GB1565719A - Process for preparing butanediols - Google Patents

Description

(54) PROCESS FOR PREPARING BUTANEDIOLS (71) We, GENERAL ELECTRIC COMPANY, a corporation organised and existing under the laws of the State of New York, United States of America, of 1 River Road, Schenectady 12305, State of New York, United States of America, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: This invention relates to a process for the production of butanediol or substituted butanediols which comprises contacting an allylic alcohol, carbon monoxide and hydrogen in tbe presence of a rhodium carbonyl catalyst incorporating a triorgano phosphorus modifier bearing at least one alkyl, cycloalkyl, alkylene or cycloalkylene substituent.

It has long been known that allyl alcohol can serve as a substrate for the hydroformylation reaction, affording hydroxy?ldehyde products. Adkins and Krsek (Journal of the American Chemical Society, 70, 383 (1948) and 71, 3051 (1949) reDorted the synthesis of Shydroxybutyraldehyde in 30 O yield by the cobalt carbonyi-catalyzed hydroformylation of allyl alcohol. Brown and Wilkinson (Tetrahedron Letters 1969, (22), 1725-6 and Journal of the Chemical Society (A), 1970, 2753-64) reported hydroformylation of allyl alcohol and a number of other olefins in the presence of hydridocarbonyltris-(triphenylphosphine) rhodium (I) as catalyst, which produced the corresponding aldehydes. Pruett and Smith in U.S. Patent 3,917,661 claim a process for producing oxo aldehydes from olefins using a rhodium carbonyl catalyst system modified by triorgano phosphorus ligands of the group consisting of trialkylphosphites, tricycloalkylphosphites, triarylphosphites and triarylphosphines.

In German Patent 2,538,364, Schimizu describes a process by which allyl alcohol is converted to an aldehyde mixture by hydroformylation in the presence of a rhodium carbonvl catalyst modified by any of a number of triorgano phosphorus ligands, and the aldehydes are separated by aqueous extraction and converted to butanediol in a separate, conventional hydrogenation procedure.

U.S. Patent 3,239,566 of Slaugh et al. discloses the use of phosphine-rhodium carbonyl complex catalysts in oxo reactions producing aldehydes and/or alcohols at temperatures exemplified at 195 C.

Quite unexpectedly, it has been discovered that under the influence of a rhodium carbonyl catalyst modified by a triorganophosphorus ligand itself bearing at least one alkyl, cycloalkyl, alkylene or cycloalkylene substituent, allylic alcohols can be con vertex to butanediol or substituted butanediols in a single stage hydroformylationhydrogenation sequence. In the case of allyl alcohol, the desired 1,4-butanediol product is accompanied by varying amounts of 2-methyl-1,3-propanediol, n-propanol and isobutanol as exemplified in Equation 1.

Intermediate hydroformylation products, including 2-hydroxytetrahydrofuran, 4 hydroxybutyraldehyde, 2-(hydroxymethyl) propionaldehyde, propionaldehyde and isobutyraldehyde are detectable in the product mixture when the process is interrupted before completion.

When methallyl alcohol is used as the substrate, the major product is 2-methyl1,4-butanediol, accompanied by minor proportions of 2,2-dimethyl-1,3-propanediol and isobutanol, as indicated in Equation 2.

The disclosed process can be operated in a manner typical of rhodium carbonylcatalyzed hydroformylation processes, except that a triorganophosphorus co-ligand having at least one alkyl, cycloalkyl, alkylene or cycloalkylene substituent is employed, rather than the triarylphosphine or triorganophosphite co-ligands commonly used. The catalyst may be generated in situ from elemental rhodium, rhodium oxide or rhodium trichloride (optionally introduced on an inert support such as carbon) or from such rhodium carbonyl compounds as hexarhodium hexadecarbonyl [Rh(CO)l,;] on contact with a suitable phosphine derivative, carbon monoxide and hydrogen, or may be added in the form of a hydridocarbonyl rhodium species such as hydridocarbonyltris (tri-n-butyl-phosphine) rhodium (I). Methods known in the art for generating phosphine-modified rhodium carbonyl hydroformylation catalysts may be used within the scope of this invention.

