Organic-inorganic hybrid membrane and application thereof in isocyanate production process

Abstract

The invention discloses an organic-inorganic hybrid membrane and an application thereof in organic solvent purification in an isocyanate production process, the organic-inorganic hybrid membrane is used for purifying a solvent and removing water, hydrogen chloride and / or phosgene mixed in the organic solvent, the hybrid membrane is prepared and generated by taking BTESE as a silicon source precursor through an acid catalysis gel method, and the organic-inorganic hybrid membrane is used for purifying the organic solvent and removing water, hydrogen chloride and / or phosgene. The solvent can be directly used after being purified, so that the process flow is greatly simplified, the operation cost is reduced, the reaction quality and the process stability are improved, and meanwhile, the solvent under various severe conditions can be recycled to achieve the target of zero emission.

Description

Technical Field

[0001] The invention relates to the field of isocyanate, and in particular to an organic-inorganic hybrid membrane and application thereof in the production process of isocyanate. Background Art

[0002] Isocyanate is a general term for various esters of isocyanic acid, which are used in household appliances, automobiles, construction, footwear, furniture, adhesives and other industries. If classified by the number of -NCO groups, it includes monoisocyanate R-N=C=O and diisocyanate O=C=N-R-N=C=O and polyisocyanate. Common diisocyanates include toluene diisocyanate (TDI), isophorone diisocyanate (IPDI), diphenylmethane diisocyanate (MDI), dicyclohexylmethane diisocyanate (HMDI), hexamethylene diisocyanate (HDI), lysine diisocyanate (LDI), etc. Most of the existing industrial production methods of isocyanates use the phosgenation method, which is prepared by mixing the corresponding primary amine with an inert solvent and then reacting it with phosgene through a phosgenation reaction and a series of post-treatment processes.

[0003] In the production of isocyanates by phosgenation, the inert solvents currently used are mainly one or more of chloroaromatic hydrocarbons, benzene, alkylbenzenes, alkyl esters, carbonates, etc. The solvent is recycled in the isocyanate, which plays a vital role in the reaction quality. The main influencing factors in the circulating solvent are moisture, hydrogen chloride and phosgene, which need to be strictly controlled during the entire phosgenation reaction. In the solvent removal process, the conventional process adopts negative pressure distillation, and the system may introduce impurities such as moisture to cause the moisture in the circulating solvent to increase, participate in the phosgenation reaction, and water will react with isocyanate to generate urea substances, affecting the reaction yield, and easily causing system blockage, which is extremely undesirable. At the same time, the removed solvent contains a large amount of components such as hydrogen chloride and phosgene, which need to be further processed, resulting in a substantial increase in cost, and the process flow is complicated. In the process tail gas, inert gases such as nitrogen will carry a certain amount of solvent, and the solvent needs to be processed by adsorption analysis and other methods. The solvent in the analytical solution contains a large amount of moisture, which cannot be effectively directly recovered, resulting in a waste of solvent resources. During the start-up and shutdown process, a large amount of high-water solvents (such as chlorobenzene) are also produced. Conventional means cannot be used to recycle and dispose of them. They need to be incinerated in an incinerator or outsourced in barrels, which makes the process complicated and the operating cost higher. Impurities such as water, hydrogen chloride, and phosgene circulate in the solvent system, which can cause corrosion of equipment or pipelines for a long time, posing a huge safety hazard.

