A method for preparing hexachlorocyclotriphosphazene by reaction in an organic phase

Abstract

The invention provides a method for preparing hexachlorocyclotriphosphazene by reaction in an organic phase, and relates to the field of hexachlorocyclotriphosphazene. The method for preparing hexachlorocyclotriphosphazene by reaction in an organic phase consists of the following steps: preparing pyridine hydrochloride, preparing choline chloride / glycerol deep eutectic solvent, synthesizing hexachlorocyclotriphosphazene, and post-processing. The method for preparing hexachlorocyclotriphosphazene by reaction in an organic phase of the invention can effectively solve the problems of the existing hexachlorocyclotriphosphazene preparation method that the reaction process is difficult to control, the reaction time is long, the reaction efficiency is low, and the side reaction is easy to generate a large number of by-products, simplify the post-processing, improve the yield and purity of the prepared hexachlorocyclotriphosphazene, and reduce the generation of three wastes in the preparation process.

Description

Technical Field

[0001] The invention relates to the field of hexachlorocyclotriphosphazene, in particular to a method for preparing hexachlorocyclotriphosphazene by reaction in an organic phase. Background Art

[0002] Hexachlorocyclotriphosphazene is the most basic compound in phosphazene chemistry and the most representative intermediate. Hexachlorocyclotriphosphazene is a six-membered ring structure with P and N as the skeleton. Because it contains high content of P and N elements, and its molecular structure is N=P- with alternating single and double bonds, and each phosphorus atom has two chlorine atoms that can be replaced, etc., it has unique physical and chemical properties. Therefore, the phosphazene materials synthesized with hexachlorocyclotriphosphazene as an intermediate can be endowed with many excellent and unique properties. Taking the phosphazene flame retardant synthesized from hexachlorocyclotriphosphazene as an example, it has good thermal stability and flame retardant properties. As a halogen-free flame retardant that is the focus of future development, cyclophosphazene flame retardants are widely used in fire-retardant materials, self-extinguishing materials and other fields.

[0003] Due to the long reaction time, complicated refining process and low yield of phosphazene synthesis, phosphazene has not been produced on a large scale in China. In recent years, the research on the synthesis of hexachlorocyclotriphosphazene has mainly focused on the improvement and optimization of raw materials, catalysts and synthesis processes, and some corresponding progress has been made.

[0004] The most commonly used method for synthesizing hexachlorocyclotriphosphazene is to use PCl5 and NH4Cl as raw materials, and to heat and reflux in an inert solvent such as chlorobenzene or tetrachloroethane to synthesize it; the yield of the hexachlorocyclotriphosphazene prepared by it is limited, and the addition of divalent metal chloride and pyridine can effectively increase the yield of the reactants and shorten the reaction time. In order to further increase its yield and shorten the reaction time, the preparation method commonly used in the prior art is to use PCl5 and NH4Cl as raw materials, chlorobenzene as solvent, pyridine or its derivatives as acid binding agent, divalent metal chloride as catalyst (common catalysts include MgCl2, ZnCl2, FeCl2, FeCl3, etc., and the molar amount of the catalyst is about 0.5% of the molar amount of PCl5), control the reflux temperature to 125-132°C, and perform reflux reaction. Although this method can effectively shorten the reaction time, its overall reaction time is still relatively long, and the yield of hexachlorocyclotriphosphazene can only reach 70-75%. The chemical equation for the synthesis of hexachlorocyclotriphosphazene from phosphorus pentachloride and ammonium chloride is as follows:

[0005] .

[0006] This process is a heterogeneous reaction, accompanied by the production of a variety of by-products. It is generally believed that hexachlorocyclotriphosphazene is produced from the intermediate [CI3P(NPCl2)2NPCI3] + CI -One molecule of PCl5 is cyclized and produced; and in its preparation, some catalysts will reduce the final yield of the reactants because the catalyst promotes the cross-linking reaction of the trimer and produces a macrocyclic byproduct. The chemical equation is as follows:

[0007] .

[0008] At the same time, the post-treatment process in the preparation of hexachlorocyclotriphosphazene is also extremely cumbersome, requiring the reaction liquid to be extracted or washed, then decolorized and distilled, and then repeatedly recrystallized using a non-polar solvent (such as n-heptane or n-hexane); the loss of hexachlorocyclotriphosphazene is difficult to avoid during the post-treatment process, which leads to a further reduction in the yield of hexachlorocyclotriphosphazene.

[0009] Further, other methods for preparing hexachlorocyclotriphosphazene in the prior art also include:

[0010] (1) Phosphorus trichloride, ammonium chloride, and chlorine synthesis method

[0011] Phosphorus trichloride, ammonium chloride and solvent chlorobenzene are added to the reactor, and then zinc chloride catalyst is added. When the temperature rises to 70-90°C, chlorine gas is introduced, and then the temperature is raised to reflux. The reflux reaction is carried out for 3-4 hours. The reactant is purified to obtain the hexachlorocyclotriphosphazene product. Although this synthesis process is relatively simple, the product yield is low (generally less than 60%) and has been basically eliminated.

[0012] (2) Phosphorus pentachloride and ammonia synthesis method

[0013] Phosphorus pentachloride and chlorobenzene are put into a reactor, and after the reactor is sealed, a small amount of dry hydrogen chloride gas is introduced to make the pressure in the reactor reach 98.07 kPa, and then ammonia is introduced for reaction, and the reaction temperature is controlled at 130 ° C. The reaction materials of this synthesis method are slightly changed. The ammonia introduced at the beginning of the reaction reacts with hydrogen chloride to generate ammonium chloride fine powder, and then reacts with phosphorus pentachloride. The yield of the product hexachlorocyclotriphosphazene is higher than that of the aforementioned ammonium chloride method. However, the disadvantage of this synthesis method is that the entire reaction process needs to be carried out under a certain pressure, the equipment requirements are high, and the reaction process is cumbersome to control.

