A method for synthesizing tris(4-aminophenyl) phosphorothioate

Abstract

The application discloses a synthesis method of tris(4-aminophenyl) thiophosphate, and belongs to the technical field of chemical synthesis, characterized by comprising the following steps: placing tris(4-nitrophenyl) thiophosphate, a catalyst and a solvent in a high-pressure reaction kettle, filling hydrogen gas with a pressure of 1.0-2.5 MPa, reacting at 50-70 DEG C for 1-2 h, sampling after being cooled to room temperature, removing the catalyst through centrifugation, and obtaining the product tris(4-aminophenyl) thiophosphate; the catalyst is a bimetallic doped platinum carbon supported catalyst, and the doped active metal is selected from any two of Al, Cu or Zn; the synthesis method of tris(4-aminophenyl) thiophosphate is characterized by adopting a novel bimetallic doped platinum carbon catalyst to catalyze the reaction, simultaneously controlling the reaction pressure and reaction time, effectively improving the conversion rate of the catalytic reduction reaction, and the catalyst is not easy to be poisoned in the reaction process.

Description

Technical Field

[0001] This invention relates to a method for synthesizing thiophosphates, specifically a method for synthesizing tris(4-aminophenyl)thiophosphates. Background Technology

[0002] Tris(4-aminophenyl)thiophosphate, with the molecular formula C3 18 H 18 N3O3PS, structural formula as follows:

[0003]

[0004] It is mainly used to synthesize tris(4-isocyanate phenyl) thiophosphate (Texamo RF), an excellent adhesive, and is also widely used in flame retardant plasticizers, photographic emulsion additives, and cholinesterase inhibitors.

[0005] Currently, tri(4-aminophenyl)thiophosphate compounds are mainly synthesized by hydrothermal methods, primarily using tri(4-nitrophenyl)thiophosphate compounds as raw materials and catalytically hydrogenating them to prepare tri(4-aminophenyl)thiophosphate compounds.

[0006] Peiyi Zhang et al. (Shiyou Huagong, 34(9), 863-865; 2005) used tri(4-nitrophenyl)thiophosphate, which was synthesized from p-nitrophenol and trichlorophosphorus, as raw material and Raney-Ni as catalyst, to catalytically reduce and prepare tri(4-aminophenyl)thiophosphate. The purity of the obtained product was greater than 94%.

[0007] Patrick WV Butler et al. (Chemical Communications (Cambridge, United Kingdom), 55(69), 10304-10307; 2019) synthesized tris(4-aminophenyl)thiophosphate from p-hydroxyaniline and 1,3-bis(1,1-dimethylethyl) ester with a yield of 90%.

[0008] Yuehua Zhang et al. (Jingxi Shiyou Huagong, 26(5), 15-19; 2009) prepared tri(4-aminophenyl)thiophosphate by esterification of acetaminophen with trichlorophosphorus, with a yield of up to about 78%.

[0009] Currently, the catalysts used for the synthesis of tris(4-aminophenyl)thiophosphate are primarily palladium-based. However, palladium is too expensive and easily generates other byproducts, resulting in high industrial production costs and difficulties in controlling byproducts, which increases the complexity of post-processing. Furthermore, the sulfur and phosphorus elements in tris(4-nitrophenyl)thiophosphate can poison metal catalysts, reducing their activity. Summary of the Invention

[0010] The first objective of this invention is to provide a method for synthesizing tris(4-aminophenyl)thiophosphate, which can effectively improve catalyst stability and reaction yield through catalyst improvement and reaction process control.

[0011] A method for synthesizing tris(4-aminophenyl)thiophosphate, characterized by comprising the following steps: placing tris(4-nitrophenyl)thiophosphate, catalyst, and solvent in a high-pressure reactor, purging with hydrogen gas at a pressure of 1.0-2.5 MPa, reacting at 50-70°C for 1-2 h, cooling to room temperature, taking a sample, centrifuging to remove the catalyst, and obtaining the product tris(4-aminophenyl)thiophosphate.

