JPS6156315B2 - - Google Patents
Info
- Publication number
- JPS6156315B2 JPS6156315B2 JP60003113A JP311385A JPS6156315B2 JP S6156315 B2 JPS6156315 B2 JP S6156315B2 JP 60003113 A JP60003113 A JP 60003113A JP 311385 A JP311385 A JP 311385A JP S6156315 B2 JPS6156315 B2 JP S6156315B2
- Authority
- JP
- Japan
- Prior art keywords
- alkali metal
- gas
- cation exchange
- halogen gas
- exchange membrane
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
- 239000012528 membrane Substances 0.000 claims description 52
- HEMHJVSKTPXQMS-UHFFFAOYSA-M Sodium hydroxide Chemical group [OH-].[Na+] HEMHJVSKTPXQMS-UHFFFAOYSA-M 0.000 claims description 36
- 229910052736 halogen Inorganic materials 0.000 claims description 32
- 150000002367 halogens Chemical class 0.000 claims description 32
- 238000005341 cation exchange Methods 0.000 claims description 28
- FAPWRFPIFSIZLT-UHFFFAOYSA-M Sodium chloride Chemical group [Na+].[Cl-] FAPWRFPIFSIZLT-UHFFFAOYSA-M 0.000 claims description 27
- 150000008044 alkali metal hydroxides Chemical class 0.000 claims description 25
- 238000000034 method Methods 0.000 claims description 24
- 229910001508 alkali metal halide Inorganic materials 0.000 claims description 20
- 150000008045 alkali metal halides Chemical class 0.000 claims description 20
- 239000011780 sodium chloride Substances 0.000 claims description 13
- 238000004519 manufacturing process Methods 0.000 claims description 9
- 239000000463 material Substances 0.000 claims description 7
- KZBUYRJDOAKODT-UHFFFAOYSA-N Chlorine Chemical compound ClCl KZBUYRJDOAKODT-UHFFFAOYSA-N 0.000 claims description 6
- KWYUFKZDYYNOTN-UHFFFAOYSA-M Potassium hydroxide Chemical group [OH-].[K+] KWYUFKZDYYNOTN-UHFFFAOYSA-M 0.000 claims description 6
- WCUXLLCKKVVCTQ-UHFFFAOYSA-M Potassium chloride Chemical group [Cl-].[K+] WCUXLLCKKVVCTQ-UHFFFAOYSA-M 0.000 claims description 4
- 239000000853 adhesive Substances 0.000 claims description 2
- 230000001070 adhesive effect Effects 0.000 claims description 2
- 239000003822 epoxy resin Substances 0.000 claims description 2
- LNEPOXFFQSENCJ-UHFFFAOYSA-N haloperidol Chemical compound C1CC(O)(C=2C=CC(Cl)=CC=2)CCN1CCCC(=O)C1=CC=C(F)C=C1 LNEPOXFFQSENCJ-UHFFFAOYSA-N 0.000 claims description 2
- 229920000647 polyepoxide Polymers 0.000 claims description 2
- 239000001103 potassium chloride Substances 0.000 claims description 2
- 235000011164 potassium chloride Nutrition 0.000 claims description 2
- 239000000565 sealant Substances 0.000 claims description 2
- 239000000126 substance Substances 0.000 claims description 2
- 239000011248 coating agent Substances 0.000 claims 1
- 238000000576 coating method Methods 0.000 claims 1
- 239000007789 gas Substances 0.000 description 40
- 238000005868 electrolysis reaction Methods 0.000 description 17
- 239000012071 phase Substances 0.000 description 11
- 235000011121 sodium hydroxide Nutrition 0.000 description 11
- 239000007788 liquid Substances 0.000 description 5
- QSHDDOUJBYECFT-UHFFFAOYSA-N mercury Chemical compound [Hg] QSHDDOUJBYECFT-UHFFFAOYSA-N 0.000 description 5
- 229910052753 mercury Inorganic materials 0.000 description 5
