A series connection material system, and a preparation method and application thereof

Abstract

This invention belongs to the field of catalytic oxidation technology of chlorine-containing volatile organic compounds, specifically relating to a tandem material system, its preparation method, and its application. The tandem material system comprises a Cu / ZSM-5 composite material and a Pt / NbCeO2 composite material, which are tandemly connected to form the tandem material. This tandem material is tested at 230 °C and a mass hourly space velocity (WHSV) of 30,000 mL·g. ‑1 ·h ‑1 Under certain conditions, the degradation rate of vinyl chloride is 90%, the CO2 selectivity is 98%, and the HCl selectivity is 82%. It has good stability and is resistant to chlorine and water, making it suitable for the catalytic oxidation of chlorine-containing volatile organic compounds.

Description

Technical Field

[0001] This invention belongs to the field of catalytic oxidation technology of chlorine-containing volatile organic compounds, specifically relating to a tandem material system, its preparation method and application, particularly a Cu / ZSM-5 composite material, a Pt / NbCeO2 composite material, a tandem material composed of Cu / ZSM-5 composite material and Pt / NbCeO2 composite material, as well as the preparation method of these materials and their application in the catalytic oxidation of vinyl chloride. Background Technology

[0002] In energy and chemical industries, industrial production, and daily life activities, large amounts of volatile organic compounds (VOCs) are emitted into the atmosphere. Chlorinated VOCs are a typical class of pollutants that are difficult to treat. Due to their high toxicity, chemical stability, and poor biodegradability, they are listed as key hazardous air pollutants for control in most countries. Vinyl chloride is an important monomer in the synthesis of polyvinyl chloride (PVC) and often enters the natural environment as waste gas during industrial production. Because of its stable chemical properties and difficulty in degradation, vinyl chloride can remain in the environment for a long time, causing persistent pollution and exhibiting significant toxicity to organisms, posing a potential threat to human health.

[0003] Existing main methods for treating chlorinated volatile organic compounds (VOCs) include catalytic oxidation, direct combustion, ozone-assisted catalysis, low-temperature plasma-coupled catalysis, and advanced oxidation treatment. Among these, catalytic oxidation, with its low reaction temperature and high removal efficiency, has become the most commonly used method for treating VOCs. However, current catalytic oxidation processes for VOCs suffer from problems such as the production of numerous chlorine-toxic byproducts and the susceptibility of catalyst active sites to chlorine deposition and deactivation, which significantly restricts the development and application of catalytic oxidation technology. Therefore, developing catalysts that can efficiently, stably, and environmentally friendly remove VOCs is of great promise.

[0004] In the catalytic oxidation of chlorinated volatile organic compounds (VOCs), removal efficiency and hydrogen chloride selectivity are important indicators for evaluating catalyst performance, which mainly depend on the catalyst's redox capacity and acidity site properties. Noble metal catalysts are commonly used for the oxidation and removal of VOCs, significantly reducing the temperature required for their oxidation. However, their high redox capacity easily leads to the deacon reaction of chlorinated intermediates, producing chlorine gas or other chlorine-poisonous byproducts. In this case, the surface Brønsted acidic sites cannot participate in the hydrogen chloride formation process in time, resulting in a decrease in hydrogen chloride selectivity. Compared to noble metal catalysts, transition metal oxides are abundant, inexpensive, and possess good redox capacity, resistance to chlorine poisoning, and thermal stability. The accumulation of chlorinated intermediates on the surface of transition metal oxides reduces acidity, hindering electron transfer between redox pairs, and consequently reducing catalyst activity.

[0005] Therefore, improving the efficiency of catalysts in removing chlorine-containing volatile organic compounds and the selectivity of hydrogen chloride, as well as improving their stability, is an urgent problem to be solved. Summary of the Invention

[0006] In view of this, one of the objectives of this invention is to provide a Pt / NbCeO2 composite material and its preparation method, in order to solve the problems that existing noble metal catalysts are prone to triggering the Deacon reaction to generate chlorine-containing toxic byproducts during deep oxidation processes, and that they have insufficient oxidation capacity for key intermediates such as CO and C2H4Cl2.

[0007] The second objective of this invention is to provide a Cu / ZSM-5 composite material and its preparation method to solve the problems of insufficient synergy between acidic sites and redox sites in existing catalysts, and weak adsorption and activation ability of C-Cl bonds in vinyl chloride.

[0008] The third objective of this invention is to provide a tandem material composed of the aforementioned Pt / NbCeO2 composite material and Cu / ZSM-5 composite material, and its application in the catalytic oxidation of vinyl chloride. This addresses the problem that single catalytic materials or simple mixed catalytic materials cannot achieve the sequential stepwise processes of vinyl chloride adsorption activation, selective C-Cl bond cleavage, deep oxidation of intermediates, and highly selective generation of HCl. It also solves the problems of insufficient low-temperature activity, low hydrogen chloride selectivity, and easy chlorine poisoning and deactivation of existing catalytic materials.

