A method for separating high-purity mesitylene from heavy aromatics by using adsorption separation technology

Abstract

A method for separating high-purity mesitylene from heavy aromatics by using adsorption separation technology, the method selects X molecular sieve treated by ammonium salt after ion exchange of alkaline earth metal and transition metal as the active component of adsorbent, uses the method of adsorption separation, passes heavy aromatics raw material into the adsorbent, adsorbs the mesitylene therein, obtains raffinate, passes in desorbent, desorbs the adsorbed mesitylene, obtains extract, the desorbent in the extract and raffinate can be recycled, the remaining components of the extract are high-purity mesitylene product, the remaining components of the raffinate can be used as gasoline blending component or high-boiling aromatic solvent oil component. The method can solve the problem that high-purity mesitylene cannot be obtained from heavy aromatics in the existing process.

Description

TECHNICAL FIELD

[0001] The present application relates to a method for separating mesitylene, in particular, to a method for obtaining high-purity mesitylene from heavy aromatics by using adsorption separation technology. BACKGROUND

[0002] The main components of heavy aromatics raw materials are C9 and above single ring and condensed ring aromatics, mainly from catalytic cracking, catalytic cracking, catalytic reforming, disproportionation, isomerization, steam cracking, benzene-styrene alkylation to produce ethylbenzene, and coal high-temperature coking, etc. reaction process, is an important by-product of petrochemical and coal chemical industry. In recent years, with the successive production of large-scale naphtha reforming, ethylene and aromatics combined device in China, the production of C9+aromatics is increasing, and the production capacity of reforming heavy aromatics is expected to reach more than 30 million tons in 2022. How to further develop and utilize C9+aromatics and improve the utilization level of C9+aromatics resources has become an increasingly urgent demand of the petrochemical industry.

[0003] Although China has started the comprehensive utilization of C9+aromatics since the 1980s, due to slow technological development, backward process and small scale, etc. The utilization rate of raw materials of the device is low, the energy consumption is high, the product added value is low, and the resource waste is serious. At present, domestic technology can only extract the components of trimethylbenzene, mesitylene, 100-120# aromatic solvent oil in C9+heavy aromatics. The separation and purification of high-value products such as methylbenzene, mesitylene, and mesitylene in heavy aromatics have not yet entered the industrialization stage. Most of the above components are burned as oil blending components or sold at a low price as high-boiling aromatic solvent oil, which affects the economic benefits of the comprehensive utilization of C9+heavy aromatics.

[0004] Trimethylbenzene is an important fine chemical intermediate, and its proportion in C9+heavy aromatics is relatively large. For example, in the heavy aromatics after extraction, rectification and separation of benzene, toluene and xylene from catalytic reforming oil, the mass fraction of trimethylbenzene is 15%-55%. Among the three isomers of trimethylbenzene, mesitylene is an important intermediate in the pharmaceutical and chemical industries, which has wide application in the production of aniline dyes, benzene tricarboxylic acid, synthesis of Tibet musk, anti-inflammatory analgesic, platelet anticoagulant and thrombosis inhibitor, etc. and has high economic value. The main use of mesitylene is to synthesize Tibet musk. In the early stage, the synthesis of Tibet musk was based on m-xylene as raw material, but this process was complex, long, low in product yield, and had strong corrosion to equipment. Therefore, most manufacturers currently use mesitylene as raw material for synthesis. This process is simple, has high product yield, and the by-products are easy to recover, have little corrosion to equipment, and are suitable for industrial production. In addition, since the entire synthesis process goes through steps such as tert-butylization, separation, nitration, and water washing and filtration, if the impurity content in the raw material mesitylene is high, it will have a great impact on the product purity and yield of Tibet musk.

[0005] At present, most industrial devices use precise rectification, extractive rectification, deep cooling crystallization and alkylation to separate mesitylene from C9+ aromatic hydrocarbons. However, since the boiling point difference between mesitylene and indane is only 0.5℃, the number of trays required for rectification is large, the reflux ratio is large, the energy consumption is very high, and it is difficult to implement in industry; the separation process of the alkylation method is complex, the variety of raw materials used is large, the consumption is large, the cost is high, and the economy is poor. Therefore, the separation of mesitylene from C9+ aromatic hydrocarbons is still a weak link, especially the large-scale extraction of high-purity mesitylene has not formed a mature process.

[0006] CN101704706B discloses a method for separating and purifying mesitylene from heavy aromatic hydrocarbons, which uses adsorption separation means to purify mesitylene and indane components, but the raw material is strictly selected before separation, and a rectification means is used to obtain a raw material rich in mesitylene and a small amount of indane, and a third component is not introduced. CN1900034A adopts an alkylation conversion method to separate and purify mesitylene, and a mesitylene product with a mass fraction of 92% or more can be obtained by using this method, but the process is complex, the economy is poor, the catalyst life is short, and it is not easy to industrialize. CN105837394B discloses a method for purifying mesitylene, which includes raw material treatment and extractive rectification. This method needs a pre-treatment light removal tower, a heavy removal tower, an extractive rectification tower and a solvent recovery tower, and the process flow is long, the number of theoretical trays of the rectification tower is large, the investment is large in industry, and the cost is high.

