Ionic liquid and preparation method thereof, carbon fiber loaded ionic liquid material and preparation method thereof, and application of carbon fiber loaded ionic liquid material in phosgene preparation

Abstract

The invention discloses an ionic liquid and a preparation method thereof, a carbon fiber loaded ionic liquid material and a preparation method thereof, and an application of the carbon fiber loaded ionic liquid material in phosgene preparation. According to the immobilized ionic liquid [PGPMims] [H3CSO3], in the phosgene absorption and purification process, a carbon fiber material loaded with the ionic liquid is adopted as a chemical absorbent for residual chlorine and bromine in phosgene, liquefied phosgene is fully absorbed, and the problem that after chlorine and bromine in phosgene are introduced into a photochemical system, the residual chlorine and bromine in phosgene cannot be recovered is solved. The problem that chloro MDI and bromo MDI are generated in the phosgenation reaction process is solved, the color number of crude MDI is increased, the impurity content is reduced, and the product quality is improved. The absorption and purification process is simple, low in operation cost and convenient to operate, and has certain effects of improving the production efficiency of the product and improving the application performance of the product.

Description

Technical Field

[0001] The invention belongs to the field of isocyanate, and relates to a solid-supported ionic liquid and a preparation method thereof, a carbon fiber-supported ionic liquid material and a preparation method thereof, and application thereof in phosgene preparation. Background Art

[0002] Phosgene is scientifically known as carbonyl chloride, and it smells like rotten apples. Pure phosgene is colorless, and industrial products are light yellow or light green. Because it has two acyl chlorides, its chemical properties are very active. Phosgene is a very important chemical raw material and has a wide range of uses in organic synthesis. It is widely used in the synthesis of pesticides, dyes, coatings, initiators, medicines, fine chemicals, isocyanates (R-NCO), diphenylmethane diisocyanate (MDI), toluene diisocyanate (TDI), polyurethane (PU), etc.

[0003] The method of industrial production of phosgene mainly uses carbon monoxide and chlorine as raw materials and activated carbon as catalyst to synthesize phosgene. As far as the phosgene synthesis reaction is concerned, high temperature will cause phosgene to decompose into carbon monoxide and chlorine again. The phosgene decomposition rate can reach more than 80%. Excessive chlorine will cause the free chlorine at the outlet of the phosgene synthesis reactor to exceed the standard, seriously affecting the quality of the phosgene product. In the phosgenation reaction environment, excessive chlorine will react with amines to form chlorine-containing compounds. These chlorine-containing impurity compounds are difficult to remove by conventional methods such as distillation and recrystallization, which seriously affects the product quality.

[0004] In addition, it is well known in the art that the raw material chlorine for phosgene synthesis is produced by the chlor-alkali process, and the sodium chloride used inevitably introduces halogen impurities such as bromine and iodine. There are few reports in patents and literature on the research of solving the quality problem by controlling the chlorine and bromine content in phosgene.

[0005] US4231959A discloses a method for preparing phosgene, which reduces the residual chlorine content in phosgene by increasing the excess rate of carbon monoxide and improves product quality. The article also mentions that in addition to using water as a cooling medium on the shell side of the reactor, boiling water can also be used, and usable steam is generated at this time. However, the steam quality is low and the economy is not high. In addition, the heat exchange medium is water, and there is a gradual high temperature that causes equipment corrosion. Water leaks into the reaction space and reacts with phosgene, further exacerbating corrosion and posing a high safety risk.

[0006] CN112239416A discloses a process for preparing toluene diisocyanate with low hydrolysis of chlorine and bromine, wherein TDI is prepared by a two-step cold and hot phosgene method, and in the hot reaction process, the hot reaction liquid is subjected to high-temperature stripping treatment by a mixed gas formed by a phosgene tail gas rich in carbon monoxide and nitrogen dioxide generated by a cold reaction, thereby controlling the content of chlorine-containing bromine impurities. However, nitrogen dioxide is not easy to obtain, and is easily decomposed at high temperatures, and its chemical properties are unstable. At the same time, nitrogen dioxide as a mixed gas will be brought into the system to circulate and participate in the phosgenation reaction, which may have an adverse effect on product quality.

[0007] Patent CN110294661A discloses a method for debrominating polybrominated aromatic compounds, which comprises: mixing polybrominated aromatic compounds and a photoreductant and reacting them under light to obtain completely debrominated aromatic compounds, wherein the photoreductant used is an amine substance such as N,N-dimethylacetamide and N,N-dimethylaniline. Amine substances contain active hydrogen and can react with isocyanate products to generate urea impurities, which are insoluble in isocyanate and cause system blockage. Therefore, this method is obviously not suitable for the production process of MDI.

[0008] Patent CN102745649A discloses a method for removing hydrogen bromide gas, wherein a debrominating agent is loaded into a debrominating reactor and heated to make the internal temperature of the debrominating reactor reach 100-115°C, and then hydrogen bromide gas is allowed to flow through the debrominating reactor, so that the bromine in the hydrogen bromide gas reacts with the debrominating agent under the above temperature conditions, so that the mass content of free bromine in the hydrogen bromide gas flowing out of the debrominating reactor is below the target value. This method uses a debrominating agent such as iron or aluminum, which is very likely to cause metal impurities to be mixed into phosgene if used in isocyanate production.

[0009] Although the above patents have certain effects on the removal of chlorine and bromine, the methods used have disadvantages, such as incomplete removal, easy reaction with -NCO groups or introduction of new impurities, etc., which are obviously not suitable for isocyanate systems. Therefore, it is necessary to design a method with high separation efficiency, simple operation and low operating cost, so as to control the content of chloro-MDI and bromo-MDI in the crude isocyanate product and improve the product quality. Summary of the invention

[0010] In view of this, the present invention aims to provide an ionic liquid that can be immobilized and a preparation method thereof, and to provide a carbon fiber material loaded with the ionic liquid, which can be used for purification in the preparation of phosgene to reduce the chlorine and bromine content in phosgene.

[0011] The present invention also aims to provide a method for preparing phosgene with low chlorine and bromine contents. The free chlorine and bromine contents in the phosgene purified by the method can be effectively controlled, and the contents of chloro-MDI and bromo-MDI in the crude isocyanate product can be effectively controlled in the process of producing diphenylmethane diisocyanate by the phosgene method. The method has simple process, low operating cost and is easy to operate.

