JP2005200349A - Method for producing phenolic compound - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for producing a phenolic compound in high yield through enabling the contact between an aromatic compound and hydrogen peroxide to be improved without using any organic solvent and vigorous physical agitation, etc. <P>SOLUTION: The method for producing the phenolic compound comprises carrying out a reaction between the aromatic compound and hydrogen peroxide in a heterogeneous phase system in the presence of a solid catalyst to effect direct hydroxylation of the aromatic compound. In this method, the reaction is carried out using a micropacked bed catalyst reactor. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

The present invention relates to a process for producing phenols by direct hydroxylation of an aromatic compound by reacting an aromatic compound and hydrogen peroxide in the presence of a solid catalyst in a heterogeneous phase system. Phenols are useful compounds as synthetic raw materials for pharmaceutical intermediates and various functional materials.

Representative examples of phenols include phenol and cresol. These are industrially produced by decomposing cumene hydroperoxide or cymene hydroperoxide produced by oxidation after conversion to cumene or cymene from benzene or toluene. However, such a multi-step process is not only energetically disadvantageous, but also has problems such as the generation of an equivalent amount of a non-target product such as acetone.

Thus, many methods have been studied for a long time to directly hydroxylate aromatic compounds in a single step. In particular, the method using hydrogen peroxide as an oxidant is attracting attention because it is easy to handle and can be reduced to the environment because it becomes water after the oxidation reaction.

Patent Documents 1 to 3 describe a method for directly hydroxylating an aromatic compound by reacting an aromatic compound with hydrogen peroxide in the presence of a titanosilicate catalyst. In general, hydrogen peroxide does not substantially mix with aromatic compounds in a liquid or aqueous solution. Therefore, in these methods, by contacting an appropriate organic solvent, the contact between the aromatic compound and hydrogen peroxide is improved, and the yield of phenols is increased. However, when an organic solvent is used, the organic solvent itself may react with the oxidizing agent, and there are disadvantages such as an energy cost for the separation process of the organic solvent.

Non-Patent Documents 1 and 2 describe that an aromatic compound is directly hydroxylated by reacting an aromatic compound with hydrogen peroxide in a liquid-liquid solid three-phase system without using an organic solvent in the presence of a titanosilicate catalyst. How to do is described. However, these methods require vigorous physical agitation to improve the contact between the aromatic compound and hydrogen peroxide. When vigorous physical agitation is performed, the solid catalyst to be used is crushed and it becomes difficult to recover the catalyst after the reaction.

On the other hand, a method of reacting an aromatic compound with hydrogen peroxide using a microreactor has been studied. The microreactor means a reactor having a micro space on a micrometer scale (several μm to several thousand μm).

Patent Document 4 describes a method of reacting an aromatic compound and a reactant using a microreactor. Patent Documents 5 and 6 describe a method of reacting an organic compound and a peroxide using a microreactor. It is known that reaction heat generated during an oxidation reaction can be efficiently removed by using a microreactor. However, when an aromatic compound and hydrogen peroxide are reacted by these methods, hydrogen peroxide does not substantially mix with the aromatic compound in the liquid or aqueous solution state. Insufficient phenol yields cannot be obtained.

Non-Patent Document 3 describes a method of reacting an organic compound and hydrogen peroxide in the presence of a titanosilicate catalyst using a microreactor. In these methods, since the titanosilicate catalyst is fixed to the wall surface of the microreactor, it is difficult to exchange and recover the deteriorated catalyst after the reaction. The microreactor itself must be replaced, which is disadvantageous in terms of cost.
US Pat. No. 4,396,783 British Patent No. 2169974 Japanese Patent Laid-Open No. 11-240847 Special table 2001-521913 EP 903174 specification JP-A-11-171857 Journal of Catalysis, 178 (1998) 101-107 Catalysis Today, 49 (1999) 185-191 Chemical Communications, (2002) 878-879

An object of the present invention is to solve the above-described problems in the prior art and to provide a method for producing phenols by direct hydroxylation of an aromatic compound.

As a result of extensive research, the present inventors have improved contact between an aromatic compound and hydrogen peroxide without using an organic solvent or vigorous physical stirring by using a micro packed bed catalytic reactor. And the present invention has been achieved by finding that the yield of phenols can be improved.

That is, the present invention relates to a process for producing a phenol by direct hydroxylation of an aromatic compound by reacting the aromatic compound with hydrogen peroxide in a heterogeneous phase system in the presence of a solid catalyst. This is a method for producing phenols, characterized in that the reaction of hydrogen oxide is carried out using a micro packed bed catalytic reactor. The micro packed bed catalyst reactor means a reactor having a minute space filled with a catalyst. The shape of the minute space filled with the catalyst is preferably tubular.

According to the present invention, it is possible to improve the contact between an aromatic compound and hydrogen peroxide without using an organic solvent or vigorous physical stirring, and phenols can be produced in a high yield. Moreover, the energy cost required for the organic solvent separation step can be omitted. Furthermore, since the solid catalyst is not pulverized by vigorous physical agitation, the catalyst can be easily recovered after the reaction.

