KR102307579B1 - Method for preparing benzaldehyde - Google Patents

Abstract

Disclosed are a method for producing benzaldehyde and a carbon electrode for producing benzaldehyde. In the above production method, benzaldehyde is prepared by oxidizing toluene through direct electron exchange between the carbon electrode and toluene. The above manufacturing method oxidizes toluene using only electrical energy applied to the carbon electrode under room temperature, atmospheric pressure and air conditions, thereby producing benzaldehyde in a simple and simple manner and reducing manufacturing cost. In addition, the production method has the effect of high production yield and selectivity of benzaldehyde.

Description

Method for producing benzaldehyde

Disclosed herein are a method for producing benzaldehyde and a carbon electrode for producing benzaldehyde.

The selective oxidation of toluene to benzaldehyde is a critically important technique for the production of versatile intermediates for use in the manufacture of perfumes, pharmaceuticals and plasticizers. In particular, the production of benzaldehyde through toluene oxidation reaction is a more difficult technique than the production of benzoic acid, because benzaldehyde is generally oxidized several times more easily than toluene and converted to benzoic acid. Therefore, various studies have been conducted to increase the selectivity of benzaldehyde in the oxidation reaction of toluene.

As a representative reaction for producing benzaldehyde, a method of reacting toluene with HCl and CO is known, but it has disadvantages in that high pressure CO must be used and a large amount of chloride by-products are generated. Although there are examples of using halogenated benzenes such as chlorobenzene and bromobenzene as raw materials, there is a problem in that expensive Pd catalysts must be used in this case.

A method for producing benzaldehyde from styrene by using hydrogen peroxide as an oxidizing agent in the presence of a V ₂ O ₄ -ZrO ₂ complex catalyst is also known, but the method is difficult to prepare a complex catalyst and has a low conversion rate of 61.3%. have. In addition, there is a disadvantage of using an expensive oxidizing agent, hydrogen peroxide. As such, in the past, benzaldehyde was mainly produced using a thermal oxidation method using a metal catalyst. Recently, an electrochemical toluene oxidation method capable of producing benzaldehyde at room temperature is being studied.

The electrochemical organic material oxidation reaction is largely known as an indirect oxidation method using an organic mediator and a metal complex catalyst and a method in which a reactant is directly oxidized on the electrode surface. In the case of the indirect oxidation method, there is an advantage in that the electrical energy required for the oxidation reaction can be saved by using an organic medium. In this regard, a method for preparing benzaldehyde at a relatively low oxidation voltage using N-hydroxyphthalimide (NHPI) as an organic medium is known. However, the method has a problem of showing a fairly low yield of 57% or less. Recently, a method for preparing benzaldehyde in a relatively high yield of 77% using _{Cl 4} NHPI having a lower oxidation voltage than NHPI has been reported. However, this method has a problem in that the organic medium reacts with the reactant radical or the metal complex used together chelates the product, thereby lowering the selectivity of the desired product. As one of the methods to overcome these shortcomings, a method of preventing an organic medium from reacting with a reactant radical through electrochemical iodination in advance has been proposed, but since this method also uses an organic medium, the problem of separation and recovery still remains.

CN 107879924 A

In one aspect, the present specification relates to a method for producing benzaldehyde used for various purposes throughout the industry, and a method for producing benzaldehyde from toluene by using a carbon material as an electrode and oxidizing toluene through direct electron exchange aims to provide

In another aspect, an object of the present specification is to provide a carbon electrode having a use for preparing benzaldehyde.

In one aspect, the technology disclosed herein provides a method for producing benzaldehyde through electrochemical oxidation of toluene, comprising the step of oxidizing toluene using a carbon electrode.

In an exemplary embodiment, the manufacturing method may be to induce an electrochemical oxidation reaction of toluene by applying a current to an electrochemical cell in which the cathode part and the anode part are separated by a separator.

In an exemplary embodiment, the carbon electrode may be at least one selected from the group consisting of a graphite rod, a glassy carbon plate, and carbon paper.

In an exemplary embodiment, the manufacturing method may be to apply a current of 5 mA to 30 mA to the carbon electrode.

In an exemplary embodiment, the carbon electrode may be included in the anode part.

In an exemplary embodiment, the cathode part may include a conductive metal electrode.

In an exemplary embodiment, the manufacturing method may be to add toluene and a solvent to the anode part.

In an exemplary embodiment, the solvent may include at least one of acetonitrile and hexafluoroisopropanol.

In an exemplary embodiment, the solvent may include acetonitrile and hexafluoroisopropanol.

