Process for the preparation of isopropylated triphenyl phosphate with low content of phosphoric acid triphenyl ester

Abstract

The application discloses a preparation method of isopropylated triphenyl phosphate with low phosphorus acid triphenyl ester content, which comprises the following steps: firstly, isopropyl phenol, phenol, phosphorus oxychloride and a catalyst are put into a reactor, and isopropylated triphenyl phosphate crude product is obtained after reaction; secondly, the isopropylated triphenyl phosphate crude product is subjected to vacuum distillation, and the vacuum distillation is stopped when the acid value of the isopropylated triphenyl phosphate crude product is less than or equal to 3 mgKOH / g; finally, the isopropylated triphenyl phosphate crude product after vacuum distillation is subjected to molecular distillation treatment, and isopropylated triphenyl phosphate product is obtained. The preparation method is a physical purification process, has mild conditions and simple operation, does not introduce new impurities, and does not produce a large amount of 'three wastes', so that the problem of a large amount of phosphorus acid ester organic wastewater caused by alkali washing water washing in a traditional process can be effectively avoided, and environmental pollution in the production process is greatly reduced.

Description

Technical Field

[0001] This invention belongs to the field of lubricating oil additives and organophosphate flame retardants, and relates to a method for preparing isopropylated triphenyl phosphate with low triphenyl phosphate content. Background Technology

[0002] Isopropylphenyl phosphate (IPPP) is a low-volatility, water-resistant compound with good flame retardancy, thermal oxidation stability, and anti-wear and friction-reducing properties. It is an important class of phosphorus-containing plasticizers, flame retardants, and extreme-pressure anti-wear agents. This type of product can be widely used as a flame-retardant plasticizer for polyvinyl chloride, polypropylene, polyester, polyurethane foam, phenolic resins, and rubber, and also as an extreme-pressure anti-wear additive for lubricating oils and a base oil for flame-retardant hydraulic fluids. Due to the long-standing controversy surrounding the toxicity of tricresyl phosphate, and the fact that tris(xylene) phosphate is listed as a substance of very high concern under the EU REACH regulation due to its reproductive toxicity, with its usage limited to no more than 1000 ppm, the relatively low-toxicity and biodegradable isopropylphenyl phosphate has become a substitute for tricresyl phosphate. Given the significant concern about "aircraft cabin air pollution," there have been reports of using isopropylphenyl phosphate to replace tricresyl phosphate in aviation engine oils. Undoubtedly, isopropyltriphenyl phosphate, which is relatively low in toxicity and has a certain degree of biodegradability, has good application prospects in the fields of flame retardant plasticizers and lubricants.

[0003] Currently, in industrial production, isopropylphenol is prepared by alkylation of phenol and propylene, followed by reaction with phosphorus oxychloride to produce crude isopropyltriphenyl phosphate. The product is then purified through methods such as atmospheric pressure acid removal, negative pressure acid removal, solvent washing with alkali and water, and high-temperature distillation (270°C). Isopropyltriphenyl phosphate produced using this traditional method often suffers from drawbacks such as high acid value, high free phenol content, and dark color. More importantly, it contains a high proportion of the harmful component—triphenyl phosphate (TPP). This is mainly because the isopropylation products of phenol are complex, often containing a small amount of phenol, a large amount of p-isopropylphenol and o-isopropylphenol, and trace amounts of diisopropylphenol, or even triisopropylphenol, with the specific composition ratio depending on the degree of alkylation of phenol. Furthermore, to obtain the desired physicochemical properties such as viscosity and phosphorus content, phenol is often intentionally introduced during the preparation of isopropyltriphenyl phosphate. To obtain isopropyltriphenyl phosphate with lower viscosity and higher phosphorus content, the proportion of phenol in the reactants must be higher than that of isopropylphenol. Conversely, to obtain high-viscosity isopropyltriphenyl phosphate, the amount of isopropylphenol added must be higher than that of phenol, or even the entire reaction may be carried out using isopropylphenol as the raw material. Therefore, industrially produced isopropyltriphenyl phosphate is not a pure substance, but a mixed triaryl phosphate ester composed of isopropyltriphenyl phosphate (TPP), diphenyl isopropylbenzene phosphate, di(isopropylbenzene) monophenyl phosphate, tri(isopropylbenzene) phosphate, and other isopropyltriphenyl phosphates. Due to the low steric hindrance and high reactivity of phenol, triphenyl phosphate (TPP) will inevitably exist as a byproduct in isopropyltriphenyl phosphate, with the content typically ranging from 5% to 50% depending on the preparation process. Although triphenyl phosphate is also a type of phosphorus-containing flame retardant, it is hygroscopic, and its hydrolytic and thermal stability are inferior to alkylated triaryl phosphates. Its presence affects the stability of isopropylated triphenyl phosphate. More importantly, triphenyl phosphate is non-biodegradable and highly toxic to aquatic organisms, potentially leading to long-term adverse effects on the ecological environment. Therefore, its high proportion in isopropylated triphenyl phosphate products significantly diminishes the inherent environmentally friendly properties of isopropylated triphenyl phosphate, making it unsuitable for application in related technological fields. Numerous technologies in this field have been developed to reduce the triphenyl phosphate content in isopropylated triphenyl phosphate products through production and post-processing steps.For example, patent CN 101426801 discloses a method for preparing low-triphenyl phosphate (<1 wt%), high-phosphorus-content (5-10 wt%), and highly ortho-alkylated isopropylphenyl phosphate. This method primarily involves controlling the degree of isopropylation of phenol from the source, resulting in a phenol content as low as 0.5% and an isopropylphenol content as high as 88% in the isopropylated phenol material. Furthermore, the preparation process employs a two-stage method. In the first stage, under the action of a catalyst, the isopropylated phenol reacts with phosphorus oxychloride to generate monoisopropylphenyl dichlorophosphate. Excess POCl3 is then removed, followed by a second-stage reaction with phenol, resulting in a triphenyl phosphate content in the crude product as low as 1 wt%. Finally, the crude product is flash-evaporated to obtain the isopropylated triphenyl phosphate product. Patent US 5206404 discloses a method for obtaining alkylated triphenyl phosphate with a triphenyl phosphate content of less than 2% using thin-film evaporation, but this method severely degrades the product's color and acid value. US Patent 6232485 discloses a method for preparing liquid alkylated triaryl phosphates with low triphenyl phosphate content, low viscosity, and high meta-alkylation. Its key feature is that after conventional alkylation of phenol, a one-step alkyl transfer reaction is carried out using a special catalyst such as acid-activated bentonite or montmorillonite, thereby increasing the meta-isomer content in the alkylphenol to approximately 40% while reducing the phenol content to approximately 20%. The alkylated triphenyl phosphates prepared by reacting the aforementioned alkylphenol with phosphorus oxychloride are all low-viscosity liquids, with a triphenyl phosphate content of less than 2%. However, its disadvantage is that the excessively long alkylation reaction stage exacerbates 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. Summary of the Invention

[0004] The purpose of this invention is to provide a method for preparing isopropyltriphenyl phosphate with low triphenyl phosphate content. This method is simple to operate, does not introduce new impurities, and does not generate a large amount of "three wastes". It can effectively avoid the problem of large amounts of phosphate-containing organic wastewater discharge caused by alkaline washing and water washing in traditional processes, and greatly reduces environmental pollution in the production process.

[0005] The technical solution adopted in this invention is a method for preparing isopropyltriphenyl phosphate with low triphenyl phosphate content, and the specific preparation steps are as follows:

[0006] Step 1: After adding isopropylphenol, phenol, phosphorus oxychloride and catalyst into the reactor, the reaction is completed to obtain crude isopropylated triphenyl phosphate.

[0007] Step 2: Perform vacuum distillation on the crude isopropylated triphenyl phosphate. Stop vacuum distillation when the acid value of the crude isopropylated triphenyl phosphate is ≤3mgKOH / g.

[0008] Step 3: Perform molecular distillation on the crude isopropylated triphenyl phosphate that was distilled under reduced pressure in Step 2 to obtain the isopropylated triphenyl phosphate product.

[0009] The invention is further characterized in that,

[0010] Isopropylphenol is any one or a mixture of several of p-isopropylphenol, o-isopropylphenol, and m-isopropylphenol.

[0011] The catalyst is a Lewis acid, specifically one or two of aluminum trichloride, magnesium chloride, and titanium tetrachloride.

[0012] The preferred molar ratio of phosphorus oxychloride, isopropylphenol, and phenol is 1:1.0-3.0:0.5-3.0.

[0013] The reaction conditions in step 1 are: slowly raise the temperature to 150-150℃ and keep the temperature for 8-16 hours.

[0014] In step 2, the crude isopropyltriphenyl 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 4–12 h.

[0015] The specific steps of molecular distillation in step 3 are as follows:

[0016] Step 3.1: The crude isopropyltriphenyl phosphate, after vacuum distillation, is subjected to primary molecular distillation to remove light phase impurities, yielding a primary light phase distillate and a primary heavy phase distillate.

[0017] 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 to obtain secondary light phase distillate and secondary heavy phase distillate;

[0018] Step 3.3: Enrich the secondary heavy phase distillate and test the secondary light phase distillate. If it meets the product index requirements, the distillation is complete and the isopropyltriphenyl phosphate product is obtained. If it does not meet the product index requirements, repeat the distillation process of steps 3.1 and 3.2 until the light phase distillate of the last distillation meets the product index requirements and the isopropyltriphenyl phosphate product is obtained.

[0019] Step 3.4: The enriched primary light phase distillate is subjected to molecular distillation to recover substances such as phenol, isopropylphenol, and triphenyl phosphate. The enriched secondary heavy phase distillate is subjected to molecular distillation to recover isopropylated triphenyl phosphate.

[0020] In step 3.1, the temperature for primary molecular distillation to remove light phase impurities is 130–180°C, the vacuum degree is 0.01–50 Pa, and the light phase distillate accounts for 5%–25% of the total distillate by mass.

[0021] In step 3.2, the temperature for secondary molecular distillation to remove heavy phase impurities from the primary heavy phase distillate is 150–180°C, and the vacuum degree is 0.01–10 Pa, maintaining the light phase distillate at 75%–95% of the total distillate mass.

[0022] The product specifications in step 3.3 are as follows: free phenol content ≤ 0.01%, triphenyl phosphate content ≤ 0.1%, acid value ≤ 0.01 mg KOH / g, effective component content ≥ 99.5%, and color APHA ≤ 100.

[0023] The beneficial effects of this invention are:

[0024] (1) The molecular distillation process used in the purification of isopropyltriphenyl 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 generated by alkaline washing and water washing in traditional processes, and greatly reduce environmental pollution in the production process.

[0025] (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, isopropylphenol, and triphenyl phosphate, and enriching isopropylated triphenyl phosphate with almost no loss of isopropylated 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;

[0026] (3) The isopropylated triphenyl phosphate prepared by the method of the present invention has a light color, high content of effective components, and low content of triphenyl phosphate. It can be used in aviation fuel 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. It can realize continuous production and is suitable for industrial production. Attached Figure Description

[0027] Figure 1 This is a liquid chromatogram of the isopropylated triphenyl phosphate product prepared by the method in Comparative Example 1 of this invention.

[0028] Figure 2 This is a liquid chromatogram of the isopropylated triphenyl phosphate product prepared according to Examples 1-2 of the preparation method of the low triphenyl phosphate content of the present invention.

[0029] Figure 3This is a liquid chromatogram of the isopropylated triphenyl phosphate product prepared by Example 2-2 of the preparation method of the low triphenyl phosphate content of the present invention.

[0030] Figure 4 This is a liquid chromatogram of the isopropylated triphenyl phosphate product prepared by Example 3 of the preparation method of the low triphenyl phosphate content of the present invention. Detailed Implementation

[0031] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments.

[0032] The present invention discloses a method for preparing isopropylated triphenyl phosphate with low triphenyl phosphate content, the specific preparation steps of which are as follows:

[0033] Step 1: After adding isopropylphenol, phenol, phosphorus oxychloride and catalyst into the reactor, the temperature is slowly raised to 150-150℃ and the reaction is maintained for 8-16 hours to obtain crude isopropylated triphenyl phosphate.

[0034] The molar ratio of phosphorus oxychloride, isopropylphenol, and phenol is 1:1.0-3.0:0.5-3.0; the isopropylphenol is any one or a mixture of several of p-isopropylphenol, o-isopropylphenol, and m-isopropylphenol; the catalyst is a Lewis acid, specifically one or two of aluminum trichloride, magnesium chloride, and titanium tetrachloride.

[0035] The isopropylphenol, phenol, phosphorus oxychloride, and catalyst can be fed in one go or in stages.

[0036] Step 2: Under conditions of 100-180℃ and vacuum degree of 0.1-5kPa, the crude isopropylated triphenyl phosphate is subjected to vacuum distillation for 4-12 hours. When the acid value of the crude isopropylated triphenyl phosphate is ≤3mgKOH / g, the vacuum distillation is stopped.

[0037] Step 3: Perform molecular distillation on the crude isopropylated triphenyl phosphate that was distilled under reduced pressure in Step 2 to obtain the isopropylated triphenyl phosphate product.

[0038] The specific steps of molecular distillation are as follows:

[0039] Step 3.1: The crude isopropyltriphenyl phosphate, after vacuum distillation, is subjected to primary molecular distillation to remove light phase impurities. The temperature for primary molecular distillation to remove light phase impurities is 130–180℃, and the vacuum degree is 0.01–50 Pa. The light phase distillate accounts for 5%–25% of the total distillate by mass. Finally, primary light phase distillate and primary heavy phase distillate are obtained. This treatment step removes free phenol, isopropylphenol, triphenyl phosphate, and low-boiling-point impurities such as mono- and diester phosphates in the form of primary light phase distillate, and collects isopropyltriphenyl phosphate in the form of primary heavy phase distillate.

[0040] Step 3.2: The primary heavy phase distillate is subjected to heavy phase impurity removal treatment. The temperature for heavy phase impurity removal treatment of the primary heavy phase distillate is 150-180℃ and the vacuum degree is 0.01-10Pa. The light phase distillate accounts for 75%-95% of the total distillate mass percentage, resulting in secondary light phase distillate and secondary heavy phase distillate. This treatment step collects the isopropyltriphenyl phosphate product in the form of secondary light phase distillate and removes high-boiling-point impurities such as polyphosphate esters and pigments in the form of secondary heavy phase distillate.

[0041] Step 3.3: Enrich the secondary heavy phase distillate and test the secondary light phase distillate. If it meets the product index requirements, the distillation is complete and the isopropyltriphenyl phosphate product is obtained. If it does not meet the product index requirements, repeat the distillation process of steps 3.1 and 3.2 until the light phase distillate of the last distillation meets the product index requirements and the isopropyltriphenyl phosphate product is obtained.

[0042] The product requirements are as follows: the free phenol content in the isopropyltriphenyl phosphate product is ≤0.01%, the triphenyl phosphate content is ≤0.1%, the acid value is ≤0.01mgKOH / g, the effective component content is ≥99.5%, and the color APHA is ≤100.

[0043] Step 3.4: The enriched primary light phase distillate is subjected to molecular distillation at a temperature of 130–180°C and a vacuum of 0.01–50 Pa, maintaining the light phase distillate at 5%–25% of the total distillate mass to recover substances such as phenol, isopropylphenol, and triphenyl phosphate. The enriched secondary heavy phase distillate is then subjected to molecular distillation at a temperature of 150–180°C and a vacuum of 0.01–10 Pa, maintaining the light phase distillate at 75%–95% of the total distillate mass to recover isopropylated triphenyl phosphate.

[0044] The preparation method of the present invention will be described below by way of comparison and examples:

[0045] Comparative Example 1

[0046] To better illustrate the key technical features of the present invention, this embodiment uses a product of isopropylated triphenyl phosphate prepared by conventional processes such as adsorption by adsorbent, alkaline washing, water washing, and dehydration as a comparative example to illustrate the present invention.

[0047] In a 3000 mL reactor equipped with a mechanical stirrer, thermometer, condenser, and hydrogen chloride tail gas absorption device, 613 g of phosphorus oxychloride and 2.00 g of anhydrous aluminum chloride catalyst were added. The mixture was stirred and slowly heated to 100 °C. At this temperature, 545 g of o-isopropylphenol was slowly added. After the o-isopropylphenol was added, the reaction was continued for 3 hours. Then, 829 g of molten phenol was slowly added to the above reaction system in five batches, and the temperature was raised to 150 °C and the reaction was continued for 8 hours. The reaction product was then distilled under reduced pressure at 180 °C and 5 kPa for 6 hours, and its acid value was measured. When the acid value was found to be 1.18 mg KOH / g, the reduced pressure distillation was stopped. After cooling to room temperature, 5% (by mass) of adsorbent was added to the crude product, and the mixture was heated to 90 °C for 2 hours to equilibrate before filtering to remove the adsorbent. 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 isopropylated triphenyl phosphate product. Liquid chromatography and routine analyses, including phosphorus content detection, were performed. 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 kg of waste solvent, and about 10 kg of wastewater containing a small amount of phosphate ester, resulting in a large discharge of "three wastes."

[0048] Example 1

[0049] In a 3000 mL reactor equipped with a mechanical stirrer, thermometer, condenser, and hydrogen chloride tail gas absorption device, 613 g of phosphorus oxychloride and 2.00 g of anhydrous aluminum chloride catalyst were added. The mixture was stirred and slowly heated to 100 °C, at which point 545 g of o-isopropylphenol was slowly added. After the o-isopropylphenol was added, the reaction was continued for 3 hours. Then, 829 g of phenol was slowly added to the reaction system in five batches, and the temperature was raised to 150 °C and the reaction was continued for 8 hours to obtain crude isopropylated triphenyl phosphate. The crude isopropylated triphenyl phosphate was subjected to vacuum distillation at 180 °C and 5 kPa for 6 hours, and its acid value was measured. When the acid value was found to be 2.35 mg KOH / g, vacuum distillation was stopped. The vacuum-distilled crude isopropylated triphenyl phosphate was then introduced into a molecular distillation apparatus for primary molecular distillation to remove light phase impurities. The evaporation temperature was set at 145℃ and the vacuum degree at 10Pa. Other molecular distillation parameters were adjusted to maintain the light phase distillate at 10% of the total distillate mass, and distillation was continued. The first-stage light phase distillate was recovered and enriched, while the first-stage heavy phase distillate directly entered the second-stage molecular distillation for heavy phase impurity removal. The evaporation temperature was set at 156℃ and the vacuum degree at 0.1Pa. Other molecular distillation parameters were adjusted to maintain the light phase distillate at 90% of the total distillate mass. The resulting second-stage heavy phase distillate was recovered and enriched. The second-stage light phase distillate was isopropyltriphenyl phosphate. It underwent liquid chromatography analysis and routine analysis such as phosphorus content detection. The analytical results are shown in Table 1, Example 1-1. Since the acid value and effective component content did not meet the requirements, the first and second-stage molecular distillation steps were repeated. The analytical results of the obtained isopropyltriphenyl phosphate product are shown in Table 1, Example 1-2. The entire preparation process of this method, except for the hydrogen chloride tail gas which requires a special absorption device, basically does not generate other "three wastes". The distillates generated in each step can be recovered, enriched and then treated by molecular distillation for reuse.

[0050] Example 2

[0051] In a 3000 mL reactor equipped with a mechanical stirrer, thermometer, condenser, and hydrogen chloride tail gas absorption device, 613 g of phosphorus oxychloride and 2.15 g of anhydrous titanium tetrachloride catalyst were added. The mixture was stirred and slowly heated to 100 °C. At this temperature, 709 g of p-isopropylphenol was slowly added. After the p-isopropylphenol was added, the reaction was continued for 4 hours. Then, 704 g of phenol was added to the reaction system at once, and the temperature was raised to 145 °C and the reaction was continued for 16 hours. The reaction product was then distilled under reduced pressure at 180 °C and 5 kPa for 12 hours, and its acid value was measured. When the acid value was found to be 2.01 mg KOH / g, the reduced pressure 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 130 °C and the vacuum degree at 0.01 Pa. The remaining molecular distillation parameters were adjusted to maintain the light phase distillate accounting for 10% of the total distillate mass, and the distillation process was continued. The obtained light-phase distillate was recovered and enriched, while the heavy-phase distillate was directly fed into the second-stage molecular distillation for heavy-phase impurity removal. The evaporation temperature was set to 180℃ and the vacuum to 10Pa. 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 obtained heavy-phase distillate was recovered and enriched, and the light-phase distillate was identified as isopropyltriphenyl phosphate. Liquid chromatography and routine analyses, including phosphorus content testing, were performed. The results are shown in Table 1, Example 2-1. Since the acid value and purity did not meet the requirements, the first and second-stage molecular distillation steps were repeated. The analytical results of the obtained isopropyltriphenyl 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, generates virtually no other waste. The distillates produced at each stage can be recovered, enriched, and then reused after further molecular distillation.

[0052] Example 3

[0053] In a 3000mL reaction flask equipped with a mechanical stirrer, thermometer, condenser, and hydrogen chloride tail gas absorption device, 613g of phosphorus oxychloride and 2.50g of anhydrous magnesium chloride catalyst were added. The mixture was stirred and slowly heated to 100℃, at which point 1090g of m-isopropylphenol was slowly added. After the addition of m-isopropylphenol, the reaction was continued for 3 hours. Then, 414g of molten phenol was added to the above reaction system in five batches, and the temperature was raised to 155℃ and the reaction was continued for 12 hours. The reaction product was then distilled under reduced pressure at 100℃ and 0.1kPa for 10 hours, and its acid value was measured. When the acid value was found to be 1.79mgKOH / g, the reduced pressure 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 180℃ and the vacuum degree at 50Pa. The remaining molecular distillation parameters were adjusted to maintain the light phase distillate accounting for 15% of the total distillate by 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 to 150°C and the vacuum to 0.01 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 identified as isopropyltriphenyl phosphate. Liquid chromatography and routine analyses, including phosphorus content detection, were performed. The results are shown in Table 1, Example 3. The entire preparation process, except for the hydrogen chloride tail gas which requires a dedicated absorption device, generates virtually no other waste. The distillates produced at each stage can be recovered, enriched, and then reused after further molecular distillation.

[0054] Table 1. Analytical data of isopropyltriphenyl phosphate prepared in the examples.

[0055]

[0056] The data analysis in Table 1 shows that the isopropylated triphenyl phosphate product prepared by Comparative Example 1 using conventional processes such as adsorption with adsorbent, solvent addition, alkali washing, water washing, solvent removal, and dehydration is inferior to the isopropylated triphenyl phosphate products prepared by Examples 1, 2, and 3 of this invention in terms of color and isopropylated triphenyl phosphate content, especially in terms of triphenyl 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 2.752 min is triphenyl phosphate. The preparation method of this invention can achieve the preparation of isopropylated triphenyl phosphate with low triphenyl phosphate content and different viscosity levels 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. Figure 2Appendix Figure 3 and attached Figure 4 The characteristic chromatographic peaks of triphenyl phosphate did not appear in the medium liquid chromatograms at a retention time of approximately 2.75 min, indicating that the content of triphenyl phosphate in Examples 1-2, 2-2, and 3 was extremely low.

