JPH0899920A - Production of alcohols from carbon dioxide gas - Google Patents

Abstract

PURPOSE: To provide a new method for producing an alcohol using carbon dioxide as a raw material, capable of preventing global warming caused by carbon dioxide and utilizing discharged carbon dioxide as a carbon source and reusing it as resource. CONSTITUTION: This method for producing an alcohol comprises catalytically hydrogenating carbon dioxide in an organic phosphine oxide compound or an aprotic liquid solvent by using a ruthenium compound or a cobalt compound as a catalyst and a lithium salt as a cocatalyst under pressure and under heating. Carbonyl compounds are used as the ruthenium and the cobalt compounds and lithium bromine as the lithium salt. An aprotic toluene or tributylphosphine oxide is used as a liquid solvent. The objective alcohol can be produced by the reaction at 160-260 deg.C under 30-200kgf/cm<2> .

Description

Detailed Description of the Invention

[0001]

The present invention relates to a novel method for efficiently synthesizing alcohols from carbon dioxide and hydrogen. More specifically, the present invention relates to a method for synthesizing alcohols such as ethanol and methanol by a liquid phase direct synthesis method using an organic phosphine oxide compound or an aprotic liquid solvent using a mixed gas of carbon dioxide and hydrogen as a raw material. is there.

[0002]

2. Description of the Related Art With respect to methanol, there are known some examples of so-called direct processes in which a synthesis gas (a mixed gas of carbon monoxide and hydrogen) is used as a raw material and a ruthenium catalyst is used for synthesis. In addition, ethanol is an important chemical product, and about 150,000 tons are produced in Japan. A fermentation method in which waste molasses and the like are fermented with yeast to produce the method,
Synthetic methods for producing ethylene by hydration with an acid catalyst such as phosphoric acid have been established. Also, a production process from synthesis gas and methanol, which is a derivative of synthesis gas, has been studied.

With the recent expansion of the scale of global industrial and economic activities, environmental destruction at the global level has become an important issue, and countermeasures against it have begun to be studied worldwide. In particular, it is estimated that the global warming problem will have a significant adverse effect not only on humans but also on the earth itself, and to prevent the emission of carbon dioxide, which is a major factor in global warming, to the atmosphere. There is a strong demand for establishing countermeasures. By the way, the carbon dioxide emitted can be considered as a carbon resource, and if we can develop a process that can recover this carbon dioxide and recycle it to synthesize useful chemicals from carbon dioxide, from the viewpoint of carbon dioxide emission control and resource utilization. It can be established as the most effective measure.

[0004]

SUMMARY OF THE INVENTION The present invention is directed to a new method for producing an alcohol using carbon dioxide as a raw material which can prevent global warming due to carbon dioxide and can utilize and reuse the discharged carbon dioxide as a carbon resource. The task is to provide

[0005]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies on a method for synthesizing alcohol from carbon dioxide as a technology for effectively utilizing carbon dioxide. As a result, catalytic hydrogenation of carbon dioxide with a specific catalyst system was carried out. And found that ethanol and methanol are produced at a predetermined ratio.
The present invention has been accomplished based on this finding. That is, in the present invention, in an organic phosphine oxide compound or an aprotic liquid solvent, a ruthenium compound and a cobalt compound are used as catalysts, and a lithium salt is used as a co-catalyst to pressurize and catalytically hydrogenate carbon dioxide under heating. A method for producing alcohols.

The present invention will be described in detail below. In the present invention, the ruthenium compound used as a catalyst is
Compounds capable of forming a ruthenium complex having carbon monoxide as a ligand under the reaction conditions can be widely used.
For example, in addition to ruthenium metal, ruthenium oxides such as ruthenium dioxide and ruthenium tetraoxide, hydrates thereof, ruthenium chloride, ruthenium iodide, ruthenium minerals such as ruthenium nitrate, ruthenium acetate, ruthenium propionate. Such as ruthenium organic acid salts. The ruthenium compound can also be used directly in the form of a coordination compound.Examples of these include ruthenium carbonyl such as triruthenium dodecacarbonyl, and oxygen, sulfur, halogen, nitrogen, and ruthenium.
Examples include a ruthenium complex to which a ligand containing phosphorus, arsenic, antimony, bismuth, or the like is coordinated, and salts thereof.

