Preparation method of morphology-controllable cerium and lanthanum-containing solid waste-based composite material and application of morphology-controllable cerium and lanthanum-containing solid waste-based composite material in halogenated VOCs degradation

Abstract

The present application relates to solid waste resource application field, especially in a kind of preparation method of morphology controllable cerium-containing lanthanum solid waste-based composite material and its application in halogenated VOCs degradation.The preparation method includes the following steps: rare earth polishing powder is obtained by acid leaching leaching liquor;Leaching liquor is mixed with oxalic acid and precipitated, and the obtained precipitate is dried, calcined, to obtain morphology controllable lanthanum cerium oxide;Lanthanum cerium oxide is mixed with silicon source, aluminum source, template agent, etc., by hydrothermal reaction, centrifugal, drying, calcination and ion exchange, to obtain composite catalyst.The present application uses "leaching-morphology control-zeolite loading" synergistic strategy, successfully prepares a kind of composite catalyst with waste rare earth polishing powder as raw material, with lanthanum cerium co-leaching and morphology controllable characteristics.The method not only realizes the high-value resource utilization of waste rare earth polishing powder, but also shows excellent catalytic performance in the degradation of dichloromethane reaction, and shows good application prospect in VOCs pollution control field.

Description

Technical Field

[0001] This invention relates to the field of solid waste resource utilization, and in particular to a method for preparing a morphology-controllable cerium-lanthanum-containing solid waste-based composite material and its application in the degradation of halogenated VOCs. Background Technology

[0002] Rare earth polishing powders (REPPs) are functional materials with cerium oxide (CeO2) as the main component. Since the 1990s, with the rapid development of the electronics and information industry, their market demand has continued to grow, driving the development and application of advanced polishing powders with high cerium content. However, after a limited number of polishing cycles, the polishing powder usually becomes ineffective, generating a large amount of rare earth polishing powder waste (REPPWs). These wastes are rich in valuable rare earth elements such as cerium and lanthanum, and have significant potential for secondary resource recovery. However, the industrial recycling of rare earth polishing powder waste still faces many challenges, mainly due to the complex composition and diverse phases of the waste, resulting in low efficiency, poor selectivity, high energy consumption, and easy generation of secondary pollution in existing recycling processes.

[0003] Currently used recovery methods include physical separation (such as screening, flotation, gravity separation, etc.), acid leaching, alkaline leaching, sulfation roasting, alkaline roasting, and combined processing. Physical separation methods are generally difficult to achieve efficient enrichment of rare earth elements and often require chemical purification. Acid and alkaline leaching processes tend to generate large amounts of waste liquid, increasing treatment costs. Furthermore, cerium oxide has low solubility in most acids at room temperature, typically requiring leaching under high temperature or high-concentration acid conditions, and leaching efficiency and selectivity still need improvement. More importantly, existing recovery technologies mostly focus on the extraction and separation of rare earth elements, failing to fully utilize their potential as precursors for functional materials, thus limiting their high-value applications.

[0004] On the other hand, the pyrolysis or incineration of solid waste such as electronic waste, waste wires and cables, waste circuit boards, and waste photovoltaic panels generates a large amount of volatile organic compounds (VOCs) containing halogenated elements such as chlorine, bromine, and fluorine, such as dichloromethane. These halogenated VOCs are characterized by high toxicity, difficulty in degradation, and easy accumulation in the environment, posing a serious threat to the ecological environment and human health. Therefore, developing efficient and stable catalytic materials for the degradation of halogenated VOCs is of significant practical importance.

