GB2024811A - Manufacturers of vicinal glycol esters from synthesis gas - Google Patents

Abstract

A process for the formation of ester mixtures, comprising esters of monohydric and dihydric alcohols, by reacting synthesis gas (CO + H2) and carboxylic acid, at a temperature of 100 to 350 DEG C and a pressure of at least 34 atmospheres (500 psi) in the presence of a catalyst comprising ruthenium or osmium. Optionally a co-catalyst selected from alkali metal salts, alkaline earth metal salts, quaternary ammonium salts, iminium salts and quaternary aliphatic phosphonium salts is also employed. A typical reaction product comprises methyl acetate, ethyl acetate and ethylene glycol diacetate.

Description

SPECIFICATION Manufacture of vicinal glycol esters from synthesis gas This invention concerns an improved process for preparing alkanol and vicinal glycol ester compounds, including ester derivatives of ethylene glycol, by reaction of oxides of carbon with hydrogen.

More particularly, the invention concerns the selective co-synthesis of alkanol and glycol esters, particularly the ester derivative of ethylene glycol, methanol and ethanol, by the catalytic reaction of carbon monoxide and hydrogen in the presence of a liquid medium containing a carboxylic acid coreactant. Catalysis is effected in the presence of a catalyst containing osmium or ruthenium, with the latter being most preferred.The process is exemplified by, but not limited to, the one step co-synthesis of ethylene glycol diacetate, methyl acetate and ethyl acetate from carbon monoxide, hydrogen mixtures in the presence of an acetic acid (HOAc) liquid medium according to the stoichiometry of eqs. (1) to (3):

2CO + 4H2 + HOAc eCH3CH20Ac + 2H2O (2) CO + 2H2 + HOAc eCH30Ac + H20 (3) Methyl acetate, ethyl acetate and glycol diacetate are all products of recognized commercial value, particularly as chemical intermediates and extractive solvents. Methyl and ethyl acetates are used widely as solvents, primarily for surface coatings. Ethylene glycol diacetate is useful in the production of ethylene glycol, an important component in polyester fiber and antifreeze formulations.Free glycol may be generated from its diacetate derivative via hydrolysis as disclosed, for example, in Belgian Patent No.749,685.

It is the purpose of this invention to provide new routes to the preparation of alkanol and diol esters using mixtures of carbon monoxide and hydrogen (hereinafter sometimes referred to as synthesis gas or syngas). This is particularly true where methyl acetate, ethyl acetate and glycol diacetate are the principal products (eqs. 1-3), since in this case acetic acid is the co-reactant medium, and one route to HOAc manufacture is from synthesis gas via methanol cabonylation. ("Trends in Petrochemical Technology" by A.M. Brownstein, Chapter 5 (1976).

In recent years, a large number of patents have been issued dealing with the synthesis of lower molecular weight hydrocarbons, olefins, and alkanols, from synthesis gas. Of particular note, U.S.

Patent No. 2,636,046 discloses the synthesis of polyhydric alcohols and their derivatives by reaction between carbon monoxide and hydrogen at elevated pressures ( > 1500 atm or 22,000 psi) and temperatures to 4000C using certain cobalt-containing catalysts. More recently, in Belgian Patent No.793,086 and U.S. Patent No.3,940,432 there is described the co-synthesis of methanol and ethylene glycol from mixtures of carbon monoxide and hydrogen using a rhodium complex catalyst. Typically, CO hydrogenation is effected at 544 atmospheres (8000 psi) of 1:1 HJCO synthesis gas, at 220"C, using tet raethylene glycol methyl ether as the solvent, and dicarbonylacetyl - acetonatorhodium(l) in combina tion with an organic Lewis base as the catalyst pre cursor. (For a summary of the work, see: R.L. Purett, Annals New York Academy of Sciences, Vol. 295 p.

239(1977)). While other metals of Group VIII of the Periodic Table have been tested for activity under similar conditions, including cobalt, ruthenium, copper, manganese, iridium and platinum, only cobalt was found to have slight activity. The use of ruthenium compounds in particular failed to pro duce polyfunctional products such as ethylene glycol. This is illustrated in U.S. Patent No. 3,833,634 for solutions of triruthenium dodecacarbonyl.

The present invention provides a process for the concurrent synthesis of alkanol and vicinal glycol esters which comprises heating a reaction mixture of carbon monoxide and hydrogen, (with sufficient carbon monoxide and hydrogen to satisfy the stoichiometry of the desired ester syntheses), a liquid medium containing one or more carboxylic acids and a catalyst containing ruthenium, osmium or a mixture thereof, at a temperature between 100"C and 350"C, and a superatmospheric pressure of at least 34 atmospheres (500 psi).

In one preferred embodiment, the reaction mix ture contains, as a co-catalyst one or more alkali metal salts, alkaline earth metal salts, quaternary ammonium salts, iminium salts or quaternary phos phonium salts.

Further details of the invention are as follows: A. CatalystComposition - Catalysts that are suit able in the practice of this invention contain osmium or ruthenium or mixtures of these metals. The ruthenium or osmium-containing catalyst may be chosen from a wide variety of organic or inorganic compounds or complexes, as will be shown and illustrated below. It is only necessary that the catal yst precursor actually employed contain the transi tion metal (i.e. ruthenium or osmium) in any of its ionic states. The actual catalytically active species are then believed to comprise ruthenium or osmium in in complex combination with carbon monoxide and hydrogen.The most effective catalysis is achieved where the ruthenium or osmium hydrocarbonyl species are solubilized in the carboxylic acid co reactant employed to satisfy the stoichiometry of eq i1-3.

