Chlorobenzene tail gas treatment catalyst and preparation method thereof

Abstract

The invention discloses a chlorobenzene tail gas treatment catalyst and a preparation method thereof, and belongs to the technical field of chemical catalysis. According to the catalyst, cordierite porous ceramic, hydroxyl copper phosphate and boron nitride nanosheets form a composite carrier, and Fe-Co-Li-Pr quaternary composite oxide active components are loaded. A unique chemical adsorption-heat management dual-path chlorine poisoning resisting mechanism is formed through the reversible complexing effect of phosphate radical groups of copper hydroxyphosphate and chloride ions and a heat conduction network constructed by the boron nitride nanosheets, and inactivation of active sites is effectively inhibited. Meanwhile, the cascade effect of electron transfer, acid-base optimization and oxygen circulation is realized through the synergistic effect of the Fe-Co spinel structure, Li and Pr, and the reaction energy barrier is remarkably reduced. The catalyst has the comprehensive advantages of low-temperature high activity, excellent moisture resistance, excellent long-acting stability and strong poisoning resistance in chlorobenzene tail gas treatment.

Description

Technical Field

[0001] This invention belongs to the field of chemical catalysis technology, specifically relating to a chlorobenzene tail gas treatment catalyst and its preparation method. Background Technology

[0002] Chlorobenzene tail gas treatment is a crucial environmental protection step in chemical production, its core being the conversion and removal of harmful substances in the tail gas through highly efficient catalysts. Currently, precious metal catalysts or transition metal oxide catalysts are commonly used in industry for the catalytic treatment of chlorobenzene tail gas to reduce pollutant emissions and improve resource utilization. However, existing technologies still have certain limitations in catalyst performance, preparation processes, and practical applications.

[0003] Patent application CN111233621A discloses a method for treating dichlorobenzene distillation residue. This method involves a hydrodechlorination reaction using a noble metal catalyst in a fixed-bed reactor. Specifically, the dichlorobenzene distillation residue achieves high polychlorinated benzene conversion and benzene selectivity under the action of the noble metal catalyst, while avoiding the use of alkaline solutions and the generation of saline wastewater. However, this technical solution mainly targets the treatment of distillation residue, and the application scenarios of its catalyst are relatively limited, failing to fully consider the complex components and high concentrations of pollutants that may exist in the treatment of chlorobenzene tail gas. In addition, the noble metal catalyst is expensive and may experience a decrease in activity under high-temperature conditions, affecting its long-term operational stability and economic efficiency. Patent application CN115536186A discloses a method and apparatus for treating phosphine- and chlorobenzene-containing wastewater. This method utilizes a combination of a liquid catalyst and an oxidant to synergistically treat wastewater and exhaust gas in a UV generator. This technology achieves effective removal of organophosphine and chlorobenzene through homogeneous catalytic oxidation and solves the problem of catalyst clogging caused by phosphate scaling. However, this scheme mainly targets the combined treatment of wastewater and waste gas, and its catalyst design is not specifically optimized for the characteristics of chlorobenzene tail gas. In addition, the recovery and reuse of catalysts in homogeneous catalytic systems are difficult, which may lead to increased treatment costs. Furthermore, it does not adequately consider the generation and control of other byproducts in the tail gas.

[0004] In summary, there is still room for improvement in the design and application of catalysts for chlorobenzene tail gas treatment, especially in terms of catalyst versatility, stability, and economic efficiency. Summary of the Invention

[0005] One of the objectives of this invention is to provide a chlorobenzene tail gas treatment catalyst to solve the problems of high ignition temperature, poor resistance to chlorine poisoning, and insufficient long-term stability of existing catalysts, thereby achieving low-temperature and high-efficiency purification of chlorobenzene tail gas.

[0006] The second objective of this invention is to provide a method for preparing a chlorobenzene tail gas treatment catalyst, which is simple in process, highly controllable, and suitable for large-scale industrial production.

[0007] The objective of this invention can be achieved through the following technical solutions: In a first aspect, a chlorobenzene tail gas treatment catalyst includes a composite support and an active component loaded on the surface of the composite support; the composite support is composed of cordierite porous ceramic, copper hydroxyphosphate and boron nitride nanosheets; the active component is a Fe-Co-Li-Pr quaternary composite oxide.

[0008] Furthermore, the mass ratio of cordierite porous ceramic, copper hydroxyphosphate and boron nitride nanosheets in the composite carrier is 100:(15-25):(5-10).

[0009] Furthermore, the molar ratio of Fe, Co, Li, and Pr in the active component is 1:(0.6-0.8):(0.2-0.4):(0.1-0.2).

