JPS6353166B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a method for synthesizing ethanol directly from synthesis gas, ie carbon monoxide and hydrogen. More particularly, the present invention relates to an improved method for directly synthesizing ethanol from synthesis gas by a liquid phase homogeneous catalytic reaction using ruthenium and cobalt compounds as catalysts and halogen compounds as cocatalysts.

Ethanol is a compound that has a wide range of uses as an intermediate raw material or solvent for various chemicals.

(Problems to be Solved by the Prior Art and the Invention) Synthesis gas containing carbon monoxide and hydrogen is continuously fed into a catalyst-containing liquid medium containing a ruthenium compound and a halogen compound held in a reactor. The present inventors have already filed an application for a method of producing ethanol by supplying ethanol to produce ethanol and taking out the produced ethanol along with unreacted synthesis gas (Japanese Patent Application Laid-open No. 218540/1983). According to this method, a catalyst-containing liquid medium is held in a reactor, and ethanol is synthesized with this liquid medium. According to this method, alcohols or esters are entrained in unreacted synthesis gas, making it possible to produce highly concentrated ethanol.

However, among the catalyst components, a part of the ruthenium compound evaporates out of the reaction system along with unreacted synthesis gas or gaseous reaction products, and the amount of ruthenium in the reaction system decreases with time. As a result, the ethanol production activity decreases as the amount of ruthenium in the reactor decreases, resulting in a drawback that ethanol cannot be produced stably. Therefore, a technique is needed to recover the volatilized ruthenium and recycle it to the reactor.

As a result of studies conducted by the present inventors, ruthenium evaporates along with unreacted synthesis gas in the form of ruthenium pentacarbonyl (Ru(CO) ₅ ), which is a low boiling point. This compound transforms into triruthenium dodecacarbonyl (Ru ₃ (CO) ₁₂ ), which is sparingly soluble in various solvents, when exposed to heat or light at temperatures of several tens of degrees.

When the unreacted synthesis gas is condensed, most of the volatile ruthenium is removed as a component of the condensate along with the product. A method for recovering ruthenium from this condensate and recycling it in a reactor has been completed by the present inventors and has already been applied for.

On the other hand, ruthenium also accompanies non-condensable gases. Usually, a part of this non-condensable gas is exhausted to the outside of the system, and the rest is recycled to the reactor again by a gas compressor together with the raw material synthesis gas. As a result, ruthenium precipitates or adheres in the gas compressor, which not only adversely affects the gas compressor but also causes loss of expensive ruthenium and significantly reduces economic efficiency.

A method for recovering volatilized ruthenium with methanol or ethanol in a homogeneous catalytic reaction using a ruthenium compound has already been disclosed (US-412033). According to this method, ruthenium compounds are recovered with a large amount of methanol or ethanol. However, methanol or ethanol has a low solubility of ruthenium (the solubility of ruthenium in methanol and ethanol is 1000ppm at 50℃
(below), ruthenium will precipitate if it is concentrated to the extent that it does not affect the reaction in order to be recycled to the reactor. Additionally, methanol and ethanol have low boiling points and are easily entrained in gases, resulting in loss of their absorption solvents. Furthermore, when unreacted synthesis gas is recycled to the reactor, methanol or ethanol is entrained to the gas compressor.
Adversely affects gas compressor. Ruthenium must be recovered at low temperatures to prevent entrainment into this gas. This increases the cost of cooling equipment and energy costs. Therefore, methanol or ethanol is not preferred as an absorption solvent.

Thus, in order to stably produce ethanol, a technology is required to recover and homogenize the volatilized ruthenium, and to recycle it to the reactor without affecting the reaction or equipment.

An object of the present invention is to provide a method for continuously and stably producing ethanol from synthesis gas by solving problems associated with recovering volatilized ruthenium, such as the solubility of ruthenium or loss of absorption solvent. It is something.

(Means for solving the problem) In order to solve the problem, the present inventors
We conducted intensive studies on the solubility of ruthenium and the influence of absorption solvents on the reaction. As a result, in a liquid-phase homogeneous catalytic reaction using a ruthenium compound, a cobalt compound as a catalyst, and a halogen compound as a co-catalyst, a non-condensable gas accompanied by volatile ruthenium is recovered by contacting with a liquid phase containing acetic acid, They discovered that even if the acetic acid solution was concentrated to an amount that could be recycled to the reactor, it remained a homogeneous solution, leading to the completion of the present invention.

