A method for separating polycyclic aromatic hydrocarbons

Abstract

This invention provides a method for separating polycyclic aromatic hydrocarbons (PAHs), belonging to the field of PAH separation technology. The method involves first mixing a mixed solvent and the mixture to be separated, followed by filtration to obtain a filter cake and a filtrate. Then, a back-extraction agent is mixed with the filtrate for separation. The mixed solvent is either a naphthyl-based mixed solvent or an imidazole-based mixed solvent, and the mixture to be separated is either a mixture containing bicyclic and tricyclic aromatic hydrocarbons or a mixture containing tricyclic and tetracyclic aromatic hydrocarbons. This invention utilizes a naphthyl-based mixed solvent to separate mixtures containing bicyclic and tricyclic aromatic hydrocarbons, and an imidazole-based mixed solvent to separate mixtures containing tricyclic and tetracyclic aromatic hydrocarbons. Furthermore, the naphthyl-based mixed solvent or the imidazole-based mixed solvent can be recycled. The separation method provided by this invention is simple in procedure, low in energy consumption, and has a simple process flow.

Description

Technical Field

[0001] This invention relates to the field of polycyclic aromatic hydrocarbon (PAH) separation technology, and more particularly to a method for separating PAHs. Background Technology

[0002] Polycyclic aromatic hydrocarbons (PAHs) are fundamental raw materials in the chemical industry, possessing high application value and applicable to various research fields. Tricyclic and tetracyclic APAs exhibit good fluorescence effects and can be used as raw materials for preparing optoelectronic materials. Furthermore, hydrogenated tricyclic and tetracyclic APAs can be used as additives in high-energy-density fuels to improve fuel performance. Coal tar is rich in PAHs, with bicyclic, tricyclic, and tetracyclic APAs being particularly abundant.

[0003] Currently, the main separation methods include distillation, supercritical fluid extraction, zone melting, column chromatography, and extraction. Among these, distillation is the most widely used, but it has disadvantages such as high energy consumption and a long process flow. Conversely, extraction is simple to operate and has lower equipment requirements, but because it is difficult to find obvious recognition sites for bicyclic, tricyclic, and tetracyclic aromatic hydrocarbons, it is currently difficult to find suitable solvents to separate them. Therefore, it is of great significance to provide a method for separating polycyclic aromatic hydrocarbons, and to achieve the separation of mixtures of bicyclic and tricyclic aromatic hydrocarbons and mixtures of tricyclic and tetracyclic aromatic hydrocarbons. Summary of the Invention

[0004] The purpose of this invention is to provide a method for separating polycyclic aromatic hydrocarbons (PAHs) to solve the problems of cumbersome and energy-intensive separation steps for mixtures containing bicyclic and tricyclic aromatic hydrocarbons or mixtures containing tricyclic and tetracyclic aromatic hydrocarbons in the prior art.

[0005] To achieve the above-mentioned objectives, the present invention provides the following technical solution:

[0006] This invention provides a method for separating polycyclic aromatic hydrocarbons, comprising the following steps:

[0007] (1) After mixing the mixed solvent and the mixture to be separated, filter the mixture to obtain filter cake and filtrate;

[0008] (2) The back-extraction agent and the filtrate are mixed and then separated;

[0009] The mixed solvent is a naphthyl mixed solvent or an imidazole mixed solvent;

[0010] The mixture to be separated is a mixture containing bicyclic aromatic hydrocarbons and tricyclic aromatic hydrocarbons or a mixture containing tricyclic aromatic hydrocarbons and tetracyclic aromatic hydrocarbons.

[0011] Preferably, in step (1), the mass ratio of the mixed solvent to the mixture to be separated is 1 to 8:1.

[0012] Preferably, the separation of the mixture containing bicyclic aromatic hydrocarbons and tricyclic aromatic hydrocarbons is performed using a naphthyl mixed solvent, wherein the naphthyl mixed solvent is composed of a mixture of alcohol compounds and naphthyl compounds.

[0013] Preferably, the concentration of the naphthyl compound is 2–20 mol%.

[0014] Preferably, the naphthyl compound comprises one or more of naphthiacetonitrile, naphthaleneacetic acid, naphthylacetamide, naphthaleneethanol, naphthylamine, and naphthol.

[0015] Preferably, the separation of the mixture containing tricyclic aromatic hydrocarbons and tetracyclic aromatic hydrocarbons is performed using an imidazole mixed solvent, wherein the imidazole mixed solvent is composed of a mixture of alcohol compounds and imidazole compounds.

[0016] Preferably, the alcohol compound comprises one or more of ethylene glycol, propylene glycol, pentanediol, heptanediol, and octanediol.

[0017] Preferably, the imidazole compound comprises one or more of methylimidazolium, ethylimidazolium, propylimidazolium, and butylimidazolium.

[0018] Preferably, the concentration of the imidazole compound is 10–80 mol%.

