It is obtained by heating oxalic acid in anhydrous glycerol and then steam distilling it.
Or hydrolyze isoacetonitrile under the action of hydrochloric acid to obtain:
Isoacetonitrile is prepared by reacting ethylamine and chloroform. (Because isoacetonitrile has an unpleasant smell, this reaction must be carried out in a fume hood.) 1. Sodium formate method: Carbon monoxide and sodium hydroxide solution react at 160-200°C and 2MPa pressure to generate sodium formate, which is then acidolyzed by sulfuric acid , distillation to obtain the finished product.
2. Methanol oxo synthesis method (also known as methyl formate method): methanol and carbon monoxide react in the presence of catalyst sodium methoxide to generate methyl formate, which is then hydrolyzed to generate formic acid and methanol. Methanol can be recycled into the methyl formate reactor, and the formic acid can be distilled to obtain products of different specifications.
3. Formamide method: Carbon monoxide and ammonia react in methanol solution to form formamide, which is then hydrolyzed in the presence of sulfuric acid to obtain formic acid, and ammonium sulfate is produced as a by-product. Raw material consumption quota: methanol 31 kg/t, carbon monoxide 702 kg/t, ammonia 314 kg/t, sulfuric acid 1010 kg/t. In addition, the butane and light oil oxidation method is mainly used to produce acetic acid, and formic acid is recovered as a by-product. The method in the research stage is the direct synthesis of carbon monoxide and water.
Refining method: Anhydrous formic acid can be obtained by direct fractionation under reduced pressure. During fractionation, ice water is used for cooling and condensation. For aqueous formic acid, boron anhydride or anhydrous copper sulfate can be used as a desiccant. Phosphorus pentoxide and calcium chloride can interact with formic acid and are not suitable for use as desiccants. For reagent grade 88% formic acid, the water can be removed by refluxing phthalic anhydride for 6 hours and then distilling it. Fractional crystallization can be used for further purification. When formic acid and acetic acid are mixed together, aliphatic hydrocarbons can be added for boiling distillation separation.
4. React an appropriate amount of carbon monoxide and sodium hydroxide aqueous solution at 160 to 200°C to form sodium formate, which is obtained by neutralization, distillation, and condensation. Or it can be produced by reacting carbon dioxide and hydrogen in triethylamine aqueous solution using a palladium complex as a catalyst at 140 to 160°C.
5. Use sodium formate and concentrated sulfuric acid to produce industrial-grade formic acid, which can then be adsorbed with activated carbon and distilled under reduced pressure to obtain pure product. B2O3CuSO4 can also be added for vacuum distillation and refinement.
6. Carbon dioxide method: Under the catalysis of palladium complex, it is obtained by reacting carbon dioxide and hydrogen in triethylamine aqueous solution at 140 ~ 160 ℃.
7. Synthetic acidification method and high-pressure catalytic method are mainly used. Synthetic acidification method: Use carbon monoxide and sodium hydroxide produced by coke combustion to synthesize sodium formate, then acidify it with sulfuric acid, and obtain it through distillation. High-pressure catalytic method: obtained by reacting carbon monoxide and water vapor in the presence of a catalyst at high temperature and high pressure.
8. Mix formic acid and phosphorus pentoxide, perform vacuum distillation, and repeat 5 to 10 times to obtain anhydrous formic acid. However, the yield is low, takes a long time, and may cause some decomposition. Distilling formic acid and boric acid is easy to operate and has better results. The boric acid is dehydrated at medium-high temperature until no more bubbles are produced. The resulting melt is poured onto an iron sheet, cooled in a desiccator, and then ground into powder. Add boric acid phenol fine powder to formic acid and leave it for a few days to form a hard lump. Separate the clear liquid and conduct vacuum distillation. Collect the 22-25 ℃/12-18 mm fraction as the product. The still should have fully ground joints and be protected by a drying tube.
Standards
GB/T 2093-2011 Formic acid for industrial use
Formic acid content: Use phenolphthalein as indicator and titrate with sodium hydroxide solution.
Chloride: In the acidic solution of nitric acid, the chloride ions in the sample react with silver nitrate to form silver chloride, which is compared with the standard turbidimetric solution.
Sulfate: Add sodium carbonate to the sample to make the sulfate radical in formic acid generate sulfate. Add barium chloride solution in the presence of hydrochloric acid to generate barium sulfate, and perform turbidity comparison with the standard turbidimetric solution.
Iron (Fe2+): According to the regulations of GB/T 3049-2006.
Evaporation residue: According to the regulations of GB/T 6026-1998.