WO2010087599A2

WO2010087599A2 - Method for preparing aromatic carbonate compound

Info

Publication number: WO2010087599A2
Application number: PCT/KR2010/000344
Authority: WO
Inventors: Eun Duck Park; Yong Tae Kim
Original assignee: Ajou University Industry-Academic Cooperation Foundation
Priority date: 2009-02-02
Filing date: 2010-01-19
Publication date: 2010-08-05
Also published as: KR101002123B1; WO2010087599A3; KR20100088901A

Abstract

Provided is a method for preparing an aromatic carbonate compound with a high yield and selectivity over a broader range of reaction temperatures by reacting an aromatic hydroxyl compound with a dialiphatic carbonate and/or aliphatic-aromatic carbonate compound in the presence of an ammonium molybdate compound having a specific chemical structure as a catalyst.

Description

METHOD FOR PREPARING AROMATIC CARBONATE COMPOUND

The present invention relates to a method for preparing an aromatic carbonate compound. More concretely, the present invention relates to a method for preparing an aromatic carbonate compound with a high yield and selectivity by reacting an aromatic hydroxyl compound with a dialiphatic carbonate and/or aliphatic-aromatic carbonate compound in the presence of a specific ammonium molybdate-based catalyst.

In general, aromatic carbonate compounds may be prepared through the following reaction. Concretely, an aromatic hydroxyl compound (i.e., phenolic compound) is allowed to react with a dialiphatic carbonate and/or aliphatic-aromatic carbonate compound to obtain an aromatic carbonate compound such as an aliphatic-aromatic carbonate, a diaromatic carbonate or a mixture thereof.

As used herein, it is to be understood that the term “aromatic carbonate” is the concept of including both aliphatic-aromatic carbonate and diaromatic carbonate.

The reaction paths of between an aromatic hydroxyl compound and a dialiphatic carbonate compound and/or aliphatic-aromatic carbonate compound to produce aromatic carbonate may be represented by the following Reaction Formulas 1 and 2:

[Reaction Formula 1]

[Reaction Formula 2]

wherein R and R’ independently represent an aliphatic alkyl group.

When synthesizing aromatic carbonates (typically, methylphenyl carbonate and diphenyl carbonate) through the reaction paths as shown in the above Reaction Formulas 1 and 2, the reaction equilibrium constants, K₁ and K₂ are low and the reaction rates are also low, and thus the yield of aromatic carbonates becomes low. Many studies have been conducted to solve the above problem. Then, it has been found that K₁ and K₂ which are law at a relatively low reaction temperature have increased when the reaction temperature has increased above 100℃. It has been also found that when the reaction is performed at a relatively high temperature of 150-320℃, high-quality aromatic carbonate can be obtained with a high yield in a short period of time.

However, under such high-temperature reaction conditions, side reactions also increase according to the following Reaction Formulas 3 and 4, resulting in degradation of the selectivity of aromatic carbonate:

[Reaction Formula 3]

[Reaction Formula 4]

ROCO₂Ph -> PhOR + CO₂

wherein R and R’ are the same as defined above.

Particularly, the representative example of PhOR is anisole (methoxybenzene), which is a main byproduct causing degradation of the yield and selectivity of desired aromatic carbonate.

There is a need for developing a catalyst system capable of improving reactivity and selectivity of aromatic carbonate in order to solve the above-mentioned problems. In this context, Lewis acids or Lewis acid-forming compounds, Ti- or Al-based compounds, Pb compounds, organotin compounds, etc. have been used as a catalyst for esterification.

Japanese Patent Laid-Open No. Sho51-105032 discloses a catalyst using Lewis acid, Lewis acid-forming metal compound and transition metal compounds, and particular examples thereof include SnX₄(wherein X is halogen, acetoxy, alkoxy or aryloxy group).

Japanese Patent Laid-Open No. Sho51-10503 discloses AlX₃, TiX₃, TiX₄, UX₄, VOX₃, VX₅, ZnX₂ and FeX₃(wherein X is halogen, acetoxy, alkoxy or aryloxy group) as examples of the Lewis acid, Lewis acid-forming metal compound and transition metal compounds.

However, Lewis acids are not adequate because they are corrosive to cause damage on the reaction system. Further they are not industrially useful because of a low yield of desired product.

Japanese Patent Laid-Open No. Sho54-48733 discloses an organotin catalyst free from tin-halogen bonding. Although the tin-containing catalyst may improve the yield of desired products to some degree, it still has insufficient catalytic activity. The tin-containing catalyst is also disadvantageous in that it easily causes coloration of the reaction mixtures and makes it difficult to purify the products.