[0009] To achieve the above objectives, the present invention adopts the following technical solution: The present invention provides a Pt / NbCeO2 composite material, wherein the Pt / NbCeO2 composite material comprises NbCeO2 and Pt nanoparticles supported on NbCeO2.

[0010] Preferably, the mass ratio of the Pt nanoparticles to the NbCeO2 is 0.5 to 2: 100.

[0011] Preferably, the mass percentage of Nb in the NbCeO2 is 8% to 12%.

[0012] In this Pt / NbCeO2 composite material, the Nb-doped CeO2 support effectively stores and releases reactive oxygen species, working synergistically with the active component, platinum nanoparticles, to deeply oxidize key intermediates such as CO and C2H4Cl2 produced from the partial oxidation of vinyl chloride, completely converting them into CO2 and HCl. Compared with existing noble metal catalysts, this composite material significantly inhibits the Deacon reaction by regulating the redox performance and surface oxygen vacancy concentration of CeO2 with Nb, thereby greatly improving the selectivity of hydrogen chloride. This effectively solves the problems of existing noble metal catalysts easily initiating the Deacon reaction to generate chlorine-containing toxic byproducts during deep oxidation and their insufficient oxidation capacity for key intermediates such as CO and C2H4Cl2.

[0013] This invention provides a method for preparing a Pt / NbCeO2 composite material, comprising the following steps: NbCeO2 was prepared by impregnation using CeO2 as a carrier. Pt nanoparticles were prepared using the ethylene glycol reduction method. The Pt nanoparticles were loaded onto NbCeO2 using an impregnation method to obtain the Pt / NbCeO2 composite material.

[0014] Preferably, the method specifically includes the following steps: S1. Preparation of NbCeO2: Niobium ammonium oxalate is dissolved in water to obtain an aqueous solution of niobium ammonium oxalate. CeO2 is added to the aqueous solution of niobium ammonium oxalate and stirred. The resulting solid is dried and calcined to obtain NbCeO2. S2. Preparation of Pt nanoparticle solution: Dissolve chloroplatinic acid hexahydrate in ethylene glycol to obtain mixed solution A; dissolve NaOH in ethylene glycol to obtain mixed solution B; mix mixed solution A and mixed solution B, heat and stir under nitrogen atmosphere, and cool under nitrogen atmosphere after the reaction is completed to obtain Pt nanoparticle solution; S3. The NbCeO2 obtained in S1 is redispersed in water, and the Pt nanoparticle solution obtained in S2 is added dropwise. The mixture is stirred, filtered and washed, the solid is collected, dried, and calcined to obtain the Pt / NbCeO2 composite material.

[0015] Preferably, in S1, the concentration of niobium oxalate in the aqueous solution of niobium oxalate is 0.04–0.05 mol / L, the ratio of CeO2 to the aqueous solution of niobium oxalate is 1 g: 25 mL, the stirring time is 10–12 h, the drying temperature is 70–90 °C, the calcination atmosphere is air, the calcination temperature is 400–500 °C, and the calcination time is 4–6 h.

[0016] Preferably, in S2, the concentration of chloroplatinic acid in the mixed solution A is 18–22 g / L, the concentration of NaOH in the mixed solution B is 0.2–0.3 mol / L, and the temperature of the heating and stirring reaction is 160–180 °C for 3–5 h.

[0017] Preferably, in step S3, the ratio of NbCeO2 to water is 1 g: 10 mL, the ratio of Pt nanoparticle solution to NbCeO2 is 2.0–3.0 mL: 1 g, the stirring time is 6–8 h, the drying temperature is 70–90 °C, the drying time is 8–12 h, the calcination atmosphere is air, the calcination temperature is 400–500 °C, and the calcination time is 4–6 h.

[0018] This preparation method uses ethylene glycol reduction to obtain uniformly sized platinum nanoparticles, which are then uniformly loaded onto an NbCeO2 support via impregnation. This avoids the aggregation of platinum particles and ensures efficient exposure of active sites. At the same time, the entire preparation process is green and mild, making it suitable for large-scale production.

[0019] This invention provides a series of materials, including Pt / NbCeO2 composite material and Cu / ZSM-5 composite material.

[0020] Preferably, the Cu / ZSM-5 composite material comprises ZSM-5 molecular sieve and CuO supported on ZSM-5 molecular sieve.

[0021] Preferably, the silicon-aluminum molecular ratio of the ZSM-5 molecular sieve is 10 to 25.

[0022] ZSM-5 molecular sieves utilize commercially available ZSM-5 molecular sieves, possessing unique three-dimensional ten-membered ring channels and tunable acidity. The acid site density is moderate, predominantly L-acids, which facilitates the adsorption and activation of C-Cl bonds. The silica-alumina molecular ratio of ZSM-5 molecular sieves ranges from 10 to 25, exhibiting optimal acid site density, variety, and catalytic activity within this range.

