JPS632941B2 - - Google Patents

Description

[Detailed description of the invention]

(Industrial Application Field) The present invention relates to a method for directly synthesizing ethanol from carbon monoxide and hydrogen (hereinafter referred to as synthesis gas). More specifically, the present invention relates to an improved method for directly synthesizing ethanol from synthesis gas by a liquid phase homogeneous catalytic reaction using ruthenium compounds and halogen compounds as catalysts. Ethanol is a compound that has a wide range of uses as an intermediate raw material or solvent for various chemicals. (Prior Art and Problems to be Solved by the Invention) Many methods have been proposed for directly producing ethanol from synthesis gas using a ruthenium liquid-phase homogeneous catalyst. For example, a method for directly producing methanol, ethylene glycol, and ethanol or their carboxylate derivatives by reacting synthesis gas in a suitable solvent containing a solubilized ruthenium carbonyl complex (Japanese Patent Application Laid-open No. 115834/1983); Examples include a method of selectively producing methanol and ethanol by bringing synthesis gas into contact with a homogeneous ruthenium catalyst, a halogen or a halogenation promoter, and an organic oxidized phosphine compound (Japanese Patent Application Laid-Open No. 82327/1982). To date, the technology for producing ethanol directly from synthesis gas has not yet been industrialized. Industrial implementation of this technology necessarily requires a continuous production process in which ethanol is synthesized by bringing synthesis gas into contact with a catalyst liquid, and then ethanol is separated from the catalyst liquid. Unfortunately, to date, the development efforts for producing ethanol by liquid-phase homogeneous catalysis using ruthenium have been focused on improving the performance of the catalyst, including the economical separation of the product and the catalyst liquid. The technology is little known. Synthesize ethanol from syngas, then
In the continuous production process of separating ethanol from the catalyst liquid, the catalyst liquid and synthesis gas are usually fed into a reactor and reacted, and after the catalyst liquid containing the product is taken out from the reactor, the product and catalyst are separated. Processes consisting of separation into liquids are known. Such methods include, for example, a method for producing ethylene glycol, methanol, and ethanol using a ruthenium catalyst (Japanese Patent Application Laid-open No. 130936/1983);
A method for continuously producing methanol, ethylene glycol, and ethanol by repeatedly removing the liquid phase using a ruthenium catalyst before the total glycol products in the liquid phase exceed 50% by weight (Japanese Patent Application Laid-Open No. 57-82328
No.) etc. However, these methods require a separate process (equipment) to separate the low concentration products from the catalyst liquid. Moreover, according to the experiments of the present inventors, when a ruthenium liquid-phase homogeneous catalyst is used, the accumulation of the produced alcohol in the catalyst liquid deteriorates the catalyst performance. This fact is explained in the above-mentioned Japanese Patent Application Laid-Open No. 57-82328: ``Experiments have shown that as the concentration of ethylene glycol increases in the liquid phase during the reaction process, the rate of ethylene glycol production decreases correspondingly.'' This is consistent with the statement "It was done". For these reasons, although a higher product concentration in the catalyst solution is economically preferable in order to separate the product from the catalyst solution, it is important to suppress product accumulation as much as possible in order to obtain an appropriate production rate. Must. Furthermore, as in the prior art, in the homogeneous liquid phase catalytic reaction of ruthenium, the catalyst is reused after the reaction at high temperature and high pressure and is separated from the reaction products. It is questionable whether the active species generated below remain stable under and after being handled under separation conditions. The object of the present invention is to take into account the above-mentioned problems of the prior art and to provide an economical method for continuously producing ethanol from synthesis gas. (Means for Solving the Problems) The present inventors have conducted extensive studies to solve these problems. As a result, they discovered that ethanol could be produced by supplying synthesis gas to the catalyst liquid held in the reactor, and stripping the produced ethanol with unreacted synthesis gas to obtain ethanol. Completed the invention. That is, the present invention provides a method for producing ethanol by contacting a catalyst-containing liquid medium containing a ruthenium compound and a halogen compound as main components with a synthesis