GB2143229A - Process for preparing low molecular weight oxygenated compounds - Google Patents

Abstract

Low molecular weight oxygenated compounds, and particularly ethylene glycol and methanol, are prepared in good yield by contacting a mixture of carbon monoxide and hydrogen (syngas) with a catalyst system comprising a rhodium-containing compound, an organic ligand and a sulfonium salt, preferably dissolved in a suitable solvent, at an elevated temperature and pressure.

Description

SPECIFICATION Process for preparing low molecular weight oxygenated compounds This invention relates to a new process for preparing low molecular weight oxygenated compounds. More particularly, the invention relates to an improved process for preparing low molecular weight oxygenated compounds, and particularly ethylene glycol and methanol, from carbon monoxide and hydrogen (syngas) using a novel catalyst system.

Specifically, the invention provides a process for preparing low molecular weight oxygenated products which comprises contacting a mixture of carbon monoxide and hydrogen with a catalyst system comprising a rhodium-containing compound, an organic ligand and a sulfonium salt, at an elevated temperature and pressure.

Low molecular weight oxygenated compounds, such as ethylene glycol and methanol, are chemicals which have found wise use in industry. Ethylene glycol, for example, is used in the preparation of plasticizers for vinyl polymers, and as a component of polyester fibres and antifreeze formulations. Low molecular weight alcohols, such as methanol, find use as solvents and in the production of esters, such as ethyl esters, which can be subsequently used to produce ethylene. In view of these many uses, there is a need to find new and more economical methods for preparing these chemicals.

One proposed method of making ethylene glycol involves the reaction of carbon monoxide with hydrogen in the presence of various catalyst systems. In general, the mixture of carbon monoxide and hydrogen, commonly known as synthesis gas or syngas, is reacted at elevated temperatures and pressures in the presence of the proposed catalyst. U.S. Patent No.

2,636,046 discloses the production of ethylene glycol from syngas using a cobalt catalyst.

Belgian Patent No. 793,086 and U.S. Patent No. 3,940,432 describe the cosynthesis of ethylene glycol and methanol from mixtures of carbon monoxide and hydrogen using a complex rhodium catalyst. U.S. Patent No. 3,833,634 describes the use of various other metals as catalysts but indicates that only rhodium and cobalt are effective in producing ethylene glycol.

Other patents disclosing catalyst systems for converting syngas into polyhydric alcohols are listed in U.S. Patent No. 4,162,261.

Many of these proposed processes are limited, however, by the nature and activity of the catalyst systems. For example, many of the catalyst systems have poor selectivity towards the desired polyhydric alcohols, or are based on very expensive components. Other catalyst systems have poor solubility in conventional reaction solvents, or have limited solubility, with a plating out of the expensive components, such as rhodium, during the reaction.

The object of the present invention, therefore, is to provide an improved process for preparing low molecular weight oxygenated compounds, and particularly ethylene glycol and methanol, in good yields and improved selectivity. It is a further object to provide a new catalyst system for producing ethylene glycol and methanol from syngas which has improved solubility in conventional reaction solvents. It is a further object to provide a new process for preparing ethylene glycol and methanol from syngas which avoids the plating out of expensive components, such as rhodium, during the reaction.

It has now been discovered that these and other objects can be accomplished by the process of the invention employing a novel catalyst system comprising a rhodium-containing compound, an organic ligand and a sulfonium salt, preferably dissolved in a suitable solvent. It was surprising that the use of the above-noted new catalyst systems leads to improved selectivity and better yields in the formation of the desired ethylene glycol. In addition, the new catalyst system has improved solubility in many of the-conventional solvents and thus is more easily utilized in the reaction. Further, the new process surprisingly avoids the plating out of the expensive catalyst components, such as rhodium, during the reaction and during recovery of the product.Further advantage is found in the fact that the process can be operated at moderate temperature and pressure and avoids the use of the extreme conditions required in many of the known processes.