[0010] Furthermore, the composite carrier is prepared by the following method: A1. After pretreating the cordierite porous ceramic, it was immersed in a mixed solution of copper sulfate and ammonium dihydrogen phosphate, and the cordierite-copper hydroxyphosphate intermediate was obtained by hydrothermal reaction. A2. The cordierite-copper hydroxyphosphate intermediate was immersed in an ethanol dispersion of boron nitride nanosheets, and the composite carrier was obtained after stirring, drying and calcination.

[0011] Furthermore, in step A1, the pretreatment method for the cordierite porous ceramic is as follows: ultrasonically cleaned with deionized water and ethanol for 25-35 minutes in sequence, and then calcined in a muffle furnace at 480-520℃ for 1.5-2.5 hours.

[0012] Furthermore, in step A1, the hydrothermal reaction temperature is 120-140℃ and the reaction time is 4-6h; in step A2, the calcination temperature is 300-400℃ and the calcination time is 2h.

[0013] Secondly, a method for preparing a chlorobenzene tail gas treatment catalyst includes the following steps: S1. Prepare a solution containing ferric nitrate, cobalt nitrate, lithium nitrate, and praseodymium nitrate according to the molar ratio of Fe, Co, Li, and Pr, and add a complexing agent to obtain a precursor solution; S2. The composite support is impregnated and loaded in the precursor solution to obtain the catalyst precursor. S3. The catalyst precursor is activated by calcination to obtain a chlorobenzene tail gas treatment catalyst.

[0014] Furthermore, in step S1, the complexing agent is at least one of citric acid and disodium ethylenediaminetetraacetate; the molar ratio of the complexing agent to the total metal ions is (1.2-1.4):1, and the concentration of metal ions in the precursor solution is 0.5-0.8 mol / L.

[0015] Furthermore, in step S2, the impregnation time is 12-16 hours, and after impregnation, the mixture is evaporated to dryness under reduced pressure at 80°C using a rotary evaporator.

[0016] Furthermore, in step S3, the calcination heating rate is 5℃ / min, the calcination temperature is 500-600℃, and the calcination time is 4-6h.

[0017] Furthermore, in step S3, after calcination and activation, a post-treatment step is also included: the calcined catalyst is naturally cooled to room temperature, washed with deionized water until the filtrate is neutral, and then dried at 80-100℃ for 2-4 hours.

[0018] Furthermore, the chlorobenzene tail gas treatment catalyst is suitable for treating tail gases containing chlorobenzene, o-dichlorobenzene, p-dichlorobenzene, or trichlorobenzene chloroaromatic hydrocarbons, with a tail gas concentration range of 500-10000 mg / m³. 3 The airspeed range is 5000-50000h. -1 .

[0019] The beneficial effects of this invention are: (1) The phosphate groups on the surface of the copper hydroxyphosphate used in this invention form a dynamic coordination equilibrium with chloride ions, and migrate chloride ions from the active site to the support surface through reversible complexation, avoiding the accumulation of chloride in the metal active center. Boron nitride nanosheets, with their unique two-dimensional layered structure, construct a heat conduction network, effectively dispersing the reaction heat energy and inhibiting the strong chlorine-metal bonding caused by local high temperature. The two form a "chemisorption-thermal management" dual-pathway mechanism: the phosphate groups reduce the chloride ion migration energy barrier, while the heat conduction network maintains the stability of the electronic structure of the active site, so that the chlorine poisoning process changes from irreversible deactivation to reversible dynamic equilibrium. This synergistic effect breaks through the passive protection mode of traditional catalysts that only rely on material tolerance, and realizes the active regulation of chlorine poisoning.

[0020] (2) This invention constructs a Fe-Co-Li-Pr quaternary composite oxide system. The Fe-Co spinel structure provides a bimetallic redox cycle, and the valence state change of iron / cobalt promotes oxygen activation and C-Cl bond breaking. Lithium, by embedding into the lattice, regulates the surface acid-base distribution, reduces side reactions caused by strong acid sites, and directs the reaction path towards complete oxidation. Praseodymium utilizes its 4f electron layer characteristics to regulate the electron cloud density of iron / cobalt, accelerating oxygen vacancy regeneration and active oxygen transfer. The three elements form a cascade reaction of "electron transfer-acid-base optimization-oxygen cycle": the acid-base regulation of lithium creates a suitable microenvironment for the reaction, the electronic regulation of praseodymium improves the redox efficiency, and the iron-cobalt bimetallic synergy ensures efficient C-Cl bond breaking. This multi-dimensional synergy significantly reduces the reaction energy barrier at low temperatures, achieving high-efficiency conversion at low temperatures.

