A method for reducing antioxidant tmq impurities

Abstract

This invention provides a method for reducing impurities in antioxidant TMQ. During the continuous one-step preparation of antioxidant TMQ from acetone and aniline hydrochloride, a certain flow rate of gas is introduced to significantly reduce the impurity content in antioxidant TMQ, thereby increasing the effective content of antioxidant TMQ.

Description

Technical Field

[0001] This invention belongs to the field of fine chemical technology and relates to a method for reducing impurities in the antioxidant TMQ.

[0002] This invention relates to a method for reducing the impurity content of antioxidant TMQ during a continuous one-step preparation process, thereby increasing the effective content of antioxidant TMQ. Background Technology

[0003] Antioxidant TMQ, chemically known as 2,2,4-trimethyl-1,2-dihydroquinoline polymer, also called antioxidant RD, is mainly used as a rubber antioxidant and is one of the most in-demand rubber antioxidant products in both domestic and international markets. Currently, the industrial production processes for antioxidant TMQ include a two-step method (condensation and polymerization) and a one-step method (polymerization).

[0004] The two-step process involves aniline and acetone undergoing a condensation reaction in the presence of a catalyst (such as p-toluenesulfonic acid or benzenesulfonic acid). The reaction solution, or the neutralized reaction solution, is then distilled or fractionally purified to obtain 2,2,4-trimethyl-1,2-dihydroquinoline, i.e., the TMQ monomer. The TMQ monomer is then polymerized in the presence of a catalyst (such as hydrochloric acid) to obtain the 2,2,4-trimethyl-1,2-dihydroquinoline polymer. After neutralization, dehydration, and distillation, the antioxidant TMQ is obtained. The two-step method yields high-quality TMQ, with a dimer content exceeding 50% and a di, tri, and tetramer content exceeding 80%. However, the process is complex and has been largely phased out. Currently, some domestic manufacturers are using solid acids as condensation catalysts, synthesizing TMQ with an effective monomer content of approximately 80%, of which the dimer content is around 45%.

[0005] The one-step process involves aniline and acetone undergoing condensation and polymerization under the action of a catalyst (such as hydrochloric acid) to directly obtain a condensation solution containing 2,2,4-trimethyl-1,2-dihydroquinoline polymer. This condensation solution is then neutralized with liquid alkali, dehydrated, and distilled to obtain the antioxidant TMQ. The one-step production process typically adds benzene, cyclohexane, toluene, or xylene as solvents to azeotropically dehydrate the material and improve its flowability. Therefore, the synthesis methods for antioxidant TMQ can be categorized as "solvent-free" or "solvent-free" methods. In China, the industrial production of antioxidant TMQ mainly employs the solvent-free one-step synthesis process, including batch reactor processes and continuous tower or batch reactor processes. Regardless of the continuous process used, the solvent-free one-step synthesis process uses hydrochloric acid as a catalyst to condense aniline and acetone. The polymer contains approximately 30% dimers and 45-50% dimers, trimers, and tetramers.

[0006] Currently, the research focus of domestic antioxidant TMQ synthesis process is on how to increase the content of dimers, trimers, and tetramers while reducing the content of primary amines (such as 2,2-bis(4-aminophenyl)propane, abbreviated as IBA). Many production enterprises and research institutes have done a lot of research.

[0007] A representative example is Hu Shengyong and Yang Xinli's report in "Process Research on One-Step Synthesis of Antioxidant RD" (Fine Petrochemicals, 2005, (3): 36-38), which reported the one-step synthesis of antioxidant RD (i.e., antioxidant TMQ) using boron trifluoride as a polycondensation catalyst and toluene as a solvent. The content of di, tri, and tetramers was 86.66%, the primary amine was less than 1.0%, and the product quality reached the quality of antioxidant FR.

[0008] Sun Fengjuan and Meng Qingbao reported an improved two-step production process in "Research and Development of Antioxidant RD with High Effective Ingredient Content" (Rubber Technology Market, 2012, (3): 19-22). The process uses solid acid as a condensation and polymerization catalyst. The resulting product has a di, tri, and tetramer content of more than 80% and an IBA content of less than 0.1%. The product quality is comparable to that of similar foreign products and has been industrialized with an annual output of 10,000 tons.