The formation of the desired ethylene glycol by the process of the invention can be represented by the following equation:

Typical yields of ethylene glycol, based on liquid weight charged, are from 0.9 to 20%. Other products, besides the ethylene glycol and methanol, include other alcohols, such as ethanol and propylene glycol, alone with methyl formate and small amounts of dioxolane.

In one embodiment of the process of the invention, the low molecular weight oxygenated compounds, and particularly the ethylene glycol and methanol, can be prepared concurently from a synthesis gas mixture of carbon monoxide and hydrogen by: (a) contacting the mixture of carbon monoxide and hydrogen with the catalyst, preferably dissolved in a suitable solvent, (b) heating the resulting mixture to an elevated temperature, e.g. at least 150 C, and an elevated pressure, e.g. at least 35 bars, with sufficient carbon monoxide and hydrogen to satisfy the above-noted stoichiometry of the desired ethylene glycol synthesis, until substantial formation of the desired products has been achieved, and (c) preferably isolating the desired products, such as the ethylene glycol and methanol, from the reaction mixture by suitable means, such as fractional distillation.

As noted, the new catalyst system used in the process of the invention contains a rhodiumcontaining compound, an organic ligand and a sulfonium salt. The rhodium-containing compound to be used may be chosen from a wide variety of organic or inorganic compounds, or complexes. It is only necessary that the compound actually employed contains the rhodium in any state which becomes soluble during the reaction.

The rhodium-containing compound may take many different forms. For instance, the rhodium may be added to the reaction mixture as the salt of an organic acid, for example, rhodium(ll) formate, rhodium(ll) acetate, rhodium(ll) propionate, rhodium(ll) butyrate, rhodium(ll) valerate, rhodium(lil) naphthenate, or rhodium(lll) acetylacetonate; as a carbonyl or hydrocarbonyl derivatives, for example, tetrarhodium dodecacarbonyl, dirhodium octacarbonyl, hexarhodium hexadecacarbonyl, a rhodium tetracarbonyl salt, or a substituted carbonyl compound, such as rhodium dicarbonyl acetylacetonate.

Preferred rhodium-containing compounds include the rhodium salts of organic carboxylic acids containing up to 10 carbon atoms and rhodium carbonyls or hydrocarbonyl derivatives. Among these includes, for example, rhodium diacetate, rhodium dipropionate, rhodium dicarbonyl acetylacetonate, rhodium(lil) acetylacetonate, hexarhodium hexadecacarbonyl, and mixtures thereof.

Any suitable ligand can be used in the catalyst system of the present invention. Examples of those ligands which form complexes or associations with the rhodium-containing compound include, among others, those which contain at least one Lewis base oxygen atom, as well as those having a Group VB tertiary donor ligand, e.g at least one Lewis base nitrogen atom, or ligands containing phosphorus, arsenic or antimony. The only requirement is that they form a suitable electronic or ionic association with the rhodium.

Organic ligands which contain at least one Lewis base nitrogen atom preferably contain carbon, hydrogen and nitrogen atoms. The carbon atoms can be acrylic and/or cyclic such as aliphatic, cycloaliphatic, or aromatic (including fused and bridged) carbon atoms. Preferably, the organic ligands contain from 2 to 20 carbon atoms. The nitrogen atoms can be present in imino (- N ), amino or nitrilo groups. Desirably the Lewis base nitrogen atoms are present in imino and/or amino groups.

Illustrative examples of the organic nitrogen ligands include, N,N,N',N'-tetramethylethylenediamine, N, N,N',N'-tetraethylethylenediamine, N,N, N', N'-tetraisobutylmethylenediamine, piperazine, N-methylpiperazine, N-ethylpiperazine, 2-methy-N-methylpiperazine, 2,2'-dipyridyl, purine, 2-aminopyridine, 2-(dimethylamino)-pyridine, 1,1 0-phenanthroline, methyl-substituted 1,10-phe- nanthroline, piperidine, 2-methylpiperidine, pyridine, triethylamine, tri-n-butylamine, dibutylamine, methylamine, dodecylamine, morpholine, aniline, benzylamine, octadecylamine, naphthylamine, cyclohexylamine, and mixtures thereof.