Acetic acid is the main product in the ruthenium and cobalt catalyst system used in the process of the present invention, but when acetic acid is recycled to the reactor, the amount of acetic acid recovered minus the recycled amount, i.e., the net amount of acetic acid produced. It has already been found that the selectivity of ethanol is greatly improved by reducing the
- Publication No. 63536). Therefore, acetic acid can be recycled in large quantities to the reactor, and is also preferable in terms of reaction results.

Furthermore, the solubility of ruthenium in acetic acid is more than twice that of methanol and ethanol, and because the boiling point of acetic acid is higher than these alcohols, less amount is entrained in the gas, and therefore less acetic acid is lost. few.

Thus, the use of acetic acid as an absorption solvent is highly advantageous for the solvent system used in the process of the invention.

That is, the present invention continuously supplies synthesis gas to a liquid medium containing a ruthenium compound, a cobalt compound, and a halogen compound held in a reactor under high temperature and high pressure to produce an oxygen-containing compound mainly composed of ethanol. In this method, the unreacted synthesis gas is condensed below the reaction temperature, and the separated non-reacted This is a method for producing ethanol in which a condensable gas is brought into contact with a liquid phase containing acetic acid and volatile ruthenium is recovered.

As the ruthenium compound used in the method of the present invention, any ruthenium compound that forms a complex having carbon monoxide coordination under the reaction conditions can be used. Examples of these include, in addition to metal ruthenium, ruthenium oxides such as ruthenium dioxide and ruthenium tetroxide, their hydrates, mineral acid salts of ruthenium such as ruthenium chloride, ruthenium iodide, and ruthenium nitrate, ruthenium acetate, Examples include 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, and ruthenium combined with oxygen, sulfur, halogens, nitrogen, phosphorous, arsenic, etc. , antimony,
Examples include ruthenium complexes coordinated with ligands such as bismuth, and their salts. Among these ruthenium compounds, ruthenium oxide, ruthenium halide, ruthenium carbonyl, ruthenium acetylacetonate, or ruthenium in which at least some of the carbon monoxide ligands of ruthenium carbonyl are replaced with other ligands. Complexes and the like are preferred.

The amount of the ruthenium compound used in the method of the present invention in the liquid medium is 0.1 to 300 parts by weight of the liquid medium in terms of ruthenium metal.
Parts by weight range.

In addition to metal cobalt, cobalt compounds include cobalt oxide, cobalt hydroxide, cobalt chloride, cobalt iodide, cobalt mineral salts such as cobalt nitrate, cobalt acetate, cobalt benzoate, and cobalt naphthenate. These include organic acid salts of cobalt. In addition, coordination compounds can also be used, such as cobalt carbonyl, such as dicobalt octacarbonyl, tetracobalt dodecacarbonyl, cyclopentanedienyl cobalt dicarbonyl, and cobalt with oxygen. Examples include cobalt complexes coordinated with ligands containing sulfur, halogen, nitrogen, phosphorus, arsenic, antimony, bismuth, etc., and their salts. Among these cobalt compounds, at least some of the carbon monoxide ligands of cobalt oxide, cobalt halide, cobalt carbonyl, cobalt organic acid salt, cobalt acetylacetonate, or cobalt carbonyl are replaced with other ligands. Cobalt complexes and the like are preferred.

The amount of the ruthenium compound used in the method of the present invention in the liquid medium is 0.1 to 300 parts by weight of the liquid medium in terms of ruthenium metal.
Parts by weight range.

The amount of cobalt compound used in the method of the invention in the liquid medium is also in the range of 0.1 to 100 gram atoms, preferably 1 to 10 gram atoms of cobalt per gram atom of ruthenium.