[0023] Preferably, the mass ratio of CuO to ZSM-5 molecular sieve is 0.04 to 0.06:1.

[0024] In this Cu / ZSM-5 composite material, the acidic ZSM-5 support and CuO synergistically enhance the adsorption and activation capacity of C-Cl bonds in vinyl chloride molecules, enabling selective cleavage of C-Cl bonds in vinyl chloride at lower temperatures. This creates favorable conditions for subsequent deep oxidation while avoiding over-oxidation and the generation of byproducts such as chlorine gas. Compared with existing technologies, this composite material optimizes the matching of acidic and redox sites by precisely controlling the CuO loading, thereby greatly improving the low-temperature adsorption and activation efficiency of vinyl chloride. It effectively solves the problems of insufficient synergy between acidic and redox sites and weak adsorption and activation capacity of C-Cl bonds in vinyl chloride in existing catalysts.

[0025] This invention provides a method for preparing Cu / ZSM-5 composite material, comprising the following steps: Add ZSM-5 molecular sieve and oxalic acid to water and stir until a gel is formed; Copper acetate was dissolved in water and added dropwise to the gel, and the mixture was stirred to form a gel mixture. The gel mixture was filtered, washed, dried, and calcined to obtain the Cu / ZSM-5 composite material.

[0026] Preferably, the method specifically includes the following steps: S1. Add ZSM-5 molecular sieve and oxalic acid to water and stir for the first time at room temperature to form a gel; S2. Dissolve copper acetate in water and then add it dropwise to the gel obtained in S1. Stir a second time to form a gel mixture. Filter, wash, and dry to obtain the precursor. S3. The precursor obtained in S2 is calcined and cooled to obtain the Cu / ZSM-5 composite material.

[0027] Preferably, the ratio of ZSM-5 molecular sieve, oxalic acid, and water is 2 g : 0.4 g to 1.6 g : 100 mL; the first stirring time is 1 to 2 h; the ratio of copper acetate to water is 0.1 g to 0.6 g : 10 mL; the second stirring time is 2 to 5 h; the drying temperature is 80 to 100 °C; the drying time is 8 to 12 h; and the calcination atmosphere is air, the calcination temperature is 500 to 550 °C, and the calcination time is 4 to 6 h.

[0028] This preparation method uses an oxalic acid-assisted gelation process to uniformly disperse copper species on the surface of ZSM-5 molecular sieves, followed by controlled calcination to form a highly dispersed CuO active phase. The operation is simple, and the resulting Cu / ZSM-5 composite material has a stable structure and excellent catalytic performance.

[0029] The present invention also provides an application of Pt / NbCeO2 composite material or tandem material in the catalytic oxidation of vinyl chloride.

[0030] Preferably, the tandem material is composed of Cu / ZSM-5 composite material and Pt / NbCeO2 composite material layered in a 1:1 mass ratio, with the two separated by quartz sand.

[0031] Preferably, the Cu / ZSM-5 composite material in the series material is located at the inlet end of the reaction device, and the Pt / NbCeO2 composite material in the series material is located at the outlet end of the reaction device.

[0032] This tandem material design fully leverages the complementary advantages of two catalytic materials: the reaction gas stream first passes through a pre-stage Cu / ZSM-5 composite material, where the acidic ZSM-5 and CuO synergistically adsorb and activate the C-Cl bonds in vinyl chloride, causing selective cleavage and generating chlorine-containing intermediates and hydrocarbon intermediates. Subsequently, the gas stream enters a post-stage Pt / NbCeO2 composite material, utilizing its oxygen pump support and the deep oxidation capabilities of platinum nanoparticles to completely oxidize key intermediates such as CO and C2H4Cl2 into CO2 and HCl. Through this stepwise tandem catalytic approach, the entire reaction proceeds sequentially at different active sites, effectively avoiding interference between intermediates and chlorine poisoning at active sites. Compared with single catalytic materials or simple physical mixtures of catalytic materials, this tandem material exhibits significantly improved vinyl chloride removal efficiency, near-complete CO2 selectivity, and high HCl selectivity at low temperatures. It also possesses good long-term stability and resistance to chlorine and water. This effectively solves the problem that single catalytic materials or simple mixtures of catalytic materials cannot achieve vinyl chloride adsorption activation, selective C-Cl bond breaking, deep oxidation of intermediates, and high-selective HCl generation in a sequential stepwise manner. At the same time, it solves the problems of insufficient low-temperature activity, low hydrogen chloride selectivity, and easy chlorine poisoning and deactivation of existing catalytic materials.

[0033] The tandem material was tested at 230 °C and a mass hourly space velocity of 30,000 mL·g. -1 ·h -1 Under certain conditions, the degradation rate of vinyl chloride is 90%, the CO2 selectivity is 98%, and the HCl selectivity is 82%. It has good stability and is resistant to chlorine and water, making it suitable for the catalytic oxidation of chlorine-containing volatile organic compounds.