While the invention will be more specifically dis cussed below in terms of typical ruthenium containing forms or species, it is understood that osmium may be employed in like forms in most cases without departing from the scope of the inven tion.

The preferred ruthenium catalyst precursors may take many different forms. For instance, the ruthenium may be added to the reaction mixture in an oxide form, as in the case of, for example, ruthenium(lV) oxide, hydrate, anhydrous ruthenium(lV) dioxide and ruthenium(Vlll) tetraox ide. Alternatively, it may be added as the salt of a mineral acid, as in the case of ruthenium(lll) chloride hydrate, ruthenium(lll) bromide, anhydrous ruthenium(lll) chloride and ruthenium nitrate, or as the salt of a suitable organic carboxylic acid (see Section B, below), for example, ruthenium(lll) ace tate, ruthenium(lll) propionate, ruthenium butyrate, ruthenium(lll) trifluoroacetate, ruthenium octanoate, ruthenium napththenate, ruthenium valerate and ruthenium(lil) acetylacetonate.The ruthenium may also be added to the reaction zone as a carbonyl or hydrocarbonyl derivative. Here, suitable examples include triruthenium dodecacarbonyl, hydrocar bonyls such as H2Ru4(CO),3 and H4Ru4(CO)12, and substituted carbonyl species such as the tricarbonyl ruthenium (II) chloride dimer, [Ru(CO)3Cl2]2.

In a preferred embodiment of the invention ruthenium is added to the reaction zone as one or more oxide, salt or carbonyl derivative species in combination with one or more group VB tertiary donor ligands. The key elements of the Group VB ligands include nitrogen, phosphorus, arsenic and antimony. These elements, in their trivalent oxidation states, particularly tertiary phosphorus and nitrogen, may be bonded to one or more alkyl, cycloalkyl, aryl, substituted aryl, aryloxide, alkoxide, alkaryl or aralkyl radicals, each containing from 1 to 12 carbon atoms, or they may be part of a heterocyclic ring system, or be mixtures thereof.Illustrative examples of suitable ligands that may be used in this invention include: triphenylphosphine, tri - n - butylphosphine, triphenyl phosphite, triethylphosphite, trimethylphosphite, trimethylphosphine, tri -p - methoxyphenylphos phine, triethylphosphine, trimethylarsine, triphenylarsine, tri -p - tolylphosphine, tricyclohexylphosphine, dimethylphenylphosphine, trioctyl phosphine, tri - 0- tolylphosphine, 1,2 - bis(diphenyl - phosphino)ethane, triphenylstibine, trimethylamine, triethylamine, tripropylamine, tri - n - octylamine, pyridine, 2,2' - dipyridyl, 1,10 - phenan- throline, quinoline, N,N'dimethylpiperazine, 1,8 - bis(dimethylamino)naphthalene and N,N dimethylaniline.

One or more of these ruthenium-teriary Group VB donor ligand combinations may be preformed, before addition to the reaction mixture, as in the case, for example, of tris (triphenylphos phine)ruthenium(ll) chloride and tricarbonyl bis(triphenylphosphine)ruthenium or alternatively, said complexes may be formed in situ.

The performances of each of these classes of ruthenium catalyst precursors are illustrated by the accompanying examples, described below.

Similar catalyst combinations, containing osmium rather than ruthenium as the transition-metal com ponent, are also suitableforthe desired synthesis of alkanol and polyhydric alcohol esters from synthesis gas.

B. CarboxylicAcids: Carboxylic acids useful in the process of this invention form the acid moiety of the sesired methyl, ethyl and glycol ester products. Pre ferably, said acids are also useful as solvents for the transition-metal catalysts, particularly the ruthenium catalyst combinations. Suitable carboxylic acids include aliphatic acids, alicyclic monocarboxylic acids, heterocyclic acids and aromatic acids, both substituted and non-substituted. For example, this invention contemplates the use of aliphatic monocarboxylic acids of 1 to 12 carbon atoms such as formic acid, acetic, propionic, butyric, isobutyric, valeric, caproic, capric, perlargonic and lauric acids, together with aliphatic dicarboxylic acids of 2 to 6 carbons, such as oxalic, malonic, succinic and adinic acids.Alternatively substituted aliphatic monocarboxylic acids containing one or more functional substituents, such as chlorine or fluorine atoms, or alkoxy, cyano, alkylthio, or amino groups. Examples of such acids include acetoacetic acid, dichloroacetic acid, trifluoroacetic acid, chloropropionic acid, trichloroacetic acid, and monofluoroacetic acid. Among suitable aromatic acids are benzoic acid, napthoic acids, toluic acids, chlorobenzoic acids, aminobenzoic acids and phenylaceticacid. The alicyclic moncarboxylic acids may contain from 3 to 6 carbons in the (substituted or unsubstituted) ring and may contain one or more carboxyl groups, such as cyclopentane - carboxylic acid or hexahydrobenzoic acid.The heterocyclic acids may contain 1 to 3 fused rings, which may be substituted or unsubstituted, together with one or more carboxylic groups, examples include quinolinic, furoic and picolinic acids. Mixtures of said classes of carboxylic acids, in any ratio, may also be used in the inventive process. The preferred carboxylic acids are the aliphatic acids such as acetic acid, propionic acid and butyric acid, and substituted aliphatic acids such as trifluoroacetic acid.

