RU2842337C1 - Method of producing 2-furonitrile and method of producing carbonate ester - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: present invention relates to organic synthesis, specifically to a method of producing 2-furonitrile and a method of producing a carbonate ester, involving dehydration of 2-furamide. Method of producing 2-furonitrile involves dehydration of 2-furamide in presence of a catalyst, which is Mo/SiO₂, in which molybdenum is supported on a substrate of SiO₂.

EFFECT: method allows a dehydration reaction by which the desired compound can be selectively obtained in high output, while reducing formation of a by-product, when regenerating the nitrile by dehydrating the amide compound, and providing a method for efficiently producing a carbonate ester by applying said method, in the form of regenerating a nitrile compound in a method for producing a carbonate ester.

11 cl, 1 dwg, 1 tbl, 8 ex

Description

Field of technology

[0001]

The present invention relates to a process for producing 2-furonitrile and to a process for producing a carbonate ester.

State of the art

[0002]

Carbonate ester is a general name for compounds obtained by replacing one or two of the two hydrogen atoms of carbonic acid, CO(OH) ₂ , by alkyl groups or aryl groups, and having a structure represented by the formula RO-C(=O)-OR' (each R and R' represents a saturated hydrocarbon group or an unsaturated hydrocarbon group).

Carbonate esters are very important compounds which are used as additives such as gasoline octane improvers and diesel fuel additives to reduce particulate matter in exhaust gases; as alkylating agents, carbonylating agents, solvents or the like used for synthesizing resins and organic compounds such as polycarbonates, urethanes, pharmaceuticals and agricultural chemicals; electrolytes for lithium-ion batteries; raw materials for lubricating oils; and raw materials for deoxidizers to prevent corrosion in steam boiler tubes.

[0003]

The conventional method most often used to produce carbonate esters is a method in which phosgene, which is used as a source of carbonyl group, is directly brought into contact with alcohol. Since this method uses extremely harmful and corrosive phosgene, extreme precautions must be taken when handling it during transportation and storage; in addition, huge costs are required for the operation and maintenance of production facilities and for ensuring safety. In addition, if the carbonate ester is obtained by this method, halogen such as chlorine is contained in the raw material and catalyst, and therefore the resulting carbonate ester contains trace amounts of halogen, which cannot be removed by a simple purification process. When used for gasoline additives, light oil additives and electronics, such a carbonate ester must be subjected to a fine purification process to reduce the trace halogen contained therein to an extremely low trace content, since halogen can cause corrosion. In addition, strict administrative rules have recently been established, according to which it is forbidden to build new production facilities based on the described method using phosgene, which is very dangerous for humans. For this reason, the development of a new method for producing carbonate esters without using phosgene is urgently needed.

[0004]

In addition, there is also another known method for directly synthesizing carbonate esters from alcohols and carbon dioxide using a heterogeneous catalyst. This method uses 2-cyanopyridine or benzonitrile as a dehydrating agent to increase the amount of carbonate ester produced, and is intended to significantly increase the amount and production rate of carbonate ester, to enable the reaction to proceed rapidly under a pressure close to ordinary pressure, and to increase the reaction rate (see Patent Documents 1 and 2). However, the described method still has some drawbacks that need to be addressed from the viewpoint of purifying and utilizing benzamide or the like generated as a by-product.

For example, the use of benzamide formed by the reaction of benzonitrile and water is limited to a small number of pharmaceutical and agricultural intermediates. Therefore, in the production of carbonate ester using benzonitrile as a dehydrating agent, it is preferable to recover benzonitrile from the benzamide formed as a by-product and reuse the recovered benzonitrile. However, the problem still lies in the need to carry out said regeneration reaction with high selectivity (since reuse as a dehydrating agent is considered difficult if the by-product is formed) and high yield (since low yield increases the amount of residual benzamide, that is, the amount of benzamide that needs to be separated, resulting in an increase in the workload of separating it from benzonitrile).

[0005]

In view of the fact that, as described above, there are some aspects that need to be improved in terms of regenerating benzonitrile or the like from benzamide or the like, there is a known method of carrying out the regeneration described above without using a strong reagent while reducing the formation of a by-product (Patent Document 3).

