NZ210406A - Production of carboxylic acids and esters - Google Patents

Description

New Zealand Paient Spedficaiion for Paient Number £10406 NO DRAWINGS Priority Date(s): .3D-"^ Complete Specification Filed:^?:^-Class: co-^mj^p.e.^s 3 0 AW 1987.

Publication Date: P.O. Journal. No: Patents Form No. 5 PATENTS ACT 1953 COMPLETE SPECIFICATION PROCESS FOR THE PRODUCTION OF CARBOXYLIC ACIDS AND/OR ESTERS THEREOF I/W(S?HE BRITISH PETROLEUM COMPANY p.I.e. of Britannic House Moor Lane, London, EC2Y 9BU, a British company do hereby declare the invention for which J^we pray that a Patent may be granted to njc/us, and the method by which it is to be performed, to be particularly described in and by the following statement: - 1 - (followed by page la) 210406 x» JN X) 1 N 1U O EE IL. 0 25 t~ (»— 1 a 2 The present invention relates to a process for the production of carboxylic acids and/or esters thereof from benzylic and aromatic mercaptans.

Because of the long-term potential availability of carbon monoxide, a vast amount o£ research has been directed in recent times towards its utilisation in chemicals syntheses. This concentration of effort has led to commercial processes for the production of acetic acid by the reaction of methanol and carbon monoxide, and to another process whereby acetic anhydride is produced by the reaction of methyl acetate and carbon monoxide.

Many other materials, for example alkyl halides, are reported to react with carbon monoxide but the development of commercial processes based on these reactions is still in che formative stages.

We have now found that benzylic and aromatic mercaptans will react with carbon monoxide and water to produce carboxylic acids and with aqueous alcohols to give carboxylic acid esters in the presence of suitable catalysts.

Accordingly, the present invention provides a process for the production of a carboxylic acid ester of the formula RC00R* and/or a carboxylic acid of the formula RC00H which process comprises reacting at elevated temperature a mercaptan of the formula RSH wherein R is a benzylic or an aromatic moiety with carbon monoxide and at least one compound of the formula R^-OH wherein R^ is either hydrogen or a hydrocarbyl group (and when r' is a hydrocarbyl group water must be present) in the or essence as catalyst of a cobalc carbonvl, Che product comprisine a carboxylic 1 a r 210406 acid when R^OH is water and a carboxylic acid ester when R^-OH is an aqueous alcohol.

In the formula RSH, R may be either a benzylic or an aromatic moiety. The benzylic moiety may be substituted in the benzene 5 nucleus portion thereof by, for example hydrocarbyl groups such as alkyl groups, or by functional groups, such as for example halide or alkoxy groups. The aromatic moiety may be phenyl or naphthyl and may be substituted by for example a hydroxyl group or hydroxyl groups. Examples of suitable mercaptans of formula RSH which may be 10 used in the process of the invention include p-methylbenzyl thiol, o-methylbenzyl thiol, p-methoxybenzyl thiol, p-chlorobenzyl thiol, 2,4-dichlorobenzyl thiol, thiophenol, m-thiocresol and 2-naphthalene thiol.

Carbon monoxide may be obtained from a wide variety of 15 carbonaceous sources using well-established conversion technology. The carbon monoxide may be pure or may contain such impurities as carbon dioxide, nitrogen or hydrogen. The carbon monoxide pressure may suitably be the autogenous pressure at the reaction temperature employed. Alternatively, carbon monoxide pressures In excess of the 20 autogenous pressure, for example from 2 to 250 psig above the autogenous pressure, may suitably be employed.

As regards the compound(s) of formula Rl-OH, there may be employed either water or an aqueous alcohol. Using water alone the product is a carboxylic acid. Using aqueous alcohols the product 25 comprises carboxylic acid esters, generally free from carboxylic acids when the amount of water present is in the range from 5 to 12% by volume of the mixture. The presence of water is essential for the production of carboxylic acid esters. If water is omitted, hydrocarbons are formed in preference to esters, which reaction is 30 the subject of published Euro-application No. 16 7 2 6 1 . Clearly, it is possible Co produce mixtures of carboxylic acids and carboxylic acid esters, for example when Che proportion of water in the aqueous alcohol exceeds 122 by volume of the mixture.

