Preparation method and device of polycyclic aromatic hydrocarbon oligomer

Abstract

The invention provides a preparation method and device of a polycyclic aromatic hydrocarbon oligomer, and the preparation method comprises the following steps: 1) carrying out polymerization reaction on raw materials comprising a polycyclic aromatic hydrocarbon compound, an acidic ionic liquid catalyst and a solvent to obtain a reaction system; 2) carrying out extraction treatment on the reaction system by adopting an extraction agent to obtain an extraction phase containing a polymer and a raffinate phase containing an acidic ionic liquid catalyst; the solvent and the extracting agent respectively and independently comprise at least one of benzene and benzene homologues. The preparation method can significantly reduce the usage amount of acid liquor or alkali liquor, and is beneficial to environmental protection; according to the preparation method, the catalyst cannot be inactivated, the catalyst can be repeatedly used, and the industrial cost is effectively reduced.

Description

Technical Field

[0001] This invention relates to the field of organic chemistry, and in particular to a method and apparatus for preparing polycyclic aromatic hydrocarbon oligomers. Background Technology

[0002] Mesophase pitch plays a crucial precursor role in the preparation of mesophase pitch-based carbon fibers, and its quality directly determines the mechanical properties of the final carbon fibers. Currently, the main raw materials for preparing mesophase pitch include petroleum pitch, coal tar pitch, and pure aromatic compounds. Among these, pure aromatic compounds are considered ideal for preparing high-quality mesophase pitch due to their relatively simple molecular structure (containing only carbon and hydrogen elements), absence of ash, and high aromaticity. Taking naphthalene as an example, it typically first polymerizes under the catalysis of an acidic catalyst to form naphthalene oligomers, followed by a high-temperature thermal condensation reaction to prepare mesophase pitch. The catalytic polymerization of naphthalene to prepare naphthalene oligomers is a critical step in this process.

[0003] Currently, the catalytic preparation of naphthalene oligomers can utilize aluminochloroaluminate ionic liquids. During the preparation process, aluminochloroaluminate ionic liquids combine the high reactivity of liquid acids with the non-volatility of solid acids, and their structure and acidity can be modulated according to the composition, significantly improving the preparation efficiency of naphthalene oligomers. However, in the post-reaction processing, to achieve the separation of the aluminochloroaluminate ionic liquid and the naphthalene oligomers, it is often necessary to add a large amount of acid or alkali to the reaction system. While this helps improve the separation efficiency, the large amounts of acid or alkali wastewater severely pollute the environment. Furthermore, after treatment with acid or alkali, the aluminochloroaluminate ionic liquid becomes severely deactivated and cannot be regenerated, thus leading to high costs associated with the catalytic reaction.

[0004] Therefore, there is an urgent need for a method to prepare polycyclic aromatic hydrocarbon oligomers that can reduce pollution and lower costs. Summary of the Invention

[0005] This invention provides a method for preparing polycyclic aromatic hydrocarbon oligomers, which can significantly reduce the amount of acid or alkali solution used, thus protecting the environment; the method does not deactivate the catalyst, allowing the catalyst to be reused, effectively reducing industrial costs.

[0006] This invention provides an apparatus for preparing the aforementioned polycyclic aromatic hydrocarbon oligomers. Using this apparatus for the preparation of polycyclic aromatic hydrocarbon oligomers reduces the consumption of acid or alkali solutions, allowing for catalyst recycling, thus lowering industrial costs and protecting the environment. Furthermore, this apparatus supports continuous industrial production, significantly increasing product yield and improving industrial economics.

[0007] The first aspect of the present invention provides a method for preparing a polycyclic aromatic hydrocarbon oligomer, comprising the following steps:

[0008] 1) Performing a polymerization reaction on a raw material comprising a polycyclic aromatic hydrocarbon compound, an acidic ionic liquid catalyst, and a solvent to obtain a reaction system;

[0009] 2) Extracting the reaction system with an extractant to obtain an extract phase comprising a polymer and a raffinate phase comprising an acidic ionic liquid catalyst;

[0010] The solvent and the extractant each independently comprise at least one of benzene and benzene homologues.

[0011] In the method for preparing a polycyclic aromatic hydrocarbon oligomer as described above, the polycyclic aromatic hydrocarbon compound comprises at least one of naphthalene, an alkyl-substituted naphthalene, anthracene, an alkyl-substituted anthracene, phenanthrene, an alkyl-substituted phenanthrene, pyrene, and an alkyl-substituted pyrene.

[0012] In the method for preparing a polycyclic aromatic hydrocarbon oligomer as described above, the benzene and benzene homologues comprise at least one of toluene, p-xylene, m-xylene, o-xylene, mesitylene, and ethylbenzene.

[0013] In the method for preparing a polycyclic aromatic hydrocarbon oligomer as described above, the benzene and benzene homologues comprise o-xylene, m-xylene, and p-xylene, wherein the volume percentage content of o-xylene is 15% - 25%, the volume percentage content of m-xylene is 45% - 55%, and the volume percentage content of p-xylene is 20% - 30%.

[0014] In the method for preparing a polycyclic aromatic hydrocarbon oligomer as described above,

[0015] The stirring speed of the polymerization reaction is 50 - 200 revolutions per minute; and / or

[0016] The temperature of the polymerization reaction is 20 - 130 °C; and / or

[0017] The stirring speed of the extraction treatment is 50 - 200 revolutions per minute; and / or,

[0018] The temperature of the extraction treatment is 20 - 130 °C.

