Application of a deep eutectic solvent in the extraction of pyridine

Abstract

The present invention relates to the field of energy conservation and environmental protection, and specifically to the application of a low eutectic solvent in the extraction of pyridine. The method is as follows: placing a tetrabutylammonium bromide-lactic acid low eutectic solvent in an n-octane solution containing pyridine, and extracting pyridine under constant temperature and magnetic stirring conditions; the tetrabutylammonium bromide and lactic acid have the structural formulas shown in (Ⅰ) and (Ⅱ). The low eutectic solvent prepared by the present invention has a strong capture ability for pyridine; at the same time, the low eutectic solvent is insoluble in n-octane, has good phase-forming ability, and can achieve phase separation at a smaller dosage. When the mass ratio of the low eutectic solvent to pyridine is 1:5, the extraction efficiency of pyridine is as high as 97.6%. The tetrabutylammonium bromide-lactic acid low eutectic solvent extractant of this invention experiment has high separation efficiency, is environmentally friendly and is low in price.

Description

Technical Field

[0001] The present invention relates to the field of energy conservation and environmental protection, and in particular to application of a deep eutectic solvent in extracting pyridine. Background Art

[0002] Nitrogen compounds in oil products are primarily classified into two categories: basic and non-basic. Currently, the basic nitrogen compounds that have been isolated and identified include pyridine, aniline, quinoline, azaanthracene, azaphenanthrene, and their homologues. Non-basic nitrogen compounds primarily include pyrrole, carbazole, indole, and their homologues. During the use of oil products, the presence of nitrogen compounds reduces oil stability, hindering their storage and use. NOx released during oil combustion is a major contributor to smog and acid rain. Therefore, the removal of heterocyclic nitrogen compounds from fuel oil products such as gasoline, diesel, and lubricating oil is crucial for improving oil quality and protecting the environment.

[0003] Commonly used industrial oil hydrodenitrogenation technologies suffer from low denitrification rates, demanding conditions, and high costs. Techniques such as organic solvent extraction denitrification suffer from poor stability, limiting their widespread application. Ionic liquids, a newly emerging class of separation media, have made significant progress in processes such as ammonia absorption and nitrogen-containing heterocycle extraction. However, challenges such as low nitride solubility and extraction efficiency, high cost, and poor environmental compatibility continue to hinder their further development.

[0004] Deep eutectic solvents (DESs), a new class of green materials, are synthesized by directly mixing hydrogen bond acceptors (HBAs) such as substituted quaternary ammonium salts with hydrogen bond donors (HBDs) such as metal halides, amides, and carboxylic acids. They not only possess similar physicochemical characteristics to ionic liquids, such as low volatility, good solubility, and customizable structures and properties, but also benefit from readily available, inexpensive raw materials, simple preparation, and excellent biocompatibility. In recent years, deep eutectic solvents have garnered significant attention in separation processes, offering new opportunities for the separation and recovery of nitrogen-containing compounds.

[0005] The quaternary ammonium salt tetrabutylammonium bromide (TBAB) is inexpensive, environmentally friendly, highly selective, non-corrosive, and easily recyclable. Acidic deep eutectic solvents have more reactive sites than ionic liquids, increasing their acidity while also enhancing their binding efficiency with nitrides. This provides an effective method for extracting the basic nitride pyridine from organic solvents. Summary of the Invention

[0006] The invention can effectively extract pyridine in an organic solvent, and has the advantages of simple operation, low cost, high efficiency and strong stability.

[0007] To achieve the above object, the technical solution adopted by the present invention is: use of a deep eutectic solvent in the extraction of pyridine, the method is as follows: placing a tetrabutylammonium bromide-lactic acid deep eutectic solvent in an n-octane solution containing pyridine, and extracting pyridine under constant temperature and stirring conditions; the structural formulas of tetrabutylammonium bromide and lactic acid used to synthesize the tetrabutylammonium bromide-lactic acid deep eutectic solvent are specifically shown as (I) and (II):

[0008]

[0009] The above-mentioned deep eutectic solvent is used in the extraction of pyridine, and the ratio of tetrabutylammonium bromide-lactic acid deep eutectic solvent to n-octane solution containing pyridine is 1g:5g.

[0010] The above-mentioned deep eutectic solvent is used for extracting pyridine, wherein the pyridine concentration in the n-octane solution containing pyridine is 300 mg / L.