[0019] The beneficial effects of this invention are:

[0020] (1) The present invention uses a naphthyl mixed solvent to separate a mixture containing bicyclic aromatic hydrocarbons and tricyclic aromatic hydrocarbons, and uses an imidazole mixed solvent to separate a mixture containing tricyclic aromatic hydrocarbons and tetracyclic aromatic hydrocarbons, and the naphthyl mixed solvent or the imidazole mixed solvent can be recycled.

[0021] (2) The separation method provided by the present invention has simple steps, low energy consumption, simple process flow, low solvent toxicity, and the naphthyl mixed solvent and imidazole mixed solvent used can be efficiently recycled by back extraction. Detailed Implementation

[0022] This invention provides a method for separating polycyclic aromatic hydrocarbons, comprising the following steps:

[0023] (1) After mixing the mixed solvent and the mixture to be separated, filter the mixture to obtain filter cake and filtrate;

[0024] (2) The back-extraction agent and the filtrate are mixed and then separated;

[0025] The mixed solvent is a naphthyl mixed solvent or an imidazole mixed solvent;

[0026] The mixture to be separated is a mixture containing bicyclic aromatic hydrocarbons and tricyclic aromatic hydrocarbons or a mixture containing tricyclic aromatic hydrocarbons and tetracyclic aromatic hydrocarbons.

[0027] In this invention, the mixture containing bicyclic aromatic hydrocarbons and tricyclic aromatic hydrocarbons is a model mixture containing bicyclic aromatic hydrocarbons and tricyclic aromatic hydrocarbons or a fraction of coal tar at 220-320°C, preferably a model mixture containing bicyclic aromatic hydrocarbons and tricyclic aromatic hydrocarbons.

[0028] In this invention, the model mixture containing bicyclic aromatic hydrocarbons and tricyclic aromatic hydrocarbons is a mixture containing two or more of naphthalene, methylnaphthalene, anthracene, phenanthrene, and fluorene, preferably a mixture of naphthalene and phenanthrene, a mixture of naphthalene and anthracene, or a mixture of naphthalene, phenanthrene, and fluorene.

[0029] In this invention, the mixture containing tricyclic aromatic hydrocarbons and tetracyclic aromatic hydrocarbons is a model mixture containing tricyclic aromatic hydrocarbons and tetracyclic aromatic hydrocarbons or a fraction of coal tar at 300-400°C, preferably a model mixture containing tricyclic aromatic hydrocarbons and tetracyclic aromatic hydrocarbons.

[0030] In this invention, the model mixture containing tricyclic and tetracyclic aromatic hydrocarbons is a mixture of two or more of anthracene, phenanthrene, fluorene, pyrene and fluoranthene, preferably a mixture of phenanthrene and pyrene, or a mixture of phenanthrene, pyrene and fluoranthene, or a mixture of phenanthrene, anthracene, pyrene and fluoranthene, or a mixture of phenanthrene, anthracene, fluorene, pyrene and fluoranthene.

[0031] In this invention, in step (1), the mass ratio of the mixed solvent to the mixture to be separated is 1 to 8:1, preferably 1:1, 2:1, 3:1, 5:1, or 6:1, and more preferably 3:1 or 5:1.

[0032] In this invention, in step (1), the mixed solvent and the mixture to be separated are mixed and then stirred, wherein the stirring temperature is controlled at 20-90°C, preferably 30-80°C, and more preferably 30°C, 40°C, 50°C, or 70°C.

[0033] In the invention, in step (2), the back-extraction agent and the filtrate are mixed and stirred, wherein the stirring temperature is controlled at 20-40°C, preferably 25-35°C, and more preferably 30°C.

[0034] In this invention, the separation of the mixture containing bicyclic aromatic hydrocarbons and tricyclic aromatic hydrocarbons is performed using a naphthyl mixed solvent, wherein the naphthyl mixed solvent is composed of a mixture of alcohol compounds and naphthyl compounds.

[0035] In this invention, the alcohol compounds in the naphthalene mixed solvent include one or more of ethylene glycol, propylene glycol, pentanediol, heptahydrin, and octanediol, preferably one or more of ethylene glycol, propylene glycol, and pentanediol, and more preferably ethylene glycol.

[0036] In this invention, the concentration of the naphthyl compound is 2-20 mol%, preferably 5-18 mol%, and more preferably 10-15 mol%.

[0037] In this invention, the naphthyl compound comprises one or more of naphthiacetonitrile, naphthaleneacetic acid, naphthylacetamide, naphthaleneethanol, naphthylamine, and naphthol, preferably one or more of naphthiacetonitrile, naphthaleneacetic acid, naphthaleneethanol, and naphthol, and more preferably naphthaleneethanol.

[0038] In this invention, the back-extraction agent used for separating the mixture containing bicyclic aromatic hydrocarbons and tricyclic aromatic hydrocarbons is one or more of n-hexane, n-heptane, n-octane, n-nonane and n-decane, preferably one or more of n-hexane, n-heptane, n-octane and n-nonane, and more preferably n-hexane and / or n-heptane.

