Note: Descriptions are shown in the official language in which they were submitted.
1- 133~974
The present invention relates to an electrolyzing
method, and more particularly to a method for
electrolytically manufacturing an alkali hydroxide or the
like at a lower voltage while suppressing the formation of
S surplus gases minimum.
Heretofore, many useful compounds have been made by
means of various electrolyzing reactions employing an ion
exchange membrane. Generally, in these electrolyzing
reactions, hydrogen is generated on a cathode and oxygen or a
halogen gas is generated on an anode. In the ordinary
electrolyzing reactions, a main object is to obtain an alkali
and an acid, and obtaining gases is not intended or is a
secondary object.
The energy for generating the gases is quite high as is
apparent from the fact that enormous energy is generated when
these hydrogen and oxygen are subjected to combustion. In
the conventional electrolyzing reaction which inevitably
accompanies evolution of the above gases, a plenty of useless
electrical energy has been wasted for producing the gases.
Many proposals for reducing the electrical energy in
electrolysis have been made. However, many of these
proposals intend to reduce the energy without suppressing
evolution of the gas. An example of the proposals is an
improvement of electrode material, that is, the proposal of a
dimensionally stable electrode which usually comprises a
_ - 2 - 1335974
titanium substrate plated with a noble metal oxide. Another
example is to reduce the resistance between the electrodes
by, for instance, removing an evolved gas present between an
electrode and a membrane or by contacting the electrode to
the membrane (for example, U.S.P No. 4,409,074). Although
these two proposals have contributed to reduction of the
voltage, further reduction is expected.
The invention provides an electrolyzing method in which
the hydrogen gas evolved in the cathode chamber is
effectively used for lowering the energy consumption in the
anode chamber.
The invention is an electrolyzing method which comprises
placing a solution of a compound represented by the formula
A-B (wherein A is an alkali metal cation or an alkaline earth
metal cation and B is an anion) in an electrolytic cell which
is divided into an anode chamber and a cathode chamber by
means of an ion exchange membrane electrolyzing the solution
while providing hydrogen evolved in the cathode chamber to
the anode chamber by means of a communicating tube connecting
the both chambers, and producing a solution cont~;n;ng an
alkali represented by the formula A(OH)X and an acid
represented by the formula HyB (wherein X is a valency of A
and Y is a valency of B) in the cathode chamber and the anode
- chamber, the anode chamber, respectively.
In this invention, at least part of hydrogen gas
produced in the
1335974
~3)
cathode chamber i5 provide~ into ~n anode ch~ml~er b~Y means o~ J
communic~till~ tube without takin~ it out of ~n electrolYtic cell. the
hy~rogen gas is oxi~ize~ in the anode chamber to tl~ hYdrogen ion which is
then combined with an anion already exiSting therein to form an ~cid. When
5 the hYdrogen ~s is not provided to the anod~ ~hflmber. the said cation
already existing therein ig oxidized tO the correspvllding ~as. For ex~mple.
in Lh~ ca8e of Such a h~lo8en iOIl as a ~hlorine ion ~nd a flu~rine iOIl, they
ar~ oxidi~ed to such a h~k~gen ax chlorine and fl4crille; in the c~se of a
sulphatc ion ~n~l a nitr~t:e ion, theY are c~llvert~ t.rJ ~xyg-qn which is t~lken
10 out of the cell withol~t fllrther treatment; an~ in ~he ca~e of ~n vrganic
aci~l ion, it. i~; oxidized and the resultant organic molecule is destroyed.