[0034] This application scheme not only significantly reduces reaction energy consumption (efficient degradation can be achieved at 230 °C), but also greatly reduces the generation of toxic chlorine-containing byproducts. At the same time, due to the tandem structure, the total amount of precious metal platinum used is reduced (half compared to a single precious metal catalyst).

[0035] The beneficial effects of this invention are: The Pt / NbCeO2 composite material provided by this invention, by introducing niobium into the CeO2 support to form NbCeO2 with an "oxygen pump" function, and loading uniformly dispersed platinum nanoparticles, can effectively regulate the redox performance of the support and the surface oxygen vacancy concentration, significantly inhibit the occurrence of the Deacon reaction, and solve the technical problem that existing noble metal catalysts are prone to generating chlorine-containing toxic byproducts.

[0036] The Cu / ZSM-5 composite material provided by this invention significantly enhances the adsorption and activation capacity of C-Cl bonds in vinyl chloride by loading CuO onto ZSM-5 molecular sieves with a specific silicon-to-aluminum ratio and utilizing the synergistic effect of acidic ZSM-5 support and CuO, thus solving the problem of low adsorption and activation efficiency of vinyl chloride by existing pre-catalyst materials.

[0037] This invention provides a tandem material composed of Cu / ZSM-5 composite material and Pt / NbCeO2 composite material, and its application in the catalytic oxidation of vinyl chloride. It fully utilizes the complementary advantages of the two catalytic materials: the pre-stage acidic ZSM-5 and CuO synergistically adsorb and activate the C-Cl bonds in vinyl chloride, while the post-stage oxygen pump carrier NbCeO2 and platinum nanoparticles synergistically deeply oxidize the intermediate. This allows the catalytic reaction to proceed sequentially at different active sites, effectively solving the problem that single catalytic materials or simple mixed catalytic materials cannot simultaneously achieve adsorption activation, selective bond breaking, deep oxidation, and high-selectivity hydrogen chloride generation. Experimental data show that this tandem material achieves optimal performance at a mass hourly space velocity (MSV) of 30,000 mL·g⁻¹. -1 ·h -1 It can catalytically oxidize 90% of vinyl chloride at 230 ℃, greatly reducing reaction energy consumption; CO2 selectivity is as high as 98%, and HCl selectivity reaches 82%, effectively reducing the generation of toxic chlorine-containing byproducts; its activity remains stable during continuous long-term testing, and its activity does not decrease significantly after passing through 5 vol% water vapor, demonstrating excellent resistance to chlorine deposition and water vapor.

[0038] Therefore, the Pt / NbCeO2 composite material, Cu / ZSM-5 composite material, and the tandem material composed of the two provided by this invention have extremely high industrial application potential and broad market prospects in the field of catalytic oxidation of chlorine-containing volatile organic compounds, especially in the treatment of vinyl chloride waste gas. Attached Figure Description

[0039] Figure 1 The XRD patterns of the Cu / ZSM-5 series composite materials obtained in Example 1 and Comparative Examples 1-2 of this invention are shown below. Figure 2 The XRD pattern of the Pt / NbCeO2 composite material obtained in Example 2 of this invention; Figure 3This is a SEM image of the Cu / ZSM-5 composite material obtained in Example 1 of the present invention; Figure 4 This is a SEM image of the Pt / NbCeO2 composite material obtained in Example 2 of the present invention; Figure 5 The diagram shows the catalytic activity of the single catalytic materials obtained in Examples 1-2 and the tandem catalytic materials obtained in Examples 3 and Comparative Examples 3-4 in the ethylene chloride oxidation reaction. Figure 6 The graph shows the CO2 production in the ethylene chloride oxidation reaction of the single catalytic material obtained in Examples 1-2 and the tandem catalytic material obtained in Examples 3 and Comparative Examples 3-4. Figure 7 The graphs show the stability and water resistance test results of the tandem catalytic material obtained in Example 3 of this invention. Figure 8 The graph shows the HCl yield and selectivity in the vinyl chloride oxidation reaction of the single catalytic material obtained in Examples 1-2 and the tandem catalytic material obtained in Examples 3 and Comparative Examples 3-4. Detailed Implementation

[0040] The following description, with reference to preferred embodiments, illustrates the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention. It should be understood that the preferred embodiments are merely illustrative of the present invention and not intended to limit the scope of protection of the present invention.

[0041] To make the technical problems, technical solutions, and beneficial effects solved by this application clearer, the following will provide a more detailed description of a tandem material system, its preparation method, and its application, in conjunction with specific embodiments and accompanying drawings. Obviously, the described specific embodiments are merely some embodiments of this application, and not all embodiments. The following description of at least one exemplary embodiment is merely illustrative and is in no way intended to limit this application or its applications. Based on the specific embodiments in this application, all other embodiments obtained by those skilled in the art without inventive effort are within the scope of protection of this application.