- 239000000243 solution Substances 0.000 description 5
- 239000007864 aqueous solution Substances 0.000 description 4
- 229920000557 Nafion® Polymers 0.000 description 3
- 229910001514 alkali metal chloride Inorganic materials 0.000 description 3
- 238000009792 diffusion process Methods 0.000 description 3
- 239000003792 electrolyte Substances 0.000 description 3
- 230000007935 neutral effect Effects 0.000 description 3
- 230000003647 oxidation Effects 0.000 description 3
- 238000007254 oxidation reaction Methods 0.000 description 3
- 238000000926 separation method Methods 0.000 description 3
- SUKJFIGYRHOWBL-UHFFFAOYSA-N sodium hypochlorite Chemical compound [Na+].Cl[O-] SUKJFIGYRHOWBL-UHFFFAOYSA-N 0.000 description 3
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Chemical compound O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 3
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 2
- 239000000460 chlorine Substances 0.000 description 2
- 230000000052 comparative effect Effects 0.000 description 2
- 238000007796 conventional method Methods 0.000 description 2
- UQSQSQZYBQSBJZ-UHFFFAOYSA-N fluorosulfonic acid Chemical compound OS(F)(=O)=O UQSQSQZYBQSBJZ-UHFFFAOYSA-N 0.000 description 2
- 239000003014 ion exchange membrane Substances 0.000 description 2
- 150000002500 ions Chemical class 0.000 description 2
- 239000000047 product Substances 0.000 description 2
- 239000011347 resin Substances 0.000 description 2
- 229920005989 resin Polymers 0.000 description 2
- RRZIJNVZMJUGTK-UHFFFAOYSA-N 1,1,2-trifluoro-2-(1,2,2-trifluoroethenoxy)ethene Chemical class FC(F)=C(F)OC(F)=C(F)F RRZIJNVZMJUGTK-UHFFFAOYSA-N 0.000 description 1
- 239000004925 Acrylic resin Substances 0.000 description 1
- 229920000178 Acrylic resin Polymers 0.000 description 1
- QGZKDVFQNNGYKY-UHFFFAOYSA-N Ammonia Chemical compound N QGZKDVFQNNGYKY-UHFFFAOYSA-N 0.000 description 1
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 description 1
- 229910010413 TiO 2 Inorganic materials 0.000 description 1
- BZHJMEDXRYGGRV-UHFFFAOYSA-N Vinyl chloride Chemical compound ClC=C BZHJMEDXRYGGRV-UHFFFAOYSA-N 0.000 description 1
- 239000002253 acid Substances 0.000 description 1
- 239000003513 alkali Substances 0.000 description 1
- 229910052783 alkali metal Inorganic materials 0.000 description 1
- 150000001340 alkali metals Chemical class 0.000 description 1
- 239000010425 asbestos Substances 0.000 description 1
- 125000002843 carboxylic acid group Chemical group 0.000 description 1
- 150000001768 cations Chemical class 0.000 description 1
- 238000011109 contamination Methods 0.000 description 1
- 229920001577 copolymer Polymers 0.000 description 1
- 238000005260 corrosion Methods 0.000 description 1
- 230000007797 corrosion Effects 0.000 description 1
- 238000000354 decomposition reaction Methods 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 239000012153 distilled water Substances 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 238000003912 environmental pollution Methods 0.000 description 1
