Method for extracting high-purity bicyclic aromatic naphthalene from direct coal liquefaction oil

Abstract

The invention provides a method for extracting high-purity bicyclic aromatic naphthalene from direct coal liquefaction oil, and belongs to the technical field of direct coal liquefaction oil separation. The method comprises the following steps: carrying out fraction cutting and component analysis on the direct coal liquefaction oil, and selecting a fraction section; extracting the selected fraction by using a polar aprotic solvent, and separating out a raffinate phase 1 rich in alkane components and an extract phase 2 rich in aromatic hydrocarbons and phenols; extracting the extraction phase 2 by using a polar protic solvent to separate out a raffinate phase 3 rich in aromatic hydrocarbon components and an extraction phase 4 rich in phenolic components; carrying out reverse extraction on the extract phase 4 to obtain phenolic components; and purifying the raffinate phase 3 to obtain naphthalene. The method provided by the invention can fully utilize the composition characteristics of the direct coal liquefaction oil, not only can obtain three components of alkane, aromatic hydrocarbon and phenols at one time, but also can obtain the high-purity bicyclic aromatic hydrocarbon monomer, and has the advantages of simple and convenient process, low energy consumption, wide industrial application prospect, remarkable economic benefit and the like.

Description

Technical Field

[0001] This invention relates to the field of coal direct liquefaction oil separation technology, and in particular to a method for extracting high-purity bicyclic aromatic naphthalene from coal direct liquefaction oil. Background Technology

[0002] Direct Coal Liquefaction Oil (DCLO) is a liquid product obtained by directly hydrogenating and liquefying coal under high temperature, high pressure, and with the aid of a catalyst. Its composition is complex, mainly consisting of various organic compounds such as alkanes, aromatics, and phenols. These components are important raw materials for high-value-added chemicals such as synthetic fibers, pharmaceuticals, dyes, and pesticides, and possess extremely high comprehensive utilization value.

[0003] In recent years, with the rapid development of my country's coal chemical industry, the output of direct coal liquefaction oil has continued to grow. How to efficiently and cleanly separate and further process it has become a key issue in realizing the high-value utilization of resources.

[0004] Currently, the efficient utilization of coal direct liquefaction oil mainly falls into the following categories: its alkane components are used to produce high-quality liquid fuels, its aromatic components are used to prepare fine chemicals, and its phenolic components, due to their certain antibacterial properties, can destroy bacterial cell membranes or interfere with their metabolic functions, and are used to prepare disinfectants and preservatives.

[0005] Currently, existing invention patents include: CN 117776850 A, which provides a method for extractive distillation to purify crude naphthalene. Its core process route is as follows: using sulfolane as the extractant, crude naphthalene is purified through a continuous dual-tower distillation system consisting of an "extractive distillation tower" and an "extractant recovery tower," ultimately obtaining high-purity naphthalene.

[0006] CN 105802651 A discloses a method for extracting phenolic compounds from medium- and low-temperature coal tar using monoethanolamine carboxylic acid ionic liquid. The core steps are as follows: First, the ionic liquid is mixed and reacted with coal tar under mild conditions. After standing and separating into layers, the lower layer of ionic liquid rich in phenols is taken. Then, back-extraction is performed with diethyl ether, and the lower layer is taken again. Finally, the diethyl ether is removed by distillation at 45°C, and the phenolic compounds are finally obtained with an extraction rate of over 90%.

[0007] CN 114768747 A discloses a method for preparing a hierarchical porous 5A molecular sieve adsorbent material for the directional adsorption and separation of n-alkanes from naphtha. The core technology lies in using a composite template agent mainly composed of trimethyl-(3,5-dimethylphenyl)-ammonium hydroxide, through hydrothermal synthesis and ion exchange processes, to prepare a molecular sieve with a hierarchical pore structure that simultaneously possesses micropores and mesopores. The liquid-phase diffusion rate of this material for n-alkanes is 2 to 4 times that of traditional microporous 5A molecular sieves. When applied to fixed-bed adsorption and separation of naphtha, it can efficiently separate the raw material into desorbed oil rich in n-alkanes and residual oil rich in isoalkanes, cycloalkanes, and aromatics, and significantly shorten the adsorption saturation time from 41 minutes in the traditional method to approximately 20 minutes.

