KR100748999B1 - Preparation method of membrane using oxidized metal and carbon powder - Google Patents

Abstract

A method of preparing a metal membrane by a series of processes of oxidizing polymer in a membrane precursor prepared using metal oxide powder and carbon powder and reducing and sintering metal oxide in an atmosphere of carbon dioxide gas is provided to increase stability and economic efficiency as compared with a conventional method using a mixed gas of nitrogen and hydrogen in the preparation of the metal membrane. A preparation method of a metal membrane comprises: a first step of dispersing and dissolving 40 to 75 wt.% of a metal oxide with a particle size of 0.05 to 15 mum, 5 to 20 wt.% of carbon powder with a particle size of 0.5 to 20 mum, and 5 to 15 wt.% of polymer into 15 to 25 wt.% of a polar solvent, and spinning or casting the solution to prepare a membrane precursor; a second step of oxidizing polymer of the membrane precursor in a temperature range from 500 to 700 deg.C in a reduction furnace under an air atmosphere without injecting carbon dioxide gas; a third step of reducing metal oxide of the polymer oxidized membrane precursor by the reduction reaction between metal oxide and carbon, and carbon dioxide gas in a temperature range from 700 to 900 deg.C under a carbon dioxide atmosphere; and a fourth step of sintering the reduced membrane precursor in a temperature range from 1000 to 1400 deg.C under a carbon dioxide gas atmosphere to prepare a membrane.

Description

Separation method using metal oxide and carbon powder {Preparation method of membrane using oxidized metal and carbon powder}

1 is a photograph taken with a scanning electron microscope (SEM) of the cross section of the metal hollow fiber membrane prepared according to Example 1 of the present invention.

2 is a photograph taken with a scanning electron microscope of the surface of the metal hollow fiber membrane prepared according to Example 1 of the present invention, it can be seen a myriad of fine pores of the surface.

The present invention relates to a method of manufacturing a separator using a metal oxide powder, and specifically, metal oxide particle powder and carbon powder having a specific particle diameter are dissolved together with a polymer in a polar solvent at a predetermined ratio, followed by spinning or casting. To prepare a separator precursor, add the prepared membrane precursor to a reduction furnace to oxidize the polymer in the precursor, and then reduce and sinter the metal oxide by reaction between the metal oxide and carbon and carbon dioxide under a carbon dioxide atmosphere. The present invention relates to a method for producing a metal separator, which is economical and maintains high porosity and excellent physical properties compared to a metal filter manufactured by using a mixed gas of nitrogen and hydrogen.

Membranes were developed around the 1920s with the extensive use of dialysis to recover alkali from the pulp waste of the Rayon industry. Afterwards, electrodialysis was developed around 1940. In the 1950's, reverse osmosis membranes were used for seawater desalination, and facility development was in progress for practical use, and it is now appearing as an essential medium for all industrial fields.

Currently, most of the separators used in industrial fields are polymer separators, but have a low physical strength, low chemical stability, and low temperature resistance. On the other hand, ceramic separators have high strength and temperature resistance, but their use is limited because of the risk of breaking them due to brittleness. On the other hand, the metal separator is excellent in durability and temperature resistance, but the cost is very high in the manufacturing process, and when manufacturing a hollow fiber membrane has a large diameter problem, it is used only in a special case that can not be used as a polymer membrane.

In the conventional technology related to the metal separator, Korean Patent No. 10-562043 discloses a method for preparing a metal separator, in which a three-cycle transition metal, an alloy particle powder thereof, and a synthetic polymer are dissolved at a predetermined ratio, followed by spinning or casting to prepare a separator precursor. After immersing the separator precursor in water, the synthetic polymer is oxidized in a mixed gas atmosphere of nitrogen and hydrogen, and then sintered at a specific temperature to provide a method of preparing a metal separator. The above technique provides a method of manufacturing a metal hollow fiber membrane having a reduced diameter, but there is a risk of handling the hydrogen gas because the mixed gas of nitrogen and hydrogen is used. There is a disadvantage in that the manufacturing cost is high because a large amount of gas is required.

Accordingly, the present inventors added carbon powder together with metal oxides and polymers and injected low-cost carbon dioxide gas into a reduction furnace in the process of trying to develop a more economical method while having excellent physical properties in manufacturing a metal separator. The experiment was carried out, and as a result, the present invention was developed by developing a metal separation membrane manufacturing method which can reduce the cost compared to the conventional metal membrane manufacturing method by reducing and sintering under a low-cost carbon dioxide instead of expensive nitrogen and hydrogen mixed gas. Completed.