However, the said method also has some disadvantages that need to be addressed: one is that such a method cannot be used in combination with the carbonate ester synthesis reaction because it takes 400 hours to obtain (regenerate) the nitrile by dehydrating the amide compound, which is disproportionate to the carbonate ester synthesis reaction that is completed in 24 hours; and another is that extraction and filtration are required to remove the catalyst by the liquid-solid separation method, which makes the process longer and more complicated.

List of references

Patent literature

[0006]

Patent Document 1: Japanese Patent No. 2010-77113, Publicly Laid Out

Patent Document 2: Japanese Patent No. 2012-162523, which has been made publicly available

Patent Document 3: International Publication No. WO 2015/099053

The essence of the invention

Technical problem

[0007]

In view of the above-described problems inherent in the prior art solutions, the object of the present invention is to provide a method that allows for a dehydration reaction to be carried out, by means of which the desired compound can be selectively obtained in high yield while simultaneously reducing the formation of a by-product during the regeneration of the nitrile by dehydration of the amide compound.

Another objective of the present invention is to provide a method for efficiently producing a carbonate ester by using the above-mentioned method for producing (regenerating) a nitrile compound in a method for producing a carbonate ester.

Solution to the problem

[0008]

In order to solve the above-described problems, the author of the present invention conducted a comprehensive study on a method for producing a nitrile compound by dehydrating an amide compound, and as a result, it was found that 2-furonitrile as a target compound can be obtained selectively and with a high yield, while the formation of a by-product is reduced by dehydrating 2-furamide in the presence of a specific catalyst.

The discovery of this fact made it possible to balance the rate of regeneration of the nitrile compound from the amide compound by means of the dehydration reaction and the rate of synthesis of the carbonate ester from _CO2 and alcohol using the nitrile compound, that is, to carry out the dehydration reaction and the reaction of synthesis of the carbonate ester as a group of industrial processes. Thus, the author of the present invention further studied the application of the discovered fact in the method for producing the carbonate ester.

More specifically, the present invention provides the following aspects.

<1> A method for producing 2-furonitrile, comprising dehydrating 2-furamide in the presence of a catalyst, which is Mo/SiO ₂ , in which molybdenum (Mo) is supported on a SiO ₂ substrate.

<2> A method for producing 2-furonitrile according to item <1>, characterized in that dehydration is additionally carried out in the presence of a desiccant.

<3> A method for producing 2-furonitrile according to item <2>, characterized in that the desiccant is a molecular sieve.

<4> A method for producing 2-furonitrile according to any one of paragraphs <1>-<3>, characterized in that 2-furancarboxylic acid is obtained together with 2-furonitrile.

<5> A method for producing a carbonate ester, comprising:

a first reaction step comprising a reaction for producing a carbonate ester in which an alcohol and carbon dioxide react in the presence of a solid catalyst, 2-furonitrile and a solvent to produce a carbonate ester, and a hydration reaction in which 2-furonitrile is hydrated with the resulting water to produce 2-furamide; and

a second reaction stage in which 2-furamide is separated from the reaction system of the first reaction stage, and then dehydration of 2-furamide is carried out in the presence of a Mo/SiO ₂ catalyst, in which molybdenum (Mo) is supported on a SiO ₂ substrate, to regenerate 2-furonitrile, wherein

at least a portion of the 2-furonitrile regenerated in the second reaction stage is used in the first reaction stage.

<6> A method for producing a carbonate ester according to paragraph <5>, characterized in that dehydration is additionally carried out in the presence of a desiccant.

<7> A method for producing a carbonate ester according to paragraph <6>, characterized in that the desiccant is a molecular sieve.

<8> A method for producing a carbonate ester according to any one of paragraphs <5>-<7>, characterized in that said alcohol includes an alcohol containing from 1 to 6 carbon atoms.

<9> A method for producing a carbonate ester according to any one of paragraphs <5>-<8>, characterized in that the solid catalyst includes at least one selected from CeO ₂ and ZrO ₂ .

<10> A method for producing a carbonate ester according to any one of paragraphs <5>-<9>, characterized in that at the first stage of the reaction a solvent is used that has a boiling point higher than the boiling point of the resulting 2-furamide.

