A method for preparing N,N-dibutyl-m-aminophenol

Abstract

This invention belongs to the field of fine chemical process technology, specifically relating to a method for preparing N,N-dibutyl-m-aminophenol. The method combines three techniques: catalytic N-alkylation with sodium m-aminophenol and n-butanol via hydrogenation, sulfation with dioxide, and purification by vacuum distillation. This effectively solves the technical bottlenecks of existing N,N-dibutyl-m-aminophenol production methods, such as the difficulty in controlling the N-alkylation reaction and the difficulty in treating large amounts of high-salt wastewater, and avoids the need for distillation purification of m-aminophenol. Compared with existing methods, this invention has advantages such as high economic efficiency, low environmental impact, high catalytic efficiency, and simple operation, meeting the requirements of green chemistry processes and facilitating large-scale application.

Description

Technical Field

[0001] This invention belongs to the field of fine chemical process technology, specifically relating to a method for preparing N,N-dibutyl-m-aminophenol. Background Technology

[0002] ODB-2, a mainstream colorless thermosensitive dye, is widely used in thermal paper (such as invoices and express delivery labels), thermal films, and other fields. BBA (2-[4-(dibutylamino)-2-hydroxybenzoyl]benzoic acid), as a key intermediate in the preparation of the thermosensitive dye ODB-2, plays a crucial role. In existing technologies, the key intermediate BBA (2-[4-(dibutylamino)-2-hydroxybenzoyl]benzoic acid) for the thermosensitive dye ODB-2 is generally obtained through a Friedel-Crafts reaction between the colorless liquid N,N-dibutylm-aminophenol and phthalic anhydride. The reaction equation is shown in equation (II).

[0003]

[0004] Equation (II).

[0005] N,N-Dibutylm-aminophenol is an important raw material for the synthesis of BBA. Currently, in industry, the target product N,N-dibutylm-aminophenol is mainly formed by N-alkylation reaction of m-aminophenol and 1-halobutane (chloro, bromine, iodine), as shown in equation (III). However, this method has difficulties such as multiple reaction sites and poor selectivity (Bioorganic & Medicinal Chemistry Letters (2023), 93, 129425, CN116102439 A, Molecules (2023), 28(17), 6404, CN108558710 A, CN104927392 A, Journal of Medicinal Chemistry (2008), 51(12), 3654-3658, Nanjing Daxue Xuebao, Ziran Kexue (2001), 37(5), 643-648, EP831081 A1, JP09169708 A, JP09020734 A, JP05186407). The low cost and easy availability of 1-chlorobutane make it more suitable for completing the corresponding N-alkylation reaction steps. However, its inert C-Cl bond means that the SN2 nucleophilic substitution reaction process often requires a high reaction temperature, which increases the competitive reaction of N / O alkylation, resulting in the generation of more impurities with similar properties that are difficult to separate and purify.

[0006]

[0007] Formula (III).

[0008] In addition, m-aminophenol is an important reactant in the synthesis of N,N-dibutylm-aminophenol. Its industrial production mainly involves the alkali fusion of sodium m-aminobenzenesulfonate to obtain sodium m-aminophenol, followed by acidification and distillation purification to obtain the target product (CN114835612 A, CN113929561 A), as shown in equation (IV). However, the acidification process requires a large amount of hydrochloric acid to neutralize the sodium hydroxide and sodium sulfite in the alkali fusion solution, generating a large amount of high-salt wastewater that is difficult to treat. Treating the wastewater by evaporation and crystallization faces significant energy consumption. Furthermore, the high-temperature (>200°C) vacuum distillation purification of m-aminophenol further increases the energy consumption of the process, raising production costs.

[0009]

[0010] Formula (IV).

[0011] In summary, the synthesis of N,N-dibutyl-m-aminophenol faces challenges such as poor selectivity of N-alkylation products, difficulty in separation and purification, and large amounts of acidified wastewater with low reuse value. Therefore, developing a new synthetic method that is economically efficient and easy to implement industrially is of great significance. Summary of the Invention

[0012] To address the shortcomings of existing technologies, this invention provides a method for preparing N,N-dibutyl-m-aminophenol. The target product is obtained through three steps: N-alkylation, acidification, and purification.