Organic ligands which contain at least one Lewis base oxygen atom preferably contain carbon, hydrogen and oxygen atoms. The carbon atoms can be acyclic and/or cyclic, e.g. in aliphatic, cycloaliphatic or aromatic (including fused and bridged) groups. Preferably, the ligand contains from 2 to 20 carbon atoms. The oxygen atom can be in the form of groups such as hydroxyl (aliphatic or phenolic) or carboxyl, the oxygen atom in the hydroxyl group or carboxyl group, being the Lewis base oxygen atom. Such ligands may, of course, contain other atoms and/or groups, such as alkyl, cycloalkyl, aryl, chloro, thiaalkyl or thiaalkylsilyl.

Illustrative examples of the organic ligands containing oxygen include glycolic acid, methoxyacetic acid, ethoxyacetic acid, diglycolic acid, thiodiglycolic acid, diethyl ether, tetrahydrofuran, dioxane, tetrahydropyran, pyrocatechol, citric acid, 2-methoxyethanol, 2-n-butanol, 1,2,3-trihydroxybenzene, 2,3-dihydroxynaphthalene, cyclohexane-1 ,2-diol, oxetane, 1,2,di-methoxybenzene, 1 ,2dimethoxybenzene, 1 -4,dimechcoybenzene, methyl acetate, ethanol, 1 ,2-dipropoxy- ethane, hexane-2,4-dione, 1-phenyl-butane-1,3-dione, 3-methylpentane-2,4-dione, the monoand dialkyl ethers of propylene glycol, or of poly-(alkylene glycols), e.g. diethylene glycol or dipropylene glycol, and mixtures thereof.

Illustrative examples of those compounds containing both oxygen and nitrogen include, ethanolamine, diethanolamine, isopropanolamine, N,N-dimethylglycine, iminodiacetic acid, Nmethyliminodiacetic acid, N-methyldiethanolamine, 2-hydroxypyridine, 3-hydroxypyridine, 4hydroxypyridine, picolinic acid, methyl-substituted picolinic acid, nitrilotriacetic acid, 2,5dicarboxypiperazine, N-(2hydroxyethyl)iminodiacetic acid, ethylenediaminetetracetic acid, 2,6 dicarboxypyridine, 8-hydroxyquinoline, cyclohexane- 1 ,2-diamine-N, N, N', N'-tetracetic acid, the tetramethyl ester of ethylendiaminetetracetic acid, and mixtures thereof.

Coming under special consideration are the Group VB tertiary donor ligands, preferably containing nitrogen, phosphorus, arsenic and antimony. Illustrative examples of this group include, among others, triphenylphosphine, tributylphosphine, triphenylphosphite, triethylphosphite, trimethylarsine, triphenylarsine, tricyclohexylphosphine, trioctylphosphine, dimethylphenylphosphine, triphenylstilbine, trimethylamine, triethylamine, tripropylamine, pyridine, 2-2'dipyridyl, N, N-dimethylpiperazine, 1, 8-bis(dimethylamino)naphthalene and N, N-dimethylaniline.

The above-noted ligands can be combined with the rhodium-containing compound before addition to the reaction mixture, or the two components can be added separately. In general, it is preferred to add the two components separately to the reaction mixture.

The promoter to be added to the catalyst system comprises a sulfonium salt. Any suitable sulfonium salt can be used, but the preferred salts have the formula (R3S)+ Xwherein R is an organic radical, preferably a hydrocarbon or substituted hydrocarbon radical, and X is any suitable anion, including anions derived from mineral acids and carboxylic acids.