[0005] Therefore, if a composite material with controllable morphology and excellent catalytic performance can be prepared using rare earth polishing powder waste as raw material, and applied to the catalytic degradation of halogenated VOCs, it can not only realize the high-value resource utilization of rare earth waste, but also provide a green and sustainable technical path for the field of air pollution control. Summary of the Invention

[0006] Based on the above, this invention provides a method for preparing a morphology-controllable cerium-lanthanum-containing solid waste-based composite material and its application in the degradation of halogenated VOCs. Addressing the current problems of high energy consumption, unsatisfactory leaching rates, difficulty in separating lanthanum and cerium, and low value-added utilization of rare earths, especially their limited use in catalyst preparation, this invention cleverly utilizes the co-leaching characteristics of lanthanum and cerium. Using their mixed leachate as raw material, the morphology of lanthanum and cerium oxides is controlled by oxalic acid precipitation, and then combined with HZSM-5 molecular sieves to prepare a catalyst capable of catalytically oxidizing and degrading dichloromethane. This method not only solves the problem of insufficient rare earth recycling and achieves high-value utilization, but also provides a new pathway for dichloromethane degradation, possessing economic, environmental, and social benefits.

[0007] To achieve the above objectives, the present invention provides the following solution: One of the technical solutions of this invention is a method for preparing a cerium-lanthanum-containing solid waste-based composite material with controllable morphology, comprising the following steps: Step 1: Mix rare earth polishing powder and acid solution for leaching to obtain leachate; Step 2: The leachate is mixed with oxalic acid solution and reacted to obtain a precipitate; Step 3: Dry and calcine the precipitate to obtain lanthanum cerium oxide; Step 4: Mix the lanthanum cerium oxide with sodium chloride, polyethylene glycol, tetrapropylammonium hydroxide, and water, and add... Aluminum isopropoxide and tetraethyl silicate are mixed to obtain a mixed solution; Step 5: Perform a hydrothermal reaction on the mixed solution, then dry and calcine the solid obtained by centrifugation to obtain powder; Step 6: Place the powder in an ammonium salt solution for ion exchange, then dry and calcine to obtain a cerium-lanthanum-containing solid waste-based composite material with controllable morphology.

[0008] The second technical solution of the present invention is a cerium-lanthanum-containing solid waste-based composite material with controllable morphology prepared by the above-mentioned preparation method.

[0009] The third technical solution of the present invention is the application of the above-mentioned morphology-controllable cerium-lanthanum solid waste-based composite material as a catalyst in the catalytic oxidation degradation of chlorine-containing volatile organic compounds.

[0010] The fourth technical solution of the present invention is a method for catalytic oxidation degradation of dichloromethane using the above-mentioned morphology-controllable cerium-lanthanum-containing solid waste-based composite material. The method involves contacting a mixed gas containing dichloromethane with the morphology-controllable cerium-lanthanum-containing solid waste-based composite material to carry out a catalytic oxidation reaction.

[0011] Compared with the prior art, the present invention has the following beneficial effects: (1) This invention realizes the efficient recycling and high-value utilization of rare earth resources. By cleverly using rare earth polishing powder acid leaching solution as raw material, it not only solves the problems of high energy consumption and unsatisfactory leaching rate in traditional recycling methods, but also bypasses the problem of lanthanum and cerium separation, directly converting the coexisting lanthanum and cerium elements into high-value-added composite catalysts, which greatly enhances the recycling value of rare earth resources.

[0012] (2) This invention innovates the preparation route of catalysts with controllable morphology: the morphology of lanthanum cerium oxide can be controlled by oxalic acid precipitation, enabling the preparation of catalytic materials with specific structures and abundant active sites. This method provides a novel and controllable strategy for designing and synthesizing high-performance, customized rare earth oxide catalysts.

[0013] (3) This invention provides an efficient catalytic solution for recalcitrant pollutants. The morphology-controllable cerium-lanthanum solid waste-based composite material (lanthanum cerium oxide / HZSM-5 composite catalyst, hereinafter referred to as the composite catalyst) shows good application potential in the catalytic oxidation degradation of dichloromethane, providing a new and effective technical route for treating this toxic and recalcitrant volatile organic compound, with significant environmental benefits and application prospects. Attached Figure Description

[0014] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0015] Figure 1 The diagram shows the conversion rate of dichloromethane by the composite catalysts prepared in Examples 1-4.

[0016] Figure 2 This is a schematic diagram showing the selectivity of the composite catalysts prepared in Examples 1-4 for CO2 and CO.