[0013] To achieve the above objectives, the present invention adopts the following technical solution:

[0014] A method for preparing N,N-dibutyl-m-aminophenol includes the following steps:

[0015] S1. Add copper powder, polyethylene glycol, and n-butanol to the alkaline melt of sodium m-aminophenol. Stir until the system is uniformly dispersed, then heat to carry out the reaction. After the reaction is completed, cool down, filter and recover the copper powder to obtain an aqueous solution of sodium N,N-dibutylm-aminophenol.

[0016] S2. Sulfur dioxide gas is introduced into the aqueous solution of sodium N,N-dibutyl-m-aminophenol obtained in step S1 to obtain an acidified reaction solution. The solution is allowed to stand and separate into layers, with the upper layer being the oil phase and the lower layer being the aqueous phase.

[0017] S3. The oil phase after step S2 was allowed to stand and separate into layers was subjected to vacuum distillation to obtain N,N-dibutyl-m-aminophenol.

[0018] The reaction equation is as follows:

[0019]

[0020] Formula (I).

[0021] Preferably, the sodium m-aminophenol solution in step S1 has a sodium m-aminophenol mass fraction of 25.7 wt%.

[0022] Preferably, the mass of the copper powder in step S1 is 0.01-0.1 times the mass of sodium m-aminophenol.

[0023] More preferably, the mass of the copper powder in step S1 is 0.01-0.08 times the mass of sodium m-aminophenol.

[0024] Preferably, the copper powder in step S1 has a mesh size of 180-220.

[0025] Preferably, the mass of polyethylene glycol in step S1 is 0.01-0.05 times the mass of sodium m-aminophenol.

[0026] Preferably, the polyethylene glycol in step S1 is one or more of polyethylene glycol 200, polyethylene glycol 300, polyethylene glycol 400, polyethylene glycol 600, polyethylene glycol 800, polyethylene glycol 1000, and polyethylene glycol 1200.

[0027] More preferably, the polyethylene glycol in step S1 is one or more of polyethylene glycol 200, polyethylene glycol 400, polyethylene glycol 800, and polyethylene glycol 1200.

[0028] Preferably, the amount of n-butanol in step S1 is 3-4 times the amount of sodium m-aminophenol.

[0029] Preferably, the reaction temperature in step S1 is 130-150°C and the reaction time is 9-12 h.

[0030] Preferably, in step S2, sulfur dioxide gas is introduced into the aqueous solution of N,N-dibutyl-m-aminophenol obtained in step S1 using a flow meter for acidification.

[0031] More preferably, the flow meter is a Venturi flow meter, and the flow velocity of the sulfur dioxide gas is 1-3 m / s. 3 / h.

[0032] More preferably, the flow rate of the sulfur dioxide gas is 2-3 m. 3 / h.

[0033] Preferably, the acidification reaction solution in step S2 has a pH of 6-7.

[0034] More preferably, the acidification reaction solution in step S2 has a pH of 6-6.5.

[0035] Preferably, in step S2, the pH of the lower aqueous phase is adjusted to 9-10.5 using sodium hydroxide solid to obtain an aqueous solution of sodium sulfite; in step S3, the upper oil phase is subjected to vacuum distillation to first recover n-butanol for reuse, and then the fraction with a distillation temperature of 125-130℃ at 0.26 kPa is collected as the target product N,N-dibutyl-m-aminophenol.

[0036] Compared with the prior art, the present invention has the following beneficial effects:

[0037] (1) This invention effectively solves the technical bottlenecks faced by existing methods for producing N,N-dibutyl-m-aminophenol by combining three technologies: catalytic N-alkylation with sodium m-aminophenol and n-butanol via hydrogenation, sulfation with dioxide, and purification by vacuum distillation. This avoids the need for distillation purification of m-aminophenol. Compared with existing methods, this invention has advantages such as high economic benefits, low environmental burden, high catalytic efficiency, and simple operation, meeting the requirements of green chemical processes and being easy to scale up.

[0038] (2) The method of this invention uses alcohols to complete the N-alkylation process via catalytic hydrogenation, with water as the only byproduct. This eliminates the need for alkyl halides, resulting in high atom economy and economic benefits, and effectively overcomes the problem of poor N-alkylation selectivity. Simultaneously, the sodium m-aminophenol alkali melt contains a large amount of sodium hydroxide and sodium sulfite, which can effectively promote the catalytic hydrogenation N-alkylation reaction between sodium m-aminophenol and n-butanol in the alkali melt, thus preparing N,N-dibutylm-aminophenol sodium.

[0039] (3) In this invention, an excess of n-butanol is used as an alkylating agent. The excess n-butanol can be recovered and reused by vacuum distillation.

