A method and device for separating a mixture of carbon nine aromatic hydrocarbons

Abstract

The present invention belongs to the technical field of separation of polymethyl aromatic compounds, and specifically relates to a method and device for separating a carbon nine aromatic mixture. The method comprises the following steps: introducing the carbon nine aromatic mixture after removing light components with a boiling point lower than 164.5°C and heavy components with a boiling point higher than 165.5°C into an extractive distillation tower, and performing extractive distillation in the presence of a first extractant, wherein the first extractant is a mixed solution including trimethyl trimesic acid and n-octanol. The method and device provided by the present invention can separate and purify the effective components in the by-product resources of the refinery, the product has a wide range of application, the added value is greatly improved, and the comprehensive utilization of precious resources is realized.

Description

Technical Field

[0001] The invention belongs to the technical field of separation of polymethyl aromatic compounds, and in particular relates to a method and a device for separating a carbon nine aromatic mixture. Background Art

[0002] Aromatic complexes in large refineries have a large amount of reformed carbon nine aromatic resources, which are complex in composition and usually have more than 40 components, each of which has different uses. Among them, there are generally no more than three components that can form economic value. The current technology only extracts one component, trimethylbenzene, and the rest of the components are used as raw materials for aromatic solvents or for other purposes. Many components with higher economic value have not been well separated and purified due to the limitations of technology and equipment, resulting in a huge waste of resources. Summary of the invention

[0003] In view of the deficiencies in the prior art, the purpose of the present invention is to provide a method and device for separating a carbon nine aromatic mixture, which can separate the para-trimethylbenzene, iso-trimethylbenzene, tri-trimethylbenzene and o-ethylmethylbenzene components in the carbon nine aromatic mixture system, and realize the separation, purification and comprehensive utilization of high value-added components in the carbon nine heavy aromatics by-products of large-scale refinery aromatic complexes, and is energy-saving, emission-reducing and environmentally friendly.

[0004] Specifically, the present invention provides the following technical solutions.

[0005] A method for separating a C9 aromatics mixture, wherein the C9 aromatics mixture contains mesitylene and o-ethylmethylbenzene, the method comprising the following steps:

[0006] (1) introducing a C9 aromatic hydrocarbon mixture into a first light-removal tower, drawing out light components with a boiling point lower than 164.5° C. from the top of the first light-removal tower, and drawing out heavy components containing mesitylene and o-ethylmethylbenzene from the bottom of the tower;

[0007] (2) introducing the heavy components described in step (1) into a mesitylene removal tower, drawing out light components containing mesitylene and o-methylethylbenzene from the top of the mesitylene removal tower, and drawing out heavy components with a boiling point higher than 165.5° C. from the bottom of the tower;

[0008] (3) introducing the light component containing mesitylene and o-methylethylbenzene described in step (2) into a mesitylene extractive distillation tower, performing extractive distillation in the presence of a first extractant, drawing out the o-methylethylbenzene product from the top of the mesitylene extractive distillation tower, and drawing out the heavy component containing the first extractant and mesitylene from the bottom of the tower;

[0009] Wherein, the first extractant is a mixed solution including trimethyl trimesic acid and n-octanol.

[0010] Preferably, in the above method for separating a C9 aromatic hydrocarbon mixture, the molar ratio of trimethyl trimesic acid to n-octanol is 3 to 5:1, more preferably 3.5 to 4.5:1, and further preferably 3.8 to 4.2:1.

[0011] Preferably, the above method for separating a carbon nine aromatic hydrocarbon mixture further comprises the following steps: introducing the heavy component containing the first extractant and mesitylene described in step (3) into a mesitylene analysis tower, drawing out the mesitylene product from the top of the mesitylene analysis tower, and drawing out the first extractant from the bottom of the tower.

[0012] Preferably, in the above method for separating a C9 aromatic mixture, the C9 aromatic mixture further contains unsymmetrical trimethylol, trimethylol and at least one selected from p-methyl cumene and indane, and the method further comprises the following steps:

[0013] (4) introducing the heavy components with a boiling point higher than 165.5° C. described in step (2) into a trimethylolbenzene distillation tower, drawing out a trimethylolbenzene product from a side line of the trimethylolbenzene distillation tower, drawing out a light component with a boiling point between 165.5° C. and 169.3° C. from the top of the tower, and drawing out a heavy component with a boiling point higher than 170° C. from the bottom of the tower;

[0014] (5) introducing the heavy components with a boiling point higher than 170° C. described in step (4) into a trimethylol light-removal tower, drawing out light components with a boiling point between 170° C. and 176° C. from the top of the trimethylol light-removal tower, and drawing out heavy components with a boiling point higher than 176° C. from the bottom of the tower;

[0015] (6) introducing the heavy components with a boiling point higher than 176° C. in step (5) into a trimethylol removal tower, drawing out light components containing trimethylol and at least one selected from p-methylisopropylbenzene and indane from the top of the trimethylol removal tower, and drawing out the heavy components with a boiling point higher than 177.2° C. from the bottom of the tower;

[0016] (7) introducing the light component described in step (6) into a trimethylol extractive distillation tower, performing extractive distillation in the presence of a second extractant, drawing out at least one selected from p-methyl cumene and indane from the top of the trimethylol extractive distillation tower, and drawing out a heavy component containing the second extractant and trimethylol from the bottom of the tower;

[0017] Wherein, the second extractant is a mixed solution of 3,4,5-trimethylphenol and n-octanol. More preferably, the molar ratio of 3,4,5-trimethylphenol to n-octanol is 1.5-2.5:1. Further preferably, the molar ratio of 3,4,5-trimethylphenol to n-octanol is 1.8-2.2:1.

[0018] The invention utilizes the different properties of component molecular structures, selects appropriate 3,4,5-trimethylphenol and n-octanol binary system polar solvent as extractant, and skillfully separates trimethylol from indane and p-methylisopropylbenzene, which have very close boiling points and are difficult to separate even by super distillation.

[0019] Preferably, the above method for separating a carbon nine aromatic hydrocarbon mixture further includes the following steps: introducing the heavy component containing the second extractant and trimethylol described in step (7) into a trimethylol analysis tower, drawing out the trimethylol product from the top of the trimethylol analysis tower, and drawing out the second extractant from the bottom of the tower.

[0020] The present invention also provides a device for separating a carbon nine aromatic hydrocarbon mixture, comprising a first light removal tower, a mesitylene removal tower, a mesitylene extraction distillation tower and a mesitylene analytical tower;

[0021] A feed port for a C9 aromatic hydrocarbon mixture is provided on the side of the first light-removal tower, and a bottom discharge port of the first light-removal tower is connected to a feed port for a raw material of the mesitylene removal tower;

[0022] The top discharge port of the mesitylene removal tower is connected to the raw material feed port of the mesitylene extraction distillation tower;

[0023] The mesitylene extraction and distillation tower is provided with a first extractant feed port, the top discharge port of the mesitylene extraction and distillation tower leads out the o-methylethylbenzene product, and the bottom discharge port is connected to the raw material feed port of the mesitylene analysis tower;

[0024] The mesitylene product is drawn out from the top discharge port of the mesitylene analysis tower.

