| This paper conducted a detailed study of the reaction condition of five common synthesis methods of4-hydroxybenzonitrile, including p-hydroxybenzoic acid direct melt method, p-hydroxybenzoic acid direct solvent dehydration ammoniation method, p-hydroxybenzoic acid high-pressure ammonia method, p-hydroxybenzoic acid step-by-step ammoniation method as well as methyl p-hydroxybenzoate gas-solid phase catalytic ammoniation method and proposed a new reaction mechanism of carboxylic acid dehydration ammoniation.(1) Through inspecting the impact of reaction yield from mole ratio of reaction materials, dehydrating agent and catalyst’s selection and dosage, reaction temperature, pressure and reaction time etc, which was to chose the best suitable for the production of green chemical process-the carboxylic direct solvent dehydration ammoniation method and this the best process condition is:0.1mol p-hydroxybenzoic acid,0.25mol urea and0.3mol dehydrating agent sulfamic acid are dissolved in60ml solvent benzoate, and added the Al2O3is catalyst which mass is3%of the solvent. Slowly heated to150℃for1hour, and then raise to190℃, added0.05mol urea, heated preservation for1.5hour, then prepared the yield was78%-82%of the desired product.(2) Finding the main component of the waste residue was cyan uric acid and ammonia sulfate by infrared analysis, confirmed the truth that the route of reaction raw material urea thermal decomposition was direct delaminate product burette and cyan uric acid not direct decomposition of ammonia and CO2reported in the literature. After the hydrolysis of the dehydrating agent sulfamic acid used in the reaction, ammonium bisulfate was generated, then ammonium bisulfate and ammonia generate ammonium sulfate finally. As a result, obtain a new reaction mechanism of carboxylic acid dehydration ammoniated. |
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