[0040] (4) The method of the present invention utilizes sulfur dioxide to form sulfurous acid (which has both reducing and acidic properties) when it comes into contact with water to acidify the N-alkylated system. After separating the product, the lower aqueous phase obtained is an aqueous solution rich in sodium sulfite / sodium bisulfite, which can be used as a raw material for cement additives to achieve economical, efficient and environmentally friendly treatment. It can overcome the high energy consumption problem caused by the evaporation and crystallization of a large amount of high-salt sodium chloride wastewater generated by acidification with hydrochloric acid in existing industrial production, and further enhance the competitiveness of the process. Attached Figure Description

[0041] Figure 1 The HPLC spectrum of N,N-dibutyl-m-aminophenol prepared in Example 1 of this invention;

[0042] Figure 2 The N,N-dibutyl-m-aminophenol prepared in Example 1 of this invention 1H NMR spectrum. Detailed Implementation

[0043] Specific embodiments of the preparation method provided by this invention are as follows to further describe the technical solution of this invention; however, the scope of protection of this invention is not limited to these embodiments. All changes or equivalent substitutions that do not depart from the concept of this invention are included within the scope of protection of this invention.

[0044] The method for preparing the alkaline melt of sodium m-aminophenol used in this embodiment of the invention is as follows:

[0045] Mix m-aminobenzenesulfonic acid with water to form a slurry, heat to 60°C, neutralize with sodium hydroxide solution (mass concentration 32%, molar ratio of sodium hydroxide to m-aminobenzenesulfonic acid 1:1), filter and set aside. Add an appropriate amount of prepared sodium hydroxide solution (mass concentration 32%, molar ratio of sodium hydroxide to m-aminobenzenesulfonic acid 4:1) to an alkaline melting pot, heat to 273~275°C, slowly add the above filtrate to it, and react at this temperature for 2 hours. Then dilute with water, filter to remove sodium sulfite, wash with hot water and filter while hot to obtain an alkaline fusible solution of sodium m-aminophenol (mass fraction 25.7%).

[0046] Copper powder: purchased from Shanghai Maclean Biochemical Technology Co., Ltd. (Product No.: C804488, purity: 99.9% metals basis, mesh size: 200)

[0047] The purity of N,N-dibutyl-m-aminophenol was determined by high performance liquid chromatography.

[0048] Example 1:

[0049] The preparation method of N,N-dibutyl-m-aminophenol includes the following steps:

[0050] (1) N-alkylation: At room temperature, 0.66 g of copper powder (200 mesh), 0.39 g of polyethylene glycol 200, and 29.65 g (0.4 mol) of n-butanol were added to 51.01 g of sodium m-aminophenol (sodium m-aminophenol mass fraction was 25.7%). After stirring until the system was uniformly dispersed, the temperature was raised to 150 ℃ and kept at the temperature for 10 h. After cooling, the copper powder was recovered by filtration to obtain an aqueous solution of sodium N,N-dibutylm-aminophenol.

[0051] (2) Acidification: Sulfur dioxide gas (gas flow rate of 2 m) is uniformly introduced into the reaction solution obtained in step (1) through a Venturi flow meter. 3 / h) to obtain an acidified reaction solution (pH 6.5 after acidification), and then let it stand to separate into layers;

[0052] (3) Purification: The lower aqueous phase of the acidified reaction solution obtained in step (2) is separated and the pH value is adjusted to 9.5 with sodium hydroxide solid to obtain sodium sulfite aqueous solution. The upper oil phase is subjected to vacuum distillation. First, n-butanol is recovered for reuse. Then, the fraction collected at 125~130℃ / 0.26 kPa is the target product N,N-dibutyl-m-aminophenol (20.38 g).

[0053] The yield of N,N-dibutyl-m-aminophenol was 92.1%, and the purity was 99.37%.

[0054] The liquid chromatogram of the prepared N,N-dibutyl-m-aminophenol is shown below. Figure 1 As shown, the peak of N,N-dibutyl-m-aminophenol is located at a retention time of 7.729 min.

[0055] The preparation of N,N-dibutyl-m-aminophenol 1 H NMR spectrum as shown Figure 2 As shown, its 1 The H NMR data are as follows: 1 HNMR (400 MHz, Chloroform- d ) δ 7.07 (t, J = 8.1 Hz, 1H), 6.36 – 6.07 (m, 3H), 5.07 (s, 1H), 3.35 – 3.15 (m, 4H), 1.59 (p, J = 7.6 Hz, 4H), 1.37 (h, J = 7.3 Hz, 4H), 0.98 (t, J = 7.3 Hz, 6H).