gas containing carbon monoxide and hydrogen under high temperature and high pressure. A method for producing ethanol, which comprises continuously supplying synthesis gas to a catalyst-containing liquid medium held in a container to produce ethanol, and extracting the produced ethanol along with unreacted synthesis gas. . Any ruthenium compound used in the present invention can be used as long as it forms a ruthenium complex having a carbon monoxide ligand under the reaction conditions. Examples of these include, in addition to ruthenium metal, ruthenium oxides such as ruthenium dioxide and ruthenium tetroxide, their hydrates, mineral salts of ruthenium such as ruthenium chloride, ruthenium iodide, and ruthenium nitrate, and ruthenium acetate. , organic acid salts of ruthenium such as ruthenium propionate. Ruthenium compounds can also be used directly in the form of coordination compounds, examples of which include ruthenium carbonyl such as triruthenium dodecacarbonyl, ruthenium combined with oxygen,
Examples include ruthenium complexes and their salts coordinated with ligands containing sulfur, halogen, nitrogen, phosphorus, arsenic, antimony, bismuth, etc. Among these ruthenium compounds, ruthenium oxide, ruthenium halide, ruthenium carbonyl, and ruthenium complexes in which at least some of the carbon monoxide ligands of ruthenium carbonyl are replaced with other ligands are preferred. Further, in the method of the present invention, it is necessary to use a halogen compound as a promoter for the ruthenium compound. In the absence of these halogen compounds, ethanol activity and selectivity are significantly lower. These halogen compounds include metal salts such as alkali metal salts and alkaline earth metal salts having halogen ions such as chloride ions, bromide ions, and iodine ions as anions constituting the salts;
Examples include salts such as ammonium salts, quaternary phosphonium salts, and iminium salts, and hydrocarbon halides such as alkyl halides and aryl halides. Further, hydrogen halides, acid halides, transition metal halides, and the like can also be used. More specifically, examples of metal salts include lithium chloride, lithium bromide, lithium iodide, sodium chloride, potassium bromide, cesium iodide, magnesium chloride, and lanthanum iodide; examples of ammonium salts include trimethylammonium Quaternary phosphonium salts such as chloride, trimethylammonium bromide, trimethylammonium iodide, dimethylethylammonium chloride, methyldiethylammonium iodide, tetramethylammonium chloride, tetramethylammonium iodide, tetraphenylammonium chloride, cetyltriethylammonium bromide, etc. Examples include tetraphenylphosphonium chloride, tetra n-butylphosphonium bromide,
Examples of iminium salts include bis(triphenylphosphine)iminium chloride, bis(triphenylphosphine)iminium bromide, such as n-heptyltriphenylphosphonium bromide, benzyltriphenylphosphonium iodide, and methyltriphenylphosphonium chloride. Examples of alkyl halides include methyl chloride, chloride, etc., such as bis(triphenylphosphine)iminium iodide and iminium salts in which at least a portion of the phenyl group of these iminium compounds is substituted with a methyl group, ethyl group, etc. methylene, chloroform, carbon tetrachloride, methyl iodide,
Examples of hydrogen halides include hydrogen chloride, hydrogen bromide, and hydrogen iodide; examples of acid halides include acetyl chloride and acetyl bromide; and transition metals such as acetyl chloride and acetyl bromide. Examples of halides include nickel chloride, ruthenium chloride, and copper iodide. These halogen compounds can be used alone or in combination of two or more. In the method of the present invention, the amount of these halogen compounds used per gram atom of ruthenium is:
The halogen atoms range from 0.1 to 200 gram atoms, more preferably from 1 to 20 gram atoms. The method of the invention is carried out in a liquid medium. The liquid medium used is preferably an aprotic liquid solvent. In protic liquid media such as water and alcohol, the ethanol production activity is low and the selectivity is also poor. In the method of the present invention, examples of the aprotic liquid solvent preferably used include heptane,
Saturated and aromatic hydrocarbons such as octane, cyclohexane, decalin, tetralin, kerosene, benzene, toluene, xylene, diylene, hexamethylbenzene, chloropentane, o-dichlorobenzene, p-chlorotoluene, fluorobenzene, etc. Ethers such as halogenated hydrocarbons, dioxane, tetrahydrofuran, ethyl ether, anisole, phenyl ether, diglyme, tetraglyme, 18-crown-6,
Methyl acetate, ethyl butyrate, methyl benzoate, γ-
Esters such as butyrolactone, ketones such as acetone, acetophenone, benzophenone,
N-substituted amides such as N-methylpyrrolidin-2-one, N-ethylpyrrolidin-2-one, N,N-dimethylacetamide, N-methylpiperidone, hexamethylphosphorictriamide,