 In the present invention, the membrane precursor prepared by using the metal oxide particle powder and carbon powder is introduced into a reduction furnace to oxidize the polymer in the precursor, and then the metal oxide is reduced by the reaction between the metal oxide and carbon and carbon dioxide under a carbon dioxide gas atmosphere. By providing a method for manufacturing a metal separator by a series of sintering process, to improve the safety and economics compared to the conventional method using a mixed gas of nitrogen and hydrogen in the manufacture of the metal separator.

The present invention dissolves a metal oxide particle powder and a carbon powder having a specific particle diameter with a polymer in a polar solvent at a ratio, and then spinning or casting to prepare a membrane precursor, and the prepared membrane precursor is reduced to And then oxidizing the polymer in the precursor, and then sequentially reducing and sintering the metal oxide under carbon dioxide, and having a pore size of 0.05 to 10 μm, which has a uniform pore distribution and a porosity of 30. It relates to the production of a metal separator of 50%.

The method for producing the separator of the present invention is 40 to 75% by weight of the metal oxide particles having a particle size of 0.05 to 15 ㎛, 5 to 20% by weight of carbon powder having a particle size of 0.5 to 20 ㎛, cellulose acetate, polyolefin , 5 to 15% by weight of a polymer selected from among polymers such as polyimide, polysulfone, polyamide, polysaccharide and the like is dimethylamide, N-methyl-2-pyrrolidone, dimethylformamide, dimethylacetamide Dispersing and dissolving with 15 to 25% by weight of a solvent selected from solvents such as dimethyl sulfoxide, and then wet spinning or casting through a nozzle of a predetermined size to prepare a membrane precursor;

Oxidizing the polymer at a temperature range of 500 to 700 ° C. under an air atmosphere without injecting carbon dioxide gas into the separator precursor;

A step of reducing the metal oxide by the reduction reaction between the metal oxide and carbon and carbon dioxide gas in the membrane precursor in which the polymer is oxidized in a carbon dioxide atmosphere at a temperature of 700 to 900 ° C .; And

Sintering the reduced membrane precursor in a carbon dioxide gas atmosphere at a temperature range of 1000 ~ 1400 ℃ characterized in that it comprises a four step of producing a metal film having a pore size in the range of 0.05 to 10 ㎛ and porosity of 30 to 50% .

Looking at the method of manufacturing a metal separator according to the present invention in more detail as follows.

First, in the first step of dispersing and dissolving a metal oxide powder and a carbon powder in a solvent together with a polymer, and then spinning or casting to prepare a separator precursor, the metal oxide is specifically a metal oxide selected from nickel oxide, copper oxide and iron oxide. Powders may be used, and in the present invention, it is more preferable to use copper oxide and nickel oxide, which have a relatively low sintering temperature, higher resistance to oxidation, and lower cost than other metal oxides. In addition, if the particle size of the metal oxide powder is less than 0.05 ㎛ ball milling for a long time in order to obtain the desired size, the unit price is high and economic efficiency is low, if the size of the metal oxide powder exceeds 15 ㎛ particles are too large, the viscosity is high and spinning In order to increase the nozzle internal diameter and not easy to radiate itself, the size of the pore is 10 μm or more, which makes it unsuitable for industrial applications such as air purification and water treatment. It is preferable to maintain the range of -15 µm. In addition, in the production of the separator, when the metal oxide powder is less than 40% by weight, the viscosity is weak, which makes it difficult to spin the nozzle, and the strength of the final metal film is considerably dropped. The problem of difficulty in uniform dispersion and dissolution occurs, so it is desirable to maintain the range of 40 to 75% by weight.

Carbon powder is mixed to reduce metal oxides. When the carbon powder is less than 5% by weight, the reduction of the metal oxide may not be performed properly. When the carbon powder is more than 20% by weight, it is difficult to sinter the metal oxide. Therefore, it is preferable to maintain the range of 5 to 20% by weight.

The polymer is selected from cellulose acetate, polyolefin, polyimide, polysulfone, polyamide, and polysaccharide. If the amount of the synthetic polymer is less than 5% by weight, it is difficult to form a membrane precursor due to its difficulty in molding and strength, and when it exceeds 15% by weight, the spinning solution becomes viscous, so that spinning is difficult and pore formation is not easy. Therefore, it is preferable to maintain the range of 5 to 15% by weight.

The solvent for dissolving these may be a solvent having a property capable of dissolving the polymer, specifically, selected from dimethylamide, N-methyl-2-pyrrolidone, dimethylformamide, dimethylacetamide and dimethyl sulfoxide. . When the amount of the solvent used is less than 15% by weight, it is difficult to uniformly dissolve the metal oxide powder, the carbon powder, and the polymer, and thus, it is difficult to manufacture the separation membrane. When the amount of the solvent exceeds 25% by weight, the viscosity of the spinning solution is very weak so that the spinning of the nozzle is difficult. Since a problem of remarkably falling strength is caused, it is preferable to maintain the range of 15 to 25% by weight.

