Method for purifying hydrogen and method for producing hydrogen by reforming methanol

Abstract

The invention relates to the field of energy and fuel cells, and discloses a hydrogen purification method and a methanol reforming hydrogen production method, the method comprises the following steps: adsorbing a mixed gas containing hydrogen and carbon monoxide, and then carrying out at least one-stage membrane separation; wherein the hydrogen-containing mixed gas contains hydrogen and carbon monoxide. The method for purifying hydrogen has the advantages of high yield and high purity, and carbon monoxide and hydrogen can be efficiently separated by adopting membrane separation. The methanol reforming hydrogen production system provided by the invention can efficiently purify hydrogen from a methanol reforming product.

Description

Technical Field

[0001] This invention relates to the field of energy and fuel cells, and more specifically, to a method for purifying hydrogen and a method for producing hydrogen by methanol reforming. Background Technology

[0002] Hydrogen, as a green, environmentally friendly, and renewable energy source, has garnered increasing attention worldwide in recent years. Its high calorific value, several times that of conventional fossil fuels of the same weight, makes it one of the most ideal clean energy sources. However, due to the unique properties of hydrogen, its storage, transportation, and the safety of hydrogen refueling stations are not easily guaranteed. Therefore, directly using hydrogen fuel as an energy source has significant drawbacks, making on-site hydrogen production technology the preferred method for efficient hydrogen energy utilization. Traditional hydrogen production processes include coal-to-hydrogen, natural gas-to-hydrogen, and water electrolysis. Natural gas and water electrolysis are suitable for small to medium-sized on-site hydrogen production, but natural gas, like hydrogen, is complex to transport and store, and water electrolysis consumes a significant amount of electricity. Methanol reforming for hydrogen production consumes less energy, methanol is easier to store and transport, and my country has an overcapacity of methanol production, providing abundant raw materials. After several years of development, methanol reforming technology has become more mature and its costs have decreased, making it the preferred choice for small to medium-scale hydrogen production.

[0003] Methanol reforming for hydrogen production yields a mixture of byproducts including hydrogen, carbon dioxide, and small amounts of carbon monoxide and methane. Carbon monoxide can poison and deactivate the catalyst in proton exchange membrane fuel cells (PEMFCs). For a fuel cell to function properly, the CO content must be below 10 ppm. Therefore, while purifying the hydrogen produced from methanol reforming, it is also necessary to reduce the CO content. Currently, the main purification methods are adsorption, membrane separation, and cryogenic separation. Among these, membrane separation requires less volume and consumes less energy compared to adsorption and cryogenic separation methods.

[0004] In current industrial membrane separation technologies, palladium membranes are commonly used due to their excellent purification effect. However, palladium membranes require high operating temperatures (membrane temperatures are all above 300℃, resulting in long heating and cooling times during start-up and shutdown), and the systems are complex and costly, making them unsuitable for large-scale production. They also exhibit poor stability and short service life in industrial applications. The most critical drawback is the hydrogen embrittlement effect, meaning that after absorbing a certain amount of hydrogen atoms, the palladium membrane becomes more brittle, less tough, and less able to withstand pressure, making it prone to breakage.

[0005] In summary, for online methanol reforming to produce hydrogen for fuel cells, not only should efficient purification be considered, but also economic efficiency. Existing technologies and processes cannot simultaneously achieve both economic efficiency and efficient purification. Summary of the Invention

[0006] The purpose of this invention is to overcome the problem that the economy and high efficiency of purification cannot be achieved simultaneously in the existing technology, and to provide a method for purifying hydrogen and a method for producing hydrogen by methanol reforming. The method for purifying hydrogen has the advantages of high yield and high purity in the process of purifying hydrogen.

[0007] To achieve the above objectives, the first aspect of the present invention provides a method for purifying hydrogen in a hydrogen-containing mixture, the method comprising: subjecting the hydrogen-containing and carbon monoxide-containing mixture to at least one stage of membrane separation after adsorption; wherein the hydrogen-containing mixture comprises hydrogen and carbon monoxide.

[0008] A second aspect of the present invention provides a method for producing hydrogen from methanol reforming, the method comprising: sequentially adsorbing and separating the products of the methanol reforming reaction using at least one primary membrane.

[0009] The adsorption and membrane separation are performed in accordance with the adsorption and membrane separation described in the method described in the first aspect.

