JP3702343B2 - Method for producing higher alcohols from carbon dioxide - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a novel production method for selectively and efficiently producing higher alcohols using carbon dioxide, hydrogen, and unsaturated organic compounds as raw materials.
[0002]
[Prior art]
C3 or higher alcohols are produced by hydration or hydroformylation of unsaturated organic compounds. Of these, the hydroformylation method is an important reaction widely used industrially. However, since carbon monoxide, which is extremely toxic, is used as a raw material, much investment is required for safety management and environmental protection.
As a solution for solving this problem, the present inventors have found a hydroformylation method using carbon dioxide as a raw material using a ruthenium compound as a catalyst, as described in JP-A No. 2001-233795. This method is the only hydroformylation method using carbon dioxide as a raw material.
[0003]
However, according to the subsequent studies by the present inventors, in this method, a hydrogenation reaction of an unsaturated bond, which is a side reaction, proceeds simultaneously, and an organic compound having an unsaturated bond inside the molecule that is difficult to be hydrogenated is used as a raw material. Can produce higher alcohols in high yields, but when starting from organic compounds with unsaturated bonds at the molecular ends that are susceptible to hydrogenation, higher alcohols can be produced in sufficient yields. Proved difficult to do.
[0004]
[Problems to be solved by the invention]
The present invention controls the hydrogenation reaction, which is a side reaction, and as the raw material unsaturated organic compound, not only an organic compound having an unsaturated bond in the molecule but also an organic compound having an unsaturated bond at the molecular end can be used. It is an object of the present invention to provide a process for producing a higher alcohol using carbon dioxide as a raw material, which is industrially advantageous, and can produce a higher alcohol in a high yield.
[0005]
[Means for Solving the Problems]
As a result of intensive studies in view of the above-described technical situation, the present inventor has found that hydrogen, which is a side reaction when using a non-aqueous ionic solvent composed of an organic / inorganic salt that becomes a liquid at the reaction temperature, is used. It has been found that higher alcohols can be selectively and efficiently produced compared to conventional methods even when using organic compounds that can control the hydrogenation reaction and are susceptible to hydrogenation and have unsaturated bonds at the molecular ends. It is a thing.
That is, according to the present invention, the following inventions are provided.
(1) Production of a higher alcohol characterized by using a non-aqueous ionic solvent in a process for producing a higher alcohol by hydroformylating an organic compound having an unsaturated bond, carbon dioxide and hydrogen in the presence of a ruthenium compound catalyst. Method.
(2) The method for producing a higher alcohol as described in (1) above, wherein the ruthenium compound catalyst is previously dispersed in a non-aqueous ionic solvent.
(3) The method for producing a higher alcohol as described in (1) or (2) above, wherein the reaction is performed at a temperature of 100 ° C. to 180 ° C. and a pressure of 1 to 20 MPa.
(4) The method for producing a higher alcohol as described in any one of (1) to (3) above, wherein the organic compound having an unsaturated bond is an organic compound having an unsaturated bond at the molecular end.
(5) The method for producing a higher alcohol according to any one of (1) to (4) above, wherein the non-aqueous ionic solvent is a quaternary ammonium salt and / or a fourth phosphonium salt.
[0006]
DETAILED DESCRIPTION OF THE INVENTION
The method of the present invention is characterized by using a non-aqueous ionic solvent as a catalyst for the hydroformylation reaction.
When such a solvent is used, unlike the method described in JP-A-2001-233895, the unsaturated organic compound as a raw material is not only an organic compound having an unsaturated bond inside the molecule, but also an unsaturated bond at the molecular end that is easily hydrogenated. Even when an organic compound having the above is used, a higher alcohol can be produced in a high yield.
[0007]
The reason for this is not clear at this time, but is thought to be due to the following reasons.
In other words, since non-aqueous ionic solvents are difficult to dissolve low-polarity raw organic compounds, a heterogeneous two-phase system consisting of an organic phase in which the raw organic compounds dissolve and an ionic solvent phase in which the catalyst is dispersed appears. To do. The raw carbon dioxide gas is easily dissolved in the ionic solvent phase, and the hydrogen gas is dissolved in any phase. Hydrogenation and hydroformylation occur at the interface between these organic and ionic solvent phases, but the reaction with carbon dioxide (hydroformylation) takes precedence over the hydrogenation of the starting organic compound, resulting in hydroformyl as a result. It is presumed that the selectivity of the fluorination reaction is improved and a higher alcohol can be obtained in a high yield.