~ omParison of the ener~y quantity required for generation of ~e ~s
throu~h oxidation of the chlnrine i~n and the lik~ and of that requir~d for
~ener~tion of the hydrogen ion throu~h vxidation of the h,~clrv~en ~ax revea
15 th~t th~ enery ~uantity of the l~tter is muc:l~ sm~ller. an~ efl~nolll~cal
opera~i~n which greatlY decreascs ~he electric~l enel gy required f~r the
produc~ion of l:he same ~uantity of ~n ~Ik~li can l~e performe~ accordin~ to
th~ pre~ent invention.
l`he St~rting m~terial of th~ electrol~zing nlet.l~ocl of this illvention is
20 generally represented bY A-~. A is an alkali metal c~tinn or al~ alkallne
earth me~l such as a sodium ion, a POt~S~iUm ion. a lit.h ium ion. ?l c~lcium
ion an~ magne~iutn ion. B inclu~es ~ ~ulPhate ion, a h~Y~ro8ensul~ tc ion,
a nitr.~te iun, a chlorine ion, a flu~rine ion ~nd an or~niu aci~l ion.
Th~refore, thc starLing material A-B of the inventisn inclu~ s f;D~lium
25 :~ul~h~tf~. sodium chlorid~, ~odiwll hy~rogen~ulph~tt~ utassillm fllloride,
lithium nitr~tc~ calciurn ~ulPhate~ ~odium ox;~ alld sudiurn ci l.r . l he
star~in~ material maY be a purc material or maY ~c ~ mixl.ur~ therevf,
While ~ny one l~f the commerciallY avail~bl~ iun cxct~.~n~e m~mbrancs may
~4) 133S97~
be emPloYed for the Pr~sent invelltion, a ~luorine-containir~ ion exchange
membrnne h~ving th~ Superior ~orrosion rç~ nc i~ preferably entl)ioye(l
In Ihe case of Placing the salt solution of Lh~ rlin~ materi~l in the
~node chamber the c.q~ion exchange mem~riane is emPlo~Yed .~o that lhe ion A
S and the ion B are coll~cted to the athode chamber ~nd 1o ~he anode chalnbel,
resPectively. On the other harld in the case vf placinf~ the sollltion in the
cathode chamber the anion exch~nge membrane is elnploYed~
El~ctrocies t~ be emPloYed ~re desir~bly ~;o-call~ci gæ~ p~r~ Abl~
rlectrodes. The g~qs permeable electrode is one hAvin~: Ihe pro~erty uf
~:elec:tivelY le11ing a gas such ag hYdrogen or lI-e like p(rmoate ;lnd of
pre~entillfS Perme~tion of such a liquid a~: w~ter 1~ ne ex;~nlple ~n
clectrode ~omPrising a composite membralle con~;i.s ting of twn l;~r~ havir)~
the dif~rent propertie~; one l~yel- of which i~ ;l hydrophilic one ~Invin~ the
él~ctrode flln~Lion anci facill~ the counter ele~t:rode ;~nd l.hF~ ot.h~r layer of
which is a hydrol~hobic one cornPrisihg h~drophobic cari~oll hl~ck and
pc~lYtetrafluoroe~hyl~ne (hereinafter referred tc~ ;ts P~FE) is kn~wn
(for ex~mple ll. S P. No. 4.748.0~5). In ~clditi- ~I to the ~i.lS ~)enlleahl~
electrode aAn vrdinary sc)-c~ d dimen~;ionally ~;tal~lc electro-i- n~ay be
employed.
When the g~:~ permea~le electrode is erllploytd ns th~ cathod- th~ ga~
evolved on lhF! electrode surface facin~ the ~node is led lo ilfi r~r ~;urface
l~y I~Assing throllgh l.h~ electrode ~o th~t the illterele-:trvde vv It;lYe i~i not
elevat~?d becausc the 8~ e~rolved does not exi:3t betW~!e~ ? e l~?clr~lcx
which ~ttains muoh m~re voltage droP. and th~ itl hytlrOf~n g~S c~n be morc
~?~sily introdueed to the communicating tuh~. Wl.~n, nn l.lle olller h;~nd, ~I~eg~ permcable eleot~ode i,s emPloYed a:~ the ~n~d~, I.he hydrogen ~a~e; c~lning
from the cathode ch~mher can bc easily oxidi~ y ~ir~ lY ~)rv-idi~lx the ~as
to the re~r vf the anode, which t.hen passes throus3h the ;tnVIie cvlllprisirlx the
133~974
(~)
gas permcable electrode to re~ch tlle electrode surf~ct~ fa~inf~ th~ cathode.
