Process for the preparation of tertiary butylated triphenyl phosphate

Abstract

The application discloses a preparation method of tert-butylated triphenyl phosphate, which comprises the following steps: using tert-butyl phenol, phenol and phosphorus oxychloride as raw materials, using a Lewis acid as a catalyst, putting the raw materials and the catalyst into a reactor at one time or in sections, and obtaining a crude tert-butylated triphenyl phosphate after reaction; performing vacuum distillation on the crude tert-butylated triphenyl phosphate, stopping the vacuum distillation when the acid value of the crude tert-butylated triphenyl phosphate is less than or equal to 3 mgKOH / g, and performing molecular distillation treatment on the crude tert-butylated triphenyl phosphate with the acid value less than or equal to 3 mgKOH / g. The tert-butylated triphenyl phosphate prepared by the method has low triphenyl phosphate content, high effective component content, simple preparation method, low production cost and is suitable for industrialized production. The tert-butylated triphenyl phosphate prepared by the method is suitable for the fields of aviation oil and hydraulic oil base oil, plasticizer, flame retardant, lubricating oil extreme pressure anti-wear agent and the like.

Description

Technical Field

[0001] This invention belongs to the technical field of lubricating oil additives and organophosphate flame retardants, and relates to a green and environmentally friendly method for preparing tert-butylated triphenyl phosphate with low triphenyl phosphate content. Background Technology

[0002] tert-butyltriphenyl phosphate (TBPP) is a class of halogen-free organophosphorus flame retardants with excellent thermal and hydrolytic stability. Its overall performance is significantly superior to that of triphenyl phosphate (TPP). Its excellent thermal stability allows it to be used as a flame retardant for engineering plastics and also improves the melting properties of plastics. Its good hydrolytic stability results in better durability in resins and reduces the likelihood of surface stress cracking. Therefore, it is widely used in flame-retardant PVC, cellulosic resins, synthetic rubber, phenolic resins, epoxy resins, polyester fibers, and other industries. Furthermore, studies have shown that TBPP, tested using the OECD 301F rapid biodegradability method, has a much higher biodegradability rate than aryl phosphates such as TPP and tricresyl phosphate (TCP), exhibiting better biodegradability and lower ecotoxicity. Therefore, it is a highly regarded extreme pressure anti-wear additive and flame-retardant hydraulic fluid base oil in the lubricating oil field. Especially in lubrication systems in enclosed environments with passengers, such as aircraft cabins and elevators, the use of tricresyl phosphate (TCP) has been strictly restricted. Therefore, tert-butyltriphenyl phosphate, which is relatively low in toxicity and easily biodegradable, has become an alternative to tricresyl phosphate (TCP).

[0003] Currently, in industry, crude tert-butyltriphenyl phosphate is prepared by reacting tert-butylphenol, phenol, and phosphorus oxychloride. The product is then post-processed through adsorption, solvent washing with alkali, water washing, drying, or high-temperature distillation (310±5℃). The purpose of adding phenol is to adjust the physical properties of tert-butyltriphenyl phosphate, such as viscosity and phosphorus content. If tert-butylphenol is used exclusively as a raw material, the final product is often very viscous, even solid, which cannot meet the requirements of industrial applications. However, introducing phenol into the reaction raw materials will generate a harmful component—triphenyl phosphate—in the product. This is because phenol has less steric hindrance than alkylphenol, resulting in higher reactivity and unavoidable formation of triphenyl phosphate during the reaction. Although triphenyl phosphate is also a type of phosphorus-containing flame retardant, it is hygroscopic, and its hydrolytic and thermal stability are inferior to that of tert-butyltriphenyl phosphate, affecting the stability and overall performance of tert-butyltriphenyl phosphate. More importantly, triphenyl phosphate is non-biodegradable and highly toxic to aquatic organisms, potentially causing long-term adverse effects on the ecological environment. Its high concentration in the product inevitably reduces the excellent biodegradability and low toxicity of tert-butyltriphenyl phosphate. Therefore, the biggest drawback of tert-butyltriphenyl phosphate produced by traditional methods is its high proportion of triphenyl phosphate, which varies from 5% to 50% depending on the preparation process. For example, patent CN104262389 discloses a method for preparing tert-butyltriphenyl phosphate, which involves adding phosphorus trichloride dropwise to a solution of phenol, tert-butylphenol, and aluminum trichloride. After the reaction is complete, a large amount of methylcyclohexane and toluene are added to the crude ester as solvents, followed by multiple alkaline and water washes. Finally, the organic phase is evaporated to remove the solvent, yielding the tert-butyltriphenyl phosphate product. The method produces tert-butyltriphenyl phosphate with a high yield (>95%) and low acid value (<0.05 mg KOH / g). However, liquid chromatography analysis shows that the product contains approximately 40% triphenyl phosphate. Triphenyl phosphate is a harmful component of tert-butyltriphenyl phosphate; without its removal, tert-butyltriphenyl phosphate cannot meet the demands of modern industry for high-quality flame retardants, plasticizers, extreme pressure anti-wear agents, and fire-resistant hydraulic oils. Furthermore, tert-butyltriphenyl phosphate products produced using traditional methods generally suffer from high acid values, high free phenol content, and dark color. The alkaline and water washing processes also easily lead to product loss and generate large amounts of hazardous waste containing phosphate esters. The large volume of "three wastes" (waste gas, wastewater, and solid waste) is difficult to treat and has a significant negative impact on the environment, failing to meet the current societal advocacy of ecological civilization and green chemistry.