[0042] Where specific techniques or conditions are not specified in the detailed embodiments, they shall be performed in accordance with the techniques or conditions described in the literature in this field or in accordance with the product instructions. Reagents or instruments whose manufacturers are not specified are all commercially available conventional products.

[0043] Example 1

[0044] A method for preparing a Cu / ZSM-5 composite material includes the following steps: S1. Add 2 g of commercial ZSM-5 molecular sieve powder (silicon-aluminum molecular ratio of 21) to 100 mL of aqueous solution containing 0.99 g of oxalic acid, and then stir at room temperature (about 25 °C) for 1 hour to form a gel. S2. Dissolve 0.31 g of copper acetate in 10 mL of water to obtain an aqueous solution of copper acetate. Add the aqueous solution of copper acetate dropwise to the gel obtained in S1. Continue stirring at room temperature (about 25 °C) for 3 hours to form a gel mixture. Filter to collect the solid and wash the solid 5 times with deionized water. Then dry the washed solid in an oven at 80 °C for 12 hours to obtain the precursor. S3. The precursor obtained in S2 is placed in a muffle furnace and heated to 550 ℃ at a rate of 5 ℃ / min. It is then calcined at 550 ℃ in air for 4 hours and then naturally cooled to room temperature (about 25 ℃) to obtain a Cu / ZSM-5 composite material, denoted as Cu5 / ZSM-5.

[0045] Example 2

[0046] A method for preparing a Pt / NbCeO2 composite material includes the following steps: S1. Preparation of NbCeO2: Dissolve 0.326 g of ammonium niobate oxalate in 25 mL of water, then add 1 g of CeO2 to the ammonium niobate oxalate aqueous solution, stir for 10 hours, and then dry in a vacuum drying oven at 80 °C for 12 hours to obtain precursor A. Place precursor A in a muffle furnace and heat to 500 °C at 5 °C / min, and calcine at 500 °C in air atmosphere for 4 hours, and then cool naturally to room temperature (about 25 °C) to obtain NbCeO2. S2, Preparation of Pt NPs 1 g of chloroplatinic acid hexahydrate was completely dissolved in ethylene glycol to obtain a chloroplatinic acid-ethylene glycol solution with a concentration of 20 g / L. Simultaneously, a NaOH-ethylene glycol solution with a concentration of 0.26 mol / L was prepared. Then, 5 mL of each of the two solutions were mixed and stirred thoroughly under a nitrogen atmosphere. The mixture was then heated to 175 °C and stirred continuously at 175 °C for 3 hours. After the reaction was complete, the mixture was cooled to room temperature (approximately 25 °C) under a nitrogen atmosphere. Finally, the reduced dark brown platinum nanoparticles (Pt) were collected. NPs Solution; S3. Redisperse 1 g of NbCeO2 obtained in S1 into 10 mL of water, then add 2.66 mL of Pt obtained in S2 dropwise. NPsThe solution was stirred at room temperature (approximately 25 °C) for 8 hours, filtered and washed, and then dried in an oven at 80 °C for 12 hours to obtain precursor B. Precursor B was placed in a muffle furnace and heated to 400 °C at a rate of 5 °C / min, and calcined at 400 °C in air atmosphere for 4 hours. It was then naturally cooled to room temperature (approximately 25 °C) to obtain a Pt / NbCeO2 composite material.

[0047] Example 3

[0048] A method for combining materials in series includes the following steps: The Cu / ZSM-5 composite material obtained in Example 1 and the Pt / NbCeO2 composite material obtained in Example 2 were layered in a fixed-bed quartz reactor at a mass ratio of 1:1 (50 mg each). The inlet end (pre-stage) of the reactor was Cu / ZSM-5 composite material, and the outlet end (post-stage) was Pt / NbCeO2 composite material. The two were separated by quartz sand with a thickness of 2 mm. One layer of Cu / ZSM-5 composite material and one layer of Pt / NbCeO2 composite material were laid.

[0049] The tandem catalytic materials obtained in this embodiment are labeled as Cu / Z5 & Pt / NbCeO2 in the figure.

[0050] Example 4

[0051] The test method for the catalytic oxidation reaction of vinyl chloride using a single catalyst material is as follows: The catalytic oxidation of vinyl chloride was carried out in a fixed-bed quartz reactor at atmospheric pressure. A total of 100 mg of a single catalyst (the single catalyst from Example 1 or Example 2) was used, and catalytic performance and stability were tested under conditions of a mixed gas flow rate of 50 mL / min, corresponding to a WHSV of 30000 mL·g. -1 ·h -1 The reaction gas consisted of vinyl chloride and purified air (composed of 21% O2 and 79% N2) in a 1:1 volume ratio, with a vinyl chloride concentration of 500 ppm. Each test temperature was maintained for 25 minutes to ensure sample temperature stability. The composition of the effluent gas was analyzed using an online gas chromatograph (GC-9790 plus).