[0039] In this invention, the separation of the mixture containing bicyclic aromatic hydrocarbons and tricyclic aromatic hydrocarbons involves a back-extraction agent to filtrate mass ratio of 2 to 20:1, preferably 5 to 15:1, and more preferably 8 to 12:1.

[0040] In this invention, the mixture containing bicyclic aromatic hydrocarbons and tricyclic aromatic hydrocarbons is separated to obtain a mixture of back-extractant and bicyclic aromatic hydrocarbons, which is then subjected to vacuum distillation to obtain the back-extractant and bicyclic aromatic hydrocarbons. The vacuum distillation temperature is 30-70°C, preferably 40-60°C, more preferably 50°C, and the time is 30-90 min, preferably 40-80 min, more preferably 50-70 min.

[0041] In this invention, the separation of the mixture containing tricyclic aromatic hydrocarbons and tetracyclic aromatic hydrocarbons is performed using an imidazole mixed solvent, wherein the imidazole mixed solvent is composed of a mixture of alcohol compounds and imidazole compounds.

[0042] In this invention, the alcohol compound comprises one or more of ethylene glycol, propylene glycol, pentanediol, heptahydrin, and octanediol, preferably one or more of ethylene glycol, propylene glycol, and pentanediol, and more preferably ethylene glycol.

[0043] In this invention, the imidazole compound comprises one or more of methylimidazolium, ethylimidazolium, propylimidazolium and butylimidazolium, preferably one or more of ethylimidazolium, propylimidazolium and butylimidazolium, and more preferably ethylimidazolium and / or butylimidazolium.

[0044] In this invention, the concentration of the imidazole compound is 10–80 mol%, preferably 15–75 mol%, and more preferably 20–60 mol%.

[0045] In this invention, the separation of the mixture containing tricyclic aromatic hydrocarbons and tetracyclic aromatic hydrocarbons is preferably achieved by using ethylene glycol as the back-extraction agent, and the mixing of ethylene glycol and filtrate is preferably achieved by slowly adding ethylene glycol to the filtrate.

[0046] 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.

[0047] Example 1

[0048] 2g of naphthalene and 1g of phenanthrene were mixed in dichloromethane and heated with stirring at room temperature. The dichloromethane was then removed by distillation to obtain a mixture of naphthalene and phenanthrene. The mixture of naphthalene and phenanthrene was mixed with a naphthyl mixed solvent (which was a mixture of naphthalene methanol and ethylene glycol with a concentration of 10 mol%) and the mixture of naphthalene and phenanthrene at a mass ratio of 1:1 and stirred at 30°C. Finally, the mixture was filtered to obtain a filter cake (tricyclic aromatic hydrocarbon) and a filtrate.

[0049] Hexane and filtrate were mixed at a mass ratio of 10:1 and stirred at 30°C for 50 min. Finally, the mixture was washed and filtered to separate the naphthyl mixed solvent and the mixture of hexane and bicyclic aromatic hydrocarbons.

[0050] A mixture of n-hexane and bicyclic aromatic hydrocarbons was distilled under reduced pressure at 50 °C for 50 min to obtain n-hexane and bicyclic aromatic hydrocarbons. The purity of the bicyclic aromatic hydrocarbons was 89.1% and the yield was 60%. The purity of the tricyclic aromatic hydrocarbons was 87.2% and the yield was 60%.

[0051] Example 2

[0052] 2g of naphthalene and 1g of phenanthrene were mixed in dichloromethane and heated with stirring at room temperature. The dichloromethane was then removed by distillation to obtain a mixture of naphthalene and phenanthrene. The mixture of naphthalene and phenanthrene was mixed with a naphthyl mixed solvent (which was a mixture of naphthalene methanol and ethylene glycol with a concentration of 10 mol%) at a mass ratio of 2:1 and stirred at 30°C. Finally, the mixture was filtered to obtain a filter cake (tricyclic aromatic hydrocarbon) and a filtrate.

[0053] After mixing n-heptane and the filtrate at a mass ratio of 15:1, the mixture was stirred at 30°C for 50 min. Finally, the mixture was washed and filtered to separate the naphthyl mixed solvent and the mixture of n-heptane and bicyclic aromatic hydrocarbons.

[0054] A mixture of n-heptane and bicyclic aromatic hydrocarbons was distilled under reduced pressure at 60 °C for 40 min to obtain n-heptane and bicyclic aromatic hydrocarbons. The purity of the bicyclic aromatic hydrocarbons was 90.5% and the yield was 62%. The purity of the tricyclic aromatic hydrocarbons was 89.5% and the yield was 61%.