[0009] In his paper “Research on New Process for Continuous Production of High-Quality TMQ” (China Rubber, 2017(20):46-48), Zhao Feng reported a tower-type continuous production process: qualified dehydrated aniline and aniline hydrochloride materials continuously enter the top of the tower-type polycondensation reactor, and acetone continuously enters from the bottom of the tower-type polycondensation reactor. The two materials fully contact and react under the action of the packing, and the final TMQ has a di, tri, and tetramer content of more than 65% and an IBA content of less than 0.1%.

[0010] Due to the highly complex reaction process during the polycondensation of TMQ, its composition is also exceptionally complex, containing over 60 components. Currently, only aniline, monomers, IBA, dimers, trimers, and tetramers can be qualitatively and quantitatively analyzed; the rest are unknown. Analysis of the liquid chromatography chromatogram of the continuously synthesized antioxidant TMQ revealed a large impurity peak between the dimer and trimer, with a higher concentration than the trimer. Qualitative analysis confirmed this impurity to be...

[0011] 2,2-bis(5,5,7-trimethyl-4,5-dihydroquinoline)propane (abbreviated as IBTMQ, hereinafter the same), has the following structural formula:

[0012] .

[0013] This impurity has the same structure as IBA, the difference being the substituent attached to the carbon atom at the 2-position of propane. However, there are currently no reports on how to control this IBTMQ impurity.

[0014] The typical liquid chromatogram and results of the continuously synthesized antioxidant TMQ are shown in the appendix. Figure 1 . Summary of the Invention

[0015] The purpose of this invention is to reduce the content of impurity IBTMQ in the existing continuous one-step preparation process of antioxidant TMQ, thereby increasing the content of active antioxidant TMQ.

[0016] This invention provides a method for reducing impurities in antioxidant TMQ. During the continuous one-step preparation of antioxidant TMQ from acetone and aniline hydrochloride, a certain flow rate of gas is introduced to significantly reduce the impurity content in antioxidant TMQ, thereby increasing the effective content of antioxidant TMQ.

[0017] The impurity is 2,2-bis(R)propane, where R is 4-aminophenyl or 2,2,4-trimethyl-1,2-dihydroquinoline.

[0018] The apparatus for the continuous one-step preparation of antioxidant TMQ is a tubular reactor with a volume of about 1L. Acetone and aniline hydrochloride are mixed and fed into the reactor at a rate of 10~25mL / min, preferably 15~20mL / min.

[0019] The molar ratio of acetone to aniline hydrochloride is 1 to 4:1, preferably 1 to 2.5:1.

[0020] The acidity of the aniline hydrochloride is 5-15%, preferably 8-10%.

[0021] The reaction temperature for the continuous preparation of antioxidant TMQ from acetone and aniline hydrochloride is controlled at 100~150℃, preferably 110~130℃.

[0022] The introduced gas does not affect the existing reaction system. The gas may be hydrogen, helium, methane, ethane, propane, argon, air, nitrogen, etc., with hydrogen, helium, argon, air, and nitrogen being preferred.

[0023] The ratio of the introduced gas flow rate to the acetone aniline hydrochloride flow rate is 0.015~0.03, preferably 0.016~0.025.

[0024] Beneficial effects:

[0025] Compared with existing technologies, introducing a certain flow rate of gas during the continuous one-step preparation of antioxidant TMQ from acetone and aniline hydrochloride significantly reduces the impurity content in antioxidant TMQ, thereby increasing the effective content of antioxidant TMQ. Attached Figure Description

[0026] Figure 1The image shows the liquid chromatogram and results of a typical continuously synthesized antioxidant TMQ.

[0027] Figure 2 This is a flowchart illustrating the method of an embodiment of the present invention. Detailed Implementation

[0028] The present invention will now be described in detail with reference to the embodiments and accompanying drawings. It should be noted that, unless otherwise specified, the embodiments and features described in the embodiments of this application can be combined with each other.