[0004] The prior art mainly refines circulating solvents by distillation to reduce the impurities such as moisture, hydrogen chloride, phosgene, etc. in the circulating solvents. The distillation method has a long process route, high investment and operating costs, and requires a large amount of steam to meet the process requirements. In the process of starting and stopping and tail gas treatment, it is inevitable to produce solvents with high water concentrations. This part of high water solvents (such as chlorobenzene) cannot be recycled by conventional means such as distillation, which is bound to cause a waste of chlorobenzene resources. In view of the problems existing in the prior art, it is of great significance to develop a purification method for organic solvents to separate and remove impurities such as moisture, hydrogen chloride, phosgene, etc. from solvents in a more efficient, lower cost, safer and more reliable manner. Summary of the invention

[0005] The purpose of the present invention is to overcome the shortcomings of the prior art and provide an organic-inorganic hybrid membrane and its application in the production of isocyanates. The organic-inorganic hybrid membrane is used to purify organic solvents and remove water, hydrogen chloride and / or phosgene in the solvents. It can be used to refine circulating solvents, greatly simplify the process flow, reduce operating costs, improve reaction quality and process stability, and at the same time recycle solvents under various harsh conditions to achieve the goal of zero emissions.

[0006] The first aspect of the present invention aims to provide a method for preparing an organic-inorganic hybrid membrane.

[0007] The second aspect of the present invention aims to provide the use of the organic-inorganic hybrid membrane prepared as above in the production of isocyanate, using the organic-inorganic hybrid membrane to purify the solvent, remove water, hydrogen chloride and phosgene from the solvent, and use it to refine the circulating solvent.

[0008] The present invention aims to provide a method for preparing an organic-inorganic hybrid membrane, comprising the following steps:

[0009] (a) Preparation of BTESE sol: 1,2-bis(triethoxysilyl)ethane (BTESE) organic solution was prepared, and HCl / H2O solution was added to react to obtain BTESE sol;

[0010] (b) Preparation of BTESE membrane: A particle layer is coated on a porous α-Al2O3 ceramic tube support, calcined at high temperature, then a transition layer is coated, calcined at high temperature, and then a BTESE sol is coated and calcined to form a separation layer, and finally an organic-inorganic hybrid membrane is obtained.

[0011] In step (a) of the present invention, the solvent of the organic solution is selected from alcohol solvents, preferably alcohols with carbon numbers of C1-C6, more preferably methanol and ethanol, and further preferably ethanol.

[0012] As a preferred solution, in step (a) of the present invention, the mass fraction of the BTESE organic solution is 5%-10%.

[0013] In step (a) of the present invention, the molar ratio of BTESE, H2O and HCl is BTESE:H2O:HCl=1:X:0.2 (X=20-300, for example 20, 50, 100, 150, 200, 250, 300).

[0014] In step (a) of the present invention, the process of adding HCL / H2O is preferably accompanied by stirring, the stirring speed is 20-60r / min, the reaction temperature is 40-60°C, and the reaction time is 1-3h; the reaction temperature can be specifically controlled by a water bath.

[0015] In step (b) of the present invention, the overall structure of the porous α-Al2O3 ceramic tube is a hollow cylindrical tube with a pore size of 0.8-1.5 μm and a porosity of 20%-40%.

[0016] Preferably, the porous αAl2O3 ceramic tube has a length of 600-1200 mm and an outer diameter of 8-16 mm.

[0017] As a preferred solution, in step (b) of the present invention, the particle layer is two kinds of αAl2O3 particles;

[0018] Preferably, the particle sizes of the two αAl2O3 particles are 0.8-1.2 μm and 0.1-0.4 μm, respectively. The more preferred coating order is to coat the αAl2O3 particles with larger particle size first.

[0019] Preferably, the calcination temperature after coating the particle layer is 400-800° C., more preferably 500-700° C.; the calcination time is 20-30 min; the calcination times are preferably multiple times, more preferably 2-4 times.

[0020] In step (b) of the present invention, the transition layer is applied by coating SiO2-ZrO2 sol on the particle layer;

[0021] Preferably, the concentration of the SiO2-ZrO2 sol is 0.5-5wt%, and the molar ratio of Si to Zr is Si:Zr=1:(0.5-2).

[0022] Preferably, the calcination temperature after coating the transition layer is 400-800° C., more preferably 500-700° C.; the calcination time is 20-30 min; the calcination times are preferably multiple times, more preferably 6-8 times.