<11> A method for producing a carbonate ester according to item <10>, characterized in that said solvent includes at least one selected from dialkylbenzene, alkylnaphthalene and diphenylbenzene.

Beneficial effects of the invention

[0009]

As described above, the present invention provides the possibility of efficiently producing (regenerating) a nitrile compound from an amide compound. In particular, in the dehydration reaction of the amide compound for the above-described regeneration, it is possible to selectively produce the desired compound with a high yield while simultaneously reducing the formation of a by-product. Thus, the present invention provides the possibility of significantly reducing the dehydration reaction time for regenerating a nitrile compound compared with the conventional method.

In addition, the present invention also provides the possibility of carrying out a method for efficiently producing a carbonate ester by producing a nitrile compound in the manner described above.

Brief description of the drawing

[0010]

[Figure 1] Figure 1 is a schematic diagram illustrating the reactor (furnace) used in the Examples and Comparative Examples.

Description of embodiments of the invention

[0011]

Preferred embodiments of the present invention are described in detail below.

<Method for obtaining 2-furonitrile>

A method for producing 2-furonitrile according to one embodiment of the present invention is a method in which the dehydration of 2-furamide is carried out in the presence of a Mo/SiO ₂ catalyst obtained by depositing molybdenum (Mo) on a SiO ₂ support, to produce 2-furonitrile.

[0012]

[0013]

The catalyst used in the above-mentioned dehydration reaction according to the present invention is obtained, for example, by the following method. As the support, commercially available SiO ₂ powder or commercially available spherical SiO ₂ particles can be used. In order to uniformly distribute molybdenum (Mo) as an active metal on the support, SiO ₂ preferably has a size of 100 mesh (0.15 mm) or less and is pre-calcined in air at 700°C for 1 hour to remove moisture. There are various types of SiO ₂ differing in properties, but SiO ₂ having a large surface area is preferable since molybdenum (Mo) can be dispersed in a large amount, thereby increasing the amount of 2-furonitrile obtained. In particular, a surface area of 300 m ² /g or more is preferable. It should be noted that there is a case where the surface area of the obtained catalyst is smaller than that of pure SiO ₂ , which is caused by, for example, interactions between SiO ₂ and molybdenum (Mo). In such a case, the surface area of the obtained catalyst is preferably 150 m ² /g or more. Molybdenum (Mo), which acts as active particles, can be supported on a support by an impregnation method such as an incipient wetness impregnation method or a dry evaporation method.

[0014]

The metal salt for use as a catalyst precursor is not particularly limited, provided that it is soluble in water, and various compounds can be used. The catalyst used can be obtained by impregnating a support with an aqueous solution of a base metal precursor, followed by drying and calcining the resulting product. The calcination temperature depends on the precursor used, but is preferably from 400 to 600°C.

[0015]

The concentration of the catalyst may be set depending on the circumstances, but, for example, the concentration of molybdenum oxide (Mo) in terms of metal relative to the total weight of the catalyst is preferably about 0.1 to 1.5 mmol/g, and is particularly preferably about 0.1 to 1 mmol/g. If the concentration exceeds the upper limit specified above, the activity may decrease.

[0016]

The amount of the catalyst used in the reaction can be set depending on the circumstances, but is preferably 20 to 150 parts by weight, more preferably 30 to 130 parts by weight, per 100 parts by weight of 2-furamide used.

[0017]

The catalyst used in the present invention is preferably a catalyst obtained by supporting only molybdenum oxide (Mo) on a support of SiO ₂ , but it may contain, in addition to the above elements, unavoidable impurities included, for example, in the process of preparing the catalyst. However, it is desirable to prevent the inclusion of impurities as much as possible.

[0018]

The catalyst used in the present invention, which is obtained by applying molybdenum oxide (Mo) acting as active particles to a support, may be in the form of powder or shaped particles. In the case of shaped particles, the catalyst may have any shape such as a spherical shape, a grain shape, a cylindrical shape, a ring shape, a wheel shape, or a granular shape.

[0019]

In the method for producing 2-furonitrile using the catalyst according to the present invention, the reaction type is not particularly limited, and any reactor such as a batch reactor, a semi-continuous reactor, or a flow reactor such as a continuous stirred reactor or a plug flow reactor can be used. The catalyst can be introduced into any fixed bed reactor, three-phase fluidized bed reactor, or the like.