[0025] Preferably, the above-mentioned device for separating the C9 aromatic hydrocarbon mixture further comprises a trimethylol distillation tower, a trimethylol lightness removal tower, a trimethylol removal tower, a trimethylol extractive distillation tower and a trimethylol analytical tower;

[0026] The tower bottom discharge port of the mesitylene removal tower is connected to the raw material feed port of the para-trimethylbenzene distillation tower;

[0027] The trimethylolbenzene distillation tower is provided with a side discharge port, and the side discharge port leads out the trimethylolbenzene product; the bottom discharge port of the trimethylolbenzene distillation tower is connected to the raw material feed port of the trimethylolbenzene light removal tower;

[0028] The tower bottom discharge port of the trimethylol removal tower is connected to the raw material feed port of the trimethylol removal tower;

[0029] The top discharge port of the trimethylol removal tower is connected to the raw material feed port of the trimethylol extractive distillation tower;

[0030] The trimethylol extractive distillation tower is provided with a second extractant feed port, the top discharge port of the trimethylol extractive distillation tower is used to discharge methyl isopropylbenzene and / or indane, and the bottom discharge port is connected to the raw material feed port of the trimethylol analytical tower;

[0031] The trimethylol product is drawn out from the top discharge port of the trimethylol analysis tower.

[0032] Preferably, in the above-mentioned device for separating a carbon nine aromatic hydrocarbon mixture, at least packing or plates with a height equivalent to eight theoretical plates are provided between the side discharge port of the trimethylolbenzene distillation tower and the top of the tower.

[0033] Preferably, in the above-mentioned device for separating a carbon nine aromatic hydrocarbon mixture, the first light-removing tower, the mesitylene removing tower, the mesitylene extracting and distilling tower, the mesitylene light-removing tower, the mesitylene removing tower and the mesitylene extracting and distilling tower are filled with bidirectional curved wave high-efficiency structured packing;

[0034] The interiors of the mesitylene analysis tower, the unsymmetrical trimethylol distillation tower and the trimethylol analysis tower are filled with bidirectional oblique wave high-efficiency structured packing.

[0035] The present invention also provides a method for separating mesitylene and o-methylethylbenzene, comprising the following steps: subjecting a system containing mesitylene and o-methylethylbenzene to extractive distillation in the presence of an extractant, wherein the extractant is a mixed solution comprising trimethyl trimesic acid and n-octanol.

[0036] Preferably, in the above method for separating mesitylene and o-ethylmethylbenzene, the molar ratio of trimethyl trimesic acid ester to n-octanol is 3 to 5:1, more preferably 3.5 to 4.5:1, and most preferably 3.8 to 4.2:1.

[0037] Beneficial effects achieved by the present invention:

[0038] The method and device provided by the present invention can separate and purify effective components in refinery by-product resources, the product has a wide range of application, the added value is greatly improved, and the comprehensive utilization of precious resources is achieved. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1It is a schematic diagram of the device described in the specific implementation mode; wherein, 1. a raw material delivery pump, 2. a first light removal tower, 3. a light component delivery pump, 4. a first light removal tower kettle delivery pump, 5. a mesitylene removal tower, 6. a mesitylene enrichment delivery pump, 7. a mesitylene removal tower kettle component delivery pump, 8. a partial trimethylol distillation tower, 9. a partial trimethylol product delivery pump, 10. a partial trimethylol distillation tower kettle component delivery pump, 11. a first extractant delivery pump, 12. a mesitylene extraction distillation tower, 13. a delivery pump for enriching o-methylethylbenzene, 14. a delivery pump for the component of the mesitylene extraction distillation tower kettle, 15. a mesitylene analysis tower, 16. a mesitylene product delivery pump, 17. a mesitylene analysis tower, The first extractant delivery pump to the bottom of the tower, 18. The component delivery pump with a boiling point of 165.5-169.3℃, 19. The trimethylol removal tower, 20. The component delivery pump with a boiling point of 170-176℃, 21. The component delivery pump to the bottom of the trimethylol removal tower, 22. The trimethylol removal tower, 23. The enriched trimethylol delivery pump, 24. The component delivery pump to the bottom of the trimethylol removal tower, 25. The second extractant delivery pump, 26. The trimethylol extraction distillation tower, 27. The indane and methyl isopropylbenzene delivery pumps, 28. The component delivery pump to the bottom of the trimethylol extraction distillation tower, 29. The trimethylol analysis tower, 30. The trimethylol product delivery pump, 31. The second extractant delivery pump to the bottom of the trimethylol analysis tower.

[0040] Figure 2 The gas chromatogram of the final product trimethylol in Example 1 is shown in FIG.

[0041] Figure 3 The gas chromatogram of the final product mesitylene in Example 1 is shown in FIG.

[0042] Figure 4 The gas chromatogram of the final product trimethylol in Example 1 is shown in FIG.

[0043] Figure 5 The gas chromatogram of the final product o-methylethylbenzene in Example 1 is shown in FIG. DETAILED DESCRIPTION

[0044] In view of the deficiency in the prior art that high value-added components in C9 heavy aromatics cannot be effectively separated and purified, the present invention provides a method and device for separating a C9 aromatics mixture, so as to achieve the separation, purification and comprehensive utilization of para-trimethylbenzene, mesitylene, trimethylbenzene and o-ethylmethylbenzene components in the C9 heavy aromatics by-products of large-scale refinery aromatics complex, and achieve energy conservation, emission reduction and environmental friendliness.

[0045] The method firstly adds the reformed carbon nine heavy aromatics raw material of the refinery into a distillation tower equipped with internal parts at a certain speed, and removes light components with a lower boiling point than mesitylene under specific temperature, pressure and reflux conditions.

[0046] The carbon nine heavy aromatics with light components removed enter the distillation tower equipped with internals at a certain speed. Under specific temperature, pressure and reflux conditions, mesitylene and o-ethylmethylbenzene, which has a boiling point very close to mesitylene, evaporate from the top of the tower and enter the extractive distillation tower. In the extractive distillation tower, the binary extractant system absorbs mesitylene but not o-ethylmethylbenzene. O-ethylmethylbenzene-rich vapor evaporates from the top of the tower as a by-product. The rich liquid of the extractant that has absorbed mesitylene is sent to the decomposition tower at a certain speed. Under specific temperature, pressure and reflux conditions, high-purity mesitylene is decomposed as a product and escapes from the top of the tower. The lean extract in the bottom of the tower is returned to the extractive distillation tower for recycling.

