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    Process for electrolysis of aqueous alkali metal halide solution
    4.
    发明授权
    Process for electrolysis of aqueous alkali metal halide solution 失效
    电解碱金属卤化物水溶液的方法

    公开(公告)号：US4123336A

    公开(公告)日：1978-10-31

    申请号：US781410

    申请日：1977-03-25

    申请人： Maomi Seko ,  Yasumichi Yamakoshi ,  Hirotsugu Miyauchi ,  Kyoji Kimoto ,  Yoshinori Masuda

    发明人： Maomi Seko ,  Yasumichi Yamakoshi ,  Hirotsugu Miyauchi ,  Kyoji Kimoto ,  Yoshinori Masuda

    IPC分类号： C08J5/22 ,  C25B1/46 ,  C25B13/08

    CPC分类号： C25B1/46

    摘要： An aqueous alkali metal halide solution is electrolyzed in an electrolytic cell using a cation exchange membrane which is a fluorocarbon polymer containing sulfonic acid groups and at least one cation exchange group which is less acidic than the sulfonic acid group with higher proportion of the latter in surface stratum on the cathode side of the membrane than in the entire membrane, while controling proton concentration in the anolyte at not higher than critical proton concentration at which no substantial amount of protons in the anolyte penetrate into the membrane.This invention relates to a process for electrolysis of an aqueous alkali metal halide solution using a cation exchange membrane comprising a fluorocarbon polymer containing sulfonic acid groups and at least one cation exchange group with weaker acidity than the sulfonic acid group.It has been known to the art to utilize for electrolysis of aqueous alkali halide solutions, a cation exchange membrane of a perfluorocarbon polymer containing pendant sulfonic acid groups obtained by saponification of a membrane prepared from a copolymer of tetrafluoroethylene and perfluoro-3,6-dioxa-4-methyl-7-octene sulfonyl fluoride. This known perfluorocarbon type cation exchange membrane containing onyl sulfonic acid groups, however, has the disadvantage that the membrane tends to permit penetration therethrough of hydroxyl ions back migrating from the cathode compartment because of the high hydrophilicity of the sulfonic acid groups. As a result, the current efficiency during electrolysis is low. This is a special problem when the electrolysis is used for the production of aqueous solution of caustic soda at concentrations of more than 20 percent. In this reaction, the current efficiency is so low that the process is economically disadvantageous compared with electrolysis of aqueous solutions of sodium chloride by conventional mercury or diaphragm processes.The disadvantage of such low current efficiency can be alleviated by lowering the exchange capacity of the sulfonic acid group to less than 0.7 milliequivalent per gram of the H form dry resin. Such lowering results in decrease in water content in the membrane, whereby the concentration of fixed ions in the membrane is relatively higher than in a membrane of higher exchange capacity so that the loss of current efficiency during electrolysis is slightly improved. For example, when a caustic soda solution with a concentration of 20% is to be recovered during electrolysis of sodium chloride, the current efficiency can be improved to about 80%. Improvement of current efficiency by decrease of ion exchange capacity of the membrane, however, results in a serious decrease in the electroconductivity of the membrane, so that the method is at an economic disadvantage. Moreover, it is difficult to produce a commercial cation exchange membrane of perfluorosulfonic acid type which can be improved in current efficiency to approximately 90% by increase of membrane resistance.In order to overcome the drawbacks mentioned above, it has been suggested in U.S. Pat. No. 3,784,399, German Pat. OLS No. 2437395, U.S. Pat. No. 3,969,285 and Japanese Patent Applications No. 84111/1975 and No. 84112/1975 (U.S. Patent Application Ser. No. 701,515) to use cation exchange membranes comprising fluorocarbon polymers containing cation exchange groups with weaker acidity than sulfonic acid on one side of the cation exchange membrane of sulfonic acid type for electrolysis of an aqueous alkali metal halide solution. When electrolysis is carried out by use of such a cation exchange membrane, a high current efficiency can be attained by decrease in water content on the side on which the exchange groups with weaker acidity are present. The thickness of the stratum wherein said groups are present can be as thin as 100 A or more, which is extremely thin as compared with the entire thickness of the membrane, whereby electric resistance can be made very low so as to achieve a lower cell voltage.Even in electrolysis by use of such a cation exchange membrane as mentioned above, however, current efficiency is found to be lowered, and there is an increase of voltage when the proton concentration in the anolyte surpasses a certain critical value. In some cases, cleavage or peel-off may occur on a part of the membrane. Said critical value is dependent on various factors such as the temperature, current density, current efficiency, the anolyte concentration, the thickness of the stratum on the cathode side on which the exchange groups with weaker acidity are present, the thickness of desalted layer, etc. It has now been found that these difficulties usually occur at high temperature, current density and current efficiency, which are just the conditions most favorable for commercial practice of the process from the standpoint of decreased fixed charges and proportional costs.The object of the present invention is to provide a process for electrolysis of an aqueous alkali metal halide solution free from the above problems.The above object is found to be accomplished by use of a specifically selected cation exchange membrane and by carrying out electrolysis while controlling proton concentration in the anolyte at a value which is not higher than a critical value at which no substantial number of protons will penetrate into the membrane. As a result, electrolysis at a high current efficiency with lower voltage can be effected stably for a long period of time.The present invention provides a process for electrolysis of an aqueous alkali metal halide solution in an electrolytic cell in which anode and cathode are separated by a cation exchange membrane to divide said cell into anode and cathode chambers, said cation