[0029] The following examples illustrate methods for reducing impurities in the antioxidant TMQ. (Refer to Appendix) Figure 2 .

[0030] Example 1

[0031] Dehydrated aniline hydrochloride was mixed thoroughly with acetone (ketone-amine ratio 2.5, molar ratio) and fed into a packed tubular reactor via a metering pump and preheater at a feed rate of 17 mL / min. Once the temperature at the bottom, middle, and top of the reactor stabilized at 115-120℃, the TMQ reaction solution was collected over a certain period. The gas phase was condensed and recovered via a condenser and separator, while non-condensable gases were vented. The reaction solution was neutralized, dehydrated, and vacuum distilled to obtain the final TMQ product, whose components were analyzed.

[0032] Example 2

[0033] Dehydrated aniline hydrochloride was mixed thoroughly with acetone (ketone-amine ratio 2.5, molar ratio) and fed into a packed tubular reactor via a metering pump and preheater at a feed rate of 17 mL / min. Simultaneously, air was introduced, passing through the preheater and entering the tubular reactor, with the exhaust gas flow rate controlled at 0.3 L / min. Once the temperature at the bottom, middle, and top of the reactor stabilized at 115-120℃, the TMQ reaction solution was collected over a certain period. The gas phase was condensed and recovered via a condenser and separator, while non-condensable gases were vented. Subsequently, the reaction solution was neutralized, dehydrated, and vacuum distilled to obtain the final TMQ product, whose composition was analyzed.

[0034] Example 3

[0035] Dehydrated aniline hydrochloride was mixed thoroughly with acetone (ketone-amine ratio 1.5, molar ratio) and fed into a packed tubular reactor via a metering pump and preheater at a feed rate of 12.15 mL / min. Simultaneously, air was introduced, passing through the preheater and entering the tubular reactor, with the exhaust gas flow rate controlled at 0.3 L / min. Once the temperature at the bottom, middle, and top of the reactor stabilized at 115-120℃, the TMQ reaction solution was collected over a certain period. The gas phase was condensed and recovered via a condenser and separator, while non-condensable gases were vented. Subsequently, the reaction solution was neutralized, dehydrated, and vacuum distilled to obtain the final TMQ product, and its composition was analyzed.

[0036] Example 4

[0037] Dehydrated aniline hydrochloride was mixed thoroughly with acetone (ketone-amine ratio 1.5, molar ratio) and fed into a packed tubular reactor via a metering pump and preheater at a feed rate of 17 mL / min. Simultaneously, air was introduced, passing through the preheater and entering the tubular reactor, with the exhaust gas flow rate controlled at 0.3 L / min. Once the temperature at the bottom, middle, and top of the reactor stabilized at 115-120℃, the TMQ reaction solution was collected over a certain period. The gas phase was condensed and recovered via a condenser and separator, while non-condensable gases were vented. Subsequently, the reaction solution was neutralized, dehydrated, and vacuum distilled to obtain the final TMQ product, whose composition was analyzed.

[0038] Example 5

[0039] Dehydrated aniline hydrochloride was mixed thoroughly with acetone (ketone-amine ratio 2, molar ratio) and fed into a packed tubular reactor via a metering pump and preheater at a feed rate of 14.58 mL / min. Simultaneously, air was introduced, passing through the preheater and entering the tubular reactor, with the exhaust gas flow rate controlled at 0.3 L / min. Once the temperature at the bottom, middle, and top of the reactor stabilized at 115-120℃, the TMQ reaction solution was collected over a certain period. The gas phase was condensed and recovered via a condenser and separator, while non-condensable gases were vented. Subsequently, the reaction solution was neutralized, dehydrated, and vacuum distilled to obtain the final TMQ product, whose composition was analyzed.

[0040] Example 6

[0041] Dehydrated aniline hydrochloride was mixed thoroughly with acetone (ketone-amine ratio 1, molar ratio) and fed into a packed tubular reactor via a metering pump and preheater at a feed rate of 9.72 mL / min. Simultaneously, air was introduced, passing through the preheater and entering the tubular reactor, with the exhaust gas flow rate controlled at 0.3 L / min. Once the temperature at the bottom, middle, and top of the reactor stabilized at 115-120℃, the TMQ reaction solution was collected over a certain period. The gas phase was condensed and recovered via a condenser and separator, while non-condensable gases were vented. Subsequently, the reaction solution was neutralized, dehydrated, and vacuum distilled to obtain the final TMQ product, whose composition was analyzed.

