Organic solvent reverse osmosis membrane separation technology for dearomatization of diesel oil

Abstract

The invention relates to the technical field of chemical engineering, and discloses an organic solvent reverse osmosis membrane separation technology for dearomatization of diesel oil, and the method comprises the following steps: construction of a composite membrane material: preparation of a membrane material P1, and preparation of a thin-layer composite membrane; the organic solvent reverse osmosis testing device is mainly composed of a high-pressure pump, a pressure release valve, three parallel membrane components (membrane tanks 1, 2 and 3), a three-way valve, a pressure gauge, a pressure regulator, a flow meter, a feeding barrel and a pipeline; separating a binary organic solvent mixed system; and separation of an FCC diesel oil simulation system: testing the separation performance of the multi-component organic solvent of the simulated diesel oil by adopting a cross flow permeation system. Compared with a traditional thermal separation mode, the low-energy-consumption and non-phase-change organic solvent reverse osmosis membrane separation technology has the energy use efficiency of 10 times or above, and can become an effective technology for separating aromatic hydrocarbons in diesel oil.

Description

Technical Field

[0001] The invention relates to the technical field of chemical industry, in particular to an organic solvent reverse osmosis membrane separation technology for dearomatization of diesel. Background Art

[0002] With the changes in the supply and demand structure of my country's oil and chemical products market, my country has a surplus of diesel and a shortage of important chemical products such as aromatics. Efficiently extracting high-value aromatics from the surplus diesel can not only alleviate my country's diesel surplus problem, but also fill the gap in my country's demand for aromatic raw materials.

[0003] In recent years, my country's refined oil consumption structure has undergone tremendous changes, the most prominent of which is the structural overcapacity of diesel. How to achieve high-value and clean utilization of diesel has become one of the major problems facing refining and chemical companies. Nearly 60% of my country's diesel pool is straight-run diesel, 30% is catalytic cracking (FCC) diesel, as well as coking and other diesel. Straight-run diesel contains ~70% alkanes and ~30% aromatics (mainly monocyclic aromatics). Straight-run diesel can be used as a raw material for ethylene cracking after dearomatization, and aromatics are used as high-value chemicals. However, FCC diesel with a content of 30% is difficult to process and utilize due to its excessively high total aromatic content and a large proportion of condensed-ring aromatics. It is generally necessary to prepare an alkane / monocyclic aromatic mixture through processes such as hydrogenation / cracking before utilization. How to extract high-value aromatics from diesel and optimize diesel components is the core theme of efficient utilization of diesel.

[0004] In recent years, my country's refined oil consumption structure has undergone tremendous changes, the most prominent of which is the structural overcapacity of diesel. How to achieve high-value and clean utilization of diesel has become one of the major problems facing refining and chemical companies. Nearly 60% of my country's diesel pool is straight-run diesel, 30% is catalytic cracking (FCC) diesel, as well as coking and other diesel. Straight-run diesel contains ~70% alkanes and ~30% aromatics (mainly monocyclic aromatics). Straight-run diesel can be used as a raw material for ethylene cracking after dearomatization, and aromatics are used as high-value chemicals. However, FCC diesel with a content of 30% is difficult to process and utilize due to its excessively high total aromatic content and a large proportion of condensed-ring aromatics. It is generally necessary to prepare an alkane / monocyclic aromatic mixture through processes such as hydrogenation / cracking before utilization. How to extract high-value aromatics from diesel and optimize diesel components is the core theme of efficient utilization of diesel.

[0005] The traditional method of separating aromatics from diesel relies on energy-intensive separation methods such as extraction and distillation, which require high equipment investment and high energy consumption. Therefore, it is necessary to design corresponding technical solutions to solve this problem. Summary of the invention

[0006] 1. Technical issues to be resolved

[0007] In view of the deficiencies of the prior art, the present invention provides an organic solvent reverse osmosis membrane separation technology for dearomatization of diesel, which solves the technical problems.

[0008] (II) Technical solution

[0009] To achieve the above objectives, the present invention is implemented by the following technical scheme: a diesel dearomatization organic solvent reverse osmosis membrane separation technology, the method steps include the following:

[0010] S1. Construction of composite membrane materials: preparation of membrane material P1, preparation of thin-layer composite membrane;

[0011] S2. Construction of membrane separation equipment: All organic liquid separation tests are carried out through the cross-flow permeation test system;

[0012] The organic solvent reverse osmosis test device is mainly composed of a high-pressure pump, a pressure relief valve, three parallel membrane assemblies (membrane pools 1, 2, and 3), a three-way valve, a pressure gauge, a pressure regulator, a flow meter, a feed barrel, and a pipeline;

[0013] S3, Separation of FCC diesel simulation system: The separation performance of organic solvent was tested using a cross-flow permeation system;

[0014] It includes separation test of toluene / methylcyclohexane binary mixture system, separation test of toluene / isooctane binary mixture system, and separation test of aromatic / alkane multi-component mixture system with toluene as the main component.