[0056] Example 2:

[0057] The preparation method of N,N-dibutyl-m-aminophenol includes the following steps:

[0058] (1) N-alkylation: At room temperature, 3.93 g of copper powder (200 mesh), 0.79 g of polyethylene glycol 400, and 77.83 g (1.05 mol) of n-butanol were added to 153.07 g of sodium m-aminophenol (sodium m-aminophenol mass fraction was 25.7%). After stirring until the system was uniformly dispersed, the temperature was raised to 130 ℃ and kept at the temperature for 9.5 h. The temperature was lowered and the copper powder was recovered by filtration to obtain an aqueous solution of sodium N,N-dibutylm-aminophenol.

[0059] (2) Acidification: Sulfur dioxide gas (gas flow rate of 1 m) is uniformly introduced into the reaction solution obtained in step (1) through a Venturi flow meter. 3 / h) to obtain an acidified reaction solution (pH 7 after acidification), and then let it stand to separate into layers;

[0060] (3) Purification: The lower aqueous phase of the acidified reaction solution obtained in step (2) was separated and the pH was adjusted to 9 with sodium hydroxide solid to obtain sodium sulfite aqueous solution. The upper oil phase was subjected to vacuum distillation. The n-butanol was recovered first for reuse, and then the fraction collected at 125~130 ℃ / 0.26 kPa was the target product N,N-dibutyl-m-aminophenol (59.77 g).

[0061] The yield of N,N-dibutyl-m-aminophenol was 90%, and the purity was 99.35%.

[0062] Example 3:

[0063] The preparation method of N,N-dibutyl-m-aminophenol includes the following steps:

[0064] (1) N-alkylation: At room temperature, 0.33 g copper powder (200 mesh), 0.33 g polyethylene glycol 800, and 55.59 g (0.75 mol) n-butanol were added to 127.55 g sodium m-aminophenol (sodium m-aminophenol mass fraction was 25.7%). After stirring until the system was uniformly dispersed, the temperature was raised to 145 ℃ and kept at the temperature for 9 h. After cooling and filtration, the copper powder was recovered to obtain an aqueous solution of N,N-dibutylm-aminophenol sodium.

[0065] (2) Acidification: Sulfur dioxide gas (gas flow rate of 3 m) is uniformly introduced into the reaction solution obtained in step (1) through a Venturi flow meter. 3 / h) to obtain an acidified reaction solution (pH 6 after acidification), and then let it stand to separate into layers;

[0066] (3) Purification: The lower aqueous phase of the acidified reaction solution obtained in step (2) was separated and the pH was adjusted to 10.5 with sodium hydroxide solid to obtain sodium sulfite aqueous solution. The upper oil phase was subjected to vacuum distillation. The n-butanol was recovered first for reuse, and then the fraction collected at 125~130℃ / 0.26 kPa was the target product N,N-dibutyl-m-aminophenol (52.57 g).

[0067] The yield of N,N-dibutyl-m-aminophenol was 95%, and the purity was 99.26%.

[0068] Example 4:

[0069] The preparation method of N,N-dibutyl-m-aminophenol includes the following steps:

[0070] (1) N-alkylation: At room temperature, 1.84 g of copper powder (200 mesh), 1.31 g of polyethylene glycol 1200 and 54.85 g (0.74 mol) of n-butanol were added to 102.06 g of sodium m-aminophenol (sodium m-aminophenol mass fraction was 25.7%). After stirring until the system was uniformly dispersed, the temperature was raised to 140 ℃ and kept at the temperature for 12 h. After cooling, the copper powder was recovered by filtration to obtain an aqueous solution of sodium N,N-dibutylm-aminophenol.

[0071] (2) Acidification: Sulfur dioxide gas (gas flow rate of 2.5 m) is uniformly introduced into the reaction solution obtained in step (1) through a Venturi flow meter. 3 / h) to obtain an acidified reaction solution (pH 6.3 after acidification), and then let it stand to separate into layers;

[0072] (3) Purification: The lower aqueous phase of the acidified reaction solution obtained in step (2) was separated and the pH was adjusted to 9.3 with sodium hydroxide solid to obtain sodium sulfite aqueous solution. The upper oil phase was subjected to vacuum distillation. The n-butanol was recovered first for reuse, and then the fraction collected at 125~130℃ / 0.26 kPa was the target product N,N-dibutyl-m-aminophenol (41.54 g).

