A method and system for recovering valuable aromatic components from styrene tar

Abstract

The present invention relates to a method and system for recovering valuable aromatic components from styrene tar, which includes: (1) mixing styrene tar with a depolymerization solvent in a mixer and then feeding it into a separator. After standing and separating layers, the upper depolymerized liquid is fed into a first polymerization inhibitor filter; (2) adding a sedimentation agent S1 to the first polymerization inhibitor filter. After sufficient reaction and filtration, the filtrate F1 enters a second polymerization inhibitor filter; (3) adding a sedimentation agent S2 to the second polymerization inhibitor filter. After sufficient reaction and filtration, the resulting filtrate F2 enters an aromatic hydrocarbon separator; (4) recovering the solvent in the aromatic hydrocarbon separator, and the remaining liquid is the recovered aromatic hydrocarbon. The method of the present invention has the advantages of good recovery effect, good quality of the recovered aromatic hydrocarbon, relatively low recovery cost, and no secondary pollution, etc.

Description

Technical Field

[0001] The present invention relates to a method and system for recovering valuable aromatic components from styrene tar, belonging to the technical field of solid waste treatment. Background Art

[0002] Styrene tar is a common solid waste in the styrene production process and is also a hazardous waste specified in the National List of Hazardous Wastes (2021 Edition). It mainly includes aromatics, oligomers, polymerization inhibitors, etc. Among them, aromatics mainly include monocyclic aromatics, bicyclic aromatics, and polycyclic aromatics, etc. Monocyclic aromatics are mainly styrene, ethylbenzene, etc., bicyclic aromatics are mainly from diphenylethane to diphenylhexane, most of which are oligomers of styrene monomer, and polycyclic aromatics are mainly indene, naphthalene, anthracene, phenanthrene, etc. Styrene tar has a high carbon-hydrogen ratio, contains a large number of unsaturated bonds, a low ash content, and almost no heavy metals. It is a substance with a relatively high viscosity (>100 mm 2 / s, 20 °C) at room temperature. At present, most manufacturers use it as fuel for co-combustion or outsource the disposal, failing to realize the resource utilization of styrene tar and increasing the disposal cost at the same time.

[0003] Patent CN110594758A discloses a method for treating styrene tar. Styrene tar is mixed with fuel oil to obtain a mixed oil slurry. The mixed oil slurry is transported through a pipeline to a waste alkali incinerator and atomized by an oil gun with an air-cooled jacket, and burned in the waste alkali incinerator. The calorific value generated by the combustion is used by a waste heat boiler to by-product saturated steam and enter the steam pipe network. The treatment method of this invention can achieve the smooth and complete combustion of styrene tar, finally generating carbon dioxide and water, meeting the requirements of environmental protection emissions. The calorific value generated by the combustion is used by the waste heat boiler to by-product saturated steam and enter the steam pipe network to generate additional value. However, this invention cannot recover and utilize the valuable components in styrene tar.

[0004] With the development of society and the improvement of production level, the recycling of waste has begun to receive wide attention, and styrene tar also needs to be resourcefully utilized. At present, the utilization of styrene tar is mainly divided into two ways: as a material component and extracting valuable monomers. As a material component, styrene tar can copolymerize with maleic anhydride, dienes, hydroxyl compounds, etc. The obtained copolymer is used as a coating composition; or adding styrene tar or its copolymer to the coating can improve the performance of the coating in terms of anti-corrosion, waterproof, drying speed, viscosity, insulation, etc.; or it is an additive to the adhesive to improve the viscosity, elasticity, etc. of the adhesive. Moreover, since styrene tar contains a certain amount of valuable components such as styrene, methylstyrene, polyethylbenzene, etc., the recovery of these components has also become a widely studied treatment method. At present, most recovery methods are conventional vacuum distillation, rectification and other recovery methods.

[0005] Patent CN110511783A discloses a device and method for comprehensive utilization of styrene heavy fraction oil, including a styrene device distillation tower, a styrene heavy fraction oil storage tank, a riser reactor and a catalytic cracking device fractionation tower, the bottom of the styrene device distillation tower is connected to the styrene heavy fraction oil storage tank through the heavy fraction pipeline at the bottom of the styrene device distillation tower, the styrene heavy fraction oil storage tank is connected to the riser reactor through a cross-line, and the top of the riser reactor is connected to the catalytic cracking device fractionation tower through the riser reactor outlet oil and gas pipeline. This method allows the styrene heavy fraction oil to contact and react with the catalyst of the catalytic cracking unit, and most of it is converted into high-value catalytic gasoline, diesel and liquefied gas and other products, while a small amount of dry gas and coke are produced as by-products, achieving the purpose of high-value and environmentally friendly processing and utilization of styrene heavy fraction oil.