Further, according to the present invention, heat of reaction generated during the oxidation reaction can be efficiently removed. Therefore, precise temperature control becomes possible and the yield of phenols can be improved. In addition, safety during production can be improved. In addition, deterioration of the catalyst due to overheating can be suppressed.

In addition, according to the present invention, since the solid catalyst is not fixed to the wall surface of the microreactor, the catalyst deteriorated after the reaction can be easily replaced and recovered. It is also possible to regenerate the recovered catalyst and use it again in the reaction.

In the present invention, the micro packed bed catalyst reactor preferably has two or more inflow channels and one or more outflow channels, and a space where the two or more inflow channels merge, and the space has the shortest diameter 1 to 1. A reactor which is a minute space having a size of 10,000 μm, preferably a shortest diameter of 10 to 2000 μm is used. Particularly preferably, a tubular reactor having a minute space with a shortest diameter of 1 to 10,000 μm, preferably a shortest diameter of 10 to 2000 μm is used.

In the present invention, there are no restrictions on the shape of the inflow path, the merge space, and the outflow path of the micro packed bed catalyst reactor used, and the cross-sectional shape perpendicular to the flow direction may be circular or rectangular. May be. In the present invention, a reactor having two or more merge spaces may be used in which the inflow path of the micro packed bed catalyst reactor used is branched into two or more upstream of the merge space.

In the present invention, the microreactor is filled with a solid catalyst such as various metal catalysts and metal oxide catalysts. A zeolite catalyst is preferably used, and a titanosilicate catalyst is more preferably used. Moreover, a solid catalyst may be used alone or a plurality of solid catalysts may be used in combination. Further, a solid catalyst supported on a carrier may be used, or a solid catalyst diluted with a binder may be used.

In the present invention, a microreactor having a microstatic mixer may be used as one of its configurations. The micro static mixer means a static mixer having a micro space on a micrometer scale (several μm to several thousand μm).

The present invention preferably uses a microreactor capable of controlling the temperature. As a method for controlling the temperature, the microreactor may be immersed in a thermostat such as an oil bath, or an electric heater or a heat medium flow path may be attached to the microreactor.

In the present invention, hydrogen peroxide is used as an oxidizing agent in a liquid or aqueous solution state.

In the present invention, the aromatic compound used is not limited. For example, in addition to benzene, alkyl-substituted aromatic hydrocarbons such as toluene, ethylbenzene, xylenes and trimethylbenzenes, aromatic aldehydes such as benzaldehyde, phenol, Examples thereof include phenols such as cresol, aromatic alcohols such as benzyl alcohol and phenethyl alcohol, halogenated benzenes such as chlorobenzene and bromobenzene, and aromatic ethers such as anisole and diphenyl ether.

In the present invention, the produced phenols are compounds in which at least one carbon-hydrogen bond in the carbon forming the aromatic ring of the aromatic compound is converted to a carbon-hydroxy bond. , Phenol, catechol, hydroquinone, resorcin, etc. are produced. From toluene, cresols, polyhydroxytoluenes, etc. are produced. From phenol, catechol, hydroquinone, resorcin, etc. are produced. From anisole, methoxyphenol, Methoxyresorcin is produced. Depending on the reaction conditions, quinones such as benzoquinone may be produced at the same time as the above phenols.

FIG. 1 shows an example of a micro packed bed catalytic reactor used in the present invention, FIG. 1 (a) is a perspective view, and FIG. 1 (b) is a schematic diagram of a cross-sectional shape parallel to the flow direction. . In the figure, 1 is an inflow channel, 2 is an outflow channel, and 3 is a space where the inflow channel merges. For example, the inner diameters of 1 and 2 are 500 μm, and the solid catalyst 4 is filled downstream from the merge space of the outflow path.

FIG. 2 shows another example of the micro packed bed catalytic reactor used in the present invention, FIG. 2 (a) is a perspective view, and FIG. 2 (b) is a schematic diagram of a cross-sectional shape parallel to the flow direction. It is. In the figure, 1 is an inflow channel, 2 is an outflow channel, and 3 is a space where the inflow channel merges. For example, the widths and heights of 1 and 2 are 500 μm, and the solid catalyst 4 is filled downstream from the merge space of the outflow path.
FIG. 3 shows another example of the micro packed bed catalyst reactor used in the present invention, FIG. 3 (a) is a perspective view, and FIG. 3 (b) is a schematic view of a cross-sectional shape parallel to the flow direction. It is. In the figure, 1 is an inflow channel, 2 is an outflow channel, and 3 is a space where the inflow channel merges. For example, the width of 1 and 2 is 5000 μm, the height of 1 and 2 is 50 μm, and the solid catalyst 4 is filled downstream of the merge space of the outflow path.

FIG. 4 shows another example of the micro packed bed catalyst reactor used in the present invention, and is a schematic view of a cross-sectional shape parallel to the flow direction. In the figure, 1 is an inflow channel, 2 is an outflow channel, and 3 is a space where the inflow channel merges. For example, two inflow paths 1 are branched into two upstream of the merge space to form two merge spaces 3, and the width and height of 1 and 2 are 50 μm, and the merge space of the two outflow paths Further, the solid catalyst 4 is filled downstream.