[0004] Currently, numerous technologies in this field are dedicated to reducing the triphenyl phosphate content in tert-butylated triphenyl phosphate through production processes and post-processing. For example, patent CN103224519 A discloses a method for preparing p-tert-butylphenyl phosphate, which involves mixing p-tert-butylphenol with molten phenol, adding phosphorus oxychloride and a catalyst in batches to the mixture, then gradually increasing the temperature and the vacuum level of the reaction system to carry out the reaction, and finally performing distillation to obtain p-tert-butylphenyl phosphate from the fraction at 310±5℃. Theoretically, this method can yield tert-butylated triphenyl phosphate with a low triphenyl phosphate content, but the patent does not provide compositional analysis or explanation, and the high-temperature distillation above 300℃ will inevitably lead to a darker product color and result in huge energy consumption throughout the production process. Patent CN102268036A attempts to reduce the triphenyl phosphate content in the final product by first reacting tert-butylphenol with phosphorus oxychloride, and then adding phenol to the reaction system. After solvent addition, alkali washing, water washing, and solvent removal, the target compound is obtained. However, liquid chromatography analysis shows that the product still contains approximately 40% triphenyl phosphate, and the entire preparation process inevitably causes significant waste emissions due to alkali washing, water washing, and solvent use. Patent US5206404 uses thin-film evaporation to reduce the triphenyl phosphate content in alkylated triaryl phosphate products. While this method can reduce the triphenyl phosphate content to 2.0 wt%, it significantly darkens the color of the final alkylated triaryl phosphate product (the crude ester color is 60 APHA, and after treatment, the color darkens to over 500 APHA) and increases the acid value. Patent US6232485 starts with the raw material tert-butylphenol. By using special alkylation catalysts such as acid-activated bentonite or montmorillonite, the proportion of tert-butylphenol at the intermediate position in the alkylphenol material is greatly increased (around 40%), while the proportion of phenol decreases (around 20%). The final tert-butylated triphenyl phosphate product has a triphenyl phosphate content of less than 2.0 wt%. However, its drawback is that the alkylation step is too long, which can exacerbate the formation of various alkylphenol homologues, such as disubstituted and even trisubstituted alkylphenols, thus making the product composition more complex and product quality control more difficult. It can be seen that all existing technologies have defects. How to provide a green and environmentally friendly method for preparing tert-butylated triphenyl phosphate with low triphenyl phosphate content is currently a challenge. Summary of the Invention

[0005] The purpose of this invention is to provide a method for preparing tert-butylated triphenyl phosphate, thereby producing a green and environmentally friendly tert-butylated triphenyl phosphate with a low triphenyl phosphate content.

[0006] The technical solution adopted in this invention is a method for preparing tert-butylated triphenyl phosphate, which is specifically implemented according to the following steps:

[0007] S1 uses tert-butylphenol, phenol, and phosphorus oxychloride as reactants and Lewis acid as a catalyst. The reactants and catalyst are added to the reactor in one step or in stages. After the reaction is complete, crude tert-butylated triphenyl phosphate is obtained. The molar ratio of phosphorus oxychloride, tert-butylphenol, and phenol is 1:(0.5–3.5):(0.5–3.5).

[0008] S2. The crude tert-butylated triphenyl phosphate is subjected to vacuum distillation. The vacuum distillation is stopped when the acid value of the crude tert-butylated triphenyl phosphate is ≤3mgKOH / g.