The alcohol of formula R^OH may be a monohydric, dihydric or N~\V7 •' • : 25FFBI9S7 Z 104G& polyhydric alcohol. Thus R* may suitably be alkyl or hydroxyalkyl and nay be straight-chain or branched-chain. Alternatively, Rl may suitably be a cycloaliphatic or a cycloaromatic group. Examples of alcohols which may be used in the process of the invention include 5 methanol, ethanol, propanols, butanols, pentanols, hexanols, for example 2-ethyl hexanol, and 1,4-butane diol. The amount of alcohol ^ employed may suitably be at least the stoichiometric amount required to react with the mercaptan. It is preferred however, to employ a substantial excess of alcohol over the stoichiometric amount, the 10 alcohol then performing the dual role of reactant and diluent for the reaction.

The catalyst is a cobalt carbonyl. This may be added as such or may be formed under the reaction conditions either during the reaction or in a separate preparative step in the absence of 15 reactants. Thus, there may be added cobalt metal, suitably in finely divided form, or a cobalt compound, for example a soluble salt such as the nitrate, chloride or acetate. The cobalt carbonyl may suitably be added in an amount from 0.1 to 50% by weight of cobalt, based on the total weight of mercaptan employed. 20 A supplemental diluent may be employed if so desired. Suitable diluents include oxygenated hydrocarbons such as tetrahydrofuran.

The elevated temperature may suitably be in the range from 100 to 300°C, preferably from 150 to 250°C.

The process of the invention may be operated batchwise or 25 continuously, preferably continuously.

The invention will now be further illustrated by reference to the following Examples.

Example 1 To ethanol (30 ml) was added water (2 ml), p-methylbenzyl thiol 30 (10 mmol) and dicobalt octacarbonyl (0.5 mmol). The mixture was heated to 185-190°C at 850-900 psi carbon monoxide pressure for 24 v hours, after which the reaction mixture was filtered and the filtrate concentrated. The product was purified by silica gel chromatography and distillation. ec. £10406 4 Example 2 The procedure of Example 1 was repeated except that methanol was used in place of ethanol.

Example 3 The procedure of Example 1 was repeated except that isopropanol was used In place of ethanol.

Example 4 The procedure of Example 1 was repeated except that t-butanol was used In place of ethanol.

Example 5 The procedure of Example 1 was repeated except that o-methyl-benzyl thiol was used In place of p-methylbenzyl thiol.

Example 6 The procedure of Example 1 was repeated except that p-methoxybenzyl thiol was used in place of p-methylbenzyl thiol. Example 7 The procedure of Example 1 was repeated except that p-chlorobenzyl thiol was used in place of p-methylbenzyl thiol. Example 8 The procedure of Example 1 was repeated except that 2,4-dichlorobenzyl thiol was used in place of p-methylbenzyl thiol. Example 9 The procedure of Example 1 was repeated except that thiophenol was used in place of p-methylbenzyl thiol.

Example 10 The procedure of Example 1 was repeated except that nr-thiocresol was used in place of p-methylbenzyl thiol.

