A method for efficiently synthesizing tris-(dimethylphenyl) phosphate

Abstract

The present invention proposes a method for efficiently synthesizing tris (dimethylphenyl) phosphate, comprising the steps of: taking a certain amount of ionic liquid catalyst and dissolving it in methanol, adding an appropriate amount of silica gel and fully stirring, then removing methanol in vacuo, and obtaining a silica gel-supported ionic liquid catalyst; the crude dimethylphenol is dissolved in an organic solvent, adding a silica gel-supported ionic liquid catalyst, fully stirring, rising to a suitable temperature, slowly adding phosphorus oxychloride, continuing stirring, after the reaction terminates, adding enough organic solvent and deionized water, extracting, obtaining a water layer and an organic layer, distilling the organic layer, and obtaining tris (dimethylphenyl) phosphate. The present invention, by adding an ionic liquid catalyst to a reaction system in the form of a silica gel load, improves the catalytic efficiency of the catalyst, can improve the purity and yield of the prepared tris (dimethylphenyl) phosphate by simple operation, and reduces the content of by-products.

Description

Technical Field

[0001] The invention relates to the technical field of fire-resistant oil preparation, and in particular to a method for efficiently synthesizing tris-(dimethylphenyl) phosphate. Background Art

[0002] With the development of the electric power industry, the superheated steam temperature of high-parameter and large-capacity steam turbine generator sets has gradually increased, and some have reached above 600°C. Because the steam turbine regulation system is mostly close to the superheated steam pipeline, if mineral steam turbine oil is used as the working medium of the regulation system, oil leakage will greatly increase the probability of fire. In order to improve the fire prevention ability of power plants, phosphate ester fire-resistant oil is generally used as the hydraulic working medium of the steam turbine regulation system at this stage. Phosphate ester fire-resistant oil has excellent fire retardant and lubricating properties, and its main component is triaryl phosphate. Triaryl phosphate includes tri-(dimethylphenyl) phosphate, triphenyl phosphate, triisopropylphenyl phosphate and tert-butylphenyl diphenyl phosphate. Among them, tri-(dimethylphenyl) phosphate has become one of the most important components of phosphate ester fire-resistant oil due to its excellent chemical stability.

[0003] Tris-(dimethylphenyl) phosphate is mainly obtained by reacting phosphorus oxychloride and dimethylphenol under the catalytic action of Lewis acid catalysts such as aluminum chloride. The purity of dimethylphenol determines the purity of tris-(dimethylphenyl) phosphate. At present, dimethylphenol is mainly extracted from coal tar or petroleum cracking products produced by coal cracking. Because the boiling points of compounds such as phenol, methylphenol and ethylphenol in coal tar are very close to dimethylphenol, some impurities such as phenol, methylphenol and ethylphenol are often mixed into the dimethylphenol extraction process, resulting in a low purity of dimethylphenol. The purity of tris-(dimethylphenyl) phosphate produced with this as raw material is also low, and it is difficult to meet the requirements of phosphate fire-resistant oil. At present, in order to improve the purity of tris-(dimethylphenyl) phosphate, the method of optimizing the distillation process and improving the distillation equipment is mainly adopted, but the method requires a long cycle, high cost and complex process. Summary of the invention

[0004] The present invention aims to solve one of the technical problems in the related art at least to a certain extent. To this end, the embodiment of the present invention provides a method for efficiently synthesizing tris-(dimethylphenyl) phosphate, which can synthesize tris-(dimethylphenyl) phosphate through simple operation, improve the purity and yield of tris-(dimethylphenyl) phosphate, and reduce the content of by-products.

