Process for efficiently extracting aromatic hydrocarbon-rich components in catalytic diesel oil by composite extraction agent-back extraction composite method

Abstract

The invention provides a process for efficiently extracting an aromatic hydrocarbon-rich component in catalytic cracking diesel oil by a composite extraction agent-back extraction composite method, and aims to obtain the aromatic hydrocarbon-rich component with high purity and high yield. The process comprises the following steps: fully contacting a raw material with a composite extraction agent in a mixing coalescer, and separating under the action of fiber bundles to obtain an aromatic hydrocarbon-rich component and an alkane-rich component; the aromatic hydrocarbon-rich component enters the next mixing coalescer to be subjected to a back extraction treatment process, and the aromatic hydrocarbon-rich component material obtained through the reaction enters the mixing settling tank to be subjected to a secondary back extraction treatment process; the obtained aromatic hydrocarbon component enters a stripping tower, the reaction effluent is a pure aromatic hydrocarbon-rich component, and the aromatic hydrocarbon content is not less than 98%. The process provided by the invention can realize reasonable and efficient extraction of the aromatic hydrocarbon-rich component from the catalytic cracking diesel oil, has the advantages of short operation period and low energy consumption, obviously improves the quality and recovery rate of the high-added-value aromatic hydrocarbon-rich product, and is easier to realize efficient extraction and purification of the aromatic hydrocarbon-rich component from the industrial catalytic cracking diesel oil.

Description

Technical Field

[0001] The invention relates to a process route for efficiently extracting aromatic-rich components from catalytic cracking diesel as a raw material through a composite extractant-back extraction composite method, and belongs to the technical field of efficient utilization of petrochemical industry. Background Art

[0002] Catalytic cracking diesel is mainly used as a blending component for automotive diesel in the product structure of refineries, and its proportion is relatively high, some reaching 30%. The indicators of finished diesel in my country have very strict requirements on the content of aromatics in diesel, especially polycyclic aromatics. Therefore, my country's automotive diesel standards have been upgraded from National V standards to National VI standards, and the limit on the mass fraction of polycyclic aromatics in diesel has been reduced from 11% to 7%. Considering the principle of "oil is suitable for oil, and aromatics are suitable for aromatics", separating a large amount of aromatics in catalytic cracking diesel through extraction, an efficient and low-carbon approach, is an important idea for the high-value utilization of catalytic cracking diesel. In addition, aromatic-rich oil is one of the important raw materials in the field of petrochemicals, and is also a key research object for the separation of diesel family components. The main technologies for extracting aromatics from catalytic cracking diesel include solvent extraction, membrane separation, and adsorption separation. At present, there are some studies on these processes, but all of them have technical problems. Solvent extraction mainly has the problems of difficult solvent recovery, high energy consumption and low aromatic purity; membrane separation process has the problems of high price of membrane products and pollution in the preparation process; adsorption separation is still in the research stage of model oil. Therefore, it has become an urgent problem for oil refining enterprises to find an economical, reasonable and efficient processing method for extracting aromatic-rich components from catalytic cracking diesel and comprehensively improve the high-value utilization of catalytic diesel.

[0003] CN114763490A provides a catalytic cracking diesel processing process, wherein the raw material is pretreated to obtain an aromatics-rich material and an alkane-rich material, the aromatics-rich material is recovered and pretreated to obtain an aromatic fraction, the aromatic fraction enters a fractionation unit for separation to obtain a light fraction, a middle fraction and a heavy fraction, wherein the heavy fraction enters a fixed bed for hydrogenation reaction to obtain a liquid phase effluent, the middle fraction and hydrogen enter an ebullating bed for hydrogenation reaction to obtain a gas phase and a liquid phase, and the liquid phase enters a fractionation unit for treatment.

[0004] CN1262264A discloses a combined process of extractive distillation and liquid-liquid extraction, in which raw materials are pre-fractionated to obtain a first fraction containing benzene and a second fraction containing a small amount of benzene, the first fraction is subjected to extractive distillation to obtain a benzene product; the second fraction is mixed with the raffinate oil obtained by the extractive distillation operation and then subjected to liquid-liquid extraction to obtain toluene and a small amount of benzene. The process has relatively few restrictions on raw materials, a wide range of applications, low operating energy consumption, and is suitable for the expansion and reconstruction of the original liquid-liquid extraction device of the refinery. However, the process is only specifically implemented and applied to the case where o-xylene is used as a co-solvent, and is limited to the extractive distillation operation of the combined process.