[0055] Example 3

[0056] 2g of naphthalene and 1g of phenanthrene were mixed in dichloromethane and heated with stirring at room temperature. The dichloromethane was then removed by distillation to obtain a mixture of naphthalene and phenanthrene. The mixture of naphthalene and phenanthrene was mixed with a naphthyl mixed solvent (which was a mixture of naphthalene methanol and ethylene glycol with a concentration of 10 mol%) at a mass ratio of 3:1 and stirred at 50°C. Finally, the mixture was filtered to obtain a filter cake (tricyclic aromatic hydrocarbon) and a filtrate.

[0057] After mixing n-octane and the filtrate at a mass ratio of 5:1, the mixture was stirred at 50°C for 50 min. Finally, the mixture was washed and filtered to separate the naphthyl mixed solvent and the mixture of n-octane and bicyclic aromatic hydrocarbons.

[0058] A mixture of n-octane and bicyclic aromatic hydrocarbons was distilled under reduced pressure at 30 °C for 90 min to obtain n-octane and bicyclic aromatic hydrocarbons. The purity of the bicyclic aromatic hydrocarbons was 94.5% and the yield was 67%. The purity of the tricyclic aromatic hydrocarbons was 94.9% and the yield was 68%.

[0059] Example 4

[0060] 2g of naphthalene and 1g of phenanthrene were mixed in dichloromethane and heated with stirring at room temperature. The dichloromethane was then removed by distillation to obtain a mixture of naphthalene and phenanthrene. The mixture of naphthalene and phenanthrene was mixed with a naphthyl mixed solvent (which was a mixture of naphthalene methanol and ethylene glycol with a concentration of 15 mol%) at a mass ratio of 5:1 and stirred at 30°C. Finally, the mixture was filtered to obtain a filter cake (tricyclic aromatic hydrocarbon) and a filtrate.

[0061] After mixing n-octane and the filtrate at a mass ratio of 20:1, the mixture was stirred at 20°C for 90 min. Finally, the mixture was washed and filtered to separate the naphthyl mixed solvent and the mixture of n-octane and bicyclic aromatic hydrocarbons.

[0062] A mixture of n-octane and bicyclic aromatic hydrocarbons was distilled under reduced pressure at 30 °C for 90 min to obtain n-octane and bicyclic aromatic hydrocarbons. The purity of the bicyclic aromatic hydrocarbons was 92.5%, and the yield was 65%. The purity of the tricyclic aromatic hydrocarbons was 93.1%, and the yield was 66%.

[0063] Example 5

[0064] 2g of naphthalene and 1g of phenanthrene were mixed in dichloromethane and heated with stirring at room temperature. The dichloromethane was then removed by distillation to obtain a mixture of naphthalene and phenanthrene. The mixture of naphthalene and phenanthrene was mixed with a naphthyl mixed solvent (which was a mixture of naphthyl acetonitrile and ethylene glycol, with a concentration of 8 mol%) and the mixture at a mass ratio of 2:1 and stirred at 30°C. Finally, the mixture was filtered to obtain a filter cake (tricyclic aromatic hydrocarbon) and a filtrate.

[0065] After mixing n-octane and the filtrate at a mass ratio of 20:1, the mixture was stirred at 20°C for 90 min. Finally, the mixture was washed and filtered to separate the naphthyl mixed solvent and the mixture of n-octane and bicyclic aromatic hydrocarbons.

[0066] A mixture of n-octane and bicyclic aromatic hydrocarbons was distilled under reduced pressure at 30 °C for 90 min to obtain n-octane and bicyclic aromatic hydrocarbons. The purity of the bicyclic aromatic hydrocarbons was 90.5%, and the yield was 62%. The purity of the tricyclic aromatic hydrocarbons was 91.6%, and the yield was 62%.

[0067] Example 6

[0068] 2g of naphthalene and 1g of phenanthrene were mixed in dichloromethane and heated with stirring at room temperature. The dichloromethane was then removed by distillation to obtain a mixture of naphthalene and phenanthrene. The mixture of naphthalene and phenanthrene was mixed with a naphthyl mixed solvent (which was a mixture of naphthaleneacetic acid and ethylene glycol, with a concentration of 12 mol%) and the naphthalene and phenanthrene mixture at a mass ratio of 3:1 and stirred at 30°C. Finally, the mixture was filtered to obtain a filter cake (tricyclic aromatic hydrocarbon) and a filtrate.

[0069] After mixing n-octane and the filtrate at a mass ratio of 20:1, the mixture was stirred at 20°C for 90 min. Finally, the mixture was washed and filtered to separate the naphthyl mixed solvent and the mixture of n-octane and bicyclic aromatic hydrocarbons.

[0070] A mixture of n-octane and bicyclic aromatic hydrocarbons was distilled under reduced pressure at 50 °C for 60 min to obtain n-octane and bicyclic aromatic hydrocarbons. The purity of the bicyclic aromatic hydrocarbons was 91.8% and the yield was 61%. The purity of the tricyclic aromatic hydrocarbons was 92.8% and the yield was 64%.

