JPH06263665A - Catalytic hydrogenation of carbon dioxide gas - Google Patents

Abstract

PURPOSE:To produce methanol, methane, carbon monoxide, etc., by hydrogenating carbon dioxide gas in the presence of a homogeneous liquid-phase reaction catalyst. CONSTITUTION:Methanol, methane, carbon monoxide, etc., are produced by hydrogenating carbon dioxide gas in the presence of a homogeneous liquid-phase reaction catalyst consisting of a combination of a ruthenium carbonyl complex with an iodine compound. Methanol, methane or carbon monoxide useful as a fuel or a chemical synthesis raw material can be produced from carbon dioxide gas exhausted in large quantity from a thermoelectric power plant, cement factory, etc. Since the catalyst is soluble in solvent in contrast with conventional heterogeneous catalyst, it can be used in a liquid-phase reaction system at an easily controllable temperature.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a carbon dioxide catalytic hydrogenation method using a homogeneous liquid phase reaction catalyst, and more particularly to methanol by hydrogenating carbon dioxide in the presence of a homogeneous liquid phase reaction catalyst having a specific composition. , Methane, carbon monoxide and the like.

[0002]

2. Description of the Related Art Regarding the method for producing methanol, methane, carbon monoxide and the like by hydrogenation of carbon dioxide, various metals and metal oxides are known to be effective as catalysts, and many patent applications have been filed. And reports are known [eg
Hironori Arakawa, Catalyst, 31 , 558 (1989), etc.].

These metal or metal oxide catalysts are generally used by supporting them on a carrier, but in the case of gas-solid heterogeneous reaction involving considerable heat generation such as hydrogenation reaction of carbon dioxide gas. However, there is a drawback that it is difficult to control the temperature of the reactor, and it is difficult to apply this method especially to a large reactor required for large-scale treatment of carbon dioxide gas. In order to solve such a drawback, a method of hydrogenating carbon dioxide gas in a liquid phase using a transition metal complex as a homogeneous catalyst can be considered.

However, until now, formic acid, formic acid amide, formic acid ester and the like have been obtained by hydrogenation of carbon dioxide using a transition metal complex as a homogeneous liquid phase reaction catalyst [eg Darensbourg, Chemtech]. , 636, (198
5)], methanol, methane, and carbon monoxide have not been obtained. On the other hand, regarding the method of hydrogenating carbon monoxide,
There is known a method of producing methanol, methane or the like by using various transition metal complexes as a homogeneous catalyst.

For example, Muettertis et al. Reported that an osmium carbonyl or iridium carbonyl complex is hydrogenated by carbon monoxide (J. Am. Chem. Soc. 98 , 1296,
1976.) or ethane (J. Am. Chem. Soc. 99 , 2796,
1977.) has been reported to be effective as a catalyst for synthesis. On the other hand, a ruthenium carbonyl complex is effective as a catalyst for the synthesis of methanol by hydrogenation of carbon monoxide, but in this case, it is said that a high pressure of 1000 atm or higher is required (JS Bradley, J. Am. Chem. Soc. 101 , 74
19 (1979)].

[0006] Dombek also reported that by adding an iodine compound to a ruthenium carbonyl complex, methanol, ethylene glycol and ethanol can be obtained from carbon monoxide, and the reaction pressure can be lowered to about 400 atm. (BD Dombek, J. Am. Chem.
Soc. 102 , 6508 (1981)]. However, when applied to carbon dioxide gas under such a high pressure, there was a problem that the ruthenium carbonyl complex decomposed.

Further, nickel complex (it is considered to be a nickel carbonyl complex in the reaction system).
Is useful as a catalyst for liquid-phase methanol synthesis from carbon monoxide and hydrogen even at a relatively low pressure of about 100 atm, but it was not very effective for methanol synthesis by hydrogenation of carbon dioxide [Seiichi Oyama, Central Research Institute of Electric Power Industry Report T9002
7 (1990)].

[0008]

The problem to be solved by the present invention is that the production of methanol, methane, carbon monoxide and the like by hydrogenation of carbon dioxide in the presence of a homogeneous liquid phase reaction catalyst has hitherto been known. That's not the point.