[0014] (3) Phosphorus pentachloride and ammonium carbamate synthesis method

[0015] Sun De (Sun De, Li Ran, Zhang Long. Research on the synthesis of hexachlorocyclotriphosphazene from phosphorus pentachloride and ammonium carbamate [J]. Natural Gas Chemical Industry, 2009, (2): 48-50) et al. disclosed a method for synthesizing hexachlorocyclotriphosphazene by catalytic reaction of ammonium carbamate with phosphorus pentachloride in an inert organic solvent instead of ammonium chloride. Although the yield of the method is improved by using organic amine (ammonium carbamate) instead of ammonium chloride to react with phosphorus pentachloride, the price of organic amine is relatively high and it is not suitable for large-scale industrial production of hexachlorotriphosphazene.

[0016] It can be seen that the existing preparation method of hexachlorocyclotriphosphazene has the problems of difficult control of the reaction process, long reaction time, low reaction efficiency, and easy occurrence of side reactions to generate a large number of by-products, which further leads to cumbersome post-processing, low yield and low purity of the hexachlorocyclotriphosphazene, and a large amount of solid waste and waste liquid in the preparation process, which is difficult to handle and has high processing costs.

[0017] Chinese patent CN104558044A discloses a method for synthesizing hexachlorocyclotriphosphazene, wherein PCl5 and NH4Cl are reacted in a chlorobenzene solvent under the catalysis of a catalyst, and finally a crude hexachlorocyclotriphosphazene is obtained by filtration and reduced pressure distillation; the obtained crude hexachlorocyclotriphosphazene is then further dissolved in an organic solvent, and recrystallized to obtain a high-purity hexachlorocyclotriphosphazene. However, the reaction process of this method is not easy to control, and a large amount of linear phosphazenes will be produced if the reaction rate is too fast; the feed amount is small and the insulation time is long, and as the insulation reaction continues, the amount of by-product large cyclic phosphazenes increases; at the same time, there are also defects such as large amount of ammonium chloride and large amount of solid waste.

[0018] Chinese patent CN115819460A discloses a method for preparing hexachlorocyclotriphosphazene. First, chlorobenzene, composite metal chloride powder and pyridine are mixed and stirred, and hydrogen chloride is introduced until the solid dissolves to obtain an ionic liquid catalyst; then, under high temperature and nitrogen protection, phosphorus pentachloride chlorobenzene is added dropwise to chlorobenzene, ammonium chloride and the ionic liquid catalyst, and the hexachlorocyclotriphosphazene crude product chlorobenzene solution is obtained after the dripping and insulation reaction, and the hexachlorocyclotriphosphazene is recrystallized through a mixed solvent after post-treatment. Although this method can shorten the reaction time to 2-3h, the dripping time is long and the reaction cycle is too long; and the mixed solvent used in the recrystallization process is difficult to recycle; the amount of solid waste generated is relatively large, and post-treatment is difficult.

[0019] Chinese patent CN101602780A discloses a catalytic synthesis method of hexachlorocyclotriphosphazene, wherein quaternary ammonium salt and anhydrous metal chloride are added to a reactor, stirred at 80-120°C for 1-2h to obtain an ionic liquid; chlorobenzene, ammonium chloride and phosphorus pentachloride are then added to the reactor, stirred at 100-130°C for 1-5h to obtain a reaction mixture; the reaction mixture is subjected to liquid separation or / and filtration treatment to separate the ionic liquid from the chlorobenzene solution containing the reaction product, and then the chlorobenzene solution containing the reaction product is washed with water and subjected to reduced pressure distillation to obtain the hexachlorocyclotriphosphazene product. Similarly, this method has the problem that the reaction process is difficult to control, and the reaction rate is too fast, which will lead to the generation of a large amount of linear phosphazenes; therefore, the method has a high yield but a low product purity; and more wastewater is generated during the preparation process, which increases the difficulty of three waste treatments. Summary of the invention

[0020] In order to solve the technical problems existing in the prior art, the present invention provides a method for preparing hexachlorocyclotriphosphazene by reaction in an organic phase, which can effectively solve the problems existing in the prior art of preparing hexachlorocyclotriphosphazene, namely, the reaction process is difficult to control, the reaction time is long, the reaction efficiency is low, and a large amount of by-products are easily generated by side reactions, simplifies post-treatment, improves the yield and purity of the prepared hexachlorocyclotriphosphazene, and reduces the generation of three wastes in the preparation process.

[0021] In order to solve the above technical problems, the technical solution adopted by the present invention is as follows:

[0022] A method for preparing hexachlorocyclotriphosphazene by reaction in an organic phase, comprising the following steps: preparing pyridine hydrochloride, preparing choline chloride / glycerol deep eutectic solvent, synthesizing hexachlorocyclotriphosphazene, and post-processing;

[0023] The method for synthesizing hexachlorocyclotriphosphazene comprises: mixing pyridine hydrochloride and an extraction solvent, heating and azeotropically removing water; adding a metal chloride catalyst and a phase transfer catalyst, mixing evenly, dripping a phosphorus pentachloride solution, mixing evenly, and dripping an ammonium chloride solution in three batches; during the dripping of the first batch of ammonium chloride solution, heat-keeping reaction at 95-100° C.; during the dripping of the second batch of ammonium chloride solution, heat-keeping reaction at 125-130° C.; during the dripping of the third batch of ammonium chloride solution, heat-keeping reaction at 125-130° C.; after the heat-keeping reaction is completed, layering is performed to obtain an extraction solvent solution of hexachlorocyclotriphosphazene;

[0024] The ammonium chloride solution is a choline chloride / glycerol deep eutectic solvent in which ammonium chloride is dissolved;

[0025] The phosphorus pentachloride solution is an extraction solvent solution in which phosphorus pentachloride is dissolved;

[0026] The post-treatment method is as follows: the extraction solvent solution of the hexachlorocyclotriphosphazene is subjected to distillation to remove the extraction solvent, followed by extraction and decolorization; and then concentrated and crystallized to obtain the hexachlorocyclotriphosphazene.

[0027] Preferably, in the synthesized hexachlorocyclotriphosphazene, the molar ratio of phosphorus pentachloride to ammonium chloride is 1:1-1.34.

[0028] Preferably, the concentration of the phosphorus pentachloride solution is 25-35wt%;

[0029] The weight ratio of pyridine hydrochloride, extraction solvent and phosphorus pentachloride solution is 1:0.6-0.8:1-1.2;

[0030] The weight ratio of pyridine hydrochloride to the choline chloride / glycerol deep eutectic solvent in the ammonium chloride solution is 1:0.2-1.

