CN114558466B - Modified zeolite membrane, preparation method and application thereof, and system for separating methanol from crude alcohol - Google Patents
Modified zeolite membrane, preparation method and application thereof, and system for separating methanol from crude alcohol Download PDFInfo
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Abstract
The invention relates to the technical field of membrane separation, and discloses a modified zeolite membrane, a preparation method and application thereof, and a system for separating methanol from crude alcohol, wherein hydrophobic organic matters are adsorbed on hydroxyl groups of the modified zeolite membrane, and the adsorption rate of the hydroxyl groups is 40% -60%; the preparation method of the modified zeolite membrane comprises the following steps: reacting the zeolite membrane with hydrophobic organic steam at 300-400 ℃ for 20-120min to obtain the modified zeolite membrane. According to the technical scheme, the zeolite membrane is treated by the hydrophobic organic steam, so that the hydrophobic organic matters cover the hydroxyl positions in the zeolite membrane, and the zeolite membrane with high selectivity on methanol adsorption and desorption is obtained, so that the high-grade alcohol is obtained through zeolite membrane separation, the equipment investment is low, the operation is simple, the methanol aqueous solution can be directly separated, and the raw material ethanol is not wasted.
Description
Technical Field
The invention relates to the technical field of membrane separation, in particular to a modified zeolite membrane, a preparation method and application thereof, and a system for separating methanol from crude alcohol.
Background
Pectin consists of a long chain of methyl galacturonic acid linked to form a pectin containing a plurality of methoxy-OCH' s 3 Hydrolysis is carried out under the action of heat and enzyme to release methoxy groups, and methanol is easily reduced.
[RCOOCH 3 ]n+11H 2 O———→[RCOOH]n+11CH 3 OH
Edible alcohol is based on grains, and many grains contain pectin, such as corn pericarp, dried potato, bran coat, rice hull, etc. In the traditional alcohol production process, the main production of methanol is caused by three aspects: firstly, the raw materials are decomposed by heating; secondly, the pectic substance is decomposed to generate methoxy under the action of pectase in the saccharification process, and methanol is formed after reduction; thirdly, during distillation, the residual pectic substance generates methanol under the conditions of acid and heating. Thus the formation of methanol is accompanied by the overall process of refining alcohol production by conventional methods.
Methanol is a highly toxic substance for the human body, and for adult males, an intake of 7g leads to poisoning, visual impairment, and death at 70ml, so that many countries have strict control over the methanol content in alcohol. Common methods for reducing methanol impurities in edible alcohol in industrial production are a multi-tower rectification method, a zeolite adsorption method and a chemical reaction method, but the method is difficult and high in cost, and methanol-free alcohol is realized. The multi-tower rectification method generally needs 5-9 separation towers, has high manufacturing cost, complex equipment and increased carbon emission, and causes energy waste, and in addition, the methanol content in the head rectification liquid and the tail rectification liquid is higher and is generally discarded, so that raw materials are wasted; the zeolite adsorption method requires a large amount of zeolite, and in addition, high-temperature activation is required for better zeolite adsorption effect, and intermittent regeneration is required after zeolite adsorption saturation, which eventually leads to increased cost; the chemical method for removing the methanol needs to add substances such as soda lime, potassium permanganate, calcium chloride, magnesium chloride and the like, the methanol removal rate is less than 10 percent, the edible alcohol can be polluted, and the method has no practical value.
Therefore, the prior art lacks a method capable of efficiently separating methanol from alcohol on the premise of low energy consumption, less pollution and convenient operation.
Disclosure of Invention
The invention aims to solve the problems of high energy consumption, large pollution and inconvenient operation of a method for separating methanol from alcohol in the prior art, and provides a modified zeolite membrane, a preparation method and application thereof and a system for separating methanol from crude alcohol.
