CN112316758B - Gaseous film and preparation method thereof, and method for preparing bromine-free or low-bromine brine - Google Patents
Gaseous film and preparation method thereof, and method for preparing bromine-free or low-bromine brine Download PDFInfo
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- CN112316758B CN112316758B CN202010907574.2A CN202010907574A CN112316758B CN 112316758 B CN112316758 B CN 112316758B CN 202010907574 A CN202010907574 A CN 202010907574A CN 112316758 B CN112316758 B CN 112316758B
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- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
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- B01D71/06—Organic material
- B01D71/76—Macromolecular material not specifically provided for in a single one of groups B01D71/08 - B01D71/74
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D69/00—Semi-permeable membranes for separation processes or apparatus characterised by their form, structure or properties; Manufacturing processes specially adapted therefor
- B01D69/02—Semi-permeable membranes for separation processes or apparatus characterised by their form, structure or properties; Manufacturing processes specially adapted therefor characterised by their properties
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
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- B01D69/00—Semi-permeable membranes for separation processes or apparatus characterised by their form, structure or properties; Manufacturing processes specially adapted therefor
- B01D69/08—Hollow fibre membranes
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
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- B01D71/00—Semi-permeable membranes for separation processes or apparatus characterised by the material; Manufacturing processes specially adapted therefor
- B01D71/06—Organic material
- B01D71/30—Polyalkenyl halides
- B01D71/32—Polyalkenyl halides containing fluorine atoms
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- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
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- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F2101/00—Nature of the contaminant
- C02F2101/10—Inorganic compounds
- C02F2101/12—Halogens or halogen-containing compounds
Abstract
The invention discloses a gaseous film and a preparation method thereof, and relates to a method for preparing bromine-free or low-bromine brine. The gaseous film is hollow porous gamma-MnO2Coated perfluorooctyltrichlorosilane-modified ethylene-trichlorofluoroethylene copolymer hollow fiber membrane, the hollow porous gamma-MnO2The size of the microsphere is 0.5-2.0 μm, and the pore size is 5-20 nm. The gaseous film has the advantages of strong acid and alkali resistance, strong oxidation resistance, strong corrosion resistance, high porosity, stable operation and the like. The technical route of 'oxidation of light salt water and bromine extraction by a gaseous film' is adopted to deeply remove bromine in the salt water, so that the bromine content in chlorine can be reduced to within 50ppm from the source, the quality of the phosgenation reaction is improved, the content of color development impurities such as brominated MDI in the product is reduced, and the aims of improving the color number and the quality of the product are fulfilled. The method has the advantages of simple process, low operation cost, great economic benefit and remarkable improvement on product quality.
Description
Technical Field
The invention relates to the field of separation and purification, in particular to a gaseous membrane and a method for debrominating brine.
Technical Field
Isocyanate is an important intermediate in the field of organic chemistry, has very wide application in the aspects of polyurethane foam plastics, rubber, elastic fiber, coating, adhesive, synthetic leather, artificial wood and the like, and has wide development prospect in the emerging fields of high-speed rails, new energy sources and the like by virtue of excellent performance. Most of the current industrial production processes for isocyanates employ the phosgenation process, such as diphenylmethane series of isocyanates (MDI) which is an important application, and is prepared by condensation of aniline and formaldehyde to obtain diphenylmethanediamine (diamine) or polymethylene polyphenyl polyamine (polyamine), followed by phosgenation and a series of post-treatment and separation processes, including two major classes of products, i.e., diphenylmethane diisocyanate (MMDI) and polymethylene polyphenyl Polyisocyanate (PMDI), but the MDI series of products generate dark color substances during the phosgenation and post-treatment processes, which affect the visual effect and product uniformity of the polyurethane product, and this is very disadvantageous for downstream applications.
The person skilled in the art has now found that the bromine content of the chlorine used for the synthesis of phosgene has a significant influence on the color of MDI series products, the bromine in the chlorine is mainly derived from the corresponding bromine content of the salts used for the production of chlorine, bromine or bromine compounds are converted into bromine gas or bromine chloride after electrolysis of the aqueous salt solution, dibromophosgene or bromochlorophosgene is formed during the synthesis of phosgene, and bicyclic or polycyclic brominated MDI color impurities are formed after the phosgenation reaction, resulting in a deepened product color. Many attempts have been made by those skilled in the art to improve the process for the preparation of chlorine or isocyanates in order to improve the product quality.
CN1356980A discloses a process for preparing isocyanates containing only small amounts of color-imparting components by reacting an amine or a mixture of two or more amines with phosgene containing less than 50ppm of bromine in molecularly bound form or other mixtures. However, no purification of the phosgene used for the preparation of isocyanates with bromine or bromine compounds is described here.
CN104609370A discloses a process for extracting bromine by air blowing, which comprises adding hydrochloric acid into brine, acidifying, oxidizing with chlorine gas to oxidize bromide ions into bromine molecules, and blowing out with air. Although the process is stable, the method has the advantages of large required air stripping amount, large occupied area of equipment, high power consumption, large acid and alkali consumption when the bromine content in the brine is low, higher operation cost, low bromine removal rate and poor economic benefit.