[0015] Further improved, in step S1, the preparation method of the membrane material P1 comprises the following steps:

[0016] S101, 2,7-dibromo-9,9-bis(2,2,3,3,4,4,5,5,6,6,7,7,7-tridecafluoroheptyl)-9H-fluorene(M1,1231.1mg,1.0mmol,1.0equiv),4,4'-(perfluoropropane-2,2-diyl)dianiline(M2,44.6mg,1.0mmol,1.0equiv),BrettPhos Pd G3(13.5mg,0.015mmol,0.015equiv),NaOtBu(288.3mg,3.0mmol,3.0equiv)were added into a dried pressure-resistant reaction tube in sequence;

[0017] S102, the pressure-resistant reaction tube was then replaced with nitrogen three times, and then anhydrous THF (5.0 mL) was added and stirred at room temperature for 5 minutes, and then placed in an oil bath at 80° C. and stirred for 48 hours;

[0018] S103, after the reaction is completed, the reaction tube is taken out from the oil bath, cooled to room temperature, THF (20 mL) and H2O (5 mL) are added and stirred for 10 minutes to quench and dilute the reaction solution. After quenching, the diluted solution is transferred to a separatory funnel and washed 2-3 times with 40 mL of saturated brine. The organic phases are combined and the solution containing the crude product is concentrated to 10 mL by means of a rotary evaporator. The polymer concentrate is added dropwise to methanol under stirring to precipitate and purify. The filtered solid is dried in a vacuum oven at 60°C overnight to obtain a brown powdery polymer solid P1 (1.2 g, yield 86%).

[0019] Preferably, in step S1, the method for preparing the thin layer composite membrane comprises the following steps:

[0020] S1011, 0.2 g of P1 and 9.8 g of anhydrous THF solution were added to a 20 mL glass bottle, ultrasonicated for 1-2 hours, and filtered using a 0.22 μm filter membrane to prepare a 2 wt % P1 polymer solution;

[0021] S1012, first use high-purity nitrogen to purge the spin coating chamber for 5 minutes to remove moisture, and then put a paper towel soaked in THF into the spin coating chamber for 5 minutes to obtain a THF saturated vapor environment;

[0022] S1013, then, 0.6 ml of the P1 polymer solution prepared in step S1011 is quickly dropped onto the Matrimid 5218 support film rotating at 3500 rpm, and the spin coating process lasts for three minutes to ensure that the surface layer is completely dry;

[0023] S1014, the spin-coated thin layer composite was air-dried overnight and stored in a vacuum oven at 60 °C overnight before use.

[0024] All membranes were thin-layer composites with a thin P1 skin layer prepared by spin coating a 2 wt % P1 polymer solution on a cross-linked porous Matrimid 5218 support specimen, which had high mechanical integrity.

[0025] Preferably, in step S3, the separation test method of the toluene / methylcyclohexane binary mixed system comprises the following steps:

[0026] S301, weighing 250 g of toluene and 250 g of methylcyclohexane and mixing them evenly to prepare a mixed solution of toluene and methylcyclohexane (50 wt %:50 wt %), and adding the mixed solution into a feed barrel of a membrane separation device;

[0027] S302, soaking three thin composite membranes having a P1 polymer selective layer in a toluene solution for more than 1 hour, and then placing the three membranes in membrane pool 1, membrane pool 2, and membrane pool 3 respectively in a wet state;

[0028] S303, turning on the high-pressure pump, adjusting the flow rate to 25 L / min and the pressure to 7 MPa, and running the pump under high pressure for more than 12 hours until the membrane is stable;

[0029] S304, then, taking the permeates 1, 2, and 3 at a timed interval, respectively, and analyzing the contents of toluene and methylcyclohexane in the feed liquid and the permeate by gas chromatography;

[0030] S305, finally, the separation flux is calculated by time and permeate mass, and the selectivity and methylcyclohexane retention rate are calculated by the contents of toluene and methylcyclohexane in the feed liquid and the permeate.

