JPS60193944A - Production of cinnamic acid - Google Patents

Abstract

PURPOSE:To produce cinnamic acid economically, in an industrial scale, in improved yield, suppressing the side reactions, by oxidizing cinnamaldehyde with molecular oxygen in the presence of a heterogeneous high-performance catalyst containing copper and silver. CONSTITUTION:The objective compound is produced by oxidizing cinnamaldehyde with molecular oxygen at 20-80 deg.C, preferably 50-60 deg.C, in an alkaline aqueous medium (preferably keeping the pH of the system to >=9 with sodium hydroxide) using a heterogeneous catalyst containing silver and copper. The heterogeneous catalyst is, e.g. silver and copper supported on a carbonaceous carrier. The silver and copper are used preferably in the form of metal, oxide, etc. The atomic ratio of copper to silver is 0.1-200, pref. about 3-40.

Description

[Detailed description of the invention] The present invention relates to a method for producing cinnamic acid. Conventional.

A method for producing cinnamic acid is the so-called Perk method, in which benzaldehyde is condensed with acetic anhydride and sodium acetate.
It was common to use an in reaction. However, this method has the disadvantage of requiring large amounts of expensive raw materials. Recently, as a new method, cinnamaldehyde obtained by condensation of benzaldehyde and acetaldehyde,
A method for producing cinnamic acid by oxidation with molecular oxygen was proposed. That is, metallic silver or activated carbon is added to a strongly alkaline aqueous solution containing sodium hydroxide, etc.
The supported catalyst was suspended, cinnamaldehyde was added, and 1
When molecular oxygen is blown into the solution, an aqueous solution of cinnamic acid salt is obtained under relatively mild conditions, and cinnamic acid is easily recovered by acid precipitation. This liquid phase oxidation method has low raw material costs and is relatively easy to operate, but since the activity of the silver catalyst is low, a large amount of catalyst must be used, and the condensation and decomposition of the raw material cinnamaldehyde Side reactions such as these often occur together.

It cannot be said that this method is necessarily sufficient as an industrial manufacturing method.

In order to solve these problems, the inventors of the present invention have completed the present invention as a result of intensive studies to find a high-performance catalyst for use in the liquid phase oxidation reaction of cinnamaldehyde in a highly twisted alkaline aqueous medium.

That is, 1. The gist of the present invention is to produce cinnamic acid by oxidizing cinnamaldehyde with molecular oxygen in an alkaline aqueous medium, using a heterogeneous catalyst containing silver and copper as a catalyst. It consists in the method of producing acid.

The method of the present invention will be explained in detail below.

The method of the present invention requires the use of a heterogeneous catalyst containing silver and copper as a catalyst when cinnamaldehyde is oxidized with molecular oxygen in a strongly alkaline aqueous medium to produce cinnamic acid. As such a catalyst, a heterogeneous catalyst in which silver and copper are supported on a carbonaceous carrier can be used. The form of silver and copper as a heterogeneous catalyst is preferably a metal, oxide, etc., and specific examples include metallic silver, iron oxide, metallic copper, cupric oxide, cupric oxide, etc. Particularly with regard to copper, it is well known that the surface state has an intermediate degree of oxidation that cannot be clearly identified, and such a state does not pose any problem. In order to prepare a catalyst in such a state, for example, it is preferable to use a so-called coprecipitation method in which a precipitant or further a reducing agent is added to a mixed aqueous solution of water-soluble salts of silver and copper. Another method that can be used is to impregnate an insoluble copper component with an aqueous silver salt solution and then add a precipitant to deposit it. A representative example of the precipitating agent is a strong alkali such as sodium hydroxide, and the reducing agent is arbitrarily selected from those commonly used as reducing agents such as formalin aqueous solution, hydrazine, aldehydes, and sugars. The ratio (atomic ratio) of copper to silver can vary within a wide range, but may be, for example, 0. / or λθθ, preferably lj: / or λθθ,
More preferably, a value of about 3 to about θ is appropriate.

The catalyst component containing silver and copper as essential elements in the present invention can be used by being supported on a carrier. The carrier is preferably carbonaceous. Examples of carbonaceous carriers include activated carbon, carbon black, graphite, etc., and porous carbon particles obtained by sintering carbon black (macropore carbon, JP-A-F!3-rp-
&/,! (Refer to Publication No. 6) has an appropriate particle size, is easy to handle, has good silver and copper support, and has 4!
Since the pore volume in the small region around 1O-20A, which is a characteristic of the catalyst, is extremely small, the degree of deactivation of the catalyst due to the formation and adhesion of resinous substances is small.

Preferably used. The amount of the carrier to be used is not particularly defined, and for example, it is 1.0 for the total iK of silver and copper (in terms of oxide). It may be about /~/θO times.

The oxidation reaction of the present invention is carried out in a strongly alkaline aqueous medium. As the strong alkali to be used, alkali hydroxides and alkaline earth hydroxides are advantageous from a cost standpoint, and sodium hydroxide is particularly preferred. The hydrogen ion concentration and pH of the solution are preferably maintained at 2 or more during the reaction. As the reaction progresses, cinnamic acid is produced and alkali is consumed, so it is necessary to pay attention to the amount of alkali used and use a slightly excess amount of the alkali compared to the commercial amount.

The amount of water used is not particularly limited and can vary within a wide range; for example, for sodium hydroxide.

By weight ratio! It is sufficient to set the value to about /θθ times.