CN102471241A discloses a process for preparing light-colored polymethylene polyphenyl Polyisocyanates (PMDI) by reacting a portion of excess phosgene from isocyanate synthesis with at least one polymethylene polyphenyl polyamine to form a light-colored PMDI. However, in the actual phosgenation reaction process, the phosgene synthesized by phosgene still contains dibromophosgene or bromochlorophosphine in a certain proportion, the problem of PMDI color development caused by the reaction cannot be solved, and a part of excessive phosgene is cut out for separate reaction, so that the process flow is complex, and the operation safety risk is increased.
CN1896052A discloses a method for preparing isocyanates from phosgene and amines, in which hydrogen chloride produced in the production of isocyanates is electrolytically oxidized to produce chlorine gas, which is recycled to produce phosgene. However, the content of organic impurities in hydrogen chloride is required to be high in hydrogen chloride electrolysis, high cost is generated in the production process, and a large amount of hydrogen gas is produced as a byproduct, so that the requirement of a matched device is needed.
The control of bromine content in chlorine gas or the control of bromide content in isocyanate products in the prior art has the problems of large occupied area, high operation cost, complex process, low bromine removal rate and the like, so a process method for effectively reducing the bromine content in chlorine gas needs to be developed.
Disclosure of Invention
The invention aims to overcome the defects in the prior art and provides a gaseous film and a preparation method thereof, wherein the gaseous film has the advantages of strong acid and alkali resistance, strong oxidation resistance, strong corrosion resistance, high porosity, stable operation and the like, can quickly remove volatile components in an aqueous solution, and is particularly suitable for the working condition of extracting bromine from brine.
The invention also provides a method for preparing bromine-free or low-bromine brine, which adopts a technical route of 'light brine oxidation + gaseous film bromine extraction' to deeply remove bromine in the brine, so as to reduce bromine or bromine compounds in chlorine from the source, improve phosgene quality, further reduce the content of color development impurities such as brominated MDI and the like in the product, and realize the purpose of preparing colorless or light-color isocyanate. The method has the advantages of simple process, low operation cost, great economic benefit and remarkable improvement on product quality.
In order to achieve the above purpose, the technical scheme of the invention is as follows:
a gaseous film which is hollow porous gamma-MnO2Coated perfluorooctyltrichlorosilane-modified ethylene-trichlorofluoroethylene copolymer hollow fiber membrane, the hollow porous gamma-MnO2The size of the microsphere is 0.5-2.0 μm, and the pore size is 5-20 nm.
A method of making said gaseous membrane comprising the steps of:
(a) preparation of modified ethylene-trichlorofluoroethylene copolymer (ECTFE) hollow fiber membrane: uniformly mixing ECTFE and a lubricant, adding a pore-forming agent and a modifier to prepare a membrane casting solution, preparing a hollow fiber membrane from the membrane casting solution through a spinning device, soaking the hollow fiber membrane in water for 36-48 h, and drying the hollow fiber membrane in vacuum at the temperature of 60-80 ℃ for 4-8 h;
(b) hollow porous gamma-MnO2The preparation of (1): MnSO with the concentration of 2.0 to 4.0 weight percent4The solution and the modifier are mixed evenly, and then NH with the concentration of 1.0-3.0 percent is dripped into the mixture4HCO3The solution is reacted, then filtered, washed, dried and roasted to prepare the hollow porous gamma-MnO2；
(c) Modified ECTFE-gamma-MnO2Preparing a composite hollow fiber gaseous membrane: immersing the modified ECTFE hollow fiber membrane in gamma-MnO2The aqueous suspension is subjected to ultrasonic treatment for 4 to 8 hours, washed and dried to obtain the modified ECTFE-gamma-MnO2A composite hollow fiber gaseous membrane.
As a preferable scheme, in the step (a), the ECTFE and the lubricant are uniformly mixed, then the pore-forming agent and the modifier are added, and the mixture is slowly stirred in a water bath at the temperature of 40-60 ℃ for 60-90 min to prepare the clear and transparent casting solution. The slow stirring is preferably 15-25 r/min.
As a preferable scheme, in the step (a), the casting solution is extruded by a spinning device under the external pressure of 2-3 barg nitrogen to prepare the hollow fiber membrane.
In step (a) of the present invention, the lubricant is one or more of polyethylene glycol, n-propanol and n-butanol, preferably polyethylene glycol, and has a number average molecular weight of 200-600.
In step (a) of the present invention, the mass ratio of the lubricant to ECTFE is 3:1 to 10:1, preferably 5:1 to 7: 1.
In the step (a) of the present invention, as a preferable embodiment, the pore-forming agent and the modifying agent are added simultaneously, the pore-forming agent is diethylene glycol (DEG), and the modifying agent is perfluorooctyltrichlorosilane.
In step (a) of the present invention, the mass ratio of ECTFE to DEG is 1:1 to 4:1, preferably 2:1 to 3: 1.
In step (a) of the present invention, the mass ratio of ECTFE to perfluorooctyltrichlorosilane is 2:1 to 6:1, preferably 3:1 to 4: 1.
In the step (a), the ECTFE hollow fiber membrane modified by the perfluorooctyl trichlorosilane reduces the surface energy of the membrane and greatly improves the wetting depth of the membrane. The application of the invention in the debromination of saline water can block the solute in water or ion state from passing through the membrane pores, thus greatly improving the migration and diffusion speed of bromine.
In step (b) of the present invention, the reaction is preferably carried out under ultrasonic irradiation.
In step (b), the modifier is perfluorooctyltrichlorosilane, and the MnSO is4The mass ratio of the solution to the perfluorooctyl trichlorosilane is 20:1-100:1, preferably 40:1-60: 1.