[0073] The yield of N,N-dibutyl-m-aminophenol was 93.8%, and the purity was 99.31%.

[0074] This invention uses an alkaline melt of sodium m-aminophenol and n-butanol as raw materials to catalyze the N-alkylation of sodium m-aminophenol and n-butanol via hydrogenation to obtain N,N-dibutylm-aminophenol sodium. Subsequently, the N-alkylation product is acidified using sulfur dioxide gas, and finally, after further purification, N,N-dibutylm-aminophenol is obtained. The method of this invention is of great significance for promoting the upgrading of the N,N-dibutylm-aminophenol production process.

Claims

1. A method for preparing N,N-dibutyl-m-aminophenol, characterized in that, Includes the following steps: S1. Add copper powder, polyethylene glycol, and n-butanol to the alkaline melt of sodium m-aminophenol. Stir until the system is uniformly dispersed, then heat to carry out the reaction. After the reaction is completed, cool down, filter and recover the copper powder to obtain an aqueous solution of sodium N,N-dibutylm-aminophenol. S2. Sulfur dioxide gas is introduced into the aqueous solution of sodium N,N-dibutyl-m-aminophenol obtained in step S1 to obtain an acidified reaction solution. The solution is allowed to stand and separate into layers, with the upper layer being the oil phase and the lower layer being the aqueous phase. S3. The oil phase after step S2 was allowed to stand and separate into layers was subjected to vacuum distillation to obtain N,N-dibutyl-m-aminophenol. The reaction equation is as follows: Formula (I).

2. The method for preparing N,N-dibutyl-m-aminophenol according to claim 1, characterized in that, The mass of the copper powder in step S1 is 0.01-0.1 times the mass of sodium m-aminophenol; the mesh size of the copper powder in step S1 is 180-220 mesh; the mass of the polyethylene glycol in step S1 is 0.01-0.05 times the mass of sodium m-aminophenol; and the amount of n-butanol in step S1 is 3-4 times the amount of sodium m-aminophenol.

3. The method for preparing N,N-dibutyl-m-aminophenol according to claim 2, characterized in that, The mass of the copper powder in step S1 is 0.01-0.08 times the mass of sodium m-aminophenol; the polyethylene glycol in step S1 is one or more of polyethylene glycol 200, polyethylene glycol 300, polyethylene glycol 400, polyethylene glycol 600, polyethylene glycol 800, polyethylene glycol 1000, and polyethylene glycol 1200.

4. The method for preparing N,N-dibutyl-m-aminophenol according to claim 3, characterized in that, The polyethylene glycol mentioned in step S1 is one or more of polyethylene glycol 200, polyethylene glycol 400, polyethylene glycol 800, and polyethylene glycol 1200; the reaction temperature in step S1 is 130-150°C, and the reaction time is 9-12 h.

5. The method for preparing N,N-dibutyl-m-aminophenol according to claim 1, characterized in that, In step S2, sulfur dioxide gas is introduced into the aqueous solution of sodium N,N-dibutylm-aminophenol obtained in step S1 using a flow meter for acidification.

6. The method for preparing N,N-dibutyl-m-aminophenol according to claim 5, characterized in that, The flow meter is a Venturi flow meter, and the flow velocity of the sulfur dioxide gas is 1-3 m / s. 3 / h.

7. The method for preparing N,N-dibutyl-m-aminophenol according to claim 6, characterized in that, The flow rate of the sulfur dioxide gas is 2-3 m. 3 / h.

8. The method for preparing N,N-dibutyl-m-aminophenol according to claim 1, characterized in that, The acidification reaction solution described in step S2 has a pH of 6-7; in step S2, the pH of the lower aqueous phase is adjusted to 9-10.5 using sodium hydroxide solid to obtain an aqueous solution of sodium sulfite.

9. The method for preparing N,N-dibutyl-m-aminophenol according to claim 8, characterized in that, The acidification reaction solution described in step S2 has a pH of 6-6.

5.

10. The method for preparing N,N-dibutyl-m-aminophenol according to claim 1, characterized in that, The reduced pressure distillation described in step S3, collecting the fraction with a distillation temperature of 125~130℃ at 0.26kPa, is the target product N,N-dibutyl-m-aminophenol.

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