C. Catalyst Concentration - The quantity of ruthenium or osmium catalyst employed in the invention is not critical and may vary over a wide range. In general, the novel process is desirably conducted in the presence of a catalytically effective quantity of the active ruthenium or osmium species which gives the desired ester products in reasonable yields. Reaction proceeds when employing as little as 1 x 10-6 weight percent, and even lesser amounts, of ruthenium or osmium, basis the total weight of the reaction mixture.The upper concentration is dictated by a variety of factors including catalyst cost, partial pressures of carbon monoxide and hydrogen, operating temperature and choice of carboxylic acid diluentlreactant A concentration of from 1 x 10-5 to 10 weight percent of ruthenium, or osmium based on the total weight of reaction mixture, is generally desirable in the practice of this invention.

D. Operating Temperature-Thetemperature range which can usefully be employed in these ester syntheses is variable dependent upon other experimental factors, including the choice of carboxylic acid co-reactant, the pressure, and the concentration and particular choice of catalyst among other things. Again using ruthenium as the active metal, the range of operability is from 100" to 350"C when superatmospheric pressures of syngas are employed. A narrower range of 150-260"C represents the preferred temperature range when the major products are methyl, ethyl and glycol acetates.

Table I is evidence of how the narrower range is derived.

E Pressure - Superatmospheric pressures of 34 atmospheres (500 psi) or greater lead to substantial yield of desirable alkanol and vicinal glycol ester by the process of this invention. A preferred operating range for solutions of ruthenium (III) acetylacetonate in acetic acid is from 68 to 510 atmospheres (1000 to 7500 psi) although pressures above 510 atmospheres (7500 psi) also provide useful yields of desired ester. Table I is evidence of this preferred, narrower range of operating pressures. The pressures referred to here represent the total pressure generated by all the reactants, although they are substantially due to the carbon monoxide and hydrogen fractions in these examples.

F. Gas Composition -The relative amounts of carbon monoxide and hydrogen which may 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 - to - H2 is in the range from 20:1 up to 1:20, preferably from 5:1 to 1:5, although ratios outside these ranges may also be employed.

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, they may include gases that may, or may not, undergo reaction under CO hydrogenation conditions such as carbon dioxide; hydrocarbons such as methane, ethane or propane; ethers such dimethyl ether, methyl ethyl ether and diethyl ether, alkanols such as methanol; and acid esters such as methyl acetate.

In all syntheses, the amount of carbon monoxide and hydrogen present in the reaction mixture should be sufficient to satisfy the stoichiometry of eq (1) to (3).

G. Product Distribution -- As far as can be determined, without limiting the invention thereby, the ruthenium or osmium catalyst one-step COhydrogenation process disclosed herein leads to the formation of three classes of primary products, namely the methanol, ethanol and ethylene glycol ester derivatives of the corresponding co-reactant the principal products are methyl acetate, ethyl acetate and ethylene glycol diacetate. Minor byproducts detected in the liquid product fraction include small amounts of water, glycol monoacetate, propyl acetate and dimethyl ether. Carbon dioxide, methane and dimethyl ether may be detected in the off-gas together with unreacted carbon monoxide and hydrogen.

H. Mode of Operation - The novel process of this invention can be conducted in a batch, semicontinuous or continuous fashion. The catalyst may 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 ester product, and said material may be recovered by methods well known in the art, such as distillation, fractionation, extraction and the like. A fraction rich in ruthenium or osmium catalyst components may then be recycled to the reaction zone, if desired, and additional ester products generated by CO hydrogenation.

1. ldentification Procedures -The products of CO-hydrogenation 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.

J. Co-Catalyst-There are several classes of suitable co-catalysts for use in one embodiment of the invention. One such class which may be added to the reaction mixtures to enhance the activity of the solubilized ruthenium or osmium catalysts are the salts of the alkali and alkaline earth metals. Illustrative examples of effective alkali metal salts include the alkali metal halides, for instance, the fluoride, chloride, bromide and iodide salts, and alkali and alkaline earth metal salts of suitable carboxylic acids.

The preferred alkali and alkaline earth metal carboxylates are the acetate, propionate and butyrate salts of sodium, potassium, barium and cesium. These salts may be added over a wide range of concentrations, e.g. from 0.01 to 102 moles of alkali or alkaline earth salt per gm atom of ruthenium or osmium present in the reaction mixture. The most preferred ratios are from 5:1 to 15:1 (See Table II).

The following are typical combinations of ruthenium - co - catalyst combinations useful in the inventive process: ruthenium chloride - cesium acetate, ruthenium(lV) oxide - cesium acetate, ruthenium chloride - cesium trifluoroacetate, ruthenium chloride - sodium acetate, ruthenium chloride - cesium proprionate, triruthenium dodecacarbonylcesium acetate, ruthenium, oxidecesium fluoride. Their effectiveness is illustrated in Examples 18 to 28.