[0017] Figure 3 This is a schematic diagram showing the selectivity of the composite catalysts prepared in Examples 1-4 for HCl and Cl2.

[0018] Figure 4 This is a schematic diagram showing the selectivity of the composite catalysts prepared in Examples 1-4 for CH3Cl.

[0019] Figure 5 The diagram shows the conversion rate of dichloromethane by the composite catalysts prepared in Comparative Examples 1 and 2.

[0020] Figure 6 This is a schematic diagram illustrating the selectivity of the composite catalysts prepared in Comparative Examples 1 and 2 for CO2 and CO.

[0021] Figure 7 This is a schematic diagram illustrating the selectivity of the composite catalysts prepared in Comparative Examples 1 and 2 for HCl and Cl2.

[0022] Figure 8 This is a schematic diagram illustrating the selectivity of the composite catalysts prepared in Comparative Examples 1 and 2 for CH3Cl.

[0023] Figure 9 Scanning electron microscope images of the composite catalysts prepared in Examples 1-4; where a is Example 1, b is Example 2, c is Example 3, and d is Example 4.

[0024] Figure 10 X-ray powder diffraction images of the composite catalysts prepared in Examples 1-4.

[0025] Figure 11 Scanning electron microscope images of the composite catalysts prepared for comparative examples 1 and 2; where a is comparative example 1 and b is comparative example 2.

[0026] Figure 12 This is a schematic diagram of the in-situ infrared spectrum of the composite catalyst prepared in Example 3 for the removal of dichloromethane.

[0027] Figure 13 The image shows the in-situ infrared spectra of the composite catalysts prepared for comparative examples 1 and 2 for the removal of dichloromethane; where a is comparative example 1 and b is comparative example 2. Detailed Implementation

[0028] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0029] It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the invention. Furthermore, with respect to numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Any stated value or intermediate value within a stated range, as well as each smaller range between any other stated value or intermediate value within said range, is also included in this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0030] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials have been described herein, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of this invention. All references to this specification are incorporated by way of citation to disclose and describe methods and / or materials associated with those references. In the event of any conflict with any incorporated reference, the content of this specification shall prevail.

[0031] Various modifications and variations can be made to the specific embodiments described in this specification without departing from the scope or spirit of the invention, as will be apparent to those skilled in the art. Other embodiments derived from this specification will also be apparent to those skilled in the art. This specification and embodiments are merely exemplary.

[0032] The terms “include,” “including,” “have,” “contain,” etc., used in this article are all open-ended terms, meaning that they include but are not limited to.

[0033] The naturally occurring cerium-lanthanum combination in rare earth polishing powder waste forms an element-matching system, particularly suitable for catalytic applications. Direct synthesis of high-value-added materials (such as cerium-lanthanum oxide catalysts) from polishing powder waste leachate offers significant sustainability advantages. CeO2-based catalysts exhibit superior catalytic performance in the degradation of chlorinated volatile organic compounds (CVOCs), primarily attributed to their excellent oxygen storage capacity and reversible CeO2 oxidation. 4+ / Ce 3+ Oxidation-reduction cycle. This invention proposes a method for preparing a composite catalyst based on rare earth polishing powder acid leaching-oxalic acid precipitation to generate morphology-controllable lanthanum-cerium oxide and HZSM-5. It successfully constructs a novel synergistic treatment system integrating "leaching-morphology control-zeolite assembly," realizing the targeted and high-value transformation of rare earth polishing powder waste into high-performance catalytic materials. This invention not only provides an environmentally friendly and integrated method for rare earth resource recovery and reuse but also pioneers a technical route for preparing highly efficient CVOCs catalytic degradation catalysts using rare earth materials. It possesses strong industrial feasibility and significant environmental value, providing strong technical support and theoretical basis for waste resource utilization and air pollution control.