Among these ruthenium compounds, a ruthenium complex in which ruthenium carbonyl or a part of carbon monoxide ligand thereof is replaced with another ligand is preferable. The concentration of the ruthenium compound in the liquid solvent used in the method of the present invention is, as a weight converted into ruthenium metal, 0.1 to 1000 parts by weight of the liquid solvent.
It is in the range of 100 parts by weight.

The cobalt compound is also capable of forming a cobalt complex having carbon monoxide as a ligand under the reaction conditions. As with ruthenium, a wide variety of cobalt complex precursors can be used, including, in addition to metallic cobalt, cobalt oxides, cobalt chloride, cobalt bromide, cobalt mineral salts such as cobalt nitrate, and acetic acid. There are organic acid salts of cobalt such as cobalt and cobalt benzoate. In addition, a coordination compound can also be used. Examples of the coordination compound include a cobalt carbonyl such as dicobalt octacarbonyl, and a coordination compound containing oxygen, sulfur, halogen, nitrogen, phosphorus, arsenic, antimony, bismuth, etc. Cobalt complexes coordinated with
The salt etc. are mentioned.

Among these cobalt compounds, a cobalt complex in which cobalt carbonyl or a part of the carbon monoxide ligand thereof is replaced with another ligand is preferable. The concentration of the cobalt compound in the liquid solvent used in the method of the present invention is in the range of 0.1 to 100 parts by weight per 1000 parts by weight of the liquid solvent in terms of weight in terms of cobalt metal. Further, as a precursor of the ruthenium compound and the cobalt compound, a compound containing ruthenium and cobalt can be used in addition to the above.

Examples of the lithium salt used in the present invention include halides such as lithium chloride, lithium bromide and lithium iodide, and hydrates thereof. Of these, lithium bromide is particularly preferable. Two or more kinds of lithium salts can be added simultaneously. The amount of lithium salt added is
The number of gram atoms of ruthenium is 0.5 to 100 times, preferably 1 to 50 times as lithium atoms.

Examples of the organic phosphine oxide compound used in the method of the present invention include tributylphosphine oxide,
Phosphine oxides such as triphenylphosphine oxide and trioctylphosphine oxide can be used. Examples of the aprotic liquid solvent used in the method of the present invention include aromatic compounds such as toluene and diphenyl ether, and N-substituted amides such as 1-methyl-2-pyrrolidone. For use as a reaction solvent, tributylphosphine oxide is most preferably used alone. However, since it is a solid at ordinary temperature (liquid under the reaction conditions), one or more liquid solvents can be used in combination, if necessary.

In the method of the present invention, the reaction temperature is from 160 to 26.
It can be carried out at 0 ° C, particularly preferably at 180 to 220 ° C. Reaction pressure is 30 to 200 kgf / c
It can be implemented at m ² or more. The molar ratio of carbon dioxide to hydrogen used as a raw material is 1:10 to 1
A range of 0: 1 is preferred. The source gas may contain other components inert to the reaction, such as methane and nitrogen.

The method of the present invention can be carried out by any of a batch system and a semi-continuous system. The ruthenium compound, cobalt compound, lithium salt, phosphine oxide and the like may be added to the reactor in a batch system, or may be supplied in a semi-continuous system or a continuous system. The product can be taken out by a known method, for example, a method such as distillation or stripping. Further, if necessary, a solvent containing a ruthenium compound, a cobalt compound, a lithium salt, a phosphine oxide and the like can be recycled to the reactor and used again.

[0014]

Next, the present invention will be specifically described based on examples, but the present invention is not limited to these examples. In the examples, unless otherwise specified, triruthenium dodecacarbonyl was used as the ruthenium compound, dicobalt octacarbonyl was used as the cobalt compound, and the amount used was expressed in milligram atoms of each metal. The amount of the lithium salt used is represented by a molar ratio (or atomic ratio) to the amount of ruthenium used. Unless otherwise specified, triruthenium dodecacarbonyl is 0.56 mg as ruthenium
-Atm, dicobalt octacarbonyl was cobalt, and 1.68 mg-atm (Co / Ru = 3) was used, and lithium salt / ruthenium (molar ratio) was 20.