As a preferred embodiment, in the step (b) of the present invention, the washing includes washing with water and an organic solvent three times.
As a preferable embodiment, in the step (b) of the present invention, the drying is air drying at 40 to 60 ℃.
In the step (b) of the present invention, the NH4HCO3The dripping time of the solution is 30min-120min, preferably 50min-100min, and more preferably 60min-90 min.
In step (b) of the present invention, the firing comprises the steps of:
(1) roasting at 380-2Crystal form transformation;
(2) roasting at 480-520 ℃ for 2-5h to form hexagonal phase gamma-MnO2；
(3) Roasting at 580-620 ℃ for 2-5h to eliminate gamma-MnO2To obtain gamma-MnO of high crystallinity2。
In the step (b), the temperature programming rate of the roasting is 5-20 ℃/min.
The calcination method in step (b) of the present invention can obtain high-crystallinity gamma-MnO2The elimination of gamma-MnO with the increase of time and temperature2Internal defects of in gamma-MnO2Pore structures with different sizes are formed on the surfaces of the microspheres, so that the gamma-MnO is greatly improved2Mechanical strength and mechanical properties.
γ-MnO2Is a three-dimensional porous structure, and is calcined at high temperature during the preparation process to generate an intermediate MnCO3To gamma-MnO2Conversion with CO2The gas release causes pores with different sizes among lamellar particles to become sparse, the roughness of the surface of the membrane can be effectively increased, a lotus-leaf-like nano-scale porous structure is constructed on the surface of the membrane with a micron rough structure, and the mechanical strength and the hydrophobicity of the membrane are obviously improved.
In the step (b) of the present invention, the hollow porous γ -MnO2The size of the microsphere is 0.5-2.0 μm, and the pore size is 5-20 nm.
As a preferred embodiment, in step (c) of the present invention, γ -MnO is added under ultrasonic conditions2Dispersing in water to obtain gamma-MnO2The aqueous suspension of (a).
In the step (c) of the present invention, the γ -MnO2Mass ratio to ECTFEIs 1:10 to 1:100, preferably 1:20:1 to 1:80, more preferably 1:40 to 1: 60.
In some embodiments, in steps (b), (c), the ultrasonic radiation has an ultrasonic pulse frequency of 10 to 30kHz, preferably 12 to 25kHz, more preferably 15 to 20 kHz; the pulse width is 50-500ms, preferably 100-450ms, more preferably 150-300 ms; ultrasonic radiation under the optimal condition is adopted, so that chemical modification can be better cured.
As a preferred embodiment, in the step (c) of the present invention, the washing includes washing with water and an organic solvent respectively for a plurality of times.
As a preferable scheme, in the step (c) of the present invention, the drying is vacuum drying at 60 ℃ to 80 ℃ for 6h to 8 h.
In the step (c) of the present invention, the γ -MnO2The modified ECTFE membrane is coated on the surface of the ECTFE membrane, so that the surface roughness of the membrane can be effectively increased, porous structures with different sizes are constructed on the surface of the membrane with a micron rough structure, the mechanical strength and the hydrophobicity of the membrane are obviously improved, and the stable operation time of the membrane is prolonged.
Modified ECTFE-gamma-MnO prepared by the invention2The composite hollow fiber gaseous film has the advantages of strong acid and alkali resistance, strong oxidation resistance, strong corrosion resistance, high porosity, stable operation and the like, can quickly remove volatile components in an aqueous solution, and is particularly suitable for the working condition of extracting bromine from saline water.
The invention also provides a method for removing bromine in the brine by the process technology of 'dilute brine oxidation + gaseous membrane bromine extraction', which comprises the following steps:
(1) mixing the light salt water and fresh water to obtain crude salt water;
(2) the crude brine is delivered to a system comprising modified ECTFE-gamma-MnO as described herein2The bromine gas in the crude brine is extracted by a membrane component of the composite hollow fiber gaseous membrane under the action of the gaseous membrane to prepare bromine-free or low-bromine brine.
In the step (1), the dilute brine is acidic dilute brine containing certain effective chlorine after the ionic membrane electrolysis in the chlor-alkali industry.
In the step (1), the bromine content in the weak brine is 5-200 ppm; the concentration of sodium chloride is 190g/L-230g/L, preferably 200g/L-220 g/L.
In the step (1) of the present invention, the pH of the weak brine is 0.5 to 3.5, preferably 0.8 to 2.0, and more preferably 1.0 to 1.5; the available chlorine content is 200-2500ppm, preferably 400-1800ppm, more preferably 600-1200 ppm.
In step (1) of the present invention, the raw salt is one or more of well salt, mineral salt, sea salt or mineral potassium chloride, and in order to reduce raw salt procurement cost, mineral salt and/or sea salt are preferred, and sea salt is more preferred.
In the step (1) of the present invention, the bromine content in the crude salt is 100-1000 ppm.
In step (1) of the present invention, bromide ions in the raw salt are oxidized into bromine gas by the available chlorine in the dilute brine under acidic conditions (provided by the dilute brine).
As a preferable scheme, the crude brine is saturated brine, the bromine content is 10-500ppm, the temperature of the crude brine is 30-80 ℃, the temperature is preferably 35-70 ℃, the temperature is more preferably 40-60 ℃, and the NaCl concentration in the crude brine is preferably 300-320 g/L.