[0012] It is well known to those skilled in the art that the chemical properties of chloroisocyanates are very similar to those of isocyanates and are not easy to decompose or remove. If they are introduced into products, they will cause the color to deepen, the acid content and hydrolyzed chlorine to increase, and affect the activity of the product and downstream application performance.

[0013] After continuous research, the inventors have found that there are two main reasons for the sources of chlorinated isocyanates in the process of preparing isocyanates: one is that the reaction of chlorine is incomplete during the synthesis of phosgene, and during the phosgenation reaction or degassing and desolvation process, phosgene undergoes self-decomposition at high temperature to generate chlorine, and the free chlorine reacts with isocyanate to generate monochloroisocyanate and / or polychloroisocyanate; the other is that during the phosgenation reaction, phosgene reacts with urea or carbodiimide to generate phosgene adducts, and the phosgene adducts decompose at high temperature to generate monochloroisocyanate and / or polychloroisocyanate.

[0014] The inventors have found that in the process of preparing isocyanates, the main source of bromoisocyanates is that the raw material chlorine for phosgene synthesis is produced by the chlor-alkali process, and halogen impurities such as bromine and iodine are inevitably introduced into the sodium chloride raw material. The inventors also found in the research process that the mechanism of the influence of bromine on the production process of diphenylmethane diisocyanate (MDI) is free radical reaction. Taking the mixing of bromine element (Br2) in phosgene as an example, Br2 will undergo a chain initiation process to generate bromine free radicals during the phosgenation reaction, and the active bromine free radicals will replace the methylene hydrogen on the MDI molecule to generate bromo-MDI. Since the molecular weight of bromo-MDI is similar to that of MDI, it is also difficult to remove the molecule by conventional methods after it is generated. This substance will cause the color number of the isocyanate product to deepen, especially when the bromine content in the phosgene exceeds 20ppm, the color number of the isocyanate will deteriorate significantly.

[0015] Therefore, the present invention has studied how to solve the quality problem of isocyanate by controlling the chlorine and bromine content in phosgene. In the process of producing isocyanate by phosgene method, the chlorine and bromine content in the phosgene raw material is reduced to solve the problem of the darkening of the isocyanate product caused by chloro-MDI and bromo-MDI, and the increase of acid content and hydrolysis chlorine caused by the impurities, which affects the activity of the product and the downstream application performance.

[0016] To achieve the above-mentioned object of the invention, the scheme of the present invention is as follows:

[0017] In the first aspect, the present invention provides an immobilized ionic liquid [PGPMim][H3CSO3], the structure of which is shown in formula (1):

[0018]

[0019] In the formula, n is 1-10, preferably 3-5.

[0020] The present invention also provides a method for preparing the above-mentioned immobilizable ionic liquid, the steps comprising:

[0021] 1) mixing polyethylene glycol mono(4-nonylphenyl) ether with methanesulfonyl chloride, an acid-binding agent and a solvent for reaction, then removing the solvent, washing with water, drying and extracting to obtain an intermediate;

[0022] 2) The intermediate is mixed with N-methylimidazole for reaction, and then washed and dried to obtain an ionic liquid that can be immobilized.

[0023] In the present invention, the molecular formula of the polyethylene glycol mono(4-nonylphenyl) ether (CAS No. 26027-38-3) in step 1) is (C2H4O)nC 15 H 23 O, wherein n is 1-10, preferably 3-5.

[0024] In the present invention, the acid binding agent in step 1) is selected from organic amine compounds, preferably one or more of diisopropylethylamine and triethylamine.

[0025] In the present invention, the solvent in step 1) is selected from an organic solvent that is inert in the reaction system, preferably one or more of acetone and dichloromethane.

[0026] In the present invention, the molar ratio of the polyethylene glycol mono(4-nonylphenyl) ether to methanesulfonyl chloride in step 1) is 1:1.2-2, preferably 1:1.5-1.8.

[0027] In the present invention, the molar ratio of the polyethylene glycol mono(4-nonylphenyl) ether to the acid binding agent in step 1) is 1:2-3, preferably 1:2.3-2.5.

[0028] In the present invention, the molar ratio of the polyethylene glycol mono(4-nonylphenyl) ether to the solvent in step 1) is 1:5-10, preferably 1:8-10.

[0029] In the present invention, the reaction in step 1) is carried out at a temperature of -5 to 5°C, preferably -2 to 0°C, and for a time of 100 to 120 min, preferably 105 to 110 min;

[0030] During the reaction, the methanesulfonyl chloride is preferably added continuously, more preferably dropwise, with the addition time being 2 to 3 hours, preferably 2.5 to 2.8 hours.

[0031] In the present invention, after the reaction in step 1) is completed, post-treatment processes such as solvent removal, water washing, drying, and extraction are also included, which are conventional operations in the art. In some specific examples, the drying is preferably carried out by vacuum distillation, such as vacuum distillation at 30 kPaA to remove water;

[0032] For the extraction, the extracting liquid is preferably a petroleum ether / ethyl acetate mixture with a molar ratio of 1:1.5 to 1:2.

[0033] In the present invention, the molar ratio of the polyethylene glycol mono(4-nonylphenyl) ether in step 1) to the N-methylimidazole in step 2) is 1:1.1-1.4, preferably 1:1.2-1.3.

[0034] In the present invention, the reaction in step 2) is carried out at a temperature of 50 to 70° C., preferably 60 to 65° C., and for a time of 1 to 1.5 h, preferably 1.2 to 1.4 h.

[0035] In the present invention, after the reaction in step 2) is completed, post-treatment processes such as removal, washing, and drying are also included, which are conventional operations in the field. In some specific examples, the product is washed with ethyl acetate; the drying is preferably carried out by vacuum drying, for example, drying under vacuum conditions for 48 hours.

[0036] As one example, the synthesis process of the above-mentioned immobilizable ionic liquid can be represented by the following formula:

[0037]

[0038] In a second aspect, the present invention provides a carbon fiber-loaded ionic liquid material, which is prepared by loading the above-mentioned immobilizable ionic liquid on a carbon material;

[0039] Preferably, the loading amount of the immobilizable ionic liquid on the carbon material is 10 to 30 wt%, preferably 20 to 25 wt%;

[0040] Preferably, the carbon material is selected from activated carbon or multi-walled carbon nanotubes.

[0041] At the same time, the present invention also provides a method for preparing the above-mentioned carbon fiber-supported ionic liquid material, which can usually be prepared by a conventional method for supporting a catalyst, such as an impregnation method.