Further, in the method of the present invention, it is necessary to use a halogen compound as a promoter for the ruthenium compound and the cobalt 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, (1) examples of metal salts include lithium chloride, lithium bromide, lithium iodide, sodium chloride, potassium bromide, cesium iodide, magnesium chloride, lanthanum iodide, etc.; (2) ammonium salts; Examples include trimethylammonium chloride, trimethylammonium bromide, trimethylammonium iodide, dimethylethylammonium chloride, methyldiethylammonium iodide, tetramethylammonium chloride, tetramethylammonium iodide, tetraphenylammonium chloride, cetyltriethylammonium bromide, etc. , (3) Examples of quaternary phosphonium salts include tetraphenylphosphonium chloride, tetra n-butylphosphonium bromide,
Examples of (4) iminium salts include bis(triphenylphosphine) iminium chloride, bis(triphenylphosphine) iodide, etc. (5) Examples of alkyl halides, such as minium bromide, 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. as methyl chloride, methylene chloride,
Chloroform, carbon tetrachloride, methyl iodide, ethyl iodide, benzyl chloride, benzyl iodide, etc.
(6) Examples of hydrogen halides include hydrogen chloride, hydrogen bromide, and hydrogen iodide; (7) Examples of acid halides include acetyl chloride and acetyl bromide; and (8) transition metal halides. Examples include nickel chloride, ruthenium chloride, and copper iodide.

Moreover, iodine, chlorine gas, and bromine gas can also be used.

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 50 gram atoms.

The method of the invention is carried out in a liquid medium. The liquid medium used is preferably an aprotic liquid solvent.

For example, saturated and aromatic hydrocarbons such as heptane, octane, cyclohexane, decalin, tetralin, kerosene, benzene, toluene, xylene, diylene, hexamethylbenzene,
Halogenated hydrocarbons such as chloropentane, o-dichlorobenzene, p-chlorotoluene, fluorobenzene, dioxane, tetrahydrofuran,
Ethers such as ethyl ether, anisole, phenyl ether, diglyme, tetraglyme, and 18-crown-6, esters such as methyl acetate, ethyl butyrate, methyl benzoate, and γ-butyrolactone, and ketones such as acetone, acetophenone, and benzophenone. N-methylpyrrolidin-2-one, N-ethylpyrrolidin-2-one,
N-substituted amides such as N,N-dimethylacetamide, N-methylpiperidone, hexamethylphosphoric triamide, tertiary amines such as N,N-diethylaniline, N-methylmorpholine, pyridine, quinoline, sulfolane, etc. sulfones, sulfoxides such as dimethyl sulfoxide, urea derivatives such as 1,3-dimethyl-2-imidazolidinone, and triethylphosphine oxide, tri-n-propylphosphine oxide, tri-n-butyl. phosphine oxide, tri-n-heptylphosphine oxide, tri-n-octylphosphine oxide,
Triphenylphosphine oxide, tri-p-
Examples include oxides of trivalent organic phosphorus compounds such as tolylphosphine oxide, tri-p-chlorophenylphosphine oxide, and tributylphosphine oxide, and silicone oil.

Among these, particularly preferred liquid solvents include saturated hydrocarbons, aromatic hydrocarbons, halogenated hydrocarbons, ethers, and oxides of trivalent organic phosphorus compounds.

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. Also, if the reaction temperature exceeds 300℃,
Methane by-product increases significantly and ethanol selectivity decreases.

Further, the reaction pressure is in the range of 150 to 800 kg/cm ² G, preferably in the range of 300 to 500 kg/cm ² G. The higher the reaction pressure, the better for the reaction of carbon monoxide and hydrogen, but the practical pressure is preferably 800 kg/cm ² G or less.

The molar ratio of carbon monoxide and hydrogen used as raw materials is preferably in the range of 1:10 to 10:1. However, extreme examples include the use of pure carbon monoxide in the presence of water,
By selecting the reaction conditions, it is possible to carry out the method of the invention even when using pure hydrogen in the presence of carbon dioxide. Further, other components inert to the present invention, such as methane, nitrogen, etc., may be present in the raw material synthesis gas.

In the method of the present invention, the method of condensing the unreacted synthesis gas below the reaction temperature and separating the non-condensable gases is carried out by methods known to those skilled in the art. For example, a method is usually used in which unreacted synthesis gas is passed through a cooling pipe and separated into a condensate and non-condensable gas in a gas-liquid separator. The cooling temperature at this time is -5 to 100
℃ range, preferably 30-100℃.

Furthermore, in the method of the present invention, the method of contacting the non-condensable gas with the liquid phase containing acetic acid is carried out in a manner known to those skilled in the art. For example, there is a method in which an acetic acid solution containing acetic acid is introduced from the upper part of the scrubber, and a non-condensable gas is introduced from the lower part. In this case, the scrubber is equipped with a filler, baffle plate, etc. in order to improve the contact efficiency between the two.