In the step (2), the membrane component is a single membrane component, and a set of modified ECTFE-gamma-MnO fixed at two ends is filled in the single membrane component2The composite hollow fiber gaseous membrane is used as a crude brine flow channel, the shell side is used as an absorption liquid flow channel, bromine gas in the crude brine is diffused to the absorption liquid flow channel through micropores in the gaseous membrane, and the bromine gas is absorbed by the absorption liquid.
In the step (2) of the invention, the absorption liquid can be NaOH solution or Na solution2CO3Solution, Ca (OH)2Solution, sodium formate solution or NaBr solution, preferably NaOH solution or Na solution2CO3The solution is more preferably a NaOH solution.
In the step (2) of the invention, the bromine content in the bromine-free or low-bromine brine is within 10 ppm.
In some embodiments, the 'light brine oxidation' process route organically combines the brine debromination process route and the light brine dechlorination process route, breaks through the current air blowing dechlorination or vacuum dechlorination process route in the chlor-alkali industry, and has the outstanding advantages of small equipment investment, high economic benefit and the like.
In another aspect, the invention provides a method for preparing bromine-free or low-bromine chlorine gas, comprising the following steps: the bromine-free or low-bromine brine is processed by a series of impurity removal (calcium, magnesium and other metal ions removal) units to prepare refined brine, and the refined brine is sent to an ion membrane for electrolysis to generate bromine-free or low-bromine chlorine.
The bromine content of the bromine-free or low-bromine chlorine gas is within 50ppm, and the bromine exists in the form of one or more of bromine gas, bromine chloride and bromine trichloride.
Using the process known to those skilled in the art, reacting the bromine-free or low-bromine chlorine gas with carbon monoxide in a phosgene synthesis tower to generate bromine-free or low-bromine phosgene; mixing dimethylene diphenyl diamine and/or polymethylene polyphenyl polyamine with an inert solvent according to a certain proportion to prepare a mixed solution, reacting with excessive bromine-free or low-bromine phosgene, and removing phosgene and the inert solvent from a mixture generated by the reaction through processes of aftertreatment, separation and the like to prepare colorless or light-colored diphenylmethane diisocyanate and/or polymethylene polyphenyl polyisocyanate.
The phosgene synthesis tower can be a tubular reaction tube, a spiral tubular reactor, a fixed bed tubular reactor and a double-tube plate type fixed bed reactor, and preferably a fixed bed tubular reactor widely used in the field.
The molar ratio of chlorine to carbon monoxide in the process of the invention is 0.8 to 1.0, preferably 0.85 to 0.98, more preferably 0.90 to 0.95.
The inert solvents described in the present invention can be used all solvents suitable for the preparation of isocyanates, for example chlorinated aromatic hydrocarbons, aliphatic hydrocarbons, diethyl isophthalate. Preference is given to hydrocarbons substituted by halogen atoms, such as chlorobenzene, dichlorobenzene, o-dichlorobenzene or mixtures thereof, more preferably chlorobenzene. The mass ratio of the inert solvent to the dimethylene diphenyl diamine and/or polymethylene polyphenyl polyamine is 1:1 to 10:1, preferably 2:1 to 7:1, and more preferably 3:1 to 5: 1.
The mass ratio of phosgene to dimethylene diphenyl diamine and/or polymethylene polyphenyl polyamine is 2:1-8:1, preferably 3:1-6:1, and more preferably 3.5:1-5: 1.
As a preferred variant, the work-up or separation of the phosgenation reaction mixture is carried out in a sequential manner according to the boiling point of the individual components. Wherein the pressure of the phosgene removal system is preferably 10-50KPaG, the temperature is preferably 130-150 ℃, the pressure of the chlorobenzene removal system is preferably 20-50KPaA, and the temperature is preferably 160-200 ℃.
The brominated MDI content of the diphenylmethane diisocyanate and/or polymethylene polyphenyl polyisocyanate is within 10 ppm. The color is characterized by a color L known to those skilled in the art, which is above 85.
The technical scheme provided by the invention has the following beneficial effects:
modified ECTFE-gamma-MnO prepared by the invention2The composite hollow fiber gaseous film has the advantages of strong acid and alkali resistance, strong oxidation resistance, strong corrosion resistance, high porosity, stable operation and the like, can quickly remove volatile components in an aqueous solution, and is particularly suitable for the working condition of extracting bromine from saline water.
The working condition of extracting bromine from brine is acid brine, sodium hypochlorite strong oxidant is contained in the brine, the equipment material is required to be acid-base resistant, oxidation resistant and corrosion resistant, meanwhile, the porosity of the gaseous film is high, the diffusion of bromine in the brine to the shell side of the film device is facilitated, and the bromine is absorbed by absorption liquid.
The technological route of 'light brine oxidation + gaseous membrane bromine extraction' provided by the invention organically combines the two technological routes of brine debromination and light brine dechlorination, breaks through the vacuum dechlorination technological route of the current chlor-alkali industry, and has the outstanding advantages of small equipment investment, high economic benefit and the like.
The invention provides a method for removing bromine in brine based on a process technical route of 'dilute brine oxidation + gaseous film bromine extraction', provides an application in the preparation of chlorine and isocyanate, and can greatly reduce the bromine content in the chlorine to be within 50ppm, further reduce the bromine content in the synthetic phosgene and improve the quality of a phosgenation reaction, thereby reducing the content of color development impurities such as brominated MDI (diphenyl-methane-diisocyanate) in diphenylmethane diisocyanate or/and polymethylene polyphenyl polyisocyanate and achieving the purpose of improving the color number and the quality of products.