- 238000002474 experimental method Methods 0.000 description 1
- 238000000605 extraction Methods 0.000 description 1
- 239000012530 fluid Substances 0.000 description 1
- NBVXSUQYWXRMNV-UHFFFAOYSA-N fluoromethane Chemical compound FC NBVXSUQYWXRMNV-UHFFFAOYSA-N 0.000 description 1
- 238000007429 general method Methods 0.000 description 1
- 229930195733 hydrocarbon Natural products 0.000 description 1
- 150000002430 hydrocarbons Chemical class 0.000 description 1
- XLYOFNOQVPJJNP-UHFFFAOYSA-M hydroxide Chemical compound [OH-] XLYOFNOQVPJJNP-UHFFFAOYSA-M 0.000 description 1
- 239000012535 impurity Substances 0.000 description 1
- 238000009434 installation Methods 0.000 description 1
- 229910052742 iron Inorganic materials 0.000 description 1
- 229910000000 metal hydroxide Inorganic materials 0.000 description 1
- 150000004692 metal hydroxides Chemical class 0.000 description 1
- 230000001590 oxidative effect Effects 0.000 description 1
- 230000035515 penetration Effects 0.000 description 1
- 230000035699 permeability Effects 0.000 description 1
- 239000012466 permeate Substances 0.000 description 1
- 239000004033 plastic Substances 0.000 description 1
- 229920003023 plastic Polymers 0.000 description 1
- 229920000642 polymer Polymers 0.000 description 1
- 238000011160 research Methods 0.000 description 1
- 229910052895 riebeckite Inorganic materials 0.000 description 1
- 150000003839 salts Chemical class 0.000 description 1
- 125000000542 sulfonic acid group Chemical group 0.000 description 1
- 238000012360 testing method Methods 0.000 description 1
- 239000012808 vapor phase Substances 0.000 description 1
Classifications
-
- C—CHEMISTRY; METALLURGY
- C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
- C25B—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES FOR THE PRODUCTION OF COMPOUNDS OR NON-METALS; APPARATUS THEREFOR
- C25B1/00—Electrolytic production of inorganic compounds or non-metals
- C25B1/01—Products
- C25B1/34—Simultaneous production of alkali metal hydroxides and chlorine, oxyacids or salts of chlorine, e.g. by chlor-alkali electrolysis
- C25B1/46—Simultaneous production of alkali metal hydroxides and chlorine, oxyacids or salts of chlorine, e.g. by chlor-alkali electrolysis in diaphragm cells
Landscapes
- Chemical & Material Sciences (AREA)
- Inorganic Chemistry (AREA)
- Engineering & Computer Science (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Electrochemistry (AREA)
- Materials Engineering (AREA)
- Metallurgy (AREA)
- Organic Chemistry (AREA)
- Electrolytic Production Of Non-Metals, Compounds, Apparatuses Therefor (AREA)
Description
本発明は高純度なアルカリ金属水酸化物の製造
法に関する。詳しくは、略垂直に張設された陽イ
オン交換膜により陽極室と陰極室とに分離された
所謂竪型電解槽で、アルカリ金属ハロゲン化物水
溶液を電解して、高純度なアルカリ金属水酸化物
を製造する方法に関する。
本発明の目的は、アルカリ金属ハロゲン化物濃
度の低い高純度なアルカリ金属水酸化物を得るこ
とにある。
従来より、アルカリ金属ハロゲン化物水溶液を
電解してアルカリ金属水酸化物を得る方法とし
て、水銀法と隔膜法とがある。近年水銀による環
境汚染問題を契機として後者が注目されている
が、それぞれの方法によつて製造されたアルカリ
金属水酸化物の性状には大きな差異が認められ、
不純物濃度が著しく異なる。塩化ナトリウム水溶
液を電解して苛性ソーダを得る場合を例にとれ
ば、50％苛性ソーダ水溶液中で、水銀法では塩化
ナトリウム含量が数ppm〜数十ppmであるのに
対し、隔膜法では塩化ナトリウム含量が約
10000ppmもある。
隔膜法で得られる苛性ソーダ中の塩化ナトリウ
ムを除去する方法として、液体アンモニア抽出
法、水和物法及び複塩法等が研究され、一部実用
