium-based catalyst.

[0013] Furthermore, the ruthenium precursor includes at least one of ruthenium nitrate and ruthenium chloride.

[0014] Furthermore, the phosphorus precursor includes at least one of trimethyl phosphate and phosphoric acid.

[0015] Furthermore, the molybdenum precursor includes at least one of ammonium molybdate (e.g., ammonium heptamolybdate tetrahydrate) and molybdenum chloride.

[0016] Furthermore, the calcination temperature is 350~420℃, and even more specifically 400℃.

[0017] Furthermore, the calcination time is 4 to 6 hours, and even more specifically, 5 hours.

[0018] Thirdly, the present invention provides the application of the ruthenium-based catalyst described in the first aspect for the catalytic combustion of chlorinated VOCs. Further, the chlorinated VOCs include one or more of chloromethane, dichloromethane, and chlorobenzene.

[0019] Fourthly, the present invention provides a method for catalytic combustion of chlorinated VOCs, utilizing the ruthenium-based catalyst described in the first aspect to catalytically combust the chlorinated VOCs. Further, the chlorinated VOCs include one or more of chloromethane, dichloromethane, chlorobenzene, vinyl chloride, and dichloroethylene.

[0020] The ruthenium-based catalyst described in this invention maintains excellent catalytic activity and stability under a wide range of conditions, including high temperature, high humidity, and high concentrations of chlorine-containing VOCs.

[0021] Compared with the prior art, the beneficial effects of this invention are as follows: In actual waste gas conditions, the precious metal Ru is prone to chlorination during the reaction, leading to the loss of active components. This invention introduces phosphorus (P) to increase the acidity of the support surface, thereby improving the catalyst's resistance to chlorine poisoning. Furthermore, it introduces synergistic molybdenum, which better anchors the precious metal Ru through intermetallic interactions, significantly reducing Ru loss.

[0022] The catalyst of this invention exhibits excellent comprehensive performance in the catalytic combustion of various CVOCs such as dichloromethane, chlorobenzene, vinyl chloride, and dichloroethylene, including high catalytic activity, excellent chlorine resistance, high selectivity for target products, and long-term thermal stability, showing broad prospects for industrial application. Detailed Implementation

[0023] 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.

[0024] The ZSM-5 molecular sieve used below has a silica-to-alumina ratio of 70 and a pore size of 0.53~0.58 nm.

[0025] Example 1: 1.08 g of a 10.8 wt% ruthenium nitrate solution, 0.962 g of trimethyl phosphate, and 0.368 g of ammonium heptamolybdate tetrahydrate were weighed and dissolved in 2.5 g of deionized water. After stirring for 30 min, an impregnation solution was obtained. 10 g of ZSM-5 molecular sieve was weighed. The impregnation solution was added dropwise to the support while stirring. After the addition was complete, the solution was allowed to stand for 4 h. Subsequently, it was dried at 80 °C for 8 h, and finally calcined at 400 °C for 5 h to obtain the ruthenium-based catalyst.

[0026] Example 2: 1.62 g of a 10.8 wt% ruthenium nitrate solution, 0.962 g of trimethyl phosphate, and 0.368 g of ammonium heptamolybdate tetrahydrate were weighed and dissolved in 2.5 g of deionized water. After stirring for 30 min, an impregnation solution was obtained. 10 g of ZSM-5 molecular sieve was weighed. The impregnation solution was added dropwise to the support while stirring. After the addition was complete, the solution was allowed to stand for 4 h. Subsequently, it was dried at 80 °C for 8 h, and finally calcined at 400 °C for 5 h to obtain the ruthenium-based catalyst.

[0027] Example 3: 1.08 g of a 10.8 wt% ruthenium nitrate solution, 1.443 g of trimethyl phosphate, and 0.368 g of ammonium heptamolybdate tetrahydrate were weighed and dissolved in 2.5 g of deionized water. After stirring for 30 min, an impregnation solution was obtained. 10 g of ZSM-5 molecular sieve was weighed. The impregnation solution was added dropwise to the support while stirring. After the addition was complete, the solution was allowed to stand for 4 h. Subsequently, it was dried at 80 °C for 8 h, and finally calcined at 400 °C for 5 h to obtain the ruthenium-based catalyst.