The coagulation bath for coagulating the polymer solution after spinning or casting may use alcohol, water and a specific solvent, but it is preferable to consider water in terms of economics. In this case, if the temperature of the coagulation bath is less than 0 ℃, the membrane after spinning Precursor solidifies rapidly and may cause slight cracking in the precursor. If the precursor exceeds 70 ° C, the strength of the membrane precursor becomes weak, brittleness occurs during the oxidation process of the polymer, and the solvent evaporates and is harmful to the body. It is preferable to maintain a temperature in the range of 0-70 degreeC.

In the second step of oxidizing the polymer, the prepared membrane precursor is placed in a reduction furnace to oxidize the polymer in the membrane precursor without supplying carbon dioxide at a temperature of 500 to 700 ° C. In this case, when the temperature is less than 500 ℃, incomplete oxidation occurs and time consumption is large, and when the temperature exceeds 700 ℃, the problem that the molding of the precursor precursor is not constant and distortion occurs, it is necessary to maintain the temperature range desirable.

In the third step of reducing the metal oxide, a reduction temperature of 700 to 900 ° C. is maintained, and carbon dioxide gas is injected into the reduction furnace from this time. The amount of gas injected depends on the size and volume of the electric furnace. As a result of many experiments, 1.5 L / min was most suitable for the 400 (W) × 400 (H) × 700 (L) ㎣ size furnace. When the reduction temperature is less than 700 ℃, the reduction between the metal oxide and carbon and carbon dioxide gas is hardly made because the physical properties are weak and easily broken. If the temperature exceeds 900 ℃, the reduction is already complete and gas injection for reduction is It is desirable to maintain the temperature range as it becomes meaningless.

In the fourth step of sintering the metal film, the reduced separator precursor is sintered at a temperature of 1000 to 1400 ° C. under carbon dioxide gas. If the sintering temperature is less than 1000 ℃ sintering hardly occurs, the physical properties are weak to take advantage of the advantages of the metal film, if it exceeds 1400 ℃ sintering is excessively proceeded so that the pore formation is not good, but the strength is good as a separation membrane Since the value is low, it is more preferable to maintain the temperature range. The metal film prepared as described above has a pore size of 0.05 to 10 μm, a uniform pore distribution, and a porosity of 30 to 50% as compared to the conventional metal separator. The metal separator may be manufactured in the form of a hollow fiber membrane or a flat membrane.

The following examples illustrate the invention in more detail. The following examples are presented to help the understanding of the present invention, but the present invention is not limited thereto.

Example 1

After preparing a spinning solution consisting of 60% by weight of nickel oxide (3 μm), 10% by weight of carbon powder (10 μm), 22% by weight of dimethyl formamide (DMF), and 8% by weight of polyimide, the outer diameter was 2.5 mm, the inner diameter was It is injected into this 1.5 mm single nozzle spinning nozzle (meaning a general nozzle having one hollow fiber hole), water is injected into the inside and spun into hollow fiber, and then solidified in distilled water. Thereafter, the precursor was immersed in water for one day to remove through exchange of solvent and water, and then the hollow fiber membrane precursor was placed in a reduction furnace to raise the polymer to 700 ° C. at a rate of 6 ° C./min, and maintained for 1 hour for oxidation. Nickel oxide was reduced to nickel by a reduction reaction between metal oxides and carbon and carbon dioxide while raising the temperature at a gas flow rate of 1.5 l / min at a rate of 6 ℃ / min in a carbon dioxide gas atmosphere at a rate of 6 ℃ / min. The metal particles were sintered by increasing the temperature to 1250 ° C. under the same conditions as the above. At this time, the prepared hollow fiber membrane was confirmed that the pore size is about 0.1 ~ 1 ㎛ and porosity is about 35%.

Comparative Example 1-1

The same process as in Example 1 was carried out, but the carbon powder was removed and pure nickel oxide was used as 70 wt% to prepare a separation membrane. As a result, reduction was not performed properly, and thus no membrane was produced.

Comparative Example 1-2

In the same manner as in Example 1, but using a solvent instead of dimethyl formamide (DMF) dimethyl sulfoxide (DMSO) to prepare a separator showed the same results as in Example 1.

Comparative Example 1-3

Example 1 was carried out in the same manner as in Example 1, but the separation membrane was prepared using polysulfone instead of polyimide.