[0031] Preferably, in step S3, the separation test method of the toluene / isooctane binary mixed system comprises the following steps:

[0032] S3011, weighing 250 g of toluene and 250 g of isooctane and mixing them evenly to prepare a mixed solution of toluene and isooctane (50 wt %:50 wt %), and adding the mixed solution into a feed barrel of a membrane separation device;

[0033] S3012, soaking three thin composite membranes with P1 polymer selective layers in a toluene solution for more than 1 hour, and then placing the three membranes in membrane pool 1, membrane pool 2, and membrane pool 3 respectively in a wet state;

[0034] S3013, turn on the high-pressure pump, adjust the flow rate to 25 L / min, the pressure to 7 MPa, and run under high pressure for more than 12 hours until the membrane is stable;

[0035] S3014, then, taking the permeates 1, 2, and 3 at a timed interval, respectively, and analyzing the contents of toluene and isooctane in the feed liquid and the permeate by gas chromatography;

[0036] S3015, finally, the separation flux is calculated by time and permeate mass, and the selectivity and isooctane retention rate are calculated by the toluene and isooctane contents in the feed liquid and the permeate.

[0037] Preferably, in step S3, the separation test method of the toluene-based aromatic / alkane multi-component mixed system comprises the following steps:

[0038] S30111, weigh 300 g toluene, 50 g m-xylene, 25 g isooctane, 25 g n-octane, 50 g methylcyclohexane, 25 g n-dodecane and 25 g n-hexadecane, mix them evenly to prepare an aromatic / alkane multi-component mixture mainly composed of toluene, and add the mixed solution into a feed barrel of a membrane separation device;

[0039] S30112, soak three thin composite membranes with P1 polymer selective layers in a toluene solution for more than 1 hour, and then place the three membranes in membrane pool 1, membrane pool 2, and membrane pool 3 respectively in a wet state;

[0040] S30113, turn on the high-pressure pump, adjust the flow rate to 25 L / min, the pressure to 7 MPa, and run at high pressure for more than 12 hours until the membrane is stable;

[0041] S30114, then, taking the permeate 1, 2, and 3 at a time, respectively, and analyzing the contents of toluene, m-xylene, isooctane, n-octane, methylcyclohexane, n-dodecane, and n-hexadecane in the feed liquid and the permeate by gas chromatography;

[0042] S30115, finally, the separation flux is calculated by time and permeate mass, and the retention rates of isooctane, n-octane, methylcyclohexane, n-dodecane and n-hexadecane are calculated by the contents of toluene and other components in the feed liquid and permeate.

[0043] (III) Beneficial effects

[0044] Compared with the prior art, the invention has the following beneficial effects: compared with the traditional thermal separation method, the low-energy consumption, non-phase-change organic solvent reverse osmosis (OSRO) membrane separation technology has an energy utilization efficiency of more than 10 times, and can become an effective technology for separating aromatics from diesel. Aiming at the contradiction between supply and demand of domestic oil products and chemical products in my country, the invention develops a new type of fluorine-rich and aromatic-rich separation membrane with application prospects, and realizes the efficient and low-energy separation of aromatics from diesel;

[0045] The core difference between membrane separation and traditional separation technology is that there is no phase change in the separation process, which can greatly reduce the energy consumption of separation; the present invention proposes to develop organic solvent separation membrane technology to realize the low-energy membrane separation process of aromatic diesel, reduce the energy consumption and cost of optimizing diesel utilization in my country, support the large-scale, full and efficient utilization of strategic diesel resources, and has a very important significance for the security of energy and material supply;

[0046] The composite membrane material for diesel dearomatization is prepared by using fluorine-rich polyarylamine polymer membrane material and highly cross-linked polyimide material as supporting membrane material; the organic solvent reverse osmosis system designed by using the composite membrane material can efficiently complete the membrane separation of high-value aromatics in the hydrogenation / cracking components of FCC-like diesel, so as to solve the key problem of excessively high energy consumption of diesel dearomatization;

[0047] The present invention proposes a technology for achieving dearomatization of diesel by non-phase change membrane separation, and achieves low-energy membrane separation of aromatic / alkane mixtures by non-phase change, which can solve the important problem of excessively high energy consumption in purifying high-value aromatics in diesel. The composite method of fluorine-rich polymer and high-crosslinking support membrane can effectively prepare high-performance organic solvent reverse osmosis separation membrane materials.

[0048] A non-thermal membrane separation method is used to separate high-value aromatics directly from aromatic / alkane mixtures at room temperature. Compared with the thermal phase change distillation separation method, this technology can theoretically reduce energy consumption by 90%, which meets the needs of green chemical industry. BRIEF DESCRIPTION OF THE DRAWINGS

[0049] Figure 1 It is a schematic diagram of a cross-flow permeation test system for organic solvent reverse osmosis of the present invention;

[0050] Figure 2 This is an electron microscope image of a cross section of the composite membrane of the present invention;

[0051] Figure 3 It is the standard curve diagram of toluene and n-octane of the present invention.

[0052] Figure 4 It is the standard curve diagram of toluene and isooctane of the present invention.