The hydrocarbon radicals represented by R may be aliphatic, hexyl, octyl, dodecyl, octadecyl, cyclohexyl, cyclopentyl, cyclohexenyl, cyclopentadienyl, allyl, 1,6-octadienyl, 2-ethylhexyl, phenyl, 2,4-dimethylphenyl, or naphthyl. Examples of substituted hydrocarbon radicals include those radicals noted above substituted with 1 or more halogen atoms, (preferably chlorine and bromine), hydroxy, alkoxy, amino, or sulfonyl groups. Preferred sulfonium salts include those of the above formula wherein R is an aliphatic, cycloaliphatic or aromatic hydrocarbon group containing up to 20 carbon atoms, or an aliphatic, cycloaliphatic or aromatic hydrocarbon group containing up to 20 carbon atoms substituted with one or more (e.g. 1 to 3) halogen, hydroxy, or alkoxy groups.

Illustrative examples of such sulfonium salts include trioctylsulfonioum bromide, triphenylsulfonium chloride, tricyclohexylsulfonium acetate, tridodecylsulfonium chromate, tri(2,4-dimethylphenyl)sulfonium benzoate, tri(hydroxyphenyl)sulfonium chloride, tri(hydroxyphenyl)sulfonium bromide, tri(chlorophenyl)sulfonium acetate, tri(methoxyphenyl)suifonium chloride, tri(methoxycyclohexyl)sulfonium bromide, tri(cyclohexenyl)sulfonium tetrafluoroborate, tri(2,4-dihydroxyphenyl)sulfonium chromate, tri(3, 5-dioctylphenyl)sulfonium chloride and tri(3, 5-dimethoxyphenyl)- sulfonium acetate.

The particularly preferred sulfonium salts to be used in the new catalyst system are trialkylsulfonium salts, tricycloalkylsulfonium salts and triarylsulfonium salts, and such salts substituted on the hydrocarbon radical with from 1 to 3 halogen atoms, (and particularly chlorine or bromine), hydroxy groups, amino groups, alkoxy groups or sulfonyl groups, said salts preferably containing no more than 1 2 carbon atoms.

Coming under special consideration are triarylsulfonium salts, tri(alkylaryl)sulfonium salts, and their hydroxy- and halogen-substituted derivatives. One of the requrements for the salt is that it be stable at the reaction conditions. The triaryl and triaralkyl salts are the best by far in this regard.

The amount of the rhodium-containing compound to be used in the process may vary over a wide range. The process is conducted in the presence of a catalytically effective quantity of the rhodium-containing compound which gives the desired products in a reasonable yield. The reaction proceeds when employing as little as 1 x 10-6 weight percent, and even lesser amounts of the rhodium-containing compound. The upper concentration is dictated by a variety of factors including catalyst cost, partial pressures of carbon monoxide and hydrogen, and operating temperatures. A rhodium-containing compound concentration of from 1 x 10-5 to 10 weight percent, based on the total weight of the reaction mixture, is generally desirable in the practice of the invention.

The amount of the organic ligand to be used in the process of the invention may vary within a wide range, depending upon the type of complex to be formed. For example, the amount may be from the stoichiometric amount needed to form the required complex with the rhodium, up to 5 or more times the molar amount needed for the formation of such complexes. Preferably the amount of ligand utilized is from 0.5 to 2.0 moles of ligand per mole of rhodium (contained in the rhodium-containing compound). Ratios outside this range can be employed, especially when it is desirable to use diluent quantities of the organic ligand.

A method for determining the optimum amount of the ligand to be used with the rhodium catalyst is disclosed in British Patent No. 1,565,979.

The sulfonium salts are generally added to the reaction mixture in amounts from 0.3 to 2.0 moles for every five atoms of rhodium present. Preferably the salt is added in amounts from 0.9 to 1.6 moles per 5 atoms of the rhodium contained in the catalyst system.

Particularly superior results are obtained when the above-mentioned three components of the catalyst are employed as follows: rhodium-containing compound 1 to 1 5 moles; organic ligand 0.5 moles to 1 5 moles; and sulfonium salt 0.5 to 5 moles.

Solvents can be, and preferably are, employed in the process of the invention. As noted above, one of the advantages of the present invention is that the new catalysts are readily soluble in the conventional solvents used in this type of reaction. In general, the preferred solvents are those which are not of the ligand type but which act chiefly to- fluidize the catalysts.