[0005] The embodiment of the present invention provides a method for efficiently synthesizing tris-(dimethylphenyl) phosphate, comprising the following steps: taking a certain amount of ionic liquid catalyst and dissolving it in methanol, wherein the ratio of the added amount of the ionic liquid catalyst to the methanol is 1-2 g: 50 mL, adding an appropriate amount of silica gel and stirring it fully, and then removing the methanol in vacuo to obtain a silica gel-supported ionic liquid catalyst; dissolving a crude dimethylphenol in an organic solvent, adding a certain amount of the ionic liquid catalyst and stirring it fully, and after heating to a suitable temperature, slowly adding phosphorus oxychloride and continuing stirring to obtain a first solution, tracking and detecting the content of dimethylphenol during the reaction until the content of dimethylphenol no longer changes; after the reaction is completed, adding a sufficient amount of organic solvent and deionized water to the first solution for extraction to obtain a water layer and an organic layer, and distilling the organic layer after removing the water layer to obtain tris-(dimethylphenyl) phosphate.

[0006] In some embodiments, the organic solvent is any one of hexane, cyclohexane, toluene and ethyl acetate.

[0007] In some embodiments, the volume ratio of the organic solvent and deionized water added to the first solution is 1:1, and the total volume of the organic solvent and deionized water added to the first solution is 3 to 5 times the volume of the organic solvent added before adding the silica gel-supported ionic liquid catalyst.

[0008] In some embodiments, after adding the organic solvent and deionized water to the first solution, extraction is performed three times.

[0009] In some embodiments, the molar ratio of dimethylphenol to phosphorus oxychloride in the crude dimethylphenol is 3-5:1.

[0010] In some embodiments, the mesh size of the silica gel is 200-400 mesh.

[0011] In some embodiments, the ionic liquid catalyst is [Et3NH]Cl-AlCl3 or [Et3NH]Cl-FeCl3.

[0012] In some embodiments, the amount of the silica gel-supported ionic liquid catalyst added is 0.5% to 3% by mass of phosphorus oxychloride.

[0013] In some embodiments, the suitable temperature is 70°C to 100°C.

[0014] In some embodiments, the ratio of silica gel to methanol is 1 g:2 mL. DETAILED DESCRIPTION

[0015] The embodiments of the present invention are described in detail below. The embodiments described below are exemplary and intended to be used to explain the present invention, but should not be construed as limiting the present invention.

[0016] The following describes a method for efficiently synthesizing tris-(dimethylphenyl) phosphate according to an embodiment of the present invention.

[0017] The embodiment of the present invention provides a method for efficiently synthesizing tris-(dimethylphenyl) phosphate, comprising the following steps:

[0018] (1) Preparation of silica gel supported ionic liquid catalyst: a certain amount of ionic liquid catalyst is dissolved in methanol, the ratio of ionic liquid catalyst to methanol is 1-2 g:50 mL, an appropriate amount of silica gel is added and stirred thoroughly, and then the methanol is removed in vacuo to obtain a silica gel supported ionic liquid catalyst.

[0019] (2) Preparation of tri-(dimethylphenyl) phosphate: Dissolve crude dimethylphenol in an organic solvent, add a certain amount of silica gel-supported ionic liquid catalyst, stir thoroughly, and after heating to a suitable temperature, slowly add phosphorus oxychloride and continue stirring to obtain a first solution. During the reaction, track and detect the content of dimethylphenol until the content of dimethylphenol no longer changes. After the reaction is completed, add a sufficient amount of organic solvent and deionized water to the first solution for extraction to obtain an aqueous layer and an organic layer. Distill the organic layer after removing the aqueous layer to obtain tri-(dimethylphenyl) phosphate.

[0020] The embodiment of the present invention can significantly increase the contact area between the catalyst and the reactant and improve the catalytic efficiency of the catalyst by adding the ionic liquid catalyst in the form of silica gel loading to the reaction system. The prepared tris-(dimethylphenyl) phosphate meets the requirements of phosphate fire-resistant oil base oil through index detection. The purity of the prepared tris-(dimethylphenyl) phosphate can be improved by simple operation, the content of by-products can be reduced, the reaction conditions are mild, low toxicity and environmental protection, the preparation and purification process costs are low, and it has high economic value.

[0021] The silica gel-supported ionic liquid catalyst used in the embodiment of the present invention can directional catalyze the synthesis of tri-(dimethylphenyl) phosphate, reduce the content of by-products, and improve the yield and purity of the target product. The yield can reach more than 80%, and the purity after distillation can be more than 99.5%.