[0052] The test method for the catalytic oxidation reaction of vinyl chloride using tandem catalytic materials is as follows: The catalytic oxidation of vinyl chloride was carried out in a fixed-bed quartz reactor at atmospheric pressure. A total of 100 mg of tandem catalyst (prepared as a tandem catalyst according to Example 3 or Comparative Examples 3-4) was used. Catalytic performance and stability were tested under conditions of a mixed gas flow rate of 50 mL / min, corresponding to a WHSV of 30000 mL·g. -1 ·h -1 The reaction gas consisted of vinyl chloride and purified air (composed of 21% O2 and 79% N2) in a 1:1 volume ratio, with a vinyl chloride concentration of 500 ppm. Each test temperature was maintained for 25 minutes to ensure sample temperature stability. The composition of the effluent gas was analyzed using an online gas chromatograph (GC-9790 plus).

[0053] Comparative Example 1 A method for preparing a Cu / ZSM-5 composite material includes the following steps: S1. Add 2 g of commercial ZSM-5 molecular sieve powder (silicon-aluminum molecular ratio of 21) to 100 mL of aqueous solution containing 0.51 g of oxalic acid. Stir the mixture at room temperature (about 25 °C) for 1 hour to form a gel. S2. Dissolve 0.16 g of copper acetate in 10 mL of water to obtain an aqueous solution of copper acetate. Add the aqueous solution of copper acetate dropwise to the gel obtained in S1. Continue stirring at room temperature (about 25 °C) for 3 hours to form a gel mixture. Filter to collect the solid and wash the solid 5 times with deionized water. Then dry it in an oven at 80 °C for 12 hours to obtain the precursor. S3. The precursor obtained in S2 is placed in a muffle furnace and heated to 550 °C at a rate of 5 °C / min. It is then calcined at 550 °C in air for 4 hours, followed by natural cooling to room temperature (approximately 25 °C) to obtain a Cu / ZSM-5 composite material, denoted as Cu. 2.5 / ZSM-5.

[0054] Comparative Example 2 A method for preparing Cu / ZSM-5 includes the following steps: S1. Add 2 g of commercial ZSM-5 molecular sieve powder (silicon-aluminum molecular ratio of 21) to 100 mL of aqueous solution containing 1.49 g of oxalic acid. Stir the mixture at room temperature (about 25 °C) for 1 hour to form a gel. S2. Dissolve 0.47 g of copper acetate in 10 mL of water to obtain an aqueous solution of copper acetate. Add the aqueous solution of copper acetate dropwise to the gel obtained in S1. Continue stirring at room temperature (about 25 °C) for 3 hours to form a gel mixture. Filter to collect the solid and wash the solid 5 times with deionized water. Then dry it in an oven at 80 °C for 12 hours to obtain the precursor. S3. The precursor obtained in S2 is placed in a muffle furnace and heated to 550 °C at a rate of 5 °C / min. It is then calcined at 550 °C in air for 4 hours, followed by natural cooling to room temperature (approximately 25 °C) to obtain a Cu / ZSM-5 composite material, denoted as Cu. 7.5 / ZSM-5.

[0055] Comparative Example 3 A method for combining materials in series includes the following steps: The Cu / ZSM-5 composite material obtained in Example 1 and the Pt / NbCeO2 composite material obtained in Example 2 were layered in a fixed-bed quartz reactor at a mass ratio of 1:1 (50 mg each). The inlet end (pre-stage) of the reactor was Pt / NbCeO2 composite material, and the outlet end (post-stage) was Cu / ZSM-5 composite material. The two were separated by quartz sand with a thickness of 2 mm. One layer of Cu / ZSM-5 composite material and one layer of Pt / NbCeO2 composite material were laid.

[0056] The tandem catalysts obtained in this comparative example are labeled as Pt / NbCeO2 & Cu / Z5 in the figure.

[0057] Comparative Example 4 A method for combining materials in series includes the following steps: The Cu / ZSM-5 composite material obtained in Example 1 and the Pt / NbCeO2 composite material obtained in Example 2 were mixed evenly at a mass ratio of 1:1 (50 mg each) and then fixed in a fixed-bed quartz reactor.

[0058] The tandem catalyst obtained in this comparative example is labeled as Cu / Z5 + Pt / NbCeO2 in the figure.

[0059] Detection and Analysis 1) Characterization of materials The crystal structure and microstructure of the catalytic materials obtained in Examples 1-2 and Comparative Examples 1-2 were characterized and analyzed.

[0060] The crystal structure of the catalytic material was studied by X-ray diffraction (XRD), and the morphology of the catalytic material was observed by scanning electron microscopy (SEM). The results are as follows: Figures 1 to 4 As shown.