[0023] In step (b) of the present invention, the calcination temperature for forming the separation layer is 400-800°C, preferably 500-700°C; the calcination time is 20-30min; the calcination times are preferably multiple times, more preferably 2-4 times.

[0024] As a preferred solution, the porous αAl2O3 ceramic tube support of the present invention is pretreated before coating in step (b), which may include water washing, alkali washing, acid washing, etc.

[0025] Preferably, the porous αAl2O3 ceramic tube of the present invention is immersed in deionized water for washing for 1-3 hours, during which ultrasonic treatment is performed, and the deionized water is replaced every 20 minutes.

[0026] Preferably, the ceramic tube of the present invention is immersed in an alkaline solution for alkaline washing, during which ultrasonic treatment is preferably performed. The alkaline solution can be selected from sodium hydroxide solution, etc. The concentration of the alkaline solution is 0.5wt%-2wt%, and the alkaline washing time is 0.5-2h.

[0027] Preferably, the pickling of the ceramic tube of the present invention is carried out by immersing it in an acid solution, the acid solution can be selected from hydrochloric acid, etc., the concentration of the acid solution can be selected from 0.5wt%-2wt%, and the pickling time is 0.5-2h.

[0028] Preferably, the ceramic tube of the present invention is acid-washed to neutrality, dried and calcined;

[0029] Preferably, the drying temperature is 80-120°C, and the drying time is 5-20h, more preferably 10-15h; preferably, the calcination temperature is 400-800°C, more preferably 500-700°C; and the calcination time is 5-20h, more preferably 10-15h.

[0030] Another object of the present invention is to provide a method for purifying an organic solvent in isocyanate production, using the organic-inorganic hybrid membrane prepared above to remove water, hydrogen chloride and / or phosgene from the organic solvent.

[0031] The organic solvent used in the production of isocyanate of the present invention is preferably one or more of chlorinated aromatics, alkyl esters, carbonates, toluene and xylene, more preferably one or more of chlorobenzene, dichlorobenzene, toluene and xylene, further preferably chlorobenzene.

[0032] The organic solvent of the present invention may contain one or more of water, hydrogen chloride and phosgene, such as water, water and hydrogen chloride, water, hydrogen chloride and phosgene.

[0033] Preferably, based on the total mass of the mixture of water and / or hydrogen chloride and / or phosgene and the organic solvent, the water content can reach 0.0001wt%-80wt%, preferably 0.1wt%-20wt%, more preferably 0.1wt%-2wt%; and / or: the hydrogen chloride content can reach 0.0001wt%-80wt%, preferably 0.1wt%-20wt%; and / or: the phosgene content can reach 0.0001wt%-80wt%, preferably 0.1wt%-20wt%, and the rest is the organic solvent.

[0034] In a specific embodiment, the mixture can be in a gas phase, a liquid phase, a gas-liquid two-phase state, or a gas-liquid-liquid three-phase state. The process for removing organic solvents by the organic-inorganic hybrid membrane of the present invention is a continuous process or a cyclic intermittent process, preferably a one-pass continuous process.

[0035] As a preferred embodiment, the method for purifying an organic solvent in isocyanate production described in the present invention is to pass an organic solvent mixed with water, hydrogen chloride and / or phosgene into an organic-inorganic hybrid membrane device, and the organic solvent passes through the outside of the membrane tube, wherein the water, hydrogen chloride and / or phosgene penetrate into the inside of the membrane tube for separation and removal, and the membrane outlet is the purified qualified organic solvent.

[0036] Preferably, the organic-inorganic hybrid membrane device is a single-stage or multi-stage membrane separator connected in series, wherein the number of stages is 1-10, preferably 1-8, and more preferably 2-6.

[0037] Preferably, the temperature of the organic-inorganic hybrid membrane device is 20-120°C, preferably 40-110°C, and more preferably 60-100°C.

[0038] Preferably, the flow rate of the organic solvent in the organic-inorganic hybrid membrane device is 0.01-3 m / s, preferably 0.05-2 m / s, and more preferably 0.3-1.5 m / s.

