Organic compounds -- part of the class 532-570 series – Organic compounds – Carboxylic acid esters
Patent
1997-05-14
1998-06-30
Geist, Gary
Organic compounds -- part of the class 532-570 series
Organic compounds
Carboxylic acid esters
562517, 562519, 562520, C07C 6736, C07C 5112
Patent
active
057736421
DESCRIPTION:
BRIEF SUMMARY
This application claims the benefit of priority under 35 U.S.C. .sctn. 365 to International Application No. PCT/FR95/00625 filed on May 15, 1995.
The present invention concerns a process for the preparation of carboxylic acids or the corresponding esters by carbonylation of an alcohol in the liquid phase in the presence of an iridium based catalyst.
The production of carboxylic acids, more particularly acetic acid, by reacting carbon monoxide with an alcohol such as methanol in the presence of a homogeneous catalyst is a well known process and has formed the subject matter of numerous patents and articles. Examples of catalysts which can be used in this type of reaction are cobalt, rhodium and iridium catalysts.
Only carbonylation processes using rhodium based catalysts have formed the basis of new developments on the industrial scale. The most recent generations of these processes thus use rhodium, large quantities of soluble iodide salts stabilizing that metal and small quantities of water. They perform well and can attain rates for the carbonylation of methanol to acetic acid which are in excess of 10 mol/l.h..
The preparation of carboxylic acids catalysed by cobalt is not currently used in new operations as the reaction conditions are very severe as regards pressure and temperature. Despite these conditions, the results obtained as regards selectivity towards the acid formed are not very satisfactory compared with the imposed constraints.
The results obtained for processes which use iridium based catalysts are poor. Carbonylation rates are of the order of 2 to 4 mol/l.h of acid formed and the number of moles of iridium used in the reaction is very high. Such processes cannot satisfactorily be used on an industrial scale.
European patent EP-A-0 618 184 describes a process for the carbonylation of an alcohol such as methanol in the presence of a catalytic system based on iridium and a halogenated promoter. This process is an improvement over the process described above. It was found that by maintaining a particular composition of the reaction mixture, comprising up to 10% of water, alcohol and halogenated promoter and up to 40% of an ester corresponding to the alcohol and the acid, it was possible to attain carbonylation rates which were in excess of or equal to 10 mol/h.l of acid formed. Such carbonylation rates are comparable with those obtained using carbonylation processes which are catalysed by rhodium.
The aim of the present invention is to provide a process for the preparation of carboxylic acids by a carbonylation reaction with a suitable reactant which does not use a rhodium based catalyst and which has a productivity which is comparable to that obtained using that catalyst.
The invention thus provides a process for the production of carboxylic acids or their corresponding esters containing (n+1) carbon atoms, by reacting carbon monoxide with at least one alcohol containing n carbon atoms in the liquid phase, in the presence of a catalytic system based on an iridium compound and a halogenated promoter. The process of the invention is characterized in that during the reaction, the water content is maintained at a level which is in the range 0 (exclusive limit) to 10%, the halogenated promoter concentration is maintained at a level in the range 0 (exclusive limit) to 10%, the concentration of the ester corresponding to the carboxylic acid and alcohol is maintained at a level which is in the range 2% to 40%, and the concentration of soluble iodides is such that the atomic ratio of iodides to iridium is in the range 0 (exclusive limit) to 10, the carboxylic acid constituting the reaction solvent.
In the description below, unless otherwise indicated, the percentages indicated are expressed as percentages by weight with respect to the total weight of the reaction mixture.
We have surprisingly discovered that the process of the invention, carried out in the presence of an iridium based catalyst under the stable conditions defined above, performs far better than prior art processes which use such a cata
REFERENCES:
patent: 4482497 (1984-11-01), Rizkalla
patent: 4681707 (1987-07-01), Alper et al.
patent: 5144068 (1992-09-01), Smith et al.
patent: 5420345 (1995-05-01), Smith
Denis Philippe
Nobel Dominique
Perron Robert
Perrona Philippe
Schwartz Joel
Acetex Chimie
Geist Gary
Keys Rosalynd
LandOfFree
Process for the preparation of carboxylic acids or the correspon does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Process for the preparation of carboxylic acids or the correspon, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Process for the preparation of carboxylic acids or the correspon will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-1861296