Salts of quaternary ammonium and phosphonium cations are alse effective as co-catalysts in the process of this invention. Suitable quaternary phosphonium salts are those which are substantially inert under the CO-hydrogenation conditions and which have the formula:

where R1, R2, R2 and R4 are organic radicals bonded to the phosphorus atom by a saturated aliphatic carbon atom, and Xis an anionic species, preferably of a carboxylic acid, defined below. The organic radicals useful in this instance include those having 1 to 20 carbon atoms in a branched or linear alkyl chain; they include the methyl, ethyl,n - butyl,iso - butyl, octyl, 2 - ethylhexyl and dodecyl radicals. Tetramethylphosphonium acetate and tetrabutylphosphonium acetate are typical commerically available phosphonium salts.The corresponding quaternary phosphonium and ammonium hydroxides, nitrates and halides, such as the corresponding chlorides, bromides and iodides, are also satisfactory in this instance, as are quaternary ammonium salts of carboxylic acids such as terra -n - butylammonium acetate, and tetra - n - octylammonium propionate as well as the corresponding iminium salts such as bis (triphenylphosphine) iminium acetate. Examples 17, 18,32 and 33 provide evidence of the effectiveness of the ruthenium chloride - tetrabutylphosphonium acetate couple.

Similar catalyst combinations, containing osmium rather than ruthenium as the transition-metal component, are also suitable for the desired synthesis of alkanol and polyhydric alcohol esters from synthesis gas.

Having described the inventive process in general terms, the following examples are submitted to supply specific and illustrative embodiments. All percentages are by weight.

EXAMPLE 7 To a degassed sample of acetic acid (50 ml) contained in a 300 ml glass-lined reactor equipped for pressurizing, heating and means of agitation is added, under a nitrogen environment, 0.40 gm of ruthenium acetylacetonate (1.0 mole). The reactor is sealed, flushed with COSH2 and pressured to 184 atmospheres (2700 psi, with synthesis gas (1:1, COlH2). The mixture is then heated to 220 C, with agitation for 18 hr, and then allowed to cool.Gas uptake is 27.2 atmospheres (400 psi.) Excess gas is sampled and vented, the yellow-red liquid product, analyzed by glc, shows the presence of: 1.9% methyl acetate 0.3% ethyl acetate 1.4% ethylene glycol diacetate Yellow, crystalline triruthenium dodecacarbonyl slowly precipitates from this product solution upon standing and upon exposure to air.

The vented off-gas typically has the composition: 4P/o hydrogen 48% carbon monoxide 1.3% carbon dioxide 2.2% methane EXAMPLE2 In the preparation, CO-hydrogenation is carried out as described in Example 1, except that the charge mixture consists of 0.426 gm of triruthenium dodecacarbonyl (0.66 mmole) solubilized in 50 ml of acetic acid. Analysis of the product liquid by glc shows the presence of: 4.2% methyl acetate 0.5% ethyl acetate 0.4% ethylene glycol diacetate EXAMPLE 3 In this preparation, CO-hydrogenation is carried out as described in Example 1 except that the charge mixture consists of 0.71 gm of tricarbonylbis(triphenylphosphine) ruthenium (1.0 mmole) in 50 ml of glacial acetic acid.Analysis of the product liquid shows: 3.4 wt. % methyl acetate 0.8 wt. % ethyl acetate 0.2 wt. % ethylene glycol diacetate EXAMPLE4 In this preparation, CO-hydrogenation is carried out as described in Example 1, except that the charge mixture consists of 0.722 gm of ruthenium (III) hexafluoroacetylacetonate (1 mmole) in 50 ml of acetic acid. Analysis of the product liquid shows: 5.7% methyl acetate 0.2% ethyl acetate 0.26% ethylene glycol diacetate EXAMPLES In this preparation, CO-hydrogenation is carried out as described in Example 1, except that the charge mixture consists of 0.40 gm of ruthenium (III) acetylacetonate (1 mmole), 0.40 gm of tri -n - butylphosphine, and 50 ml of acetic acid.Analysis of the product liquid shows the presence of significant quantities of methyl acetate, ethyl acetate and ethylene glycol diacetate.

EXAMPLE 6 In this preparation, CO-hydrogenation is carried out as described in Example 1, except that the charge mixture consists of 0.598 gm of triosmium dodecacarbonyl (0.66 mmole) solubilized in 50 ml of acetic acid. Analysis of the product liquid by glc shows the presence of methyl acetate and ethylene glycol diacetate.

EXAMPLES 7 TO 12 In these examples, using the techniques and procedures of Example 1, the effect of varying the operating temperature and pressure upon the yield and distribution of acetic ester products has been examined. The standard catalyst here is ruthenium (III) acetylacetonate (1-2 mmole) solubilized in glacial acetic acid. The results are summarized in Table 1. It is evident from the data that methyl, ethyl and ethylene glycol acetates may each be generated via CO hydrogenation with the solubilized ruthenium catalyst at least over the operating temperature, pressure ranges of 180-260"C and 88.5 to 500 atmospheres (1300-7350 psi).