exchange membrane being made of a fluorocarbon polymer containing cation exchange groups consisting of sulfonic acid groups and at least one weaker cation exchange group with weaker acidity than the sulfonic acid group, the cation exchange groups in the surface stratum on the cathode side of the membrane being richer in said weaker cation exchange groups than in the entire membrane, proton concentration in anolyte being maintained at not higher than the critical proton concentration.The term "critical proton concentration" herein used in the specification and claims refers to the critical value of the concentration of protons in the anolyte at which hydroxyl ions migrating through the cation exchange membrane are neutralized on the interfacial liquid film on the anode side of the membrane so that no substantial amount of protons in the anolyte may penetrate into the membrane, and is generally determined from the equations as set forth below.The cation exchange membrane used in the present invention comprises a copolymer having the repeating units (I) and (II) as shown below:--CF.sub.2 --CXX'-- (I) ##STR1## wherein X represents F, Cl, H or --CF.sub.3 ; X', F, Cl, H or --CF.sub.3 ; R pendant group containing cation exchange groups. Said copolymer may further contain other units derived from copolymerizable monomers. The membrane contains cation exchange groups as mentioned above in the amount of 900 to 2,000, preferably 1,000 to 1,600, in terms of equivalent weight (grams of dry resin containing one equivalent of ion exchange groups). The ratio of the weaker cation exchange groups based on the total cation exchange groups through the entire membrane is up to 40 mol %, the mol percent being based upon the weight of the whole membrane, preferably up to 20 mol %. The thickness of the membrane to be used in commercial application is from 50 to 500 microns, preferably from 100 to 250 microns.According to the presently preferred method, the membrane of the invention is prepared by subjecting the membrane containing sulfonic acid groups as cation exchange groups to chemical treatment, especially on the surface thereof, to convert a part of sulfonic acid groups into the weaker cation exchange groups. Details of the methods for production of the membrane used in the present invention, i.e., the membrane containing sulfonic groups as cation exchange groups as mentioned above, are described in, for example, U.S. Pat. Nos. 3,282,875 and 3,718,627 and GB 1,184,321. The subject matter in these patents are incorporated herein by reference.The cation exchange membrane used in the present invention may have a homogeneous equivalent weight throughout the membrane or alternatively be a composite film consisting of two or more layers with different equivalent weights. In the latter case, the composite consists preferably of two layers with a difference in equivalent weight of 150 or more. The layer with larger equivalent weight is present on the cathode side of the membrane with a thickness of up to 1/2 of the entire thickness of the composite.The cation exchange groups with lower acidity than sulfonic acid group may include carboxylic acid groups, phosphoric acid groups, phosphite groups, sulfonamide groups, N-mono-substituted sulfonamide groups, alcoholic or phenolic hydroxyl groups, thiol groups and sulfinic acid groups. Among them, carboxylic acid groups and phosphoric acid groups are preferable from the standpoint of their characteristics and stabilities. In particular, carboxylic acid groups are most preferred.One example of the cation exchange membranes preferably used in the present invention is the cation exchange membrane comprising a fluorocarbon polymer containing on one side pendant groups R having terminal groups --OCF.sub.2 COOM (wherein M is hydrogen, metal or ammonium ion) with the remainder of terminal groups being the groups --OCF.sub.2 CF.sub.2 SO.sub.3 M (M is the same as defined above). This membrane can be produced by treatment with a reducing agent of a membrane containing sulfonyl derivatives such as sulfonyl halide groups, as disclosed by Japanese Patent Applications No. 84111/1975 and 84112/1975, the subject matter of which is herein incorporated be reference.The proportion of the exchange groups with weaker acidity than sulfonic acid group in surface stratum on the cathode side of the membrane based on the total exchange groups in said stratum may ordinarily fall within the range from 10 to 100 mol %, preferably from 20 to 100 mol %, most preferably from 40 to 100 mol %. The thickness of the stratum, in which the exchange groups with weaker acidity than sulfonic acid group are present, will normally be from 100 A to 20 microns.The membranes used in the present invention are desirably reinforced with backings made of nets of polytetrafluoroethylene fibers or porous films of polytetrafluoroethylene, etc. to increase the methanical strength thereof.The weaker cation exchange groups may be present throughout the entire membrane together with sulfonic acid groups, provided that their proportion increases relative to sulfonic acid groups in the direction towards the surface on the cathode side of the membrane. Further, the weaker exchange groups may also be present on the anode side of the membrane in lower proportion than in the surface stratum on the cathode side of the membrane. Practically, however, to practice commercial electrolysis while using less electric power, it is sufficient and advantageous to have the weaker cation exchange groups present substantially in a surface stratum with a thickness of 100 A to 20 microns only on the cathode side of the membrane, with the cation exchange groups in residual portion, especially on the anode side of the membrane, being mostly sulfonic acid groups.According to the present invention, it is also required to maintain proton concentration in the anolyte at not higher than the critical proton concentration as mentioned above, thereby to maintain a high current efficiency and prevent increase in voltage, and also to prevent the stratum with higher proportion of the weaker cation exchange groups on the cathode side of the membrane from being peeled away from the membrane. By this method, the membrane life can be prolonged to a great extent to make possible stable running periods of long duration.