[0020]

In the method for producing 2-furonitrile according to the present invention, the reaction can be generally carried out under conditions of a reaction liquid temperature of 160 to 230°C, a pressure of ordinary pressure (101.3 (kPa) (760 Torr)) to reduced pressure (1.33 (kPa) (10 Torr)) and a time of about several hours to 100 hours, but the reaction conditions are not specifically limited to these conditions.

For example, the temperature of the reaction liquid is preferably 170 to 220°C, more preferably 180 to 210°C. Preferably, the reaction time is 6 to 90 hours, more preferably 10 to 80 hours, particularly preferably 20 to 75 hours. The pressure is preferably ordinary pressure from the viewpoint of not requiring a pressure relief device and energy efficiency.

[0021]

In the method for producing 2-furonitrile according to the present invention, dehydration of 2-furamide is preferably carried out in the presence of a desiccant in addition to a Mo/SiO ₂ catalyst. The type of the desiccant is not particularly limited, but a molecular sieve is preferably used.

When using molecular sieves as a dehydrating agent, the type and shape of the molecular sieves are not particularly limited, but, for example, spherical or granular molecular sieves which generally have high water absorption capacity, such as type 3A, 4A or 5A, can be used. For example, Zeolum manufactured by Tosoh Corporation can be used. In addition, the molecular sieves are preferably pre-dried at 300 to 500°C for about 1 hour.

[0022]

[0023]

In the present invention, there may be a case where, as shown above, 2-furancarboxylic acid is formed as a by-product in the decomposition of 2-furamide in the dehydration reaction of 2-furamide. However, the reaction liquid after the dehydration reaction using the reaction conditions of the present invention contains a large amount of unreacted 2-furamide and 2-furonitrile as a product, and the by-product shown in the above formula is less likely to be formed.

[0024]

<Method for producing carbonate ester using 2-furonitrile>

As described above, by regenerating 2-furonitrile from 2-furamide by the dehydration reaction, the desired compound can be obtained selectively and at a high yield without using a strong reagent, and the formation of a by-product is reduced. This makes it possible to balance the rate of regenerating 2-furonitrile from 2-furamide by the dehydration reaction and the rate of synthesizing a carbonate ester from _CO2 and alcohol using 2-furonitrile, that is, to combine the dehydration reaction and the reaction of synthesizing a carbonate ester to carry out these reactions as a group of industrial processes. Thus, the inventor of the present invention applied this finding to a method for producing a carbonate ester, which made it possible to develop a method for producing a carbonate ester described below.

[0025]

(First stage of the reaction)

The first reaction step in the method for producing a carbonate ester according to the present invention comprises a reaction (carbonate ester production reaction) in which an alcohol and carbon dioxide are directly reacted in the presence of a solid catalyst such as CeO ₂ , 2-furonitrile and a solvent to produce a carbonate ester.

[0026]

In this stage, as a result of the reaction between alcohol and carbon dioxide, water is also formed in addition to the carbonate ester. However, since 2-furonitrile is present, 2-furamide is formed as a result of hydration involving the formed water. In addition, by removing the formed water from the reaction system or reducing the amount of formed water in the reaction system, it is possible to accelerate the production of the carbonate ester. An example of the described stage is represented by the following formula.

[0027]

[0028]

(Alcohol)

The alcohol used may be any one or more alcohols selected from a primary alcohol, a secondary alcohol and a tertiary alcohol. For example, the use of methanol, ethanol, 1-propanol, isopropanol, 1-butanol, 1-pentanol, 1-hexanol, 1-heptanol, 1-octanol, 1-nonanol, allyl alcohol, 2-methyl-1-propanol, cyclohexanemethanol, benzyl alcohol, ethylene glycol, 1,2-propanediol or 1,3-propanediol is preferable because the product can be obtained in high yield and a high reaction rate is achieved. The carbonate esters obtained in this case are, respectively, dimethyl carbonate, diethyl carbonate, dipropyl carbonate, diisopropyl carbonate, dibutyl carbonate, dipentyl carbonate, dihexyl carbonate, diheptyl carbonate, dioctyl carbonate, dinonyl carbonate, diallyl carbonate, di-2-methylpropyl carbonate, dicyclohexanemethyl carbonate, dibenzyl carbonate, ethylene carbonate, 1,2-propylene carbonate, and 1,3-propylene carbonate.