Maximum Operating Pressure -Concfwt /OJ in Liquid Product Example Temp (0C) (atmospheresipsi) H20 MeOAc EtOAc (CH2OAc)2 7 180 470/6900 0.7 0.7 0.1 0.1 8 220 88.5/1300 0.2 0.7 0.5 0.1 9 220 161.5/2375 1.0 3.4 0.7 0.5 10 220 296/4350 2.5 3.5 0.8 0.4 11 220 463/6800 2.0 15.6 0.8 1.0 12 260 500/7350 5.1 47.7 2.9 0.8 EXAMPLE 13 Following the procedure of Example 1,0.80 gm of ruthenium acetylacetonate (2.0 mmole) is added to a degassed sample of acetic acid (50 ml) set in the 300 glass-lined reactor. The reactor is sealed, flushed with COlH2 and pressurised to 272 atmospheres (4000 psi) with 1:1 synthesis gas. The mixture is then heated to 220"C with agitation, for 18 hrs. and allowed to cool. Gas uptake is 68 atmospheres (1000 psi). Excess gas is vented and a small (1 ml) liquid sampled recovered for analysis. Glc shows the presence of: 12.3% methyl acetate 1.0% ethylene glycol diacetate 0.5% ethyl acetate The remainder of the product liquid is recycled to the 300 ml reactor, repressurised with 1:1 synthesis gas, and CO-hydrogenation effected as described above. The final product after repeated cycling shows the following composition: 44.9% methyl acetate 2.20/0 ethylene glycol diacetate 1.4% ethyl acetate together with unreacted acetic acid and an aqueous by-product. The methyl acetate, ethyl acetate and ethylene glycol diacetate are recovered as overhead fractions via distillation under reduced pressure (0.1-10mm Hg).A bottoms fraction (2 gm) plus crystallized triruthenium dodecacarbonyl (0.2 gm) are recycled to the reactor with fresh acetic acid (50 ml), and conversion of CO/H2 to acetate esters is carried out as described above. Recovered, clear, yellow liquid product (46 ml) shows the presence of: 11.6% methyl acetate 2.2% ethylene glycol diacetate 0.5% ethyl acetate The following Examples 14 and 15 provided for purposes of comparison show that seeming equivalent catalysts, cobalt and rhodium are relatively ineffective for use in the process here.

EXAMPLE 14 (For Comparison) To degassed sample of acetic acid (50 ml) contained in a 300 ml glass-lined reactor equipped for pressurizing, heating and means of agitation is added, under a nitrogen environment, 0.80 gm of rhodium (III) acetylacetonate (1.0 mmole). The reactor is sealed, flushed with CO/H2 and pressurised to 184 atmospheres (2700 psi) with syntheses gas (184 atm, 1:1, CO/H2). The mixture is then heated to 220"C, with agitation, for 18 hr, and then allowed to cool.Excess gas is sampled and vented, the liquid product, analyzed by glc, shows the presence of: 0.5% methyl acetate 1.2% ethyl acetate 0.1% glycol diacetate EXAMPLE 15 (For Comparison) In this preparation, CO-hydrogenation is carried out as described in Example 14, except that the charge mixture consists of 0.34 gm of dicobalt octacarbonyl (1 mmole) and 50 ml of acetic acid.

Analysis of the product liquid (49 ml) by glc shows the presence of: 0.7% methyl acetate 2.7% ethyl acetate 0.1% glycol diacetate EXAMPLE 16 Following the procedure of Example 1,0.40 gm of ruthenium (Ill) acetylacetonate (1.0 mmole) and 50 ml of trifluoroacetic acid are charged to a glass-lined, 450 ml reactor. The reactor is sealed, flushed with CO/H2, pressured to 272 atmospheres (4000 psi) with CO/H2 (1:1) and heated to 2200C overnight. Gas uptake is 95.25 atmospheres (1400 psi).Upon cooling, the green liquid product, containing suspended solids, is recovered and analyzed by glc. Analysis shows this material to consist of: 37% methyl trifluoroacetate 2.3% ethyl trifluoroacetate 2.2% ethylene glycol di (trifluoroacetate) 43.0 /O unreacted trifluoroacetic acid The following Examples 17 to 36 illustrate the embodiment of the invention employing a cocatalyst.

EXAMPLE 17 To an 850ml glass-lined autoclave reactor equipped for pressurizing, heating, cooling and means of agitation is charged 1.04gm of ruthenium chloride, hydrate (4.0 mmole), 12.7gm of tetrabutyl- phosphonium acetate (40 mmole) and acetic acid (50 gm). Upon stirring, all solids dissolve to give a clear, deep-red solution. The reactor is then sealed, flushed with CO/H2 and pressurised to 272 atmospheres (4000 psi) with synthesis gas (a 1:1 mixture of hydrogen and carbon monoxide.) Over a period of 60-75 minutes, the autoclave is heated, with agitation, to 220"C, and held at temperature overnight.

Total gas uptake is 122.5 atmospheres (1800 psi).

After cooling, the excess gases are sampled and vented, and the deep-red liquid product (58 ml) removed for analysis. There is no solid product fraction.

Analyses of this liquid fraction by gas-liquid phase chromatography (glc) shows the presence of: 63.9 wt. % methyl acetate 6.28 wt. % ethylene glycol diacetate 5.9 wt. % ethyl acetate 19.7 wt. % unreacted acetic acid EXAMPLE 18 To a 300 ml glass-lined autoclave equipped for pressurizing, heating and means of agitation is charged 0.52 gm of ruthenium chloride, hydrate (2.0 mmole), 19.08 gm of tetrabutylphosphonium acetate (60 mmole) and cetic acid (25 gm). The mixture is stirred to dissolve solids, the reactor sealed, flushed with CO/H2 and pressurised to 272 atmosphere (4000 psi) with synthesis gas (1:1, CO/H2). Over a period of 60-75 minutes, the autoclave is heated, with agitation, to 2200C and held at temperature overnight.

