# Patent

## Title
Conversion of synthesis gas to liquid hydrocarbons

## Abstract

A process for producing aliphatic alcohols by reacting carbon monoxide and hydrogen in a liquid phase in the presence of catalyst components, characterized in that rhodium and a trialkylphosphine represented by the general formula PR.sub.1 R.sub.2 R.sub.3 where each of R.sub.1, R.sub.2 and R.sub.3 is a primary alkyl group, a secondary alkyl group, a tertiary alkyl group or a cycloalkyl group, are used as the catalyst components.

## Background
The present invention relates to a process for producing aliphatic alcohols by reacting carbon monoxide and hydrogen in a liquid phase. More particularly, the present invention relates to a process for producing lower aliphatic alcohols, particularly ethylene glycol and methanol, directly from a mixture of carbon monoxide and hydrogen (hereinafter referred to simply as "synthesis gas") in a liquid phase.

Ethylene glycol is an industrially important chemical substance useful as a starting material for polyester fibers and organic solvents or as a non-volatile antifreezing agent. At present, it is usually prepared from ethylene as the starting material, by subjecting ethylene to an oxidation reaction and a hydration reaction. On the other hand, methanol is an important basic chemical substance which is widely used as a raw material for formalin, acetic acid, dimethyl phthalate or methacrylic acid or as a solvent, and is usually prepared by reacting the synthesis gas in a gas phase under a high temperature high pressure condition.

In recent years, there have been proposed various methods for producing lower aliphatic alcohols in a liquid phase directly from synthesis gas as the starting material. In these methods, it is known to use a catalyst containing rhodium or a catalyst containing ruthenium.

For the use of a catalyst containing rhodium, there have been proposed a number of methods. For instance, Japanese Unexamined Patent Publications Nos. 36403/1976, 32506/1976 and 63110/1976, disclose that an addition of an alkali metal salt, a quaternary ammonium salt or a bis(tertiary phosphine) iminium salt as a cocatalyst is effective. Further, Japanese Unexamined Patent Publications Nos. 68509/1973, 42809/1977 and 42810/1977 disclose an addition of an organic nitrogen ligand or an organic oxygen ligand. Furthermore, Japanese Unexamined Patent Publication No. 9065/1980 discloses the use of a phosphine oxide as a co-catalyst.

As other references which disclose the use of rhodium as a catalyst, there may be mentioned Japanese Unexamined Patent Publications Nos. 32117/1975, 32118/1975, 32507/1976, 88902/1976, 125203/1976, 42808/1977, 108889/1978, 121714/1978, 124204/1978, 16415/1979, 48703/1979, 71098/1979, 92903/1979, 122211/1979, 75498/1981, 128645/1982, 130941/1982 and 130942/1982, Japanese Examined Patent Publication No. 43821/1980, and U.S. Pat. Nos. 4,013,700, 4,199,520, 4,133,776, 4,151,192, 4,153,623, 4,225,530, 4,199,521, 4,190,598, 4,302,547 and 4,211,719. However, none of these methods is fully satisfactory with respect to the catalytic activity and selectivity, or it is thereby difficult to recycle the catalyst for reuse. For these reasons, these methods have not yet been industrially employed.

Catalysts containing ruthenium are disclosed in e.g. Japanese Unexamined Patent Publications Nos. 115834/1980, 100728/1981, 51426/1981, 109735/1982, 123128/1982, 130937/1982 and 130939/1982. These catalysts are also inadequate in catalytic activity, and their selectivity for ethylene glycol is at a low level.

Further, a method for carrying out the reaction in the presence of both rhodium and ruthenium, is disclosed in e.g. Japanese Unexamined Patent Publications Nos. 123925/1981, 128644/1982, 123128/1982, 118527/1983, 118528/1983 and 121227/1983. These catalysts are also inadequate in their catalytic activity, and their selectivity for ethylene glycol is at a low level.

Thus, in the prior art processes mentioned above, the catalytic activity which justifies the use of expensive rhodium has not yet been realized, and none of them is qualified as a process employable in an industrial scale.

Under these circumstances, the present inventors have conducted extensive research with an aim to overcome the difficulties of the conventional catalysts, and have finally found that by using rhodium and a trialkyl phosphine as catalyst components, the activity for the production of lower aliphatic alcohols can be remarkably improved, and the yield of ethylene glycol can substantially be increased, and that the coexistence of an amine compound is further effective. More surprisingly, it has been found that by using a trialkylphosphine in the presence of both rhodium and ruthenium, the activity for the production of lower aliphatic alcohols can further be improved, and that the coexistence of an amine compound is effective also in this case. The present invention has been accomplished based on these discoveries.

The object of the present invention is to provide a process for industrially advantageously producing aliphatic alcohols such as ethylene glycol and methanol, which are industrially important chemical substances.

In the broadest sense, the present invention provides a process for producing aliphatic alcohols by reacting carbon monoxide and hydrogen in a liquid phase in the presence of catalyst components, characterized in that rhodium and a trialkylphosphine represented by the general formula PR.sub.1 R.sub.2 R.sub.3 where each of R.sub.1 R.sub.2 and R.sub.3 is a primary alkyl group, a secondary alkyl group, a tertiary alkyl group or a cycloalkyl group, are used as the catalyst components.

Now, the present invention will be described in detail with reference to the preferred embodiments.

In the present invention, the presence of rhodium as a catalytic component is essential. The rhodium component may be supplied in the form of rhodium metal or a rhodium compound which is capable of forming a rhodium carbonyl compound in the reaction zone.

As specific examples of such rhodium compounds, there may be mentioned a zero valence compound such as dirhodium octacarbonyl; a monovalent complex compound such as acetylacetonatobis(carbonyl)rhodium or bromotris(pyridine)rhodium; a salt such as rhodium trichloride, rhodium nitrate, rhodium formate, rhodium acetate, rhodium (II) propionate, rhodium (II) butyrate, rhodium (II) valerate or rhodium (II) naphthenate; an oxide such as rhodium oxide or rhodium trihydroxide; a trivalent complex compound such as tris(acetylacetonato) rhodium; a cluster such as tetrarhodium dodecacarbonyl or hexarhodium hexadecacarbonyl; and an anion complex such as rhodium tetracarbonyl-anion or carbidohexarhodium pentadecacarbonyl-dianion.

Further, it is also possible to use a rhodium compound to which a trialkylphosphine having a function to facilitate the reaction as a catalyst component, as will be described hereinafter, is coordinated beforehand. As specific examples, there may be mentioned RhH[P(i-Pr).sub.3 ].sub.3, RhH(PEt.sub.3).sub.4, RhH(PEt.sub.3).sub.3, (trans-Rh(CO)(py) [P(i-Pr)BPh.sub.4, trans-RhH(CO)[P(c-C.sub.6 H.sub.11).sub.3 ].sub.2, trans-RhH(CO)[P(i-Pr).sub.3 ].sub.2 .sub.3 ].sub.2, Rh(CO)[P(n-Bu).sub.3 ].sub.2, RhH[P(t-Bu) .sub.3 ].sub.2, RhH[P(c-C.sub.6 H.sub.11).sub.3 ].sub.2, [Rh(CO).sub.3 P(i-Pr).sub.3 ].sub.2, Rh.sub.2 (CO).sub.3 [P(i-Pr).sub.3 ].sub.3, Rh.sub.2 (CO).sub.4 [P(t-Bu).sub.3 ].sub.2 and Rh.sub.2 (CO).sub.4 [P(c-C.sub.6 H.sub.11).sub.3 ].sub.2. (In the above chemical formulas, i-Pr is an isopropyl group, Et is an ethyl group, py is pyridine, Ph is a phenyl group, c-C.sub.6 H.sub.11 is a cyclohexyl group, n-Bu is a n-butyl group, and t-Bu is a t-butyl group.)

The concentration of rhodium in the reaction solution is usually within a range of from 0.0001 to 10 g atom, preferbly from 0.001 to 10 g atom, more preferably from 0.001 to 1 g atom, as rhodium atom, per 1 liter of the reaction solution.

In the process of the present invention, it is effective to use ruthenium as a catalyst component in combination with rhodium. The ruthenium component may be supplied in the form of ruthenium metal or a ruthenium compound capable of forming a ruthenium carbonyl compound in the reaction zone.