[0009] S3 subjected crude tert-butylated triphenyl phosphate with an acid value ≤3mgKOH / g to molecular distillation to finally obtain the tert-butylated triphenyl phosphate product.

[0010] The invention is further characterized by:

[0011] The raw material tert-butylphenol is one or more of o-tert-butylphenol, m-tert-butylphenol, and p-tert-butylphenol, or it can be the product of phenol and butene after Friedel-Crafts alkylation reaction; the catalyst is one or two of aluminum trichloride, magnesium chloride, and titanium tetrachloride.

[0012] In the preparation method of tert-butylated triphenyl phosphate, the preferred reaction conditions in step S1 are: slowly heating to 150±5℃ and continuously maintaining the temperature for 8 to 16 hours.

[0013] In the preparation method of tert-butylated triphenyl phosphate, in step S1, the preferred molar ratio of phosphorus oxychloride, tert-butylphenol, and phenol is 1:(1.0-2.5):(1.0-3.0).

[0014] In the preparation method of tert-butyltriphenyl phosphate, step S2, the preferred conditions for vacuum distillation of the crude tert-butyltriphenyl phosphate are: vacuum distillation at 100–180°C and 0.1–5 kPa for 6–12 hours. This removes most of the unreacted raw materials phenol, tert-butylphenol, and a small amount of small-molecule acidic residues.

[0015] In the preparation method of tert-butylated triphenyl phosphate, in step S2, it is preferred that the distillate be collected simultaneously during the vacuum distillation, and the distillate can be recycled as a raw material.

[0016] In the preparation method of tert-butylated triphenyl phosphate, step S3 preferably includes a molecular distillation process to remove light phase impurities, adjusting the evaporation temperature to 130–180°C and the vacuum degree to 0.01–50 Pa, maintaining the light phase distillate at 10%–30% of the total distillate mass percentage, to obtain a primary light phase distillate and a primary heavy phase distillate.

[0017] The evaporation vacuum is preferably between 1 Pa and 50 Pa, maintaining the light phase distillate at 5% to 20% of the total distillate by mass. This treatment step removes free phenol, tert-butylphenol, triphenyl phosphate, and low-boiling-point impurities such as mono- and diester phosphates in the form of primary light phase distillate, and collects tert-butylated triphenyl phosphate in the form of primary heavy phase distillate.

[0018] A method for preparing tert-butyltriphenyl phosphate, wherein, preferably, the primary light phase distillate is enriched and then subjected to molecular distillation, with the evaporation temperature adjusted to 130–180°C and the vacuum degree to 0.01–50 Pa, maintaining the light phase distillate accounting for 10%–30% of the total distillate by mass. The resulting light phase distillate is a mixture of phenol, tert-butylphenol, and triphenyl phosphate, which can be recycled as a reaction feedstock; the resulting heavy phase distillate is tert-butyltriphenyl phosphate.

[0019] In the preparation method of tert-butyltriphenyl phosphate, step S3 preferably includes a further step of molecular distillation to remove heavy phase impurities from the primary heavy phase distillate. The evaporation temperature is adjusted to 150–190°C, and the vacuum degree to 0.01–10 Pa, maintaining the light phase distillate at 75%–95% of the total distillate mass percentage, resulting in a secondary light phase distillate, i.e., the tert-butyltriphenyl phosphate product, and a secondary heavy phase distillate. More preferably, the light phase distillate is maintained at 85%–95% of the total distillate mass percentage. This step collects the tert-butyltriphenyl phosphate product as a secondary light phase distillate and removes high-boiling-point impurities such as polyphosphate esters and pigments as a secondary heavy phase distillate.

[0020] A preferred method for preparing tert-butyltriphenyl phosphate involves enriching the secondary heavy phase distillate and then subjecting it to molecular distillation. The evaporation temperature is adjusted to 150–190°C, the vacuum degree to 0.01–10 Pa, and the light phase distillate is maintained at 75%–85% of the total distillate mass. The resulting heavy phase distillate is considered an impurity, and the resulting light phase distillate is the tert-butyltriphenyl phosphate product.

[0021] A method for preparing tert-butyltriphenyl phosphate, wherein, preferably, the obtained tert-butyltriphenyl phosphate product, if qualified in testing, is the final product; if unqualified, molecular distillation treatment is continued; the conditions for the tert-butyltriphenyl phosphate product to be qualified in testing are: free phenol content ≤0.01%, triphenyl phosphate content ≤0.1%, acid value ≤0.01mgKOH / g, effective component content ≥99.5%, and color APHA ≤100.

