Clean production method of vanillin

Abstract

The invention discloses a clean production method of oxidizing 3-methoxy-4-hydroxy mandelic acid for joint production of vanillin and superfine silver powder under an alkaline condition by adopting silver nitrate. The clean production method comprises the following steps: adding a silver nitrate solution, a 3-methoxy-4-hydroxy mandelic acid solution and a sodium hydroxide solution in a parallel flow manner into a reactor, reacting to generate a 3-methoxy-4-hydroxy acetophenone sodium solution and superfine silver powder, filtering and separating the generated silver powder, washing with deionized water and ethyl alcohol sequentially, and drying to obtain the superfine silver powder, wherein the reduction yield of the silver powder is 99.4 per cent to 100 per cent; acidizing filter liquor after the silver powder is separated, performing decarboxylation on 3-methoxy-4-hydroxy benzoylformic acid to generate the vanillin, using methylbenzene to extract the vanillin therein, recycling the methylbenzene solvent, and performing recrystallization on residues in an ethanol aqueous solution to obtain the vanillin, wherein the oxidation yield of the methoxy-4-hydroxy mandelic acid is 95.7 per cent to 98.5 per cent. The silver nitrate is taken as an oxidizing agent to prepare the vanillin, so that the oxidation yield is improved, and the oxidation reaction time is shortened. Two practical fine chemical products can be produced simultaneously, the raw materials can be sufficiently utilized, the generation of waste materials is reduced, the production cost is reduced, and the technological process is safe and environment-friendly.

Description

technical field [0001] The invention relates to a clean production method of vanillin, in particular to a clean production method for jointly producing vanillin and superfine silver powder by oxidizing 3-methoxy-4-hydroxymandelic acid under alkaline conditions with silver nitrate, Two kinds of practical fine chemical products can be obtained at the same time, belonging to the fields of new chemical materials and environmental protection. Background technique [0002] Vanillin (English name Vanillin), chemical name 3-methoxy-4-hydroxybenzaldehyde, chemical formula C 8 h 8 O 3 , Molecular weight 152.2, white needle crystal, melting point 81-83 ℃, boiling point 284 ℃, slightly soluble in water, soluble in ethanol and chloroform, with vanilla aroma and strong milky aroma. Vanillin is one of the most produced synthetic flavors in the world, and it is also an important intermediate for synthetic drugs and chemical products. China has a production capacity of 25,000 tons of vani...

AI Technical Summary

Problems solved by technology

For example, the air catalytic oxidation method is adopted in the industrial production of vanillin, the oxidation reaction yield is 86%-90%, and the oxidation reaction time is 12-24 hours. The acid is not stable enough, and there is a relatively serious decomposition or polymerization phenomenon in the long-term oxidation process at a higher temperature

[0007] The study found that if copper oxide is used for chemical oxidation, the oxidation reaction yield is as high as 98%, and the oxidation reaction time is only 1.5-2.5 hours. The problem is that the formed cuprous oxide exists in the form of colloid, which is difficult to separate from the reaction solution and To achieve recycling, it is necessary to select an oxidant that is easy to separate after the oxidation reaction is completed

[0012] The deficiencies in the preparation of reducing agents from fine silver powder include: (1) The reducing agents hydrazine hydrate, formaldehyde and hydroquinone are poisonous, highly irritating, and have serious environmental and safety problems; (2) The cost of reducing agents sodium borohydride and hydroquinone is too high , affecting the production efficiency of silver powder; (3) The reducing agent ascorbic acid is sensitive to changes in the acidity, concentration and temperature of the reducing system, and the production conditions are not easy to control; (4) Most reducing agents need to be used in conjunction with a large number of dispersants, resulting in the subsequent separation of silver powder Difficult; (5) The feed ratio of commonly used reducing agents is too large, and there is a lack of safe and stable new reducing agents

[0013] In the above ultra-fine silver powder production process, the reducing agent is oxidized to generate a large amount of useless waste. The treatment process of these pollutants is troublesome. At present, only because of the high added value of product production and small production scale, the problem of environmental pollution has not been fully addressed. Pay attention to