[0008] The extractive distillation column mentioned above uses an excessively high mass ratio of extractant to feedstock, resulting in high operating costs for the entire process. While ionic liquids exhibit unique advantages in separation, such as high selectivity and low volatility, their industrial application is still limited by several factors, including high cost, low mass transfer efficiency due to high viscosity, difficulties in recovery and reuse, uncertainties regarding potential environmental impact, and a lack of basic physical property data. Meanwhile, adsorption separation technology is also constrained in its further promotion and application in practical industrial scenarios due to limited adsorption capacity, potential risks of insufficient selectivity, and operational challenges during engineering scale-up. Summary of the Invention

[0009] The purpose of this invention is to provide a method for extracting high-purity bicyclic aromatic naphthalene from coal direct liquefaction oil, which solves the technical problems of high energy consumption, low selectivity, and difficulty in scale-up caused by existing coal direct liquefaction oil separation methods.

[0010] To achieve the above-mentioned objectives, the present invention provides the following technical solution: This invention provides a method for extracting high-purity bicyclic aromatic naphthalene from coal direct liquefaction oil, comprising the following steps: Step 1) The direct coal liquefaction oil is fractionated and the resulting fractions are analyzed to obtain the separated feedstock oil; Step 2) The raw oil and extractant 1 are mixed and extracted to obtain raffinate phase 1 and extract phase 2; Step 3) After mixing the extractant phase 2 and extractant 2, extraction is performed to obtain raffinate phase 3 and extractant phase 4; Step 4) After mixing the extract phase 4 and the back-extractant, back-extracting is performed to obtain the back-extract solution and the regenerated organic phase. Then, the back-extractant in the back-extract solution is removed to obtain the phenolic component. Step 5) Pass the raffinate phase 3 through two column chromatography cycles to obtain the bicyclic aromatic naphthalene monomer; In step 1), the separated feedstock oil is the fraction with the highest content of bicyclic aromatic naphthalene; In step 2), the raffinate phase 1 is rich in alkane components, and the extract phase 2 is rich in aromatic and phenolic components; In step 3), the raffinate phase 3 is rich in aromatic components, and the extract phase 4 is rich in phenolic components.

[0011] Furthermore, in step 1), the reflux ratio of the fraction cutting is ≥3, and the temperature range is ≤300℃.

[0012] Furthermore, in step 2), the mixing is carried out under stirring for 10-30 minutes, the mass ratio of extractant 1 to the separated raw oil is 4, and the extraction temperature is 20-35°C. The extractant 1 is a polar aprotic solvent; The polar aprotic solvent includes dimethyl sulfoxide, N-methylpyrrolidone, or N,N-dimethylformamide.

[0013] Furthermore, in step 3), the mixing is carried out under stirring conditions for 10-30 minutes, and the amount of extractant 2 is 10-40% of the sum of the masses of extractant 2 and extractant 1. The extractant 2 is a polar protic solvent, which includes water.

[0014] Furthermore, in step 4), the mixing is carried out under stirring conditions for 10 to 30 minutes.

[0015] Furthermore, in step 4), the back-extraction is performed 2 to 5 times, the back-extraction agent includes dichloromethane, and the amount of back-extraction agent used is 2 to 5 mL each time.

[0016] Furthermore, in step 4), the temperature for removing the back-extraction agent is 20~35℃.

[0017] Furthermore, in step 5), in the two column chromatography processes, the stationary phase of the first column chromatography is chromatographic silica gel and / or neutral alumina, and the mobile phase contains eluent 1 and eluent 2 used independently. When the stationary phase is silica gel and neutral alumina, the mass ratio of the silica gel to the neutral alumina is 3~4:2~3.

[0018] Furthermore, in step 5), the volume ratio of eluent 1 to eluent 2 is 1:3~5; The eluent 1 and eluent 2 independently include one or more of n-pentane, isopentane, petroleum ether, n-hexane, n-heptane, dichloromethane, ethyl acetate, and chloroform.