[0042] Example 7

[0043] Dehydrated aniline hydrochloride was mixed thoroughly with acetone (ketone-amine ratio 2.5, molar ratio) and fed into a packed tubular reactor via a metering pump and preheater at a feed rate of 12 mL / min. Simultaneously, air was introduced, passing through the preheater and entering the tubular reactor, with the exhaust gas flow rate controlled at 0.3 L / min. Once the temperature at the bottom, middle, and top of the reactor stabilized at 115-120℃, the TMQ reaction solution was collected over a certain period. The gas phase was condensed and recovered via a condenser and separator, while non-condensable gases were vented. Subsequently, the reaction solution was neutralized, dehydrated, and vacuum distilled to obtain the final TMQ product, whose composition was analyzed.

[0044] Example 8

[0045] Dehydrated aniline hydrochloride was mixed thoroughly with acetone (ketone-amine ratio 1.7, molar ratio) and fed into a packed tubular reactor via a metering pump and preheater at a feed rate of 13.15 mL / min. Simultaneously, nitrogen gas was introduced, passing through the preheater and entering the tubular reactor, with the tail gas flow rate controlled at 0.3 L / min. Once the temperature at the bottom, middle, and top of the reactor stabilized at 115-120℃, the TMQ reaction solution was collected over a certain period. The gas phase was condensed and recovered via a condenser and separator, while non-condensable gases were vented. Subsequently, the reaction solution was neutralized, dehydrated, and vacuum distilled to obtain the final TMQ product, whose composition was analyzed.

[0046] Experimental results

[0047]

Claims

1. A method for reducing impurities in antioxidant TMQ, characterized by introducing a certain flow rate of gas during the continuous one-step preparation of antioxidant TMQ from acetone and aniline hydrochloride, thereby reducing the impurity content in antioxidant TMQ and increasing the effective content of antioxidant TMQ; the introduced gas does not affect the existing reaction system, and the gas selected is hydrogen, helium, methane, ethane, propane, argon, air, or nitrogen, and the flow rate ratio of the introduced gas to the flow rate of acetone-aniline hydrochloride is 0.015~0.

03.

2. The method according to claim 1, characterized in that... The impurity is 2,2-bis(R)propane, where R is 4-aminophenyl or 2,2,4-trimethyl-1,2-dihydroquinoline.

3. The method according to claim 1, characterized in that... The apparatus for the continuous one-step preparation of antioxidant TMQ from acetone and aniline hydrochloride is a tubular reactor with a volume of 1L. The acetone and aniline hydrochloride are mixed and fed into the reactor at a rate of 10~25mL / min.

4. The method according to claim 3, characterized in that... The feed rate is 15~20 mL / min.

5. The method according to claim 1, characterized in that... The molar ratio of acetone to aniline hydrochloride is 1 to 4:

1.

6. The method according to claim 5, characterized in that... The molar ratio of acetone to aniline hydrochloride is 1~2.5:

1.

7. The method according to claim 1, characterized in that... The acidity of the aniline hydrochloride is 5-15%.

8. The method according to claim 7, characterized in that The acidity of the aniline hydrochloride is 8-10%.

9. The method according to claim 1, characterized in that... The reaction temperature for the continuous preparation of antioxidant TMQ by acetone and aniline hydrochloride was controlled at 100~150℃.

10. The method according to claim 9, characterized in that... The reaction temperature for the continuous preparation of antioxidant TMQ from acetone and aniline hydrochloride was controlled at 110~130℃.

11. The method according to claim 1, characterized in that... The gas introduced can be helium, argon, air, or nitrogen.

12. The method according to claim 1, characterized in that... The ratio of the gas flow rate to the acetone aniline hydrochloride flow rate is 0.016~0.025.

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