[0019] In the method for preparing a polycyclic aromatic hydrocarbon oligomer as described above, the acidic ionic liquid catalyst is Et3NHCl-xAlCl3, wherein x represents the molar ratio of Et3NHCl to AlCl3 in the acidic ionic liquid catalyst, and 1 < x ≤ 2; and / or.

[0020] The volume ratio of the extractant to the acidic ionic liquid catalyst solution is (10 - 200):1; and / or,

[0021] The acidic ionic liquid catalyst accounts for 10% to 100% of the total mass of the polycyclic aromatic hydrocarbons.

[0022] The method for preparing polycyclic aromatic hydrocarbon oligomers as described above, after step 2), further includes:

[0023] The extracted phase is subjected to impurity separation treatment to obtain the polymer and the recovered solvent, and the recovered solvent is returned to participate in the polymerization reaction and / or extraction treatment.

[0024] The above method for preparing polycyclic aromatic hydrocarbon oligomers includes, in sequence, washing and distillation of the impurity separation process.

[0025] The washing process includes at least one of acid washing, alkaline washing, and alcohol washing; and / or,

[0026] The distillation process is carried out at a temperature of 150–250°C.

[0027] A second aspect of the present invention provides an apparatus for preparing polycyclic aromatic hydrocarbon oligomers, for performing the preparation method of polycyclic aromatic hydrocarbon oligomers according to claims 1-8; comprising a reaction unit and an extraction unit, wherein the outlet of the reaction unit is connected to the inlet of the extraction unit.

[0028] The apparatus for preparing polycyclic aromatic oligomers as described above further includes a washing unit and a distillation unit;

[0029] The extract phase outlet of the extraction unit is connected to the inlet of the washing unit, the outlet of the washing unit is connected to the inlet of the distillation unit, and the low-boiling outlet of the distillation unit is connected to the feed inlet of the reaction unit and / or the extractant inlet of the extraction unit.

[0030] The method for preparing polycyclic aromatic hydrocarbon oligomers of the present invention utilizes a special reagent that functions as both a solvent and an extractant to generate polycyclic aromatic hydrocarbon oligomers from polycyclic aromatic hydrocarbon compounds. Effective extraction can be performed after the preparation of the polycyclic aromatic hydrocarbon oligomers, and by treating only the extract phase, the consumption of acid or alkali solutions is effectively reduced, which is beneficial to environmental protection. Since the catalyst in the raffinate phase is not deactivated in the present invention, the mass of polycyclic aromatic hydrocarbon compounds catalyzed by the present invention is 5 to 10 times that of current methods using acidic ionic catalysts to catalyze the generation of polycyclic aromatic hydrocarbon oligomers, effectively reducing industrial costs. Attached Figure Description

[0031] Figure 1 This is a schematic diagram of the apparatus for preparing polycyclic aromatic hydrocarbon oligomers provided by the present invention;

[0032] Figure 2 This is a schematic diagram of an apparatus for preparing polycyclic aromatic hydrocarbon oligomers according to another embodiment of the present invention;

[0033] Figure 3 This is a matrix-assisted laser desorption / ionization time-of-flight mass spectrum of the naphthalene oligomer prepared in Example 1 of this invention;

[0034] Figure 4 This is a laser desorption / ion-time mass spectrum of the naphthalene-based mesophase pitch prepared in Experimental Example 1 of this invention;

[0035] Figure 5 Thermogravimetric analysis diagram of the naphthalene-based mesophase pitch prepared in Experimental Example 1 of this invention;

[0036] Figure 6 This is a polarized light micrograph of the naphthalene-based mesophase pitch prepared in Experimental Example 1 of this invention.

[0037] Explanation of reference numerals in the attached figures:

[0038] 1: Reactor;

[0039] 2: Extraction tower;

[0040] 3: Alkaline washing unit;

[0041] 4: Acid washing unit;

[0042] 5: Alcohol washing unit;

[0043] 6: Deionized water washing unit;

[0044] 7: Distillation unit;

[0045] 71: Recycled solvent outlet;

[0046] 72: Product export;

[0047] 8: Hybrid unit;

[0048] 81: Raw material entry point;

[0049] 82: Raw material input;

[0050] 83: Raw material input;

[0051] 84: Raw material entry point. Detailed Implementation

[0052] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions in the embodiments of this invention will be clearly and completely described below in conjunction with the embodiments of this invention. Obviously, the described embodiments are only some embodiments of this invention, not all embodiments. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0053] The polymerization of polycyclic aromatic hydrocarbons (PAHs) to prepare PAH oligomers is an important method for the industrial production of mesophase pitch. Taking naphthalene as an example, the preparation of naphthalene oligomers requires the participation of an acidic catalyst. After the polymerization reaction, a large amount of alkali solution needs to be added to the reaction system to deactivate the acidic catalyst in order to separate the catalyst from the product. However, this method consumes a large amount of alkali solution, generates a large amount of waste liquid, which is detrimental to environmental protection. Furthermore, acidic catalysts are expensive, and deactivating them after only one use increases industrial costs.

[0054] Therefore, reducing the amount of acid or alkali solution used, while also reducing the amount of acidic catalyst used, is an urgent problem to be solved in the preparation of polycyclic aromatic hydrocarbon oligomers.

[0055] Based on this, the first aspect of the present invention provides a method for preparing polycyclic aromatic hydrocarbon oligomers, comprising the following steps:

[0056] 1) A polymerization reaction is carried out on raw materials including polycyclic aromatic hydrocarbons, acidic ionic liquid catalysts and solvents to obtain a reaction system;

[0057] 2) The above reaction system is extracted using an extractant to obtain an extract phase comprising the polymer and a raffinate phase comprising the acidic ionic liquid catalyst;

[0058] The solvents and extractants mentioned above each independently include at least one of benzene and benzene homologues.