[0031] Further, in the synthesis of hexachlorocyclotriphosphazene, the extraction solvent is one of the following: chlorobenzene, tetrachloroethane, xylene, N,N-dimethylformamide, 1,3-dimethyl-2-imidazolidinone;

[0032] The metal chloride catalyst is one or two of the following: magnesium chloride, zinc chloride, barium chloride, calcium chloride, iron chloride, aluminum chloride, nickel chloride;

[0033] The phase transfer catalyst is one of the following: tetrabutylammonium chloride, benzyltriethylammonium chloride TEBA, tetraphenylphosphonium chloride, benzyltriphenylphosphonium chloride.

[0034] Preferably, in the synthesized hexachlorocyclotriphosphazene, the weights of the first batch of ammonium chloride solution, the second batch of ammonium chloride solution, and the third batch of ammonium chloride solution are equal;

[0035] The amount of metal chloride catalyst added is 1-3% of the total weight of phosphorus pentachloride;

[0036] The added amount of the phase transfer catalyst is 2-5% of the total weight of phosphorus pentachloride.

[0037] Furthermore, the method for preparing pyridine hydrochloride is to add dry HCl gas into a reaction container containing pyridine and chlorobenzene, keep the reaction at a temperature of 95-100° C., separate the layers, and obtain pyridine hydrochloride;

[0038] The HCl gas is HCl gas prepared by using concentrated sulfuric acid and dilute hydrochloric acid; and / or HCl gas produced as a by-product in the synthesis of hexachlorocyclotriphosphazene.

[0039] Preferably, in the preparation of pyridine hydrochloride, the molar ratio of HCl to pyridine is 1.4-1.6:1.

[0040] Furthermore, the method for preparing the choline chloride / glycerol deep eutectic solvent is to mix dry choline chloride and glycerol, raise the temperature to 80-85° C. under the protection of an inert gas, and keep the temperature to react to obtain the choline chloride / glycerol deep eutectic solvent.

[0041] Preferably, in the preparation of the choline chloride / glycerol deep eutectic solvent, the molar ratio of choline chloride to glycerol is 1:0.4-2.

[0042] Compared with the prior art, the present invention has the following beneficial effects:

[0043] (1) The method for preparing hexachlorocyclotriphosphazene by reaction in an organic phase of the present invention comprises the following steps: during the reaction, phosphorus pentachloride and ammonium chloride are used as raw materials, an extraction solvent is used to dissolve the phosphorus pentachloride, and then a choline chloride / glycerol deep eutectic solvent containing ammonium chloride is added dropwise in batches; a mixed solvent of choline chloride / glycerol deep eutectic solvent and pyridine hydrochloride is used to provide a reaction environment for phosphorus pentachloride and ammonium chloride, and the hexachlorocyclotriphosphazene is extracted with the extraction solvent, thereby effectively increasing the reaction rate, improving the controllability of the reaction, and shortening the reaction time; at the same time, the ammonium chloride solution (i.e., the choline chloride / glycerol deep eutectic solvent containing ammonium chloride) is added dropwise in batches, thereby effectively reducing the generation of by-products, linear phosphazenes and macrocyclic phosphazenes, effectively inhibiting the increase of by-products, and without the need to increase the amount of ammonium chloride used, thereby effectively reducing the generation of solid waste; and the reaction stability is improved, and the obtained hexachlorocyclotriphosphazene has high purity and high yield; the yield can reach 87.3% and the purity can reach 99.8wt%.

[0044] (2) In the method for preparing hexachlorocyclotriphosphazene by reaction in an organic phase of the present invention, in the step of synthesizing hexachlorocyclotriphosphazene, the pyridine hydrochloride and the remaining intermediate solution recovered by hot layering after the reaction is completed can be directly recycled and reused; after 10 cycles of recycling, the purity and yield of the hexachlorocyclotriphosphazene finally prepared are not significantly reduced compared with those without recycling, which can greatly reduce the generation of reaction waste; and the extraction solvent recovered in the post-treatment step can be washed with water and then distilled and recovered for reuse.

[0045] (3) The method for preparing hexachlorocyclotriphosphazene by reaction in an organic phase of the present invention comprises the following steps: in the reaction process, the ground ammonium chloride is first dissolved in a choline chloride / glycerol deep eutectic solvent, and then the mixture is added dropwise to a mixed system containing phosphorus pentachloride, a catalyst and an extraction solvent, which can effectively increase the reaction contact area and improve the reaction rate; at the same time, the pyridine hydrochloride used can, on the one hand, be used as an acid binding agent to absorb the by-product HCl and promote the forward progress of the reaction; on the other hand, it can be used as a reaction solvent and cooperate with the choline chloride / glycerol deep eutectic solvent to provide a controllable and stable reaction environment for ammonium chloride and phosphorus pentachloride; at the same time, an extraction solvent is used in combination to extract the hexachlorocyclotriphosphazene generated in the reaction.

[0046] (4) In the method for preparing hexachlorocyclotriphosphazene by reaction in an organic phase of the present invention, a non-polar solvent is used to extract the product hexachlorocyclotriphosphazene in the post-treatment stage, thereby avoiding the generation of waste water, and the non-polar solvent used for extraction can be distilled, recovered and reused; at the same time, in the process of distillation, concentration and crystallization, the crystallization mother liquor can also be reused multiple times, further reducing the generation of reaction waste.

[0047] (5) The method of preparing hexachlorocyclotriphosphazene by reaction in an organic phase of the present invention can effectively reduce the generation of three wastes, reduce the difficulty of three waste treatment, and save the cost of three waste treatment; wherein, the HCl gas produced as a by-product in the reaction process can be recycled to prepare pyridine hydrochloride; the generation of solid waste ammonium chloride is reduced by changing the molar ratio of raw materials, and the catalyst and reaction solvent are effectively recovered and reused; and non-polar solvents such as petroleum ether are used for post-treatment to avoid the generation of wastewater. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] Figure 1 The present invention is a schematic diagram of the process flow of the method for preparing hexachlorocyclotriphosphazene by reaction in an organic phase.

[0049] Figure 2 This is the liquid chromatogram of hexachlorocyclotriphosphazene obtained in Example 2. DETAILED DESCRIPTION

[0050] In order to have a clearer understanding of the technical features, purposes and effects of the present invention, the specific implementation methods of the present invention are now described.