[0071] Example 7

[0072] 2g of naphthalene and 1g of phenanthrene were mixed in dichloromethane and heated with stirring at room temperature. The dichloromethane was then removed by distillation to obtain a mixture of naphthalene and phenanthrene. The mixture of naphthalene and phenanthrene was mixed with a naphthyl mixed solvent (which was a mixture of naphthylacetamide and ethylene glycol, with a naphthylacetamide concentration of 18 mol%) and the mixture at a mass ratio of 6:1 and stirred at 70°C. Finally, the mixture was filtered to obtain a filter cake (tricyclic aromatic hydrocarbon) and a filtrate.

[0073] After mixing n-octane and the filtrate at a mass ratio of 20:1, the mixture was stirred at 20°C for 90 min. Finally, the mixture was washed and filtered to separate the naphthyl mixed solvent and the mixture of n-octane and bicyclic aromatic hydrocarbons.

[0074] A mixture of n-octane and bicyclic aromatic hydrocarbons was distilled under reduced pressure at 40 °C for 30 min to obtain n-octane and bicyclic aromatic hydrocarbons. The purity of the bicyclic aromatic hydrocarbons was 86.8%, and the yield was 55%. The purity of the tricyclic aromatic hydrocarbons was 89.1%, and the yield was 61%.

[0075] Example 8

[0076] 2g of naphthalene and 1g of phenanthrene were mixed in dichloromethane and heated with stirring at room temperature. The dichloromethane was then removed by distillation to obtain a mixture of naphthalene and phenanthrene. The mixture of naphthalene and phenanthrene was mixed with a naphthyl mixed solvent (which was a mixture of naphthyl ethanol and ethylene glycol with a concentration of 18 mol%) at a mass ratio of 8:1 and stirred at 40°C. Finally, the mixture was filtered to obtain a filter cake (tricyclic aromatic hydrocarbon) and a filtrate.

[0077] After mixing n-octane and the filtrate at a mass ratio of 20:1, the mixture was stirred at 20°C for 90 min. Finally, the mixture was washed and filtered to separate the naphthyl mixed solvent and the mixture of n-octane and bicyclic aromatic hydrocarbons.

[0078] A mixture of n-octane and bicyclic aromatic hydrocarbons was distilled under reduced pressure at 70 °C for 30 min to obtain n-octane and bicyclic aromatic hydrocarbons. The purity of the bicyclic aromatic hydrocarbons was 89.6% and the yield was 60%. The purity of the tricyclic aromatic hydrocarbons was 90.5% and the yield was 63%.

[0079] Example 9

[0080] 2g of naphthalene and 1g of phenanthrene were mixed in dichloromethane and heated with stirring at room temperature. The dichloromethane was then removed by distillation to obtain a mixture of naphthalene and phenanthrene. The mixture of naphthalene and phenanthrene was mixed with a naphthyl mixed solvent (which was a mixture of naphthol and ethylene glycol with a naphthol concentration of 18 mol%) at a mass ratio of 3:1 and stirred at 50°C. Finally, the mixture was filtered to obtain a filter cake (tricyclic aromatic hydrocarbon) and a filtrate.

[0081] After mixing n-octane and the filtrate at a mass ratio of 20:1, the mixture was stirred at 20°C for 90 min. Finally, the mixture was washed and filtered to separate the naphthyl mixed solvent and the mixture of n-octane and bicyclic aromatic hydrocarbons.

[0082] A mixture of n-octane and bicyclic aromatic hydrocarbons was distilled under reduced pressure at 30 °C for 90 min to obtain n-octane and bicyclic aromatic hydrocarbons. The purity of the bicyclic aromatic hydrocarbons was 91.3% and the yield was 61%. The purity of the tricyclic aromatic hydrocarbons was 93.3% and the yield was 63%.

[0083] Example 10

[0084] 2g of naphthalene and 1g of anthracene were mixed in dichloromethane and heated with stirring at room temperature. The dichloromethane was then removed by distillation to obtain a mixture of naphthalene and anthracene. The mixture of naphthalene and anthracene was mixed with a naphthyl mixed solvent (which was a mixture of naphthalene methanol and ethylene glycol with a concentration of 5 mol%) at a mass ratio of 3:1 and stirred at 40°C. Finally, the mixture was filtered to obtain a filter cake (tricyclic aromatic hydrocarbon) and a filtrate.

[0085] After mixing n-octane and the filtrate at a mass ratio of 20:1, the mixture was stirred at 20°C for 90 min. Finally, the mixture was washed and filtered to separate the naphthyl mixed solvent and the mixture of n-octane and bicyclic aromatic hydrocarbons.

[0086] A mixture of n-octane and bicyclic aromatic hydrocarbons was distilled under reduced pressure at 30 °C for 90 min to obtain n-octane and bicyclic aromatic hydrocarbons. The purity of the bicyclic aromatic hydrocarbons was 96.5% and the yield was 67%. The purity of the tricyclic aromatic hydrocarbons was 96.8% and the yield was 66%.