[0047] After removing mesitylene and o-methylethylbenzene, which has a boiling point very close to mesitylene, the carbon nine heavy aromatics enter the distillation tower equipped with internals at a certain speed. Under specific temperature, pressure and reflux conditions, high-purity mesitylene products are extracted from the side line near the top of the tower. The gas phase at the top of the tower is a component with a boiling point between mesitylene and mesitylene (including o-toluene). The bottom of the tower is a component with a boiling point higher than mesitylene.

[0048] After removing the trimethylol component, the remaining carbon nine heavy aromatics enter the distillation tower equipped with internals at a certain speed. Under specific temperature, pressure and reflux conditions, the components with boiling points between trimethylol and 3-trimethylol are removed at the top of the tower. The bottom of the tower contains 3-trimethylol and components with higher boiling points than it. It is sent to the distillation tower equipped with internals at a certain speed. Under specific temperature, pressure and reflux conditions, the components evaporated from the top of the tower are 3-trimethylol and indane and p-methylisopropylbenzene with similar boiling points. It is sent to the extractive distillation tower equipped with internals at a certain speed. The bottom of the tower obtains other components with boiling points heavier than 3-trimethylol (including indane and p-methylisopropylbenzene).

[0049] In the extractive distillation tower, under specific temperature, pressure and reflux conditions, the binary extractant system absorbs trimethylol but does not absorb indane and p-methylisopropylbenzene. Indane-rich and p-methylisopropylbenzene-rich vapors are distilled out from the top of the tower as by-products. The extractant-rich liquid that has absorbed trimethylol is sent to the desorption tower at a certain speed. Under specific temperature, pressure and reflux conditions, high-purity trimethylol is desorbed and escapes from the top of the tower. The lean liquid in the bottom of the tower is returned to the extractive distillation tower for recycling.

[0050] Through the above steps, the three types of trimethylbenzenes in the reforming carbon nine raw material are completely separated, and the resources are effectively utilized to the greatest extent. The key point is that the present invention uses the different properties of the molecular structures of components with very close boiling points and difficult to separate even by super distillation to select a suitable binary system polar solvent as an extractant, and skillfully separates mesitylene from o-methylethylbenzene; and separates trimethylbenzene from indane and p-methylisopropylbenzene.

[0051] At the same time, the technical solution provided by the present invention is more suitable for industrial production, using super distillation technology, extractive distillation technology, thermal coupling technology and thermal integration technology. Specifically, the trimethylol tower is designed to be positive pressure, and the trimethylol vapor of the tower side line can be led back to the reboiler of the light tower as a heat source to form thermal coupling; the o-ethylmethylbenzene vapor at the top of the mesitylene extractive distillation tower is led back to the reboiler heat source of the tri-trimethylol tower to form thermal coupling; the indane and p-methylisopropylbenzene vapor at the top of the tri-trimethylol extractive distillation tower are led back to the reboiler heat source of the tri-trimethylol tower to form thermal coupling; the steam condensate is collected according to the temperature ladder and used as a preheating heat source and a heating heat source for feeding multiple sections of raw materials and semi-finished products, so as to form an effective utilization of energy ladder. It saves energy consumption and effectively reduces production costs. The entire production process is easy to control and runs continuously and smoothly. It has high separation accuracy, high product purity, reliable product quality, and high yield of target products. It can be widely used in large-scale refineries to separate high-value-added trimethylbenzene, mesitylene and trimethylbenzene from by-product reforming carbon nine aromatics, so as to achieve efficient and comprehensive utilization of precious resources.

[0052] In a preferred embodiment, Figure 1 As shown, the device for separating a carbon nine aromatic hydrocarbon mixture provided by the present invention comprises a raw material delivery pump 1, a first light component removal tower 2, a light component delivery pump 3, a first light component removal tower kettle delivery pump 4, a mesitylene removal tower 5, a mesitylene enrichment delivery pump 6, a mesitylene removal tower kettle component delivery pump 7, a partial trimethylol distillation tower 8, a partial trimethylol product delivery pump 9, a partial trimethylol distillation tower kettle component delivery pump 10, a first extractant delivery pump 11, a mesitylene extractive distillation tower 12, an enrichment o-methylethylbenzene delivery pump 13, a mesitylene extractive distillation tower kettle component delivery pump 14, a mesitylene analysis tower 15, a mesitylene product delivery pump 16, a mesitylene analysis tower 17, a mesitylene product delivery pump 18, and a mesitylene analysis tower 19. The first extractant delivery pump 17 for the tower bottom, the component delivery pump 18 with a boiling point of 165.5 to 169.3°C, the trimethylol light-removal tower 19, the component delivery pump 20 with a boiling point of 170 to 176°C, the trimethylol light-removal tower bottom component delivery pump 21, the trimethylol removal tower 22, the trimethylol enrichment delivery pump 23, the trimethylol removal tower bottom component delivery pump 24, the second extractant delivery pump 25, the trimethylol extractive distillation tower 26, the indane and methyl isopropylbenzene delivery pump 27, the trimethylol extractive distillation tower bottom component delivery pump 28, the trimethylol analysis tower 29, the trimethylol product delivery pump 30, and the second extractant delivery pump 31 for the trimethylol analysis tower bottom.

[0053] A feed port for a carbon nine aromatic hydrocarbon mixture is provided on the side of the first light-removal tower 2, and a discharge port of the bottom of the first light-removal tower 2 is connected to a feed port for a raw material of the mesitylene removal tower 5;

[0054] The top discharge port of the mesitylene removal tower 5 is connected to the raw material feed port of the mesitylene extraction distillation tower 12;

[0055] The mesitylene extraction distillation tower 12 is provided with a first extractant feed port, the top discharge port of the mesitylene extraction distillation tower 12 leads out the o-methylethylbenzene product, and the bottom discharge port is connected to the raw material feed port of the mesitylene analysis tower 15;

[0056] The bottom discharge port of the mesitylene removal tower 5 is connected to the raw material feed port of the para-trimethylbenzene distillation tower 8;

[0057] The trimethylolbenzene distillation tower 8 is provided with a side discharge port, and the side discharge port leads out the trimethylolbenzene product. The bottom discharge port of the trimethylolbenzene distillation tower 8 is connected to the raw material feed port of the trimethylolbenzene light removal tower 19;

[0058] The bottom discharge port of the trimethylol removal tower 19 is connected to the raw material feed port of the trimethylol removal tower 22;

[0059] The top discharge port of the trimethylol removal tower 22 is connected to the raw material feed port of the trimethylol extraction distillation tower 26;

[0060] The trimethylol extractive distillation tower 26 is provided with a second extractant feed port, the top discharge port of the trimethylol extractive distillation tower 26 is used to discharge methyl isopropylbenzene and indane, and the bottom discharge port is connected to the raw material feed port of the trimethylol analytical tower 29;

[0061] The top outlet of the trimethylol analysis tower 29 draws out the trimethylol product.