[0012] The catalyst is a bimetallic doped platinum-carbon supported catalyst, and the active metal being doped is selected from any two of Al, Cu, or Zn.

[0013] The amount of catalyst added is 2-5% of the raw material mass.

[0014] The catalyst, a bimetallic doped platinum-carbon supported catalyst, is prepared by the following method: chloroplatinic acid solution is added to a pretreated carbon support to react and prepare a platinum-carbon catalyst; an active metal precursor is weighed according to a certain ratio, dissolved and mixed in water, and then added dropwise to the above platinum-carbon catalyst; the pH is adjusted with Na2CO3 aqueous solution, dried, and then heated and reduced in a furnace with H2 atmosphere to obtain the bimetallic doped platinum-carbon catalyst.

[0015] The catalyst removed by centrifugation was washed with hydrochloric acid and sodium hydroxide, and then washed successively with deionized water, ethanol and acetone. It was then reused in the catalytic reaction. After 10 cycles, it still had good catalytic activity.

[0016] The solvent is methanol, ethanol, n-butanol, tert-butanol, n-octanol, ethylene glycol dimethyl ether, cumene, or xylene.

[0017] Preferably, the reaction pressure is 2.5 MPa, the reaction temperature is 70°C, and the reaction time is 1.5 h.

[0018] This invention discloses a method for synthesizing tris(4-aminophenyl)thiophosphate, employing a novel bimetallic doped platinum-carbon catalyst. By controlling the reaction pressure and time, the conversion rate of the catalytic reduction reaction is effectively improved, and the catalyst is less prone to poisoning during the reaction. Furthermore, the post-reaction processing is simple, and the product has good purity. Experimental tests show that the catalyst can be repeatedly recycled dozens of times with essentially unchanged activity, which is of great significance for reducing reaction costs and making it suitable for large-scale industrial production.

[0019] The second aspect of the present invention is to provide a bimetallic doped platinum-carbon catalyst suitable for catalyzing the above-mentioned reaction, characterized in that it is prepared by the following method: (1) adding chloroplatinic acid solution to a pretreated carbon support, controlling the pH range to 9.5-10.0, and reacting to prepare a platinum-carbon catalyst; (2) weighing an active metal precursor according to a certain proportion, dissolving the active metal precursor in water and mixing it, then adding it dropwise to the above-mentioned platinum-carbon catalyst, adjusting the pH with Na2CO3 aqueous solution, drying, and then heating and reducing in a furnace with H2 atmosphere to obtain a bimetallic doped platinum-carbon catalyst; wherein the active metal is selected from any two of Al, Cu or Zn, and the prepared bimetallic doped platinum-carbon catalyst is Al-Zn-Pt / C, Cu-Zn-Pt / C or Al-Cu-Pt / C.

[0020] Furthermore:

[0021] In step (1):

[0022] The carbon support pretreatment process is as follows: the carbon black support is dispersed in acetone and stirred to remove oil. After washing and drying, it is calcined in nitrogen at 200-400℃ for 2-4 hours. A mixed solution of nitric acid and hydrogen peroxide is added, and the mixture is stirred and refluxed at 60-100℃ for 6-10 hours. The carbon support is then washed and dried with deionized water to obtain the pretreated carbon support.

[0023] In step (2), the active metal precursor is selected from any two of aluminum triacetylacetonate, copper glycinate, or zinc gluconate.

[0024] Preferably, better catalytic effects can be obtained when the content of the doped active metal is within the following range.

[0025] The doped metal Al has an Al to Pt mass ratio of 7%-22%;

[0026] The doped metal Zn has a Zn to Pt mass ratio of 9%-22%;

[0027] The doped metal Cu has a Cu to Pt mass ratio of 8%-11%.

[0028] In step (2), the heating reduction temperature is 200-700℃ and the time is 2-4h.