Next, the present invention will be described more specifically with reference to examples. However, the present invention is not limited by these examples.

Example 1
An example of the developed micro packed bed catalyst reactor is given below. A polytetrafluoroethylene tube having an inner diameter of 1000 μm and a length of 50 mm was provided with an in-line filter having a pore diameter of 2 μm and filled with 15 mg of titanosilicate catalyst TS-1 having a particle diameter of 2 to 1000 μm. A tube packed with this catalyst was connected to the outlet of a static micromixer (Single Mixer, IMM, Germany) with a flow path width of 30 μm to produce a micro packed bed catalyst reactor. Since the connector for high performance liquid chromatography was used for the connection part, it could be easily attached and removed, and the catalyst could be easily recovered and replaced. The temperature was controlled by immersing the microreactor in a thermostat set at a predetermined temperature.

Using two syringe pumps (Model 11-IW manufactured by Harvard, USA), benzene and 10 wt% hydrogen peroxide solution were fed and introduced into the microreactor described above. The mass ratio of benzene and hydrogen peroxide was 1: 1, the pump flow rate was set to achieve a predetermined residence time, and the reaction was carried out at 25 ° C.
FIG. 5 is a schematic diagram of the micro packed bed catalyst reactor used in Example 1 of the present invention. Benzene is introduced from one inflow path 1a, 10 wt% hydrogen peroxide water is introduced from the other inflow path 1b, and the liquid that has been merged inside the micro static mixer 5 is attached to a solid catalyst 4 with a filter 6. The reaction is carried out by passing the inside of the filled tube 7, and then taken out from the outflow passage 2 to be an analysis sample.

A certain amount of the mixed solution after the reaction is weighed in a cooled container, and acetonitrile is added to make a homogeneous solution. Phenol was obtained. In addition, benzoquinone was also detected as a sequential oxidation reaction product. With a residence time of 15 seconds, the phenol yield reached 0.4%. In addition, at a residence time of 150 seconds, the phenol yield reached 1.0% (phenol selectivity 82.1%). The phenol yield and phenol selectivity were based on the amount of benzene supplied.

Comparative Example 1
For comparison, a similar reaction was performed using a round bottom flask with a stirrer. Place 1g of titanosilicate catalyst TS-1 with a particle size of 2-1000μm and benzene in a condenser-connected round bottom flask, heat it with vigorous stirring and set to 25 ° C. Was added (the substance ratio of benzene and hydrogen peroxide was 1: 1), and the reaction was carried out while stirring and maintaining the temperature.

The mixed solution after the reaction was analyzed by gas chromatography in the same manner as in Example 1. As a result, 30 minutes were required for the phenol yield to reach 1.0% (phenol selectivity 81.6%). This shows that the phenol packed bed catalytic reactor shown in Example 1 has improved phenol yield per unit time.

Examples 2-6
Furthermore, the reaction was carried out in the same manner as in Example 1 except that the reaction temperature was changed to 35 ° C, 45 ° C, 55 ° C, 65 ° C or 75 ° C. Table 1 shows the phenol yield at a residence time of 15 seconds.

The schematic which shows the shape of the cross section parallel to the perspective view and example of a flow direction of an example of the micro packed bed catalyst reactor used for this invention. The schematic which shows the shape of the cross section parallel to the perspective view and flow direction of another example of the micro packed bed catalyst reactor used for this invention. The schematic which shows the shape of the cross section parallel to the perspective view and flow direction of another example of the micro packed bed catalyst reactor used for this invention. Schematic which shows the shape of the cross section parallel to the flow direction of another example of the micro packed bed catalyst reactor used for this invention. The schematic diagram of an example of the micro packed bed catalyst reactor used for this invention.

Explanation of symbols

1, 1a, 1b Inlet channel
2 Outflow channel
3 Junction space
4 Solid catalyst
5 Micro static mixer
6 Filter
7 tubes

Claims (6)

In a method for producing phenols by direct hydroxylation of an aromatic compound by reacting an aromatic compound with hydrogen peroxide in the presence of a solid catalyst in a heterogeneous phase system,
A process for producing phenols, wherein a reaction between an aromatic compound and hydrogen peroxide is carried out using a micro packed bed catalytic reactor. The micro packed bed catalytic reactor has two or more inflow channels, one or more outflow channels, and a space where the two or more inflow channels merge, and the space is a minute space having a shortest diameter of 1 to 10,000 μm. The method of claim 1, which is a reactor. 3. A process according to claim 2, characterized in that the micro packed bed catalytic reactor has a microspace with a shortest diameter of 10 to 2000 [mu] m. The process according to claim 1, wherein the micro packed bed catalytic reactor comprises a micro static mixer as one of its configurations. The method of claim 1, wherein the micro packed bed catalytic reactor is temperature controllable. The process according to claim 1, wherein the solid catalyst is a titanosilicate catalyst.

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