Integrated process for deep regeneration of hydrogen peroxide working solution

Abstract

This invention discloses an integrated process for deep regeneration of hydrogen peroxide working fluid. The process includes: (1) pretreatment: after precision filtration, the deactivated hydrogen peroxide working fluid is dehydrated by azeotropic dehydration with cyclohexane until the water content is not higher than 0.05%; (2) catalytic oxidation: the dehydrated working fluid is mixed with hydrogen peroxide at a mass ratio of 1:8-10 and selectively oxidized in a fixed-bed reactor filled with modified TS-1 titanium-silicon molecular sieve under nitrogen protection; (3) posttreatment: the oxidized material is decomposed by activated carbon to remove residual hydrogen peroxide, then the catalyst is separated by a ceramic membrane, and finally purified by a light-removal tower to obtain the regenerated working fluid. This invention achieves efficient and highly selective regeneration of deactivated anthraquinone, with an active anthraquinone recovery rate of not less than 95% and a regeneration rate of not less than 92%. The process produces no saline wastewater, the catalyst can be recycled, the cost is low, and it meets the requirements of clean production.

Description

Technical Field

[0001] This invention belongs to the field of chemical technology, specifically relating to the regeneration technology of working fluid in the anthraquinone process for producing hydrogen peroxide, and in particular to an integrated process for deep regeneration of hydrogen peroxide working fluid. Background Technology

[0002] The anthraquinone process is currently the mainstream method for industrial production of hydrogen peroxide. During this process cycle, the active anthraquinone in the working fluid gradually degrades and becomes inactive due to incomplete hydrogenation and side reactions, leading to a decrease in production efficiency. Therefore, the working fluid must be regenerated periodically.

[0003] Currently, common regeneration methods mainly include alkaline oxidation and adsorption. For example, an existing patent discloses a regeneration process using alkaline oxidation, but this process easily leads to the over-oxidation and degradation of some active anthraquinones, and generates a large amount of saline wastewater, resulting in high treatment costs and a heavy environmental burden. Another example is the adsorption method described in the literature "Research on the Working Solution for Anthraquinone Regeneration by Molecular Sieve Adsorption," which, although less polluting, suffers from low regeneration rates (usually below 85%), high adsorbent loss, and high operating costs.

[0004] Therefore, developing a deep regeneration process that can efficiently recover active anthraquinone, has a high regeneration rate, produces no secondary pollution, and has low operating costs is of great significance for clean production and cost reduction and efficiency improvement in the hydrogen peroxide industry. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of existing regeneration technologies, such as severe anthraquinone degradation, high levels of saline wastewater, low regeneration efficiency, or large adsorbent losses, and to provide an integrated deep regeneration process for hydrogen peroxide working fluid that is highly efficient, low-loss, and environmentally friendly.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: An integrated process for deep regeneration of hydrogen peroxide working fluid includes the following steps: (1) Pretreatment: The deactivated hydrogen peroxide working solution is precisely filtered and then passed into a cyclohexane azeotropic dehydration tower for azeotropic dehydration. The water content in the working solution after dehydration is controlled to be no higher than 0.05%. (2) Catalytic oxidation: The working solution after dehydration in step (1) is mixed with hydrogen peroxide and passed into a fixed bed reactor filled with modified TS-1 titanium silicon molecular sieve catalyst under the protection of an inert gas (such as nitrogen) to carry out the oxidation reaction. (3) Post-processing: The material after the oxidation reaction in step (2) is first contacted with activated carbon to decompose the residual hydrogen peroxide, and then the modified TS-1 titanium-silicon molecular sieve catalyst is separated and recovered through a ceramic membrane separation system. Finally, it is purified by a light-removal tower to obtain the regenerated working liquid.

[0007] Specifically, in step (1), the operating parameters for cyclohexane azeotropic dehydration are: the mass ratio of cyclohexane to deactivated hydrogen peroxide working solution is 1:4-6, the operating vacuum degree of the dehydration tower is -0.07 ~ -0.09MPa, the tower top temperature is 69-70℃, and the reflux ratio is 1.1-1.3:1.

