Method for preparing triglycidyl isocyanurate by electrocatalytic olefin epoxidation

Abstract

The invention discloses a method for preparing triglycidyl isocyanurate through electro-catalysis olefin epoxidation. According to the method, triallyl isocyanurate serves as a raw material, and the triglycidyl isocyanurate is prepared through electro-catalysis olefin epoxidation. According to the method disclosed by the invention, the triglycidyl isocyanurate is obtained by adopting a method of anodizing under an electro-catalysis condition and taking water as an oxygen source in the oxidation process, so that the use of an additional oxidizing agent is avoided, and the defects that the additional oxidizing agent is needed, the production raw material cost is high, the product yield is low and the like in the method in the prior art are overcome.

Description

Technical Field

[0001] This invention relates to the field of photoinitiator preparation technology, specifically to a method for preparing triglycidyl isocyanurate by electrocatalytic olefin epoxidation. Background Technology

[0002] Triglycidyl isocyanate (TGIC), also known as 1,3,5-Triglycidyl isocyanurate, is commonly used as a crosslinking curing agent in coatings made from polyester or acrylic resins. Its reactive epoxy groups can crosslink with carboxyl groups in acid anhydrides and phenolic resins, forming highly crosslinked polymers that are insoluble. Compared to other epoxy resin curing agents, TGIC has advantages such as small molecular weight, fast curing speed, high epoxy value, and excellent weather resistance and chemical stability. TGIC can also be used as an additive in halogenated flame retardants to delay their decomposition.

[0003]

[0004] Currently, the main industrial synthesis methods for TGIC include: isocyanuric acid-epoxychloropropane method, trichloroisocyanuric acid-epoxychloropropane method, and isocyanate-epoxychloropropane method. The most widely used industrial synthesis method both domestically and internationally is the isocyanuric acid-epoxychloropropane method.

[0005] The isocyanuric acid-epoxychloropropane synthesis method uses a certain amount of isocyanuric acid and an excess of epichlorohydrin as the main raw materials. The catalyst is generally a quaternary ammonium salt phase transfer catalyst. This production method is also called the one-step method. In the one-step method, the amount of epichlorohydrin added is too large, the reaction time is long, the yield per batch is low, and the yield is low (Die Angewandte MakromolekulareChemie:Applied Macromolecular Chemistry and Physics,1995,228(1):25-40).

[0006] Adding a ring-closing reaction to the one-step process creates the two-step process, as shown in the diagram. This two-step process is currently the most widely used method for producing TGIC worldwide. However, this process also suffers from the drawback of adding excess epichlorohydrin. Furthermore, the yield is low during the ring-closing reaction stage with the addition of NaOH solution, and chlorine remains in the incompletely ring-closed molecules, resulting in chlorine residue in the product and affecting its performance. Additionally, this process generates a large amount of chlorine-containing wastewater.

[0007]

[0008] The cyanochloro-epoxychloropropane synthesis method uses cyanochloro and epichlorohydrin as the main raw materials. In this synthesis method, the price of cyanochloro is twice that of isocyanuric acid, and it is not as economical or technical as the isocyanuric acid-epoxychloropropane synthesis method.

[0009] The isocyanate-epoxychloropropane synthesis method uses alkali metal isocyanates and epichlorohydrin as main raw materials to prepare TGIC in a one-pot process through substitution condensation reaction under the action of a catalyst. This synthesis method also has the problem of chlorine residue in the product and generates a large amount of chlorine-containing waste liquid (CN201611157829.8).

[0010] The triallyl isocyanurate-hydrogen peroxide synthesis method uses triallyl isocyanurate (TAIC) as a raw material to prepare TGIC, thus avoiding the use of ECH at the source. The structural formula of TAIC is shown in the figure below.

[0011]

[0012] TAIC and TGIC have similar chemical configurations, differing only in the terminal group distribution. TGIC can be prepared by converting the three carbon-carbon double bonds of TAIC into three epoxy bonds. The oxidation of carbon-carbon double bonds to epoxy bonds can be further divided into the following three methods:

[0013] (1) Hydrogen peroxide-nitrile epoxidation method: In the hydrogen peroxide-nitrile epoxidation system, under alkaline conditions, H2O2 reacts with nitriles to generate peroxide imine, which transfers active oxygen to TAIC, epoxidizing TAIC to TGIC. Peroxide imine loses active oxygen and is converted into amide, as shown in the figure below.