Further, tributylphosphine oxide (14.0 g) was used as a solvent unless otherwise specified. The reaction was carried out at 200 ° C. unless otherwise specified, and the reaction time was 18 hours after reaching the predetermined reaction temperature unless otherwise specified. The amount of reaction products produced is absolute (mmo
1), and the selectivity was expressed as {absolute amount of each reaction product / (methanol + ethanol + carbon monoxide + methane)} × 100 after conversion on a carbon basis.

In the tables and sentences, each molecular formula and symbol indicate the following compound. Ru ₃ (CO) ₁₂ : tolyruthenium dodecacarbonyl, Co ₂ (CO) ₈ : dicobalt octacarbonyl, CoBr ₂ : cobalt bromide, LiCl: lithium chloride, LiBr: lithium bromide, LiBr · H ₂
O: lithium bromide monohydrate, Bu ₃ PO: tri-n-butylphosphine oxide, NMP: 1-methyl-2-
Pyrrolidone, MeOH: methanol, EtOH: ethanol.

Example 1 Ru ₃ (CO) was placed in an autoclave having an internal volume of 100 ml.
0.12 g of ₁₂ (0.56 mg-atm as Ru);
0.28 g of Co ₂ (CO) ₈ (1.68 m as Co)
g-atm, Co / Ru = 3), 0.48 g of LiCl
(11.2 mmol, LiCl / Ru = 20), Bu ₃
After charging 14 g of PO and introducing a mixed gas of carbon dioxide and hydrogen (H ₂ / CO ₂ = 5) to replace the air in the autoclave, the mixed gas was cooled to room temperature at room temperature for 20 minutes.
It was charged up to 0 kgf / cm ² . Next, the autoclave was heated and stirred when the internal temperature reached 90 ° C. (500
rpm) was started, and when the internal temperature reached 200 ° C., the temperature was kept constant and the reaction was performed for 18 hours. After completion of the reaction, the mixture was cooled to room temperature, the contents were taken out and analyzed by gas chromatography. In the liquid phase, methanol 11.1
mmol and 1.92 mmol of ethanol were detected, and in the gas phase, 48.5 mmol of carbon dioxide, 5.6 mmol of carbon monoxide, and 3.3 mmol of methane were detected.
This is referred to as Experimental Example 1.

In Experimental Example 1, a system using no cobalt (Experimental Example 2), a system in which LiBr was changed to LiCl (Experimental Example 3), and a system in which LiBr was changed to LiCl without using Cobalt (Experimental Example 4) were used. The reaction was carried out. These results are shown in Table 1 together with Experimental Example 1. Experimental Examples 2 and 4 are not examples of the present invention. In Experimental Example 1, Co /
A system in which the Ru ratio was changed (Experimental Examples 5 to 7), reaction time (Experimental Examples 8 to 12), reaction time (Experimental Example 13), H ₂ / CO ₂ ratio of mixed gas (Experimental Examples 14 to 16), The reaction was carried out in a system in which the reaction conditions such as the filling pressure (Experimental Examples 17 to 19) were changed. The results are shown in Table 1.

In Experimental Example 1, Ru and Co (Experimental Example 20), LiBr (Experimental Examples 21 and 23), Ru and C
Table 1 shows a system in which o and LiBr (Experimental Example 22) are doubled. Of these, Experimental Examples 20 to 22 carry out the reaction at a high filling pressure of the mixed gas. Furthermore, Experimental Example 1
In the system using CoBr ₂ for cobalt (Experimental Example 2
4), a system using LiBr monohydrate (Experimental Example 25),
Table 1 shows the reaction results in a system using both LiBr and LiCl (Experimental Example 26). Further, in Experimental Example 1, the liquid solvent NM was used.
System containing P (Experimental Example 27), 47% HBr and 36% H
System added with an acid such as Cl (Experimental Examples 28 to 32), LiC
Table 1 shows the reaction results in a system (Experimental Example 33) to which 47% HBr was added using l.

[0020]

[Table 1]

[0021]

[Table 2]

[0022]

[Table 3]

[0023]

[Table 4]

[0024]

As described in detail above, according to the present invention,
Alcohol with increased ethanol yield can be synthesized from carbon dioxide and hydrogen, which will be an effective method for recycling carbon dioxide.

Claims (1)

[Claims] 1. Catalytic hydrogenation of carbon dioxide under pressure and heat using a ruthenium compound and a cobalt compound as catalysts and a lithium salt as a cocatalyst in an organic phosphine oxide compound or an aprotic liquid solvent. A method for producing alcohols, comprising: