Efficient preparation method of antioxidant 168

Abstract

The invention relates to the technical field of organic synthesis, in particular to an efficient preparation method of an antioxidant 168, which comprises the following steps: by taking 2, 4-di-tert-butylphenol and phosphorus trichloride as raw materials, reacting for a certain time at a certain reaction temperature and pressure under the action of a catalyst to obtain a crude product, and refining to obtain the antioxidant 168. According to the method provided by the invention, the antioxidant 168 product with high yield and high purity can be obtained; meanwhile, the amine hydrochloride is used as the catalyst and can be recycled, so that the utilization rate of the raw materials is increased; in addition, according to the method provided by the invention, no solvent is involved in the synthesis stage, so that the efficiency of discharging the byproduct hydrogen chloride is greatly improved, the requirement on the vacuum degree is reduced, the reaction time is shortened, the preparation cost is reduced, the production operation process is simplified, and the method has a relatively great application prospect.

Description

Technical Field

[0001] The present invention belongs to the technical field of organic synthesis, and in particular relates to a method for efficiently preparing an antioxidant 168. Background Art

[0002] Antioxidant 168, chemical name tris (2,4-di-tert-butylphenyl) phosphite, is a phosphite auxiliary antioxidant with excellent performance. It has very low volatility and toxicity, high thermal stability, good hydrolysis stability, and can effectively decompose the hydroperoxides produced in the processing of polymer materials, thereby playing an antioxidant role. It is often used in combination with hindered phenol main antioxidants to give full play to the synergistic effect. It is widely used in polymer materials such as polyolefins, styrene monomers and copolymers, elastomers, adhesives, rubbers and engineering plastics.

[0003] At present, the method for synthesizing antioxidant 168 mainly uses phosphorus trichloride and 2,4-di-tert-butylphenol as raw materials, dichloroethane, xylene, toluene, 2,4-di-tert-butylphenol as solvents, triethylamine, DMAP, DMF, pyridine as catalysts, and generates the target product antioxidant 168 under the action of the catalyst. Unfortunately, the prior art uses amine catalysts such as triethylamine and di-n-butylamine, and the generated amine hydrochloride either becomes waste residue (CN109897062A) or is sold as a by-product (CN109593101A). Fortunately, the present invention finds that amine hydrochloride catalysts such as triethylamine hydrochloride and di-n-butylamine hydrochloride have better catalytic effects than their corresponding amine catalysts and can be recycled. In addition, most existing processes use a large amount of solvents in the synthesis stage of synthesizing antioxidant 168 in order to make the reaction system uniform. For example, patent CN110590834 A uses 50% to 80% of the mass of 2,4-di-tert-butylphenol as solvent. Patent CN 110590834 A uses 1 to 3 times the mass of 2,4-di-tert-butylphenol as solvent xylene. Patent CN 109593101 A uses 5.0 to 6.7 times the mass of phosphorus trichloride as 2,4-di-tert-butylphenol as solvent, and the synthesis time is 5 to 12 h. However, the presence of solvent makes it more difficult for the system to discharge the by-product hydrogen chloride through negative pressure or nitrogen, increases the incidence of side reactions, reduces the product yield, and prolongs the reaction time; in addition, the removal of solvent and the recycling of solvent complicate the post-processing process and greatly increase the preparation cost. What's worse, most of the existing technologies that use solvents in the synthesis stage separate the suspension into solid and liquid after the reaction is completed, and the filtrate needs to use a large amount of methanol, isopropanol and other solvents to crystallize the product. For example, patent CN117327115 A adds 5 times the weight of the solid material (w / v) of isopropanol and methyl tert-butyl ether = 5:1 mixed solvent (v / v) to the solid material obtained by distilling the solvent after the reaction. In summary, it is of great significance to find an efficient catalyst that is easy to prepare, low-cost, and recyclable, and to overcome the various shortcomings caused by the use of solvents. Summary of the invention

[0004] The technical problem to be solved by the present invention is to solve the problem that the prior art cannot utilize amine hydrochlorides, and to overcome the problems of the prior art that the use of solvents reduces product yield, complicates post-processing, and increases costs, thereby providing an efficient preparation method for antioxidant 168 to obtain a higher product yield and a simpler post-processing method, thereby reducing production costs to a certain extent.

[0005] In order to solve the above problems, the scheme of the present invention is as follows: Overview of synthesis and post-processing: 2,4-di-tert-butylphenol and phosphorus trichloride are used as raw materials, under the action of a catalyst, at a certain reaction temperature and pressure, and after a certain reaction time, a crude product is obtained, and then antioxidant 168 is obtained after purification.

[0006] Synthesis stage: heating at 60-90°C to melt 2,4-di-tert-butylphenol into liquid, adding catalyst and phosphorus trichloride at 55-65°C and carrying out the first stage of heat preservation, heating until the solution becomes slightly turbid, raising the temperature to 70-80°C to clarify the reaction system and carrying out the second stage of heat preservation, heating until the solution becomes slightly turbid, raising the temperature to 120-130°C to clarify the reaction system and carrying out the third stage of heat preservation, heating until the solution becomes slightly viscous, raising the temperature to 185-195°C to clarify the reaction system and carrying out the fourth stage of heat preservation, heating until no hydrogen chloride is discharged, stopping the reaction and waiting for refining.

[0007] During this stage, the reaction pressure gradually decreased from the initial 990 mbar to 800 mbar.

[0008] Key technology in the synthesis stage: By step-by-step heating to the appropriate temperature, the reaction system is kept homogeneous, thus eliminating the need for solvents.

[0009] Post-treatment refining stage: After the reaction, the high-temperature liquid is cooled under nitrogen atmosphere and stirring to precipitate white crystalline particles, which are then washed with alcohol, filtered and dried.

[0010] Catalyst recycling: After the alcohol washing liquid in the post-processing stage accumulates to a certain amount, the alcohol is distilled out, and a large amount of catalyst remains in the distillation kettle, which can be directly used as a raw material for reaction.

[0011] Furthermore, the catalyst is selected from amine catalysts such as triethylamine, tri-n-propylamine, di-n-butylamine, tri-n-butylamine, or amine hydrochloride catalysts such as triethylamine hydrochloride, tri-n-propylamine hydrochloride, di-n-butylamine hydrochloride, tri-n-butylamine hydrochloride.

[0012] Preferably, the catalyst is an amine hydrochloride catalyst such as triethylamine hydrochloride, tri-n-propylamine hydrochloride, di-n-butylamine hydrochloride, tri-n-butylamine hydrochloride, etc.

[0013] Preferably, the molar ratio of the catalyst to phosphorus trichloride is 0.01-0.20, and the molar ratio of 2,4-di-tert-butylphenol to phosphorus trichloride is 2.80-3.30.

[0014] Compared with the existing preparation method, the present invention has the following advantages: (1) The present invention uses a single catalyst, amine hydrochloride, which can be recycled. Other prior arts mistakenly believe that amine hydrochloride is a by-product. In addition, the present invention does not require the preparation of a complex catalyst like some prior arts.

[0015] (2) The method provided by the present invention does not involve solvents in the synthesis stage. On the one hand, for the synthesis stage, the solubility of hydrogen chloride in solvents such as xylene is extremely high, and the experimental synthesis stage of the present invention does not use solvents, so the by-product hydrogen chloride can be better discharged and does not require a large vacuum degree; in addition, the raw materials in the system without solvents are in direct contact in a molten state, and the reaction rate is faster than that of the system with solvents, shortening the reaction time. On the other hand, for the post-processing stage, the reaction system without solvents does not require distillation to remove solvents or add more solvents to crystallize the product, and no solvents such as xylene will remain in the product. After the reaction of the present invention, the high-temperature liquid is cooled under nitrogen atmosphere and stirring to precipitate white crystalline particles, washed with alcohol, filtered, and dried, which has the advantages of simple operation, low cost, and high product purity. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 HPLC chromatogram of the antioxidant 168 prepared in Example 1.

[0017] Figure 2 HPLC chromatogram of antioxidant 168 prepared in Example 2.

[0018] Figure 3 HPLC chromatogram of antioxidant 168 prepared in Example 3.

[0019] Figure 4 High performance liquid chromatogram of the reaction product of Comparative Example 1.

[0020] Figure 5 High performance liquid chromatogram of antioxidant 168 prepared in Comparative Example 2.