[0042] Preferably, a method for preparing the above-mentioned carbon fiber-loaded ionic liquid material comprises the following steps:

[0043] (1) washing the carbon material with water until it is neutral, drying it, and then calcining it in a nitrogen atmosphere;

[0044] (2) The immobilized ionic liquid ([PGPMim][H3CSO3]) was dissolved in ethanol and ultrasonically mixed, and then the carbon material was added thereto and fully impregnated. After drying, the carbon fiber loaded ionic liquid material was obtained.

[0045] In the present invention, the water in step (1) is washed to a neutral pH of 7.0 to 7.5.

[0046] In the present invention, the calcination in step (1) is carried out at a temperature of 300 to 500° C., preferably 450 to 460° C., for a time of 20 to 30 hours, preferably 24 to 25 hours.

[0047] In the present invention, the molar ratio of the immobilizable ionic liquid to ethanol in step (2) is 1:2-3, preferably 1:2.4-2.6.

[0048] In the present invention, the ultrasonic mixing in step (2) is carried out for 1 to 2 hours, preferably 1 to 1.5 hours; and the ultrasonic frequency is 10 to 20 kHz, preferably 18 to 20 kHz.

[0049] In the present invention, the immersion time in step (2) is 2 to 3 hours, preferably 2.5 to 2.6 hours;

[0050] The impregnation process has no special requirements on the amount of impregnation solution and carbon material, as long as the carbon material can be immersed in the solution.

[0051] In the present invention, the drying in step 2) is firstly dried at 45-60° C. for 3-3.3 h, and then dried at 85-90° C. for 5-6 h.

[0052] In a third aspect, the present invention provides a method for preparing phosgene with low chlorine and bromine content. The method can be based on the method disclosed in the prior art. During the phosgene synthesis process, the carbon fiber-loaded ionic liquid material of the present invention is used to adsorb and remove free chlorine and bromine impurities.

[0053] Preferably, a method for preparing phosgene with low chlorine and bromine content as described above comprises the following steps:

[0054] S1: mixing carbon monoxide and chlorine and passing them into a primary phosgene synthesis tower, where carbon monoxide and chlorine react to synthesize phosgene under the action of a catalyst;

[0055] S2: the gas phase stream obtained in step S1 is passed through a secondary phosgene synthesis tower for further reaction;

[0056] S3 sends the gas phase stream obtained in step S2 into a heat exchanger;

[0057] S4: passing the liquid phase stream obtained in step S3 through a chemical absorption tower, in which the carbon fiber-loaded ionic liquid material is loaded, and obtaining the separated and purified liquid phase phosgene from the bottom of the tower.

[0058] In the present invention, the specific processes of steps S1 and S2 can refer to conventional methods in the art, and the present invention has no special requirements, for example, refer to the methods disclosed in patents CN 111760581 B and CN 112441585 B;

[0059] Preferably, the gas phase stream obtained in step S1 (i.e., fresh phosgene synthesized by the reaction) contains less than 500 ppm (mass ratio) of free chlorine and less than 200 ppm of the total amount of bromine and hydrogen bromide.

[0060] Preferably, in step S3, the heat exchanger is a shell and tube heat exchanger, and the heat exchange medium is chilled water;

[0061] Preferably, in step S3, the operating pressure of the heat exchanger is 0.2-0.8 MPaA, preferably 0.3-0.5 MPaA; the outlet temperature of the liquid phase stream is 0-6°C, preferably 2-4°C.

[0062] Preferably, in step S4, the chemical absorption tower is a packed tower or a plate tower, and a packing carbon fiber loaded ionic liquid material is installed in the tower, and the total packing height of the packing is 8 to 9 m, preferably 8.5 m;

[0063] During the absorption process, the liquid phase flows from the top of the packing into the downward direction.

[0064] Preferably, in step S4, the absorption pressure is 0.2-0.8 MPaA, preferably 0.3-0.5 MPaA; the absorption temperature is 0-6°C, preferably 2-4°C; and the residence time is 5-30 min, preferably 10-15 min.

[0065] The inventors have found that when carbon fiber-loaded ionic liquid materials are used as adsorbents, when the cations in the ionic liquid have a multi-ether structure, they can produce strong hydrogen bond interactions with halogen elements and chemically absorb free chlorine and bromine in phosgene; for anions in the ionic liquid, the chemical absorption effects of methanesulfonic acid and thiocyanate ions on chlorine and bromine are significantly higher than those of chlorine, acetic acid, lactic acid, methylsulfate and other ions, so the carbon material loaded with the immobilized ionic liquid ([PGPMim Mim][H3CSO3]) of the present invention has a good adsorption effect on free chlorine and bromine in phosgene.

[0066] The phosgene with low chlorine and bromine content prepared by the above method of the present invention has a free chlorine content of 20 to 50 ppm, usually 25 to 30 ppm, and a free bromine content of 5 to 10 ppm, usually 7 to 8 ppm.

[0067] In a fourth aspect, based on the above-mentioned method for preparing phosgene with low chlorine and bromine content, the present invention provides a method for operating a chemical absorption tower and regenerating a carbon fiber-loaded ionic liquid material:

[0068] In step S4, two chemical absorption towers are connected in parallel. One of the two towers is in operation and the other is in a standby state. Low-pressure inert solvent vapor is continuously introduced into the standby tower to regenerate the carbon fiber-loaded ionic liquid material.

[0069] Preferably, during the regeneration process, the operating pressure in the chemical absorption tower is 0.2-0.3 MPaG, preferably 0.25 MPaG; the operating temperature is 50-80° C., preferably 60-65° C.; and the regeneration time is 3-4 h.

[0070] Preferably, the inert solvent vapor is selected from benzene series, preferably one or more of ethyl isophthalate, benzene, toluene, xylene, chlorobenzene and o-dichlorobenzene, more preferably chlorobenzene and / or o-dichlorobenzene, further preferably chlorobenzene.

[0071] Compared with the prior art, the technical solution of the present invention has the following positive effects:

[0072] (1) The present invention prepares a solid-supported ionic liquid ([PGPMim][H3CSO3]) that has a good adsorption effect on free chlorine and bromine in phosgene.

