Acetaldehyde production from synthesis gas

Acetaldehyde is prepared by contacting hydrogen and carbon monoxide with a catalyst system comprising an iodide-free ruthenium powder, an iodide-free quaternary phosphonium or ammonium base or salt and a halide-free cobalt-containing compound, such as cobalt(III) acetylacetonate or dicobalt octacarbonyl. Conducting the reaction in a substantially inert solvent such as p-dioxane is preferred.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
This invention relates to an improved process for preparing acetaldehyde 
selectively from hydrogen and carbon monoxide directly. 
2. Description of Other Related Processes in the Field 
Acetaldehyde is a well known chemical, useful in the production of 
materials such as acetic acid, acetic anhydride, n-butanol, 
2-ethylhexanol, peracetic acid, pentaerythritol, pyridines, chloral, 
1,3-butylene glycol and trimethylolpropane. Acetaldehyde has been produced 
conventionally by methods such as the hydration of acetylene or the 
oxidation of ethylene, but such methods have their limitations, 
particularly as to cost and it would be desirable to find a more economic 
method for the preparation of this compound. 
A great number of processes have been described in the art for reacting 
methanol and other C-1 derived chemicals such as formaldehyde and methyl 
acetate with carbon monoxide and hydrogen in the presence of catalyst 
systems to produce a wide variety of compounds. A general disadvantage of 
the art described processes is that they all produce a wide variety of 
by-products such as higher molecular weight alcohols, aldehydes, 
hydrocarbons, carboxylic acids, esters, etc. in addition to the desired 
one. 
U.S. Pat. No. 4,151,208 teaches that acetaldehyde may be selectively 
produced by contacting methanol, hydrogen and carbon monoxide with 
cobalt(II) meso-tetraaromatic porphine and an iodine promoter. 
Other examples for acetaldehyde synthesis from methanol and CO/H.sub.2 are 
seen in U.S. Pat. Nos. 4,239,704; 4,239,705; 4,225,517; 4,201,868; 
4,337,365; 4,306,091 and 4,348,541, J. Molecular Catalysis, Vol. 17 
(1982), 339-347, Organometallics, Vol. 2, No. 12 (1983), 1881, and 
European Pat. Nos. 11042, 37588 and 22735. Most of these catalysts 
involved and use of homogeneous cobalt and/or ruthenium compounds with an 
iodine promoter. 
A palladium catalyst with iodide promoter was disclosed by Halcon in Ger. 
Offen. No. 2,952,517 and U.S. Pat. No. 4,302,611 for acetaldehyde 
synthesis from the reaction of methyl acetate and CO/H.sub.2. 
Furthermore, National Distillers and Chemical Corp. disclosed in U.S. Pat. 
Nos. 4,291,179 and 4,267,384 the conversion of formaldehyde into 
acetaldehyde by the use of rhodium and ruthenium catalysts. 
Processes for making a distribution of two-carbon atom oxygenated 
hydrocarbons such as acetic acid, ethanol and acetaldehyde are well known. 
For example, U.S. Pat. No. 4,014,913 teaches a method for making these 
three latter compounds by continuously reacting synthesis gas (hydrogen 
and carbon monoxide) with a rhodium-manganese catalyst system. A similar 
product distribution results when synthesis gas is reacted over a solid 
catalyst comprising rhodium in combination with molybdenum and/or tungsten 
according to U.S. Pat. No. 4,096,164. A similar technique using a rhodium 
and thorium and/or uranium system is noted in U.S. Pat. No. 4,162,262. 
A homogeneous ruthenium catalyst has been disclosed in Fischer-Tropsch type 
reaction for producing oxygenates directly from synthesis gas. For 
example, in U.S. Pat. Nos. 4,301,253 (Nov. 17, 1981) and 4,333,852 (June 
8, 1982), alkanols are selectively produced as the major product directly 
from synthesis gas under mild conditions, using a homogeneous ruthenium 
catalyst, a halogen or halide promoter, especially elemental iodine, and a 
phosphine oxide compound as solvent. There are related disclosures in J. 