[0014]

[0015] This reaction system simultaneously involves the epoxidation of TAIC to TGIC and a competing side reaction where nitrile reacts directly with hydrogen peroxide via the Raziszewski reaction to form amides. The feed ratio of TAIC to benzonitrile in this process is 1:3, and the reaction produces a large amount of benzamide. Because benzamide and TGIC have similar polarities, multiple crystallization processes are required to separate these two substances, increasing production costs.

[0016] (2) Hydrogen peroxide-phosphotungstic acid epoxidation method: using phosphotungstic acid (PWA) as a catalyst, TAIC is epoxidized to prepare TGIC (The Journal of Organic Chemistry, 1983, 48(21): 3831-3833). As shown in the figure below, in the reaction system, H2O2 needs to be added in excess. At the end of the reaction, some H2O2 and phosphotungstic acid still form a composite catalyst that cannot be separated. After extraction and evaporation, the product and the catalyst are still difficult to separate, and the catalyst is difficult to recycle.

[0017]

[0018] (3) Hydrogen peroxide-inorganic manganese salt epoxidation method: Inorganic manganese salt (MnSO4 to MnCO3 mass ratio 1:1) is used as catalyst, and H2O2 is used as oxygen source to epoxidize TAIC to prepare TGIC. The utilization rate of H2O2 is 15%, and the selectivity of TGIC is 69%. This preparation method requires a large amount of buffer solution, and the catalyst is difficult to recycle (Applied Chemistry, 2008, 25(9):1090-1094).

[0019] In summary, although various synthetic methods have been developed for TGIC, they suffer from problems such as high cost, significant pollution, and chlorine residue. Therefore, it is essential to develop a low-cost, clean TGIC production process and improve the key equipment for its industrial production. Summary of the Invention

[0020] This invention discloses a method for preparing triglycidyl isocyanurate by electrocatalytic epoxidation of olefins. The method uses triallyl isocyanurate as a raw material and prepares triglycidyl isocyanurate through electrocatalytic epoxidation of olefins. The method of this invention employs anodic oxidation under electrocatalytic conditions and water as an oxygen source to obtain triglycidyl isocyanurate during the oxidation process, avoiding the use of external oxidants and overcoming the disadvantages of existing methods, such as the need for external oxidants, high raw material costs, and low product yield.

[0021] The use of H2O as an oxygen source to drive the oxidation of olefins has shown great potential. In triallyl isocyanurate, the olefin reacts with reactive oxygen species generated during the anodic electrolytic dehydrogenation of H2O, resulting in direct epoxidation. Utilizing the pre-existing oxygen atoms on weakly bonded surfaces (such as Ag, Pt, and some transition metal oxides), epoxidation is a readily occurring reaction at room temperature. By applying a certain potential at room temperature and performing H2O electrolysis on a weakly bonded anodic surface to generate surface-adsorbed oxygen atoms, it is possible to achieve the direct oxidation of olefins to epoxidized products using H2O without relying on O2 as a starting material.

[0022] To achieve the above-mentioned objectives, this invention provides a method for the electrocatalytic preparation of triglycidyl isocyanurate, comprising the following steps:

[0023] In a non-segmented electrolytic cell equipped with cathode and anode electrodes, under constant voltage electrolysis conditions, water is used as the oxygen source, and in the presence of an electrolyte and an acid, the compound shown in formula (I) is oxidized and epoxidized under electrocatalytic conditions to obtain triglycidyl isocyanurate shown in formula (II).

[0024]

[0025] According to the method for electrocatalytic preparation of triglycidyl isocyanurate of the present invention, preferably, the electrolyte is one or more of lithium perchlorate, tetrabutylammonium bromide, tetrabutylammonium iodide, and tetrabutylammonium hexafluorophosphate.

[0026] According to the method for electrocatalytic preparation of triglycidyl isocyanurate of the present invention, the anode is one of platinum black electrode, platinum electrode, PtO2 electrode, graphite electrode, glassy carbon mesh (RVC) electrode, etc.

[0027] According to the method for electrocatalytic preparation of triglycidyl isocyanurate of the present invention, the cathode is one of a platinum black electrode, a graphite electrode, a platinum electrode, a nickel electrode, a silver electrode, etc.

[0028] According to the method for electrocatalytic preparation of triglycidyl isocyanurate of the present invention, the voltage is 1.0 to 3.0 V.

[0029] According to the method for electrocatalytic preparation of triglycidyl isocyanurate of the present invention, the electrolyte is one of lithium perchlorate, tetrabutylammonium bromide, tetrabutylammonium iodide, tetrabutylammonium hexafluorophosphate, etc.

[0030] According to the present invention, the method for electrocatalytic preparation of triglycidyl isocyanurate is one of phosphoric acid, trifluoroacetic acid, acetic acid, sulfuric acid, etc.

