Preparation method of composite catalyst based on waste polishing powder and application of composite catalyst in degradation of chlorinated VOCs
By in-situ growing HZSM-5 molecular sieve on the surface of waste polishing powder to prepare a cerium-lanthanum composite catalyst, the problems of high catalyst cost and poor stability were solved, and the efficient degradation of CVOCs and recycling of resources were achieved, which has environmental and economic benefits.
Patent Information
- Application Number
- CN202510848085.7
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-06-24
- Publication Date
- 2025-09-23
AI Technical Summary
The catalysts in existing catalytic oxidation technologies are expensive, have low resource utilization, have limited catalytic effects on chlorinated volatile organic compounds (CVOCs), and have poor stability and chlorine tolerance.
Using waste polishing powder as raw material, HZSM-5 molecular sieve was synthesized on its surface by in situ growth method to form HZSM-5@WPP composite catalyst with cerium and lanthanum as the main components. Combined with the synergistic effect of rare earth elements, the redox ability and acidic sites were enhanced, and the adsorption and activation performance of CVOCs were improved.
It realizes the recycling and utilization of rare earth resources, reduces production costs, significantly improves catalytic oxidation performance, increases the conversion rate of CVOCs, reduces the generation of intermediate products and harmful by-products, and reduces energy consumption and environmental pollution risks.
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Figure CN120679592A_ABST
Abstract
Description
Technical Field
[0001] The present invention belongs to the field of solid waste resource application, and particularly relates to a preparation method of a composite catalyst based on waste polishing powder and its application in the degradation of chlorinated VOCs. Background Art
[0002] Volatile organic compounds (VOCs) come from a wide range of sources. In industrial production, such as petrochemicals, paint manufacturing, printing and packaging, a large amount of raw materials containing VOCs are used in the production process, resulting in their emission in the form of waste gas. In the field of electronic waste recycling, a large amount of chlorinated volatile organic compounds (CVOCs) are produced during the pyrolysis treatment of waste enameled wires. The insulating coating on the surface of the enameled wire is usually composed of polyvinyl chloride (PVC), polyvinylidene chloride (PVDC) or chlorinated resin. During the pyrolysis process, it releases highly toxic substances such as chlorobenzenes (such as chlorobenzene and dichlorobenzene), chlorinated hydrocarbons (such as dichloromethane and trichloroethylene) and even dioxins. The exhaust gas composition is complex and the environmental risks are prominent. In addition, as an important subclass of VOCs, the chlorine atoms in the molecular structure of CVOCs make their chemical properties more stable and difficult to degrade. In addition, during the combustion process, highly toxic byproducts such as dioxins may be generated, which poses a more serious threat to the environment and human health. They are important precursors to the formation of photochemical smog and fine particulate matter (PM2.5), which reduce atmospheric visibility, exacerbate haze weather, and have a negative impact on the ecological environment and climate change. CVOCs can also pollute soil and water bodies through rainwater deposition, posing long-term ecological risks. Regarding human health, most VOCs are toxic. Long-term exposure or inhalation can irritate the human respiratory tract, eyes, and skin, causing symptoms such as headaches, nausea, and allergies, and may even lead to serious diseases such as cancer. Due to their high toxicity and bioaccumulation, CVOCs are particularly harmful to the nervous system, liver, and immune system.
[0003] Among CVOCs treatment technologies, catalytic oxidation technology has attracted much attention due to its advantages such as high efficiency and low energy consumption. Catalytic oxidation technology mainly uses high temperature to cause CVOCs to undergo an oxidation reaction with oxygen, converting them into harmless or low-harm substances such as carbon dioxide, water and hydrogen chloride (for CVOCs). At present, the more commonly used catalytic oxidation technologies are based on supported precious metal catalysts or transition metal oxide catalysts. Supported precious metal catalysts such as platinum (Pt) and palladium (Pd) have high catalytic activity and can achieve oxidative degradation of VOCs at lower temperatures, but their catalytic effect on CVOCs is limited, and the scarcity and high price of precious metal resources limit their large-scale application. Transition metal oxide catalysts such as manganese oxide and cobalt oxide, although relatively low in cost, have poor catalytic activity and stability for CVOCs and are easily inactivated by chlorine poisoning.