As specific examples of such a ruthenium compound, there may be mentioned a salt such as ruthenium (III) chloride, ruthenium (III) bromide, ruthenium (III) nitrate or ruthenium (III) acetate; an oxide such as ruthenium (IV) oxide; a complex compound such as tris(acetylacetonato)ruthenium, dicarbonyl(methyl)(cyclopentadienyl)ruthenium, dicarbonyl-bis(allyl)ruthenium, dichlorotricarbonylruthenium dimer or ruthenocene; and a cluster such as tetrahydridotetraruthenium dodecacarbonyl or triruthenium dodecacarbonyl. In the case where ruthenium is used in combination with rhodium, the amount of ruthenium is related to the amount of rhodium. Namely, the sum of the amounts of rhodium and ruthenium as metals should be within the above-mentioned range for the amount of rhodium. Namely, the total concentration of rhodium and ruthenium as metals in the reaction solution is usually within a range of from 0.0001 to 10 g atom, preferably from 0.001 to 10 g atom, more preferably from 0.001 to 1 g atom, per 1 liter of the reaction solution.

The ratio of the rhodium component to the ruthenium component is not critical and is not particularly limited. However, the atomic ratio of ruthenium to the sum of ruthenium and rhodium as metals (Ru/Ru+Rh) is preferably from 0.1 to 0.9. The use of ruthenium serves to stabilize the catalyst and to prevent the loss of expensive rhodium.

In the present invention, it is essential to use a trialkylphosphine having a function to facilitate the reaction, as a catalyst component.

The trialkylphosphine is believed to be coordinated to rhodium as the main catalyst and have a function to control the electronic state. The mechanism of the control is not clearly understood. However, it is believed that the ability of the trialkylphosphine as an electron donor plays an important role. In fact, the hydrogenation activity of the rhodium-phosphine catalyst system and the selectivity for ethylene glycol in the reaction intended by the present invention, substantially vary depending upon the type of the phosphine. Accordingly, in order to attain a high level of the ethylene glycol yield, it is particularly effective to employ, among various phosphines, a trialkylphosphine represented by the general formula PR.sub.1 R.sub.2 R.sub.3 where each of R.sub.1, R.sub.2 and R.sub.3 is a primary alkyl group, a secondary alkyl group, a tertiary alkyl group or a cycloalkyl group, and they may be the same or different from one another. In this case, it is believed that the electronic interaction among the alkyl groups in the trialkylphosphine molecule serves to adjust the physical constant for the above-mentioned ability as the electron donor to a desirable state, whereby a favorable property as the accelerator is brought about.

Further, by using such a phosphine, it is possible to improve the stability of the catalyst and to prevent the formation of metallic precipitation which used to be a serious problem when a rhodium catalyst was used.

As specific examples of the trialkylphosphine which may be used in the present invention, there may be mentioned a trialkylphosphine having three primary alkyl groups, such as trimethylphosphine, triethylphosphine, tri-n-propylphosphine, tri-n-butylphosphine, tri-n-hexylphosphine, tri-n-octylphosphine, tri-iso-butylphosphine, tris(2-ethylhexyl)phosphine or di-n-butyl-iso-butylphosphine; a trialkylphosphine having three secondary alkyl, tertiary alkyl or cycloalkyl groups (hereinafter referred to generally as ".alpha.-branched alkyl groups"), such as tri-iso-propylphosphine, tri-sec-butylphosphine, tri-t-butylphosphine, tricyclopentylphosphine, tricyclohexylphosphine, tri-t-amylphosphine, tris(dimethylisopropyl)phosphine, tris(pentamethylethyl)phosphine, di-iso-propyl-cyclopentylphosphine, di-isopropyl-sec-butylphosphine, di-iso-propyl-t-butylphosphine, di-t-butyl-iso-propylphosphine, di-t-butyl-sec-butylphosphine, di-sec-butyl-iso-propylphosphine, di-sec-butyl-t-butylphosphine, di-iso-propyl-cyclohexylphosphine, di-t-butyl-cyclopentylphosphine, di-t-buty-cyclohexylphosphine, di-sec-butyl-cyclohexylphosphine, dicyclopentyl-iso-propylphosphine, dicyclopentyl-t-butylphosphine, dicyclohexyl-iso-propylphosphine, dicyclohexyl-t-butylphosphine, dicyclohexyl-sec-butylphosphine, diadamantyl-iso-propylphosphine, cyclopentyl-cyclohexyl-t-butylphosphine, tris(1-bicyclo[2,2,2]octyl)phosphine or tris(1-bicyclo[2,2,1]heptyl)phosphine; a trialkylphosphine having two primary alkyl groups and one .alpha.-branched alkyl group, such as iso-propyl-diethylphosphine, iso-propyl-di-n-butylphosphine, iso-propylethyl-n-butylphosphine, t-butyl-diethylphosphine, t-butyl-di-n-propylphosphine, t-butyl-di-n-butyl phosphine, cyclopentyl-diethylphosphine, di-n-butyl cyclopentylphosphine, cyclopentyl-di-n-propylphosphine, cyclopentyl-ethyl-n-butylphosphine, cyclohexyl-diethylphosphine, cyclohexyl-di-n-octylphosphine, adamantyldiethylphosphine, adamantyl-di-n-butylphosphine, norbornyl-diethylphosphine or norbornyl-di-n-butylphosphine; and a trialkylphosphine having one primary alkyl group and two .alpha.-branched alkyl groups, such as di-iso-propyl-ethylphosphine, di-iso-propyl-n-butylphosphine, di-t-butyl-methylphosphine, di-t-butyl-ethylphosphine, di-t-butyl-n-propylphosphine, di-t-butyl-n-butylphosphine, dicyclopentyl-ethylphosphine, dicyclopentyl-n-propylphosphine, dicyclopentyl-n-butylphosphine, dicyclohexyl-methylphosphine, dicyclohexylethylphosphine, dicyclohexyl-n-butylphosphine, dicyclohexyl-n-propylphosphine, diadamantyl-ethylphosphine, diadamantyl-n-butylphosphine, dinorbornylethylphosphine, dinorbornyl-n-butylphosphine, iso-propyl-t-butyl-n-butylphosphine, t-butyl-cyclohexylethylphosphine or iso-propyl-cyclopentyl-n-octyl-phosphine.

Among the above-mentioned phosphines, a suitable trialkylphosphine varies depending upon many factors of the catalyst system employed, such as the type and amount of the metal components (rhodium and, if applicable, ruthenium) or the type and amount of the amine compound. In practice, a suitable trialkylphosphine is selected by experiments.

Among the above trialkylphosphines, those having both primary alkyl and .alpha.-branched alkyl groups, i.e. trialkylphosphines represented by the general formula PR.sub.1 R.sub.2 R.sub.3 where R.sub.1 is a primary alkyl group, R.sub.2 is a secondary alkyl group, a tertiary alkyl group or a cycloalkyl group, and R.sub.3 is a primary alkyl group, a secondary alkyl group, a tertiary alkyl group or a cycloalkyl group, include many trialkylphosphines having delicately different characteristics, and in the practical selection of a suitable trialkylphosphine, it is advantageous to select a suitable phosphine from such trialkylphosphines.

As parameters with which the function of the phosphine compound as a ligand to control the electronic state of metal is explained, C. A. Tolman has proposed a parameter .theta. (unit: deg) for a steric factor and a parameter .nu.(unit: cm.sup.-1) for an electronic factor, in Chemical Reviews (1977), Vol. 77, No. 3, pages 313-348. Further, T. T. Derencsenyi has proposed a chemical shift value .delta.(ppm) of .sup.31 P-nmr of the corresponding phosphine oxide as a parameter relating to the basicity of the phosphine compound and the reaction rate in a uniform complex reaction, in Inorganic Chemistry (1981), Vol. 20, No. 3, pages 665-670.

The trialkylphosphines to be used in the present invention may be represented by .theta., .nu. and .delta., as follows: usually .theta.(115-190 deg), .nu.(2050-2080 cm.sup.-1), .delta.(-80 -0 ppm), preferably .theta.(140-185 deg), .nu.(2055-2070 cm.sup.-1), .delta. (-75--30 ppm), more preferably .theta.(150-185 deg), .nu. (2055-2060 cm.sup.-1), .delta.(-70--40 ppm).