[0031] According to the method for electrocatalytic preparation of triglycidyl isocyanurate of the present invention, the solvent is trifluoroethanol or hexafluoroisopropanol.

[0032] The beneficial effects of this invention are:

[0033] This invention provides a method for preparing triglycidyl isocyanurate by electrocatalytic epoxidation of olefins. The method of this invention uses anodic oxidation under electrocatalytic conditions and water as an oxygen source to obtain the oxidized epoxidation product, avoiding the use of an external oxidant; it overcomes the disadvantages of existing methods, such as the need for an external oxidant, high raw material costs, and low product yield. Attached Figure Description

[0034] Figure 1 This is the 1H NMR spectrum of Example 1 in this invention. Detailed Implementation

[0035] To make the objectives, technical solutions, and advantages of the present invention clearer, the embodiments of the present invention will be further described in detail below with reference to specific examples and the accompanying drawings.

[0036] Example 1

[0037] This embodiment of a method for the electrocatalytic preparation of triglycidyl isocyanurate includes the following steps:

[0038] In a 100 mL reaction flask, triallyl isocyanurate (0.508 g, 2.0 mmol, 1.0 equivalent), lithium perchlorate (0.424 g, 4 mmol, 2.0 equivalent), phosphoric acid (0.118 g, 1.0 equivalent, 83% purity), and 2,2,2-trifluoroethanol aqueous solution (30 mL, 98% by mass) were added. A flask cap with an anode (platinum black electrode) and a cathode (platinum electrode) was inserted into the mixture, and the reaction was carried out at a constant voltage of 1.0 V for 5 h at room temperature. After electrolysis, the anode electrode was rinsed with dichloromethane, the solvent was removed under vacuum, the residue was washed with diethyl ether, and the residue was dried under vacuum to obtain triglycidyl isocyanurate, a white solid, 0.491 g, with a yield of 91%. Melting point: 95-96 °C.

[0039] 1H NMR spectrum: 1 H NMR (400MHz, CDCl3): δ4.19 (dd, J=5.6Hz, J=14.0Hz, 1H), 4.05 (d, dd, J=5.6Hz, J=14. 0Hz, 1H), 3.29-3.25 (m, 1H), 2.84 (t, J = 4.4Hz, 1H), 2.70 (dd, J = 2.8Hz, J = 4.8Hz, 1H).

[0040] High-resolution mass spectrometry: HRMS (ESI-TOF) (m / z): calcd for C 12 H 16 N3O6 + ([M+H)) + ),298.1034,found,298.1040.

[0041] Example 2

[0042] In a 100 mL reaction flask, triallyl isocyanurate (0.508 g, 2.0 mmol, 1.0 equivalent), tetrabutylammonium bromide (0.212 g, 2.0 mmol, 1.0 equivalent), trifluoroacetic acid (0.172 g, 1.5 equivalent, 99% purity), and 2,2,2-trifluoroethanol aqueous solution (40 mL, 98% by mass) were added. A flask cap with an anode (PtO2 electrode) and a cathode (graphite electrode) was inserted into the mixture, and the reaction was carried out at a constant voltage of 2.0 V for 5 h at room temperature. After electrolysis, the anode electrode was rinsed with dichloromethane, the solvent was removed under vacuum, the residue was washed with diethyl ether, and the residue was dried under vacuum to obtain 0.459 g of triglycidyl isocyanurate, a pale yellow solid, with a yield of 85%.

[0043] Example 3

[0044] In a 100 mL reaction flask, triallyl isocyanurate (0.508 g, 2.0 mmol, 1.0 equivalent), tetrabutylammonium hexafluorophosphate (0.318 g, 3.0 mmol, 1.5 equivalent), acetic acid (0.12 g, 2.0 equivalent, 99% purity), and hexafluoroisopropanol aqueous solution (45 mL, 98% by mass) were added. A cap with an anode (platinum electrode) and a cathode (nickel electrode) was inserted into the mixture, and the reaction was carried out at a constant voltage of 3.0 V for 5 h at room temperature. After electrolysis, the anode electrode was rinsed with dichloromethane, the solvent was removed under vacuum, the residue was washed with diethyl ether, and the residue was dried under vacuum to obtain 0.437 g of triglycidyl isocyanurate, a pale yellow solid, with a yield of 81%.