[0022] It should be noted that the embodiment of the present invention ultimately adopts distillation for purification. Compared with the rectification method in the prior art, the required equipment cost is low and the operation is simple.

[0023] It should be noted that crude dimethylphenol is extracted from coal tar, and byproducts such as phenol, methylphenol and ethylphenol are obtained. In the method of the present invention, crude dimethylphenol can be used directly without further purification. The method of the embodiment of the present invention can significantly reduce the byproduct content in the finally prepared tris-(dimethylphenyl) phosphate, thereby improving the yield and purity of tris-(dimethylphenyl) phosphate, and the operation method is also simpler.

[0024] In some alternative embodiments, the distillation method can be replaced by column chromatography, and the purity that can be achieved is also higher. However, column chromatography is suitable for situations where the processing volume is small, and when the processing volume is relatively large, distillation is still the best method.

[0025] Furthermore, after the reaction, the catalyst can be quickly recovered through filtration and other methods to achieve recycling.

[0026] Furthermore, the stirring time after adding silica gel is 60-90 minutes.

[0027] Furthermore, the stirring time after adding the silica gel supported ionic liquid catalyst is 60-90 minutes.

[0028] Furthermore, the method for tracking and detecting the content of dimethylphenol during the reaction is a thin layer chromatography analysis method. The dimethylphenol consumed during the reaction is determined by comparing the thin layer chromatography with that of a dimethylphenol standard product, and the method has the characteristics of being quick and easy to operate.

[0029] In some embodiments, the organic solvent is any one of hexane, cyclohexane, toluene and ethyl acetate.

[0030] In some embodiments, the volume ratio of the organic solvent and deionized water added to the first solution is 1:1, and the total volume of the organic solvent and deionized water added to the first solution is 3 to 5 times the volume of the organic solvent added before adding the silica gel-supported ionic liquid catalyst.

[0031] In some embodiments, after adding the organic solvent and deionized water to the first solution, extraction is performed three times.

[0032] It should be noted that the total volume of the organic solvent and deionized water added to the first solution is the total volume of the organic solvent and deionized water required for three extractions.

[0033] In some embodiments, the molar ratio of dimethylphenol to phosphorus oxychloride in the crude dimethylphenol is 3-5:1.

[0034] It should be noted that if the molar ratio is lower than 3:1, the reaction will be incomplete, resulting in a low yield of the final product; if the molar ratio is higher than 5:1, on the one hand, it will lead to an increase in the content of other types of phosphate by-products, and on the other hand, it will also cause a waste of the raw material dimethylphenol.

[0035] In some embodiments, the mesh number of silica gel is 200 to 400 meshes. If the mesh number of silica gel is less than 200 meshes, the pore size is larger, resulting in insufficient silica gel adsorption and reduced adsorption efficiency; if the mesh number of silica gel is greater than 400 meshes, the pore size is too small, resulting in clogging of silica gel pores and affecting the adsorption effect.

[0036] In some embodiments, the ionic liquid catalyst is a quaternary ammonium ionic liquid, such as [Et3NH]Cl-AlCl3 or [Et3NH]Cl-FeCl3.

[0037] In some embodiments, the amount of the silica gel-supported ionic liquid catalyst added is 0.5% to 3% of the mass of phosphorus oxychloride. If the amount of the silica gel-supported ionic liquid catalyst added is less than 0.5%, the catalytic reaction rate will be slowed down and the yield of the final product will be reduced; if the amount of the silica gel-supported ionic liquid catalyst added is more than 3%, it is easy to cause side reactions and increase the reaction cost.

[0038] In some embodiments, the suitable temperature is 70°C to 100°C. If the reaction temperature is lower than 70°C, the reaction rate in the preparation process of tris-(dimethylphenyl) phosphate will be slowed down, the reaction time will be prolonged, and the by-products of the reaction will increase, which will reduce the purity and yield of the tris-(dimethylphenyl) phosphate product; if the reaction temperature is higher than 100°C, the by-products of the reaction will increase, and even the activity of the ionic liquid catalyst supported by silica gel will be affected, making the reaction difficult to proceed. Therefore, the reaction temperature needs to be controlled within the range of 70°C to 100°C.

