Process for electrochemical reduction of terephthalic acid
AssigneeStandard Oil Company (Indiana)
InventorJohn A. Donohue
Life of this patent
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Abstract
Terephthalic acid is electrochemically reduced to p-hydroxymethylbenzoic acid in a process in an electrolysis cell in which (a) the cathode is solid and metal with an amalgam of mercury surface and has a hydrogen overvoltage which is greater than the potential for the reduction of terephthalic acid to p-hydroxymethylbenzoic acid, and, (b) sufficient mercury is added of a mercury compound to maintain the process.
Claims23
A process for the preparation of p-hydroxymethylbenzoic acid which comprises electrochemical reduction of terephthalic acid in an electrolysis cell wherein (a) the cathode is solid and metal, said solid, metal cathode having an overlay surface of an amalgam of mercury, said metal of said cathode having a hydrogen overvoltage which is greater than the potential for the reduction of terephthalic acid to p-hydroxymethylbenzoic acid, and (b) sufficient mercury is added therein as a mercury compound to maintain said process.
A process for the preparation of p-hydroxymethylbenzoic acid which comprises electrochemical reduction of terephthalic acid in an electrolysis cell wherein (a) the cathode is solid and metal, said solid, metal cathode having an overlay surface of an amalgam of mercury, said metal of said cathode having a hydrogen overvoltage which is greater than the potential for the reduction of terephthalic acid to p-hydroxymethylbenzoic acid, (b) sufficient mercury is added therein as a mercury compound to maintain said process, (c) said process is a continuous process;
- (d) the catholyte of said process comprises water, terephthalic acid, ammonia, mercuric acetate, an ammonium salt selected from the group consisting of ammonium chloride, ammonium sulfate and ammonium carbonate, the temperature of said catholyte is within the range of from about 0.degree. C. to 100.degree. C.;
- (e) current density applied to said process is within the range of from about 1 to 200 A/dm.sup.2 ;
- (f) concentration of said terephthalic acid in said catholyte is greater than 2% by weight of the total solution;
- (g) concentration of said ammonium salt in said catholyte is within the range of from about 0.1 to about 10% by weight of the total solution;
- (h) concentration of said ammonia as ammonium hydroxide is within the range of from about 1 gram of ammonium hydroxide per 2 grams of terephthalic acid to about 1 gram of ammonium hydroxide per gram of terephthalic acid and wherein pH of the resulting solution is within the range of from about 6.5 to about 9.5;
- (i) said metal of said cathode is selected from the group consisting of lead and alloys of lead with metals selected from the group consisting of cadmium, antimony, tin and bismuth;
- (j) said reduction of said terephthalic acid is less than 96%;
- (k) said process uses a separating diaphragm.
Dependencies are inferred from the claim text.