Drawings
FIG. 1 is a process flow diagram of an embodiment of the present invention for preparing bromine-free or low-bromine chlorine gas, wherein 1 is a salt dissolving tank, 2 is crude brine, 3 is a gaseous membrane module, 4 is debrominated brine, 5 is an absorption liquid tank, 6 is an absorption liquid transfer pump, 7 is absorption liquid, 8 is a brine refining system, 9 is refined brine, 10 is an ionic membrane, 11 is chlorine gas, and 12 is weak brine.
Detailed Description
The invention is further illustrated by the following examples in conjunction with the drawings, but the invention is not limited thereto. Test methods without specific conditions shown in the following examples are generally performed under conventional conditions.
γ-MnO2Analysis method of microsphere size and pore size: and testing and characterizing by using a Hitachi TM-1000 scanning electron microscope. SEM test conditions: placing a small amount of sample into alcohol, ultrasonically dispersing for 30min, dropping a small amount of liquid onto a silicon wafer, drying at 50 deg.C, spraying gold for 20mA for 40s, and finally placing into a sample chamber to observe the microstructure of the sample.
Analysis of bromine content in brine: diluting with pure water, and performing ion chromatography. The ion chromatography model is Switzerland model 930 particle chromatography, the anion ASUPP7-250 model, and the mobile phase is 3.6mm sodium carbonate.
Analysis of bromine content in chlorine or phosgene: absorbing a certain amount of chlorine gas and phosgene by using 100g/L potassium iodide solution to convert bromine or bromine compounds into Br—And diluting the absorption liquid by pure water and then carrying out ion chromatography analysis. The ion chromatography model is Switzerland model 930 particle chromatography, the anion ASUPP7-250 model, and the mobile phase is 3.6mm sodium carbonate.
Analysis of brominated MDI content in isocyanate: the diphenylmethane diisocyanate or polymethylene polyphenyl polyisocyanate is diluted by 5 times by using a reagent dichloromethane, and the diluted solution is subjected to gas chromatography analysis. The gas chromatography model was Agilent 7890A, the detector FID, and the column DB-5(30 m.times.0.53 mm. times.1.5 μm).
L color analysis of isocyanate: measured by the L, a, b values of the CIE color system well known to those skilled in the art.
Polyethylene glycol: the polyethylene glycol has a number average molecular weight of 400 and is from chemical reagents of national drug group, and is an industrial product.
ECTFE: dongguan drama fluororubber Co., Ltd., industrial product.
EXAMPLE 1 preparation of ECTFE-MnO2Composite modified hollow fiber gaseous membrane
Adding 1t of ECTFE into 5t of polyethylene glycol, uniformly mixing, adding 0.33t of DEG and 0.25t of perfluorooctyltrichlorosilane simultaneously, and slowly stirring (stirring speed of 20r/min) for 60min in a water bath at 50 ℃ to prepare a clear and transparent casting solution. Under the extrusion of external pressure 2barg nitrogen, the casting solution is made into a hollow fiber membrane by a spinning device, and the hollow fiber membrane is soaked in pure water for 36 hours and is dried in vacuum at 60 ℃ for 4 hours.
Respectively preparing 2t 2.0% NH at 25 DEG C4HCO3And 3.0% MnSO4Solution to MnSO4And adding 33.3kg of perfluorooctyl trichlorosilane into the solution, and fully stirring and dissolving to obtain a mixed solution. NH is treated under the environment of ultrasonic radiation4HCO3Slowly dripping the solution into the mixed solution for 60min, ultrasonic pulse frequency of 15kHz and pulse width of 150ms, filtering the mixed solution after reaction is completed, washing with distilled water and ethanol for 3 times, air drying, crystallizing at 400 deg.C, 500 deg.C and 600 deg.C for 2 hr to obtain hollow porous gamma-MnO2(the microsphere size is 0.5-1.5 μm, and the pore size is 5-15nm), drying and storing.
16.7kgγ-MnO2Dispersing in pure water under ultrasonic condition to obtain completely suspended turbid liquid. Immersing the modified ECTFE hollow fiber membrane in gamma-MnO2Continuing to perform ultrasonic treatment for 4h in the suspension, washing with distilled water and ethanol for 3 times, and vacuum drying at 60 deg.C for 6h to obtain modified ECTFE-gamma-MnO2A composite hollow fiber gaseous membrane.
Example 2
Adding 1t of ECTFE into 7t of polyethylene glycol, uniformly mixing, simultaneously adding 0.5t of DEG and 0.33t of perfluorooctyltrichlorosilane, and slowly stirring (stirring speed of 20r/min) for 90min in a water bath at 50 ℃ to prepare a clear and transparent casting solution. Under the extrusion of external pressure of 3barg nitrogen, the casting solution is made into a hollow fiber membrane by a spinning device, and the hollow fiber membrane is soaked in pure water for 48 hours and is dried in vacuum at 80 ℃ for 8 hours.