化もされているが、いづれもコストアツプを招
き、更にはかかる方法で精製された苛性ソーダ中
にも塩化ナトリウムが数百〜数千ppm残存し、
高純度な苛性ソーダを必要とする市場分野には使
用出来ないのが実状である。
従つて、近年、隔膜法で一般に用いられるアス
ベスト等の中性隔膜にかえて、陽イオン交換膜を
用いる隔膜電解法が例えば特開昭48−61397号等
により提案されている。この陽イオン交換膜は陽
極で発生するハロゲンガス、陽極液中に生成する
次亜ハロゲン酸イオン等の酸化性物質により著し
く劣化をうけるために、耐酸化性を有する必要が
ある。このような要求に対して、最近、パーフル
オロ化炭化水素とスルホン化パーフルオロビニル
エーテルの共重合体で作られた改良された膜が開
発されている。種々の実験において、かかる陽イ
オン交換膜はアルカリ金属水酸化物の製造用に耐
え得ることがわかつている。
しかしながら、このような膜を１枚だけ略垂直
に張設して電解を行う２室式電解法においては、
得られるアルカリ金属水酸化物中のアルカリ金属
塩化物含量は末だ数百〜数千ppmにも達し、高
純度を必要とする市場分野での使用に耐えないと
されている。最近、この問題を解決する方法とし
ては、略垂直に張設した陽イオン交換膜と中性隔
膜とをそれぞれ１枚以上用いる多室式電解法が研
究され、提案されている。この方法によれば、水
銀法と同等の低アルカリ金属塩化物含有の高純度
なアルカリ金属水酸化物を製造し得ることが知ら
れている。しかしながら、この多室式電解法は下
記の如き幾多の欠陥が指摘出来、工業的に極めて
不利な方法といわざるを得ない。
膜を２枚以上用いるために、必然的に槽電圧
の上昇を招き、エネルギーコストが大巾にアツ
プする。
電解槽構造が複雑化し、設備コストが過大と
なる。
電解槽操作が煩雑化し、運転性が悪化する。
本発明者等は、上記従来方法の欠点を克服すべ
く、略垂直に張設した陽イオン交換膜を用いる隔
膜電解法につき鋭意研究を重ねた結果、一般に公
知な耐酸化性陽イオン交換膜を用いた隔膜電解法
で、アルカリ金属ハロゲン化物濃度の非常に低い
高純度なアルカリ金属水酸化物を工業的に極めて
有利に製造出来る方法を見出した。
即ち、本発明は略垂直に張設された陽イオン交
換膜により陽極室と陰極室とに分離された竪型電
解槽で、アルカリ金属ハロゲン化物水溶液を電解
してアルカリ金属水酸化物を製造する方法におい
て、陽極室で発生するハロゲンガスが陽極液と分
離することによつて生ずるハロゲンガスからなる
気相中に露出している陽イオン交換膜の片面又は
両面をガス不透過性物質で被覆させて電解を行わ
せることを特徴とするアルカリ金属ハロゲン化物
濃度の低い高純度なアルカリ金属水酸化物の製造
法を内容とするものである。
本発明者等は、略垂直に張設した陽イオン交換
膜を用いるアルカリ金属ハロゲン化物水溶液の電
解によつて得られるアルカリ金属水酸化物中のア
ルカリ金属ハロゲン化物の混入原因につき、詳細
に研究した結果、主たる原因は、陽極室の上部に
形成されるハロゲンガスからなる気相部に陽イオ
ン交換膜が露出している場合に、気相中のハロゲ
ンガスが膜を通つて陰極室に拡散し、そのハロゲ
ンガスと陰極室で生成されるアルカリ金属水酸化
物とが直ちに反応して、アルカリ金属ハロゲン化
物を生成するためであることをつきとめた。陽イ
オン交換膜の片側がハロゲンガスに直接露出した
場合、膜の反対側にハロゲンガスが容易に拡散す
ることは、下記の実験事実より理解出来る。
第１図に示す如く、内容積１（10cm×10cm×
10cm）のアクリル樹脂製容器１′の中央に、イ
ー・アイ・デユポン・デ・ニモアース・アンド・
カンパニー製パーフルオロスルホン酸膜（商品名
“ナフイオンXR315”）（図中記号２′）をはさみこ
んで、３′及び４′の２つの室を成形させ、室３′
に20％苛性ソーダを一杯に充填し、室４′に塩素
ガスを常圧で1.2/hrを３時間通気し、その間に
20％苛性ソーダ中に増加した塩化ナトリウムを測
定した所、735ppmであつた。
次に、第２図に示す如く、膜２′が水平になる
如くし、下室３′に20％苛性ソーダを一杯に充填
し、上室４′に半容量の蒸溜水を充填し、この水
層の上部に塩素ガスを常圧で1.2/hrを３時間通
気し、その間に20％苛性ソーダ中に増加した塩化
ナトリウムを測定した所、27ppmであつた。従
つて、陽極室内の気液分離により形成されるハロ
ゲンガス相中に陽イオン交換膜が露出することが
ないように電解することが、アルカリ金属ハロゲ
ン化物を殆んど含まない高純度なアルカリ金属水
酸化物を得ることを可能にする要点である。
従来から種々発表されている陽イオン交換膜を
隔膜とする竪型電解槽としては、電解槽内の上部
で気液分離を行わせるものである。このタイプの
電解槽は、膜の装着の容易さから膜の上端は電解
槽の上面に付属するフランジ等に装着されるた
め、陽極液上部に形成されるハロゲンガス相に陽
イオン交換膜の上部が露出しているのが一般であ
る。
従つて、上記従来方法により略垂直に張設され
た陽イオン交換膜を隔膜として電解を行う場合
は、陽極室で発生するハロゲンガスが膜を通つて
陰極室に拡散しアルカリ金属水酸化物中にアルカ
リ金属ハロゲン化物が含有される結果となる。
本発明は、略垂直に張設された陽イオン交換膜
を陽極液の上部に形成されるハロゲンガスからな
る気相部中に露出させないために、陽極室で発生
するハロゲンガスが陽極液と分離することによつ
て生ずるハロゲンガスからなる気相中に露出して
いる陽イオン交換膜面を、ガス不透過性物質で被
覆させることである。ガス不透過性物質として
は、フツ素系樹脂、エポキシ樹脂等のプラスチツ
クス、あるいはシーリング剤、接着剤等を耐食性
を考慮して適宜選択出来る。
本発明の理解を容易にするために、図面により
説明する。
本発明は塩化ナトリウムや塩化カリウムの如き
アルカリ金属塩化物水溶液を略垂直に張設された
陽イオン交換膜を隔膜として電解し、塩素ガスの
如きハロゲンガスと水酸化ナトリウムや水酸化カ
リウムの如きアルカリ金属水酸化物を製造する一
般的な方法に適用出来る。電解槽内の上部で気液
分離を行わせる典型的な従来法竪型電解槽を第３
図に示す。陽イオン交換膜１によつて２分割され
た２室からなり、陽極室２は陽極４を、陰極室３
は陰極５を有し、膜１は極室２及び３の外周のフ
ランジ６により所定の位置に装着される。アルカ
リ金属ハロゲン化物水溶液７は、電解液供給口９
から陽極室２内に供給される。電解によつて発生
したハロゲンガスは陽極室ガス排出口１３から取
出され、電解された電解液は電解液抜出し口１１
から取出される。陰極室３へは水あるいはアルカ
リ金属水酸化物８が注液口１０から供給され、電
解によつて発生した水素ガスは陰極室ガス排出口
１４から、製品のアルカリ金属水酸化物は製品抜
出し口１２から取出される。陽イオン交換膜１は
公知の膜が用いられ、一般にこれらの膜物質は、
電解環境に対し物理的及び化学的に安定であり、
かつ、スルホン酸基、カルボン酸基等の活性なカ
チオン交換基を有する重合体からなる。代表的か