[0006] Patent CN112574783A discloses a method for comprehensive utilization of styrene tar, wherein the styrene tar is produced by extraction of pyrolysis gasoline or by dehydrogenation of ethylbenzene, and the comprehensive utilization method includes: firstly pre-treating the styrene tar and collecting the oil phase; then distilling the oil phase to obtain gas phase 1 and liquid phase 1, and the gas phase 1 is subjected to a separation step to obtain styrene and derivatives; then the liquid phase 1 is cracked and fractionated to obtain gas phase 2 and liquid phase 2, and the gas phase 2 is subjected to a cooling step to obtain styrene and derivatives; finally, the liquid phase 2 is subjected to hydrogenation refining to obtain liquid phase 3, and the liquid phase 3 is distilled to obtain gas phase 3 and liquid phase 4, and the gas phase 3 is cooled to generate tar resin, and the liquid phase 4 is rich in valuable components. This patent realizes the overall resource utilization of styrene tar by extracting the valuable components in styrene tar in batches, and can achieve clean production.

[0007] Patent CN 111056905S1 discloses a system for recovering effective components in styrene tar, which mainly distills out light components in styrene tar by setting up "distillation tower-tower top condenser-recovery tank-tower bottom pump-reboiler-cracking reactor-product collection", and the heavy components in the tower bottom are recovered through the reboiler on the one hand, and enter the cracking reactor for cracking reaction on the other hand.

[0008] The above patents mainly use cracking, distillation and other methods to achieve resource recovery of styrene tar, but the main problems are: (1) In industrial production, distillation towers are used to refine styrene and recover light components in styrene tar. Distillation towers are connected in series after the existing distillation towers to increase the number of stages, and the treatment (separation) effect is average; (2) The thermal cracking process itself increases the processing energy consumption and catalyst consumption; (3) There are nitrogen-containing inhibitors in styrene tar. Direct cracking not only pollutes the product, but also may produce NOx waste gas. Summary of the invention

[0009] To solve the problems existing in the disposal of styrene tar at the present stage, the present invention provides a method and a system for recovering valuable aromatic components from styrene tar. The method of the present invention has the advantages of good recovery effect, good quality of recovered aromatics, low recovery cost and no secondary pollution, etc.

[0010] A method for recovering aromatic components from styrene tar provided by the present invention specifically comprises the following steps:

[0011] (1) After mixing styrene tar with a depolymerization solvent in a mixer, the mixture is sent into a separator. After standing for layering, the upper depolymerization liquid is sent into a first polymerization inhibitor filter;

[0012] (2) A sedimentation agent S1 is added to the first polymerization inhibitor filter. After sufficient reaction and filtration, the filtrate F1 enters a second polymerization inhibitor filter;

[0013] (3) A sedimentation agent S2 is added to the second polymerization inhibitor filter. After sufficient reaction and filtration, the generated filtrate F2 enters an aromatic separator;

[0014] (4) The solvent is recovered in the aromatic separator, and the remaining liquid is the recovered aromatics.

[0015] The styrene tar described in step (1) comes from the rectification residue generated in the production process of ethylbenzene dehydrogenation to produce styrene, mainly including aromatics, oligomers, polymerization inhibitors, etc. Among them, the aromatics mainly include monocyclic aromatics, bicyclic aromatics and polycyclic aromatics, etc.

[0016] The depolymerization solvent described in step (1) is an alkane and its mixture, preferably one or more of straight-chain alkanes, branched-chain alkanes, cycloalkanes, etc. with C2-C12, and more preferably one or more of pentane, hexane, heptane, octane, nonane, etc.

[0017] The mass ratio of the styrene tar to the depolymerization solvent described in step (1) is 1:1-4, preferably 1:2-3.5.

[0018] The mixing in step (1), the implementation means includes but is not limited to stirring, forced circulation, etc., that is, it can achieve the full mixing of various substances in the system.