[0073] (2) Under the absorption effect of the immobilized ionic liquid carbon fiber, the content of free chlorine and free bromine in phosgene is greatly reduced, and isocyanate products with lower chlorinated and bromine impurity contents can be obtained. By selecting the process parameters of the chemical absorption reaction (for example, operating pressure and operating temperature), the total amount of free chlorine and bromine impurities in phosgene used for isocyanate synthesis can be controlled within a reasonable range, thereby avoiding the occurrence of side reactions during the phosgenation reaction to a great extent and significantly improving the product quality.

[0074] (3) This method has simple process control, convenient operation, low cost, and the absorbent filler used can be regenerated multiple times, which has strong industrial applicability. BRIEF DESCRIPTION OF THE DRAWINGS

[0075] Figure 1 This is a schematic flow diagram of the phosgene synthesis device used in Example 7.

[0076] Among them, A, primary phosgene synthesis tower, B, secondary phosgene synthesis tower, C, heat exchanger, D, chemical absorption tower (D1, D2). DETAILED DESCRIPTION

[0077] The present invention is further described below by means of specific examples. The examples described in the present invention are only used to illustrate the present invention and do not limit the scope of the present invention.

[0078] The main sources of raw materials involved in the examples and comparative examples of the present invention are as follows. Other sources are obtained from common commercial channels unless otherwise specified:

[0079] Ethylene glycol mono(4-nonylphenyl) ether: Shanghai Yien Chemical Technology Co., Ltd., analytical grade;

[0080] Methanesulfonyl chloride: Chengdu Grecia Chemical Technology Co., Ltd., analytical grade;

[0081] Diisopropylethylamine: Shanghai Jizhi Biochemical Technology Co., Ltd., analytical grade;

[0082] N-Methylimidazole: Shanghai Haohong Biopharmaceutical Technology Co., Ltd., analytical grade;

[0083] Carbon monoxide: produced by the gasification device in Yantai Wanhua Industrial Park, industrial products;

[0084] Chlorine: Produced by the chlorine and hydrogen workshop of Yantai Wanhua Chlor-Alkali Company, industrial product;

[0085] Activated carbon: produced by Tsurumi Co., Ltd., Japan, industrial product;

[0086] Multi-walled carbon nanotubes: Jiangsu Xianfeng Nanomaterial Technology Co., Ltd.

[0087] The main analytical methods used in the examples and comparative examples of the present invention are:

[0088] 1. Detection method of free chlorine content in phosgene:

[0089] (1) Detection principle:

[0090] Cl2+2KI→2KCl+I2

[0091] I2+2Na2S2O3→2NaI+Na2S4O6

[0092] (2) Detection process:

[0093] Prepare enough KI solution, freeze the phosgene sampling bottle and connect it to the glass funnel, add KI solution to the glass funnel, open the middle connecting valve to allow the KI solution to fully absorb the free chlorine in the phosgene, and then titrate with the prepared Na2S2O3 standard solution until the KI solution changes from purple-red to colorless.

[0094] (3) Calculation method of free chlorine in phosgene:

[0095]

[0096] Where Cl is the content of free chlorine in phosgene, mg / Nm 3 ;

[0097] V1 is the volume of Na2S4O6 standard solution consumed in titration, ml;

[0098] V2 is the volume of the gas sampling bottle, L;

[0099] C is the actual concentration of Na2S4O6 standard solution, mol / L.

[0100] (4) Method for detecting free bromine content in phosgene: The phosgene in the sampling bottle is passed into 10% NaOH for full absorption, and the bromine content of the absorption liquid is analyzed using an X-ray fluorescence spectrometer (XRF) analyzer (Axids-advanced, produced by Panalitical of the Netherlands). The method for calculating free bromine in phosgene is:

[0101]

[0102] Where Br is the content of free bromine in phosgene, mg / Nm 3 ;

[0103] m3 is the mass of NaOH solution after absorbing phosgene, g;

[0104] V4 is the volume of the gas sampling bottle, L;

[0105] w is the bromine content of the NaOH solution after absorbing phosgene, mg / kg.

[0106] 2. Analysis of chloroisocyanate and bromoisocyanate content: The content was determined by gas chromatography, which was a Hewlett Packard HP 5890 model. The chromatographic column was Restak TMRTX-1 Crossbond 100% dimethylpolysiloxane, with an inner diameter of 0.25 mm and a length of 105 m. The gas chromatography conditions were 50°C for 10 minutes, followed by a temperature program of 15°C / min to 200°C.

[0107] [Example 1]

[0108] Synthesis of immobilized ionic liquid 1 ([PGPMim][H3CSO3]):

[0109] 1) Take 1 mol of ethylene glycol mono(4-nonylphenyl) ether (n=3), mix it with 8 mol of dichloromethane, add 2.5 mol of diisopropylethylamine after mixing, gradually add 1.5 mol of methanesulfonyl chloride dropwise within 2.5 hours, react at 0°C for 105 minutes, then add 20 mol of deionized water, repeat washing six times, remove water from the washed liquid by reduced pressure distillation at 30 KPaA, then extract with 2.5 mol of extractant (petroleum ether / ethyl acetate in a molar ratio of 1:2), repeat extraction 5 times to obtain an intermediate.

[0110] Intermediate NMR characterization:

[0111] 1H NMR (500MHz, DMSO-d6): δ0.88(d,3H),1.29(m,12H),1.58(t,2H),2.62(m,2H),3.16( s,3H), 3.52(t,6H), 3.70(t,2H), 3.80(t,2H), 4.31(t,2H), 6.95(d,2H), 7.18(d,2H)

[0112] 2) The intermediate was mixed with 1.2 mol N-methylimidazole and reacted at 60°C for 1.2 h. After the reaction was completed, the product was washed with 3 mol ethyl acetate, and the washing was repeated 5 times. After vacuum drying for 48 h, a solid-supported ionic liquid 1 ([PGPMim][H3CSO3]) with a purity higher than 99% was obtained.

[0113] NMR characterization of immobilized ionic liquid 1:

[0114] 1H NMR (500MHz, DMSO-d6): δ0.88(d,3H),1.29(m,6H),1.52(t,4H),2.62(m,2H),3.02( s,6H), 3.52(t,6H), 3.80(t,2H), 4.20(t,2H), 4.31(t,2H), 6.95(d,2H), 7.18(d,2H)

[0115] [Example 2]

[0116] Synthesis of immobilized ionic liquid 2:

[0117] 1) Take 1 mol of ethylene glycol mono(4-nonylphenyl) ether (n=1), mix it with 5 mol of acetone, add 2 mol of triethylamine after mixing, gradually add 1.2 mol of methanesulfonyl chloride dropwise within 2 hours, react at -5°C for 100 minutes, then add 20 mol of deionized water, repeat washing six times, remove water from the washed liquid by reduced pressure distillation at 30 KPaA, then extract with 2.5 mol of extractant (petroleum ether / ethyl acetate in a molar ratio of 1:1.5), repeat extraction 8 times to obtain an intermediate.