US Patent No. 4,410,464 discloses a method for preparing diphenyl carbonate from dimethyl carbonate by using various organotitanium and organotin compounds as catalysts. Particularly, the method disclosed in the ‘464 patent includes reacting dimethyl carbonate with phenol by transesterification to produce methylphenyl carbonate, separating methylphenyl carbonate from the reaction mixture, adding phenol thereto, and forming diphenyl carbonate through disporportionation, etc. However, the methods include a separate two-step reaction, and thus require a relatively high cost for the separation and the equipments.

Japanese Patent Publication No. Sho61-5467 discloses the use of silica-titania (SiO₂-TiO₂) composite oxide as a disproportionation catalyst, Japanese Patent Laid-Open No. Hei4-266856 and US Patent No. 5,354,925 disclose the method for using of titanium dioxide having a large surface area as a catalyst, and Japanese Patent Laid-Open No. Hei8-231472 discloses the use of Ti-supported active carbon as a catalyst.

However, the silica-titania composite oxide catalyst has strong acidity to easily cause decarboxylation as a side reaction, thereby providing a high yield of byproducts. In addition, the titania catalyst has low activity, thereby providing a low yield of the main product. Further, although the above-mentioned catalysts are present as non-homogeneous catalysts at the initial time of reaction, a relatively large portion of the catalysts may be leached into the reaction mixture as the reaction proceeds. Thus, the catalysts may be dissolved into a mixture of the reactants and the products, and thus require separation and purification from the products. Therefore, the above-mentioned catalysts are not sufficient to solve the problems of homogeneous catalysts related to separation and purification.

In addition, Japanese Patent Laid-Open No. Hei8-231472 discloses a method for using a molybdenum-supported silica catalyst, and US Patent No. 5,166,393 discloses a method for preparing diphenyl carbonate by carrying out disproportionation of methyl phenyl carbonate in the presence of lead oxide (PbO₂) as a catalyst at a reaction temperature of 190℃ with a yield of about 50%. Japanese Patent Laid-Open No. Hei7-033714 and US Patent No. 4,182,726 disclose the method for using of a metal compound as a catalyst, such as Fe(OPh₃) or Ti(OPh)₄, in the transesterification between dimethyl carbonate and phenol.

Meanwhile, according to Japanese Patent Laid-Open No. Sho54-63023, when the existing catalysts are used at high temperature, the catalytic reaction produces an ether compound (byproduct, such as anisole, as depicted in the above Reaction Formulas) in addition to the aromatic carbonate compound. In addition, since the starting material, dialiphatic carbonate or aliphatic-aromatic carbonate is decomposed, selectivity to aromatic carbonate decreases, resulting in a drop in yield.

Further, Korean Patent Laid-Open No. 2001-49648 discloses a method for preparing methylphenyl carbonate by reacting dimethyl carbonate with phenol in a batchwise liquid phase reactor in the presence of a molybdenum oxide-supported active carbon catalyst, obtained by supporting a molybdenum precursor on active carbon, and oxidizing the supported catalyst by heat treatment. However, according to the method, it is required that the reaction is carried out at 150℃ or higher. The catalyst shows substantially no activity at a temperature of 140℃ or lower. Thus, the catalyst cannot be applied to a process including a reaction to be performed at low temperature so as to minimize byproducts, such as anisole.

As described above, the catalyst systems according to the prior art may be deactivated, cause the decomposition of the main product, i.e., methylphenyl carbonate and/or diphenyl carbonate, or cause production of an excessive amount of byproducts, such as anisole, when the reaction temperature increases above a predetermined level during the synthesis of aromatic carbonate. Thus, the catalyst systems according to the prior art have limitations in solving the problem of the low yield and low selectivity of a desired product. Under these circumstances, there is an imminent need for overcoming these limitations.

We have conducted a lot of studies to develop a catalyst system that overcomes the problems in the prior art as mentioned above. As a result, it has been found that when an aromatic hydroxyl compound is allowed to react with dialiphatic carbonate and/or aliphatic-aromatic carbonate in the presence of an ammonium molybdate catalyst having a specific chemical structure, an aromatic carbonate can be obtained with a high yield within a short time at a low reaction temperature. It has been also found that the ammonium molybdate catalyst can inhibit formation of byproducts such as anisole at a relatively high reaction temperature, as compared with other catalysts of prior art.

Therefore, it is an object of the present invention to provide a method for preparation of an aromatic carbonate compound with a high yield and high selectivity in a wide range of reaction temperatures including a relatively low reaction temperature (for example, at 150℃ or lower).

It is another object of the present invention to provide a method for preparing an aromatic carbonate compound, which minimizes formation of byproducts during the reaction.