[0034] The first aspect of this invention provides a method for preparing a morphology-controllable cerium-lanthanum-containing solid waste-based composite material, comprising the following steps: Step 1: Mix rare earth polishing powder and acid solution for leaching to obtain leachate; Step 2: The leachate is mixed with oxalic acid solution and reacted to obtain a precipitate; Step 3: Dry and calcine the precipitate to obtain lanthanum cerium oxide; Step 4: Mix the lanthanum cerium oxide with sodium chloride, polyethylene glycol, tetrapropylammonium hydroxide, and water, and add... Aluminum isopropoxide and tetraethyl silicate are mixed to obtain a mixed solution; Step 5: Perform a hydrothermal reaction on the mixed solution, then dry and calcine the solid obtained by centrifugation to obtain powder; Step 6: Place the powder in an ammonium salt solution for ion exchange, then dry and calcine to obtain a cerium-lanthanum-containing solid waste-based composite material with controllable morphology.

[0035] In a preferred embodiment of the present invention, in step 1, the particle size of the rare earth polishing powder is no greater than 200 mesh (more preferably, the particle size of the rare earth polishing powder is 80~200 mesh); the acid solution is a sulfuric acid solution or nitric acid solution with a concentration of 1~10 mol / L; the leaching temperature is 60~80 ℃, and the leaching time is 1~3 h; the liquid-solid ratio of the rare earth polishing powder to the acid solution is 5~20 mL / g.

[0036] In a preferred embodiment of the present invention, in step 1, a reducing agent is added when the rare earth polishing powder and the acid solution are mixed or during the leaching process; the reducing agent is ascorbic acid; the concentration of the reducing agent in the acid solution is 7.4 g / L.

[0037] In a preferred embodiment of the present invention, in step 2, the volume ratio of the leachate to the oxalic acid solution is 1:1.5; the concentration of the oxalic acid solution is 0.02~0.2 mol / L (the solvent of the oxalic acid solution is water); the reaction time is 5~10 min; and stirring is also performed during the reaction (the present invention does not impose a special limitation on the stirring speed, and adopts the stirring speed commonly used by those skilled in the art).

[0038] In a preferred embodiment of the present invention, in step 3, the drying temperature is 60~80 ℃ and the drying time is 12~24 h; the calcination temperature is 400~550 ℃ and the calcination time is 1~5 h. Excessive calcination temperature leads to excessive grain growth of lanthanum cerium oxide, while insufficient temperature results in incomplete precursor decomposition. Excessive calcination time intensifies grain growth and sintering, while insufficient calcination time leads to incomplete phase transformation and poor stability. Excessive hydrothermal reaction temperature may result in excessively rapid crystallization, forming larger grains; insufficient hydrothermal temperature results in low crystallinity, incomplete pore structure, and slow crystallization. Excessive hydrothermal reaction time may lead to grain agglomeration, while insufficient time results in incomplete crystallization and low crystallinity.

[0039] In step 4, aluminum isopropoxide is calculated as Al2O3, tetraethyl silicate as SiO2, and the molar ratio of sodium chloride to polyethylene glycol, tetrapropylammonium hydroxide, aluminum isopropoxide, tetraethyl silicate and water is 8.69∶6.83∶11.31∶1∶(25~150)∶2277.04; the mass ratio of lanthanum cerium oxide to aluminum isopropoxide is 1∶(0.056~0.36).

[0040] In step 4, the substances are mixed by stirring for 12-25 hours. The present invention does not impose a special limitation on the stirring speed; the stirring speed commonly used by those skilled in the art can be used.

[0041] In a preferred embodiment of the present invention, in step 5, the temperature of the hydrothermal reaction is 80~180 ℃ and the time is 12~72 h; in a more preferred embodiment of the present invention, the hydrothermal reaction is specifically: first, the temperature is kept at 80 ℃ for 24 h, and then the temperature is raised to 170 ℃ and kept at 170 ℃ for 48 h (the present invention does not specifically limit the heating rate, and the heating rate commonly used by those skilled in the art can be used); the calcination temperature is 400~550 ℃ and the calcination time is 3~5 h.

[0042] In step 5, the centrifugation speed is 1000-3000 r / min.