[0028] Example 4: 1.08 g of a 10.8 wt% ruthenium nitrate solution, 0.962 g of trimethyl phosphate, and 0.736 g of ammonium heptamolybdate tetrahydrate were weighed and dissolved in 2.5 g of deionized water. After stirring for 30 min, an impregnation solution was obtained. 10 g of ZSM-5 molecular sieve was weighed. The impregnation solution was added dropwise to the support while stirring. After the addition was complete, the solution was allowed to stand for 4 h. Subsequently, it was dried at 80 °C for 8 h, and finally calcined at 400 °C for 5 h to obtain the ruthenium-based catalyst.

[0029] Comparative Example 1: 1.08 g of a 10.8 wt% ruthenium nitrate solution and 0.368 g of ammonium heptamolybdate tetrahydrate were weighed and dissolved in 2.5 g of deionized water. After stirring for 30 min, an impregnation solution was obtained. 10 g of ZSM-5 molecular sieve was weighed. The impregnation solution was added dropwise to the support while stirring. After the addition was complete, the solution was allowed to stand for 4 h. Subsequently, it was dried at 80 °C for 8 h, and finally calcined at 400 °C for 5 h to obtain the ruthenium-based catalyst.

[0030] Comparative Example 2: 1.08 g of a 10.8 wt% ruthenium nitrate solution and 0.962 g of trimethyl phosphate were weighed and dissolved in 2.5 g of deionized water. After stirring for 30 min, an impregnation solution was obtained. 10 g of ZSM-5 molecular sieve was weighed. The impregnation solution was added dropwise to the support while stirring. After the addition was complete, the solution was allowed to stand for 4 h. Subsequently, it was dried at 80 °C for 8 h, and finally calcined at 400 °C for 5 h to obtain the ruthenium-based catalyst.

[0031] Powder catalyst activity evaluation: The activity of the powdered catalysts involved in Examples 1-4 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 66.6 mL / min, wherein the concentration of dichloromethane in the air was 3000 mg / m³. 3 The total mass hourly space velocity (MHSV) was 20000 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 .

[0032] The evaluation results of the catalyst are shown in Table 1.

[0033] Table 1

[0034] Comparing Examples 1 and 2, it can be seen that the ruthenium loading in Example 1 already has very good catalytic combustion performance of dichloromethane. Further increasing the ruthenium loading to the level of Example 2 does not significantly improve the catalytic combustion activity of the catalyst for dichloromethane.

[0035] Comparing Example 1, Example 3 and Comparative Example 1, it can be seen that in the catalyst system of the present invention, a certain amount of phosphorus can improve the catalyst's activity in catalytic combustion of dichloromethane, but if too much is added, it will also tend to reduce the catalyst's activity in catalytic combustion of dichloromethane.

[0036] Comparing Example 1, Example 4 and Comparative Example 2, it can be seen that in the catalyst system of the present invention, a certain amount of synergistic molybdenum can improve the catalyst's activity in catalytic combustion of dichloromethane, but if too much is added, it will also tend to reduce the catalyst's activity in catalytic combustion of dichloromethane.

[0037] Catalyst thermal stability test: The powdered catalysts involved in Examples 1-4 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.

[0038] Table 2

[0039] Catalyst active element loss resistance test: The powder catalysts involved in Examples 1-4 and Comparative Examples 1-2 were treated at 600°C for 10 h in an atmosphere of 10 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.

[0040] Table 3

[0041] Catalyst stability test: 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 66.6 mL / min, wherein the concentration of dichloromethane in the air is 3000 mg / m³. 3 The total mass hourly space velocity (MHSV) was 20,000 ml / (h·g), where g represents the mass of the catalyst. The reaction was carried out continuously at 350 °C for 120 h. The catalyst activity at different reaction times was recorded, and the corresponding results are shown in Table 4.