In order to achieve the above object, according to one aspect of the present invention, there is provided a modified zeolite membrane having a hydroxyl group having a hydrophobic organic substance adsorbed thereon, wherein the hydroxyl group has an adsorption rate of 40% to 60%.
In a second aspect, the present invention provides a method for preparing a modified zeolite membrane comprising: reacting the zeolite membrane with hydrophobic organic steam at 300-400 ℃ for 20-120min to obtain the modified zeolite membrane.
In a third aspect, the invention provides the use of a modified zeolite membrane for separating methanol from crude alcohol.
In a fourth aspect, the invention provides a system for separating methanol from crude alcohol, comprising a raw material storage tank, a delivery pump and a zeolite membrane assembly in series, wherein the zeolite membrane assembly comprises a modified zeolite membrane.
According to the technical scheme, the zeolite membrane is treated by the hydrophobic organic steam, so that the hydrophobic organic matters cover the hydroxyl positions in the zeolite membrane, and the zeolite membrane with high selectivity on methanol adsorption and desorption is obtained, so that the high-grade alcohol is obtained through zeolite membrane separation, the equipment investment is low, the operation is simple, the methanol aqueous solution can be directly separated, and the raw material ethanol is not wasted. Compared with the traditional rectification, the method generally removes the first alcohol and the tail alcohol, has no raw material waste, does not need reflux refining, and has low equipment investment; compared with the zeolite adsorption method, the method does not need high-temperature regeneration and intermittent operation, and is simple to operate; in contrast to chemical methods, no impurities are introduced. Therefore, the invention has the characteristics of low energy consumption, less pollution and convenient operation.
Drawings
FIG. 1 is a schematic diagram of a system for separating methanol from crude alcohol according to the present invention.
Description of the reference numerals
1. Raw material storage tank 2 and delivery pump
3. Zeolite membrane module
Detailed Description
The endpoints and any values of the ranges disclosed herein are not limited to the precise range or value, and are understood to encompass values approaching those ranges or values. For numerical ranges, one or more new numerical ranges may be found between the endpoints of each range, between the endpoint of each range and the individual point value, and between the individual point value, in combination with each other, and are to be considered as specifically disclosed herein.
The first aspect of the invention provides a modified zeolite membrane, wherein hydrophobic organic matters are adsorbed on hydroxyl groups of the modified zeolite membrane, the adsorption rate of the hydroxyl groups is 40-60%, and the carbon number of molecules of the hydrophobic organic matters is less than or equal to 6.
Further, the hydrophobic organic matter is selected from one or more of methane, ethane, ethylene, benzene and methanol; the zeolite membrane is NaA (silicon to aluminum ratio between 1 and 2), SSZ-13 (silicon to aluminum ratio between 2 and 20), ZSM-5 (silicon to aluminum ratio between 4 and 30) or NaY (silicon to aluminum ratio between 1 and 3), preferably ZSM-5 and NaY zeolite membranes, wherein the above zeolite types are named according to IUPAC naming rules, such as ZSM-5 zeolite is zeolite with MFI structure, and NaY zeolite is zeolite with FAU structure. The hydrophobic organic species adsorbed by the zeolite modified hydroxyl groups comprise methanol, methane, benzene and ethylene steam, the methanol steam can chemically react with the hydroxyl groups on the surface of the zeolite membrane at a high temperature of more than 200 ℃ to generate alkyl substances or other complex hydrophobic substances which cover the zeolite pore channels, and other organic substances have similar functions.
The second aspect of the present invention provides a method for preparing the modified zeolite membrane, comprising: reacting the zeolite membrane with hydrophobic organic steam at 300-400 ℃ for 20-120min to obtain the modified zeolite membrane.