[0039] Preferably, the permeate side pressure of the organic-inorganic hybrid membrane device is 0.01-10 KPaA, preferably 0.1-5 KPaA, and more preferably 0.5-3 KPaA.

[0040] As a preferred embodiment, after the organic solvent mixed with water, hydrogen chloride and / or phosgene of the present invention is treated by an organic-inorganic hybrid membrane device, the water mass content can be reduced to 0.1-200 ppm, preferably 1-100 ppm; the hydrogen chloride mass content can be reduced to below 50 ppm, preferably below 5 ppm; the phosgene mass content can be reduced to below 100 ppm, preferably below 10 ppm.

[0041] After the solvent described in the present invention is treated by the organic-inorganic hybrid membrane device, the solvent can be directly recycled and reused without the need for high-energy-consuming treatment methods such as conventional distillation, which greatly simplifies the process flow and reduces the operating cost by 60%-90%. At the same time, the process can recycle solvent waste liquid with high water, hydrogen chloride and / or phosgene content, effectively solving the difficult waste liquid treatment problem and achieving the goal of zero emission. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Figure 1 It is a process flow chart for purifying organic solvents in isocyanate production in the present invention, wherein 1 is a raw material, 2 is a feed pump, 3 is a preheater, 4 is a membrane device, 5 is a membrane assembly, 6 is a membrane outlet solvent, 7 is a permeate side gas phase, 8 is a condenser, 9 is tail gas, 10 is a vacuum pump, 11 is a permeate, and 12 is a purification solvent. DETAILED DESCRIPTION

[0043] The present invention is further described below by combining the accompanying drawings and examples. The examples of the present invention take chlorobenzene as an organic solvent, but the present invention is not limited thereto. The test methods in the following examples that do not indicate specific conditions are usually based on conventional conditions.

[0044] Measurement method of moisture content in chlorobenzene:

[0045] The water content in chlorobenzene was determined by Karl Fischer titration, using the Swiss Metrohm 870KF Coulometric Moisture Analyzer. The method was carried out in accordance with GBT 6283-2008 General Method for Determination of Water Content in Chemical Products.

[0046] Measurement method of hydrogen chloride content in chlorobenzene:

[0047] Hydrogen chloride in chlorobenzene is titrated by potentiometric automatic titration using conventional NaOH solution and silver nitrate solution.

[0048] Measurement method of phosgene content in chlorobenzene:

[0049] The phosgene content in chlorobenzene is determined by gas chromatography. First, dimethyl carbonate is weighed, dissolved in chlorobenzene, and diluted with dichloromethane and methanol solution to standard solutions of different concentrations. Gas phase analysis is performed, and peak area and concentration are plotted on EXCLE to draw a standard curve. Then, a methanol and dichloromethane mixture is prepared, in which the volume ratio of dichloromethane to methanol is 1:9. 0.3g of photochemical liquid is weighed, and 1g of mixed solvent is added. After the solution is mixed, it is derivatized in an oven at 70°C for 80 minutes to derive dimethyl carbonate from phosgene. Then, gas chromatography is used to measure, read the sample peak area, calculate its concentration using the standard curve, and convert it into phosgene content.

[0050] Detector: Agilent 7890A, chromatographic column HP-5 (30m×0.25um×320μm). Chromatographic conditions: column temperature: 50℃ for 0.5min, 5℃ / min to 80℃ for 1min; 10℃ / min to 280℃ for 10min, injection port temperature: 280℃, detector temperature: 295℃, septum purge gas flow rate: 3.0mL / min, carrier gas (nitrogen) flow rate: 3mL / min, air flow rate: 350mL / min, hydrogen flow rate: 35mL / min, tail gas (nitrogen) flow rate: 25mL / min, split injection, split ratio 1:10, injection volume 0.5μL.