They are thus preferably substantially inert under the reaction conditions, relatively non-polar and preferably have a boiling point greater than that of ethylene glycol and other oxygencontaining reaction products, so that recovery of the product and solvent by distillation is facilitated.

Suitable solvents include the liquid hydrocarbons, which can be aliphatic, cycloaliphatic or aromatic, for example, benzene, toluene, xylene, heptane, dodecane, cyclohexane, and mixtures thereof. Other suitable solvents include the ethers which may be cyclic, acyclic, and heterocyclic materials. Examples of these include isopropyl n-propyl ether, diethylene glycol dibutyl ether, tetraethylene glycol dimethyl ether, tetraethylene glycol dibutyl ether, diphenyl ether, heptyl phenyl ether, anisole, tetrahydrofuran, 1 ,4-dioxane, and mixtures thereof. Other suitable solvents include sulfones such as tetramethylene sulfone (sulfolane). Coming under special consideration are the dialkyl ethers of alkylene glycols and the dialkyl ethers of poly(alkylene glycols).

Less preferred solvents include alcohols, such as cyclohexanol, 2-hexanol, 2-ethylhexanol, 2octanol and neopentanol. Also less preferred are liquid esters which may be aliphatic, cycloaliphatic or aromoatic carboxylic acid esters, such as methyl benzoate, butyl cyclohexanoate, dimethyl adipate, dibutyl succinate, and mixtures thereof.

The amount of the solvent employed may vary as desired. In general, it is desirable to use sufficient solvent to fluidize the catalyst system. In general, this may be from 0.3 to 100 moles per mole of rhodium.

The temperature which can be employed in the process of the invention may lie within a considerable range, depending upon experimental factors, including the choice of catalyst, pressure and other variables. A preferred range of operability is from 1 70 to 350"C when superatmospheric pressures of syngas are employed. A narrower range of 1 70 to 290 C represents a particularly preferred temperature range.

The pressure employed may also vary over a considerable range, but in most cases is at least above 35 bars. A preferred operating range is from 70 to about 1050 bars, although pressures above 1050 bars also provide useful yields of the desired product. A particularly preferred pressure range is from 70 to 525 bars. The pressures referred to herein represent the total pressure generated by all the reactants, although they are substantially due to the carbon monoxide and hydrogen fractions.

The relative amounts of carbon monoxide and hydrogen which can be initially present in the syngas mixture are variable, and these amounts may be varied over a wide range. In general, the mole ratio of CO:H2 is in the range from 20:1 to 1:20, and preferably from 5:1 to 1:5, although ratios outside these ranges may also be employed with good results. Particularly in continuous operations, but also in batch experiments, the carbon monoxide-hydrogen gaseous mixtures may also be used in conjunction with up to 50% by volume of one or more other gases.These other gases may include one or more inert gases, such as nitrogen, argon, or neon, or they may include gases that may, or may not, undergo reaction under carbon monoxide hydrogenation conditions, such as carbon dioxide; hydrocarbons, such as methane, ethane or propane; ethers, such as dimethyl ether, methyl ethyl ether and diethyl ether; and alkanols, such as methanol.

In all these syntheses, in order to achieve a high degree of selectivity, the amount of carbon monoxide and hydrogen present in the reaction mixture should be sufficient at least to satisfy the stoichiometry of the desired formation of ethylene glycol as shown in equation (1) above.

Excess carbon monoxide and/or hydrogen over the stoichiometric amount may be present, if desired.

The desired products of the reaction, e.g. ethylene glycol and methanol, will be formed in significant quantities. Generally the ethylene glycol will be formed in amounts from 0.8 to 20% by weight of material charged in the specified amount of time. Also formed will be amounts of other lower oxygenated products, such as ethanol and acetic acid. The desired ethylene glycol and methanol can be recovered from the reaction mixture by conventional means, e.g. fractional distillation in vacuo.