[0019] Furthermore, in step 5), in the two column chromatography processes, the stationary phase of the second column chromatography is octadecylsilane-bonded silica gel or octylsilane-bonded silica gel, and the mobile phase includes eluent 3 and eluent 4. The volume ratio of eluent 3 to eluent 4 is 30~60:40~70; The eluent 3 and eluent 4 are independently one or more of methanol, acetonitrile, and water.

[0020] The beneficial effects of this invention are: This invention utilizes common polar aprotic and polar protic solvents to separate coal direct liquefaction oil into alkanes, aromatics, and phenols. Traditional extraction processes are simple and mature. Compared to traditional extractants, novel extractants are generally more expensive and have more complex recovery processes; while compared to other separation methods, traditional extractant processes have significant advantages in terms of low energy consumption and adjustable selectivity. Furthermore, the polar protic solvent used—water—is not only safe and non-toxic but also widely available and inexpensive. Moreover, the use of multiple column chromatography to purify the bicyclic aromatic naphthalene effectively ensures high product purity. Based on coal direct liquefaction oil resources, this invention provides a solution to fill the supply gap of petroleum-based naphtha in my country and to explore new ideas for efficient energy utilization. Attached Figure Description

[0021] Figure 1 This is a process flow diagram of the present invention; Figure 2 This is a liquid chromatogram of the high-purity mixed aromatics obtained after the second column chromatography in Example 1. Detailed Implementation

[0022] This invention provides a method for extracting high-purity bicyclic aromatic naphthalene from coal direct liquefaction oil, comprising the following steps: Step 1) The direct coal liquefaction oil is fractionated and the resulting fractions are analyzed to obtain the separated feedstock oil; Step 2) The raw oil and extractant 1 are mixed and extracted to obtain raffinate phase 1 and extract phase 2; Step 3) After mixing the extractant phase 2 and extractant 2, extraction is performed to obtain raffinate phase 3 and extractant phase 4; Step 4) After mixing the extract phase 4 and the back-extractant, back-extracting is performed to obtain the back-extract solution and the regenerated organic phase. Then, the back-extractant in the back-extract solution is removed to obtain the phenolic component. Step 5) Pass the raffinate phase 3 through two column chromatography cycles to obtain the bicyclic aromatic naphthalene monomer; In step 1), the separated feedstock oil is the fraction with the highest content of bicyclic aromatic naphthalene; In step 2), the raffinate phase 1 is rich in alkane components, and the extract phase 2 is rich in aromatic and phenolic components; In step 3), the raffinate phase 3 is rich in aromatic components, and the extract phase 4 is rich in phenolic components.

[0023] In this invention, in step 1), the reflux ratio of the fraction cutting is ≥3, preferably ≥7; the temperature range is ≤300℃.

[0024] In this invention, in step 1), the fractions for fraction cutting are preferably 19 fractions: <100℃, 100~110℃, 110~120℃, 120~130℃, 130~140℃, 140~150℃, 150~160℃, 160~170℃, 170~180℃, 180~190℃, 190~200℃, 200~210℃, 210~220℃, 220~230℃, 230~240℃, 250~260℃, 260~270℃, 270~280℃, 280~290℃, and 290~300℃.

[0025] In this invention, in step 2), the mixing is carried out under stirring for 10-30 minutes, preferably 25 minutes; the mass ratio of extractant 1 to the raw oil to be separated is preferably 4; the extraction temperature is 20-35°C, preferably 25°C. The extractant 1 is a polar aprotic solvent; The polar aprotic solvent includes dimethyl sulfoxide, N-methylpyrrolidone, or N,N-dimethylformamide, preferably dimethyl sulfoxide.

[0026] In this invention, in step 3), the mixing is carried out under stirring conditions, and the stirring time is 10-30 min, preferably 25 min; the amount of extractant 2 is preferably 10-40% of the sum of the mass of extractant 2 and extractant 1. The extractant 2 is a polar protic solvent, which includes water, preferably water.

[0027] In this invention, in step 4), the mixing is carried out under stirring conditions, and the stirring time is 10-30 minutes, preferably 25 minutes.

[0028] In this invention, in step 4), the number of back-extractions is 2 to 5 times, preferably 4 times; the back-extraction agent includes dichloromethane, preferably dichloromethane; the amount of back-extraction agent used is preferably 3 mL each time.