Example 11 The procedure of Example 1 was repeated except that 2-naphthalene thiol was used in place of p-methylbenzyl thiol. The results of Examples 1 to 11 are given in Table 1. 2040k 40 TABLE 1 THE PRODUCTION OF CARBOXYLIC ACID ESTERS Example Mercaptan Alcohol* Product Yield (*) 1 P-CH3C6H4CH2SH A p-CH3C6H4CH2C00C2H5 75 2 M B p-CH3 C5H4CH2COOCH3 83 3 C p-CH3C6H4CH2C00i-C3H7 34 4 D p-CH3C6H4CH2C00t-C4H9 28 O-CH3C6H4CH2SH A 0-CH3C6H4CH2COOC2H5 51 6 P-CH3OC5H4CH2SH A P-CH3OC6H4CH2COOC2H5 68 7 P-CIC5H4CH2SH A P-CIC6H4CH2COOC2H5 67 8 2,4-Cl2C6H3CH2SH A 2,4-Cl2C6H3CH2COOC2H5 9 Thiophenol A Ethyl benzoate 82 m-Thiocre8ol A Ethyl m-toluate 47 11 2-Naphthalenethiol A 2-C16B7COOC2H5 50 * A - C2H5OH B - CH3OH C - i-C3H7OH D - t^HgOH Example 12 To water (30 ml) was added p-methylbenzyl thiol (10 mmol) and dicobalt octacarbonyl (0.5 mmol). The mixture was heated to 185-190°C at 850-900 psl carbon monoxide pressure for 24 hours, after which the reaction mixture was filtered and the filtrate concentrated. The product was purified by silica gel chromatography and distillation.

Example 13 The procedure of Example 12 was repeated except that p—methoxybenzyl thiol was used in place of p—methylbenzyl thiol. Example 14 The procedure of Example 12 was repeated except that p-chlorobenzyl thiol was used in place of p-methylbenzyl thiol. Example 15 The procedure of Example 12 was repeated except that o-methylbenzyl thiol was used in place of p-methylbenzyl thiol.

H0406 6 Example 16 The procedure of Example 12 was repeated except that thlophenol was used In place of p-methylbenzyl thiol.

Example 17 The procedure of Example 12 was repeated except that m-methylbenzyl thiol was used in place of p-methylbenzyl thiol. Example 18 The procedure of Example 12 was repeated except that 2-naphthalenethiol was used in place of p-methylbenzyl thiol.

The results of Examples 12 to 18 are given in the following Table 2.

TABLE 2 THE PRODUCTION OF CARBOXYLIC ACIDS Example Mercaptan RSH Product Yield (%) 12 R-P-CH3C6H4CH2 RCOOH 13 R-P-CH3OC6H4CH2 RCOOH 28 14 R-p-ClC6H4CH2 RCOOH 72 R-0-CH3C6H4CH2 RCOOH 16 16 R-Ph RCOOH 42 17 R-m-C6H4CH2 RCOOH 81 18 R-2-naphthyl RCOOH 59 J2t040e

Claims (8)

WHAT WE CLAIM IS:

1. A process for che production of a carboxylic acid escer of the formula RCOOR' and/or a carboxylic acid of Che formula RCOOH which process comprises reacting at elevated temperature a mercaptan of the formula RSH wherein R is a benzylic or an aromatic moiety with carbon monoxide and at lease one compound of the formula r'oh wherein R^ is either hydrogen or a hydrocarbyl group (and when r' is a hydrocarbyl group water must be present) in che presence as catalyst of a cobalt carbonyl, che product comprising a carboxylic acid when r'oh is water and a carboxylic acid ester when r'oh is aqueous alcohol.

2. A process according to claim 1 wherein a mercaptan of che formula RSH is reacted with carbon monoxide and an aqueous alcohol to produce a carboxylic acid escer.

3. A process according Co claim 2 wherein the amounc of water presenc is in the range from 5 to 12% by volume of the aqueous alcohol inixCure.

A process according Co either claim 2 or claim 3 wherein the amount of alcohol employed is ac lease che sCoichiomeCric amounc required Co react wich Che mercapcan.

5. A process according Co claim 1 wherein a mercapcan of che formula RSH is reacced wich carbon monoxide and wacer Co produce a carboxylic acid.

6. A process according to any one of Che preceding claims wherein che e levated cemperacure is in che range from 100 Co

7. A process according Co claim 6 wherein Che cemperacure is in che range from 150 Co 250°C. 3 00 0 C.

8. A process according Co any one of che preceding claims wherein a supplemencal diluenc is employed. / LAND WEST-WALKER, McCABE 25FEB1987 ATTORNEYS FOR THE"APPLICANT PAT :i JT OFFICE