[0029] In step (2), the pH range is adjusted to 9.5-10.0 using Na2CO3 aqueous solution.

[0030] The bimetallic doped platinum-carbon catalyst prepared by this invention uses an active metal selected from Al, Cu, or Zn, which is inexpensive. By controlling the doping ratio of the metal precursor, a bimetallic synergistic catalyst is formed, exhibiting excellent catalytic performance. Experiments have shown that this invention solves the problem of metal particle agglomeration in platinum-carbon catalysts under long-term high-pressure hydrogenation reaction conditions, which leads to a decrease in catalyst activity. The catalyst exhibits high stability and can be reused dozens of times.

[0031] The following accompanying drawings and embodiments will enable those skilled in the art to more fully understand the present invention, but do not limit the invention in any way. Attached Figure Description

[0032] Figure 1 The image shows the X-ray diffraction (XRD) pattern of the bimetallic doped Al-Zn-Pt / C catalyst prepared in Example 2 of this invention.

[0033] Figure 2 The image shows the X-ray photoelectron spectroscopy (XPS) spectrum of the bimetallic doped Al-Zn-Pt / C catalyst prepared in Example 2 of this invention.

[0034] Figure 3 This is a scanning electron microscope (SEM) image of the bimetallic doped Al-Zn-Pt / C catalyst prepared in Example 2 of the present invention. Detailed Implementation

[0035] The following examples help to further understand the present invention, but the scope of the present invention is not limited thereto.

[0036] Example 1: Preparation of Pt / C catalyst

[0037] (1) Carbon support pretreatment:

[0038] The carbon black support was dispersed in acetone and stirred for 8 hours to remove oil. After washing and drying, it was calcined at 300°C for 3 hours under nitrogen. A mixed solution of 10 wt% nitric acid and 30 wt% hydrogen peroxide was added, and the mixture was stirred and refluxed at 80°C for 8 hours. After washing with deionized water and drying at 100°C, the pretreated carbon support was obtained.

[0039] (2) Preparation of Pt / C catalyst

[0040] 10.0 g of maleic acid complexing agent was dissolved in ethylene glycol, water, acetone, and other solvents, and sonicated for 0.5 h until dissolved. Then, 30 mL of 0.2 mol / L chloroplatinic acid solution was added dropwise, and the mixture was stirred and sonicated until homogeneous. This solution was then slowly added dropwise to 50.0 g of pretreated activated carbon support, and Na₂CO₃ solution was added to ensure the pH of the mixture remained stable at 10.0. The mixture was sonicated for 20 min. The reaction solution was poured into a reaction vessel, and after microwave reaction was completed and the mixture cooled to room temperature, nitric acid solution was added dropwise to adjust the pH to less than 4, and the mixture was sonicated for another 15 min. Finally, the product was filtered with deionized water, washed clean, and vacuum dried overnight to obtain the Pt / C catalyst.

[0041] The prepared Pt / C catalyst was used to prepare the following bimetallic doped platinum-carbon catalyst.

[0042] Example 2: Preparation of bimetallic doped platinum-carbon catalyst A

[0043] Weigh 0.5 g of aluminum triacetylacetonate and 0.3 g of zinc gluconate into a beaker, add 30 mL of deionized water, and stir thoroughly with a magnetic stirrer to prepare a solution with a doped aluminum and zinc mass ratio of 1:1. Add this solution dropwise to 1.0 g of Pt / C catalyst, and adjust the pH to 10.0 with 0.1 mol / L Na₂CO₃ aqueous solution, measuring the pH in real time with a pH meter. After the addition is complete, stir at 700 rpm for 3 h, then let stand for 5 h, filter, and wash thoroughly to obtain a solid sample. Dry the sample under vacuum at 90 °C for 5 h, and then grind it into powder. Place the sample in a U-shaped reactor and reduce it in H₂ at 500 °C for 3 h to obtain catalyst Al-Zn-Pt / C, labeled as catalyst A.