These trialkylphosphines are usually employed in an amount within a range of at least 0.2 mol, preferably from 0.2 to 1000 mols, more preferably from 0.2 to 500 mols, further preferably from 0.5 to 100 mols, relative to 1 g atom of rhodium. Particularly preferred is a range of from 0.8 to 10 mols. Further, in the case where a ruthenium component is used in combination with the rhodium component, the trialkylphosphines are employed in an amount within a range of at least 0.2 mol, preferably from 0.2 to 1000 mols, more preferably from 0.2 to 500 mols, further preferably from 0.5 to 100 mols, particularly preferably from 0.8 to 10 mols, relative to 1 g atom of the total of rhodium and ruthenium as metals.

In the process of the present invention, the activity of the catalyst can remarkably be improved by using an amine compound in combination with the trialkylphosphine.

The function of the amine compound is not clearly understood. However, it appears that the amine compound plays a role as a ligand or a role of presenting a counter cation to stabilize an anionic rhodium compound or an anionic ruthenium compound formed in the reaction system. In the present invention, various amine compounds may be used.

As specific examples of the amine compound which may be used in the present invention, there may be mentioned an inorganic amine such as ammonia, hydroxylamine or hydrazine; an aliphatic amine such as methylamine, ethylamine, n-propylamine, isopropylamine, octylamine, dimethylamine, diethylamine, di-n-propylamine, methylethylamine, trimethylamine, triethylamine, triisopropylamine, triisobutylamine or tridecylamine; an alicyclicamine such as cyclohexylamine, dicyclohexylamine, tricyclohexylamine or dicyclohexylmethylamine; an ethyleneimine such as ethyleneimine or methylethyleneimine; a pyrrolidine such as pyrrolidine or 1-methylpyrrolidine; a pyrrole such as pyrrole; a piperidine such as piperidine, 1-methylpiperidine, 2-methylpiperidine, 3-methylpiperidine or 4-ethylpiperidine; a pyridine such as pyridine, 2-methylpyridine, 3-methylpyridine, 4-ethylpyridine, 2,4,6-trimethylpyridine, 4-aminopyridine, 2-aminopyridine, 2-dimethylaminopyridine, 2-methylaminopyridine, 4-anilinopyridine, 4-methylaminopyridine, 4-dimethylaminopyridine or 2,2'-dipyridyl; a quinoline such as quinoline, 2-(dimethylamino)quinoline or 4-(dimethylamino)quinoline; a phenanthroline such as 4,5-phenanthroline or 1,8-phenanthroline; a piperazine such as piperazine, 1-methylpiperazine or 1-phenylpiperazine; a cyclic amine such as diazabicycloundecene or diazabicyclooctane; an imidazole such as imidazole, 1-methylimidazole, 2-methylimidazole, 1-ethylimidazole, 1,2-dimethylimidazole, 1,5,6-trimethylimidazole, benzimidazole, 1-methylbenzimidazole, 1-ethylbenzimidazole, 5,6-dimethylbenzimidazole, 1,5,6-trimethylbenzimidazole or 2-methylbenzimidazole; a polyazole such as triazole, 1-benzyltriazole, 1-methyltriazole, benzotriazole, 1-methylbenzotriazole, 1-ethylbenzotriazole, 2-methylbenzotriazole, 5,6-dimethylbenzotriazole, tetrazole or 1-methyltetrazole; an aromatic amine such as aniline, 1-naphthylamine, 2-naphthylamine, o-toluidine, p-toluidine, o-3-xylidine, benzylamine, diphenylamine, dimethylaniline, diethylaniline, 1,8-diaminonaphthalene or 1,8-bis(dimethylamino)naphthalene; an aliphatic or aromatic polyamine such as 1,2-ethanediamine, 1,3-propanediamine, N,N,N',N'-tetramethylethylenediamine, N,N,N',N'-tetraethylethylenediamine, tetrakis(dimethylamino)ethylene, tetrakis(piperidino)ethylene, tetrakis(morpholino)ethylene, tetramethyl-.DELTA..sup.2,2 '-bis(imidazolidine), tetrabenzyl-.DELTA..sup.2,2' -bis(imidazolidine), o-phenylenediamine, p-phenylenediamine or N,N,N',N'-tetramethyl-p-phenylene diamine; and an oxygen-containing amine such as ethanolamine, diethanolamine, morpholine, methylmorpholine, 2-hydroxypyridine, 2-methoxypyridine, 4-hydroxypyridine, 4-methoxypyridine, 4-phenoxypyridine, 2-methoxyquinoline, 2-hydroxyimidazole or 2-methoxybenzimidazole. Among the above-mentioned amines, organic amines are preferred.

The amount of the amine compound may vary depending upon the particular case. However, the amine compound is used usually in an amount within a range of from 0.001 to 1000 mols, preferably from 0.1 to 500 mols, more preferably from 1 to 100 mols, relative to 1 g atom of rhodium. Further, in the case where a ruthenium component is used in combination with the rhodium component, it is used usually in an amount within a range of from 0.001 to 1000 mols, preferably from 0.1 to 500 mols, further preferably from 1 to 100 mols, relative to 1 g atom of the total of rhodium and ruthenium as metals. However, when the amine compound is used as a solvent as will be described hereinafter, the amount of the amine compound is not necessarily limited within the above range.

The reaction of the present invention is conducted in a liquid phase. It may be conducted in the absence of a solvent, i.e. by using the starting materials for the reaction and the catalyst components as the solvent. However, it is preferred to conduct the reaction in the presence of a solvent.

As such a solvent, there may be mentioned an ether such as diethyl ether, anisole, tetrahydrofuran, ethylene glycol dimethyl ether or dioxane; a ketone such as acetone, methyl ethyl ketone or acetophenone; an alcohol such as methanol, ethanol, n-butanol, benzylalcohol, phenol, ethylene glycol or diethylene glycol; a carboxylic acid such as formic acid, acetic acid, propionic acid or toluic acid; an ester such as methyl acetate, n-butyl acetate or benzyl benzoate; an aromatic hydrocarbon such as benzene, toluene, ethylbenzene or tetralin; an aliphatic hydrocarbon such as n-hexane, n-octane or cyclohexane; a halogenated hydrocarbon such as dichloromethane, trichloroethane or chlorobenzene; a nitro compound such as nitromethane or nitrobenzene; a tertiary amine such as triethylamine, tri-n-butylamine, benzyldimethylamine, pyridine, .alpha.-picoline or 2-hydroxypyridine; a carboxylic acid amide such as N,N-dimethylformamide, N,N-dimethylacetamide or N-methylpyrrolidinone; an inorganic acid amide such as hexamethylphosphoric acid triamide or N,N,N',N'-tetraethylsulfamide; a urea such as N,N'-dimethylimidazolidinone or N,N,N',N'-tetramethylurea; a sulfone such as dimethyl sulfone or tetramethylene sulfone; a sulfoxide such as dimethyl sulfoxide or diphenyl sulfoxide; a lactone such .gamma.-butyrolactone or .epsilon.-caprolactone; a polyether such as tetraglyme or 18-crown-6; a nitrile such as acetonitrile or benzonitrile; and a carbonate such as dimethyl carbonate or ethylene carbonate.

Among the above solvent, it is preferred to use an aprotic polar solvent, such as an amine, an amide, a urea, a sulfone, a sulfoxide, a lactone, a polyether, a nitrile or a carbonate. Particularly preferred is an aprotic polar solvent having a dielectric constant of at least 20. Among the above solvents, the amine is also a catalyst component.

The starting material gases used in the present invention, i.e. carbon monoxide and hydrogen, are not particularly restricted, and they may contain a certain amount of an inert gas such as nitrogen gas, carbon dioxide or methane. The volume ratio of hydrogen to carbon monoxide is usually within a range of from 1/10 to 10/1, preferably from 1/5 to 5/1.

The reaction of the present invention may be conducted in either a homogeneous system or a heterogeneous suspension system.

The reaction temperature is usually from 100.degree. to 350.degree. C., preferably from 100.degree. to 300.degree. C., more preferably from 150.degree. to 300.degree. C.