[0061] Figure 1 The images show the XRD patterns of the Cu / ZSM-5 series composite materials obtained in Example 1 and Comparative Examples 1-2 of this invention. Figure 1 It can be seen that the characteristic diffraction peaks of the Cu / ZSM-5 composite material are consistent with the standard card PDF#44-0003 of ZSM-5, and a small number of diffraction peaks belonging to CuO species were also detected.

[0062] Figure 2 The image shows the XRD pattern of the Pt / NbCeO2 composite material obtained in Example 2 of this invention. Figure 2 As can be seen, the characteristic diffraction peak of CeO2 (standard card PDF#34-0349) appeared in the spectrum, and no characteristic peaks belonging to Nb and Pt were detected, indicating that the two are uniformly loaded.

[0063] Figure 3 This is a SEM image of the Cu / ZSM-5 composite material obtained in Example 1 of this invention. Figure 3 It can be seen that Cu5 / ZSM-5 has a columnar morphology.

[0064] Figure 4 This is a SEM image of the Pt / NbCeO2 composite material prepared in Example 2 of this invention. Figure 4 It can be seen that the morphology of the Pt / NbCeO2 composite material is blocky particles.

[0065] 2) Vinyl chloride catalytic performance test The vinyl chloride catalytic performance of the single catalytic materials obtained in Examples 1-2 and the tandem catalytic materials obtained in Examples 3 and Comparative Examples 3-4 was tested using the method described in Example 4. The results are as follows: Figures 5 to 8 As shown.

[0066] Figure 5 This diagram shows the catalytic activity of the single catalytic materials obtained in Examples 1-2 and the tandem catalytic materials obtained in Examples 3 and Comparative Examples 3-4 in the ethylene chloride oxidation reaction. Figure 5 It can be seen that when Cu / ZSM-5 composite material is used as the pre-stage and Pt / NbCeO2 composite material is used as the post-stage (marked as Cu / Z5 & Pt / NbCeO2 in the figure), this tandem material system has the best catalytic activity and can achieve a vinyl chloride degradation rate of 90% at 230 °C.

[0067] Figure 6 This diagram shows the CO2 production in the vinyl chloride oxidation reaction using the single catalytic material obtained in Examples 1-2 and the tandem catalytic material obtained in Examples 3 and Comparative Examples 3-4. Figure 6 As shown, when the Cu / ZSM-5 composite material is used as the pre-stage and the Pt / NbCeO2 composite material is used as the post-stage (labeled as Cu / Z5 & Pt / NbCeO2 in the figure), the mineralization rate of this tandem material system is the highest, at the temperature (T0) where the vinyl chloride conversion reaches 90%. 90 The CO2 selectivity (mineralization rate) can reach 98%.

[0068] Figure 7The graphs show the stability and water resistance test results of the tandem catalytic material system composed in Example 3 of this invention. Figure 7 As shown, under long-term continuous testing, the tandem catalytic material can maintain high activity, and the activity does not decrease significantly after passing 5 vol% water vapor, indicating that the tandem catalytic material has good chlorine resistance and water resistance.

[0069] Figure 8 This diagram shows the HCl yield and selectivity in the vinyl chloride oxidation reaction using the single catalytic materials obtained in Examples 1-2 and the tandem catalytic materials obtained in Examples 3 and Comparative Examples 3-4. Figure 8 As shown, the tandem material system composed of Cu / ZSM-5 composite material and Pt / NbCeO2 composite material according to Example 3 (labeled as Cu / Z5 & Pt / NbCeO2 in the figure) has an HCl selectivity of about 82%, indicating that the tandem material system produces the least amount of toxic chlorine-containing byproducts during the oxidation of vinyl chloride.

[0070] The above results fully demonstrate that the Cu / ZSM-5 composite material, Pt / NbCeO2 composite material, and the tandem material system composed of the two provided by this invention have high activity and high selectivity when applied to the catalytic oxidation of vinyl chloride. In particular, the tandem material system also has good stability and excellent resistance to chlorine and water, and has good potential and prospects for industrial application.

[0071] The above embodiments are merely preferred embodiments provided to fully illustrate the present invention, and the scope of protection of the present invention is not limited thereto. Equivalent substitutions or modifications made by those skilled in the art based on the present invention are all within the scope of protection of the present invention.

Claims

1. A Pt / NbCeO2 composite material, characterized in that, The Pt / NbCeO2 composite material includes NbCeO2 and Pt nanoparticles supported on NbCeO2; The mass ratio of the Pt nanoparticles to the NbCeO2 is 0.5–2:100; The mass percentage of Nb in the NbCeO2 is 8% to 12%.