[0021] Figure 6 High performance liquid chromatogram of antioxidant 168 prepared in Comparative Example 3. DETAILED DESCRIPTION

[0022] The following is a detailed description of an efficient preparation method of an antioxidant 168 provided by the present invention in conjunction with the examples, but they should not be understood as limiting the scope of protection of the present invention. It is clear to those skilled in the art that, in the following, unless otherwise specified, the raw materials and operating methods selected by the present invention are well known in the art. Example 1: This embodiment provides an efficient preparation method of antioxidant 168 (using triethylamine hydrochloride as a catalyst, without using a solvent, and step-wise temperature increase), comprising the following steps: 886.40 g of 2,4-di-tert-butylphenol was added to a four-necked flask, and the oil temperature was set to 80 °C. The 2,4-di-tert-butylphenol was heated to completely melt. After the 2,4-di-tert-butylphenol was completely melted, when the internal temperature dropped to 65 °C, 8.50 g of catalyst triethylamine hydrochloride (the molar ratio to phosphorus trichloride was 0.04) was added, and then phosphorus trichloride was added dropwise through a dropping funnel (the molar ratio of 2,4-di-tert-butylphenol to phosphorus trichloride was 2.95; system pressure: 990 mbar). After the addition is completed, the first stage of heat preservation is carried out (system pressure: normal pressure 900 mbar). When the solution becomes slightly turbid, the temperature is raised to 70-80 °C to clarify the reaction system and the second stage of heat preservation is carried out (system pressure: 800 mbar). When the solution becomes slightly turbid, the temperature is raised to 120-130 °C to clarify the reaction system and the third stage of heat preservation is carried out (system pressure: 850 mbar). When the solution becomes slightly viscous, the temperature is raised to 185-195 °C to clarify the reaction system and the fourth stage of heat preservation is carried out (system pressure: 800 mbar). The reaction is stopped after the hydrogen chloride is no longer discharged and the mixture is purified.

[0023] Post-processing and refining process: After the reaction, the high-temperature liquid is cooled under nitrogen atmosphere and stirring to precipitate white crystalline particles. After the product is cooled to 30-80 °C, methanol is added for stirring and washing, filtered, and vacuum dried at 50 °C for 3-5 h. 895.15 g of white powder product is obtained with a yield of 96.61%. Samples are taken and product quality indicators are tested according to HG / T 3712-2010 "Antioxidant 168". The main content of 168 in the product is 99.86% (such as Figure 1 As shown), phenol content 0.14%, acid value 0.08 mg KOH / g, melting point 184.1~184.8 ℃.

[0024] After the alcohol washing liquid in the post-treatment stage accumulates to a certain amount, the alcohol is distilled out, and the distillation kettle contains a large amount of amine hydrochloride catalyst, which can be directly used as a raw material for reaction.

[0025] Embodiment 2: This embodiment provides an efficient preparation method of antioxidant 168 (using di-n-butylamine hydrochloride as a catalyst, without using a solvent, and step-wise heating), comprising the following steps: 886.40 g of 2,4-di-tert-butylphenol was added to a four-necked flask, and the oil temperature was set to 80 °C. The 2,4-di-tert-butylphenol was heated to completely melt. After the 2,4-di-tert-butylphenol was completely melted, when the internal temperature dropped to 65 °C, 10.23 g of catalyst di-n-butylamine hydrochloride (the molar ratio to phosphorus trichloride was 0.04) was added, and then phosphorus trichloride was added dropwise through a dropping funnel (the molar ratio of 2,4-di-tert-butylphenol to phosphorus trichloride was 2.95; system pressure: 990 mbar). After the addition is completed, the first stage of heat preservation is carried out (system pressure: normal pressure 900 mbar). When the solution becomes slightly turbid, the temperature is raised to 70-80 °C to clarify the reaction system and the second stage of heat preservation is carried out (system pressure: 800 mbar). When the solution becomes slightly turbid, the temperature is raised to 120-130 °C to clarify the reaction system and the third stage of heat preservation is carried out (system pressure: 850 mbar). When the solution becomes slightly viscous, the temperature is raised to 185-195 °C to clarify the reaction system and the fourth stage of heat preservation is carried out (system pressure: 800 mbar). The reaction is stopped after the hydrogen chloride is no longer discharged and the mixture is purified.

[0026] Post-processing and refining process: After the reaction, the high-temperature liquid is cooled under nitrogen atmosphere and stirring to precipitate white crystalline particles. After the product is cooled to 30-80 °C, methanol is added for stirring and washing, filtered, and vacuum dried at 50 °C for 3-5 h. 891.09 g of white powder product is obtained with a yield of 96.17%. Samples are taken and product quality indicators are tested according to HG / T 3712-2010 "Antioxidant 168". The main content of 168 in the product is 99.85% (such as Figure 2 As shown), phenol content 0.15%, acid value 0.09 mg KOH / g, melting point 183.5~184.6 ℃.