Amer. Chem. Soc. (1981), 103, pp. 6508-6510; J. Amer. Chem. Soc. (1980), 
102, pp. 6855-6857; J.C.S. Chem. Comm. (1980), p. 1098 and J.C.S. Chem. 
Comm. (1980), p. 1101. 
The use of phosphonium salt or base in combination with a homogeneous 
ruthenium catalyst for oxygenates synthesis from synthesis gas directly 
has been disclosed in U.S. Pat. Nos. 4,366,259 (Dec. 28, 1982); 4,362,821 
(Dec. 7, 1982) and 4,332,915 (June 1, 1982) to Texaco Inc. In these cases, 
a homogeneous ruthenium compound is used and alkanols/esters and 
carboxylic acid are the major products. 
The selective synthesis of acetaldehyde by carbon monoxide hydrogenation is 
relatively difficult to achieve due to the instability of acetaldehyde 
under the usual reaction conditions. For example, in Chemistry Letters, 
pp. 131-134, 1982, there is disclosed that a rhodium catalyst supported by 
silica gel and pretreated at certain conditions produced ethanol and 
acetaldehyde with hydrocarbon by-products under the synthesis gas 
conditions. In another example (European patent application EP No. 
45,620), synthesis gas was contacted with Rh-Ag mixtures at 
150.degree.-450.degree./1-700 bar to yield acetaldehyde, ethanol, 
methanol, acetic acid and hydrocarbons. A mixture of ruthenium carbonyl 
and lithium chloride at 200.degree. C. and synthesis gas conditions 
produced methanol, acetaldehyde and ethanol which is disclosed by Fr. 
Demande FR 2,480,743 (National Distillers and Chemical Corp.). In J. of 
Catalysis, (1978), Vol. 54, p. 120, Bhasin, et al. discuss the conversion 
of synthesis gas over supported rhodium and rhodium-iron catalysts. 
Catalysts similar, but not identical, to the ones used herein are employed 
in processes to make ethanol from the homologation of methanol with 
synthesis gas described in U.S. Pat. Nos. 4,371,724; 4,374,285 and 
4,424,384. U.S. Pat. No. 4,433,178 teaches a method for making 
acetaldehyde in good yield from methanol and synthesis gas via contact 
with a ruthenium-cobalt-quaternary onium salt or base. A process similar 
to that of U.S. Pat. No. 4,433,178 is disclosed in U.S. Pat. No. 4,433,176 
except that rhodium is also included in the catalyst system. Finally U.S. 
patent application Ser. No. 344,260 filed on Feb. 1, 1982, also describes 
a process similar to that of U.S. Pat. No. 4,433,178, except that an amine 
is also present in the catalyst system. 
All of the processes described above suffer from one or more disadvantages. 
In many cases, the conversion is low, decomposition of the catalyst to 
insoluble and inactive species is observed and a wide variety of products 
in addition to the desired acetaldehyde are formed with consequent 
separation and disposal problems. There is a major disadvantage when 
iodine is used as part of the various catalyst systems. Iodine is very 
corrosive and, when used in industrial processes, is very difficult to 
dispose of. The catalyst which is the object of this invention comprises a 
ruthenium compound, a quaternary phosphonium or ammonium base or salt and 
a cobalt compound in a commercially attractive iodide-free system. 
SUMMARY OF THE INVENTION 
The invention concerns a process for preparing acetaldehyde. Carbon 
monoxide and hydrogen are contacted with an iodide-free catalyst system 
comprising elemental ruthenium, an iodide-free quaternary phosphonium or 
ammonium base or salt and a halide-free cobalt containing compound. The 
pressure is about 500 psig or greater and the temperature is about 
150.degree. C. or greater. 
Recovery of acetaldehyde from the reaction product can be carried out in 
any conventional or convenient manner such as by distillation, extraction, 
etc.