[0057] To further illustrate the preparation method of isopropylated triphenyl phosphate of the present invention, the following examples will be used for further explanation:

[0058] Example 4

[0059] In a 3000 mL reactor equipped with a mechanical stirrer, thermometer, condenser, and hydrogen chloride tail gas absorption device, 613 g of phosphorus oxychloride and 2.2 g of anhydrous aluminum chloride catalyst were added. The mixture was stirred and slowly heated to 100 °C, at which point 1367 g of m-isopropylphenol was slowly added. After the addition of m-isopropylphenol, the reaction was continued for 3 hours. Then, 188 g of phenol was slowly added to the reaction system in three batches, and the reaction was continued for 10 hours at 150 °C to obtain crude isopropyltriphenyl phosphate. The crude isopropyltriphenyl phosphate was subjected to vacuum distillation at 150 °C and 3 kPa for 6 hours, and its acid value was measured. When the acid value was found to be 2.05 mg KOH / g, vacuum distillation was stopped. The vacuum-distilled crude isopropyltriphenyl phosphate was then subjected to primary molecular distillation to remove light phase impurities. The evaporation temperature was set at 150℃ and the vacuum degree at 10Pa. Other molecular distillation parameters were adjusted to maintain the light phase distillate at 25% of the total distillate mass, and distillation was continued. The first-stage light phase distillate was recovered and enriched, while the first-stage heavy phase distillate directly entered the second-stage molecular distillation for heavy phase impurity removal. The evaporation temperature was set at 165℃ and the vacuum degree at 0.1Pa. Other molecular distillation parameters were adjusted to maintain the light phase distillate at 95% of the total distillate mass. The resulting second-stage heavy phase distillate was recovered and enriched. The second-stage light phase distillate was isopropyltriphenyl phosphate, which underwent liquid chromatography analysis and routine analysis such as phosphorus content detection. Since the acid value and effective component content did not yet meet the requirements, the first and second-stage molecular distillation steps were repeated to obtain isopropyltriphenyl phosphate product that met the detection requirements. The entire preparation process of this method, except for the hydrogen chloride tail gas which requires a dedicated absorption device, generates virtually no other waste. The distillates generated in each stage can be recovered, enriched, and then reused after further molecular distillation.

[0060] Example 5

[0061] In a 3000 mL reactor equipped with a mechanical stirrer, thermometer, condenser, and hydrogen chloride tail gas absorption device, 613 g of phosphorus oxychloride and anhydrous titanium tetrachloride and anhydrous magnesium chloride catalysts were added. A total of 2.15 g of anhydrous titanium tetrachloride and anhydrous magnesium chloride (1.2 g of anhydrous titanium tetrachloride and 0.95 g of anhydrous magnesium chloride) was weighed out. The mixture was stirred and slowly heated to 150 °C. At this temperature, 709 g of p-isopropylphenol was slowly added. After the p-isopropylphenol was added, 704 g of phenol was added to the reaction system in one go, and the reaction was continued at 150 °C for 16 h. The reaction product was then distilled under reduced pressure at 180 °C and 5 kPa for 12 h, and its acid value was measured. When the acid value was found to be 2.13 mg KOH / g, the reduced pressure 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 130℃ and the vacuum degree at 0.01 Pa. Other molecular distillation parameters were adjusted to maintain the light phase distillate at 10% of the total distillate mass, and distillation was continued. The resulting light phase distillate was recovered and enriched, while the heavy phase distillate directly entered the second-stage molecular distillation for heavy phase impurity removal. The evaporation temperature was then set and adjusted to 180℃ and the vacuum degree to 10 Pa. Other molecular distillation parameters were adjusted to maintain the light phase distillate at 75% of the total distillate mass, and distillation was continued until all products were processed. The resulting heavy phase distillate was recovered and enriched, and the light phase distillate was the isopropyltriphenyl phosphate product. It was subjected to liquid chromatography analysis and routine analysis such as phosphorus content detection. The entire preparation process, except for the hydrogen chloride tail gas which requires a dedicated absorption device, generates virtually no other waste. The distillates generated at each stage can be recovered, enriched, and then reused after further molecular distillation.

[0062] Example 6

[0063] In a 3000 mL reactor equipped with a mechanical stirrer, thermometer, condenser, and hydrogen chloride tail gas absorption device, 613 g of phosphorus oxychloride, anhydrous titanium tetrachloride and anhydrous aluminum chloride were added as catalysts. A total of 2.15 g of anhydrous titanium tetrachloride and anhydrous magnesium chloride (1.0 g of anhydrous titanium tetrachloride and 1.15 g of anhydrous aluminum chloride) were weighed out. The mixture was stirred and slowly heated to 150 °C. At this temperature, 709 g of p-isopropylphenol was slowly added. After the p-isopropylphenol was added, 704 g of phenol was added to the reaction system in one go, and the reaction was continued at 150 °C for 16 h. The reaction product was then distilled under reduced pressure at 180 °C and 5 kPa for 12 h, and its acid value was measured. When the acid value was found to be 2.18 mg KOH / g, the reduced pressure 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 130℃ and the vacuum degree at 0.01 Pa. Other molecular distillation parameters were adjusted to maintain the light phase distillate at 10% of the total distillate mass, and distillation was continued. The resulting light phase distillate was recovered and enriched, while the heavy phase distillate directly entered the second-stage molecular distillation for heavy phase impurity removal. The evaporation temperature was then set and adjusted to 180℃ and the vacuum degree to 10 Pa. Other molecular distillation parameters were adjusted to maintain the light phase distillate at 75% of the total distillate mass, and distillation was continued until all products were processed. The resulting heavy phase distillate was recovered and enriched, and the light phase distillate was the isopropyltriphenyl phosphate product. It was subjected to liquid chromatography analysis and routine analysis such as phosphorus content detection. The entire preparation process, except for the hydrogen chloride tail gas which requires a dedicated absorption device, generates virtually no other waste. The distillates generated at each stage can be recovered, enriched, and then reused after further molecular distillation.

