Production method of 1,2,3,6-tetrahydrophthalimide

Abstract

The invention provides a production method of 1,2,3,6-tetrahydrophthalimide, which comprises the following steps: a) mixing 1,2,3,6-tetrahydrophthalimide with ammonia gas, and carrying out low-temperature reaction to obtain a reaction intermediate, wherein the temperature of the low-temperature reaction is 0-30 DEG C; and b) carrying out a dehydration ring-closure reaction on the reaction intermediate obtained in the step a) to obtain the 1,2,3,6-tetrahydrophthalimide. Compared with the prior art, with 1,2,3,6-tetrahydrophthalic anhydride and ammonia gas as raw materials, a stable intermediateis generated in a low-temperature anhydrous environment through a gas-solid method, then the intermediate is subjected to a dehydration ring-closure reaction, a product is obtained, no solvent is used in the whole process, the process is simple, a large amount of water or solvent does not need to be removed in the intermediate heating process, only water generated in the reaction needs to be distilled out, and energy consumption is greatly reduced; the comprehensive two-step yield can reach 97% or higher; moreover, gases such as carbon dioxide are not generated in the reaction process, and redundant ammonia gas can be recycled, so that the environmental protection cost is greatly saved.

Description

technical field [0001] The invention relates to the technical field of organic chemical synthesis, and more specifically relates to a production method of 1,2,3,6-tetrahydrophthalimide. Background technique [0002] At present, the industrial production methods of 1,2,3,6-tetrahydrophthalimide mainly include urea method, ammonia water method and hydrogenation method, and the specific implementation schemes are as follows: [0003] (1) Urea method: use tetrahydrophthalic anhydride and urea as raw materials, use DMF as solvent, adopt a one-time feeding method according to a certain proportion, heat up to 144°C, cool down and separate the solid after reacting for 90 minutes, wash and dry, and obtain finished products 1,2, 3,6-tetrahydrophthalimide; the yield is 80%, and the purity is over 98%. [0004] (2) Ammonia water method: using 1,2,3,6-tetrahydrophthalic anhydride and ammonia water as raw materials, under a certain raw material ratio and reaction temperature, excess wate...

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Problems solved by technology

[0007] (1) Urea method: ① Currently, urea synthesis methods mostly use solvent methods. The use of organic solvents will make product purification difficult, and the amount of imine lost to the target purity will be large; ② Urea will produce side reactions such as self-polymerization at high temperatures, and a large amount of The production of by-products has an adverse effect on the synthesis of imines, so the selectivity is low and the yield is low; ③ a large amount of waste gas and waste water are generated during the reaction, and the treatment cost is high, which has a great impact on the environment

[0008] (2) Ammonia water method: ①A large amount of dehydration is required in the later stage of the ammonia water method, and the energy consumption is high; ②Ammonia water reacts with phthalic anhydride during the input process, and the heat release is large, so it needs to be input in batches and add a cooling device. , energy cost; ③ a large amount of water in ammonia water will hydrolyze phthalic anhydride at high temperature, which is not conducive to the formation of imine in the later stage, and the selectivity is low

[0009] (3) Hydrogenation method: ① Hydrogenation is a dangerous process, which requires high safety and equipment; ② The reaction time is too long, which is 6 to 7 times that of other reaction times, which is not conducive to large-scale production; ③ Use DMF as a solvent, Solvent loss increases costs

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