[0009]

The present invention is characterized in that carbon dioxide gas is hydrogenated in the presence of a homogeneous liquid phase reaction catalyst comprising a combination of a ruthenium carbonyl complex and an iodine compound. Examples of the ruthenium carbonyl complex constituting the homogeneous liquid phase reaction catalyst in the present invention include Ru (CO) ₅ , Ru ₃ (CO) _{12 and} other complexes having only carbon monoxide as a ligand, as well as carbon monoxide. Besides, a complex having hydrogen, iodine or the like as a ligand, for example, Ru ₂ I ₄ (CO) ₆ or the like can be used.

Further, as the iodine compound, iodine, KI,
NaI, alkali metal iodides such as LiI, ZnI _2, CaI ₂ of at least one element selected from transition metal iodide and the group consisting of alkaline earth metal iodides, such as are used.

The mixing ratio of the iodine compound and the ruthenium carbonyl complex is such that the iodine to ruthenium atomic ratio (I ₂ / R
u) is in the range of 1 to 50, preferably 5 to 20. When this ratio is less than 1, ruthenium is precipitated as a metal to lower the reaction rate, and when it exceeds 50, methanol is not generated and the amount of methane is increased. The homogeneous liquid phase reaction catalyst in the present invention may be separately prepared by dissolving the ruthenium carbonyl complex and the iodine compound in a solvent in a ratio in the above range outside the reaction system, and adding this to the reaction system, Usually, it is more convenient for operation to supply a ruthenium carbonyl complex, an iodine compound and a solvent to a reaction vessel to form a homogeneous liquid phase reaction catalyst in the reaction system.

As the solvent, N-methylpyrrolidone, N
A polar non-prone solvent such as -ethylpyrrolidone, 1,3-dimethylimidazolidinone is used. The reaction is carried out by dissolving the ruthenium carbonyl complex and the iodine compound in these solvents and heating under the pressure of carbon gas and hydrogen. The volume ratio (CO ₂ / H ₂ ) of carbon dioxide and hydrogen is
When the carbon dioxide gas amount is less than 0.1, the catalyst is decomposed to deposit ruthenium metal, and when it exceeds 1, the reaction rate is lowered. The total pressure of carbon dioxide gas and hydrogen during the reaction is 1 to 400 atm, preferably 20 to 200 atm, and the reaction temperature is 150 to 300 ° C, preferably 180 to 250 ° C. 15
If the temperature is lower than 0 ° C, the reaction is difficult to proceed, and if the temperature exceeds 300 ° C, the catalyst decomposes to deposit ruthenium.

The concentration of the ruthenium carbonyl complex in the solvent is 1 to 100 mmol / l, preferably 5 to 25 mmol. If it is less than 1 mmol / l, the reaction is difficult to proceed, and 100 mmo
If it exceeds l, it becomes difficult to dissolve it in the solvent. In the present invention, the products obtained by the hydrogenation reaction of carbon dioxide are mainly methanol, methane or carbon monoxide,
Ethane and the like are obtained as by-products. By changing the reaction conditions such as the reaction temperature, the reaction time, and the type of iodine compound, the production amount of methanol, methane, or carbon monoxide can be increased. Examples of the present invention will be described below.

[0014]

【Example】

Example 1 A 100 ml autoclave was charged with Ru ₃ (CO) ₁₂ (0.2 mmol), a solvent (20 ml) and an iodine compound (10 mmol), and a carbon dioxide / hydrogen (1: 3) mixed gas was introduced at 80 atm at room temperature. Then, the reaction was performed at a predetermined temperature for 3 hours. As the solvent, N
-Methylpyrrolidone (NMP), N-ethylpyrrolidone (NEP) or 1,3-dimethylimidazolidinone (DMI) is used, and iodine compounds are iodine, KI,
NaI, LiI and ZnI ₂ were used. The I / Ru ratio is 17. The analysis of the product was performed by quantifying the reaction gas and the reaction solution using gas chromatography. The results are shown in Table 1.