Tertiary amines such as N,N-diethylaniline, N-methylmorpholine, pyridine, and quinoline, sulfones such as sulfolane, sulfoxides such as dimethylsulfoxide, 1,3-dimethyl-2-imidazolidinone, etc. Examples include urea derivatives, phosphine oxides such as tributylphosphine oxide, and silicone oil. Among these, particularly preferred liquid solvents include saturated hydrocarbons, aromatic hydrocarbons, halogenated hydrocarbons, ethers, and phosphine oxides. The liquid solvent used in the method of the present invention is more preferably a liquid solvent having a boiling point of 200° C. or higher under normal pressure in order to minimize volatilization from the reactor. However, even if the boiling point is below 200°C, it can be separated from the product and recycled to the reactor for use. These liquid solvents can be used alone or in combination of two or more. Further, if the liquid solvent used in the method of the present invention is liquid at least under the reaction conditions,
It can be used even if it is solid at room temperature and pressure. In the method of the present invention, the reaction temperature is in the range of 160 to 300°C, preferably in the range of 180 to 260°C. At reaction temperatures below 160°C, the reaction between carbon monoxide and hydrogen is extremely slow. Furthermore, when the reaction temperature exceeds 300°C, the amount of methane by-product increases significantly, and the selectivity of ethanol decreases. Moreover, the reaction pressure is in the range of 150 to 800 Kg/cm ² , preferably in the range of 300 to 500 Kg/cm ² . The higher the reaction pressure is, the more preferable it is for the reaction between carbon monoxide and hydrogen, but for practical purposes, a pressure of 800 Kg/cm ² or less is preferable. The raw materials used in the method of the present invention are carbon monoxide and hydrogen. Synthesis gas is usually used. The unreacted synthesis gas that is taken out along with the produced ethanol is the remaining gas that was supplied to the reactor and was mainly consumed in the production of ethanol, and of course contains small amounts of by-product carbon dioxide and methane. This gas strips the ethanol produced at the same time. The supplied gas may be mixed with a gas inert to the reaction. By mixing an inert gas in this manner, the stripping effect of ethanol can be improved. As such a gas, an inert gas such as nitrogen, argon, helium, etc. is used. The range of gas space velocity of the gas supplied to the reactor is not particularly limited. The optimum gas hourly space velocity is determined by the reactor configuration, reaction temperature, reaction pressure, catalyst performance, etc. It is not preferable if the space velocity is too large or too small. If the space velocity is too large, the flow state of the synthesis gas relative to the catalyst liquid becomes a circular flow, which adversely affects the reaction. Furthermore, this has the undesirable effect of causing the catalyst liquid to scatter outside the reactor as mist. Also, if the space velocity is too low, the amount of product entrained in the gas will be reduced, reducing stripping efficiency. The method of the present invention will be specifically explained with reference to the drawings.
FIG. 1 is a manufacturing process diagram for carrying out the method of the present invention. In FIG. 1, a reactor 1 holds a liquid medium containing a ruthenium compound and a halogen compound. Synthesis gas is fed to reactor 1 through conduit 6. Reactor 1 has a reaction temperature of 180℃.
The reaction temperature is 260°C and the reaction pressure is 300 to 600 Kg/cm ² . Synthesis gas continuously supplied to such a reactor 1 contacts a catalyst in a liquid medium to produce ethanol. The produced ethanol and the co-produced by-products are entrained by the synthesis gas flowing unreacted in the liquid medium and are led through conduit 7 to cooler 2 . Here the ethanol and by-products are cooled and
The high-pressure gas-liquid separator 3 separates the gas into non-condensable gas and condensed liquid. The gas phase led to conduit 8 is accompanied by a small amount of products such as methanol. On the other hand, the liquid phase is led to conduit 9. The gas introduced into conduit 8 and the liquid introduced into conduit 9 are taken out through pressure reducing valves 4 and 5, respectively. (Function) The present invention produces ethanol while flowing raw material synthesis gas through a liquid medium containing a catalyst,
