Membrane Asahi Chemical

MAJOR APPLICATIONS Nafion is the DuPont trademark for its family of perfluorinated ionomers, that is, resins and membranes. Asahi Chemical Industry Company produces Aciplex and Asahi Glass Company, Ltd., Japan, produces Flemion both are competitive products to Nafion in form and function. These perfluorinated ionomers are used in a variety of applications, the largest of which are as an ion exchange resin and in membrane separators in the commercial electrolysis of brine to produce caustic and chlorine. Nafion membranes are also being used in the development of fuel cells and as heterogeneous super acid catalysts in supported, cubed, or powdered form. 

Asahi Chemical Membrane Chlor—Alkali Process, Asahi Chemical Industry Co., Ltd., Tokyo, Japan, 1987. 

A.sahi Chemical EHD Processes. In the late 1960s, Asahi Chemical Industries in Japan developed an alternative electrolyte system for the electroreductive coupling of acrylonitrile. The catholyte in the Asahi divided cell process consisted of an emulsion of acrylonitrile and electrolysis products in a 10% aqueous solution of tetraethyl ammonium sulfate. The concentration of acrylonitrile in the aqueous phase for the original Monsanto process was 15—20 wt %, but the Asahi process uses only about 2 wt %. Asahi claims simpler separation and purification of the adiponitrile from the catholyte. A cation-exchange membrane is employed with dilute sulfuric acid in the anode compartment. The cathode is lead containing 6% antimony, and the anode is the same alloy but also contains 0.7% silver (45). The current efficiency is of 88—89%, with an adiponitrile selectivity of 91%. This process, started by Asahi in 1971, at Nobeoka City, Japan, is also operated by the RhcJ)ne Poulenc subsidiary, Rhodia, in Bra2il under Hcense from Asahi. 

Hoechst Celanese Corp. Tonen Corp. Asahi Chemical Industries Mitsubishi Ube Industries Ltd. Pall RAI Celgard membranes made of polypropylene, polyethylene, and combinations Setela membranes made of polyethylene HiPore membranes made of polyethylene Exepol membranes made of polyethylene Polypropylene membranes Polyethylene membranes... 

The PEM (proton exchange membrane) material is a perfluorosulfonic acid polymer film. Several manufacturers make PEMs in one form or another. We used one made by du Pont called Nation 117. Nation 117 is a transparent polymer film about 175 microns (0.007 inches) thick. Dow Chemical Co., Asahi Chemical Co., and Chloride Engineers Ltd. make something similar. A patent describing how one PEM manufacturer s film is processed is listed in the references section at the end of this article. 

Mr Y N Yashuhide Noaki Membrane R D Department, Ion Exchange Membrane Division, Asahi Chemical Industry Co Ltd, 7-4319 Asahimachi Nobeoka City, Miyazaki, Japan. E-mail a7402023 ut.asahi-kasei.co.jp... 

Asahi Chemical has investigated the effects of this low-concentration region on the membrane performance using the three-compartment cell shown in Fig. 17.6, which... 

The ML32NCH electrolyser equipped with the Aciplex F-4401 membrane has been in commercial operation at 6 kA m-2 for approximately one year at Asahi Chemical s chlor-alkali plant. As shown in Figs 17.16 and 17.17, the electrolyser has achieved a cell voltage of 3.17 V and a current efficiency of 96%, while operating at 6kA m-2. This operation is continuing the present plan is to investigate the performance of the ML32NCH at a current density of 8 kA m-2. 

Other perfluorinated ionomer membranes, chemically very similar to Nafion, are also available commercially. Aciplex, manufactured by the Asahi Chemical Company, is very similar to Nafion, except that it has perfluoropropanesulfonic acid side chains. Flemion (Asahi Glass Company), in contrast, possesses perfluorobutanoic acid functions. 

In the United States, electrodialysis was developed primarily for desalination of water, with Ionics being the industry leader. In Japan, Asahi Glass, Asahi Chemical (a different company), and Tokuyama Soda developed the process to concentrate seawater [8], This application of electrodialysis is confined to Japan, which has no domestic salt sources. Electrodialysis membranes concentrate the salt in seawater to about 18-20% solids, after which the brine is further concentrated by evaporation and the salt recovered by crystallization. 

Perfluorinated membranes are still regarded as the best in the class for PEM fuel cell applications. - These materials are commercially available in various forms from companies such as DuPont, Asahi Glass, Asahi Chemical, 3M, Gore, and Sol-vay. Perfluorosulfonic acid (PFSA) polymers all consist of a perfluorocarbon backbone that has side chains terminated with sulfonated groups. 

Ltd.) and the perfluorinated membranes produced by the Asahi Chemical Industry Company (18). Recently, carboxylate perfluorinated materials have been available from DuPont Company. 

The Asahi Chemical Company of Japan has developed a perfluorocarboxylic acid membrane (54) (55) (56). It is reported to be formed from Nafion films wherein the SO3H groups on the cathode surface are split off and the adjacent CF2 groups thereafter oxidized to carboxylic acid groups. 

Figure 16. Power consumption of the Asahi Chemical Company membrane cell electrolyzer.

Commercial application of membrane cell technology began in 1975 with the installation of the Nobeoka No 1 (Japan) using Asahi Chemical Co. electrolyzers, Reed Paper (Canada) using Hooker MX electrolyzers and American Can of Canada (Canada) using Ionics Chloromate electrolyzers. By the end of 1982 world capa-... 

The Nafion membranes utilized in the early 1970 s produced caustic soda concentrations of 10-15wt% at electrolytic power consumptions of approximately 3450 KWH/MT NaOH. Advancements in the technology of membranes by duPont, Asahi Glass Co., and Asahi Chemical Co., Tokuyama Soda Co., have achieved membranes that today can produce caustic soda concentrations of 28-40wt% with caustic current efficiency well over 90% for long term operations. 

Seko, M., "The Asahi Chemical Membrane Chlor-Alkali... 

Ogawa, Shinsaku, "Asahi Chemical Membrane Chlor Alkali Process,"... 

Perfluorocarboxylic Acid Membrane and Membrane Chlor-Alkali Process Developed by Asahi Chemical Industry... 

After intensive research and development work, Asahi Chemical filed the basic patents of fluorinated carboxylic acid membrane and carboxylic and sulfonic acid membrane and the related electrolysis processes in 1974 (1 - 8). 

In April 1975, Asahi Chemical started operation of a membrane chlor-alkali plant with a capacity of 40,000 MT/Y of caustic soda using Nafion perfluorosulfonic acid membrane. In 1976, this membrane was replaced by perfluorocarboxylic acid membrane developed by Asahi Chemical. The total caustic production capacity of plants based on Asahi Chemical s membrane chlor-alkali technology using perfluorocarboxylic acid membrane will reach 520,000 MT/Y in 1982, at seven locations in various countries. 

With a multilayer membrane containing both carboxylic and sulfonic acid groups, however, it is possible to neutralize proton from the anolyte with hydroxyl anion at the surface of or in the membrane before the proton reaches the carboxylic acid layer facing the catholyte, and thus achieve high chlorine purity and longer anode life, as indicated in Table I. This is one of the essential features of the Asahi Chemical process patented in various countries (39). Another advantage of the... 

Chemical Treatment. Sulfonic acid groups on one surface of the membrane can be replaced by carboxylic acid groups through one of the following chemical reactions, most of which were first reported in Asahi Chemical patents and patent applications. 

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