In an exemplary embodiment, the oxidation reaction may be to use one or more selected from the group consisting of air, oxygen, and peroxides as the oxidizing agent.

In an exemplary embodiment, the oxidation reaction may be carried out at room temperature and under normal pressure.

In an exemplary embodiment, the reaction time of the oxidation reaction may be 4 to 50 hours.

In another aspect, the technology disclosed herein provides a carbon electrode for production of benzaldehyde, which has use for producing benzaldehyde from toluene, and produces benzaldehyde by inducing an electrochemical oxidation reaction of toluene.

In an exemplary embodiment, the carbon electrode may be at least one selected from the group consisting of a graphite rod, a glassy carbon plate, and carbon paper.

In one aspect, the technology disclosed herein is effective in providing a method for producing benzaldehyde from toluene by using a carbon material as an electrode and oxidizing toluene through direct electron exchange.

In another aspect, the method for producing benzaldehyde according to the present specification oxidizes toluene using only electric energy applied to a carbon electrode under normal temperature, atmospheric pressure and air conditions without using an organic medium or a metal catalyst. It has the effect of producing aldehydes.

In another aspect, the method for producing benzaldehyde according to the present specification has an effect of reducing manufacturing costs by oxidizing toluene using an inexpensive carbon material as an electrode.

In another aspect, the method for producing benzaldehyde according to the present specification has an effect of high production yield and selectivity of benzaldehyde.

In another aspect, the technology disclosed herein is effective in providing a carbon electrode having a use for preparing benzaldehyde.

1 shows a schematic diagram of an electrochemical oxidation method of toluene according to an embodiment of the present specification. Specifically, in the carbon electrode used as the anode, toluene (ArCH ₃ ) releases electrons and oxidizes to form a radical, and this radical meets oxygen to form benzaldehyde.
2 shows a scanning electron microscope (SEM) image of carbon electrodes used as an anode (anode) material according to an embodiment of the present specification.

Hereinafter, the present invention will be described in detail.

In one aspect, the technology disclosed herein provides a method for producing benzaldehyde through electrochemical oxidation of toluene, comprising the step of oxidizing toluene using a carbon electrode.

The present specification discloses a technique for producing benzaldehyde by oxidizing toluene through direct electron exchange between toluene with a carbon electrode. That is, in the present specification, benzaldehyde is prepared through an electrochemical oxidation reaction using toluene as a raw material.

For example, Scheme 1 below shows a reaction for preparing benzaldehyde from toluene.

[Scheme 1]

In an exemplary embodiment, the manufacturing method may be to induce an electrochemical oxidation reaction of toluene by applying a current to an electrochemical cell in which the cathode part and the anode part are separated by a separator.

In an exemplary embodiment, it may be preferable to select and use a relatively inexpensive and easily available material in consideration of cost reduction and the like, but using a carbon electrode having high conductivity.

In an exemplary embodiment, the carbon electrode may be at least one selected from the group consisting of a graphite rod, a glassy carbon plate, and carbon paper.

In an exemplary embodiment, the manufacturing method may be to apply a current of 5 mA to 30 mA to the carbon electrode. Accordingly, the effect of preventing the problem that the reaction time may take a long time to obtain a conversion rate close to 100% due to the low applied current, and the problem that the selectivity to benzaldehyde may be lowered due to the increase of by-products due to the high applied current there is In this aspect, the applied current may be preferably 5 mA to 15 mA.

In another exemplary embodiment, the manufacturing method is 5 mA or more, 6 mA or more, 7 mA or more, 8 mA or more, 9 mA or more, or 10 mA or more, and 30 mA or less, 28 mA or less, 26 mA or less , 24 mA or less, 22 mA or less, 20 mA or less, 18 mA or less, or 16 mA or less may be applied.

In an exemplary embodiment, the carbon electrode may be included in the anode part.

In an exemplary embodiment, the cathode part may include a conductive metal electrode.

In an exemplary embodiment, the conductive metal electrode may be, for example, but not limited to, nickel, stainless steel, and/or platinum wire.

In an exemplary embodiment, the conductive metal electrode may use a platinum wire to increase the reaction efficiency while lowering the overall voltage.

In an exemplary embodiment, the manufacturing method may be to add toluene and a solvent to the anode part.

In an exemplary embodiment, the solvent for the toluene oxidation reaction may include acetonitrile and hexafluoroisopropanol. For example, when acetone is used as a solvent, the reaction may not proceed, and when acetic acid is used as a solvent, the selectivity to benzoic acid may be higher than that of benzaldehyde. Therefore, it may be preferable in terms of yield and selectivity of benzaldehyde to use acetonitrile and hexafluoroisopropanol together as a solvent for the toluene oxidation reaction.