[0021] (3) The cordierite substrate used in this invention provides macroscopic mechanical support, while copper hydroxyphosphate forms an intermediate transition layer with phosphate groups through hydrogen bonds, and boron nitride nanosheets construct a surface protective network. Multi-level chemical bonding is formed at the interface of these three components: the hydrogen bond network between the hydroxyl groups and phosphate groups on the cordierite surface buffers thermal stress, and the coordination bonds between the phosphate groups and boron nitride enhance the interfacial bonding strength. This "rigid-flexible-protective" three-level structural design allows the carrier to maintain its intact pore structure under thermal shock and chemical corrosion environments, preventing the migration and sintering of active components. Simultaneously, the high thermal conductivity of boron nitride and the chloride ion trapping ability of the phosphate groups work together to suppress the formation of reaction hotspots and chloride corrosion, achieving a simultaneous improvement in structural stability and resistance to poisoning. Detailed Implementation

[0022] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, specific embodiments of the present invention will be described in detail below.

[0023] In some embodiments, a chlorobenzene tail gas treatment catalyst includes a composite support and an active component supported on the surface of the composite support; the composite support is composed of cordierite porous ceramic, copper hydroxyphosphate and boron nitride nanosheets; the active component is a Fe-Co-Li-Pr quaternary composite oxide.

[0024] The composite support consists of cordierite porous ceramics, copper hydroxyphosphate, and boron nitride nanosheets, with the active component being a Fe-Co-Li-Pr quaternary composite oxide. This design addresses the core challenge in chlorobenzene tail gas treatment through the complementary intrinsic properties of the materials: the cordierite porous ceramics provide high-temperature stability and mechanical support, preventing structural collapse caused by industrial vibrations; the phosphate groups on the surface of copper hydroxyphosphate specifically capture chloride ions, forming a dynamic complex equilibrium, transforming the irreversible chloride poisoning process in traditional catalysts into a reversible adsorption-desorption cycle; and the boron nitride nanosheets, with their high thermal conductivity, construct a heat conduction network, suppressing the sintering of active sites caused by reaction hotspots. Simultaneously, the Fe-Co spinel structure achieves bimetallic redox synergy, with Li elements embedded in the lattice regulating the surface acid-base distribution to reduce side reactions, and Pr elements utilizing the 4f electron layer characteristics to accelerate oxygen vacancy regeneration.

[0025] In some embodiments, the mass ratio of cordierite porous ceramic, copper hydroxyphosphate and boron nitride nanosheets in the composite carrier is 100:(15-25):(5-10).

[0026] When the concentration of copper hydroxyphosphate is below 15 wt%, the chlorine adsorption capacity is insufficient, leading to Cl... - Excessive accumulation rate; exceeding 25 wt% will block the pores and reduce gas diffusion efficiency. Boron nitride below 5 wt% cannot form a continuous heat conduction network, while above 10 wt% will cause pore structure collapse.

[0027] In some embodiments, the molar ratio of Fe, Co, Li, and Pr in the active component is 1:(0.6-0.8):(0.2-0.4):(0.1-0.2).

[0028] When the molar ratio of Co in the active component is less than 0.6, the FeCo₂O₄ spinel structure is incomplete; when it is greater than 0.8, the Co content is higher. 3+ Excessive oxidation inhibits the redox cycle; when Li is below 0.2, the density of strong acid sites on the surface is too high, which easily generates intermediate products such as phenol; when it is above 0.4, it destroys the lattice stability; when Pr is below 0.1, the oxygen storage capacity is insufficient; when it is above 0.2, it forms impurity phases.

[0029] In some embodiments, the composite carrier is prepared by the following method: A1. After pretreating the cordierite porous ceramic, it was immersed in a mixed solution of copper sulfate and ammonium dihydrogen phosphate, and the cordierite-copper hydroxyphosphate intermediate was obtained by hydrothermal reaction. A2. The cordierite-copper hydroxyphosphate intermediate was immersed in an ethanol dispersion of boron nitride nanosheets, and the composite carrier was obtained after stirring, drying and calcination.

[0030] A1 Pretreatment: Cleaning removes impurities and calcination removes organic matter to avoid affecting the load; hydrothermal treatment allows copper hydroxyphosphate to grow in situ on the cordierite surface, resulting in a strong bond that does not fall off. A2: Ethanol-dispersed boron nitride prevents agglomeration, and impregnation and calcination enhance the bonding force, ensuring effective surface protection.

[0031] In some embodiments, in step A1, the pretreatment method of the cordierite porous ceramic is as follows: ultrasonically cleaned with deionized water and ethanol for 25-35 minutes in sequence, and then calcined in a muffle furnace at 480-520℃ for 1.5-2.5 hours.

[0032] Ultrasonic cleaning removes surface oil and residual impurities; calcination at 480-520℃ removes residual organic matter. This combination of parameters ensures effective pretreatment while maximizing the preservation of the carrier's porous structure and loading activity.

[0033] In some embodiments, in step A1, the temperature of the hydrothermal reaction is 120-140℃ and the reaction time is 4-6h; in step A2, the calcination temperature is 300-400℃ and the calcination time is 2h.