The reaction pressure is usually within a range of from 100 to 3000 kg/cm.sup.2, preferably from 150 to 1000 kg/cm.sup.2, more preferably from 150 to 600 kg/cm.sup.2, as a total of the carbon monoxide partial pressure and the hydrogen partial pressure.

The process of the present invention may be conducted in any one of the reaction systems of continuous, semicontinuous and batch systems.

The products such as ethylene glycol and methanol, may readily be separated from the reaction solution by a conventional separation operation (e.g. distillation, extraction, etc.). The catalyst remaining in the solution after the separation of the products may be recycled to the reaction system after subjecting it to various regeneration treatments or without any special treatment.

Among the conventional reactions wherein rhodium catalysts are employed, those reported to give good results include the processes disclosed in the above-mentioned Japanese Unexamined Patent Publication No. 42808/1977 and U.S. Pat. No. 4,199,520. However, the data disclosed in these prior art references are those obtained under a high pressure condition at a level of at least 1000 kg/cm.sup.2, and the space time yield of ethylene glycol is reported to be at a level of about 150 g/l. hr. Likewise, according to Japanese Unexamined Patent Publication No. 121714/1978, the space time yield under the condition of 560 kg/cm.sup.2 is 23.4 g/l. hr (Example 17) at best. Whereas, according to present invention, under the pressure condition at a level of 500 kg/cm.sup.2, the space time yield can be as high as at least 150 g/l. hr or, in certain cases, can be improved to a level of at least 200 g/l. hr. Thus, the process of the present invention can be regarded as a process remarkably improved over the conventional processes.

Now, the present invention will be described in further detail with reference to Examples. However, it should be undestood that the present invention is by no means restricted by these specific Examples.

In the Examples, the following abbreviations were used.

In the Examples, the space time yield represents the rate of formation of ethylene glycol based on the feed solution, and its unit is g/l. hr.

Further, in the Examples, the amount of each product is represented by a turn-over of the product in mol per 1 g atom of rhodium and per 1 hour.

The interior of a Hastelloy C autoclave having an internal capacity of 30 ml, was flushed with nitrogen, and then 0.025 mmol of tetrarhodium-dodecacarbonyl [Rh.sub.4 (CO).sub.12 ], 0.1 mmol of triisopropylphosphine (P/Rh=1.0) and 7.5 ml of N-methylpyrrolidinone as a solvent, were fed. Then, the gas mixture of equal volumes of carbon monoxide and hydrogen was introduced to a pressure of 350 kg/cm.sup.2 at room temperature. The autoclave was heated to 240.degree. C., and the reaction was conducted at the same temperature for 1 hour. The reaction pressure was 500 kg/cm.sup.2. After the completion of the reaction, the autoclave was cooled to room temperature, the pressure was brought to normal pressure by slowly releasing the major portion of the gas. Then, the reaction mixture was taken out. The products were analyzed by gas chromatography, whereby it was found that the turn-over of EG was 21.2 mol/g atom Rh.hr and that of MeOH was 18.6 mol/g atom Rh.hr.

The experiment was conducted in the same manner as in Example 1 except that no triisopropylphosphine was added. The results were as follows.

EG: 9.9 mol/g atom Rh.hr

MeOH: 5.9 mol/g atom Rh.hr

Into the same reactor as used in Example 1, 0.075 mmol of Rh.sub.4 (CO).sub.12, triisopropylphosphine in an amount as specified in Table 1, and 7.5 ml of N-methylpyrrolidinone, were fed, and a gas mixture of equal volumes of carbon monoxide and hydrogen was introduced to a level of about 300 kg/cm.sup.2 at room temperature. Then, the reaction was conducted at 240.degree. C. for 3 hours under a pressure condition as identified in Table 1.

The results are shown in Table 1. ______________________________________ Products P(i-Pr).sub.3        Pressure EG     MeOH (mmol)       P/Rh    (kg/cm.sup.2) (mol/g atom Rh.hr) ______________________________________ Compara- 0        0       450-405 3.6    7.1 tive Example 2 Example 2 0.1      0.3     450-405 5.3    3.8 Example 3 0.3      1.0     450-405 4.9    7.4 Example 4 0.6      2.0     445-390 3.6    10.1 Example 5 1.0      3.3     450-370 2.8    13.8 Example 6 10.0     33.3    450-415 3.9    7.6 ______________________________________

Into the same reactor as used in Example 1, 0.075 mmol of Rh.sub.4 (CO).sub.12, a phosphine in an amount as specified in Table 2, and 7.5 ml of N-methylpyrrolidinone, were fed, and a gas mixture of equal volumes of carbon monoxide and hydrogen was filled. Then, the reaction was conducted at 220.degree. C. for 3 hours under a reaction pressure as identified in Table 2.

The results are shown in Table 2. ______________________________________ Products EG   MeOH Pressure (mol/g Phosphine    mmol    P/Rh    (kg/cm.sup.2) atom Rh.hr) ______________________________________ Exam- P(i-Pr).sub.3 0.3     1.0   450-400 6.1  4.3 ple 7 Exam- P(t-Bu).sub.3 0.3     1.0   450-440 3.4   0.93 ple 8 Exam- P(s-Bu).sub.3 0.3     1.0   440-400 3.8  8.3 ple 9 Exam- P(c-C.sub.6 H.sub.11).sub.3 0.3     1.0   450-410 3.7  3.1 ple 10 Com-  Nil        0       0     450-430 1.5  4.2 para- tive Exam- ple 3 ______________________________________

In the same reactor as used in Example 1, 0.075 mmol of Rh.sub.4 (CO).sub.12, 0.3 mmol of triisopropylphosphine and 7.5 ml of GBL as a solvent, were fed, and the reaction was conducted at 240.degree. C. for 3 hours in the same manner as in Example 1. The reaction pressure changed from 450 kg/cm.sup.2 to 390 kg/cm.sup.2.

The results of the analysis of the reaction solution were as follows.

EG: 1.2 mol/g atom Rh.hr

MeOH: 5.0 mol/g atom Rh.hr

Further, no precipitation of catalyst was observed in the reaction solution.

The experiment was conducted in the same manner as in Example 11 except that no triisopropylphosphine was added. The results of the analysis of the reaction solution were as follows.

EG: 0.0 mol/g atom Rh.hr

MeOH: 0.5 mol/g atom Rh.hr

In the reaction solution, the catalyst precipitated in a substantial amount.

Into a Hastelloy C autoclave having an internal capacity of 35 ml, acetylacetonatobis(carbonyl)rhodium [Rh(CO).sub.2 acac] containing 0.1 mg atom of rhodium, 0.5 mmol of tri-n-butylphosphine and 10 ml of DMI, were fed, and a gas mixture of equal volumes of carbon monoxide and hydrogen was introduced to 300 kg/cm.sup.2 at room temperature. The autoclave was heated to 240.degree. C., whereby the initial value of the reaction pressure was 480 kg/cm.sup.2. The reaction was continued under the same condition for 2 hours. Then, the autoclave was cooled, and the reaction mixture was taken out and analyzed by gas chromatography, whereby it was found that the turnover of EG was 0.42 mol/g atom Rh.hr and that of MeOH was 27.8 mol/g atom Rh.hr.