[0008] Specifically, in step (2), the dehydrated working solution is mixed with hydrogen peroxide at a mass ratio of 1:8-10. The mass concentration of the hydrogen peroxide is 28-30%.

[0009] Furthermore, in step (2), during the oxidation reaction, the reaction temperature is controlled at 45~50℃, the reaction pressure at 0.1-0.3MPa, and the liquid hourly space velocity at 0.8~1.0h. -1 The reaction time should be no less than 60 minutes.

[0010] Furthermore, in step (2), the mass content of titanium in the modified TS-1 titanium-silicon molecular sieve catalyst is 2.0%~2.5%.

[0011] Furthermore, in step (2), the modified TS-1 titanium-silicon molecular sieve catalyst in the fixed-bed reactor is loaded in a two-stage manner, wherein the upper stage is a dilute phase loading with a loading amount of 30±5% of the total loading amount, and the lower stage is a dense phase loading with a loading amount of 70±5% of the total loading amount.

[0012] Specifically, in step (3), the conditions for activated carbon to decompose residual hydrogen peroxide are: stirring and contacting at 55±5℃ for 30±10 minutes.

[0013] Furthermore, in step (3), the pore size of the ceramic membrane is 0.1 μm, and the membrane flux is 50 L / (m²·h).

[0014] In this invention, the modified TS-1 titanium-silicon molecular sieve catalyst is prepared by a combination of in-situ synthesis and post-treatment modification, with the aim of improving catalytic selectivity, stability, resistance to carbon deposition, and resistance to hydrolysis. Further, in step (2), the modified TS-1 titanium-silicon molecular sieve catalyst is prepared by the following steps: 1) Tetraethyl orthosilicate is mixed with deionized water and tetrapropylammonium hydroxide and hydrolyzed by stirring at 40-50℃ for 1-2 hours to obtain a clear silica sol; tetrabutyl titanate is dissolved in isopropanol and added dropwise to the silica sol under an ice-water bath at 0-10℃, while stirring is continued; the molar ratio of tetraethyl orthosilicate (SiO2) to tetrabutyl titanate (TBOT) (TiO2) is SiO2:TiO2:TPAOH = 1:0.020-0.025:0.20-0.30; 2) The mixed sol obtained in step 1) is transferred into a hydrothermal reactor and statically crystallized at 170-175℃ for 48-72 h. After cooling, it is centrifuged, washed until neutral, and dried to obtain TS-1 raw powder. 3) Calcination at 530–570℃ in air atmosphere for 4–6 h to remove the template agent, yielding H-type TS-1; 4) Prepare a lanthanum nitrate solution and modify H-type TS-1 by equal volume impregnation. After drying and calcination at 500-550℃ for 3-5 hours, the modified TS-1 is obtained. 5) Treat the obtained modified TS-1 with 0.1-0.5 mol / L dilute nitric acid or dilute citric acid at 60-80℃ for 2-4 h; wash until neutral, dry, and calcine at 500-550℃ for 3-5 h; 6) Mix the modified TS-1 molecular sieve obtained in step 5) with silica sol or pseudoboehmite at a mass ratio of 90:10 to 95:5, extrude into strips, dry, and calcine at 500 to 550°C for 3 to 5 hours to form the final product.

[0015] As a preferred technical solution, the specific preparation steps of the modified TS-1 titanium-silicon molecular sieve catalyst are as follows: I. Raw material composition (molar ratio): Silicon source: Tetraethyl orthosilicate (TEOS) (as SiO2); Titanium source: Tetrabutyl titanate (TBOT) (calculated as TiO2); Template agent: Tetrapropylammonium hydroxide (TPAOH); Solvent: Deionized water; Modified metal salt: Lanthanum nitrate; Molar ratio: SiO2:TiO2:TPAOH:H2O=1:0.020~0.025:0.20~0.30:20~35.