[0062] In a preferred embodiment, the parameters of the first light-removal tower 2 include: an inner diameter of 3.8 meters, a CHAOPAK6.0 high-efficiency structured packing height of 40 meters (divided into nine sections, with supporting distributors, support rings and other internal parts), a theoretical plate number of 100, and a tower body tangent height of 58.5 meters;

[0063] The parameters of the mesitylene removal tower 5 include: an inner diameter of 2.6 meters, a CHAOPAK 6.0 high-efficiency structured packing height of 44 meters (divided into eight sections, with supporting distributors, support rings and other internal parts), a theoretical plate number of 86, and a tower body tangent height of 62 meters;

[0064] The parameters of the para-trimethylbenzene distillation tower 8 include: an inner diameter of 2.2 meters, a ZUPAK5.0 high-efficiency structured packing height of 34 meters (divided into nine sections, with matching distributors, support rings and other internal parts), 76 theoretical plates, and a tower tangent height of 44.6 meters; the side discharge port of the para-trimethylbenzene distillation tower 8 is located at the lower liquid collecting tray of the second section packing;

[0065] The parameters of the mesitylene extractive distillation tower 12 include: an inner diameter of 1.6 meters, a CHAOPAK5.0 high-efficiency structured packing height of 22 meters (divided into five sections, with supporting distributors, support rings and other internal parts), 40 theoretical plates, and a tower body tangent height of 28 meters;

[0066] The mesitylene analysis tower 15 has an inner diameter of 1.2 meters, a ZUPAK5.0 high-efficiency structured packing height of 18.6 meters (divided into four sections, with supporting distributors, support rings and other internal parts), 32 theoretical plates, and a tower tangent height of 24.4 meters;

[0067] The inner diameter of the trimethylol delightening tower 19 is 2 meters, the height of CHAOPAK6.0 high-efficiency structured packing is 28.5 meters (divided into five sections, with supporting distributors, support rings and other internal parts), the number of theoretical plates is 60, and the tower body tangent height is 33.6 meters;

[0068] The toluene removal tower 22 has an inner diameter of 1.0 m, a CHAOPAK6.0 high-efficiency structured packing height of 26.6 m (divided into eight sections, with supporting distributors, support rings and other internal parts), 50 theoretical plates, and a tower body tangent height of 33.6 m;

[0069] The parameters of the trimethylol extractive distillation tower 26 include: an inner diameter of 1.4 meters, a CHAOPAK5.0 high-efficiency structured packing height of 23.6 meters (divided into five sections, with supporting distributors, support rings and other internal parts), 42 theoretical plates, and a tower tangent height of 30 meters;

[0070] The trimethylol analysis tower 29 has an inner diameter of 1.0 m, a ZUPAK5.0 high-efficiency structured packing height of 16.8 m (divided into four sections, with supporting distributors, support rings and other internal parts), 30 theoretical plates, and a tower body tangent height of 22.6 m.

[0071] The above-mentioned CHAOPAK and ZUPAK high-efficiency structured packings come from Tianjin Tianda Tianjiu Technology Co., Ltd.

[0072] The above towers are equipped with reboiler / condenser / reflux tank / reflux pump-metering delivery system, which is the equipment required for standard (super) distillation unit. All delivery units are chemical process pumps.

[0073] The method for separating a C9 aromatics mixture using the above device comprises the following steps:

[0074] (1) The by-product reformed carbon nine heavy aromatics of the refinery are fed into the first light removal tower 2 at a rate of 80-120 kmol / h. Under the operating conditions of tower top pressure of 10-20 kPa.A, temperature of 95-115°C, and reflux ratio of 3-4:1, the components with a boiling point lower than 164.5°C (i.e., components lower than mesitylene) are removed from the tower top, which can be used as SA1000# aromatic solvent product. The mesitylene content entrained in the tower top components is lower than 2% (wt). The tower bottom contains mesitylene and components with higher boiling points than mesitylene, and the light component content is lower than 0.5%. The heating heat source for the initial operation of the first light removal tower 2 is external steam. After the mesitylene distillation tower 8 is normal, the mesitylene steam is introduced as the heating heat source;

[0075] (2) The bottom components obtained from the first light-removal tower 2 are fed into the mesitylene removal tower 5 at a rate of 60-90 kmol / h. Under the operating conditions of a top pressure of 5-10 kPa.A, a temperature of 105-118°C, and a reflux ratio of 4-4.8:1, mesitylene and o-methylethylbenzene components with a boiling point close to mesitylene are removed from the top of the tower to form a mesitylene-enriched liquid (the total content of the two components is ≥99.5%wt). The bottom of the tower contains components with a boiling point higher than 165.5°C (i.e., aromatic components with a boiling point higher than that of mesitylene and o-methylethylbenzene), the content of mesitylene is less than 2% (wt), and the heating heat source is the low-pressure steam flashed from the medium-pressure condensate, forming the first heat integration of the present invention;

[0076] (3) The bottom components of the mesitylene removal tower 5 are fed into the mesitylene distillation tower 8 at a rate of 50-80 kmol / h. Under the operating conditions of a top pressure of 110-150 kPa.A, a temperature of 180-200°C, and a reflux ratio of 10-15:1, the top of the tower is a mixture of components with a boiling point between 165.5-169.3°C (i.e., components with a boiling point between mesitylene and mesitylene (including o-methylethylbenzene)), and the content of mesitylene is less than 3.5% (wt). The mesitylene product with a purity exceeding 99% (wt) is extracted at the side line outlet, i.e., the lower part of the second stage filler, with a yield of ≥91%, and enters the reboiler of the first light-removal tower 2 as a heat source, forming the maximum heat coupling of the present invention, and is extracted as a product after all the latent heat and part of the sensible heat are absorbed. The bottom of the tower is a component with a boiling point higher than 170°C, and the content of mesitylene is less than 2% (wt). The heating steam of the bottom of the tower uses external medium-pressure steam as a heat source;

[0077] (4) The top component of the mesitylene removal tower 5 is fed into the mesitylene extraction distillation tower 12 at a rate of 10 to 15 kmol / h. Under the operating conditions of a top pressure of 110 to 150 kPa.A, a temperature of 170 to 180°C, and a reflux ratio of 10 to 15:1, a binary mixed solvent of trimethyl trimesic acid and n-octanol is used as an extractant, the molar ratio of trimethyl trimesic acid to n-octanol is 3 to 5:1, and the molar ratio of the extraction solvent to mesitylene is 8 to 12:1. The top of the extractive distillation tower is the by-product of o-methylethylbenzene that is not absorbed by the solvent, with a purity of ≥98% (wt), and the content of mesitylene is less than 2% (wt). The bottom of the tower is a mixture of the binary extraction solvent and mesitylene, and the heating steam of the bottom of the tower uses external medium-pressure steam as a heat source;

[0078] (5) The bottom components of the mesitylene extraction distillation tower 12 are fed into the mesitylene analysis tower 15 at a rate of 30-40 kmol / h. Under the operating conditions of a top pressure of 20-50 kPa.A, a temperature of 110-125°C, and a reflux ratio of 3-4:1, the top of the tower is a mesitylene product with a purity of ≥99% (wt), and the bottom of the tower is a regenerated binary extraction solvent, which is recycled back to the mesitylene extraction distillation tower 12 for use, and the yield of mesitylene is ≥85% (relative to the content in the raw material, wt);