[0039] In some embodiments, the ratio of silica gel to methanol is 1 g:2 mL.

[0040] The present invention is further described below through specific examples.

[0041] Embodiment 1:

[0042] A method for efficiently synthesizing tris-(dimethylphenyl) phosphate comprises the following steps:

[0043] (1) Preparation of silica gel supported ionic liquid catalyst: 0.26 g of [Et3NH]Cl-AlCl3 ionic liquid catalyst was fully dissolved in 10.0 mL of methanol solution, and about 5.00 g of 200 mesh silica gel was added. The mixture was stirred thoroughly, and then the methanol was removed in vacuo to obtain a silica gel supported [Et3NH]Cl-AlCl3 catalyst.

[0044] (2) Preparation of tri-(dimethylphenyl) phosphate: 36.70 g of crude dimethylphenol was dissolved in 250 mL of toluene solution, and the silica gel-supported ionic liquid catalyst prepared in step (1) was added, stirred thoroughly, heated to 80° C., 15.32 g of phosphorus oxychloride was slowly added, and stirring was continued. The dimethylphenol content was tracked and detected during the reaction until it no longer changed. After the reaction was completed, 750 mL of toluene and 750 mL of deionized water were added, extracted three times, the water layer was removed, and the organic layer liquid was passed into a distillation system, and 32.82 g of tri-(dimethylphenyl) phosphate was obtained by distillation, with a yield of 80% and a purity of 99.6%. The acid value, volume resistivity, foam characteristics and air release value of tri-(dimethylphenyl) phosphate were tested, and the test results are shown in Table 1.

[0045] Embodiment 2:

[0046] A method for efficiently synthesizing tris-(dimethylphenyl) phosphate comprises the following steps:

[0047] (1) Preparation of silica gel supported ionic liquid catalyst: 0.53 g of [Et3NH]Cl-AlCl3 ionic liquid catalyst was fully dissolved in 20.0 mL of methanol solution, and about 10.00 g of 200 mesh silica gel was added. The mixture was stirred thoroughly, and then the methanol was removed in vacuo to obtain the silica gel supported [Et3NH]Cl-AlCl3 catalyst.

[0048] (2) Preparation of tri-(dimethylphenyl) phosphate: 48.91 g of crude dimethylphenol was dissolved in 500 mL of toluene solution, and the silica gel-supported ionic liquid catalyst prepared in step (1) was added, stirred thoroughly, heated to 85° C., 15.30 g of phosphorus oxychloride was slowly added, and stirring was continued. The dimethylphenol content was tracked and detected during the reaction until it no longer changed. After the reaction was completed, 1000 mL of toluene and 1000 mL of deionized water were added, washed three times, the water layer was removed, and the organic layer liquid was passed into a distillation system, and 34.95 g of tri-(dimethylphenyl) phosphate was obtained by distillation, with a yield of 85% and a purity of 99.7%. The acid value, volume resistivity, foam characteristics and air release value of tri-(dimethylphenyl) phosphate were tested, and the test results are shown in Table 1.

[0049] Embodiment 3:

[0050] A method for efficiently synthesizing tris-(dimethylphenyl) phosphate comprises the following steps:

[0051] (1) Preparation of silica gel supported ionic liquid catalyst: 0.60 g of [Et3NH]Cl-FeCl3 ionic liquid catalyst was fully dissolved in 20.0 mL of methanol solution, and about 10.00 g of 400 mesh silica gel was added. The mixture was stirred thoroughly, and then the methanol was removed in vacuo to obtain the silica gel supported [Et3NH]Cl-FeCl3 catalyst.