[0019] The polymerization inhibitor filters described in steps (2)-(3) have both the functions of reaction and filtration, and can avoid the deposition of reaction materials in the pipeline during transportation to cause blockage. Specifically, a reaction tank with a stirring function and an openable / closable bottom is arranged above the filter. The depolymerization liquid or filtrate and the sedimentation agent first enter the reaction tank for stirring reaction. After the reaction is completed, the bottom of the reaction tank is opened, and the mixed liquid enters the filter arranged below under the action of gravity for filtration to obtain a filtrate and solids.

[0020] The settling agent S1 described in step (2) is one or more of sodium hydroxide solution, potassium hydroxide solution, etc., with a mass concentration of 2.5%-20%, preferably 5%-15%.

[0021] In step (2), the settling agent S1 is added according to the volume ratio of the settling agent S1 to the upper layer of depolymerized liquid of 1:50-200, preferably 1:80-150.

[0022] When adding the settling agent S1 in step (2), it is preferably added slowly while stirring to prevent the quality of the recovered aromatic hydrocarbons from deteriorating due to rapid addition. The stirring rate is 60-200 rpm, preferably 80-120 rpm.

[0023] The settling agent S2 described in step (3) is one or more of ammonia water, sodium carbonate solution, ammonium carbonate solution, potassium carbonate solution, etc., and the mass concentration of the solution is 3%-20%, preferably 5%-10%.

[0024] In step (3), the settling agent S2 is added according to the volume ratio of the settling agent S2 to the filtrate F1 of 1:15-120, preferably 1:30-90.

[0025] When adding the settling agent S2 in step (3), it is preferably added slowly while stirring to prevent the quality of the recovered aromatic hydrocarbons from deteriorating due to rapid addition at one time. The stirring rate is 150-300 rpm, preferably 180-220 rpm.

[0026] In the filtrate F2 entering the aromatic hydrocarbon separator in step (4), the solvent mixed in the recovered aromatic hydrocarbons is separated. The separation temperature is mainly to recover the depolymerized solvent, generally lower than 150 °C, preferably 100-150 °C, and the recovered solvent can be recycled. After the separation is completed, the remaining liquid obtained is the recovered aromatic hydrocarbons.

[0027] The present invention also provides a recovery system for the recovery method of valuable aromatic hydrocarbon components in the above-mentioned styrene tar, mainly including a mixer, a separator, a first polymerization inhibitor filter, a second polymerization inhibitor filter, an aromatic hydrocarbon separator, etc. Among them, the mixer is used for the full mixing of styrene tar and depolymerized solvent, and the mixed liquid is sent into the separator. After standing and stratifying, the upper layer of depolymerized liquid is sent into the first polymerization inhibitor filter; the first polymerization inhibitor filter is used for the reaction and filtration of the depolymerized liquid and the settling agent S1, and the filtrate F1 is sent into the second polymerization inhibitor filter; the second polymerization inhibitor filter is used for the reaction and filtration of the filtrate F1 and the settling agent S2, and the filtrate F2 is sent into the aromatic hydrocarbon separator to recover the depolymerized solvent, and the remaining liquid obtained is the recovered aromatic hydrocarbons.

[0028] In the recovery system of the present invention, the inhibitor filter serves both the functions of reaction and filtration, and can prevent the blockage caused by the deposition of materials in the pipeline during transportation. Specifically, a reaction tank with a stirring function and an openable / closable bottom is arranged above the filter. The depolymerized liquid or filtrate and the sedimentation agent are transported to the reaction tank. After stirring and reacting, the bottom of the tank is opened, and the mixed liquid enters the filter arranged below under the action of gravity for filtration.

[0029] Compared with the prior art, the present invention has the following effects:

[0030] (1) In the present invention, the styrene tar is first treated with a depolymerization solvent, and then combined with a two-step inhibitor filtration and sequential addition of caustic solutions with different characteristics to achieve the efficient recovery of styrene tar. The recovered aromatic hydrocarbons have good quality and relatively low recovery cost.

[0031] (2) The styrene tar treated in the present invention contains components such as oligomers and polycyclic aromatic hydrocarbons. The depolymerization solvent can efficiently remove such substances, improving the quality of the recovered aromatic hydrocarbons.

[0032] (3) The upper-layer depolymerized liquid after treatment with the depolymerization solvent in the present invention is treated by a two-step inhibitor filtration method, combined with the sequential addition of caustic solutions with different characteristics, further improving the recovery effect of valuable aromatic hydrocarbon components.