[0015]

As is clear from Table 1, the amount of methanol, methane or carbon monoxide produced in the product can be increased by changing the type of iodine compound and the reaction temperature. For example, when an alkali metal salt such as potassium iodide or sodium iodide is used as the iodine compound and reacted at 240 ° C, methanol is obtained as the main product.
In the case of (1), carbon monoxide becomes the main product. When zinc iodide is used, carbon monoxide becomes the main product even at 240 ° C, while when iodine is added,
Methane was mainly produced. Also in this case, the ruthenium catalyst is not decomposed into metal, and it is considered that the reaction proceeds in a homogeneous system. Therefore, it is a reaction different from the production of methane in a heterogeneous system by ruthenium metal.

Example 2 The same reaction as in Example 1 was carried out. However, N as a solvent
MP was performed using potassium iodide as an iodine compound and changing the reaction time. The results are shown in Fig. 1. At 30 minutes after the start of the reaction, carbon monoxide was 10.2 as the main product.
It was obtained in a yield of mmol, and formation of methanol (7.4 mmol) and a small amount of methane was observed. When the reaction time was longer than 1.5 hours, methanol was obtained as the main product, but the production amount of methane increased as the reaction time became longer.
In this way, each product is considered to be produced by a sequential reaction, so by setting the reaction time appropriately,
The ratio of products can be varied.

[0018]

As described above, according to the present invention, methanol, methane or carbon monoxide useful as a fuel or a raw material for chemical synthesis can be produced from carbon dioxide gas discharged in large amounts from a thermal power plant or a cement plant. it can. Since the catalyst of the present invention is soluble in a solvent unlike conventional heterogeneous catalysts, it has a great advantage that it can be used in a liquid phase reaction in which temperature control is easy.

Further, by changing the reaction conditions,
If necessary, the main product can be methanol, methane or carbon monoxide, which has the advantage of high process flexibility.

[Brief description of drawings]

FIG. 1 is a diagram showing a relationship between a reaction time and a methane production amount when using a Ru ₃ (CO) ₁₂ -potassium iodide catalyst and an NMP solvent.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification number Office reference number FI technical display location C07C 29/157 8930-4H // C07B 61/00 300 C10G 2/00 2115-4H (72) Invention Masahiro Saito 16-3, Onogawa, Tsukuba-shi, Ibaraki Institute of Industrial Science and Technology (72) Inventor Kenichi Tominaga 16-3, Onogawa, Tsukuba-shi, Ibaraki Institute of Industrial Science and Technology (72) Inventor Watanabe Daiki 2-8-11 Nishi-Shimbashi, Minato-ku, Tokyo 7th Toyo Kaijuku Building 8F Research Institute for Global Environmental Technology CO2 fixation etc. Project room (72) Inventor Motoi Kawai 2 Nishi-Shimbashi, Minato-ku, Tokyo -8-11 7th Toyo Kaiji Building 8F Foundation for Global Environmental Technology Research Institute CO2 Immobilization Project Room (72) Inventor Masami Takeuchi 2-8-11 Nishi-Shimbashi, Minato-ku, Tokyo 7th Tokai Maritime Building 8F Foundation for Global Environmental Technology Research Institute CO2 fixation etc. (72) Inventor Yuki Kanai 2- Nishi-shinbashi, Minato-ku, Tokyo 8-11 7th Toyo Kaijuku Building 8F Foundation for Research on Innovative Technology for the Earth Environment CO2 fixation etc. Project room (72) Inventor Keiko Moriya 2-8-11 Nishishinbashi, Minato-ku, Tokyo 7th Toyo Kaijuku Building 8F Research Institute for Global Environment and Industrial Technology CO2 Immobilization Project Room (72) Inventor Terumitsu Kakumoto 2-8-11 Nishishinbashi, Minato-ku, Tokyo 7th Toyo Kaiji Building 8F Foundation for Global Environmental and Industrial Technology Research Institute Project room for CO2 fixation

Claims (2)

[Claims] 1. A carbonic acid characterized by producing methanol, methane, carbon monoxide, etc. by hydrogenating carbon dioxide in the presence of a homogeneous liquid phase reaction catalyst comprising a combination of a ruthenium carbonyl complex and an iodine compound. Gas contact hydrogenation method. 2. The method according to claim 1, wherein the iodine compound is at least one selected from the group consisting of iodine, alkali metal iodides, alkaline earth metal iodides and transition metal iodides.