Total gas uptake is 105.5 atmospheres (1550 psi).

After cooling, the excess gas is vented and the deep-red liquid product (43 ml) removed from the reactor.

Analysis of this liquid fraction by glc shows the presence of: 52.3 wt. % methyl acetate 6.71 wt. % ethylene glycol diacetate 4.2 wt. % ethyl acetate 25.4 wt. % unreacted acetic acid A similar product distribution is achieved using an equivalent amount of ruthenium (IV) dioxide as the catalyst precursor and tetraethylphosphonium acetate of tetramethylphosphonium acetate as the cocatalyst component.

EXAMPLE 19 To the autoclave reactor of Example 17 is charged 1.04 gm of ruthenium chloride hydrate (4.0 mmole), 8.0 gm of cesium acetate and acetic acid (50 gm).

Upon stirring, all solids dissolve to give a clear, deep-red solution. The reactor is then sealed, flushed with CO/H2 and pressurised to 272 atmospheres (4000 psi) with synthesis gas (1:1 H2/CO).

Over a period of 90 minutes, the autoclave is heated, with agitation, to 2200C and held at temperature overnight. Total gas uptake is 68 atmospheres (1000 psi). After cooling, the excess gases are sampled and vented, and the liquid product recovered for analysis. Gas-liquid chromotography shows the pre sence of: 42.0 wt. % methyl acetate 5.7 wt. % ethyl acetate 3.2 wt. % ethylene glycol diacetate 48.4 wt. % unreacted acetic acid.

EXAMPLES 20 TO25 Following the procedure of Example 19, 1.04 gm of ruthenium chloride hydrate (4.0 mmole), acetic acid (50 gm) and various quantities of cesium acetate (0 to 60 mmole) are charged to the glass-lined reactor.

The reactor is sealed, flushed with CO/H2 pressured to 272 atmospheres (4000 psi) with H2/CO (1:1) and heated to 220"C overnight. Upon cooling, the liquid product is recovered and analyzed by glc. Table II summarizes the results. The formation of methyl acetate and ethylene glycol diacetate both appears to be favoured by the addition of cesium salt. Both the ruthenium chloride and cesium acetate salts are readily solubilized in acetic acid, and initial (Cs)/(Ru) ratios of 5 to 15 appearto provide the highest yields of glycol diacetate.

TABLET Cesium Salt CslRu --Cone lwt.o/ol In product Liquid- Example (mmoleJ Ratio H20 MeOAc EtOAc (CK2OAc)2 20 0 0 6.8 19.9 23.1 0.22 21 4 1 1.1 18.4 15.6 0.18 22 12 3 0.4 23.0 3.8 0.86 23 20 5 0.3 38.9 4.2 2.28 24 40 10 0.4 42.0 5.7 3.2 25 60 15 0.5 33.1 5.6 2.66 EXAMPLE 26 To a 450 ml glass-lined autoclave reactor equipped for pressurizing, heating, cooling and means of agitation is charged 0.383 gm of ruthenium oxide, hydrate (2.0 mmole), 4.0 gm of cesium acetate and glacial acetic acid (25 gm). The reactor is then sealed, flushed with CO/H2 and pressured to 272 atmospheres (4000 psi) with synthesis gas (1:1, CO/H2.

Over a period of 90 minutes, the crave is heated, with agitation, to 220"C and held at temperature overnight. Total gas uptake is 54.5 atmospheres (800 psi).

After cooling, the excess gases are sampled and vented, and the brown liquid product (28 gm) containing suspended solids is removed for analysis. The liquid fraction shows the presence of: 7.3 wt. % methyl acetate 2.59 wt. % ethylene glycol diacetate 1.8 wt. % ethyl acetate The vented off-gases typically have the composition: 44% hydrogen 39% carbon monoxide 11% carbon dioxide 3.3 /O methane EXAMPLE 27 Following the procedures of Example 19, 1.04 gm of ruthenium chloride hydrate (4.0 mmole), 3.28 gm of sodium acetate (40 mmole) and 50 gm of acetic acid are charged to a glass-lined reactor.The reactor is flushed with CO/H2 pressurised to 272 atmospheres (4000 psi) with CO/H2 (1:1) and heated to 220"C overnight, gas uptake is 54.5 atmospheres (800 psi). Upon cooling, the liquid product is recovered and analyzed by glc. Data are as follows: 27.8 wt. % methyl acetate 1.8 wt. % ethyl acetate 1.67 wt. % ethylene glycol diacetate EXAMPLE 28 Following the procedures Example 19, 1.04 gm of ruthenium chloride hydrate (4.0 mmole), 2.1 gm of cesium propionate (10 mmole) and 25 ml of prop ionic acid are charged to a glass-lined, 450 ml reactor. The reactor is sealed, flushed with CO/H2, pressured to 272 atmospheres (4000 psi) with CO/H2 (1:1) and heated to 220"C overnight.When cooling, the yellow liquid product is recovered and analyzed by glc as follows: 28.1% methyl propionate 1.30% ethylene glycol dipropionate 0.3% ethyl propionate 64.9% unreacted propionic acid The residual off-gas consists primarily of unreacted carbon monoxide and hydrogen, viz: 47% hydrogen 43% carbon monoxide 7.2% carbon dioxide A similar product distribution is achieved using the equivalent amount of barium propionate as cocatalyst instead of cesium propionate.