When the obtained carbonate ester is used as a starting material of a diaryl carbonate, the alcohol used is preferably an alcohol containing 1 to 6 carbon atoms, more preferably an alcohol containing 2 to 4 carbon atoms.

In addition, it is preferable to use monovalent or divalent alcohol.

[0029]

(Catalyst for the production of carbonate ester)

In the first step of the reaction for producing the carbonate ester, one or both of _CeO2 and _ZrO2 are preferably used as solid catalysts. For example, _CeO2 alone, _ZrO2 alone, a mixture of _CeO2 and _ZrO2 , or a solid solution or a CeO2 _{- ZrO2} composite oxide are preferable, and _CeO2 alone is particularly preferably used. In the case of the CeO2 _{- ZrO2} solid solution or composite oxide, the mixing ratio between _CeO2 and _ZrO2 is generally 50:50, but may be changed depending on the circumstances.

[0030]

The solid catalyst used in the first stage of the reaction may be in the form of powder or shaped particles. In the case of shaped particles, the solid catalyst may have any shape such as spherical shape, grain shape, cylindrical shape, ring shape, wheel shape or granular shape.

[0031]

(Carbon dioxide)

The carbon dioxide used in the present invention may be not only carbon dioxide obtained as industrial gas, but also carbon dioxide separated and recovered from gas emissions of various product manufacturing plants, steel plants, power plants, or the like.

[0032]

(Solvent for the reaction of obtaining carbonate ester)

In the reaction for producing a carbonate ester, a solvent which has a boiling point higher than the boiling point of the obtained 2-furamide is preferably used. More preferably, the solvent used in the reaction for producing a carbonate ester includes at least one selected from dialkylbenzene, alkylnaphthalene and diphenylbenzene, and specific examples of such a solvent include B-28AN drum process oil and B-30 drum process oil (manufactured by Matsumura Oil Co., Ltd.), each of which contains components such as dialkylbenzene, alkylnaphthalene and diphenylbenzene.

[0033]

(Reaction solution temperature)

The temperature of the reaction solution in the reaction for producing the carbonate ester is preferably from 50 to 300°C. If the temperature of the reaction solution is less than 50°C, the synthesis reaction of the carbonate ester and the hydration reaction of 2-furonitrile hardly proceed due to the low reaction rates, and therefore the productivity of the carbonate ester is low. On the other hand, if the temperature of the reaction solution exceeds 300°C, the rate of each reaction is high, but the carbonate ester is easily decomposed or denatured, and 2-furamide easily reacts with the alcohol, and therefore the yield of the carbonate ester is low. More preferably, the temperature of the reaction solution is from 100 to 150°C. However, it should be noted that the preferable temperature of the reaction solution varies depending on the type or amount of the solid catalyst or the amount or ratio of the starting materials (alcohol and 2-furonitrile), and therefore it is desirable to adjust the optimum temperature according to the circumstances. Since the preferred temperature of the reaction solution is from 100 to 150°C, it is desirable to preheat the reactants (alcohol and 2-furonitrile) with steam or the like in a step preceding the carbonate ester reactor.

[0034]

(Reaction pressure)

The reaction pressure for producing carbonate ester is preferably 0.1 to 20 MPa (absolute pressure). If the reaction pressure is less than 0.1 MPa (absolute pressure), a pressure relief device is needed, which complicates the production equipment and increases the cost. In addition, power and energy are needed to reduce the pressure, which reduces the energy efficiency. On the other hand, if the reaction pressure exceeds 20 MPa, the hydration reaction of 2-furonitrile is difficult to proceed, which reduces the yield of carbonate ester. In addition, power and energy are needed to increase the pressure, which reduces the energy efficiency. From the viewpoint of increasing the yield of carbonate ester, the reaction pressure is more preferably 0.5 to 15 MPa (absolute pressure), still more preferably 1.0 to 10 MPa (absolute pressure).

