Post-treatment modification method of ts-1 molecular sieve catalyst and application thereof

Abstract

The application belongs to the technical field of hydroxylamine solution synthesis, and particularly relates to a post-treatment modification method of TS-1 molecular sieve catalyst and application thereof. The post-treatment modification method of the TS-1 molecular sieve catalyst is as follows: TS-1 molecular sieve catalyst is subjected to reduction treatment of (5R)-5-[(1S)-1,2-dihydroxyethyl]-3,4-dihydroxyfuran-2(5H)-one, then subjected to oxidation treatment by using hydrogen peroxide, and finally subjected to impregnation treatment, so that the modified TS-1 molecular sieve catalyst is obtained, which is a TS-1 molecular sieve catalyst with high catalytic activity for hydroxylamine oxidation reaction. The application also simultaneously provides a method for synthesizing hydroxylamine by using the modified TS-1 molecular sieve catalyst.

Description

Technical Field

[0001] This invention belongs to the field of chemical engineering technology for the synthesis of hydroxylamine solutions. Specifically, it relates to the post-treatment modification of a high-performance TS-1 molecular sieve catalyst for the catalytic ammoniaxation of hydrogen peroxide to prepare hydroxylamine solutions, and a method for synthesizing hydroxylamine solutions. Background Technology

[0002] Hydroxylamine (NH2OH) is one of the key raw materials for the synthesis of various chemicals and basic materials in modern industrial production, and it is widely used in fields such as biomedicine, pesticide production, mineral flotation, and semiconductor cleaning. Therefore, efficient, large-scale, and sustainable hydroxylamine synthesis technology is of great practical significance for meeting the surging market demand driven by rapid socio-economic development.

[0003] Currently, the traditional synthesis methods for hydroxylamine solutions mainly involve neutralizing hydroxylamine salts produced by methods such as the Raschig process, NO reduction process, and HPO process with alkaline solutions. In this process, hydroxylamine salts (mainly hydroxylamine hydrochloride and hydroxylamine sulfate) react with alkalis (mainly sodium hydroxide, potassium hydroxide, and ammonia) to generate hydroxylamine solution. This reaction is highly exothermic, easily causing the decomposition of hydroxylamine and producing a large amount of waste salt. Furthermore, the hydroxylamine solution contains a large number of metal ions, making subsequent purification and desalination processes cumbersome and complex. This synthesis method suffers from drawbacks such as long production routes, low product yields, high energy consumption, and significant waste. In addition, electrocatalytic nitrate reduction has emerged as a potential route for producing hydroxylamine solutions in recent years. However, due to the tendency for hydroxylamine to be over-reduced to NH3 during electroreduction, and the numerous engineering challenges involved in the electrosynthesis of hydroxylamine, large-scale industrial production has not been achieved. Therefore, to achieve efficient and sustainable large-scale production of hydroxylamine solutions, researchers have developed direct ammoniation methods using hydrogen peroxide as an oxidant to synthesize free hydroxylamine. Hydroxylamine solution is directly synthesized from hydrogen peroxide and ammonia via an ammonium oxime reaction catalyzed by TS-1 molecular sieve catalyst. The reaction formula is as follows: NH3 + H2O2 → NH2OH + H2O. This method is disclosed in CN115215307 B, "A Method for Synthesizing Hydroxylamine Solution". The specific reaction conditions for this synthesis method are: catalyst:hydrogen peroxide:solvent weight ratio of 1:(0.5~5):(5~100), ammonia:hydrogen peroxide molar ratio of (1~10):1, reaction temperature of 20~80℃, and reaction time of 0.5~5 hours. The solvent used is a mixture of alcohol and water. This method avoids the complex process of conversion via intermediates such as hydroxylamine salts or ketoximes. This synthetic route is short, less polluting, and meets the requirements of green and environmentally friendly processes. It is one of the most promising industrial-scale technologies for the synthesis of free hydroxylamine solution. However, this method still has the following shortcomings: the use of alcohols as solvents makes it difficult to separate the products; the reaction conditions of traditional TS-1 molecular sieves in the hydrogen peroxide ammonoxime synthesis of hydroxylamine solution are harsh, the catalytic performance is poor, the stability is poor, and the concentration of hydroxylamine in the synthesis solution is not high.