[0118] 2) The intermediate was mixed with 1.1 mol N-methylimidazole and reacted at 50°C for 1 h. After the reaction was completed, the product was washed with 3 mol ethyl acetate, and the washing was repeated 5 times. After vacuum drying for 48 h, a solid-supported ionic liquid 2 ([PGPMim][H3CSO3]) with a purity higher than 99% was obtained.

[0119] [Example 3]

[0120] Synthesis of immobilized ionic liquid 3:

[0121] 1) Take 1 mol of ethylene glycol mono(4-nonylphenyl) ether (n=10), mix it with 10 mol of acetone, add 3 mol of triethylamine after mixing, gradually add 2 mol of methanesulfonyl chloride dropwise within 3 hours, react at 5°C for 120 minutes, then add 20 mol of deionized water, repeat washing six times, remove water from the washed liquid by reduced pressure distillation at 30 KPaA, then extract with 2.5 mol of extractant (petroleum ether / ethyl acetate in a molar ratio of 1:2), repeat extraction 8 times to obtain an intermediate.

[0122] 2) The intermediate was mixed with 1.4 mol N-methylimidazole and reacted at 70°C for 1.5 h. After the reaction was completed, the product was washed with 3 mol ethyl acetate, and the washing was repeated 5 times. After vacuum drying for 48 h, a solid-supported ionic liquid 3 ([PGPMim][H3CSO3]) with a purity higher than 99% was obtained.

[0123] [Example 4]

[0124] Preparation of carbon fiber loaded ionic liquid material 1:

[0125] First, the multi-walled carbon nanotubes were washed with water until pH = 7, dried, calcined at 450° C. for 24 h in a nitrogen atmosphere, and cooled to 25° C. for later use.

[0126] Take 1 mol of the solid-supported ionic liquid 1 prepared in Example 1, mix it with 2.4 mol of anhydrous ethanol and ultrasonicate it at a frequency of 18 kHz for 1 hour. After it is fully mixed, add multi-walled carbon nanotubes and fully impregnate them. After impregnation for 2.5 hours, continue drying at 45°C for 3 hours and continue drying at 85°C for 5 hours to obtain carbon fiber-supported ionic liquid material 1. The loading amount of the solid-supported ionic liquid 1 on the multi-walled carbon nanotubes is 25wt%.

[0127] [Example 5]

[0128] Preparation of carbon fiber loaded ionic liquid material 2:

[0129] First, the activated carbon was washed with water to pH = 7.2, dried, calcined at 300°C for 20 h in a nitrogen atmosphere, and cooled to 25°C for standby use.

[0130] Take 1 mol of the immobilized ionic liquid 2 prepared in Example 2, mix it with 2 mol of anhydrous ethanol and ultrasonicate it at a frequency of 10 kHz for 1 hour. After it is fully mixed, add multi-walled carbon nanotubes and fully impregnate them. After impregnation for 2 hours, continue drying at 45°C for 3 hours and continue drying at 85°C for 5 hours to obtain carbon fiber loaded ionic liquid material 2. The loading amount of the immobilized ionic liquid 2 on the activated carbon is 10 wt%.

[0131] [Example 6]

[0132] Preparation of carbon fiber loaded ionic liquid material 3:

[0133] First, the multi-walled carbon nanotubes were washed with water until the pH value was 7.5, dried, calcined at 500° C. for 30 h in a nitrogen atmosphere, and cooled to 25° C. for standby use.

[0134] Take 1 mol of the solid-supported ionic liquid 3 prepared in Example 3, mix it with 3 mol of anhydrous ethanol and ultrasonicate it at a frequency of 20 kHz for 2 hours. After it is fully mixed, add multi-walled carbon nanotubes and fully impregnate them. After impregnation for 3 hours, continue drying at 45°C for 3 hours and continue drying at 85°C for 6 hours to obtain carbon fiber-supported ionic liquid material 3. The loading amount of the solid-supported ionic liquid 3 on the multi-walled carbon nanotubes is 30 wt%.

[0135] [Example 7]

[0136] Preparation of phosgene with low chlorine and bromine content:

[0137] Process such as Figure 1 As shown, the chemical absorption towers D1 and D2 are filled with the carbon fiber-supported ionic liquid material 1 prepared in Example 4, and the filling method is:

[0138] The chemical absorption tower is filled along the flow direction of liquid phosgene. The first part (referred to as layer 1) is filled with porous inert ceramic balls (high thermal conductivity inert material) with a filling height of 2000 mm; the second part (referred to as layer 2) is filled with a mixture of porous inert ceramic balls and carbon fiber-loaded ionic liquid material 1 in a volume ratio of 20:70 (porous inert ceramic balls: carbon fiber-loaded ionic liquid material 1) with a filling height of 3000 mm; the third part (referred to as layer 3) is filled with carbon fiber-loaded ionic liquid material 1 with a filling height of 3500 mm.

[0139] The specific steps of the preparation process are:

[0140] S1 Phosgene primary synthesis reaction: 169 kmol / h carbon monoxide and 164 kmol / h chlorine are mixed at a molar ratio of 1.03 and then enter the primary phosgene synthesis tower A to react and generate phosgene. The reaction pressure is 0.2 MPaA and the reaction termination temperature is 60°C.

[0141] S2 Phosgene secondary synthesis reaction: The mixed gas after the reaction in the primary phosgene synthesis tower A is added to the secondary phosgene synthesis tower B for further reaction to obtain phosgene and phosgene synthesis tail gas whose main component is carbon monoxide. The fresh phosgene entering the secondary phosgene synthesis tower B (i.e. the mixed gas after the reaction in the primary phosgene synthesis tower A) has a free chlorine content of 400ppm and a total amount of bromine and hydrogen bromide of 70ppm.

[0142] S3 liquefaction: All the mixed gases from the secondary phosgene synthesis reaction enter the shell and tube heat exchanger C, and use chilled water at a temperature of -5°C for heat exchange. The operating pressure is 0.4MPaA; the outlet temperature of the liquid-phase phosgene at the heat exchanger outlet is 3°C.