The experiments were conducted in the same manner as in Example 12 except that the amounts of rhodium, tri-n-butylphosphine and DMI, and the reaction conditions were changed as shown in Table 3. The results are shown in Table 3. ______________________________________ Products Rh,                           EG     MeOH P(n-Bu).sub.3       DMI    Temp. Time (mol/g (mmol)      P/Rh    (ml)   (.degree.C.) (hr) atom Rh.hr) ______________________________________ Com-  0.1    0       0    10   240   2    12.3 8.6 para- tive Exam- ple 5 Exam- 0.1    0.5     5    10   240   2    0.4  27.8 ple 13 Exam- 0.1    1.0    10    10   240   2    2.3  52.9 ple 14 Exam- 0.1    2.0    20    10   240   2    6.0  69.6 ple 15 Exam- 0.1    4.0    40    10   240   2    11.1 89.9 ple 16 Exam- 0.1    8.0    80    10   240   2    9.5  99.6 ple 17 Exam- 0.1    20.0   200    5   240   2    2.4  59.4 ple 18 Exam- 0.05   2.0    40    10   260   1    14.5 229.6 ple 19 Exam- 0.05   4.0    80    10   260   1    23.0 265.8 ple 20 ______________________________________

The experiments were conducted in the same manner as in Example 12 except that tricyclohexylphosphine was used instead of tri-n-butylphosphine. The results are shown in Table 4. ______________________________________ Products Rh         P(c-C.sub.6 H.sub.11).sub.3 EG     MeOH (mmol)                P/Rh    (mol/g atom Rh.hr) ______________________________________ Example 21 0.1    0.5         5    9.3    34.4 Example 22 0.1    1.0        10    8.0    25.4 ______________________________________

The experiments were conducted in the same manner as Example 13 except that tricyclopentylphosphine in an amount specified in Table 5 was used instead of tri-n-butylphosphine, NMP or DMI was used as the solvent, and the reaction was conducted at 230.degree. C. for 2 hours. The results are shown in Table 5. ______________________________________ Products EG   MeOH Rh        P(c-C.sub.5 H.sub.9).sub.3 Solvent (mol/g (mmol)              P/Rh    (10 ml) atom Rh.hr) ______________________________________ Example 23 0.1   0.1       1     NMP    20.5 14.9 Compara- 0.1   0         0     NMP    7.1  5.8 tive Example 6 Example 24 0.1   0.1       1     DMI    18.5 29.3 Compara- 0.1   0         0     DMI    6.8  4.2 tive Example 7 ______________________________________

The experiments were conducted in the same manner as in Example 13 except that 16 mmol and 25 mmol of tri-n-propylphosphine was used instead of tri-n-butylphosphine, as the trialkylphosphine. The results are shown in Table 6. ______________________________________ Products Rh,                           EG     MeOH P(n-Pr).sub.3       DMI    Temp  Time (mol/g (mmol)      P/Rh    (ml)   (.degree.C.) (hr) (atom Rh.hr) ______________________________________ Example 0.1   16.0   160   10   240   2    17.5 111 25 Example 0.1   25.0   250   10   240   2    13.5 138 26 ______________________________________

Into a Hastelloy C autoclave having an internal capacity of 35 cc, acetylacetonatobis(carbonyl)rhodium [Rh(CO).sub.2 (acac)] containng 0.1 mmol of rhodium, 0.1 mmol of di(t-butyl)-n-butylphosphine and 10 ml of N-methylpyrrolidinone, were fed, and a gas mixture of equal volumes of carbon monoxide and hydrogen was introduced to 300 kg/cm.sup.2 at room temperature. The autoclave was heated to 240.degree. C. whereby the initial value of the reaction pressure was 485 kg/cm.sup.2. The reaction was continued for 2 hours under the same condition. Then, the autoclave was cooled, and the reaction mixture was taken out and analyzed by gas chromatography, whereby it was found that 22.3 mol/g atom Rh.hr of ethylene glycol and 10.8 mol/g atom Rh.hr of methanol formed.

The reaction was conducted in the same manner as in Example 27 except that N,N'-dimethylimidazolidinone was used instead of N-methylpyrrolidinone, as the solvent, whereby it was found that 20.6 mol/g atom Rh.hr of ethylene glycol and 13.4 mol/g atom Rh.hr of methanol formed.

The reactions were conducted in the same manner as in Example 28 except that the amount of di(t-butyl)-n-butylphosphine was changed as shown in Table 7. The results are shown in Table 7. ______________________________________ Products Amount of   (mol/g atom Rh.hr) P(t-Bu).sub.2 (n-Bu) Ethylene (mmol)      glycol   Methanol ______________________________________ Example 29 0.05          13.04     9.68 Example 30 0.5           18.55    30.10 ______________________________________

The reactions were conducted in the same manner as in Example 28 except that the phosphines identified in Table 8 were used instead of di(t-butyl)-n-butylphosphine, and the reaction temperature and the amount of the phosphine were changed as shown in Table 8. the results are shown in Table 8. ______________________________________ Reaction Products (mol/g- Phosphine          temper-  atom Rh.hr) Amount   ature    Ethylene Meth- Type          (mmol)   (.degree.C.) glycol anol ______________________________________ Exam- P(n-Bu).sub.2 (t-Bu) 0.1      230    11.07  16.58 ple 31 Exam- P(n-Bu).sub.2 (t-Bu) 0.2      230    8.80   19.05 ple 32 Exam- P(c-        0.05     220    4.67   20.29 ple 33 C.sub.6 H.sub.11).sub.2 (n-Bu) ______________________________________

The reactions were conducted in the same manner as in Example 27 except that the phosphines identified in Table 9 were used instead of di(t-butyl)-n-butylphosphine, and the reaction temperature was changed to 230.degree. C. The results are shown in Table 9. ______________________________________ Products (mol/g-atom Rh.hr) Ethylene Phosphine  glycol   Methanol ______________________________________ Example 34 P(i-Pr).sub.2 (n-Bu) 8.12     8.70 Example 35 P(t-Bu).sub.2 Et 8.62     3.80 ______________________________________

The reaction was conducted in the same manner in Example 27 except that the reaction temperature was changed to 230.degree. C. without using di(t-butyl)-n-butylphosphine, whereby it was found that 7.63 mol/g atom Rh.hr of ethylene glycol and 5.78 mol/g atom Rh.hr of methanol formed.

Into a Hastelloy C autoclave having an internal capacity of 35 cc, acetylacetonatobis(carbonyl)rhodium [Rh(CO).sub.2 (acac)] containing 0.6 mmol of rhodium, 0.6 mmol of di(t-butyl)-n-butylphosphine and 4 ml of N,N'-dimethylimidazolidinone, were fed and a gas mixture of equal volumes of carbon monoxide and hydrogen was introduced to 300 kg/cm.sup.2 at room temperature. The autoclave was heated to 230.degree. C., whereby the initial value of the reaction pressure was 480 kg/cm.sup.2. A gas mixture of equal volumes of carbon monoxide and hydrogen was supplemented to a pressure of 520 kg/cm.sup.2, and the reaction was initiated. The gas was supplemented when the pressure dropped to 500 kg/cm.sup.2, thereby to return the pressure to 520 kg/cm.sup.2. While this operation was repeated, the reaction was continued for 1 hour. Then, autoclave was cooled, and the reaction mixture was taken out and analyzed by gas chromatography, whereby it was found that the turn-over of ethylene glycol was 12.85 mol/g atom Rh.hr and that of methanol was 19.21 mol/g atom Rh.hr. The space time yield of ethylene glycol reached to a level of 120 g/l.hr based on the feed solvent. [In the typical conventional rhodium catalyst system of rhodium/cesium benzoate/N-methylmorpholine/sulforane (solvent), the space time yield of ethylene glycol is as low as 118 g/l.hr even when a high pressure of 1030 kg/cm.sup.2 and a high temperature of 260.degree. C. were used as reaction conditions. (Jose, L, Vidal, and W. E. Walker, Inorganic Chemistry, Vol. 19, page 896)]

The reaction was conducted in the same manner as in Example 36 except that the amount of rhodium was changed to 0.9 mmol, and the amount of di(t-butyl)-n-butylphosphine was changed to 0.9 mmol, whereby it was found that 9.39 mol/g atom Rh.hr of ethylene glycol and 19.98 mol/g atom Rh.hr of methanol formed. The space time yield of ethylene glycol reached 130 g/l.hr based on the feed solvent.

Into a Hastelloy C autoclave having an internal capacity of 35 cc, acetylacetonatobis(carbonyl)rhodium [Rh(CO).sub.2 (acac)] containing 0.1 mg atom of rhodium, 0.1 mmol of tri-iso-propylphosphine, 0.5 mmol of tetrakis(dimethylamino)ethylene and 10 ml of N,N'-dimethylimidazolidinone, were fed, and a gas mixture of equal volumes of carbon monoxide and hydrogen was introduced to 300 kg/cm.sup.2 at room temperature. The autoclave was heated to 240.degree. C., whereby the initial value of the reaction pressure was 480 kg/cm.sup.2. The reaction was continued for 2 hours under the same condition. Then, the autoclave was cooled, and the reaction mixture was taken out and analyzed by gas chromatography, whereby it was found that 17.72 mol/g atom Rh.hr of ethylene glycol and 16.07 mol/g atom Rh.hr of methanol formed.