EXAMPLE 29 Following the procedure of Example 26,0.763 gm of ruthenium oxide hydrate (4.0 mmole), 12.0 gm of bis (triphenylphosphine) iminium acetate and 50 gm of acetic acid are charged to the glass-lined reactor.

The reactor is flushed with CO/H2, pressured to 272 atmospheres (4000 psi) with CO/H2(1 :1) and heated to 220"C overnight. Upon cooling, the liquid product is recovered and analyzed by glc. Analysis shows the presence of: 26.7 wt.% of methyl acetate 9.5 wt. % of ethyl acetate 7.6 wt. % of water 1.39 wt. % of glycol diacetate Similar methyl, ethyl and glycol acetate yield distributions are achieved using an equivalent quantity of bis (triphenylphospine) iminium nitrate, tetramethylammonium acetate and/or tetrapropylam- monium acetate as the co-catalyst component, instead of bis (triphenylphosphine) iminium acetate.

EXAMPLE 30 Here the procedures, ruthenium catalyst and solvent of Example 17 are employed, butthe reactor is pressured to 4000 psi with a 2:1 mixture of hydrogen and carbon monoxide. After heating to 220"C, with agitation, the cooled liquid product shows the presence of: 29.4 wt. % methyl acetate 11.4 wt. % ethyl acetate 0.9 wt. % ethylene glycol diacetate 5.4 wt. % water 48.3 wt. % unreacted acetic acid EXAMPLE31 Again the procedures, ruthenium catalyst and solvent of Example 17 are employed, but the reactor is pressured to 272 atmospheres (4000 psi) with a 1:2 mixture of hydrogen and carbon monoxide.After heating to 220"C with agitation, the cooled liquid shows the presence of: 33.6 wt.% methyl acetate 1.8 wt. % ethyl acetate 2.60 wt. % ethylene glycol diacetate 47.4 wt. % unreacted acetic acid EXAMPLE 32 To an 850 ml glass-lined autoclave equipped with pressurizing, heating, cooling and means of agitation is charged 1.04 gm of ruthenium chloride hydrate (4.0 mmole), 12.7 gm of tetrabutylphosphonium acetate and glacial acetic acid (50 gm). The reactor is then sealed, flushed with CO/H2 and pressured to 136 atmospheres (2000 psi) with synthesis gas (1:1, CO/H2). Heat is applied to the reactor and contents, the mixture agitated, and when the temperature reaches 220"C, the pressure is raised to 429 atmospheres (6300 psi) with 1:1 synthesis gas.The temperature is maintained at 220"C overnight, the pressure is held in the range 408 to 429 atmospheres (6000 to 6300 psi) by continuous addition of more syngas. Upon cooling, the excess gases are sampled and vented, and the deep-red liquid product (62 gm) is removed for analysis. There is no solid product.

The liquid fraction, analyzed by glc, shows the presence of: 61.9 wt. % methyl acetate 8.2 wt. % ethyl acetate 5.61 wt. % ethylene glycol diacetate 18.3 wt.% unreacted acetic acid EXAMPLE 33 Following the procedure of Example 32, 1.04 gm of ruthenium chloride, hydrate (4.0 mmole), 50 gm of glacial acetic acid and 10.72 gm oftetrabutylphos- phonium acetate, freshly prepared from tri-n-butylphosphine and n-butyl acetate, are charged to an 850 ml glass-lined autoclave. The reactor is sealed, flushed with CO/H2 and pressured to 136 atmospheres (2000 psi) with synthesis gas (1:1, CO/H2).Heat is applied to the reactor and contents, the mixture agitated, and when the temperature reaches 220"C, the pressure is raised to 429 atmospheres (6300 psi) with 1:1 synthesis gas. The temperature is maintained at 220"C overnight, the pressure is held in the range 408 to 429 atmospheres (6000-6300 psi) by continuous addition of more syngas. Upon cooling, the excess gases are sampled and vented, and the deep-red liquid product (62 gm) is recovered for analysis. There is no solid product.

The liquid fraction, analyzed by glc, shows the presence of: 66.8 wt. % ethyl acetate 7.3 wt. % ethyl acetate 6.11 wt. % ethylene glycol diacetate 2.07 wt. % ethylene glycol monoacetate EXAMPLE 34 Following the procedure of Example 30, 1.04 gm of ruthenium chloride hydrate (4.0 mmole), acetic acid (50 gm), together with cesium acetate (40 mmole) and triethylphosphite (12 mmole), are charged to the glass-lined reactor. The reactor is sealed, flushed with CO/H2 pressured to 272 atmospheres (4000 psi) with CO/H2 (1:1) and heated to 220"C overnight.