[0004] The core of existing catalytic oxidation technology lies in the catalyst. However, most of the catalysts currently used are synthesized based on existing raw materials, and less attention is paid to resource recycling. In addition, the catalytic oxidation technology for CVOCs still faces problems such as insufficient catalyst stability and poor chlorine tolerance. This patent takes a different approach and innovatively proposes a technical solution that combines resource recovery and catalytic oxidation for the resource of waste polishing powder. In the process of recycling rare earth polishing powder, rare earth elements such as cerium and lanthanum are often difficult to separate. This patent makes full use of this feature. Using waste polishing powder as raw material, HZSM-5 molecular sieve is grown on its surface by an in-situ growth method to synthesize an HZSM-5 composite catalyst (HZSM-5@WPP) with cerium and lanthanum as the main components. This composite catalyst not only realizes the recycling of rare earth resources and reduces production costs, but also the synergistic effect of cerium and lanthanum elements improves the redox ability and chlorine tolerance of the catalyst. At the same time, the acidic sites provided by the HZSM-5 molecular sieve further enhance the catalyst's adsorption and activation ability for CVOCs, thereby significantly improving the catalytic oxidation performance, providing a new method for CVOCs treatment that is efficient, environmentally friendly and economically beneficial. Summary of the Invention
[0005] This invention aims to propose a method for preparing a composite catalyst based on waste polishing powder and its application in the degradation of chlorinated VOCs. Given the significant challenges of existing VOC catalytic oxidation technologies, such as high catalyst costs and low resource utilization, this invention utilizes the abundant rare earth elements, such as cerium and lanthanum, in polishing powder. This synergistic effect enhances the catalyst's redox capacity, while also leveraging the acidic sites provided by HZSM-5 molecular sieves to enhance the adsorption and activation of CVOCs. This approach achieves the dual goals of efficient resource utilization and high-efficiency catalytic oxidation of CVOCs.
[0006] In order to achieve the above object, the present invention provides a composite catalyst based on waste polishing powder and a method for degrading chlorinated organic pollutants thereof, comprising the following steps:
[0007] (1) After calcination as a pretreatment, the waste polishing powder is subjected to ball milling surface treatment, and the polishing powder after ball milling is ground and sieved until all of it is sieved for use;
[0008] (2) The sieved polishing powder, sodium chloride, polyethylene glycol, tetrapropylammonium hydroxide, aluminum isopropylate and tetraethyl silicate were added to deionized water in a molar ratio of the main components of each material of n(NaCl):n(PEG):n(TPAOH):n(Al2O3):n(SiO2):n(H2O)=8.69:6.83:11.31:1:25-150:2277.04, and stirred at room temperature for 12-24 hours;
[0009] (3) hydrothermal reaction of the mixed solution for 12-72 hours;
[0010] (4) centrifuging the mixed solution after the reaction in step (3), and drying and calcining the precipitate after centrifugation;
[0011] (5) The powder obtained in step (4) was ion-exchanged three times in an ammonium chloride solution, dried, and calcined to obtain HZSM-5@WPP (such as Figure 1 、 2 shown).
[0012] Furthermore, in step (1), the calcination temperature is 450-550° C., the calcination time is 3-5 h, the ball milling time is 3-6 h, and the sieve is 80-200 mesh;
[0013] Furthermore, the stirring time in step (2) is 12-24 hours;
[0014] Furthermore, the hydrothermal temperature in step (3) is 120-180° C. and the hydrothermal time is 12-48 hours;
[0015] Furthermore, in step (4), the centrifugal speed is 1000-3000 r / min; the drying time is 12-24 hours; the calcination temperature is 400-500° C.; and the calcination time is 3-5 hours;
[0016] Furthermore, in step (5), the number of ion exchanges is 3 times; the temperature of the ion exchange water bath is 70-90° C.; the drying time is 12-24 hours; the calcination temperature is 400-500° C.; and the calcination time is 3-5 hours.