[0004] Invention CN116574026 B, entitled "A Method for Preparing Isopropylhydroxylamine," discloses that a modified catalyst is prepared by adding an activator and a compatibilizer to a conventional TS-1 molecular sieve. The activator is composed of molybdenum trioxide, tungsten trioxide, and calcium oxide in a specific ratio, while the compatibilizer is composed of triethanolamine. The activator prevents reactants from clogging the pores of the TS-1 molecular sieve, thus preventing a decrease in activity. The compatibilizer increases the pore size, pore volume, and specific surface area of ​​the TS-1 molecular sieve, reducing the resistance of reactants in the catalyst and facilitating diffusion. Together, they improve the conversion activity of the TS-1 molecular sieve, ensuring complete reaction of isopropylhydroxylamine during production, thereby improving both the isopropyl hydroxylamine conversion rate and selectivity. However, this modified catalyst cannot solve the problems of poor catalytic performance and low yield of hydroxylamine products in the hydrogen peroxide oxidation synthesis reaction (hydrogen peroxide conversion rate of 99.5%, isopropyl hydroxylamine selectivity of 71%).

[0005] In summary, the current solution route for the synthesis of hydroxylamine by hydrogen peroxide ammonoxime catalysis using TS-1 molecular sieves suffers from problems such as poor catalytic performance, low hydroxylamine yield, and significant decrease in catalyst stability due to harsh synthesis conditions. Summary of the Invention

[0006] The technical problem to be solved by the present invention is to provide a post-treatment modification method for TS-1 molecular sieve catalyst and its application.

[0007] To solve the above-mentioned technical problems, the present invention provides a post-treatment modification method for TS-1 molecular sieve catalyst. The TS-1 molecular sieve catalyst is subjected to reduction treatment by (5R)-5-[(1S)-1,2-dihydroxyethyl]-3,4-dihydroxyfuran-2(5H)-one, then oxidation treatment by hydrogen peroxide, and finally impregnation treatment to obtain the modified TS-1 molecular sieve catalyst (TS-1 molecular sieve catalyst with high ammonia oxime reaction catalytic activity).

[0008] An improvement to the post-treatment modification method of the TS-1 molecular sieve catalyst of the present invention includes the following steps, by mass fraction: 1) Reduction process: 100 parts of TS-1 molecular sieve catalyst (common commercial TS-1 molecular sieve catalyst), 1 to 50 parts (preferably 5 to 12 parts, more preferably 9 to 12 parts) of (5R)-5-[(1S)-1,2-dihydroxyethyl]-3,4-dihydroxyfuran-2(5H)-one (as a reducing agent) and 100±20 parts of water were added to the reactor and the reactor was subjected to reduction treatment at 10 to 30°C for 1 to 2 hours under stirring conditions, followed by filtration and washing with water. The purpose of washing with water is to remove the reducing agent; 2) Oxidation treatment: Add the catalyst obtained in step 1), 50-200 parts (preferably 50-100 parts) of 30-35 wt% H2O2 solution and 100±20 parts of water to the reactor, stir and react at 10-30°C for 0.5-1 hour, and then filter and wash with water. The purpose of washing with water is to remove H2O2; 3) Impregnation treatment: Add the catalyst obtained in step 2), 1-10 parts (preferably 4-6 parts) of potassium salt, and 100±20 parts of water to the reactor and stir at 10-30°C for 3-6 hours. Then, remove the water by rotary evaporation (at about 100°C until the water is completely removed) to obtain the modified TS-1 molecular sieve catalyst.

[0009] As an improvement to the post-treatment modification method of the TS-1 molecular sieve catalyst of the present invention: the stirring speed in steps 1) to 3) is 100 to 500 rpm.

[0010] As a further improvement to the post-treatment modification method of the TS-1 molecular sieve catalyst of the present invention: the potassium salt in step 3) is at least one of the following: potassium chloride, potassium fluoride.

[0011] As a further improvement to the post-treatment modification method of the TS-1 molecular sieve catalyst of the present invention: the potassium salt in step 3) is composed of equal weights of potassium chloride and potassium fluoride, and the potassium salt is 5 ± 1 parts.

[0012] This invention also provides a method for synthesizing hydroxylamine, characterized in that: the modified TS-1 molecular sieve catalyst prepared using any of the above methods includes the following steps: A reaction system is formed by mixing 0.05-0.15 parts of modified TS-1 molecular sieve catalyst, 7-13 parts of 30-35 wt% H2O2 solution, 15-25 parts of ammonia water (mass concentration 25%-28%), and 8-12 parts of water. The mixture is heated to 20-70℃ and stirred for 2-7 hours to directly synthesize hydroxylamine (the resulting reaction solution contains hydroxylamine).