[0010] The above technical solution can achieve at least the following beneficial effects:

[0011] (1) The method for purifying hydrogen in this invention has the advantages of high yield and high purity.

[0012] (2) The membrane separation of the present invention can efficiently separate carbon monoxide and hydrogen.

[0013] (3) The methanol reforming hydrogen production system of the present invention can efficiently purify hydrogen from methanol reforming products. Attached Figure Description

[0014] Figure 1 This is a process flow diagram of methanol reforming to produce hydrogen in Example 1.

[0015] Explanation of reference numerals in the attached figures

[0016] S1 is a methanol and water solution; S2 is a methanol-water solution after mixing; S3 is a methanol-water solution after preheating; S4 is methanol and water vapor; S5 is mainly the mixture after the reforming reaction; S6 is mainly the mixture after the heat exchange is completed; S7 is mainly the water vapor mixture after cooling and liquefaction; S8 is mainly the gaseous substance after gas-liquid separation; S9 is mainly the liquid substance after gas-liquid separation; S10 is mainly the gas remaining after adsorption; S11 is mainly the adsorbed gas; S12 is mainly the permeate side gas after membrane separation; S13 is mainly the permeate side gas after membrane separation. Detailed Implementation

[0017] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0018] The first aspect of the present invention provides a method for purifying hydrogen in a hydrogen-containing mixture, the method comprising: adsorbing a mixture containing hydrogen and carbon monoxide and then performing at least one stage of membrane separation; wherein the hydrogen-containing mixture contains hydrogen and carbon monoxide.

[0019] In this invention, a mixture of hydrogen and carbon monoxide is efficiently separated by a combination of adsorption and membrane separation, resulting in hydrogen with high yield and high purity.

[0020] In this invention, preferably, the hydrogen concentration in the hydrogen-containing and carbon monoxide-containing mixture is >50 vol%, and the carbon monoxide concentration is <5 vol%. More preferably, the hydrogen concentration in the hydrogen-containing and carbon monoxide-containing mixture can be 60-100 vol% (for example, it can be any two values ​​from 60 vol%, 62 vol%, 65 vol%, 67 vol%, 70 vol%, 75 vol%, 85 vol%, 95 vol%, 100 vol%, or any value within that range), and the carbon monoxide concentration can be 0-2 vol% (for example, it can be any two values ​​from 0 vol%, 0.5 vol%, 0.8 vol%, 1 vol%, 1.3 vol%, 1.5 vol%, 1.7 vol%, 2 vol%, or any value within that range).

[0021] In this invention, preferably, the mixture of hydrogen and carbon monoxide further contains carbon dioxide and methane.

[0022] In this invention, preferably, the carbon dioxide concentration in the hydrogen-containing and carbon monoxide-containing mixture is <45 vol%, and the methane concentration is <10 vol%. More preferably, the carbon dioxide concentration in the hydrogen-containing and carbon monoxide-containing mixture can be 0-27 vol% (for example, it can be any two values ​​from 0 vol%, 5 vol%, 10 vol%, 15 vol%, 20 vol%, 22 vol%, 24 vol%, 27 vol%, and values ​​within that range), and the methane concentration can be 0-5 vol% (for example, it can be any two values ​​from 0 vol%, 0.5 vol%, 1 vol%, 1.5 vol%, 2 vol%, 2.5 vol%, 3 vol%, 3.5 vol%, 4 vol%, 4.5 vol%, 5 vol%, and values ​​within that range).

[0023] In this invention, preferably, the adsorption method can be at least one of pressure swing adsorption, alkaline adsorption and ion exchange adsorption.

[0024] In this invention, preferably, the adsorbent is selected from at least one of molecular sieves, activated carbon, and metal-organic framework materials (MOFs).

[0025] In this invention, preferably, the adsorption conditions include: a pressure of 0.2-15 MPa, more preferably 8-12 MPa (e.g., a range formed by any two values ​​from 8 MPa, 8.5 MPa, 9 MPa, 9.5 MPa, 10 MPa, 10.5 MPa, 11 MPa, 11.5 MPa, and 12 MPa, and values ​​within that range); a temperature of -60°C to 100°C, more preferably -25°C to 60°C (e.g., a range formed by any two values ​​from -25°C, -20°C, -15°C, -10°C, -5°C, 0°C, 5°C, 10°C, 15°C, 20°C, 25°C, 30°C, 35°C, 40°C, 45°C, 50°C, 55°C, and 60°C, and values ​​within that range); and a volume hourly space velocity (VHSV) of 10-110 h⁻¹ for the hydrogen-containing mixture. -1 More preferably 30-110h -1 (For example, it could be 30h) -1 35h -1 40h -1 45h -1 50h -1 55h -1 60h -1 65h -1 70h -1 75h -1 80h -1 85h -1 90h-1 95h -1 100h -1 105h -1 110h -1 (The range formed by any two values ​​in the range and the values ​​within that range).