[0143] S4 absorption: All the liquid phosgene at the outlet of the heat exchanger enters the chemical absorption tower D (D1, D2), the absorption pressure is 0.4MpaA; the absorption temperature is 3°C, the residence time is 15min, and the separated and purified liquid phosgene is obtained from the bottom of the tower.

[0144] During operation, one of the chemical absorption towers D1 and D2 is in operation, and the other is in a standby state. Chlorobenzene vapor at 60°C is continuously introduced into the standby tower, and the vapor pressure is 0.25MpaG. After continuous regeneration for 3 hours, the regeneration of the carbon fiber-loaded ionic liquid material is completed.

[0145] In this embodiment, the free chlorine content in the liquid phase phosgene at the bottom of the tower is 27 ppm, and the free bromine content is 8 ppm.

[0146] The bottom liquid phase phosgene was used to prepare crude isocyanate according to the method of Example 3 in patent CN 111961185 A. The crude isocyanate had a chloroisocyanate content of 15 ppm and a bromoisocyanate content of 5 ppm.

[0147] [Example 8]

[0148] Preparation of phosgene with low chlorine and bromine content:

[0149] Process such as Figure 1 As shown, the chemical absorption towers D1 and D2 are filled with the carbon fiber-supported ionic liquid material 2 prepared in Example 5, and the filling method is:

[0150] The chemical absorption tower is filled along the flow direction of liquid phosgene. The first part (referred to as layer 1) is filled with porous inert ceramic balls (high thermal conductivity inert material) with a filling height of 2000 mm; the second part (referred to as layer 2) is filled with a mixture of porous inert ceramic balls and carbon fiber-loaded ionic liquid material 2 in a volume ratio of 20:70 (porous inert ceramic balls: carbon fiber-loaded ionic liquid material 2) with a filling height of 3000 mm; the third part (referred to as layer 3) is filled with carbon fiber-loaded ionic liquid material 2 with a filling height of 4000 mm.

[0151] The specific steps of the preparation process are:

[0152] S1 Phosgene primary synthesis reaction: 169 kmol / h carbon monoxide and 164 kmol / h chlorine are mixed at a molar ratio of 1.03 and then enter the primary phosgene synthesis tower A to react and generate phosgene. The reaction pressure is 0.2 MPaA and the reaction termination temperature is 60°C.

[0153] S2 Phosgene secondary synthesis reaction: The mixed gas after the reaction in the primary phosgene synthesis tower A is added to the secondary phosgene synthesis tower B for further reaction to obtain phosgene and phosgene synthesis tail gas whose main component is carbon monoxide. The fresh phosgene entering the secondary phosgene synthesis tower B (i.e. the mixed gas after the reaction in the primary phosgene synthesis tower A) has a free chlorine content of 400ppm and a total amount of bromine and hydrogen bromide of 70ppm.

[0154] S3 liquefaction: All the mixed gases from the secondary phosgene synthesis reaction enter the shell and tube heat exchanger C, and use chilled water at a temperature of -5°C for heat exchange. The operating pressure is 0.2MPaA; the outlet temperature of the liquid-phase phosgene at the heat exchanger outlet is 0°C.

[0155] S4 absorption: all the liquid phosgene at the heat exchanger outlet enters the chemical absorption tower D (D1, D2), the absorption pressure is 0.2MpaA; the absorption temperature is 0℃, the residence time is 30min, and the separated and purified liquid phosgene is obtained from the bottom of the tower.

[0156] During operation, one of the chemical absorption towers D1 and D2 is in operation, and the other is in standby operation. Chlorobenzene vapor at 50°C is continuously introduced into the standby tower, and the vapor pressure is 0.2MpaG. After continuous regeneration for 4 hours, the regeneration of the carbon fiber-loaded ionic liquid material is completed.

[0157] In this embodiment, the free chlorine content in the liquid phase phosgene at the bottom of the tower is 20 ppm, and the free bromine content is 5 ppm.

[0158] The bottom liquid phase phosgene was used to prepare crude isocyanate according to the method of Example 3 in patent CN 111961185 A. The crude isocyanate had a chloroisocyanate content of 12 ppm and a bromoisocyanate content of 3 ppm.

[0159] [Example 9]

[0160] Preparation of phosgene with low chlorine and bromine content:

[0161] Process such as Figure 1 As shown, the chemical absorption towers D1 and D2 are filled with the carbon fiber-supported ionic liquid material 3 prepared in Example 6, and the filling method is:

[0162] The chemical absorption tower is filled along the flow direction of liquid phosgene. The first part (referred to as layer 1) is filled with porous inert ceramic balls (high thermal conductivity inert material) with a filling height of 2000 mm; the second part (referred to as layer 2) is filled with a mixture of porous inert ceramic balls and carbon fiber-loaded ionic liquid material 3, with a volume ratio of 20:70 (porous inert ceramic balls: carbon fiber-loaded ionic liquid material 3) and a filling height of 3000 mm; the third part (referred to as layer 3) is filled with carbon fiber-loaded ionic liquid material 3 with a filling height of 3000 mm.

[0163] The specific steps of the preparation process are:

[0164] S1 Phosgene primary synthesis reaction: 169 kmol / h carbon monoxide and 164 kmol / h chlorine are mixed at a molar ratio of 1.03 and then enter the primary phosgene synthesis tower A to react and generate phosgene. The reaction pressure is 0.2 MPaA and the reaction termination temperature is 60°C.

[0165] S2 Phosgene secondary synthesis reaction: The mixed gas after the reaction in the primary phosgene synthesis tower A is added to the secondary phosgene synthesis tower B for further reaction to obtain phosgene and phosgene synthesis tail gas whose main component is carbon monoxide. The fresh phosgene entering the secondary phosgene synthesis tower B (i.e. the mixed gas after the reaction in the primary phosgene synthesis tower A) has a free chlorine content of 400ppm and a total amount of bromine and hydrogen bromide of 70ppm.

[0166] S3 liquefaction: All the mixed gases from the secondary phosgene synthesis reaction enter the shell and tube heat exchanger C, and use chilled water at a temperature of -5°C for heat exchange. The operating pressure is 0.8MPaA; the outlet temperature of the liquid-phase phosgene at the heat exchanger outlet is 6°C.