[0017] The catalyst prepared by the present invention can be used for the degradation of chlorinated volatile organic compounds. The specific technical scheme is as follows:
[0018] A method for degrading chlorinated organic pollutants using a composite catalyst based on waste polishing powder, characterized by comprising:
[0019] reacting the gas containing chlorinated volatile organic compounds under the action of the catalyst;
[0020] The gas is a mixed gas consisting of 21 volume percent of O2 and the balance of N2, which contains 200-500 ppm of DCM;
[0021] Furthermore, the reaction temperature was 150°C-450°C, and the catalytic performance of the catalyst for DCM and the byproduct carbon monoxide yield (as shown in Table 1, Table 2 and Figure 3 、 Figure 4 The test temperature of in-situ infrared spectroscopy is 30-450℃ (as shown in Figure 5 shown).
[0022] Furthermore, during the reaction process, water vapor is introduced into the gas; after the water vapor is introduced, the content accounts for 0-15.0% of the total volume of the reaction system.
[0023] The beneficial effects of the present invention are:
[0024] (1) This invention successfully realizes the resource utilization of waste polishing powder, converting waste that would otherwise be discarded into high-value catalyst raw materials. This innovative measure not only reduces dependence on the mining of natural rare earth resources and reduces production costs, but also solves the problem of waste disposal and resource waste, and has extremely high resource recycling value and environmental significance.
[0025] (2) The synergistic effect of the cerium and lanthanum rare earth elements in the composite catalyst of the present invention significantly enhances redox capacity, achieving a certain catalytic oxidation effect on CVOCs and reducing energy consumption. Furthermore, the acidic sites provided by the HZSM-5 molecular sieve enhance the adsorption and activation of CVOCs molecules, significantly improving the CVOC conversion rate compared to waste polishing powder.
[0026] (3) The catalyst prepared by the present invention can effectively reduce the generation of intermediate products and harmful by-products of CVOCs, greatly reduce the risk of secondary pollution, play an important role in improving air quality and protecting the ecological environment, and has significant environmental benefits.
[0027] The difficulties in preparing the catalyst mainly focus on the following aspects:
[0028] 1. Surface pretreatment and roughening of spent polishing powder: First, high-temperature calcination (450-550°C) is required to remove organic impurities from the spent polishing powder. Ball milling is then used to roughen the surface to provide sufficient active sites for the subsequent growth of the ZSM-5 molecular sieve. This step requires strict control of calcination temperature, time, and ball milling process, otherwise insufficient surface activity or structural damage may occur.
[0029] 2. Precise control of hydrothermal synthesis conditions: During the hydrothermal reaction, the ratio of the synthesis solution (such as sodium chloride, polyethylene glycol, and tetrapropylammonium hydroxide) directly affects the nucleation and growth of the ZSM-5 zeolite. Furthermore, the hydrothermal temperature (120-180°C) and time (12-72 hours) must be precisely controlled. Excessively high temperatures or prolonged times may lead to excessive crystallization of the zeolite or the formation of impurities, while insufficient conditions may prevent uniform coating of the zeolite.
[0030] 3. In-situ growth interface bonding: In-situ growth of ZSM-5 molecular sieve on the polishing powder surface requires addressing the compatibility issue at the interface between the two. By adjusting the ratio of aluminum isopropoxide and tetraethyl silicate, the molecular sieve precursor is ensured to uniformly adhere and crystallize on the polishing powder surface while preventing particle agglomeration or shedding.
[0031] 4. Ion exchange and calcination optimization: The subsequent ammonium chloride ion exchange and calcination process (400-500°C) is crucial for the catalyst's acidic sites and stability. The number of exchanges (2-3), water bath temperature (70-90°C), and calcination conditions must be coordinated to balance catalytic activity and structural stability. BRIEF DESCRIPTION OF THE DRAWINGS
[0032] Figure 1 This is a scanning electron microscope image of Example 1.
[0033] Figure 2 The X-ray powder diffraction images of Example 1 and Comparative Example 4 are shown.
[0034] Figure 3 Schematic diagram for comparing DCM removal rates in the examples.
[0035] Figure 4 Schematic diagram for comparing the yields of by-product carbon monoxide in the examples.
