Preparation method and application of sulfonation catalyst for the synthesis of methacrylonitrile

Abstract

This invention discloses a method for preparing a sulfonation catalyst for the synthesis of methacrylonitrile. A large specific surface area support powder is added to a beaker, followed by an acid solution. After stirring until homogeneous, the mixture is filtered, washed, and dried to obtain an acid-washed support. The acid-washed support is then added to a hydrothermal reactor with a polytetrafluoroethylene liner, along with a sulfonation reagent and organic reagent A. The hydrothermal reactor is sealed and placed in an oven for treatment. After further filtration, washing, and drying, the sulfonation catalyst is obtained. A manganese precursor and auxiliary precursor are weighed and added to a beaker, along with organic reagent B. After thorough dissolution by magnetic stirring, the sulfonation catalyst is added to the beaker. The mixture is stirred at room temperature, filtered, washed, and dried. Finally, it is calcined in a muffle furnace to obtain the sulfonation catalyst. Acid washing obtains support vacancies, effectively anchoring sulfonic acid groups and active and auxiliary elements, resulting in a catalyst with good stability.

Description

Technical Field

[0001] This invention belongs to the field of catalytic ammonia oxidation technology, specifically relating to a method for preparing and applying a sulfonation catalyst for the synthesis of methacrylonitrile. Background Technology

[0002] Methacrylonitrile is an important chemical raw material, currently mainly used in the production of polymethacrylimide (PMI) foam, and to a certain extent, it is irreplaceable. As a high-performance polymer material, PMI foam has the characteristics of high specific strength, high specific modulus, high heat resistance, and high closed-cell rate. It can be used as a structural core material in aerospace, rail transportation, medical devices, wind power generation, radar antennas and other fields. The core product layout targets a market of over 50 billion yuan per year.

[0003] Currently, domestic PMI foam preparation technology has gradually matured, but the main constraint on its development is the source of the raw material, methacrylonitrile. In recent years, domestic research institutes have conducted extensive research on methacrylonitrile production processes. Among these, the process using methacrolein as a raw material and preparing methacrylonitrile products via ammonia oxidation has advantages such as being green and environmentally friendly, having low energy consumption, and producing few toxic byproducts, making it a potential industrially applicable route. However, the raw material methacrolein used in this process is a very reactive aldehyde, which easily undergoes dimerization even in the presence of polymerization inhibitors, forming 3,4-dihydro-2,5-dimethyl-2H-pyran-2-carboxaldehyde (methacrylonitrile dimer). For commercially available reagents, the purity of methacrolein is generally above 95% at the time of manufacture, and the total mass fraction of methacrolein plus methacrolein dimer can reach over 99%. After a period of storage, some methacrolein will polymerize to form methacrolein dimer; in severe cases, the mass fraction of methacrolein dimer in the reagent can reach over 15%. When using methacrylaldehyde containing dimers as a raw material, the dimers can react with ammonia and / or oxygen during the ammonia oxidation reaction to generate corresponding byproducts. These byproducts can lead to a decrease in the final yield of methacrylonitrile and can also cover the active sites of the catalyst, poisoning the catalyst. At this time, the catalyst needs to undergo a complicated regeneration process to restore its activity. Otherwise, the accumulation of byproducts will lead to catalyst deactivation. Summary of the Invention

[0004] The purpose of this invention is to solve the above-mentioned technical problems and provide a method for preparing a highly active and stable sulfonation catalyst for the synthesis of methacrylonitrile, as well as its application.

[0005] To achieve the above objectives, the present invention provides a method for preparing a sulfonation catalyst for the synthesis of methacrylonitrile, as detailed below:

[0006] 1) Preparation of acid-washed carriers

[0007] A large specific surface area carrier powder was added to a beaker, followed by an acid solution. The mixture was then magnetically stirred in a water bath. After stirring, the mixture was filtered, washed, and dried to obtain the acid-treated carrier.

[0008] 2) Preparation of sulfonated carriers

[0009] The acid-washed carrier was added to a hydrothermal reactor with a polytetrafluoroethylene liner, along with a sulfonating agent and organic reagent A. The hydrothermal reactor was then sealed, placed in an oven for treatment, and subsequently filtered, washed, and dried to obtain the sulfonated carrier.

[0010] 3) Preparation of sulfonation catalyst

[0011] Weigh out the manganese precursor and auxiliary precursor, add them to a beaker, add organic reagent B, stir magnetically until fully dissolved, add the sulfonated carrier to the beaker, stir at room temperature, filter, wash, dry, and finally calcine in a muffle furnace to obtain the sulfonated catalyst.