2. A method for preparing the Pt / NbCeO2 composite material as described in claim 1, characterized in that, Includes the following steps: NbCeO2 was prepared by impregnation using CeO2 as a carrier. Pt nanoparticles were prepared using the ethylene glycol reduction method. The Pt nanoparticles were loaded onto NbCeO2 using an impregnation method to obtain the Pt / NbCeO2 composite material.

3. The preparation method according to claim 2, characterized in that, Includes the following steps: S1. Preparation of NbCeO2: Niobium ammonium oxalate is dissolved in water to obtain an aqueous solution of niobium ammonium oxalate. CeO2 is added to the aqueous solution of niobium ammonium oxalate and stirred. The resulting solid is dried and calcined to obtain NbCeO2. S2. Preparation of Pt nanoparticle solution: Dissolve chloroplatinic acid hexahydrate in ethylene glycol to obtain mixed solution A; dissolve NaOH in ethylene glycol to obtain mixed solution B; mix mixed solution A and mixed solution B, heat and stir under nitrogen atmosphere, and cool under nitrogen atmosphere after the reaction is completed to obtain Pt nanoparticle solution; S3. The NbCeO2 obtained in S1 is redispersed in water, and the Pt nanoparticle solution obtained in S2 is added dropwise. The mixture is stirred, filtered and washed, the solid is collected, dried, and calcined to obtain the Pt / NbCeO2 composite material. And / or, in S1, the concentration of niobium oxalate in the aqueous solution of niobium oxalate is 0.04–0.05 mol / L, the ratio of CeO2 to the aqueous solution of niobium oxalate is 1 g: 25 mL, the stirring time is 10–12 h, the drying temperature is 70–90 ℃, the calcination atmosphere is air, the calcination temperature is 400–500 ℃, and the calcination time is 4–6 h; And / or, in S2, the concentration of chloroplatinic acid in the mixed solution A is 18–22 g / L, the concentration of NaOH in the mixed solution B is 0.2–0.3 mol / L, and the temperature of the heating and stirring reaction is 160–180 °C and the time is 3–5 h; And / or, in S3, the ratio of NbCeO2 to water is 1 g: 10 mL, the ratio of Pt nanoparticle solution to NbCeO2 is 2.0–3.0 mL: 1 g, the stirring time is 6–8 h, the drying temperature is 70–90 ℃ and the drying time is 8–12 h, the calcination atmosphere is air, the calcination temperature is 400–500 ℃ and the calcination time is 4–6 h.

4. A tandem material, characterized in that, Includes the Pt / NbCeO2 composite material and Cu / ZSM-5 composite material as described in any one of claims 1 to 3.

5. The tandem material according to claim 4, characterized in that, The Cu / ZSM-5 composite material includes ZSM-5 molecular sieve and CuO supported on ZSM-5 molecular sieve; The silicon-aluminum molecular ratio of the ZSM-5 molecular sieve is 10-25; The mass ratio of CuO to ZSM-5 molecular sieve is 0.04 to 0.06:

1.

6. The tandem material according to claim 4, characterized in that, The preparation method of the Cu / ZSM-5 composite material includes the following steps: Add ZSM-5 molecular sieve and oxalic acid to water and stir until a gel is formed; Copper acetate was dissolved in water and added dropwise to the gel, and the mixture was stirred to form a gel mixture. The gel mixture was filtered, washed, dried, and calcined to obtain the Cu / ZSM-5 composite material.

7. The tandem material according to claim 4, characterized in that, The preparation method of the Cu / ZSM-5 composite material includes the following steps: S1. Add ZSM-5 molecular sieve and oxalic acid to water and stir for the first time at room temperature to form a gel; S2. Dissolve copper acetate in water and then add it dropwise to the gel obtained in S1. Stir a second time to form a gel mixture. Filter, wash, and dry to obtain the precursor. S3. Calcine the precursor obtained in S2 and cool it to obtain the Cu / ZSM-5 composite material; And / or, the ratio of ZSM-5 molecular sieve, oxalic acid and water is 2 g : 0.4 g to 1.6 g : 100 mL, the first stirring time is 1 to 2 h, the ratio of copper acetate and water is 0.1 g to 0.6 g : 10 mL, the second stirring time is 2 to 5 h, the drying temperature is 80 to 100 ℃ and the drying time is 8 to 12 h, the calcination atmosphere is air, the calcination temperature is 500 to 550 ℃ and the calcination time is 4 to 6 h.

8. The application of the Pt / NbCeO2 composite material as described in claims 1 to 3 or the tandem material as described in any one of claims 4 to 7 in the catalytic oxidation of vinyl chloride.

9. The application according to claim 8, characterized in that, The tandem material is composed of Cu / ZSM-5 composite material and Pt / NbCeO2 composite material layered in a 1:1 mass ratio, with quartz sand separating the two.

10. The application according to claim 9, characterized in that, The Cu / ZSM-5 composite material in the series is located at the inlet end of the reaction device, and the Pt / NbCeO2 composite material in the series is located at the outlet end of the reaction device.

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