[0022] The preparation method of tert-butyltriphenyl phosphate of the present invention can economically and quickly reduce the content of harmful component—triphenyl phosphate, and increase the content of effective component of tert-butyltriphenyl phosphate. Moreover, the preparation method of the present invention abandons the traditional preparation methods such as solvent addition, alkaline washing, water washing, vacuum distillation, dehydration, and high-temperature distillation, which greatly reduces the discharge of wastewater and waste residue and energy consumption in the production process of tert-butyltriphenyl phosphate. It also significantly reduces the loss of tert-butyltriphenyl phosphate in the refining stage. Furthermore, the impurities removed in each stage can be recovered, enriched and then processed for reuse, reducing the discharge of hazardous chemical waste and exhibiting significant green and environmentally friendly characteristics. Attached Figure Description

[0023] Figure 1 This is a liquid chromatogram of the tert-butylated triphenyl phosphate product prepared in Comparative Example 1 of this invention;

[0024] Figure 2 This is a liquid chromatogram of the tert-butylated triphenyl phosphate product prepared in Examples 1-2 of this invention;

[0025] Figure 3 This is a liquid chromatogram of the tert-butylated triphenyl phosphate product prepared in Example 2-2 of this invention. Detailed Implementation

[0026] The preparation method of tert-butylated triphenyl phosphate of the present invention will be described in detail below with reference to the accompanying drawings and specific embodiments.

[0027] To better illustrate the key technical features of the present invention, this embodiment describes a tert-butylated triphenyl phosphate product prepared by conventional processes such as adsorption with an adsorbent, solvent washing with alkali and water, and dehydration after the reaction is completed. This product is used as a comparative example to illustrate the present invention.

[0028] Comparative Example 1

[0029] In a 3000 mL reactor equipped with a mechanical stirrer, thermometer, condenser, and hydrogen chloride tail gas absorption device, 600 g of p-tert-butylphenol, 613 g of phosphorus oxychloride, and 2 g of anhydrous magnesium chloride catalyst were added. The mixture was stirred and slowly heated to 150 °C, and reacted at this temperature for 3 hours. Then, 800 g of phenol was added in batches to the above system, and the reaction was continued at 150 °C for 8 hours. The reaction product was then subjected to vacuum distillation at 150 °C and 5 kPa for 10 hours, and its acid value was measured. Vacuum distillation was stopped when the acid value was found to be 2.38 mg KOH / g. After cooling the crude product to room temperature, 5% (by mass) of adsorbent was added, and the mixture was heated to 90 °C for 2 hours to equilibrate. The adsorbent was then removed by filtration. The crude product was mixed with an equal volume of carbon tetrachloride, washed three times with a 5% sodium hydroxide aqueous solution at a 1:1 volume ratio, and then washed four times with distilled water. The solvent and a small amount of water were then removed under vacuum to obtain the tert-butylated triphenyl phosphate product. Liquid chromatography and routine analyses, including phosphorus content detection, were performed on the product. The results are shown in Table 1 (Comparative Example 1). The entire preparation process, besides requiring a dedicated absorption device for the hydrogen chloride tail gas, also generates approximately 0.1 kg of adsorbent residue, about 1.5 kg of waste solvent, and about 12 kg of wastewater containing a small amount of phosphate ester, resulting in a large discharge of "three wastes."

[0030] Example 1

[0031] In a 3000 mL reactor equipped with a mechanical stirrer, thermometer, condenser, and hydrogen chloride tail gas absorption device, 600 g of p-tert-butylphenol, 613 g of phosphorus oxychloride, and 2 g of anhydrous magnesium chloride catalyst were added. The mixture was stirred and slowly heated to 150 °C, and reacted at this temperature for 3 hours. Then, 800 g of phenol was added in batches to the above system, and the reaction was continued at 150 °C for another 8 hours. The reaction product was then subjected to vacuum distillation at 150 °C and 5 kPa for 10 hours, and its acid value was measured. Vacuum distillation was stopped when the acid value was found to be 2.71 mg KOH / g. The crude product was then introduced into a molecular distillation apparatus for the first stage of light phase impurity removal. The evaporation temperature was set at 140 °C and the vacuum degree at 5 Pa. Other molecular distillation parameters were adjusted to maintain the light phase distillate at approximately 15% of the total distillate mass, and distillation was continued. The resulting light phase distillate was recovered and enriched, while the heavy phase distillate was directly fed into the second stage of molecular distillation for heavy phase impurity removal. The evaporation temperature was set to 155℃ and the vacuum degree to 0.1 Pa. Other molecular distillation parameters were adjusted to maintain the light phase distillate at 85% of the total distillate mass. Distillation continued until all products were processed. The resulting heavy phase distillate was recovered and enriched, while the light phase distillate was identified as tert-butylated triphenyl phosphate. Gas chromatography analysis and phosphorus content determination were performed on this product. The analytical results are shown in Table 1, Example 1-1.

