A copper-carbon composite material for dehalogenation of chlorinated waste paint-covered wire paint pyrolysis tail gas and a preparation method thereof

Abstract

A copper-carbon composite material for dehalogenation of chlorine-containing waste enameled wire varnish pyrolysis tail gas and its preparation method belong to the field of environmental catalysis. This invention first involves carbonizing, oxidizing, activating, and molding buckwheat hull powder after sieving to obtain shaped activated carbon (Shape-OAC); then, modified shaped activated carbon (H-Shape-OAC) is prepared using an acid modification method; Cu(NO3)2 solution is dropwise added to the surface of H-Shape-OAC and vacuum dried and calcined to obtain a secondary modified copper-carbon composite material (CuO@H-Shape-OAC); waste enameled wire varnish is mixed with CuO@H-Shape-OAC and subjected to a first thermal degradation dechlorination and a second adsorption-degradation to remove chlorinated VOCs (CVOCs). The resulting composite material can provide protons (H... + This method promotes the breaking of C-Cl bonds in CVOCs and accelerates the dechlorination reaction to generate HCl. It also reduces the gas flow pressure drop and ensures uniform contact of the reaction medium with CuO, thereby enhancing the catalytic degradation of CVOCs and facilitating the production of high-purity regenerated Cu. This method is less prone to introducing other metallic impurities, and the reaction conditions are mild, environmentally friendly, and exhibit excellent catalytic performance, good stability, and long lifespan.

Description

Technical Field

[0001] This invention belongs to the field of environmental catalysis technology, specifically relating to a copper-carbon composite material for dehalogenation of chlorine-containing waste enameled wire pyrolysis tail gas and its preparation method. Background Technology

[0002] In the field of electrical equipment scrapping and dismantling, the treatment of special waste chlorine-containing enameled wire varnish has become a key bottleneck restricting resource utilization. This type of chlorine-containing enameled wire varnish typically contains components such as polyvinyl chloride (PVC) and chlorinated rubber (CRP), which produce highly toxic substances such as HCl and dioxins during pyrolysis. According to data from the China National Resources Recycling Association, in 2024, approximately 180,000 tons of chlorine-containing waste enameled wire awaited treatment nationwide, accounting for 23% of the total waste enameled wire, and its treatment cost is 40-60% higher than that of ordinary enameled wire. Furthermore, the copper recovery rate from waste chlorine-containing enameled wire is generally below 92% due to chlorine corrosion losses, and the purity of recycled copper fluctuates between 99.5% and 99.9%, making it difficult to meet the requirements of high-end electromagnetic wire production. Therefore, research on the removal of chlorine and efficient copper recovery from the pyrolysis tail gas of waste chlorine-containing enameled wire varnish is of great significance.

[0003] To address this issue, several technologies for thermal dehalogenation and / or copper recovery from waste enameled wire have been reported. Commonly used methods include high-temperature incineration (>800℃), mechanical stripping, and wet chemical dechlorination. These processes all face certain challenges. For example, while high-temperature incineration can decompose organic matter, it releases 1.2-1.8% chlorine contaminants, accounting for 1.2%-1.8% of the total treated volume. Mechanical stripping results in 10-15% copper loss, and the residual chlorine content remains at 200-500 ppm. Wet chemical dechlorination requires the use of strong alkalis such as sodium hydroxide, generating 3-5 mg / L of chlorine per ton treated. 3 High-salinity wastewater. To address these issues, a few reports have emerged in recent years regarding the reduction of halogen-containing pollutants through the pyrolysis of chlorinated enameled wire varnish for copper recovery. CN117089707A discloses a method for reducing the halogen-containing pollutant content in the co-pyrolysis products of enameled wire varnish and polyvinyl chloride. This work involves co-pyrolyzing polyester enameled wire varnish, PVC, and CuO in a crucible (200-800℃) to reduce chlorine-containing pollutants and recover copper. The chlorine originates from PVC waste mixed into the waste enameled wire. This method utilizes CuO or Cu2O to absorb the HCl gas produced by PVC decomposition, generating solid inorganic matter CuCl2 to achieve chlorine fixation, emission reduction, and copper recovery simultaneously. Besides CuO generating solid chlorides, introducing other transition metal oxides (such as MnO2, Fe2O3) or composite materials based on porous carriers such as zeolites (such as HZSM-5, β-zeolite, type A zeolite, type X / Y zeolite), metal-organic frameworks, etc., to degrade CVOCs is also a good approach to achieving chlorine-containing pollutant emission reduction.

[0004] However, introducing non-copper metal oxides inevitably introduces metallic impurities, affecting the purity of copper recovery; similarly, non-copper-based oxide composite materials introduced as carriers are also prone to introducing other impurity components. It is well known that commercial activated carbon has excellent adsorption and removal capabilities for common highly toxic VOCs (such as benzene and formaldehyde), but its ability to remove chlorine from CVOCs is limited. Generally, there are two main pathways for CVOC dechlorination: one is the introduction of transition metal oxides (TMOs), which are easily replaced by chlorine to form TMOCl. x And through TMO, O2 is released and further oxidized to generate Cl2; secondly, it introduces Acidic sites are used to promote HCl formation and prevent the adsorption of inorganic chlorine species on the active sites of TMO (DOI:10.1016 / j.apcatb.2019.02.065). However, single metal oxides tend to promote the conversion of chlorine species into polychlorinated byproducts under high-temperature conditions, while porous materials modified with a single acid face challenges in CVOC treatment due to their lack of oxidation capacity. Therefore, designing a composite catalyst that does not introduce additional impurity components is a challenge, as is designing a catalyst containing... High-surface-area porous supports with acidic sites to accelerate the conversion of CVOCs to chlorine-containing intermediates, and low-cost composite catalysts with high activity for CVOCs, are also issues worth considering. Summary of the Invention

[0005] To address the problems existing in the prior art, this invention provides a copper-carbon composite material for dehalogenating the tail gas from the pyrolysis of chlorine-containing waste enameled wire and its preparation method. The copper-carbon composite material prepared by this method can thermally catalytically degrade CVOCs in the tail gas from the pyrolysis of chlorine-containing waste enameled wire without introducing additional impurities, which is beneficial for recovering high-purity copper products.