[0059] The polycyclic aromatic hydrocarbons (PAHs) in this invention belong to fused-ring compounds, which are all hydrocarbons formed by two or more benzene rings sharing a common edge (i.e., fusion), and each ring exhibits aromaticity. High-quality mesophase pitch can be prepared using PAHs.

[0060] The acidic ionic liquid catalyst in this invention comprises a superacidic metal salt, synthesized from the superacidic metal salt and a ligand. For example, the superacidic metal salt in the acidic ionic liquid catalyst includes at least one of ferric chloride and aluminum chloride, and the ligand can be any compound capable of forming an ionic liquid with the aforementioned superacidic metal salt. For example, the ligand can be triethylamine hydrochloride, pyridine, imidazole, or other compounds. Using the acidic ionic liquid catalyst to catalyze polycyclic aromatic hydrocarbons can effectively increase the formation of polycyclic aromatic hydrocarbon oligomers.

[0061] Specifically, the solvent and extractant in this invention are the same reagent. That is, during the polymerization reaction, the reagent acts as a solvent, which is beneficial to the thermal management of the entire polymerization reaction system and makes the raw materials more uniformly dispersed, so as to generate more specific surface area for polymerization. In the extraction process, the reagent acts as an extractant, which can effectively extract the polycyclic aromatic hydrocarbon oligomers and separate them from the acidic ionic liquid catalyst solution. The polycyclic aromatic hydrocarbon oligomers can be highly concentrated in the extraction phase, while the acidic ionic liquid catalyst exists in the raffinate phase.

[0062] To achieve optimal polymerization and extraction results, the inventors conducted experiments with various reagents and ultimately discovered that using benzene and its homologues as solvents and extractants not only ensured the efficient execution of the polymerization reaction but also achieved effective phase separation of the polycyclic aromatic hydrocarbon oligomers from the acidic ionic catalyst. Here, benzene homologues refer to compounds with one or more alkyl substituents introduced onto the benzene ring.

[0063] The inventors speculate that this may be because polycyclic aromatic hydrocarbon oligomers contain multiple benzene rings, which are very similar in structure to benzene and benzene homologues. According to the principle of "like dissolves like," polycyclic aromatic hydrocarbon oligomers are more likely to enter the solvents of benzene and benzene homologues. At the same time, the solubility and density of benzene and benzene homologues are quite different from those of acidic ionic liquid catalyst solutions, and the two are immiscible, so effective phase separation can occur.

[0064] In the preparation method of this invention, by using the same reagent as both the reaction medium for the polymerization reaction and the extractant for the extraction treatment, the synthesis of the polycyclic aromatic hydrocarbon oligomer and its effective separation from the acidic ionic liquid catalyst are effectively achieved. Therefore, in subsequent processing, only a very small amount of acidic ionic liquid catalyst entrained in the extract phase needs to be treated, effectively reducing the requirements for reagent usage in subsequent processing. Simultaneously, since the polycyclic aromatic hydrocarbon oligomer and the acidic ionic liquid catalyst can be effectively separated, there is no need for additional steps to deactivate the acidic ionic liquid catalyst in the raffinate phase to promote its separation from the product. The acidic ionic liquid catalyst can be reused in production to participate in the polymerization reaction, effectively reducing industrial costs.

[0065] In the preparation method provided by this invention, the polycyclic aromatic hydrocarbon compound can be selected according to the requirements of the product. For example, at least one of naphthalene, alkyl-substituted naphthalene, anthracene, alkyl-substituted anthracene, phenanthrene, alkyl-substituted phenanthrene, pyrene, and alkyl-substituted pyrene can be used as the polycyclic aromatic hydrocarbon compound. The alkyl group has 1 to 6 carbon atoms and can be either a branched alkyl group or a branched alkyl group. For example, the alkyl group can be methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, n-pentyl, neopentyl, or n-hexyl.

[0066] Furthermore, benzene and its homologues include at least one of toluene, p-xylene, m-xylene, o-xylene, trimethylbenzene, ethylbenzene, and methylethylbenzene. This invention does not specifically limit the substitution position of the methyl group in trimethylbenzene; for example, at least one of mesitylene, pseudomesitylene, and isotrimethylbenzene can be used as a solvent and extractant. Similarly, this invention does not specifically limit the substitution positions of the methyl and ethyl groups in methylethylbenzene; for example, at least one of ortho-methylethylbenzene, meta-methylethylbenzene, and para-methylethylbenzene can be used as a solvent and extractant. When using the above compounds for polymerization and extraction, the raw materials can be evenly dispersed in the polymer to obtain a product with a relatively concentrated molecular weight. Simultaneously, the product can be further purified during extraction, resulting in a higher product quality.

[0067] In the above-mentioned raw materials, o-xylene, m-xylene, and p-xylene were used as solvents and extractants. The volume percentage of o-xylene was 15%–25%, that of m-xylene was 45%–55%, and that of p-xylene was 20%–30%. When preparing naphthalene oligomers with a volume percentage of 25%:45%:30% for o-xylene, m-xylene, and p-xylene, the polycyclic aromatic hydrocarbons and the acidic ionic liquid catalyst can be uniformly dispersed in the reaction system. Furthermore, the naphthalene oligomers and the acidic ionic liquid catalyst can undergo effective phase separation under the action of the extractant. This not only facilitates the preparation of polycyclic aromatic hydrocarbon oligomers with a more concentrated molecular weight distribution, thus improving product quality, but also reduces the amount of reagents used in subsequent treatment of the extraction phase.