つ非常に良好な性質を持つ膜はイー・アイ・デユ
ポン・デ・ニモアース・アンド・カンパニー製パ
ーフルオロスルホン酸膜（商品名、ナフイオン）
である。主要な操作条件は特に限定されるもので
はないが、約50〜300ｇ/の濃度のアルカリ金属
ハロゲン化物水溶液を供給し、10〜70A/dm2の電
流密度で、分解率10〜70％で電解する。得られる
アルカリ金属水酸化物の濃度は10〜50％である。
本発明は、かかる竪型電解槽において、第４図
に示す如く、陽極室で発生するハロゲンガスが陽
極液と分離することによつて生ずるハロゲンガス
からなる気相中に露出している陽イオン交換膜１
の片面又は両面を、ガス不透過性物質１５で陽イ
オン交換膜の上部を被覆して、陽極液抜出し口１
１が被覆面下端より上部に位置せしめるようにし
て電解を行わせる。この場合、膜１は陽極室のハ
ロゲンガス気相部１７に露出されない。
上記の如き方法によれば、陽極室で発生するハ
ロゲンガスが陽極液と分離することによつて生ず
るハロゲンガスからなる気相中に陽イオン交換膜
を露出させることなく電解を行うことが出来るの
で、ハロゲンガスが膜を通つて陰極室に拡散され
ず、従つて水銀法並みの低アルカリ金属ハロゲン
化物濃度の高純度なアルカリ金属水酸化物を製造
し得る。この優れた効果の理由については、下記
の如く説明出来る。
イオン交換膜は、イオン選択透過性及び液不浸
透性には優れているが、ガス不透過性に対しては
必ずしも十分ではない。従つて、ハロゲンガス相
中に膜が露出していると、ハロゲンガスは膜を通
つて陽極室から陰極室に浸透、拡散する。陰極室
にはアルカリ金属水酸化物が存在するので、ハロ
ゲンガスはこれと瞬時に反応し、アルカリ金属ハ
ロゲン化物とアルカリ金属次亜ハロゲン酸とを生
成する。
例えば、Cl2＋2NaOH→NaCl＋NaClO＋H2O
NaClOは陰極で直ちにNaClに還元される。
NaClO＋H2O＋2e→NaCl＋2OH
即ち、陰極室に拡散してきたCl2ガスは、苛性
ソーダ中にNaClとして固定される結果となる。
依つて、略垂直に張設された膜を通してのハロ
ゲンガスの浸透、拡散を防ぐために、前記した如
く、ハロゲンガス気相中に露出している膜面をガ
ス不透過性物質で被覆して電解すれば、アルカリ
金属水酸化物中のアルカリ金属ハロゲン化物の濃
度が顕著に減少する。
尚、本発明方法は陽極室側に略垂直に張設した
フツ素樹脂系中性多孔質膜又は陽イオン交換膜を
用いる多室式竪型電解槽にも適用出来、陽極室か
ら膜間室へのハロゲンガスの浸透、拡散を防止し
得るので、膜間室液の純度向上及び陰極室側のイ
オン交換膜の耐酸化性保護に対し多大な効力を持
つものであることはいうまでもない。
以下に、本発明を実施例及び比較例に基づいて
説明する。
実施例 １
第４図に示す構造の耐熱塩化ビニール樹脂製電
解槽（有効膜面積20cm×20cm）において、陽極に
TiO2−RuO2よりなる不溶性電極、陰極にメツシ
ユ状鉄製電極を使用して、飽和食塩水を電解し
た。電解隔膜はフツ素樹脂系の陽イオン交換膜
“ナフイオンXR315”を使用した。実験条件及び
実験結果を第１表に示す。
The present invention relates to a method for producing highly pure alkali metal hydroxide. Specifically, in a so-called vertical electrolytic cell, which is separated into an anode chamber and a cathode chamber by a cation exchange membrane stretched almost vertically, an aqueous alkali metal halide solution is electrolyzed to produce highly pure alkali metal hydroxide. Relating to a method of manufacturing. An object of the present invention is to obtain a highly pure alkali metal hydroxide with a low alkali metal halide concentration. Conventionally, there are a mercury method and a diaphragm method as methods for electrolyzing an aqueous alkali metal halide solution to obtain an alkali metal hydroxide. In recent years, the latter has attracted attention due to the environmental pollution problem caused by mercury, but there are large differences in the properties of alkali metal hydroxides produced by each method.
Impurity concentrations are significantly different. For example, when obtaining caustic soda by electrolyzing a sodium chloride aqueous solution, in a 50% caustic soda aqueous solution, the sodium chloride content is from several ppm to several tens of ppm in the mercury method, whereas the sodium chloride content is low in the diaphragm method. about
There is also 10000ppm. As methods for removing sodium chloride from caustic soda obtained by the diaphragm method, liquid ammonia extraction method, hydrate method, double salt method, etc. have been researched and some have been put into practical use, but all of them result in increased costs. Furthermore, sodium chloride remains in the caustic soda refined by such a method in an amount of several hundred to several thousand ppm.