[0033] (4) The present invention does not use a catalyst and only has heating in the solvent recovery link. The overall energy consumption is small, the cost is low, and there is no problem of secondary pollution.

[0034] (5) Compared with the traditional processes of extracting aromatic hydrocarbons by distillation and cracking, the present invention has a simple process, good recovery effect, strong practicability. The recovered aromatic hydrocarbons can be used as oil blending, additives for asphalt and rubber production, and can also be used as raw materials for catalytic cracking and other devices. Description of the Drawings

[0035] Figure 1 is a flow chart for recovering aromatic hydrocarbon components from styrene tar in the present invention;

[0036] Among them, 1 - mixer, 2 - separator, 3 - first inhibitor filter, 4 - second inhibitor filter, 5 - aromatic hydrocarbon separator; 1.1 - styrene tar, 1.2 - depolymerization solvent, 1.3 - sedimentation agent S1, 1.4 - sedimentation agent S2, 1.5 - recovered aromatic hydrocarbons, 1.6 - depolymerized liquid, 1.7 - recovered depolymerization solvent. Detailed Embodiments

[0037] The following specific examples are used to further illustrate the method and its effects of the present invention. The examples are implemented on the premise of the technical solution of the present invention, and detailed implementation methods and specific operation processes are given. However, the protection scope of the present invention is not limited to the following examples.

[0038] The experimental methods in the following examples, unless otherwise specified, are all conventional methods in the art. The experimental materials used in the following examples, unless otherwise specified, were purchased from conventional biochemical reagent stores.

[0039] Embodiments The present invention is used Figure 1 The recovery system of valuable aromatic components in styrene tar shown in the figure recovers aromatics, and mainly includes a mixer 1, a separator 2, a first anti-agglomeration filter 3, a second anti-agglomeration filter 4 and an aromatics separator 5, wherein the mixer 1 is used to mix the styrene tar 1.1 with the depolymerization solvent 1.2, and the mixed liquid is sent to the separator 2. After standing and stratification, the upper depolymerization liquid 1.6 is sent to the first anti-agglomeration filter 3; the first anti-agglomeration filter 3 is used for the reaction and filtration of the depolymerization liquid and the sedimentation agent S1 (1.3), and the filtrate F1 is sent to the second anti-agglomeration filter 4; the second anti-agglomeration filter is used for the reaction and filtration of the filtrate F1 and the sedimentation agent S2 (1.4), and the filtrate F2 is sent to the aromatics separator to recover the depolymerization solvent 1.7, and the residual liquid obtained is the recovered aromatics 1.5.

[0040] The styrene tar in this embodiment comes from the distillation residue produced in the production process of ethylbenzene dehydrogenation to styrene in a refinery of Sinopec, and mainly includes monocyclic aromatic hydrocarbons, dicyclic aromatic hydrocarbons, condensed aromatic hydrocarbons, oligomers, etc. The details are shown in Table 1 and Table 2.

[0041] Table 1 Distillation range distribution

[0042] Styrene tar Initial boiling point 10 30 50 70 90 Final boiling point Temperature 137.3 176.8 258.1 296.5 507.5 615.1 701.0

[0043] Table 2 Components and contents

[0044] Composition Monocyclic aromatic hydrocarbon Bicyclic aromatic hydrocarbon Polycyclic aromatic hydrocarbon Others Styrene tar 18.24 61.03 15.2 5.53

[0045] Example 1

[0046] 1000 mL of styrene tar was added to a mixer, and 3000 mL of a depolymerization solvent was added, wherein the depolymerization solvent was a mixture of n-heptane and n-octane in a mass ratio of 1:1. After being fully mixed, the mixture was sent to a separator. After standing for stratification, the upper depolymerization liquid was transported to a first polymerization inhibition filter, and a sedimentation agent S1, i.e., a sodium hydroxide solution with a mass concentration of 5 wt%, was added, and the volume ratio of the sedimentation agent S1 to the upper depolymerization liquid was 1:120. The mixture was slowly added while stirring at a stirring rate of 80 rpm. After sufficient reaction and filtration, the filtrate F1 was obtained and sent to a second polymerization inhibition filter, and a sedimentation agent S2, i.e., a sodium carbonate solution with a mass concentration of 10 wt%, was added, and the volume ratio of the sedimentation agent S2 to the filtrate F1 was 1:30. The mixture was slowly added while stirring at a stirring rate of 220 rpm. The filtrate F2 was transported to an aromatics separator, and desolventized at 125° C. to obtain recovered aromatics, totaling 658 mL. The distillation range distribution and composition content test results of recovered aromatics are shown in Tables 3 and 4.