[0064] Example 7

[0065] In a 3000 mL reactor equipped with a mechanical stirrer, thermometer, condenser, and hydrogen chloride tail gas absorption device, 613 g of phosphorus oxychloride, anhydrous magnesium chloride and anhydrous aluminum chloride catalysts, and 2.15 g of anhydrous titanium tetrachloride and anhydrous magnesium chloride (1.0 g of anhydrous magnesium chloride and 1.15 g of anhydrous aluminum chloride) were added. The mixture was stirred and slowly heated to 150 °C, at which point 709 g of p-isopropylphenol was slowly added. After the p-isopropylphenol was added, 704 g of phenol was added to the reaction system in one go, and the reaction was continued at 150 °C for 16 h. The reaction product was then distilled under reduced pressure at 180 °C and 5 kPa for 12 h, and its acid value was measured. When the acid value was found to be 1.97 mg KOH / g, the reduced pressure 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 130℃ and the vacuum degree at 0.01 Pa. Other molecular distillation parameters were adjusted to maintain the light phase distillate at 10% of the total distillate mass, and distillation was continued. The resulting light phase distillate was recovered and enriched, while the heavy phase distillate directly entered the second-stage molecular distillation for heavy phase impurity removal. The evaporation temperature was then set and adjusted to 180℃ and the vacuum degree to 10 Pa. Other molecular distillation parameters were adjusted to maintain the light phase distillate at 80% of the total distillate mass, and distillation was continued until all products were processed. The resulting heavy phase distillate was recovered and enriched, and the light phase distillate was the isopropyltriphenyl phosphate product, which underwent liquid chromatography analysis and routine analysis such as phosphorus content detection. The entire preparation process, except for the hydrogen chloride tail gas which requires a dedicated absorption device, generates virtually no other waste. The distillates generated at each stage can be recovered, enriched, and then reused after further molecular distillation.

[0066] Example 8

[0067] In a 3000 mL reactor equipped with a mechanical stirrer, thermometer, condenser, and hydrogen chloride tail gas absorption device, 613 g of phosphorus oxychloride and 2.0 g of anhydrous magnesium chloride catalyst were added. The mixture was stirred and slowly heated to 150 °C. At this temperature, 1090 g of isopropylphenol (with a mass ratio of 1:1 for p-isopropylphenol and o-isopropylphenol) was slowly added. After the addition of isopropylphenol, 414 g of phenol was added to the reaction system in one go, and the reaction was continued at 150 °C for 14 h. The reaction product was then distilled under reduced pressure at 180 °C and 5 kPa for 12 h, and its acid value was measured. When the acid value was found to be 2.43 mg KOH / g, the reduced pressure 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 130 °C and the vacuum degree at 0.01 Pa. The remaining molecular distillation parameters were adjusted to maintain the light phase distillate at 10% 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 to 180℃ and the vacuum to 10Pa. Other molecular distillation parameters are adjusted to maintain the light-phase distillate at 85% 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 isopropyltriphenyl phosphate product. This product undergoes liquid chromatography analysis and routine analyses such as phosphorus content detection. The entire preparation process generates virtually no other waste, except for hydrogen chloride tail gas, which requires a dedicated absorption device. Distillates generated at each stage can be recovered, enriched, and reused after further molecular distillation.

[0068] Example 9

[0069] In a 3000 mL reactor equipped with a mechanical stirrer, thermometer, condenser, and hydrogen chloride tail gas absorption device, 613 g of phosphorus oxychloride and 2.0 g of anhydrous magnesium chloride catalyst were added. The mixture was stirred and slowly heated to 150 °C. At this temperature, 1090 g of isopropylphenol (with a mass ratio of 1:1 between meta-isopropylphenol and o-isopropylphenol) was slowly added. After the isopropylphenol was added, 414 g of phenol was added to the reaction system in one go, and the reaction was continued at 150 °C for 14 h. The reaction product was then distilled under reduced pressure at 180 °C and 5 kPa for 12 h, and its acid value was measured. When the acid value was found to be 2.43 mg KOH / g, the reduced pressure 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 130 °C and the vacuum degree at 0.01 Pa. The remaining molecular distillation parameters were adjusted to maintain the light phase distillate at 10% 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 to 180℃ and the vacuum to 10Pa. Other molecular distillation parameters are adjusted to maintain the light-phase distillate at 85% 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 isopropyltriphenyl phosphate product. This product undergoes liquid chromatography analysis and routine analyses such as phosphorus content detection. The entire preparation process generates virtually no other waste, except for hydrogen chloride tail gas, which requires a dedicated absorption device. Distillates generated at each stage can be recovered, enriched, and reused after further molecular distillation.