[0087] Example 11

[0088] 2g of naphthalene, 0.5g of phenanthrene, 0.3g of anthracene, and 0.2g of fluorene were mixed in dichloromethane and heated with stirring at room temperature. The dichloromethane was then removed by distillation to obtain a mixture of naphthalene, phenanthrene, anthracene, and fluorene. A mixture of naphthyl mixed solvent (which was a mixture of naphthalene methanol and ethylene glycol with a concentration of 10 mol%), naphthalene, phenanthrene, anthracene, and fluorene was mixed at a mass ratio of 3:1 and stirred at 50°C. Finally, the mixture was filtered to obtain a filter cake (tricyclic aromatic hydrocarbons) and a filtrate.

[0089] Hexane and filtrate were mixed at a mass ratio of 20:1 and stirred at 20°C for 90 min. Finally, the mixture was washed and filtered to separate the naphthyl mixed solvent and the mixture of hexane and bicyclic aromatic hydrocarbons.

[0090] A mixture of n-hexane and bicyclic aromatic hydrocarbons was distilled under reduced pressure at 30 °C for 90 min to obtain n-hexane and bicyclic aromatic hydrocarbons. The purity of the bicyclic aromatic hydrocarbons was 95.4%, and the yield was 66%. The purity of the tricyclic aromatic hydrocarbons was 96.5%, and the yield was 67%.

[0091] Example 12

[0092] 2g of phenanthrene and 1g of pyrene were mixed in dichloromethane, stirred and heated at room temperature, and then distilled to remove the dichloromethane, yielding a mixture of phenanthrene and pyrene. An imidazole mixed solvent (in which the imidazole mixed solvent was composed of ethyl imidazole and ethylene glycol, with the concentration of ethyl imidazole being 30 mol%), the mixture of phenanthrene and pyrene were mixed at a mass ratio of 1:1 and stirred at 30°C. Finally, the mixture was filtered to obtain a filter cake (tricyclic aromatic hydrocarbons) and a filtrate.

[0093] Ethylene glycol was slowly added to the filtrate while maintaining the temperature at 30°C until the solid mass became constant. The addition was then stopped. Finally, the mixture was washed and filtered to obtain an imidazole mixed solvent and a tetracyclic aromatic compound. In Example 12, the purity of the tricyclic aromatic hydrocarbon was 84.5%, with a yield of 58%, and the purity of the tetracyclic aromatic hydrocarbon was 83.5%, with a yield of 52%.

[0094] Example 13

[0095] 2g of phenanthrene and 1g of pyrene were mixed in dichloromethane, stirred and heated at room temperature, and then distilled to remove the dichloromethane, yielding a mixture of phenanthrene and pyrene. An imidazole mixed solvent (in which the imidazole mixed solvent was composed of ethylimidazolium and propylene glycol, with the concentration of ethylimidazolium being 40 mol%), the mixture of phenanthrene and pyrene were mixed at a mass ratio of 2:1 and stirred at 40°C. Finally, the mixture was filtered to obtain a filter cake (tricyclic aromatic hydrocarbons) and a filtrate.

[0096] Ethylene glycol was slowly added to the filtrate while maintaining the temperature at 40°C until the solid mass became constant. The addition was then stopped. Finally, the mixture was washed and filtered to obtain an imidazole mixed solvent and a tetracyclic aromatic compound. In Example 13, the purity of the tricyclic aromatic hydrocarbon was 88.4%, with a yield of 60%, and the purity of the tetracyclic aromatic hydrocarbon was 86.5%, with a yield of 58%.

[0097] Example 14

[0098] 2g of phenanthrene and 1g of pyrene were mixed in dichloromethane, stirred and heated at room temperature, and then distilled to remove the dichloromethane, yielding a mixture of phenanthrene and pyrene. An imidazole mixed solvent (in which the imidazole mixed solvent was composed of ethyl imidazole and ethylene glycol, with the concentration of ethyl imidazole being 40 mol%), the mixture of phenanthrene and pyrene were mixed at a mass ratio of 3:1 and stirred at 40°C. Finally, the mixture was filtered to obtain a filter cake (tricyclic aromatic hydrocarbons) and a filtrate.

[0099] Ethylene glycol was slowly added to the filtrate while maintaining the temperature at 20°C until the solid mass became constant. The addition was then stopped. Finally, the mixture was washed and filtered to obtain an imidazole mixed solvent and a tetracyclic aromatic compound. In Example 14, the purity of the tricyclic aromatic compound was 86.4%, with a yield of 58%, and the purity of the tetracyclic aromatic compound was 83.5%, with a yield of 52%.