[0047] Example 2

[0048] Take 1000 mL of styrene tar and add it to a mixer. Then add 3500 mL of depolymerization solvent, which is a mixture of n-pentane and n-hexane with a mass ratio of 1:1. After thorough mixing, it enters a separator. After standing and separating into layers, the upper-layer depolymerization liquid is transported to a first polymerization inhibitor filter, and a settling agent S1, that is, a sodium hydroxide solution with a mass concentration of 15 wt%, is added. The volume ratio of the settling agent S1 to the upper-layer depolymerization liquid is 1:90, and it is slowly added while stirring at a stirring rate of 120 rpm. After full reaction and filtration, the filtrate F1 is sent to a second polymerization inhibitor filter, and a settling agent S2, that is, a potassium carbonate solution with a mass concentration of 5 wt%, is added. The volume ratio of the settling agent S2 to the filtrate F1 is 1:45, and it is slowly added while stirring at a stirring rate of 210 rpm. The filtrate F2 is transported to an aromatic hydrocarbon separator, and solvent removal treatment is carried out at 100 °C to obtain 612 mL of recovered aromatic hydrocarbons in total. The detection results of the distillation range distribution and composition content of the recovered aromatic hydrocarbons are shown in Table 3 and Table 4.

[0049] Example 3

[0050] Take 1000 mL of styrene tar and add it to a mixer. Then add 3000 mL of depolymerization solvent, which is a mixture of n-octane and n-nonane with a mass ratio of 1:4. After thorough mixing, it enters a separator. After standing and separating into layers, the upper-layer depolymerization liquid is transported to a first polymerization inhibitor filter, and a settling agent S1, that is, a potassium hydroxide solution with a mass concentration of 5 wt%, is added. The volume ratio of the settling agent S1 to the upper-layer depolymerization liquid is 1:80, and it is slowly added while stirring at a stirring rate of 90 rpm. After full reaction and filtration, the filtrate F1 is sent to a second polymerization inhibitor filter, and a settling agent S2, that is, ammonia water with a mass concentration of 5 wt%, is added. The volume ratio of the settling agent S2 to the filtrate F1 is 1:60, and it is slowly added while stirring at a stirring rate of 200 rpm. The filtrate F2 is transported to an aromatic hydrocarbon separator, and solvent removal treatment is carried out at 150 °C to obtain 688 mL of recovered aromatic hydrocarbons in total. The detection results of the distillation range distribution and composition content of the recovered aromatic hydrocarbons are shown in Table 3 and Table 4.

[0051] Example 4

[0052] Take 1000 mL of styrene tar and add it to a mixer. Then add 2000 mL of depolymerization solvent. The depolymerization solvent is a mixture of n - hexane and n - heptane, and the mass ratio of the two is 1:1. After thorough mixing, it enters a separator. After standing and separating into layers, the upper - layer depolymerized liquid is transported to the first inhibitor filter, and a sedimentation agent S1 is added, which is a potassium hydroxide solution with a mass concentration of 15 wt%. The volume ratio of the sedimentation agent S1 to the upper - layer depolymerized liquid is 1:145. It is added slowly while stirring, and the stirring rate is 85 rpm. After full reaction and filtration, the filtrate F1 is sent to the second inhibitor filter, and a sedimentation agent S2 is added, which is an ammonium carbonate solution with a mass concentration of 5 wt%. The volume ratio of the sedimentation agent S2 to the filtrate F1 is 1:75. It is added slowly while stirring, and the stirring rate is 190 rpm. The filtrate F2 is transported to an aromatic hydrocarbon separator, and solvent removal treatment is carried out at 100 °C to obtain 606 mL of recovered aromatic hydrocarbons in total. The distillation range distribution and composition content test results of the recovered aromatic hydrocarbons are shown in Table 3 and Table 4.