[0012] Further, in step 1), the mass ratio of the acid solution to the high specific surface area carrier powder is (20-80):1; the high specific surface area carrier powder is aluminum oxide, titanium dioxide, or silicon dioxide carrier powder, with a specific surface area of ​​150-300 m². 2 / g; the acid solution is one or more of nitric acid solution, hydrochloric acid solution, and acetic acid solution, and the concentration of acid in the acid solution is 10-50 mmol / L.

[0013] Further, in step 1), the specific process of washing and drying is as follows: the filter cake powder is washed with ultrapure water until the conductivity of the filtrate is lower than 50 μS / cm; then the filter cake powder washed with ultrapure water is washed three times with alcohol washing solution, the amount of alcohol washing solution used each time being 5 to 20 times the mass of the filter cake powder washed with ultrapure water; finally, the alcohol-washed filter cake powder is placed in a vacuum oven and dried at 40 to 80°C under vacuum for 5 to 10 hours.

[0014] Further, in step 2), the mass ratio of the sulfonating reagent to organic reagent A is 1:(100-300); the mass ratio of the pickling carrier to the sulfonating reagent is determined according to the specific surface area of ​​the pickling carrier, where the specific surface area of ​​the pickling carrier is 150-200 m². 2 When the surface area of ​​the pickled carrier is 200-250 m² / g, the mass ratio of the pickled carrier to the sulfonating reagent is (5-15):1; 2 When the surface area of ​​the pickled carrier is 250-300 m² / g, the mass ratio of the pickled carrier to the sulfonating agent is (3-12):1; 2 When the mass ratio of the acid-washed carrier to the sulfonating reagent is / g, the mass ratio is (2-10):1.

[0015] The sulfonating agent is one of chlorosulfonic acid or aminosulfonic acid; organic reagent A is one or more of anhydrous methanol, anhydrous ethanol, acetone, acetonitrile, tetrahydrofuran, N,N-dimethylformamide, thionyl chloride, carbon tetrachloride, chloroform, pyridine, and pyrrole.

[0016] Furthermore, in step 1), the water bath temperature is 40–80°C; in step 2), the hydrothermal reactor is placed in an oven and treated at 110–150°C for 10–24 hours.

[0017] Further, in step 2), the specific process of washing and drying is as follows: the filter cake powder is washed three times with an alcohol washing solution, the amount of alcohol washing solution used each time being 5 to 20 times the mass of the filter cake powder, and then placed in a vacuum oven and dried at 40 to 80°C under vacuum for 5 to 10 hours.

[0018] Further, in step 3), the molar ratio of manganese precursor to auxiliary precursor is (1-10):1; the mass ratio of manganese precursor to organic reagent B is 1:(1000-5000); and in the sulfonation catalyst, the mass fraction of manganese is 0.5-2.5%, and the mass fraction of auxiliary element is 0.06-3.0%.

[0019] The manganese precursor is one or more of anhydrous manganese acetate, manganese acetylacetone, and bis(cyclopentadienyl)manganese; the auxiliary agent precursor is one or two of copper auxiliary agent precursor and zinc auxiliary agent precursor, wherein the copper auxiliary agent precursor is one or more of copper acetylacetone, copper glycinate, copper citrate, copper acetoacetate, and copper oxalate, and the zinc auxiliary agent precursor is one or more of anhydrous zinc acetate, zinc isopropoxide, zinc acrylate, zinc propionate, and zinc glycinate; organic reagent B is one or more of anhydrous methanol, anhydrous ethanol, acetonitrile, tetrahydrofuran, acetylacetone, pyridine, and pyrrole.

[0020] Further, in step 3), the specific process of washing and drying is as follows: the filter cake powder is washed three times with an alcohol washing solution, the amount of alcohol washing solution used each time being 5 to 20 times the mass of the filter cake powder, and then placed in a vacuum oven and dried at 40 to 80°C under vacuum for 5 to 10 hours; and then calcined in a muffle furnace at 250 to 400°C for 2 to 10 hours.

[0021] In step 3), the alcohol washing solution is one or more of anhydrous methanol, anhydrous ethanol, anhydrous ethylene glycol, anhydrous glycerol, and anhydrous propylene glycol.

[0022] An application of the sulfonation catalyst as described above is also provided, wherein the sulfonation catalyst is used to prepare methacrylonitrile from methacrolein containing dimers;

[0023] The reaction is a slurry-bed reaction. Sulfonation catalyst, methacrolein raw material containing dimers, and organic reagent C are added to the reactor. Ammonia is introduced into the system as an ammonia source and oxygen is introduced as an oxygen source. Under stirring, an ammonia oxidation reaction is carried out to prepare methacrylonitrile. At the same time, for the methacrolein dimers present in the raw materials, the sulfonation catalyst can first depolymerize them into methacrolein monomers, and then react with the ammonia and oxygen sources to generate the target product methacrylonitrile. The total conversion rate of methacrolein and its dimers is greater than 98%, and the yield of methacrylonitrile can reach more than 95%. Moreover, the catalyst can be regenerated by simple filtration and drying. After 10 cycles of application, no significant decrease in activity was observed.

