JPS6125692B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for producing ethanol and butanol by homologation reaction of methanol. More specifically, methanol is reacted with carbon monoxide or hydrogen-containing carbon monoxide (e.g., synthesis gas) using a catalyst system in which a transition metal compound is used as the main catalyst and an organic base is used as a co-catalyst to produce ethanol. This invention relates to a method for synthesizing butanol. The method for producing higher alcohols by the homologation reaction of methanol has been known for a long time, and since useful products such as ethanol, which were conventionally produced from petroleum-based raw materials, can be obtained from methanol, hydrogen and carbon monoxide, Research has been active again in recent years. A cobalt compound is usually used as the main catalyst for methanol homologation, but if no co-catalyst component is added to it, there are no advantages in terms of catalyst stability, activity or selectivity. I can not say. To overcome this problem, methods have been proposed to add tertiary phosphine, arsine, iodine compounds, or ruthenium compounds as co-catalyst components, but these co-catalysts are expensive or require equipment. In addition, its addition does not necessarily affect the stability of the catalyst,
This method has not yet been recognized as an industrially advantageous method due to the fact that it is not possible to improve the three factors of activity and selectivity at the same time. In order to overcome the above-mentioned problems in the conventionally known catalyst systems for methanol homologation reaction, the present inventors have carried out research and exploration of new catalyst systems. discovered the surprising and interesting fact that a catalyst system that combines an iron compound with a tertiary amine exhibits an excellent catalytic effect in the reaction for producing ethanol from methanol and carbon monoxide. The present inventors have found that the presence of alcohol can significantly accelerate the production of butanol, and that it is possible to obtain butanol depending on the conditions.Based on these findings, comprehensive research has led to the completion of the present invention. That is, the present invention uses a catalyst system containing a combination of an iron compound and a tertiary amine as a basic component in the absence of a halogen or a halogen compound, and uses methanol and carbon monoxide, or carbon monoxide containing hydrogen (e.g. The present invention provides a method for producing ethanol and butanol, which is characterized by reacting the ethanol and butanol with a synthetic gas (synthesis gas). The content of the present invention will be described below as catalyst, solvent, reaction temperature,
, pressure, and gas composition, and will be explained in detail step by step. Catalyst In the method of the present invention, an iron compound is used as the main catalyst and a tertiary amine is used as the co-catalyst. It is believed that the iron compound is transformed into a catalytically active form under the reaction conditions of the present invention, and in this case, this active species coordinates carbon monoxide by reaction with the reaction component carbon monoxide. Therefore, the most preferred form of iron compound is the metal carbonyl, although it goes without saying that any precursor that is carbonylated by coordinating carbon monoxide under the reaction conditions can be used as the catalytic iron compound. However, in this case, halides are excluded due to equipment corrosion. Examples of such iron compounds include simple iron metals, oxides, carboxylates, acetylacetonates, carbonyl compounds, and various complexes of iron compounds. The amount of iron compound used as the main catalyst is not particularly limited and can be used in any amount, but usually 1/10 or less (molar ratio) of the amount of methanol charged is sufficient. The amount used can be appropriately determined depending on factors such as price, synthesis gas composition and pressure, reaction temperature, solvent, type and amount of co-catalyst. In the method of the present invention, the presence of a tertiary amine as a cocatalyst is essential, and without it, the reaction will not substantially proceed. As a tertiary amine,
Generally, tertiary amines containing a nitrogen atom in the ring are preferable to chain amines, and diamines tend to have higher activity than monoamines.
There are exceptions. Examples of amines suitable for the practice of this invention include N-methylpyrrolidine, N-methylpiperidine, N-methylhexamethyleneimine, N-methylpyrrolidine, N-methylpiperidine, N-methylhexamethyleneimine,
-Methylmorpholine, N,N-dimethylpiperazine, N,N,N',N'-tetramethylethylenediamine, trimethylamine, pyridine and the like. The amount of tertiary amine used as a promoter is usually 1/10 to 100/1 (mole ratio) to the methanol used.
is preferred. If this amount is too large, the ethanol selectivity will decrease, and if it is too small, the reaction will not proceed substantially, so the amount to be added should be determined by taking into consideration the type of tertiary amine used, the reaction rate, and the selectivity of the product. Ru. Note that the selectivity of ethanol may be improved by adding a ruthenium compound in addition to the tertiary amine as a cocatalyst. In this case, the amount of ruthenium compound added is the number of moles per iron compound, which is the main catalyst.
A molar ratio of 1/1000 to 1/1 is preferred. Regarding the action of the tertiary amine in the process of the invention, it acts as a ligand to the main catalyst, activates methanol as an acid and enhances its nucleophilicity towards the main catalyst, and the dioxide formed after the reaction. It is thought that it functions to trap carbon and maintain the main catalyst in an activated state, but it is not yet clear, but it is thought that the above functions and effects are intricately related. Solvent In the method of the present invention, the reaction proceeds even without a solvent, but
It is preferable to carry out the reaction in a suitable solvent from the viewpoint of reaction rate and product selectivity. Examples of such solvents include aliphatic or aromatic hydrocarbons, amides, ketones, ethers, nitriles, and alcohols other than methanol. The specific solvent used is determined depending on the type of main catalyst and co-catalyst. Reaction Temperature The reaction temperature in the method of the present invention varies depending on the pressure, type of catalyst, concentration, solvent, and other reaction conditions, but is usually in the range of 50 to 350°C. When iron carbonyl is used as the main catalyst and the reaction is carried out under high syngas pressure, the methanol conversion rate increases as the temperature decreases, but the ethanol selectivity decreases, and if the reaction temperature is too high, the amount of methyl formate by-product increases significantly. Therefore, a temperature range of 130-250°C is preferred. Pressure and Gas Composition In the method of the present invention, the reaction proceeds even under pressure of carbon monoxide alone, and ethanol is produced, but its selectivity tends to be low. In this case, introducing hydrogen into the system reduces the amount of by-products and increases selectivity. The process of the invention is therefore more preferably carried out under pressure of synthesis gas. The higher the hydrogen partial pressure and the lower the carbon monoxide partial pressure, the higher the selectivity for ethanol, but these partial pressures have a large effect on the reaction rate and the composition of other products, and the manifestation of their effects is Since the method depends on other reaction conditions, it can be determined by comprehensively considering these factors. In addition, in the method of the present invention, carbon dioxide generated during the reaction and accumulated in the system is led into the carbon dioxide absorbent together with unreacted gas (for example, unreacted synthesis gas), and a part of it is absorbed and removed. The unreacted gas after this treatment is mixed with separately supplied raw material gas and used again. As described above, the method of the present invention uses a catalyst system in which an iron compound is used as a main catalyst in combination with a tertiary amine as a co-catalyst, and the catalyst is relatively inexpensive and does not exhibit corrosive properties. According to the method of the present invention, the desired ethanol, butanol, etc. can be obtained from methanol with high selectivity, so it is suitable as a method to be implemented industrially. Next, the present invention will be explained in more detail based on examples. In addition, the structure determination of the product after the reaction in the example is
This was done using GCMS, and all composition calculations were performed using gas chromatography. The columns used are as follows.