[0016] II. Preparation steps: 1. Silicon source hydrolysis: TEOS was mixed with deionized water and TPAOH and hydrolyzed by stirring at 40-50℃ for 1-2 h to obtain a clear silica sol.

[0017] 2. Low temperature dripping of titanium source: Dissolve TBOT in isopropanol (the amount of isopropanol is 200% to 500% of the mass of TBOT), and slowly add it dropwise to silica sol under an ice-water bath at 0 to 10°C for 30 to 60 minutes. Continue stirring for 1 hour to prevent TiO2 agglomeration.

[0018] 3. Crystallization synthesis: The mixed sol was transferred to a hydrothermal reactor and statically crystallized at 170–175 °C for 48–72 h. After cooling, it was centrifuged, washed until neutral, and dried at 110 °C for 12 h to obtain TS-1 raw powder.

[0019] 4. Removal of template agent by baking: The template agent was removed by calcination at 530–570℃ in air for 4–6 h to obtain H-type TS-1.

[0020] 5. Metal modification (key step): Modification was performed using an equal-volume impregnation method: Prepare a modified metal salt solution (concentration 0.1–0.5 mol / L). Measured by metal loading of 0.5–1.5 wt%; Soak at room temperature for 12 hours; dry at 110℃ for 12 hours; The metal-modified TS-1 was obtained by calcination at 500℃ for 4 h.

[0021] Preferred: La modification can significantly improve structural stability and anthraquinone oxidation selectivity.

[0022] 6. Post-treatment after pore enlargement and pickling (to further improve performance): Treat with 0.1–0.5 mol / L dilute nitric acid or dilute citric acid at 60–80℃ for 2–4 h; then wash until neutral, dry (dry at 110℃ for 12 h), and then calcine at 550℃ for 4 h.

[0023] Objective: To remove non-framework titanium, unclog pores, and improve activity and resistance to carbon buildup.

[0024] 7. Molding (for use with fixed-bed reactors) The modified molecular sieve is mixed with silica sol or pseudoboehmite at a ratio of 90:10 to 95:5, extruded into strips, dried, and then calcined at 500 to 550°C for 3 to 5 hours to form a strip-shaped modified TS-1 titanium-silicon molecular sieve catalyst that can be used in fixed beds.

[0025] III. Key performance indicators of the final catalyst: Titanium content: 2.0 wt%~2.5 wt%; Crystal structure: MFI topology, without anatase TiO2; Specific surface area: ≥ 400 m² / g; Average pore size: 0.5–0.6 nm (mainly micropores); Modified metal loading: 0.5–1.5 wt% Appearance: Strips or granules, strength ≥ 30 N / cm.

[0026] The modified TS-1 titanium-silicon molecular sieve, as a highly selective oxidation catalyst, can directionally oxidize and regenerate deactivated anthraquinone into effective anthraquinone under mild conditions with a selectivity of ≥98% and inhibit excessive degradation of anthraquinone. The modification treatment improves the hydrothermal stability and cycle life of the catalyst, and when combined with ceramic membrane separation, it can achieve near-zero loss recovery, which is the core of the integrated process of this invention.

[0027] The integrated process for deep regeneration of hydrogen peroxide working fluid described in this invention achieves a recovery rate of active anthraquinone in the working fluid of no less than 95%, a regeneration rate of no less than 92%, and a solvent loss rate of no more than 0.5% after regeneration. Compared with the prior art, the process principle and beneficial effects of this invention are as follows: 1) Deep dehydration to ensure reaction efficiency: Through cyclohexane azeotropic dehydration, the water content in the working solution can be removed to below 0.05%, which effectively avoids the ineffective decomposition of hydrogen peroxide due to the presence of water in subsequent steps, improves the utilization rate of oxidant, and creates a prerequisite for efficient oxidation.