[0034] 120-140℃ is the optimal temperature for the crystallization of copper hydroxyphosphate. Below 120℃, the crystallinity is low, resulting in insufficient resistance to chlorine. Above 140℃, coarse grains easily form, clogging the pores. 4-6 hours ensures a complete reaction. Boron nitride calcination parameters: 300-400℃ can remove the ethanol dispersant and promote interfacial bonding; 2 hours is the optimal holding time, balancing bonding effect and energy consumption.

[0035] In some embodiments, a method for preparing a chlorobenzene tail gas treatment catalyst includes the following steps: S1. Prepare a solution containing ferric nitrate, cobalt nitrate, lithium nitrate, and praseodymium nitrate according to the molar ratio of Fe, Co, Li, and Pr, and add a complexing agent to obtain a precursor solution; S2. The composite support is impregnated and loaded in the precursor solution to obtain the catalyst precursor. S3. The catalyst precursor is activated by calcination to obtain a chlorobenzene tail gas treatment catalyst.

[0036] The complexing agent forms a stable chelate with the metal ions, preventing premature precipitation during impregnation. Rotary evaporation at 80°C under reduced pressure avoids the migration and aggregation of metal ions caused by moisture evaporation, ensuring uniform distribution of the active components within the pores. Omitting the complexation step will result in the accumulation of active components on the outer surface of the support, leading to insufficient utilization of the inner pores. If atmospheric pressure drying is used, metal salts will crystallize and precipitate, reducing the density of active sites.

[0037] In some embodiments, in step S1, the complexing agent is at least one of citric acid and disodium ethylenediaminetetraacetate; the molar ratio of the complexing agent to the total metal ions is (1.2-1.4):1, and the concentration of metal ions in the precursor solution is 0.5-0.8 mol / L.

[0038] The complexing agent has strong chelating ability and leaves no residue after calcination; if the ratio is too low, the complexation will be insufficient, and if it is too high, the energy consumption will be high; if the concentration is too low, the loading will be insufficient, and if it is too high, it will easily precipitate, thus balancing loading and dispersibility.

[0039] In some embodiments, in step S2, the impregnation time is 12-16 hours, and after impregnation, the mixture is evaporated to dryness under reduced pressure at 80°C using a rotary evaporator.

[0040] Too short a time results in insufficient pore filling and inadequate loading of active components; too long a time offers no significant gain and reduces efficiency. Rotary evaporation, performed under reduced pressure at 80°C, allows for slow solvent removal, maintaining capillary pressure balance and preventing the migration of metal salts to the outer surface of the support.

[0041] In some embodiments, in step S3, the calcination heating rate is 5°C / min, the calcination temperature is 500-600°C, and the calcination time is 4-6h.

[0042] Too rapid a heating rate leads to violent decomposition of citric acid, generating gas pressure that causes the carrier to crack; too slow a rate results in low efficiency. Below 500℃, crystallinity is insufficient, while above 600℃, Pr6O... 11 Decomposition. The time is 4-6 hours to ensure complete decomposition of nitrates and appropriate grain growth. If the time is shorter than this range, residual nitrate poisoning active sites will remain, and if the time is longer than this range, the grains will sinter.

[0043] In some embodiments, step S3 further includes a post-treatment step after calcination and activation: the calcined catalyst is naturally cooled to room temperature, washed with deionized water until the filtrate is neutral, and then dried at 80-100℃ for 2-4 hours.

[0044] NO in unwashed samples 3- High residual levels can trigger side reactions during the reaction; high-temperature drying leads to the dehydration phase transition of copper hydroxyphosphate. Drying at 80-100℃ for 2-4 hours removes moisture while maintaining the stability of the phosphate groups, allowing Cl to form a more stable phosphate group. - The accumulation rate has decreased.

[0045] In some embodiments, the chlorobenzene tail gas treatment catalyst is suitable for treating tail gases of chlorobenzene, o-dichlorobenzene, p-dichlorobenzene, or trichlorobenzene chloroaromatic hydrocarbons, with a tail gas concentration range of 500-10000 mg / m³. 3 The airspeed range is 5000-50000h. -1 .

[0046] Leveraging its advantages of dual chlorine resistance (adsorption + barrier), high specific surface area and good mass transfer, and quaternary components adaptable to a wide range of operating conditions, it can handle high concentrations and various types of chlorinated aromatic hydrocarbons, thereby enhancing industrial value.

[0047] The specific embodiments of the present invention will be described in detail below, but it should be understood that the scope of protection of the present invention is not limited to the specific embodiments.