[0006] This invention discloses a copper-carbon composite material for dehalogenation of chlorine-containing waste enameled wire pyrolysis tail gas and its preparation method, comprising the following steps:

[0007] Buckwheat hull powder, sieved through a 60-80 mesh, is preheated at 280-320℃ for 1-2 hours under a nitrogen atmosphere, then carbonized at 450-650℃ for 2-3 hours to obtain carbonized material. This carbonized material is then mixed with an oxidant and calcined at 400-550℃ for 5-7 hours. After washing 2-3 times with water and drying at 100-120℃ for 20-30 hours, powdered OAC is obtained. The powdered OAC is then mixed with a binder at a mass ratio of (2-4):1 and pressed at 30-60 MPa at room temperature to obtain cylindrical blocks. These blocks are then dried a second time at 100-120℃ for 15-20 hours and calcined at 210-270℃ for 30-80 minutes to obtain Shape-OAC. The binder is one or two of coal tar pitch, phenolic resin, and carboxymethyl cellulose aqueous solution.

[0008] In this invention, the mass ratio of the carbonized material to the oxidant is 1:(2-5); the oxidant is one or both of HNO3 solution and (NH4)2S2O8 solution, with concentrations of 6-8 mol / L and 6-10 mol / L, respectively; the mass-volume concentration of the carboxymethyl cellulose aqueous solution is 1-3 g / L; the cylindrical block has a diameter of 0.8-1.2 cm and a height of 1.5-2 cm; the secondary drying temperature is 100-120℃, and the drying time is 15-20 h.

[0009] The cooled Shape-OAC was added to an acidic solution, and the mixture was stirred and filtered at room temperature to obtain acid-treated Shape-OAC. After washing with deionized water until neutral and drying, H-Shape-OAC was obtained.

[0010] The acidic solution is one or two of the following: HNO3 solution, H2SO4 solution, HCl solution, H3PO4 solution, and citric acid solution, with concentrations of 6-8 mol / L, 6-10 mol / L, 6-9 mol / L, 6-12 mol / L, and 1-2 mol / L, respectively; the mass ratio of Shape-OAC to the acidic solution is (1-6):8; the stirring time is 1-3 h; the drying temperature is 105-120℃, and the drying time is 18-24 h;

[0011] A copper-carbon composite material (CuO@H-Shape-OAC) after secondary modification of H-Shape-OAC was prepared by an in-situ copper-loaded composite method of initial wet impregnation-heat treatment. Specifically, CuO@H-Shape-OAC was prepared using an in-situ copper-loaded composite method of initial wet impregnation-heat treatment: First, a Cu(NO3)2 metal salt solution was prepared and then dropped onto the surface of the H-Shape-OAC support until the mass ratio of H-Shape-OAC to Cu(NO3)2 was (0.5-1):4, obtaining a Cu-doped H-Shape-OAC loaded sample; then, the sample was cleaned with oxalic acid solution, irradiated with ultraviolet light, and then vacuum dried at 60-80℃ and placed in a tube furnace under N2 protection for secondary calcination at 160-210℃ for 3-6 hours to obtain the CuO-loaded H-Shape-OAC composite material, i.e., CuO@H-Shape-OAC; the Cu content in the solution was controlled. 2+ The concentration of the oxalic acid solution is 0.03-0.06 g / mL, and the concentration of the oxalic acid solution is 0.05-0.12 g / mL; the number of rinsing times with oxalic acid solution is 2-3 times, the power of the ultraviolet lamp is 40-60W, and the irradiation time of the ultraviolet lamp is 5-9 hours.

[0012] In a specific embodiment, the composite catalyst is preferably stored in N2 or under vacuum.

[0013] This invention provides a copper-carbon composite material for dehalogenating the tail gas from the pyrolysis of chlorine-containing waste enameled wire and its preparation method, which is used for the catalytic degradation of CVOCs in the tail gas from the pyrolysis of chlorine-containing waste enameled wire. The specific steps are as follows:

[0014] (1) The crucible containing waste enameled wire enamel was placed in a tube furnace for pyrolysis; then the pyrolysis tail gas of the waste enameled wire enamel was introduced into a gas treatment device. Figure 1 a-1e), and the VOCs (including CVOCs) content at the outlet of the device was detected using GC-MS equipment. Figure 1 f);

[0015] (2) The waste enameled wire varnish and CuO@H-Shape-OAC are subjected to synergistic thermal degradation treatment in a tubular furnace, with other conditions being the same as those in (1); then the waste enameled wire varnish mixed with CuO@H-Shape-OAC is introduced into a gas treatment device after the thermal degradation and primary dechlorination tail gas. Figure 1 a-1e), and the VOCs (including CVOCs) content at the outlet of the device was detected using GC-MS equipment. Figure 1 f);

[0016] (3) The primary dechlorination tail gas from the thermal degradation in step (2) is subjected to a secondary adsorption-degradation treatment, and the primary dechlorination tail gas is mixed with O2 and then introduced into a quartz tube reactor containing fresh CuO@H-Shape-OAC for adsorption-degradation reaction at 130-380℃. Figure 1 h), the secondary dechlorination tail gas after the adsorption-degradation reaction is introduced into the gas treatment device ( Figure 1 i-1m), and the VOCs (including CVOCs) content at the outlet of the device was detected using GC-MS equipment. Figure 1 g);