[0051] In order to have a clearer understanding of the technical features, purposes and effects of the present invention, the specific embodiments of the present invention are now described. It should be noted that the following detailed descriptions are exemplary and are intended to provide further explanation of the present invention. Unless otherwise specified, all technical and scientific terms used in the present invention have the same meanings as those commonly understood by those of ordinary skill in the art to which the present invention belongs.

[0052] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit exemplary embodiments according to the present invention. As used herein, "first", "second", etc. are used to distinguish similar objects, and are not used to describe a specific order or sequence. In addition, it should be understood that when the terms "comprising" and / or "including" are used in this specification, it indicates the presence of features, steps, operations, devices, components and / or combinations thereof.

[0053] The embodiment of the present invention provides a method for preparing hexachlorocyclotriphosphazene by reaction in an organic phase, which comprises the following steps: preparing pyridine hydrochloride, preparing choline chloride / glycerol deep eutectic solvent, synthesizing hexachlorocyclotriphosphazene, and post-processing.

[0054] The preparation of pyridine hydrochloride (PyH]Cl) can be carried out by two preparation schemes. The first preparation scheme is to use newly prepared HCl gas to contact and react with pyridine to obtain pyridine hydrochloride; the second preparation scheme is to collect the byproduct HCl gas in the reaction process of phosphorus pentachloride and ammonium chloride in the subsequent synthesis of hexachlorocyclotriphosphazene step, and contact and react with pyridine to obtain pyridine hydrochloride.

[0055] In the preparation of pyridine hydrochloride, the molar ratio of HCl to pyridine is 1.4-1.6:1.

[0056] Specifically, the first preparation scheme is: slowly drop concentrated sulfuric acid into a four-necked bottle containing dilute hydrochloric acid, so that the concentrated sulfuric acid absorbs water and releases heat, thereby volatilizing HCl gas; in order to promote the volatilization of HCl gas, the temperature is appropriately raised to 40-50°C; the generated HCl gas is dried and then passed into a four-necked bottle filled with pyridine and chlorobenzene in a mass ratio of 1:1, and the reaction is carried out at a temperature of 95-100°C with heat preservation and stirring. After a period of heat preservation and stirring, the light yellow transparent liquid soluble in chlorobenzene will change into a white solid, and then into a colorless transparent liquid insoluble in chlorobenzene. The overall heat preservation and stirring reaction time is 3-5h, and the layers are separated to obtain pyridine hydrochloride.

[0057] The second preparation scheme is: the by-product HCl gas in the subsequent reaction process of phosphorus pentachloride and ammonium chloride is dried through drying tubes filled with chlorobenzene and calcium chloride respectively, and then the dried HCl gas is introduced into a four-necked bottle filled with pyridine and chlorobenzene in a mass ratio of 1:1, and the reaction is carried out at a temperature of 95-100°C with heat preservation and stirring. After a period of heat preservation and stirring, the light yellow transparent liquid soluble in chlorobenzene will change into a white solid, and then into a colorless transparent liquid insoluble in chlorobenzene. The overall heat preservation and stirring reaction time is 3-5h, and the layers are separated to obtain pyridine hydrochloride.

[0058] The preparation route for preparing pyridine hydrochloride (PyH]Cl) is as follows:

[0059] .

[0060] The method for preparing the choline chloride / glycerol deep eutectic solvent comprises: placing choline chloride and glycerol in a vacuum drying oven at 55° C. for 24 hours to remove water; then weighing the dried choline chloride (hydrogen bond acceptor HBA) and glycerol (hydrogen bond donor HBD), adding them into a four-necked flask, stirring and heating to 80-85° C. under nitrogen protection, and stirring and reacting for 1-2 hours; during the stirring and keeping warm, when a uniform and transparent solution is obtained, stirring and reacting for 20 minutes, and stopping the reaction after the formed solution is further stabilized, so as to prepare the choline chloride / glycerol deep eutectic solvent (ChCl / GlycerolDES); after the ammonium chloride is ground and dried, the ammonium chloride is dissolved in the choline chloride / glycerol deep eutectic solvent to obtain an ammonium chloride solution.

[0061] Preferably, in the preparation of the choline chloride / glycerol deep eutectic solvent, the molar ratio of choline chloride to glycerol used is 1:0.4-2; a more preferred molar ratio is one of the following: 1:2, 1:0.4, 1:0.6, 1:0.8.

[0062] Preferably, the particle size of the ammonium chloride is ≤100 μm.

[0063] The preparation route of the choline chloride / glycerol deep eutectic solvent (ChCl / Glycerol DES) is as follows:

[0064] .

[0065] The method for synthesizing hexachlorocyclotriphosphazene comprises the following steps: adding the pyridine hydrochloride and the extraction solvent prepared above into a four-necked flask, heating the flask to 130-132° C., and removing water by azeotropy; clarifying the evaporated solvent, cooling the flask to 95-100° C., adding a metal chloride catalyst and a phase transfer catalyst, and stirring the reaction for 20-60 minutes to obtain a light yellow transparent solution; dissolving phosphorus pentachloride in the extraction solvent to obtain a phosphorus pentachloride solution with a mass concentration of 25-35wt%, and dripping the solution into a four-necked flask containing pyridine hydrochloride, the metal chloride catalyst, the phase transfer catalyst and the extraction solvent, heating and stirring the solution at 95-100° C., and after uniform mixing, dripping a 1 / 3 mass amount of an ammonium chloride solution; keeping the temperature at 95-100° C. and stirring the reaction for 1 hour; and then stirring and heating the solution to 12 5-130°C, add 1 / 3 of the mass amount of ammonium chloride solution again, keep warm and stir to react for 2h; finally add the remaining amount (i.e. 1 / 3 of the mass amount) of ammonium chloride solution, keep warm and stir to react for 1h; keep warm for another 30min until no HCl gas is generated; cool to 90-100°C and separate layers while hot, the upper layer is the extraction solvent solution of hexachlorocyclotriphosphazene extracted by the extraction solvent, containing a small amount of linear phosphazene intermediates, which is used for subsequent post-treatment steps; the lower layer is pyridine hydrochloride and other intermediate solutions, which can be recycled and applied to the step of synthesizing hexachlorocyclotriphosphazene after separation, and the synthesis of hexachlorocyclotriphosphazene is continued, which not only fully reuses the pyridine hydrochloride in the lower layer, but also the intermediates contained in the lower layer can continue to participate in the reaction during the recycling process of synthesizing hexachlorocyclotriphosphazene.