[0100] Example 15

[0101] 2g of phenanthrene and 1g of pyrene were mixed in dichloromethane, stirred and heated at room temperature, and then distilled to remove the dichloromethane, yielding a mixture of phenanthrene and pyrene. An imidazole mixed solvent (in which the imidazole mixed solvent was composed of ethyl imidazole and ethylene glycol, with the concentration of ethyl imidazole being 40 mol%), the mixture of phenanthrene and pyrene were mixed at a mass ratio of 5:1 and stirred at 30°C. Finally, the mixture was filtered to obtain a filter cake (tricyclic aromatic hydrocarbons) and a filtrate.

[0102] Ethylene glycol was slowly added to the filtrate while maintaining the temperature at 30°C until the solid mass became constant. The addition was then stopped. Finally, the mixture was washed and filtered to obtain an imidazole mixed solvent and a tetracyclic aromatic compound. In Example 15, the purity of the tricyclic aromatic hydrocarbon was 81.9%, and the yield was 52%. The purity of the tetracyclic aromatic hydrocarbon was 80.4%, and the yield was 52%.

[0103] Example 16

[0104] 2g of phenanthrene and 1g of pyrene were mixed in dichloromethane, stirred and heated at room temperature, and then distilled to remove the dichloromethane, yielding a mixture of phenanthrene and pyrene. An imidazole mixed solvent (in which the imidazole mixed solvent was composed of methylimidazolium and pentylene glycol, with a methylimidazolium concentration of 50 mol%), the mixture of phenanthrene and pyrene were mixed at a mass ratio of 2:1 and stirred at 40°C. Finally, the mixture was filtered to obtain a filter cake (tricyclic aromatic hydrocarbons) and a filtrate.

[0105] Ethylene glycol was slowly added to the filtrate while maintaining the temperature at 30°C until the solid mass became constant. The addition was then stopped. Finally, the mixture was washed and filtered to obtain an imidazole mixed solvent and a tetracyclic aromatic compound. In Example 16, the purity of the tricyclic aromatic hydrocarbon was 84.2%, with a yield of 56%, and the purity of the tetracyclic aromatic hydrocarbon was 83.9%, with a yield of 55%.

[0106] Example 17

[0107] 2g of phenanthrene and 1g of pyrene were mixed in dichloromethane, stirred and heated at room temperature, and then distilled to remove the dichloromethane, yielding a mixture of phenanthrene and pyrene. An imidazole mixed solvent (in which the imidazole mixed solvent was composed of propylimidazolium and ethylene glycol, with a propylimidazolium concentration of 20 mol%), the mixture of phenanthrene and pyrene were mixed at a mass ratio of 2:1 and stirred at 40°C. Finally, the mixture was filtered to obtain a filter cake (tricyclic aromatic hydrocarbons) and a filtrate.

[0108] Ethylene glycol was slowly added to the filtrate while maintaining the temperature at 30°C until the solid mass became constant. The addition was then stopped. Finally, the mixture was washed and filtered to obtain an imidazole mixed solvent and a tetracyclic aromatic compound. In Example 17, the purity of the tricyclic aromatic hydrocarbon was 83.9%, with a yield of 57%, and the purity of the tetracyclic aromatic hydrocarbon was 84.9%, with a yield of 59%.

[0109] Example 18

[0110] 2g of phenanthrene and 1g of pyrene were mixed in dichloromethane, stirred and heated at room temperature, and then distilled to remove the dichloromethane, yielding a mixture of phenanthrene and pyrene. An imidazole mixed solvent (in which the imidazole mixed solvent was composed of butylimidazol and octanediol, with a butylimidazol concentration of 60 mol%), the mixture of phenanthrene and pyrene were mixed at a mass ratio of 8:1 and stirred at 40°C. Finally, the mixture was filtered to obtain a filter cake (tricyclic aromatic hydrocarbons) and a filtrate.

[0111] Ethylene glycol was slowly added to the filtrate while maintaining the temperature at 30°C until the solid mass became constant. The addition was then stopped. Finally, the mixture was washed and filtered to obtain an imidazole mixed solvent and a tetracyclic aromatic compound. In Example 18, the purity of the tricyclic aromatic hydrocarbon was 83.2%, with a yield of 58%, and the purity of the tetracyclic aromatic hydrocarbon was 82.7%, with a yield of 56%.

[0112] Example 19

[0113] 2g phenanthrene, 0.5g pyrene, and 0.5g fluoranthene were mixed in dichloromethane and heated with stirring at room temperature. The dichloromethane was then removed by distillation to obtain a mixture of phenanthrene, pyrene, and fluoranthene. An imidazole mixed solvent (in which the imidazole mixed solvent was composed of ethyl imidazole and ethylene glycol, with the concentration of ethyl imidazole being 40 mol%), a mixture of phenanthrene, pyrene, and fluoranthene, were mixed at a mass ratio of 2:1 and stirred at 50°C. Finally, the mixture was filtered to obtain a filter cake (tricyclic aromatic hydrocarbons) and a filtrate.