[0036] Figure 5 Schematic diagram of the in situ infrared spectrum of DCM removal in Example 1. DETAILED DESCRIPTION
[0037] [Example 1]
[0038] This embodiment provides a method for preparing a chlorinated volatile organic compound degradation catalyst, comprising:
[0039] (1) After calcination as a pretreatment, the waste polishing powder is subjected to ball milling surface treatment, and the polishing powder after ball milling is ground and sieved until all of it is sieved for use;
[0040] (2) The sieved polishing powder, sodium chloride, polyethylene glycol, tetrapropylammonium hydroxide, aluminum isopropylate, and tetraethyl silicate were added to deionized water in a molar ratio of the main components of each material of n(NaCl):n(PEG):n(TPAOH):n(Al2O3):n(SiO2):n(H2O)=8.69:6.83:11.31:1:25:2277.04, and stirred at room temperature;
[0041] (3) hydrothermal reaction of the mixed solution;
[0042] (4) centrifuging the mixed solution after the reaction in step (3), and drying and calcining the precipitate after centrifugation;
[0043] (5) The powder obtained in step (4) was ion-exchanged three times in an ammonium chloride solution, dried, and calcined to obtain HZSM-5@WPP (such as Figure 1 、 2 shown).
[0044] Furthermore, in step (1), the calcination temperature is 550° C. and the calcination time is 3 h; the ball milling time is 3 h; and the sieve is 80 mesh;
[0045] Furthermore, the stirring time in step (2) is 12 h;
[0046] Furthermore, in step (3), the hydrothermal temperature is 160° C. and the hydrothermal time is 24 h;
[0047] Furthermore, in step (4), the centrifugal speed is 3000 r / min; the drying time is 12 h; the calcination temperature is 450° C.; and the calcination time is 4 h;
[0048] Furthermore, in step (5), the number of ion exchanges is 3 times; the temperature of the ion exchange water bath is 90° C.; the drying time is 12 h; the calcination temperature is 450° C.; and the calcination time is 4 h.
[0049] The catalyst prepared in this embodiment can be used for the degradation of chlorinated volatile organic compounds. The specific technical solution is as follows:
[0050] A method for degrading chlorinated organic pollutants using a composite catalyst based on waste polishing powder, characterized by comprising:
[0051] reacting the gas containing chlorinated volatile organic compounds under the action of the catalyst;
[0052] The gas is a mixed gas consisting of 21 volume percent O2 and the balance N2, which contains 500 ppm of DCM;
[0053] Furthermore, during the reaction process, water vapor is introduced into the gas; after the water vapor is introduced, the content accounts for 0% of the total volume of the reaction system;
[0054] Furthermore, the reaction temperature sampling points were 30, 150, 200, 250, 300, 350, 400 and 450 ° C, and the catalytic performance of the catalyst for DCM and the by-product carbon monoxide yield (as shown in Table 1, Table 2 and Figure 3 、 Figure 4 The test temperatures of in-situ infrared spectroscopy are 30, 150, 200, 250, 300, 350, 400 and 450°C (as shown in Figure 5 shown).
[0055] [Example 2]
[0056] This embodiment provides a method for preparing a chlorinated volatile organic compound degradation catalyst, comprising:
[0057] (1) After calcination as a pretreatment, the waste polishing powder is subjected to ball milling surface treatment, and the polishing powder after ball milling is ground and sieved until all of it is sieved for use;
[0058] (2) The sieved polishing powder, sodium chloride, polyethylene glycol, tetrapropylammonium hydroxide, aluminum isopropylate, and tetraethyl silicate were added to deionized water in a molar ratio of the main components of each material of n(NaCl):n(PEG):n(TPAOH):n(Al2O3):n(SiO2):n(H2O)=8.69:6.83:11.31:1:25:2277.04, and stirred at room temperature;
[0059] (3) hydrothermal reaction of the mixed solution;
[0060] (4) centrifuging the mixed solution after the reaction in step (3), and drying and calcining the precipitate after centrifugation;
[0061] (5) The powder obtained in step (4) is subjected to ion exchange three times in an ammonium chloride solution, and then dried and calcined to obtain (such as Figure 1 、 2 shown).
