Amines are organic compounds in which the hydrogen atoms of ammonia are replaced by hydrocarbon groups. The compounds formed by replacing one, two or three hydrogen atoms in the ammonia molecule with a hydrocarbon group are called the first amine (primary amine), the second amine (secondary amine) and the third amine (tertiary amine). Their general formula is: RNH2—primary amine, R2NH—secondary amine, R3N—tertiary amine. Amines are widely present in the biological world and have extremely important physiological roles. Therefore, the vast majority of drugs contain an amine functional group - an amino group. Proteins, nucleic acids, many hormones, antibiotics, and alkaloids, all contain amino groups, which are complex derivatives of amines.
Industrially, primary amines are synthesized with methanol and ammonia at high temperature through a converter equipped with activated alumina catalysts from time to time, but the methylation reaction does not stop at the one methylamine stage, so the obtained monomethylamine, dimethylamine A mixture of amine and trimethylamine. Controlling the ratio of methanol and ammonia to make ammonia excessive, adding water and circulating trimethylamine is conducive to the generation of monomethylamine and dimethylamine. When the amount of ammonia is 2.5 times that of methanol, the reaction temperature is 425°C, and the reaction pressure is 2.45MPa, Mixed amines with 10-12% monomethylamine, 8-9% dimethylamine and 11-13% trimethylamine can be obtained. Since trimethylamine forms an azeotrope with ammonia and other methylamines under normal pressure, the reaction product adopts a separation method combining pressurized rectification and extractive rectification. Calculated to produce 1t of mixed methylamine, 1500kg of methanol and 500kg of liquid ammonia are needed. According to relevant literature reports, changing the ratio of methanol and ammonia is an effective method to obtain the desired product. When the ratio of methanol and ammonia is 1:1.5, it is the best condition to generate trimethylamine, while the ratio of methanol and ammonia is 1:4. is the optimal condition for the formation of monomethylamine.
Primary amines have a wide range of industrial uses. It can be used as medicine (hormones, caffeine, ephedrine, etc.), pesticides (carbamate, dimethoate, ciprofloxacin, etc.), dyes (alizarin intermediates, anthraquinone-based intermediates, etc.), explosives and fuels (water Raw materials such as gel explosives, monomethyl hydrazine, etc.), surfactants, accelerators, rubber auxiliaries, photographic chemicals and solvents.