[0051] Porous αAl2O3 ceramic tube support (provided by Nanjing University of Technology): average pore size 1 μm, porosity 30%, length 800 mm, outer diameter 12 mm;

[0052] 1,2-Bis(triethoxysilyl)ethane (BTESE, 96%, Aladdin Reagent Co., Ltd.);

[0053] Hydrochloric acid (HCl, analytical grade, Sinopharm Reagent Co., Ltd.);

[0054] Anhydrous ethanol (99.8%, Sinopharm Reagent Co., Ltd.);

[0055] Alumina (αAl2O3 particles, 99.9%, Aladdin Reagent Co., Ltd.).

[0056] Organic-inorganic hybrid membrane preparation example 1

[0057] Take 20 kg of 1,2-bis(triethoxysilyl)ethane (BTESE) and dissolve it in 380 kg of anhydrous ethanol. Add HCl / H2O solution while stirring in a water bath, wherein the molar ratio of BTESE, H2O and HCl is BTESE:H2O:HCl=1:20:0.2, the water bath temperature is 50°C, the stirring speed is 60 r / min, the reaction time is 1 h, and the BTESE sol is obtained by reaction.

[0058] The porous αAl2O3 ceramic tube was soaked in deionized water for 3 hours, ultrasonically treated during the process, and the deionized water was replaced every 20 minutes. After washing, it was soaked in 1wt% sodium hydroxide solution for alkali washing for 0.5 hours, and then soaked in 0.5wt% hydrochloric acid for acid washing for 2 hours, ultrasonically treated during the process, and washed to neutrality after acid washing, and then dried and calcined, wherein the drying temperature was 80℃, the drying time was 20 hours, the calcination temperature was 600℃, and the calcination time was 15 hours. Then, two αAl2O3 particles with particle sizes of 0.8μm and 0.3μm were coated on the ceramic tube in sequence to form a particle layer, and calcined at 600℃ for 30 minutes, and the calcination was repeated twice. Then, 0.5wt% SiO2-ZrO2 sol was coated on the outside of the particle layer to form a transition layer, wherein the molar ratio of Si to Zr was Si:Zr=1:2, and calcined at 400℃ for 30 minutes, and the calcination was repeated 6 times. Then, BTESE sol was coated on the outside of the transition layer, calcined at 400°C for 20 min, and the calcination was repeated 4 times to form a separation layer, and finally an organic-inorganic hybrid membrane was obtained.

[0059] Organic-inorganic hybrid membrane preparation example 2

[0060] Take 20 kg of 1,2-bis(triethoxysilyl)ethane (BTESE) and dissolve it in 180 kg of anhydrous ethanol. Add HCl / H2O solution while stirring in a water bath, wherein the molar ratio of BTESE, H2O and HCl is BTESE:H2O:HCl=1:300:0.2, the water bath temperature is 40°C, the stirring speed is 40 r / min, the reaction time is 3 h, and the BTESE sol is obtained by reaction.

[0061] The porous αAl2O3 ceramic tube was soaked in deionized water for 1 hour, ultrasonically treated during the process, and the deionized water was replaced every 20 minutes. After washing, it was soaked in 2wt% sodium hydroxide solution for 2 hours, and then soaked in 1wt% hydrochloric acid for acid washing for 1 hour, ultrasonically treated during the process, and washed to neutrality after acid washing, and then dried and calcined, wherein the drying temperature was 120℃, the drying time was 10 hours, the calcination temperature was 400℃, and the calcination time was 20 hours. Then, two αAl2O3 particles with particle sizes of 1.2μm and 0.1μm were coated on the ceramic tube in sequence to form a particle layer, and calcined at 800℃ for 20 minutes, and the calcination was repeated 4 times. Then, 5wt% SiO2-ZrO2 sol was coated on the outside of the particle layer to form a transition layer, wherein the molar ratio of Si and Zr was Si:Zr=1:1, and calcined at 600℃ for 20 minutes, and the calcination was repeated 8 times. Then, BTESE sol was coated on the outside of the transition layer, calcined at 800°C for 30 minutes, and the calcination was repeated twice to form a separation layer, and finally an organic-inorganic hybrid membrane was obtained.