The triorganophosphorus component of the catalyst can be represented by the formulae:

wherein Rl, R2 and R3 are independently C1 to Cz9 alkyl, C1 to CZO alkoxy, Ca to Q cycloalkyl, aryloxy of 6 to 20 carbon atoms, aryl of 6 to 20 carbon atoms, alkaryl of 7 to 20 carbon atoms, aralkyl of 7 to 20 carbon atoms, or mixtures thereof; R4 is independently Cl to C10 alkylene, C3 to C10 cycloalkylene, arylene of 6 to 20 carbon atoms, alkarylene of 7 to 20 carbon atoms or aralkylene of 7 to 20 carbon atoms; provided that at least one of the R groups is alkyl, cycloalkyl, alkylene or cycloalkylene.

Of course, these radicals may have substituents that do not interfere with the catalytic activity.

Examples of agents suitable as the triorganophosphorus component of the catalyst include tri-n-butylphosphine, tri-n-octylphosphine, triethylphosphine, phenyldiethylphosphine, methyldiphenylphosphine, o-methoxyphenyldiethylphosphine, diethylmethoxyphosphine, diethyl-(4-hydroxy-n-butoxy) phosphine, 1,2-di(phenylmethylphosphino) ethylene, 1,4-diphenyl-1,4-diphosphacyclohexane, tricyclohexyiphosphine, diethyl(methoxymethyl) phosphine, and triisobutylphosphine. Preferred triorganophosphorus coligands are tri-n-butylphosphine, tri-n-octylphosphine, triethylphosphine and phenyldiethylphosphine.

The triorganophosphorus complexing agents of the present invention may also be used in admixture with other agents known in the art as modifying ligands for metal carbonyl compounds, especially those that have been used in rhodium carbonylcatalyzed hydroformylation processes. These may include such complexing agents as triphenylphosphine, triphenylphosphite, triphenylarsine, triphenylantimony, trimethylphosphite, tri-n-propylphosphite, tri(4-hydroxybutyl) phosphite, diphenyl sulfide, tri-otolylphosphine and triphenylphosphine oxide.

The allylic alcohols of the present invention include all allylic alcohols, that is, compounds characterized by the basic allylic alcohol structural arrangement: C=C-C-OH Examples of suitable allylic alcohols include allyl alcohol, methallyl alcohol, crotyl alcohol, cinnamyl alcohol, 2-butene-1,4-diol and 3-hydroxycyclohexene.

The disclosed process may be carried out at pressures up to 10,000 psig or even higher, preferably from 100 psig to 5000 psig, most preferably in the range of from 300 psig to 1500 psig. The process may be effected at temperatures ranging from 50"C to 200 C, preferably in the range of from 75"C to 150 C, and most preferably in the range of from 85"C to 130 C.

The temperature and pressure can be varied, even within a given reaction, so as co improve the efficiency of the respective hydroformylation and hydrogenation steps of the conversion from allylic alcohol to butanediol or substituted butanediol. For example, a particular process can be conducted under conditions of relatively low temperature and/or pressure so as to enhance the selectivity of the hydroformylation reaction, and can subsequently (without isolation of intermediates) be operated under conditions of higher temperature and/or pressure so as to enhance the conversion of the initial hydroformylation products to the desired diol products.

The ratio of hydrogen to carbon monoxide employed in the present invention may b varied widely. While mole ratios of hydrogen to carbon monoxide as high as 10, or even higher, and as low as 0.1, and even lower, may be employed, the preferred ratios are in the range of from 1 to 5. A more preferable molar ratio of hydrogen to carbon monoxide is in the range of from 1.5 to 3.

In a preferred embodiment, the ratio of phosphorus in the triorganophosphorus modifier to rhodium in the rhodium carbonyl is from 2: 1 to 16: 1.

A solvent may be employed to advantage in the disclosed process, preferably one which is inert with respect to the starting materials and products. It is also possible to use reaction products as the solvent. A wide variety of solvents such as, for example, aromatic and aliphatic hydrocarbons, esters, ethers, nitriles, alcohols, and halogenated hydrocarbons, including benzene, hexane, toluene, mesitylene, xylene, cyclohexane, ethyl acetate, methyl alcohol, methanol, n-propanol, tetrahydrofuran, chlorobenzene, methylene chloride, acetonitrile, and mixtures thereof may be employed.

The reaction can, if desired, be carried out in the presence of a water-immiscible solvent. In such a case, the butanediol or substituted butanediol products can, it desired, be separated from the catalyst and water-immiscible solvent by aqueous extraction.

The process may be carried out batchwise or on a continuous or semicontinuous basis. Typically in a continuous or semicontinuous process, the allylic alcohol is supplied to a reactor in which the temperature and pressure conditions for reaction are already established. The reactor will also contain the solvent and the catalyst. The diol products can be isolated from the catalyst by aqueous extraction, or by distillation.