[0017] The Figure 1 This is a schematic diagram of a pyrolysis tail gas treatment device, where ①②③④⑤⑥⑦ represent the furnace plug, refractory material, furnace shell, stainless steel cover, stainless steel support, mass flow meter (MFC), and heating zone, respectively; (a)(b)(c)(d)(e)(f)(g)(h)(i)(j)(k)(m) represent the tubular furnace, washing bottle 1#, washing bottle 2#, drying gas cylinder 1#, drying gas cylinder 2#, GC-MC equipment 1#, built-in quartz tube reactor catalytic device, washing bottle 3#, washing bottle 4#, drying gas cylinder 3#, drying gas cylinder 4#, and GC-MC equipment 2#, respectively; the gas treatment device... Figure 1 b / 1c and 1i / 1j are wash bottles containing NaOH solution and saturated saline solution respectively, used to remove residual Cl2 and HCl from the tail gas; Figure 1 d / 1e and Figure 1 The k / 1m is a tail gas drying bottle, which is filled with concentrated sulfuric acid to remove free water and anhydrous CaCl2 for deep dehydration, which is beneficial for drying tail gas and reducing the competition of moisture for active sites.

[0018] The composite catalyst CuO@H-Shape-OAC was prepared by the preparation method described in the above technical solution;

[0019] The chlorine in the pyrolysis tail gas may exist in the form of chlorine gas (Cl2), hydrogen chloride (HCl), or organochlorine compounds. Residual Cl2 and HCl in the tail gas are removed by washing the bottle, and free water is removed and the gas undergoes further dehydration by drying the bottle. The remaining low concentration of organochlorine compounds is further detected using a GC-MS device.

[0020] In this embodiment of the invention, the mass of the waste enameled wire enamel is 20-45 mg, and the mass ratio of the waste enameled wire enamel to CuO@H-Shape-OAC is (1-8):1; the atmosphere inside the tubular furnace is N2, the heating rate of the tubular furnace is 8-10℃ / min, the thermal degradation temperature is 200-550℃, and the thermal degradation time is 3-10 h; N2 is introduced into the tubular furnace at a rate of 30-40 mL / min for 8-15 min and stabilized at 10-30 mL / min; the O2 flow rate is 20-50 mL / min; the total flow rate of the reaction gas is 30-60 mL / min; and the space velocity of the catalytic oxidation is 10000-16000 mL / (g·h).

[0021] This invention designs a copper-carbon composite catalyst for dehalogenation of chlorine-containing waste enameled wire pyrolysis tail gas, avoiding the drawbacks of traditional single activated carbon or TMO in VOC removal. Activated carbon has good adsorption and removal capacity for VOCs, but its lack of redox ability limits its ability to remove chlorine from CVOCs. Although single CuO has good oxidation capacity, there are some considerations. First, strong chlorine adsorption: compared with other catalysts (such as Pt), CuO is more prone to chlorine deposition. Its surface Lewis acidic sites readily adsorb Cl- released from CVOC reactions, forming stable Cu-Cl bonds, covering the active center and hindering VOC molecule contact, leading to a rapid decline in catalytic efficiency. Second, loss of active components: copper chloride (such as CuCl2) formed at high temperatures is easily volatilized (melting point approximately 498℃), causing irreversible loss of active copper components and significantly shortening catalyst life. Third, it may lead to the formation of highly toxic phosgene (COCl2): When chlorinated organic compounds are incompletely oxidized, if a CO intermediate is present in the reaction system, CuO has high catalytic activity for the side reaction of Cl2 and CO to form phosgene, increasing safety risks. Fourth, accumulation of polychlorinated byproducts: Chlorine free radicals easily initiate substitution / addition reactions to generate more toxic polychlorinated organic compounds (such as dioxin precursors), and CuO lacks the ability to directionally inhibit such side reactions.

[0022] Compared with the prior art, the advantages of the present invention are:

[0023] The copper and carbon components introduced in this invention both contain elements found in chlorine-containing waste enameled wire or its pyrolysis products, thus avoiding the introduction of additional pollutants. Based on this, the oxidatively modified OAC increases the content of oxygen-containing groups (such as -COOH) and surface polarity on its surface, giving OAC stronger adsorption performance for polar CVOCs and providing greater potential for copper components loaded on H-Shape-OAC to catalyze CVOCs. The composite material obtained by depositing CuO, formed from the in-situ degradation of Cu(NO3)2, onto acid-modified activated carbon has advantages such as enhanced dechlorination of chlorine-containing VOCs to generate HCl. Specifically, firstly, it increases surface acidic groups: acid modification (such as nitric acid or sulfuric acid oxidation) imparts additional... The acidic sites increase the number of oxygen-containing acidic functional groups such as carboxyl and phenolic hydroxyl groups on the surface of activated carbon. These groups can provide protons (H). + This promotes the breaking of C-Cl bonds in chlorine-containing VOCs, accelerating the dechlorination reaction to produce HCl. It is worth noting that, unlike... Acidic sites, Lewis acidic sites on the CuO surface (i.e., Cu 2+ Firstly, it can adsorb Cl- to form Cu-Cl bonds through empty orbitals, providing active chlorine species to attack the carbon chains of organic matter and generate polychlorinated compounds. Furthermore, it readily induces Cl2 release through the Deacon reaction, and polychlorinated benzene byproducts (such as hexachlorobenzene) are more easily generated under Lewis acid catalysis, which are key precursors for dioxin synthesis. Secondly, it improves adsorption performance: acid treatment may adjust the pore structure of activated carbon, increasing the adsorption capacity for hydrophobic chlorinated VOCs. High adsorption capacity prolongs the residence time of pollutants on the activated carbon surface, creating conditions for dechlorination reactions. In addition, the designed in-situ copper-loaded Shape-OAC combines strong rigidity and high specific surface area to avoid incomplete oxidation and carbon deposition leading to active site deactivation, and has the advantage of significant CVOC degradation. Moreover, Shape-OAC facilitates reducing gas pressure drop and ensuring uniform contact of the reaction medium with CuO during the reaction process, thus improving energy efficiency. Its high mechanical strength makes it less prone to breakage under the impact of pyrolysis tail gas flow, preventing dust from clogging the catalyst active sites and facilitating regeneration and recycling. Attached Figure Description