[0024] The mass ratio of sulfonation catalyst, methacrolein containing dimer, and organic reagent C is 1:(6-20):(50-100); the molar ratio of methacrolein containing dimer (the dimer is converted to methacrolein), ammonia, and oxygen is 1:(0.5-10):(0.5-10).

[0025] The reaction pressure is 2–6 MPa, the temperature is 30–70 °C, and the reaction time is 2–30 min.

[0026] Furthermore, the organic reagent C is one or more of acetonitrile, tetrahydrofuran, dimethyl sulfoxide, toluene, ethyl acetate, and butyl acetate.

[0027] The catalyst support disclosed in this invention uses a large specific surface area (≥150m²). 2The carrier is made of alumina, titanium dioxide, or silica ( / g), in powder form. Commercial or self-made products can be used. A carrier with a large specific surface area, after acid washing, provides more vacancy sites, facilitating the subsequent loading of sulfonic acid groups, active components, and additives. First, the carrier is treated with a certain concentration of dilute acid. This removes impurities from the carrier surface, such as residual sodium and potassium from the preparation process, as well as carbonates and hydroxyl groups formed by adsorbing small molecules from the air. It also creates uniformly distributed vacancy sites, facilitating the subsequent loading of sulfonic acid groups, active components, and additives. The concentration of dilute acid must be strictly controlled during this process. Too high a concentration will lead to over-etching of the carrier, resulting in carrier waste; too low a concentration will result in incomplete removal of residues on the carrier surface and insufficient vacancy sites. Subsequently, the support is subjected to sulfonation treatment. The support, sulfonating reagent, and solvent are placed in a hydrothermal reactor for a solvothermal reaction. The support obtained from the previous acid washing step can be sulfonated, resulting in a uniform distribution of sulfonic acid groups on the support. By controlling the ratio of support to sulfonating reagent, the surface density of sulfonic acid groups on the support can be effectively controlled. If the surface density of sulfonic acid groups is too low, the number of depolymerization active sites for catalytic dimer depolymerization will be insufficient, resulting in residual methacrolein dimers during the ammonia oxidation reaction, causing side reactions and covering the catalyst active sites. If the surface density of sulfonic acid groups is too high, there will be insufficient vacancies on the support when loading subsequent active components and additives, resulting in some components failing to be effectively loaded or having unstable loading positions. This can easily lead to the aggregation of active components and additives during the reaction, resulting in a decrease in activity. Finally, the active manganese component and additive elements are adsorbed onto the vacancies of the sulfonated support by electrostatic adsorption. After drying and calcination, the sulfonated catalyst is obtained. Benefiting from the electrochemical properties of sulfonic acid groups, active components and additives electrostatically adsorbed onto the support preferentially fill the vacancies around the sulfonic acid groups obtained through acid washing. During the reaction, these active and additive elements are stable and do not easily migrate or aggregate. Simultaneously, the sulfonic acid groups catalyze the depolymerization of methacrolein dimers, and the resulting methacrolein monomers rapidly migrate to nearby active sites for ammoxidation to produce methacrylonitrile. This process fully utilizes the dimers in the raw materials and reduces side reactions. Furthermore, throughout the catalyst preparation process, except for the unavoidable contact between water from the dilute acid and the support during the initial dilute acid washing, and subsequent washing with anhydrous organic reagents to remove water, all other reagents and washing agents are anhydrous. This effectively avoids the formation of hydroxyl groups on the catalyst surface, further reducing side reactions. Additionally, low-temperature drying in a vacuum oven prevents the migration and aggregation of effective components.

[0028] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0029] 1) The support used in the sulfonation catalyst prepared by this invention is a conventional support, which can be commercial samples or prepared by ourselves, and the cost is low. The reagents used in subsequent acid washing and sulfonation are also conventional reagents, which are inexpensive. The preparation method is simple and easy to implement, and is convenient for industrial production.

[0030] 2) This invention obtains carrier vacancies through acid washing, which can effectively anchor sulfonic acid groups and active elements and auxiliary elements. The catalyst has good stability and can be regenerated by simple filtration and drying. After 10 cycles of application, no significant decrease in activity was observed.

