JP5822191B2 - Method for producing cyclohexanone - Google Patents
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Description
本発明は、シクロヘキサンをコバルト化合物を触媒として酸化することによりラクタム原料として有用なシクロヘキサノンを選択性良く製造する方法に関する。 The present invention relates to a method for producing cyclohexanone useful as a lactam raw material with high selectivity by oxidizing cyclohexane using a cobalt compound as a catalyst.
シクロヘキサノンは、カプロラクタム、ナイロン、アジピン酸の製造原料、高沸点溶剤、剥離剤、金属等の洗浄剤、染料の安定剤など、様々な分野で用いられている。中でも特に、カプロラクタムの原料として有用であり、カプロラクタムの製造量のうち、およそ90%以上がシクロヘキサノンのオキシムを経由する方法によって製造されている。そして、シクロヘキサノンは、シクロヘキサンの酸化もしくはフェノールの水素化によって製造されており、シクロヘキサノン製造量の約80%がシクロヘキサン酸化法に基づいている。 Cyclohexanone is used in various fields such as caprolactam, nylon, adipic acid production raw materials, high boiling point solvents, release agents, detergents for metals, dye stabilizers, and the like. Especially, it is useful as a raw material of caprolactam, and about 90% or more of the production amount of caprolactam is produced by a method via an oxime of cyclohexanone. Cyclohexanone is produced by oxidation of cyclohexane or hydrogenation of phenol, and about 80% of the amount of cyclohexanone produced is based on the cyclohexane oxidation method.
しかし、シクロヘキサノンの従来の製造方法は、その転化率が低いという欠点を有する。加えて、これらの反応からは様々なシクロヘキサンの酸化生成物の分解物が生成するので、生成物選択率が80%を超えることは難しい。 However, the conventional method for producing cyclohexanone has the disadvantage that its conversion rate is low. In addition, since the decomposition products of various oxidation products of cyclohexane are generated from these reactions, it is difficult for the product selectivity to exceed 80%.
例えば、特許文献1及び2には、極性プロトン溶剤及び極性非プロトン溶剤から選択される溶剤中において、反応媒体に溶解させた触媒の存在下、酸素又は酸素含有ガスにより、炭化水素、アルコール及び/又はケトンが液相で酸化しカルボン酸となることが記載されている。 For example, in Patent Documents 1 and 2, in a solvent selected from polar protic solvents and polar aprotic solvents, in the presence of a catalyst dissolved in a reaction medium, oxygen, oxygen-containing gas, hydrocarbon, alcohol and / or Alternatively, it is described that a ketone is oxidized in a liquid phase to become a carboxylic acid.
特許文献1及び2の記載の通り、シクロヘキサノンは、酸化反応条件下において、エステルやカルボン酸などの副生物を生成する。また、特許文献3に記載の通り、シクロヘキサンの分子状酸素による酸化により、シクロヘキサノンのみならずシクロヘキサノールが生成することも知られている。シクロヘキサノールが副生する場合には、シクロヘキサノールとシクロヘキサノンを蒸留操作等で分離し、シクロヘキサノールを脱水素反応等によってシクロヘキサノンに変換する工程が必要となるため、シクロヘキサノン製造工程が煩雑となり、シクロヘキサノン製造コストが増大する。
このため、通常、工業的には3〜4%と言う低い転化率で酸化反応を行い、できるだけ選択率を高める工夫をしなければならないという問題がある。
As described in Patent Documents 1 and 2, cyclohexanone generates by-products such as esters and carboxylic acids under oxidation reaction conditions. Further, as described in Patent Document 3, it is also known that not only cyclohexanone but also cyclohexanol is generated by oxidation of cyclohexane with molecular oxygen. When cyclohexanol is produced as a by-product, it is necessary to separate cyclohexanol and cyclohexanone by distillation, etc., and to convert cyclohexanol to cyclohexanone by dehydrogenation, etc., making the cyclohexanone production process complicated and producing cyclohexanone Cost increases.
For this reason, there is a problem that usually, industrially, it is necessary to devise an oxidation reaction at a low conversion rate of 3 to 4% to increase the selectivity as much as possible.
そこで、本発明は、上記のような問題を鑑みてなされたものであって、シクロヘキサンをコバルト触媒を用いて酸化させる際に、選択性良く高効率でシクロヘキサノンを製造することができるシクロヘキサノンの製造方法を提供することを目的とする。 Therefore, the present invention has been made in view of the above problems, and a method for producing cyclohexanone capable of producing cyclohexanone with high selectivity and high efficiency when cyclohexane is oxidized using a cobalt catalyst. The purpose is to provide.