[0024] Figure 1 Schematic diagram of pyrolysis tail gas treatment device, where ①②③④⑤⑥⑦ represent furnace plug, refractory material, furnace shell, stainless steel cover, stainless steel support, mass flow meter (MFC), and heating zone, respectively; (a)(b)(c)(d)(e)(f)(g)(h)(i)(j)(k)(m) represent tubular furnace, washing bottle 1#, washing bottle 2#, drying gas cylinder 1#, drying gas cylinder 2#, GC-MC equipment 1#, built-in quartz tube reactor catalytic device, washing bottle 3#, washing bottle 4#, drying gas cylinder 3#, drying gas cylinder 4#, and GC-MC equipment 2#, respectively. Detailed Implementation

[0025] To further illustrate the present invention, the following detailed description, in conjunction with embodiments, provides a copper-carbon composite material for dehalogenating pyrolysis tail gas of chlorine-containing waste enameled wire and its preparation method, but the embodiments of the present invention are not limited thereto. In the following description, specific features, structures, or characteristics in one or more embodiments may be combined in any suitable form.

[0026] Example 1

[0027] A copper-carbon composite material, CuO@H-Shape-OAC, for dehalogenation of chlorine-containing waste enameled wire pyrolysis tail gas, is synthesized as follows:

[0028] S1. Buckwheat hull powder sieved through 60 mesh was preheated at 280℃ for 1 hour under N2 atmosphere, and then carbonized at 450℃ for 2 hours to obtain carbonized material. Subsequently, the carbonized material was mixed with nitric acid solution (6mol / L) at a mass ratio of 1:2, and then activated by calcination at 400℃ for 5 hours, washed with water 3 times, and dried at 110℃ for 20 hours to obtain powdered OAC. Then, the powdered OAC was mixed with phenolic resin at a mass ratio of 2:1, and pressed into cylindrical blocks with a diameter of 0.8cm and a height of 1.5cm at room temperature under a pressure of 30MPa. After drying at 110℃ for 20 hours, it was calcined at 210℃ for 30 minutes to obtain Shape-OAC.

[0029] S2. The cooled Shape-OAC is added to H2SO4 solution (8mol / L) to form a mixture, wherein the mass ratio of Shape-OAC to sulfuric acid solution is 1:4; the mixture is stirred at room temperature for 1 hour, filtered to obtain acid-treated Shape-OAC, washed with deionized water until neutral, and dried at 105℃ for 18 hours to obtain H-Shape-OAC.

[0030] S3. Based on the above steps, first prepare a 0.03 g / mL Cu(NO3)2 metal salt solution and drop it onto the surface of the H-Shape-OAC support until the mass ratio of H-Shape-OAC to Cu(NO3)2 is 0.5:4, to obtain a Cu salt-doped H-Shape-OAC loaded sample; then wash it twice with 0.05 g / mL oxalic acid solution, irradiate it with a 40W ultraviolet lamp for 5 h, and place the irradiated sample in a tube furnace under N2 protection and calcine it at 160℃ for 3 h to obtain a copper-carbon composite material (CuO@H-Shape-OAC) after secondary modification of H-Shape-OAC, i.e., CuO@H-Shape-OAC.

[0031] S4. A crucible containing waste enameled wire enamel is placed in a tube furnace for pyrolysis. The pyrolysis tail gas of the waste enameled wire enamel is then introduced into a gas treatment device, and the VOCs (including CVOCs) content at the outlet of the device is detected by GC-MS. The mass of the waste enameled wire enamel is 20 mg, and the mass ratio of the waste enameled wire enamel to CuO@H-Shape-OAC is 1:1. The atmosphere inside the tube furnace is N2, the heating rate of the tube furnace is 8℃ / min, the thermal degradation temperature is 450℃, and the thermal degradation time is 3 h. N2 is introduced into the tube furnace at a rate of 30 mL / min for 8 min and stabilized at 10 mL / min.

[0032] S5. A primary synergistic thermal degradation treatment of waste enameled wire varnish and CuO@H-Shape-OAC is carried out in a tubular furnace, with other conditions being the same as those in S4; then the primary dechlorination tail gas of the waste enameled wire varnish mixed with CuO@H-Shape-OAC is introduced into a gas treatment device, and the VOCs (including CVOCs) content at the outlet of the device is detected by GC-MS equipment.

[0033] S6. The thermal degradation primary dechlorination tail gas obtained in S5 is subjected to secondary adsorption-degradation treatment. The primary dechlorination tail gas is mixed with O2 and then introduced into a quartz tube reactor containing fresh CuO@H-Shape-OAC for adsorption-degradation reaction at 265℃. The secondary dechlorination tail gas after adsorption-degradation reaction is introduced into a gas treatment device, and the VOCs (including CVOCs) content at the outlet of the device is detected by GC-MS equipment. The total flow rate of the reaction gas is 30 mL / min; the O2 flow rate is 20 mL / min; and the space velocity of catalytic oxidation is 10000 mL / (g·h). Experimental results show that, based on measurements and calculations, the main low-concentration VOCs components in the original pyrolysis tail gas include dichloromethane, benzene, chlorobenzene, acrylonitrile, vinyl chloride, 1,4-dichlorobenzene, and 1,2-dichlorobenzene, with contents of 3.05 wt%, 2.17 wt%, 0.96 wt%, 0.57 wt%, 0.31 wt%, 0.28 wt%, and 0.26 wt%, respectively; the low-concentration VOCs components in the primary dechlorination tail gas include dichloromethane, benzene, chlorobenzene, and acrylonitrile, with contents of 1.84 wt%, 1.25 wt%, 0.51 wt%, and 0.24 wt%, respectively; and the low-concentration VOCs components in the secondary dechlorination tail gas include dichloromethane and benzene, with contents of 0.06 wt% and 0.05 wt%, respectively.

