JP2012250930A - Process for producing carbamate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a process for producing a carbamate which can directly produce a carbamate from raw materials without producing by-products such as a ketone and a hydrogen halide by using carbon dioxide, an alcohol, and an amine as the raw materials and can directly produce a carbamate with higher selectivity than in the past when an aliphatic primary monoamine is used as the amine, and furthermore meets all conditions capable of directly producing a carbonate even with the use of an amine other than an aliphatic primary monoamine as the amine.SOLUTION: The process for producing a carbamate comprises reacting carbon dioxide, an alcohol, and an amine as raw materials in the presence of cerium oxide and/or a cerium complex oxide.

Description

  The present invention relates to a method for producing carbamate by directly reacting carbon dioxide, an alcohol, and an amine in the presence of cerium oxide and / or a cerium-based composite oxide.

Various methods for synthesizing carbamate directly from carbon dioxide, alcohol, and amine as raw materials are known.
Carbamate refers to an ester of carbamic acid (hydrogen bonded to nitrogen of carbamic acid may be substituted).
First, these methods and problems will be described.

1. Alkylation method As a method of directly synthesizing carbamate from carbon dioxide, alcohol and amine, for example, there is a method of synthesizing carbamate in the presence of an alkylating agent such as an alkyl halide, an onium salt of a catalyst and an inorganic base. Are known.

  Specific examples include the method disclosed in J. Org. Chem., 2001, 66, 1035 (Non-Patent Document 1). Non-Patent Document 1 discloses a method of synthesizing carbamate by a reaction route represented by the following chemical reaction formula, for example.

このような方法では、アミンの量に対するアルキル化剤の量が化学量論量以上必要となるうえ、カーバメートを合成する過程で腐食性のハロゲン化水素が副成する。生成したハロゲン化水素を中和するためには、該ハロゲン化水素の量に対する中和剤としての無機塩基化合物の量が化学量論量以上に必要となり、しかも、該中和により新たに生成した無機塩基化合物は再生が困難な塩である。これにより、製造コストや製造工程が増加するという問題が生じる。

In such a method, the amount of the alkylating agent with respect to the amount of amine requires a stoichiometric amount or more, and corrosive hydrogen halide is formed as a by-product in the process of synthesizing carbamate. In order to neutralize the produced hydrogen halide, the amount of the inorganic base compound as a neutralizing agent relative to the amount of the hydrogen halide is required to be more than the stoichiometric amount, and newly produced by the neutralization. Inorganic base compounds are salts that are difficult to regenerate. Thereby, the problem that manufacturing cost and a manufacturing process increase arises.

  The onium salt catalyst is generally a homogeneous catalyst, and is used for the above reaction through complicated steps to recover the onium salt catalyst separated from the reaction system or to reuse the recovered omnium salt catalyst. There is also a problem that the treated omnium salt catalyst needs to be treated.

2. Acetal method As described above, in order to avoid the problem of consumption of the reaction by-products (stoichiometric amount above the stoichiometric amount, which is a reagent used to advance the reaction, which is not incorporated into the product skeleton), There is a method of synthesizing carbamate using a renewable acetal as a reaction auxiliary material.

  Specific examples include the method represented by the following scheme diagram disclosed in J. Chem. Soc. Chem. Commun., 2001, 2238 (Non-patent Document 2).

非特許文献２に記載の方法では、上記スキーム図に示されるように、原料である二酸化炭素、アルコールおよびアミンと、スズ触媒と、アセタールとを共存させてカーバメートを合成する。アセタールは化学量論量以上使用する。

In the method described in Non-Patent Document 2, carbamate is synthesized by coexisting raw materials such as carbon dioxide, alcohol and amine, tin catalyst, and acetal, as shown in the above-mentioned scheme. Use at least stoichiometric amount of acetal.

  In this method, water produced in the reaction system reacts with acetal to produce a ketone. Although this reaction is important for promoting the formation of carbamate, the ketone itself produced by the reaction causes a side reaction. And the process for isolate | separating the side reaction product derived from the ketone produced by this side reaction and carbamate is required.

  Further, after the reaction, the ketone needs to be separated from the mixture obtained after the reaction and reacted with the alcohol to induce the acetal again in order to regenerate the acetal, but this requires a complicated process. Become.