[0068] In polymerization reactions, the stirring speed is 50–200 rpm. For example, the stirring speed for polymerization reactions includes, but is not limited to, 50 rpm, 100 rpm, 150 rpm, 200 rpm, or any combination thereof. By limiting the stirring speed of the polymerization reaction, the raw materials can be dispersed more uniformly, increasing the contact area between the polycyclic aromatic hydrocarbons and the catalyst, resulting in a more complete reaction. The resulting polycyclic aromatic hydrocarbon oligomers have a more concentrated molecular weight distribution, thus improving the quality of the final polycyclic aromatic hydrocarbon oligomers.

[0069] It is understandable that, in order to prevent the raw materials and products from being oxidized, nitrogen can be introduced into the atmosphere for the polymerization reaction.

[0070] To achieve a relatively complete polymerization reaction, the present invention controls the temperature of the polymerization reaction to be 20-130 °C. For example, the temperature of the polymerization reaction includes but is not limited to 20 °C, 40 °C, 60 °C, 80 °C, 100 °C, 120 °C, 130 °C or the range composed of any two of them. By controlling the temperature of the polymerization reaction within the above range, on the one hand, the diffusion effect of the solvent on the solute therein can be maximally exerted, and on the other hand, the reaction rate of the polymerization reaction can be increased, thereby improving the quality of the product polycyclic aromatic hydrocarbon oligomers.

[0071] During the extraction process, the stirring speed of the extraction treatment is 50-200 revolutions per minute. For example, the stirring speed of the extraction treatment includes but is not limited to 50 revolutions per minute, 100 revolutions per minute, 150 revolutions per minute, 200 revolutions per minute, or the range composed of any two of them. By limiting the stirring speed, a better extraction effect can be achieved, enabling the product to be locally concentrated in the extraction phase, and the obtained product is relatively pure, improving the quality of the product polycyclic aromatic hydrocarbon oligomers.

[0072] In a specific embodiment, the temperature of the extraction treatment is 20-130 °C. For example, the temperature of the extraction treatment includes but is not limited to 20 °C, 40 °C, 60 °C, 80 °C, 100 °C, 120 °C, 130 °C or the range composed of any two of them. By controlling the temperature of the extraction treatment within the above range, the efficiency of the extraction treatment can be improved, and a relatively pure product can be obtained, thereby improving the quality of the product polycyclic aromatic hydrocarbon oligomers.

[0073] In the polymerization reaction, the present invention further uses an acidic ionic liquid catalyst Et3NHCl-xAlCl3 as the catalyst for the polymerization reaction, where x represents the molar ratio of Et3NHCl and AlCl3 in the acidic ionic liquid catalyst, and 1 < x ≤ 2. The acidic ionic liquid catalyst used in the present invention combines the high reaction activity of liquid acid and the non-volatility of solid acid, and its structure and acidity can be adjusted according to the composition. By using the acidic ionic liquid catalyst to catalyze the polymerization reaction, the preparation efficiency of the product polycyclic aromatic hydrocarbon oligomers can be significantly improved.

[0074] In another embodiment, the volume ratio of the extractant to the acidic ionic liquid catalyst solution is (10–200):1. This volume ratio is the ratio of the volume of the added extractant to the volume of the acidic ionic liquid catalyst solution; that is, the acidic ionic liquid catalyst solution includes both solvent and acidic ionic liquid catalyst. For example, the volume ratio of the extractant to the acidic ionic liquid catalyst solution includes, but is not limited to, 10:1, 50:1, 100:1, 150:1, 200:1, or any combination thereof. By limiting the volume ratio of the extractant to the acidic ionic liquid catalyst solution to the above range, the reaction selectivity of the polycyclic aromatic hydrocarbon oligomer can be improved while simultaneously increasing the extraction efficiency of the product, resulting in a more uniform molecular weight and lower ash content, thus achieving higher product quality.

[0075] In another embodiment, the molar amount of the acidic ionic liquid catalyst accounts for 10% to 100% of the total molar amount of the polycyclic aromatic hydrocarbons (PAHs). Specifically, the molar amount of the acidic ionic liquid catalyst is the molar amount of the pure acidic ionic liquid catalyst, and the total molar amount of the PAHs is the total molar amount of the pure PAHs added to the reaction system. For example, the mass of the acidic ionic liquid catalyst as a percentage of the total mass of the PAHs can be, but is not limited to, 10%, 20%, 40%, 60%, 80%, 100%, or any combination thereof. By limiting the relationship between the molar amount of the acidic ionic liquid catalyst and the total molar amount of the PAHs, better catalytic polymerization can be achieved while saving industrial costs, further improving the selectivity of the reaction and the quality of the product.

[0076] Furthermore, the above-mentioned method for preparing polycyclic aromatic hydrocarbon oligomers also includes impurity separation treatment of the extraction phase to obtain polymer and recovered solvent, and the recovered solvent is returned to participate in the polymerization reaction and / or extraction treatment. It is understood that the recovered solvent includes some unreacted raw material polycyclic aromatic hydrocarbon compounds, which can be reused in the polymerization reaction and / or extraction treatment along with the recovered solvent. Due to the above-mentioned method for preparing polycyclic aromatic hydrocarbon oligomers, this invention can achieve the effect of completely removing the residual catalyst from the extraction phase using only a simple impurity separation treatment method, obtaining the polymer (product polycyclic aromatic hydrocarbon oligomer) and recovered solvent, with only a very small loss of catalyst and solvent during the process. By supplementing the polymerization reaction and / or extraction treatment with 5-15% of the original solvent volume of new acidic ionic liquid catalyst and 2-10% of new solvent, the recovered solvent can achieve the same effect as the original solvent in the process of returning to participate in the polymerization reaction and / or extraction treatment, greatly saving industrial costs.