[0079] (6) The bottom components of the trimethylol distillation tower 8 are fed into the trimethylol light removal tower 19 at a rate of 20-30 kmol / h. Under the operating conditions of the top pressure of 2-12 kPa.A, the temperature of 120-140°C, and the reflux ratio of 5-8:1, a light component mixture with a boiling point between 170 and 176°C (i.e., a light component between trimethylol and trimethylol (including indane and p-methylisopropylbenzene)) is produced at the top of the tower, and the trimethylol content is less than 2% (wt). The bottom of the tower is a component with a boiling point higher than 176°C (i.e., enriched with trimethylol and carbon nine aromatic components with a higher boiling point than it), and the light component content is less than 0.5% (wt);

[0080] (7) The bottom components of the trimethylol light toluene removal tower 19 are fed into the trimethylol removal tower 22 at a rate of 15-20 kmol / h. Under the operating conditions of tower top pressure of 5-10 kPa.A, temperature of 105-118°C, and reflux ratio of 4-4.8:1, the top of the tower is trimethylol rich liquid formed by trimethylol and p-methylisopropylbenzene and indane with similar boiling points, and the total content of the three components is ≥99.6% (wt). The bottom of the tower is the component with a boiling point higher than 177.2°C (i.e., the heavy carbon nine aromatic component) as a by-product, and the content of trimethylol is less than 2% (wt);

[0081] (8) The top component of the mesitylene removal tower 22 is fed into the mesitylene extraction distillation tower 26 at a rate of 8 to 12 kmol / h. Under the operating conditions of a top pressure of 110 to 150 kPa.A, a temperature of 170 to 180°C, and a reflux ratio of 10 to 15:1, a binary mixed solvent of 3,4,5-trimethylphenol and n-octanol is used as an extractant, the molar ratio of 3,4,5-trimethylphenol to n-octanol is 1.5 to 2.5:1, and the molar ratio of the extraction solvent to mesitylene is 6 to 8:1; the top of the tower contains p-methylisopropylbenzene and indane components that are not absorbed by the solvent, the content of mesitylene is less than 2% (wt), the bottom of the tower is a mixture of the binary extraction solvent and mesitylene, and the heating steam of the bottom of the tower uses external medium-pressure steam as a heat source;

[0082] (9) The bottom components of the trimethylol extractive distillation tower 26 are fed into the trimethylol analytical tower 29 at a rate of 30-40 kmol / h. Under the operating conditions of a top pressure of 10-40 kPa.A, a temperature of 115-135°C, and a reflux ratio of 4-6:1, a trimethylol product with a purity of ≥99% (wt) is produced at the top of the tower, and the trimethylol yield is ≥82% (relative to the content in the raw material, wt). The bottom of the tower is the regenerated binary extraction solvent, which is recycled back to the trimethylol extractive distillation tower 26 for use.

[0083] Through the above steps, the by-product carbon nine components of the refinery aromatics complex, including para-trimethylbenzene, mesitylene, trimethylbenzene and o-ethylmethylbenzene, can be completely separated, and the high value-added single component can be purified to the maximum extent.

[0084] In a preferred embodiment, in the above steps, the trimethylol distillation tower 8 is operated at positive pressure, and the refined trimethylol vapor from the side line of the tower can be introduced back to the reboiler of the first light removal tower 2 as a heat source to form a first thermal coupling, and then returned to the trimethylol reflux tank.

[0085] In a preferred embodiment, in the above steps, the mesitylene extraction distillation tower 12 is operated at positive pressure, and the by-product o-methylethylbenzene vapor at the top of the tower can be introduced back to the reboiler of the mesitylene removal tower 5 as a heat source to form a second thermal coupling, and then returned to the o-methylethylbenzene reflux tank.

[0086] In a preferred embodiment, in the above steps, the trimethylol extractive distillation tower 26 is operated at positive pressure, and the indane-rich and methyl isopropylbenzene vapors at the top of the tower can be led back to the reboiler of the trimethylol remover tower 22 as a heat source to form a third thermal coupling, and then returned to the reflux tank of the trimethylol extractive distillation tower 26.

[0087] In a preferred embodiment, in the above step (1), the operating pressure of the kettle of the first light-removing tower 2 is 20-24 kPa, and the kettle temperature control range is 130-135°C. The purpose of such control is to remove components with a boiling point lower than 164.5°C from the components in the kettle to ensure that the mesitylene product is qualified; the operating pressure of the top of the tower is 12-16 kPa, the top temperature control range is 98-105°C, and the reflux ratio is 3.2-3.7:1. The purpose of such control is to control the amount of mesitylene removed from here to ensure that the comprehensive yield of the target product is ≥85% (wt). The low-pressure steam of the pipeline network is used as the heating source for the kettle of the first light-removing tower 2 when it is started up. After the mesitylene refining tower is started up normally, the oil and gas at the top of the tower are introduced as the heat source to form thermal coupling.

[0088] In a preferred embodiment, in the above step (2), the operating pressure of the kettle of the mesitylene removal tower 5 is 15-20 kPa, and the kettle temperature control range is 135-140°C. The purpose of such control is to remove the mesitylene + o-methylethylbenzene components from the tower kettle components as much as possible to ensure that the comprehensive yield of the mesitylene target product is ≥85% (wt); the operating pressure of the tower top is 6-8 kPa, the top temperature control range is 108-112°C, and the reflux ratio is 4.2-4.6:1. The purpose of such control is to control the purity of the mesitylene + o-methylethylbenzene in the tower top distillation group to be ≥99.5% to ensure that the mesitylene product is of qualified quality. The heating heat source of the kettle of the mesitylene removal tower 5 uses the low-pressure steam of the pipeline network when starting up, and the by-product o-methylethylbenzene steam from the top of the mesitylene extraction distillation tower 12 is used after the whole plant is normal.

[0089] In a preferred embodiment, in the above step (3), the operating pressure of the bottom of the paratrimethylbenzene distillation tower 8 is 130-150 kPa, and the control range of the bottom temperature is 195-205°C. The purpose of such control is to remove the paratrimethylbenzene component from the bottom components as much as possible, so as to ensure that the comprehensive yield of the paratrimethylbenzene target product extracted from the liquid collecting tray at the lower part of the second stage of the packing of the paratrimethylbenzene distillation tower 8 is ≥91% (wt); the operating pressure of the top of the tower is 120-140 kPa, the top temperature control range is 188-195°C, and the reflux ratio is 11.5-13.5:1. The purpose of such control is to control the paratrimethylbenzene content in the top distillation group to be ≤2%, so as to ensure that the comprehensive yield of the paratrimethylbenzene target product is ≥91% (wt).