The catalyst can be recycled to the reactor in these respective cases in the non-aqueous extraction phase or in the distillation residue. When the starting substrate is allyl alcohol and a hydrocarbon solvent is employed (particularly an aliphatic hydrocarbon), the immiscible butanediol product can be isolated from the solvent and catalyst by direct phase separation, the addition of water not being required.

The following examples are set forth to illustrate more clearly the principle and practice of this invention to those skilled in the art.

EXAMPLE I A 300 cc Autoclave Engineers Magnedrive autoclave was charged with 50.0 grams of allyl alcohol (861 mmol), 65 ml of benzene, 0.20 grams of hexarhodium hexadecacarbonyl (Rh(CO)11; (0.188 mmol, 1.13 meq Rh), and 0.92 grams of tri-n-butylphosphine (4.52 mmol). The mixture was pressurized to 900 psi with 2:1 H2/CO and heated at 125 C for 1.5 hours, with 2:1 gas replenished at 600-900 psi (4750 psi total taken up).

The reaction product mixture was subjected to quantitative glpc (gas-liquid partition chromatography) analysis using n-pentanol as an added internal standard. The presence of 31.6 grams of 1,4-butanediol (41fro (41fro yield), 7.3 grams of 2-methyl-1,3propanediol (9,., yield), 19.7 grams of n-propanol (38% yield), and 4.1 grams of isobutanol (6 " yield) was indicated. The identities were verified by comparison of mass spectra and infrared spectra of the glpc-isolated products with those of authentic samples.

EXAMPLE II The process was carried out as in Example I but with 65 ml hexane as the solvent. In 1.5 hours at 125"C, 4150 psi of 600-900 psi 2:1 H2/CO was taken up.

The product mixture was a somewhat viscous, two-phase liquid. Analysis as in the above example indicated the presence of 31.9 grams of 1,4-butanediol (41). yield), 10.1 grams of 2-methyl-1,3-propanediol (13% yield), 17.2 grams of n-propanol (33% yield) and 3.1 grams of isobutanol (5% yield). Also detected was a 1,4-butanediol precursor designated as 2-hydroxytetrahydrofuran on the basis of its mass spectrum and infrared spectrum (1.1 grams, 1% yield).

EXAMPLE III The autoclave was charged with 0.205 grams of hexarhodium hexadecacarbonyl, 1.84 grams of tri-n-butyl-phosphine and 65 ml of benzene, then pressurized with 1200 psi ot 2:1 Ho/CO and heated to 100"C. After 15 minutes, the mixture was cooled and vented. Then 50.0 grams of allyl alcohol was added and the vessel was repressurized to 1200 psi with 2:1 H2/CO and heated slowly to 709C. An exothermic reaction occurred and was controlled with cooling water. A total of 3350 psi of 2:1 gas was taken up and replenished at 9001200 psi over 30 minutes. Analysis of the mixture at that point showed the presence of 1,4-butanediol and 2-methyl-1,3-propanediol as the major products, along with propanol, propionaldehyde, isobutanol, isobutyraldehyde and the 1,4-butanediol precursor 2-hydroxytetrahydrofuran.

To complete the conversion, the vessel was repressurized with 1200 psi of 2:1 Ho/CO and heated at 125"C for one hour, then cooled and analyzed. The products were 38.4 grams of 1,4-butanediol (50 , yield), 17.7 grams of 2-methyl-1,3-propanediol (23,0, yield), 5.0 grams of n-propanol (1096, yield) and 7.1 grams of isobutanol (11 ; yield). The yield of diol precursors totaled about 1%.

EXAMPLE IV The autoclave was charged with the reagents described in Example I, but with 6.7 grams of tri-n-octylphosphine (18.1 mmol) substituted for the tri-n-butylphosphine.

The mixture was contacted with 1200 psi of 2:1 H2/CO and heated to 85"C. A total of 3800 psi of gas was taken up in 1.5 hours and replenished at 900-1200 psi, affording a mixture of which 1,4butanediol and 2-methyl-1,3-propanediol were the principal hydroformylation product components. Reheating at 100"C under fresh 2:1 H2/CO for another hour completed the conversion, producing a mixture which contained 35.6 grams of 1,4-butanediol (46% yield), 5.8 grams of 2-methyl-1,3-propanediol (7 , yield), 9.0 grams of mpropanol (17 s yield) and 10.7 grams of isobutanol (17% yield).