The electroly~ic cell to be ernployed is not e~eciallY r~s;îrict~d~ and
any cell equipped with the communicatin~ tube for ,orovidill~ th~ hydrng~n ~a~
evolv~d in the cathode chambcr to the ~node ~halnb~r rn~ be ~.!mploy~d ln l.ho
S ini~ial stage of the ~lectrolYsi~. the inl~rior ~r i.h~ eomrnunica~in~ t,lbc
and of the both chambers is desir~bly repla~ed with ~ hYdros~ c~.
The electrolYsis condition:~ may be the same as those of the prior ~rt
except for voltage. ~ecording ~o th~se conditions, ~h~ amount; of th~
cnn~;um~d cnc~r~y c~n be lower-ed to ol~e-fifth to one- t~nth ~f th~t ot` the
10 prior ~rt dependin~ on the electrolyte em~loyed ~nd th~ stru~tur~ of th~
electrolytic c~ll.
In the ordinary electrolysis, muc~h ell~r~y i~ re(l-llrcd fur c~nv~r~
an ~nion to the correspondin8 ga~, ror example, a chlorit-e ion Lo a chlorine
~as an~ a hydroxide ion to ~n oxYgen gas. Tn the presellt invelltion, the
lS ~nioll in the anode ch~mber rn~Y be reacted wit.h the hy~lr~en ihn pro-luced
from t.h~ ~id hydrogcll ~as to form thc corrcspondirl~ acid. 1 ho cnorgy
required for the conver~ion of the hydroRcn gas to its i~n is mllch :~maller
th~n th~t for the conver.sinn of th~ ;~ni~n to th~ corr~sp~l-din~ R;~s
Accordin~3 tv the present invention. therefore, the eners~Y r~quired fol- the
20 ~volution of the ~as in the ~node chamber can be ~aved ~o th~t thc eMicient
electrolYsis uper~tion can be achieved.
Furt.her, when the ~as permeable electrode is ~m~loYe<~. the ~a~; evolved
on the electrode can be~e~sily t~ken out ~nd the hydro~en ~21S evolved i~l the
cathode ch~mber m~Y be more smooth~Y ~ir~lllated to the ~ ode chalrlbel-, aT-d
~5 thc hydro~en ga~ provided P~sses throu~h the allode to r-ei1ch the allod~
surface f~ein~ the ~thode on which the g~ ; oxi~ t
The invention will now be illu~;trated by Lhe ~'o.ll(lwin~ l xample~, which,
however, ~re to be con~idered 3x merP~Iy ext?ll~plar~ o~ the~ Pra~tiGC of t~
(6) i3359~ ~
il~vention, and nvt as delimi~ive thereof.
Example l
A gas perrneable electrod~ for an anode and 2~ cathode was pr~p~r~d
according In thc followir~g Procedure.
A reactio n laye~ of which a Lhickno~;s was t~.l mm havir~ ele~trode
function w;,s preparcd by mixin~ Platinutn fine p;~rt.icl~ ol` wllicl, a mcan
Parti~le ~i7e was lO ~8L, hydruphilic c~rbon bl~ck Fin~ particle~ t~f which ~
mean ~rti~le size w~ 450 A an~i Pt~E fine p~rtiele~ of which a mean
particle si~ w~s 0.3 ~I in the proportioll of 3; 3: ~. Th~ t 1~
permeable l~yer uf which ~ thicknes~ WJS 0.5 mm waS prepared b~ mlxinx
hydrophobic carbvn black fil~e P~rticle~ nf which a mean particle size wz~Y
420 A and PTFr: fine p~rtictes of which a mean P~rti~le sk~ was ~3 ~ in
the ProPortinn of 7: 3.
The both Iayers were joined to~ether with a cur~ t colle~tor nlacle of
~vPP~?r wirc interr~u~ed therebetween to form ~ gas per~e~hle electro~e.