[0007] Therefore, if an efficient, energy-saving and environmentally friendly separation process can be developed to extract mesitylene single component from heavy aromatic hydrocarbons, it can promote the formation of a C9+ aromatic hydrocarbon efficient utilization product chain, solve the problem of C9+ aromatic hydrocarbon by-product outlet of large petrochemical enterprises, extend the industrial chain, bring considerable profits to downstream enterprises, and pass through the necessary link from heavy aromatic hydrocarbon raw material to high-end functional products, and significantly improve the economic benefit and social benefit of heavy aromatic hydrocarbon comprehensive utilization. SUMMARY

[0008] In order to solve the problems in the prior art, the present application provides a method for separating mesitylene single component from heavy aromatic hydrocarbons by using adsorption separation technology, which has the advantages of strong adaptability of raw materials, no side reaction, low operation energy consumption, simple process, precise process control, high efficiency, good product purity, high yield, environmental friendliness and the like, and significantly improves the economic benefit of C9+ heavy aromatic hydrocarbon comprehensive utilization.

[0009] The application provides a method for separating high-purity mesitylene from heavy aromatics by using adsorption separation technology, comprising the following steps: introducing heavy aromatic raw material into an adsorbent, so that the mesitylene in the heavy aromatic raw material is adsorbed by the adsorbent, and the components not adsorbed are discharged as raffinate of adsorption separation; introducing desorbent into the adsorbent, so that the adsorbed mesitylene is desorbed, and an extract is obtained; and the raffinate containing desorbent and the extract are separated by rectification respectively, so that other heavy aromatics and mesitylene are obtained, and the desorbent is recovered and recycled, characterized in that,

[0010] The heavy aromatic raw material is heavy aromatics containing a plurality of C9+ aromatic components and having a wide distribution of mass fraction of mesitylene.

[0011] The adsorbent is X-type molecular sieve treated by an ammonium salt.

[0012] The adsorbent is ion-exchanged with one or two of IIA, IIB and VIII metal cations after being shaped.

[0013] The method for separating mesitylene single component from heavy aromatics by using adsorption separation technology provided by the application has strong adaptability to raw materials, allows the raw material to contain more other heavy aromatic components, greatly simplifies the operation process, can accurately control the process parameters, effectively reduces the energy consumption and production cost of the device, can exclude the interference of indane components, obtains mesitylene monomer product with high purity and yield, and separates the desorbent in the raffinate and the extract by rectification and recycles the desorbent, so that the separation process is environmentally friendly. The other heavy aromatic components obtained by rectification and separation can be used as gasoline blending components or high-boiling aromatic solvent oil components, the high-purity mesitylene product can be used as a fine chemical intermediate to further produce high-end functional materials, and the economic efficiency is greatly improved. BRIEF DESCRIPTION OF DRAWINGS

[0014] Figure 1 The pulse spectrum is for Example 3.

[0015] Figure 2 The pulse spectrum is for Example 5.

[0016] Figure 3 The small-scale simulated moving bed adsorption separation schematic diagram of the application. DETAILED DESCRIPTION

[0017] The application will be further described in detail through the drawings and examples. Through these descriptions, the features and advantages of the application will become more apparent.

[0018] The word "exemplary" is used herein to mean "serving as an example, instance, or illustration." Any implementation described herein as "exemplary" is not necessarily to be construed as preferred or advantageous over other implementations. Although various aspects of an implementation can be presented in terms of sequences, orientation, or relative positioning, unless otherwise specified, these orientations and arrangements are not limiting. The terms "first," "second," "third," "fourth," and / or the like can be understood as distinguishing between entities, but these designations can not necessarily be understood as a physical or logical prioritization. Unless otherwise specified, a sequence(s) employed can commute or relocate in time and / or space without departing from the scope of an implementation. Although a feature can appear to be described in relation to particular terminology, this feature can be implemented using a different terminology.

[0019] Furthermore, the technical features involved in the different embodiments of the present application described below can be combined with each other as long as there is no conflict.

[0020] In the present application, the term "C9" refers to containing 9 carbons, and the term "C9+ aromatic hydrocarbon" refers to aromatic hydrocarbon containing 9 carbons or more, which has the same meaning as "heavy aromatic hydrocarbon".

[0021] The present application separates high-purity mesitylene from heavy aromatic hydrocarbon raw materials by adsorption separation technology. A feed containing more heavy aromatic hydrocarbon components and a heavy aromatic hydrocarbon raw material containing mesitylene in a wide mass fraction range are introduced into the adsorbent. The mesitylene in the raw material is adsorbed after contacting the adsorbent, and the components not adsorbed are discharged as raffinate. A desorbent, which is an alkylbenzene or a mixture of alkylbenzene and alkane, is introduced into the adsorbent to desorb the adsorbed mesitylene, and an extract is obtained. Both the raffinate and the extract contain the desorbent, which can be recycled and separated by rectification. The extract can be separated to obtain high-purity mesitylene (extract remaining components), which is used as a product in the downstream fine chemical industry. The raffinate can be separated to obtain the remaining heavy aromatic hydrocarbon (raffinate remaining components), which can be used as a gasoline blending component or a high-boiling aromatic solvent oil component. This method can solve the problem that high-purity mesitylene cannot be obtained from heavy aromatic hydrocarbon in the existing process.