[0034] Comparative Example 1

[0035] The OAC in Comparative Example 1 was not subjected to the continuous molding process and was kept as powdered OAC for the remaining experiments; all other steps and experimental conditions were the same as in Example 1, and its synthesis method is as follows:

[0036] S1. Buckwheat hull powder sieved through a 60-mesh sieve was preheated at 280°C for 1 hour under a N2 atmosphere, and then carbonized at 450°C for 2 hours to obtain carbonized material. Subsequently, the carbonized material was mixed with nitric acid (6 mol / L) at a mass ratio of 1:4, and then activated by calcination at 400°C for 5 hours, washed with water 3 times, and dried at 110°C for 20 hours to obtain powdered OAC. The OAC was not subjected to further molding and was kept as powdered OAC for the remaining experiments. Other steps and experimental conditions were the same as in Example 1.

[0037] Experimental results showed that the main low-concentration VOCs components in the original pyrolysis tail gas, as determined and calculated, included dichloromethane, benzene, chlorobenzene, acrylonitrile, vinyl chloride, 1,4-dichlorobenzene, and 1,2-dichlorobenzene, with contents of 3.01 wt%, 2.15 wt%, 0.94 wt%, 0.55 wt%, 0.28 wt%, 0.26 wt%, and 0.25 wt%, respectively. The low-concentration VOCs components in the primary dechlorination tail gas included dichloromethane, benzene, chlorobenzene, and acrylonitrile, with contents of 2.46 wt%, 2.15 wt%, 0.44 wt%, and 0.36 wt%, respectively. The low-concentration VOCs components in the secondary dechlorination tail gas included dichloromethane and benzene, with contents of 0.07 wt% and 0.09 wt%, respectively. These results indicate that, compared to Example 1, the original pyrolysis tail gas components in Comparative Example 1 remained almost unchanged, but the decrease in VOCs content in the primary dechlorination tail gas was smaller. This may be related to the high gas flow pressure drop caused by the unformed powdered OAC and the uneven contact between the reaction medium and the catalyst, which leads to a significant decrease in the catalytic performance of the powdered copper-carbon composite material for CVOCs.

[0038] Example 2

[0039] A copper-carbon composite material, CuO@H-Shape-OAC, for dehalogenation of chlorine-containing waste enameled wire pyrolysis tail gas, is synthesized as follows:

[0040] S1. Buckwheat hull powder sieved through a 70-mesh sieve was preheated at 300℃ for 1.5 hours under a N2 atmosphere, and then carbonized at 550℃ for 3 hours to obtain carbonized material. Subsequently, the carbonized material was mixed with 7 mol / L nitric acid at a mass ratio of 1:3, and then activated by calcination at 550℃ for 6 hours, washed with water 3 times, and dried at 110℃ for 20 hours to obtain powdered OAC. Then, the powdered OAC was mixed with 2 g / L carboxymethyl cellulose aqueous solution at a mass ratio of 3:1, and pressed into cylindrical blocks with a diameter of 1 cm and a height of 1.5 cm at room temperature under a pressure of 45 MPa. Subsequently, it was dried twice at 120℃ for 28 hours and calcined at 245℃ for 30 minutes to obtain Shape-OAC.

[0041] S2. The cooled Shape-OAC was added to HNO3 solution (7mol / L) to form a mixture, and the mass ratio of Shape-OAC to acidic solution was 1:5. The mixture was stirred at room temperature for 2 hours, filtered to obtain acid-treated Shape-OAC, washed with deionized water until neutral, and dried at 120℃ for 22 hours to obtain H-Shape-OAC.

[0042] S3. Based on the above steps, first prepare a 0.05 g / mL Cu(NO3)2 metal salt solution and drop it onto the surface of the H-Shape-OAC support until the mass ratio of H-Shape-OAC to Cu(NO3)2 is 1:3, to obtain a Cu salt-doped H-Shape-OAC loaded sample; then wash it three times with 0.1 g / mL oxalic acid solution, irradiate it with a 50W ultraviolet lamp for 8 hours, and place the irradiated sample in a tube furnace under N2 protection and calcine it at 190℃ for 4 hours to obtain a copper-carbon composite material (CuO@H-Shape-OAC) after secondary modification of H-Shape-OAC, i.e., CuO@H-Shape-OAC.

[0043] S4. The crucible containing waste enameled wire enamel is placed in a tube furnace for pyrolysis experiment; then the pyrolysis tail gas of the waste enameled wire enamel is introduced into a gas treatment device, and the VOCs (including CVOCs) content at the outlet of the device is detected by GC-MS equipment; the mass of the waste enameled wire enamel is 30mg, and the mass ratio of waste enameled wire enamel to CuO@H-Shape-OAC is 6:1; the atmosphere in the tube furnace is N2, the heating rate of the tube furnace is 8℃ / min, the thermal degradation temperature is 550℃, and the thermal degradation time is 8h; N2 is introduced into the tube furnace at a rate of 40mL / min for 15min and stabilized at 30mL / min.

[0044] S5. A primary synergistic thermal degradation treatment of waste enameled wire varnish and CuO@H-Shape-OAC is carried out in a tubular furnace, with other conditions being the same as those in S4; then the primary dechlorination tail gas of the waste enameled wire varnish mixed with CuO@H-Shape-OAC is introduced into a gas treatment device, and the VOCs (including CVOCs) content at the outlet of the device is detected by GC-MS equipment.