In a third aspect, the present invention provides the use of the modified zeolite membrane described above for separating methanol from crude alcohol, comprising the steps of: filtering and separating the crude alcohol by using the modified zeolite membrane with the pore diameter of 0.45-0.72 nm; or filtering and separating the crude alcohol by using the modified zeolite membrane with the aperture of 0.6-0.72nm, and then filtering and separating the crude alcohol by using the modified zeolite membrane with the aperture of 0.45-0.6nm to obtain purified alcohol, wherein the methanol content in the purified alcohol is lower than 60mg/kg. Preferably, the crude alcohol is filtered and separated by the modified zeolite membrane with the aperture of 0.6-0.72nm, and then the crude alcohol is filtered and separated by the modified zeolite membrane with the aperture of 0.45-0.6 nm.
In a fourth aspect, the present invention provides a system for separating methanol from crude alcohol, as shown in fig. 1, comprising a raw material storage tank 1, a transfer pump 2 and a zeolite membrane module 3, which are sequentially connected in series, the zeolite membrane module comprising the modified zeolite membrane described above.
Further, the zeolite membrane module comprises two or more of the modified zeolite membranes in series. Preferably, the zeolite membrane assembly comprises two modified zeolite membranes connected in series, wherein the modified zeolite membrane at the inflow end of the crude alcohol is a large-pore-size membrane, and the modified zeolite membrane at the outflow end of the crude alcohol is a small-pore-size membrane. The large-aperture membrane has the characteristics of high flux and poor selectivity, and the small-aperture membrane has the characteristics of good selectivity and poor flux; and the selectivity is good when the concentration is high, and the selectivity is poor when the concentration is low. The combination of the two pore size membranes can simultaneously utilize the advantages of the two pore size membranes, and ensures the selectivity while ensuring the flux. For example, the large-pore NaY zeolite membrane is used for rapidly removing methanol in the front stage (crude alcohol inflow end), and after the methanol concentration in the rear stage (crude alcohol outflow end) is reduced, the ZSM-5 zeolite membrane with higher selectivity and smaller pores is used for removing methanol in the rear stage.
Compared with the traditional separation technology, the membrane separation technology has the advantages of low energy consumption, less pollution, convenient operation and the like, thereby receiving extensive attention of the academia and the industry. However, there is no case of separating methanol from alcohol using zeolite membrane. Wherein the kinetic diameter of the methanol molecules is 0.38nm, the kinetic diameter of the ethanol molecules is about 0.44nm, and the preparation of the zeolite membrane with the pore diameter of about 0.44nm can effectively separate methanol from alcohol. It can be seen from the high-grade pure alcohol that the methanol content needs to be lower than 62ppm, which belongs to the deep methanol removal range, and has great challenges on flux and selectivity of zeolite membranes. According to the pervaporation principle, the flux of methanol and the partial pressure of methanol are related to adsorption, diffusion and desorption of methanol on the surface of a membrane, wherein the adsorption and the desorption are a pair of mutually restricted conditions, the stronger the adsorption of zeolite is, the weaker the desorption of zeolite is, the weaker the adsorption of zeolite is, the extremely extreme both can lead to the flux reduction of the zeolite membrane, and the balance between the two needs to be achieved to bring the performance of the zeolite membrane into play extremely.
To achieve this object, the present invention has been studied from two points of view by selectively separating methanol from alcohol using zeolite membrane to obtain an excellent alcohol. One is zeolite membrane selection, wherein the pore diameters of NaA, ZSM-5 and NaY zeolite are respectively 0.41nm, 0.55nm and 0.72nm, and are near the molecular diameter of ethanol, so that the invention utilizes NaA, ZSM-5 and NaY zeolite membranes to separate methanol in the ethanol. The other is to carry out the adsorption and desorption performance improvement to the zeolite membrane, the methanol has hydrophilic hydroxyl and hydrophobic methyl at the same time, the zeolite membrane also has a hydrophobic silicon region and a hydrophilic hydroxyl base region at the same time, and the adsorption and desorption properties of the zeolite membrane to the methanol are reasonably regulated through the treatment of the hydroxyl region, so that the methanol removal performance of the zeolite membrane is effectively improved.