It is still another object of the present invention to provide a method for preparing an aromatic carbonate compound, which uses a catalyst system particularly effective for synthesizing aromatic carbonate to accomplish high conversion in a short time, thereby realizing excellent cost-efficiency.

In one aspect, there is provided a method for preparing an aromatic carbonate compound, comprising:

- reacting at least one carbonate compound selected from the group consisting of the compounds represented by the following Chemical Formula 1 with an aromatic hydroxyl compound represented by the following Chemical Formula 2, in the presence of a catalyst including an ammonium molybdate compound to convert the carbonate compound into an aromatic carbonate compound represented by the following Chemical Formula 3,

wherein the ammonium molybdate compound is represented by the following Chemical Formula 4:

[Chemical Formula 1]

(R¹O)CO(OR²)

[Chemical Formula 2]

R³OH

[Chemical Formula 3]

(R¹O)CO(OR³)

wherein R¹ is a substituted or non-substituted C1-C10 alkyl group, C3-C7 cycloalkyl group, C6-C12 aryl group, or C7-C20 arylalkyl group;

R² is a substituted or non-substituted C1-C10 alkyl group, C3-C7 cycloalkyl group, or C7-C20 arylalkyl group; and

R³ is a substituted or non-substituted C6-C12 aryl group,

[Chemical formula 4]

(NH₄)_xMo_yO_z·nH₂O

wherein x ranges from 7 to 9, y ranges from 8 to 12, x+6y=2z, and n ranges from 0 to 50.

The method for preparing an aromatic carbonate compound according to one aspect of the present invention uses, as a catalyst, species having a specific chemical formula among ammonium molybdate compounds, thereby providing a high yield and selectivity of aromatic carbonate in a wide range of reaction temperatures within a short time, as compared to conventional metal catalysts including tin or lead, or other catalysts using a different ammonium molybdate compounds. The method according to one aspect of the present invention also minimizes formation of byproducts during the reaction. Therefore, it is expected that the method of the present invention effectively substitutes for the conventional methods for preparing aromatic carbonate compounds.

The above and other aspects, features and advantages of the disclosed exemplary embodiments will be more apparent from the following detailed description taken in conjunction with the accompanying drawings in which:

Fig. 1 is a graph showing the variation in weight of a molybdenum compound according to the variation of the pretreatment temperature of hexaammonium molybdate ((NH₄)₆Mo₇O₂₄ ^.4H₂O);

Fig. 2 is a X-ray diffraction analysis graph showing the variation in composition of a molybdenum compound according to the variation of the pretreatment temperature of hexaammonium; and

Fig. 3 is a graph showing the variation in composition of a molybdenum compound according to the variation of the pretreatment temperature of hexaammonium molybdate as determined by infrared spectrometry.

As described above, according to the present invention, the aliphatic component in the aliphatic carbonate and/or aliphatic-aromatic carbonate is exchanged with the aromatic component in the aromatic hydroxyl compound via the reaction in the presence of an ammonium molybdate compound as a catalyst.

Aliphatic Carbonate and/or Aliphatic-aromatic Carbonate Compounds

The aliphatic carbonate and/or aliphatic-aromatic carbonate compounds used in the present invention as a starting material are represented by the following Chemical Formula 1:

[Chemical Formula 1]

(R¹O)CO(OR²)

wherein R¹ is a substituted or non-substituted C1-C10 alkyl group, C3-C7 cycloalkyl group, C6-C12 aryl group, or C7-C20 arylalkyl group; and R² is a substituted or non-substituted C1-C10 alkyl group, C3-C7 cycloalkyl group, or C7-C20 arylalkyl group.

In the case of the aliphatic carbonates, R¹ and R² independently represent an aliphatic group. When they are substituted, the substituents may be a C6-C12 aryl group or C7-C20 alkylaryl group. Particular examples of R¹ and R² include methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl, nonyl, cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, benzylmethyl, naphthylmethyl, etc. Preferably, the aliphatic carbonate is dimethyl carbonate.

In the case of the aliphatic-aromatic carbonates, R¹ is an aryl group and R² is an aliphatic group. When they are substituted, the substituents may be a C6-C12 aryl group or C7-C20 alkylaryl group. Particular examples of R¹ include phenyl, naphthyl, pyridyl, etc., and those of R² include methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl, nonyl, cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, benzylmethyl, naphthylmethyl, etc. Preferably, the aliphatic-aromatic carbonate is methylphenyl carbonate.

