Preparation of a silver sponge catalyst and its application in the oxidation of cinnamaldehyde to cinnamic acid

Abstract

The invention provides a sponge silver catalyst preparation method and application of a sponge silver catalyst to oxidation and synthesis of cinnamic acid from cinnamaldehyde. The sponge silver catalyst is prepared by means of adding silver chloride into 5-15% ammonium hydroxide with stirring for more than 30 minutes, then dropwise adding 5-15% of sodium borohydride or potassium borohydride solution, continuing reacting for more than 15 minutes after dropping and performing filtering and washing after action is finished. In the whole reaction process, the mass ratio among ammonia, sodium borohydride or potassium borohydride and the silver chloride is 2-10:0.5-2:10, and the reaction temperature is 0-30 DEG C. The sponge silver is used as the catalyst to be applied to a method for preparing the cinnamic acid from pure oxygen and the cinnamaldehyde. The catalyst prepared by the method can be reused for hundreds of times, and yield of the synthetic cinnamic acid can reach above 95%.

Description

technical field [0001] The invention belongs to the technical field of fine chemical synthesis, and specifically provides preparation of a sponge silver catalyst and its application in oxidative synthesis of cinnamic acid from cinnamaldehyde. technical background [0002] Cinnamic acid (chemical name 3-phenyl-2-acrylic acid) is a very important chemical raw material, which is widely used in the fields of medicine, spices, food, polymer materials, photosensitive materials and synthetic intermediates. At present, there are many synthetic routes for cinnamic acid, mainly perkin method, benzaldehyde-ketene method, styrene-carbon tetrachloride method, benzaldehyde-acetate method and cinnamaldehyde oxidation method. The perkin method is to prepare cinnamic acid from benzaldehyde and acetic anhydride under the catalysis of anhydrous sodium acetate. Rising, its cost is gradually rising, coupled with the low yield and serious pollution of this method, it has gradually lost its compe...

AI Technical Summary

Problems solved by technology

The perkin method is to prepare cinnamic acid from benzaldehyde and acetic anhydride under the catalysis of anhydrous sodium acetate. rising, its cost is gradually rising, coupled with the low yield and serious pollution of this method, it has gradually lost its competitiveness

The styrene-carbon tetrachloride method is to generate 1.3.3.3-tetrachlorophenylpropane by addition of styrene and carbon tetrachloride under the action of a catalyst, and then generate cinnamic acid by alkaline hydrolysis. This process has serious environmental pollution and poor product quality. Difference

The benzaldehyde-acetate method is to condense benzaldehyde and ethyl methyl ester (or ethyl ethyl ester) into cinnamic acid ester under sodium alkoxide, and generate cinnamic acid through acid hydrolysis, alkali hydrolysis, and acidification. The by-product of this process is 3 -Methoxy-phenylpropionic acid is difficult to separate, and the quality is difficult to meet the requirements of commercial products

The benzaldehyde-ketene method is a process developed by BASF in Germany, ketene is highly toxic, and the industry report is unknown

The above-mentioned cinnamic acid preparation methods all have defects that are difficult to overcome, and are gradually eliminated.

[0003] In recent years, people have begun to gradually study the process of preparing cinnamic acid by catalytic oxidation of cinnamaldehyde. For example, Japanese public reports use cinnamaldehyde and pure oxygen as raw materials and Ag / c as a catalyst to prepare cinnamic acid. The yield of cinnamic acid synthesized by this method is relatively high. The pollution is small, but the catalyst is easy to fall off, and the activated carbon is easy to absorb cinnamaldehyde to deactivate the catalyst. After the catalyst is reused for more than 10 times, the activity is greatly reduced. At present, there are only literature reports, and there is no industrial production report.

Chinese patent (publication number: CN102826992A) reports that cinnamaldehyde is used as raw material, pure oxygen is used as oxidant, and nano-silver particles are used as catalyst to oxidize under a pressure lower than 0.45MPa. Its cinnamaldehyde yield of the technique disclosed in this patent is 95.8%, but the Explosion is easy to occur during oxidation in the process, which requires extremely high equipment

Moreover, the conditions for the preparation of nano-silver particle catalysts are quite harsh. Due to the small size of nano-scale silver particles, the loss during filtration is serious, and the number of repetitions is limited. The number of repetitions of the catalyst is only 48-55 times.

[0004] Sponge silver is the silver particle with sponge structure, and the preparation method of existing sponge silver mainly is to reduce silver chloride or silver nitrate with reducing agent, and existing reducing agent generally adopts hydrazine hydrate, sodium thiosulfate, iron-sulfuric acid, Water-soluble aldehydes, etc., in the whole reduction reaction, the phenomenon of incomplete reaction often occurs, and a lot of impurities will appear, causing the sponge silver prepared by the existing method to be limited in purity, surface area, etc., and the activity is small, and even some impurities such as iron, Sulfur, etc. will use catalyst poisoning and lose activity

Images