[0062] Furthermore, in step (1), the calcination temperature is 550° C. and the calcination time is 3 h; the ball milling time is 3 h; and the sieve is 80 mesh;
[0063] Furthermore, the stirring time in step (2) is 12 h;
[0064] Furthermore, in step (3), the hydrothermal temperature is 160° C. and the hydrothermal time is 24 h;
[0065] Furthermore, in step (4), the centrifugal speed is 3000 r / min; the drying time is 12 h; the calcination temperature is 450° C.; and the calcination time is 4 h;
[0066] Furthermore, in step (5), the number of ion exchanges is 3 times; the temperature of the ion exchange water bath is 90° C.; the drying time is 12 h; the calcination temperature is 450° C.; and the calcination time is 4 h.
[0067] The catalyst prepared in this embodiment can be used for the degradation of chlorinated volatile organic compounds. The specific technical solution is as follows:
[0068] A method for degrading chlorinated organic pollutants using a composite catalyst based on waste polishing powder, characterized by comprising:
[0069] reacting the gas containing chlorinated volatile organic compounds under the action of the catalyst;
[0070] The gas is a mixed gas consisting of 21 volume percent O2 and the balance N2, which contains 200 ppm DCM;
[0071] Furthermore, during the reaction process, water vapor is introduced into the gas; after the water vapor is introduced, the content accounts for 0% of the total volume of the reaction system;
[0072] Furthermore, the reaction temperature sampling points were 30, 150, 200, 250, 300, 350, 400 and 450 ° C, and the catalytic performance of the catalyst for DCM and the by-product carbon monoxide yield (as shown in Table 1, Table 2 and Figure 3 、 Figure 4 shown).
[0073] [Example 3]
[0074] (This embodiment provides a method for preparing a chlorinated volatile organic compound degradation catalyst, comprising:
[0075] (1) After calcination as a pretreatment, the waste polishing powder is subjected to ball milling surface treatment, and the polishing powder after ball milling is ground and sieved until all of it is sieved for use;
[0076] (2) The sieved polishing powder, sodium chloride, polyethylene glycol, tetrapropylammonium hydroxide, aluminum isopropylate, and tetraethyl silicate were added to deionized water in a molar ratio of the main components of each material of n(NaCl):n(PEG):n(TPAOH):n(Al2O3):n(SiO2):n(H2O)=8.69:6.83:11.31:1:25:2277.04, and stirred at room temperature;
[0077] (3) hydrothermal reaction of the mixed solution;
[0078] (4) centrifuging the mixed solution after the reaction in step (3), and drying and calcining the precipitate after centrifugation;
[0079] (5) The powder obtained in step (4) was ion-exchanged three times in an ammonium chloride solution, dried, and calcined to obtain HZSM-5@WPP (such as Figure 1 、 2 shown).
[0080] Furthermore, in step (1), the calcination temperature is 550° C. and the calcination time is 3 h; the ball milling time is 3 h; and the sieve is 80 mesh;
[0081] Furthermore, the stirring time in step (2) is 12 h;
[0082] Furthermore, in step (3), the hydrothermal temperature is 160° C. and the hydrothermal time is 24 h;
[0083] Furthermore, in step (4), the centrifugal speed is 3000 r / min; the drying time is 12 h; the calcination temperature is 450° C.; and the calcination time is 4 h;
[0084] Furthermore, in step (5), the number of ion exchanges is 3 times; the temperature of the ion exchange water bath is 90° C.; the drying time is 12 h; the calcination temperature is 450° C.; and the calcination time is 4 h.
[0085] The catalyst prepared in this embodiment can be used for the degradation of chlorinated volatile organic compounds. The specific technical solution is as follows:
[0086] A method for degrading chlorinated organic pollutants using a composite catalyst based on waste polishing powder, characterized by comprising:
[0087] reacting the gas containing chlorinated volatile organic compounds under the action of the catalyst;
[0088] The gas was a mixture of 21 volume percent O2 and the balance N2, containing 200 ppm DCM. After the first test, the catalyst was calcined in air and then tested again with 500 ppm DCM.
[0089] Furthermore, during the reaction process, water vapor is introduced into the gas; after the water vapor is introduced, the content accounts for 0% of the total volume of the reaction system;
[0090] Furthermore, the reaction temperature sampling points were 30, 150, 200, 250, 300, 350, 400 and 450 ° C, and the catalytic performance of the catalyst for DCM and the by-product carbon monoxide yield (as shown in Table 1, Table 2 and Figure 3 、 Figure 4 shown).