    摘要翻译： 碱性金属卤化物水溶液在电解池中电解，使用阳离子交换膜，该阳离子交换膜是含有磺酸基的氟碳聚合物和至少一个阳离子交换基团，该阳离子交换基团比磺酸基团酸性低，后者表面的比例较高 同时控制阳极电解液中的质子浓度不高于阳极电解液中大量质子渗透到膜中的临界质子浓度。

    Multi-cell electrolyzer
    5.
    发明授权
    Multi-cell electrolyzer 失效
    多池电解槽

    公开(公告)号：US4643818A

    公开(公告)日：1987-02-17

    申请号：US760897

    申请日：1985-07-31

    申请人： Maomi Seko ,  Reiji Takemura ,  Hideharu Miyamori

    发明人： Maomi Seko ,  Reiji Takemura ,  Hideharu Miyamori

    IPC分类号： C25B9/00 ,  C25B9/04 ,  C25B9/20 ,  C25B15/08

    CPC分类号： C25B9/206 ,  C25B9/04 ,  C25B9/045

    摘要： A multi-cell electrolyzer comprising a plurality of unit cells, each of which is composed of an anode chamber containing an anode and a cathode chamber containing a cathode and a cation exchange membrane for partitioning said unit cell into said anode chamber and said cathode chamber, and each of which is adapted to have an internal pressure maintained at a level higher than the atmospheric pressure in operation of the electrolyzer, said plurality of unit cells being arranged in series and adapted to be energized through a plurality of current lead plates, and rigid multi-contact electrically conductive means provided between the adjacent unit cells and/or between each current lead plate and the unit cell adjacent thereto, thereby establishing electrical connection between the adjacent unit cells and/or between each current lead plate and the unit cell adjacent thereto. With such a structure, not only is the electrical contact resistance between the adjacent unit cells and between each current lead plate and the unit cell adjacent thereto extremely reduced but also the current density in the unit cells is rendered uniform. Further, the present multi-cell electrolyzer can be easily constructed either in a bipolar form or in a monopolar form using unit cells common to both of the bipolar and monopolar forms.

    摘要翻译： 一种多单元电解槽，包括多个单元电池，每个单元电池由包含阳极的阳极室和含有阴极的阳极室和用于将所述单电池分隔成所述阳极室和所述阴极室的阳离子交换膜组成， 并且其中的每一个适于在电解槽的操作中将内部压力维持在高于大气压力的水平面上，所述多个单元电池串联布置并适于通过多个电流引线板通电，并且刚性 设置在相邻单元电池之间和/或每个电流引线板和与其相邻的单元电池之间的多触点导电装置，从而在相邻单元电池之间和/或每个电流引线板与与其相邻的单元电池之间建立电连接 。 通过这样的结构，不仅相邻单位电池之间和每个电流引线板与与其相邻的单位电池之间的电接触电阻极大地降低，而且单元电池中的电流密度也是均匀的。 此外，本发明的多单元电解器可以容易地以双极形式或单极形式使用双极和单极形式共同的单元电池。

    Method of simultaneous concentration and dilution of isotopes
    9.
    发明授权
    Method of simultaneous concentration and dilution of isotopes 失效
    同时浓缩和稀释同位素的方法

    公开(公告)号：US3953568A

    公开(公告)日：1976-04-27

    申请号：US272250

    申请日：1972-07-17

    申请人： Maomi Seko ,  Hidetake Kakihana

    发明人： Maomi Seko ,  Hidetake Kakihana

    IPC分类号： B01D59/30 ,  C22B60/02 ,  C01G43/00 ,  C01G53/00 ,  C01G57/00

    CPC分类号： B01D59/30 ,  C22B60/0265 ,  Y10S423/07 ,  Y10S423/14

    摘要： A method of simultaneously obtaining separate enriched fractions of heavier and lighter isotopes from mixtures thereof with the use of an ion exchange resin column by passing a ligand body containing this isotope mixture through the column. The isotopes, as they are passed through the column, are present in the forms of ligand-containing coordination compounds having different valence states and are followed by an eluant and form a band which travels through the column, the front and rear portions of which are respectively enriched in one of the isotopes and depleted in the other.

    摘要翻译： 一种通过使含有该同位素混合物的配体通过该柱而使用离子交换树脂柱同时从混合物中获得较重和较轻同位素的分离的富集部分的方法。 当它们通过色谱柱时，同位素以具有不同价态的配体配位化合物的形式存在，并且随后是洗脱剂并形成行进通过柱的带，其前部和后部是 分别富集了一种同位素，另一种是耗尽的。