[0026] In this invention, the adsorption can remove some of the carbon dioxide from the mixture of hydrogen and carbon monoxide. After the adsorption is completed, a membrane separation step is performed, which solves the problem that it is difficult to remove carbon dioxide by using membrane separation alone, and also reduces the concentration requirements of each substance in the mixture.

[0027] In this invention, preferably, the separation membrane used for membrane separation can be a gas separation membrane made of at least one of polysulfone, polyethersulfone, polyimide, polyamide, polypropylene, polyethylene, synthetic resin, polyvinylidene fluoride, polytetrafluoroethylene, polyether ether ketone, polybenzimidazole, block copolymer, cellulose acetate membrane, polycarbonate membrane, polymethyl methacrylate membrane, silica membrane, zeolite molecular sieve membrane, carbon molecular sieve membrane, and metal-organic framework materials, more preferably at least one of polybenzimidazole gas separation membrane, polyimide gas separation membrane, and polyamide gas separation membrane.

[0028] In a preferred embodiment of the present invention, the separation membrane used for membrane separation is a polybenzimidazole gas separation membrane, wherein the polybenzimidazole gas separation membrane has an interpenetrating network pore structure and a nanoscale pore structure, wherein the pore size distribution of the nanoscale pore structure is 0.1-30 nm and the average pore size of the nanoscale pore structure is 1-80 nm.

[0029] According to the present invention, preferably, the pore size distribution of the nanoscale pore structure is 0.2-30 nm, more preferably 0.2-25 nm, more preferably 0.5-20 nm, and even more preferably 0.57-19 nm.

[0030] According to the present invention, preferably, the average pore size of the nanoscale pore structure is 2-50 nm, more preferably 3-20 nm, and even more preferably 5-18 nm.

[0031] The inventors of this invention have discovered that the gas separation membrane in this invention has an interpenetrating network pore structure and an internal nanoporous structure. This pore structure can maintain or even further improve the gas selectivity of the gas separation membrane while increasing its permeability coefficient, especially achieving highly selective separation of gas pairs such as He / N2, He / CH4, H2 / CO2, H2 / N2, H2 / CH4, CO2 / N2, and CO2 / CH4.

[0032] According to the present invention, the porosity of the gas separation membrane is 3-30%, preferably 3-22%, more preferably 5-15%, and even more preferably 5.98-14.82%. In the present invention, the porosity of the gas separation membrane meets the above range, which can further improve the permeability coefficient of the gas separation membrane.

[0033] According to the present invention, the permeability coefficient of the gas separation membrane is 5-30 Barrer, preferably 10-20 Barrer, and more preferably 10.56-18.75 Barrer. It should be noted in this invention that the permeability coefficient of the gas separation membrane refers to its permeability coefficient relative to helium (He).

[0034] In this invention, when the permeability coefficient meets the above-mentioned range, the gas separation membrane can maintain a high gas selectivity at the permeability coefficient.

[0035] Additionally, it should be noted that the unit of permeability coefficient in this invention is "Barrer" (1 Barrer = 7.5 × 10⁻⁶). -18 m 3 (STP)m / (m 2 ·s·Pa).

[0036] In a preferred embodiment of the present invention, the method for preparing a polybenzimidazole gas separation membrane includes:

[0037] S1. Polybenzimidazole and a protic solvent are mixed and degassed to obtain a casting solution;

[0038] S2. After coating the casting solution onto the substrate to form a thin layer of casting solution, it is then immersed in a non-solvent to solidify into a film. After separating the film from the substrate, a nascent porous film is obtained.

[0039] S3. The nascent porous membrane is sequentially immersed in an alkaline solution and a washing solution to obtain a porous membrane;

[0040] S4. The porous membrane is dried to obtain a polybenzimidazole gas separation membrane.