[0028] 2) Directed catalytic oxidation with high selectivity: Using modified TS-1 titanium-silicon molecular sieve with a specific titanium content (2.0%~2.5%) as a catalyst, under a nitrogen protective atmosphere, it can selectively (≥98%) oxidize and regenerate deactivated anthraquinone into active anthraquinone, greatly reducing degradation losses caused by over-oxidation. The catalyst in the reactor adopts a two-stage packing with a thinner top and a denser bottom, optimizing material distribution and reaction kinetics.

[0029] 3) Precise post-treatment, clean and efficient: Activated carbon is used to gently decompose residual hydrogen peroxide, avoiding the potential harm of strong oxidants to subsequent equipment and the final product. Ceramic membrane separation technology is employed to achieve near-zero loss recovery and recycling of catalyst particles. Finally, a high-quality regeneration working fluid is obtained through purification in a light-light-removal tower.

[0030] 4) Significant Comprehensive Benefits: This integrated process organically combines pretreatment, core reaction, and post-treatment, resulting in a compact workflow. Ultimately, it achieves an active anthraquinone recovery rate of no less than 95%, an overall working fluid regeneration rate of no less than 92%, and solvent loss of no more than 0.5%. Furthermore, the entire process generates no saline wastewater. Compared to the traditional alkaline oxidation method, the regeneration cost per ton of working fluid can be reduced by approximately 40%, demonstrating outstanding economic and environmental benefits. Detailed Implementation

[0031] The technical solution of the present invention will be further described in detail below with reference to the embodiments, but the scope of protection of the present invention is not limited thereto.

[0032] In the following examples, all raw materials used are common commercially available products that can be purchased directly, or can be prepared using conventional techniques in the art.

[0033] For example, the preparation process of the modified TS-1 titanium-silicon molecular sieve catalyst used in the examples is as follows.

[0034] I. Raw material composition (molar ratio) Silicon source: Tetraethyl orthosilicate (TEOS) (as SiO2); Titanium source: Tetrabutyl titanate (TBOT) (calculated as TiO2); Template agent: Tetrapropylammonium hydroxide (TPAOH); Solvent: Deionized water; Modified metal salt: Lanthanum nitrate; Molar ratio: SiO2:TiO2:TPAOH:H2O=1:0.022:0.25:30.

[0035] II. Preparation Steps 1. Silicon source hydrolysis: TEOS was mixed with deionized water and TPAOH and hydrolyzed at 45°C for 1.5 h to obtain a clear silica sol.

[0036] 2. Low temperature dripping of titanium source: Dissolve TBOT in isopropanol (the amount of isopropanol is 400% of the mass of TBOT), and slowly add it dropwise to silica sol under an ice-water bath at 0°C for 45 min. Continue stirring for 1 h to prevent TiO2 agglomeration.

[0037] 3. Crystallization synthesis: The mixed sol was transferred to a hydrothermal reactor and statically crystallized at 172°C for 60 h. After cooling, it was centrifuged, washed until neutral, and dried at 110°C for 12 h to obtain TS-1 raw powder.

[0038] 4. Removal of template agent by baking: The template agent was removed by calcination at 550℃ in air atmosphere for 5 h to obtain H-type TS-1.

[0039] 5. Metal Modification (Key Step) Modification was performed using an equal-volume impregnation method: Prepare a modified metal salt solution (lanthanum nitrate concentration 0.1–0.5 mol / L). Measured based on a metal loading of 1.0 wt%; Soak at room temperature for 12 hours; dry at 110℃ for 12 hours; The metal-modified TS-1 was obtained by calcination at 500℃ for 4 h.

[0040] 6. Pore enlargement and pickling post-treatment (to further improve performance) Treat with 0.1–0.5 mol / L dilute nitric acid at 70°C for 3 h; wash until neutral, dry (dry at 110°C for 12 h), and then calcine at 550°C for 4 h.