[0053] Figure 5 It is a standard curve diagram of toluene and m-xylene of the present invention.

[0054] Figure 6 It is the standard curve diagram of toluene and methylcyclohexane of the present invention.

[0055] Figure 7 It is the standard curve diagram of toluene and n-dodecane of the present invention.

[0056] Figure 8 It is the standard curve diagram of toluene and n-hexadecane of the present invention.

[0057] Fig. 9 It is a schematic diagram of the interception results of various components in the FCC diesel simulation system of the present invention.

[0058] Fig.10 It is a schematic diagram of the aromatics enrichment results in the FCC diesel simulation system of the present invention. DETAILED DESCRIPTION

[0059] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0060] See also Figure 1-Figure 10 The embodiment of the present invention provides a technical solution: an organic solvent reverse osmosis membrane separation technology for diesel dearomatization, the method steps include the following:

[0061] S1. Construction of composite membrane materials: preparation of membrane material P1, preparation of thin-layer composite membrane;

[0062] S2. Construction of membrane separation equipment: All organic liquid separation tests are carried out through the cross-flow permeation test system;

[0063] The organic solvent reverse osmosis test device is mainly composed of a high-pressure pump, a pressure relief valve, three parallel membrane assemblies (membrane pools 1, 2, and 3), a three-way valve, a pressure gauge, a pressure regulator, a flow meter, a feed barrel, and a pipeline;

[0064] S3, Separation of FCC diesel simulation system: The separation performance of organic solvent was tested using a cross-flow permeation system;

[0065] It includes separation test of toluene / methylcyclohexane binary mixture system, separation test of toluene / isooctane binary mixture system, and separation test of aromatic / alkane multi-component mixture system with toluene as the main component.

[0066]

[0067] Further improved, in step S1, the preparation method of the membrane material P1 comprises the following steps:

[0068] S101, 2,7-dibromo-9,9-bis(2,2,3,3,4,4,5,5,6,6,7,7,7-tridecafluoroheptyl)-9H-fluorene(M1,1231.1mg,1.0mmol,1.0equiv),4,4'-(perfluoropropane-2,2-diyl)dianiline(M2,44.6mg,1.0mmol,1.0equiv),BrettPhos Pd G3(13.5mg,0.015mmol,0.015equiv),NaOtBu(288.3mg,3.0mmol,3.0equiv)were added into a dried pressure-resistant reaction tube in sequence;

[0069] S102, the pressure-resistant reaction tube was then replaced with nitrogen three times, and then anhydrous THF (5.0 mL) was added and stirred at room temperature for 5 minutes, and then placed in an oil bath at 80° C. and stirred for 48 hours;

[0070] S103, after the reaction is completed, the reaction tube is taken out from the oil bath, cooled to room temperature, THF (20 mL) and H2O (5 mL) are added and stirred for 10 minutes to quench and dilute the reaction solution. After quenching, the diluted solution is transferred to a separatory funnel and washed 2-3 times with 40 mL of saturated brine. The organic phases are combined and the solution containing the crude product is concentrated to 10 mL by means of a rotary evaporator. The polymer concentrate is added dropwise to methanol under stirring to precipitate and purify. The filtered solid is dried in a vacuum oven at 60°C overnight to obtain a brown powdery polymer solid P1 (1.2 g, yield 86%).

[0071] Further improved, in step S1, the method for preparing the thin layer composite membrane comprises the following steps:

[0072] S1011, 0.2 g of P1 and 9.8 g of anhydrous THF solution were added to a 20 mL glass bottle, ultrasonicated for 1-2 hours, and filtered using a 0.22 μm filter membrane to prepare a 2 wt % P1 polymer solution;

[0073] S1012, first use high-purity nitrogen to purge the spin coating chamber for 5 minutes to remove moisture, and then put a paper towel soaked in THF into the spin coating chamber for 5 minutes to obtain a THF saturated vapor environment;

[0074] S1013, then, 0.6 ml of the P1 polymer solution prepared in step S1011 is quickly dropped onto the Matrimid 5218 support film rotating at 3500 rpm, and the spin coating process lasts for three minutes to ensure that the surface layer is completely dry;

[0075] S1014, the spin-coated thin layer composite was air-dried overnight and stored in a vacuum oven at 60 °C overnight before use.

[0076] All membranes were thin-layer composites with a thin P1 skin layer prepared by spin coating a 2 wt % P1 polymer solution on a cross-linked porous Matrimid 5218 support specimen, which had high mechanical integrity.