[0045] Example 4

[0046] In a 100 mL reaction flask, triallyl isocyanurate (0.508 g, 2.0 mmol, 1.0 equivalent), tetrabutylammonium hexafluorophosphate (0.424 g, 4.0 mmol, 2.0 equivalent), sulfuric acid (0.098 g, 1.0 equivalent, 98% purity), and hexafluoroisopropanol aqueous solution (30 mL, 98% by mass) were added. A cap with an anode (graphite electrode) and a cathode (silver electrode) was inserted into the mixture, and the reaction was carried out at a constant voltage of 2.0 V for 5 h at room temperature. After electrolysis, the anode electrode was rinsed with dichloromethane, the solvent was removed under vacuum, the residue was washed with diethyl ether, and the residue was dried under vacuum to obtain 0.469 g of triglycidyl isocyanurate, a light yellow solid, with a yield of 87%.

[0047] Example 5

[0048] In a 100 mL reaction flask, triallyl isocyanurate (0.508 g, 2.0 mmol, 1.0 equivalent), tetrabutylammonium hexafluorophosphate (0.424 g, 4.0 mmol, 2.0 equivalent), phosphoric acid (0.354 g, 3.0 equivalent, 83% purity), and 2,2,2-trifluoroethanol aqueous solution (50 mL, 98% by mass) were added. A flask cap with an anode (RVC electrode) and a cathode (platinum black electrode) was inserted into the mixture, and the reaction was carried out at a constant voltage of 1.5 V for 5 h at room temperature. After electrolysis, the anode electrode was rinsed with dichloromethane, the solvent was removed under vacuum, the residue was washed with diethyl ether, and the residue was dried under vacuum to obtain 0.432 g of triglycidyl isocyanurate, a pale yellow solid, with a yield of 80%.

[0049] Comparative example:

[0050] Triallyl isocyanurate, H2O2, and an inorganic manganese salt catalyst (a mixture of MnSO4 and MnCO3 in a mass ratio of 1:1) were added at a molar ratio of 1:15:0.1. A stoichiometric amount of triallyl isocyanurate was dissolved in an appropriate amount of t-BuOH, and then poured into a three-necked flask equipped with a thermometer. The temperature was controlled at 25°C. While stirring, an equilibrium solution of H2O2 and NH4HCO3 in ethanol was added dropwise. The reaction time was 25 h. Finally, the mixture was extracted with CH2Cl2, and the oil layer was collected, dried, and the product triglycidyl isocyanurate was obtained, with a yield <70% (Applied Chemistry, 2008, 25(9):1090-1094).

[0051] Comparative analysis shows that, using the method of this invention, the yield is increased from <70% to over 80%, and even reaches 91%, without the use of an external oxidant, demonstrating a significant improvement in yield. Therefore, this invention overcomes the shortcomings of existing methods, such as the need for an external oxidant and low product yield, and possesses significant advantages.

[0052] Those skilled in the art should understand that the discussion of any of the above embodiments is merely exemplary and is not intended to imply that the scope of the invention (including the claims) is limited to these examples. Within the framework of the invention, technical features of the above embodiments or different embodiments can be combined, and many other variations of the different aspects of the invention as described above exist, which are not provided in the details for the sake of brevity. Therefore, any omissions, modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the invention should be included within the protection scope of the invention.

Claims

1. A method for preparing triglycidyl isocyanurate by electrocatalytic epoxidation of olefins, characterized in that, The method includes: in a non-segmented electrolytic cell equipped with cathode and anode electrodes, under constant voltage electrolysis conditions, water is used as an oxygen source, and in a solvent, in the presence of an electrolyte, and in the presence of an acid, the compound shown in formula (I) is oxidized and epoxidized under electrocatalytic conditions to obtain triglycidyl isocyanurate shown in formula (II).

2. The method according to claim 1, characterized in that, The anode is one of a platinum black electrode, a platinum electrode, a PtO2 electrode, a graphite electrode, or an RVC electrode.

3. The method according to claim 1, characterized in that, The cathode is one of a platinum black electrode, a graphite electrode, a platinum electrode, a nickel electrode, or a silver electrode.

4. The method according to claim 1, characterized in that, The voltage is 1.0 to 3.0V.

5. The method according to claim 1, characterized in that, The electrolyte is one of lithium perchlorate, tetrabutylammonium bromide, tetrabutylammonium iodide, or tetrabutylammonium hexafluorophosphate.

6. The method according to claim 1, characterized in that, The acid is one of phosphoric acid, trifluoroacetic acid, acetic acid, or sulfuric acid.

7. The method according to claim 1, characterized in that, The molar ratio of the compound, electrolyte, and acid shown in formula (I) is 1:1 to 2:1 to 3.

8. The method according to claim 1, characterized in that, The solvent is trifluoroethanol or hexafluoroisopropanol, and the amount of solvent used is such that the molar concentration of formula (I) is 0.04 to 0.1 mmol / mL.

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