3. Cesium carbonate catalyst method Unlike the above method, there is also known a method in which carbamate is directly synthesized from carbon dioxide, alcohol, and amine as raw materials without using reaction auxiliary raw materials.

  For example, Green Chem., 2008, 10, 111 (Non-patent Document 3) discloses a method for producing carbamate by a reaction route represented by the following chemical formula. In this method, carbamate is obtained in the presence of a cesium carbonate catalyst. Carbamate is directly synthesized from carbon dioxide, an alcohol, and an amine, which are raw materials for synthesizing the compound.

この方法における反応条件は、反応系内の二酸化炭素の反応初期圧が２．５ＭＰａ、反応時間が４〜４８時間、反応温度が１７０〜２２０℃である。この方法により、二酸化炭素と、アルキルアミンと、一級アルコールとから、種々の脂肪族カーバメートを最高で４０％台の収率で得られる。

The reaction conditions in this method are that the initial reaction pressure of carbon dioxide in the reaction system is 2.5 MPa, the reaction time is 4 to 48 hours, and the reaction temperature is 170 to 220 ° C. By this method, various aliphatic carbamates can be obtained in a yield of up to 40% from carbon dioxide, alkylamine and primary alcohol.

  This method uses only raw materials (carbon dioxide, alcohol, and amine) and a catalyst, but the ratio of aliphatic carbamate in the total amount of 100% of the molar amount of urea and the molar amount of carbamate ( There is a problem that the selectivity is as low as 70% and the yield is as high as 40%. Moreover, in this method, only aliphatic carbonates can be obtained, and there is a problem that carbonates other than aliphatic carbonates such as industrially important aromatic carbamates cannot be obtained.

Next, the technical background of cerium oxide used in the present invention will be described.
As a reaction using cerium oxide, a carbon dioxide immobilization reaction using cerium oxide is known.

  For example, Green Chem., 2004, 6, 206 (Non-patent Document 4) and Catalysis Today, 2006, 115, 95 (Non-patent Document 5) react carbon dioxide with alcohol in the presence of cerium oxide to produce carbonate. A method of synthesizing is disclosed. Non-Patent Document 4 and Non-Patent Document 5 disclose, for example, reactions represented by the following chemical reaction formulas.

これら方法では、アルコールとしてメタノールを用いるとジメチルカーボーネートが得られる。同じく、アルコールとしてエタノールを用いるとジエチルカーボネートのような鎖状カーボネートやジエチレングリコールからエチレンカーボネートが得られ、アルコールとして１，２−プロピレングリコールを用いるとプロピレンカーボネートが得られる。

In these methods, dimethyl carbonate is obtained when methanol is used as the alcohol. Similarly, when ethanol is used as the alcohol, ethylene carbonate is obtained from a chain carbonate such as diethyl carbonate or diethylene glycol, and when 1,2-propylene glycol is used as the alcohol, propylene carbonate is obtained.

  The yield of the carbonate obtained is restricted by chemical equilibrium due to the water generated in the reaction system, and the reaction yield of carbonate based on the amount of alcohol used is only about 1%.

J. Org. Chem., 2001, 66, 1035 J.Chem.Soc.Chem.Commun., 2001,2238 Green Chem., 2008, 10, 111 Green Chem., 2004, 6, 206 Catalysis Today, 2006,115,95

The subject of this invention is providing the manufacturing method of the carbamate which satisfy | fills all the following conditions.
Carbamate can be produced directly from carbon dioxide, alcohol, and amine without using by-products such as ketones and hydrogen halides generated from the reaction of water and acetal as described above.
-When an aliphatic primary monoamine is used as the amine, carbamate can be directly produced with a higher selectivity than in the past.
-Carbamate can be directly produced even when an amine other than an aliphatic primary monoamine is used as the amine.

  As a result of intensive studies to solve the above problems, the present inventors have reacted carbon dioxide, alcohol, and amine as raw materials in the presence of cerium oxide and / or cerium-based composite oxide. The present inventors have found that the problems can be solved and completed the present invention.

That is, the present invention relates to the following carbamate production methods.
(1) A method for producing carbamate, comprising reacting carbon dioxide, an alcohol, and an amine in the presence of cerium oxide and / or a cerium-based composite oxide.
(2) The method for producing carbamate according to (1) above, wherein the cerium oxide is cerium dioxide.
(3) The method for producing carbamate according to (1) above, wherein the amine is an aromatic amine.
(4) The method for producing carbamate according to (1) above, wherein the amine is a diamine.