[0011] The use of the above-mentioned deep eutectic solvent in the extraction of pyridine, the preparation method of the deep eutectic solvent comprises the following steps:

[0012] 1) Drying of tetrabutylammonium bromide: drying tetrabutylammonium bromide in vacuum;

[0013] 2) Purification and drying of lactic acid: rotary evaporation of lactic acid;

[0014] 3) Synthesis of a deep eutectic solvent: Tetrabutylammonium bromide and lactic acid were mixed and stirred to react until a homogeneous transparent liquid was formed, and then vacuum dried to obtain the target deep eutectic solvent.

[0015] The use of the above-mentioned low eutectic solvent in the extraction of pyridine, in step 1), the vacuum drying conditions are: a vacuum degree of 0.09 MPa, a temperature of 55° C., and vacuum drying for 48 hours.

[0016] The use of the above-mentioned low eutectic solvent in the extraction of pyridine, in step 2), the vacuum degree of rotary evaporation is 0.09 MPa, and vacuum rotary heating is performed at a temperature of 65° C. for 12 hours.

[0017] The use of the above-mentioned deep eutectic solvent in the extraction of pyridine, in step 3), the molar ratio of tetrabutylammonium bromide to lactic acid is 1:2.

[0018] The use of the above-mentioned deep eutectic solvent in the extraction of pyridine, in step 3), the stirring reaction temperature is 60° C., and the reaction time is 2 h.

[0019] Compared with the prior art, the present invention has the following significant advantages:

[0020] 1. The tetrabutylammonium bromide-lactic acid deep eutectic solvent prepared by the present invention has a simple synthesis method, has a wide liquid range, is non-volatile, is an excellent green solvent, and reduces energy consumption and environmental pollution.

[0021] 2. The tetrabutylammonium bromide-lactic acid deep eutectic solvent prepared by the present invention is insoluble in organic solvents such as n-octane and has a strong capture ability for pyridine.

[0022] 3. The tetrabutylammonium bromide-lactic acid deep eutectic solvent prepared by the present invention can both undergo an acid-base neutralization reaction with pyridine and form a hydrogen bond with pyridine, thereby achieving the purpose of efficiently extracting and separating pyridine.

[0023] 4. The tetrabutylammonium bromide-lactic acid deep eutectic solvent prepared by the present invention has low price, good chemical stability, wide liquid range and high extraction efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 This is the hydrogen spectrum of the tetrabutylammonium bromide-lactic acid deep eutectic solvent prepared in Example 1.

[0025] Figure 2 This is the infrared spectrum of the tetrabutylammonium bromide-lactic acid deep eutectic solvent prepared in Example 1.

[0026] Specific implementation methods

[0027] The present invention is further described below by way of specific examples. The present invention is not limited to the examples, and slight variations are possible without departing from the scope of the examples.

[0028] Example 1 A Tetrabutylammonium Bromide-Lactic Acid Deep Eutectic Solvent for Extracting Pyridine

[0029] The preparation method is as follows:

[0030] 1) Place tetrabutylammonium bromide in a vacuum drying oven at 0.09 MPa and 55°C for 48 hours.

[0031] 2) Add lactic acid to a round-bottom flask and use a rotary evaporator to heat the mixture under vacuum at 0.09 MPa and 65°C for 12 h.

[0032] 3) Weigh tetrabutylammonium bromide and lactic acid in a molar ratio of 1:2 and place in a sample bottle. Stir and react at 60°C for 2 hours to form a homogeneous, transparent liquid. Vacuum dry the mixture at 0.09 MPa and 60°C for 48 hours to remove moisture, yielding the final product, a tetrabutylammonium bromide-lactic acid (molar ratio 1:2) deep eutectic solvent.

[0033] Characterization of deep eutectic solvents:

[0034] (1) Hydrogen Spectrum: Hydrogen Nuclear Magnetic Resonance Spectrum of Tetrabutylammonium Bromide-Lactic Acid (Molar Ratio 1:2) Deep Eutectic Solvent 1 H NMR characterization (300MHz, solvent: DMSO-d6). 1 The chemical shift and number of resonance peaks of H NMR were consistent with those of the target deep eutectic solvent, and no impurity peaks were found.