[0022] According to the exemplary embodiments of the present application, the heavy aromatic hydrocarbon raw materials that can be processed by the present application come from reformate, pyrolysis gasoline, naphtha, ethylbenzene plant by-products, and catalytic cracking gasoline. Among them, the C9+ aromatic hydrocarbons are selected from the following components: mesitylene, p-ethylmethylbenzene, m-ethylmethylbenzene, o-ethylmethylbenzene, propylbenzene, cumene, mesitylene, pseudomesitylene, indane, p-diethylbenzene, m-diethylbenzene, o-diethylbenzene, tetramethylbenzene, meso-tetramethylbenzene, pseudotetramethylbenzene, p-methylpropylbenzene, m-methylpropylbenzene, o-methylpropylbenzene, methylcumene, ethyl-p-xylene, ethyl-m-xylene, ethyl-o-xylene, naphthalene, methylnaphthalene, methylindene, methylindane, and / or acenaphthene, etc.

[0023] In the present application, the mass fraction of trimethylbenzene in heavy aromatic hydrocarbon feedstock is wide, and the mass fraction of trimethylbenzene accounts for 5-95% of C9+ aromatic hydrocarbon component. The present application can treat heavy aromatic hydrocarbon with a wide mass fraction of trimethylbenzene, so that the heavy aromatic hydrocarbon feedstock does not need to be pre-concentrated or purified before treatment, which can greatly simplify the operation process of the whole method, reduce energy consumption and production cost, and produce significant economic benefits.

[0024] According to the exemplary embodiments of the present application, the desorbent used in the present application is alkylbenzene, preferably toluene, p-xylene, and / or p-diethylbenzene, or the desorbent used in the present application is a mixture of alkylbenzene and alkane, wherein the mass fraction of alkane in the desorbent is not more than 50%.

[0025] According to the exemplary embodiments of the present application, the adsorption temperature of the adsorption separation of the present application is 110-195℃, preferably 120-180℃, more preferably 135-165℃, and the adsorption pressure is 0.6-1.6 MPa, preferably 0.8-1.0 MPa. By optimizing the operation conditions of the adsorption separation process, the extract of the adsorption separation can contain substantially only trimethylbenzene, and the content of other components is very low, so that high-purity separation of trimethylbenzene single component is achieved.

[0026] According to the exemplary embodiments of the present application, the active component of the adsorbent used in the present application is X-type molecular sieve after stirring and impregnation with ammonium salt, washing and drying. The ammonium salt can be selected from soluble inorganic ammonium salt and / or organic ammonium salt in the art, the inorganic ammonium salt can be selected from one or more of ammonium chloride, ammonium nitrate, ammonium sulfate, ammonium carbonate, and ammonium acetate, and the organic ammonium salt can be selected from one or more of dodecyltrimethylammonium chloride, tetradecyltrimethylammonium bromide, hexadecyltrimethylammonium chloride, benzyltriethylammonium chloride, benzyltributylammonium chloride, benzyltrimethylammonium bromide, tetramethylammonium chloride, tetrabutylammonium hydrogen sulfate, and tetrabutylammonium chloride. It is believed that after treatment with ammonium salt, the adsorption selectivity and adsorption capacity of the adsorbent for trimethylbenzene can be significantly improved, so that the preferential adsorption of trimethylbenzene on the adsorbent is achieved.

[0027] According to the exemplary embodiments of the present application, the X-type molecular sieve after treatment with ammonium salt needs to be subjected to a molding process, for example, a rolling ball molding process can be used for the molding process. In the molding process, a binder such as kaolin mineral can also be added. Preferably, water or water glass solution can be added to the adsorbent during the molding process to improve the molding process. The amount of water or water glass added is 5-10% of the mass of solid materials in the molding process (i.e. the total mass of binder and molecular sieve). It is believed that this treatment is helpful to improve the structure of the molecular sieve, enhance the strength of the adsorbent after molding, and prolong the service life of the adsorbent.

[0028] According to the exemplary embodiments of the present application, the adsorbent used in the present application needs to be treated with alkali after being shaped, and the alkali treatment impregnation solution is a mixed solution of sodium hydroxide and water glass. It is believed that this treatment is beneficial to the crystallization of the binder, increases the crystallinity of the adsorbent, and reduces the ineffective adsorption volume of the adsorbent.

[0029] According to the exemplary embodiments of the present application, the molar ratio of silicon oxide to aluminum oxide in the X-type molecular sieve used in the present application is 2.4-2.9, and the particle size of the crystal grains is 0.3-0.8 microns. Without wishing to be bound by theory, it is believed that the particle size of the crystal grains of the molecular sieve will affect the mass transfer and strength of the adsorbent, and the larger the particle size of the crystal grains, the worse the mass transfer of the heavy aromatic hydrocarbon raw material and the desorbent in the adsorbent, which will affect the efficiency of the adsorption separation, and the smaller the particle size of the crystal grains, the lower the strength of the adsorbent, which will affect the service life of the adsorbent. Similarly, without wishing to be bound by theory, it is believed that the molar ratio of silicon oxide to aluminum oxide in the molecular sieve will also have a significant impact on the adsorption capacity of the adsorbent, and a too high molar ratio will result in poor selectivity of the adsorbent, and a too low molar ratio will not only reduce the adsorption capacity of the adsorbent, but also change the internal structure of the molecular sieve. Through long-term research and practice, the present application has obtained the suitable particle size range of the crystal grains of the molecular sieve and the suitable molar ratio range of silicon oxide to aluminum oxide for separating p-cymene.