[0048] Example 1

[0049] This embodiment provides a chlorobenzene tail gas treatment catalyst, which is prepared through the following steps: 1. Preparation of composite carriers A1. Pretreatment: Take 100g of cordierite porous ceramic, clean it with deionized water and ethanol for 30min each, place it in a muffle furnace at 500℃ for 2h, and cool it for later use. A2. Preparation of intermediate: Weigh 20g copper sulfate and 10g ammonium dihydrogen phosphate (mass ratio 2:1), dissolve in 500mL deionized water, and stir for 30min until completely dissolved (copper sulfate mass concentration 40g / L); immerse pretreated cordierite in the solution, sonicate for 20min, then transfer to a high-pressure reactor and react at 130℃ for 5h; after reaction, wash until the filtrate is neutral, and dry at 110℃ for 9h to obtain cordierite-copper hydroxyphosphate intermediate; A3. Composite carrier molding: Weigh 7g of boron nitride nanosheets, dissolve them in 300mL of ethanol, and disperse them evenly by sonication for 30min (concentration 23.3g / L); immerse the cordierite-copper hydroxyphosphate intermediate in the dispersion, stir at 70℃ for 2.5h; after removal, dry at 90℃ for 5h, calcine in a muffle furnace at 350℃ for 2h, and cool to obtain the composite carrier.

[0050] 2. Catalyst Preparation

[0051] S1. Precursor preparation: Weigh 24.1 g of ferric nitrate (0.05 mol), 10.2 g of cobalt nitrate (0.035 mol), 1.23 g of lithium nitrate (0.015 mol), and 3.65 g of praseodymium nitrate (0.0075 mol) according to the Fe:Co:Li:Pr=1:0.7:0.3:0.15 molar ratio, and dissolve them in 200 mL of deionized water; add 6.5 g of citric acid (molar ratio to total metal ions 1.3:1), stir for 30 min, and obtain a precursor solution with a metal ion concentration of 0.65 mol / L; S2. Impregnation and loading: The composite support is immersed in the precursor solution and impregnated at room temperature for 14 hours. It is then rotary evaporated at 80°C until dry to obtain the catalyst precursor. S3. Calcination and activation: The catalyst precursor is placed in a muffle furnace and heated to 550°C at a rate of 5°C / min. It is then calcined for 5 hours and naturally cooled to room temperature to obtain the chlorobenzene tail gas treatment catalyst.

[0052] Example 2

[0053] The difference between this embodiment and Example 1 is that the complexing agent used in step S1 is EDTA-2Na. The specific steps are as follows: 8.7g of EDTA-2Na (total molar ratio of 1.3:1 to metal ions) is added to S1 and stirred for 40min until completely dissolved.

[0054] The remaining raw materials and preparation process are the same as in Example 1.

[0055] Example 3

[0056] Compared with Example 1, the difference in this embodiment is that a post-processing step is added in step S3. The specific steps are as follows: after calcination in S3, the catalyst is naturally cooled to room temperature, washed with deionized water until the pH of the filtrate is 7, and dried at 80°C for 3 hours to obtain the chlorobenzene tail gas treatment catalyst.

[0057] The remaining raw materials and preparation process are the same as in Example 1.

[0058] Example 4

[0059] The difference between this embodiment and Example 1 is that the mass ratio of the composite carrier is cordierite:copper hydroxyphosphate:boron nitride = 100:15:5, while the other raw materials and preparation process are the same. Specific steps: Weigh 15g of copper sulfate and 8.3g of ammonium dihydrogen phosphate in A2; weigh 5g of boron nitride nanosheets in A3.

[0060] The remaining raw materials and preparation process are the same as in Example 1.

[0061] Example 5

[0062] The difference between this embodiment and Example 1 is that the mass ratio of the composite carrier is cordierite:copper hydroxyphosphate:boron nitride = 100:25:10. The specific steps are as follows: 25g of copper sulfate and 12.5g of ammonium dihydrogen phosphate are weighed in A2; 10g of boron nitride nanosheets are weighed in A3.

[0063] The remaining raw materials and preparation process are the same as in Example 1.

[0064] Example 6

[0065] The difference between this embodiment and Example 1 is that the molar ratio of the active components is Fe:Co:Li:Pr=1:0.6:0.2:0.1. The specific steps are as follows: In S1, 24.1g of ferric nitrate (0.05mol), 8.7g of cobalt nitrate (0.03mol), 0.82g of lithium nitrate (0.01mol), and 2.43g of praseodymium nitrate (0.005mol) are weighed out, and 5.2g of citric acid is used (molar ratio 1.2:1).

[0066] The remaining raw materials and preparation process are the same as in Example 1.

[0067] Example 7

[0068] The difference between this embodiment and Example 1 is that the molar ratio of the active components is Fe:Co:Li:Pr=1:0.8:0.4:0.2. The specific steps are as follows: In S1, 24.1g of ferric nitrate (0.05mol), 11.6g of cobalt nitrate (0.04mol), 1.64g of lithium nitrate (0.02mol), and 4.86g of praseodymium nitrate (0.01mol) are weighed out, and 7.8g of citric acid is used (molar ratio 1.5:1).