[0053] Example 5

[0054] Take 1000 mL of styrene tar and add it to a mixer. Then add 2500 mL of depolymerization solvent. The depolymerization solvent is n - nonane. After thorough mixing, it enters a separator. After standing and separating into layers, the upper - layer depolymerized liquid is transported to the first inhibitor filter, and a sedimentation agent S1 is added, which is a mixed solution of potassium hydroxide and sodium hydroxide (mass ratio 1:1) with a mass concentration of 10 wt%. The volume ratio of the sedimentation agent S1 to the upper - layer depolymerized liquid is 1:100. It is added slowly while stirring, and the stirring rate is 110 rpm. After full reaction and filtration, the filtrate F1 is sent to the second inhibitor filter, and a sedimentation agent S2 is added, which is a mixed solution of sodium carbonate and potassium carbonate (mass ratio 1:1) with a mass concentration of 8 wt%. The volume ratio of the sedimentation agent S2 to the filtrate F1 is 1:80. It is added slowly while stirring, and the stirring rate is 185 rpm. The filtrate F2 is transported to an aromatic hydrocarbon separator, and solvent removal treatment is carried out at 100 °C to obtain 614 mL of recovered aromatic hydrocarbons in total. The distillation range distribution and composition content test results of the recovered aromatic hydrocarbons are shown in Table 3 and Table 4.

[0055] Example 6

[0056] 1000 mL of styrene tar was added to a mixer, and 3000 mL of a depolymerization solvent was added. The depolymerization solvent was a mixture of isopentane and n-octane in a mass ratio of 1:1.5. After being fully mixed, the mixture was sent to a separator. After standing for stratification, the upper depolymerization liquid was transported to a first polymerization inhibition filter, and a sedimentation agent S1, i.e., a sodium hydroxide solution with a mass concentration of 7 wt%, was added. The volume ratio of the sedimentation agent S1 to the upper depolymerization liquid was 1:125. The mixture was slowly added while stirring at a stirring rate of 100 rpm. After sufficient reaction and filtration, the filtrate F1 was obtained and sent to a second polymerization inhibition filter. A sedimentation agent S2, i.e., ammonia water with a mass concentration of 7 wt%, was added. The volume ratio of the sedimentation agent S2 to the filtrate F1 was 1:90. The mixture was slowly added while stirring at a stirring rate of 180 rpm. The filtrate F2 was transported to an aromatics separator and subjected to a desolventizing treatment at 125° C. to obtain recovered aromatics, totaling 664 mL. The distillation range distribution and composition content test results of the recovered aromatics are shown in Table 3 and Table 4. Comparative Example 1

[0057] The same as Example 1, except that the depolymerization solvent is xylene. A total of 660 mL of recovered aromatics are obtained, and the distillation range distribution and composition content test results of the recovered aromatics are shown in Tables 3 and 4.

[0058] Comparative Example 2

[0059] The same as Example 1, except that ethyl acetate was used as the depolymerization solvent. A total of 653 mL of recovered aromatics were obtained, and the distillation range distribution and composition content test results of the recovered aromatics are shown in Tables 3 and 4.

[0060] Comparative Example 3

[0061] The same as Example 1, except that the first inhibitor filter and the sedimentation agent S1 were not used, and the amount of the sedimentation agent S2 was the sum of the sedimentation agents S1 and S2 in Example 1. A total of 582 mL of recovered aromatics were obtained, and the distillation range distribution and composition content test results of the recovered aromatics are shown in Tables 3 and 4.

[0062] Comparative Example 4

[0063] The same as Example 1, except that the second inhibitor filter and the sedimentation agent S2 were not used, and the amount of the sedimentation agent S1 was the sum of the sedimentation agents S1 and S2 in Example 1. A total of 604 mL of recovered aromatics were obtained, and the distillation range distribution and composition content test results of the recovered aromatics are shown in Tables 3 and 4.

[0064] Comparative Example 5

[0065] The same as Example 1, except that the settling agents S1 and S2 were added at one time. A total of 589 mL of recovered aromatics were obtained. The distillation range distribution and composition content test results of the recovered aromatics are shown in Tables 3 and 4.

[0066] The distillation range distribution and composition of the aromatic hydrocarbons recovered in the above-mentioned examples and comparative examples were detected, and the results are shown in Tables 3 and 4.