[0090] In a preferred embodiment, in the above step (4), the operating pressure of the bottom of the mesitylene extractive distillation tower 12 is 125-140 kPa, and the control range of the bottom temperature is 208-215°C. The purpose of such control is to remove the o-methylethylbenzene component from the bottom components as much as possible to ensure that the mesitylene product is of qualified quality; the operating pressure of the top of the tower is 115-130 kPa, the top temperature control range is 172-178°C, and the reflux ratio is 14-14.6:1. The purpose of such control is to ensure that the mesitylene content in the o-methylethylbenzene product distilled from the top of the tower is ≤2% (wt), so as to ensure that the comprehensive yield of the target mesitylene product is ≥85% (wt).

[0091] In a preferred embodiment, in the above step (5), the operating pressure of the kettle of the mesitylene decomposition tower 15 is 33-48 kPa.A, and the kettle temperature control range is 130-145°C. The purpose of such control is to completely parse out the mesitylene in the extraction solvent to ensure that the comprehensive yield of the mesitylene product is ≥85% (wt); the operating pressure of the tower top is 25-40 kPa.A, the top temperature control range is 115-120°C, and the reflux ratio is 3.2-3.8:1. The purpose of such control is to ensure that the purity of the mesitylene product distilled from the tower top is ≥99% (wt).

[0092] In a preferred embodiment, in the above step (6), the operating pressure of the bottom of the trimethylol removal tower 19 is 10-20 kPa, and the control range of the bottom temperature is 140-155°C. The purpose of such control is to remove the components with a boiling point lower than 176°C from the bottom components to ensure that the trimethylol product is qualified; the operating pressure of the top of the tower is 5-9 kPa, the top temperature control range is 125-135°C, and the reflux ratio is 6-7:1. The purpose of such control is to control the amount of trimethylol removed from here to ensure that the comprehensive yield of the target product is ≥82% (wt).

[0093] In a preferred embodiment, in the above step (7), the operating pressure of the kettle of the trimethylol removal tower 22 is 15-20 kPa, and the kettle temperature control range is 130-140°C. The purpose of such control is to remove trimethylol and indane and p-methylisopropylbenzene components with very close boiling points from the components in the kettle as much as possible, so as to ensure that the comprehensive yield of the trimethylol target product is ≥82% (wt); the operating pressure of the tower top is 6-8 kPa, the top temperature control range is 108-116°C, and the reflux ratio is 4.2-4.6:1. The purpose of such control is to control the total content of trimethylol and indane + p-methylisopropylbenzene with very close boiling points in the tower top distillation group to be ≥99.6% (wt), so as to ensure that the trimethylol product quality is qualified. The heating heat source of the kettle of the trimethylol removal tower 22 uses the low-pressure steam of the pipeline network when starting up, and the gas phase of the top of the trimethylol extraction distillation tower 26 is used after the whole plant is normal.

[0094] In a preferred embodiment, in the above step (8), the operating pressure of the bottom of the trimethylol extractive distillation tower 26 is 130-150 kPa, and the control range of the bottom temperature is 185-205°C. The purpose of such control is to remove the indane + p-methylisopropylbenzene component from the bottom components as much as possible to ensure that the trimethylol product is of qualified quality; the operating pressure of the top of the tower is 120-140 kPa, the top temperature control range is 172-176°C, and the reflux ratio is 11-12:1. The purpose of such control is to ensure that the trimethylol content in the top distillate is ≤2% (wt) to ensure that the comprehensive yield of the target trimethylol product is ≥82% (wt).

[0095] In a preferred embodiment, in the above step (9), the operating pressure of the kettle of the trimethylol decomposition tower 29 is 25-40 kPa.A, and the kettle temperature control range is 135-150°C. The purpose of such control is to completely decompose the trimethylol in the extraction solvent to ensure that the comprehensive yield of the trimethylol product is ≥82% (wt); the operating pressure of the tower top is 15-30 kPa.A, the top temperature control range is 120-130°C, and the reflux ratio is 4.5-5.5:1. The purpose of such control is to ensure that the purity of the trimethylol product distilled from the tower top is ≥99% (wt).

[0096] In specific engineering practice, medium-pressure steam and low-pressure steam condensate are collected according to temperature levels and used as preheating heat sources and heating heat sources for multiple stages of raw materials and semi-finished product feeds, thus achieving full and effective utilization of energy.

[0097] The method provided by the invention makes the entire distillation process safe, efficient, environmentally friendly, energy-saving, highly integrated and economical.

[0098] The present invention is further described in detail below with reference to specific embodiments, but is not intended to limit the scope of the present invention.

[0099] Example 1

[0100] Follow the steps below to separate unsymmetrical trimethylol, mesitylene and trimethylol from the C9 heavy aromatics feedstock in the refinery reforming plant and produce o-ethylmethylbenzene as a by-product:

[0101] (1) The reformed C9 heavy aromatics raw material from the refinery is fed into the first light-removal tower 2 at a feed rate of 10 t / h. The operating conditions of the first light-removal tower 2 are: a kettle temperature of 133°C, a top temperature of 100°C; a top pressure of 15 KPa.A; a reflux ratio of 3.5; the amount of light components delivered by the light component delivery pump 3 is 1.65 t / h, and the amount delivered by the first light-removal tower kettle delivery pump 4 to the mesitylene removal tower 5 is 8.35 t / h;

[0102] (2) The operating conditions of the mesitylene removal tower 5 are: kettle temperature 138° C., top temperature 111° C.; top pressure 7 KPa.A; reflux ratio 4.5; the amount of the mesitylene-rich component output by the mesitylene enrichment pump 6 sent to the mesitylene extraction distillation tower 12 is 1.62 t / h; the feed amount of the mesitylene removal tower kettle component delivery pump 7 sent to the partial trimethylol distillation tower 8 is 6.73 t / h;

[0103] (3) The operating conditions of the trimethylol distillation tower 8 are: kettle temperature 211°C, top temperature 192°C, side line outlet temperature 190°C; top pressure 133KPa.A; reflux ratio 12. The side line trimethylol product delivery pump 9 extracts 4.11 t / h of trimethylol product, the amount of narrow-cut aromatic solvent SA1000#-A with a boiling point of 165.5-169.3°C delivered by the component delivery pump 18 is 0.86 t / h, and the feed amount delivered by the trimethylol distillation tower kettle component delivery pump 10 to the trimethylol light removal tower 19 is 1.76 t / h. Calculated based on the trimethylol content in the feed raw material, the trimethylol product yield is 92.32% (wt);

[0104] (4) The operating conditions of the mesitylene extraction distillation tower 12 are: kettle temperature 195°C, top temperature 175°C; top pressure 122 KPa.A; reflux ratio 14; the molar ratio of trimethyl trimesic acid to n-octanol in the extraction solvent is 4:1, and the molar ratio of the extraction solvent to mesitylene is 10:1. The amount of by-product o-methylethylbenzene product output by the o-methylethylbenzene enrichment delivery pump 13 is 0.65 t / h, and the feed rate sent by the mesitylene extraction distillation tower kettle component delivery pump 14 to the mesitylene analysis tower 15 is 24.18 t / h;