[0069] The remaining raw materials and preparation process are the same as in Example 1.

[0070] Example 8

[0071] The difference between this embodiment and embodiment 1 is that the calcination temperature is 500℃ and the time is 4h. The specific steps are as follows: the muffle furnace in S3 is heated to 500℃ and calcined for 4h.

[0072] The remaining raw materials and preparation process are the same as in Example 1.

[0073] Example 9

[0074] The difference between this embodiment and embodiment 1 is that the calcination temperature is 600℃ and the time is 6h. The specific steps are as follows: the muffle furnace in S3 is heated to 600℃ and calcined for 6h.

[0075] The remaining raw materials and preparation process are the same as in Example 1.

[0076] Example 10

[0077] Compared with Example 1, the difference in this embodiment is that the amount of composite carrier is increased. The specific steps are as follows: the amount of ferric nitrate in S1 is 30.1g (0.0625mol), the other active components are increased proportionally, and the amount of citric acid is 8.1g.

[0078] The remaining raw materials and preparation process are the same as in Example 1.

[0079] Comparative Example 1

[0080] The difference between this comparative example and Example 1 is that a single Al2O3 support and a Fe-Co binary active component are used. The specific steps are as follows: 100g of Al2O3 support is taken; when preparing the precursor, only 24.1g of ferric nitrate and 10.2g of cobalt nitrate (Fe:Co=1:0.7) are weighed, without adding lithium nitrate and praseodymium nitrate, and 4.2g of citric acid is used; the rest of the preparation process is the same as in Example 1, and the catalyst is obtained.

[0081] Comparative Example 2

[0082] The difference between this comparative example and Example 1 is that copper hydroxyphosphate was removed from the composite carrier to verify its anti-chlorine poisoning effect: In the preparation of the composite support, pretreated cordierite was directly immersed in boron nitride ethanol dispersion (step A2 omitted) to obtain cordierite-boron nitride support (mass ratio 100:7); the rest of the preparation process was the same as in Example 1 to obtain the catalyst.

[0083] Comparative Example 3

[0084] The difference between this comparative example and Example 1 is that boron nitride was removed from the composite carrier to verify its thermal conductivity and protective effect. In the preparation of the composite support, cordierite-copper hydroxyphosphate intermediate was used as the support (step A3 omitted); the rest of the preparation process was the same as in Example 1, and the catalyst was obtained.

[0085] Comparative Example 4

[0086] The difference between this comparative example and Example 1 is that Pr was removed from the active component to verify its valence state regulation and oxygen storage function: Praseodymium nitrate was not added during precursor preparation, Fe:Co:Li = 1:0.7:0.3, and citric acid was used in an amount of 5.5g; the rest of the preparation process was the same as in Example 1, and the catalyst was obtained.

[0087] Comparative Example 5

[0088] The difference between this comparative example and Example 1 is that Li was removed from the active component to verify its dispersing and acid-adjusting effects. Lithium nitrate was not added during precursor preparation; Fe:Co:Pr = 1:0.7:0.15; citric acid was used in an amount of 5.0 g; the rest of the preparation process was the same as in Example 1, and the catalyst was obtained.

[0089] Comparative Example 6

[0090] Commercially available Pt / Al2O3 catalyst (Pt loading 0.5%) was used directly as the catalyst to compare cost and stability.

[0091] The remaining raw materials and preparation process are the same as in Example 1.

[0092] Comparative Example 7

[0093] The difference between this comparative example and Example 1 is that EDTA was used as the complexing agent and no post-treatment was performed, thus verifying the effect of post-treatment on impurity removal: 8.7 g of EDTA-2Na was added during the preparation of the precursor, and no washing and drying steps were required after calcination; the rest of the preparation process was the same as in Example 1, and the catalyst was obtained.

[0094] Comparative Example 8

[0095] The difference between this comparative example and Example 1 is that the calcination heating rate is increased to verify the effect of the heating rate on the carrier structure. In step S3, the heating rate is 10℃ / min, and the rest of the preparation process is the same as in Example 1, to obtain the catalyst.

[0096] Performance testing

[0097] Specific tests were conducted on Examples 1-10 and Comparative Examples 1-8, with three parallel tests performed. The relative deviation was ≤2% to ensure data reliability. The specific items are as follows: 1. Catalytic performance test Test conditions: catalyst dosage 1g, reaction tube inner diameter 10mm, chlorobenzene concentration 3000mg / m³ 3 Oxygen concentration 21% (volume fraction), nitrogen balance, space velocity 20000 h⁻¹ -1 The heating rate was 5℃ / min, and the test temperature was 100-400℃. The concentration of chlorobenzene at the inlet and outlet was detected by GC, the conversion rate was calculated, and the ignition temperature T50 (the temperature when the conversion rate reaches 50%) and the complete conversion temperature T90 (the temperature when the conversion rate reaches 90%) were recorded.