[0062] Organic-inorganic hybrid membrane preparation example 3

[0063] Take 20 kg of 1,2-bis(triethoxysilyl)ethane (BTESE) and dissolve it in 230 kg of anhydrous ethanol. Add HCl / H2O solution while stirring in a water bath, wherein the molar ratio of BTESE, H2O and HCl is BTESE:H2O:HCl=1:150:0.2, the water bath temperature is 60°C, the stirring speed is 20 r / min, the reaction time is 2 h, and the BTESE sol is obtained by reaction.

[0064] The porous αAl2O3 ceramic tube was soaked in deionized water for 2 hours, ultrasonically treated during the process, and the deionized water was replaced every 20 minutes. After washing, it was soaked in 0.5wt% sodium hydroxide solution for 1 hour, and then soaked in 2wt% hydrochloric acid for acid washing for 0.5 hours, ultrasonically treated during the process, and washed to neutrality after acid washing, and then dried and calcined, wherein the drying temperature was 100℃, the drying time was 12 hours, the calcination temperature was 800℃, and the calcination time was 5 hours. Then, two αAl2O3 particles with particle sizes of 1μm and 0.4μm were coated on the ceramic tube in sequence to form a particle layer, and calcined at 400℃ for 25 minutes, and the calcination was repeated 3 times. Then, 2wt% SiO2-ZrO2 sol was coated on the outside of the particle layer to form a transition layer, wherein the molar ratio of Si to Zr was Si:Zr=1:0.5, and calcined at 800℃ for 25 minutes, and the calcination was repeated 7 times. Then, BTESE sol was coated on the outside of the transition layer, calcined at 600°C for 25 min, and the calcination was repeated three times to form a separation layer, and finally an organic-inorganic hybrid membrane was obtained.

[0065] Example 1

[0066] Chlorobenzene mixed with 100 ppm water, 80 wt % hydrogen chloride and 10 wt % phosgene was continuously introduced into an organic-inorganic hybrid membrane device. The membrane device was a single-stage membrane. The temperature was controlled at 20°C and the osmotic pressure was 0.01 KPa. Chlorobenzene passed through the outside of the membrane tube at a flow rate of 1 m / s. The analysis results of water, hydrogen chloride and phosgene in chlorobenzene at the membrane outlet are shown in Table 1.

[0067] Example 2

[0068] Chlorobenzene mixed with 80wt% water, 1wt% hydrogen chloride and 100ppm phosgene was continuously introduced into an organic-inorganic hybrid membrane device. The membrane device was a 5-stage membrane separator connected in series. The temperature was controlled at 120°C and the osmotic pressure was 10KPa. Chlorobenzene passed through the outside of the membrane tube at a flow rate of 0.01m / s. The analysis results of water, hydrogen chloride and phosgene in chlorobenzene at the membrane outlet are shown in Table 1.

[0069] Example 3

[0070] Chlorobenzene mixed with 500ppm water, 100ppm hydrogen chloride and 80wt% phosgene was continuously introduced into an organic-inorganic hybrid membrane device. The membrane device was a 10-stage membrane separator in series. The temperature was controlled at 80°C and the osmotic pressure was 2KPa. Chlorobenzene passed through the outside of the membrane tube at a flow rate of 3m / s. The analysis results of water, hydrogen chloride and phosgene in chlorobenzene at the membrane outlet are shown in Table 1.

[0071] Comparative Example 1

[0072] Chlorobenzene mixed with 100 ppm of water, 80 wt% of hydrogen chloride and 10 wt% of phosgene was refined and purified by conventional distillation. The pressure of the chlorobenzene refining tower was 1.5 barg, with 10 trays. The chlorobenzene solution was fed from above the first tray, and the bottom of the tower was heated to 165°C with steam. The analysis results of water, hydrogen chloride and phosgene in the refined chlorobenzene are shown in Table 1.