[0032] Since the acid value and triphenyl phosphate content did not meet the requirements, the first and second molecular distillation steps were repeated. The analytical results of the obtained tert-butylated triphenyl phosphate product are shown in Table 1, Examples 1-2. The entire preparation process, except for the hydrogen chloride tail gas which requires a dedicated absorption device, basically does not generate other waste. The distillates generated in each step can be recovered, enriched, and then subjected to molecular distillation for reuse.

[0033] Example 2

[0034] In a 3000mL four-necked round-bottom flask equipped with a mechanical stirrer, thermometer, condenser, and hydrogen chloride tail gas absorption device, 600g of o-tert-butylphenol, 613g of phosphorus oxychloride, and 2g of anhydrous magnesium chloride catalyst were added. The mixture was stirred and slowly heated to 150℃, and reacted at this temperature for 3 hours. Then, 800g of phenol was added in batches to the above system, and the reaction was continued at 150℃ for another 8 hours. The reaction product was then subjected to vacuum distillation at 150℃ and 5kPa for 10 hours, and its acid value was measured. Vacuum distillation was stopped when the acid value was found to be 1.26mgKOH / g. The crude product was then introduced into a molecular distillation apparatus for the first stage of light phase impurity removal. The evaporation temperature was set at 140℃ and the vacuum degree at 4Pa. Other molecular distillation parameters were adjusted to maintain the light phase distillate at approximately 13% of the total distillate mass, and distillation was continued. The resulting light phase distillate was recovered and enriched, while the heavy phase distillate was directly fed into the second stage of molecular distillation for heavy phase impurity removal. The evaporation temperature was set to 156℃ and the vacuum degree to 0.1 Pa. Other molecular distillation parameters were adjusted to maintain the light phase distillate at 85% of the total distillate mass. Distillation continued until all products were processed. The resulting heavy phase distillate was recovered and enriched, while the light phase distillate was identified as tert-butylated triphenyl phosphate. Gas chromatography analysis and phosphorus content determination were performed on this product. The results are shown in Table 1, Example 2-1.

[0035] Since the acid value and triphenyl phosphate content did not meet the requirements, the first and second molecular distillation steps were repeated. The analytical results of the obtained tert-butylated triphenyl phosphate product are shown in Table 1, Example 2-2. The entire preparation process, except for the hydrogen chloride tail gas which requires a dedicated absorption device, basically does not generate other waste. The distillates generated in each step can be recovered, enriched, and then subjected to molecular distillation for reuse.

[0036] Table 1. Analytical data of tert-butylated triphenyl phosphate prepared in the examples

[0037]

[0038] The data analysis in Table 1 shows that the tert-butyltriphenyl phosphate product prepared by Comparative Example 1 using conventional processes such as adsorption with adsorbent, solvent addition, alkaline washing, water washing, solvent removal, and dehydration is inferior to the tert-butyltriphenyl phosphate products prepared by Examples 1 and 2 of this invention in terms of color and tert-butyltriphenyl phosphate content, especially in terms of tert-butyltriphenyl phosphate content. The liquid chromatogram of Comparative Example 1 clearly shows the presence of a high proportion of the harmful component—triphenyl phosphate. Figure 1 The chromatographic peak with a retention time of 2.68 min is triphenyl phosphate. The preparation method of this invention can achieve the preparation of tert-butylated triphenyl phosphate with low triphenyl phosphate content in a green, environmentally friendly, economical, and convenient manner, meeting the requirements of free phenol content ≤0.01%, triphenyl phosphate content ≤0.1%, acid value ≤0.01 mgKOH / g, effective component content ≥99.5%, and color APHA ≤100. (Appendix) Figure 2 and attached Figure 3 The characteristic chromatographic peaks of triphenyl phosphate did not appear in the medium liquid chromatograms at a retention time of approximately 2.68 min, indicating that the content of triphenyl phosphate in Examples 1-2 and 2-2 was extremely low.