[0077] Specifically, the impurity separation process includes washing and distillation. Washing yields a catalyst-free extract phase, while distillation thoroughly separates the polycyclic aromatic hydrocarbon oligomers from the extractant, resulting in a cleaner recovered solvent. This recovered solvent can be reused in polymerization reactions and / or extraction processes.

[0078] The washing process includes at least one of acid washing, alkaline washing, and alcohol washing. In one embodiment, the acid washing process can be performed using an acid solution containing at least one acid selected from hydrochloric acid and nitric acid, wherein the mass percentage of the acid solution used is 20-40%.

[0079] In another embodiment, the alkaline washing treatment can be performed using an alkaline solution comprising at least one of sodium hydroxide, potassium hydroxide, ammonia, and organic bases, wherein the mass percentage of the alkaline solution used is 10-50%.

[0080] In another embodiment, the alcohol washing treatment can be performed using an alcohol solution comprising at least one alcohol selected from methanol, ethanol, isopropanol, n-butanol, and ethylene glycol, wherein the mass percentage of the alcohol solution used is 20-80%.

[0081] In the above washing process, one of acid washing, alkali washing, and alcohol washing can be used alone, or two or three of them can be used. The inventors have found that the washing process can achieve better results when multiple treatment methods are used. In one specific embodiment, after sequentially treating the extract phase with alkali, acid, and alcohol, a relatively pure extract phase is obtained, in which the content of the acidic ionic liquid catalyst is extremely low. It is understood that after the above washing methods, deionized water can also be used for washing to remove the washing reagents remaining in the above washing process. The present invention does not impose special limitations on the time and temperature of acid washing, alkali washing, alcohol washing, and deionized water washing, as long as the cleaning purpose is achieved.

[0082] This invention utilizes at least one washing method, including acid washing, alkali washing, and alcohol washing, to obtain a catalyst-free extract phase. This facilitates the production of polycyclic aromatic hydrocarbon oligomers with lower impurities and better quality. Furthermore, because the product and impurities are separated through extraction, the content of the acidic ionic liquid catalyst in the extract phase is extremely low. Therefore, only minimal washing is required to remove impurities from the extract phase. The inventors have found through experiments that the amount of washing reagents used in this invention is only 5-15% of that required by conventional methods that involve adding alkali or acid to deactivate the catalyst. This significantly reduces industrial costs associated with reagent consumption and is beneficial for environmental protection.

[0083] It is important to clarify that temperature control is necessary for distillation to achieve optimal separation. Therefore, this invention controls the distillation temperature to be between 150 and 250°C. For example, the distillation temperature may include, but is not limited to, 150°C, 180°C, 200°C, 250°C, or any combination thereof. By further limiting the distillation temperature, this invention improves product quality, separates the product from the extractant, yields a cleaner recovered solvent, and saves industrial costs.

[0084] A second aspect of the present invention provides an apparatus for preparing polycyclic aromatic hydrocarbon oligomers, which can be used to perform the above-described method for preparing polycyclic aromatic hydrocarbon oligomers. The apparatus includes a reaction unit and an extraction unit, wherein the outlet of the reaction unit is connected to the inlet of the extraction unit.

[0085] In detail, such as Figure 1 As shown, the reaction unit of the present invention can be a conventional reactor 1, and the extraction unit can be a conventional extraction tower 2. The raw material undergoes a polymerization reaction in the reactor 1 and is extracted in the extraction tower 2.

[0086] In another implementation, such as Figure 2 As shown, the reaction unit and the extraction unit can be integrated into a reaction-extractor 1 (2). In the reaction-extractor 1 (2), the polymerization reaction of raw materials including polycyclic aromatic hydrocarbons, acidic ionic liquid catalysts and solvents can be completed. After the polymerization reaction, the generated polycyclic aromatic hydrocarbon oligomers are immediately dissolved in the extractant (i.e., the solvent between polymerization reactions) in the reaction-extractor and undergo phase separation with the acidic ionic liquid catalyst solution to produce an extract phase including the polymer and a raffinate phase including the acidic ionic liquid catalyst.

[0087] Furthermore, in this apparatus, a mixing unit can be placed before the reaction unit to mix the raw materials, and the mixing unit can perform stirring operations on the raw materials; alternatively, the raw materials can be mixed directly in the reaction unit, where stirring operations are performed. This invention does not impose specific limitations on the speed and temperature of the stirring operation during the mixing process, as long as the goal of uniform mixing is achieved. The inclusion of a mixing unit facilitates thorough mixing of the raw materials, thereby improving the quality of the product.

[0088] This invention uses this device to prepare the above-mentioned polycyclic aromatic hydrocarbon oligomers. By using benzene and benzene homologues as solvents and extractants in this device, the activity of the acidic ionic liquid catalyst can be maintained, and the acidic ionic liquid catalyst can be reused. At the same time, there is no need to use a large amount of acid or alkali solution for product separation, which greatly saves industrial costs and is beneficial to environmental protection.

[0089] Furthermore, the device also includes a washing unit and a distillation unit;

[0090] The extract phase outlet of the extraction unit is connected to the inlet of the washing unit, the outlet of the washing unit is connected to the inlet of the distillation unit, and the low-boiling outlet of the distillation unit is connected to the feed inlet of the reaction unit and / or the extractant inlet of the extraction unit.