Respectively preparing 2t 2.0% NH at 25 DEG C4HCO3And 3.0% MnSO4Solution to MnSO4And adding 50kg of perfluorooctyl trichlorosilane into the solution, and fully stirring and dissolving to obtain a mixed solution. NH is treated under the environment of ultrasonic radiation4HCO3Slowly dripping the solution into the mixed solution for 90min, ultrasonic pulse frequency of 20kHz and pulse width of 300ms, filtering the mixed solution after reaction is completed, washing with distilled water and ethanol for 3 times, air drying, crystallizing at 400 deg.C, 500 deg.C and 600 deg.C for 5h to obtain hollow porous gamma-MnO2(the microsphere size is 1.0-2.0 μm, and the pore size is 10-20nm), drying and storing.
25kgγ-MnO2Dispersing in pure water under ultrasonic condition to obtain completely suspended turbid liquid. Immersing the modified ECTFE hollow fiber membrane in gamma-MnO2Continuing to perform ultrasonic treatment for 8h in the suspension, washing with distilled water and ethanol for 3 times respectively, and vacuum drying at 80 ℃ for 8h to obtain modified ECTFE-gamma-MnO2A composite hollow fiber gaseous membrane.
Example 3
Adding 1t of ECTFE into 6t of polyethylene glycol, uniformly mixing, simultaneously adding 0.4t of DEG and 0.3t of perfluorooctyltrichlorosilane, and slowly stirring (stirring speed of 20r/min) for 75min in a water bath at 50 ℃ to prepare a clear and transparent casting solution. Under the extrusion of external pressure 2.5barg nitrogen, the casting solution is made into a hollow fiber membrane by a spinning device, and the hollow fiber membrane is soaked in pure water for 42 hours and is dried in vacuum at 70 ℃ for 6 hours.
Respectively preparing 2t 2.0% NH at 25 DEG C4HCO3And 3.0% MnSO4Solution to MnSO4And adding 40kg of perfluorooctyl trichlorosilane into the solution, and fully stirring and dissolving to obtain a mixed solution. NH is treated under the environment of ultrasonic radiation4HCO3Slowly dripping the solution into the above mixed solution for 75min, with ultrasonic pulse frequency of 18kHz and pulsePunching width of 220ms, suction-filtering the mixed liquid after reaction, washing with distilled water and ethanol for 3 times, air-drying, crystallizing at 400 deg.C, 500 deg.C and 600 deg.C for 3.5 hr to obtain hollow porous gamma-MnO2(the microsphere size is 0.8-1.8 μm, and the pore size is 8-18nm), drying and storing.
20kgγ-MnO2Dispersing in pure water under ultrasonic condition to obtain completely suspended turbid liquid. Immersing the modified ECTFE hollow fiber membrane in gamma-MnO2Continuing to perform ultrasonic treatment for 6h in the suspension, washing with distilled water and ethanol for 3 times respectively, and vacuum drying at 70 ℃ for 7h to obtain modified ECTFE-gamma-MnO2A composite hollow fiber gaseous membrane.
Comparative example 1
Modified ECTFE-MnO in comparative example 12The composite hollow fiber gaseous membrane was prepared in the same manner as in example 1 except that MnO was added2Of the crystalline form of (1), MnO used in comparative example 12In the form of conventional alpha-MnO2. The alpha-MnO2The preparation process comprises the following steps:
respectively preparing 2t 2.5 percent KMnO at the temperature of 25 DEG C4And 3.0% MnSO4Solution to MnSO4And adding 33.3kg of perfluorooctyl trichlorosilane into the solution, and fully stirring and dissolving to obtain a mixed solution. KMnO is subjected to ultrasonic radiation4Slowly dripping the solution into the mixed solution for 90min, ultrasonic pulse frequency of 20kHz and pulse width of 300ms, filtering the mixed solution after reaction is completed, washing with distilled water and ethanol for 3 times, air drying, crystallizing at 200 deg.C for 4h, grinding, and sieving to obtain alpha-MnO2(the microsphere size is 3-8 μm, and the pore size is 12-35nm) and storing.
Comparative example 2
Comparative example 2 differs from example 1 in γ -MnO2The roasting treatment mode of comparative example 2 is heating at 400 ℃ for 4h to prepare hollow porous gamma-MnO2The size of the microsphere is 5-15 μm, and the pore size is 15-60 nm.
Comparative example 3
Comparative example 3 differs from example 1 in γ -MnO2At the roasting siteIn principle, the roasting treatment used in comparative example 3 was heating at 500 ℃ for 4 hours to obtain hollow porous γ -MnO2The size of the microsphere is 3-10 μm, and the pore size is 15-40 nm.
Comparative example 4
Comparative example 4 differs from example 1 in γ -MnO2The roasting treatment mode of comparative example 4 is heating at 600 ℃ for 4h to prepare hollow porous gamma-MnO2The size of the microsphere is 1-5 μm, and the pore size is 10-30 nm.
Comparative example 5
Comparative example 5 differs from example 1 in γ -MnO2The roasting treatment mode of comparative example 5 is that the hollow porous gamma-MnO prepared by respectively heating at 400 ℃ and 500 ℃ for 4h2The size of the microsphere is 0.8-3 μm, and the pore size is 8-25 nm.
Comparative example 6
Comparative example 6 differs from example 1 in that ECTFE hollow fiber membranes were not modified with perfluorooctyltrichlorosilane.