[0039] To further illustrate the preparation method of the tert-butylated triphenyl phosphate of the present invention, the following examples will be used for further explanation:

[0040] Example 3

[0041] In a 5000mL four-necked round-bottom flask equipped with a mechanical stirrer, thermometer, condenser, and hydrogen chloride tail gas absorption device, 1082g of p-tert-butylphenol, 613g of phosphorus oxychloride, and 2.5g of titanium tetrachloride catalyst were added. The mixture was stirred and slowly heated to 150°C, and reacted at this temperature for 3 hours. Then, 1317g of phenol was added in batches to the above system, and the reaction was continued at 150°C for 15 hours. The reaction product was then subjected to vacuum distillation at 100°C and 2.5kPa for 10 hours, and its acid value was measured. Vacuum distillation was stopped when the acid value was found to be 1.5mgKOH / g. The crude product was then introduced into a molecular distillation apparatus for the first stage of light phase impurity removal. The evaporation temperature was set at 178°C and the vacuum degree at 10Pa. The remaining molecular distillation parameters were adjusted to maintain the light phase distillate at approximately 20% of the total distillate mass, and distillation was continued. The resulting light-phase distillate was recovered and enriched, while the heavy-phase distillate was directly fed into a second-stage molecular distillation process to remove heavy-phase impurities. The evaporation temperature was set at 157°C and the vacuum degree at 0.1 Pa. Other molecular distillation parameters were adjusted to maintain the light-phase distillate at 90% of the total distillate mass. Distillation continued until all products were processed. The resulting heavy-phase distillate was recovered and enriched, and the light-phase distillate was the tert-butylated triphenyl phosphate product.

[0042] Example 4

[0043] In a 5000mL four-necked round-bottom flask equipped with a mechanical stirrer, thermometer, condenser, and hydrogen chloride tail gas absorption device, 1502g of a mixture of o-tert-butylphenol and m-tert-butylphenol, 613g of phosphorus oxychloride, and 2g of catalyst (a mixture of aluminum trichloride and magnesium chloride) were added. The mixture was stirred and slowly heated to 150℃ and reacted at this temperature for 3 hours. Then, 753g of phenol was added in batches to the above system, and the reaction was continued at 150℃ for 8 hours. The reaction product was then subjected to vacuum distillation at 150℃ and 0.1kPa for 10 hours, and its acid value was measured. When the acid value was found to be 2.3mgKOH / g, vacuum distillation was stopped. The crude product was then introduced into a molecular distillation apparatus for the first stage of light phase impurity removal. The evaporation temperature was set at 175℃ and the vacuum degree at 10Pa. The remaining molecular distillation parameters were adjusted to maintain the light phase distillate at approximately 25% of the total distillate mass, and the distillation process was continued. The resulting light-phase distillate is recovered and enriched, while the heavy-phase distillate is directly fed into a second-stage molecular distillation process to remove heavy-phase impurities. The evaporation temperature is set at 158°C and the vacuum degree at 0.1 Pa. Other molecular distillation parameters are adjusted to maintain the light-phase distillate at 90% of the total distillate mass. Distillation continues until all products are processed. The resulting heavy-phase distillate is recovered and enriched, while the light-phase distillate is the tert-butylated triphenyl phosphate product.

[0044] Example 5

[0045] In a 5000mL four-necked round-bottom flask equipped with a mechanical stirrer, thermometer, condenser, and hydrogen chloride tail gas absorption device, 1202g of a mixture of o-tert-butylphenol and p-tert-butylphenol, 613g of phosphorus oxychloride, and 2g of catalyst (a mixture of aluminum trichloride and titanium tetrachloride) were added. The mixture was stirred and slowly heated to 150°C, and reacted at this temperature for 3 hours. Then, 753g of phenol was added in batches to the above system, and the reaction was continued at 150°C for 14 hours. The reaction product was then subjected to vacuum distillation at 150°C and 5kPa for 11 hours, and its acid value was measured. Vacuum distillation was stopped when the acid value was found to be 1.36mgKOH / g. The crude product was then introduced into a molecular distillation apparatus for the first stage of light phase impurity removal. The evaporation temperature was set at 170°C and the vacuum degree at 16Pa. The remaining molecular distillation parameters were adjusted to maintain the light phase distillate at approximately 25% of the total distillate mass, and the distillation process was continued. The resulting light-phase distillate was recovered and enriched, while the heavy-phase distillate was directly fed into a second-stage molecular distillation process to remove heavy-phase impurities. The evaporation temperature was set at 156°C and the vacuum degree at 0.1 Pa. Other molecular distillation parameters were adjusted to maintain the light-phase distillate at 85% of the total distillate mass. Distillation continued until all products were processed. The resulting heavy-phase distillate was recovered and enriched, and the light-phase distillate was the tert-butylated triphenyl phosphate product.

