Molecular formula: C2H2O4
Molecular weight: 90.04
Melting point: 190℃
Chinese name: oxalic acid; Ethoxylic acid; Acid remediation
English name: oxalic acid; ; Ethoxylic acid; aquisal
Description: oxalic acid generally contains two molecules of crystal water, which is colorless and transparent. Its crystal structure has two forms, namely α (rhombic) and β (monoclinic). The melting points are α: 189.5℃ and β: 182℃ respectively. Relative density, α type: 1.900, β type: 1.895. The refractive index is 1.540.
Oxalic acid began to sublimate at 100℃, quickly sublimated at 125℃, and sublimated in large quantities at 157℃ and began to decompose. Soluble in ethanol, soluble in water, slightly soluble in ether, insoluble in benzene and chloroform.
Production method: Oxalic acid is widely distributed in nature, and often exists in the cell membranes of plants such as Funiu flower, sheep hoof, Oxalis, Rumex, etc. Almost all plants contain calcium oxalate.
The industrial production methods of oxalic acid mainly include sodium formate method, oxidation method, carbonyl synthesis method, ethylene glycol oxidation method, propylene oxidation method and carbon monoxide coupling method.
1. Carbon monoxide is purified by sodium formate method, and reacts with sodium hydroxide under pressure to generate sodium formate, which is dehydrogenated at high temperature to generate sodium oxalate, and the sodium oxalate is subjected to lead (or calcification), acidification, crystallization, dehydration and drying to obtain the finished product oxalic acid. The synthesis pressure of carbon monoxide and sodium hydroxide is generally 1.8-2.0MPa, and the dehydrogenation temperature is 400℃.
2. The oxidation method takes starch or glucose mother liquor as raw material and reacts with nitric acid-sulfuric acid in the presence of alum catalyst to obtain oxalic acid. Nitric oxide in the waste gas is sent to the absorption tower for recovery, and dilute nitric acid is generated.
3. Carbon monoxide was purified to more than 90% by carbonylation, and reacted with butanol in the presence of palladium catalyst to produce dibutyl oxalate, and then hydrolyzed to obtain oxalic acid. This method can be divided into two types: liquid phase method and gas phase method. The reaction conditions of gas phase method are low, and the reaction pressure is 300-400kPa. The reaction pressure of liquid phase method is 13.0- 15.0MPa.
4. Ethylene glycol oxidation method is obtained by air oxidation with ethylene glycol as raw material in the presence of nitric acid and sulfuric acid.
5. Oxidation process of propylene
The oxidation process is carried out in two steps. Firstly, oxidizing with nitric acid to convert propylene into α-nitrolactic acid; Then further catalytic oxidation is carried out to obtain oxalic acid. In the second step, mixed acids can also be used as oxidants. The total yield of industrial oxalic acid dihydrate produced by propylene oxidation is over 90%.
Raw material consumption quota: coke (84%) 510 kg/t; Sulfuric acid (100%) 950kg/ton; Caustic sodium (100%) 920kg/ton
Uses: Oxalic acid is mainly used to produce antibiotics, borneol and other drugs, as well as solvents for extracting rare metals, dye reductants, tanning agents and so on.
In addition, oxalic acid can also be used to synthesize oxalate, oxalate, oxamide and other products, among which diethyl oxalate, sodium oxalate and calcium oxalate have the largest output.
Oxalic acid can also be used to produce Co-Mo-Al catalyst, clean metal and marble, and bleach textiles. The answer is added, hehe! Generally sold in Wujinjiaodian and chemical appliance stores; Generally used to wipe the floor in decoration.