[0029] In this invention, in step 4), the temperature for removing the back-extractant is 20~35℃, preferably 25℃.

[0030] In this invention, in step 5), in the two column chromatography processes, the stationary phase of the first column chromatography is silica gel and / or neutral alumina, preferably silica gel and neutral alumina; the mobile phase includes eluent 1 and eluent 2 used independently. When the stationary phase is silica gel and neutral alumina, the preferred mass ratio of silica gel to neutral alumina is 3~4:2~3.

[0031] In this invention, the volume ratio of eluent 1 to eluent 2 is 1:3~5, preferably 1:4; The eluent 1 and eluent 2 independently include one or more of n-pentane, isopentane, petroleum ether, n-hexane, n-heptane, dichloromethane, ethyl acetate, and chloroform, preferably one or more of n-pentane, isopentane, petroleum ether, n-hexane, n-heptane, and dichloromethane, and more preferably one or more of n-pentane, isopentane, petroleum ether, and n-hexane.

[0032] In this invention, in step 5), the stationary phase of the second column chromatography is octadecylsilane-bonded silica gel or octylsilane-bonded silica gel, preferably octadecylsilane-bonded silica gel. The mobile phase contains eluent 3 and eluent 4; The volume ratio of eluent 3 to eluent 4 is 30~60:40~70, preferably 40~50:50~60; The eluent 3 and eluent 4 are independently one or more of methanol, acetonitrile and water, preferably acetonitrile and / or water.

[0033] The technical solutions provided by the present invention will be described in detail below with reference to the embodiments, but they should not be construed as limiting the scope of protection of the present invention.

[0034] Example 1

[0035] Take 4g of coal direct liquefaction oil fraction at 200~210℃, add extractant 1, i.e., 16g of dimethyl sulfoxide, to it, the mass ratio of extractant 1 to the raw oil is 4, and the extraction temperature is 30℃; after extraction, extract phase 2 rich in aromatics and phenols, and raffinate phase 1 rich in alkane components are obtained. Extraction phase 2 and 11g of deionized water were mixed and subjected to secondary extraction separation at an extraction temperature of 25℃ to obtain a new extraction phase 4 rich in phenols and extractant 1, and a raffinate phase 3 rich in aromatic components. Extraction phase 4 was mixed with dichloromethane and back-extracted. The back-extraction process was repeated 5 times, with 3 mL of back-extraction agent used each time. Then, the dichloromethane was removed at 25°C to obtain the phenolic component. The raffinate phase 3 was subjected to a first column chromatography (the lower stationary phase consisted of 4.12 g of silica gel, and the upper stationary phase consisted of 3.022 g of neutral alumina; the column size was 15). First, 18 mL of n-hexane (eluent 1) was used to remove alkanes. Then, 72 mL of eluent 2 (a mixed solution of dichloromethane and n-hexane, with a volume ratio of 2:1) was used to elute and obtain a high-purity aromatic mixture. The specific composition of the high-purity aromatic mixture is shown in Table 1. Using a mixture of eluent 3 and eluent 4 (volume ratio 1:1) as the mobile phase, the high-purity aromatic mixture was separated by a second column chromatography. The specific chromatogram is shown in Table 2. The fraction collected from 17 to 19 min yielded naphthalene with a purity ≥99%.

[0036] Table 1 Composition of high-purity aromatic hydrocarbon mixtures

[0037] As demonstrated by the above embodiments, this invention provides a method for extracting high-purity bicyclic aromatic naphthalene from direct coal liquefaction oil. This invention sequentially extracts and separates specific fractions using polar aprotic solvents and polar protic solvents, achieving the separation of direct coal liquefaction oil into alkanes, aromatics, and phenols. Furthermore, the obtained aromatic components can also be separated into high-purity bicyclic aromatic naphthalene using distillation or semi-preparative liquid chromatography. Compared to other separation methods, this invention offers advantages such as low energy consumption and adjustable selectivity, providing a solution to fill the supply gap of petroleum-based naphtha in my country and exploring new ideas for efficient energy utilization.