  According to the carbamate production method of the present invention, a carbamate is directly produced from carbon dioxide, alcohol and amine as raw materials without using reaction by-products and without generating by-products such as ketones and hydrogen halides. it can.

According to the carbamate production method of the present invention, when an aliphatic primary monoamine is used as the amine, the carbamate can be directly produced with a higher selectivity than in the past.
Furthermore, according to the carbamate production method of the present invention, even when an aromatic amine, polyamine or secondary amine is used as the amine, the carbamate can be produced directly from carbon dioxide, alcohol and the amine.

The present invention is described in detail below.
The present invention is a method for producing carbamate, comprising reacting carbon dioxide, an alcohol, and an amine in the presence of cerium oxide and / or a cerium-based composite oxide.

Hereinafter, production conditions (reaction conditions), raw materials, and the like will be described.
1. Manufacturing conditions (reaction conditions)
In the carbamate production method of the present invention, a solvent or the like can be used as necessary in addition to carbon dioxide, alcohol and amine as raw materials, and cerium oxide or cerium-based composite oxide as catalysts.

The above reaction may be carried out by a batch method or a continuous method.
It is preferable from the following viewpoints to react carbon dioxide, alcohol, and amine as raw materials at the same time. That is, in the embodiment in which carbon dioxide, alcohol and amine are reacted at the same time, the yield tends to be higher than in the embodiment in which carbon dioxide and alcohol are reacted first, and then the obtained product and amine are reacted. Also, the reactivity tends to be higher than in the embodiment in which carbon dioxide and amine are reacted first, and then the obtained product and alcohol are reacted.

  In addition, although water is by-produced in the above reaction, water may be removed from the reaction system as necessary. If water is removed from the reaction system, the chemical equilibrium of the above reaction can be tilted in the direction in which carbamate is generated. As a result, the yield and selectivity of carbamate can be improved, and carbamate can be produced more efficiently. it can.

  Here, the selectivity of carbamate (hereinafter also referred to simply as selectivity) is the mol of carbamate produced relative to the molar amount (denominator) of the amine reacted in the starting amine as shown in the following formula (I). It is a 100 minute ratio of the quantity (denominator).

＜反応温度＞
本発明における上記反応の反応温度は、特に限定されないが、９０℃〜２００℃の範囲が好適である。このような範囲で上記反応を行なうと、反応の進行が速く、かつ、工業的な実施も容易である。さらには、高い選択率と収率で、カーバメートを製造することができる。

<Reaction temperature>
Although the reaction temperature of the said reaction in this invention is not specifically limited, The range of 90 to 200 degreeC is suitable. When the above reaction is carried out in such a range, the reaction proceeds rapidly and industrial implementation is easy. Furthermore, carbamate can be produced with high selectivity and yield.

<Reaction pressure>
The reaction pressure (gauge pressure, the same applies hereinafter) of the above reaction in the present invention is not particularly limited, but is preferably in the range of normal pressure of 0.1 MPa to 20 MPa, more preferably 0.2 MPa to 10 MPa.
When the above reaction is performed in such a range, the reaction proceeds rapidly and a large-scale apparatus is not required. Furthermore, carbamate can be produced with high selectivity and yield.

<Reaction time>
Although the reaction time of the said reaction in this invention is not specifically limited, The range of 0.1 to 16 hours is suitable, and 2 to 8 hours are more suitable. When the above reaction is carried out in such a range, carbamate can be produced with high selectivity and yield.

2. Raw materials
<Amine>
In the carbamate production method of the present invention, a primary amine and / or a secondary amine is used as the amine.

  More specifically, examples of the primary amine include acyclic aliphatic amines such as ammonia, methylamine, ethylamine, propylamine, butylamine, hexylamine, octylamine, and benzylamine, and cycloaliphatic amines such as cyclohexylamine. Monoamines such as aliphatic primary amines, aromatic primary amines such as aniline, anisidine, p-aminophenol, and the like.

  Secondary amines include aliphatic secondary amines such as dimethylamine, diethylamine, dipropylamine, dibutylamine, N-methylhexylamine, N-methylbenzylamine, piperidine, pyrrolidine, morpholine; N-methylaniline, N- Monoamines such as aromatic secondary amines such as methylanisidine and p-hydroxy-N-methylaniline can be used.