The reactions were conducted in the same manner as in Example 38 except that the amine compounds identified in Table 10 were added in the respective amounts identified in Table 10, instead of tetrakis(dimethylamino)ethylene. The results are shown in Table 10. ______________________________________ Products (mol/g Amine compound          atom Rh.hr) Amount   Ethylene Meth- Type               (mmol)   glycol   anol ______________________________________ Exam- 4-Dimethylaminopyridine 0.02     18.90  21.17 ple 39 Exam- 4-Dimethylaminopyridine 0.05     16.76  19.04 ple 40 Exam- 1-methylimidazole 1.5      16.27  14.19 ple 41 Exam- 1-methylimidazole 5.0      18.44  12.46 ple 42 Exam- Nil              0.0      14.26  18.73 ple 43 ______________________________________

Into a Hastelloy C autoclave having internal capacity of 35 cc, acetylacetonatobis(carbonyl)rhodium [Rh(CO).sub.2 (acac)] containing 0.4 mg atom of rhodium, 0.4 mmol of tri-iso-propylphosphine, 6.0 mmol of 1-methylimidazole and 4 ml of N,N'-dimethylimidazolidinone, were fed, and a gas mixture of equal volumes of carbon monoxide and hydrogen was introduced to 300 kg/cm.sup.2 at room temperature. The autoclave was heated to 250.degree. C., whereby the initial value of the reaction pressure was 490 kg/cm.sup.2. Further, a gas mixture of equal volumes of carbon monoxide and hydrogen was supplemented to 520 kg/cm.sup.2, and then reaction was initiated. When the pressure dropped to 500 kg/cm.sup.2, the gas was supplemented to return the pressure to 520 kg/cm.sup.2, and while repeating this operation, reaction was continued for 1 hour. Then, autoclave was cooled, and the reaction mixture was taken out and analyzed by gas chromatography, whereby it was found that 18.68 mol/g atom Rh.hr of ethylene glycol and 18.00 mol/g atom Rh.hr of methanol formed.

The reactions were conducted in the same manner as in Example 44 except that the amounts of rhodium, triisopropylphosphine and 1-methylimidazole were changed, and reaction temperature was varied as shown in Table 11. The results are shown in Table 11. __________________________________________________________________________ Products Ethylene glycol 1-Methyl- Reaction Amount Space time Methanol Rh(CO).sub.2 (acac) P(i-Pr).sub.3 imidazole temp. (mol/g atom yield (mol/g atom (mg-atom Rh)  (mmol) (mmol) (.degree.C.) Rh.hr) (g/l.hr) Rh.hr) __________________________________________________________________________ Example 45 0.4     0.2  6.0   240  17.48  108   13.53 Example 46 0.4     0.8  4.0   240  18.33  114   11.98 Example 47 0.4     0.4  4.0   240  30.75  191   21.20 Example 48 0.4     0.4  4.0   230  26.18  162   18.55 Example 49 0.6     0.6  6.0   235  20.67  192   12.60 Example 50 0.6     0.6  6.0   230  25.0   233   12.80 Example 51 0.6     0.6  6.0   225  19.35  180   8.93 Example 52 0.6     0.6  6.0   220  17.60  164   6.45 Example 53 0.9     0.9  6.0   230  19.51  272   12.83 Example 54 0.9     0.9  4.5   230  20.11  281   12.89 Compara- 0.4     0.0  6.0   240  7.68   --    18.17 tive Example 9 __________________________________________________________________________

The reactions were conducted in the same manner as in Example 44 except that the trialkylphosphines identified in Table 12 were added in the respective amounts identified in Table 12, instead of tri-iso-propylphosphine, and the amounts of rhodium and 1-methylimidazole were changed as shown in Table 12. The results are shown in Table 12. __________________________________________________________________________ Products Rh(CO).sub.2                     Ethylene glycol (acac)    Trialkylphosphine 1-Methyl Reaction Amounts Space time Methanol (mg-atom          Amount imidazole temp. (mol/g atom yield (mol/g atom Rh)       Type    (mmol) (mmol) (.degree.C.) Rh.hr) (g/l.hr) Rh.hr) __________________________________________________________________________ Example 0.6  P(c-C.sub.5 H.sub.9).sub.3 0.6  6.0  230  22.38  208   16.02 55 Example 0.6  "       0.6  3.0  230  22.98  214   15.7 56 Example 0.6  "       0.3  6.0  230  16.25  151   8.22 57 Example 0.6  P(t-Bu).sub.2 (n-Bu) 0.6  0.6  230  16.39  153   10.14 58 Example 0.9  "       0.9  4.5  230  19.80  276   13.15 59 __________________________________________________________________________

The reactions were conducted in the same manner as in Example 38 except that the amine compounds identified in Table 13 were added in the respective amounts identified in Table 13, instead of 0.5 mmol of tetrakis(dimethylamino)ethylene, and tetraglyme was employed instead of N,N'-dimethylimidazolidinone. The results are shown in Table 13. ______________________________________ Products (mol/g Amine compound        atom Rh.hr) Amount    Ethylene Type            (mmol)    glycol   Methanol ______________________________________ Example Tetrakis(dimethyl- 0.05      8.3    25.2 60     amino)ethylene Example 4-Dimethylamino- 0.1       10.15  16.4 61     pyridine Example 1-Methylimidazole 0.4       15.95  17.35 62 Example 1-Methylimidazole 5.0       16.45  19.40 63 Example Nil          0.0       0.0    22.05 64 ______________________________________

The reaction was conducted in the same manner as in Example 38 except that 4.0 mmol of tri-n-butylphosphine was used instead of 0.1 mmol of tri-iso-propylphosphine, and 0.5 mmol of 1-methylimidazole was used instead of 0.5 mmol of tetrakis(dimethylamino)ethylene, whereby it was found that 1.95 mol/g atom Rh.hr of ethylene glycol and 44.70 mol/g atom Rh.hr of methanol formed.

The reaction was conducted in the same manner as in Example 38 except that 0.1 mmol of tricyclopentylphosphine was used instead of 0.1 mmol of tri-isopropylphosphine, and 1.0 mmol of 1-methylimidazole was used instead of 0.5 mmol of tetrakis(dimethylamino)ethylene, whereby it was found that 22.25 mol/g atom Rh.hr of ethylene glycol and 20.20 mol/g atom Rh.hr of methanol formed.

The reactions were conducted in the same manner as in Example 50 except that the amount of 1-methylimidazole was changed as shown in Table 14 and tetraglyme was used instead of N,N'-dimethylimidazolidinone. The results are shown in Table 14. ______________________________________ Products (mol/g atom Rh.hr) 1-Methylimidazole Ethylene (mmol)        glycol   Methanol ______________________________________ Example 67 3.0             19.49    20.0 Example 68 6.0             17.75    16.90 ______________________________________

The reactions were conducted in the same manner as in Example 38 except that the amine compounds identified in Table 15 were added in the respective amounts identified in Table 15, instead of tetrakis(dimethylamino)ethylene, and N-methylpyrrolidinone was used instead of N,N'-dimethylimidazolidinone. The results are shown in Table 15. ______________________________________ Products (mol/g Amine compound         atom Rh.hr) Amount   Ethylene Type              (mmol)   glycol   Methanol ______________________________________ Example 4-Dimethylamino- 0.5      21.75  16.7 69      pyridine Example 1-Methylimidazole 0.5      23.05  12.65 70 Example Nil           0.0      13.78  11.55 71 Compara- 1-Methylimidazole 0.5      10.45  9.15 tive* Example 10 ______________________________________ *Tri-iso-propyl phosphine was not added.