DETAILED DESCRIPTION OF THE INVENTION 
The catalyst system suitable for the practice of this invention comprises 
an iodide-free ruthenium-containing compound, an iodide-free quaternary 
phosphonium base or salt and a halide-free cobalt compound as exemplified 
by cobalt(III) acetylacetonate or dicobalt octacarbonyl. 
A higher degree of conversion of reactants to the desired acetaldehyde is 
achieved with the above-described catalyst combination. Also, the 
stability of this catalyst system is such that it can be conveniently 
recovered from the reaction mixture and recycled to the process. 
Generally, with regard to the metallic components of the catalyst system it 
will contain from about 15 to about 80 mole percent of the ruthenium 
compound with the balance being halide-free cobalt compound based on the 
total number of moles of the ruthenium compound and the total number of 
moles of the cobalt compound in the system. Preferably, the catalyst 
system will contain about equimolar amounts of the ruthenium and cobalt 
compounds. 
The iodide-free ruthenium compounds useful in this invention include any of 
the ruthenium oxides, such as, for example, ruthenium(IV) dioxide hydrate, 
anhydrous ruthenium(IV) dioxide and ruthenium(VIII) tetraoxide. 
Alternatively, ruthenium may be added as the salt of certain mineral acids, 
as in the case of ruthenium(III) chloride hydrate, ruthenium(III) bromide, 
anhydrous ruthenium(III) chloride and ruthenium nitrate, or as the salt of 
a suitable organic carboxylic acid, for example ruthenium(III) acetate, 
ruthenium(III) propionate, ruthenium butyrate, ruthenium(III) 
trifluoroacetate, ruthenium octanoate, ruthenium(III) trifluoroacetate, 
ruthenium octanoate, ruthenium naphthenate, ruthenium valerate and 
ruthenium(III) acetylacetonate. The ruthenium may also be added to the 
reaction zone as a carbonyl or hydrocarbonyl derivative. Other examples 
include triruthenium dodecacarbonyl, hydrocarbonyls, such as H.sub.2 
Ru.sub.4 (CO).sub.13 and H.sub.4 Ru.sub.4 (CO).sub.12 and substituted 
carbonyl species such as the tricarbonyl ruthenium(II) chloride dimer 
[Ru(CO).sub.3 Cl.sub.2 ].sub.2. 
Although all of these ruthenium compounds would be useful in the production 
of acetaldehyde, the best results in accordance with the present invention 
are obtained only when elemental ruthenium is used as a ruthenium source, 
such as in the form of ruthenium powder of any mesh size. However, a 
second preferred embodiment is the use of ruthenium powder in combination 
with one or more of the iodide-free ruthenium compounds described supra. 
A wide variety of halide-free cobalt compounds are useful in the catalyst 
system of this invention. These halide-free containing compounds may be 
chosen from a wide variety of organic or inorganic compounds, complexes, 
etc., as will be shown and illustrated below. It is only necessary that 
the catalyst precursor actually employed contain said metal in any of its 
ionic states. The actual catalytically active species is then believed to 
comprise cobalt in complex combination with carbon monoxide and hydrogen. 
The halide-free cobalt-containing catalyst precursors may take many 
different forms. For instance, the cobalt may be added to the reaction 
mixture in an oxide form, as in the case of, for example, cobalt(II) 
oxide, (CoO) or cobalt(II,III) oxide (Co.sub.3 O.sub.4). Alternatively, it 
may be added as the salt of a halide-free mineral acid, as in the case of 
cobalt(II) nitrate hydrate [Co(NO.sub.3).sub.2 .multidot.6H.sub.2 O] 
cobalt(II) phosphate, cobalt(II) sulfate, etc., or as the salt of a 
suitable organic carboxylic acid; for example, cobalt(II) formate, 
cobalt(II) acetate, cobalt (II) propionate, cobalt naphthenate, cobalt 
acetylacetonate, etc. The cobalt may also be added to the reaction zone as 
a halide-free carbonyl or hydrocarbonyl derivative. Here, suitable 
examples include dicobalt octacarbonyl, [Co.sub.2 (CO).sub.8 ], cobalt 
hydrocarbonyl [HCo(CO).sub.4 ] and substituted carbonyl species such as 
the triphenylphosphine cobalt tricarbonyl dimer, etc. 