The reality is that it cannot be used in market areas that require high purity caustic soda. Therefore, in recent years, a diaphragm electrolysis method using a cation exchange membrane instead of a neutral diaphragm such as asbestos commonly used in the diaphragm method has been proposed, for example, in JP-A-48-61397. This cation exchange membrane must have oxidation resistance because it is significantly deteriorated by oxidizing substances such as halogen gas generated at the anode and hypohalite ions generated in the anolyte. In response to these needs, improved membranes made of copolymers of perfluorinated hydrocarbons and sulfonated perfluorovinyl ethers have recently been developed. In various experiments, such cation exchange membranes have been found to be viable for use in the production of alkali metal hydroxides. However, in the two-chamber electrolysis method in which only one such membrane is stretched almost vertically and electrolysis is carried out,
The alkali metal chloride content in the resulting alkali metal hydroxide reaches several hundred to several thousand ppm, making it unsuitable for use in market fields that require high purity. Recently, as a method to solve this problem, a multichamber electrolysis method using one or more each of a cation exchange membrane and a neutral diaphragm stretched approximately vertically has been researched and proposed. It is known that this method can produce a highly pure alkali metal hydroxide containing low alkali metal chloride equivalent to the mercury method. However, this multi-chamber electrolysis method has a number of defects as described below, and it must be said that it is an extremely disadvantageous method from an industrial perspective. The use of two or more membranes inevitably leads to an increase in cell voltage, which significantly increases energy costs. The electrolyzer structure becomes complicated and the equipment cost becomes excessive. Electrolyzer operation becomes complicated and drivability deteriorates. In order to overcome the drawbacks of the above-mentioned conventional methods, the present inventors have conducted extensive research on diaphragm electrolysis using a cation exchange membrane stretched almost vertically, and have developed a generally known oxidation-resistant cation exchange membrane. Using the diaphragm electrolysis method used, we have found a method that can industrially and extremely advantageously produce highly pure alkali metal hydroxides with extremely low alkali metal halide concentrations. That is, the present invention produces an alkali metal hydroxide by electrolyzing an aqueous alkali metal halide solution in a vertical electrolytic cell separated into an anode chamber and a cathode chamber by a cation exchange membrane stretched approximately vertically. In this method, one or both sides of the cation exchange membrane exposed to the gas phase consisting of halogen gas generated when the halogen gas generated in the anode chamber is separated from the anolyte is coated with a gas-impermeable material. The content is a method for producing a highly pure alkali metal hydroxide with a low alkali metal halide concentration, which is characterized by carrying out electrolysis. The present inventors conducted a detailed study on the cause of contamination of alkali metal halides in alkali metal hydroxides obtained by electrolysis of aqueous alkali metal halide solutions using a cation exchange membrane stretched approximately vertically. As a result, the main cause is that when the cation exchange membrane is exposed to the gas phase consisting of halogen gas formed in the upper part of the anode chamber, the halogen gas in the gas phase diffuses into the cathode chamber through the membrane. It was discovered that this was because the halogen gas and the alkali metal hydroxide produced in the cathode chamber immediately reacted to produce an alkali metal halide. It can be understood from the following experimental facts that when one side of a cation exchange membrane is directly exposed to halogen gas, the halogen gas easily diffuses to the other side of the membrane. As shown in Figure 1, internal volume 1 (10cm x 10cm x
In the center of the acrylic resin container 1' (10 cm), place E.I.
A perfluorosulfonic acid membrane (trade name: "NAFION
was filled with 20% caustic soda, and chlorine gas was vented into chamber 4' at normal pressure at a rate of 1.2/hr for 3 hours.
The increased sodium chloride in 20% caustic soda was measured to be 735 ppm. Next, as shown in Figure 2, the membrane 2' is made horizontal, the lower chamber 3' is fully filled with 20% caustic soda, the upper chamber 4' is filled with half a volume of distilled water, and this water is Chlorine gas was bubbled through the top of the layer at a rate of 1.2/hr at normal pressure for 3 hours, and the amount of sodium chloride that had increased in the 20% caustic soda during this period was measured and found to be 27 ppm. Therefore, it is important to conduct electrolysis so that the cation exchange membrane is not exposed in the halogen gas phase formed by gas-liquid separation in the anode chamber. This is the key point that makes it possible to obtain hydroxide. Various vertical electrolytic cells using a cation exchange membrane as a diaphragm, which have been published in the past, perform gas-liquid separation in the upper part of the electrolytic cell. In this type of electrolytic cell, the upper end of the membrane is attached to a flange attached to the top of the electrolytic cell for ease of membrane installation, so the halogen gas phase formed above the anolyte is exposed to the upper part of the cation exchange membrane. is generally exposed. Therefore, when electrolysis is carried out using a cation exchange membrane stretched approximately vertically as a diaphragm in accordance with the conventional method described above, halogen gas generated in the anode chamber diffuses into the cathode chamber through the membrane and is absorbed into the alkali metal hydroxide. This results in the alkali metal halide being contained in the alkali metal halide. In the present invention, in order to prevent the