  In addition to the above monoamines, ethylenediamine, trimethylenediamine, tetramethylenediamine, hexamethylenediamine, 1,3-diaminocyclohexane, 1,4-diaminocyclohexane, 1,3-diaminomethylcyclohexane, 1,4-diamino Aliphatic diamines such as methylcyclohexane, isophoronediamine, m-xylylenediamine, p-xylylenediamine; m-phenylenediamine, p-phenylenediamine, 2,4-diaminotoluene, 2,6-diaminotoluene, 3,3 Diamines such as aromatic diamines such as' -diaminobiphenyl, 4,4'-diaminodiphenylmethane, and the like can be used.

In the present invention, ammonia is included in the amine.
In the present invention, the aromatic amine refers to an amine having an amino group directly bonded to an aromatic ring, and an amine having an amine bonded to an aromatic ring through a methylene group such as benzylamine is an aliphatic amine. And
The said amine may be used individually by 1 type, and may be used in combination of 2 or more type.

<Alcohol>
In the carbamate production method of the present invention, a primary alcohol and / or a secondary alcohol is used as the alcohol.

  More specifically, as alcohol, primary alcohols such as methanol, ethanol, 1-propanol, 1-butanol, isobutanol, pentyl alcohol, hexyl alcohol, 1-octanol; isopropanol, sec-butyl alcohol, cyclopentanol, Monoalcohols such as secondary alcohols such as cyclohexanol;

  In addition to the monoalcohol, the alcohol includes diols such as ethylene glycol, propylene glycol, 1,3-propanediol, and 1,4-butanediol, triols such as glycerin and trimethylolpropane; penta Polyols such as tetraols such as erythritol can also be used.

These alcohols may be used alone or in combination of two or more.
In the present invention, the alcohol is used in such an amount that the amount of the amine with respect to 1 mol of the alcohol is at least equal to or higher than that.
In addition, alcohol can be used not only as a raw material but also as a solvent by using alcohol in a large excess and using an excess that does not participate in the reaction as a solvent.

<CO2>
As a method for obtaining carbon dioxide used in the present invention, a method of collecting carbon dioxide by-produced in an industrial process and purifying it as necessary can be used. For example, carbon dioxide generated when producing or refining oil, coal, or natural gas, or carbon dioxide generated when processing waste plastics to extract energy or chemicals, and recovering as needed A method is mentioned. Further, when a mixture of carbon dioxide and another substance is obtained, it is preferable to carry out a purification treatment to obtain high-purity carbon dioxide, and the purity of carbon dioxide is preferably 99% or more.

  The amount of carbon dioxide used in the present invention is not particularly limited, but carbon dioxide may be introduced into the reaction system until the pressure in the reaction system is within the above-described reaction pressure range, and the amount thereof may be adjusted.

When the reaction is performed at normal pressure, carbon dioxide may be introduced into the reaction system by bubbling or the like.
When pressurizing the above reaction in a sealed container, for example, the pressure in the reaction system is adjusted by the amount of carbon dioxide gas introduced, and carbon dioxide is introduced until the pressure in the reaction system falls within the aforementioned reaction pressure range. do it.

<Cerium oxide, cerium-based composite oxide>
In the present invention, cerium oxide may be used alone, cerium-based composite oxide may be used alone, or cerium oxide and cerium-based composite oxide may be used in combination.

  As cerium oxide, there are dicerium trioxide (the valence of cerium atom: 3) and cerium dioxide (the valence of cerium atom: 4), any of which may be used, from the viewpoint of the yield of carbamate, More preferred is cerium dioxide.

Examples of the cerium-based composite oxide include composite oxides containing cerium, zinc, and zirconium.
In the present invention, cerium oxide and cerium-based composite oxide are used as a catalyst for the above reaction.

  The cerium oxide and the cerium-based composite oxide can be used in the form of a powder catalyst, or a supported catalyst in which cerium oxide and / or a cerium-based composite oxide is supported on activated carbon, silica, alumina, titania, zeolite, or the like. It can also be used in the form.

In the present invention, cerium oxide and cerium-based composite oxide can be reused.
For example, after the reaction, the obtained mixed solution (reaction solution) is subjected to filtration, and cerium oxide and / or cerium-based composite oxide can be collected by filtration and used again as a catalyst for the reaction.