[0105] (5) The operating conditions of the mesitylene analysis tower 15 are: kettle temperature 140°C, top temperature 118°C; top pressure 30KPa.A; reflux ratio 3.5. The amount of mesitylene product output by the mesitylene product delivery pump 16 is 0.92t / h, and the amount of extraction solvent sent to the mesitylene extraction distillation tower 12 for recycling by the first extractant delivery pump 17 of the mesitylene analysis tower kettle is 23.26t / h. Calculated based on the mesitylene content in the feed raw material, the mesitylene product yield is 86.71% (wt);

[0106] (6) The operating conditions of the trimethylol light-removal tower 19 are: a kettle temperature of 148°C, a top temperature of 130°C; a top pressure of 8 kPa.A; a reflux ratio of 6; a boiling point of 170-176°C component delivery pump 20 outputs 0.45 t / h of light components, and a trimethylol light-removal tower kettle component delivery pump 21 delivers 1.31 t / h of light components to the trimethylol light-removal tower 22;

[0107] (7) The operating conditions of the trimethylol removal tower 22 are: kettle temperature 135° C., top temperature 110° C.; top pressure 6 KPa.A; reflux ratio 4.6; the amount of the trimethylol rich component output by the trimethylol enrichment delivery pump 23 sent to the trimethylol extractive distillation tower 26 is 1.05 t / h, and the amount of the trimethylol removal tower kettle component delivery pump 24 sent to the storage tank area is 0.26 t / h;

[0108] (8) The operating conditions of the mesitylene extraction distillation tower 26 are: kettle temperature 200°C, top temperature 175°C; top pressure 130 KPa.A; reflux ratio 11; the molar ratio of 3,4,5-trimethylphenol to n-octanol in the extraction solvent is 2:1, and the molar ratio of the extraction solvent to mesitylene is 7:1. The amount of the methyl isopropylbenzene and indane-rich stream output by the indane and methyl isopropylbenzene delivery pump 27 is 0.32 t / h, and the feed amount sent by the mesitylene extraction distillation tower kettle component delivery pump 28 to the mesitylene analysis tower 29 is 6.44 t / h;

[0109] (9) The operating conditions of the trimethylol decomposition tower 29 are: kettle temperature 145°C, top temperature 126°C; top pressure 20 KPa.A; reflux ratio 5. The amount of trimethylol product output by the trimethylol product delivery pump 30 is 0.71 t / h, and the amount of extraction solvent sent to the trimethylol extraction distillation tower 26 for recycling by the second extractant delivery pump 31 of the trimethylol decomposition tower kettle is 5.73 t / h. Calculated based on the trimethylol content in the feed raw material, the trimethylol product yield is 82.35% (wt).

[0110] (10) Thermal coupling

[0111] The first thermal coupling is to introduce the steam from the top of the trimethylbenzene distillation tower 8 into another reboiler of the first light removal tower 2 as a heat source, and then return to the reflux tank of the trimethylbenzene distillation tower 8 after completely releasing latent heat and part of sensible heat and turning into liquid phase. The reboiler of the first light removal tower 2 using low-pressure steam as a heat source is completely stopped, saving 6.35t / h of low-pressure steam.

[0112] The second thermal coupling is to introduce the steam from the top of the mesitylene extraction distillation tower 12 into another reboiler of the mesitylene removal tower 5 as a heat source, and then return to the reflux tank of the mesitylene extraction distillation tower 12 after completely releasing latent heat and part of sensible heat and turning into liquid phase. The reboiler of the mesitylene removal tower 5 using low-pressure steam as a heat source is completely stopped, saving 3.66t / h of low-pressure steam.

[0113] The third thermal coupling is to introduce the steam from the top of the trimethylol extracting and distilling tower 26 into another reboiler of the trimethylol extracting and distilling tower 22 as a heat source, and then return to the reflux tank of the trimethylol extracting and distilling tower 26 after completely releasing latent heat and part of sensible heat and turning into liquid phase. The reboiler of the trimethylol extracting and distilling tower 22 using low-pressure steam as a heat source is completely stopped, saving 2.2 t / h of low-pressure steam.

[0114] (11) Thermal integration (I)

[0115] After all the medium-pressure condensate is collected, it is introduced into the low-pressure steam flash tank, and the low-pressure steam flashed out is incorporated into the low-pressure steam pipeline network for use.

[0116] (12) Thermal Integration (II)

[0117] In industrial equipment, the heat exchange between the feed to be heated and the discharge to be cooled can not only reduce the steam consumption, but also reduce the consumption of circulating water. Materials at various temperatures are gradually heated or cooled according to the temperature ladder. Although the process becomes relatively complicated and the initial investment is high, the energy saved in long-term operation is very considerable.

[0118] The condensate produced by low-pressure steam can also be reasonably utilized in stages according to different temperature levels.

[0119] This example further tests the three final products and one by-product obtained. The tests are specifically:

[0120] (1) According to the method specified in HS / T-2016 Customs Industry Standard of the People's Republic of China, the three end products and one by-product were measured using an Agilent GC-7890 gas chromatograph. The specific parameters include: FID detector: 7×10 -6 mg / ml, PEG-20M capillary column; column temperature: 40℃ / 4min to 80℃ / 8min; heating rate: 22℃ / min; vaporization chamber temperature: 188℃; split ratio: 120:1, solvent: toluene;

[0121] The chromatogram of the final product trimethylol is as follows Figure 2 shown.

[0122] The analysis result is: the purity of trimethylol in the final product is 99.32% (wt).

[0123] The chromatogram of the final product mesitylene is as follows Figure 3 shown.

[0124] The analysis result is: the purity of mesitylene in the final product is 99.09% (wt).

[0125] The chromatogram of the final product trimethylol is as follows Figure 4 shown.

[0126] The analysis results showed that the purity of trimethylol in the final product was 99.16% (wt).

[0127] The chromatogram of the byproduct o-methylethylbenzene is as follows Figure 5 shown.

[0128] The analysis results showed that the purity of the by-product o-ethylmethylbenzene was 95.56% (wt).

[0129] Example 2

[0130] Compared with Example 1, the difference is that the molar ratio of trimethyl trimesic acid to n-octanol in the extraction solvent of step (4) is 3:1.

[0131] The three final products and one by-product were tested, and the results were as follows:

[0132] The purity of trimethylol in the final product is 99.29% (wt);

[0133] The purity of mesitylene in the final product is 98.63% (wt);

[0134] The purity of trimethylol in the final product is 99.10% (wt);

[0135] The purity of the by-product o-ethylmethylbenzene is 93.28% (wt).

[0136] Compared with Example 1, the yield of mesitylene decreased (relative to the content in the raw material) to 80.29%, a decrease of 6.42%; the yield of o-ethylmethylbenzene decreased (relative to the content in the raw material) by about 10%.