[0052] (2) Preparation of tri-(dimethylphenyl) phosphate: 48.95 g of crude dimethylphenol was dissolved in 500 mL of toluene solution, and the silica gel-supported ionic liquid catalyst prepared in step (1) was added, stirred thoroughly, heated to 85° C., 15.35 g of phosphorus oxychloride was slowly added, and stirring was continued. The dimethylphenol content was tracked and detected during the reaction until it no longer changed. After the reaction was completed, 1000 mL of toluene and 1000 mL of deionized water were added, washed three times, the water layer was removed, and the organic layer liquid was passed into a distillation system, and 33.72 g of tri-(dimethylphenyl) phosphate was obtained by distillation, with a yield of 82% and a purity of 99.6%. The acid value, volume resistivity, foam characteristics and air release value of tri-(dimethylphenyl) phosphate were tested, and the test results are shown in Table 1.

[0053] Table 1 Key index test results of tris-(dimethylphenyl) phosphate prepared in Examples 1-3

[0054]

[0055]

[0056] Test results: Table 1 shows the test results of the acid value, volume resistivity, foam characteristics and air release value of the tris-(dimethylphenyl) phosphate prepared in Examples 1-3. The results all meet the requirements of the DL / T571 "Guidelines for Operation and Maintenance of Phosphate Fire-Resistant Oils for Power Plants" standard, indicating that the tris-(dimethylphenyl) phosphate prepared by this method has high purity and meets the requirements of phosphate fire-resistant oil base oil.

[0057] In the present invention, the terms "one embodiment", "some embodiments", "examples", "specific examples", or "some examples" etc. mean that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the described specific features, structures, materials or characteristics may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, without contradiction.

[0058] Although the embodiments of the present invention have been shown and described above, it is to be understood that the above embodiments are exemplary and are not to be construed as limitations of the present invention. A person skilled in the art may change, modify, replace and vary the above embodiments within the scope of the present invention.

Claims

1. A method for efficiently synthesizing tris-(dimethylphenyl) phosphate, characterized in that: The steps include: A certain amount of ionic liquid catalyst is dissolved in methanol, the ratio of the ionic liquid catalyst to the methanol is 1-2 g:50 mL, an appropriate amount of silica gel is added and stirred thoroughly, and then the methanol is removed in vacuo to obtain a silica gel-supported ionic liquid catalyst; Dissolving crude dimethylphenol in an organic solvent, adding a certain amount of silica gel-supported ionic liquid catalyst, stirring fully, and slowly adding phosphorus oxychloride after heating to a suitable temperature, and continuing stirring to obtain a first solution, tracking and detecting the content of dimethylphenol during the reaction until the content of the dimethylphenol no longer changes; After the reaction is completed, a sufficient amount of the organic solvent and deionized water are added to the first solution for extraction to obtain a water layer and an organic layer, and the organic layer after removing the water layer is distilled to obtain tris-(dimethylphenyl) phosphate; The ionic liquid catalyst is [Et3NH]Cl-AlCl3 or [Et3NH]Cl-FeCl3, the amount of the silica gel-supported ionic liquid catalyst added is 0.5% to 3% of the mass of the phosphorus oxychloride, the suitable temperature is 70°C to 100°C, and the ratio of the amount of silica gel to the amount of methanol added is 1g:2mL.

2. The method for efficiently synthesizing tris-(dimethylphenyl) phosphate according to claim 1, characterized in that: The organic solvent is any one of hexane, cyclohexane, toluene and ethyl acetate.

3. The method for efficiently synthesizing tris-(dimethylphenyl) phosphate according to claim 1, characterized in that: The volume ratio of the organic solvent and the deionized water added to the first solution is 1:1, and the total volume of the organic solvent and the deionized water added to the first solution is 3 to 5 times the volume of the organic solvent added before adding the silica gel-supported ionic liquid catalyst.

4. The method for efficiently synthesizing tris-(dimethylphenyl) phosphate according to claim 3, characterized in that: After adding the organic solvent and the deionized water to the first solution, extraction is performed three times.

5. The method for efficiently synthesizing tris-(dimethylphenyl) phosphate according to claim 1, characterized in that: The molar ratio of the dimethylphenol in the dimethylphenol crude product to the phosphorus oxychloride is 3 to 5:

1.

6. The method for efficiently synthesizing tris-(dimethylphenyl) phosphate according to claim 1, characterized in that: The mesh number of the silica gel is 200 to 400 meshes.

Images