According to a particularly preferred embodiment of the present invention, a modified zeolite membrane having hydrophobic organic matter adsorbed on hydroxyl groups, the hydroxyl groups having an adsorption rate of 45% to 51%, the modified zeolite membrane is prepared by a process comprising: reacting the zeolite membrane with hydrophobic organic steam at 300-400 ℃ for 20-40min to obtain the modified zeolite membrane. The application of the modified zeolite membrane in separating methanol from crude alcohol is specifically as follows: filtering and separating the crude alcohol by using a modified NaY zeolite membrane with the aperture of 0.63-0.70nm, and filtering and separating the crude alcohol by using a modified ZSM-5 zeolite membrane with the aperture of 0.48-0.55nm, wherein the methanol content in the obtained purified alcohol is lower than 60mg/kg.
The present invention will be described in detail by examples. In the following examples, the test conditions for ethanol methanol separation were: the raw material liquid was 99.5wt%/0.5wt% ethanol/methanol solution, the pervaporation test temperature was 100 ℃, and the ethanol and methanol contents on the permeate side and the raw material side were measured by a chromatograph. The raw materials are all commercial products.
Adsorption rate of hydroxyl groups on modified zeolite membrane using NH 3 TPD test, test procedure as follows:
1. hydroxyl group determination of untreated zeolite membranes:
the zeolite membrane is first treated under inert gas at 400 deg.c for 1 hr, cooled to 150 deg.c and treated with 5% NH 3 Adsorption for 1h, followed by purging with inert gas for 0.5h, then programmed to 500 ℃ at a ramp rate of 5 ℃/min, recording data with TCD, and integrating the data to obtain NH of untreated zeolite 3 Adsorption amount according to hydroxyl and NH 3 The adsorption relationship gives hydroxyl data 1.
2 zeolite membrane hydroxyl determination after treatment:
the zeolite membrane is first treated with inert gas at 400 deg.c for 1 hr, then with corresponding organic vapor at specific temperature for a certain period of time, then with N 2 Purging for 30min, removing weakly adsorbed organic substances, cooling to 150deg.C, and adding 5% NH 3 Adsorption for 1h, followed by purging with inert gas for 0.5h, then programmed to 500 ℃ at a ramp rate of 5 ℃/min, recording data with TCD, and integrating the data to obtain NH of untreated zeolite 3 Adsorption amount according to hydroxyl and NH 3 The adsorption relationship gives hydroxyl data 2.
And 3, dividing the difference between the hydroxyl data 1 and the hydroxyl data 2 by the hydroxyl data 1 to obtain the coverage rate of the hydroxyl, namely the hydroxyl adsorption rate.
Example 1
Synthesis and methanol separation effect test of modified ZSM-5 zeolite membrane:
(1) ZSM-5 seed crystal synthesis
The preparation molar ratio is 1SiO 2 :0.5NaOH:0.05Al 2 O 3 ：50H 2 O:0.4TPAOH sol, transferring the sol to a 100ml reaction kettle, placing the reaction kettle in a baking oven at 170 ℃, taking out and centrifuging after crystallization for 4 days to obtain ZSM-5 seed crystals;
(2) Seed tube preparation
Putting 1g of ZSM-5 seed crystal into 99g of water, carrying out ultrasonic treatment for 1 min to obtain suspension seed crystal liquid, putting an alumina support body with the length of 20cm into the seed crystal liquid, standing for 30s, lifting out at the speed of 0.5cm/s, airing, putting into a muffle furnace, heating to 500 ℃ at the speed of 5 ℃/min, roasting for 2h, and naturally cooling to room temperature to obtain a seed crystal tube;
(3) Synthesis of ZSM-5 zeolite membrane by secondary growth method
The preparation molar ratio is 1SiO 2 :0.57NaOH:137.5H 2 O:0.0050(Al 2 (SO 4 ) 3 ·18H 2 O)), then transferring the sol into a 300ml reaction kettle, then placing a seed crystal tube into the reaction kettle, transferring the reaction kettle into a 170 ℃ oven, taking out the solution after crystallization for 1 day, and washing the solution with deionized water to obtain a ZSM-5 zeolite membrane;
(4) Synthesis of modified ZSM-5 zeolite membrane
At normal temperature, 1% methane/nitrogen is heated to 400 ℃, and is introduced into the obtained ZSM-5 zeolite membrane, after being treated for about 20 minutes, the temperature is naturally reduced to room temperature, and the modified ZSM-5 zeolite membrane with the pore diameter of 0.5nm is obtained, wherein the hydroxyl adsorption rate is 45%.