Aromatic Hydroxyl Compounds

The aromatic hydroxyl compounds used in the present invention are represented by the following Chemical Formula 2:

[Chemical Formula 2]

R³OH

wherein R³ is a substituted or non-substituted C6-C12 aryl group. When they are substituted, the substituents may be a C1-C10 alkyl group, C3-C7 cycloalkyl group, etc. Particular examples of the aromatic hydroxyl compounds include phenol, o-, m-, p-cresol, o-, m-, p-ethylphenol, o-, m-, p-propylphenol, etc. Preferably a monohydroxyl compound and more preferably phenol are used. Optionally, a combination of at least two of the aromatic hydroxyl compounds may be used.

Ammonium Molybdate Compounds

The ammonium molybdate compounds used in the present invention as a catalyst are represented by the following Chemical Formula 4:

[Chemical formula 4]

(NH₄)_xMo_yO_z·nH₂O

Although it is known that an ammonium molybdate compound is a precursor of molybdenum oxides, the present invention is characterized in that the ammonium molybdate compound is used as a catalyst in the form of a precursor, unlike the prior arts (e.g. Korean Patent Laid-Open No. 2001-49648).

According to a particularly preferred embodiment of the present invention, (NH₄)₈Mo₁₀O₃₄is used as a catalytically active ingredient. Typically, the ammonium molybdate compounds may be obtained in the process of heat treatment (pretreatment) of hexaammonium molybdate ((NH₄)₆Mo₇O₂₄·4H₂O). Although there is no particular limitation regarding gas atmosphere in the heat treatment process, the heat treatment is carried out preferably under gas atmosphere of such as nitrogen, steam, air, etc. The temperature of the heat treatment is preferably about 100-200℃, more preferably about 120-170℃.

Fig. 1 is a graph showing the variation in weight of a molybdenum compound according to the variation of the pretreatment temperature of hexaammonium molybdate ((NH₄)₆Mo₇O₂₄ ^.4H₂O).As can be seen from Fig. 1, the weight of hexaammonium molybdate ((NH₄)₆Mo₇O₂₄ ^.4H₂O) decreases as the pretreatment temperature increases. Particularly, a sharp drop of thermo gravity is observed at 200℃ or higher, which suggests that a change in the composition of the catalyst occurred. Such a change in the composition of the catalyst can be determined through the X-ray diffraction and Infrared spectrometry of hexaammonium molybdate ((NH₄)₆Mo₇O₂₄ ^.4H₂O).

Fig. 2 is an X-ray diffraction analysis graph showing the variation in composition of a molybdenum compound according to the variation of the pretreatment temperature change of hexaammonium molybdate. As can be seen from Fig. 2, there have been changes in the composition of the molybdenum compound in the order of hexaammonium heptamolybdate ((NH₄)₆Mo₇O₂₄ ^.4H₂O), octaammonium decamolybdate ((NH₄)₈Mo₁₀O₃₄), tetraammonium octamolybdate ((NH₄)₄Mo₈O₂₆), and molybdenum trioxide (MoO₃), as the pretreatment temperature has increased.

Fig. 3 is a graph showing the variation in composition of a molybdenum compound according to the variation of the pretreatment temperature of hexaammonium molybdate as determined by infrared spectrometry. As can be seen from the graph, the wavelength areas of 882, 855 and 790cm^-1 are caused by asymmetric stretching (882, 855 cm^-1: corner-sharing oxygen, 790cm^-1: edge-sharing oxygen). In addition, the wavelength area of 990-960 cm^-1 corresponds to the vibration area by v_as (Mo=O). In the case of a sample pretreated with air at 250℃, the presence of molybdenum trioxide (MoO₃) can be seen from the vibration area. The presence of water in a sample can be seen from the following areas: 3490 cm^-1: O-H stretching, 1600 cm^-1: H-O-H bending, 3300-3000 cm^-1: bending movement in free water. The presence of ammonia in a sample can be seen from the following areas: 3200 cm^-1: asymmetric stretching of the ammonium ions v₃ (N-H), 1400 cm^-1: bending v₄ (H-N-H).

According to the present invention, one or more of the ammonium molybdate compounds represented by Chemical Formula 4 may be used.

The catalyst makes it possible to carry out synthesis of aromatic carbonate, particularly, reaction between a hydroxyl compound and dialiphatic carbonate or aliphatic-aromatic carbonate at a lower temperature as compared to the prior art, thereby enlarging the reaction temperature range and producing a desired product with a high yield and high selectivity over the reaction temperature range.

Meanwhile, according to one embodiment of the present invention, the ammonium molybdate compound may be used as a catalyst as it is. Herein, the catalyst may be introduced directly to a reaction system including a carbonate compound and an aromatic hydroxyl compound as reactants to perform the reaction.