The cerium oxide and cerium-based composite oxide recovered by filtration are activated to a complete or near state when fired in a temperature range of 300 to 900 ° C., for example.
The molar ratio of the cerium oxide and / or cerium-based composite oxide to the raw material in the above reaction of the present invention is not particularly limited, but when the above reaction is carried out as a batch reaction, cerium oxide and / or It is preferable to use the cerium-based composite oxide in an amount of 0.1 mol% to 50 mol%. When cerium oxide and / or cerium-based composite oxide is used in such a range, the reaction efficiency and reaction rate of the above reaction are high.

<Solvent>
The solvent used in the present invention is not particularly limited as long as the above reaction proceeds. For example, an alcohol as a reaction raw material can be preferably used.

  In addition, alcohol solvents other than the above-mentioned reaction raw material alcohol; hydrocarbon solvents such as pentane, heptane, hexane, cyclohexane, heptane; aromatic hydrocarbon solvents such as benzene, toluene, xylene; diethyl ether, diisopropyl ether , Dibutyl ether, tetrahydrofuran, tetrahydropyran, dioxane, and other ether solvents; acetonitrile, propionitrile, and other nitrile solvents; methyl acetate, ethyl acetate, propyl acetate, butyl acetate, and other ester solvents; .

These solvents can be used as a mixture, but it is desirable to use an alcohol alone from the viewpoint of recovering the used solvent after the reaction and reusing it.
When a solvent other than alcohol is used, it is used in an amount of 2 to 50 times by weight, preferably 5 to 30 times by weight with respect to the amine.

  When alcohol is used as a reaction solvent, it is necessary to use at least an equimolar amount of alcohol with respect to 1 mol of amine, and preferably 10 to 200 times the amount of alcohol is used with respect to amine. The alcohol can be recovered by distillation after the above reaction, and can be reused after appropriate dehydration treatment. Thereby, the usage-amount of a solvent can be reduced.

<Carbamate>
The fact that carbamate is obtained, its selectivity and yield, etc. can be measured, for example, by subjecting the obtained product to gas chromatography (GC).

  In the method for producing carbamate of the present invention, for example, when monoamine is used as an amine and monoalcohol is used as an alcohol as a raw material, for example, as in Example 2 (the reaction formula of Example 2 is shown below) As shown in reaction formula (1)), one type of carbamate is obtained.

  EXAMPLES Hereinafter, although this invention is demonstrated concretely with reference to an Example, this invention is not restrict | limited at all to these.

<Product Analysis Device>
Analysis of each component in the product obtained in each example (hereinafter also referred to as reaction mixture) was performed using a gas chromatograph apparatus (6890N manufactured by Agilent). A DB-1 column (length 30 m, diameter 0.32 mm, film thickness 1 μm) manufactured by J & W was used as an analysis column, and FID (hydrogen flame ion detector) was used as a detector.

<Manufacture of carbamate>
[Example 1]
In a 100 ml autoclave, aminomethylcyclohexane (0.57 g), methanol (16.02 g) and cerium dioxide (0.17 g) were added and mixed.

Next, the gas phase in the reactor was replaced with carbon dioxide, and carbon dioxide was introduced into the reactor until the pressure (gauge pressure) in the reactor reached 5 MPa.
The autoclave was then heated at 150 ° C. for 12 hours.

  The reaction mixture after the reaction was subjected to GC, and the components in the reaction mixture were quantified. As a result, N-cyclohexylmethyl-methylcarbamate was produced, the yield was 61.6%, and the selectivity was 85. 3%.

[Example 2]
In Example 1, carbamate was produced in the same manner as in Example 1 except that the alcohol was changed from methanol to ethanol (23.04 g).

  The reaction mixture after the reaction was subjected to GC and the components in the reaction mixture were quantified. As a result, N-cyclohexylmethyl-ethyl carbamate was produced, the yield was 42.0%, and the selectivity was 95. .5%.

[Example 3]
In Example 1, carbamate was produced in the same manner as in Example 1 except that the alcohol was changed from methanol to 1-propanol (30.05 g).

  The reaction mixture after the reaction was subjected to GC, and the components in the reaction mixture were quantified. As a result, N-cyclohexylmethyl-n-propylcarbamate was produced, and the yield was 26.0%. Was 92.2%.