[0043] In a preferred embodiment of the present invention, in step 6, the ammonium salt solution is a 1 mol / L ammonium chloride solution; the ion exchange temperature is 70-90 °C, the number of ion exchanges is 2-3 times, and the time for each ion exchange is 2-3 hours; the drying temperature is 60-80 °C, and the drying time is 12-24 hours; the calcination temperature is 400-550 °C, and the calcination time is 3-5 hours. Ion exchange is used to exchange the hydrothermal ZSM-5 from the Na form to the H form, obtaining H-ZSM-5. Calcination after ion exchange is to remove the residue of the template agent (tetrapropylammonium hydroxide) used in the hydrothermal reaction.

[0044] A second aspect of the present invention provides a morphology-controllable cerium-lanthanum-containing solid waste-based composite material prepared by the above-described preparation method.

[0045] The third aspect of this invention provides the application of the above-mentioned morphology-controllable cerium-lanthanum-containing solid waste-based composite material as a catalyst in the catalytic oxidation degradation of chlorine-containing volatile organic compounds.

[0046] In a preferred embodiment of the present invention, the chlorine-containing volatile organic compound is dichloromethane.

[0047] The fourth aspect of the present invention provides a method for catalytic oxidation degradation of dichloromethane using the above-mentioned morphology-controllable cerium-lanthanum-containing solid waste-based composite material, wherein a mixed gas containing dichloromethane is contacted with the morphology-controllable cerium-lanthanum-containing solid waste-based composite material to carry out a catalytic oxidation reaction.

[0048] The temperature for the catalytic oxidation degradation is 150~450 ℃; the concentration of dichloromethane in the mixed gas is 500~3000 ppm.

[0049] Unless otherwise specified, the technical solutions described in this invention are all conventional solutions in the field, and the reagents or raw materials used are all purchased from commercial channels or are publicly available unless otherwise specified.

[0050] The rare earth polishing powder used in this embodiment of the invention is a rare earth polishing powder that has failed after polishing cycle. The composition by mass percentage is: CeO2 (75.93%), La2O3 (19.59%), Pr2O3 (2.70%), Fe2O3 (1.30%), SiO2 (0.16%), Al2O3 (0.14%), P2O5 (0.08%), SO3 (0.06%) and K2O (0.04%).

[0051] The technical solutions provided by the present invention will be described in detail below with reference to the embodiments, but they should not be construed as limiting the scope of protection of the present invention.

[0052] Example 1 (1) Pass the rare earth polishing powder through a 200-mesh sieve and set the sieved powder aside; (2) The sieved powder was leached in 100 mL of 1 mol / L sulfuric acid solution for 2 h at a leaching temperature of 80 °C and a liquid-to-solid ratio of 20 mL / g. Ascorbic acid reducing agent was added at a dosage of 0.74 g. The ascorbic acid reducing agent was added at the same time as the rare earth polishing powder. (3) Mix the leachate obtained in step (2) with the oxalic acid solution and stir. The volume ratio of the leachate to the oxalic acid solution is 1:1.5. The concentration of the oxalic acid solution is 0.02 mol / L and the concentration of the leachate solution is 0.2 mol / L. The concentration of the leachate refers to the total concentration of Ce and La. The precipitation stirring time is 5 min. (4) The mixed solution was filtered, and the precipitate was dried for 24 h. Then it was calcined at 450 °C for 1 h to obtain the flower-shaped precipitate product, which is lanthanum cerium oxide. (5) Lanthanum cerium oxide, sodium chloride, polyethylene glycol (PEG), and tetrapropylammonium hydroxide (TPAOH) were added to deionized water and stirred at room temperature. Aluminum isopropoxide and tetraethyl silicate were added during stirring. The molar ratio of sodium chloride to PEG, TPAOH, aluminum isopropoxide (calculated as Al2O3), and tetraethyl silicate (calculated as SiO2) was: n(NaCl):n(PEG):n(TPAOH):n(Al2O3):n(SiO2):n(H2O) = 8.69:6.83:11.31:1:25:2277.04; the mass ratio of lanthanum cerium oxide to aluminum isopropoxide was 1:0.36; the mixed solution was stirred for 12 h. (6) The mixed solution was first hydrothermally reacted at 80 °C for 24 h, and then the temperature was raised to 170 °C for 48 h. (7) After hydrothermal reaction, the mixed solution is centrifuged (centrifugation speed is 3000 r / min), and the resulting solid powder is dried and calcined. The drying temperature is 80 ℃ and the drying time is 12 h; the calcination temperature is 550 ℃ and the calcination time is 4 h. (8) The powder obtained by calcination in step (7) is subjected to ion exchange in a 1 mol / L ammonium chloride solution. The number of ion exchanges is 3, the water bath temperature for ion exchange is 80 ℃, and the time for each ion exchange is 2 h. After that, it is dried at 80 ℃ for 24 h and calcined at 450 ℃ for 4 h to obtain the composite catalyst (cerium lanthanum solid waste-based composite material).

