Colorless or light yellow ribbed crystal or liquid, crystal deliquescence. The melting point is 15ºC, the boiling point is 50.5ºC, the relative density is 1.14 (20/4ºC), and the refractive index is 1.3826. The vapor is green and burns with a purple flame. Rapid polymerization when placed, exposed to water (violent reaction), or dissolved in aqueous solvents. It usually exists in various aggregate forms. The anhydrous polymer is transformed into a monomer when heated. A monomer solution can be obtained by co-heating the polymer with p-allyl anisole, phenylethyl ether, safrole, methyl nonyl ketone or benzaldehyde. The aqueous solution contains single molecule glyoxal, which is weakly acidic and chemically active, and can be added or condensed with ammonia, amide, aldehyde and carboxyl-containing compounds. Soluble in water, easily soluble in common organic solvents. The main industrial production methods are ethylene glycol vapor phase catalytic oxidation and acetaldehyde nitric acid oxidation. 1. Glyoxal phase catalytic oxidation method glycol and air in the presence of copper catalyst, at 250-300ºC catalytic oxidation, glyoxal: the catalyst active group is divided into copper oxide (containing Cu03-8), the carrier is alumina or corundum, aluminum sand, with copper nitrate impregnation and roasting. The service life is up to one year, and it is regenerated by burning. After preheating and gasification, ethylene glycol is mixed with circulating gas into the catalytic reactor to control the amount of fresh air to prevent the deep oxidation of ethylene glycol, and the halogen compound is brought into the nitrogen stream as the inhibitor of deep oxidation. The reaction is carried out at 275ºC and 0.74MPa pressure, the reaction product is chilled with water, and the concentration is absorbed as the finished product. The conversion rate of ethylene glycol plus one way is 80-85. 2. Acetaldehyde nitric acid oxidation method uses copper nitrate as catalyst and nitric acid for liquid phase oxidation: under the condition of stirring and sufficient cooling, acetaldehyde and nitric acid are respectively prepared into a solution of about 50, copper nitrate into a solution of 40, and sodium nitrite into a solution of 5. First add a small amount of nitric acid solution and acetaldehyde solution into the reaction pot, and then put in sodium nitrite solution, slightly heated until brown-red gas occurs, the natural temperature rises to 30ºC, and start to add a small amount of nitric acid solution and acetaldehyde solution at the same time, about 4h after adding, the reaction temperature is controlled at 40-45ºC, the escape of acetaldehyde gas is absorbed by water and added to the reaction pot, and continue to react for 3h. The dosage of acetaldehyde in the reaction is excessive (according to the molar ratio, nitric acid: acetic acid = 1:2), after the reaction, the acetaldehyde is heated to 98ºC. Then add activated carbon to decolorize, cool, filter, wash. The filtrate and lotion were combined, and the organic acids were steamed below 70ºC (21.33kPa), and the water was repeatedly replenished and re-steamed until the impurities were removed from the acidic cation exchange resin and weak basic anion exchange resin in the distillate. Exchange fluid and elution hydraulic concentration to obtain acceptable concentration of glyoxal. The yield was about 32 % by acetaldehyde.
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