[0077] Further improved, in step S3, the separation test method of the toluene / methylcyclohexane binary mixed system comprises the following steps:

[0078] S301, weighing 250 g of toluene and 250 g of methylcyclohexane and mixing them evenly to prepare a mixed solution of toluene and methylcyclohexane (50 wt %:50 wt %), and adding the mixed solution into a feed barrel of a membrane separation device;

[0079] S302, soaking three thin composite membranes having a P1 polymer selective layer in a toluene solution for more than 1 hour, and then placing the three membranes in membrane pool 1, membrane pool 2, and membrane pool 3 respectively in a wet state;

[0080] S303, turning on the high-pressure pump, adjusting the flow rate to 25 L / min and the pressure to 7 MPa, and running the pump under high pressure for more than 12 hours until the membrane is stable;

[0081] S304, then, taking the permeates 1, 2, and 3 at a timed interval, respectively, and analyzing the contents of toluene and methylcyclohexane in the feed liquid and the permeate by gas chromatography;

[0082] S305, finally, the separation flux is calculated by time and permeate mass, and the selectivity and methylcyclohexane retention rate are calculated by the contents of toluene and methylcyclohexane in the feed liquid and the permeate.

[0083] Further improved, in step S3, the separation test method of the toluene / isooctane binary mixed system comprises the following steps:

[0084] S3011, weighing 250 g of toluene and 250 g of isooctane and mixing them evenly to prepare a mixed solution of toluene and isooctane (50 wt %:50 wt %), and adding the mixed solution into a feed barrel of a membrane separation device;

[0085] S3012, soaking three thin composite membranes with P1 polymer selective layers in a toluene solution for more than 1 hour, and then placing the three membranes in membrane pool 1, membrane pool 2, and membrane pool 3 respectively in a wet state;

[0086] S3013, turn on the high-pressure pump, adjust the flow rate to 25 L / min, the pressure to 7 MPa, and run under high pressure for more than 12 hours until the membrane is stable;

[0087] S3014, then, taking the permeates 1, 2, and 3 at a timed interval, respectively, and analyzing the contents of toluene and isooctane in the feed liquid and the permeate by gas chromatography;

[0088] S3015, finally, the separation flux is calculated by time and permeate mass, and the selectivity and isooctane retention rate are calculated by the toluene and isooctane contents in the feed liquid and the permeate.

[0089] Specifically, in step S3, the separation test method of the toluene-based aromatic / alkane multi-component mixed system includes the following steps:

[0090] S30111, weigh 300 g toluene, 50 g m-xylene, 25 g isooctane, 25 g n-octane, 50 g methylcyclohexane, 25 g n-dodecane and 25 g n-hexadecane, mix them evenly to prepare an aromatic / alkane multi-component mixture mainly composed of toluene, and add the mixed solution into a feed barrel of a membrane separation device;

[0091] S30112, soak three thin composite membranes with P1 polymer selective layers in a toluene solution for more than 1 hour, and then place the three membranes in membrane pool 1, membrane pool 2, and membrane pool 3 respectively in a wet state;

[0092] S30113, turn on the high-pressure pump, adjust the flow rate to 25 L / min, the pressure to 7 MPa, and run at high pressure for more than 12 hours until the membrane is stable;

[0093] S30114, then, taking the permeate 1, 2, and 3 at a time, respectively, and analyzing the contents of toluene, m-xylene, isooctane, n-octane, methylcyclohexane, n-dodecane, and n-hexadecane in the feed liquid and the permeate by gas chromatography;

[0094] S30115, finally, the separation flux is calculated by time and permeate mass, and the retention rates of isooctane, n-octane, methylcyclohexane, n-dodecane and n-hexadecane are calculated by the contents of toluene and other components in the feed liquid and permeate.

[0095] Compared with the traditional thermal separation method, the low-energy consumption, non-phase-change organic solvent reverse osmosis (OSRO) membrane separation technology has an energy utilization efficiency of more than 10 times, and can become an effective technology for separating aromatics from diesel. The present invention aims at the contradiction between supply and demand of domestic oil and chemical products in my country, develops a new type of fluorine-rich and aromatic separation membrane with application prospects, and realizes the efficient and low-energy separation of aromatics in diesel;

[0096] The core difference between membrane separation and traditional separation technology is that there is no phase change in the separation process, which can greatly reduce the energy consumption of separation; the present invention proposes to develop organic solvent separation membrane technology to realize the low-energy membrane separation process of aromatic diesel, reduce the energy consumption and cost of optimizing diesel utilization in my country, support the large-scale, full and efficient utilization of strategic diesel resources, and has a very important significance for the security of energy and material supply;

[0097] A composite membrane material for diesel dearomatization is prepared by using fluorine-rich polyarylamine polymer membrane material and highly cross-linked polyimide material as supporting membrane material. Using the composite membrane material, the designed organic solvent reverse osmosis system can efficiently complete the membrane separation of high-value aromatics in the hydrogenation / cracking components of FCC diesel, so as to solve the key problem of excessively high energy consumption in the current diesel dearomatization.