A small amount of a 1,4-butanediol precursor component designated as 2-hydroxytetrahydrofuran (24 grams, 3-5 % yield) was also detected.

EXAMPLE V The general procedure described in Example I was followed, but-with phenyldiethylphosphine (1.5 grams, 9.0 mmol) used as the modifying ligand. In 30 minutes at 85 C, a total of 2250 psi of 900-1200 psi 2:1 H2/CO was taken up, producing a mixture containing the diol precursors as major components. On heating at 125"C (900-1200 psi) for three hours conversion to the diols was nearly complete. Analysis of the products showed the presence of 38.7 grams of 1,4-butanediol (50% yield), 15.6 grams of 2-methyl-1,3-propanediol (20:'i, yield), 10.8 grams of n-propanol (21 yield), 1.4 grams isobutanol (20,', yield) and 5.0 grams of the 2-hydroxytetrahydrofuran precursor to 1,4-butanediol (7 SO yield).

EXAMPLE VI The reagents and general procedure described in Example I were employed, but with 0.92 grams of tri-n-butylphosphine (4.5 mmol), the reaction temperature maintained at 85--100"C, and the pressure maintained in the 300600 psi range. In one hour under these conditions, a mixture of diols and diol precursors in about 2:1 ratio was produced. The temperature was increased to 125"C and the pressure to the 8001200 psi range. After an additional hour under the latter conditions, conversion to the diols was essentially complete. Analysis showed the presence in the product mixture of 31.1 grams of 1,4-butanediol (40';,, yield), 6.0 grams of 2-methyl-1,3 propanediol (8% yield), 14.3 grams of n-propanol (28"L yield) and 6.8 grams of isobutanol (1136, yield). The residual precursor to 1,4-butanediol (a mixture of 2-hydroxytetrahydrofuran and 4-hydroxybutylraldehyde) totaled about 2 grams (2 / yield).

EXAMPLE VII The general procedure described in Example I was employed, using 100 grams of allyl alcohol, 0.40 grams of hexarhodium hexadecacarbonyl and 1.84 grams of trin-butylphosphine (no added solvent), with the pressure maintained at 600-900 psi with 2:1 H/CO and the temperature maintained at 900C for one hour and at 1250C for the second hour. The products obtained in this case were 42.6 grams of 1,4-butanediol (27 /, yield), 6.6 grams of 2-methyl-1,3-propanediol (4 /O yield), 38.1 grams of n-propanol (37 Y yield) and 15.1 grams of isobutanol (12% yield).

EXAMPLE VIII This example is included to demonstrate that the diol products of the present invention can be separated from the catalyst by aqueous extraction and that the catalyst may be directly recycled to the reaction vessel.

The procedure described in Example I was followed initially. At conclusion of the reaction period, the product mixture was removed from the autoclave and extracted with 100 ml of water. The lower aqueous phase, which was somewhat emulsified, contained, according to glpc analysis, 30.3 grams of 1,4-butanediol (39% yield) and 4.9 grams of 2-methyl-1,3-propanediol (6% yield).

The upper phase was retuned to the autoclave with 50.0 grams of allyl alcohol.

After a second reaction cycle and separation of the diol products as described above, the aqueous phase was found to contain 26.5 grams of 1,4 butanediol (34% yield) and 13.9 grams of 2-methyl-1,3-propanediol (18 i', yield).

EXAMPLE IX The autoclave was charged with 62.2 grams of methallyl alcohol (861 mmol), 0.20 grams of hexarhodium hexadecacarbonyl (0.188 mmol, 1.13 meq Rh), 0.80 grams of 68to, triethylphosphine in isopropanol (0.53 grams of triethylphosphine, 4.5 mmol) and 65 ml of benzene, then pressurized to 1200 psi of 2:1 H2/CO and heated to 1000C. In three hours, a total of 7200 psi of gas was taken up and replenished at 900-1200 psi. Analysis of the products showed the presence of 77.1 grams of 2 methyl-l,4-butanediol (86% yield), 4.5 grams of 2,2-dimethyl-1,3-propanediol (5% yield), 2.5 grams of 3-methyl-4-butyrolactone (3% yield) and 1.1 grams of isobutanol (20/o yield). The identities were verified by comparison of mass spectra and infrared spectra of the isolated products with those of authentic samples.