[0031] 3) The sulfonic acid group can catalyze the depolymerization of methacrolein dimer into methacrolein monomer. At the same time, thanks to the electrical properties of the sulfonic acid group, the active elements and auxiliary elements are loaded around the sulfonic acid group, which facilitates the tandem occurrence of the two reactions of dimer depolymerization and methacrolein ammoxidation. This can make full use of the methacrolein dimer in the raw material. The total conversion rate of methacrolein and its dimer is greater than 98%, and the yield of methacrylonitrile can reach more than 95%. At the same time, it can effectively avoid the side reaction of the dimer covering the active site, which would lead to catalyst deactivation. Attached Figure Description

[0032] Figure 1 The image shows the gas chromatogram of the methacrolein raw material used in Experiment Example 1. Detailed Implementation

[0033] The present invention will be further described below with reference to specific embodiments.

[0034] Example 1

[0035] Preparation of 2.50wt%Mn and 2.89wt%Cu / Al2O3 catalyst

[0036] Weigh 30g of industrial large specific surface area (216m²) 2 Alumina powder (g) was added to a beaker, followed by 600g of a prepared 45mmol / L dilute hydrochloric acid solution. The mixture was magnetically stirred for 15h in a 45℃ water bath, filtered, and the filter cake powder was washed with ultrapure water until the conductivity of the filtrate was below 50μS / cm (the actual measured conductivity of the final filtrate was 43μS / cm). The filter cake powder was then washed three times with anhydrous methanol, with 200g of anhydrous methanol used each time. The mixture was then placed in a vacuum oven and dried at 40℃ under vacuum for 6h to obtain the acid-washed carrier.

[0037] Weigh 25g of the pickling-treated carrier (the measured specific surface area after pickling is 225m²). 2Add 5g of chlorosulfonic acid and 600g of anhydrous methanol to a hydrothermal reactor lined with polytetrafluoroethylene. Seal the hydrothermal reactor and place it in an oven. Treat at 115°C for 20 hours. Filter the mixture and wash the filter cake powder three times with 180g of anhydrous methanol each time. Place the mixture in a vacuum oven and dry at 40°C under vacuum for 6 hours to obtain the sulfonated carrier.

[0038] Weigh 1.664 g of anhydrous manganese acetate and 2.517 g of copper acetylacetone, add them to a beaker, add 1664 g of acetylacetone, and stir magnetically until fully dissolved. Add 20 g of sulfonated support to the beaker, stir at room temperature for 30 h, filter, and wash the filter cake powder three times with anhydrous methanol, each time using 150 g of anhydrous methanol. Place it in a vacuum oven and dry at 40 °C under vacuum for 6 h. Finally, calcine the sample in a muffle furnace at 250 °C for 5 h to obtain a 2.50 wt% Mn 2.89 wt% Cu / Al2O3 sulfonated catalyst.

[0039] Example 2

[0040] Preparation of 1.00wt%Mn and 0.39wt%Cu / TiO2 catalyst

[0041] Weigh out 50g of the homemade high specific surface area (183m²) 2 Titanium dioxide powder (g) was added to a beaker, followed by 3000g of a prepared 18mmol / L dilute nitric acid solution. The mixture was magnetically stirred in a 50℃ water bath for 20h, filtered, and the filter cake powder was washed with ultrapure water until the conductivity of the filtrate was below 50μS / cm (the actual measured conductivity of the final filtrate was 45μS / cm). The filter cake powder was then washed three times with anhydrous ethanol, with 500g of anhydrous ethanol used each time. The mixture was then placed in a vacuum oven and dried at 55℃ under vacuum for 6h to obtain the acid-washed carrier.

[0042] Weigh 20g of the pickling-treated carrier (the measured specific surface area after pickling is 194m²). 2 / g), added to a hydrothermal reactor lined with polytetrafluoroethylene, along with 2.0g chlorosulfonic acid and 400g anhydrous ethanol, sealed the hydrothermal reactor, placed it in an oven, treated at 130℃ for 15h, filtered, and the filter cake powder was washed three times with anhydrous ethanol, each time using 200g of anhydrous ethanol, and placed in a vacuum oven, dried at 55℃ under vacuum for 6h to obtain the sulfonated carrier.

[0043] Weigh 0.547 g of bis(cyclopentadienyl)manganese and 0.211 g of copper glycine, add them to a beaker, add 1641 g of pyridine, stir magnetically until fully dissolved, add 16 g of sulfonated support to the beaker, stir at room temperature for 15 h, filter, wash the filter cake powder three times with anhydrous ethanol, each time using 150 g of anhydrous ethanol, place in a vacuum oven, dry at 55 °C under vacuum for 6 h, and finally calcine the sample in a muffle furnace at 350 °C for 8 h to obtain a 1.00 wt% Mn0.39 wt% Cu / TiO2 sulfonated catalyst.