[0030] According to the exemplary embodiments of the present application, the X-type molecular sieve treated with ammonium salt used in the present application is ion-exchanged with one or two of the IIA, IIB and VIII metal cations after being shaped. Preferably, the IIA metal cation used for ion exchange is Mg 2+ or Ca 2+ , the VIII metal cation is Fe 2+ or Co 2+ , and the IIB metal cation is Zn 2+ or Cd 2+ . The exchange degree of Na ions in the adsorbent after the metal cation exchange is 75.0-99.9 mol%, preferably 85.0-99.9 mol%, and more preferably 90.5-99.9 mol%. It is believed that through the modification of cation exchange, the electrostatic field in the adsorbent changes, thereby making the adsorbent have special selectivity for p-cymene.

[0031] According to the exemplary embodiments of the present application, the salt solution of the metal can be used for the cation exchange modification of the adsorbent after being shaped. In the present application, the molar concentration of the metal salt used for the metal cation exchange is 0.05-0.65 mol / L, and preferably 0.15-0.50 mol / L. In the present application, the temperature for the metal cation exchange is 80-100°C, and preferably 85-95°C.

[0032] According to the exemplary embodiments of the present application, a binder can be contained in the adsorbent of the present application in addition to the X-type molecular sieve to facilitate the molding of the adsorbent. The adsorbent of the present application contains 90 to 99 wt% of the X-type molecular sieve and 1 to 10 wt% of the binder. The binder that can be used is kaolin, bentonite and / or attapulgite.

[0033] According to the exemplary embodiments of the present application, the adsorptive separation technology of the present application employs a simulated moving bed, but the present application is not limited thereto. As shown in Figure 3 the simulated moving bed apparatus of the present application can contain one or more adsorption columns, each column containing a plurality of adsorbent-packed adsorption beds. Each bed has its own material inlet and outlet lines, and the materials flow from top to bottom in the adsorption column, and are transported between columns by a circulating pump, and the materials flow through the adsorption beds of different adsorption columns to form a closed loop. The materials that enter and exit the adsorption beds include at least the feed (F), the desorbent (D), the extract (E) and the raffinate (R). The materials that enter and exit the simulated moving bed divide the adsorption beds therein into desorption zones, purification zones, adsorption zones and isolation zones. The adsorption bed between the injection of the desorbent and the withdrawal of the extract is the desorption zone, the adsorption bed between the withdrawal of the extract and the injection of the feed is the purification zone, the adsorption bed between the injection of the feed and the withdrawal of the raffinate is the adsorption zone, and the adsorption bed between the withdrawal of the raffinate and the injection of the desorbent is the isolation zone. The number ratio of the adsorption zone, the purification zone, the desorption zone and the isolation zone is 25±10%:38±15%:25±5%:12±4%. In the operation of the simulated moving bed, the positions of the materials entering and exiting the adsorption beds of the adsorption column can be periodically changed. A multi-way rotary valve or a program-controlled on-off valve group can be used to control the materials entering and exiting different adsorption beds. At a certain time, each material is connected to a specific bed, and every certain time interval, i.e., a step time, the positions of the materials entering and exiting are all moved down by one adsorption bed, as shown in Figure 3 from the solid arrow to the dashed arrow position, and the step time is usually 60 to 160 seconds, preferably 70 to 120 seconds. The time required for the position of a material entering an adsorption bed (or the position of a material exiting an adsorption bed) to return to the starting position after passing through all the adsorption beds is a cycle period, and the cycle period is usually 12 minutes to 70 minutes, preferably 20 minutes to 40 minutes.

[0034] According to the exemplary embodiments of the present application, the adsorption selectivity of each component in the heavy aromatic hydrocarbon feedstock on the adsorbent is different, and the adsorbent has higher adsorption selectivity for tri-methyl benzene. The extract liquid is rich in tri-methyl benzene and contains a part of desorbent. The desorbent in the extract liquid is removed by a rectifying tower, and then the light components such as dimethyl benzene are removed to obtain a high-purity tri-methyl benzene product. The raffinate liquid contains a small amount of tri-methyl benzene, and the smaller the amount, the higher the efficiency of the adsorption separation. The main components of the raffinate liquid are the desorbent and the components in the feedstock except for tri-methyl benzene. After the desorbent in the raffinate liquid is removed by the rectifying tower, the obtained raffinate liquid is subjected to corresponding subsequent processing, and can be used as a gasoline blending component or a high-boiling aromatic hydrocarbon solvent oil component, or is continuously separated for use as a raw material for downstream fine chemical products.