[0044] The Al-Zn-Pt / C catalyst prepared in Example 2 was characterized as follows:

[0045] The catalyst was characterized and analyzed by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), and inductively coupled plasma atomic emission spectrometry (ICP-AES). Figure 1 The crystal properties of the catalyst were studied by X-ray diffraction. Since the prepared bimetallic doped catalyst Al-Zn-Pt / C is amorphous, only carbon diffraction peaks appeared in the figure, and no diffraction peaks of Pt and other metals appeared. Figure 2 The X-ray photoelectron spectroscopy (XPS) spectrum shows the response peak of Pt, but there is no response peak due to the low content of the doped metal. Figure 3The scanning electron microscope (SEM) images show the surface morphology of the catalyst at different magnifications. It can be seen that the prepared catalyst exhibits irregular particles of a few micrometers in size. The inductively coupled plasma atomic emission spectrometry (ICP-AES) test results in Table 1 show that Al and Zn active metals are well incorporated into the supported catalyst precursor, and a bimetallic doped catalyst Al-Zn-Pt / C with high catalytic performance has been successfully prepared.

[0046] Example 3: Preparation of bimetallic doped platinum-carbon catalyst B

[0047] Weigh 0.25 g of aluminum triacetylacetonate and 0.3 g of zinc gluconate into a beaker, add 30 mL of deionized water, and stir thoroughly with a magnetic stirrer to prepare a solution with a doped aluminum to zinc mass ratio of 1:2. Add this solution dropwise to 1.0 g of Pt / C catalyst, and adjust the pH to 10.0 with 0.1 mol / L Na₂CO₃ aqueous solution, measuring the pH in real time with a pH meter. After the addition is complete, stir at 700 rpm for 3 h, then let stand for 5 h, filter, and wash thoroughly to obtain a solid sample. Dry the sample under vacuum at 90 °C for 5 h, and then grind it into powder. Place the sample in a U-shaped reactor and reduce it in H₂ at 500 °C for 3 h to obtain catalyst Al-Zn-Pt / C, labeled as catalyst B.

[0048] Example 4: Preparation of bimetallic doped platinum-carbon catalyst C

[0049] Weigh 0.5 g of aluminum triacetylacetonate and 0.15 g of zinc gluconate into a beaker, add 30 mL of deionized water, and stir thoroughly with a magnetic stirrer to prepare a solution with a doped aluminum to zinc mass ratio of 2:1. Add this solution dropwise to 1.0 g of Pt / C catalyst, and adjust the pH to 10.0 with 0.1 mol / L Na₂CO₃ aqueous solution, measuring the pH in real time with a pH meter. After the addition is complete, stir at 700 rpm for 3 h, then let stand for 5 h, filter, and wash thoroughly to obtain a solid sample. Dry the sample under vacuum at 90 °C for 5 h, and then grind it into powder. Place the sample in a U-shaped reactor and reduce it in H₂ at 500 °C for 3 h to obtain catalyst Al-Zn-Pt / C, labeled as catalyst C.

[0050] Example 5: Preparation of bimetallic doped platinum-carbon catalyst D

[0051] Weigh 0.15 g of copper glycinate and 0.3 g of zinc gluconate into a beaker, add 30 mL of deionized water, and stir thoroughly with a magnetic stirrer to prepare a solution with a copper-zinc doping ratio of 1:1. Add this solution dropwise to 1.0 g of Pt / C catalyst, adjust the pH to 10.0 with 0.1 mol / L Na₂CO₃ aqueous solution, and measure the pH in real time with a pH meter. After the addition is complete, stir at 700 rpm for 3 h, then let stand for 5 h, filter, and wash thoroughly to obtain a solid sample. Dry the sample under vacuum at 90 °C for 5 h, and then grind it into powder. Place the sample in a U-shaped reactor and reduce it in H₂ at 500 °C for 3 h to obtain catalyst Cu-Zn-Pt / C, labeled as catalyst D.