The modified ZSM-5 zeolite membrane was mounted to zeolite membrane module 3. Heating ethanol and methanol (99.5/0.5) solution to 100 ℃, introducing the solution into a zeolite membrane assembly 3 by a conveying pump 2 at a speed of 50kg/h, wherein the concentration of methanol in ethanol at the outlet of the zeolite membrane assembly 3 is 60ppm, the concentration of ethanol reaches the standard of high-grade ethanol, the industrial alcohol with the concentration of methanol of about 32% is obtained at the permeation side, and the loss rate of raw materials is 1.5%.
Example 2
Synthesis and methanol separation effect test of modified NaY zeolite membrane:
(1) Preparing a synthetic solution according to the following method;
preparation of solution A 1 :30.22g of NaOH is dissolved in 360g of deionized water, then 3.6g of sodium metaaluminate is added, and solution A is obtained after dissolution 1 ；
Solution B 1 :30.22g NaOH was dissolved in 360g deionized water and then 66.6g silica sol (containing SiO therein was added 2 40% of the total mass of the solution B is obtained by dissolving 1 ；
Solution A 1 And solution B 1 Fully mixing to obtain a uniform and clear synthetic solution. The obtained synthetic solution contains 70Na according to mole ratio 2 O:Al 2 O 3 :20SiO 2 :2000H 2 O。
(2) Transferring the synthetic liquid into a synthesis kettle; a tubular porous alumina ceramic support having a length of 20cm and a diameter of 1.2cm was completely immersed in the synthesis liquid. Before microwave synthesis, placing the synthesis kettle in a baking oven at 60 ℃ to enable the support body to age for 8 hours in the presence of a synthesis liquid; after aging, placing all the synthesis kettles in a microwave oven, and uniformly heating to 95 ℃ within 4 minutes; and then maintaining the temperature of the system at 95 ℃, taking out the synthesis kettle after reacting for 30 minutes, and taking out the support.
(3) Repeating the step (1) and the step (2) for one time to obtain a NaY zeolite membrane;
(4) At normal temperature, 3% of ethylene/nitrogen is heated to 300 ℃, introduced into the obtained NaY zeolite membrane, treated for 40 minutes, and naturally cooled to room temperature, so as to obtain the modified NaY zeolite membrane with the pore diameter of 0.67nm, and the hydroxyl adsorption rate of the modified NaY zeolite membrane is 51%.
The modified NaY zeolite membrane was mounted to zeolite membrane module 3. Heating ethanol and methanol (99.5/0.5) solution to 60 ℃ in a raw material storage tank 1, introducing the solution into a zeolite membrane assembly 3 by a conveying pump 2 at a speed of 50kg/h, setting the temperature of the zeolite membrane assembly 3 to 100 ℃, setting the concentration of methanol in ethanol at the outlet of the zeolite membrane assembly 3 to be 50ppm, reaching the standard of high-grade ethanol, obtaining industrial alcohol with the methanol concentration of about 40% at 0.625kg/h at the permeation side, and ensuring the raw material loss rate to be 1.25%.