In an exemplary embodiment, the oxidation reaction may be to use at least one selected from the group consisting of air, oxygen, and peroxides as an oxidizing agent for the toluene oxidation reaction.

In an exemplary embodiment, the peroxide may include tert-butyl hydroperoxide (tBuOOH).

In an exemplary embodiment, the manufacturing method may be to perform the oxidation reaction of toluene under air conditions by applying an electric current to the carbon electrode.

In an exemplary embodiment, the oxidation reaction may be carried out at room temperature and/or under normal pressure.

In an exemplary embodiment, the reaction time of the oxidation reaction may be 4 to 50 hours. If the reaction time is less than 4 hours, the yield may be low, and since the yield is not significantly increased even if it exceeds 50 hours, efficiency may be reduced if the reaction time is too long.

In another exemplary embodiment, the reaction time of the oxidation reaction is 4 hours or more, 6 hours or more, 8 hours or more, 10 hours or more, 12 hours or more, 14 hours or more, 16 hours or more, 18 hours or more, or 20 hours or more. and 50 hours or less, 48 hours or less, 46 hours or less, 44 hours or less, 42 hours or less, or 40 hours or less.

In an exemplary embodiment, in the manufacturing method, the selectivity and/or the yield of benzaldehyde may be adjusted by changing at least one of the type of the carbon electrode, the current applied to the carbon electrode, and the oxidation reaction time.

The method for producing benzaldehyde according to the present specification can oxidize toluene electrochemically through direct electron exchange using a conductive carbon electrode having a low price and excellent durability.

By carrying out the electrochemical oxidation reaction using the direct electron transfer method as described above, it is possible to produce benzaldehyde very simply and effectively without the aid of an organic medium or an oxidizing agent, as well as control the selectivity and yield. In particular, since the electrode and reaction raw materials according to the present specification are materials that can be easily purchased at a low price, the cost and time required for the entire reaction can be significantly reduced.

In another aspect, the technology disclosed herein provides a carbon electrode for production of benzaldehyde, which has use for producing benzaldehyde from toluene, and produces benzaldehyde by inducing an electrochemical oxidation reaction of toluene. Benzaldehyde can be produced by directly oxidizing toluene using a carbon electrode.

In an exemplary embodiment, the carbon electrode may be at least one selected from the group consisting of a graphite rod, a glassy carbon plate, and carbon paper.

Hereinafter, the present invention will be described in more detail through examples. These examples are only for illustrating the present invention, and it will be apparent to those of ordinary skill in the art that the scope of the present invention is not to be construed as being limited by these examples.

Experimental Example 1.

Using an electrochemical cell in which the cathode part and the anode part were separated by a Nafion membrane, toluene 230 mg (2.5 mmol), hexafluoroisopropanol (HFIP) 5 mL, acetonitrile (CH ₃ CN) in the anode part 45 mL, lithium perchlorate (LiClO ₄ ) 532 mg (5 mmol) was added, and 50 mL _{of 0.5M sulfuric acid (0.5MH 2} SO _{4 ) was added to the cathode part.} A carbon electrode was used as an anode and a platinum wire was used as a cathode. A graphite rod was used as the carbon electrode. Benzaldehyde was prepared by applying 10 mA for 4 hours at room temperature and pressure under air conditions.

The reaction product was _{diluted with CH 3} CN, and the yield and selectivity of benzaldehyde were quantitatively analyzed by high performance liquid chromatography (HPLC). The yield and selectivity of benzaldehyde were calculated by the following method.

Yield (%) of benzaldehyde (BA) = 100 x amount of BA produced / amount of toluene before reaction

Selectivity (%) of (BA) of benzaldehyde = 100 x Amount of BA produced / Amount of conversion of toluene after reaction

Experimental Example 2.

Benzaldehyde was prepared in the same manner as above and Experimental Example 1, but by variously changing the applied current, and the results are shown in Table 1 below.

Applied current (mA) Toluene conversion (%) Benzaldehyde yield (%) Benzoic acid yield (%) Benzaldehyde selectivity (%) 5 5.5 5.1 0.4 93 10 7.9 7.3 0.6 92 15 13 12 One 92 20 16.2 11 5.2 68 25 20.9 11.1 9.8 53 30 23.8 10.7 13.1 45

As can be seen from Table 1, the yield of benzaldehyde increased from 5.1% to 12% as the applied current was increased from 5 mA to 15 mA, but when the applied current was increased from 25 mA to 30 mA, the yield of benzaldehyde was increased. Rather, it showed a tendency to decrease from 11.1% to 10.7%.