cation exchange membrane stretched approximately vertically from being exposed to the gas phase consisting of halogen gas formed above the anolyte, the halogen gas generated in the anode chamber is separated from the anolyte. The surface of the cation exchange membrane, which is exposed to the gas phase of halogen gas generated by this process, is coated with a gas-impermeable material. As the gas-impermeable material, plastics such as fluorocarbon resins and epoxy resins, sealants, adhesives, etc. can be appropriately selected in consideration of corrosion resistance. In order to facilitate understanding of the present invention, the present invention will be explained with reference to drawings. The present invention electrolyzes an aqueous solution of an alkali metal chloride such as sodium chloride or potassium chloride using a cation exchange membrane stretched almost vertically as a diaphragm, and electrolyzes a halogen gas such as chlorine gas and an alkali such as sodium hydroxide or potassium hydroxide. It can be applied to general methods for producing metal hydroxides. A typical conventional vertical electrolytic cell that performs gas-liquid separation in the upper part of the electrolytic cell is
As shown in the figure. Consisting of two chambers divided into two by a cation exchange membrane 1, the anode chamber 2 houses the anode 4 and the cathode chamber 3
has a cathode 5, and the membrane 1 is mounted in position by flanges 6 on the outer periphery of the electrode chambers 2 and 3. The alkali metal halide aqueous solution 7 is supplied to the electrolyte supply port 9
is supplied into the anode chamber 2 from. Halogen gas generated by electrolysis is taken out from the anode chamber gas outlet 13, and electrolyzed electrolyte is taken out from the electrolyte outlet 11.
taken from. Water or alkali metal hydroxide 8 is supplied to the cathode chamber 3 from a liquid inlet 10, hydrogen gas generated by electrolysis is supplied from a cathode chamber gas outlet 14, and alkali metal hydroxide of the product is supplied from a product outlet. 12. A known membrane is used as the cation exchange membrane 1, and these membrane materials generally include:
Physically and chemically stable in electrolytic environments,
In addition, it is made of a polymer having active cation exchange groups such as sulfonic acid groups and carboxylic acid groups. A typical membrane with very good properties is the perfluorosulfonic acid membrane (trade name, Nafion) manufactured by E.I. Dupont de Nimoers & Co.
It is. The main operating conditions are not particularly limited, but an aqueous alkali metal halide solution with a concentration of about 50 to 300 g/dm is supplied, and electrolysis is performed at a current density of 10 to 70 A/dm 2 and a decomposition rate of 10 to 70%. do. The concentration of alkali metal hydroxide obtained is 10-50%. In such a vertical electrolytic cell, as shown in FIG. 4, the present invention provides cations exposed in a gas phase consisting of halogen gas generated when halogen gas generated in the anode chamber is separated from the anolyte. Exchange membrane 1
The upper part of the cation exchange membrane is coated with a gas-impermeable material 15 on one or both sides of the anolyte outlet 1.
1 is positioned above the lower end of the coated surface to perform electrolysis. In this case, the membrane 1 is not exposed to the halogen gas vapor phase part 17 of the anode chamber. According to the method described above, electrolysis can be performed without exposing the cation exchange membrane to the gas phase consisting of halogen gas generated when the halogen gas generated in the anode chamber is separated from the anolyte. In this method, halogen gas is not diffused into the cathode chamber through the membrane, and therefore a highly pure alkali metal hydroxide with a low alkali metal halide concentration comparable to that of the mercury method can be produced. The reason for this excellent effect can be explained as follows. Ion exchange membranes are excellent in ion selective permeability and liquid impermeability, but are not necessarily sufficient in gas impermeability. Therefore, when the membrane is exposed in the halogen gas phase, the halogen gas permeates and diffuses through the membrane from the anode chamber to the cathode chamber. Since the alkali metal hydroxide is present in the cathode chamber, the halogen gas instantly reacts with it to produce an alkali metal halide and an alkali metal hypohalous acid. For example, Cl 2 + 2NaOH → NaCl + NaClO + H 2 O NaClO is immediately reduced to NaCl at the cathode. NaClO+H 2 O+2e→NaCl+2OH That is, the Cl 2 gas that has diffused into the cathode chamber ends up being fixed as NaCl in the caustic soda. Therefore, in order to prevent the permeation and diffusion of halogen gas through the membrane stretched almost vertically, the membrane surface exposed in the halogen gas gas phase is coated with a gas-impermeable material as described above. Then, the concentration of the alkali metal halide in the alkali metal hydroxide is significantly reduced. The method of the present invention can also be applied to a multi-chamber vertical electrolytic cell using a fluororesin-based neutral porous membrane or cation exchange membrane stretched almost vertically on the anode chamber side. Needless to say, it is highly effective in improving the purity of the intermembrane chamber fluid and protecting the oxidation resistance of the ion exchange membrane on the cathode chamber side, since it can prevent the penetration and diffusion of halogen gas into the membrane. . The present invention will be explained below based on Examples and Comparative Examples. Example 1 In a heat-resistant vinyl chloride resin electrolytic cell (effective membrane area 20 cm x 20 cm) with the structure shown in Figure 4, the anode was
A saturated saline solution was electrolyzed using an insoluble electrode made of TiO 2 -RuO 2 and a mesh-shaped iron electrode as the cathode. The electrolytic diaphragm used was a fluororesin-based cation exchange membrane "NAFION XR315." The experimental conditions and experimental results are shown in Table 1.