[0035] According to the exemplary embodiments of the present application, in the adsorption separation technology of the present application, the mass flow ratio of the desorbent to the heavy aromatic hydrocarbon feedstock entering the simulated moving bed is not more than 2.75, preferably 1.75, and more preferably not more than 1.50; and the heavy aromatic hydrocarbon feedstock flow per unit mass of adsorbent is not less than 0.30 kg / (h·kg adsorbent), preferably not less than 0.50 kg / (h·kg adsorbent), and more preferably not less than 0.60 kg / (h·kg adsorbent). It is believed that selecting appropriate flow ratio and flow rate of the desorbent to the heavy aromatic hydrocarbon feedstock, and making the desorbent and the heavy aromatic hydrocarbon feedstock fully contact so that tri-methyl benzene is fully adsorbed, can significantly increase the content of tri-methyl benzene in the extract liquid and reduce the content of other components.

[0036] The present application is further illustrated by the following examples, but the present application is not limited thereto.

[0037] Example 1

[0038] Preparation of adsorbent A used in the adsorption separation process

[0039] The X-type molecular sieve with a silica / alumina molar ratio of 2.6 was stirred and impregnated with 0.35 mol / L of ammonium chloride at 40°C, washed and dried, then mixed with kaolin minerals and water at a mass ratio of 95:5:10, rolled into balls, dried, and calcined at 540°C for 5 hours. The obtained balls after calcination were stirred and impregnated with a mixed solution of sodium hydroxide and water glass (the concentration of Na2O was 56 g / L and the concentration of SiO2 was 10 g / L in terms of oxides) in a water bath at 93°C for 8 hours, washed with deionized water until neutral, dried in an oven at 80°C for 8 hours, then subjected to cation exchange with 0.45 mol / L of zinc nitrate solution after being treated with alkali and dried, the exchange time was 7 hours, the temperature was 91°C, the liquid-solid ratio of the solution to the adsorbent was 50, and the exchange degree calculated according to the residual sodium content after exchange was 99.9 mol%. The exchanged balls were dried at 100°C for 3 hours and activated at 200°C for 2 hours.

[0040] Example 2

[0041] Preparation of adsorbent B for adsorptive separation

[0042] X zeolite with a silica / alumina molar ratio of 2.4 was impregnated with 0.30 mol / L of dodecyltrimethylammonium chloride at 40°C with stirring, washed and dried, then mixed with kaolin mineral and water glass solution at a mass ratio of 91:9:5, rolled into spheres, dried and calcined at 530°C for 8 hours. The spheres obtained after calcination were impregnated with a mixed solution of sodium hydroxide and water glass (the concentration of Na2O was 56 g / L and the concentration of SiO2 was 10 g / L in terms of oxides) at 94°C in a water bath for 8 hours, washed with deionized water until neutral, dried in an oven at 80°C for 8 hours, then cation exchanged with 0.50 mol / L of calcium chloride solution after alkaline treatment and drying, the exchange time was 10 hours, the temperature was 95°C, the liquid / solid ratio of the solution to the adsorbent was 40, and the exchange degree calculated based on the residual sodium content after exchange was 99.2 mol%.

[0043] Example 3

[0044] To evaluate the adsorption selectivity of the adsorbent, a dynamic pulse experiment device was used to determine the adsorption selectivity and the adsorption and desorption rates of the target product. The device was composed of a feeding system, an adsorption column, a heating furnace, a pressure control valve and the like. The adsorption column was a Ф8x900 mm stainless steel tube. The inlet at the lower end of the adsorption column was connected to the feeding and nitrogen gas system, and the outlet at the upper end was connected to the pressure control valve, which was then connected to the effluent collector.

[0045] The method for determining the adsorption selectivity of the adsorbent was as follows: the measured adsorbent particles with a particle size of 500 μm to 800 μm were weighed, loaded into the adsorption column and shaken, and nitrogen was introduced to remove the air remaining in the system at room temperature. The system pressure was raised to 0.80 MPa, and the temperature was raised to 145°C. The desorbent was stopped, 5 mL to 10 mL of pulse feed liquid containing a tracer that was not adsorbed was introduced at a volume space velocity of 1.0 h -1 -1, and then the desorbent was introduced at the same volume space velocity. Every 2 mL, 3 drops of desorption liquid sample were taken, and gas chromatography was used for analysis. The desorption curves of each component of the pulse feed liquid were plotted with the volume of the desorbent as the abscissa and the concentration of each component of the pulse feed liquid as the ordinate. Figure 1The tracer not adsorbed can be used to obtain the dead volume of the adsorption system. The midpoint of the tracer peak is taken as zero point, and the net retention volume of the midpoint of each component peak to the zero point is determined. The net retention volume of any component is proportional to the distribution coefficient at adsorption equilibrium, reflecting the interaction between each component and the adsorbent. The ratio of the net retention volumes of two components is the separation coefficient β, such as the ratio of the net retention volume of mesitylene to that of pseudocumene, which is the ratio of the adsorption performance of the adsorbent to the two components, and is the separation coefficient of mesitylene relative to pseudocumene, denoted as β 连三甲苯 / 偏三甲苯 The resolution can also be used as an indicator of the separation efficiency of the adsorbent. The resolution is equal to the difference between the net retention volumes of adjacent pulse peaks divided by the average half-peak width of the two pulse peaks, such as the ratio of the difference between the net retention volumes of mesitylene and pseudocumene to the average half-peak width of the two pulse peaks, which is the resolution between the two peaks, denoted as R 连三甲苯 / 偏三甲苯 .