[0073] Table 1 Results of Examples 1-3 and Comparative Example 1

[0074]

Claims

1. A method for preparing an organic-inorganic hybrid membrane, characterized in that: The steps include: (a) preparing a 1,2-bis(triethoxysilyl)ethane organic solution, adding HCl / H2O solution, and reacting to obtain a BTESE sol; (b) A particle layer and a transition layer are sequentially coated on a porous α-Al2O3 ceramic tube support, calcined at high temperature, and then coated with BTESE sol, calcined to form a separation layer, thereby obtaining an organic-inorganic hybrid membrane.

2. The preparation method according to claim 1, characterized in that: The solvent of the organic solution in step (a) is selected from alcohol solvents, preferably alcohols with carbon numbers of C1-C6, more preferably methanol and ethanol; preferably, the mass fraction of 1,2-bis(triethoxysilyl)ethane organic solution is 5%-10%; and / or: the reaction temperature in step (a) is 40-60°C, and the reaction time is 1-3h; preferably, the molar ratio of BTESE, H2O, and HCl in step (a) is 1:20-300:0.

2.

3. The preparation method according to claim 1, characterized in that: In the step (b), the porous α-Al2O3 ceramic tube structure is a hollow cylindrical tube with a pore size of 0.8-1.5 μm and a porosity of 20%-40%; preferably, the porous α-Al2O3 ceramic tube has a length of 600-1200 mm and an outer diameter of 8-16 mm.

4. The preparation method according to claim 1, characterized in that: In the step (b), the particle layer uses two types of α-Al2O3 particles to be coated on a porous α-Al2O3 ceramic tube support, and then calcined at high temperature; preferably, the particle sizes of the two types of α-Al2O3 particles are 0.8-1.2μm and 0.1-0.4μm, respectively; the calcination temperature is 400-800℃, more preferably 500-700℃; the calcination time is 20-30min; and the number of calcinations is preferably 2-4 times.

5. The preparation method according to claim 1 or 4, characterized in that: The transition layer in step (b) is formed by coating SiO2-ZrO2 sol on the particle layer and then calcining at high temperature; Preferably, the concentration of the SiO2-ZrO2 sol is 0.5-5wt%, and the molar ratio of Si to Zr is Si:Zr=1:(0.5-2); Preferably, the transition layer is calcined at a temperature of 400-800° C., more preferably 500-700° C.; the calcination time is 20-30 min; and the number of calcinations is preferably 6-8 times.

6. The preparation method according to claim 1, characterized in that: In the step (b), the separation layer is calcined at a temperature of 400-800° C., preferably 500-700° C.; the calcination time is 20-30 min; and the calcination times are preferably 2-4 times.

7. The preparation method according to any one of claims 1 to 6, characterized in that: The porous α-Al2O3 ceramic tube support is pretreated before coating in step (b), and the pretreatment includes water washing, alkali washing, acid washing and drying.

8. A method for purifying an organic solvent in the production of isocyanates, characterized in that: An organic solvent mixed with water, hydrogen chloride and / or phosgene is introduced into an organic-inorganic hybrid membrane device, and the organic solvent passes through the outside of the membrane tube, wherein water, hydrogen chloride and / or phosgene penetrate into the inside of the membrane tube for separation and removal, and the membrane outlet is the purified qualified organic solvent.

9. The purification method according to claim 8, characterized in that The organic-inorganic hybrid membrane device is a single-stage or multi-stage membrane separator connected in series, wherein the number of stages is 1-10, preferably 1-8, and more preferably 2-6.

10. The purification method according to claim 8 or 9, characterized in that: The temperature of the organic-inorganic hybrid membrane device is 20-120°C, preferably 40-110°C; and / or: the flow rate of the organic solvent in the organic-inorganic hybrid membrane device is 0.01-3 m / s, preferably 0.05-2 m / s; And / or: the permeate side pressure of the organic-inorganic hybrid membrane device is 0.01-10 KPaA, preferably 0.1-5 KPaA.

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