[0091] In detail, there can be multiple washing units. For example, at least one washing unit selected from the categories of alkali washing unit, acid washing unit, alcohol washing unit, and deionized water washing unit can be provided. In this invention, only one of the above-mentioned washing units can be used to wash the extract phase, or multiple washing units can be used to wash the extract phase. When multiple washing units are used, these washing units can be arranged in a certain order. When arranged in the order of alkali washing unit, acid washing unit, alcohol washing unit, and deionized water washing unit, the washing operation can achieve better results. The washing units in this invention only generate a small amount of waste liquid. By setting up washing units and distillation units, further separation and purification of the product can be achieved, resulting in a product with high purity.

[0092] The apparatus for preparing polycyclic aromatic hydrocarbon oligomers provided by this invention enables continuous industrial production. During the preparation process, raw materials including polycyclic aromatic hydrocarbons, an acidic ionic liquid catalyst, and a solvent undergo polymerization in the reaction unit, extraction in the extraction unit, and washing in the washing unit, resulting in an extract phase containing the polymer and a raffinate phase containing the acidic ionic liquid catalyst. The recovered solvent obtained by distilling the washed raffinate phase can be reused in the polymerization reaction and / or extraction. Raw materials can continuously enter the apparatus, undergoing polymerization under the influence of the acidic ionic liquid catalyst solution that remains in the apparatus. In the continuous preparation process, small amounts of acidic ionic liquid catalyst and solvent can be added to maintain the stability of the components throughout the process, achieving stable preparation of polycyclic aromatic hydrocarbon oligomers and high product quality. Compared to conventional batch preparation apparatus, this apparatus improves industrial economics.

[0093] In one implementation, such as Figure 2As shown, the reaction unit and extraction unit of the device of the present invention are a reaction-extractor 1 (2). A mixing unit 8 is placed before the reaction-extractor 1 (2). The washing unit consists of an alkali washing unit 3, an acid washing unit 4, an alcohol washing unit 5, and a deionized water washing unit 6 connected in sequence. The outlet of the mixing unit 8 is connected to the inlet of the reaction-extractor 1 (2). The outlet of the reaction-extractor 1 (2) is connected to the inlet of the alkali washing unit 3. The outlet of the alkali washing unit 3 is connected to the inlet of the acid washing unit 4. The outlet of the acid washing unit 4 is connected to the inlet of the alcohol washing unit 5. The outlet of the alcohol washing unit 5 is connected to the inlet of the deionized water washing unit 6. The outlet of the deionized water washing unit 6 is connected to the inlet of the distillation unit 7. The solvent recovery outlet 71 of the distillation unit 7 is connected to the raw material inlet 84 of the mixing unit 8.

[0094] The mixing unit includes four feed inlets: feed inlet 81 is used to introduce polycyclic aromatic hydrocarbons; feed inlet 82 is used to replenish the acidic ionic liquid catalyst; feed inlet 83 is used to replenish the new solvent; and feed inlet 84 is used to introduce the recycled solvent.

[0095] The distillation unit includes two outlets: outlet 71 is used to output the product polycyclic aromatic hydrocarbon oligomers, and outlet 72 is used to output the recovered solvent.

[0096] Specifically, the process for the continuous preparation of polycyclic aromatic hydrocarbon oligomers using this device is as follows:

[0097] The raw materials, including polycyclic aromatic hydrocarbons, acidic ionic liquid catalysts and solvents, are fed into mixing unit 8 and dispersed uniformly in mixing unit 8 to obtain a mixed liquid.

[0098] The above mixture is passed into the reaction-extractor 1 (2) for polymerization. After the polymerization reaction occurs, the solvent can act as an extractant to extract the polymer product of the polymerization reaction. After phase separation, the extract phase including the polymer and the raffinate phase including the acidic ionic liquid catalyst are obtained in the reaction-extractor 1 (2). The extract phase is located in the upper layer of the reactor 2, and the raffinate phase is located in the lower layer of the reaction-extractor 1 (2).

[0099] The upper extract phase in reaction-extractor 1(2) is output and sequentially washed through alkaline washing unit 3, acid washing unit 4, alcohol washing unit 5, and deionized water washing unit 6 to obtain the washed extract phase.

[0100] The washed extract phase is passed into the distillation unit 7 for distillation to obtain polycyclic aromatic hydrocarbon oligomers and recovered solvent. The polycyclic aromatic hydrocarbon oligomers are collected from the product outlet 72, and the recovered solvent is returned to the mixing unit 8 from the recovered solvent outlet 71 to continue to participate in the mixing of raw materials.

[0101] The present invention will be further described below through specific embodiments.

[0102] Example 1

[0103] The method for preparing polycyclic aromatic hydrocarbon oligomers in this embodiment includes the following steps:

[0104] 1) Under normal pressure and nitrogen atmosphere, 100g of refined naphthalene, 50g of Et3NHCl-1.2AlCl3 (volume 35mL), and 500mL of mixed xylenes (volume percentage of o-xylene, m-xylene, and p-xylene is 25%:45%:30%) were polymerized at 130℃ with a stirring speed of 50 rpm to obtain the reaction system;

[0105] 2) The above mixture was extracted at 130°C with a stirring speed of 100 rpm using mixed xylene to obtain an extract phase containing polymer and a raffinate phase containing acidic ionic liquid catalyst.

[0106] 3) After alkali washing, acid washing, alcohol washing, deionized water washing and distillation treatment of the extract phase, naphthalene oligomer and recovered solvent are obtained; the recovered solvent is refluxed to participate in the polymerization reaction in step 1).

[0107] Among them, alkaline washing is performed by washing with 200 mL of 20 wt% sodium hydroxide aqueous solution;

[0108] Pickling was performed using 500 mL of 40 wt% hydrochloric acid.