[0114] Ethylene glycol was slowly added to the filtrate while maintaining the temperature at 30°C until the solid mass became constant. The addition was then stopped. Finally, the mixture was washed and filtered to obtain an imidazole mixed solvent and a tetracyclic aromatic compound. In Example 19, the purity of the tricyclic aromatic compound was 88.1%, with a yield of 58%, and the purity of the tetracyclic aromatic compound was 88.6%, with a yield of 59%.

[0115] Example 20

[0116] 1 g of phenanthrene, 1 g of anthracene, 0.5 g of pyrene, and 0.5 g of fluoranthene were mixed in dichloromethane and heated with stirring at room temperature. The dichloromethane was then removed by distillation to obtain a mixture of phenanthrene, anthracene, pyrene, and fluoranthene. A mixture of imidazole mixed solvent (in which the imidazole mixed solvent was composed of ethylimidazolium and ethylene glycol, with the concentration of ethylimidazolium being 70 mol%), phenanthrene, anthracene, pyrene, and fluoranthene was mixed at a mass ratio of 3:1 and stirred at 40 °C. Finally, the mixture was filtered to obtain a filter cake (tricyclic aromatic hydrocarbons) and a filtrate.

[0117] Ethylene glycol was slowly added to the filtrate while maintaining the temperature at 30°C until the solid mass became constant. The addition was then stopped. Finally, the mixture was washed and filtered to obtain an imidazole mixed solvent and a tetracyclic aromatic compound. In Example 20, the purity of the tricyclic aromatic compound was 89.1%, with a yield of 60%, and the purity of the tetracyclic aromatic compound was 92.5%, with a yield of 61%.

[0118] Example 21

[0119] 1 g phenanthrene, 1 g anthracene, 0.2 g fluorene, 0.5 g pyrene, and 0.5 g fluoranthene were mixed in dichloromethane and heated with stirring at room temperature. The dichloromethane was then removed by distillation to obtain a mixture of phenanthrene, anthracene, fluorene, pyrene, and fluoranthene. A mixture of imidazole mixed solvent (which was a mixture of ethylimidazol and heptanediol, with an ethylimidazol concentration of 80 mol%), phenanthrene, anthracene, fluorene, pyrene, and fluoranthene was mixed at a mass ratio of 6:1 and stirred at 50 °C. Finally, the mixture was filtered to obtain a filter cake (tricyclic aromatic hydrocarbons) and a filtrate.

[0120] Ethylene glycol was slowly added to the filtrate while maintaining the temperature at 30°C until the solid mass became constant. The addition was then stopped. Finally, the mixture was washed and filtered to obtain an imidazole mixed solvent and a tetracyclic aromatic compound. In Example 21, the purity of the tricyclic aromatic compound was 87.1%, with a yield of 57%, and the purity of the tetracyclic aromatic compound was 90.5%, with a yield of 60%.

[0121] As can be seen from the above embodiments, the present invention provides a method for separating polycyclic aromatic hydrocarbons (PAHs). The method involves first mixing a mixed solvent and the mixture to be separated, followed by filtration to obtain a filter cake and a filtrate. Then, a back-extraction agent is mixed with the filtrate for separation. The mixed solvent is either a naphthyl mixed solvent or an imidazole mixed solvent, and the mixture to be separated is either a mixture containing bicyclic and tricyclic aromatic hydrocarbons or a mixture containing tricyclic and tetracyclic aromatic hydrocarbons. The present invention utilizes a naphthyl mixed solvent to separate mixtures containing bicyclic and tricyclic aromatic hydrocarbons, and an imidazole mixed solvent to separate mixtures containing tricyclic and tetracyclic aromatic hydrocarbons. Furthermore, the naphthyl mixed solvent or the imidazole mixed solvent can be recycled. The separation method provided by the present invention is simple in steps, low in energy consumption, and has a simple process flow.

[0122] 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 separating polycyclic aromatic hydrocarbons, characterized in that, Includes the following steps: (1) After mixing the mixed solvent and the mixture to be separated, filter the mixture to obtain filter cake and filtrate; (2) The back-extraction agent and the filtrate are mixed and then separated; The mixed solvent is an imidazole-based mixed solvent; The mixture to be separated is a mixture containing tricyclic aromatic hydrocarbons and tetracyclic aromatic hydrocarbons.

2. The separation method according to claim 1, characterized in that, In step (1), the mass ratio of the mixed solvent to the mixture to be separated is 1 to 8:

1.

3. The separation method according to claim 1 or 2, characterized in that, The imidazole mixed solvent is composed of a mixture of alcohols and imidazoles.

4. The separation method according to claim 3, characterized in that, The alcohol compounds include one or more of ethylene glycol, propylene glycol, pentanediol, heptahydrin, and octanediol.

5. The separation method according to claim 3, characterized in that, The imidazole compounds include one or more of methylimidazolium, ethylimidazolium, propylimidazolium, and butylimidazolium.

6. The separation method according to claim 4 or 5, characterized in that, The concentration of the imidazole compound is 10–80 mol%.