Preferred cobalt-containing compounds include oxides of cobalt, cobalt 
salts of a halide-free mineral acid, cobalt salts or organic carboxylic 
acids and cobalt carbonyl or hydrocarbonyl derivatives. Among these, 
particularly preferred are cobalt acetylacetonate, cobalt(II) acetate, 
cobalt(II) propionate and dicobalt octacarbonyl. 
Quaternary phosphonium and ammonium salts suitable for use in this process 
have the formula: 
##STR1## 
where M is phosphorous or nitrogen, R.sub.1, R.sub.2, R.sub.3 and R.sub.4 
are organic radicals, particularly alkyl, aryl or alkaryl radicals bonded 
to the phosphorous or nitrogen atom, and X is an anionic species other 
than iodide. The organic radicals useful in this instance include these 
alkyl radicals having 1 to 20 carbon atoms in a branched or linear alkyl 
chain. They include, for example, the methyl, ethyl, n-butyl, iso-butyl, 
octyl, 2-ethylhexyl and dodecyl radicals. Tetraoctylphosphonium bromide 
and tetrabutylphosphonium bromide are typical examples presently in 
commercial production. The corresponding quaternary phosphonium and 
ammonium acetate, hydroxides, chloride, nitrates, chromates and 
tetrafluoroborates are also satisfactory in this instance. Also useful are 
the corresponding quaternary ammonium bases and salts of the above series 
of compounds. 
Equally useful are the iodide-free phosphonium and ammonium salts 
containing phosphorus or nitrogen bonded to a mixture of alkyl, aryl and 
alkaryl radicals. Said aryl and alkaryl radicals may each contain 6 to 20 
carbon atoms. The aryl radical is most commonly phenyl. The alkaryl group 
may comprise phenyl substituted with one or more C.sub.1 -C.sub.10 alkyl 
substituents, bonded to the phosphorus or nitrogen atom through the aryl 
function. 
Illustrative examples of suitable iodide-free quaternary phosphonium and 
ammonium bases and salts include tetrabutylphosphonium bromide, 
tetraoctylphosphonium bromide, heptyltriphenylphosphonium bromide, 
tetrabutylphosphonium chloride, tetrabutylphosphonium nitrate, 
tetrabutylphosphonium hydroxide, (n-butyl)triphenylphosphonium bromide, 
(n-dodecyl)triphenylphosphonium bromide, tetrabutylphosphonium 
tetrafluoroborate, tetrabutylphosphonium acetate, tetrabutylammonium 
bromide, tetramethylammonium bromide and trimethyldodecylammonium bromide. 
The preferred iodide-free quaternary salts are generally the 
tetraalkylphosphonium or alkyl-triaryl phosphonium salts containing alkyl 
groups having 3 to 8 carbon atoms, such as butyl, hexyl and octyl and 
where the aryl group is phenyl. Iodide-free tetrabutylphosphonium salts, 
such as tetrabutylphosphonium bromide, constitute a preferred group of 
tetraalkylphosphonium salts for the practice of this invention. 
Preferred iodide-free tetrabutylphosphonium salts or bases include the 
bromide, chloride, acetate salts and hydroxide base. Preferred iodide-free 
alkyl-triaryl phosphonium salts include, for example, 
heptyltriphenylphosphonium bromide, butyltriphenylphosphonium bromide, and 
methyltriphenylphosphonium bromide as well as the corresponding chlorides. 
Generally, in the catalyst system the molar ratio of the ruthenium compound 
to the quaternary phosphonium or ammonium salt or base will range from 
about 1:0.01 to about 1:100 or more, and preferably will be from about 
1:0.5 to about 1:20. 