[0137] Example 3

[0138] Compared with Example 1, the difference is that the molar ratio of trimethyl trimesic acid to n-octanol in the extraction solvent of step (4) is 5:1.

[0139] The three final products and one by-product were tested, and the results were as follows:

[0140] The purity of trimethylol in the final product is 99.25% (wt);

[0141] The purity of mesitylene in the final product is 98.68% (wt);

[0142] The purity of trimethylol in the final product is 99.20% (wt);

[0143] The purity of the by-product o-ethylmethylbenzene is 95.61% (wt).

[0144] Compared with Example 1, the yield of mesitylene increased (relative to the content in the raw material) to 86.92%, an increase of 0.21%; the yield of o-methylethylbenzene increased (relative to the content in the raw material) by about 1%; but the energy consumption of the whole device increased by about 6.5%, showing a relatively large negative correlation in terms of economy. And the purity of the mesitylene product decreased to below 99%.

[0145] Example 4

[0146] Compared with Example 1, the difference is that the molar ratio of 3,4,5-trimethylphenol to n-octanol in the extraction solvent of step (8) is 1.5:1.

[0147] The three final products and one by-product were tested, and the results were as follows:

[0148] The purity of trimethylol in the final product is 99.18% (wt);

[0149] The purity of mesitylene in the final product is 99.12% (wt);

[0150] The purity of trimethylol in the final product is 99.21% (wt);

[0151] The purity of the by-product o-ethylmethylbenzene is 95.37% (wt).

[0152] Compared with Example 1, the trimethylol yield decreased (relative to the content in the raw material) to 76.54%, a decrease of 5.81%, which is a large decrease.

[0153] Example 5

[0154] Compared with Example 1, the difference is that the molar ratio of 3,4,5-trimethylphenol to n-octanol in the extraction solvent of step (8) is 2.5:1.

[0155] The three final products and one by-product were tested, and the results were as follows:

[0156] The purity of trimethylol in the final product is 99.22% (wt);

[0157] The purity of mesitylene in the final product is 99.06% (wt);

[0158] The purity of trimethylol in the final product is 98.39% (wt);

[0159] The purity of the by-product o-ethylmethylbenzene is 95.44% (wt).

[0160] Compared with Example 1, the trimethylol yield increased (relative to the content in the raw material) to 83.02%, an increase of 0.67%; however, the energy consumption of the whole device increased by about 5.35%, showing a relatively large negative correlation in terms of economy. And the product purity dropped to below 99%.

[0161] Although the present invention has been described in detail above by general description, specific implementation methods and experiments, it is obvious to those skilled in the art that some modifications or improvements can be made to the present invention. Therefore, these modifications or improvements made without departing from the spirit of the present invention all belong to the scope of protection claimed by the present invention.

Claims

1. A method for separating a mixture of carbon nine aromatic hydrocarbons, characterized in that: The carbon nine aromatic hydrocarbon mixture contains mesitylene and o-ethylmethylbenzene, and the method comprises the following steps: (1) introducing a C9 aromatics mixture into a first light-removal tower, drawing out light components with a boiling point lower than 164.5°C from the top of the first light-removal tower, and drawing out heavy components containing mesitylene and o-ethylmethylbenzene from the bottom of the tower; (2) introducing the heavy components described in step (1) into a mesitylene removal tower, drawing out light components containing mesitylene and o-methylethylbenzene from the top of the mesitylene removal tower, and drawing out heavy components with a boiling point higher than 165.5° C. from the bottom of the tower; (3) introducing the light component containing mesitylene and o-methylethylbenzene described in step (2) into a mesitylene extractive distillation tower, performing extractive distillation in the presence of a first extractant, drawing out o-methylethylbenzene product from the top of the mesitylene extractive distillation tower, and drawing out heavy components containing the first extractant and mesitylene from the bottom of the tower; Wherein, the first extractant is a mixed solution including trimethyl trimesic acid and n-octanol, and the molar ratio of trimethyl trimesic acid to n-octanol is 3.8-4.2:

1.

2. The method for separating a mixture of carbon nine aromatic hydrocarbons according to claim 1, characterized in that: The following steps are also included: The heavy component containing the first extractant and mesitylene described in step (3) is introduced into a mesitylene analysis tower, and the mesitylene product is drawn out from the top of the mesitylene analysis tower, and the first extractant is drawn out from the bottom of the tower.

3. The method for separating a mixture of carbon nine aromatic hydrocarbons according to claim 1 or 2, characterized in that: The C9 aromatic hydrocarbon mixture further contains unsymmetrical trimethylol, trimethylol and at least one selected from p-methylisopropylbenzene and indane, and the method further comprises the following steps: (4) introducing the heavy components with a boiling point higher than 165.5° C. described in step (2) into a trimethylolbenzene distillation tower, drawing out a trimethylolbenzene product from a side line of the trimethylolbenzene distillation tower, drawing out a light component with a boiling point between 165.5° C. and 169.3° C. from the top of the tower, and drawing out a heavy component with a boiling point higher than 170° C. from the bottom of the tower; (5) introducing the heavy components with a boiling point higher than 170° C. described in step (4) into a trimethylol light-removal tower, drawing out light components with a boiling point between 170° C. and 176° C. from the top of the trimethylol light-removal tower, and drawing out heavy components with a boiling point higher than 176° C. from the bottom of the tower; (6) introducing the heavy components with a boiling point higher than 176° C. in step (5) into a trimethylol removal tower, drawing out light components containing trimethylol and at least one selected from p-methylisopropylbenzene and indane from the top of the tower, and drawing out the heavy components with a boiling point higher than 177.2° C. from the bottom of the tower; (7) introducing the light component in step (6) into a trimethylol extractive distillation tower, performing extractive distillation in the presence of a second extractant, drawing out at least one selected from p-methyl cumene and indane from the top of the trimethylol extractive distillation tower, and drawing out a heavy component containing the second extractant and trimethylol from the bottom of the tower; The second extractant is a mixed solution of 3,4,5-trimethylphenol and n-octanol, and the molar ratio of 3,4,5-trimethylphenol to n-octanol is 1.8-2.2:

1.

4. The method for separating a mixture of carbon nine aromatic hydrocarbons according to claim 3, characterized in that: The following steps are also included: The heavy component containing the second extractant and trimethylol described in step (7) is introduced into a trimethylol analysis tower, and the trimethylol product is drawn out from the top of the trimethylol analysis tower, and the second extractant is drawn out from the bottom of the tower.

5. A method for separating mesitylene and o-methylethylbenzene, characterized in that: The method comprises the following steps: extracting and rectifying a system containing mesitylene and o-ethylmethylbenzene in the presence of an extractant, wherein the extractant is a mixed solution of trimethyl trimesic acid ester and n-octanol, and the molar ratio of the trimethyl trimesic acid ester to n-octanol is 3.8-4.2:1.

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