[0052] Example 6: Preparation of bimetallic doped platinum-carbon catalyst E

[0053] Weigh 0.5 g of aluminum triacetylacetonate and 0.15 g of copper glycine into a beaker, add 30 mL of deionized water, and stir thoroughly with a magnetic stirrer to prepare a solution with a doped aluminum and copper mass ratio of 1:1. Add this solution dropwise to 1.0 g of Pt / C catalyst, and adjust the pH to 10.0 with 0.1 mol / L Na₂CO₃ aqueous solution, measuring the pH in real time with a pH meter. After the addition is complete, stir at 700 rpm for 3 h, then let stand for 5 h, filter, and wash thoroughly to obtain a solid sample. Dry the sample under vacuum at 90 °C for 5 h, and then grind it into powder. Place the sample in a U-shaped reactor and reduce it in H₂ at 500 °C for 3 h to obtain catalyst Al-Cu-Pt / C, labeled as catalyst E.

[0054] The bimetallic doped platinum-carbon catalysts prepared in Examples 2-6 were tested by inductively coupled plasma atomic emission spectrometry (ICP-AES), and the results are shown in Table 1.

[0055] Table 1. ICP test results of five different catalyst types

[0056] Serial Number catalyst Pt content / % Al content / % Zn content / % Cu content / % Example 2 A 1.67 0.166 0.182 0 Example 3 B 1.64 0.162 0.334 0 Example 4 C 1.70 0.365 0.176 0 Example 5 D 1.68 0.157 0 0.146 Example 6 E 1.65 0 0.162 0.174

[0057] In the table: the content of each element is a mass percentage.

[0058] Example 7: Preparation of tris(4-nitrophenyl)thiophosphate:

[0059] Add p-nitrophenol (13.55 g, 0.1 mol) and sodium hydroxide solution (6.0 g dissolved in 50 mL water) to a 250 mL round-bottom flask. Add tetrabutylammonium bromide (1.0 g) and 50 mL dichloromethane to this solution and stir rapidly. Slowly add thiophosphoric chloride (5.50 g) dropwise through an addition funnel. Stir the solution at room temperature for 2 h, then pour the contents of the stirred flask into a separatory funnel, separate the organic phase with 100 mL dichloromethane, and extract the aqueous layer. Wash the combined organic extract three times with saturated brine and dry with anhydrous magnesium sulfate. Filter and concentrate the solution, then aspirate into 100 mL of hot n-heptane and stir for 0.5 h. Filter to obtain a white solid, which is tris(4-nitrophenyl)thiophosphate, in 84% yield.

[0060] Example 8: Preparation of tris(4-aminophenyl)thiophosphate

[0061] 1.0 g of the prepared tris(4-nitrophenyl)thiophosphate, 0.05 g of catalyst, and 15 mL of ethanol were placed in a high-pressure reactor, which was then filled with hydrogen gas at a pressure of 2.5 MPa. The reaction was carried out at 70 °C for 1.5 h. After cooling to room temperature, the sample was taken, the catalyst was removed by centrifugation, filtered, and the yield was determined by nuclear magnetic resonance after rotary evaporation.

[0062] According to the above synthesis method, the catalysts were the bimetallic doped platinum-carbon catalysts prepared in Examples 2 to 6, and the yields are shown in Table 2.

[0063] Table 2. Comparison of catalytic performance of five different catalyst types

[0064]

[0065]

[0066] Combining Tables 1 and 2, we can see that:

[0067] 1. By changing the type and ratio of doped metals, the catalytic performance of bimetallic doped platinum-carbon catalysts varies significantly.

[0068] 2. The catalytic effect is best when the doped metal is 0.166% Al and 0.182% Zn.