[0098] The present invention proposes a technology for achieving dearomatization of diesel by means of non-phase change membrane separation, and achieves low-energy membrane separation of aromatic / alkane mixtures by means of non-phase change, which can solve the important problem of excessive energy consumption in purifying high-value aromatics in diesel. The composite method of fluorine-rich polymers and high-crosslinking support membranes can effectively prepare high-performance organic solvent reverse osmosis separation membrane materials.

[0099] A non-thermal membrane separation method is used to separate high-value aromatics directly from aromatic / alkane mixtures at room temperature. Compared with the thermal phase change distillation separation method, this technology can theoretically reduce energy consumption by 90%, which meets the needs of green chemical industry.

[0100] P1 polymer: 1H NMR (400 MHz, THF-d8) δ7.80 (s, 1H), 7.61 (d, J = 8.1 Hz, 1H), 7.33 (s, 1H), 7.23 (d, J = 8.2 Hz, 2H), 7.18 (d, J = 7.2 Hz, 1H), 7.05 (s, 3H), 2.45 (s, 2H), 2.41 (s, 2H), 1.50 (s, 2H), 1.28 (s, 2H). 19F NMR (376 MHz, THF-d8) δ -81.9, -122.5, -123.5 (d, J = 70.8 Hz), -126.9.13C NMR(101MHz,THF-d8)δ147.4,144.9,142.0,135.0,130.9,123.4,120.1,119.3,114.5, 113.3,66.2,66.0,52.7,29.7,25.9,24.1,23.9.IR(cm-1):3924(vw),3408(vw),2945( vw),1605(m),1519(m),1471(m),1325(w),1240(s),1138(vs),1170(vs),1200(vs),10 30(vw),963(w),932(w),817(w),734(vw),704(w),524(vw).GPC(againstpolystyrene standards, THF): Mn=22.9kg / mol, Mw=297.3kg / mol,

[0101] Thin layer composite membrane: The coating thickness of Matrimid 5218 support membrane is 254nm, the thickness of P1 polymer selection layer is 160-200nm, and the diameter of composite membrane is 5.0cm.

[0102] Test parameters (unless otherwise specified, the separation tests in the present invention all use the following parameters): temperature 25°C, flow rate 25 L / min, pressure 7 MPa, effective membrane area 12.57 cm2, high pressure stabilization time 24 h, Stage Cut 2%, and the test result is the average of three valid data.

[0103] Calculation formula:

[0104] Permeability = V / (A×t×P), the unit is LMHB (L m-2h-1bar-1), where V (L) is the volume of the cumulative permeate, A (m2) is the effective membrane area, t (h) is the permeation test time, and P (bar) is the pressure applied to the feed side.

[0105] Retention rate = (1-yp / xf) × 100, in %, where xf and yp are the mole fractions of intercepted solvent in the feed and permeate, respectively.

[0106] Separation factor = (yAp / yBp) / (xAf / xBf), where xAf, xBf, yAp and yBp are the mole fractions of solvents A and B in the feed and permeate, respectively.

[0107] Quantitative analysis of each component by gas chromatography:

[0108] Mixed solutions with mass fraction ratios of toluene and each substance of 99:1, 98:2, 95:5, 90:10, 70:30, 50:50, 30:70, and 10:90 were prepared for gas chromatography analysis, and a standard curve was made. Then, the content of each component in the unknown mixed solution was quantitatively analyzed according to the formula Atoluene / Ax=ktoluene / x+b, wherein Atoluene is the peak area of ​​toluene in the gas chromatography, Ax is the peak area of ​​the other substance in the gas chromatography, k is the slope, toluene is the mass fraction of toluene, x is the mass fraction of the other substance, and b is the intercept.

[0109] Separation results of membrane separation binary system:

[0110] (1) The separation test results of the binary mixed system of toluene and methylcyclohexane are as follows (m toluene: m methylcyclohexane = 50:50)

[0111]

[0112] The present invention can enrich a mixed solution of 50% toluene and 50% methylcyclohexane into a mixed solution of 59.35% toluene and 40.65% methylcyclohexane through a single membrane component, the retention rate of methylcyclohexane is 19.19%, the separation factor is 1.46, and the flux is 13.4L m-2h-1.

[0113] (2) Separation test results of toluene and isooctane binary mixture system (m toluene: m isooctane = 50:50)

[0114]

[0115]

[0116] The present invention can enrich a mixed solution of 50% toluene and 50% isooctane into a mixed solution of 65.48% toluene and 34.52% isooctane through a single membrane component, the rejection rate of isooctane is 33.17%, the separation factor is 1.90, and the flux is 12.2 L m-2h-1.