[0041] The inventors discovered that current methods for preparing PBI porous membranes mainly involve non-solvent-induced phase separation using aprotic organic solvents. This results in membranes with high permeability but poor selectivity and mechanical properties. This invention provides a novel type of solvent for preparing PBI porous membranes: protic solvents. By utilizing the excellent solubility between protic solvents and polymers, the rate of phase separation is slowed down, allowing the preparation of PBI membranes with a nanoporous structure. This results in gas-porous membranes exhibiting high selectivity, high permeability, and high mechanical stability (see 202411548166.7 for details).

[0042] In this invention, preferably, the membrane separation can employ 2-3 stage membrane separation. Using 2-3 stage membranes not only ensures complete separation of the hydrogen and carbon monoxide mixture, but also reduces costs (including both construction costs and energy consumption).

[0043] In this invention, preferably, the membrane separation conditions include: a membrane separation temperature of 0-300℃, more preferably 50-150℃ (for example, a range formed by any two values ​​from 50℃, 60℃, 70℃, 80℃, 90℃, 100℃, 110℃, 120℃, 130℃, 140℃, 150℃, and values ​​within that range); and a membrane pressure of 0.1-10MPa, more preferably 2-5MPa (for example, a range formed by any two values ​​from 2MPa, 2.5MPa, 3MPa, 3.5MPa, 4MPa, 4.5MPa, 5MPa, and values ​​within that range).

[0044] In this invention, adsorption and membrane separation are combined to achieve a separation temperature of only 0-300℃, preferably 50-150℃, which greatly reduces the energy consumption of the operating conditions.

[0045] A second aspect of the present invention provides a method for producing hydrogen from methanol reforming, the method comprising: sequentially adsorbing and separating the products of the methanol reforming reaction using at least one primary membrane.

[0046] The adsorption and membrane separation are performed in accordance with the adsorption and membrane separation described in the method described in the first aspect.

[0047] In this invention, preferably, the reaction conditions for the methanol reforming reaction include: a reaction temperature of 100-400℃, more preferably 150-300℃ (for example, a range formed by any two values ​​from 150℃, 160℃, 170℃, 180℃, 190℃, 200℃, 210℃, 220℃, 230℃, 240℃, 250℃, 260℃, 270℃, 280℃, 290℃, 300℃, and values ​​within that range); and a reaction pressure of 0-10MPa, more preferably 0-1MPa (for example, a range formed by any two values ​​from 0MPa, 0.1MPa, 0.2MPa, 0.3MPa, 0.4MPa, 0.5MPa, 0.6MPa, 0.7MPa, 0.8MPa, 0.9MPa, 1MPa, and values ​​within that range).

[0048] In this invention, preferably, the raw materials in the methanol reforming reaction process include methanol and water.

[0049] In this invention, preferably, the molar ratio of water to methanol can be 1-3:1, more preferably 1.2-2.5:1, and even more preferably 1.4-1.8:1.

[0050] In this invention, preferably, the method further includes: cooling the product after methanol reforming reaction, performing gas-liquid separation on the cooled mixture, and re-reforming the separated liquid with methanol.

[0051] In a preferred embodiment of the present invention, the method for producing hydrogen from methanol reforming can be as follows:

[0052] (1) Send methanol and water into the storage tank and control the feed ratio of water to methanol;

[0053] (2) After being preheated by the heat exchanger, it enters the evaporator for heating and vaporization;

[0054] (3) The vaporized methanol water vapor enters the reactor for reforming reaction;

[0055] (4) The product after the reforming reaction is preheated by a heat exchanger;

[0056] (5) The product after heat exchange in the heat exchanger is cooled;

[0057] (6) The cooled mixture enters the gas-liquid separator to separate the unreacted methanol-water solution and recover it to the storage tank for reuse. The mixed gas separated by the gas-liquid separator is adsorbed.

[0058] (7) The adsorbed gas mixture enters the membrane separation system;

[0059] (8) The permeate gas after separation is high-purity hydrogen gas suitable for fuel cells, and the residual permeate gas is the exhaust gas.

[0060] In the method for producing hydrogen from methanol reforming, the heat transfer oil system first heats the reforming reaction system to allow it to react within a specific temperature range. Subsequently, the residual heat can be used to heat the evaporator to vaporize the methanol-water solution, or to heat the membrane separation system.