[0091] [Example 4]
[0092] (This embodiment provides a method for preparing a chlorinated volatile organic compound degradation catalyst, comprising:
[0093] (1) After calcination as a pretreatment, the waste polishing powder is subjected to ball milling surface treatment, and the polishing powder after ball milling is ground and sieved until all of it is sieved for use;
[0094] (2) The sieved polishing powder, sodium chloride, polyethylene glycol, tetrapropylammonium hydroxide, aluminum isopropylate, and tetraethyl silicate were added to deionized water in a molar ratio of the main components of each material of n(NaCl):n(PEG):n(TPAOH):n(Al2O3):n(SiO2):n(H2O)=8.69:6.83:11.31:1:25:2277.04, and stirred at room temperature;
[0095] (3) hydrothermal reaction of the mixed solution;
[0096] (4) centrifuging the mixed solution after the reaction in step (3), and drying and calcining the precipitate after centrifugation;
[0097] (5) The powder obtained in step (4) is subjected to ion exchange three times in an ammonium chloride solution, and then dried and calcined to obtain (such as Figure 1 、 2 shown).
[0098] Furthermore, in step (1), the calcination temperature is 550° C. and the calcination time is 3 h; the ball milling time is 3 h; and the sieve is 80 mesh;
[0099] Furthermore, the stirring time in step (2) is 12 h;
[0100] Furthermore, in step (3), the hydrothermal temperature is 160° C. and the hydrothermal time is 24 h;
[0101] Furthermore, in step (4), the centrifugal speed is 3000 r / min; the drying time is 12 h; the calcination temperature is 450° C.; and the calcination time is 4 h;
[0102] Furthermore, in step (5), the number of ion exchanges is 3 times; the temperature of the ion exchange water bath is 90° C.; the drying time is 12 h; the calcination temperature is 450° C.; and the calcination time is 4 h.
[0103] The catalyst prepared in this embodiment can be used for the degradation of chlorinated volatile organic compounds. The specific technical solution is as follows:
[0104] A method for degrading chlorinated organic pollutants using a composite catalyst based on waste polishing powder, characterized by comprising:
[0105] reacting the gas containing chlorinated volatile organic compounds under the action of the catalyst;
[0106] The gas is a mixed gas consisting of 21 volume percent O2 and the balance N2, which contains 500 ppm of DCM;
[0107] Furthermore, during the reaction process, water vapor is introduced into the gas; the content of the water vapor after introduction accounts for 5% of the total volume of the reaction system;
[0108] Furthermore, the reaction temperature sampling points were 30, 150, 200, 250, 300, 350, 400 and 450 ° C, and the catalytic performance of the catalyst for DCM and the by-product carbon monoxide yield (as shown in Table 1, Table 2 and Figure 3 、 Figure 4 shown).
[0109] [Example 5]
[0110] (This embodiment provides a method for preparing a chlorinated volatile organic compound degradation catalyst, comprising:
[0111] (1) After calcination as a pretreatment, the waste polishing powder is subjected to ball milling surface treatment, and the polishing powder after ball milling is ground and sieved until all of it is sieved for use;
[0112] (2) The sieved polishing powder, sodium chloride, polyethylene glycol, tetrapropylammonium hydroxide, aluminum isopropylate, and tetraethyl silicate were added to deionized water in a molar ratio of the main components of each material of n(NaCl):n(PEG):n(TPAOH):n(Al2O3):n(SiO2):n(H2O)=8.69:6.83:11.31:1:25:2277.04, and stirred at room temperature;
[0113] (3) hydrothermal reaction of the mixed solution;
[0114] (4) centrifuging the mixed solution after the reaction in step (3), and drying and calcining the precipitate after centrifugation;
[0115] (5) The powder obtained in step (4) was ion-exchanged three times in an ammonium chloride solution, dried, and calcined to obtain HZSM-5@WPP (such as Figure 1 、 2 shown).