Experimental Example 3.

Benzaldehyde was prepared in the same manner as in Experimental Example 1, but the reaction time was changed to prepare benzaldehyde, and the results are shown in Table 2 below.

reaction time Toluene conversion (%) Benzaldehyde yield (%) Benzoic acid yield (%) Benzaldehyde selectivity (%) 12 35 31.5 3.5 90 50 95 82 13 86

As can be seen from Table 2, as the reaction time was increased, the yield of benzaldehyde increased in proportion to the reaction time.

Experimental Example 4.

Benzaldehyde was prepared in the same manner as in Experimental Example 3, but the toluene oxidation reaction was performed for 50 hours using a glassy carbon plate and carbon paper as a carbon electrode. As a result, the results shown in Table 3 below were obtained.

carbon electrode Toluene conversion (%) Benzaldehyde yield (%) Benzoic acid yield (%) Benzaldehyde selectivity (%) Glassy Carbon Plate 41.7 17.4 24.3 41 carbon paper 34.8 8.5 26.3 24

As can be seen from Table 3, the yield and selectivity of benzaldehyde were changed as the carbon electrode was changed. When the glassy carbon plate was used, the yield and selectivity of benzaldehyde were 17.4% and 41%, respectively, and when carbon paper was used, the yield and selectivity of benzaldehyde were 8.5% and 24%, respectively.

Comparative Example 1.

Benzaldehyde was prepared in the same manner as in Experimental Example 1, but the reaction did not proceed when benzaldehyde was prepared by changing the _{solvent from CH 3 CN to acetone.}

comparative example 2.

Benzaldehyde was prepared in the same manner as in Experimental Example 1, but the oxidizing agent was changed to tert-butyl hydroperoxide (tBuOOH) under air conditions, and 400 μL of tBuOOH was added to the anode part to prepare benzaldehyde as shown in Table 4 below. Both the yield and selectivity of benzaldehyde were greatly reduced.

oxidizer Toluene conversion (%) Benzaldehyde yield (%) Benzoic acid yield (%) Benzaldehyde selectivity (%) ^t BuOOH 8 2 73 27

Comparative Example 3.

Benzaldehyde was prepared in the same manner as in Experimental Example 1, but the toluene oxidation reaction was performed for 4 hours using a metal electrode instead of a carbon electrode. As a result, it was confirmed that the reaction did not proceed. Gold (Au) was used as the metal electrode.

As described above, the preparation method according to the present specification can produce benzaldehyde by a simple, simple and economical method with a high selectivity of 80% or more at an applied current of 5 mA to 15 mA. In addition, the yield of benzaldehyde can be increased up to 82% when the reaction is performed at 10 mA for a long time. In particular, when a graphite rod was used as an anode, the selectivity of benzaldehyde was as high as 86%.

Above, a specific part of the present invention has been described in detail, for those of ordinary skill in the art, this specific description is only a preferred embodiment, and the scope of the present invention is not limited thereby. It will be obvious. Accordingly, the substantial scope of the present invention will be defined by the appended claims and their equivalents.

Claims (13)

An electrochemical oxidation reaction of toluene is induced by applying an electric current to the electrochemical cell in which the cathode part and the anode part are separated by a separator,
Oxidizing toluene using a carbon electrode included in the anode part,
The anode part comprises toluene and a solvent,
The method for producing benzaldehyde through the electrochemical oxidation of toluene, wherein the solvent includes acetonitrile and hexafluoroisopropanol.
delete The method of claim 1,
The carbon electrode is at least one selected from the group consisting of a graphite rod, a glassy carbon plate, and carbon paper. A method for producing benzaldehyde through electrochemical oxidation of toluene.
The method of claim 1,
The method for producing benzaldehyde through the electrochemical oxidation of toluene is to apply a current of 5 mA to 30 mA to the carbon electrode.
delete The method of claim 1,
The method for producing benzaldehyde through the electrochemical oxidation of toluene, wherein the cathode part includes a conductive metal electrode.
delete delete The method of claim 1,
In the oxidation reaction, at least one selected from the group consisting of air, oxygen and peroxides as an oxidizing agent is used. A method for producing benzaldehyde through electrochemical oxidation of toluene.
The method of claim 1,
The method for producing benzaldehyde through the electrochemical oxidation of toluene, wherein the oxidation reaction is carried out at room temperature and under normal pressure.
The method of claim 1,
The reaction time of the oxidation reaction is 4 to 50 hours, the method for producing benzaldehyde through the electrochemical oxidation of toluene.
delete delete

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