[0053] Example 2 The only difference from Example 1 is that in step (5), n(NaCl):n(PEG):n(TPAOH):n(Al2O3):n(SiO2):n(H2O) = 8.69:6.83:11.31:1:50:2277.04; the other steps and parameters are the same as in Example 1.

[0054] Example 3 The only difference from Example 1 is that in step (5), n(NaCl):n(PEG):n(TPAOH):n(Al2O3):n(SiO2):n(H2O) = 8.69:6.83:11.31:1:100:2277.04; the other steps and parameters are the same as in Example 1.

[0055] The in-situ infrared spectrum of the composite catalyst prepared in Example 3 for the removal of dichloromethane is shown in Figure 3. Figure 12 As shown, the in-situ infrared spectroscopy was tested at temperatures of 30, 150, 200, 250, 300, 350, 400, and 450 °C; [The remaining text appears to be incomplete and requires further context.] Figure 12It can be seen that the intensity of the CH and C-Cl peaks of dichloromethane decreases over time, and intermediate products do not accumulate on the catalyst surface.

[0056] Example 4 The only difference from Example 1 is that in step (5), n(NaCl):n(PEG):n(TPAOH):n(Al2O3):n(SiO2):n(H2O) = 8.69:6.83:11.31:1:150:2277.04; the other steps and parameters are the same as in Example 1.

[0057] Figure 9 Scanning electron microscope images of the composite catalysts prepared in Examples 1-4; where a is Example 1, b is Example 2, c is Example 3, and d is Example 4. Figure 9 It can be seen that changing the ratio of n(Al2O3)∶n(SiO2) has virtually no effect on the morphology of the composite catalyst.

[0058] Figure 10 These are X-ray powder diffraction images of the composite catalysts prepared in Examples 1-4. Figure 10 It can be seen that the phase composition of the composite catalysts is similar, and the ratio of n(Al2O3)∶n(SiO2) affects the peak intensity.

[0059] Example 1 The composite catalysts prepared in Examples 1-4 were used for the degradation of dichloromethane, and the specific technical solutions are as follows: Dichloromethane gas was reacted with a mixture of 21 vol% O2 and equilibrium N2 under the action of a composite catalyst; the mixed gas contained 3000 ppm dichloromethane; 0.5 g of composite catalyst and 0.5 g of quartz sand were physically mixed and placed in a fixed-bed reactor for reaction; the reaction space velocity was 15000 mL / g / h; the reaction temperatures were 150, 200, 250, 300, 350, 400 and 450 °C, respectively. The catalytic performance and product selectivity of the catalyst for dichloromethane were obtained (as shown in Tables 1, 2, 3, 4, 5, 6 and 7). Figure 1 , Figure 2 , Figure 3 , Figure 4 (As shown).

[0060] Table 1. Conversion rate of dichloromethane by catalyst in Examples 1, 2, 3, and 4.

[0061] Table 2. CO2 selectivity of catalysts in Examples 1, 2, 3, and 4.

[0062] Table 3. CO selectivity of catalysts in Examples 1, 2, 3, and 4.

[0063] Table 4. HCl selectivity of catalysts in Examples 1, 2, 3, and 4.