[0044] Example 3

[0045] Preparation of 0.50wt%Mn0.06wt%Zn / SiO2 catalyst

[0046] Weigh 20g of industrial large specific surface area (264m²) 2 / g) Silica powder was added to a beaker, followed by 1600g of a prepared 11mmol / L dilute acetic acid solution. The mixture was magnetically stirred for 17h in an 80℃ water bath, filtered, and the filter cake powder was washed with ultrapure water until the conductivity of the filtrate was below 50μS / cm (the actual measured conductivity of the final filtrate was 36μS / cm). The filter cake powder was then washed three times with anhydrous ethylene glycol, with 300g of anhydrous ethylene glycol used each time. The mixture was then placed in a vacuum oven and dried at 80℃ under vacuum for 10h to obtain the acid-washed carrier.

[0047] Weigh 15g of the pickling-treated carrier (the measured specific surface area after pickling is 293m²). 2 / g), added to a hydrothermal reactor lined with polytetrafluoroethylene, along with 3.0g aminosulfonic acid and 800g pyridine, sealed the hydrothermal reactor, placed it in an oven, treated at 150℃ for 20h, filtered, and the filter cake powder was washed three times with anhydrous ethylene glycol, each time using 220g of anhydrous ethanol, and placed in a vacuum oven, dried at 80℃ under vacuum for 10h to obtain the sulfonated carrier.

[0048] Weigh 0.322 g of manganese acetylacetone and 0.0115 g of zinc isopropoxide, add them to a beaker, add 1288 g of tetrahydrofuran, stir magnetically until fully dissolved, add 10 g of sulfonated support to the beaker, stir at room temperature for 36 h, filter, wash the filter cake powder three times with anhydrous ethylene glycol, each time using 150 g of anhydrous ethanol, place in a vacuum oven, dry at 80 °C under vacuum for 10 h, and finally calcine the sample in a muffle furnace at 400 °C for 7 h to obtain a 0.50 wt% Mn0.06 wt% Zn / SiO2 sulfonated catalyst.

[0049] Example 4

[0050] Preparation of 1.00wt%Mn0.29wt%Cu0.30%Zn / TiO2 catalyst

[0051] Weigh out 50g of the homemade high specific surface area (183m²) 2 Titanium dioxide powder (g) was added to a beaker, followed by 3000g of a prepared 18mmol / L dilute nitric acid solution. The mixture was magnetically stirred in a 50℃ water bath for 20h, filtered, and the filter cake powder was washed with ultrapure water until the conductivity of the filtrate was below 50μS / cm (the actual measured conductivity of the final filtrate was 45μS / cm). The filter cake powder was then washed three times with anhydrous ethanol, with 500g of anhydrous ethanol used each time. The mixture was then placed in a vacuum oven and dried at 55℃ under vacuum for 6h to obtain the acid-washed carrier.

[0052] Weigh 20g of the pickling-treated carrier (the measured specific surface area after pickling is 194m²). 2 / g), added to a hydrothermal reactor lined with polytetrafluoroethylene, along with 2.0g chlorosulfonic acid and 400g anhydrous ethanol, sealed the hydrothermal reactor, placed it in an oven, treated at 130℃ for 15h, filtered, and the filter cake powder was washed three times with anhydrous ethanol, each time using 200g of anhydrous ethanol, and placed in a vacuum oven, dried at 55℃ under vacuum for 6h to obtain the sulfonated carrier.

[0053] Weigh 1.042 g of manganese acetylacetone, 0.194 g of copper acetylacetone, and 0.0929 g of zinc isopropoxide, add them to a beaker, add 2605 g of acetonitrile, and stir magnetically until fully dissolved. Add 16 g of sulfonated support to the beaker, stir at room temperature for 18 h, filter, and wash the filter cake powder three times with anhydrous ethanol, each time using 150 g of anhydrous ethanol. Place it in a vacuum oven and dry at 55 °C under vacuum for 6 h. Finally, calcine the sample in a muffle furnace at 300 °C for 5 h to obtain a 1.00 wt% Mn 0.29 wt% Cu 0.30% Zn / TiO2 sulfonated catalyst.

[0054] Comparative Example 1

[0055] Preparation of 1.00wt%Mn0.39wt%Cu / TiO2-unwashed-sulfonated catalyst

[0056] Directly using self-made high specific surface area (183m²) without acid washing 2 / g) Titanium dioxide powder was used as the catalyst support. The sulfonation treatment and the loading of active components and additives were consistent with those in Example 2.