[Example 4]
Benzylamine (0.54 g), methanol (16.02 g) g and cerium dioxide (0.17 g) g were mixed in an autoclave having a capacity of 100 ml.

Next, the gas phase in the reactor was replaced with carbon dioxide, and carbon dioxide was introduced into the reactor until the pressure (gauge pressure) in the reactor reached 5 MPa.
The autoclave was heated at 150 ° C. for 12 hours.

  The reaction mixture after the reaction was subjected to GC and the components in the reaction mixture were quantified. As a result, N-benzyl-methyl carbamate was produced, the yield was 88.0%, and the selectivity was 92. 4%.

[Example 5]
In Example 4, carbamate was produced in the same manner as in Example 1 except that the alcohol was changed from methanol to ethanol (23.04 g).
As a result of quantifying the reaction mixture after the reaction by GC, N-benzyl-ethyl carbamate was produced, the yield was 64.6%, and the selectivity was 95.8%.

[Example 6]
In Example 4, the carbamate was produced in the same manner as in Example 1 except that the alcohol was changed from methanol to 1-propanol (30.05 g).

  The reaction mixture after the reaction was subjected to GC and the components in the reaction mixture were quantified. As a result, N-benzyl-n-propyl carbamate was produced, the yield was 42.2%, and the selectivity was It was 93.8%.

[Example 7]
In a 100 ml autoclave, aniline (0.47 g), methanol (16.02 g) and cerium dioxide (0.17 g) were added and mixed.

Next, the gas phase in the reactor was replaced with carbon dioxide, and carbon dioxide was introduced into the reactor until the pressure (gauge pressure) in the reactor reached 1 MPa.
The autoclave was then heated at 150 ° C. for 12 hours.

  The reaction mixture after the reaction was subjected to GC and the components in the reaction mixture were quantified. As a result, N-phenyl-methyl carbamate was produced, the yield was 1.8%, and the selectivity was 56. 3%.

[Example 8]
In Example 7, carbamate was produced in the same manner as in Example 1 except that the alcohol was changed from methanol to ethanol (23.04 g).

  The reaction mixture after the reaction was subjected to GC, and the components in the reaction mixture were quantified. As a result, N-phenyl-ethyl carbamate was produced, the yield was 1.2%, and the selectivity was 66. 7%.

[Example 9]
In Example 7, carbamate was produced in the same manner as in Example 1 except that the alcohol was changed from methanol to 1-propanol (30.05 g).

  The reaction mixture after the reaction was subjected to GC and the components in the reaction mixture were quantified. As a result, N-phenyl-n-propyl carbamate was produced, the yield was 1.8%, and the selectivity was It was 69.2%.

[Example 10]
1,4-diaminomethylcyclohexane (0.71 g), methanol (16.02 g) and cerium dioxide (0.17 g) were placed in a 100 ml capacity autoclave and mixed.

Next, the gas phase in the reactor was replaced with carbon dioxide, and carbon dioxide was introduced into the reactor until the pressure (gauge pressure) in the reactor reached 1 MPa.
The autoclave was then heated at 150 ° C. for 12 hours.
The reaction mixture after the reaction was subjected to GC, and the components in the reaction mixture were quantified. As a result, the corresponding dicarbamate was produced, and the yield was 0.2%.

[Example 11]
N-methyl-benzylamine (1.21 g), methanol (16.02 g) and cerium dioxide (0.17 g) were placed in a 100 ml autoclave and mixed.

Next, the gas phase in the reactor was replaced with carbon dioxide, and carbon dioxide was introduced into the reactor until the pressure (gauge pressure) in the reactor reached 2 MPa.
The autoclave was then heated at 170 ° C. for 2 hours.

The reaction mixture after the reaction was subjected to GC and the components in the reaction mixture were quantified. As a result, N-methyl and N-benzyl-methylcarbamate were produced, and the yield was 42.0%.
The results of each Example are summarized in Table 1 and Table 2 below.

Claims (4)

  A method for producing carbamate, comprising reacting carbon dioxide, an alcohol, and an amine in the presence of cerium oxide and / or a cerium-based composite oxide.   The method for producing carbamate according to claim 1, wherein the cerium oxide is cerium dioxide.   The method for producing carbamate according to claim 1, wherein the amine is an aromatic amine.   The method for producing carbamate according to claim 1, wherein the amine is a diamine.