【表】【table】
【表】
比較例 １
第３図に示す構造の電解槽において、実施例１
と全く同様な実験条件で電解を行つた結果を第２
表に示す。[Table] Comparative Example 1 In the electrolytic cell having the structure shown in Fig. 3, Example 1
The second result of electrolysis under exactly the same experimental conditions as
Shown in the table.
第１図及び第２図は、塩素ガスの拡散状況を調
べるために用いた試験装置の概略断面図。第３図
は従来法竪型電解槽、第４図は本発明の竪型電解
槽を示す断面図である。
FIGS. 1 and 2 are schematic cross-sectional views of a test device used to examine the diffusion status of chlorine gas. FIG. 3 is a sectional view showing a conventional vertical electrolytic cell, and FIG. 4 is a sectional view showing a vertical electrolytic cell according to the present invention.
Claims (1)
極室と陰極室とに分離された竪型電解槽で、アル
カリ金属ハロゲン化物水溶液を電解してアルカリ
金属水酸化物を製造する方法において、陽極室で
発生するハロゲンガスが陽極液と分離することに
よつて生ずるハロゲンガスからなる気相中に露出
している陽イオン交換膜の片面又は両面をガス不
透過性物質で被覆させて電解を行わせることを特
徴とするアルカリ金属ハロゲン化物濃度の低い高
純度なアルカリ金属水酸化物の製造法。 ２ ガス不透過性物質がフツ素系樹脂、エポキシ
樹脂、シーリング剤、接着剤から選択される特許
請求の範囲第１項記載の製造法。 ３ アルカリ金属ハロゲン化物が塩化ナトリウ
ム、アルカリ金属水酸化物が水酸化ナトリウム、
およびハロゲンガスが塩素ガスである特許請求の
範囲第１項記載の製造法。 ４ アルカリ金属ハロゲン化物が塩化カリウム、
アルカリ金属水酸化物が水酸化カリウム、および
ハロゲンガスが塩素ガスである特許請求の範囲第
１項記載の製造法。[Claims] 1. In a vertical electrolytic cell separated into an anode chamber and a cathode chamber by a cation exchange membrane stretched approximately vertically, an aqueous alkali metal halide solution is electrolyzed to produce an alkali metal hydroxide. In the manufacturing method, one or both sides of the cation exchange membrane, which is exposed to the gas phase consisting of halogen gas generated when the halogen gas generated in the anode chamber is separated from the anolyte, is covered with a gas-impermeable material. A method for producing a highly pure alkali metal hydroxide with a low concentration of alkali metal halides, the method comprising coating and electrolyzing the alkali metal hydroxide. 2. The manufacturing method according to claim 1, wherein the gas-impermeable substance is selected from fluororesins, epoxy resins, sealants, and adhesives. 3 The alkali metal halide is sodium chloride, the alkali metal hydroxide is sodium hydroxide,
and the manufacturing method according to claim 1, wherein the halogen gas is chlorine gas. 4 The alkali metal halide is potassium chloride,
2. The manufacturing method according to claim 1, wherein the alkali metal hydroxide is potassium hydroxide and the halogen gas is chlorine gas.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP60003113A JPS60187687A (en) | 1985-01-10 | 1985-01-10 | Manufacture of alkali metallic hydroxide of high purity |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP60003113A JPS60187687A (en) | 1985-01-10 | 1985-01-10 | Manufacture of alkali metallic hydroxide of high purity |
Related Parent Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP6195276A Division JPS5844749B2 (en) | 1976-05-27 | 1976-05-27 | Method for producing high-purity alkali metal hydroxide |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPS60187687A JPS60187687A (en) | 1985-09-25 |
| JPS6156315B2 true JPS6156315B2 (en) | 1986-12-02 |
Family
ID=11548292
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP60003113A Granted JPS60187687A (en) | 1985-01-10 | 1985-01-10 | Manufacture of alkali metallic hydroxide of high purity |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPS60187687A (en) |
Citations (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS5220980A (en) * | 1975-08-12 | 1977-02-17 | Asahi Glass Co Ltd | Fluororesin cation exchange membrane for electrolysis |
-
1985
- 1985-01-10 JP JP60003113A patent/JPS60187687A/en active Granted
Patent Citations (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS5220980A (en) * | 1975-08-12 | 1977-02-17 | Asahi Glass Co Ltd | Fluororesin cation exchange membrane for electrolysis |
Also Published As
| Publication number | Publication date |
|---|---|
| JPS60187687A (en) | 1985-09-25 |
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