以上の目的を達成するために、本発明者らは鋭意研究を重ねた結果、通常、室温ではシクロヘキサンに溶解し難いコバルト化合物を触媒として用いて、酸化処理を無溶媒で行うと、予期に反し選択性良くシクロヘキサノンが製造できることを見出した。 In order to achieve the above object, the present inventors have conducted extensive research. As a result, it is contrary to expectation that the oxidation treatment is usually carried out in the absence of solvent using a cobalt compound that is difficult to dissolve in cyclohexane as a catalyst at room temperature. It has been found that cyclohexanone can be produced with good selectivity.
すなわち、本発明は、シクロヘキサンを酸素又は酸素含有ガスと接触させて、コバルト化合物を触媒として酸化させるシクロヘキサノンの製造方法であって、前記酸化処理は、無溶媒で行うことを特徴とするシクロヘキサノンの製造方法である。 That is, the present invention is a process for producing cyclohexanone by contacting cyclohexane with oxygen or an oxygen-containing gas and oxidizing using a cobalt compound as a catalyst, wherein the oxidation treatment is carried out in the absence of a solvent. Is the method.
以上のように本発明によれば、シクロヘキサンをコバルト触媒を用いて酸化させる際に、選択性良く高効率でシクロヘキサノンを製造することができるシクロヘキサノンの製造方法を提供することができる。 As described above, according to the present invention, it is possible to provide a method for producing cyclohexanone capable of producing cyclohexanone with high selectivity and high efficiency when cyclohexane is oxidized using a cobalt catalyst.
本発明は、触媒としてコバルト化合物の存在下に、シクロヘキサンを酸素又は酸素含有ガスと接触させることにより、酸化反応を行う。この酸化反応は、液相、気相のいずれでも行うことができるが、液相にて行うことがより好ましい。 In the present invention, an oxidation reaction is performed by contacting cyclohexane with oxygen or an oxygen-containing gas in the presence of a cobalt compound as a catalyst. This oxidation reaction can be carried out either in the liquid phase or in the gas phase, but it is more preferably carried out in the liquid phase.
本発明に係るシクロヘキサノンの製造方法において、上記酸化反応は、無溶媒で行うことを特徴とする。無溶媒で行うことにより、シクロヘキサノールを副生することなく、高効率でシクロヘキサノンを製造できる。また、溶媒を蒸留等で分離除去するという煩雑な工程を省略することができる。 In the method for producing cyclohexanone according to the present invention, the oxidation reaction is performed without a solvent. By carrying out without solvent, cyclohexanone can be produced with high efficiency without producing by-product cyclohexanol. Moreover, the complicated process of separating and removing the solvent by distillation or the like can be omitted.
本発明に係るシクロヘキサノンの製造方法において、酸素又は酸素含有ガスとしては、酸素ガス、空気、または酸素ガスもしくは空気を窒素、二酸化炭素、ヘリウム等の不活性ガスで希釈したものを用いることができる。シクロヘキサンと酸素又は酸素含有ガスとの接触は、例えば、シクロヘキサンおよびコバルト化合物を含む液を、酸素又は酸素含有ガスの雰囲気下に置くことにより行ってもよいし、この液中に酸素又は酸素含有ガスを吹き込むことにより行ってもよい。 In the method for producing cyclohexanone according to the present invention, as oxygen or an oxygen-containing gas, oxygen gas, air, or oxygen gas or air diluted with an inert gas such as nitrogen, carbon dioxide, or helium can be used. The contact between cyclohexane and oxygen or an oxygen-containing gas may be carried out, for example, by placing a liquid containing cyclohexane and a cobalt compound in an atmosphere of oxygen or an oxygen-containing gas. May be performed by blowing.
本発明に係るシクロヘキサノンの製造方法において、触媒として用いられるコバルト化合物は、硝酸コバルト、アセチルアセトンコバルト、塩化コバルト、過塩素酸コバルト、テトラフルオロホウ酸コバルト及び炭酸コバルト並びにそれらの水和物より選ばれる1以上であることが好ましく、中でも硝酸コバルト六水和物あるいはアセチルアセトンコバルトがより好ましい。 In the method for producing cyclohexanone according to the present invention, the cobalt compound used as a catalyst is selected from cobalt nitrate, acetylacetone cobalt, cobalt chloride, cobalt perchlorate, cobalt tetrafluoroborate, cobalt carbonate, and hydrates thereof. Of these, cobalt nitrate hexahydrate or acetylacetone cobalt is more preferable.