According to another embodiment of the present invention, the ammonium molybdate compound may be dissolved into a solvent and then introduced into the reaction system in the solution form. There is no particular limitation in the solvent that may be used herein, as long as the solvent is capable of dissolving the ammonium molybdate compound. In this embodiment, the catalyst compound may be dissolved into the reactants, i.e., the carbonate compound (e.g. dimethyl carbonate) and/or aromatic hydroxyl compound (e.g. phenol) to form a catalyst solution. As a solvent different from the reactants, water, acetone or a mixture thereof may be used. Optionally, such a different solvent may be mixed with the reactants to be used as the solvent for the catalyst. However, when using the solvent different from the reactants, the catalyst solution may be controlled preferably in the range of concentration of at most about 10 wt%, and more preferably to at most about 5%, so that the presence of the solvent does not adversely affect the characteristics of the reaction or the product.

In one embodiment of the present invention, the starting materials, i.e., the aromatic hydroxyl compound and the dialiphatic carbonate and/or aliphatic-aromatic carbonate may be used at any ratio depending on the particular desired product. In general, the hydroxyl compound and the carbonate compound may be used in a molar ratio of about 10:1 ~ 1:10, more typically about 5:1 ~ 1:5. Particularly, when using an aromatic hydroxyl compound and a dialiphatic carbonate compound, the molar ratio may be advisably controlled to about 1:4 ~ 1:6, particularly about 1:5, in view of yield and selectivity. Under these conditions, it is possible to obtain a desired aromatic carbonate at a high production rate per unit volume of the reaction device.

Meanwhile, a preferred embodiment of the method for producing aromatic carbonate in accordance with the present invention is carried out as follows. However, the scope of the present invention is not limited thereto.

Preferably, the reaction is carried out while removing l the byproduct of alcohol out of the reaction system, so as to maximize the yield of aromatic carbonate. In other words, reaction paths, in which the equilibrium constants of the above Reaction Formulas 1 and 2 are increased so that the reaction equilibrium moves toward the production of aromatic carbonate (aliphatic-aromatic carbonate and/or diaromatic carbonate), may also be applied to the present invention. In this case, considering that the equilibrium constants, K₁ and K₂ in the reaction system using the ammonium molybdate-based catalyst are higher than those of the prior art, the byproduct of alcohol may be removed during the reaction through distillation using a column with fewer number of trays so as to improve the reactivity to the forward reaction, and thereby to increase the yield of aromatic carbonate more effectively. For example, when using dimethyl carbonate (CH₃OCO₂CH₃) as a starting material, methanol and dimethyl carbonate form an azeotropic mixture during the distillation. Then, the azeotropic mixture may be separated from a distillation tower and solely the methanol may be removed to increase the yield of aromatic carbonate.

In the case of the above-described embodiment of the present invention, higher equilibrium constants, K₁ and K₂ facilitate the removal of alcohol by distillation. Thus, it is possible to reduce the cost required for the equipment and labor. As known to those skilled in the art, the byproduct of alcohol may be removed efficiently from the reaction product by adding an azeotropic agent, such as benzene or heptane, to the reaction system so that the alcohol is allowed to form an azeotropic mixture with the azeotropic agent.

According to an embodiment of the present invention, the reaction between the reactants, i.e., the aromatic hydroxyl compound and the aliphatic and/or aliphatic-aromatic carbonate compound may be carried out in a liquid phase. In this case, a known reaction mode (batch or continuous mode) and reaction equipment may be used without any particular limitation. Preferably, considering the cost-efficiency, a continuous liquid phase reactor may be used.

If the amount of the ammonium molybdate-based catalyst is too low in the reaction, it is not possible to obtain sufficient reactivity. On the other hand, if the amount of the catalyst is too high in the reaction, the excessive catalyst remains after the reaction and should be removed. Considering this, the concentration of molybdenum (Mo) metal in the ammonium molybdate-based catalyst is controlled to preferably about 5X10^-9 to 5X10^-3 mol, more preferably about 5X10^-8 to 1X10^-4 mol, based on the mol of the aromatic hydroxyl compound.

Meanwhile, if the reaction is carried out at too low temperature, reactivity becomes low and the reaction time (or contact time) also increases, resulting in degradation of the yield of aromatic carbonate. On the other hand, an excessively high reaction temperature increases formation of byproducts, resulting in an excessive increase in the internal pressure of the reactor. Considering this, the reaction may be carried out at about 120-300℃, preferably about 120-240℃. Particularly, a reaction temperature of about 120-170℃ is advisable in order to prepare a desired aromatic carbonate compound with a high yield and high selectivity.

Referring to the reaction pressure, there is no particular limitation in the reaction pressure, because the reaction pressure does not significantly affect the overall reaction. However, in advance to avoid the possibility of the reaction being lowered due to the subsequent vaporization of the reactants and vaporization of the alcohol byproduct, it is preferred that the reaction pressure is maintained constantly. For example, the reaction pressure may be controlled to at most 500 psig, more typically at most about 300 psig.