[0057] Weigh 20g of the self-made high specific surface area (183m²) 2Titanium dioxide powder (g) was added to a hydrothermal reactor lined with polytetrafluoroethylene, along with 2.0 g of chlorosulfonic acid and 400 g of anhydrous ethanol. The reactor was sealed and placed in an oven at 130°C for 15 h. The mixture was then filtered, and the filter cake powder was washed three times with 200 g of anhydrous ethanol each time. The mixture was then placed in a vacuum oven and dried at 55°C under vacuum for 6 h to obtain the sulfonated carrier.

[0058] Weigh 0.547 g of bis(cyclopentadienyl)manganese and 0.211 g of copper glycine, add them to a beaker, add 1641 g of pyridine, stir magnetically until fully dissolved, add 16 g of sulfonated support to the beaker, stir at room temperature for 15 h, filter, wash the filter cake powder three times with anhydrous ethanol, each time using 150 g of anhydrous ethanol, place in a vacuum oven, dry at 55 °C under vacuum for 6 h, and finally calcine the sample in a muffle furnace at 350 °C for 8 h to obtain 1.00 wt% Mn 0.39 wt% Cu / TiO2-unwashed-sulfonated catalyst.

[0059] Comparative Example 2

[0060] Preparation of 1.00wt%Mn0.39wt%Cu / TiO2-acid-washed-unsulfonated catalyst

[0061] Self-made titanium dioxide powder with large specific surface area, which was acid-washed, was used as a catalyst support. The active component and auxiliary agent were loaded directly without sulfonation treatment, consistent with Example 2.

[0062] Weigh out 50g of the homemade high specific surface area (183m²) 2 Titanium dioxide powder (g) was added to a beaker, followed by 3000g of a prepared 18mmol / L dilute nitric acid solution. The mixture was magnetically stirred in a 50℃ water bath for 20h, filtered, and the filter cake powder was washed with ultrapure water until the conductivity of the filtrate was below 50μS / cm (the actual measured conductivity of the final filtrate was 45μS / cm). The filter cake powder was then washed three times with anhydrous ethanol, with 500g of anhydrous ethanol used each time. The mixture was then placed in a vacuum oven and dried at 55℃ under vacuum for 6h to obtain the acid-washed carrier.

[0063] Weigh 0.547 g of bis(cyclopentadienyl)manganese and 0.211 g of copper glycine, add them to a beaker, add 1641 g of pyridine, stir magnetically until fully dissolved, add 16 g of acid-washed support to the beaker, stir at room temperature for 15 h, filter, wash the filter cake powder three times with anhydrous ethanol, each time using 150 g of anhydrous ethanol, place in a vacuum oven, dry at 55 °C under vacuum for 6 h, and finally calcine the sample in a muffle furnace at 350 °C for 8 h to obtain a 1.00 wt% Mn 0.39 wt% Cu / TiO2-acid-washed-unsulfonated catalyst.

[0064] Experimental Example 1: The catalysts prepared in the above examples and comparative examples were used to catalyze the ammoxidation of methacrylaldehyde and its dimer to prepare methacrylonitrile.

[0065] The sulfonation catalysts prepared in Examples 1-4 were used, with the catalysts prepared in Comparative Examples 1-2 as controls, to investigate their performance in catalyzing the ammoxidation of methacrylaldehyde containing dimers to produce methacrylonitrile in a slurry bed reactor. Simultaneously, the ammoxidation regeneration stability of the catalysts prepared in Example 2 and Comparative Examples 1-2 was investigated.

[0066] 1g of catalyst, 10g of methacrolein raw material containing the dimer, and 70g of tetrahydrofuran solvent were added to a slurry bed reactor. The reactor was sealed, and 3.5g of ammonia and 3MPa of air (approximately 6.5g of oxygen) were introduced. The reactor was heated to 50°C, and mechanical stirring was started. The reaction was allowed to proceed for 15 minutes. After the reaction was completed, the temperature was lowered and the gas was slowly released to atmospheric pressure. The reactor was then opened, and the resulting solution was analyzed by chromatography to determine the total conversion rate of methacrolein and the dimer, as well as the selectivity and yield of methacrylonitrile.

[0067] like Figure 1 As shown, the mass fraction of methacrylaldehyde in the methacrylaldehyde feedstock containing the dimer is 82.3%, and the mass fraction of methacrylaldehyde dimer is 16.9%. Based on this, the conversion rate of the ammonia oxidation reaction and the selectivity and yield of methacrylonitrile are calculated.