[0066] Preferably, the molar ratio of phosphorus pentachloride to ammonium chloride is 1:1-1.34; more preferably, the molar ratio is one of the following: 1:1, 1:1.07, 1:1.16, 1:1.25, 1:1.34.

[0067] Preferably, the concentration of the phosphorus pentachloride solution is 25-35 wt %.

[0068] Preferably, the weight ratio of pyridine hydrochloride, extraction solvent and phosphorus pentachloride solution is 1:0.6-0.8:1-1.2.

[0069] Preferably, the weight ratio of pyridine hydrochloride to the choline chloride / glycerol deep eutectic solvent in the ammonium chloride solution is 1:0.2-1; the preferred weight ratio is one of the following: 1:1, 1:0.8, 1:0.6, 1:0.4, 1:0.2; under the premise of the aforementioned predetermined molar ratio of phosphorus pentachloride to ammonium chloride, the total weight of the ammonium chloride solution added is calculated according to its actual concentration.

[0070] Preferably, the extraction solvent is one of the following: chlorobenzene, tetrachloroethane, xylene, N,N-dimethylformamide, 1,3-dimethyl-2-imidazolidinone; more preferably, the extraction solvent is chlorobenzene.

[0071] Preferably, the metal chloride catalyst is one or a combination of two of the following: magnesium chloride, zinc chloride, barium chloride, calcium chloride, iron chloride, aluminum chloride, nickel chloride. Preferably, the amount of the metal chloride catalyst added is 1-3% of the total weight of phosphorus pentachloride.

[0072] Preferably, the phase transfer catalyst is one of tetrabutylammonium chloride, benzyltriethylammonium chloride (TEBA), tetraphenylphosphonium chloride, and benzyltriphenylphosphonium chloride. Preferably, the amount of the phase transfer catalyst added is 2-5% of the total weight of phosphorus pentachloride.

[0073] The preparation route of the synthetic hexachlorocyclotriphosphazene is as follows:

[0074] .

[0075] In the synthesis of hexachlorocyclotriphosphazene, phosphorus pentachloride and ammonium chloride are used as raw materials, an extraction solvent is used to dissolve the phosphorus pentachloride, and then a choline chloride / glycerol deep eutectic solvent dissolved with ammonium chloride is added dropwise in batches; a mixed solvent of choline chloride / glycerol deep eutectic solvent and pyridine hydrochloride is used to provide a reaction environment for phosphorus pentachloride and ammonium chloride, and the hexachlorocyclotriphosphazene is extracted with the extraction solvent, so that the reaction rate can be effectively increased, the reaction controllability can be improved, and the reaction time can be shortened; at the same time, the ammonium chloride solution (i.e., the choline chloride / glycerol deep eutectic solvent dissolved with ammonium chloride) is added dropwise in batches, so that the generation of linear phosphazenes and macrocyclic phosphazenes can be effectively reduced, the increase of by-products can be effectively avoided, and there is no need to increase the amount of ammonium chloride used, so that the generation of solid waste can be effectively reduced.

[0076] In the synthesis of hexachlorocyclotriphosphazene, the ground ammonium chloride is first dissolved by using a choline chloride / glycerol deep eutectic solvent, and then the mixture is added dropwise to a mixed system containing phosphorus pentachloride, a catalyst and an extraction solvent, which can effectively increase the reaction contact area and improve the reaction rate; at the same time, the pyridine hydrochloride used can be used as an acid binding agent to absorb the by-product HCl and promote the forward progress of the reaction; at the same time, it can be used as a reaction solvent and cooperate with the choline chloride / glycerol deep eutectic solvent to provide a controllable and stable reaction environment for ammonium chloride and phosphorus pentachloride; at the same time, the extraction solvent is used to extract the hexachlorocyclotriphosphazene generated in the reaction.

[0077] The post-treatment method is as follows: after the above reaction process is optimized, the reaction conversion rate is greatly improved; the hexachlorocyclotriphosphazene chlorobenzene solution extracted with the extraction solvent obtained in the above step is subjected to reduced pressure distillation to remove most of the extraction solvent, and then extracted with petroleum ether, and activated carbon is added for decolorization during the extraction with petroleum ether, and after decolorization, the activated carbon is filtered out, the lower layer of the extraction solvent is separated and recovered, and the upper layer is subjected to distillation to remove most of the petroleum ether, and then distilled, concentrated and crystallized to obtain hexachlorocyclotriphosphazene with a purity of not less than 99.5wt%.

[0078] In the post-treatment, a non-polar solvent (petroleum ether) is used to extract the product hexachlorocyclotriphosphazene, thereby avoiding the generation of waste water, and the non-polar solvent (petroleum ether) used for extraction can be distilled, recovered and reused; at the same time, in the process of distillation, concentration and crystallization, the crystallization mother liquor can also be used multiple times, further reducing the generation of reaction waste.

[0079] The method for preparing hexachlorocyclotriphosphazene by reaction in an organic phase, the process flow diagram is as follows Figure 1 shown.

[0080] The present invention is further described below in conjunction with some specific embodiments.

[0081] Example 1

[0082] This embodiment provides a method for preparing hexachlorocyclotriphosphazene by reaction in an organic phase, specifically:

[0083] 1. Preparation of pyridine hydrochloride (PyH]Cl)

[0084] Weigh 50 g of concentrated sulfuric acid with a concentration of 98 wt% and pour it into a constant pressure dropping funnel, then weigh 100 g of dilute hydrochloric acid (concentration 36 wt%) into a four-necked flask, slowly drop the concentrated sulfuric acid into the four-necked flask containing the dilute hydrochloric acid, control the temperature of the dilute hydrochloric acid to 40°C, collect the volatilized HCl gas; pass the volatilized HCl gas through a U-shaped drying tube filled with calcium chloride to obtain dry HCl gas; pass the dry HCl gas into a four-necked flask containing 75 g of pyridine and 75 g of chlorobenzene, keep warm and stir the reaction at 95°C for 4 hours, until a colorless transparent liquid insoluble in chlorobenzene is obtained, separate the layers, and obtain pyridine hydrochloride.