[0070] Example 10

[0071] In a 3000 mL reactor equipped with a mechanical stirrer, thermometer, condenser, and hydrogen chloride tail gas absorption device, 613 g of phosphorus oxychloride and 2.0 g of anhydrous magnesium chloride catalyst were added. The mixture was stirred and slowly heated to 150 °C. At this temperature, 1090 g of isopropylphenol (with a mass ratio of p-isopropylphenol to m-isopropylphenol of 1:1) was slowly added. After the isopropylphenol was added, 414 g of phenol was added to the reaction system in one go, and the reaction was continued at 150 °C for 14 h. The reaction product was then distilled under reduced pressure at 180 °C and 5 kPa for 12 h, and its acid value was measured. When the acid value was found to be 2.43 mg KOH / g, the reduced pressure 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 130 °C and the vacuum degree at 0.01 Pa. The remaining molecular distillation parameters were adjusted to maintain the light phase distillate accounting for 10% of the total distillate by 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 to 180℃ and the vacuum to 10Pa. 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 isopropyltriphenyl phosphate. This was subjected to liquid chromatography and routine analyses such as phosphorus content testing. Since the acid value and purity did not yet meet the requirements, the first and second-stage molecular distillation processes were repeated to obtain the isopropyltriphenyl phosphate product. The entire preparation process, except for the hydrogen chloride tail gas which requires a dedicated absorption device, generates virtually no other waste. The distillates produced at each stage can be recovered, enriched, and then reused after further molecular distillation.

Claims

1. A method for preparing isopropylated triphenyl phosphate with low triphenyl phosphate content, characterized in that, The specific preparation steps are as follows: Step 1: After adding isopropylphenol, phenol, phosphorus oxychloride and catalyst into the reactor, the reaction is completed to obtain crude isopropylated triphenyl phosphate. Step 2: Perform vacuum distillation on the crude isopropylated triphenyl phosphate. Stop vacuum distillation when the acid value of the crude isopropylated triphenyl phosphate is ≤3mgKOH / g. Step 3: Perform molecular distillation on the crude isopropylated triphenyl phosphate product obtained by vacuum distillation in Step 2 to obtain the isopropylated triphenyl phosphate product. The specific steps of molecular distillation are as follows: Step 3.1: The crude isopropyltriphenyl 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 5%–25% 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 150-180℃, the vacuum degree is 0.01-10Pa, 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 index requirements, the distillation is complete and the isopropyltriphenyl phosphate product is obtained. If it does not meet the product index requirements, repeat the distillation process of steps 3.1 and 3.2 until the light phase distillate of the last distillation meets the product index requirements and the isopropyltriphenyl phosphate product is obtained. Step 3.4: The enriched primary light phase distillate is subjected to molecular distillation to recover phenol, isopropylphenol, and triphenyl phosphate. The enriched secondary heavy phase distillate is subjected to molecular distillation to recover isopropylated triphenyl phosphate.

2. The method for preparing isopropylated triphenyl phosphate with low triphenyl phosphate content according to claim 1, characterized in that, The isopropylphenol is any one or a mixture of several of p-isopropylphenol, o-isopropylphenol, and m-isopropylphenol.

3. The method for preparing isopropylated triphenyl phosphate with low triphenyl phosphate content according to claim 1, characterized in that, The catalyst is a Lewis acid, specifically one or two of aluminum trichloride, magnesium chloride, and titanium tetrachloride.

4. The method for preparing isopropylated triphenyl phosphate with low triphenyl phosphate content according to claim 1, characterized in that, The molar ratio of phosphorus oxychloride, isopropylphenol, and phenol is 1:1.0~3.0:0.5~3.

0.

5. The method for preparing isopropylated triphenyl phosphate with low triphenyl phosphate content 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.

6. The method for preparing isopropylated triphenyl phosphate with low triphenyl phosphate content according to claim 1, characterized in that, In step 2, the crude isopropyltriphenyl 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 4–12 h.

7. A method for preparing isopropylated triphenyl phosphate with low triphenyl phosphate content according to claim 6, characterized in that, The product specifications mentioned in step 3.3 are as follows: the free phenol content in the isopropyltriphenyl phosphate product is ≤0.01%, the triphenyl phosphate content is ≤0.1%, the acid value is ≤0.01mgKOH / g, the effective component content is ≥99.5%, and the color APHA is ≤100.

Images