The catalyst is used as a suspended or fixed bed. When the reaction is carried out batchwise in a suspended bed, the amount of catalyst used is O0/ to 07,000 weight'Jt relative to the raw material cinnamaldehyde.
Preferably! No! It is sufficient to use about 0% by weight. Of course, the reaction can also be carried out continuously. For batch reactions.

It is preferable not to add the entire amount of cinnamaldehyde from the beginning, but to add it gradually as one reaction progresses.

The reaction temperature is 20°C to ro°C, preferably 3θ°C.
A temperature of about 60°C to 60°C is appropriate. Pure oxygen, air, etc. are used as the oxidizing gas.

When using pure oxygen, care must be taken to avoid accidents such as explosions and combustion within the reaction system.

Although the reaction pressure may be normal pressure, it is desirable to slightly increase the pressure, especially when air is used as the oxidizing gas. Although the reaction time can be selected arbitrarily, it is usually preferable to proceed with the reaction until substantially all of the cinnamaldehyde as a raw material is converted. In the case of a batch reaction, the used catalyst is separated and recovered from the reaction system, and then
It can be used as is in the next reaction.

According to the method of the present invention, the amount of expensive silver used as a catalyst can be greatly reduced, and cinnamic acid can be obtained in high yield, so it is extremely useful industrially.

Next, the present invention will be explained more specifically using an example.
The present invention does not go beyond its gist.

The present invention is not limited to the following examples.

Example / Ay-Ou-MFO +7) N silver nitrate 3.20f, nitrate! , 4tg2. Tokukai Shoj4t
Macropore carbon (</θQmesh) having the properties described in -4/, 2-6 Publication Table A, and Example D
A solution prepared by adding 300 - of demineralized water to ♂, 00v is cooled on ice to 0 to 4°C while stirring well. 3j for this thing
After adding 74 f of formalin, 100 g of 4 t, 6N aqueous sodium hydroxide solution was added dropwise until the temperature of the solution was reached. Do not exceed ℃. After the dropwise addition was completed, stirring was continued for 7 hours at a temperature below j°C. After stopping stirring, filter and wash with water (
The catalyst was dried at 1001HtH, 0) and further dried at 720° C. for a day and night, and then used as a catalyst.

A 100 Goff 2 Scooter equipped with a cinnamaldehyde oxidation stirrer, a thermometer, a cinnamaldehyde feed pump, and a gas inlet pipe is equipped with 6 liters of demineralized water.
Add the above catalyst, Of, sodium hydroxide, and stir vigorously.

next! Oxygen-nitrogen mixed gas at 7θcc/min
The liquid temperature is adjusted to aO°C. After this cinnamaldehyde4. ．． (f (0, O1 mol) is fed into the rough feed pump in λ time. After stopping the feed,
Oxygen absorption is observed for a while, but absorption stops after 6 hours. The reaction was stopped after one hour, and the reaction solution was filtered and washed with ethanol. Hydrochloric acid was added to the solution to bring the pH of the reaction solution to about 1.

Analysis by gas chromatography showed that the aldehyde conversion rate was 0%, the cinnamic acid selectivity was -2%, and the benzoic acid selectivity was $/J%.

Example λ A catalyst prepared in the same manner as in Example 1 except that only silver nitrate and copper nitrate were used without adding macropore carbon was used as a catalyst.

When the reaction was carried out using the above catalyst under the same reaction conditions as in Example, the aldehyde conversion rate was 94 tons, the cinnamic acid selectivity was 94 tons, 2%, and the benzoic acid selectivity was 2%. , got a male chi.

Example 3 In the catalyst 3tM manufacturing method of Example/, carbon black (specific surface area 30w1/
f/) was used as a catalyst.

When the reaction was carried out using the above catalyst under the same reaction conditions as in Example, the aldehyde conversion rate was high! , Section 9, a cinnamic acid selectivity of 96.7% and a benzoic acid selectivity of 3.3% were obtained.

Example 2 A solution of silver nitrate, cuprous oxide y, and ta 2 added to 700-g of demineralized water was poured into an icy formalin solution θ while stirring well.
,! ! After adding f, 0.7N aqueous sodium hydroxide solution/θ- was added, and stirring was continued for 30 minutes while maintaining the temperature at 0 to 4°C. After stopping the stirring, the mixture was washed with water and dried under vacuum at 60° C. or lower, which was then used as a catalyst.

When the reaction was carried out using the above catalyst under the same reaction conditions as in Example, the cinnamic acid selectivity was ? 3. ．． 2%.

Benzoic acid selectivity6. I got a male chi.

Example of silver nitrate O0? ? A solution of f, macropore carbon j, Of and demineralized water λθθ- is cooled with water while stirring well to 0~! Cool to ℃. 3 for this one! Thiformin 0.
After adding 4t9f, θ, 7N aqueous sodium hydroxide solution d was added, and stirring was continued for 30 minutes while maintaining the temperature at 0 to 6°C.

After stopping the stirring, it was thoroughly washed and then heated to -0℃.
When the reaction was carried out using the above catalyst under the same reaction conditions, the aldehyde conversion rate was 23.24 #m.
10g% was obtained.

Sender: Mitsubishi Chemical Industries, Ltd. Representative Patent Attorney Hase - (7 others)

Claims (2)

[Claims] (1) A method for producing cinnamic acid, which comprises using a heterogeneous catalyst containing silver and copper as a catalyst when producing cinnamic acid by oxidizing cinnamaldehyde with molecular oxygen in an alkaline aqueous medium. (2) The method according to claim (1), characterized in that a catalyst in which heterogeneous silver and copper are supported on a carbonaceous carrier is used as a catalyst.