Example 3
300 modified ZSM-5 zeolite membranes and 300 modified NaY zeolite membranes synthesized in example 1 and example 2 respectively were installed in zeolite membrane module 3, the modified NaY zeolite membrane with higher flux was installed in the former stage membrane module, and the modified ZSM-5 zeolite membrane with better selectivity was installed in the latter stage membrane module.
At normal temperature, methanol vapor with mass concentration of 5% is heated to 350 ℃, is introduced into the zeolite membrane assembly 3, is treated for 60 minutes, is naturally cooled to room temperature, and is purged with nitrogen. Heating an ethanol-methanol (99.5/0.5) solution to 60 ℃ in a raw material storage tank 1, introducing the solution into a zeolite membrane assembly 3 by a conveying pump 2 at a speed of 50kg/h, setting the temperature of the zeolite membrane assembly 3 to 100 ℃, setting the concentration of methanol in ethanol at an outlet of the zeolite membrane assembly 3 to be 20ppm, reaching the standard of high-grade ethanol, obtaining industrial alcohol with the methanol concentration of 29% at 0.86kg/h at a permeation side, and ensuring the raw material loss rate to be 1.7%.
Comparative example 1
600 ZSM-5 zeolite membranes of 20cm length obtained in example 1 were packed in a zeolite membrane module 3, an ethanol methanol (99.5/0.5) solution was heated to 60℃in a raw material storage tank 1, and fed to the membrane module at a speed of 50kg/h by a feed pump 2, the temperature of the zeolite membrane module 3 was set to 100℃and the methanol concentration at the outlet of the zeolite membrane module 3 was 0.01% by weight close to the excellent ethanol standard, the permeation side was 0.78kg/h of industrial alcohol having a methanol concentration of 32%, and the raw material loss rate was 1.5%.
Comparative example 2
600 NaY zeolite membranes of 20cm length obtained in example 2 were packed into a zeolite membrane module 3, an ethanol methanol (99.5/0.5) solution was heated to 60℃in a raw material tank 1, and fed into the zeolite membrane module 3 at a speed of 50kg/h by a feed pump 2, the temperature of the zeolite membrane module 3 was set to 100℃and the methanol concentration at the outlet of the zeolite membrane module 3 was 150ppm, which was close to the standard of high-grade ethanol, and 2.08kg of industrial alcohol having a methanol concentration of 12% was obtained on the permeate side and the raw material loss rate was 4.2%.
Comparative example 3
300 pieces of ZSM-5 zeolite membranes and 300 pieces of NaY zeolite membranes synthesized in example 1 and example 2 respectively were mounted in zeolite membrane module 3, the former stage membrane module was mounted with NaY zeolite membranes having higher flux, and the latter stage membrane module was mounted with ZSM-5 zeolite membranes having better selectivity. The ethanol-methanol (99.5/0.5) solution is heated to 60 ℃ in a raw material storage tank 1, and is introduced into a zeolite membrane assembly 3 by a conveying pump 2 at a speed of 50kg/h, the temperature of the zeolite membrane assembly 3 is set to 100 ℃, the methanol concentration at the outlet of the zeolite membrane assembly 3 is 90ppm, the standard of the superior ethanol is approximate, the industrial alcohol with the methanol concentration of about 32% is obtained at the permeation side, the raw material loss rate is 1.5%. The zeolite membrane module 3 combination is capable of achieving a higher alcohol with a lower methanol content at a loss rate of only 1.5%.
According to the separation results of examples 1-3 and comparative examples 1-3, it is known that the zeolite membrane can be treated with hydrophobic organic gas to improve the methanol removal performance of the zeolite membrane and to achieve the requirement of high grade alcohol after the zeolite membrane is treated. From the separation results of examples 1 to 3, it was found that the separation effect (i.e., the methanol concentration at the outlet of the zeolite membrane module 3 in examples 1 to 3) using the large-pore-diameter modified zeolite membrane followed by the small-pore-diameter modified zeolite membrane was superior to that using the single-pore-diameter modified zeolite membrane.