[0013] An improvement to the method for synthesizing hydroxylamine according to the present invention: The molar ratio of ammonia to H2O2 is 1 to 10:1 (preferably 2 to 3:1).

[0014] This invention provides a post-treatment modification method for TS-1 molecular sieve catalyst and its application in the direct ammoniation synthesis of hydroxylamine solution using hydrogen peroxide. The modified TS-1 catalyst prepared by this invention significantly improves both the conversion rate (H2O2 conversion rate) and the hydroxylamine solution concentration in the ammoniation reaction using hydrogen peroxide as the oxidant.

[0015] This invention involves reducing a commercial catalyst with (5R)-5-[(1S)-1,2-dihydroxyethyl]-3,4-dihydroxyfuran-2(5H)-one, followed by oxidation with hydrogen peroxide (as an oxidant), and finally impregnation to obtain a TS-1 molecular sieve catalyst with high catalytic activity for ammonium oxime reactions. This invention utilizes this reduction-oxidation treatment to effectively regulate the active Ti species in the TS-1 catalyst. Furthermore, potassium salt impregnation post-treatment is used to regulate the surface hydrophobicity and adsorption characteristics of the catalyst, thereby improving the adsorption-reaction behavior of hydrogen peroxide on the catalyst surface. The TS-1 catalysts prepared by this modification process all have an MFI structure, with Ti existing in the molecular sieve framework as TiO4.

[0016] This invention employs a redox-salt modification post-treatment method to modify TS-1 molecular sieve catalysts. The TS-1 molecular sieve is subjected to redox treatment with (5R)-5-[(1S)-1,2-dihydroxyethyl]-3,4-dihydroxyfuran-2(5H)-one / hydrogen peroxide, which modulates the catalyst surface structure and promotes the formation of active titanium species. Subsequent KCl and KF composite salt impregnation effectively regulates the hydrogen bonding interaction between hydrogen peroxide and the TS-1 molecular sieve catalyst, as well as the hydrophobicity of the catalyst surface, thereby significantly improving the hydrogen peroxide ammonium oxime reaction performance of the TS-1 molecular sieve catalyst. This post-treatment modification method can efficiently and conveniently prepare highly catalytically active TS-1 molecular sieve catalysts, whose catalytic performance is significantly higher than that of currently commercially available TS-1 molecular sieve catalysts.

[0017] The present invention has the following significant advantages: (1) The post-treatment method is simple and quick, which can effectively regulate the active Ti species in the catalyst. At the same time, simple impregnation with salt can significantly optimize the hydrophobic properties of the catalyst surface and enhance the adsorption and activation ability of hydrogen peroxide.

[0018] (2) The modified TS-1 catalyst is used to catalyze the ammonium oxime reaction with hydrogen peroxide as oxidant to directly synthesize hydroxylamine solution. This method is simple and efficient, avoids the synthesis steps of ketoxime or hydroxylamine salt intermediates, and reduces the production of by-products such as waste salt, thereby realizing the green and sustainable production of hydroxylamine solution.

[0019] (3) The reaction conditions of this invention are mild and controllable, avoiding the use of strong acids and bases and the emission of by-product salts in the traditional hydroxylamine solution synthesis. The reaction has a high safety factor, is environmentally friendly and energy-saving, and is suitable for large-scale industrial production. Attached Figure Description

[0020] The specific embodiments of the present invention will be further described in detail below with reference to the accompanying drawings.

[0021] Figure 1Phase analysis of TS-1 molecular sieve catalyst before and after modification treatment; Figure 1 middle: a: XRD pattern of a common commercial TS-1 molecular sieve catalyst; b: XRD pattern of the modified TS-1 molecular sieve catalyst obtained in Example 1.

[0022] Figure 2 Morphological characterization of the modified TS-1 molecular sieve catalyst (SEM image of the modified TS-1 catalyst in Example 1). Figure 2 middle: a: SEM image (1 μm) of the overall distribution of the modified TS-1 catalyst in Example 1. b: Local SEM image (200 nm) of the modified TS-1 catalyst in Example 1. c: SEM image (100 nm) of a selected magnified region of the TS-1 catalyst after modification in Example 1. d: SEM image (100 nm) of the specific particle characteristics of the modified TS-1 catalyst in Example 1. Detailed Implementation

[0023] The present invention will be further described below with reference to specific embodiments, but the scope of protection of the present invention is not limited thereto.