[0035]

(Amount of 2-furonitrile used)

It is desirable that 2-furonitrile used in the hydration reaction be previously introduced into the reactor before the reaction in such a molar amount that it is 0.2 times or more to 5 times or less of the theoretical molar amount of water generated as a by-product in the reaction between the alcohol and _CO2 as raw materials. More preferably, the molar amount of 2-furonitrile is 0.5 times or more to 3 times or less, particularly preferably 0.8 times or more to 1.5 times or less of the theoretical molar amount of water generated as a by-product in the reaction between the alcohol and _CO2 as raw materials. If the molar amount of 2-furonitrile is too small, there is a concern that the amount of 2-furonitrile promoting the hydration reaction will be small, so that the yield of the carbonate ester decreases. On the other hand, if 2-furonitrile is introduced in a molar amount excessively large with respect to the alcohol used as a raw material, the side reaction of 2-furonitrile is undesirably enhanced. In addition, it is considered that the amount of alcohol and 2-furonitrile with respect to the solid catalyst varies depending on the type or amount of the solid catalyst, the type of alcohol, or the ratio between alcohol and 2-furonitrile, and therefore it is desirable that optimum conditions be properly established.

[0036]

(Separation by distillation)

After the reaction, the carbonate ester as the main product, 2-furamide as the by-product, unreacted 2-furonitrile and solid catalyst such as _CeO2 are separated by distillation. As a result, the product can be collected.

[0037]

(Second stage of the reaction)

Then, in the second reaction step according to the present invention, 2-furamide obtained as a by-product in the first reaction step is separated from the system after the carbonate ester production reaction and then subjected to a dehydration reaction to obtain 2-furonitrile. The second reaction step corresponds to the above-described method for producing 2-furonitrile, and therefore, the detailed description thereof is not repeated.

[0038]

(Reuse of 2-furonitrile)

2-Furonitrile regenerated in the second reaction step can be reused in the first reaction step (hydration reaction).

Examples

[0039]

Below, the present invention is described in more detail with reference to examples, but the present invention is not limited to the examples provided.

[0040]

<Gas chromatographic (GC) analysis of the reaction product>

Each obtained reaction product was dissolved in 20 g of acetone and the resulting solution was passed through a filter, placed in a vial for GC analysis and subjected to GC analysis.

(GC and measurement conditions)

GC column: CP-Sil 5 CB (50 m length, 0.25 µm membrane thickness, 0.25 mm inner diameter) manufactured by Agilent Technologies Inc.

Inlet pressure: 100 kPa

Evaporation chamber temperature: 320°C

Column flow rate: 0.83 ml/min

Linear speed: 19.9 cm/s

Flow division ratio: 25.0

Total flow rate: 24.5 ml/min

Carrier gas: N ₂

Detector: Hydrogen Flame Ionization Detector (FID)

Detector temperature: 320°C

Internal standard substance: dodecane (manufactured by FUJIFILM Wako Pure

Chemical Corporation, purity 97%)

Column temperature increase program:

(Initial stage) temperature 50°C, holding time 0 min

(First stage) temperature increase rate 30°C/min, reaching temperature 130°C, holding time 0 min

(Second stage) temperature increase rate 5°C/min, reaching temperature 180°C, holding time 0 min

(Third stage) temperature increase rate 30°C/min, reaching temperature 300°C, holding time 10 min

[0041]

(Example of obtaining 1 catalyst on a substrate)

Based on the incipient wetness impregnation method, a supported catalyst was obtained according to the following procedure.

In a 5 ml vial, an accurately weighed portion of 0.089 g (NH ₄ )6Mo ₇ O ₂₄ ⋅4H ₂ O (MoO ₃ content 81%, manufactured by Wako Pure Chemical Industries, Ltd., special grade chemical reagent, distributor 010-06905, lot No. PTN1484) was taken and diluted with 3 ml of distilled water to obtain a catalyst precursor solution.

The catalyst precursor solution was gradually dropped into a 100 mL beaker containing 0.96 g of SiO ₂ while heating and stirring the resulting mixture. The resulting mixture was continued to be heated on a hot stirrer to evaporate moisture, and then dried in an oven at 110 °C for 12 hours. The resulting catalyst was placed in a muffle furnace and heated to 500 °C at a temperature increase rate of 10 °C/min, and then continuously calcined at 500 °C for 3 hours to obtain a SiO ₂ -supported Mo catalyst with a molybdenum concentration of 0.5 mmol/g.