The reactions were conducted in the same manner as in Example 44 except that the amount of rhodium was changed to 0.6 mg atom Rh, the amounts of the trialkylphosphine and the amine compound were changed as shown in Table 16, N-methylpyrrolidinone was used instead of N,N'-dimethylimidazolidinone, and the reaction temperature was changed to 230.degree. C. The results are shown in Table 16. __________________________________________________________________________ Products Ethylene glycol Trialkylphosphine Amine compound Amount Space time Methanol Amount         Amount (mol/g atom yield (mol/g Type        (mmol) Type      (mmol) Rh.hr) (g/l.hr) atom Rh.hr) __________________________________________________________________________ Example 72 P(i-Pr).sub.3 0.6  1-Methylimidazole 10.0 18.37  171   8.11 Example 73 P(i-Pr).sub.3 0.6  1-Methylimidazole 6.3  19.98  180   10.5 Example 74 P(i-Pr).sub.3 0.6  1-Methylimidazole 3.0  17.72  165   10.3 Example 75 P(i-Pr).sub.3 0.6  4-Dimethylamino- 3.0  14.18  132   7.38 pyridine Example 76 P(i-Pr).sub.3 0.6  4-Dimethylamino- 0.3  17.73  165   13.26 pyridine Example 77 P(c-C.sub.5 H.sub.9).sub.3 0.6  1-Methylimidazole 6.0  16.84  157   10.38 Example 78 P(c-C.sub.5 H.sub.9).sub.3 0.6  Nil       0.0  11.22  105   27.47 __________________________________________________________________________

The interior of a shaking-type Hastelloy C autoclave having an internal capacity of 30 ml was flushed with nitrogen, and then tetrarhodium dodecacarbonyl[Rh.sub.4 (CO).sub.12 ] containing 0.3 mg atom of rhodium, 0.3 mmol of triisopropylphosphine, 0.3 mmol of N-methylpiperidine and 7.5 ml of N-methylpyrrolidinone as a solvent, were fed. The mixture was thoroughly mixed, and then the autoclave was closed. The interior of the autoclave was flushed with a gas mixture of equal volumes of carbon monoxide and hydrogen, and the same gas was introduced to a pressure of 400 kg/cm.sup.2. The reaction was conducted at 240.degree. C. for 2 hours while shaking the autoclave. The reaction pressure changed from 510 kg/cm.sup.2 to 450 kg/cm.sup.2. After the completion of the reaction, the autoclave was cooled to room temperature, and the internal pressure was brought to normal pressure by slowly releasing the major portion of the gas. Then, the reaction mixture was taken out, and analyzed by gas chromatography, whereby it was found that 9.14 mol/g atom Rh.hr of ethylene glycol and 10.78 mol/g atom Rh.hr of methanol formed.

The reactions were conducted in the same manner as in Example 79 except that the amine compounds identified in Table 17 were added in the respective amounts identified in Table 17, instead of N-methylpiperidine. The results are shown in Table 17. ______________________________________ Products (mol/g Amine compound          atom Rh.hr) Amount   Ethylene Meth- Type               (mmol)   glycol   anol ______________________________________ Example 80 N--Methylpiperidine 1.0      11.38  9.53 Example 81 N--Methylpiperidine 3.0      11.34  7.65 Example 82 N--Methylpiperidine 10.0     11.37  7.11 Example 83 1-Ethylimidazole 1.0      16.09  14.25 Example 84 Imidazole      1.0      15.42  13.77 Example 85 1-Methylbenz-  1.0      9.21   18.62 imidazole Example 86 Benzimidazole  1.0      8.70   13.49 Example 87 4-Dimethylamino- 1.0      14.61  8.81 pyridine Example 88 Pyridine       1.0      9.44   14.83 Example 89 2-Hydroxypyridine 1.0      10.53  13.74 Example 90 Triethylamine  1.0      14.05  12.93 Example 91 Morpholine     1.0      10.24  17.32 Example 92 Aniline        1.0      11.03  17.80 Example 93 Nil            0.0      7.54   9.75 ______________________________________

The reactions were conducted in the same manner as in Example 79 except that the amine compounds identified in Table 18 were added in the respective amounts identified in Table 18, instead of using 0.3 mmol of N-methylpiperidine, the amount of N-methylpyrrolidinone was changed to 3.75 ml, and the reaction time was changed to 1 hour. The results are shown in Table 18. ______________________________________ Products Ethylene glycol Amount   Space    Methanol Amine compound    (mol/g   time     (mol/g Amount   atom     yield  atom Type         (mmol)   Rh.hr)   (g/l.hr) Rh.hr) ______________________________________ Exam- N--methyl- 1.0      20.47  102    13.39 ple 94 piperidine Exam- 4-Dimethyl- 1.0      17.80   88    9.74 ple 95 amino- pyridine Exam- 1-Ethyl-   1.0      23.53  116    15.73 ple 96 imidazole ______________________________________

The reaction was conducted in the same manner as in Example 79 except that the reaction temperature was changed to 220.degree. C., and .gamma.-butyrolactone was used instead of N-methylpyrrolidinone, whereby it was found that 6.07 mol/g atom Rh.hr of ethylene glycol, 5.82 mol/g atom Rh.hr of methanol and 0.4 mol/g atom Rh.hr of methyl formate formed.

The reaction was conducted in the same manner as in Example 97 except that no triisopropylphosphine was added, whereby it was confirmed that 1.95 mol/g atom Rh.hr of ethylene glycol, 2.40 mol/g atom Rh.hr of methanol and 0.05 mol/g atom Rh.hr of methyl formate formed.

The reactions were conducted in the same manner as in Example 38 except that tri-n-butylphosphine was added in the amounts identified in Table 19, instead of 0.1 mmol of tri-iso-propylphosphine, and 10 ml of 1-methylimidazole was used instead of tetrakis(dimethylamino)ethylene and N,N'-dimethylimidazolidinone. The results are shown in Table 19. ______________________________________ Products (mol/g Trialkylphosphine atom Rh.hr) Amount    Ethylene Type    (mmol)    glycol   Methanol ______________________________________ Example 98 Tri-n-butyl- 0.1       1.35   1.5 phosphine Example 99 Tri-n-butyl 5.0       4.63   34.10 phosphine Comparative Nil       0.0       0.0    0.0 Example 12 ______________________________________

The reactions were conducted in the same manner as in Example 70 except that the trialkylphosphines identified in Table 20 were used in an amount of 0.1 mmol, instead of 0.6 mmol of tri-iso-propylphosphine. The results are shown in Table 20. ______________________________________ Products (mol/g atom Rh.hr) Ethylene Trialkylphosphine glycol    Methanol ______________________________________ Example 100 P(t-Bu).sub.3 13.46     6.07 Example 101 P(c-C.sub.6 H.sub.11).sub.3 18.10     16.56 ______________________________________

Into the same autoclave as used in Example 79, 0.075 mmol of Rh.sub.4 (CO).sub.12, 0.05 mmol of cesium acetate, 1.00 mmol of 2-hydroxypyridine, 0.30 mmol of tri-iso-propylphosphine and 7.5 ml of tetraglyme as a solvent, were fed, and reacted at 220.degree. C. for 2 hours in the same manner as in Example 79. The reaction pressure changed from 450 kg/cm.sup.2 to 430 kg/cm.sup.2. The results of the analysis of the reaction solution were as follows.

EG: 4.25 mol/g atom Rh.hr

MeOH: 4.43 mol/g atom Rh.hr

In the reaction solution, no precipitation of e.g. catalyst was observed.

The reaction was conducted in the same manner as in Example 102 except that no tri-iso-propylphosphine was added. The reaction pressure was 450 kg/cm.sup.2.

The results of the analysis of the reaction solution were as follows:

EG: 1.08 mol/g atom Rh.hr

MeOH: 1.53 mol/g atom Rh.hr

In the reaction solution, a small amount of the precipitate of catalyst was observed.

The interior of a Hastelloy C autoclave having an internal capacity of 30 cc, was flushed with nitrogen, and then 0.025 mmol of tetrarhodium dodecacarbonyl [Rh.sub.4 (CO).sub.12 ], 0.033 mmol of triruthenium dodecacarbonyl [Ru.sub.3 (CO).sub.12 ], 0.4 mmol of triisopropylphosphine, 1.0 mmol of 4-N,N-dimethylaminopyridine and 7.5 ml of N-methylpyrrolidinone as a solvent, were fed, and a gas mixture of equal volumes of carbon monoxide and hydrogen was introduced to 350 kg/cm.sup.2 at room temperature. The autoclave was heated to a temperature of 240.degree. C., and the reaction was continued for 2 hours under the same condition. The reaction pressure was 500 kg/cm.sup.2

After the completion of the reaction, the autoclave was cooled to room temperature, and the internal pressure was brought to normal pressure by slowly releasing the major portion of the gas. The reaction mixture was taken out, and the products were analyzed by gas chromatography, whereby it was found that 24.9 mol/g atom Rh.hr of ethylene glycol and 15.0 mol/g atom Rh.hr of methanol formed.

