1. Glyoxal oxidation method Glyoxal is oxidized by air or oxygen under the action of catalyst to produce glyoxalic acid, and then refined to obtain the finished product. In addition, sodium dimethoxyacetate was synthesized by condensation of dichloroacetic acid with sodium methanol, and then hydrolyzed with hydrochloric acid to produce glyoxylic acid.

2. Sodium methanol and methanol were put into the reaction tank by dichloroacetic acid method, heated to 40-50 C, slowly dripped with dichloroacetic acid, refluxed for 2 hours after completion, condensation was completed, and then cooled to room temperature, filtered, washed with methanol, and combined with filtrate to obtain sodium dimethoxyacetate methanol solution. The solution is then concentrated to dry under vacuum, heated in a water bath with 2.8 phr of hydrochloric acid, and stirred into a paste to obtain hydrolysate. The hydrolysate is then heated to 90 C, cooled to about 10 C, filtered and separated, and the finished product is obtained.

3. Oxalic acid electrolysis

Oxalic acid aqueous solution was electrolytically reduced to glyoxylic acid dilute solution, then evaporated, concentrated, frozen and filtered gradually to concentrate, and finally qualified products were packaged.

4. Maleic anhydride is dissolved in formic acid by ozonation-reduction method, then oxidized by ozone, and then reduced by zinc powder to glyoxylic acid.

The 5. system:

In the reaction bottle with agitator, thermometer, ventilation duct and dropping funnel, 40% glyoxal 500g (3.4mol), sodium nitrite 1g, 40% nitric acid 90g (0.57mol), water 160 mL were added. The temperature was raised to 60 C under stirring. After the reaction started (brown gas was generated), the exothermic propylene was heated automatically and the air was introduced. The reaction solution was maintained at 60 C and 40% nitric acid was added. It takes about 5 hours to control the acceleration of droplets, 10 g per hour and 50 g in total. After adding, the reaction temperature rises to 75 C, stirring for 2 hours, and adding 40% nitric acid 10 g slowly, then reacting at 85% - 100 C until glyoxal complete nitric acid (GC tracking), which takes about 3 - 5 hours. At room temperature, the concentration of glyoxylic acid in water was 745-769g, 28.2%. 40% glyoxylic acid aqueous solution can be obtained by vacuum concentration, and the yield is 80% - 85%.