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Catalytic oxidation method for preparing vanillin

A catalytic oxidation and vanillin technology, which is applied in the preparation of carbon-based compounds, chemical instruments and methods, and the preparation of organic compounds, can solve the problems of inconvenient recycling, difficult product separation, wide explosion limit, etc., and achieve less discharge of three wastes , good selectivity and low cost

Active Publication Date: 2014-11-05
ZHEJIANG NHU CO LTD +2
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

However, in the process of preparing vanillin with p-cresol as a raw material, the one-step oxidation of 4-methylguaiacol to prepare vanillin is a difficult point of the process, which makes the yield of the process relatively low. Selecting a suitable catalyst is Key issues with the process
[0004] In recent years, many patent documents report that using salts of transition metals (such as Co, Cr, Mn, Cu, Ni, Zn, etc.) as catalysts, reacting in strong alkali and methanol solution to synthesize vanillin can obtain 90% conversion (Wherein common is also the cobalt salt catalyst that uses more, and the yield of vanillin can reach more than 70%), but usually this kind of catalyst is difficult to separate from the product in the post-treatment process, and it is inconvenient to recycle and use
Simultaneously, the solvent used in the present p-cresol process is methyl alcohol, because methanol is a kind of poisonous, flammable liquid, flash point is very low (11 ℃), has very wide explosion limit (6~35% / L), very unsafe to use

Method used

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  • Catalytic oxidation method for preparing vanillin
  • Catalytic oxidation method for preparing vanillin
  • Catalytic oxidation method for preparing vanillin

Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0024] The preparation of embodiment 1 catalyst

[0025] a. Synthesis of Schiff base (B)

[0026] Add 50g of acetylacetone to 150ml of ethanol in a 250ml four-necked flask, dropwise add 15g of ethylenediamine, react at 55-60°C for 5 hours after the dropwise addition, cool and crystallize, recrystallize with ethanol, and dry in vacuo to obtain Schiff Base (B), yield 91%.

[0027] With reference to the preparation method of step a, select different raw materials, reaction solvent and reaction temperature, the yield that obtains is shown in the following table:

[0028]

[0029] b. Synthesis of bromo-Schiff base (C)

[0030] Add 10 g of Schiff base (B) and 50 ml of acetonitrile into a 250 ml three-neck flask, add 15.8 g of NBS at room temperature, react for 2 hours, recrystallize with chloroform, and dry in vacuo to obtain brominated Schiff base (C), with a yield of 60%.

[0031] With reference to the preparation method of step b, select different reaction solvents and reac...

Embodiment 2

[0046] The preparation of embodiment 2 vanillin

[0047] In the reaction bottle of 250ml, add 40g4-methylguaiacol respectively, 40g sodium hydroxide, 175g ethylene glycol, the Schiff base metal chelate catalyst (R in formula I) of 0.5g salt group modification 1 , R 2 is H, R is pyridyl, Y - for PF 6 , M is Co), stirring, at a constant temperature of 80°C, under normal pressure, oxygen was introduced to react for 16 hours. After the reaction, water equal to the volume of ethylene glycol was added to the reaction solution, the catalyst was recovered by centrifugation, and the reaction solution of the catalyst was removed. After adding seed crystals and standing at -18°C for 12 hours, vanillin sodium salt crystals are produced, and then the crystals are separated by suction filtration. The crystals obtained by filtration were neutralized with 3.5N dilute hydrochloric acid to pH=4, cooled at 7°C and filtered, the filter cake was dried to obtain a crude product, and recrystalliz...

Embodiment 11

[0051] The preparation of embodiment 11 vanillin

[0052] In the reaction flask of 250ml, add 40g4-methylguaiacol respectively, 40g sodium hydroxide, 150g ethylene glycol, 25g water, the Schiff alkali metal chelate catalyst (R 1 , R 2 Is H, R is N-methylimidazole group, Y - for PF 6 - , M is Fe) and 0.2g salt group modified Schiff base metal chelate catalyst (R 1 , R 2 is H, R is N-methylimidazole group, Y is PF 6 , M is Cu), stirring, at a constant temperature of 85°C, under normal pressure, oxygen was introduced to react for 20 hours. After the reaction, water equal to the volume of ethylene glycol was added to the reaction solution, the catalyst was recovered by centrifugation, and the reaction solution of the catalyst was removed. After adding seed crystals and standing at -18°C for 12 hours, the crystals of vanillin sodium salt were produced. The filtered crystals were neutralized with 3.5N dilute hydrochloric acid to pH=5, cooled at 6°C and filtered, the filter ca...

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Abstract

The invention relates to a method for preparing vanillin. Currently, a vanillin synthesis reaction is carried out in highly basic and methanol solution with transition metal salt as a catalyst and can have a conversion rate of 90%. However, the catalyst is hard to be separated from a product in a post-treatment and inconvenient for recovery. According to the invention, a raw material of 4-methyl guaiacol, a solvent of a mixed solution of glycol or glycol and water and a catalyst selected from one or two of salt group modified schiff base metal chelates are treated with oxidation reaction for 6-25 h with existence of alkali and oxygen or air let in under a normal pressure and at a temperature of 60-120 DEG C. The catalyst employed by the invention has characteristics of stable structure, high activity, good selectivity and convenience for recovery and reuse, and realizes 4-methyl guaiacol conversion rate of 100%, product yield of 85-95% and a vanillin selectivity higher than 85%.

Description

technical field [0001] The invention relates to the preparation of vanillin, in particular to a method for obtaining vanillin by catalyzing and oxidizing 4-methylguaiacol with a Schiff base metal chelate catalyst modified by a salt group. Background technique [0002] Vanillin is an essential ingredient in the processing of food and cosmetics, and it is also a new product with a very large demand. However, relying on natural separation and extraction can not meet the needs of industry. The traditional synthesis routes of vanillin include eugenol route, sassafras oil route, lignin route and guaiacol route, but there are problems such as long synthetic route, many side reactions, low yield, and many industrial wastes to varying degrees. How to find a green chemical process route with simple process, high yield, low cost, easy treatment of three wastes, and suitable for industrialization needs further research. [0003] Since the 1980s, the p-cresol process for preparing vani...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): C07C47/58C07C45/36B01J31/16
Inventor 胡敬辉毛建拥李浩然陈志荣
Owner ZHEJIANG NHU CO LTD