[0085] Wherein, the molar ratio of HCl to pyridine is 1.5:1.

[0086] 2. Preparation of Choline Chloride / Glycerol Deep Eutectic Solvent (ChCl / Glycerol DES)

[0087] After drying choline chloride and glycerol in a vacuum drying oven at 55°C for 24 hours, 13.9 g of dried choline chloride and 18.4 g of glycerol (molar ratio 1:2) were weighed respectively, added into a four-necked flask, and heated to 80°C with stirring under nitrogen protection, and stirred for reaction (about 1-2 hours). When a uniform and transparent solution was obtained, the reaction was continued for another 20 minutes, and the formed solution was further stabilized before the reaction was stopped to prepare a choline chloride / glycerol deep eutectic solvent (ChCl / Glycerol DES); ammonium chloride was ground to a particle size of 80 μm and then dried, and then the ammonium chloride was dissolved in a choline chloride / glycerol deep eutectic solvent to obtain an ammonium chloride solution.

[0088] 3. Synthesis of hexachlorocyclotriphosphazene

[0089] 110 g of pyridine hydrochloride prepared above and 75 g of chlorobenzene as extraction solvent were added to a four-necked flask, and the temperature was raised to 130°C for azeotropic removal of water. When the evaporated solvent was clarified, the temperature was lowered to 95°C, 0.5 g of magnesium chloride catalyst and 1 g of tetrabutylammonium chloride were added, and the reaction was stirred for 30 min to obtain a light yellow transparent solution.

[0090] Weigh 40g of phosphorus pentachloride and 75g of chlorobenzene respectively, mix and heat at 95°C to dissolve, and add the obtained chlorobenzene solution of phosphorus pentachloride dropwise into a four-necked bottle containing the aforementioned light yellow transparent solution (pyridine hydrochloride, chlorobenzene, magnesium chloride, tetrabutylammonium chloride) using a jacketed constant pressure dropping funnel, heat and stir at 95°C for 1h to obtain a yellow liquid insoluble in chlorobenzene; wherein the weight ratio of the aforementioned pyridine hydrochloride, the extraction solvent chlorobenzene, and the chlorobenzene solution of phosphorus pentachloride is 1:0.68:1.05.

[0091] Add 1 / 3 of the mass amount of ammonium chloride solution to a four-necked flask; keep stirring and react at 95°C for 1 hour; then stir and heat to 125°C, add 1 / 3 of the mass amount of ammonium chloride solution again, keep stirring and react for 2 hours; finally add the remaining amount (i.e. 1 / 3 of the mass amount) of ammonium chloride solution, keep stirring and react for 1 hour; keep warm for another 30 minutes until no HCl gas is generated; cool to 90°C and separate layers while hot, the upper layer is a chlorobenzene solution of hexachlorocyclotriphosphazene extracted with chlorobenzene, containing a small amount of linear phosphazene intermediates, which is used for subsequent post-treatment steps; the lower layer is pyridine hydrochloride and other intermediate solutions, which can be recycled and applied to the step of synthesizing hexachlorocyclotriphosphazene after separation, and the synthesis of hexachlorocyclotriphosphazene is continued, which not only fully reuses the pyridine hydrochloride in the lower layer, but also the intermediates contained in the lower layer can continue to participate in the reaction during the recycling process of synthesizing hexachlorocyclotriphosphazene. According to the test, after the pyridine hydrochloride and the other intermediate solutions were recycled for 10 times, the purity and yield of the hexachlorocyclotriphosphazene finally prepared were not significantly reduced compared with the case without recycling.

[0092] Wherein, the molar ratio of phosphorus pentachloride to ammonium chloride is 1:1.07;

[0093] The weight ratio of pyridine hydrochloride to the choline chloride / glycerol deep eutectic solvent in the ammonium chloride solution is 1:0.6.

[0094] 4. Post-processing

[0095] The chlorobenzene-extracted hexachlorocyclotriphosphazene chlorobenzene solution obtained in the above step is subjected to reduced pressure distillation to remove most of the extraction solvent, and then petroleum ether is used to extract and layer the layers, and activated carbon is added for decolorization. After the decolorization is completed, the activated carbon is filtered out, and the lower layer of the extraction solvent is separated and recovered. After most of the petroleum ether is removed from the upper layer by distillation, the upper layer is distilled, concentrated and crystallized to obtain a white hexachlorocyclotriphosphazene wet material; after the hexachlorocyclotriphosphazene wet material is dried, hexachlorocyclotriphosphazene with a purity of 99.6wt% is obtained, and the yield is 86.5%.

[0096] Example 2

[0097] This embodiment provides a method for preparing hexachlorocyclotriphosphazene by reaction in an organic phase, specifically:

[0098] 1. Preparation of pyridine hydrochloride (PyH]Cl)

[0099] This step is the same as that in Example 1 and will not be repeated here.

[0100] 2. Preparation of Choline Chloride / Glycerol Deep Eutectic Solvent (ChCl / Glycerol DES)

[0101] This step is the same as that in Example 1 and will not be repeated here.

[0102] 3. Synthesis of hexachlorocyclotriphosphazene

[0103] 110 g of pyridine hydrochloride and 75 g of chlorobenzene prepared above were added to a four-necked flask, and the temperature was raised to 132°C for azeotropic removal of water; when the evaporated solvent was clarified, the temperature was lowered to 97°C, 0.25 g of magnesium chloride catalyst, 0.25 g of zinc chloride catalyst and 1 g of tetraphenylphosphine chloride were added, and the reaction was stirred for 40 min to obtain a light yellow transparent solution.

[0104] Weigh 40g of phosphorus pentachloride and 75g of chlorobenzene respectively, mix and heat to dissolve at 100°C to obtain a chlorobenzene solution of phosphorus pentachloride. Use a jacketed constant pressure dropping funnel to drop the chlorobenzene solution of phosphorus pentachloride into a four-necked bottle containing the aforementioned light yellow transparent solution (pyridine hydrochloride, chlorobenzene, magnesium chloride, tetrabutylammonium chloride), heat and stir at 100°C for 1h to obtain a yellow liquid insoluble in chlorobenzene; wherein the weight ratio of the aforementioned pyridine hydrochloride, chlorobenzene as the extraction solvent, and the chlorobenzene solution of phosphorus pentachloride is 1:0.68:1.05.