[0027] After the alcohol washing liquid in the post-treatment stage accumulates to a certain amount, the alcohol is distilled out, and the distillation kettle contains a large amount of amine hydrochloride catalyst, which can be directly used as a raw material for reaction.

[0028] Embodiment 3: This embodiment provides an efficient preparation method of antioxidant 168 (using triethylamine as a catalyst, without using a solvent, and step-wise temperature increase), comprising the following steps: 886.40 g of 2,4-di-tert-butylphenol was added to a four-necked flask, and the oil temperature was set to 80 °C. The 2,4-di-tert-butylphenol was heated to completely melt. After the 2,4-di-tert-butylphenol was completely melted, when the internal temperature dropped to 65 °C, 8.50 g of catalyst triethylamine (the molar ratio to phosphorus trichloride was 0.04) was added, and then phosphorus trichloride was added dropwise through a dropping funnel (the molar ratio of 2,4-di-tert-butylphenol to phosphorus trichloride was 2.95; system pressure: 990 mbar). After the addition is completed, the first stage of heat preservation is carried out (system pressure: normal pressure 900 mbar). When the solution becomes slightly turbid, the temperature is raised to 70-80 °C to clarify the reaction system and the second stage of heat preservation is carried out (system pressure: 800 mbar). When the solution becomes slightly turbid, the temperature is raised to 120-130 °C to clarify the reaction system and the third stage of heat preservation is carried out (system pressure: 850 mbar). When the solution becomes slightly viscous, the temperature is raised to 185-195 °C to clarify the reaction system and the fourth stage of heat preservation is carried out (system pressure: 800 mbar). The reaction is stopped after the hydrogen chloride is no longer discharged and the mixture is purified.

[0029] Post-processing and refining process: After the reaction, the high-temperature liquid is cooled under nitrogen atmosphere and stirring to precipitate white crystalline particles. After the product is cooled to 30-80 °C, methanol is added for stirring and washing, filtered, and vacuum dried at 50 °C for 3-5 h. 887.34 g of white powder product is obtained with a yield of 95.77%. Samples are taken and product quality indicators are tested according to HG / T 3712-2010 "Antioxidant 168". The main content of 168 in the product is 99.80% (such as Figure 3 As shown), phenol content 0.20%, acid value 0.10 mg KOH / g, melting point 183.7~184.6 ℃.

[0030] After the alcohol washing liquid in the post-treatment stage accumulates to a certain amount, the alcohol is distilled out, and the distillation kettle contains a large amount of amine hydrochloride catalyst, which can be directly used as a raw material for reaction.

[0031] Comparative Example 1: This comparative example is compared with Example 1, and in order to explore the importance of the catalyst (no catalyst, no solvent, step-by-step temperature increase), the following steps are included: 886.40 g of 2,4-di-tert-butylphenol was added to a four-necked flask, and the oil temperature was set to 80 °C. The 2,4-di-tert-butylphenol was heated to completely melt. After the 2,4-di-tert-butylphenol was completely melted, when the internal temperature dropped to 65 °C, phosphorus trichloride was added dropwise through a dropping funnel (the molar ratio of 2,4-di-tert-butylphenol to phosphorus trichloride was 2.95; system pressure: 990 mbar). After the addition is completed, the first stage of heat preservation is carried out (system pressure: normal pressure 900 mbar), and after 1 hour of heat preservation, the temperature is raised to 70~80℃ and the second stage of heat preservation is carried out (system pressure: 800 mbar), and after 1 hour of heat preservation, the temperature is raised to 120~130℃ and the third stage of heat preservation is carried out (system pressure: 850 mbar), and after 1 hour of heat preservation, the temperature is raised to 185~195℃ and the fourth stage of heat preservation is carried out (system pressure: 800 mbar), and the reaction is stopped after the heat preservation is completed. Samples are taken and product quality indicators are tested according to HG / T 3712-2010 "Antioxidant 168". The results of HPLC test show that no antioxidant 168 is generated in the product (such as Figure 4 No post-processing was performed.

