Organic compounds -- part of the class 532-570 series – Organic compounds – Oxygen containing
Reexamination Certificate
1999-07-14
2001-02-13
Shippen, Michael L. (Department: 1621)
Organic compounds -- part of the class 532-570 series
Organic compounds
Oxygen containing
C568S803000, C568S806000
Reexamination Certificate
active
06187964
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a method of producing a phenol compound from an aromatic aldehyde. The phenol compound is a very useful compound as a material or intermediate for producing a synthetic resin, an insecticide, an antioxidant, etc.
The phenol compound such as phenol, alkylphenol, etc. has been produced by separation of tar acids or various synthetic methods such as a cymene method. However, a high-purity phenol compound is difficult to obtain by the separation due to small difference in the physical properties between the isomers as well as the homologies. In the synthetic methods, a sulfonation-alkali fusion method is disadvantageous because isomers are by-produced and waste disposal is required. The cymene method requires complicated facilities.
One of other known synthetic method is a method utilizing Baeyer-Villiger reaction, in which the phenol compound is produced through a reaction between the aromatic aldehyde and a peroxide such as peracetic acid, perbenzoic acid, etc. This method is suitable for producing a high-purity phenol compound with less isomers.
Although Baeyer-Villiger reaction generally provides the phenol compound quantitatively in the reaction between an aromatic aldehyde having an electron donative group and a peroxide, provides a large amount of aromatic carboxylic acid with a little phenol compound in the reaction between an aromatic aldehyde having an electron attractive group and an peroxide. Therefore, various proposals have been made to increase the yield of the phenol compound.
For example, Japanese Patent Application Laid-Open No. 47-27933 proposes to quantitatively synthesize the alkylphenol from an aromatic aldehyde using an organic peracid derived from a carboxylic acid showing pKa smaller than 4 in water.
Japanese Patent Application Laid-Open No. 48-56635 proposes a method where the alkylphenol is obtained by a reaction between hydrogen peroxide and an aromatic aldehyde in the presence of an inorganic acid.
However, since performic acid, peracetic acid, hydrogen peroxide, etc. used in these methods are relatively expensive and have danger of explosion, special care has to be made in handling them.
To avoid the danger of direct handling, Japanese Patent Application Laid-Open No. 1-121229 proposes a method of producing a phenol compound, where an aqueous hydrogen peroxide is added to a solution of an aromatic aldehyde in formic acid to form performic acid in situ in the reaction system, and the aromatic aldehyde is oxidized by performic acid to an aryl formate which is then hydrolyzed. However, this method involves the following problems:
(1) Although the method is carried out safely as compared with a method directly utilizing an organic peracid such as performic acid, perbenzoic acid and peracetic acid, a cyclic perether is generated by the reaction between the aromatic aldehyde and hydrogen peroxide. The cyclic perether is in danger of explosion and requires very expensive facilities for safety.
(2) A high-boiling product is produced in the step of forming the aryl formate by the reaction between hydrogen peroxide and a phenol compound formed from a part of the synthesized aryl formate. This reduces the yield of the phenol compound.
Further proposed is a method using another oxidizing agent in place of the peroxide. U.S. Pat. No. 5,237,092 proposes a method where an aromatic aldehyde is oxidized in a water-free condition to an aryl formate and an aromatic carboxylic acid using an oxygen-containing gas as the oxidizing agent. Although this method uses an inexpensive oxidizing agent and is easy to practice, it involves the following problems:
(1) The unreacted aromatic aldehyde and its corresponding aryl formate are hardly separated from each other by distillation due to the extremely small difference between the boiling points. For example, the boiling point of 2,4-dimethylbenzaldehyde is 117° C./25 Torr, while 114° C./25 Torr for 2,4-xylyl formate.
(2) An approach avoiding the above problem is to first completely oxidize the aromatic aldehyde to an aromatic peracid thereby reducing the amount of the unreacted aromatic aldehyde. Thereafter, the aromatic peracid is reacted with freshly supplied aromatic aldehyde to produce the aryl formate and the aromatic carboxylic acid. However, this method requires two-stage reaction and increases the selectivity of the aromatic carboxylic acid with significant decrease in the selectivity of the aryl formate.
SUMMARY OF THE INVENTION
Accordingly, an object of the present invention is to provide a safe and industrially efficient method of producing the phenol compound without using an organic peracid and hydrogen peroxide which are expensive and in danger of explosion.
Another object of the present invention is to provide a method of producing the phenol compound using hydrogen peroxide, which is improved in safety and efficiency.
As a result of intense research on safe and efficient production method of the phenol compound, the inventors have found that the aryl formate and the aromatic carboxylic acid can be advantageously produced, without requiring a solvent in the oxidation of the aromatic aldehyde, by oxidizing the aromatic aldehyde to the aryl formate and the aromatic carboxylic acid with an oxygen-containing gas in a water-free condition, and then separating the aromatic carboxylic acid while recycling a mixture of the aryl formate and the residual aromatic aldehyde difficult to separate by distillation into the oxidation process, thereby concentrating the aryl formate in the reaction liquid from the oxidation process to make the separation of the aryl formate and the residual aromatic aldehyde by distillation easy. The inventors have also found that the phenol compound can be efficiently obtained by decomposing and converting the resulting aryl formate into a corresponding phenol compound, and that an alkali metal compound exhibits a specific catalytic effect in decomposing the aryl formate to efficiently produce the phenol compound.
The inventors have further found that the conversion of the aromatic aldehyde and the selectivity of the aryl formate can be increased without increasing the selectivity of the aromatic carboxylic acid to thereby produce the aryl formate in a high yield, i.e., produce the phenol compound efficiently when the oxidation of the aromatic aldehyde with the oxygen-containing gas is carried out in an organic solvent having substantially no ability of dissolving water.
In addition, the inventors have made intense research on the methods of producing the phenol compound from the aromatic aldehyde using hydrogen peroxide. As a result thereof, the inventors have found that the amounts of the cyclic perether and the high-boiling product in the synthesis of the aryl formate by the reaction between the aromatic aldehyde having at least one substituent group on the aromatic ring, formic acid and the aqueous hydrogen peroxide can be significantly reduced by using an organic solvent having substantially no ability of dissolving water, thereby improving the yield of the phenol compound and the safety of the production method.
The present invention has been achieved by these findings.
Thus, in a first aspect of the present invention, there is provided a method of producing a phenol compound comprising a first step of producing an aryl formate and an aromatic carboxylic acid by oxidizing an aromatic aldehyde with an oxygen-containing gas to form a reaction product; a second step of separating the aromatic carboxylic acid, a mixture of the aryl formate and an unreacted aromatic aldehyde and the aryl formate from the reaction product obtained in the first step; and a third step of decomposing the aryl formate to the phenol compound; the mixture of aryl formate and the unreacted aromatic aldehyde separated in the second step being recycled to the first step.
In a second aspect of the present invention, there is provided a method of producing an aryl formate and an aromatic carboxylic acid comprising a first step of producing an aryl formate and an a
Sakai Yukio
Shoji Yasuhiro
Tanaka Kazuo
Yoshimura Masatoshi
Yoshimura Takafumi
Antonelli Terry Stout & Kraus LLP
Mitsubishi Gas Chemical Company Inc.
Shippen Michael L.
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