上記触媒の量は、シクロヘキサン1モルに対して0.00001モル〜10モルが好ましく、シクロヘキサン1モルに対して0.005モル〜0.1モルが特に好ましい。触媒添加量が少ない程、反応効率が高いため好ましい。また、触媒添加量を減じても、シクロヘキサン転化率は充分に高く、シクロヘキサノン選択性が高い。 The amount of the catalyst is preferably 0.00001 mol to 10 mol with respect to 1 mol of cyclohexane, and particularly preferably 0.005 mol to 0.1 mol with respect to 1 mol of cyclohexane. The smaller the amount of catalyst added, the better the reaction efficiency. Moreover, even if the catalyst addition amount is reduced, the cyclohexane conversion is sufficiently high and the cyclohexanone selectivity is high.
本発明に係るシクロヘキサノンの製造方法において、反応温度が100℃以下の時には著しく反応が遅いため、100℃より高い反応温度が好ましく、110℃〜180℃がより好ましい。 In the method for producing cyclohexanone according to the present invention, when the reaction temperature is 100 ° C. or lower, the reaction is remarkably slow. Therefore, a reaction temperature higher than 100 ° C. is preferable, and 110 ° C. to 180 ° C. is more preferable.
反応圧力については、特に限定されないが、過度に低いと反応速度が低下するので、通常0.1MPa以上、好ましくは0.5MPa以上、特に2MPa以上が好ましい。また、反応圧力が過度に高い場合には、耐圧性を高めた特殊な反応装置が必要となることもあり、通常100MPa以下、好ましくは50MPa以下、特に30MPa以下が好ましい。 The reaction pressure is not particularly limited. However, if the reaction pressure is too low, the reaction rate is lowered. Therefore, the reaction pressure is usually 0.1 MPa or more, preferably 0.5 MPa or more, particularly 2 MPa or more. In addition, when the reaction pressure is excessively high, a special reaction apparatus with improved pressure resistance may be required, and is usually 100 MPa or less, preferably 50 MPa or less, and particularly preferably 30 MPa or less.
本発明に係るシクロヘキサノンの製造方法によれば、高い選択性でシクロヘキサノンを製造することが可能であるが、反応終了後の反応混合物には、シクロヘキサノンのほかに、未反応の原料、副反応による生成物が含まれることもある。シクロヘキサノンを分離する方法としては、特に限定されず、蒸留、抽出など公知の方法が挙げられる。 According to the method for producing cyclohexanone according to the present invention, cyclohexanone can be produced with high selectivity. However, in addition to cyclohexanone, the reaction mixture after the reaction includes unreacted raw materials and production by side reactions. Sometimes things are included. The method for separating cyclohexanone is not particularly limited, and examples thereof include known methods such as distillation and extraction.
以下、実施例により本発明を具体的に説明するが、本発明はこれらの実施例に限定されるものではない。 EXAMPLES Hereinafter, although an Example demonstrates this invention concretely, this invention is not limited to these Examples.
(実験例1)
まず、ステンレス製オートクレーブ(耐圧硝子工業株式会社製、10ml)にシクロヘキサン(10mmol)、表1に示す種々のコバルト化合物(10mol%)を加え、酸素:窒素(21:79)混合ガスを10MPaに充填した後に系を閉じた。135℃で24時間加熱撹拌した。その後、反応混合物をサンプリングし、1H−NMRの測定を行い、その積分比から算出した生成物の組成比を表1に示す。また、比較として、触媒を用いなかった場合についても同様にして、結果を表1に示す。
(Experimental example 1)
First, cyclohexane (10 mmol) and various cobalt compounds (10 mol%) shown in Table 1 are added to a stainless steel autoclave (made by pressure-resistant glass industry, 10 ml), and an oxygen: nitrogen (21:79) mixed gas is filled to 10 MPa. After that, the system was closed. The mixture was heated and stirred at 135 ° C. for 24 hours. Thereafter, the reaction mixture was sampled, 1 H-NMR was measured, and the composition ratio of the product calculated from the integration ratio is shown in Table 1. For comparison, the results are shown in Table 1 in the same manner even when no catalyst was used.