[0046] Example 6

[0047] In a 5000mL four-necked round-bottom flask equipped with a mechanical stirrer, thermometer, condenser, and hydrogen chloride tail gas absorption device, 1021g of a mixture of o-tert-butylphenol, m-tert-butylphenol, and p-tert-butylphenol, 613g of phosphorus oxychloride, and 2g of anhydrous magnesium chloride catalyst were added. The mixture was stirred and slowly heated to 155℃ and reacted at this temperature for 3 hours. Then, 1129g of phenol was added in batches to the above system, and the reaction was continued at 155℃ for 8 hours. The reaction product was then subjected to vacuum distillation at 155℃ and 3kPa for 12 hours, and its acid value was measured. When the acid value was found to be 2.62mgKOH / g, vacuum distillation was stopped. The crude product was then introduced into a molecular distillation apparatus for the first stage of light phase impurity removal. The evaporation temperature was set at 135℃ and the vacuum degree at 2Pa. The remaining molecular distillation parameters were adjusted to maintain the light phase distillate at approximately 15% of the total distillate mass, and the distillation process was continued. The resulting light-phase distillate was recovered and enriched, while the heavy-phase distillate was directly fed into a second-stage molecular distillation process to remove heavy-phase impurities. The evaporation temperature was set at 156°C and the vacuum degree at 0.1 Pa. Other molecular distillation parameters were adjusted to maintain the light-phase distillate at 85% of the total distillate mass. Distillation continued until all products were processed. The resulting heavy-phase distillate was recovered and enriched, and the light-phase distillate was the tert-butylated triphenyl phosphate product.

[0048] In the molecular distillation process of this invention, other molecular distillation parameters such as injection flow rate, film formation speed, and condensation surface temperature can be set and adjusted appropriately by those skilled in the art based on actual conditions and operational experience.

[0049] The preparation method of tert-butyltriphenyl phosphate of the present invention can also appropriately adjust the molecular distillation treatment sequence after the synthesis reaction, and finally obtain a tert-butyltriphenyl phosphate product with low triphenyl phosphate content. For example, if liquid chromatography is performed immediately after the first stage of molecular distillation to remove light phase impurities, and if the removal of light phase impurities is not complete, the removal of light phase impurities can continue until the light phase impurities are completely removed, and then the removal of heavy phase impurities is performed until the tert-butyltriphenyl phosphate meets the requirements of free phenol content ≤0.01%, triphenyl phosphate content ≤0.1%, acid value ≤0.01mgKOH / g, effective component content ≥99.5%, and color APHA ≤100, thus obtaining the tert-butyltriphenyl phosphate product.

[0050] The present invention has the following beneficial effects:

[0051] (1) The molecular distillation process used in the purification of tert-butylated triphenyl phosphate in the preparation method of the present invention is a physical purification process with mild conditions and simple operation. It does not introduce new impurities or generate a large amount of "three wastes". It can effectively avoid the problem of large amounts of phosphate ester-containing organic wastewater and waste solvents generated by solvent addition, alkaline washing and water washing in traditional processes, and significantly reduce environmental pollution in the production process.

[0052] (2) The preparation method of the present invention has low product loss and high yield. The collected light phase impurity fraction and heavy phase impurity fraction can be enriched and then subjected to molecular distillation, thereby recovering phenol, tert-butylphenol, and triphenyl phosphate, and enriching tert-butylated triphenyl phosphate with almost no loss of tert-butylated triphenyl phosphate, generating only a small amount of waste. Therefore, it also greatly reduces the emission of hazardous chemical waste and significantly reduces environmental pollution during the production process.

[0053] (3) The tert-butylated triphenyl phosphate prepared by the method of the present invention has a light color and low triphenyl phosphate content, and can be used in aviation oil and hydraulic oil base oil, plasticizer, flame retardant, extreme pressure anti-wear agent for lubricating oil, etc., and has a good market prospect. Moreover, the preparation method of the present invention is simple, low in cost, and has a short production cycle, which can realize continuous production and is suitable for industrial production.

Claims

1. A method for preparing tert-butylated triphenyl phosphate, characterized in that, The specific steps are as follows: Step 1: Using tert-butylphenol, phenol, and phosphorus oxychloride as reactants and Lewis acid as catalyst, the reactants and catalyst are added to the reactor at once or in stages. After the reaction is completed, crude tert-butylated triphenyl phosphate is obtained. The molar ratio of phosphorus oxychloride, tert-butylphenol, and phenol is 1:0.5-3.5:0.5-3.