Comparative example 4
To 1kg of an alcoholic solution having a methanol concentration of 5000mg/kg, 300g of 4 conventional zeolite were added, respectively: SSZ-13 zeolite, naA zeolite, ZSM-5 zeolite and NaY zeolite were stirred at 100℃for 3 hours, then filtered, and the filtrate was tested for methanol concentration, and the results are shown in Table 1. As can be seen from the results, the methanol content of the alcohol solution after adsorption using these 4 conventional zeolites was far higher than 60mg/kg (the methanol concentration at the outlet of zeolite membrane module 3 in examples 1-3), indicating that no superior alcohol could be obtained by simple adsorption of conventional zeolite.
TABLE 1 methanol content in alcohol before and after adsorption
According to the separation results of examples 1-3 and comparative example 4, the methanol removal effect of the technical scheme of the invention is obviously better than that of the conventional adsorption method after the zeolite membrane is treated by the hydrophobic organic gas.
The preferred embodiments of the present invention have been described in detail above, but the present invention is not limited thereto. Within the scope of the technical idea of the invention, a number of simple variants of the technical solution of the invention are possible, including combinations of the individual technical features in any other suitable way, which simple variants and combinations should likewise be regarded as being disclosed by the invention, all falling within the scope of protection of the invention.
Claims (9)
1. A modified zeolite membrane for separating methanol from crude alcohol, characterized in that a hydrophobic organic substance is adsorbed on hydroxyl groups of the modified zeolite membrane,
wherein the zeolite membrane is a NaA zeolite membrane, an SSZ-13 zeolite membrane, a ZSM-5 zeolite membrane or a NaY zeolite membrane;
the hydrophobic organic matter is obtained by reacting zeolite membrane with hydrophobic organic steam at 300-400 deg.C for 20-120 min;
wherein the hydrophobic organic steam is selected from any one or more of methane, ethane, ethylene, benzene and methanol;
wherein the adsorption rate of the hydroxyl is 40% -60%;
wherein the silicon-aluminum ratio of the NaA zeolite membrane is 1-2: 1. the silica-alumina ratio of the SSZ-13 zeolite membrane is 2-20: 1. the ZSM-5 zeolite membrane has a silica-alumina ratio of 4 to 30: 1. the silicon-aluminum ratio of the NaY zeolite membrane is 1-3:1.
2. the modified zeolite membrane of claim 1, wherein the hydrophobic organic matter has a molecular carbon number of less than or equal to 6.
3. A method of preparing a modified zeolite membrane according to any one of claims 1-2, comprising: reacting the zeolite membrane with hydrophobic organic steam at 300-400 ℃ for 20-120min to obtain the modified zeolite membrane.
4. Use of a modified zeolite membrane according to any one of claims 1-2 for separating methanol from crude alcohol.
5. The use according to claim 4, characterized in that it comprises the following steps:
filtering and separating the crude alcohol by using the modified zeolite membrane to obtain purified alcohol.
6. The use according to claim 5, wherein said filtering of the crude alcohol with the modified zeolite membrane is specifically:
filtering and separating the crude alcohol by using the modified zeolite membrane with the pore diameter of 0.45-0.72 nm;
or filtering and separating the crude alcohol by using the modified zeolite membrane with the aperture of 0.6-0.72nm, and then filtering and separating the crude alcohol by using the modified zeolite membrane with the aperture of 0.45-0.6 nm.
7. The use according to claim 5, wherein the purified alcohol has a methanol content of less than 60mg/kg.
8. A system for separating methanol from crude alcohol comprising a feed tank, a transfer pump and a zeolite membrane module in series, the zeolite membrane module comprising a modified zeolite membrane according to any one of claims 1-2.
9. The system of claim 8, wherein the zeolite membrane assembly comprises two or more of the modified zeolite membranes in series.
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