The novel process of the invention can be conducted in a batch, semi-continuous or continuous manner. The process is preferably conducted in a batch manner. The catalyst can be initially introduced into the reaction zone batchwise, or it may be continuously or intermittently introduced into such a zone during the course of the synthesis reaction. Operating conditions can be adjusted to optimize the formation of the desired ethylene glycol product, which may be recovered by methods known to the art, such as distillation, fractionation, or extraction. A fraction rich in the catalyst components may then be recycled to the reaction zone, if desired, and additional product generated.

The products have been identified in this work by one or more of the following analytical procedures: viz, gas-liquid phase chromatography (glc), infrared (ir) mass spectrometry, nuclear magnetic resonance (nmr) and elemental analyses, or a combination of these techniques.

Analyses have, for the most part, been by parts by weight; percentages are by weight, all temperatures are in degrees centrigrade and all pressures in bars.

To illustrate the process of the invention, the following Examples are given. It is to be understood, however, that the Examples are given in the way of illustration and are not to be regarded as limiting the invention in any way.

EXAMPLE I This Example illustrates the preparation of ethylene glycol and methanol by the process of the invention.

Into a glass liner, designed to fit into a stainless steel rocking autoclave, were introduced 0.1658 g (0.75 mmole) of rhodium diacetate, 0.2375 g (2.5 mmole) of 2-hydroxypyridine, 0.075 mmole of tris-(4-hydroxyphenyl) sulfonium chloride and 19.0 9 (0.082 moles) of tetraethylene glycol dimethyl ether. The resulting suspension was placed in the autoclave, sealed and flushed with 1:1 CO/H2, then pressurized with this gas mixture to 208 bars, while rocking at room temperature. The temperature was then gradually increased to 220"C and stabilized.

The system was then pressurized to 587 bars and repressurized periodically over an 1 8 hour span as the pressure dropped to 566.5 bars. The system was then dismantled, after cooling and relieving of pressure. The off gas sample was collected. A weight gain of 0.6843 g was observed. The contents of the liner recovered were found to include 5.65% ethylene glycol and 5.03% methanol, along with a small amount of ethyl alcohol, methyl formate, 2-hydroxypyridine and triethylene glycol dimethyl ether.

During the reaction there was complete solution of the reactants and catalyst, and there was no evidence of any plating out of the rhodium compound.

EXAMPLE I (Comparative Test) Example I was repeated with the exception that the reaction was conducted in the solvent without the tris-(4-hydroxyphenyl) sulfonium chloride. The recovered sample showed no weight gain and brown and black solids were dispersed in the liquid layer recovered. In addition, a rhodium mirror and a layer of undissolved solids covered the immersed portion of the liner. A g.c. analysis showed the liquid to contain 0.69% glycol and 0.88% methanol.

EXAMPLE II Example I was repeated, with the exception that the rhodium compound was rhodium dicarbonyl acetylacetonate 0.1935 g (0.75 mmole) and the reaction was conducted for 16 hours. All other conditions and reactants were identical. The liquid product was completely homogeneous (no undissolved solids) and a weight gain of 3.1 9 g was observed. The solution was found to contain (by g.c. analysis) ethylene glycol 8.03%, methanol 10.4%, methyl formate 1.3%, ethanol 0.37% and tetraethylene glycol dimethyl ether 77.85%. Analysis of the solution by atomic absorption revealed that 97.5% of the rhodium was recovered.

EXAMPLES 111 to XII A series of reactions were conducted using tris-(4-hydroxyphenyl) sulfonium chloride as the promoter, and the ratio between the halide and the rhodium compound was varied. All the reactions were conducted in the equipment described in Example I, employing rhodium(lil) acetylacetonate 0.300 g (0.75 mmole), and 2-hydroxypyridine 0.2375 g (2.5 mmole) in tetraethylene glycol dimethyl ether 20.0 g (0.09 moles). The results are shown in Table I. These results demonstrate the productivity increases when the promoter is used. It also shows the improvement in glycol to methanol ratio, and the optimum ratio of rhodium to sulfonium salt promoter.

Temp. = 220 C Press. = 573 bars Time = 16-18 hrs.