In addition, the reaction is carried out for about 2 minutes to 10 hours, preferably about 10 minutes to 1 hour. Such a reaction time is shorter than the time required for the conventional processes (8-24 hours on average), thereby improving the cost-efficiency.

Meanwhile, before carrying out the reactions according to the above Reaction Formulas 1 and 2, it is preferred that the ammonium molybdate compound is pretreated (dried) at a predetermined temperature, for example, at a temperature lower than about 200℃, in order to maintain the maximum activity of the ammonium molybdate-containing catalyst. There is no particular limitation in the gas that may be used in the pretreatment. For example, nitrogen or air may be used.

The present invention is described in greater detail with reference to the following examples. However, the examples are for illustrative purposes only and not intended to limit the scope of the present invention.

Example 1

To a 100 ml autoclave, 0.06 mol of phenol and 0.28 mol of dimethyl carbonate (DMC) are introduced, followed by mixing. Various molybdenum-containing catalysts are used in an amount controlled in such a manner that the concentration of molybdenum in each catalyst is 1.39X10^-4 mol to perform a reaction. The reaction pressure is set to 300 psig, and the reaction mixture is agitated with a magnetic agitator under a constant speed of 100 rpm. Herein, the reaction temperature and the reaction time are varied in a range of 140-180℃ and 0-1 hour, respectively.

Then, the yield of the main product, aromatic carbonate (i.e., methyl phenyl carbonate and diphenyl carbonate) and that of anisole as a byproduct are measured, and the results are shown in the following Table 1.

Catalyst Compound	Mo(molⅹ10⁴)	Reaction conditions		Formation(μmol)
Catalyst Compound	Mo(molⅹ10⁴)	Temperature(℃)	Time (hr)	Anisole	MPC ¹⁾	DPC ²⁾
(NH₄)₆Mo₇O₂₄·4H₂O (Control)	1.39	140	0	0	88.4	0
(NH₄)₆Mo₇O₂₄·4H₂O (Control)	1.39	140	1	0	1517.6	0
(NH₄)₆Mo₇O₂₄·4H₂O (Control)	1.39	180	0	0.1	3481.6	8.0
(NH₄)₆Mo₇O₂₄·4H₂O (Control)	1.39	180	1	0.2	3724.8	12.5
Na₂MoO₄·2H₂O (Control)	1.39	140	0	0	0	0
Na₂MoO₄·2H₂O (Control)	1.39	140	1	0	6.0	0
(NH₄)₃PO₄12MoO₃·nH₂O (Control)	1.39	140	0	0	0	0
(NH₄)₃PO₄12MoO₃·nH₂O (Control)	1.39	140	1	0	10.8	0
(NH₄)₈Mo₁₀O₃₄	1.39	140	0	0	48.4	0
(NH₄)₈Mo₁₀O₃₄	1.39	140	1	0	2869.0	5.41
(NH₄)₈Mo₁₀O₃₄	1.39	180	1	20	4616.3	16.4

1) MPC = methylphenyl carbonate

2) DPC = diphenyl carbonate

3) The measurement is based on the time point when the predetermined reaction temperature is attained, after the reactor is warmed from room temperature.

As shown in Table 1, when octaammonium decamolybdate ((NH₄)₈Mo₁₀O₃₄) is used as a catalyst, the yield of methyl phenyl carbonate increases as the reaction temperature increases. In addition, a significantly higher yield of methyl phenyl carbonate is obtained in the same reaction temperature in the presence of octaammonium decamolybdate ((NH₄)₈Mo₁₀O₃₄) as a catalyst, compared to hexaammonium molybdate ((NH₄)₆Mo₇O₂₄·4H₂O). Further, when using, as a catalyst, molybdenum compounds other than ammonium molybdate compounds, the desired product, aromatic carbonate is hardly produced or is produced in a very small amount in a reaction temperature of about 140℃. Particularly, when using the ammonium molybdate compound according to the present invention as a catalyst, the highest yield of aromatic carbonate is attained, compared to other known catalysts.

Example 2

A solution including either hexaammonium heptamolybdate ((NH₄)₆Mo₇O₂₄·4H₂O) and octaammonium decamolybdate ((NH₄)₈Mo₁₀O₃₄) were respectively dissolved in a solvent containing dimethyl carbonate and phenol and then is taken in a predetermined amount to be used as a catalyst. A reaction was carried out between phenol and dimethyl carbonate in the same manner as described in Example 1 to obtain methylphenyl carbonate and diphenyl carbonate. Herein, the reaction temperatures were set to 140℃ and 180℃, respectively. The rate of formation of the main product, aromatic carbonate (methylphenyl carbonate and diphenyl carbonate), is measured and the results are shown in the following Table 2.