The quantity of ruthenium compound employed in the instant 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 species and of the cobalt compound which gives the 
desired product in reasonable yield. The reaction proceeds when employing 
as little as about 1.times.10.sup.-6 wt.%, and even lesser amounts of 
ruthenium, together with about 1.times.10.sup.-6 wt.% or less of cobalt, 
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, etc. A 
ruthenium concentration of from about 1.times.10.sup.-5 to about 5 wt.% in 
conjunction with a cobalt concentration of from about 1.times.10.sup.-5 to 
about 5 wt.%, based on the total weight of reaction mixture is generally 
desirable in the practice of this invention. 
A wide variety of substantially inert solvents are useful in the process of 
this invention including hydrocarbon and oxygenated hydrocarbon solvents. 
Suitable oxygenated hydrocarbon solvents are compounds composed only of 
carbon, hydrogen and oxygen and those in which the only oxygen atoms 
present are in ether groups, ester groups, ketone carbonyl groups or 
hydroxyl groups of alcohols. Generally, the oxygenated hydrocarbon will 
contain 3 to 12 carbon atoms, and preferably a maximum of 3 oxygen atoms. 
The solvent must be substantially inert under reaction conditions, it must 
be relatively non-polar and it must be one which has a normal boiling 
point of at least 65.degree. C. at atmospheric pressure. Preferably, the 
solvent will have a boiling point greater than that of acetaldehyde and 
other oxygen-containing reaction products so that recovery of the solvent 
by distillation is facilitated. 
Preferred ester type solvents are the aliphatic and acyclic carboxylic acid 
monoesters as exemplified by butyl acetate, methyl benzoate, isopropyl 
iso-butyrate and propyl propionate as well as dimethyl adipate. Useful 
alcohol-type solvents include monohydric alcohols such as cyclohexanol, 
1-hexanol, 2-hexanol, pentanol, 2-octanol, etc. Suitable ketone-type 
solvents include, for example, cyclic ketones such as cyclohexanone, 
2-methylcyclohexanone, as well as acylic ketones such as 2-pentanone, 
butanone, acetophenone, etc. Ethers which may be utilized as solvents 
include cyclic, acyclic and heterocyclic materials. Preferred ethers are 
the heterocyclic ethers as illustrated by 1,4-dioxane and 1,3-dioxane. 
Other suitable ether solvents include isopropyl propyl ether, diethylene 
glycol dibutyl ether, dibutyl ether, ethyl butyl ether, diphenyl ether, 
heptyl phenyl ether, anisole, tetrahydrofuran, etc. The most useful 
solvents of all of the above groups include the ethers as represented by 
monocyclic, heterocyclic ethers such as 1,4-dioxane or p-dioxane, etc. 
Hydrocarbon non-polar solvents, such as hexane, heptane, decane, dodecane, 
tetradecane, etc. are also suitable solvents for use in this invention. 
In the practice of this invention, it is also possible to add a small 
amount of water to the solvent and still obtain satisfactory results. 
If an inert solvent such as p-dioxane is employed, it is preferred that a 
co-catalyst be employed to help enhance the selectivity to the desired 
acetaldehyde rather than another of the many possible by-products. The 
preferred co-catalysts are one or more rhodium-containing compounds, such 
as rhodium chloride. 
The temperature range which can usefully be employed in these syntheses is 
a variable dependent upon other experimental factors, including the 
pressure, and the concentration and choice of a particular species of 
ruthenium catalyst, cobalt catalyst and quaternary compound utilized among 
other things. The range of operability is from about 150.degree. C. to 
about 350.degree. C. when superatmospheric pressures of syngas (synthesis 
gas) are employed. A narrow range of about 180.degree.-250.degree. C. 
represents the preferred temperature range. 
Superatmospheric pressures of 500 psig or greater lead to substantial 
yields of acetaldehyde by the process of this invention. A preferred 
operating range is from about 2,000 psig to about 100,000 psig, although 
pressures above 10,000 psig also provide useful yields of acetaldehyde. 