[0109] The alcohol wash was performed using 250 mL of 50 wt% n-butanol.

[0110] The distillation process was carried out at a temperature of 200℃.

[0111] The matrix-assisted laser desorption / ionization time-of-flight mass spectra of the obtained naphthalene oligomers are shown below. Figure 3 As shown in the figure, its molecular weight ranges from 200 to 800 Da.

[0112] The total amount of washing reagent used, the molecular weight distribution of the naphthalene oligomers, and the ash content of the naphthalene oligomers in this embodiment are shown in Table 1.

[0113] Example 2

[0114] This embodiment is basically the same as Embodiment 1, except that the acidic ionic liquid catalyst used in this embodiment is Et3NHCl-1.4AlCl3.

[0115] Example 3

[0116] This embodiment is basically the same as Embodiment 1, except that the acidic ionic liquid catalyst used in this embodiment is Et3NHCl-1.6AlCl3.

[0117] Example 4

[0118] This embodiment is basically the same as Example 1, except that the acidic ionic liquid catalyst used in this embodiment is Et3NHCl-1.8AlCl3.

[0119] Example 5

[0120] This embodiment is basically the same as Embodiment 1, except that the acidic ionic liquid catalyst used in this embodiment is Et3NHCl-2.0AlCl3.

[0121] Example 6

[0122] This embodiment is basically the same as Embodiment 1, except that the mass of the acidic ionic liquid catalyst used in this embodiment is 10% of the mass of refined naphthalene.

[0123] Example 7

[0124] This embodiment is basically the same as Embodiment 1, except that the mass of the acidic ionic liquid catalyst used in this embodiment is 50% of the mass of refined naphthalene.

[0125] Example 8

[0126] This embodiment is basically the same as Embodiment 1, except that the mass of the acidic ionic liquid catalyst used in this embodiment is 75% of the mass of refined naphthalene.

[0127] Example 9

[0128] This embodiment is basically the same as Embodiment 1, except that the mass of the acidic ionic liquid catalyst used in this embodiment is 100% of the mass of refined naphthalene.

[0129] Example 10

[0130] This embodiment is basically the same as Embodiment 1, except that the polymerization temperature in this embodiment is 20°C.

[0131] Example 11

[0132] This embodiment is basically the same as Embodiment 1, except that the polymerization temperature in this embodiment is 60°C.

[0133] Example 12

[0134] This embodiment is basically the same as Embodiment 1, except that the polymerization temperature in this embodiment is 100°C.

[0135] Example 13

[0136] This embodiment is basically the same as Embodiment 1, except that the volume ratio of the extractant to the acidic ionic liquid catalyst solution in this embodiment is 10:1.

[0137] Example 14

[0138] This embodiment is basically the same as Embodiment 1, except that the volume ratio of the extractant to the acidic ionic liquid catalyst solution in this embodiment is 50:1.

[0139] Example 15

[0140] This embodiment is basically the same as Embodiment 1, except that the volume ratio of the extractant to the acidic ionic liquid catalyst solution in this embodiment is 150:1.

[0141] Example 16

[0142] This embodiment is basically the same as Embodiment 1, except that the volume ratio of the extractant to the acidic ionic liquid catalyst solution in this embodiment is 200:1.

[0143] Example 17

[0144] This embodiment is basically the same as Embodiment 1, except that toluene is used as the solvent and extractant in this embodiment.

[0145] Example 18

[0146] This embodiment is basically the same as Example 1, except that the solvent and extractant used in this embodiment is mesitylene.

[0147] Example 19

[0148] This embodiment is basically the same as Embodiment 1, except that ethylbenzene is used as the solvent and extractant in this embodiment.

[0149] Example 20

[0150] This embodiment is basically the same as Example 1, except that the solvent and extractant used in this embodiment are a mixed solvent of toluene and ethylbenzene in a 1:1 volume ratio.

[0151] Example 21

[0152] This embodiment is basically the same as that of Embodiment 1, except that the polycyclic aromatic hydrocarbon compound in this embodiment is methylnaphthalene.

[0153] Example 22

[0154] This embodiment is basically the same as Embodiment 1, except that the polycyclic aromatic hydrocarbon compound in this embodiment is anthracene.

[0155] Example 23

[0156] This embodiment is basically the same as Embodiment 1, except that the polycyclic aromatic hydrocarbon compound in this embodiment is pyrene.

[0157] Example 24

[0158] This embodiment is basically the same as Embodiment 1, except that the polycyclic aromatic hydrocarbon compound in this embodiment is a mixture of naphthalene and methylnaphthalene in a 1:1 molar ratio.

[0159] Comparative Example 1

[0160] This comparative example was prepared using the following method:

[0161] Add 100g of naphthalene and 50g of Et3NHCl-1.2AlCl3 to a 500mL three-necked flask. Then, under nitrogen protection, transfer the three-necked flask to a 130℃ oil bath and heat it with a stirrer. Start timing when the system temperature reaches 130℃. Stop stirring after 5 hours and separate the reaction products (add alkali to the reaction system to destroy the ionic liquid, then wash out the reaction products such as naphthalene oligomers with dichloromethane, and then remove the organic solvent by rotary evaporation under reduced pressure to separate the reaction products).

[0162] The alkali solution used was a 20wt% sodium hydroxide aqueous solution to break down the ionic liquid. The total amount of alkali solution used was 2000 mL.

[0163] Test case

[0164] The molecular weight distribution was obtained using matrix-assisted laser desorption / ionization time-of-flight mass spectrometry (MALS), and the results are shown in Table 1.