[0061] The present invention will be described in detail below through embodiments. In the following embodiments,

[0062] All gas concentration units are calculated by volume; gas concentration parameters are measured using an online gas concentration meter. The formulas for calculating the gas output from the gas-liquid separator, the gas output from the pressure swing adsorption (PSA) system, the permeate from the first-stage membrane, the residual gas from the first-stage membrane, the permeate from the second-stage membrane, and the residual gas from the second-stage membrane are as follows:

[0063] Preparation Example 1

[0064] This preparation example illustrates a nanoporous polybenzimidazole gas separation membrane prepared using the method of the present invention.

[0065] (S1) Preparation of casting solution:

[0066] 0.8 g of polybenzimidazole (with a number-average molecular weight of 74,800 and structural units as shown in formula (A5)) was added to an Erlenmeyer flask, followed by 9.2 g of methanesulfonic acid. After mechanical stirring at 75°C for 24 h, the polymer was completely dissolved, and an 8 wt% polybenzimidazole casting solution was prepared. The solution was cooled to room temperature and vacuumed to -0.1 MPa to remove bubbles, yielding the polybenzimidazole casting solution, which was then placed in an oven at 60°C for later use.

[0067] (S2) Preparation of primary porous membrane:

[0068] Polybenzimidazole casting solution was uniformly coated onto the surface of a glass plate, and then immersed in deionized water at room temperature for 0.5 h to solidify into a film. After separation of the plate and the film, a primary porous membrane was obtained.

[0069] (S3) Preparation of porous membranes:

[0070] The nascent porous membrane was transferred to a 0.1 mol / L sodium hydroxide aqueous solution and soaked at room temperature for 24 hours. Then the membrane was transferred to deionized water and soaked at 80°C for another 24 hours. The deionized water was changed every 8 hours to obtain the porous membrane.

[0071] (S4) Preparation of polybenzimidazole gas separation membrane:

[0072] After removing the porous membrane, the surface moisture was absorbed with absorbent paper and then dried in a 50℃ forced-air oven for 2 hours, followed by drying in a 100℃ vacuum oven for 8 hours to obtain a dry membrane (polybenzimidazole gas separation membrane), labeled S1. The obtained polybenzimidazole porous membrane S1 has a pore size distribution of 0.8-12.5 nm, an average pore size of 7 nm, and a porosity of 8.75%.

[0073] Preparation Example 2

[0074] This preparation example illustrates a nanoporous polybenzimidazole gas separation membrane prepared using the method of the present invention.

[0075] (S1) Preparation of casting solution: Same as in preparation example 1;

[0076] (S2) Preparation of primary porous membrane:

[0077] The polybenzimidazole casting solution was uniformly coated onto the surface of a glass plate, and then immersed in ethanol at room temperature for 1 hour to solidify into a film. After separation of the plate and film, a primary porous membrane was obtained.

[0078] (S3) Preparation of porous membranes:

[0079] The nascent porous membrane was transferred to a 0.1 mol / L sodium bicarbonate aqueous solution and soaked at room temperature for 24 hours. Then the membrane was transferred to deionized water and soaked at 80°C for another 24 hours. The deionized water was changed every 8 hours to obtain the porous membrane.

[0080] (S4) Preparation of polybenzimidazole gas separation membrane:

[0081] After removing the porous membrane, the surface moisture was absorbed with absorbent paper, and then it was dried in a 50℃ forced-air oven for 2 hours, followed by drying in a 100℃ vacuum oven for 8 hours to obtain a dry membrane (polybenzimidazole gas separation membrane), labeled S2. The obtained polybenzimidazole porous membrane S2 has a pore size distribution of 0.78-13.6 nm, an average pore size of 6.8 nm, and a porosity of 8.02%.

[0082] Preparation Example 3

[0083] This preparation example illustrates a nanoporous polybenzimidazole gas separation membrane prepared using the method of the present invention.

[0084] (S1) Preparation of casting solution: Same as in preparation example 1;

[0085] (S2) Preparation of primary porous membrane:

[0086] The polybenzimidazole casting solution was uniformly coated onto the surface of a glass plate, and then immersed in deisopropanol at room temperature for 1 hour to cure it into a film. After separating the plate and the film, the nascent porous membrane was obtained.

[0087] (S3) Preparation of porous membranes:

[0088] The nascent porous membrane was transferred to a 0.1 mol / L sodium bicarbonate aqueous solution and soaked at room temperature for 24 hours. Then the membrane was transferred to deionized water and soaked at 80°C for another 24 hours. The deionized water was changed every 8 hours to obtain the porous membrane.