[0042]

(Example of obtaining 2 catalyst on a substrate)

A _SiO2- supported Cs-based catalyst having a Cs concentration of 0.5 mmol/g was obtained in the same manner as in Preparation Example 1 except that 0.081 g of cesium carbonate (anhydrous) (assay: 95.0 to 102.0% (titration), manufactured by FUJIFILM Wako Pure Chemical Corporation, 1 Wako brand, distributor 034-06542, lot No. CAG5233) was used instead of (NH ₄ )6Mo ₇ O24⋅4H ₂ O.

[0043]

<Example 1>

(2-furamide dehydration reaction)

Into a reaction tube containing a stirrer, 340 mg (3 mmol) of 2-furamide (manufactured by AK Scientific, Inc., purity 98.0%) as a starting material, 400 mg of the _SiO2- supported Mo catalyst obtained in Preparation Example 1, 0.1 g of dodecane (manufactured by FUJIFILM Wako Pure Chemical Corporation) as an internal standard substance, 20 g of mesitylene as a solvent, a gauze, cotton wool, and 2 g of 3A molecular sieves previously calcined at 300°C for 1 hour as a desiccant were successively placed. The tube was placed in the reactor (furnace) shown in Fig. 1, which has a cooler located above the connecting portion and a balloon located above the cooler.

The reactor (furnace) was set at 180°C and 600 rpm, and the reaction solution was subjected to reaction for 72 hours after the reaction solution boiled. The time of detection of the reaction solution boiling was defined as the reaction start time. The reaction solution was removed from the reactor and cooled to obtain the reaction product. The time of removing the reaction solution from the reactor was defined as the reaction stop time. The yield of the obtained 2-furonitrile was 91%.

It should be noted that the yield (%) of 2-furonitrile was calculated based on the amount of 2-furamide using the following calculation formula.

Yield (%) of 2-furonitrile = amount of 2-furonitrile obtained [mmol] / amount of 2-furamide as raw material [mmol] × 100

[0044]

<Example 2>

The reaction product was obtained in the same manner as in Example 1, except that 680 mg (6.0 mmol) of 2-furamide (manufactured by AK Scientific, Inc., purity 98.0%) was used as the starting material. The yield of the obtained 2-furonitrile was 88%.

[0045]

<Example 3>

The reaction product was obtained in the same manner as in Example 1, except that the drying agent (molecular sieve) was not used. The yield of the obtained 2-furonitrile was 86%.

[0046]

<Example 4>

The reaction product was obtained in the same manner as in Example 1, except that the amount of catalyst added was changed from 400 mg to 100 mg, and the reaction time was changed from 72 hours to 24 hours. The yield of 2-furonitrile obtained was 57%.

[0047]

<Example 5>

The reaction product was obtained in the same manner as in Example 4, except that the drying agent (molecular sieve) was not used. The yield of the obtained 2-furonitrile was 53%.

[0048]

<Example 6>

The reaction product was obtained in the same manner as in Example 1, except that the reaction time was changed from 72 hours to 6 hours. The yield of the obtained 2-furonitrile was 25%.

[0049]

<Example 7>

The reaction product was obtained in the same manner as in Example 6, except that the drying agent (molecular sieve) was not used. The yield of the obtained 2-furonitrile was 17%.

[0050]

<Comparative example 1>

The reaction product was obtained in the same manner as in Example 4, except that the Cs catalyst on a SiO ₂ support obtained in Preparation Example 2 was used as a catalyst. The yield of the obtained 2-furonitrile was 38%.

[0051]

<Comparative example 2>

The reaction product was obtained in the same manner as in Example 5, except that the Cs catalyst on a SiO ₂ support obtained in Preparation Example 2 was used as a catalyst. The yield of the obtained 2-furonitrile was 27%.

[0052]

<Comparative example 3>

The reaction product was obtained in the same manner as in Example 6, except that the Cs catalyst on a SiO ₂ support obtained in Preparation Example 2 was used as a catalyst. The yield of the obtained 2-furonitrile was 14%.