The present invention can also be carried out by simply blowing a non-condensable gas into the acetic acid solution.

However, the method of the present invention is not limited even if the two are brought into contact by other methods.

The method of the present invention will be specifically explained with reference to the drawings.

In FIG. 1, a reactor 1 holds a liquid medium containing a ruthenium compound and a halogen compound. Synthesis gas passes through conduit 2 to reactor 1
supplied to The typical reaction temperature in reactor 1 is
180~260℃, typical reaction pressure is 300~500
Kg/cm ² G range. Such synthesis gas continuously supplied to the reactor 1 contacts a catalyst in a liquid medium to produce ethanol.

The produced ethanol, the by-products produced at the same time, and the easily volatile ruthenium complex (Ru(CO) ₅ ) produced in the reactor are entrained in the synthesis gas flowing unreacted in the liquid medium and passed through conduit 3 to the cooler. Guided by 4. Here, the ethanol, by-products and volatile ruthenium are cooled and separated into non-condensable gas and condensate in a high-pressure gas-liquid separator 5. The liquid level in this high-pressure gas-liquid separator 5 is kept constant by a liquid level control valve 10.

The gas phase introduced into the conduit 6 is depressurized through the pressure reducing valve 8 to usually 10 to 30 kg/cm ² G. Further, it passes through a cooler 9 and is guided to a low pressure gas-liquid separator 11.

On the other hand, the liquid phase led to the conduit 7 is
and is led to the low-pressure gas-liquid separator 11. This low-pressure gas-liquid separator 11 separates the gas into non-condensable gas and condensed liquid again. The liquid level of this low pressure gas-liquid separator 11 is kept constant by a liquid level control valve 13.

The liquid phase introduced into the conduit 12 is taken out via the liquid level control valve 13. This liquid phase contains a ruthenium compound in addition to reaction products such as ethanol.

On the other hand, the gas phase passes through conduit 14 and is led to ruthenium scrubber 15 . This gas phase is accompanied by volatile ruthenium, unreacted synthesis gas, small amounts of carbon dioxide and products such as methane and small amounts of methanol.

This gas phase, ie non-condensable gas, is contacted in the ruthenium scrubber 15 with acetic acid conducted through conduit 16 and the volatile ruthenium is absorbed into the acetic acid solution. Ruthenium scrubber 15 is usually 20-50
Operated at °C. In addition, usually a low pressure gas-liquid separator 1
It is operated at 10 to 30 kg/cm ² G, which is almost the same as 1.

Further, the non-condensable gas that does not contain volatile ruthenium passes through the cooler 17 and is taken out via the pressure reducing valve 18.

On the other hand, acetic acid taken out from the lower part of the ruthenium scrubber 15 is taken out by the pump 19 so that the liquid level in the ruthenium scrubber becomes constant, and is led to the conduit 20.

A portion of this acetic acid solution containing volatile ruthenium is reduced to normal pressure through a pressure reducing valve 21, and then guided to a thin film evaporator 22, where it is converted into ruthenium-free acetic acid and contains ruthenium concentrated to an amount that can be recycled. Separated into acetic acid solution.

This ruthenium-containing concentrated acetic acid solution is pressurized through pump 23 and recycled through conduit 24 to the reactor.

(Operation) The method of the present invention involves bringing a non-condensable gas into contact with a liquid phase containing acetic acid to recover volatile ruthenium.

According to this method, the volatilized ruthenium compound can be efficiently recovered and recycled to the reactor as a homogeneous liquid, and the loss of ruthenium is extremely reduced. Additionally, ruthenium precipitation or adhesion to the gas compressor due to recycling of unreacted synthesis gas is eliminated.

Additionally, the amount of acetic acid entrained in the gas is suppressed by the ruthenium scrubber, reducing acetic acid loss.

Furthermore, recycling acetic acid reduces the net amount of acetic acid produced and has the advantage of greatly improving ethanol selectivity.

In other words, the method of the present invention is more effective than the conventional method.
This will improve C1 chemistry technology to an industrial level.

(Example) Hereinafter, the method of the present invention will be explained in more detail with reference to Examples.