[0089] (S4) Preparation of polybenzimidazole gas separation membrane:

[0090] After removing the porous membrane, the surface moisture was absorbed with absorbent paper and then dried in a 50℃ forced-air oven for 2 hours, followed by drying in a 100℃ vacuum oven for 8 hours to obtain a dry membrane (polybenzimidazole gas separation membrane), labeled S3. The obtained polybenzimidazole porous membrane S3 has a pore size distribution of 0.77-13.7 nm, an average pore size of 5.8 nm, and a porosity of 7.83%.

[0091] Example 1

[0092] Figure 1The methanol reforming hydrogen production process shown is as follows: First, methanol and demineralized water are fed into a storage tank. The storage tank is used to store the methanol-water solution and monitor its concentration, thereby controlling the ratio of water to methanol in process S1. The methanol-water solution S2 in the storage tank is preheated by a heat exchanger to obtain a preheated methanol-water solution S3, which is then heated and vaporized in an evaporator. The vaporized methanol-water vapor S4 enters the reactor for reforming reaction, resulting in a mixed gas S5 after the reforming reaction. This mixed gas mainly consists of hydrogen, carbon dioxide, some unreacted methanol, water, and trace amounts of carbon monoxide and methane. The mixed gas S5 is then... The mixture S2 is preheated by a heat exchanger. After the heat exchange, the mixture S6 is cooled and liquefied to obtain a water-vapor mixture S7. S7 enters a gas-liquid separator, where unreacted methanol-water solution S9 is separated and recycled to a storage tank for reuse. The mixed gas S8 separated by the gas-liquid separator enters an adsorption system (adsorbed gas S11) to remove carbon dioxide from the mixed gas. The mixed gas S10 after carbon dioxide removal enters a membrane separation system. After separation, the permeate S12 is high-purity hydrogen suitable for fuel cells and is used in the fuel cell module. The residual permeate S13 is the tail gas. The heat transfer oil system in the process first heats the reforming reaction system to allow it to react within a specific temperature range. Subsequently, the residual heat can be used to heat the evaporator to vaporize the methanol-water solution and also to heat the membrane separation system.

[0093] The water-to-ethanol molar ratio in the storage tank was 1.5, meaning the methanol-water solution concentration was 54.2%. The reaction temperature in the reactor was 220℃, and the pressure was 0.1 MPa. The adsorption unit was PSA molecular sieve pressure swing adsorption, with 13X molecular sieve as the adsorbent. The adsorption pressure was 4.2 MPa, and the gas hourly space velocity (GHSV) was 30 / h. The separation membrane obtained in Preparation Example 1 was used, with a membrane pressure of 3 MPa and a membrane temperature of 100℃. Two-stage membrane separation was employed. The gas composition before entering the adsorption unit was: hydrogen 71.11 vol%, carbon dioxide 25.16 vol%, carbon monoxide 0.77 vol%, and methane 2.95 vol%. The treatment results are shown in Table 1 below, where the hydrogen concentration was >99.98%, the carbon monoxide concentration was <0.5 ppm, the methane concentration was <5 ppm, and the hydrogen yield was >94%.

[0094] Table 1

[0095]

[0096]

[0097] Example 2

[0098] The water-to-ethanol molar ratio in the storage tank was 1.5, meaning the methanol-water solution concentration was 54.2%. The reaction temperature in the reactor was 300℃, and the pressure was 0.1 MPa. The adsorption unit was PSA molecular sieve pressure swing adsorption, with 13X molecular sieve as the adsorbent. The adsorption pressure was 4.2 MPa, and the gas hourly space velocity (GHSV) was 30 / h. The separation membrane obtained in Preparation Example 2 was used, with a membrane pressure of 3 MPa and a membrane temperature of 100℃. Two-stage membrane separation was employed. The gas composition before entering the adsorption unit was: hydrogen 69.26 vol%, carbon dioxide 24.35 vol%, carbon monoxide 3.14 vol%, and methane 3.24 vol%. The treatment results are shown in Table 2 below, where the hydrogen concentration was >99.97%, the carbon monoxide concentration was <0.5 ppm, the methane concentration was <5 ppm, and the hydrogen yield was >93%.