[0046] 60 mL of the adsorbent A prepared in Example 1 was taken for liquid pulse experiment to determine the adsorption selectivity, resolution, and adsorption and desorption rates of mesitylene. The desorbent used in the experiment was 50 wt% toluene and 50 wt% n-heptane. The pulse feed liquid composition was 3 wt% of each of the three isomers of trimethylbenzene, p-xylene, propylbenzene, cumene, three isomers of ethylbenzene, indane, n-nonane (NC9), and 67 wt% of the desorbent, wherein n-nonane was the tracer. The separation coefficients and resolutions between mesitylene and pseudocumene, mesitylene, indane, o-ethylbenzene, and propylbenzene are shown in Table 1, and the pulse spectrum is shown in Figure 1. Figure 1 .

[0047] Example 4

[0048] Mesitylene in the mixed C9+ aromatic hydrocarbon was separated by the method of Example 3, except that the adsorbent was the adsorbent B prepared in Example 2, and the desorbent was 60 wt% toluene and 40 wt% n-heptane. The selective adsorption performance is shown in Table 1.

[0049] Table 1

[0050]

[0051] Example 5

[0052] A liquid phase pulse experiment was carried out to determine the adsorption selectivity, separation degree and adsorption and desorption rate of mesitylene using a Ф6x900 mm stainless steel tube as the adsorption column and 26 mL of the adsorbent A prepared in Example 1. The desorbent was 50 wt% toluene and 50 wt% n-heptane. The composition of the pulse feed liquid was 3 wt% each of mesitylene, m-cymene, p-cymene, m-diethylbenzene, p-diethylbenzene, m-propyltoluene, p-propyltoluene, 2-ethyl-p-xylene, 4-ethyl-m-xylene, n-nonane (NC9) and 70 wt% of the desorbent, wherein n-nonane was the tracer. The separation factor and separation degree between mesitylene and m-cymene, m-diethylbenzene, m-propyltoluene, p-diethylbenzene and 2-ethyl-p-xylene are shown in Table 2, and the pulse spectrum is shown in Figure 2 .

[0053] Example 6

[0054] Mesitylene was separated from the mixed C9+ aromatic hydrocarbons by the method of Example 5, except that the adsorbent was the adsorbent B prepared in Example 2 and the desorbent was 60 wt% toluene and 40 wt% n-heptane. The selective adsorption performance is shown in Table 2.

[0055] Table 2

[0056]

[0057]

[0058] Example 7

[0059] A liquid phase adsorption separation was carried out to separate mesitylene using a small-scale simulated moving bed device. The device was composed of 24 columns connected in series. The cavity for accommodating the adsorbent in each column was 200 mm in height and 40 mm in diameter. A total of 2245 g of the adsorbent A prepared in Example 1 was loaded into the columns. The 24th column was connected to the 1st column by a pump to circulate the fluid in the columns. Each column was connected to introduce or take out the material. There were 7 columns between the raffinate outlet and the feed inlet, which was the adsorption zone; there were 9 columns between the feed inlet and the extract outlet, which was the purification zone; there were 5 columns between the extract outlet and the desorbent inlet, which was the desorption zone; and there were 3 columns between the desorbent inlet and the raffinate outlet, which was the isolation zone. The positions of the inlets and outlets of the materials are shown in Figure 3 The positions of the inlets and outlets of the materials were changed at a step time. The inlets and outlets of the materials were moved forward by one column at every other step time. The inlets and outlets of the materials were moved from the solid arrow positions to the dotted arrow positions as shown in Figure 3 , and were moved forward in the intended direction at the next step time. The positions of the inlets and outlets of the materials were changed in the same way until the inlets and outlets of the materials returned to the starting positions, which was one cycle. One step time was 90 seconds, and one cycle was 36 minutes.

[0060] The adsorption feedstock is heavy aromatics, including 19.5 wt% mesitylene, 9.0 wt% 1,3,5-trimethylbenzene, 8.2 wt% 1,2,4-trimethylbenzene, 6.5 wt% indane, 9.5 wt% p-ethyltoluene, 11.5 wt% m-ethyltoluene, 11.8 wt% o-ethyltoluene, 5.6 wt% propylbenzene, 4.0 wt% cumene, 2.0 wt% p-methylpropylbenzene, 2.0 wt% m-methylpropylbenzene, 3.4 wt% o-methylpropylbenzene, 2.0 wt% 2-ethyl-p-xylene, 2.0 wt% 4-ethyl-m-xylene, and 3.0 wt% 4-ethyl-o-xylene. The temperature of the adsorption feedstock entering the adsorption bed is controlled at 145°C, and the operating pressure is 0.90 MPa. Adsorbent A is used, and the desorbent is 99.9 wt% toluene. The feedstock feed rate is 1.35 kg / h, the desorbent injection rate is 1.65 kg / h, the extract rate is 1.21 kg / h, the raffinate rate is 1.79 kg / h, the ratio of the mass flow rates of the desorbent and the heavy aromatic feedstock entering the simulated moving bed is 1.22, and the heavy aromatic feedstock flow rate per unit mass of adsorbent is 0.61 kg / (h·kg adsorbent). The yield of the target product mesitylene is 99.05 wt%, and the purity is 99.65 wt%.