[0053]

<Comparative example 4>

The reaction product was obtained in the same manner as in Example 7, except that the Cs catalyst on a SiO ₂ support obtained in Preparation Example 2 was used as a catalyst. The yield of the obtained 2-furonitrile was 16%.

[0054]

<Example 8>

Cerium oxide (manufactured by Solvay Special Chem Japan, Ltd., HSA-20SP, average particle diameter of about 10 μm, impurity concentration of 0.02% or less) was calcined in an air atmosphere at 600°C for 3 hours to obtain a powdery solid catalyst.

Then, 0.344 g (2.0 mmol) of the solid catalyst, 2.33 g (25.0 mmol) of 2-furonitrile obtained in Example 1, and 0.751 g of 1-propanol (12.5 mmol, manufactured by FUJIFILM Wako Pure Chemical Corporation) were placed in an autoclave (with two inclined stirrers for stirring, material SUS316, capacity 190 mL). After purging with _CO2 , the system was filled with _CO2 to increase the pressure to 5 MPa to carry out the reaction (i.e., the reaction for producing an aliphatic carboxylic acid ester) at a reaction temperature of 132°C for 4 hours.

Then, the autoclave was cooled and depressurized to collect the reaction liquid. The reaction liquid was analyzed by gas chromatography. As a result, 7.31 g (5.0 mmol) of dipropyl carbonate (DPrC) were found as the desired product and 0.67 g (6.0 mmol) of 2-furamide, 0.0412 g (0.04 mmol) of propyl carbamate, 0.0154 g (0.10 mmol) of propylfuran-2-carboxylate and 0.0153 g (0.10 mmol) of propylfuran-2-imidate were found as by-products.

Then, 2-furamide obtained as a by-product was separated, and then the same operation as in Example 1 was performed using 2-furamide to regenerate 2-furonitrile. Then, the regenerated 2-furonitrile was reused in the reaction for producing an ester of an aliphatic carboxylic acid.

Claims (16)

1. A method for producing 2-furonitrile comprising dehydrating 2-furamide in the presence of a catalyst which is Mo/SiO ₂ , in which molybdenum (Mo) is supported on a SiO ₂ substrate. 2. A method for producing 2-furonitrile according to claim 1, characterized in that dehydration is additionally carried out in the presence of a desiccant. 3. A method for producing 2-furonitrile according to claim 2, characterized in that the desiccant is a molecular sieve. 4. A method for producing 2-furonitrile according to any of paragraphs 1-3, characterized in that 2-furancarboxylic acid is obtained together with 2-furonitrile. 5. A method for producing a carbonate ester, comprising: a first reaction step comprising a reaction for producing a carbonate ester in which an alcohol and carbon dioxide react in the presence of a solid catalyst, 2-furonitrile and a solvent to produce a carbonate ester and water, and a hydration reaction in which 2-furonitrile is hydrated with the resulting water to produce 2-furamide; and a second reaction stage in which 2-furamide is separated from the reaction system from the first reaction stage, and then 2-furamide is dehydrated in the presence of a Mo/SiO ₂ catalyst in which molybdenum (Mo) is supported on a SiO ₂ substrate to regenerate 2-furonitrile, wherein at least a portion of the 2-furonitrile regenerated in the second reaction stage is used in the first reaction stage. 6. A method for producing a carbonate ester according to paragraph 5, characterized in that dehydration is additionally carried out in the presence of a desiccant. 7. A method for producing a carbonate ester according to claim 6, characterized in that said drying agent is a molecular sieve. 8. A method for producing a carbonate ester according to any one of paragraphs 5-7, characterized in that said alcohol includes an alcohol containing from 1 to 6 carbon atoms. 9. A method for producing a carbonate ester according to any one of paragraphs 5-8, characterized in that the solid catalyst includes at least one selected from CeO ₂ and ZrO ₂ . 10. A method for producing a carbonate ester according to any one of paragraphs 5-9, characterized in that at the first stage of the reaction a solvent is used that has a boiling point higher than the boiling point of the resulting 2-furamide. 11. A method for producing a carbonate ester according to claim 10, characterized in that said solvent includes at least one selected from dialkylbenzene, alkylnaphthalene, and diphenylbenzene.