Example 2

After preparing a spinning solution consisting of 62% by weight of nickel oxide (1 μm), 10% by weight of carbon powder (10 μm), 21% by weight of dimethyl formamide (DMF), and 7% by weight of polysulfone, an outer diameter of 2 mm and an inner diameter were obtained. It is injected into this 1-mm three-spinning nozzle (nozzle having three inner holes), water is injected into the inside and spun into hollow fiber, and then solidified in distilled water. After immersing the precursor in water for one day to remove through the exchange of solvent and water, and then put the hollow fiber membrane precursor in a reduction furnace to oxidize the polymer by raising the temperature to 700 ℃ at a rate of 5 ℃ / min 1 hour, Nickel oxide was reduced to nickel by a reduction reaction between metal oxides and carbon and carbon dioxide while raising the temperature at a rate of 5 ° C./min up to 900 ° C. under a carbon dioxide gas atmosphere at a rate of 1.5 l / min of carbon dioxide gas. The metal particles were sintered by heating up to 1300 ° C. under the same conditions as reduction. At this time, the prepared hollow fiber membrane was found to have a pore size of about 0.05 to 0.7 μm and a porosity of about 30%.

Comparative Example 2-1

In the same manner as in Example 2, the separation membrane was prepared using dimethyl sulfoxide (DMSO) instead of dimethyl formamide (DMF) solvent was almost the same as in Example 2. In addition, it was carried out in the same manner as in Example 2, but the separation membrane was prepared using polysulfone instead of polyimide polymer showed almost the same results as in Example 2.

Comparative Example 2-2

In the same manner as in Example 2, but after the reduction and sintering experiment without injecting carbon dioxide from 700 ℃ as a result of a film having no strength at all was not possible to manufacture a metal film.

Example 3

61 wt% of copper oxide (10 μm), 10 wt% of carbon powder (10 μm), 21 wt% of dimethyl sulfoxide (DMSO), and 8 wt% of polysulfone were prepared. It is injected into this 1-mm three-spinning nozzle (nozzle having three inner holes), water is injected into the inside and spun into hollow fiber, and then solidified in distilled water. Thereafter, the precursor was immersed in water for one day, and then removed by exchange of a solvent and water, and the hollow fiber membrane precursor was placed in a reduction furnace to raise the polymer to 700 ° C. at a rate of 5 ° C./min, and maintained for 1 hour for oxidation. The nickel oxide is reduced to nickel by a reduction reaction between metal oxides and carbon and carbon dioxide while raising the temperature of carbon dioxide gas to 1.5 ℓ / min and raising the temperature at a rate of 5 ℃ / min up to 900 ℃ under a carbon dioxide gas atmosphere. The metal particles were sintered by raising the temperature to 1200 ° C. under the same conditions as in the reduction. At this time, the prepared hollow fiber membrane was found to have a pore size of about 0.05 to 0.5 μm and a porosity of about 35%.

As described above, according to the method of manufacturing the metal separator of the present invention, the pore size is small and the porosity is high, and the strength is excellent, so that the metal separator can be manufactured in various fields such as air purification and water treatment. Compared to the method of manufacturing a metal separator using a mixed gas of hydrogen and hydrogen, there is an advantage of being safe and cost-saving.

Claims (6)

40 to 75% by weight of a metal oxide having a particle size of 0.05 to 15 μm, 5 to 20% by weight of a carbon powder having a particle size of 0.5 to 20 μm, and 5 to 15% by weight of a polymer to 15 to 25% by weight of a polar solvent. Dispersing, dissolving and spinning or casting to prepare a membrane precursor; Oxidizing the polymer at a temperature range of 500 to 700 ° C. under an air atmosphere without injecting carbon dioxide gas into the separator precursor; 3 steps of reducing the metal oxide by the reduction reaction between the metal oxide and carbon and carbon dioxide gas in the membrane precursor oxidized the polymer at a temperature range of 700 ~ 900 ℃ under a carbon dioxide atmosphere; And And sintering the reduced separator precursor at a temperature ranging from 1000 to 1400 ° C. under a carbon dioxide gas atmosphere to produce a separator. The method of claim 1, wherein the metal oxide is any one selected from copper oxide, nickel oxide, and iron oxide. The method of claim 1, wherein the polymer is any one selected from cellulose acetate, polyolefin, polyimide, polysulfone, polyamide, and polysaccharide. The method of claim 1, wherein the polar solvent is any one selected from N-methyl-2-pyrrolidone, dimethylformamide, dimethylacetamide, and dimethyl sulfoxide. The method of claim 1, wherein the metal separator has a pore size of 0.05 to 10 µm and a porosity of 30 to 50%. The method of claim 1, wherein the metal separation membrane is made of any one of a hollow fiber membrane, a flat membrane and a capillary membrane.

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