The relative amounts of carbon monoxide and hydrogen which may be initially 
present in the syngas mixture can be varied widely. In general, the mole 
ratio of CO to H.sub.2 is in the range from about 20:1 up to about 1:20, 
preferably from about 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, neon and the like, or they may include gases that may, or may not, 
undergo reaction under CO hydrogenation conditions, such as carbon 
dioxide, hydrocarbons such as methane, ethane, propane and the like, 
ethers such as dimethyl ether, methyl ether and diethyl ether, alkanols 
such as methanol and acid esters such as methyl acetate. 
Alcohols and carboxylic acid esters may also be formed while carrying out 
the process of this invention. Most often these derivatives are methanol, 
ethanol, n-propanol, methyl formate, methyl acetate, ethyl acetate, ethyl 
ether, etc. The major by-products of the process such as the higher 
molecular weight alcohols and carboxylic acid esters, are, of course, also 
useful compounds and major articles of commerce. The higher alcohols, the 
carboxylic acid esters and ethers can easily be separated from one another 
by conventional means; e.g., fractional distillation in vacuo. 
The novel process of this invention can be conducted in a batch, 
semi-continuous 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 acetaldehyde product, and after recovery of the aldehyde 
and other products, a fraction rich in ruthenium and cobalt catalyst 
components may then be recycled to the reaction zone, if desired, and 
additional products generated. 
The products have been identified in this work by one or more of the 
following analytical procedures; viz, gas-liquid phase chromatograph 
(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 in weight. All temperatures are in 
degrees centigrade and all pressure in pounds per square inch gauge 
(psig). 
The mole percent selectivities to acetaldehyde, as well as other major 
products of these syntheses, particularly methanol, ethyl acetate and 
acetic acid, have been estimated in this work using the formula: 
##EQU1## 
where 
x=the product of interest; e.g., acetaldehyde, ethanol, methanol, acetic 
acid, methyl acetate or ethyl acetate. 
W.sub.X =the wt.% of the product x in the crude liquid product, as 
determined by GLC. 
Various embodiments of the process of this invention are illustrated in the 
following examples which are not to be considered limitative. 
EXAMPLES 1-11 
These examples illustrate the preparation of acetaldehyde (CH.sub.3 CHO) 
directly from synthesis gas. Each example uses as catalyst precursors 
ruthenium powder, dicobalt octacarbonyl and tetrabutylphosphonium bromide. 
The solvent is p-dioxane. In Examples 5-10, a second ruthenium source; 
namely, ruthenium(IV) oxide, has been included also. Rhodium(III) chloride 
is used in Example 11 as an additional co-catalyst. 
EXAMPLE 1 
A 183 ml glass-lined reactor was charged with ruthenium powder (0.050 g, 
0.5 mmole) tetra-n-butylphosphonium bromide (3.40 g, 10 mmoles) dicobalt 
octacarbonyl (0.34 g, 1 mmole) and p-dioxane (15 ml). The reactor was 
flushed with syngas, sealed and pressured to 1,000 psi with CO/H.sub.2 
=1:2 molar ratio syngas, then heated to 200.degree. C. with agitation. The 
pressure was brought up to 6,300 psi and these conditions maintained for 
17 hours. Then the reactor was allowed to cool and the off-gas sample was 
taken via a gas bomb. The liquid sample was analyzed by gas-liquid 
chromatography and showed: 
Acetaldehyde, %: 3.6 
Ethyl acetate, %: 1.7 
p-Dioxane, %: 94 
The product selectivities are calculated to be 60% for acetaldehyde and 28% 
for ethyl acetate. 
The off-gas showed the composition of: 
CO, %: 52 
H.sub.2, %: 25 
CH.sub.4, %: 0 
CO.sub.2, %: 1.2 
Other examples are summarized in Table I showing the relative product 
selectivities. 