[0165] The ash content was tested using the People's Republic of China Petroleum and Chemical Industry Standard SHT 0422-2000, Asphalt Ash Content Determination Method. The results are shown in Table 1.

[0166] 120g of the naphthalene oligomer prepared in Example 1 was added to a thermopolymerization reactor, and N2 was repeatedly purged three times to displace the air inside the reactor. After stopping the purging, the reactor was sealed. Subsequently, the reaction was carried out at 10°C / min. -1 The reactor was heated from room temperature to 400°C at a controlled heating rate, and the naphthalene oligomers were subjected to a self-pressurized thermal polycondensation reaction for 4 hours at this temperature. Finally, after purging with N2 for another 2 hours, naphthalene-based mesophase pitch was obtained. The laser desorption / ionization time-of-flight mass spectrum of the obtained naphthalene-based mesophase pitch is shown below. Figure 4 As shown, the molecular weight is mainly concentrated between 400-4000 Da, and the molecular weight distribution is bimodal. Its thermogravimetric analysis plot is shown below. Figure 5 As shown, the carbon yield was 87%. Its polarized light micrograph is shown below. Figure 6As shown, it is a well-developed streamlined mesophase asphalt with an anisotropic component content close to 100%.

[0167] Table 1

[0168]

[0169]

[0170] As shown in the table, Examples 1-25 significantly reduced the total amount of washing reagent used in alkaline washing compared to Comparative Example 1. Furthermore, Examples 1-24 exhibited a more concentrated molecular weight distribution and lower ash content compared to Comparative Example 1; therefore, the products obtained through this invention have higher quality.

[0171] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing polycyclic aromatic hydrocarbon oligomers, characterized in that, It includes the following steps: 1) Performing a polymerization reaction on a raw material including a polycyclic aromatic hydrocarbon compound, an acidic ionic liquid catalyst, and a solvent to obtain a reaction system; 2) Using an extractant to perform extraction treatment on the reaction system to obtain an extraction phase including a polymer and a raffinate phase including an acidic ionic liquid catalyst; The solvent and the extractant each independently include at least one of benzene and benzene homologs.

2. The method for preparing polycyclic aromatic hydrocarbon oligomers according to claim 1, characterized in that, The polycyclic aromatic hydrocarbon compound includes at least one of naphthalene, an alkyl-substituted naphthalene, anthracene, an alkyl-substituted anthracene, phenanthrene, an alkyl-substituted phenanthrene, pyrene, and an alkyl-substituted pyrene.

3. The method for preparing polycyclic aromatic hydrocarbon oligomers according to claim 1 or 2, characterized in that, The benzene and benzene homologs include at least one of toluene, p-xylene, m-xylene, o-xylene, mesitylene, ethylbenzene, and methyl ethylbenzene.

4. The method for preparing polycyclic aromatic hydrocarbon oligomers according to claim 3, characterized in that, The benzene and benzene homologs include o-xylene, m-xylene, and p-xylene, wherein the volume percentage content of o-xylene is 15% - 25%, the volume percentage content of m-xylene is 45% - 55%, and the volume percentage content of p-xylene is 20% - 30%.

5. The method for preparing a polycyclic aromatic hydrocarbon oligomer according to any one of claims 1 - 4, wherein the stirring speed of the polymerization reaction is 50 - 200 revolutions per minute; and / or, the temperature of the polymerization reaction is 20 - 130 °C; and / or, the stirring speed of the extraction treatment is 50 - 200 revolutions per minute; and / or, the temperature of the extraction treatment is 20 - 130 °C.

6. The method for preparing polycyclic aromatic hydrocarbon oligomers according to any one of claims 1-5, characterized in that, The acidic ionic liquid catalyst is Et3NHCl - xAlCl3, wherein x represents the molar ratio of Et3NHCl and AlCl3 in the acidic ionic liquid catalyst, and 1 < x ≤ 2; and / or, the volume ratio of the extractant to the acidic ionic liquid catalyst solution is (10 - 200):1; and / or, the mass of the acidic ionic liquid catalyst accounts for 10 - 100% of the total mass of the polycyclic aromatic hydrocarbon compound.

7. The method for preparing polycyclic aromatic hydrocarbon oligomers according to any one of claims 1-6, characterized in that, After step 2), it further includes: Performing impurity separation treatment on the extraction phase to obtain the polymer and a recycled solvent, and returning the recycled solvent to participate in the polymerization reaction and / or extraction treatment.

8. The method for preparing polycyclic aromatic hydrocarbon oligomers according to claim 7, characterized in that, The impurity separation treatment sequentially includes washing treatment and rectification treatment; wherein the washing treatment includes at least one of pickling treatment, alkali washing treatment, and alcohol washing treatment; and / or, the temperature of the rectification treatment is 150 - 250 °C.

9. An apparatus for preparing polycyclic aromatic hydrocarbon oligomers, characterized in that, For implementing the method for preparing a polycyclic aromatic hydrocarbon oligomer according to any one of claims 1 - 8; it includes a reaction unit and an extraction unit, and the outlet of the reaction unit is connected to the inlet of the material to be extracted of the extraction unit.

10. The apparatus for preparing polycyclic aromatic hydrocarbon oligomers according to claim 9, characterized in that, It further includes a washing unit and a rectification unit; The extraction phase outlet of the extraction unit is connected to the inlet of the washing unit, the outlet of the washing unit is connected to the inlet of the rectification unit, and the low-boiling outlet of the rectification unit is connected to the raw material inlet of the reaction unit and / or the extractant inlet of the extraction unit.

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