[0005] CN1393507 proposes a method for extractive distillation separation of aromatic hydrocarbons and the use of a composite solvent. The composite solvent described in the process includes a main solvent and a co-solvent, and a modifier. The co-solvent is selected from any one of C8-C11 aromatic hydrocarbons or a mixture of two aromatic hydrocarbons with different carbon numbers, and its content is 3-39%, and the carbon number of the smallest aromatic hydrocarbon in the co-solvent should be greater than the carbon number of the largest aromatic hydrocarbon in the aromatic hydrocarbon to be separated; when the co-solvent is selected from any one of C8-C11 aromatic hydrocarbons, the composite solvent contains 0.01-10% of the modifier, and when the co-solvent is selected from a mixture of any two aromatic hydrocarbons with different carbon numbers in C8-C11 aromatic hydrocarbons, the composite solvent contains 0-10% of the modifier, and the main solvent and the modifier are selected from cyclopentane sulfone, N-formylmorpholine or N-methylpyrrolidone, respectively, provided that the acidity and alkalinity of the modifier are opposite to that of the main solvent. Most of the above processes are limited to overly complex operation processes or specific solvents. Summary of the invention

[0006] In order to solve the problems existing in the prior art, the main purpose of the present invention is to provide a process for efficiently extracting the rich aromatic components in catalytic cracking diesel by a composite extractant-back extraction composite method, so as to obtain high-purity and high-yield rich aromatic components. The process is based on the concept of molecular refining, and the components in catalytic cracking diesel are separated by selecting the polarity of the composite extractant, and a back extraction combination process is added, which can greatly reduce the proportion of alkanes in the rich aromatic components, and efficiently separate the alkanes and aromatics in the catalytic cracking diesel, solve the technical problems of poor product purity, low recovery rate and solvent recovery in the existing catalytic cracking diesel extraction of aromatics, and realize the reasonable and efficient extraction of aromatic components from catalytic cracking diesel, and the purity and recovery rate of high value-added rich aromatic products are significantly improved, and the device cycle is short and the energy consumption is greatly reduced.

[0007] The present invention provides a process for efficiently extracting aromatic-rich components in catalytic cracking diesel by a composite extractant-strip extraction composite method, wherein the processing process comprises the following contents:

[0008] (1) According to the agent-oil ratio, catalytic cracking diesel and composite extractant are introduced into a mixing coalescer, and under sufficient contact, the alkane-rich component and the aromatics-rich component are separated through the action of the fiber bundle in the pipeline packing;

[0009] (2) the aromatics-rich component in (1) is fed into the next mixer-coalescer for stripping treatment, a stripping agent is added according to the agent-to-oil ratio, and the aromatics-rich component is separated through the fiber bundle in the pipeline packing under sufficient contact;

[0010] (3) the aromatics-rich components in (2) are fed into a mixing settling tank according to the agent-oil ratio, and a stripping recovery solvent (an organic compound solvent composed of elements such as CHO) is added. Under sufficient contact, the obtained aromatics-rich components are fed into the next mixing settling tank for separation, and the aromatics-rich components are obtained from the top of the tower. The lean solvent obtained at the bottom of the tower is fed into a vacuum liquid-liquid distillation tower;

[0011] (4) The aromatic-rich component in (3) is sent to a stripping tower to remove light components in the form of steam, and the pure aromatic-rich component is discharged from the bottom of the tower.

[0012] The composite extractant of the present invention is a composite combination of one or more of sulfolane, dimethyl sulfoxide, N-methylpyrrolidone and N,N-dimethylformamide.

[0013] The composite ratio of the composite extractant of the present invention is 2:8-7:3, the extraction temperature is 30-70°C, and the agent-oil ratio is 0.5-2.0.

[0014] The stripping agent of the invention is No. 6 solvent oil, No. 90 solvent oil, dichloromethane and n-heptane, and the stripping agent / oil ratio is 0.1-1.0.