[0099] Table 2

[0100]

[0101]

[0102] Example 3

[0103] The water-to-ethanol molar ratio in the storage tank was 1.8, meaning the methanol-water solution concentration was 49.7%. The reaction temperature in the reactor was 250℃, and the pressure was 0.1 MPa. The adsorption unit was PSA molecular sieve pressure swing adsorption, with 13X molecular sieve as the adsorbent. The adsorption pressure was 3.2 MPa, and the gas hourly space velocity (GHSV) was 50 / h. The separation membrane was the one obtained in Preparation Example 3, with a permeabilization pressure of 3 MPa and a permeabilization temperature of 100℃. Since the hydrogen purity required for fuel cells could not be achieved after secondary membrane separation, tertiary membrane separation was used. The gas composition before entering the adsorption unit was 67.12 vol% hydrogen, 25.34 vol% carbon dioxide, 3.33 vol% carbon monoxide, and 4.21 vol% methane. The treatment effect is shown in Table 3 below, where the hydrogen concentration is >99.9999%, the carbon monoxide concentration is <0.2 ppm, the methane concentration is <0.2 ppm, and the hydrogen yield is >91%.

[0104] Table 3

[0105]

[0106]

[0107] Example 4

[0108] The methanol reforming hydrogen production process was carried out according to the method of Example 1, except that the water-to-methanol molar ratio in the storage tank was 1.2, that is, the concentration of methanol-water solution was 59.7%.

[0109] Since the hydrogen purity required for fuel cells could not be achieved after secondary membrane separation, tertiary membrane separation was adopted. The gas composition before entering the adsorption unit was 59.15 vol% hydrogen, 30.60 vol% carbon dioxide, 1.13 vol% carbon monoxide, and 9.12 vol% methane. The treatment effect is shown in Table 4 below, where the hydrogen concentration is >99.999%, the carbon monoxide concentration is <0.2 ppm, the methane concentration is <0.2 ppm, and the hydrogen yield is >88%.

[0110] Table 4

[0111]

[0112]

[0113] Example 5

[0114] The methanol reforming process for hydrogen production was carried out according to the method in Example 1, except that a polytetrafluoroethylene (PTFE) tubular membrane was used for separation, the membrane separation temperature was 250°C, and the permeate pressure was 6 MPa. The final product had a hydrogen concentration >99.973%, a yield of 88.54%, a carbon monoxide concentration <0.5 ppm, and a methane concentration <16 ppm.

[0115] Example 6

[0116] The methanol reforming hydrogen production process was carried out according to the method in Example 1, except that the water-to-methanol ratio in the storage tank was 1.0, the reaction temperature was 350°C, and a three-stage separation membrane was used in the membrane separation unit. The treatment results are shown in Table 5 below.

[0117] Table 5

[0118]

[0119] As shown in Table 5, compared to Example 1, an additional separation membrane is required. The carbon monoxide and methane content is much higher in Example 1, and the yield is lower than that in Example 1. The carbon monoxide requirement does not meet the national standard.

[0120] Example 7

[0121] Hydrogen was prepared using the system described in Example 1, except that the water-to-alcohol ratio in the storage tank was 0.8. The final product had a hydrogen concentration of 99.965%, a yield of 90.2%, a carbon monoxide concentration of 20 ppm, and a methane concentration of 80 ppm.

[0122] Example 8

[0123] Hydrogen was prepared according to the system of Example 1, except that a palladium membrane was used for separation. Due to the membrane temperature being only 100°C, the separation effect was poor. Therefore, the final product had a hydrogen concentration of 97.24%, a yield of 89.62%, a carbon monoxide concentration of 0.0029%, and a methane concentration of 1.006%.

[0124] Example 9

[0125] Hydrogen was prepared according to the system of Example 1, except that the gas composition before entering the adsorption unit was 54.92 vol% hydrogen, 32.3 vol% carbon dioxide, 0.18 vol% carbon monoxide, and 12.6 vol% methane. The final product had a hydrogen concentration of 99.941%, a yield of 91.58%, a carbon monoxide concentration of <0.5 ppm, and a methane concentration of 170 ppm.

[0126] Comparative Example 1

[0127] Hydrogen was prepared according to the system in Example 1, except that no membrane separation unit was added, the adsorption pressure was 5.0 MPa, the gas hourly space velocity was 5 / h, and the treatment effect is shown in Table 6 below.

[0128] Table 6

[0129]

[0130]

[0131] As can be seen from the data in Table 6, without the addition of a membrane separation unit, although there is basically no loss of hydrogen after passing through the gas-liquid separation unit and the adsorption unit, the purity is too low and the carbon monoxide concentration is too high, making it unsuitable for use in fuel cells.