5. Step 2: Perform vacuum distillation on the crude tert-butylated triphenyl phosphate. Stop vacuum distillation when the acid value of the crude tert-butylated triphenyl phosphate is ≤3mgKOH / g. Step 3: Perform molecular distillation on the crude tert-butylated triphenyl phosphate that was distilled under reduced pressure in Step 2 to obtain a tert-butylated triphenyl phosphate product with free phenol content ≤0.01%, triphenyl phosphate content ≤0.1%, acid value ≤0.01mgKOH / g, effective component content ≥99.5%, and color APHA ≤100. The specific steps of molecular distillation are as follows: Step 3.1: The crude tert-butylated triphenyl phosphate, after vacuum distillation, is subjected to primary molecular distillation to remove light phase impurities, yielding primary light phase distillate and primary heavy phase distillate; wherein, the temperature for primary molecular distillation to remove light phase impurities is 130–180℃, the vacuum degree is 0.01–50 Pa, and the light phase distillate accounts for 10%–30% of the total distillate by mass. Step 3.2: Enrich the primary light phase distillate, and perform secondary molecular distillation to remove heavy phase impurities from the primary heavy phase distillate, obtaining secondary light phase distillate and secondary heavy phase distillate; wherein, the temperature for secondary molecular distillation to remove heavy phase impurities from the primary heavy phase distillate is 150–190℃, the vacuum degree is 0.01–10 Pa, and the light phase distillate accounts for 75%–95% of the total distillate by mass; Step 3.3: Enrich the secondary heavy phase distillate and test the secondary light phase distillate. If it meets the product requirements of free phenol content ≤0.01%, triphenyl phosphate content ≤0.1%, acid value ≤0.01mgKOH / g, effective component content ≥99.5%, and color APHA ≤100, then the distillation is complete and tert-butylated triphenyl phosphate product is obtained. If it does not meet the product requirements, repeat the distillation process of steps 3.1 and 3.2 until the light phase distillate of the last distillation meets the product requirements and tert-butylated triphenyl phosphate product is obtained. Step 3.4: The enriched primary light phase distillate is subjected to molecular distillation at a temperature of 130–180℃ and a vacuum of 0.01–50 Pa, maintaining the light phase distillate at 10%–30% of the total distillate mass. Phenol, tert-butylphenol, and triphenyl phosphate are recovered from the light phase distillate, and tert-butylated triphenyl phosphate is recovered from the heavy phase distillate. Step 3.5: The enriched secondary heavy phase distillate is subjected to molecular distillation at a temperature of 150–190°C and a vacuum of 0.01–10 Pa, maintaining the light phase distillate at 75%–85% of the total distillate mass, and recovering tert-butylated triphenyl phosphate from the light phase distillate.

2. The method for preparing tert-butylated triphenyl phosphate according to claim 1, characterized in that, The tert-butylphenol is one or more of o-tert-butylphenol, m-tert-butylphenol, and p-tert-butylphenol, or is the product of phenol and butene after Friedel-Crafts alkylation reaction; the catalyst is a Lewis acid, specifically one or two of aluminum trichloride, magnesium chloride, and titanium tetrachloride.

3. The method for preparing tert-butylated triphenyl phosphate according to claim 1, characterized in that, The molar ratio of phosphorus oxychloride, tert-butylphenol, and phenol is 1:1.0-2.5:1.0-3.

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4. The method for preparing tert-butylated triphenyl phosphate according to claim 1, characterized in that, The reaction conditions in step 1 are: slowly raise the temperature to 150±5℃ and keep it at that temperature for 8 to 16 hours.

5. The method for preparing tert-butylated triphenyl phosphate according to claim 1, characterized in that, In step 2, the crude tert-butylated triphenyl phosphate is distilled under reduced pressure at a temperature of 100–180°C, a vacuum degree of 0.1–5 kPa, and a distillation time of 6–12 h.

6. The method for preparing tert-butylated triphenyl phosphate according to claim 1, characterized in that, The vacuum degree of the primary molecular distillation process for removing light phase impurities in step 3.1 is 1 Pa to 50 Pa, and the light phase distillate accounts for 5% to 20% of the total distillate by mass. This process removes free phenol, tert-butylphenol, triphenyl phosphate, and low-boiling-point impurities such as mono- and diester phosphates in the form of primary light phase distillate, and collects tert-butylated triphenyl phosphate in the form of primary heavy phase distillate.

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