[0117] Separation results of FCC diesel simulation system:

[0118] (3) Separation test results of toluene, m-xylene, isooctane, n-octane, methylcyclohexane, n-dodecane and n-hexadecane (m toluene: m m-xylene: m isooctane: m n-octane: m methylcyclohexane: m n-dodecane: m n-hexadecane = 60:10:5:5:10:5:5)

[0119]

[0120] The present invention can enrich 70% of aromatics (60% toluene + 10% m-xylene) and 30% of other alkane mixed solutions into 80.6% aromatics solution (69.8% toluene + 10.9% m-xylene) through a single membrane module, with an interception rate of 35.4% for isooctane, 21.4% for methylcyclohexane, 16.8% for n-octane, 49.3% for n-dodecane, 74.4% for n-hexadecane, and a flux of 11.9 L m-2h-1. For specific interception conditions, see Fig. 9 and Fig.10 .

[0121] According to the single membrane efficiency, it is proposed that the aromatic mass fraction of FCC diesel hydrogenation / cracking products can be increased from 70% to an ideal 95% through multi-stage membrane separation.

[0122] The above shows and describes the basic principles and main features of the present invention and the advantages of the present invention. It is obvious to those skilled in the art that the present invention is not limited to the details of the above exemplary embodiments, and the present invention can be implemented in other specific forms without departing from the spirit or basic features of the present invention. Therefore, no matter from which point of view, the embodiments should be regarded as exemplary and non-restrictive. The scope of the present invention is defined by the attached claims rather than the above description, and it is intended that all changes falling within the meaning and scope of the equivalent elements of the claims are included in the present invention. Any figure mark in the claims should not be regarded as limiting the claims involved.

[0123] In addition, it should be understood that although the present specification is described according to implementation modes, not every implementation mode contains only one independent technical solution. This description of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment may also be appropriately combined to form other implementation modes that can be understood by those skilled in the art.

Claims

1. An organic solvent reverse osmosis membrane separation technology for diesel dearomatization, characterized in that: The method steps include the following: S1. Construction of composite membrane materials: preparation of membrane material P1, preparation of thin-layer composite membrane; S2. Construction of membrane separation equipment: All organic liquid separation tests were conducted using a cross-flow permeation test system; The organic solvent reverse osmosis test device is mainly composed of a high-pressure pump, a pressure relief valve, three parallel membrane assemblies (membrane pools 1, 2, and 3), a three-way valve, a pressure gauge, a pressure regulator, a flow meter, a feed barrel, and a pipeline; S3, Separation of FCC diesel simulation system: The separation performance of organic solvent was tested using a cross-flow permeation system; It includes separation test of toluene / methylcyclohexane binary mixture system, separation test of toluene / isooctane binary mixture system, and separation test of aromatic / alkane multi-component mixture system with toluene as the main component.

2. The organic solvent reverse osmosis membrane separation technology for dearomatization of diesel according to claim 1, characterized in that: In step S1, the preparation method of the membrane material P1 includes the following steps: S101, add 2,7-dibromo-9,9-bis(2,2,3,3,4,4,5,5,6,6,7,7,7-tridecafluoroheptyl)-9H-fluorene(M1,1231.1mg,1.0mmol,1.0equiv),4,4'-(perfluoropropane-2,2-diyl)dianiline(M2,44.6mg,1.0mmol,1.0equiv),BrettPhosPd G3(13.5mg,0.015mmol,0.015equiv),NaOtBu(288.3mg,3.0mmol,3.0equiv)into a dried pressure-resistant reaction tube in sequence; S102, the pressure-resistant reaction tube was then replaced with nitrogen three times, and then anhydrous THF (5.0 mL) was added and stirred at room temperature for 5 minutes, and then placed in an oil bath at 80° C. and stirred for 48 hours; S103, after the reaction is completed, the reaction tube is taken out from the oil bath, cooled to room temperature, THF (20 mL) and H2O (5 mL) are added and stirred for 10 minutes to quench and dilute the reaction solution. After quenching, the diluted solution is transferred to a separatory funnel and washed 2-3 times with 40 mL of saturated brine. The organic phases are combined and the solution containing the crude product is concentrated to 10 mL by means of a rotary evaporator. The polymer concentrate is added dropwise to methanol under stirring to precipitate and purify. The filtered solid is dried in a vacuum oven at 60°C overnight to obtain a brown powdery polymer solid P1 (1.2 g, yield 86%).