[0032] Comparative Example 2: This comparative example is compared with Example 1, in order to explore the difference between using a solvent system and not using a solvent system (using triethylamine hydrochloride as a catalyst, using xylene as a solvent, and step-wise heating), comprising the following steps: 886.4 g of 2,4-di-tert-butylphenol and 200.0 g of xylene were added to a four-necked flask, and the oil temperature was set to 50 °C. The 2,4-di-tert-butylphenol was completely dissolved by heating and stirring. After the 2,4-di-tert-butylphenol was completely dissolved, 8.5 g of catalyst triethylamine hydrochloride (the molar ratio to phosphorus trichloride was 2.95) was added, and then phosphorus trichloride was added dropwise through a dropping funnel (the molar ratio of phenol to phosphorus trichloride was; system pressure: 990 mbar). After the addition was completed, the first stage of heat preservation was carried out (system pressure: normal pressure 900 mbar). After 1 h of heat preservation, the temperature was raised to 70-80 °C and the second stage of heat preservation was carried out (system pressure: 850 mbar). When the solution became slightly turbid, the temperature was raised to 130-150 °C to clarify the reaction system and the third stage of heat preservation was carried out (system pressure: 800 mbar). The reaction was stopped when the main content of antioxidant 168 in the product stopped increasing.

[0033] Post-processing and refining process: evaporate the solvent of the product under stirring, then cool down under nitrogen atmosphere and stirring to precipitate white crystalline particles. After the product is cooled to 30~80℃, methanol is added for stirring and washing, filtered, and vacuum dried at 50℃ for 3~5h. 872.82g of white powder product is obtained with a yield of 94.85%. Samples are taken and product quality indicators are tested according to HG / T 3712-2010 "Antioxidant 168". The main content of 168 in the product is 99.34% (such as Figure 5 As shown), phenol content is 0.27%, residual solvent xylene content is 0.39%, acid value is 0.22 mg KOH / g, and melting point is 183.2~184.4 ℃.

[0034] Comparative Example 3: This comparative example is compared with Example 1, in order to explore the importance of step-by-step heating (using triethylamine hydrochloride as a catalyst, without using a solvent, and non-step-by-step heating), comprising the following steps: This embodiment provides an efficient preparation method of antioxidant 168 (using triethylamine hydrochloride as a catalyst and without using a solvent), comprising the following steps: 886.40 g of 2,4-di-tert-butylphenol was added to a four-necked flask, and the oil temperature was set to 80 °C. The 2,4-di-tert-butylphenol was heated to completely melt. After the 2,4-di-tert-butylphenol was completely melted, when the internal temperature dropped to 65 °C, 8.50 g of the catalyst triethylamine hydrochloride (the molar ratio to phosphorus trichloride was 0.04) was added, and then phosphorus trichloride was added dropwise through a dropping funnel (the molar ratio of 2,4-di-tert-butylphenol to phosphorus trichloride was 2.95; system pressure: 990 mbar). After the addition was completed, the first stage of heat preservation was carried out (system pressure: normal pressure 900 mbar), and the temperature was raised to 185~195 °C when the solution became slightly turbid to clarify the reaction system and the second stage of heat preservation was carried out (system pressure: 800 mbar), and the reaction was stopped after the hydrogen chloride was discharged and the solution was purified.

[0035] Post-processing and refining process: After the reaction, the high-temperature liquid is cooled under nitrogen atmosphere and stirring to precipitate white crystalline particles. After the product is cooled to 30-80 °C, methanol is added for stirring and washing, filtered, and vacuum dried at 50 °C for 3-5 h. 864.30 g of white powder product is obtained with a yield of 93.28%. Samples are taken and product quality indicators are tested according to HG / T 3712-2010 "Antioxidant 168". The main content of 168 in the product is 99.71% (such as Figure 6 As shown), phenol content is 0.24%, acid value is 0.13 mg KOH / g, and melting point is 183.4~184.5 ℃.

[0036] After the alcohol washing liquid in the post-treatment stage accumulates to a certain amount, the alcohol is distilled out, and the distillation kettle contains a large amount of amine hydrochloride catalyst, which can be directly used as a raw material for reaction.