[0167] S4 absorption: All the liquid phosgene at the outlet of the heat exchanger enters the chemical absorption tower D (D1, D2), the absorption pressure is 0.8MpaA; the absorption temperature is 6°C, the residence time is 5min, and the separated and purified liquid phosgene is obtained from the bottom of the tower.

[0168] During operation, one of the chemical absorption towers D1 and D2 is in operation, and the other is in a standby state. Chlorobenzene vapor at 80°C is continuously introduced into the standby tower, and the vapor pressure is 0.3MpaG. After continuous regeneration for 3.5 hours, the regeneration of the carbon fiber-loaded ionic liquid material is completed.

[0169] In this embodiment, the free chlorine content in the liquid phase phosgene at the bottom of the tower is 50 ppm, and the free bromine content is 10 ppm.

[0170] The bottom liquid phase phosgene was used to prepare crude isocyanate according to the method of Example 3 in patent CN 111961185 A. The crude isocyanate had a chloroisocyanate content of 35 ppm and a bromoisocyanate content of 8 ppm.

[0171] [Comparative Example 1]

[0172] Preparation of supported carbon material: refer to the method of Example 4, except that the immobilizable ionic liquid 1 is replaced by an equal amount of the intermediate prepared in step 1) of Example 1, and other operations and conditions remain unchanged to obtain the supported carbon material.

[0173] Preparation of phosgene: Refer to the method of Example 7, except that the carbon fiber-loaded ionic liquid material 1 prepared in Example 4 loaded in the chemical absorption towers D1 and D2 is replaced by the above-mentioned loaded carbon material of this comparative example, and other operations and conditions remain unchanged. The free chlorine content in the liquid phase phosgene at the bottom of the tower is 180 ppm, and the free bromine content is 50 ppm.

[0174] Preparation of isocyanate: According to the method of Example 7, the isocyanate product was prepared, in which the content of chloroisocyanate was 120 ppm and the content of bromoisocyanate was 35 ppm.

[0175] [Comparative Example 2]

[0176] Preparation of ionic liquid: Referring to the method of Example 1, the only difference is that polyethylene glycol mono(4-nonylphenyl) ether is replaced by an equal amount of n-butane bromide to prepare the ionic liquid.

[0177] Preparation of supported carbon material: refer to the method of Example 4, except that the immobilizable ionic liquid 1 is replaced with an equal amount of the above ionic liquid, and other operations and conditions remain unchanged to obtain the supported carbon material.

[0178] Preparation of phosgene: Refer to the method of Example 7, except that the carbon fiber-loaded ionic liquid material 1 prepared in Example 4 loaded in the chemical absorption towers D1 and D2 is replaced by the above-mentioned loaded carbon material of this comparative example, and other operations and conditions remain unchanged. The free chlorine content in the liquid phase phosgene at the bottom of the tower is 220 ppm, and the free bromine content is 35 ppm.

[0179] Preparation of isocyanate: According to the method of Example 7, the isocyanate product was prepared, in which the content of chloroisocyanate was 141 ppm and the content of bromoisocyanate was 27 ppm.

[0180] [Comparative Example 3]

[0181] Preparation of ionic liquid: Referring to the method of Example 1, the only difference is that methanesulfonyl chloride is replaced by an equal amount of trifluoroacetic acid to prepare the ionic liquid.

[0182] Preparation of supported carbon material: refer to the method of Example 4, except that the immobilizable ionic liquid 1 is replaced with an equal amount of the above ionic liquid, and other operations and conditions remain unchanged to obtain the supported carbon material.

[0183] Preparation of phosgene: Refer to the method of Example 7, except that the carbon fiber-loaded ionic liquid material 1 prepared in Example 4 loaded in the chemical absorption towers D1 and D2 is replaced by the above-mentioned loaded carbon material of this comparative example, and other operations and conditions remain unchanged. The free chlorine content in the liquid phase phosgene at the bottom of the tower is 200 ppm, and the free bromine content is 40 ppm.

[0184] Preparation of isocyanate: According to the method of Example 7, the isocyanate product was prepared, in which the content of chloroisocyanate was 134 ppm and the content of bromoisocyanate was 32 ppm.

[0185] [Comparative Example 4]

[0186] Preparation of ionic liquid: Referring to the method of Example 1, the only difference is that N-methylimidazole is replaced by an equal amount of tetramethylguanidine to prepare the ionic liquid.

[0187] Preparation of supported carbon material: refer to the method of Example 4, except that the immobilizable ionic liquid 1 is replaced with an equal amount of the above ionic liquid, and other operations and conditions remain unchanged to obtain the supported carbon material.

[0188] Preparation of phosgene: Refer to the method of Example 7, except that the carbon fiber-loaded ionic liquid material 1 prepared in Example 4 loaded in the chemical absorption towers D1 and D2 is replaced by the above-mentioned loaded carbon material of this comparative example, and other operations and conditions remain unchanged. The free chlorine content in the liquid phase phosgene at the bottom of the tower is 280 ppm, and the free bromine content is 55 ppm.

[0189] Preparation of isocyanate: According to the method of Example 7, the isocyanate product was prepared, in which the content of chloroisocyanate was 167 ppm and the content of bromoisocyanate was 37 ppm.

[0190] [Comparative Example 5]

[0191] Preparation of supported carbon material: refer to the method of Example 4, except that the immobilizable ionic liquid 1 is replaced by imidazolium hydrogen sulfate, and other operations and conditions remain unchanged to obtain supported carbon material.

[0192] Preparation of phosgene: Refer to the method of Example 7, except that the carbon fiber-loaded ionic liquid material 1 prepared in Example 4 loaded in the chemical absorption towers D1 and D2 is replaced by the above-mentioned loaded carbon material of this comparative example, and other operations and conditions remain unchanged. The free chlorine content in the liquid phase phosgene at the bottom of the tower is 300 ppm, and the free bromine content is 60 ppm.

[0193] Preparation of isocyanate: According to the method of Example 7, the isocyanate product was prepared, in which the content of chloroisocyanate was 189 ppm and the content of bromoisocyanate was 42 ppm.

Claims

1. An ionic liquid that can be immobilized, the structure of which is shown in formula (1): In the formula, n is 1-10, preferably 3-5.