EXAMPLE X The autoclave was charged with 62.2 grams of crotyl alcohol (861 mmol), 0.202 grams of hexarhodium hexadecacarbonyl (0.188 mmol, 1.13 meq Rh), 1.84 grams of tri-n-butylphosphine (9.09 mmol) and 65 ml benzene. The mixture was heated under replenished 900-1200 psi 2:1 H2/CO for one hour at 1000C and for two hours at 1250C. Analysis of the product mixture showed the presence of 43.0 grams of 2-ethyl-1,3-propanediol (48 yield), 22.8 grams of 2-methyl-1,4-butanediol (25 yield), 7.1 grams of 2-methyl-1-butanol (9% yield), 2.0 grams of n-butanol (3% yield), 0.4 grams of isoamyl alcohol (0.5% yield) and 0.2 grams of 1,5-pentanediol (0.2 /, yield).

EXAMPLE XI On the basis of the results described in Examples I-X, it is foreseen that when cinnamyl alcohol is used as the substrate in the practice of the present invention the products would include 2-phenyl-1,4-butanediol, 2-benzyl-1,3-propanediol and 3-phenyl-1 -butanol.

EXAMPLE XII On the basis of the results described in Examples I-X, it is foreseen that when 2-butene-1,4-diol is used as the substrate in the practice of the present invention, the products would include 2-hydroxymethyl-1,4-butanediol and 2-methyl-1,4-butanedioL EXAMPLE XIII On the basis of the results described in Examples I-X, it is foreseen that when 3-hydroxycyclohexene is used as the substrate in the practice of the present invention, the products would include 3-(hydroxymethyl) cyclohexanol and 2-(hydroxymethyl) cyclohexanol.

COMPARATIVE EXAMPLE This example is included as a demonstration of the unusual tendency of allylic alcohols to undergo conversion to the alcohol (diol) hydroformylation-hydrogenation products under the conditions of the present invention, by comparison of allyl alcohol and allyl acetate as substrates for the process. The applicability of the process described by Slaugh and Mullineaux in U.S. Patent 3,239,566 to allyl acetate as disclosed differentiates that process from the present invention.

The autoclave was charged with 86.3 grams of allyl acetate (861 mmol), 0.21 grams of hexarhodium hexadecacarbonyl (0.197 mmol, 1.18 meq Rh), 0.77 grams of tri-n-butylphosphine (3.8 mmol) and 65 ml of benzene, pressurized to 900 psi with 2:1 H/CO and heated to 1250C. In two hours, a total of 6350 psi of 2:1 gas was taken up and replenished at 600-900 psi. Analysis of the products showed the presence of 36.3 grams of acetic acid (70 CO yield), 30.0 grams of 4-acetoxybutyraldehyde (27% yield), 23.4 grams of n-butyraldehyde (38% yield) and 19.9 grams of isobutyraldehyde (32 '/, yield). None of the hydroformylation hydrogenation product 4-acetoxybutanol was detected.

When the process was carried out as above with 50.0 grams of allyl alcohol substituted for the allyl acetate, the products were 29.6 grams of 1,4-butanediol (38 /e yield), 6.0 grams of 2-methyl-1,3-propanediol (8 yield), 22.2 grams n-propanol (43 % yield) and 4.7 grams of isobutanol (7% yield).

WHAT WE CLAIM IS: 1. A process for the production of butanediol or substituted butanediols which comprises contacung an allylic alcohol, carbon monoxide and hydrogen in the presence of a rhodium carbonyl catalyst incorporating a triorganophosphorus modifier having the formulae:

wherein R1, R2 and R3 are independently C1 to C20 alkyl, C1 to C20 alkoxy, C3 to C,, cycloalkyl, C, to C24 aryloxy, C to C2, aryl, C7 to C,0 alkaryl, C7 to C20 aralkyl, or mixtures thereof; R0 is independently C, to COO alkylene, C3 to C,, cycloalkylene, C, to C20 arylene, C7 to C20 alkarylene, or C7 to C, aralkylene; provided that at least one of the R groups is alkyl, cycloalkyl, alkylene or cycloalkylene.

2. A process as claimed in claim 1 wherein the allylic alcohol is allyl alcohol, methallyl, alcohol, crotyl alcohol, cinnamyl alcohol, 2-butene-1,4-diol or 3-hydroxycyclohexene.

3. A process as claimed in claim 1 or 2 wherein the triorganophosphorus modifier is tri-nbutyl-phosphine, tri-ii-octylphosphine, triethylphosphine or phenyldiethylphosphine.