TABLE I EFFECT OF TRIS-(4-HYDROXYPHENYL) SULFONIUM CHLORIDE OF THE CATALYZED GLYCOL FROM SYNGAS REACTION Promoter = tris-(4-hydroxyhenyl) sulfonium chloride Millimoles moles Rh ethylene methyl Weight %CH4 in %CO2 in Example of promoter moles promoter methanol glycol formate ethanol gain, g off-gas off-gas Solubility III 0.75 1/1 1.09 0.96 0.06 0.20 0.029 0.08 3.53 Complete IV 0.375 2/1 1.82 2.03 0.12 0.20 0.392 0.08 3.49 Complete V 0.25 3/1 3.48 3.30 0.34 0.26 1.107 0.05 3.17 Complete VI 0.1875 4/1 2.78 3.01 0.24 0.21 1.062 0.06 3.54 Complete VII 0.150 5/1 2.57 3.18 0.21 0.22 1.416 0.09 3.60 Complete VIII 0.094 8/1 3.99 4.69 0.38 0.23 1.5081 0.02 3.14 Complete Solution IX 0.083 9/1 3.50 4.64 0.31 0.23 1.3164 0.03 4.13 Complete Solution X 0.083 1/1 4.50 5.15 0.41 0.41 0.7768 0.09 2.81 Complete Solution XI 0.068 11/1 2.78 3.54 0.24 0.21 0.7691 0.13 3.95 --- XII 0.0625 12/1 3.02 3.71 0.26 0.21 0.7275 0.11 3.25 Solids EXAMPLES XIII to XXV A series of reactions was conducted using tris-(4-hydroxyphenyl) sulfonium bromide as the promoter, and the ratio between the halide and the rhodium compound was varied. All the reactions were conducted in the equipment described in Example I, employing rhodium(lil) acetylacetonate 0.3009 (0.75 mmoles), and 2-hydroxypyridine 0.2375 (2.5 mmole) in tetraethylene glycol dimethyl ether 20.0 g (0.09 moles). The results are shown in Table II.

EXAMPLE XXVI Example I was repeated, with the exception that the promoter used was tris-(4-hydroxyphenyl) sulfonium acetate, and the rhodium compound was rhodium diacetate. Related results are obtained.

EXAMPLE XXVII Example I was repeated, with the exception that the promoter was tris-(4-hydroxyphenyl) sulfonium chloride, and the rhodium compound was rhodium diacetate. Related results were obtained.

EXAMPLE XXVII I Examples I to XXVII are repeated with the exception that the ligand employed was 1,10phenanthroline. Related results are obtained.

EXAMPLE XXIX Examples I to XXVII are repeated with the exception that the solvent employed was sulfone.

Related results are obtained.

Temp. = 220 C Press. = 566.5 - 587 bars Time = 16-18 hrs.

Solvent = Tetraethylene glycol or methyl ether TABLE II EFFECT OF TRIS-(4-HYDROXYPHENYL) SULFONIUM CHLORIDE OF THE CATALYZED GLYCOL FROM SYNGAS REACTION Promoter = tris-(4-hydroxyhenyl) sulfonium bromide Millimoles moles Rh ethylene methyl Weight %CH4 in %CO2 in Example of promoter moles promoter methanol glycol formate ethanol gain, g off-gas off-gas Solubility XIII 0.75 1/1 2.2 0.95 0.13 0.64 0.900 0.23 4.26 hazy XIV 0.375 2/1 2.6 1.6 0.19 0.35 0.564 0.11 3.4 hazy XV 0.25 3/1 3.9 3.9 0.35 0.39 1.840 0.07 1.87 clear XVI 0.1875 4/1 4.34 0.387 0.35 0.914 0.09 2.51 clear XVII 0.150 5/1 4.2 4.35 0.41 0.36 2.06 0.03 3.28 clear XVIII 0.1250 6/1 4.0 0.37 0.37 0.56 ---- 5.13 clear XIX 0.107 7/1 5.0 5.69 0.58 0.446 2.40 0.06 2.99 clear XX 0.094 8/1 4.4 4.42 0.48 0.36 1.29 0.08 4.08 clear XXI 0.038 9/1 2.59 3.61 0.20 0.28 0.770 0.29 2.81 clear XXII 0.075 10/1 5.2+ 5.70 0.56 0.41 0.093 0.08 3.20 clear XXIII 0.068 11/1 4.05 4.47 0.400 0.31 1.150 0.06 3.06 3.06 hazy XXIV 0.0625 12/1 3.77 4.20 0.36 0.27 1.580 0.07 3.40 hazy XXV 0.0375 20/1 3.01 3.76 0.22 0.34 0.841 0.09 2.91 hazy