[0105] Add 1 / 3 of the mass amount of ammonium chloride solution to a four-necked flask; keep warm and stir for 1 hour at 100° C.; then stir and heat to 130° C., add 1 / 3 of the mass amount of ammonium chloride solution again, keep warm and stir for 2 hours; finally add the remaining amount (i.e. 1 / 3 of the mass amount) of ammonium chloride solution, keep warm and stir for 1 hour; keep warm for another 30 minutes until no HCl gas is generated; cool to 95° C. and separate layers while hot, the upper layer is a chlorobenzene solution of hexachlorocyclotriphosphazene extracted with chlorobenzene, containing a small amount of linear phosphazene intermediates, which is used for subsequent post-processing steps; the lower layer is pyridine hydrochloride and other intermediate solutions, which can be recycled and applied to the step of synthesizing hexachlorocyclotriphosphazene after separation, and the synthesis of hexachlorocyclotriphosphazene is continued, which not only fully reuses the pyridine hydrochloride in the lower layer, but also the intermediates contained in the lower layer can continue to participate in the reaction during the recycling process of synthesizing hexachlorocyclotriphosphazene. According to the test, after the pyridine hydrochloride and the other intermediate solutions were recycled for 10 times, the purity and yield of the hexachlorocyclotriphosphazene finally prepared were not significantly reduced compared with the case without recycling.

[0106] Wherein, the molar ratio of phosphorus pentachloride to ammonium chloride is 1:1.07;

[0107] The weight ratio of pyridine hydrochloride to the choline chloride / glycerol deep eutectic solvent in the ammonium chloride solution is 1:0.4.

[0108] 4. Post-processing

[0109] The chlorobenzene-extracted hexachlorocyclotriphosphazene chlorobenzene solution obtained in the above step is subjected to reduced pressure distillation to remove most of the extraction solvent, and then petroleum ether is used to extract and layer the layers, and activated carbon is added for decolorization. After the decolorization is completed, the activated carbon is filtered out, and the lower layer of the extraction solvent is separated and recovered. After most of the petroleum ether is removed from the upper layer by distillation, the upper layer is distilled, concentrated and crystallized to obtain a white hexachlorocyclotriphosphazene wet material; after the hexachlorocyclotriphosphazene wet material is dried, hexachlorocyclotriphosphazene with a purity of 99.6wt% is obtained, and the yield is 86.7%.

[0110] Example 3

[0111] This embodiment provides a method for preparing hexachlorocyclotriphosphazene by reaction in an organic phase, specifically:

[0112] 1. Preparation of pyridine hydrochloride (PyH]Cl)

[0113] This step is the same as that in Example 1 and will not be repeated here.

[0114] 2. Preparation of Choline Chloride / Glycerol Deep Eutectic Solvent (ChCl / Glycerol DES)

[0115] This step is the same as that in Example 1 and will not be repeated here.

[0116] 3. Synthesis of hexachlorocyclotriphosphazene

[0117] 110 g of pyridine hydrochloride and 75 g of chlorobenzene prepared above were added to a four-necked flask, and the temperature was raised to 130°C for azeotropic removal of water. When the evaporated solvent was clarified, the temperature was lowered to 95°C, 0.25 g of magnesium chloride catalyst, 0.25 g of nickel chloride catalyst and 1 g of tetraphenylphosphine chloride were added, and the reaction was stirred for 30 min to obtain a light yellow transparent solution.

[0118] Weigh 40g of phosphorus pentachloride and 75g of chlorobenzene respectively, mix and heat at 95°C to dissolve, and add the obtained chlorobenzene solution of phosphorus pentachloride dropwise into a four-necked bottle containing the aforementioned light yellow transparent solution (pyridine hydrochloride, chlorobenzene, magnesium chloride, tetrabutylammonium chloride) using a jacketed constant pressure dropping funnel, heat and stir at 95°C for 1h to obtain a yellow liquid insoluble in chlorobenzene; wherein the weight ratio of the aforementioned pyridine hydrochloride, the extraction solvent chlorobenzene, and the chlorobenzene solution of phosphorus pentachloride is 1:0.68:1.05.

[0119] Add 1 / 3 of the mass amount of ammonium chloride solution to a four-necked flask; keep stirring and react at 95°C for 1 hour; then stir and heat to 125°C, add 1 / 3 of the mass amount of ammonium chloride solution again, keep stirring and react for 2 hours; finally add the remaining amount (i.e. 1 / 3 of the mass amount) of ammonium chloride solution, keep stirring and react for 1 hour; keep warm for another 30 minutes until no HCl gas is generated; cool to 90°C and separate layers while hot, the upper layer is a chlorobenzene solution of hexachlorocyclotriphosphazene extracted with chlorobenzene, containing a small amount of linear phosphazene intermediates, which is used for subsequent post-treatment steps; the lower layer is pyridine hydrochloride and other intermediate solutions, which can be recycled and applied to the step of synthesizing hexachlorocyclotriphosphazene after separation, and the synthesis of hexachlorocyclotriphosphazene is continued, which not only fully reuses the pyridine hydrochloride in the lower layer, but also the intermediates contained in the lower layer can continue to participate in the reaction during the recycling process of synthesizing hexachlorocyclotriphosphazene. According to the test, after the pyridine hydrochloride and the other intermediate solutions were recycled for 10 times, the purity and yield of the hexachlorocyclotriphosphazene finally prepared were not significantly reduced compared with the case without recycling.

[0120] Wherein, the molar ratio of phosphorus pentachloride to ammonium chloride is 1:1.07;

[0121] The weight ratio of pyridine hydrochloride to the choline chloride / glycerol deep eutectic solvent in the ammonium chloride solution is 1:0.2.

