Molecular formula: C2H2O4
Molecular mass: 90.04
Melting point: 190 ° C
Chinese name: oxalic acid; ethanedioic acid; aquisal
English name: Oxalic acid; Ethanedioic acid; aquisal
Properties: Oxalic acid generally contains two molecules of water of crystallization, colorless and transparent crystals, its crystal structure has two forms, namely, α-type (rhombic) and β-type (monoclinic crystal form), the melting point are, α-type: 189.5 ℃, β-type: 182 ℃. Relative density, α-type: 1.900, β-type: 1.895. refractive index 1.540.
Oxalic acid begins to sublimate at 100 ℃, 125 ℃ when the rapid sublimation, 157 ℃ a large number of sublimation, and began to decompose. Soluble in ethanol, soluble in water, slightly soluble in ether, insoluble in benzene and chloroform.
Production method: oxalic acid is found throughout nature, often in the form of oxalate in the cell membranes of plants such as ambrosia, lamb's-foot grass, edelweiss and sour-molded grass, and almost all plants contain calcium oxalate.
The main industrial production methods of oxalic acid are: sodium formate method, oxidation method, carbonyl synthesis method, ethylene glycol oxidation method, propylene oxidation method, carbon monoxide coupling method.
1. Sodium formate method after carbon monoxide purification under pressure and sodium hydroxide reaction, generating sodium formate, and then high temperature dehydrogenation to generate sodium oxalate, sodium oxalate and then lead (or calcification), acidification, crystallization and dehydration drying and other processes, to get the finished product oxalic acid. The synthesis pressure of carbon monoxide and sodium hydroxide is generally 1.8-2.0MPa. the dehydrogenation temperature is 400℃.
2. Oxidation method takes starch or glucose mother liquor as raw material, in the presence of alum catalyst, and nitric acid - sulfuric acid for oxidation reaction to get oxalic acid. The nitrogen oxide in the exhaust gas is sent to the absorption tower to generate dilute nitric acid.
3. Carbonyl synthesis method carbon monoxide is purified to more than 90%, in the presence of palladium catalyst and butanol carbonylation reaction occurs to generate oxalic acid dibutyl ester, and then hydrolyzed to get oxalic acid, this method is divided into liquid phase and gas phase method two kinds of gas phase method reaction conditions are lower, the reaction pressure is 300-400kPa. while the liquid phase method reaction pressure is 13.0-15.0MPa.
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4. Glycol oxidation method is obtained by oxidizing ethylene glycol with air in the presence of nitric acid and sulfuric acid as raw material.
5. Propylene oxidation
The oxidation process is carried out in two steps. The first step is oxidized with nitric acid, so that propylene is converted to α-nitrolactic acid; then further catalytic oxidation to obtain oxalic acid. The second step can also use mixed acids as the oxidizing agent. The propylene oxidation method produces industrial grade oxalic acid dihydrate compounds with a total yield of greater than 90% in terms of propylene.
Raw material consumption quota: coke (84%) 510kg/t; sulfuric acid (100%) 950kg/t; caustic soda (100%) 920kg/t.
Use: Oxalic acid is mainly used in the production of antimicrobial agents and drugs such as ice tablets, as well as solvents for the refining of rare metals, dyes, reducing agents, tanning agents and so on.
In addition, oxalic acid can also be used to synthesize a variety of oxalate, oxalate and oxalamide and other products, and diethyl oxalate and sodium oxalate, calcium oxalate and so on the largest production.
Oxalic acid can also be used in the production of cobalt-molybdenum-aluminum catalysts, metal and marble cleaning and textile bleaching. Answer added Oh! General five cross chemical store on the sale; general decoration on the rubbing ground with more.