An elec~rolytic cell consi~tillX of an arlode charrlI~el- and a c~tl1ode
chamb~r was asscmbled empluyir~ the thII; prel~red ~ rm~able ~lectrode ~f~
the anode and the cathode. The both ch~mbers were sep~r~ted bY employing
l'lafion (registered tr~demark) 117 which was a fluorine-cont.aiI-irlg c~tion
exchange membr~ne of Du Pont with the interelect.rode dist~nce being 2 mm,
an~ tt e the re~r surf~ces of the both electrode~ were connected by means of
~ communicatirlg tube made of polyvinyl chloride of which ~ di~meter was I
cm. ln the ~node ch~ml)er and in the e~thode chamber were l)la~ed 1~0 ~ vf a
sodium suIPhate solution (1 mol/Q ) and lO0 Q of a sodium hy~iroxide
svllltion ~0.1 mol~Q ~, rcspectively. The ~tmosl~t~el-e w~s replaced by flowing
;~ hydrogen gas into the both ch~mber:~ and the ~c~mmllni~ ting tube. So~lium
hydroxide and suiphuric acid were manufactured bY çle~troly~in~ the ~vdiIlnl
(7) 1335g79~
sulPhate with the ~urrent ~f 50 A flown between ~he both electr~des dnd with
the respec~;ive electrolytes circulated in 1;he cell.
lhe interelectrode voltage durill~ tlle el~ctrt)l~si~,. the g~s evolv~d in
the an~de ~ham~er an~ the cathode cham~cr and tht~ current e~ficiencY wer~
5 shown in the Table. The current efficiency was ~AIculate~ frym the valu~ of
the ~odium hydrnxide produced and the vatue o~ tlle ~ rent.
Exarnple 2
Sodium hydroxid~ and sulphuric acid were manufactl~lecl br employing the
~ame ~lcctrnlytic cell ~nd the ~ame condition~ as tho~e o~ ~xample I except
10 that a ti~anium mesh havin8 an oPenin~ ratio of 40 ~ p~ tetl with platinum
wa~ emPloYed a~ the cathode.
The interelectrode volta8e during Lll~ ele~trolysis. the ~as evolved i
Lhe anode ~hamber and the cathod~ chamber and tlle current efficiency were
shown in thc I able.
15 Examele 3
Sodium hydroxide ~nd hYd~ochloric acid werc manufa~tured by employillg
~he s~me elecLrnlytic cell and the same c~nditions as tho~e of Example I
excePt th~t a so~ium chloride solution was emplov~d as ~he ~n~ly~e.
The interelectrode volt~e during the electrolysis, the gas ~volv~d in
20 the anode chamt~er and the cathode chamb~r ~nd ~he current eff;ciencY were
shown in the Table.
Compar~tiv~ Example
Sodium hydroxide ~nd sulphuric acid were Manufa~tlu-ed ~y emPlo~n~ the
same electrolytic cell an~ ~he ~ame con~itions as tho~e ~r Ex~mPle 2 except
~S~tha~ the communicatin~ tub~ was not equipped.
133597~
The interelecl~le voltage during the elecb~olysis, the gas evolved
in the ancde cha~ber ~ the ci~tl~ 3~..~}-. an~ the current f~ff;~
were sh~n in the Table.
T A B L E
Es~ple 1 Exal~!ple 2 E}~?le 3 Canp. Exam.
Interele~L. ~e Volt~ge 1. 6 V 1. 6V 1. SV 3 . SV
lQ Gas in An~de Chaltber NQne NQne Ncme ~ch 2
Gas in Ca~le ~1~ lyr Ncne ~ch H NQne ~ch H
C~LL~lL l;'.ff;c~;~y 98 96 98 96 98 % 98 96
C~r~r;r~ the Exa~ples an~ the C~ Live Exa ~ le revealed th~t
the ...~ de~l~ase of the Lnterele~LL~e voltage cculde ke achieved
in the Exa~ples to cnntr;hllte to the e~yy~saving.