[0045] S6. The thermal degradation primary dechlorination tail gas obtained in S5 is subjected to secondary adsorption-degradation treatment. The primary dechlorination tail gas is mixed with O2 and then introduced into a quartz tube reactor containing fresh CuO@H-Shape-OAC for adsorption-degradation reaction at 350℃. The secondary dechlorination tail gas after adsorption-degradation reaction is introduced into a gas treatment device, and the VOCs (including CVOCs) content at the outlet of the device is detected by GC-MS equipment. The total flow rate of the reaction gas is 50 mL / min; the O2 flow rate is 30 mL / min; and the space velocity of catalytic oxidation is 12000 mL / (g·h). Experimental results show that the main low-concentration VOCs components in the original pyrolysis tail gas, as determined and calculated, include dichloromethane, benzene, chlorobenzene, 1,4-dichlorobenzene, and 1,2-dichlorobenzene, with contents of 2.89 wt%, 2.02 wt%, 0.87 wt%, 0.19 wt%, and 0.21 wt%, respectively. The low-concentration VOCs components in the primary dechlorination tail gas include dichloromethane, benzene, and chlorobenzene, with contents of 1.26 wt%, 0.98 wt%, and 0.37 wt%, respectively. The low-concentration VOCs component in the secondary dechlorination tail gas is benzene at 0.03 wt%. The results indicate that the addition of copper-carbon composite material significantly reduces the number of VOC components in the pyrolysis tail gas after the addition of the copper-carbon composite material. This suggests that the copper-carbon composite material is beneficial for the dehalogenation of the waste enameled wire pyrolysis tail gas and also for the catalytic degradation of VOCs. Meanwhile, the results also showed that the types and residual concentrations of CVOCs in the secondary dechlorination tail gas obtained after adsorption-degradation were further reduced, suggesting that copper-carbon composite materials have a good CVOCs removal effect on the further treatment of waste enameled wire pyrolysis tail gas.

[0046] Comparative Example 2

[0047] In Comparative Example 2, the cooled Shape-OAC was not acid-modified, and all other steps and conditions were consistent with those in Example 2. The synthesis method is as follows:

[0048] S1. Buckwheat hull powder sieved through a 70-mesh sieve was preheated at 300°C for 1.5 hours under a N2 atmosphere, and then carbonized at 550°C for 3 hours to obtain carbonized material. Subsequently, the carbonized material was mixed with 7 mol / L nitric acid at a mass ratio of 1:3, and then activated by calcination at 550°C for 6 hours, washed three times with water, and dried at 110°C for 25 hours to obtain powdered OAC. The powdered OAC was then mixed with 2 g / L carboxymethyl cellulose aqueous solution at a mass ratio of 3.5:1, and pressed into cylindrical blocks with a diameter of 1 cm and a height of 1.5 cm at room temperature under a pressure of 40 MPa. The blocks were then dried twice at 120°C for 15 hours and calcined at 260°C for 60 minutes to obtain Shape-OAC. The cooled Shape-OAC was not acid-modified, and other steps and conditions were consistent with those in Example 2.

[0049] Experimental results show that the main low-concentration VOCs components in the pyrolysis tail gas, as determined and calculated, include dichloromethane, benzene, chlorobenzene, 1,4-dichlorobenzene, and 1,2-dichlorobenzene, with contents of 2.89 wt%, 2.02 wt%, 0.87 wt%, 0.19 wt%, and 0.21 wt%, respectively. The low-concentration VOCs components in the primary dechlorination tail gas include dichloromethane, benzene, chlorobenzene, 1,4-dichlorobenzene, and 1,2-dichlorobenzene, with contents of 1.87 wt%, 1.55 wt%, 0.46 wt%, 0.15 wt%, and 0.11 wt%, respectively. The low-concentration VOCs components in the secondary dechlorination tail gas are dichloromethane, benzene, and chlorobenzene, with contents of 0.84 wt%, 0.95 wt%, and 0.18 wt%, respectively. The results showed that, compared with the original pyrolysis tail gas, the types of low-concentration VOCs in the primary dechlorination tail gas remained unchanged and the concentration did not decrease significantly. This may be because the unmodified Shape-OAC lacks sufficient... The acidic sites are associated with the unfavorable conditions for the dechlorination of CVOCs to form HCl and further degradation into CO2 and H2O.

[0050] Example 3

[0051] A copper-carbon composite material, CuO@H-Shape-OAC, for dehalogenation of chlorine-containing waste enameled wire pyrolysis tail gas, is synthesized as follows:

[0052] S1. Buckwheat hull powder sieved through an 80-mesh sieve was preheated at 320℃ for 2 hours under a N2 atmosphere, and then carbonized at 650℃ for 3 hours to obtain carbonized material. Subsequently, the carbonized material was mixed with an 8 mol / L (NH4)2S2O8 solution at a mass ratio of 1:5, and then activated by calcination at 550℃ for 7 hours, washed with water 3 times, and dried at 120℃ for 30 hours to obtain powdered OAC. Then, the powdered OAC was mixed with a 1 g / L carboxymethyl cellulose aqueous solution at a mass ratio of 4:1, and pressed into cylindrical blocks with a diameter of 1.2 cm and a height of 2 cm at room temperature under a pressure of 60 MPa. Subsequently, it was dried twice at 120℃ for 30 hours and then calcined at 270℃ for 80 minutes to obtain Shape-OAC.

[0053] S2. The cooled Shape-OAC was added to H3PO4 solution (10mol / L) to form a mixture, and the mass ratio of Shape-OAC to acidic solution was 1:7. The mixture was stirred at room temperature for 3 hours, filtered to obtain acid-treated Shape-OAC, washed with deionized water until neutral, and dried at 120℃ for 24 hours to obtain H-Shape-OAC.

[0054] S3. Based on the above steps, first prepare a 0.06 g / mL Cu(NO3)2 metal salt solution and drop it onto the surface of the H-Shape-OAC support until the mass ratio of H-Shape-OAC to Cu(NO3)2 is 1:4, to obtain a Cu salt-doped H-Shape-OAC loaded sample; then wash it three times with 0.12 g / mL oxalic acid solution, irradiate it with a 60W ultraviolet lamp for 9 h, and place the irradiated sample in a tube furnace under N2 protection and calcine it at 210℃ for 6 h to obtain a copper-carbon composite material (CuO@H-Shape-OAC) after secondary modification of H-Shape-OAC, i.e., CuO@H-Shape-OAC.