Catalyst Compound	Mo(mol×10⁷)	Reaction conditions	Formation rate of MPC
Catalyst Compound	Mo(mol×10⁷)	Temperature(℃)	([MPC]/[Mo]/h)
(NH₄)₆Mo₇O₂₄·4H₂O(Control)	2.4	140	108
(NH₄)₈Mo₁₀O₃₄	0.7	140	774
(NH₄)₆Mo₇O₂₄·4H₂O(Control)	18.0	180	210
(NH₄)₈Mo₁₀O₃₄	2.1	180	7182

As can be seen from Table 2, when using the solution containing octaammonium decamolybdate ((NH₄)₈Mo₁₀O₃₄) as a catalyst, a significantly higher rate of formation of aromatic carbonate was obtained, when compared to hexaammonium heptamolybdate ((NH₄)₆Mo₇O₂₄·4H₂O).

Comparative Example 1

A compound containing either tin or lead (a tin-containing compound or a lead oxide) was used as a catalyst under a predetermined amount of metal. A reaction was carried out between phenol and dimethyl carbonate in the same manner as described in Example 1 to obtain methyl phenyl carbonate and diphenyl carbonate. The yield of aromatic carbonate and that of anisole as a byproduct are shown in the following Table 3.

Metal	Catalyst Compound	Metal(mol×10⁴)	Reaction conditions		Formation (μmol)
Metal	Catalyst Compound	Metal(mol×10⁴)	Temperature(℃)	Time(hr)	Anisole	MPC	DPC
Sn	(C₂H₃O₂)₂Sn	1.39	140	0	0	72.7	0
	(C₂H₃O₂)₂Sn	1.39	140	1	0	641.2	0
	Sn(CH₃COCHCOCH₃)₂	1.39	140	0	0	97.4	2.1
	Sn(CH₃COCHCOCH₃)₂	1.39	140	1	0	262.7	0
	SnCl₄·5H₂O	1.39	140	0	0	653.5	1.2
	SnCl₄·5H₂O	1.39	140	1	34.9	1733.1	2.7
Pb	PbO	1.39	140	0	0	201.4	0
	PbO	1.39	140	1	0	1751.8	4.5
	PbO	1.39	180	1	44.6	3642.2	21.1

As can be seen from Table 3, when tin chloride pentahydrate (SnCl₄.5H₂O) was used as a catalyst, the initial yield of aromatic carbonate (particularly, MPC) was slightly higher, compared to the octaammonium decamolybdate-based catalyst, at a reaction temperature of 140℃. However, after a predetermined period of reaction time (1 hour), the yield of aromatic carbonate decreased, while anisole as a byproduct was formed in a relatively large amount.

In addition, when using a lead oxide as a catalyst, the yield of methylphenyl carbonate and diphenyl carbonate was relatively high at a high reaction temperature (180℃). However, the byproduct, anisole, was also formed in a large amount, thereby providing undesirable selectivity.

Comparative Example 2

Either tin oxide or molybdenum oxide was used as a catalyst. A reaction was carried out between phenol and dimethyl carbonate in the same manner as described in Example 1 to obtain methyl phenyl carbonate and diphenyl carbonate. The yield of aromatic carbonate and that of anisole as a byproduct are shown in the following Table 4.

Catalyst Compound	Metal(mol×10⁴)	Reaction condition		Formation(μmol)
Catalyst Compound	Metal(mol×10⁴)	Temperature(℃)	Time (hr)	Anisole	MPC	DPC
SnO	1.39	140	0	0	0	0
SnO	1.39	140	1	0	0	0
SnO₂	1.39	140	0	0	0	0
SnO₂	1.39	140	1	0	0	0
MoO₃	1.39	140	0	0	0	0
MoO₃	1.39	140	1	0	0	0

As can be seen from Table 4, when tin oxide (SnO or SnO₂) or molybdenum oxide (MoO₃) was used as a catalyst, no reaction occurred at 140℃.

Comparative Example 3

A solution including lead oxide (PbO) dissolved in a solvent containing dimethyl carbonate and phenol was taken in a predetermined amount to be used as a catalyst. A reaction was carried out between phenol and dimethyl carbonate in the same manner as described in Example 1 to obtain methylphenyl carbonate and diphenyl carbonate. Herein, the reaction temperatures were set to 140℃ and 180℃, respectively. The rate of formation of the main product, aromatic carbonate (methylphenyl carbonate and diphenyl carbonate), was measured and the results are shown in the following Table 5.