[0068] As shown in Table 1, the sulfonation catalysts prepared in this invention all exhibit excellent ammonia oxidation catalytic activity, with total conversion rates of methacrolein and its dimers all exceeding 98%, and the highest yield of methacrylonitrile reaching 95.8%. In contrast, the catalysts prepared in Comparative Examples 1 and 2, namely the 1.00wt%Mn0.39wt%Cu / TiO2-un-sulfonated catalyst and the 1.00wt%Mn0.39wt%Cu / TiO2-un-sulfonated catalyst, showed lower ammonia oxidation activity. For the 1.00wt%Mn0.39wt%Cu / TiO2-unwashed-sulfonated catalyst, the lack of acid washing resulted in impurities on the support and insufficient vacancies, leading to a limited loading of sulfonic acid groups. This restricted the performance of depolymerizing methacrylaldehyde dimers. However, some dimers could react with ammonia sources and / or oxidation, so the total conversion rate of methacrylaldehyde and its dimers (93.6%) was higher than the conversion rate of methacrylaldehyde alone (83.0%). In addition, due to insufficient vacancies, the active components and additives were not fully loaded or the loading positions were unstable, which also led to some side reactions, resulting in a low yield of methacrylonitrile (75.2%). For the 1.00wt%Mn0.39wt%Cu / TiO2-acid-washed-unsulfonated catalyst, the methacrylaldehyde dimer could not be depolymerized due to the lack of sulfonation treatment. Although the dimer in the feed could react with the ammonia source and / or oxidation, it was difficult to generate the target product methacrylonitrile, resulting in a low yield of methacrylonitrile (79.1%).

[0069] Table 1

[0070]

[0071] Cyclic regeneration experiments were conducted on the 1.00 wt% Mn0.39 wt% Cu / TiO2 sulfonation catalyst prepared in Example 2, the 1.00 wt% Mn0.39 wt% Cu / TiO2-un-washed-sulfonation catalyst prepared in Comparative Example 1, and the 1.00 wt% Mn0.39 wt% Cu / TiO2-washed-un-sulfonation catalyst prepared in Comparative Example 2. The regeneration method involved filtering the reaction solution, directly drying the resulting filter cake in an oven at 110°C for 10 hours to obtain the regenerated catalyst, and evaluating its ammonia oxidation activity according to the previous proportions.

[0072] As shown in Table 2, the 1.00wt%Mn0.39wt%Cu / TiO2 sulfonation catalyst prepared in Example 2 of this invention showed no significant decrease in ammonia oxidation activity after simple regeneration. After ten regeneration experiments, the total conversion rate of methacrylaldehyde and its dimer remained above 98%, and the yield of methacrylonitrile remained around 95%. In contrast, the 1.00wt%Mn0.39wt%Cu / TiO2-un-washed-sulfonation catalyst prepared in Comparative Example 1 had poor initial activity. After one regeneration, the reaction activity decreased rapidly, and after a second regeneration, the yield of methacrylonitrile dropped to a very low level, indicating catalyst deactivation. The reason for this is that the catalyst was not acid-washed, resulting in impurities on the support and insufficient vacancies. This led to limited loading of sulfonic acid groups, active components, and additives, causing some side reactions to occur and covering some active sites. At the same time, during the reaction and regeneration process, the loading positions of some active components and additives were unstable, with weak interaction with the support, resulting in migration and aggregation, further reducing the yield of methacrylonitrile. The 1.00wt%Mn0.39wt%Cu / TiO2-acid-washed-unsulfonated catalyst prepared in Comparative Example 2 had poor initial activity. After one regeneration, the reaction activity decreased. After three regenerations, the yield of methacrylonitrile dropped below 50%. Because the catalyst was not sulfonated, the methacrylaldehyde dimer could not depolymerize. During the reaction, the dimer could react with the ammonia source and / or oxidation, generating byproducts that covered the active sites and gradually accumulated during multiple reactions, causing the catalyst to gradually deactivate.

[0073] Table 2

[0074]

[0075]

Claims

1. The application of a sulfonation catalyst, characterized in that: The specific preparation method of the sulfonation catalyst is as follows: 1) Preparation of acid-washed carriers A large specific surface area carrier powder was added to a beaker, followed by an acid solution. The mixture was then magnetically stirred in a water bath. After stirring, the mixture was filtered, washed, and dried to obtain the acid-treated carrier. 2) Preparation of sulfonated carriers The acid-washed carrier was added to a hydrothermal reactor with a polytetrafluoroethylene liner, along with a sulfonating agent and organic reagent A. The hydrothermal reactor was then sealed, placed in an oven for treatment, and subsequently filtered, washed, and dried to obtain the sulfonated carrier. 3) Preparation of sulfonation catalyst Weigh out the manganese precursor and auxiliary precursor, add them to a beaker, add organic reagent B, stir magnetically until fully dissolved, add the sulfonated carrier to the beaker, stir at room temperature, filter, wash, dry, and finally calcine in a muffle furnace to obtain the sulfonated catalyst. The sulfonation catalyst is used to prepare methacrylonitrile from methacrolein containing dimers; The reaction is a slurry bed reaction. Sulfonation catalyst, methacrylaldehyde raw material containing dimer and organic reagent C are added to the reactor. Ammonia gas is introduced into the system as an ammonia source and oxygen gas is introduced as an oxygen source. The ammonia oxidation reaction is carried out under stirring to prepare methacrylonitrile. The mass ratio of sulfonation catalyst, dimerized methacrolein, and organic reagent C is 1:(6~20):(50~100); the molar ratio of dimerized methacrolein, ammonia, and oxygen is 1:(0.5~10):(0.5~10). The reaction pressure is 2~6 MPa, the temperature is 30~70℃, and the reaction time is 2~30 min.