以上より、硝酸コバルト六水和物、塩化コバルト、及びアセチルアセトンコバルトを触媒に用いたときに、反応混合物中のシクロヘキサノンの組成比が比較的高くなることが明らかとなった。また、シクロヘキサノン選択性は、いずれも100%と非常に高かった。 From the above, it was revealed that the composition ratio of cyclohexanone in the reaction mixture was relatively high when cobalt nitrate hexahydrate, cobalt chloride, and acetylacetone cobalt were used as catalysts. Further, the cyclohexanone selectivity was very high at 100%.
(実験例2)
次に、反応に用いられる触媒量を検討した。触媒量の検討を行うにあたって、反応効率を表す指標としてEfを定義する。一般的には、そのような指標にはターンオーバー数(turnover number、TON)が用いられるが、本実験では収率をもとに算出していないために、TONに相当する指標として下記式(1)で示されるEfを使用する。
(Experimental example 2)
Next, the amount of catalyst used in the reaction was examined. In examining the amount of catalyst, Ef is defined as an index representing reaction efficiency. In general, a turnover number (TU) is used as such an index, but since it is not calculated based on the yield in this experiment, the following formula ( Ef shown in 1) is used.
硝酸コバルト六水和物あるいはアセチルアセトンコバルトを使用し、触媒量の検討を行った。具体的には、シクロヘキサンを10mmolから20mmolに変更し、触媒量を表2に示すようにそれぞれ変化させた以外は、実験例1と同様に実験を行った。結果を表2に示す。 The amount of catalyst was examined using cobalt nitrate hexahydrate or acetylacetone cobalt. Specifically, the experiment was performed in the same manner as in Experimental Example 1 except that cyclohexane was changed from 10 mmol to 20 mmol and the catalyst amount was changed as shown in Table 2. The results are shown in Table 2.
(実験例3)
次に、反応時間の検討を行った。具体的には、コバルト化合物として硝酸コバルト六水和物を用い、シクロヘキサンを10mmolから20mmolに変更し、触媒量、反応時間を表3に示すようにそれぞれ変化させた以外は、実験例1と同様に実験を行った。結果を表3に示す。本検討は、反応容器からのサンプル抜き取りによるものではなく、それぞれの反応時間で反応を停止し、分析した結果である。
(Experimental example 3)
Next, the reaction time was examined. Specifically, cobalt nitrate hexahydrate was used as the cobalt compound, cyclohexane was changed from 10 mmol to 20 mmol, and the catalyst amount and the reaction time were changed as shown in Table 3, respectively. The experiment was conducted. The results are shown in Table 3. This study is not based on sampling from the reaction vessel, but is the result of analysis after stopping the reaction at each reaction time.
(実験例4)
次に、反応圧力、反応温度の検討を行った。具体的には、コバルト化合物として硝酸コバルト六水和物2.5モル%を用い、反応圧力、反応温度を表4に示すようにそれぞれ変化させた以外は、実験例2と同様に実験を行った。結果を表4に示す。なお、反応温度115℃の場合には、反応時間を48時間とした。本検討は、実験例1と同様な方法により分析した結果である。
(Experimental example 4)
Next, the reaction pressure and reaction temperature were examined. Specifically, the experiment was conducted in the same manner as in Experimental Example 2 except that 2.5 mol% of cobalt nitrate hexahydrate was used as the cobalt compound, and the reaction pressure and reaction temperature were changed as shown in Table 4. It was. The results are shown in Table 4. When the reaction temperature was 115 ° C., the reaction time was 48 hours. This study is the result of analysis by the same method as in Experimental Example 1.
Claims (2)
前記酸化処理は、無溶媒で行い、
前記コバルト化合物が、硝酸コバルト、アセチルアセトンコバルト、塩化コバルト及び炭酸コバルト並びにそれらの水和物より選ばれる1以上であることを特徴とするシクロヘキサノンの製造方法。 A process for producing cyclohexanone, wherein cyclohexane is brought into contact with oxygen or an oxygen-containing gas and oxidized using only a cobalt compound as a catalyst,
The oxidation treatment are performed by the absence of a solvent,
The method for producing cyclohexanone, wherein the cobalt compound is one or more selected from cobalt nitrate, acetylacetone cobalt, cobalt chloride, cobalt carbonate, and hydrates thereof .
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