[0098] 2. Humidity resistance test

[0099] Test conditions: Chlorobenzene concentration 3000 mg / m³ 3 The relative humidity was 80%, and the other conditions were the same as in 1 (1. Catalytic performance test); the initial conversion rate at 300℃ and the conversion rate at 300℃ under 80%RH were calculated.

[0100] 3. Stability Test

[0101] Test conditions: 300℃, air velocity 20000h -1 It runs continuously for 1000 hours; the conversion rate is detected.

[0102] 4. Anti-poisoning performance test

[0103] Test conditions: Based on the stability test, 100 mg / m³ was introduced. 3 HCl gas was continuously run for 200 hours; the conversion rate was tested at 300℃ after poisoning.

[0104] The results are shown in Table 1: Table 1

[0105] As shown in Table 1, the ignition temperatures (T50) of Examples 1-10 are concentrated in the range of 225-245℃, and the complete conversion temperatures (T90) are in the range of 285-305℃, demonstrating excellent low-temperature catalytic activity. In particular, Examples 5 and 7 exhibited the best T50 and T90, verifying the synergistic effect of the quaternary active components: the Fe-Co spinel structure provides basic redox activity, Li modulates the surface acidity / basicity to promote C-Cl bond breaking, and Pr significantly enhances lattice oxygen mobility through its 4f electron layer characteristics, collectively lowering the reaction energy barrier. In contrast, Comparative Example 1 has a T50 as high as 320℃, proving that the low-temperature activity of the catalyst is severely limited when the valence state regulation of Li and Pr and the chlorine-capturing ability of copper hydroxyphosphate are lacking. Although Comparative Example 6 has a lower initial T50, its poor resistance to poisoning and stability highlight the limitations of noble metal catalysts in chlorobenzene treatment.

[0106] In all examples, the conversion rate decreased by ≤0.3% at 300℃ under 80% relative humidity, demonstrating the catalyst's excellent resistance to moisture. This characteristic is attributed to the hydrophobicity and high thermal conductivity of the boron nitride nanosheets, whose thermally conductive network rapidly disperses the heat of reaction, preventing water molecules from adsorbing at active sites and forming a liquid water film. Simultaneously, the phosphate groups of copper hydroxyphosphate exhibit weak competitive adsorption with water molecules, maintaining the effective adsorption and reaction of chlorobenzene molecules. Comparative Example 1 showed a significant decrease in conversion rate under high humidity because the abundant hydroxyl groups on the Al2O3 surface readily adsorb water molecules, blocking pores and competing for active sites. Comparative Example 3 showed a slight decrease, demonstrating that the hydrophobic and thermally conductive properties of boron nitride are crucial for maintaining performance stability under high humidity conditions.

[0107] Examples 1-10 maintained a conversion rate above 93.8% and a stability decrease rate of ≤0.52% after 1000 hours of continuous operation, demonstrating excellent long-term operational stability. This effect stems from the three-level structural design of the composite support: the rigid framework of cordierite provides mechanical support, copper hydroxyphosphate buffers thermal stress through hydrogen bonding with cordierite, and boron nitride nanosheets inhibit the migration and sintering of the active components. Comparative Examples 2 and 3 showed stability decreases of 10.5% and 9.2%, respectively, proving their indispensability in maintaining structural integrity. Comparative Example 6 exhibited a stability decrease rate as high as 19.4%, highlighting the sintering and poisoning defects of noble metal catalysts during long-term chlorobenzene treatment.

[0108] Introducing 100 mg / m 3 Under the harsh conditions of HCl, the conversion rate after poisoning in Examples 1-10 remained above 96%, and the poisoning reduction rate was ≤3.0%. This fully verifies the effectiveness of the dual-pathway anti-chlorine mechanism of chemisorption-thermal management: the phosphate groups of copper hydroxyphosphate reversibly complex with C... The chlorine migrates from the active site to the support surface; simultaneously, the thermal conductivity network of boron nitride inhibits the strong chlorine-metal bonding caused by local high temperatures, transforming irreversible chlorine poisoning into a reversible dynamic equilibrium process. In contrast, Comparative Example 2 showed a poisoning reduction rate as high as 15.8%, proving that copper hydroxyphosphate is the core component for resisting chlorine poisoning. The poisoning reduction rates of Comparative Example 4 and Comparative Example 5 were 10.2% and 11.4%, respectively, indicating that Pr and Li indirectly enhance the catalyst's resistance to poisoning by regulating oxygen vacancies and surface acidity / basicity.

