Claims
- 1. A process for the electrolysis of an aqueous solution of sodium chloride in an electrolytic cell comprising an anode compartment and a cathode compartment separated by a cation exchange membrane to obtain an aqueous sodium hydroxide solution with a selected sodium chloride content of up to 400 ppm based on pure sodium hydroxide in the cathode compartment at high current efficiency by carrying out the electrolysis under conditions so that a preselected value of the expression:
- (F(C-C.sub.O)/KVt.sub.m)
- is not higher than 2.74.times.10.sup.-4, by controlling the difference of concentration of sodium chloride in the anode compartment in eq. cm.sup.-3 and the limiting concentration of sodium chloride in the anode compartment in eq. cm.sup.-3 at a value from 0 to 0.001 eq. cm.sup.-3 ; the symbols in the said expression being defined as follows:
- F is the Faraday constant expressed as 96,500 sec. eq..sup.-1,
- C is the concentration of sodium chloride in the anode compartment in eq. cm.sup.-3,
- C.sub.O is the limiting concentration of sodium chloride in the anode compartment in eq. cm.sup.-3,
- K is a proportionality constant in sec. cm.sup.-3 ohm.sup.-1,
- V is the voltage drop in the membrane in volts, and
- t.sub.m is the transport number of the sodium ions in the membrane:
- and
- F is 96,500,
- C-C.sub.O is from 0 to 0.001,
- K is from 0.8.times.10.sup.5 to 1.67.times.10.sup.5,
- V is from 0.3 to 2, and
- t.sub.m is from 0.7 to 0.98.
- 2. A process as in claim 1 wherein the alkali metal halide is sodium chloride and the value of t.sub.m is from 0.8 to 0.98.
- 3. A process as in claim 1 carried out at a current density of from 1 amp. cm..sup.-2 to 0.05 amp. cm..sup.-2 under conditions such that the ratio of current density to limiting concentration is from 150 to 350 amp. cm..sup.-2 /eq. cm..sup.-3.
- 4. A process as in claim 1 wherein the cation exchange membrane is a fluorocarbon polymer containing sulfonic acid groups.
- 5. A process as in claim 1 wherein the cation exchange membrane is provided with a reinforcing material backing.
- 6. A process as in claim 5 wherein the reinforcing material backing comprises a polytetrafluoroethylene fabric.
Priority Claims (1)
Number |
Date |
Country |
Kind |
50-85777 |
Jul 1975 |
JPX |
|
Parent Case Info
This is a continuation, of application Ser. No. 856,484 filed Dec. 1, 1977, which is in turn a continuation of application Ser. No. 703,234 filed July 7, 1976, now abandoned.
US Referenced Citations (4)
Number |
Name |
Date |
Kind |
3773634 |
Stacey et al. |
Nov 1973 |
|
3904496 |
Harke et al. |
Sep 1975 |
|
3933603 |
Ishida et al. |
Jan 1976 |
|
4025405 |
Dotson et al. |
May 1977 |
|
Foreign Referenced Citations (1)
Number |
Date |
Country |
955307 |
Apr 1964 |
GBX |
Continuations (2)
|
Number |
Date |
Country |
Parent |
856484 |
Dec 1977 |
|
Parent |
703234 |
Jul 1976 |
|