[0008]
The present invention is described in detail below.
In the present invention, as described above, a non-aqueous ionic solvent is used as the solvent.
[0009]
The non-aqueous ionic solvent means a solvent composed of an organic / inorganic salt that becomes liquid at the reaction temperature. As described above, this non-aqueous ionic solvent plays a role of separating the reaction system into an organic phase and an ionic solvent phase and giving priority to the hydroformylation reaction at the interface over the hydrogenation reaction.
Any non-aqueous ionic solvent may be used as long as it has the functions described above, but it is desirable to use a solvent that is liquid at a reaction temperature of preferably 90 ° C. or lower, more preferably near room temperature.
[0010]
As such a solvent, for example, a salt having the general formula Q ⁺ A ⁻ and a melting point of 90 ° C. or lower is exemplified. The cation Q ⁺ is quaternary ammonium and / or quaternary phosphonium, but some of them may be substituted with an inorganic cation such as lithium or sodium. As typical cations, 1,3-dialkylimidazolium ion, 1-alkylpyridium ion, and the like can be used. The anion A ^- as can be used a halide ion, nitrate ion, sulfate ion, phosphate ion, acetate ion, tetrafluoroborate ion, hexafluorophosphate ion or the like, obtained by substituting a part thereof from each other May be used.
The amount of these nonaqueous ionic solvents used is about 0.1 to 50 vol%, preferably about 1 to 10%, based on the organic phase.
[0011]
Examples of the catalyst used in the present invention include all ruthenium compounds that can be dissolved in a non-aqueous ionic solvent. More preferably, clustered ruthenium compounds such as Ru ₃ (CO) ₁₂ , H ₄ Ru ₄ (CO) ₁₂ , and H ₂ Ru ₆ (CO) ₁₈ are suitable.
Moreover, the mononuclear ruthenium compound used as the raw material of these cluster compounds can also be used after being clustered before or during the reaction. The amount of the catalyst used is preferably about 0.5 to 1 wt% with respect to the ionic solvent.
In the present invention, it is preferable to use these ruthenium catalysts dispersed in the above-mentioned non-aqueous ionic solvent.
[0012]
As the organic compound having an unsaturated bond used as a raw material, an organic compound having a double bond or a triple bond can be arbitrarily selected according to the purpose.
Specific examples of raw materials having an unsaturated bond at the molecular terminal include ethylene, propylene, butene, isobutene, acetylene, and styrene, and those having an unsaturated bond inside the molecule include cyclohexene, cyclooctene, stilbene, and diphenylacetylene. and so on.
[0013]
The raw material organic compound can be used as it is as the organic phase, but it may be diluted with a hydrocarbon compound or an ether compound that does not participate in the reaction.
[0014]
The source gas used in the present invention is a mixed gas containing hydrogen and carbon dioxide as main components. The carbon dioxide content is 10 to 90 vol%, preferably 50 to 80 vol%, and the hydrogen content is 10 to 90 vol%, preferably 20 to 50 vol%. These may be supplied in the form of a mixed gas or may be supplied separately. There is no need for carbon monoxide to be mixed in the raw material gas, but there is no problem even if it is mixed.
[0015]
The method of the present invention is carried out in a non-aqueous ionic solvent. Preferably, a ruthenium compound is dissolved in the non-aqueous ionic solvent to prepare a catalyst system, a raw organic compound is added thereto, and carbon dioxide and hydrogen are added. Is carried out under pressure. This method is preferably carried out in the range of about 100 ° C to 180 ° C. A more preferable range is 120 ° C to 160 ° C. In the lower temperature range, carbon dioxide does not react, and in the higher temperature range, only hydrogenation of unsaturated bonds takes precedence. The pressure is 1 to 20 MPa, preferably 2 to 10 MPa.
[0016]
【Example】
The following examples illustrate the invention but do not limit its scope.