[0116] Furthermore, in step (1), the calcination temperature is 550° C. and the calcination time is 3 h; the ball milling time is 3 h; and the sieve is 80 mesh;
[0117] Furthermore, the stirring time in step (2) is 12 h;
[0118] Furthermore, in step (3), the hydrothermal temperature is 160° C. and the hydrothermal time is 24 h;
[0119] Furthermore, in step (4), the centrifugal speed is 3000 r / min; the drying time is 12 h; the calcination temperature is 450° C.; and the calcination time is 4 h;
[0120] Furthermore, in step (5), the number of ion exchanges is 3 times; the temperature of the ion exchange water bath is 90° C.; the drying time is 12 h; the calcination temperature is 450° C.; and the calcination time is 4 h.
[0121] The catalyst prepared in this embodiment can be used for the degradation of chlorinated volatile organic compounds. The specific technical solution is as follows:
[0122] A method for degrading chlorinated organic pollutants using a composite catalyst based on waste polishing powder, characterized by comprising:
[0123] reacting the gas containing chlorinated volatile organic compounds under the action of the catalyst;
[0124] The gas is a mixed gas consisting of 21 volume percent O2 and the balance N2, which contains 500 ppm of DCM;
[0125] Furthermore, during the reaction process, water vapor is introduced into the gas; the content of the water vapor after introduction accounts for 15% of the total volume of the reaction system;
[0126] Furthermore, the reaction temperature sampling points were 30, 150, 200, 250, 300, 350, 400 and 450 ° C, and the catalytic performance of the catalyst for DCM and the by-product carbon monoxide yield (as shown in Table 1, Table 2 and Figure 3 、 Figure 4 shown).
[0127] Table 1 Reaction performance of catalysts of Examples 1, 2, 3, 4, and 5 to DCM
[0128] Example 1 Example 2 Example 3 Example 4 Example 5 150℃ 20.04％ 31.71％ 21.06％ 4.02％ 37.96％ 200℃ 15.24％ 31.63％ 18.03％ 46.83％ 31.87％ 250℃ 16.12％ 32.64％ 13.25％ 26.06％ 43.42％ 300℃ 23.65％ 40.54％ 22.00％ 22.42％ 19.23％ 350℃ 43.78％ 60.67％ 38.32％ 20.61％ 20.36％ 400℃ 69.40％ 85.88％ 58.49％ 44.14％ 41.17％ 450℃ 87.61％ 97.69％ 80.85％ 66.70％ 67.51％
[0129] Table 2 Byproduct carbon monoxide yields of catalysts in Examples 1, 2, 3, 4, and 5
[0130] Example 1 Example 2 Example 3 Example 4 Example 5 150℃ 0.12％ 0.17％ 0.15％ 0％ 0％ 200℃ 0.26％ 0.58％ 0.37％ 0％ 0.03％ 250℃ 0.41％ 0.91％ 0.57％ 0％ 0.02％ 300℃ 0.68％ 1.33％ 0.90％ 0％ 0.03％ 350℃ 1.76％ 2.99％ 2.03％ 0％ 0.12％ 400℃ 4.16％ 7.01％ 5.61％ 0.02％ 0.17％ 450℃ 8.03％ 14.27％ 11.52％ 0.40％ 0.62％
[0131] [Comparative Example 1]
[0132] (1) Preparation of WPP catalyst:
[0133] The waste polishing powder is subjected to ball milling surface treatment after calcination as a pretreatment; the polishing powder after ball milling is ground and sieved until it passes through an 80-mesh sieve.
[0134] (2) Catalyst performance test:
[0135] The catalytic performance evaluation of the catalyst was carried out in a reaction tube with an inner diameter of 6 mm and a space velocity of 15000 h -1 The reaction system was heated to 100 ppm using a mixture of 21% by volume of O₂ and the balance of N₂, containing 500 ppm of DCM. The water vapor content after introduction was 0% of the total volume of the reaction system. The catalyst's reactivity with DCM is shown in Table 3, and the yield of byproduct carbon monoxide is shown in Table 4.
[0136] [Comparative Example 2]
[0137] (1) Preparation of commercial CeO2 catalyst:
[0138] Commercial CeO2 was calcined at 550 °C for 4 h in air as a pretreatment.
[0139] (2) Catalyst performance test:
[0140] The catalytic performance evaluation of the catalyst was carried out in a reaction tube with an inner diameter of 6 mm and a space velocity of 15000 h -1 , a mixed gas consisting of 21 volume percent O2 and the balance N2, which contains 500 ppm of DCM, and the content of water vapor after introduction accounts for 0% of the total volume of the reaction system.