[0122] 4. Post-processing

[0123] The chlorobenzene-extracted hexachlorocyclotriphosphazene chlorobenzene solution obtained in the above step is subjected to reduced pressure distillation to remove most of the extraction solvent, and then petroleum ether is used to extract and layer the layers, and activated carbon is added for decolorization. After the decolorization is completed, the activated carbon is filtered out, and the lower layer of the extraction solvent is separated and recovered. After most of the petroleum ether is removed from the upper layer by distillation, the upper layer is distilled, concentrated and crystallized to obtain a white hexachlorocyclotriphosphazene wet material; after the hexachlorocyclotriphosphazene wet material is dried, hexachlorocyclotriphosphazene with a purity of 99.8wt% is obtained, and the yield is 87.3%.

[0124] Comparative Example 1

[0125] Comparative Example 1 adopts the technical solution of Example 1, except that: 1) the step of preparing choline chloride / glycerol deep eutectic solvent is omitted, and ammonium chloride solution is not prepared; in the subsequent step of synthesizing hexachlorocyclotriphosphazene, solid ammonium chloride is directly added in three batches (the weight of solid ammonium chloride added in each batch is equal). At the same time, in order to ensure the smooth progress of the reaction, the insulation and stirring reaction time after the first batch of solid ammonium chloride is added is controlled to be 2h; the insulation and stirring reaction time after the second batch of solid ammonium chloride is added is 4h; the insulation and stirring reaction time after the third batch of solid ammonium chloride is added is 2.5h; and the temperature is kept for another 30min until no HCl gas is generated. 2) In the step of synthesizing hexachlorocyclotriphosphazene, zinc chloride is used instead of magnesium chloride.

[0126] The purity of the hexachlorocyclotriphosphazene finally obtained in Comparative Example 1 was 98.2%, and the yield was 82.1%.

[0127] Unless otherwise specified, all percentages used in the present invention are by mass.

[0128] Finally, it should be noted that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art can still modify the technical solutions described in the aforementioned embodiments or replace some of the technical features therein by equivalents. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for preparing hexachlorocyclotriphosphazene by reaction in an organic phase, characterized in that: The method comprises the following steps: preparing pyridine hydrochloride, preparing choline chloride / glycerol deep eutectic solvent, synthesizing hexachlorocyclotriphosphazene, and post-processing; The method for synthesizing hexachlorocyclotriphosphazene comprises: mixing pyridine hydrochloride and an extraction solvent, heating and azeotropically removing water; adding a metal chloride catalyst and a phase transfer catalyst, mixing evenly, dripping a phosphorus pentachloride solution, mixing evenly, and dripping an ammonium chloride solution in three batches; during the dripping of the first batch of ammonium chloride solution, heat-keeping reaction at 95-100° C.; during the dripping of the second batch of ammonium chloride solution, heat-keeping reaction at 125-130° C.; during the dripping of the third batch of ammonium chloride solution, heat-keeping reaction at 125-130° C.; after the heat-keeping reaction is completed, layering is performed to obtain an extraction solvent solution of hexachlorocyclotriphosphazene; The ammonium chloride solution is a choline chloride / glycerol deep eutectic solvent in which ammonium chloride is dissolved; The phosphorus pentachloride solution is an extraction solvent solution in which phosphorus pentachloride is dissolved; In the synthesized hexachlorocyclotriphosphazene, the molar ratio of phosphorus pentachloride to ammonium chloride is 1:1-1.34; The concentration of phosphorus pentachloride solution is 25-35wt%; The weight ratio of pyridine hydrochloride, extraction solvent and phosphorus pentachloride solution is 1:0.6-0.8:1-1.2; The weight ratio of pyridine hydrochloride to the choline chloride / glycerol deep eutectic solvent in the ammonium chloride solution is 1:0.2-1; The post-treatment method is as follows: the extraction solvent solution of the hexachlorocyclotriphosphazene is subjected to distillation to remove the extraction solvent, followed by extraction and decolorization; and then concentrated and crystallized to obtain the hexachlorocyclotriphosphazene.

2. The method for preparing hexachlorocyclotriphosphazene by reaction in an organic phase according to claim 1, characterized in that: In the synthesis of hexachlorocyclotriphosphazene, the extraction solvent is one of the following: chlorobenzene, tetrachloroethane, xylene, N,N-dimethylformamide, 1,3-dimethyl-2-imidazolidinone; The metal chloride catalyst is one or two of the following: magnesium chloride, zinc chloride, barium chloride, calcium chloride, iron chloride, aluminum chloride, nickel chloride; The phase transfer catalyst is one of the following: tetrabutylammonium chloride, benzyltriethylammonium chloride, tetraphenylphosphonium chloride, benzyltriphenylphosphonium chloride.

3. The method for preparing hexachlorocyclotriphosphazene by reaction in an organic phase according to claim 1, characterized in that: In the synthesized hexachlorocyclotriphosphazene, the weights of the first batch of ammonium chloride solution, the second batch of ammonium chloride solution, and the third batch of ammonium chloride solution are equal; The amount of metal chloride catalyst added is 1-3% of the total weight of phosphorus pentachloride; The added amount of the phase transfer catalyst is 2-5% of the total weight of phosphorus pentachloride.

4. The method for preparing hexachlorocyclotriphosphazene by reaction in an organic phase according to claim 1, characterized in that: The method for preparing pyridine hydrochloride comprises: adding dry HCl gas into a reaction container containing pyridine and chlorobenzene, keeping the temperature at 95-100° C. for reaction, and separating the layers to obtain pyridine hydrochloride; The HCl gas is HCl gas prepared by using concentrated sulfuric acid and dilute hydrochloric acid, and / or HCl gas produced as a by-product in the synthesis of hexachlorocyclotriphosphazene.

5. The method for preparing hexachlorocyclotriphosphazene by reaction in an organic phase according to claim 4, characterized in that: In the preparation of pyridine hydrochloride, the molar ratio of HCl to pyridine is 1.4-1.6:

1.

6. The method for preparing hexachlorocyclotriphosphazene by reaction in an organic phase according to claim 1, characterized in that: The method for preparing the choline chloride / glycerol deep eutectic solvent comprises: mixing dry choline chloride and glycerol, heating to 80-85° C. under the protection of an inert gas, and keeping the temperature for reaction to prepare the choline chloride / glycerol deep eutectic solvent.

7. The method for preparing hexachlorocyclotriphosphazene by reaction in an organic phase according to claim 6, characterized in that: In the preparation of the choline chloride / glycerol deep eutectic solvent, the molar ratio of choline chloride to glycerol is 1:0.4-2.

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