Catalyst Compound	Pb(mol×10⁷)	Reaction conditions	Formation rate of MPC
Catalyst Compound	Pb(mol×10⁷)	Temperature(℃)	([MPC]/[Pb]/h)
PbO	3.7	140	234
PbO	3.7	180	3300

As can be seen from Table 5, when lead oxide (PbO) was used as a catalyst, a significantly lower reaction rate was obtained in a reaction temperature of about 140℃ and 180℃, compared to octaammonium decamolybdate ((NH₄)₈Mo₁₀O₃₄).

Comparative Example 4

Molybdenum oxide (MoO₃) was dissolved in an aqueous ammonia solution and dried at about 80℃ to provide (NH₄)₂Mo₂O₇·H₂O, which, in turn, was used as a catalyst. A reaction was carried out between phenol and dimethyl carbonate in the same manner as described in Example 1 to obtain methylphenyl carbonate and diphenyl carbonate. Herein, the reaction temperatures were set to 140℃ and 180℃, respectively. The rate of formation of the main product, aromatic carbonate (methylphenyl carbonate and diphenyl carbonate), was measured and the results are shown in the following Table 6.

Catalyst Compound	Mo(molⅹ10⁴)	Reaction conditions		Formation(μmol)
Catalyst Compound	Mo(molⅹ10⁴)	Temperature(℃)	Time (hr)	Anisole	MPC ¹⁾	DPC ²⁾
(NH₄)₂Mo₂O₇·H₂O	1.39	140	0	0	87.9	0
(NH₄)₂Mo₂O₇·H₂O	1.39	140	1	0	638.6	0

It can be seen from the above experimental results that when an ammonium molybdate compound having a specific chemical formula was used as a catalyst for preparing aromatic carbonate, it was possible to provide an excellent yield and selectivity of aromatic carbonate over a broader range of reaction temperatures, compared to molybdenum oxide-based catalysts or other ammonium molybdate compound-based catalysts.

While the exemplary embodiments have been shown and described, it will be understood by those skilled in the art that various changes in form and details may be made thereto without departing from the spirit and scope of the present invention as defined by the appended claims.

Claims

A method for preparing an aromatic carbonate compound, comprising:- reacting at least one carbonate compound selected from the group consisting of the compounds represented by the following Chemical Formula 1 with an aromatic hydroxyl compound represented by the following Chemical Formula 2, in the presence of a catalyst including an ammonium molybdate compound to convert the carbonate compound into an aromatic carbonate compound represented by the following Chemical Formula 3, wherein the ammonium molybdate compound is represented by the following Chemical Formula 4:[Chemical Formula 1](R¹O)CO(OR²)[Chemical Formula 2]R³OH[Chemical Formula 3](R¹O)CO(OR³)wherein R¹ is a substituted or non-substituted C1-C10 alkyl group, C3-C7 cycloalkyl group, C6-C12 aryl group, or C7-C20 arylalkyl group;R² is a substituted or non-substituted C1-C10 alkyl group, C3-C7 cycloalkyl group, or C7-C20 arylalkyl group; andR³ is a substituted or non-substituted C6-C12 aryl group.[Chemical formula 4](NH₄)_xMo_yO_z·nH₂Owherein x ranges from 7 to 9, y ranges from 8 to 12, x+6y=2z, and n ranges from 0 to 50.
The method for preparing an aromatic carbonate compound according to claim 1, wherein the ammonium molybdate compound is (NH₄)₈Mo₁₀O₃₄.
The method for preparing an aromatic carbonate compound according to claim 1 or 2, which is carried out in a batchwise or continuous liquid-phase reaction.
The method for preparing an aromatic carbonate compound according to claim 1 or 2, wherein the ammonium molybdate compound is used as the catalyst as it is, or as a form of solution containing the ammonium molybdate compound dissolved in a solvent.
The method for preparing an aromatic carbonate compound according to claim 4, wherein the solvent is dimethyl carbonate, phenol, water, acetone or a mixture thereof.
The method for preparing an aromatic carbonate compound according to claim 1 or 2, wherein the molar ratio of said carbonate compound to said aromatic hydroxyl compound is 5:1 to 1:5.
The method for preparing an aromatic carbonate compound according to claim 1 or 2, wherein the catalyst comprises molybdenum in a range of 5X10^-9 to 5X10^-3 mol, based on the mol of said aromatic hydroxyl compound.
The method for preparing an aromatic carbonate compound according to claim 1 or 2, wherein the reaction is carried out at a temperature of 120-240℃ for 2 minutes to 10 hours.
The method for preparing an aromatic carbonate compound according to claim 1 or 2, wherein said carbonate compound is dimethyl carbonate and said aromatic hydroxyl compound is phenol.