[0015] The stripping recovery solvent of the present invention is organic compound such as methanol, ethanol, alcohols and aldehydes.

[0016] The stripping recovery solvent of the present invention contains 0.1-0.5% water, and the solvent-oil ratio is 0.5-1.5.

[0017] The lean solvent of the present invention is recycled and reused in a vacuum liquid-liquid distillation tower, with a pressure of 10-20 KPa and a temperature not exceeding 95°C.

[0018] The steam temperature of the stripping tower described in the present invention does not exceed 120°C.

[0019] The process of the present invention is characterized in that the aromatic content of the pure aromatic-rich component obtained by extracting catalytic cracking diesel is 80-100%, preferably 80-99%, and the aromatic recovery rate is preferably 50-70%.

[0020] Compared with the prior art, the present invention has the following beneficial effects:

[0021] (1) The present invention adopts a composite extraction-strip extraction method to extract the aromatic-rich components in catalytic cracking diesel, without the need for pretreatment of the raw materials, making the entire operation process simple, short cycle, low energy consumption, and greatly reducing the investment cost of the device.

[0022] (2) The present invention selects sulfolane, N-methylpyrrolidone, dimethyl sulfoxide and N, N-dimethylformamide for compounding. The composite extractant has high selectivity and high solubility for aromatic hydrocarbons, and can effectively improve the recovery rate of aromatic hydrocarbon-rich components.

[0023] (3) The present invention adds a stripping agent, which can greatly reduce the paraffin components in the aromatic-rich component and effectively improve the purity of the aromatic-rich component.

[0024] (4) The present invention adds a back-extraction recovery solvent to recover the composite extractant through reduced pressure distillation without changing the extraction effect, which can effectively reduce the consumption of organic solvents and reduce environmental pollution, thus providing technical support for industrial promotion and application. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Attached Figure 1 The figure is a schematic diagram of the process for extracting aromatics-rich components from catalytic cracking diesel of the present invention.

[0026] The process flow device shown in the attached figure is not only suitable for extracting aromatic-rich oil from catalytic cracking diesel, but also suitable for catalytic gasoline, wax oil, etc.

[0027] The accompanying drawings are described as follows:

[0028] 1. Feed 2. Composite extractant 3. Mixing coalescer 4. Alkane-rich component 5. Composite extractant and aromatic-rich component 6. Stripping agent 7. Mixing coalescer 8. Stripping agent and alkane component 9. Extractant and aromatic-rich component 10. Stripping recovery solvent 11. Mixing coalescer 12. Aromatic-rich component 13. Lean solvent 14. Stripping recovery solvent 15. Mixing coalescer 16. Aromatic-rich component 17. Lean solvent 18. Stripping tower 19. Pure aromatic-rich oil 20. Vacuum liquid-liquid distillation tower 21. Extractant recovery. DETAILED DESCRIPTION

[0029] The following is a detailed description of the process for efficiently separating the rich aromatic components in catalytic cracking diesel by the composite extractant-stripping method provided by the present invention in conjunction with the examples, but it should not be construed as limiting the present invention. Unless otherwise specified, the technical means used in the following examples are conventional means well known to those skilled in the art, and the materials, reagents, etc. used in the following examples, unless otherwise specified, can all be obtained from commercial sources.

[0030] As shown in the accompanying drawings, catalytic cracking diesel 1 and composite extractant 2 enter the mixing coalescer 3, fully contact and undergo the action of the fiber bundle in the reactor to separate the alkane-rich component 4 and the aromatic-rich component 5, and the aromatic-rich component 5 enters the stripping mixing coalescer 7 together with the stripping agent 6, fully contacted and separated with the stripping agent 6 to obtain the extractant-alkane component 8 and the aromatic-rich component 9, the aromatic-rich component 9 enters the mixing coalescer 11 together with the stripping recovery solvent 10, fully contacted with the stripping recovery solvent to obtain the aromatic-rich component 12 and the lean solvent 13, the aromatic-rich component 12 enters the mixing coalescer 15 together with the stripping recovery solvent 14, fully contacted with the stripping recovery solvent to obtain the aromatic-rich component 16 and the lean solvent 17, the aromatic-rich component 16 enters the stripping tower 18, the reaction effluent is the pure aromatic component 19, the lean solvent 13 and the lean solvent 17 enter the vacuum liquid-liquid distillation tower 20 for solvent recovery and reuse treatment 21.