[0132] Comparative Example 2

[0133] Hydrogen was prepared according to the system in Example 1, except that no adsorption unit was added. The treatment results are shown in Table 7 below.

[0134] Table 7

[0135]

[0136]

[0137] As can be seen from Table 7, without the adsorption unit, four-stage membrane separation is required to bring the hydrogen purity to a usable range, which is two more stages than in Example 1. Each additional stage of separation requires more space and consumes more energy, and the yield decreases with each stage, resulting in poorer performance.

[0138] Comparative Example 3

[0139] Hydrogen was prepared according to the system in Example 3, except that no adsorption unit was added. The treatment effect is shown in Table 8 below.

[0140] Table 8

[0141]

[0142]

[0143] As can be seen from Table 8, without the adsorption unit, four-stage membrane separation is required to bring the hydrogen purity to a usable range, which is two more stages than in Example 3. Each additional stage of separation requires more space and consumes more energy, and the yield is less than 80%.

[0144] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A method for purifying hydrogen, characterized in that, The method includes: adsorbing a mixture of hydrogen and carbon monoxide and then performing at least one stage of membrane separation; wherein the hydrogen-containing mixture contains hydrogen and carbon monoxide.

2. The method according to claim 1, wherein, In the mixture of hydrogen and carbon monoxide, the hydrogen concentration is >50 vol% and the carbon monoxide concentration is <5 vol%. More preferably, in the mixture of hydrogen and carbon monoxide, the hydrogen concentration is 60-100 vol% and the carbon monoxide concentration is 0-2 vol%.

3. The method according to claim 1 or 2, wherein, The mixture of hydrogen and carbon monoxide also contains carbon dioxide and methane. Preferably, in the mixture of hydrogen and carbon monoxide, the carbon dioxide concentration is <45 vol% and the methane concentration is <10 vol%; more preferably, in the mixture of hydrogen and carbon monoxide, the carbon dioxide concentration is 0-27 vol% and the methane concentration is 0-5 vol%.

4. The method according to claim 1 or 2, wherein, The adsorption method employs at least one of pressure swing adsorption, alkaline adsorption, and ion exchange adsorption. Preferably, the adsorbent is selected from at least one of molecular sieves, activated carbon, and metal-organic framework materials (MOFs).

5. The method according to claim 1, wherein, The adsorption conditions include: a pressure of 0.2-15 MPa, preferably 8-12 MPa; a temperature of -60°C to 100°C, preferably -25°C to 60°C; and a volume hourly space velocity (VHSV) of 10-110 h⁻¹ for the hydrogen-containing mixture. -1 Preferably 30-110h -1 .

6. The method according to claim 1 or 2, wherein, The membrane used for membrane separation is a gas separation membrane made of at least one of the following: polysulfone, polyethersulfone, polyimide, polyamide, polypropylene, polyethylene, synthetic resin, polyvinylidene fluoride, polytetrafluoroethylene, polyether ether ketone, polybenzimidazole, block copolymer, cellulose acetate membrane, polycarbonate membrane, polymethyl methacrylate membrane, silica membrane, zeolite molecular sieve membrane, carbon molecular sieve membrane, and metal-organic framework materials. Preferably, it is at least one of polybenzimidazole gas separation membrane, polyimide gas separation membrane, and polyamide gas separation membrane. Preferably, the membrane separation employs a 2-3 stage membrane separation process.

7. The method according to claim 1 or 2, wherein, The membrane separation conditions include: a membrane separation temperature of 0-300℃, preferably 50-150℃; and a membrane pressure of 0.1-10MPa, preferably 2-5MPa.

8. A method for producing hydrogen from methanol reforming, characterized in that, The method includes: sequentially adsorbing and separating the products of the methanol reforming reaction using at least one primary membrane. The adsorption and membrane separation are performed in accordance with the adsorption and membrane separation described in any one of claims 1-7.

9. The method according to claim 8, wherein, The reaction conditions for the methanol reforming reaction include: a reaction temperature of 100-400℃, preferably 150-300℃; and a reaction pressure of 0-10MPa, preferably 0-1MPa.

10. The method according to claim 8 or 9, wherein, The raw materials for the methanol reforming reaction process include methanol and water; And / or, the molar ratio of water to methanol is 1-3:1, preferably 1.2-2.5:1, more preferably 1.4-1.8:1.

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