[0037] The experimental parameters and product conditions of Examples 1 to 3 and Comparative Examples 1 to 3 are summarized in Table 1. It can be seen from the data in the table that amine hydrochloride catalysts such as triethylamine hydrochloride and di-n-butylamine hydrochloride have better catalytic effects than their corresponding amine catalysts and can be recycled. This may be related to the boiling point of amine hydrochlorides being higher than that of their corresponding amines, which is not easy to escape and lose. Secondly, Comparative Example 1 shows that no antioxidant 168 is generated when there is no catalyst. In addition, Comparative Example 2 shows that the yield of the product antioxidant 168 using the solvent system is lower than that not using the solvent system, and the solvent xylene coated therein is easily retained in the product antioxidant 168 using the solvent system. This may be because under the same micro-negative pressure conditions, the hydrogen chloride using the solvent system is more difficult to discharge than the non-solvent system, which is related to the increase in side reactions. Finally, Comparative Example 3 shows that although the purity of the non-step temperature rise synthesis product is similar to that of the step temperature rise synthesis, the yield of the non-step temperature rise synthesis product will be reduced. Combined with the experimental phenomenon observed in Comparative Example 3 (a large amount of white solid was found in the condenser, and the solid was the raw material 2,4-di-tert-butylphenol as shown by HPLC test), it was analyzed that the reason for the decrease in yield when synthesizing the product by non-step temperature increase was that 2,4-di-tert-butylphenol (melting point: 53-56 °C; boiling point: 265 °C) that did not have time to react escaped to the condenser and was lost when the temperature was directly increased to a high temperature. Therefore, it is of great significance to combine the melting and boiling points of each reaction raw material and the reaction mechanism of the three stages, and to make the reaction system always homogeneous by step-by-step temperature increase to a suitable temperature.

[0038] It can be seen from the above embodiments that the above are only preferred implementations of the present invention, and the protection scope of the present invention is not limited to the above embodiments. All technical solutions under the concept of the present invention belong to the protection scope of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be regarded as the protection scope of the present invention.

[0039] Table 1 Summary of experimental parameters and product conditions of embodiments and comparative examples

Claims

1. An efficient preparation method of antioxidant 168, characterized in that: With 2,4-di-tert-butylphenol and phosphorus trichloride as raw materials, under the action of a catalyst, at a certain reaction temperature and pressure, after a certain reaction time, a crude product is obtained, and then after refining, antioxidant 168 is obtained.

2. The method for preparing an antioxidant 168 according to claim 1, characterized in that: The certain reaction temperature is a suitable temperature which is raised in steps during the experimental synthesis stage so that the reaction system is always homogeneous, thereby eliminating the need to use a solvent.

3. The efficient preparation method of an antioxidant 168 according to claim 1, characterized in that: The stepwise heating to a suitable temperature described in claim 2 is to heat at 60-90°C to melt 2,4-di-tert-butylphenol into a liquid, add a catalyst and phosphorus trichloride at 55-65°C and carry out the first stage of heat preservation, heat preservation until the solution becomes slightly turbid, heat preservation to 70-80°C to clarify the reaction system and carry out the second stage of heat preservation, heat preservation until the solution becomes slightly turbid, heat preservation to 120-130°C to clarify the reaction system and carry out the third stage of heat preservation, heat preservation until the solution becomes slightly viscous, heat preservation to 185-195°C to clarify the reaction system and carry out the fourth stage of heat preservation, heat preservation until no hydrogen chloride is discharged, stop the reaction, and wait for refining.

4. The efficient preparation method of antioxidant 168 according to claim 1, characterized in that: The reaction pressure was gradually reduced from an initial 990 mbar to 800 mbar.

5. The efficient preparation method of antioxidant 168 according to claim 1, characterized in that: The catalyst is selected from amine catalysts such as triethylamine, tri-n-propylamine, di-n-butylamine, tri-n-butylamine, or amine hydrochloride catalysts such as triethylamine hydrochloride, tri-n-propylamine hydrochloride, di-n-butylamine hydrochloride, tri-n-butylamine hydrochloride.

6. The efficient preparation method of an antioxidant 168 according to claim 1, characterized in that: The molar ratio of the catalyst to phosphorus trichloride is 0.01-0.20, and the molar ratio of 2,4-di-tert-butylphenol to phosphorus trichloride is 2.80-3.

30.

7. The efficient preparation method of antioxidant 168 according to claim 1, characterized in that: The refining is to cool the high temperature liquid after the reaction under nitrogen atmosphere and stirring to precipitate white crystalline particles, wash with alcohol, filter and dry.

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