[0031] Example 1

[0032] This embodiment adopts the process flow chart shown in the accompanying drawings, catalytic cracking diesel and composite extractant enter the mixing coalescer, the composite extractant is cyclopentane and N-methylpyrrolidone in a composite ratio of 4:6, the agent-oil ratio is 1.0, and the extraction temperature is 45°C; the aromatic-rich component after extraction enters the stripping mixing coalescer, the stripping agent is No. 6 solvent oil, and the agent-oil ratio is 0.5; the aromatic-rich component obtained by stripping enters the mixing coalescer to fully react with the stripping recovery solvent, the stripping recovery solvent is 50% methanol, the agent-oil ratio is 0.5, and the aromatic-rich component separated after sufficient contact enters the mixing coalescer again to fully react with the stripping recovery solvent, the stripping recovery solvent is 50% methanol, and the agent-oil ratio is 0.5. The aromatic-rich component separated after sufficient contact enters the stripping tower for reaction, and the product flowing out of the reaction is a pure aromatic component. The aromatics recovery rate is 53.06wt%, and the content is 99.09%. The recovery rate of the aromatics-rich component is preferably 43.62wt%, and the content is 89.33%. The aromatics content of the solvent recovery and re-extraction is 98.89%.

[0033] Example 2

[0034] This embodiment adopts the process flow chart shown in the accompanying drawings, catalytic cracking diesel and composite extractant enter the mixing coalescer, the composite extractant is selected from cyclopentane and N-methyl pyrrolidone in a composite ratio of 4:6, the agent-oil ratio is 1.5, and the extraction temperature is 55°C; the aromatic-rich component after extraction enters the stripping mixing coalescer, the stripping agent is selected from No. 6 solvent oil, and the agent-oil ratio is 0.2; the aromatic-rich component obtained by stripping enters the mixing coalescer and fully reacts with the stripping recovery solvent, the stripping recovery solvent is selected from 50% ethanol, the agent-oil ratio is 0.5, and the aromatic-rich component is separated after full contact and enters the mixing coalescer again to fully react with the stripping recovery solvent, the stripping recovery solvent is selected from 50% ethanol, the agent-oil ratio is 0.5, and the aromatic-rich component separated after full contact enters the stripping tower for reaction, and the product of the reaction outflow is a pure aromatic component. The aromatic recovery rate is 55.53wt%, the content is 98.98%, and the recovery rate of the aromatic-rich component is 45.63wt%, and the content is 87.37%. The aromatic content of the solvent recovery and re-extraction was 98.09%.

[0035] Example 3

[0036] This embodiment adopts the process flow chart shown in the accompanying drawings, catalytic cracking diesel and composite extractant enter the mixing coalescer, the composite extractant is selected from dimethyl sulfoxide and N, N-dimethylformamide in a composite ratio of 5:5, the agent-oil ratio is 1.0, and the extraction temperature is 45°C; the aromatic-rich component after extraction enters the stripping mixing coalescer, the stripping agent is selected from No. 6 solvent oil, and the agent-oil ratio is 0.2; the aromatic-rich component obtained by stripping enters the mixing coalescer to fully react with the stripping recovery solvent, the stripping recovery solvent is selected from 50% ethanol, the agent-oil ratio is 0.5, and the aromatic-rich component separated after sufficient contact enters the mixing coalescer again to fully react with the stripping recovery solvent, the stripping recovery solvent is selected from 50% ethanol, the agent-oil ratio is 0.5, and the aromatic-rich component separated after sufficient contact enters the mixing coalescer again to fully react with the stripping recovery solvent, the stripping recovery solvent is selected from 50% ethanol, the agent-oil ratio is 0.5, and the aromatic-rich component separated after sufficient contact enters the stripping tower to react, and the product flowing out of the reaction is a pure aromatic component. The recovery rate of aromatics was 50.84wt%, the content was 98.37%, the recovery rate of aromatics-rich components was 41.62wt%, the content was 86.92%. The aromatic content of solvent recovery and re-extraction was 97.19%.