[0141] Table 3 Reaction performance of catalysts in comparative examples 1 and 2 to DCM
[0142] Comparative Example 1 Comparative Example 2 150℃ 14.45％ 5.82％ 200℃ 6.52％ 4.22％ 250℃ 1.07％ 0.93％ 300℃ 0％ 0％ 350℃ 0％ 11.21％ 400℃ 4.29％ 15.56％ 450℃ 9.70％ 28.83％
[0143] Table 4 Byproduct carbon monoxide yield of catalysts in Comparative Examples 1, 2, 3, and 4
[0144] Comparative Example 1 Comparative Example 2 150℃ 0.03％ 0.06％ 200℃ 0.03％ 0.06％ 250℃ 0.05％ 0.20％ 300℃ 0.10％ 0.39％ 350℃ 0.33％ 0.52％ 400℃ 0.88％ 1.44％ 450℃ 2.30％ 3.72％
Claims
1. A method for preparing a composite catalyst based on waste polishing powder, characterized in that: The method comprises the following steps: (1) calcining the waste polishing powder at a temperature of 450° C. to 550° C. for 3 to 5 hours, ball milling the calcined polishing powder, and sieving the calcined polishing powder to obtain pretreated polishing powder; (2) adding the polishing powder obtained in step (1) and sodium chloride, polyethylene glycol, tetrapropylammonium hydroxide, aluminum isopropylate and tetraethyl silicate into deionized water, wherein the molar ratio of the main components of each material is n(NaCl):n(PEG):n(TPAOH):n(Al2O3):n(SiO2):n(H2O)=8.69:6.83:11.31:1:25-150:2277.04, and stirring to obtain a mixed solution for 12-24 hours; (3) placing the mixed solution obtained in step (2) into a reactor and performing a hydrothermal reaction to obtain a synthetic product, wherein the hydrothermal temperature is 120-180° C. and the hydrothermal time is 12-72 h; (4) centrifuging, drying, and calcining the synthetic product obtained in step (3) to obtain a composite catalyst in which ZSM-5 molecular sieve is in situ grown on the surface of the polishing powder, the calcination temperature is 400-500° C., and the calcination time is 3-5 h; (5) The composite catalyst obtained in step (4) is subjected to ion exchange in an ammonium chloride solution, filtered, dried, and calcined to obtain a composite catalyst HZSM-5@WPP with a HZSM-5 molecular sieve coated on the surface of the polishing powder. The calcination temperature is 400-500° C. and the calcination time is 3-5 h.
2. The method for preparing a composite catalyst based on waste polishing powder and its application in the degradation of chlorinated VOCs according to claim 1, characterized in that: The ball milling time in step (1) is 3-6 hours; and the product is sieved to 80-200 mesh.
3. The method for preparing a composite catalyst based on waste polishing powder and its application in the degradation of chlorinated VOCs according to claim 1, characterized in that: The centrifugal speed in step (4) is 1000-3000 r / min; and the drying time is 12-24 hours.
4. The method for preparing a composite catalyst based on waste polishing powder and its application in the degradation of chlorinated VOCs according to claim 1, characterized in that: In step (5), the number of ion exchanges is 2-3 times; the temperature of the ion exchange water bath is 70° C.-90° C.; and the drying time is 12-24 hours.
5. The catalyst prepared by the method according to any one of claims 1 to 4.
6. The method for using the catalyst according to claim 5 in the degradation of chlorinated VOCs, characterized in that: include: reacting the gas containing chlorinated volatile organic compounds under the catalytic action of the catalyst; The gas containing chlorinated volatile organic compounds contains 21% oxygen by volume, the balance nitrogen, and 200-500 ppm dichloromethane (DCM). The reaction temperature is 150-450° C. to obtain the catalytic performance of the catalyst for DCM and the yield of byproduct carbon monoxide.
7. The use according to claim 6, characterized in that Water vapor is introduced into the gas containing chlorinated volatile organic compounds; the content of the water vapor after the introduction accounts for 0-15.0% of the total volume of the gas.