[Table] Example 1 The inside of a SUS316 autoclave with an internal volume of 50 ml was replaced with nitrogen, and 1.62 ml (40 mmol) of methanol, 1.62 ml of N-methylpyrrolidine, and iron pentacarbonyl were added.
0.27 ml (2 mmol) was charged, 80 atmospheres of carbon monoxide (at room temperature) was introduced, and the reaction was carried out at 180°C for 24 hours. A pressure drop of 21.5 atmospheres was observed when converted to room temperature. After the reaction was completed, the contents were analyzed for gas phase components by the absolute calibration curve method and for liquid phase components by the internal standard method using 100 μl of toluene. The results were as follows. The structure of the product with unknown structure estimated from the carbon balance is approximately
It is 26.3 mmol.

[Table] Production Amount Example 2 The reaction was carried out in exactly the same manner as in Example 1 except that 20 atm of hydrogen was introduced. A pressure drop of 31.5 atmospheres (at room temperature) was observed, and the results of component analysis of the gas and liquid phases were as follows. The amount of structurally unknown substances produced, estimated from the carbon balance, is approximately equivalent to the amount of methanol required.
It is 17.1 mmol.

[Table] Production Amount Comparing the results of Examples 1 and 2, it was found that although the presence of hydrogen is not necessarily required for the production of ethanol, introducing hydrogen into the system improves the mass balance regarding methanol and increases the production of ethanol. It can be seen that the selectivity is improved. In addition, when hydrogen was introduced, the amount of acetaldehyde and its acetal produced decreased, and furthermore, n-butanol was produced even though no n-propanol was observed. In a comparative experiment, under the same conditions, n-butanol was produced. Since the ethanol itself was recovered without much reaction, it is assumed that acetaldehyde is generated and hydrogenated to give ethanol, or that aldol condensation is repeated and then hydrogenated to convert into ethanol and butanol. It is inferred. Example 3 Reactions were carried out under the same conditions as in Example 2, using various transition metal compounds as the main catalyst instead of iron pentacarbonyl, and using N-methylpyrrolidine as a cocatalyst and N-methylpiperidine for comparison. The results are shown in Table 1. Note that Experiment Nos. 2 to 8 shown in Table 1 show comparative examples.

【table】

[Table] Examples 4 to 11 Table 2 shows the results of reactions conducted under the same conditions as in Example 2 using various tertiary amines in place of N-methylpyrrolidine as cocatalysts. Note that dabco shown in Table 2 is diazabicyclooctane represented by the following formula.

【table】

[Table] Examples 12 to 17 The results of a reaction under the same conditions as in Example 2 using 2 mmol of iron pentacarbonyl as the main catalyst, 1.62 ml of N-methylpiperidine as a co-catalyst, and 1.62 ml of various solvents were shown. It is shown in Table 3.

【table】

[Table] Example 18 Figure 1 or Figure 2 shows the selectivity for methanol consumed by the reaction of the main products when the hydrogen partial pressure or carbon monoxide partial pressure was changed for Example 3. Indicated. Example 19 The reaction was carried out in exactly the same manner as in Example 3 except that 0.1 mmol of activated carbon-supported ruthenium (supported amount: 5%) was added per Ru atom. As a result, the amount of ethanol produced was
It was 9.46 mmol.

[Brief explanation of the drawing]

Figure 1 shows the relationship between hydrogen partial pressure and product selectivity in Example 18 of the present invention, and Figure 2 is a graph showing the relationship between carbon monoxide partial pressure and product selectivity in the same example. It is.

Claims (1)

[Claims] 1. A method for producing ethanol and butanol, which comprises reacting methanol and carbon monoxide in the absence of a halogen or halogen compound and in the presence of a catalyst consisting of an iron compound and a tertiary amine. . 2. The method according to claim 1, which uses carbon monoxide containing hydrogen. 3. The method according to claim 1 or 2, in which carbon dioxide generated during the reaction and accumulated in the reaction system is removed, and the remaining unreacted synthesis gas is reacted with methanol while being separately supplied with synthesis gas. . 4. A method for producing ethanol and butanol, which comprises reacting methanol and carbon monoxide in the absence of a halogen or a halogen compound and in the presence of a catalyst consisting of an iron compound, a ruthenium compound, and a tertiary amine.