Example 1 12 g (56 mg atoms as Ru) of triruthenium dodecacarbonyl (Ru ₃ (CO) ₁₂ ), 28.8 g (168 mg atoms as Co) of dicobalt octacarbonyl (Co ₂ (CO) ₈ ), 47.6 g (Cl as 2240mg atom) of lithium chloride (LiCl) and as solvent
560 g of tributylphosphine oxide (Bu ₃ P0) was placed in a tubular reactor with a capacity of 1.5, and after the reactor was closed, synthesis gas was fed little by little from the bottom of the reactor. When the pressure in the reactor reached 360 Kg/cm ² G, temperature increase was started. When the temperature of the reactor reached 320℃, feed the synthesis gas and increase the reaction pressure to 450Kg/cm ²
While maintaining the pressure at G, gas was supplied at a space velocity of 2500/hour. At the same time, 150 g of acetic acid was supplied from the bottom of the reactor.

The gas at the outlet of the reactor is condensed and passed through the liquid level control valve 13 of the low-pressure gas-liquid separator 11.
226 g of liquid was collected and analyzed by gas chromatography. The results are shown in Table 1.

Table 1 Methanol 25.2g Ethanol 53.1g Propanol 13.2g Butanol 4.7g Formic acid 1.3g Acetic acid 153.9g (3.9g) Acetaldehyde 5.3g Others 7.5g * Esters such as methyl acetate and ethyl acetate are treated as the corresponding alcohol and acid, respectively. added to.

The value in parentheses represents the net production amount excluding the supplied acetic acid from the recovered acetic acid.

On the other hand, the shipping cost for non-condensable gas is 1560 per hour.
It was hot. The condensable gas at the outlet of the pressure reducing valve 18 was further blown into the acetic acid absorption liquid, and the ruthenium concentration in this acetic acid solution was analyzed by atomic absorption spectroscopy, but the ruthenium was below the detection limit.

On the other hand, Ruthenium scrubber 11 (10 cm in diameter,
130cm high pipe type scrubber) at 30℃, 10Kg/cm ²
G and fed acetic acid through conduit 16 at 20 kg/hour. After 50 hours, acetic acid was recovered through the pressure reducing valve 21, and the ruthenium was analyzed, and it was found that ruthenium existed in the form of triruthenium dodecacarbonyl (Ru ₃ (CO) ₁₂ ), and the amount was 4.37 g.
It was hot. This corresponds to ruthenium volatilization of 0.09g per hour. The recovered acetic acid was concentrated so that 0.09 g of ruthenium was present per 150 g of acetic acid recycled per hour, but the acetic acid solution was homogeneous and no precipitation of ruthenium was observed.

(Comparative example) Triruthenium dodecacarbonyl (Ru ₃
An attempt was made to dissolve 0.09 g of (CO) ₁₂ ) in the amount of methanol produced per hour, that is, 25.2 g of methanol, but a homogeneous liquid could not be obtained even at 50°C.

(Effect of the invention) If acetic acid is used as an absorption solvent, most of the ruthenium accompanying the non-condensable gas can be recovered. Furthermore, even if this acetic acid solution containing ruthenium is concentrated to a recyclable amount, ruthenium does not precipitate and can be recycled to the reactor as a homogeneous liquid.

As described above, by using the method of the present invention, the process of recovering ruthenium and recycling it to the reactor can be handled as a homogeneous liquid, and the recovery loss of expensive ruthenium can be extremely reduced.

[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, 4,9,17...Cooler, 5...High pressure gas-liquid separator, 8,18,21...Pressure reducing valve, 10,1
3...Liquid level control valve, 11...Low pressure gas-liquid separator, 15...
Ruthenium scrubber, 19, 23...pump, 2
2... Thin film evaporator, 2, 3, 6, 7, 12, 14,
16, 20, 26... Conduit.

Claims (1)

[Claims] 1. Synthesis gas is continuously supplied to a liquid medium containing a ruthenium compound, a cobalt compound, and a halogen compound held in a reactor under high temperature and high pressure to produce a reaction product consisting of an oxygen-containing compound whose main component is ethanol. In this method, the unreacted synthesis gas is condensed below the reaction temperature, and the separated non-condensable gas is converted into acetic acid. A method for producing ethanol, the method comprising recovering volatilized ruthenium by bringing it into contact with a liquid phase containing ethanol.