The generated ethanol is taken out along with the supplied synthesis gas. According to this method, the process of separating the product and the catalyst liquid can be omitted, and a highly concentrated product can be directly recovered from the reactor. Furthermore, the catalyst liquid does not need to be taken out of the reactor to separate it from the products; it is always retained within the reactor, and therefore the catalyst liquid can be used under optimal conditions to synthesize the desired product. You can leave it there. In other words, the catalyst regeneration process associated with the separation of the catalyst liquid and the product can be omitted. In addition, the products in the reactor are always accompanied by gases containing unreacted gases and are taken out of the reactor, thereby minimizing the unfavorable effects of product accumulation on the reaction. . The method of the present invention does not require a separation process (equipment) between the catalyst liquid and the product unlike the conventional method. This method produces ethanol directly from synthesis gas, and has the following characteristics: There is no need to increase the concentration of the product for this separation, and there is no risk of catalytic active species becoming inactivated under this separation condition. be. That is, the method of the present invention improves the technology of C ₁ chemistry to an industrial level compared to previously proposed methods. (Example) Hereinafter, the method of the present invention will be explained in more detail with reference to Examples and Comparative Examples. Example 1 21 mmole of triruthenium dodecacarbonyl (Ru ₃ (CO) ₁₂ ), 35 mmole of bis(triphenylphosphine)iminium bromide (Ph ₃ P) ₂ N ⁺ Br ^- ), 84 mmole of phosphoric acid and 280 g of tri-n-butylphosphine oxide was added as a liquid solvent from the top of the tubular reactor, and after the reactor was closed, synthesis gas was fed little by little from the bottom of the reactor. When the reactor pressure reached 300 Kg/cm ² , the temperature was increased. When the temperature of the reactor reached 240℃ (the pressure of the reactor at this time was 400Kg/ ^cm2 ), the gas hourly space velocity of the synthesis gas was kept at 700/hour, the reaction pressure was kept at 400Kg/ ^cm2 , and the reaction was started. I went there. Average of 8.6 per hour from the gas at the reactor outlet
g of liquid was collected. As a result of analyzing the liquid with a gas chromatograph, it was found that it was 11.5% methanol and ethanol.
68.6% as propanol, 10.5% as formic acid, 2.7% as formic acid, 4.3% as acetic acid, and 1.3% as acetaldehyde. ). Examples 2 to 9 Reactions were carried out in the same manner as in Example 1, changing the halogen compound, additive, liquid solvent, reaction temperature and space velocity as shown in Table 1. These results are shown in Table 1 together with Example 1. Comparative Example 1 Per hour, 14 mmole of ruthenium acetylacetonate (Ru(acac) ₃ ), 85 mmole of bis(triphenylphosphine)iminium chloride (Ph ₃ P) ₂ N ⁺ Cl ^- ), 15 mmole of Methyl iodide (MeI), 81 mmole phosphoric acid and 340 g γ-
A liquid catalyst consisting of butyrolactone was fed together with synthesis gas (gas hourly space velocity 1500/h) from the bottom of the tubular reactor. As a result of increasing the temperature while maintaining the pressure at 400 Kg/cm ² , a steady value was obtained about 2 hours after the reaction temperature reached 220°C. At this time, 438 g of liquid was collected per hour from the reactor outlet. The liquid was analyzed in the same manner as in the example, and the concentrations were 1.8% as methanol, 2.0% as ethanol, 0.2% as propanol, 0.1% as formic acid, 0.2% as acetic acid, and 0.2% as acetaldehyde (these indications is the same as Example 1). Comparative Example 2 A reaction was carried out in the same manner as in Comparative Example 1, with the composition ratios of the halogen compound and additives changed as shown in Table 1. The results are shown in Table 1 together with Examples 1 to 9 and Comparative Example 1.

【table】

[Table] (Effects) In Comparative Examples 1 and 2, the ethanol concentrations in the recovered liquids were both 3% or less. Furthermore, the method of the comparative example requires a step (device) for separating the product and the catalyst liquid from the recovered liquid. On the other hand, in Examples 1 to 9, the ethanol concentration in the recovered liquid was 43% or more, and in Example 2, it was 71%. As described above, by using the method of the present invention, high-concentration ethanol can be recovered without requiring a step (equipment) for separating the product and the catalyst liquid from the recovered liquid.

[Brief explanation of the drawing]

FIG. 1 shows an example of a manufacturing flow sheet for carrying out the method of the present invention. In the figure, each symbol is as follows. 1... Reactor, 2... Cooler, 3... High pressure gas-liquid separator, 4, 5... Pressure reducing valve.

Claims (1)

[Claims] 1. A method for producing ethanol by contacting a catalyst-containing liquid medium containing a ruthenium compound and a halogen compound with a synthesis gas containing carbon monoxide and hydrogen under high temperature and high pressure,
A method for producing ethanol, which comprises continuously supplying synthesis gas to a catalyst-containing liquid medium held in a reactor to produce ethanol, and removing the produced ethanol along with unreacted synthesis gas.