[0041] 7. Molding (for use with fixed-bed reactors) The modified molecular sieve and pseudoboehmite were mixed at a mass ratio of 92:8, extruded into strips, dried (at 110℃ for 12 h), and then calcined at 550℃ for 4 h to obtain the strip-shaped modified TS-1 titanium-silicon molecular sieve catalyst that can be used in fixed beds. Example 1

[0042] This embodiment illustrates the integrated process for deep regeneration of hydrogen peroxide working fluid provided by the present invention.

[0043] Raw materials and catalysts: 1000 kg of deactivated hydrogen peroxide working solution (58% active anthraquinone content, 0.8% moisture), 30% hydrogen peroxide (industrial grade), modified TS-1 titanium-silicon molecular sieve catalyst (2.2% titanium content), cyclohexane (industrial grade), activated carbon (industrial grade).

[0044] The main equipment includes a precision filter, a cyclohexane azeotropic dehydration tower, a preheater, a static mixer, a nitrogen protection system, a fixed-bed reactor, an activated carbon decomposition kettle, a ceramic membrane filter, and a light-weight component removal tower. All of these utilize conventional structures in the field or can be directly purchased from commercially available manufacturers. Since they are not the innovation of this application, they will not be described in detail here.

[0045] The process steps are as follows: (1) Pretreatment: 1000 kg of deactivated hydrogen peroxide working solution was passed through a 0.22 μm precision filter (operating pressure 0.25 MPa) to remove solid impurities. The filtrate was pumped into a cyclohexane azeotropic dehydration tower, and 200 kg of cyclohexane was added at a mass ratio of cyclohexane to deactivated hydrogen peroxide working solution of 1:5. The dehydration tower was operated under the conditions of vacuum degree -0.09 MPa, tower top temperature 69.5℃, and reflux ratio 1.2:1. After dehydration, a sample was taken for testing, and the water content of the working solution was 0.04%.

[0046] (2) Catalytic oxidation: The dehydrated working solution was preheated to 45°C using a preheater. The preheated working solution was then mixed with 111 kg of 30% hydrogen peroxide (the mass ratio of the dehydrated working solution to hydrogen peroxide was approximately 1:9) in a static mixer for 3 minutes. The mixture was then introduced into a fixed-bed reactor from the top under nitrogen protection. The reactor had an inner diameter of 0.8 m and a height of 4 m, and was packed with 100 kg of modified TS-1 titanium-silicon molecular sieve catalyst, with the upper 30% (30 kg) being dilute phase and the lower 70% (70 kg) being dense phase. The reaction temperature was controlled at 48°C, the reaction pressure at 0.2 MPa, and the liquid hourly space velocity at 0.8 h⁻¹. -1The reaction residence time is 60 minutes.

[0047] (3) Post-treatment: The material after oxidation reaction is fed into an activated carbon decomposition vessel, 1.1 kg of activated carbon is added, and the mixture is stirred at 55°C for 30 minutes. The residual hydrogen peroxide content is then measured to be reduced to 0.03%. The material is then pumped into a filter equipped with a ceramic membrane with a pore size of 0.1 μm. Cross-flow filtration is performed at a membrane flux of 50 L / (m²·h) to separate and recover the catalyst filter cake (which is returned to the catalyst pretreatment process for recycling). The filtrate is fed into a light component removal tower, where light components are removed under a vacuum of -0.08 MPa and a tower top temperature of 40°C. Finally, 992 kg of regenerated working liquid is obtained at the bottom of the tower.

[0048] Test results: The content of active anthraquinone in the regenerated working solution was 86.2%, the calculated recovery rate of active anthraquinone was 95.8%, the working solution regeneration rate was 93.5%, and the solvent loss throughout the process was 0.4%. Example 2

[0049] This example illustrates the effect of cyclohexane dosage on dehydration efficiency and final regeneration indicators.

[0050] The raw materials are the same as in Example 1.

[0051] The process steps are basically the same as those in Example 1, except that in step (1) pretreatment, the mass ratio of cyclohexane to deactivated working fluid is adjusted to 1:4, that is, 250 kg of cyclohexane is added.

[0052] Specific operating parameters: vacuum degree of dehydration tower -0.09MPa, tower top temperature 69.5℃, reflux ratio 1.2:1. The water content of the working solution after dehydration is 0.05%.

[0053] All parameters for the catalytic oxidation and post-treatment steps are exactly the same as in Example 1.

[0054] Test results: The final regenerated working solution was obtained, and the calculated recovery rate of active anthraquinone was 95.1%, the working solution regeneration rate was 92.3%, and the solvent loss throughout the process was 0.45%. Example 3

[0055] This example illustrates the effect of reaction temperature on regeneration efficiency in the catalytic oxidation step.

[0056] The raw materials are the same as in Example 1.

[0057] The process steps are basically the same as those in Example 1. The only difference is that in step (2) catalytic oxidation, the reaction temperature is controlled at 50°C. All other parameters (pressure, space velocity, catalyst, loading method, etc.) are the same as those in Example 1.

[0058] All parameters for the preprocessing and postprocessing steps are exactly the same as in Example 1.

[0059] Test results: The final regenerated working solution was obtained, and the calculated recovery rate of active anthraquinone was 95.3%, the working solution regeneration rate was 92.8%, and the solvent loss throughout the process was 0.42%.

[0060] Comparative Example 1000 kg of deactivated hydrogen peroxide working solution (58% active anthraquinone content, 0.8% moisture) from the same batch as in Example 1 was treated using a traditional alkaline oxidation method. Specifically, a 10% sodium hydroxide solution (approximately 18% of the deactivated hydrogen peroxide working solution's mass) was added to the working solution. The solution was oxidized by aeration at 80°C for 2 hours, then allowed to stand and separate. Alkaline washing (using a 5%–8% sodium hydroxide aqueous solution; endpoint determination: the pH of the upper organic phase was measured to be 7–8, indicating the endpoint of alkaline washing) and water washing were then performed. The final measured recovery rate of active anthraquinone was 82%, the regeneration rate was 78%, and approximately 0.5 tons of alkaline wastewater required treatment.

[0061] Effect Comparison As can be seen from the above examples and comparative examples, the integrated process provided by this invention is significantly superior to the traditional alkaline oxidation method in key indicators such as active anthraquinone recovery rate and overall working fluid regeneration rate (recovery rate increased from 82% to over 95%, and regeneration rate increased from 78% to over 92%). Furthermore, this invention avoids the generation of saline wastewater, allows for catalyst recycling, has low solvent loss, and reduces overall regeneration costs by approximately 40% compared to traditional methods, fully demonstrating the high efficiency, economy, and environmental friendliness of this invention.

[0062] The above description is only a preferred embodiment of the present invention. All equivalent changes and modifications made within the scope of the claims of the present invention should be included in the scope of the present invention.

Claims

1. An integrated process for deep regeneration of hydrogen peroxide working fluid, characterized in that, Includes the following steps: (1) Pretreatment: The deactivated hydrogen peroxide working solution is precisely filtered and then passed into a cyclohexane azeotropic dehydration tower for azeotropic dehydration. The water content in the working solution after dehydration is controlled to be no higher than 0.05%. (2) Catalytic oxidation: The working solution after dehydration in step (1) is mixed with hydrogen peroxide and passed into a fixed-bed reactor filled with modified TS-1 titanium-silicon molecular sieve catalyst under inert gas protection to carry out the oxidation reaction. (3) Post-processing: The material after the oxidation reaction in step (2) is first contacted with activated carbon to decompose the residual hydrogen peroxide, then separated and recovered by ceramic membrane, and finally purified by light removal tower to obtain the regenerated working liquid.

2. The integrated process for deep regeneration of hydrogen peroxide working fluid according to claim 1, characterized in that, In step (1), the operating parameters for cyclohexane azeotropic dehydration are as follows: the mass ratio of cyclohexane to deactivated hydrogen peroxide working solution is 1:4-6, the operating vacuum degree of the dehydration tower is -0.07 ~ -0.09MPa, the tower top temperature is 69-70℃, and the reflux ratio is 1.1-1.3:

1.

3. The integrated process for deep regeneration of hydrogen peroxide working fluid according to claim 1, characterized in that, In step (2), the dehydrated working solution is mixed with hydrogen peroxide at a mass ratio of 1:8-10; the mass concentration of the hydrogen peroxide is 28-30%.

4. The integrated process for deep regeneration of hydrogen peroxide working fluid according to claim 1, characterized in that, In step (2), during the oxidation reaction, the reaction temperature is controlled at 45~50℃, the reaction pressure at 0.1-0.3MPa, and the liquid hourly space velocity at 0.8~1.0h. -1 The reaction time should be no less than 60 minutes.

5. The integrated process for deep regeneration of hydrogen peroxide working fluid according to claim 1, characterized in that, In step (2), the mass content of titanium in the modified TS-1 titanium-silicon molecular sieve catalyst is 2.0%~2.5%.

6. The integrated process for deep regeneration of hydrogen peroxide working fluid according to claim 5, characterized in that, In step (2), the modified TS-1 titanium-silicon molecular sieve catalyst in the fixed bed reactor is loaded in a two-stage manner, wherein the upper stage is a dilute phase loading with a loading amount of 30±5% of the total loading amount, and the lower stage is a dense phase loading with a loading amount of 70±5% of the total loading amount.

7. The integrated process for deep regeneration of hydrogen peroxide working fluid according to claim 1, characterized in that, In step (3), the conditions for activated carbon to decompose residual hydrogen peroxide are: stirring and contacting at 55±5℃ for 30±10 minutes.

8. The integrated process for deep regeneration of hydrogen peroxide working fluid according to claim 1, characterized in that, In step (3), the pore size of the ceramic membrane is 0.1 μm, and the membrane flux is 50 L / (m²·h).

9. The integrated process for deep regeneration of hydrogen peroxide working fluid according to claim 1, characterized in that, In step (2), the modified TS-1 titanium-silicon molecular sieve catalyst is prepared by the following steps: 1) Tetraethyl orthosilicate is mixed with deionized water and tetrapropylammonium hydroxide and hydrolyzed by stirring at 40-50℃ for 1-2 h to obtain a clear silica sol; tetrabutyl titanate is dissolved in isopropanol and added dropwise to the silica sol at 0-10℃ while stirring is continued; the molar ratio of tetraethyl orthosilicate (SiO2) to tetrabutyl titanate (TBOT) (TiO2) is SiO2:TiO2:TPAOH = 1:0.020-0.025:0.20-0.30; 2) The mixed sol obtained in step 1) is transferred into a hydrothermal reactor and statically crystallized at 170-175℃ for 48-72 h. After cooling, it is centrifuged, washed until neutral, and dried to obtain TS-1 raw powder. 3) Calcination at 530–570℃ in air atmosphere for 4–6 h to remove the template agent, yielding H-type TS-1; 4) Prepare a lanthanum nitrate solution and modify H-type TS-1 by equal volume impregnation. After drying and calcination at 500-550℃ for 3-5 hours, the modified TS-1 is obtained. 5) Treat the obtained modified TS-1 with 0.1-0.5 mol / L dilute nitric acid or dilute citric acid at 60-80℃ for 2-4 h; wash until neutral, dry, and calcine at 500-550℃ for 3-5 h; 6) Mix the modified TS-1 molecular sieve obtained in step 5) with silica sol or pseudoboehmite at a mass ratio of 90:10 to 95:5, extrude into strips, dry, and calcine at 500 to 550°C for 3 to 5 hours to form the final product.