[0024] Example 1: Post-treatment modification method of TS-1 molecular sieve catalyst, comprising the following steps in sequence: Step 1: Add 100 g of ordinary commercial TS-1 molecular sieve catalyst, 10 g of (5R)-5-[(1S)-1,2-dihydroxyethyl]-3,4-dihydroxyfuran-2(5H)-one (as a reducing agent) and 100 g of water to a 500 mL three-necked flask, stir at 300 rpm at 20 °C for 2 hours, then filter, and wash the obtained solid with water to remove excess reducing agent adhering to the catalyst.

[0025] Note: The molar amount of 10 g (5R)-5-[(1S)-1,2-dihydroxyethyl]-3,4-dihydroxyfuran-2(5H)-one is approximately 56.8 mmol.

[0026] Step 2: Add the catalyst obtained in Step 1 (the catalyst after water washing), 100 g of 35% H2O2 and 100 g of water to a 500 mL three-necked flask, stir at 300 rpm for 1 hour at 20 °C, then filter, and wash the filtered solid with water to remove the hydrogen peroxide residue on the catalyst.

[0027] Step 3: Add the catalyst obtained in Step 2 (the catalyst after water washing), 5 g of potassium chloride, and 100 g of water to a single-necked flask, stir at 300 rpm for 6 hours at 20 ℃, and then perform rotary evaporation at 100 ℃ until the water is completely removed to obtain the modified TS-1 molecular sieve catalyst.

[0028] The XRD and scanning electron microscopy characterization of the modified TS-1 molecular sieve catalyst are shown in [reference needed]. Figure 1 and Figure 2 ,in Figure 2 Figures a to d in the figure reflect the morphological characteristics of the modified TS-1 molecular sieve catalyst at different sizes, both overall and locally, in Example 1.

[0029] Example 2, compared to Example 1, makes the following changes: In step one: the amount of (5R)-5-[(1S)-1,2-dihydroxyethyl]-3,4-dihydroxyfuran-2(5H)-one was changed from 10g to 5g. The rest is the same as in Example 1.

[0030] Example 3: The following changes are made compared to Example 1: In step two: the amount of 35% H2O2 used is changed from 100 g to 50 g; The rest is the same as in Example 1.

[0031] Example 4: The following changes are made compared to Example 1: In step one: the amount of (5R)-5-[(1S)-1,2-dihydroxyethyl]-3,4-dihydroxyfuran-2(5H)-one was changed from 10g to 5g. In step two: the amount of 35% H2O2 used is changed from 100 g to 50 g; The rest is the same as in Example 1.

[0032] Example 5: The following changes are made compared to Example 1: In step three: replace "5 g potassium chloride" with "5 g potassium fluoride". The rest is the same as in Example 1.

[0033] Example 6: The following changes are made compared to Example 1: In step three: change "5 g potassium chloride" to "2.5 g potassium chloride, 2.5 g potassium fluoride"; The rest is the same as in Example 1.

[0034] Comparative Example 1, compared to Example 1, is modified as follows: Cancel step three; The catalyst obtained in step two (the catalyst after water washing) was dried at 60 °C to constant weight to obtain the modified catalyst. The rest is the same as in Example 1.

[0035] Comparative Example 2, compared to Example 1, made the following changes: Cancel step two; Replace the water-washed catalyst obtained in step two with the catalyst obtained in step one, and proceed directly to step three; the rest is the same as in Example 1.

[0036] Comparative Example 3, compared to Example 1, made the following changes: Cancel step one; Replace the water-washed catalyst obtained in step one with 100 g of ordinary commercial TS-1 molecular sieve catalyst, and proceed directly to step two; the rest is the same as in Example 1.

[0037] Comparative Example 4, compared to Example 1, is modified as follows: In step one, (5R)-5-[(1S)-1,2-dihydroxyethyl]-3,4-dihydroxyfuran-2(5H)-one was replaced with sodium borohydride (NaBH4), while the molar amount remained unchanged at 56.8 mmol; the rest was the same as in Example 1.

[0038] Comparative Example 5, compared to Example 1, is modified as follows: Replace “5 g potassium chloride” in step three with “5 g sodium chloride”; the rest is the same as in Example 1.