[0055] S4. A crucible containing waste enameled wire enamel is placed in a tube furnace for pyrolysis. The pyrolysis tail gas of the waste enameled wire enamel is then introduced into a gas treatment device, and the VOCs (including CVOCs) content at the outlet of the device is detected by GC-MS. The mass of the waste enameled wire enamel is 45 mg, and the mass ratio of waste enameled wire enamel to CuO@H-Shape-OAC is 8:1. The atmosphere inside the tube furnace is N2, the heating rate of the tube furnace is 10℃ / min, the thermal degradation temperature is 550℃, and the thermal degradation time is 10 h. N2 is introduced into the tube furnace at a rate of 30 mL / min for 15 min and stabilized at 30 mL / min.

[0056] S5. A primary synergistic thermal degradation treatment of waste enameled wire varnish and CuO@H-Shape-OAC is carried out in a tubular furnace, with other conditions being the same as those in S4; then the primary dechlorination tail gas of the waste enameled wire varnish mixed with CuO@H-Shape-OAC is introduced into a gas treatment device, and the VOCs (including CVOCs) content at the outlet of the device is detected by GC-MS equipment.

[0057] S6. The thermal degradation tail gas obtained in S5 is subjected to a secondary adsorption-degradation treatment. The primary dechlorination tail gas is mixed with O2 and then introduced into a quartz tube reactor containing fresh CuO@H-Shape-OAC for adsorption-degradation reaction at 380℃. The secondary dechlorination tail gas after the adsorption-degradation reaction is introduced into a gas treatment device, and the VOCs (including CVOCs) content at the outlet of the device is detected by GC-MS equipment. The total flow rate of the reaction gas is 60 mL / min; the O2 flow rate is 20-50 mL / min; and the space velocity of catalytic oxidation is 16000 mL / (g·h). Experimental results show that the main low-concentration VOCs components in the pyrolysis tail gas, as determined and calculated, include dichloromethane, benzene, chlorobenzene, acrylonitrile, vinyl chloride, 1,4-dichlorobenzene, and 1,2-dichlorobenzene, with contents of 3.25 wt%, 2.23 wt%, 0.95 wt%, 0.66 wt%, 0.35 wt%, 0.31 wt%, and 0.35 wt%, respectively. The low-concentration VOCs components in the primary dechlorination tail gas include dichloromethane, benzene, chlorobenzene, and acrylonitrile, with contents of 1.61 wt%, 1.14 wt%, 0.48 wt%, and 0.19 wt%, respectively. The low-concentration VOCs components in the secondary dechlorination tail gas include dichloromethane and benzene, with contents of 0.06 wt% and 0.04 wt%, respectively.

[0058] Comparative Example 3

[0059] In Comparative Example 3, H-Shape-OAC was not subjected to in-situ Cu component loading treatment. All other steps and experimental conditions were consistent with those in Example 3. The synthesis method is as follows:

[0060] S1. Buckwheat hull powder sieved through an 80-mesh sieve was preheated at 320℃ for 2 hours under a N2 atmosphere, and then carbonized at 650℃ for 3 hours to obtain carbonized material. Subsequently, the carbonized material was mixed with an 8 mol / L (NH4)2S2O8 solution at a mass ratio of 1:5, and then activated by calcination at 550℃ for 7 hours, washed with water 3 times, and dried at 120℃ for 30 hours to obtain powdered OAC. Then, the powdered OAC was mixed with a 1 g / L carboxymethyl cellulose aqueous solution at a mass ratio of 4:1, and pressed into cylindrical blocks with a diameter of 1.2 cm and a height of 2 cm at room temperature under a pressure of 60 MPa. Subsequently, it was dried twice at 120℃ for 30 hours and then calcined at 270℃ for 80 minutes to obtain Shape-OAC.

[0061] S2. The cooled Shape-OAC was added to H3PO4 solution (10mol / L) to form a mixture. The mixture was stirred at room temperature for 3 hours, filtered, and then acid-treated Shape-OAC was obtained. The mixture was washed with deionized water until neutral and dried at 120°C to obtain H-Shape-OAC. The obtained H-Shape-OAC was not subjected to in-situ Cu component loading treatment. All other steps and experimental conditions were the same as in Example 3.

[0062] Experimental results show that the main low-concentration VOCs components in the pyrolysis tail gas, determined by measurement and calculation, include dichloromethane, benzene, chlorobenzene, acrylonitrile, vinyl chloride, 1,4-dichlorobenzene, and 1,2-dichlorobenzene, with contents of 3.25 wt%, 2.23 wt%, 0.95 wt%, 0.66 wt%, 0.35 wt%, 0.31 wt%, and 0.35 wt%, respectively. The low-concentration VOCs components in the primary dechlorination tail gas also include dichloromethane, benzene, chlorobenzene, acrylonitrile, vinyl chloride, 1,4-dichlorobenzene, and 1,2-dichlorobenzene. The contents of dichlorobenzene were 3.12 wt%, 2.19 wt%, 0.92 wt%, 0.61 wt%, 0.33 wt%, 0.29 wt%, and 0.28 wt%, respectively. The low-concentration VOCs in the secondary dechlorination tail gas included dichloromethane, benzene, chlorobenzene, acrylone, vinyl chloride, 1,4-dichlorobenzene, and 1,2-dichlorobenzene, with contents of 2.99 wt%, 2.01 wt%, 0.87 wt%, 0.55 wt%, 0.26 wt%, 0.21 wt%, and 0.17 wt%, respectively. The results showed that the chloride ion content in the primary and secondary dechlorination tail gases did not decrease significantly, and the types and concentrations of VOCs were almost identical to those in the original pyrolysis tail gas. This may be because the catalytic ability of H-Shape-OAC without in-situ Cu component modification was severely affected.