[0037] Example 4

[0038] This embodiment adopts the process flow chart shown in the accompanying drawings, catalytic cracking diesel and composite extractant enter the mixing coalescer, the composite extractant is selected from dimethyl sulfoxide and N, N-dimethylformamide in a composite ratio of 4:6, the agent-oil ratio is 1.8, and the extraction temperature is 50°C; the aromatic-rich component after extraction enters the stripping mixing coalescer, the stripping agent is selected from No. 6 solvent oil, and the agent-oil ratio is 0.2; the aromatic-rich component obtained by stripping enters the mixing coalescer and fully reacts with the stripping recovery solvent, the stripping recovery solvent is selected from 70% methanol, the agent-oil ratio is 1, and the aromatic-rich component separated after full contact enters the mixing coalescer again and fully reacts with the stripping recovery solvent, the stripping recovery solvent is selected from 70% methanol, the agent-oil ratio is 1, and the aromatic-rich component separated after full contact enters the stripping tower for reaction, and the product of the reaction outflow is a pure aromatic component. The aromatic recovery rate is 41.09wt%, the content is 98.41%, and the recovery rate of the aromatic-rich component is 34.45wt%, and the content is 87.83%. The aromatic content of the solvent recovery and re-extraction was 98.32%.

[0039] It should be noted that when the claims of the present invention involve numerical ranges, it should be understood that the two endpoints of each numerical range and any numerical value between the two endpoints can be selected. In order to avoid redundancy, the present invention describes a preferred embodiment.

[0040] Table 1 Content and recovery ratio of aromatic components extracted from catalytic cracking diesel

[0041]

[0042]

Claims

1. A process for efficiently extracting aromatic-rich components from catalytic cracking diesel by a composite extractant-strip extraction composite method, comprising the following steps: (1) According to the agent-oil ratio, catalytic cracking diesel and composite extractant are introduced into a mixing coalescer, and under sufficient contact, the alkane-rich component and the aromatics-rich component are separated through the action of the fiber bundle in the pipeline packing; (2) the aromatics-rich component in (1) is fed into the next mixer-coalescer for stripping treatment, a stripping agent is added according to the agent-to-oil ratio, and the aromatics-rich component is separated through the fiber bundle in the pipeline packing under sufficient contact; (3) the aromatics-rich components in (2) are fed into a mixing settling tank according to the agent-oil ratio, and a stripping recovery solvent (an organic compound solvent composed of elements such as CHO) is added. Under sufficient contact, the obtained aromatics-rich components are fed into the next mixing settling tank for separation, and the aromatics-rich components are obtained from the top of the tower. The lean solvent obtained at the bottom of the tower is fed into a vacuum liquid-liquid distillation tower; (4) The aromatic-rich component in (3) is sent to a stripping tower to remove light components in the form of steam, and the pure aromatic-rich component is discharged from the bottom of the tower.

2. The process according to claim 1, characterized in that The composite extractant described in step (1) is a composite combination of one or more of sulfolane, dimethyl sulfoxide, N-methylpyrrolidone and N,N-dimethylformamide.

3. The process according to claim 1, characterized in that The composite ratio of the composite extractant in step (1) is 2:8-7:3, the extraction temperature is 30-70°C, and the agent-oil ratio is 0.5-2.

0.

4. The process according to claim 1, characterized in that The stripping agent in step (2) is No. 6 solvent oil, No. 90 solvent oil, dichloromethane and n-heptane.

5. The process according to claim 1, characterized in that The stripping agent to oil ratio in step (2) is 0.1-1.

0.

6. The process according to claim 1, characterized in that The back extraction recovery solvent in step (3) is an organic composite compound such as alcohols or aldehydes.

7. The process according to claim 1, characterized in that The stripping recovery solvent in step (3) contains 0.1-0.5% water, and the solvent-to-oil ratio is 0.5-1.

5.

8. The process according to claim 1, characterized in that The pressure of the vacuum liquid-liquid distillation tower in step (3) is 10-20 KPa, and the temperature does not exceed 95°C.

9. The process according to claim 1, characterized in that The steam temperature of the stripping tower described in step (4) does not exceed 120°C.

10. The process according to claim 1, characterized in that The aromatic content of the pure aromatic-rich component obtained by extracting catalytic cracking diesel is 80-100%, preferably 80-99%.

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