[0039] Experiment 1: Evaluation of the performance of the ammonium oximation reaction: Take 0.1 g of any of the modified TS-1 molecular sieve catalysts prepared in Examples 1-6 and Comparative Examples 1-5, or a common commercial TS-1 molecular sieve catalyst, 10 g of 35wt% H2O2, 20 g of 25wt% ammonia (the molar ratio of NH3 / H2O2 is approximately 2.86), and 10 mL of water and add them to the ammonium oxime reactor. Heat to 60 °C and stir at 300 rpm for 2 hours. After the reaction is complete, take a sample and use a potentiometric titrator to determine the hydroxylamine content in the resulting reaction solution. The specific results are shown in Table 1.

[0040] Note: The hydroxylamine in the reaction solution is in a free state.

[0041] Table 1 Performance of TS-1 molecular sieve catalyst in the synthesis of hydroxylamine via ammonoxime synthesis

[0042] Experiment 2: Reuse of Catalysts: The catalyst obtained in Experiment 1 was recovered and washed (using pure water to remove impurities such as reactants and products adsorbed on the catalyst surface), and then Experiment 1 was repeated.

[0043] After Examples 1-6 and Comparative Examples 1-5 were reused 5 times, the activity retention rate of Examples 1-6 was >90%, while the activity retention rate of the comparative examples was significantly lower than that of the examples of the present invention. Activity retention rate = Synthetic hydroxylamine content obtained after 5 reuses / Synthetic hydroxylamine content corresponding to the first use of the catalyst in Table 1.

[0044] In contrast, the activity retention rate of ordinary commercial TS-1 molecular sieve catalysts is even lower after being reused 5 times.

[0045] Finally, it should be noted that the above examples are merely some specific embodiments of the present invention. Obviously, the present invention is not limited to the above embodiments and many variations are possible. All variations that can be directly derived or conceived by those skilled in the art from the disclosure of the present invention should be considered within the scope of protection of the present invention.

Claims

1. A post-treatment modification method for TS-1 molecular sieve catalyst, characterized in that: The TS-1 molecular sieve catalyst was reduced by (5R)-5-[(1S)-1,2-dihydroxyethyl]-3,4-dihydroxyfuran-2(5H)-one, then oxidized by hydrogen peroxide, and finally impregnated to obtain the modified TS-1 molecular sieve catalyst.

2. The post-treatment modification method for the TS-1 molecular sieve catalyst according to claim 1, characterized in that, Includes the following steps, expressed as a mass fraction: 1) Reduction process: 100 parts of TS-1 molecular sieve catalyst, 1-50 parts of (5R)-5-[(1S)-1,2-dihydroxyethyl]-3,4-dihydroxyfuran-2(5H)-one and 100±20 parts of water were added to the reactor and reduced at 10-30°C for 1-2 hours under stirring conditions, followed by filtration and water washing. 2) Oxidation treatment: Add the catalyst obtained in step 1), 50-200 parts of 30-35 wt% H2O2 solution and 100±20 parts of water to the reactor, stir and react at 10-30℃ for 0.5-1 hours, and then filter and wash with water. 3) Impregnation treatment: Add the catalyst obtained in step 2), 1-10 parts of potassium salt, and 100±20 parts of water to the reactor and stir at 10-30℃ for 3-6 hours. Then remove the water by rotary evaporation to obtain the modified TS-1 molecular sieve catalyst.

3. The post-treatment modification method for the TS-1 molecular sieve catalyst according to claim 2, characterized in that: The stirring speed for steps 1) to 3) is 100 to 500 rpm.

4. The post-treatment modification method for the TS-1 molecular sieve catalyst according to claim 3, characterized in that: The potassium salt in step 3) is at least one of the following: potassium chloride or potassium fluoride.

5. The post-treatment modification method for the TS-1 molecular sieve catalyst according to claim 4, characterized in that: The potassium salt in step 3) consists of equal weights of potassium chloride and potassium fluoride, and the potassium salt content is 5 ± 1 parts.

6. A method for synthesizing hydroxylamine, characterized in that: The modified TS-1 molecular sieve catalyst obtained by any one of claims 1 to 5 comprises the following steps: The reaction system formed by mixing 0.05~0.15 parts of modified TS-1 molecular sieve catalyst, 7~13 parts of 30~35wt% H2O2 solution, 15~25 parts of ammonia water (mass concentration 25%~28%), and 8~12 parts of water is heated to 20~70℃ and stirred for 2~7 hours to synthesize hydroxylamine.

7. The method for synthesizing hydroxylamine according to claim 6, characterized in that: The molar ratio of ammonia to H2O2 is 1 to 10:1.

Images