[0069] Example 9: Catalyst Reuse

[0070] 1.0 g of the prepared tris(4-nitrophenyl)thiophosphate, 0.05 g of catalyst A, and 15 mL of ethanol were placed in a high-pressure reactor, which was then filled with hydrogen gas at a pressure of 2.5 MPa. The reaction was carried out at 70 °C for 1.5 h. After cooling to room temperature, a sample was taken, the catalyst was removed by centrifugation, and the mixture was filtered. The yield was determined by NMR. The catalyst was washed with 0.5 M hydrochloric acid and sodium hydroxide, followed by washing with deionized water, ethanol, and acetone in sequence, and the reaction was repeated to investigate the reusability of the catalyst. The results are shown in the table below.

[0071] Table 3. Catalyst Reuse Performance

[0072]

[0073] As shown in Table 3, the catalyst still exhibits high activity after being reused 10 times. This indicates that the Al-Zn-Pt / C catalyst has good reusability.

[0074] Comparative Example

[0075] According to the synthesis method of Example 8, the catalytic performance of catalyst A prepared in Example 1 of this invention was compared with that of existing catalysts, and the results are shown in Table 4. Among them, catalyst Al-Zn-Pt / C was prepared by the method of Example 1, and catalysts Pt / C and Ru / Al2O3 were commercially available catalysts. The experimental data for catalyst Raney-Ni came from the literature "Improving of processing conditions for preparation of tris(4-aminophenyl)thiophosphate by catalytic hydrogenation". As can be seen from the table, under the same reaction conditions, the bimetallic doped catalyst Al-Zn-Ru / C exhibits superior catalytic performance compared to other catalysts.

[0076] Table 4. Comparison of the catalytic effects of different catalysts on the reaction of tris(4-nitrophenyl)thiophosphate.

[0077]

Claims

1. A method of synthesis of tris(4-aminophenyl)phosphorothioate, characterized by, The method comprises the following steps: Put tris(4-nitrophenyl) phosphorothioate, a catalyst and a solvent into a high-pressure reactor, fill hydrogen gas with a pressure of 1.0-2.5 MPa, and react at 50-70 ℃ for 1-2 h, then take samples after the temperature is lowered to room temperature, centrifuge to remove the catalyst, and obtain the product tris(4-aminophenyl) phosphorothioate; the catalyst is a bimetallic doped platinum carbon supported catalyst, and the active metals doped are any two of Al, Cu or Zn.

2. A process for the synthesis of tris(4-aminophenyl)phosphorothioate according to claim 1, characterized by: The catalyst is added in an amount of 2-5% of the mass of the raw material.

3. A process for the synthesis of tris(4-aminophenyl)phosphorothioate according to claim 1 or 2, characterized in that: The bimetallic doped platinum carbon supported catalyst is prepared by the following method: add chloroplatinic acid solution to a pretreated carbon carrier, and react to prepare a platinum carbon catalyst; weigh active metal precursors according to a proportion, dissolve and mix the active metal precursors in water, then drop them into the platinum carbon catalyst, adjust the pH with a Na2CO3 aqueous solution, dry, then heat and reduce in a H2 atmosphere furnace, and obtain the bimetallic doped platinum carbon catalyst.

4. A process for the synthesis of tris (4-aminophenyl) phosphorothioate according to claim 1, characterized by: The centrifuged catalyst is washed with hydrochloric acid and sodium hydroxide, and then washed with deionized water, ethanol and acetone in sequence, and then reused for catalytic reaction.

5. A process for the synthesis of tris (4-aminophenyl) phosphorothioate according to claim 1, characterized by: The solvent is methanol, ethanol, n-butanol, t-butanol, n-octanol, ethylene glycol dimethyl ether, isopropyl benzene or xylene.

6. A process for the synthesis of tris(4-aminophenyl)phosphorothioate according to claim 1, characterized by: The solvent is ethanol, the reaction pressure is 2.5 MPa, the reaction temperature is 70 ℃, and the reaction time is 1.5 h.

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