[0064] Table 5. Cl2 selectivity of catalysts in Examples 1, 2, 3, and 4.

[0065] Table 6. CH3Cl selectivity of catalysts in Examples 1, 2, 3, and 4.

[0066] From Tables 1-6 and Figures 1-4 It can be seen that Examples 1-4 have a high degradation effect on dichloromethane, with Example 3 reaching 98.7% at 450°C; and Examples 1-4 all have high selectivity for CO2 and HCl and low selectivity for byproducts, namely CO, Cl2 and CH3Cl.

[0067] Comparative Example 1 The only difference from Example 1 is that steps (5) to (8) are omitted; in step (3), the concentration of oxalic acid solution is 0.2 mol / L; the concentration of leachate is 0.02 M; the remaining steps and parameters are the same as in Example 1 (the concentration of leachate is adjusted to 0.02 M by adding water to the leachate for dilution).

[0068] Comparative Example 2 The only difference from Example 1 is that steps (5) to (8) are omitted; the remaining steps and parameters are the same as in Example 1.

[0069] Figure 11 Scanning electron microscope images of the catalysts prepared for Comparative Examples 1 and 2; where a is Comparative Example 1 and b is Comparative Example 2. Figure 11 It can be seen that changing the concentration of oxalic acid and leachate can alter the morphology of the precipitated product, namely, flaky and flower-like.

[0070] Example 2 The composite catalysts prepared in Comparative Examples 1 and 2 were subjected to the same performance verification as in Effect Example 1. The catalytic performance and product selectivity of the composite catalysts prepared in Comparative Examples 1 and 2 for dichloromethane at reaction temperatures of 150, 200, 250, 300, 350, 400, and 450 °C are shown in Tables 7-12. Figures 5-8 As shown in the figure. A schematic diagram of the in-situ infrared spectrum of the composite catalysts prepared in Comparative Examples 1 and 2 for the removal of dichloromethane is shown in the figure. Figure 13As shown, where a is Comparative Example 1 and b is Comparative Example 2, the in-situ infrared spectroscopy test temperatures are 30, 150, 200, 250, 300, 350, 400, and 450 °C. Figure 13 It is known that the flower-like structure of Comparative Example 2 achieves a more efficient oxidative conversion of dichloromethane by promoting surface oxygen migration and accelerating intermediate decomposition.

[0071] Table 7. Conversion rates of dichloromethane by catalysts in Comparative Examples 1 and 2

[0072] Table 8. CO2 selectivity of catalysts in Comparative Examples 1 and 2

[0073] Table 9. CO selectivity of catalysts in Comparative Examples 1 and 2

[0074] Table 10 HCl selectivity of catalysts in Comparative Examples 1 and 2

[0075] Table 11 Cl2 selectivity of catalysts in Comparative Examples 1 and 2

[0076] Table 12 CH3Cl selectivity of catalysts in Comparative Examples 1 and 2

[0077] From Tables 7-12 and Figures 5-8 It can be seen that the lanthanum cerium oxides with different morphologies in Comparative Example 1 and Comparative Example 2 have different degrees of degradation effects on dichloromethane. Among them, the flower-like structure of Comparative Example 2 is more conducive to gas mass transfer and exposure of active sites, and finally achieves a higher degradation effect than the sheet-like structure of Comparative Example 1 at 450℃. Both have high selectivity for CO2 and HCl and low selectivity for by-products, namely CO, Cl2 and CH3Cl.

[0078] Comparative Example 3 The only difference from Example 3 is that steps (1) to (4) are omitted; the lanthanum cerium oxide in step (5) is replaced with a commercially available mixture of CeO2 and La2O3 in a mass ratio of 6:1; the remaining steps and parameters are the same as in Example 3. The commercially available CeO2 and La2O3 both have a particle size of 1 μm and a purity of 99.9%.

[0079] The composite catalyst prepared in Comparative Example 3 was subjected to the same effect verification as in Effect Example 1. The results showed that the composite catalyst prepared in Comparative Example 3 had a conversion rate of 81.2% for dichloromethane at 450℃, and the product selectivity was 100% for CO2 and HCl, and 0% for CO, Cl2 and CH3Cl.