3. The organic solvent reverse osmosis membrane separation technology for dearomatization of diesel according to claim 1, characterized in that: In step S1, the preparation method of the thin layer composite membrane comprises the following steps: S1011, 0.2 g of P1 and 9.8 g of anhydrous THF solution were added to a 20 mL glass bottle, ultrasonicated for 1-2 hours, and filtered using a 0.22 μm filter membrane to prepare a 2 wt % P1 polymer solution; S1012, first use high-purity nitrogen to purge the spin coating chamber for 5 minutes to remove moisture, and then put a paper towel soaked in THF into the spin coating chamber for 5 minutes to obtain a THF saturated vapor environment; S1013, then, 0.6 ml of the P1 polymer solution prepared in step S1011 is quickly dropped onto the Matrimid 5218 support film rotating at 3500 rpm, and the spin coating process lasts for three minutes to ensure that the surface layer is completely dry; S1014, the spin-coated thin layer composite was air-dried overnight and stored in a vacuum oven at 60 °C overnight before use.

4. The organic solvent reverse osmosis membrane separation technology for dearomatization of diesel according to claim 1, characterized in that: In step S3, the separation test method of the toluene / methylcyclohexane binary mixed system comprises the following steps: S301, weighing 250 g of toluene and 250 g of methylcyclohexane and mixing them evenly to prepare a mixed solution of toluene and methylcyclohexane (50 wt %:50 wt %), and adding the mixed solution into a feed barrel of a membrane separation device; S302, soaking three thin composite membranes having a P1 polymer selective layer in a toluene solution for more than 1 hour, and then placing the three membranes in membrane pool 1, membrane pool 2, and membrane pool 3 respectively in a wet state; S303, turning on the high-pressure pump, adjusting the flow rate to 25 L / min and the pressure to 7 MPa, and running the pump under high pressure for more than 12 hours until the membrane is stable; S304, then, taking the permeates 1, 2, and 3 at a timed interval, respectively, and analyzing the contents of toluene and methylcyclohexane in the feed liquid and the permeate by gas chromatography; S305, finally, the separation flux is calculated by time and permeate mass, and the selectivity and methylcyclohexane retention rate are calculated by the contents of toluene and methylcyclohexane in the feed liquid and the permeate.

5. The organic solvent reverse osmosis membrane separation technology for diesel dearomatization according to claim 1, characterized in that: In step S3, the separation test method of the toluene / isooctane binary mixed system comprises the following steps: S3011, weighing 250 g of toluene and 250 g of isooctane and mixing them evenly to prepare a mixed solution of toluene and isooctane (50 wt %:50 wt %), and adding the mixed solution into a feed barrel of a membrane separation device; S3012, soaking three thin composite membranes with P1 polymer selective layers in a toluene solution for more than 1 hour, and then placing the three membranes in membrane pool 1, membrane pool 2, and membrane pool 3 respectively in a wet state; S3013, turn on the high-pressure pump, adjust the flow rate to 25 L / min, the pressure to 7 MPa, and run under high pressure for more than 12 hours until the membrane is stable; S3014, then, taking the permeates 1, 2, and 3 at a timed interval, respectively, and analyzing the contents of toluene and isooctane in the feed liquid and the permeate by gas chromatography; S3015, finally, the separation flux is calculated by time and permeate mass, and the selectivity and isooctane retention rate are calculated by the toluene and isooctane contents in the feed liquid and the permeate.

6. The organic solvent reverse osmosis membrane separation technology for diesel dearomatization according to claim 1, characterized in that: In step S3, the separation test method of the toluene-based aromatic / alkane multi-component mixed system includes the following steps: S30111, weigh 300 g toluene, 50 g m-xylene, 25 g isooctane, 25 g n-octane, 50 g methylcyclohexane, 25 g n-dodecane and 25 g n-hexadecane, mix them evenly to prepare an aromatic / alkane multi-component mixture mainly composed of toluene, and add the mixed solution into a feed barrel of a membrane separation device; S30112, soak three thin composite membranes with P1 polymer selective layers in a toluene solution for more than 1 hour, and then place the three membranes in membrane pool 1, membrane pool 2, and membrane pool 3 respectively in a wet state; S30113, turn on the high-pressure pump, adjust the flow rate to 25 L / min, the pressure to 7 MPa, and run at high pressure for more than 12 hours until the membrane is stable; S30114, then, taking the permeate 1, 2, and 3 at a time, respectively, and analyzing the contents of toluene, m-xylene, isooctane, n-octane, methylcyclohexane, n-dodecane, and n-hexadecane in the feed liquid and the permeate by gas chromatography; S30115, finally, the separation flux is calculated by time and permeate mass, and the retention rates of isooctane, n-octane, methylcyclohexane, n-dodecane and n-hexadecane are calculated by the contents of toluene and other components in the feed liquid and permeate.

Images