[0061] After the simulated moving bed is operated stably, a mixed sample of one cycle of the extract and the raffinate is taken and analyzed for composition. According to the analysis results, the calculation methods for the purity and the yield of mesitylene are as follows:

[0062]

[0063] X i is the mass fraction of each component in the extract except for mesitylene;

[0064]

[0065] wherein X 连三甲苯，抽出液 is the mass fraction of mesitylene in the extract, Q 抽出液 is the mass flow rate of the extract, X 连三甲苯，抽余液 is the mass fraction of mesitylene in the raffinate, Q 抽余液 is the mass flow rate of the raffinate.

[0066] Example 8

[0067] The mixed C9+ aromatics were separated by the method of Example 7, except that the apparatus was composed of 12 columns connected in series, the cavity inside the column for containing the adsorbent was 200 mm high and 80 mm in diameter, a total of 2230 g of adsorbent was packed, the 12th column was connected to the 1st column by a pump, 4 columns were provided in the adsorption zone, 4 columns were provided in the purification zone, 3 columns were provided in the desorption zone, and 1 column was provided in the isolation zone. One step time was 120 seconds, and one cycle was 24 minutes. The temperature of the adsorption feedstock entering the adsorption bed was controlled at 155°C, and the operating pressure was 0.85 MPa. The feedstock feed rate was 1.45 kg / h, the desorbent injection rate was 1.55 kg / h, the extract rate was 0.88 kg / h, the raffinate rate was 2.12 kg / h, the ratio of the mass flow rate of desorbent to C9+aromatics feedstock entering the simulated moving bed was 1.07, and the carbon nine aromatic feedstock flow rate per unit mass of adsorbent was 0.65 kg / (h·kg adsorbent). The yield of the target product mesitylene was 98.74 wt%, and the purity was 99.45 wt%.

[0068] Example 9

[0069] The mixed C9+ aromatics were separated by the method of Example 7, except that the adsorption feedstock included mesitylene at 22.5 wt%, mesitylene at 9.0 wt%, cymene at 6.2 wt%, indane at 4.5 wt%, p-cresotoluene at 9.5 wt%, m-cresotoluene at 11.5 wt%, o-cresotoluene at 11.8 wt%, propylbenzene at 5.6 wt%, isopropylbenzene at 4.0 wt%, methylisopropylbenzene at 2.0 wt%, p-methylpropylbenzene at 2.0 wt%, m-methylpropylbenzene at 2.0 wt%, o-methylpropylbenzene at 3.4 wt%, 2-ethyl-p-xylene at 1.0 wt%, 4-ethyl-m-xylene at 1.0 wt%, 4-ethyl-o-xylene at 1.0 wt%, tetramethylbenzene at 1.0 wt%, naphthalene at 1.0 wt%, methylnaphthalene at 0.5 wt%, and methylindane at 0.5 wt%. The adsorbent was the adsorbent B prepared in Example 2, and the packing mass was 2200 g. The desorbent was 97.1 wt% toluene and 2.9 wt% n-heptane. The temperature of the adsorption feedstock entering the adsorption bed was controlled at 135°C, and the operating pressure was 0.88 MPa. The ratio of the mass flow rate of desorbent to C9+aromatics feedstock entering the simulated moving bed was 1.15, and the carbon nine aromatic feedstock flow rate per unit mass of adsorbent was 0.65 kg / (h·kg adsorbent). The yield of the target product mesitylene was 98.85 wt%, and the purity was 99.20 wt%.

Claims

1. A method for separating high-purity thallium from heavy aromatics using adsorption separation technology, comprising: introducing a heavy aromatic feedstock into an adsorbent, causing the thallium in the feedstock to be adsorbed by the adsorbent; discharging the unadsorbed components as a raffinate from the adsorption separation; introducing a desorbent into the adsorbent to desorb the adsorbed thallium, obtaining an extract; separating the raffinate containing the desorbent and the extract by distillation to obtain other heavy aromatics and thallium, and recovering the desorbent for recycling, characterized in that... The heavy aromatic feedstock is a heavy aromatic hydrocarbon containing multiple C9+ aromatic components and with a wide distribution of terephthalene mass fraction, and the heavy aromatic feedstock comes from reforming products, cracked gasoline, naphtha, by-products of ethylbenzene unit or catalytic cracking gasoline. The adsorbent is an X-type molecular sieve treated with ammonium salt, and the particle size of the X-type molecular sieve is 0.3 micrometers to 0.8 micrometers; After being formed, the adsorbent undergoes ion exchange via one or two of the following metal cations: IIA, IIB, and VIII. The IIA metal cation is Mg. 2+ Ca 2+ One or two of them, wherein the VIII metal cation is Fe 2+ Co 2+ One or two of the following, wherein the IIB metal cation is Zn 2+ Cd 2+ One or two of these, the degree of exchange of Na ions in the adsorbent after metal cation exchange is 75.0 ~ 99.9 mol%; The adsorption separation technology employs a simulated moving bed process. The simulated moving bed comprises multiple adsorption beds filled with adsorbent, each bed having its own material inlet and outlet pipelines. The material entering and exiting the simulated moving bed divides the adsorption bed into a desorption zone, a purification zone, an adsorption zone, and an isolation zone. The adsorption bed between the desorbent injection and the extract is the desorption zone; the adsorption bed between the extract and the feed injection is the purification zone; the adsorption bed between the feed injection and the raffinate is the adsorption zone; and the adsorption bed between the raffinate and the desorbent injection is the isolation zone. The simulated moving bed includes an adsorption zone, a purification zone, a desorption zone, and an isolation zone, with a bed layer ratio of 25±10% : 38±15% : 25±5% : 12±4%.