2. A method for preparing the immobilized ionic liquid according to claim 1, characterized in that the steps include: 1) mixing polyethylene glycol mono(4-nonylphenyl) ether with methanesulfonyl chloride, an acid-binding agent and a solvent for reaction, then removing the solvent, washing with water, drying and extracting to obtain an intermediate; 2) The intermediate is mixed with N-methylimidazole for reaction, and then washed and dried to obtain an ionic liquid that can be immobilized.

3. The preparation method according to claim 2, characterized in that: Step 1) The molecular formula of polyethylene glycol mono(4-nonylphenyl) ether is (C2H4O)nC 15 H 23 O, wherein n is 1 to 10, preferably 3 to 5; and / or Step 1) the acid binding agent is selected from organic amine compounds, preferably one or more of diisopropylethylamine and triethylamine; and / or Step 1) The solvent is selected from an organic solvent that is inert in the reaction system, preferably one or more of acetone and dichloromethane; and / or Step 1) the molar ratio of polyethylene glycol mono(4-nonylphenyl) ether to methanesulfonyl chloride is 1:1.2-2, preferably 1:1.5-1.8; and / or Step 1) the molar ratio of polyethylene glycol mono(4-nonylphenyl) ether to the acid binding agent is 1:2-3, preferably 1:2.3-2.5; and / or Step 1) the molar ratio of polyethylene glycol mono(4-nonylphenyl) ether to the solvent is 1:5-10, preferably 1:8-10; and / or The molar ratio of the polyethylene glycol mono(4-nonylphenyl) ether in step 1) to the N-methylimidazole in step 2) is 1:1.1-1.4, preferably 1:1.2-1.3; and / or Step 1) The reaction temperature is -5 to 5°C, preferably -2 to 0°C, and the time is 100 to 120 min, preferably 105 to 110 min; During the reaction, the methanesulfonyl chloride is preferably added continuously, more preferably dropwise, for a time of 2 to 3 hours, preferably 2.5 to 2.8 hours; and / or Step 2) The reaction temperature is 50-70°C, preferably 60-65°C, and the time is 1-1.5h, preferably 1.2-1.4h.

4. A carbon fiber loaded ionic liquid material, characterized in that: Prepared by loading the immobilizable ionic liquid according to claim 1 or the immobilizable ionic liquid prepared by the method according to claim 2 or 3 on a carbon material; Preferably, the loading amount of the immobilizable ionic liquid on the carbon material is 10 to 30 wt%, preferably 20 to 25 wt%; Preferably, the carbon material is selected from activated carbon or multi-walled carbon nanotubes.

5. A method for preparing the carbon fiber-loaded ionic liquid material according to claim 4, characterized in that: The following steps are involved: (1) washing the carbon material with water until it is neutral, drying it, and then calcining it in a nitrogen atmosphere; (2) The immobilizable ionic liquid is dissolved in ethanol and ultrasonically mixed, and then the carbon material is added thereto and fully impregnated, and after drying, the carbon fiber loaded ionic liquid material is obtained.

6. The preparation method according to claim 5, characterized in that: The water in step (1) is washed to a neutral pH of 7.0 to 7.5; and / or The calcination in step (1) is carried out at a temperature of 300 to 500° C., preferably 450 to 460° C., for a time of 20 to 30 hours, preferably 24 to 25 hours; and / or The molar ratio of the immobilized ionic liquid to ethanol in step (2) is 1:2-3, preferably 1:2.4-2.6; and / or The ultrasonic mixing in step (2) is performed for 1 to 2 hours, preferably 1 to 1.5 hours; the ultrasonic frequency is 10 to 20 kHz, preferably 18 to 20 kHz; and / or The soaking time in step (2) is 2 to 3 hours, preferably 2.5 to 2.6 hours; and / or In step 2), the drying is first performed at 45-60° C. for 3-3.3 hours, and then at 85-90° C. for 5-6 hours.

7. A method for preparing phosgene with low chlorine and bromine content, characterized in that: The following steps are involved: S1: mixing carbon monoxide and chlorine and passing them into a primary phosgene synthesis tower, where carbon monoxide and chlorine react to synthesize phosgene under the action of a catalyst; S2: the gas phase stream obtained in step S1 is passed through a secondary phosgene synthesis tower for further reaction; S3 sends the gas phase stream obtained in step S2 into a heat exchanger; S4 passes the liquid phase stream obtained in step S3 through a chemical absorption tower, in which the carbon fiber-loaded ionic liquid material according to claim 4 or the carbon fiber-loaded ionic liquid material prepared by the method according to claim 5 or 6 is loaded, and separated and purified liquid phosgene is obtained from the bottom of the tower.

8. The preparation method according to claim 7, characterized in that: In step S3, the heat exchanger is a shell and tube heat exchanger, and the heat exchange medium is chilled water; and / or In step S3, the operating pressure of the heat exchanger is 0.2-0.8 MPaA, preferably 0.3-0.5 MPaA; the outlet temperature of the liquid phase stream is 0-6°C, preferably 2-4°C; and / or In step S4, the chemical absorption tower is a packed tower or a plate tower, and the tower is equipped with a packing carbon fiber loaded ionic liquid material, and the total packing height of the packing is 8 to 9 m, preferably 8.5 m; Preferably, during the absorption process, the liquid phase flows downward from above the packing; and / or In step S4, the absorption pressure is 0.2-0.8 MPaA, preferably 0.3-0.5 MPaA; the absorption temperature is 0-6°C, preferably 2-4°C; and the residence time is 5-30 min, preferably 10-15 min.

9. A method for operating a chemical absorption tower and regenerating a carbon fiber-loaded ionic liquid material, characterized in that: In step S4 of the preparation method described in claim 8, two chemical absorption towers are connected in parallel. During operation, one of the two towers is in operation and the other is in a standby state. Low-pressure inert solvent vapor is continuously introduced into the standby tower to regenerate the carbon fiber-loaded ionic liquid material.

10. The operation of the chemical absorption tower and the regeneration method of the carbon fiber loaded ionic liquid material according to claim 9, characterized in that: During the regeneration process, the operating pressure in the chemical absorption tower is 0.2-0.3 MPaG, preferably 0.25 MPaG; the operating temperature is 50-80°C, preferably 60-65°C; the regeneration time is 3-4 hours; Preferably, the inert solvent vapor is selected from benzene series, preferably one or more of ethyl isophthalate, benzene, toluene, xylene, chlorobenzene and o-dichlorobenzene, more preferably chlorobenzene and / or o-dichlorobenzene, further preferably chlorobenzene.

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