Claims (24)

1. A process for preparing low molecular weight oxygenated products which comprises contacting a mixture of carbon monoxide and hydrogen with a catalyst system comprising a rhodium-containing compound, an organic ligand and a sulfonium salt, at an elevated temperature and pressure.

2. A process as claimed in Claim 1 wherein the mixture also contains a solvent.

3. A process as claimed in Claim 2 wherein the solvent is an oxygenated hydrocarbon containing up to 12 carbon atoms.

4. A process as claimed in Claim 2 wherein the solvent is a dialkyl ether of a poly(alkylene glycol).

5. A process as claimed in Claim 4 wherein the solvent is tetraethylene glycol dimethyl ether.

6. A process as claimed in Claim 2 wherein the solvent is a sulfone.

7. A process as claimed in any preceding Claim wherein the rhodium-containing compound is a rhodium salt of an organic carboxylic acid or a rhodium carbonyl or hydrocarbonyl derivative.

8. A process as claimed in Claim 7 wherein the rhodium-containing compound is rhodium diacetate.

9. A process as claimed in Claim 7 wherein the rhodium-containing compound is rhodium dicarbonyl acetylacetonate.

10. A process as claimed in any preceding Claim wherein the ligand is an oxygen-containing ligand.

11. A process as claimed in any of Claims 1 to 9 wherein the organic ligand is a Group VB tertiary donor ligand.

1 2. A process as claimed in Claim 11 wherein the ligand is a nitrogen-containing ligand.

1 3. A process as claimed in Claim 12 wherein the organic ligand is 2-hydroxypyridine.'

14. A process as claimed in Claim 11 wherein the ligand contains phosphorus, arsenic or antimony.

1 5. A process as claimed in any preceding Claim, wherein the sulfonium salt has the formula (R3S)+ X wherein R is an organic radical and X is an anion derived from a mineral acid or carboxylic acid.

1 6. A process as claimed in Claim 1 5 wherein the sulfonium salt is a chloride, bromide, acetate, propionate, chromate or sulfate.

1 7. A process as claimed in any preceding Claim wherein the sulfonium salt is a trialkylsulfonium salt, tricycloalkylsulfonium salt, triarylsulfonium salt, tri(alkylaryl)sulfonium salt or one or more of the foregoing salts substituted on its hydrocarbon radical with from 1 to 3 halogen atoms, hydroxyl groups, alkoxy groups, or amino groups.

18. A process as claimed in any preceding Claim wherein the sulfonium salt is tris-(4hydroxyphenyl)sulfonium chloride, bromide or acetate.

1 9. A process as claimed in any preceding Claim wherein the process is conducted at a temperature from 1 70 to 350 C.

20. A process as claimed in any preceding Claim wherein the process is conducted at a pressure from 70 to 525 bars.

21. A process as claimed in any preceding Claim wherein the carbon monoxide and hydrogen are used in molar ratio of 5:1 to 1:5.

22. A process as claimed in any preceding Claim wherein the catalyst components are employed in proportions of: rhodium-containing compound 1 to 1 5 moles; organic ligand 0.5 to 1 5 moles; and sulfonium salt 0.5 to 5 moles.

23. A process as claimed in Claim 1 and substantially as hereinbefore described with reference to any of Examples I to XXIX.

24. Low molecular weight oxygenated products when prepared by a process as claimed in any of the preceding Claims.