[0067] Table 3 Distillation Range Distribution

[0068] Distillation range distribution Initial boiling point 10 30 50 70 90 Final boiling point Styrene tar 137.31 176.78 258.09 296.46 507.49 615.08 700.96 Example 1 89.30 115.49 127.52 267.03 267.03 398.99 421.72 Example 2 78.04 101.12 153.42 231.08 274.27 329.33 398.99 Example 3 111.62 239.30 356.77 387.63 399.10 470.59 629.90 Example 4 102.32 201.85 289.71 314.99 342.61 483.22 657.88 Example 5 97.49 123.02 180.47 221.39 236.91 301.31 410.04 Example 6 135.95 198.33 284.91 191.37 420.47 475.40 617.28 Comparative Example 1 152.21 194.74 365.93 457.32 632.91 702.96 720.00 Comparative Example 2 92.73 157.42 165.23 342.98 520.53 582.80 718.34 Comparative Example 3 90.30 167.38 272.87 381.48 492.19 661.97 720.00 Comparative Example 4 97.28 164.45 207.32 308.97 369.37 401.47 697.32 Comparative Example 5 102.41 149.42 239.66 314.44 357.41 428.28 685.72

[0069] Table 4 Components and Contents

[0070] Composition Monocyclic aromatic hydrocarbon Bicyclic aromatic hydrocarbon Polycyclic aromatic hydrocarbon Others Styrene tar 18.24 61.03 15.20 5.53 Example 1 40.61 52.29 5.67 1.43 Example 2 45.49 48.66 3.13 2.72 Example 3 39.81 50.87 6.21 3.11 Example 4 32.17 55.68 10.24 1.91 Example 5 41.93 51.43 4.31 2.33 Example 6 28.03 55.52 12.57 3.88 Comparative Example 1 19.39 53.08 21.32 6.21 Comparative Example 2 17.21 56.86 19.59 6.34 Comparative Example 3 18.33 48.55 20.38 12.74 Comparative Example 4 19.16 61.57 14.55 4.72 Comparative Example 5 19.20 60.89 14.88 5.03

[0071] It can be seen from Comparative Example 1 and Comparative Example 2 that when other solvents (such as xylene, ethyl acetate) are selected as the depolymerization solvent, the effect is poor. The residual heavy components make the final boiling points all higher than 700 °C. At the same time, after the solvent recovery process, these residual heavy components further polymerize, resulting in a significant increase in the proportion of polycyclic aromatic hydrocarbons and other components, and the properties of the recovered aromatic hydrocarbons deteriorate.

[0072] It can be seen from Comparative Example 3 that when the first polymerization inhibitor filter and the sedimentation agent S1 are not used, and only the sedimentation agent S2 is used, the proportion of other components in the recovered aromatic hydrocarbons increases significantly. This shows that Comparative Example 3 not only fails to effectively remove the polymerization inhibitor components, but also generates polycyclic aromatic hydrocarbons and other substances in the aromatic hydrocarbon separator, and the properties of the recovered aromatic hydrocarbons are worse than those of Example 1.

[0073] It can be seen from Comparative Example 4 that when the second polymerization inhibitor filter and the sedimentation agent S2 are not used, and only the sedimentation agent S1 is used, although the proportion of other components in the recovered aromatic hydrocarbons decreases slightly, it is still worse than that of the example. This shows that Comparative Example 4 can effectively remove the nitrogen-containing polymerization inhibitor contained therein, but there is still residue, and its final boiling point is still higher than 690 °C, which proves this point.

[0074] It can be seen from Comparative Example 5 that its distillation range distribution, components and contents are not much different from those of Comparative Example 4, and the final boiling point and the content of other components are higher than those of Example 1. This shows that adding both the sedimentation agent S1 and S2 at one time cannot achieve the removal effect of adding them step by step, and the quality of the recovered aromatic hydrocarbons is still not as good as that of Example 1.

Claims

1. A method for recovering valuable aromatic components from styrene tar, characterized in that It includes the following steps: (1) After mixing styrene tar with a depolymerization solvent in a mixer, it is sent into a separator. After standing for layering, the upper-layer depolymerized liquid is sent into a first inhibitor filter; the depolymerization solvent is one or more of straight-chain alkanes, branched-chain alkanes, and cycloalkanes with 2 to 12 carbon atoms; (2) Add a settling agent S1 to the first inhibitor filter. After sufficient reaction and filtration, the filtrate F1 enters the second inhibitor filter; the settling agent S1 is one or more of sodium hydroxide solution and potassium hydroxide solution, and the mass concentration of the solution is 2.5% - 20%; (3) Add a settling agent S2 to the second inhibitor filter. After sufficient reaction and filtration, the resulting filtrate F2 enters an aromatic hydrocarbon separator; the settling agent S2 is one or more of ammonia water, sodium carbonate solution, ammonium carbonate solution, and potassium carbonate solution, and the mass concentration of the solution is 3% - 20%; (4) Recover the solvent in the aromatic hydrocarbon separator, and the remaining liquid is the recovered aromatic hydrocarbon.