2. The method as described in claim 1, characterized in that, In the heavy aromatic feedstock, the mass fraction of thiol accounts for 5 to 95% of the C9+ aromatic component.

3. The method as described in claim 1, characterized in that, The C9+ aromatic components in the heavy aromatic feedstock are selected from the following: methylbenzene, p-methylbenzene, m-methylbenzene, o-methylbenzene, propylbenzene, isopropylbenzene, mesitylene, pseudotrimethylbenzene, indene, p-diethylbenzene, m-diethylbenzene, o-diethylbenzene, tetramethylbenzene, mesitylene, pseudotrimethylbenzene, p-methylpropylbenzene, m-methylpropylbenzene, o-methylpropylbenzene, methylisopropylbenzene, ethyl p-xylene, ethyl m-xylene, ethyl o-diethylbenzene, naphthalene, methylnaphthalene, methyl indene, methyl indene, and / or acenaphthene.

4. The method as described in claim 1, characterized in that, The desorbent is alkylbenzene.

5. The method as described in claim 4, characterized in that, The desorbent is toluene, p-xylene, and / or p-diethylbenzene.

6. The method as described in claim 1, characterized in that, The desorbent is a mixture of alkylbenzene and alkanes, with the mass fraction of alkanes in the desorbent not exceeding 50 wt%.

7. The method as described in claim 1, characterized in that, The adsorption temperature is 110 ~ 195℃.

8. The method as described in claim 7, characterized in that, The adsorption temperature is 120 ~ 180℃.

9. The method as described in claim 8, characterized in that, The adsorption temperature is 135 ~ 165℃.

10. The method as described in claim 1, characterized in that, The adsorption pressure is 0.6 MPa ~ 1.6 MPa.

11. The method as described in claim 10, characterized in that, The adsorption pressure is 0.8 MPa ~ 1.0 MPa.

12. The method as described in claim 1, characterized in that, Molecular sieves require the addition of 5% to 10% water or water glass solution by weight of the solid material during the molding process.

13. The method as described in claim 1, characterized in that, After the adsorbent is formed, it undergoes an alkali treatment process. The alkali treatment impregnation solution is a mixed solution of sodium hydroxide and water glass.

14. The method as described in claim 1, characterized in that, The molar concentration of the metal salt used for metal cation exchange is 0.05 ~ 0.65 mol / L.

15. The method as described in claim 14, characterized in that, The molar concentration of the metal salt used for metal cation exchange is 0.15 ~ 0.50 mol / L.

16. The method as described in claim 1, characterized in that, The degree of exchange of Na ions in the adsorbent after metal cation exchange is 85.0 ~ 99.9 mol%.

17. The method as described in claim 16, characterized in that, The degree of exchange of Na ions in the adsorbent after metal cation exchange is 90.5 ~ 99.9 mol.

18. The method as described in claim 1, characterized in that, The adsorbent contains 90-99 wt% X-type molecular sieve and 1-10 wt% binder.

19. The method as described in claim 1, characterized in that, The mass flow rate ratio of the desorbent to the heavy aromatic feedstock entering the simulated moving bed is no greater than 2.

75.

20. The method as described in claim 19, characterized in that, The mass flow rate ratio of the desorbent to the heavy aromatic feedstock entering the simulated moving bed is no greater than 1.

75.

21. The method as described in claim 20, characterized in that, The mass flow rate ratio of the desorbent to the heavy aromatic feedstock entering the simulated moving bed is no greater than 1.

50.

22. The method as described in claim 1, characterized in that, The flow rate of heavy aromatic feedstock relative to unit mass of adsorbent is not less than 0.3 kg / (h·kg adsorbent).

23. The method as described in claim 22, characterized in that, The flow rate of heavy aromatic feedstock relative to unit mass of adsorbent is not less than 0.50 kg / (h·kg adsorbent).

24. The method as described in claim 23, characterized in that, The flow rate of heavy aromatic feedstock relative to unit mass of adsorbent is not less than 0.60 kg / (h·kg adsorbent).

25. The method as described in claim 1, characterized in that, The cycle of the simulated moving bed is 12 to 70 minutes.

26. The method as described in claim 25, characterized in that, One cycle of the simulated moving bed is 20 to 40 minutes.

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