2. The application of the sulfonation catalyst according to claim 1, characterized in that: In step 1), the mass ratio of the acid solution to the high specific surface area carrier powder is (20~80):1; the high specific surface area carrier powder is aluminum oxide, titanium dioxide, or silicon dioxide carrier powder, with a specific surface area of ​​150~300 m². 2 / g; the acid solution is one or more of nitric acid solution, hydrochloric acid solution, and acetic acid solution, and the concentration of acid in the acid solution is 10~50 mmol / L.

3. The application of the sulfonation catalyst according to claim 1, characterized in that: In step 1), the specific process of washing and drying is as follows: the filter cake powder is washed with ultrapure water until the conductivity of the filtrate is lower than 50 μS / cm; then the filter cake powder washed with ultrapure water is washed three times with alcohol washing solution, and the amount of alcohol washing solution used each time is 5 to 20 times the mass of the filter cake powder washed with ultrapure water; finally, the alcohol-washed filter cake powder is placed in a vacuum oven and dried at 40 to 80°C under vacuum for 5 to 10 hours.

4. The application of the sulfonation catalyst according to claim 1, characterized in that: In step 2), the sulfonating agent is one of chlorosulfonic acid or aminosulfonic acid; the organic reagent A is one or more of anhydrous methanol, anhydrous ethanol, acetone, acetonitrile, tetrahydrofuran, N,N-dimethylformamide, thionyl chloride, carbon tetrachloride, chloroform, pyridine, and pyrrole.

5. The application of the sulfonation catalyst according to claim 1, characterized in that: In step 1), the water bath temperature is 40~80℃; in step 2), the hydrothermal reactor is placed in an oven and treated at 110~150℃ for 10~24 hours.

6. The application of the sulfonation catalyst according to claim 1, characterized in that: In step 2), the specific process of washing and drying is as follows: the filter cake powder is washed three times with an alcohol washing solution, the amount of alcohol washing solution used each time being 5 to 20 times the mass of the filter cake powder, and then placed in a vacuum oven and dried at 40 to 80°C under vacuum for 5 to 10 hours.

7. The application of the sulfonation catalyst according to claim 1, characterized in that: In step 3), the molar ratio of manganese precursor to auxiliary precursor is (1~10):1; the mass ratio of manganese precursor to organic reagent B is 1:(1000~5000); and in the sulfonation catalyst, the mass fraction of manganese is 0.5~2.5%, and the mass fraction of auxiliary element is 0.06~3.0%. The manganese precursor is one or more of anhydrous manganese acetate, manganese acetylacetone, and bis(cyclopentadienyl)manganese; the auxiliary agent precursor is one or two of copper auxiliary agent precursor and zinc auxiliary agent precursor, wherein the copper auxiliary agent precursor is one or more of copper acetylacetone, copper glycinate, copper citrate, copper acetoacetate, and copper oxalate, and the zinc auxiliary agent precursor is one or more of anhydrous zinc acetate, zinc isopropoxide, zinc acrylate, zinc propionate, and zinc glycinate; organic reagent B is one or more of anhydrous methanol, anhydrous ethanol, acetonitrile, tetrahydrofuran, acetylacetone, pyridine, and pyrrole.

8. The application of the sulfonation catalyst according to claim 1, characterized in that: In step 3), the specific process of washing and drying is as follows: the filter cake powder is washed three times with alcohol washing solution, and the amount of alcohol washing solution used each time is 5 to 20 times the mass of the filter cake powder. It is then placed in a vacuum oven and dried at 40 to 80°C under vacuum for 5 to 10 hours; and then calcined in a muffle furnace at 250 to 400°C for 2 to 10 hours.

9. The application of the sulfonation catalyst according to claim 1, characterized in that: The organic reagent C is one or more of acetonitrile, tetrahydrofuran, dimethyl sulfoxide, toluene, ethyl acetate, and butyl acetate.

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