[0042] Table 4

[0043] The experimental data summarized in Tables 1 to 4 show that the catalyst of this invention is significantly superior to the comparative example in terms of catalytic activity, high-temperature stability, and resistance to harsh operating conditions. Specifically: As can be seen from Table 1, the catalyst of the present invention exhibits higher initial activity compared to the comparative example.

[0044] Comparing the data in Tables 1 and 2, it can be seen that the catalyst of the present invention remains stable after being treated at 650℃, while Comparative Example 1 (lacking promoter P) and Comparative Example 2 (lacking synergistic molybdenum) show significant deactivation, proving that both contribute to thermal stability.

[0045] Table 3 further reveals that under harsh conditions of high temperature, high moisture content, and high concentration of HCl, the catalyst of this invention not only showed no activity decay but also exhibited no significant loss of active ruthenium metal; in contrast, Comparative Example 2 showed severe ruthenium loss. A comparison of Example 1 with Comparative Examples 1 and 2 shows that both the promoter P and the synergistic metal molybdenum can inhibit ruthenium loss, but the role of molybdenum is more crucial.

[0046] The data in Table 4 show that the catalyst exhibits strong stability during a continuous reaction at 350℃ for 120 hours.

[0047] In summary, this invention successfully prepared a catalyst that combines high activity, excellent resistance to chlorine poisoning, superior high-temperature stability, and efficient inhibition of active component loss. In the catalytic combustion reaction of chlorine-containing VOCs (such as chloromethane, dichloromethane, and chlorobenzene), this catalyst exhibits high catalytic activity, excellent resistance to chlorine poisoning, superior high-temperature thermal stability, and strong resistance to active component loss. It is particularly suitable for complex industrial waste gas environments characterized by high temperature, high humidity, and high corrosiveness, and shows significant promise for industrial applications.

[0048] 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. A ruthenium-based catalyst, characterized in that, It includes a ZSM-5 molecular sieve support and active metal ruthenium, synergistic metal molybdenum, and auxiliary phosphorus loaded on the surface of the support.

2. The ruthenium-based catalyst according to claim 1, characterized in that, The ZSM-5 molecular sieve support has a silicon-to-aluminum ratio of 70 and a pore size of 0.53~0.58 nm.

3. The ruthenium-based catalyst according to claim 1, characterized in that, The mass ratio of the active metal ruthenium to the ZSM-5 molecular sieve support is (0.5~2):100, and more specifically (1~2):

100.

4. The ruthenium-based catalyst according to claim 1, characterized in that, The mass ratio of the auxiliary phosphorus to the ZSM-5 molecular sieve carrier is (1~4):100, and more specifically (2~3.5):

100.

5. The ruthenium-based catalyst according to claim 1, characterized in that, The mass ratio of the synergistic molybdenum metal to the ZSM-5 molecular sieve support is (0.5~5):100, and more specifically (2~4.5):

100.

6. The method for preparing the ruthenium-based catalyst according to any one of claims 1 to 5, characterized in that, The ruthenium-based catalyst was obtained by using an equal-volume impregnation method, which included: adding a solution containing ruthenium precursor, phosphorus precursor and molybdenum precursor dropwise to a ZSM-5 molecular sieve support, and then allowing it to stand, dry and calcining.

7. The method for preparing the ruthenium-based catalyst according to claim 6, 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 molybdenum precursor includes at least one of ammonium molybdate and molybdenum chloride; The calcination temperature is 350~420℃, and more specifically 400℃; The calcination time is 4-6 hours, and more specifically 5 hours.

8. The application of the ruthenium-based catalyst according to any one of claims 1 to 5 for the catalytic combustion of chlorine-containing VOCs.

9. The application according to claim 8, characterized in that, The chlorine-containing VOCs include one or more of chloromethane, dichloromethane, chlorobenzene, vinyl chloride, and dichloroethylene.

10. A method for catalytic combustion of chlorine-containing VOCs, characterized in that, The ruthenium-based catalyst according to any one of claims 1 to 5 is used to catalytically combust chlorine-containing VOCs.

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