Example 4 preparation of brine
Fully mixing sea salt with bromine content of 800ppm, fresh pure water and light salt water with bromine content of 160ppm after ion membrane electrolysis in a salt dissolving pool, wherein the adding amount of the sea salt is 18t/h, the amount of the fresh pure water is 30t/h, the amount of the light salt water is 110t/h, and the density is 1.20t/m3The NaCl concentration in the dilute brine was 215g/L, the pH was 1.0, and the available chlorine content was 1200 ppm. The mixing temperature was 40 ℃ and the bromine content in the crude brine after mixing was 202.5ppm and the NaCl concentration was 310g/L before being sent to the modified ECTFE-gamma-MnO prepared in example 12And (3) removing bromine gas to prepare brine with bromine content of 4.2ppm by using the composite hollow fiber gaseous membrane module, and absorbing the bromine gas diffused to the shell side by using a 10% NaOH solution on the shell side of the module.
Example 5
Fully mixing sea salt with bromine content of 800ppm, fresh pure water and light salt water with bromine content of 160ppm after ion membrane electrolysis in a salt dissolving pool, wherein the adding amount of the sea salt is 18t/h, the amount of the fresh pure water is 30t/h, the amount of the light salt water is 110t/h, and the density is 1.20t/m3NaCl concentration in light salt water is 215g/L, pH is 1.5, and the effect isThe chlorine content was 600 ppm. The mixing temperature was 60 ℃ and the bromine content in the crude brine after mixing was 202.5ppm and the NaCl concentration was 310g/L before being sent to the modified ECTFE-gamma-MnO prepared in example 22And (3) removing bromine gas to prepare brine with the bromine content of 6.5ppm by using the composite hollow fiber gaseous membrane module, and absorbing the bromine gas diffused to the shell side by using a 10% NaOH solution on the shell side of the module.
Example 6
Fully mixing sea salt with bromine content of 800ppm, fresh pure water and light salt water with bromine content of 160ppm after ion membrane electrolysis in a salt dissolving pool, wherein the adding amount of the sea salt is 18t/h, the amount of the fresh pure water is 30t/h, the amount of the light salt water is 110t/h, and the density is 1.20t/m3The NaCl concentration in the dilute brine was 215g/L, the pH was 1.25, and the available chlorine content was 900 ppm. The mixing temperature was 50 ℃ and the bromine content in the crude brine after mixing was 202.5ppm and the NaCl concentration was 310g/L before being sent to the modified ECTFE-gamma-MnO prepared in example 32And (3) removing bromine gas to prepare brine with the bromine content of 5.2ppm by using the composite hollow fiber gaseous membrane module, and absorbing the bromine gas diffused to the shell side by using a 10% NaOH solution on the shell side of the module.
Comparative example 7
The gaseous membrane of comparative example 1 was used, and the rest of the conditions were the same as in example 4. Brine having a bromine content of 21.0ppm was obtained.
Comparative example 8
The gaseous membrane of comparative example 2 was used, and the rest of the conditions were the same as in example 4. Brine having a bromine content of 35ppm was obtained.
Comparative example 9
The gaseous membrane of comparative example 3 was used, and the rest of the conditions were the same as in example 4. Brine having a bromine content of 23ppm was obtained.
Comparative example 10
The gaseous membrane of comparative example 4 was used, and the rest of the conditions were the same as in example 4. Brine having a bromine content of 16.5ppm was obtained.
Comparative example 11
The gaseous membrane of comparative example 5 was used, and the rest of the conditions were the same as in example 4. Brine having a bromine content of 12.7ppm was obtained.
Comparative example 12
The gaseous membrane of comparative example 6 was used, and the rest of the conditions were the same as in example 4. Brine having a bromine content of 196ppm was obtained.
Example 7 preparation of isocyanates
The brine prepared in the example 4 is electrolyzed by an ion membrane to generate chlorine, the voltage of the ion membrane is 500V, and the current is controlled to be 13.5-15 KA. Mixing the mixture with carbon monoxide in a molar ratio of 0.93, then introducing the mixture into a gas synthesis tower to react to generate phosgene, mixing a solvent chlorobenzene, dimethylene diphenyl diamine and polymethylene polyphenyl polyamine (wherein two rings account for 60 wt%, three rings account for 12 wt%, four rings account for 10 wt%, five rings and above account for 18 wt%) in a mass ratio of 4:1 in a static mixer to generate a mixed solution, mixing the phosgene and the mixed solution in a dynamic mixer in a mass ratio of 4:1 of phosgene to diamine/polyamine, and performing cold-hot phosgenation reaction after mixing, wherein the cold reaction temperature is controlled to be 75 ℃, the pressure is 270KPaG, the thermal reactor temperature is controlled to be 125 ℃, and the pressure is 270 KPaG. The hot reaction liquid enters a phosgene removing tower to remove phosgene and hydrogen chloride, the temperature is 140 ℃, the pressure is 30KPaG, chlorobenzene is removed by a desolventizing tower with the temperature of 150 ℃ and the pressure of 30KPaA to prepare diphenylmethane diisocyanate and polymethylene polyphenyl polyisocyanate (crude MDI), and the content of brominated MDI in the crude MDI and the L color analysis result are shown in table 1.
Examples 8 and 9
Examples 8 and 9 used the brines prepared in examples 5 and 6, respectively, and the rest of the conditions were the same as in example 7.
Comparative example 13
The conditions were the same as in example 7 except that the brine of comparative example 7 was used.
Comparative example 14
The conditions were the same as in example 7 except that the brine of comparative example 8 was used.
Comparative example 15
The same procedure as in example 7 was repeated except that the brine of comparative example 9 was used.