4. A process as claimed in any preceding claim wherein the ratio of phosphorus in the triorganophosphorus modifier to rhodium in the rhodium carbonyl is from 2:1 to 16:1.

5. A process as claimed in any preceding claim, which process is carried out at a pressure of from 100 to 5000 psig.

6. A process as claimed in any preceding claim, which process is carried out at a temperature of from 50 to 2000C.

7. A process as claimed in any preceding claim, which process is carried out in the presence of a water-immiscible solvent.

8. A process as claimed in claim 7 wherein the butanediol or substituted butanediol products are separated from the catalyst and water-immiscible solvent by aqueous extraction.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (10)

**WARNING** start of CLMS field may overlap end of DESC **. COMPARATIVE EXAMPLE This example is included as a demonstration of the unusual tendency of allylic alcohols to undergo conversion to the alcohol (diol) hydroformylation-hydrogenation products under the conditions of the present invention, by comparison of allyl alcohol and allyl acetate as substrates for the process. The applicability of the process described by Slaugh and Mullineaux in U.S. Patent 3,239,566 to allyl acetate as disclosed differentiates that process from the present invention. The autoclave was charged with 86.3 grams of allyl acetate (861 mmol), 0.21 grams of hexarhodium hexadecacarbonyl (0.197 mmol, 1.18 meq Rh), 0.77 grams of tri-n-butylphosphine (3.8 mmol) and 65 ml of benzene, pressurized to 900 psi with 2:1 H/CO and heated to 1250C. In two hours, a total of 6350 psi of 2:1 gas was taken up and replenished at 600-900 psi. Analysis of the products showed the presence of 36.3 grams of acetic acid (70 CO yield), 30.0 grams of 4-acetoxybutyraldehyde (27% yield), 23.4 grams of n-butyraldehyde (38% yield) and 19.9 grams of isobutyraldehyde (32 '/, yield). None of the hydroformylation hydrogenation product 4-acetoxybutanol was detected. When the process was carried out as above with 50.0 grams of allyl alcohol substituted for the allyl acetate, the products were 29.6 grams of 1,4-butanediol (38 /e yield), 6.0 grams of 2-methyl-1,3-propanediol (8 yield), 22.2 grams n-propanol (43 % yield) and 4.7 grams of isobutanol (7% yield). WHAT WE CLAIM IS:

1. A process for the production of butanediol or substituted butanediols which comprises contacung an allylic alcohol, carbon monoxide and hydrogen in the presence of a rhodium carbonyl catalyst incorporating a triorganophosphorus modifier having the formulae:

wherein R1, R2 and R3 are independently C1 to C20 alkyl, C1 to C20 alkoxy, C3 to C,, cycloalkyl, C, to C24 aryloxy, C to C2, aryl, C7 to C,0 alkaryl, C7 to C20 aralkyl, or mixtures thereof; R0 is independently C, to COO alkylene, C3 to C,, cycloalkylene, C, to C20 arylene, C7 to C20 alkarylene, or C7 to C, aralkylene; provided that at least one of the R groups is alkyl, cycloalkyl, alkylene or cycloalkylene.

2. A process as claimed in claim 1 wherein the allylic alcohol is allyl alcohol, methallyl, alcohol, crotyl alcohol, cinnamyl alcohol, 2-butene-1,4-diol or 3-hydroxycyclohexene.

3. A process as claimed in claim 1 or 2 wherein the triorganophosphorus modifier is tri-nbutyl-phosphine, tri-ii-octylphosphine, triethylphosphine or phenyldiethylphosphine.

4. A process as claimed in any preceding claim wherein the ratio of phosphorus in the triorganophosphorus modifier to rhodium in the rhodium carbonyl is from 2:1 to 16:1.

5. A process as claimed in any preceding claim, which process is carried out at a pressure of from 100 to 5000 psig.

6. A process as claimed in any preceding claim, which process is carried out at a temperature of from 50 to 2000C.

7. A process as claimed in any preceding claim, which process is carried out in the presence of a water-immiscible solvent.

8. A process as claimed in claim 7 wherein the butanediol or substituted butanediol products are separated from the catalyst and water-immiscible solvent by aqueous extraction.

9. A process as claimed in claim 1 and substantially as hereinbefore described

with reference to any of Examples I to XIIL

10. Butanediol or a substituted butanediol when produced by a process as claimed in any of the preceding claims.