TABLE I 
__________________________________________________________________________ 
Acetaldehyde Production from Co/H.sub.2 Directly 
Produc- 
Ex- p-dioxane tivity 
am- 
Catalysts Solvent, 
Reaction 
Product Selectivity, wt. % (g/mole 
ple 
(mmole used) ml Conditions 
MeOH 
CH.sub.3 CHO 
EtOH 
MeOAc 
EtOAc 
HOAc 
Ru/hr) 
__________________________________________________________________________ 
1 Ru/n-Bu.sub.4 PBr/Co.sub.2 (CO).sub.8 
15 CO/H.sub.2 = 1:2 
0 60 0 0 28 0 .about.100 
(0.5:10:1) 6500 psi 
200.degree. C. 17 hrs 
2 Ru/n-Bu.sub.4 PBr/Co.sub.2 (CO).sub.8 
15 CO/H.sub.2 = 1:1 
0 58 0 0 32 0 66 
(0.5:10:1) 6200 psi 
200.degree. C. 18 hrs 
3 Ru/n-Bu.sub.4 PBr/Co.sub.2 (CO).sub.8 
10 CO/H.sub.2 = 1:2 
0 56 0 8 4 0 14 
(1:10:0.5) 6500 psi 
200.degree. C. 18 hrs 
4 Ru/n-Bu.sub.4 PBr/Co.sub.2 (CO).sub.8 
15 CO/H.sub.2 = 1:1 
0 20 12 16 3 6 190 
(0.5:10:1) 6600 psi 
250.degree. C. 17 hrs 
5 Ru/n-Bu.sub.4 PBr/Co.sub.2 (CO).sub.8 /RuO.sub.2 
20 CO/H.sub.2 = 1:1 
0 5 44 0 16 7 50 
(0.5:10:1:0.5) 6300 psi 
200.degree. C. 18 hrs 
6 Ru/n-Bu.sub.4 PBr/Co.sub.2 (CO).sub.8 /RuO.sub.2 
20 CO/H.sub.2 = 1:1 
33 5 19 17 7 0 110 
(0.5:10:0.5:1.0) 6300 psi 
200.degree. C. 18 hrs 
7 Ru/n-Bu.sub.4 PBr/Co.sub.2 (CO).sub.8 /RuO.sub.2 
15 CO/H.sub.2 = 1:1 
13 11 26 5 7 0 50 
(0.5:10:1.0:0.1) 6300 psi 
200.degree. C. 18 hrs 
8 Ru/n-Bu.sub.4 PBr/Co.sub.2 (CO).sub.8 /RuO.sub.2 
15 CO/H.sub.2 = 1:1 
0 43 10 13 2 0 130 
(0.5:10:1.0:0.05) 8000 psi 
200.degree. C. 17 hrs 
9 Ru/n-Bu.sub.4 PBr/Co.sub.2 (CO).sub.8 /RuO.sub.2 
10 CO/H.sub.2 = 1:2 
38 0 28 9 4 6 45 
(2.0:10:0.5:1.0) 6150-4076 psi 
200.degree. C. 17 hrs 
10 Ru/n-Bu.sub.4 PBr/Co.sub.2 (CO).sub.8 /RuO.sub.2 
5 CO/H.sub.2 = 1:2 
0 0 14 3 40 4 15 
(1.0:10:0.5:0.25) 6300-4075 psi 
200.degree. C. 17 hrs 
11 Ru/n-Bu.sub.4 PBr/Co.sub.2 (CO).sub.8 /RhCl.sub.3 
15 CO/H.sub.2 = 1:1 
72 4 0 0 20 0 500 
(0.5:10:1.0:1.0) 6300 psi 
200.degree. C. 17 hrs 
__________________________________________________________________________ 
Many modifications may be made in the method of this invention by one 
skilled in the art without departing from the spirit and scope of this 
invention which are defined only in the appended claims. For example, the 
reactants, catalysts, promoters and solvents could have their proportions 
and modes of addition changed or the pressure and temperature could be 
altered to optimize the production of acetaldehyde.