[0035] (2) Infrared spectrum: The infrared characterization of the deep eutectic solvent of tetrabutylammonium bromide-lactic acid (molar ratio 1:2) is attached. Figure 2 . Analysis of the infrared spectrum shows that the infrared spectrum of the deep eutectic solvent contains both characteristic peaks of the hydrogen bond acceptor (tetrabutylammonium bromide) and characteristic absorption peaks of the hydrogen bond donor (lactic acid), and no new characteristic peaks are generated, indicating that there is no chemical reaction between tetrabutylammonium bromide and lactic acid to produce new substances, but they are only combined through hydrogen bond interactions.

[0036] Example 2 Application of deep eutectic solvent to extract pyridine

[0037] (1) Extraction and separation experiment

[0038] Prepare a 300 mg / L pyridine solution (model oil) by dissolving a certain amount of pyridine in n-octane. Weigh 1 g of the deep eutectic solvent into a 10 mL graduated test tube and add 5 g of the model oil, achieving a mass ratio of deep eutectic solvent to pyridine of 1:5. Pyridine extraction and separation experiments were performed with magnetic stirring at 30°C and 600 rpm.

[0039] After 60 minutes of extraction, let it stand for 30 minutes. Use UV-visible spectrophotometry to measure the concentration of pyridine in the n-octane phase at a wavelength of 254 nm. Take at least three samples from the n-octane phase for quantitative determination. The relative error at equilibrium is controlled within 3% to ensure data accuracy. The extraction efficiency of pyridine (E%) is calculated according to the following formula (1-1):

[0040]

[0041] Where C0 represents the initial concentration of pyridine in the model oil, C f is the concentration of residual pyridine in the n-octane phase.

[0042] (2) Extraction rate of pyridine by deep eutectic solvent

[0043] After extraction with a tetrabutylammonium bromide-lactic acid (molar ratio 1:2) deep eutectic solvent, it was calculated that the extraction rate of pyridine with the tetrabutylammonium bromide:lactic acid (molar ratio 1:2) deep eutectic solvent was 97.6%.

Claims

1. Use of a deep eutectic solvent in extracting pyridine, characterized in that: The method is as follows: the deep eutectic solvent is tetrabutylammonium bromide-lactic acid, and the molar ratio of tetrabutylammonium bromide to lactic acid is 1:

2. The tetrabutylammonium bromide-lactic acid deep eutectic solvent is placed in an n-octane solution containing pyridine, and pyridine is extracted under constant temperature and stirring conditions; the structural formulas of tetrabutylammonium bromide and lactic acid used to synthesize the tetrabutylammonium bromide-lactic acid deep eutectic solvent are specifically shown in (I) and (II): ， （Ⅰ）、 （Ⅱ）。 2. The use of a deep eutectic solvent in extracting pyridine according to claim 1, characterized in that: Tetrabutylammonium bromide-lactic acid deep eutectic solvent: n-octane solution containing pyridine is 1g:5g.

3. Use of a deep eutectic solvent in extracting pyridine according to claim 2, characterized in that: The pyridine concentration in the n-octane solution is 300 mg / L.

4. The use of a deep eutectic solvent in extracting pyridine according to claim 1, characterized in that: The preparation method of the deep eutectic solvent comprises the following steps: 1) Drying of tetrabutylammonium bromide: Dry tetrabutylammonium bromide in vacuum; 2) Purification and drying of lactic acid: Rotary evaporation of lactic acid; 3) Synthesis of a deep eutectic solvent: Tetrabutylammonium bromide and lactic acid were mixed and stirred to react until a homogeneous transparent liquid was formed, and then vacuum dried to obtain the target deep eutectic solvent.

5. Use of a deep eutectic solvent in extracting pyridine according to claim 4, characterized in that: In step 1), the vacuum drying conditions are: vacuum degree of 0.09 MPa, vacuum drying at 55°C for 48 hours.

6. Use of a deep eutectic solvent in extracting pyridine according to claim 4, characterized in that: In step 2), the rotary evaporation conditions are: vacuum degree of 0.09 MPa, vacuum rotary heating at 65°C for 12 hours.

7. Use of a deep eutectic solvent in extracting pyridine according to claim 4, characterized in that: In step 3), the stirring reaction temperature is 60° C. and the reaction time is 2 h.

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