Upon cooling, the deep-red liquid product is recovered and analyzed by glc as follows: 22.1 wt. % methyl acetate 17.6 wt. % ethyl acetate 2.86 wt. % ethylene glycol diacetate 54.5 wt. % unreacted acetic acid EXAMPLE 35 Following the procedure of Example 19, 1.04 gm of ruthenium chloride hydrate (4.0 mmole), acetic acid (50 gm), together with cesium acetate (40 mmole) and triphenylphosphite (12 mmole) are charged to the glass-lined reactor. The reactor is sealed, flushed with CO/H2, pressured to 272 atmospheres (4000 psi) with CO/H2 (1:1) and heated to 220"C overnight.

Upon cooling, the deep-red liquid product (52 ml) is recovered and analyzed by glc as follows: 26.6 wt. % methyl acetate 16.5 wt. % ethyl acetate 2.55 wt. % ethylene glycol diacetate 50.8 wt.% unreacted glacial acetic acid EXAMPLE 36 Following the procedure of Example 19, 1.04 gm of ruthenium chloride, hydrate (4.0 mmole), acetic acid (50 gm), together with cesium acetate (40 mmole) and triethylamine (4 mmole), are charged to the glass-lined reactor. The reactor is sealed, flushed with CO/H2 (1:1), pressurised to 272 atmospheres (4000 psi) with CO/H2 (1:1) and heated to 2200C overnight. Upon cooling, the deep-red liquid product is recovered and analyzed by glc as follows: 38.1 wt.% methyl acetate 8.1 wt. % ethyl acetate 2.69 wt. % ethylene glycol diacetate 47.6 wt. % unreacted acetic acid

Claims (23)

1. A process for the concurrent synthesis of an alkanol and vicinal glycol esters which comprises heating a reaction mixture of carbon monoxide and hydrogen, (with sufficient carbon monoxide and hydrogen to satisfy the stoichiometry of the desired ester syntheses), a liquid medium containing one or more carboxylic acids and a catalyst containing ruthenium, osmium or a mixture thereof at a temperature between 100"C and 350"C, and a superatmospheric pressure of at least 34 atmospheres (500 psi).

2. A process as claimed in Claim 1 wherein the catalyst is a ruthenium oxide.

3. A process as claimed in Claim 2 wherein the ruthenium oxide is ruthenium (IV) dioxide, ruthenium (IV) dioxide hydrate or ruthenium (VIII) tetraoxide.

4. A process as claimed in Claim 1 wherein the catalyst is the salt of a carboxylic acid.

5. A process as claimed in Claim 4 wherein the salt is ruthenium acetate, ruthenium propionate, ruthernium butyrate, ruthenium trifluoroacetate, ruthenium acetylacetonate or ruthenium hexaf luoroacetylacetonate.

5

6. A process as claimed in Claim 1 wherein the catalyst is the salt of a mineral acid.

7. A process as claimed in Claim 6 wherein the salt is ruthenium chloride hydrate, ruthenium bromide or anhydrous ruthenium chloride.

8. A process as claimed in any preceding Claim wherein the ruthenium containing catalyst also con tains one or more Group VB tertiary donor ligands.

9. A process as claimed in Claim 8 wherein the Group VB tertiary donor ligand is of triphenylphos phine, tri-n-butylphospine, triphenylphosphite, triethylphosphite, trimethylphosphine, triphenylar sine, trimethylamine, triethylamine, tripropylamineS or tr;-n-octylamine.

10. A process as claimed in any preceding Claim wherein the carboxylic acid co-reactant is an aliphatic carboxylic acid having 1 to 12 carbon atoms.

11. A process as claimed in Claim 10 wherein the aliphatic carboxylic acid is acetic acid, propionic acid or butyric acid.

12. A process as claimed in any of Claims 1 to 9 wherein the carboxylic acid co-reactant is a substituted aliphatic carboxylic acid.

13. A process as claimed in Claim 12 wherein the substituted aliphatic carboxylic acid is trifluoroacetic acid, dichloroacetic acid or monofluoroacetic acid.

14. A process as claimed in any preceding Claim wherein the ruthenium catalyst is a residual catalyst from previous syntheses of alcohol and vicinal glycol esters from CO/H2 mixtures.

15. A process as claimed in any preceding Claims wherein the reaction mixture comprises a co-catalyst species selected from alkali metal salts, alkaline earth metal salts, quaternary ammonium salts, iminium salts and quaternary aliphatic phosphonium salts.

16. A process as claimed in Claim 15 wherein the co-catalyst is an alkali metal salt of carboxylic acid.

17. A process as claimed in Claim 16 wherein the co-catalyst is cesium acetate, cesium propionate, cesium butyrate, sodium acetate or cesium trifluoroacetate.

18. A process as claimed in Claim 15 wherein the co-catalyst is a quaternary ammonium or phosphonium salt of a carboxylic acid.

19. A process as claimed in Claim 18 wherein the quaternary ammonium or phosphonium salt is tetramethylammonium acetate, tetrapropylammonium acetate, tetramethylphosphonium acetate or tetrabutylphosphonium acetate.

20. A process as claimed in Claim 15 wherein the co-catalyst is bis (triphenylphosphine) iminium acetate or bis (triphenylphosphine) iminium nitrate.

21. A process as claimed in any of Claims 15 to 20 wherein the reaction mixture comprises 5 to 15 moles of co-catalyst per gram atom of ruthenium or osmium.

22. A process as claimed in Claim 1 and substantially as hereinbefore described with reference to any of the Examples.

23. Esters when synthesized by a process as claimed in any of the preceding claims.