Method for synthesizing salicylamide by continuous method

Abstract

The invention discloses a method for synthesizing salicylamide by a continuous method, which comprises the steps of (1) carrying out acylating chlorination reaction on an acylating chlorination reagent phosgene and a salicylic acid solution in a continuous reactor to obtain salicyloyl chloride; (2) carrying out esterification reaction on salicyloyl chloride and methanol in the continuous reactor to obtain methyl salicylate; and (3) carrying out ammoniation reaction on the methyl salicylate and the methanol solution of ammonia in the continuous reactor to obtain salicylamide. The process has the beneficial effects that (1) the reaction yield of methyl salicylate is increased (98% or above), and no wastewater or waste acid is discharged; (2) the reaction yield of salicylamide is improved (98% or above), and no ammonia-nitrogen-containing wastewater is discharged; (3) the process realizes the continuous reaction of salicylamide, and saves the purification energy consumption and cost of the product; and (4) the product purity is high, and the operation is simple.

Description

technical field [0001] The invention relates to a method for synthesizing salicylamide. Background technique [0002] The chemical name of salicylamide is o-hydroxybenzamide, which is an important intermediate of chemical industry, medicine, pesticide, fragrance and liquid crystal with wide application. It is also a kind of medicine itself, which is used to treat fever, headache, joint pain, neuralgia, etc. In recent years, salicylamide, as an important fine chemical intermediate, has been increasing in demand. [0003] The current industrialized production process of salicylic acid generally adopts salicylic acid as starting material, and generates methyl salicylate (for example: CN110563581A) by esterification reaction with methanol under the catalysis of sulfuric acid, and then ammonolysis of methyl salicylate in ammonia water Obtain salicylic amide (CN106518704A), this production technique has obvious deficiency, mainly is: [0004] (1) sulfuric acid consumption is bi...

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Problems solved by technology

[0004] (1) The amount of sulfuric acid is large (accounting for 10% of the total mass), and the post-treatment process will inevitably produce a large amount of waste water and waste acid. Complete conversion, methyl salicylate yield is not high (yield is no more than 85%), methyl salicylate needs rectification and purification at last, energy consumption is high, and production cost is high

[0005] (2) The ammonolysis reaction is carried out under the condition of ammonia water, and the post-reaction treatment produces a large amount of ammonia-containing wastewater. Since the reaction system is carried out in water, methyl salicylate Prone to side reaction hydrolysis to generate salicylic acid, resulting in low yield (yield lower than 90%)

[0006](3) Both esterification and ammonolysis adopt the traditional kettle-type batch process, which has low efficiency and certain fluctuations in product quality

[0007] (4) Although it has been reported in the literature that solid acid, super acid, and strong acid resin are used instead of sulfuric acid for esterification, it is difficult to large-scale industrialization due to high cost

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