The experiment was conducted in the same manner as in Example 103 except that no triisopropylphosphine and no 4-N,N-dimethylaminopyridine were added. The results are shown below.

EG: 1.1 mol/g atom Rh.hr

MeOH: 1.3 mol/g atom Rh.hr

The experiments were conducted in the same manner as in Example 103 by using the same reactor as used in Example 103 under the feeding and reaction conditions as identified in Table 21. The results as shown in Table 21 were obtained. In each case, no precipitation of metal of the catalyst was observed. __________________________________________________________________________ Products Rh*.sup.1  Ru*.sup.2 First additive Second additive Temp. Pressure*.sup.3 Time (mol/g atom Rh.hr) Example (mg atom) (mg atom) (mmol) (mmol)  Solvent (.degree.C.) (kg/cm.sup.2) (hr) EG   MeOH __________________________________________________________________________ 104  0.1   0.1    P(i-Pr).sub.3 (0.2) 2-Methyl- Toluene 240  500   2  18.1 30.8 imidazole (10) 105  0.1   0.1    P(i-Pr).sub.3 (0.4) 2-Methyl- DMI  260  500   2  21.3 10.5 imidazole (10) 106  0.1   0.1    P(i-Pr).sub.3 (0.2) Nil     NMP  240  645   2  25.2 32.9 __________________________________________________________________________ *.sup.1 Rh: Rh.sub.4 (CO).sub.12 *.sup.2 Ru: Ru.sub.3 (CO).sub.12 *.sup.3 In Examples 104-106, the CO/H.sub.2 ratio was 1.

The reactions were conducted in the same manner as in Example 103 by feeding into the same reactor as used in Example 103, 0.025 mmol of Rh.sub.4 (CO).sub.12, 0.033 mmol of Ru.sub.3 (CO).sub.12, a phosphine as identified in Table 22 and 0.2 mmol of 4-N,N-dimethylaminopyridine, whereby the results as shown in Table 22 were obtained. ______________________________________ Amount of Products Type of       phosphine (mol/g atom Rh.hr) Example phosphine  (mmol)    EG     MeOH ______________________________________ 107*.sup.1 P(i-Pr).sub.3 0.6       19.6   22.5 108*.sup.2 P(c-C.sub.6 H.sub.11).sub.3 0.4       22.3   20.7 109    P(t-Bu).sub.3 0.4       8.1    4.6 110    P(n-Bu).sub.3 1.0       6.6    39.2 ______________________________________ *.sup.1 CO/H.sub.2 ratio = 1 *.sup.2 CO/H.sub.2 ratio = 1/2-

The reactions were conducted in the same manner as in Example 103 by feeding into the same reactor as used in Example 103, 0.025 mmol of Rh.sub.4 (CO).sub.12, 0.033 mmol of Ru3(CO).sub.12, 0.2 mmol of P(i-Pr).sub.3 and 0.2 mmol of an amine as identified in Table 23, whereby the results as shown in Table 23 were obtained. ______________________________________ Products (mol/g atom Rh.hr) Example Type of amine      EG       MeOH ______________________________________ 111    Imidazole          17.6     11.8 112    N--ethylimidazole  17.7     12.2 113    Benzimidazole      18.3     16.1 114    4-N,N--dimethylaminopyridine 19.0     12.8 115    N--methylbenzimidazole 16.3     17.0 116    2-Hydroxypyridine  17.4     16.8 117    Pyridine           16.4     18.8 118    N--methylpiperidine 17.3     12.6 119    N--methylpyrrolidine 17.6     17.3 ______________________________________

The reactions were conducted in the same manner as in Example 103 by feeding into the same reactor as used in Example 103, 0.025 mmol of Rh.sub.4 (CO).sub.12, 0.033 mmol of Ru.sub.3 (CO).sub.12 and a phosphine and 7.5 ml of a solvent as identified in Table 24, whereby the results as shown in Table 24 were obtained. ______________________________________ Products Amount of           (mol/g Type of       phosphine           atom Rh.hr) Example phosphine  (mmol)     Solvent EG   MeOH ______________________________________ 120    P(i-Pr).sub.3 0.2        NMP    13.4 12.8 121    P(s-Bu).sub.3 0.2        NMP    13.5 16.8 122    P(t-Bu).sub.3 0.2        NMP    4.2  0.18 123    P(i-Bu).sub.3 0.2        NMP    1.9  1.8 124    PEt.sub.3  0.2        NMP    1.8  3.9 125    P(c-C.sub.6 H.sub.11).sub.3 0.2        NMP    13.8 13.4 126    P(i-Pr).sub.3 0.2        DMI    12.5 19.2 127    P(i-Pr).sub.3 0.2        GBL    4.4  18.2 128    P(n-Bu).sub.3 2.0        NMP    3.3  49.3 129    P(n-Bu).sub.3 10.0       NMP    5.7  62.5 ______________________________________

The reaction was conducted in the same manner as in Example 103 by feeding into the same reactor as used in Example 103, 0.025 mmol of Rh.sub.4 (CO).sub.12, 0.067 mmol of Ru.sub.3 (CO).sub.12, 0.3 mmol of tri-iso-propylphosphine and 7.5 ml of N-methylpyrrolidinone, whereby 13.5 mol/g atom Rh.hr of ethylene glycol and 13.5 mol/g atom Rh.hr of methanol formed.

## Claims

1. A process for producing aliphatic alcohols by reacting carbon monoxide and hydrogen in a liquid phase in the presence of a catalyst system, comprising: wherein each of R.sub.1, R.sub.2 and R.sub.3 is a primary alkyl group, a secondary alkyl group, a tertiary alkyl group or a cycloalkyl group, as the catalyst components.

2. The process according to claim 1 wherein said trialkylphosphine component is present in the catalyst system in an amount of at least 0.2 mole per 1 g atom of rhodium.

3. The process according to claim 1, wherein, in said trialkylphosphine, R.sub.1 is a primary alkyl group, R.sub.2 is a secondary alkyl group, a tertiary alkyl group or a cycloalkyl group, and R.sub.3 is a primary alkyl group, a secondary alkyl group, a tertiary alkyl group or a cycloalkyl group.

4. The process according to claim 1, wherein the concentration of rhodium in the reaction solution is within a range of from 0.0001 to 10 g atom per 1 liter of the reaction solution.

5. The process according to claim 1, wherein an amine compound is used as an additional catalyst component.

6. The process according to claim 5, wherein the amine compound is present in an amount of from 0.001 to 1000 mols per 1 g atom of rhodium.

7. The process according to claim 1, wherein ruthenium is present as an additional catalyst component.

8. The process according to claim 7, wherein the trialkylphosphine is present in an amount of at least 0.2 mol per 1 g atom of the sum of rhodium and ruthenium as metals.

9. The process according to claim 7, wherein the concentration of the sum of rhodium and ruthenium as metals in the reaction solution is within a range of from 0.0001 to 10 mols per 1 liter of the reaction solution.

10. The process according to claim 9, wherein the atomic ratio of ruthenium to the sum of rhodium and ruthenium as metals is within a range of from 0.1 to 0.9.

11. The process according to claim 7, wherein an amine compound is present as a further catalyst component.

12. The process according to claim 7, wherein the amine compound is present in an amount of from 0.001 to 1000 mols per 1 g atom of the sum of rhodium and ruthenium as metals.

13. The process according to claim 1, wherein the total of the carbon monoxide partial pressure and the hydrogen partial pressure in the reaction system is within a range of from 100 to 3000 kg/cm.sup.2.

14. The process according to claim 1, wherein the reaction temperature in the reaction system is within a range of from 100.degree. to 350.degree. C.

15. The process according to claim 7, wherein, in said trialkylphosphine, group R.sub.1 is a primary alkyl group, group R.sub.2 is a secondary alkyl group, a tertiary alkyl group or a cycloalkyl group, and group R.sub.3 is a primary alkyl group, a secondary alkyl group, a tertiary alkyl group or a cycloalkyl group.