[0063] The above description is only a preferred embodiment of the present invention. It should be noted that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are only the principles of the present invention. Various changes and modifications can be made to the present invention without departing from the principles and scope of the present invention. These changes and modifications should also be considered within the protection scope of the present invention.

Claims

1. A method for preparing a copper-carbon composite material for dehalogenating pyrolysis tail gas of chlorine-containing waste enameled wire, characterized in that, The method includes the following steps: Shaped activated carbon (Shape-OAC) is prepared using a carbonization-oxidation activation-shaping combined method: Buckwheat hull powder, sieved through a 60-80 mesh sieve, is preheated at 280-320℃ for 1-2 hours under a nitrogen atmosphere, then carbonized at 450-650℃ for 2-3 hours to obtain carbonized material. This carbonized material is then mixed with an oxidant, followed by calcination activation at 400-550℃ for 5-7 hours, followed by washing 2-3 times with water and drying at 100-120℃ for 20-30 hours to obtain powder. OAC; then, powdered OAC and binder are mixed at a mass ratio of (2-4):1, and pressed at 30-60 MPa at room temperature to obtain a cylindrical block. Subsequently, it is dried again at 100-120℃ for 15-20 h, and then calcined at 210-270℃ for 30-80 min to obtain Shape-OAC; the binder is one or two of coal tar pitch, phenolic resin, and carboxymethyl cellulose aqueous solution. Modified shaped activated carbon H-Shape-OAC was prepared by acid modification: Cooled Shape-OAC was added to an acidic solution, the mixture was stirred at room temperature for 1-3 hours, filtered to obtain acid-treated Shape-OAC, washed with deionized water until neutral, and dried at 105-120℃ for 18-24 hours to obtain H-Shape-OAC. A copper-carbon composite material CuO@H-Shape-OAC after secondary modification of H-Shape-OAC was prepared by an in-situ copper loading method of initial wet impregnation-heat treatment: First, a Cu(NO3)2 metal salt solution was prepared and then dropped onto the surface of the H-Shape-OAC support until the mass ratio of H-Shape-OAC to Cu(NO3)2 was (0.5-1):4, thus obtaining a Cu salt-doped H-Shape-OAC loaded sample; then, the sample was cleaned with oxalic acid solution, irradiated with ultraviolet light, and then vacuum dried at 60-80℃ and placed in a tube furnace under N2 protection for secondary calcination at 160-210℃ for 3-6 h to obtain the CuO-loaded H-Shape-OAC composite material, namely CuO@H-Shape-OAC.

2. The preparation method according to claim 1, characterized in that, The mass ratio of the carbonized material to the oxidant is 1:(2-5); the oxidant is one or both of HNO3 solution and (NH4)2S2O8 solution, with concentrations of 6-8 mol / L and 6-10 mol / L, respectively; the mass-volume concentration of the carboxymethyl cellulose aqueous solution is 1-3 g / L; the cylindrical block has a diameter of 0.8-1.2 cm and a height of 1.5-2 cm.

3. The preparation method according to claim 1, characterized in that, The acidic solution is one or two of the following: HNO3 solution, H2SO4 solution, HCl solution, H3PO4 solution, and citric acid solution, with concentrations of 6-8 mol / L, 6-10 mol / L, 6-9 mol / L, 6-12 mol / L, and 1-2 mol / L, respectively; the mass ratio of Shape-OAC to the acidic solution is (1-6):

8.

4. The preparation method according to claim 1, characterized in that, Cu(NO3)2 metal salt Cu 2+ The concentration is 0.03-0.06 g / mL; the oxalic acid solution concentration is 0.05-0.12 g / mL; the number of oxalic acid solution washes is 2-3 times; the power of the ultraviolet lamp is 40-60W; and the ultraviolet lamp irradiation time is 5-9 hours.

5. The copper-carbon composite material prepared by any one of claims 1-4.

6. The application of the copper-carbon composite material according to claim 5, characterized in that, The catalytic degradation of CVOCs includes the following steps: (1) The crucible containing waste enameled wire enamel was placed in a tube furnace to conduct a pyrolysis experiment on the waste enameled wire enamel; then the tail gas of the waste enameled wire enamel pyrolysis was introduced into a gas treatment device, and the VOCs content at the outlet of the device was detected by a gas chromatography-mass spectrometry (GC-MS) device. (2) The waste enameled wire varnish and CuO@H-Shape-OAC mixture were subjected to synergistic thermal degradation treatment in a tube furnace, with other conditions being the same as those in (1); then the waste enameled wire varnish mixed with CuO@H-Shape-OAC was introduced into a gas treatment device after thermal degradation and dechlorination, and the VOCs content at the outlet of the device was detected by GC-MS equipment. (3) The thermal degradation primary dechlorination tail gas of (2) is subjected to secondary adsorption-degradation treatment, and the primary dechlorination tail gas is mixed with O2 and introduced into a quartz tube reactor containing fresh CuO@H-Shape-OAC for adsorption-degradation reaction at 130-380℃. The secondary dechlorination tail gas after adsorption-degradation reaction is introduced into a gas treatment device, and the VOCs content at the outlet of the device is detected by GC-MS equipment.

7. The application according to claim 6, characterized in that, The mass ratio of waste enameled wire enamel to CuO@H-Shape-OAC is (1-8):1; the atmosphere inside the tubular furnace is N2, the heating rate of the tubular furnace is 8-10℃ / min, the thermal degradation temperature is 200-550℃, and the thermal degradation time is 3-10h; N2 is introduced into the tubular furnace at a rate of 30-40mL / min for 8-15min and stabilized at 10-30mL / min; the O2 flow rate is 20-50mL / min; the total flow rate of the reaction gas is 30-60mL / min; and the space velocity of catalytic oxidation is 10000-16000mL / (g·h).

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