[0038] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for extracting high-purity bicyclic aromatic naphthalene from direct coal liquefaction oil, characterized in that, Includes the following steps: Step 1) The direct coal liquefaction oil is fractionated and the resulting fractions are analyzed to obtain the separated feedstock oil; Step 2) The raw oil and extractant 1 are mixed and extracted to obtain raffinate phase 1 and extract phase 2; Step 3) After mixing the extractant phase 2 and extractant 2, extraction is performed to obtain raffinate phase 3 and extractant phase 4; Step 4) After mixing the extract phase 4 and the back-extractant, back-extracting is performed to obtain the back-extract solution and the regenerated organic phase. Then, the back-extractant in the back-extract solution is removed to obtain the phenolic component. Step 5) Pass the raffinate phase 3 through two column chromatography cycles to obtain the bicyclic aromatic naphthalene monomer; In step 1), the separated feedstock oil is the fraction with the highest content of bicyclic aromatic naphthalene; In step 2), the raffinate phase 1 is rich in alkane components, and the extract phase 2 is rich in aromatic and phenolic components; In step 3), the raffinate phase 3 is rich in aromatic components, and the extract phase 4 is rich in phenolic components.

2. The method for extracting high-purity bicyclic aromatic naphthalene from direct coal liquefaction oil according to claim 1, characterized in that, In step 1), the reflux ratio of the fraction cutting is ≥3 and the temperature range is ≤300℃.

3. A method for extracting high-purity bicyclic aromatic naphthalene from direct coal liquefaction oil according to claim 1 or 2, characterized in that, In step 2), the mixing is carried out under stirring for 10-30 minutes, the mass ratio of extractant 1 to the raw oil to be separated is 4, and the extraction temperature is 20-35℃. The extractant 1 is a polar aprotic solvent; The polar aprotic solvent includes dimethyl sulfoxide, N-methylpyrrolidone, or N,N-dimethylformamide.

4. The method for extracting high-purity bicyclic aromatic naphthalene from direct coal liquefaction oil according to claim 3, characterized in that, In step 3), the mixing is carried out under stirring conditions for 10-30 minutes, and the amount of extractant 2 is 10-40% of the sum of the masses of extractant 2 and extractant 1. The extractant 2 is a polar protic solvent, which includes water.

5. A method for extracting high-purity bicyclic aromatic naphthalene from direct coal liquefaction oil according to claim 1, 2, or 4, characterized in that, In step 4), the mixing is carried out under stirring conditions for 10 to 30 minutes.

6. The method for extracting high-purity bicyclic aromatic naphthalene from direct coal liquefaction oil according to claim 5, characterized in that, In step 4), the back-extraction is performed 2 to 5 times, and the back-extraction agent includes dichloromethane, with each back-extraction agent being 2 to 5 mL in volume.

7. A method for extracting high-purity bicyclic aromatic naphthalene from direct coal liquefaction oil according to claim 1 or 6, characterized in that, In step 4), the temperature for removing the back-extraction agent is 20~35℃.

8. The method for extracting high-purity bicyclic aromatic naphthalene from direct coal liquefaction oil according to claim 7, characterized in that, In step 5), in the two column chromatography processes, the stationary phase of the first column chromatography is chromatographic silica gel and / or neutral alumina, and the mobile phase contains eluent 1 and eluent 2, which are used independently. When the stationary phase is silica gel and neutral alumina, the mass ratio of the silica gel to the neutral alumina is 3~4:2~3.

9. A method for extracting high-purity bicyclic aromatic naphthalene from direct coal liquefaction oil according to claim 8, characterized in that, In step 5), the volume ratio of eluent 1 to eluent 2 is 1:3~5; The eluent 1 and eluent 2 independently include one or more of n-pentane, isopentane, petroleum ether, n-hexane, n-heptane, dichloromethane, ethyl acetate, and chloroform.

10. A method for extracting high-purity bicyclic aromatic naphthalene from direct coal liquefaction oil according to claim 8, characterized in that, In step 5), in the two column chromatography processes, the stationary phase of the second column chromatography is octadecylsilane-bonded silica gel or octylsilane-bonded silica gel, and the mobile phase includes eluent 3 and eluent 4. The volume ratio of eluent 3 to eluent 4 is 30~60:40~70; The eluent 3 and eluent 4 are independently one or more of methanol, acetonitrile, and water.

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