The Synthesis Of Glyoxalic Acid By Electrooxadation Of Glyoxal And The Separation Of The Electrolyte By Electrodialysis

Glyoxalic acid, an important fine chemical, is widely used in medicines, pesticide, spices and so on, which are all high value-added. Therefore, glyoxalic acid has good prospect. The synthesis of glyoxalic acid through electro oxidation of glyoxal deserves our attention.The electro oxidation of glyoxal with varying current density and fixed bed electrolytic cell allowed operation with high current density and good electrolysis result. When mean current density was 1343 A·m-2, glyoxal conversation could reach 90.8%, with selectivity for glyoxalic acid 89.9% and current efficiency 80.5%.The separation of glyoxalic acid and hydrochloric acid was done by electrodialysis when the conversation of glyoxal was about 90%. The results showed that flow rate at 4.21 cm·s-1, temperature at 30℃, AHT as anion membrane and the process with current density 628.7 A·m-2 at early stage and 456.6 A-m-2 at later stage benefitted the separation of the system of glyoxylic acid. The application of weak alkaline menberance AAV had fairly good electrodialysis result. When the migration rate of HCl was 82.4%, the loss of glyoxalic acid was 5.6% and the ratio of glyoxalic acid and HCl in weight was 7.15.According to the condition above, electrodialysis was combined with electrolysis. When glyoxal conversation was 60.2%, selectivity for glyoxalic acid was 95.9%. There was little oxalic acid in electrolyte, and therefore, the separation process was simplified. During the electrodialysis, glyoxal would diffuse through HSF. However, the diffusion of glyoxal through CMF was minor. So the application of CMF could have good result.