[0080] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made by those skilled in the art to the technical solutions of the present invention without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.

Claims

1. A method for preparing a morphology-controllable cerium-lanthanum-containing solid waste-based composite material, characterized in that, Includes the following steps: Step 1: Mix rare earth polishing powder and acid solution for leaching to obtain leachate; Step 2: The leachate is mixed with oxalic acid solution and reacted to obtain a precipitate; Step 3: Dry and calcine the precipitate to obtain lanthanum cerium oxide; Step 4: Mix the lanthanum cerium oxide, sodium chloride, polyethylene glycol, tetrapropylammonium hydroxide, and water, and add... Aluminum isopropoxide and tetraethyl silicate are mixed to obtain a mixed solution; Step 5: Perform a hydrothermal reaction on the mixed solution, then dry and calcine the solid obtained by centrifugation to obtain powder; Step 6: Place the powder in an ammonium salt solution for ion exchange, then dry and calcine to obtain a cerium-lanthanum-containing solid waste-based composite material with controllable morphology.

2. The preparation method according to claim 1, characterized in that, In step 1, the particle size of the rare earth polishing powder is no greater than 200 mesh; the acid solution is a sulfuric acid solution or nitric acid solution with a concentration of 1~10 mol / L; the leaching temperature is 60~80℃, and the leaching time is 1~3 h; the liquid-solid ratio of the rare earth polishing powder to the acid solution is 5~20 mL / g.

3. The preparation method according to claim 1, characterized in that, In step 1, a reducing agent is added when the rare earth polishing powder and acid solution are mixed or during the leaching process; the reducing agent is ascorbic acid; the concentration of the reducing agent in the acid solution is 7.4 g / L.

4. The preparation method according to claim 1, characterized in that, In step 2, the volume ratio of the leachate to the oxalic acid solution is 1:1.5; the concentration of the oxalic acid solution is 0.02~0.2 mol / L; the reaction time is 5~10 min; and stirring is also carried out during the reaction.

5. The preparation method according to claim 1, characterized in that, In step 3, the drying temperature is 60~80℃ and the drying time is 12~24 h; the calcination temperature is 400~550℃ and the calcination time is 1~5 h. In step 4, aluminum isopropoxide is calculated as Al2O3, tetraethyl silicate as SiO2, and the molar ratio of sodium chloride to polyethylene glycol, tetrapropylammonium hydroxide, aluminum isopropoxide, tetraethyl silicate and water is 8.69∶6.83∶11.31∶1∶(25~150)∶2277.04; the mass ratio of lanthanum cerium oxide to aluminum isopropoxide is 1∶(0.056~0.36).

6. The preparation method according to claim 1, characterized in that, In step 5, the hydrothermal reaction temperature is 80~180 ℃ and the time is 12~72 h; the calcination temperature is 400~550 ℃ and the calcination time is 3~5 h.

7. The preparation method according to claim 1, characterized in that, In step 6, the ammonium salt solution is an ammonium chloride solution with a concentration of 1 mol / L; the ion exchange temperature is 70~90 ℃, the number of ion exchanges is 2~3 times, and the time for each ion exchange is 2~3 h; the drying temperature is 60~80 ℃, and the drying time is 12~24 h; the calcination temperature is 400~550 ℃, and the calcination time is 3~5 h.

8. A morphology-controllable cerium-lanthanum-containing solid waste-based composite material prepared by the preparation method according to any one of claims 1 to 7.

9. The application of the morphology-controllable cerium-lanthanum solid waste-based composite material as described in claim 8 as a catalyst in the catalytic oxidation degradation of chlorine-containing volatile organic compounds.

10. A method for catalytic oxidative degradation of dichloromethane using the morphology-controllable cerium-lanthanum-containing solid waste-based composite material as described in claim 8, characterized in that, A catalytic oxidation reaction is carried out by contacting a mixed gas containing dichloromethane with a morphology-controllable cerium-lanthanum solid waste-based composite material.

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