[0017]
Example 1 (Higher alcohol synthesis using an organic compound having an unsaturated bond at the molecular end as a raw material)
In a stainless steel pressure reactor having an internal volume of 50 ml, 0.1 mmol of Ru ₃ (CO) ₁₂ as a ruthenium compound and 1.0 g of 1-butyl-3-methyl-imidazolium chloride as a non-aqueous ionic solvent at room temperature, raw materials 5.0 mmol of 1-hexene as an organic compound and 5.0 mL of benzene as a diluent were added and dissolved by stirring, and then injected with stirring at 4 MPa for carbon dioxide and 4 MPa for hydrogen at 120 ° C. for 30 hours. Retained. Thereafter, the reaction apparatus was cooled to room temperature, released, and the remaining organic phase was extracted and analyzed by a gas chromatograph. The conversion rate of 1-hexene was 84%, 44% yield of 1-heptanol as a higher alcohol and 34% yield of 2-methyl-hexanol, and 6% yield of hexane as a hydrogenation product.
[0018]
Example 2 (Synthesis of higher alcohol using an organic compound having an unsaturated bond at the molecular end as a raw material)
The reaction was carried out under the same conditions as in Example 1 using α-methylstyrene as the raw material organic compound. The conversion rate of α-methylstyrene is 88%. Among the products, 2-phenylbutanal is obtained as a aldehyde in 2% yield, 2-phenylbutanol is produced as a higher alcohol in 62%, and cumene is obtained as a hydrogenation product. 22% produced.
[0019]
Comparative Example 1 (reaction not using a non-aqueous ionic solvent)
1-hexene was used under the same conditions as in Example 1, using 0.1 mmol of Ru3 (CO) 12 as the ruthenium compound, 8.0 mL of N-methyl-2-pyrrolidone as the organic solvent, and 0.4 mmol of lithium chloride as the additive. Was hydroformylated. The conversion rate of 1-hexene is 100%. Among the products, 2-ethylpentanal is 3% as aldehyde, 2-methylhexanal is 6%, 1-heptanal is 3%, and 2-ethylpentanol is used as higher alcohol. 6%, 2-methylhexanol 15%, and 1-heptanol 42%. Further, 21% of hexane was produced as a hydrogenation product.
[0020]
Comparative Example 2 (reaction not using non-aqueous ionic solvent)
The reaction was carried out under the same conditions as in Comparative Example 1 using α-methylstyrene as the raw material organic compound. The conversion rate of α-methylstyrene was 80%. Among the products, 2-phenylbutanal was 26% as aldehyde, 30% 2-phenylbutanol as higher alcohol, and 26% cumene as a hydrogenation product.
[0021]
【The invention's effect】
In the conventional method using a Ru catalyst, a higher alcohol can be produced in a high yield when an organic compound having an unsaturated bond in the molecule is used as a raw material, but an organic compound having an unsaturated bond at the molecular end is used. When used as a raw material, the hydrogenation of unsaturated bonds, which are side reactions, proceeded, and it was difficult to produce higher alcohols in sufficient yields. High-yield alcohols can be produced in high yield by using not only organic compounds with unsaturated bonds in the molecule but also organic compounds with unsaturated bonds at the molecular terminals that are susceptible to hydrogenation as raw material unsaturated organic compounds. It becomes possible.
Therefore, the method of the present invention has a great merit that the range of applications using carbon dioxide, which is safer and less expensive, as a raw material in synthesizing higher alcohols is widened, and helps the greening of the chemical industry.

Claims (5)

A method for producing a higher alcohol, wherein a non-aqueous ionic solvent is used in a method for producing a higher alcohol by hydroformylating an organic compound having an unsaturated bond, carbon dioxide and hydrogen in the presence of a ruthenium compound catalyst. The method for producing a higher alcohol according to claim 1, wherein the ruthenium compound catalyst is dispersed in a non-aqueous ionic solvent in advance. The method for producing a higher alcohol according to claim 1, wherein the reaction is performed at a temperature of 100 ° C. to 180 ° C. and a pressure of 1 to 20 MPa. The method for producing a higher alcohol according to any one of claims 1 to 3, wherein the organic compound having an unsaturated bond is an organic compound having an unsaturated bond at the molecular end. The method for producing a higher alcohol according to any one of claims 1 to 4, wherein the non-aqueous ionic solvent is a quaternary ammonium salt and / or a fourth phosphonium salt.