[0109] The activity of Examples 8 (500℃) and 9 (600℃) was slightly lower than that of Example 1 (550℃), demonstrating that 550℃ is the optimal temperature for forming a complete spinel structure and avoiding Pr6O. 11 Optimal decomposition temperature. Post-treatment process: Example 3 (with added post-treatment) exhibited the best overall performance, indicating that washing to remove residual nitrate has a positive effect on reducing side reactions and drying to maintain the stability of phosphate groups. Ratio of carrier to active component: Examples 4 (low-hydroxy copper phosphate and boron nitride) and 5 (high-hydroxy copper phosphate and boron nitride) show that the balanced ratio of each component is crucial to achieving optimal performance; too high or too low a ratio will affect the overall performance.

[0110] The above-disclosed embodiments are merely a few specific examples of the present invention. However, the embodiments of the present invention are not limited thereto, and any variations that can be conceived by those skilled in the art should fall within the protection scope of the present invention.

Claims

1. A catalyst for treating chlorobenzene tail gas, characterized in that, It includes a composite support and an active component loaded on the surface of the composite support; the composite support is composed of cordierite porous ceramic, copper hydroxyphosphate and boron nitride nanosheets; the active component is a Fe-Co-Li-Pr quaternary composite oxide.

2. The chlorobenzene tail gas treatment catalyst according to claim 1, characterized in that, The mass ratio of cordierite porous ceramic, copper hydroxyphosphate and boron nitride nanosheets in the composite carrier is 100:(15-25):(5-10).

3. The chlorobenzene tail gas treatment catalyst according to claim 1, characterized in that, The molar ratio of Fe, Co, Li, and Pr in the active component is 1:(0.6-0.8):(0.2-0.4):(0.1-0.2).

4. The chlorobenzene tail gas treatment catalyst according to claim 1, characterized in that, The composite carrier is prepared by the following method: A1. After pretreating the cordierite porous ceramic, it was immersed in a mixed solution of copper sulfate and ammonium dihydrogen phosphate, and a cordierite-copper hydroxyphosphate intermediate was obtained through hydrothermal reaction. A2. The cordierite-copper hydroxyphosphate intermediate was immersed in an ethanol dispersion of boron nitride nanosheets, and the composite carrier was obtained after stirring, drying and calcination.

5. The chlorobenzene tail gas treatment catalyst according to claim 4, characterized in that, In step A1, the pretreatment method for the cordierite porous ceramic is as follows: ultrasonically cleaned with deionized water and ethanol for 25-35 minutes in sequence, and then calcined in a muffle furnace at 480-520℃ for 1.5-2.5 hours. In step A1, the hydrothermal reaction temperature is 120-140℃ and the reaction time is 4-6h; in step A2, the calcination temperature is 300-400℃ and the calcination time is 2h.

6. A method for preparing a chlorobenzene tail gas treatment catalyst, characterized in that, The preparation of the chlorobenzene tail gas treatment catalyst according to any one of claims 1-5 comprises the following steps: S1. Prepare a solution containing ferric nitrate, cobalt nitrate, lithium nitrate, and praseodymium nitrate according to the molar ratio of Fe, Co, Li, and Pr, and add a complexing agent to obtain a precursor solution; S2. The composite support is impregnated and loaded in the precursor solution to obtain the catalyst precursor. S3. The catalyst precursor is activated by calcination to obtain a chlorobenzene tail gas treatment catalyst.

7. The method for preparing a chlorobenzene tail gas treatment catalyst according to claim 6, characterized in that, In step S1, the complexing agent is at least one of citric acid and disodium ethylenediaminetetraacetate; the molar ratio of the complexing agent to the total metal ions is (1.2-1.4):1, and the concentration of metal ions in the precursor solution is 0.5-0.8 mol / L.

8. The method for preparing a chlorobenzene tail gas treatment catalyst according to claim 6, characterized in that, In step S2, the impregnation time is 12-16 hours, and after impregnation, the mixture is evaporated to dryness under reduced pressure at 80°C using a rotary evaporator.

9. The method for preparing a chlorobenzene tail gas treatment catalyst according to claim 6, characterized in that, In step S3, the calcination heating rate is 5℃ / min, the calcination temperature is 500-600℃, and the calcination time is 4-6h. In step S3, after calcination and activation, a post-treatment step is also included: the calcined catalyst is naturally cooled to room temperature, washed with deionized water until the filtrate is neutral, and then dried at 80-100℃ for 2-4 hours.

10. The method for preparing a chlorobenzene tail gas treatment catalyst according to claim 6, characterized in that, The chlorobenzene tail gas treatment catalyst is suitable for treating tail gases containing chlorobenzene, o-dichlorobenzene, p-dichlorobenzene, or trichlorobenzene chloroaromatic hydrocarbons, with a tail gas concentration range of 500-10000 mg / m³. 3 The airspeed range is 5000-50000h. -1 .

Images