Comparative example 16
The conditions were the same as in example 7 except that the brine of comparative example 10 was used.
Comparative example 17
The conditions were the same as in example 7 except that the brine of comparative example 11 was used.
Comparative example 18
The conditions were the same as in example 7 except that the brine of comparative example 12 was used.
Comparative example 19
The light salt water is treated by vacuum dechlorination process, then the pH value is adjusted to 9.0-11.0, and the light salt water is mixed with sea salt with the bromine content of 800ppm and fresh pure water in a salt dissolving pool, and the other conditions are the same as the conditions in the example 4. Brine having a bromine content of 472ppm was produced.
The isocyanate was then prepared according to the procedure of example 7.
The results of examples 7 to 9 and comparative examples 13 to 19 are shown in Table 1.
TABLE 1 results of examples 7 to 9 and comparative examples 13 to 19
| Bromine content (ppm) in brine | Bromine content in chlorine (ppm) | L color of crude MDI | |
| Example 7 | 4.2 | 23 | 90 |
| Example 8 | 6.5 | 42 | 87 |
| Example 9 | 5.2 | 29 | 89 |
| Comparative example 13 | 21.0 | 115 | 79 |
| Comparative example 14 | 35 | 142 | 76 |
| Comparative example 15 | 23 | 121 | 78 |
| Comparative example 16 | 16.5 | 89 | 82 |
| Comparative example 17 | 12.7 | 72 | 84 |
| Comparative example 18 | 196 | 587 | 68 |
| Comparative example 19 | 472 | 1318 | 60 |
Claims (15)
1. A gaseous film which is hollow porous gamma-MnO2Coated perfluorooctyltrichlorosilane modified ethylene-chlorotrifluoroethylene copolymer hollow fiber membrane, the hollow porous gamma-MnO2The size of the microsphere is 0.5-2.0 μm, and the pore size is 5-20 nm.
2. A method of making the gaseous membrane of claim 1, comprising the steps of:
(a) preparation of modified ECTFE hollow fiber membrane: uniformly mixing ECTFE and a lubricant, adding a pore-forming agent and perfluorooctyl trichlorosilane to prepare a membrane casting solution, preparing a hollow fiber membrane from the membrane casting solution through a spinning device, soaking the hollow fiber membrane in water for 36-48 h, and drying the hollow fiber membrane at 60-80 ℃ for 4-8 h in vacuum;
(b) hollow porous gamma-MnO2The preparation of (1): MnSO with the concentration of 2.0 to 4.0 weight percent4The solution and perfluorooctyl trichlorosilane are mixed evenly, and then NH with the concentration of 1.0-3.0 percent is dripped into the mixture4HCO3The solution is reacted, then filtered, washed, dried and roasted to prepare the hollow porous gamma-MnO2；
(c) Modified ECTFE-gamma-MnO2Preparing a composite hollow fiber gaseous membrane: immersing the modified ECTFE hollow fiber membrane in gamma-MnO2The aqueous suspension is subjected to ultrasonic treatment for 4 to 8 hours, washed and dried to obtain the modified ECTFE-gamma-MnO2A composite hollow fiber gaseous membrane.
3. The method according to claim 2, wherein in the step (a), the mass ratio of ECTFE to perfluorooctyltrichlorosilane is 2:1-6: 1.
4. The method according to claim 2, wherein in the step (a), the mass ratio of ECTFE to perfluorooctyltrichlorosilane is 3:1-4: 1.
5. According to claim2, wherein in step (b), the MnSO is4The mass ratio of the solution to the perfluorooctyl trichlorosilane is 20:1-100: 1.
6. The method of claim 2, wherein in step (b), said MnSO is present in a form selected from the group consisting of4The mass ratio of the solution to the perfluorooctyl trichlorosilane is 40:1-60: 1.
7. The method of claim 2, wherein said firing in step (b) comprises the steps of:
(1) roasting at 380-420 ℃ for 2-5 h;
(2) roasting at 480-520 ℃ for 2-5 h;
(3) roasting at 580-620 ℃ for 2-5 h.
8. The method of claim 2, wherein in step (c), said γ -MnO is2The mass ratio of the ECTFE to the ECTFE is 1:10-1: 100.
9. The method of claim 2, wherein in step (c), said γ -MnO is2The mass ratio of the ECTFE to the ECTFE is 1:20:1-1: 80.
10. The method of claim 2, wherein in step (c), said γ -MnO is2The mass ratio of the ECTFE to the ECTFE is 1:40-1: 60.
11. A method of preparing a bromine-free or low bromine brine comprising the steps of:
(1) mixing the light salt water and fresh water to obtain crude salt water;
(2) the crude brine is fed to a membrane module comprising the gaseous membrane of claim 1, and bromine gas in the crude brine is extracted by the gaseous membrane to produce bromine-free or low-bromine brine.
12. The method according to claim 11, wherein in the step (1), the pH of the weak brine is 0.5-3.5; the available chlorine content is 200-2500 ppm; and/or the bromine content in the crude salt is 100-1000 ppm.
13. The method according to claim 12, wherein in the step (1), the pH of the weak brine is 0.8-2.0; the available chlorine content is 400-1800 ppm.
14. The method according to claim 12, wherein in the step (1), the pH of the weak brine is 1.0-1.5; the available chlorine content was 600-1200 ppm.
15. The method of claim 11, wherein in step (2), the bromine content of the bromine-free or low-bromine brine is within 10 ppm.
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