2. The method according to claim 1, wherein: The styrene tar described in step (1) comes from the rectification residue generated in the production process of ethylbenzene dehydrogenation to styrene, and mainly includes aromatic hydrocarbons, oligomers, and inhibitor. Among them, the aromatic hydrocarbons mainly include monocyclic aromatic hydrocarbons, bicyclic aromatic hydrocarbons, and polycyclic aromatic hydrocarbons.

3. The method according to claim 1, wherein: The depolymerization solvent described in step (1) is one or more of pentane, hexane, heptane, octane, and nonane.

4. The method according to claim 1, wherein: The mass ratio of the styrene tar to the depolymerization solvent described in step (1) is 1:1 - 4.

5. The method according to claim 4, wherein: The mass ratio of the styrene tar to the depolymerization solvent described in step (1) is 1:2 - 3.

5.

6. The method according to claim 1, wherein: The inhibitor filter has both reaction and filtration functions. Specifically, a reaction tank with a stirring function and an openable / closable bottom is set above the filter. The depolymerized liquid or filtrate and the settling agent first enter the reaction tank for stirring reaction. After the reaction is completed, the bottom of the reaction tank is opened, and the mixed liquid enters the filter set below under the action of gravity for filtration to obtain filtrate and solids.

7. The method according to claim 1, characterized in that: In step (2), the mass concentration of the solution is 5% - 15%.

8. The method according to claim 1 or 7, characterized in that: In step (2), the settling agent S1 is added according to the volume ratio of 1:50 - 200 to the upper-layer depolymerized liquid.

9. The method according to claim 8, wherein: In step (2), the settling agent S1 is added according to the volume ratio of 1:80 - 150 to the upper-layer depolymerized liquid.

10. The method according to claim 1 or 7, characterized in that: When adding the settling agent S1 in step (2), it is added slowly while stirring, and the stirring rate is 60 - 200 rpm.

11. The method according to claim 10, characterized in that: The stirring rate is 80 - 120 rpm.

12. The method according to claim 1, characterized in that: In step (3), the mass concentration of the solution is 5% - 10%.

13. The method according to claim 1, wherein: In step (3), the settling agent S2 is added according to the volume ratio of 1:15 - 120 to the filtrate F1.

14. The method according to claim 13, wherein: In step (3), the settling agent S2 is added according to the volume ratio of 1:30 - 90 to the filtrate F1.

15. The method according to claim 1, wherein: When adding the settling agent S2 in step (3), it is added slowly while stirring, and the stirring rate is 150 - 300 rpm.

16. The method according to claim 15, wherein: The stirring rate is 180 - 220 rpm.

17. The method according to claim 1, wherein: In step (4), the solvent mixed in the aromatic hydrocarbon recovered from the filtrate F2 entering the aromatic hydrocarbon separator is recovered, the separation temperature is lower than 150 °C, and the recovered solvent is recycled.

18. The method according to claim 17, wherein: The separation temperature is 100 - 150 °C.

19. A recovery system for the recovery method of valuable aromatic hydrocarbon components in styrene tar according to any one of claims 1-18, characterized in that It mainly includes a mixer, a separator, a first polymerization inhibitor filter, a second polymerization inhibitor filter and an aromatic hydrocarbon separator. The mixer is used for the full mixing of styrene tar and depolymerization solvent. The mixed liquid is sent into the separator. After standing and stratifying, the upper depolymerized liquid is sent into the first polymerization inhibitor filter. The first polymerization inhibitor filter is used for the reaction and filtration of the depolymerized liquid and the sedimentation agent S1. The filtrate F1 is sent into the second polymerization inhibitor filter. The second polymerization inhibitor filter is used for the reaction and filtration of the filtrate F1 and the sedimentation agent S2. The filtrate F2 is sent into the aromatic hydrocarbon separator to recover the depolymerization solvent, and the remaining liquid obtained is the recovered aromatic hydrocarbon.

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