IE44411B1

IE44411B1 - Production of esters

Info

Publication number: IE44411B1
Application number: IE25/77A
Authority: IE
Original assignee: Anic Spa
Priority date: 1976-01-09
Filing date: 1977-01-04
Publication date: 1981-11-18
Also published as: JPS5289613A; NO770038L; IT1063233B; DK6877A; IE44411L; FR2337708B1; NO146495C; DE2700538C3; DE2700538A1; LU76534A1; FR2337708A1; BE850210A; DE2700538B2; GB1563519A; NO146495B; CA1098539A; NL7700042A

Abstract

Case 931 METHOD FOR THE PREPARATION OF ESTERS . . A method is disclosed for preparing esters by reacting an olefin with an acid in the presence of oxygen and a catalyst system, the improvement consisting in that the catalyst system is a compound of tin or cerium, used in the presence of iodine or of a iodine-yielding compound. High productivities are achieved and no pollution problems are to be solved.

Description

This invention relates to a process for producing esters of carboxylic acids, starting from compounds which contain at least one ethylenic centre of unsaturation and which are reacted with the carboxylic acid concerned and with oxygen in the presence of an appropriate catalytic system.

It i s known that esters of carboxylic acids can be produced by reacting olefins with carboxylic acids in the presence of oxygen using a catalytic system. For example, British Patent Specification No. 1,439,234 reTates to the use, for this purpose, of a catalytic system fonned of Ιθ tellurium or selenium coupled with chlorine or bromine. Even though the yield is satisfactory, the elements employed are rather expensive, which has a bearing on the cost of the entire process, and are such as to introduce considerable toxicity problems. In addition, the reaction is limited by the fact that certain conditions, such as temperature and pH, must be adhered to scrupulously.

It is also known to employ in the aforementioned reaction, an alternative catalytic system formed of an Iodide and a transition metal having an atomic number less than 48. This catalytic system, however, does not allow high values of hourly outputs to be attained, unless high working temperatures are adopted, which is a serious handicap when the reaction is regarded from an industrial viewpoint.

According to the present invention, there is provided a process for producing an ester of a carboxylic acid, which comprises reacting a compound containing at least one ethylenic centre of unsaturation with a carboxylic acid and oxygen in the presence of a catalytic system comprising a compound of tin or cerium, in the presence of iodine or a compound capable of liberating iodine during the reaction.

The carboxylic acid employed as a starting material in the process of the present invention can have the formula (1): R1-CO-OH, where R1 is a monovalent radical. The compound containing at least one ethylenic centre of unsaturation, which compound is sometimes hereinafter referred to as an ethylenically unsaturated compound, can have the formula (11):R2-C=C-R5 I i, r3r4 where each of K2.‘ R2. R4 and R5, which are the same or different, is a radical. Preferably, but not necessarily, the ethylenically unsaturated 2 4 5 compound is a monoolefin in which the radicals R .R and R are hydrogen atoms or hydrocarbyl radicals, If one molecule of the carboxylic acid reacts with one molecule of the ethylenically unsaturated compound, the resulting carboxylic acid ester is a monoester having one of the following formulae or a mixture of two monoesters of these formulae:- R1 - CO - 0 H I I H 0 - CO - R1 I 1? 1 1 ς R - C - C - R° I 1 , 1 1 , and r£ _ Q - c - R^ >3 >4 RJ R4 r3 r4 (111) (IV) dependinq on with which carbon atom of the ethylenic double bond the r * ί o 3 4 acid moiety becomes associated; in these two formulae, R‘, R , R , R and r5 are as defined above.

If however, two molecules of the carboxylic acid react with one molecule of the ethylenically unsaturated compound, the resulting carboxylic acid ester is a diester having the following formula: R1 - CO - 0 0 - CO - R12 I I 5 RZ - C - C - R (V) 3 4 5 wherein R , R , R , R and R are as defined above.

With the process of the present invention, it is possible to prepare esters with a high output even at comparatively low temperatures and without encountering problems associated with environmental pollution.

The reaction is not particularly dependent on the operating temperature, although it is preferred to work at temperatures over 80°C and, more particularly, at temperatures in the range from 100°C to 180°C. Similarly the operating pressure does not unduly influence the reaction run, and it is possible to work with pressures near atmospheric pressure; generally the pressure is below 50 atmospheres absolute for practical reasons.

The respective amounts of ethylenically unsaturated compound and oxygen which are caused to react can be selected from within wide ranges, from an excess of the ethylenically unsaturated compound to an excess of oxygen. It is obviously preferred to work in the presence of an excess of oxygen to prevent the formation of explosive mixtures. The quantity of the carboxylic acid is not critical, particularly as the acid may also act as the reaction medium.

The reaction, in fact, can take place in the liquid phase and the medium can be, as outlined above, the carboxylic acid as such; alternatively, the medium could be an inert solvent; the acid can play a role in the reaction in the form of an anion of the metal which belongs to the catalytic system, that is, tin or cerium. This is the case in a batchwise run; generally, however, the reaction takes place in a continuous run, on account of the regeneration of the iodine or the metallic salt by the action of oxygen.

The following Examples illustrate the present invention.

EXAMPLES 1 to 4 A polytetrafluoroethylene-coated stainless steel autoclave, equipped with a magnetic stirrer, was charged with 50 grams of glacial acetic acid, millimole of SnO (135 milligrams) and 6 millimoles of iodine (760 milligrams). A mixture of one of the ethylenically unsaturated compounds specified below and oxygen, in the volume ratio of 1:2.5, was introduced into the autoclave under a pressure of 15 atmospheres absolute. The autoclave was immersed in a thqrmostatic bath at 150°C and stirring was started.

The pressure reached 25 atmospheres absolute and was maintained at this value by allowing for the consumption of the mixture by the introduction of fresh mixture of ethylenically unsaturated compound and oxygen. After 6 hours of reaction, the solution was chromatographically analysed and the yield and selectivity were measured. The results are reported in the following table: Example No. Ethylenically unsaturated compound Diacetate millimoles Monoacetate millimoles Selectivity % 1. Ethylene 65 25 97 2. Propylene 75 20 98 3. But-2-ene 80 15 96 4. Allyl alcohol 60 15 95 The diacetates produced in Examples 1 to 4 had the formula (V) given above, and the monoacetates produced in Examples 1 to 4 were a mixture of monoesters having the formulae (111) and (IV) given above. The five radicals R1 to R5 had the meanings given below in Examples 1 to 4. 44413.

Example 1 R1 r* R3 R4 R5 1 -ch3 - H - H - H - H 2 - CH3 -ck3 - H - H - H 3 -ch3 - ch3 - H - H - CH. 4' -ch3 - ch2oh - H - H - H Selectivity v/as calculated relative t' the ethylenically unsaturated compound which had been consumed, taking into account the sum of the di acetate and monoacetate produced.

EXAMPLES 5 to 8 The procedure was the same as that for Examples 1 to 4 above, except that the operating temperature was 125°C. The selectivity was the same as for the previous cases, whereas the conversion fell by about 20% with respect to the previous values, EXAMPLES 9 to 12 The procedure was the same as that for Examples 1 to 4, but the 50 grams of glacial acetic acid were replaced by 25 grams of acetic acid and 25 grams of acetic anhydride. Mo monoacetate was formed, but the conversion and selectivity did not change appreciably.

EXAMPLES 13 to 15 The procedure was the same as that for Examples 1 to 4, but the 50 grams of glacial acid were replaced by 25 grams of acetic acid and 25 grams of water. Conversion and selectivity did not change, but there was a predominant formation of monoacetates.

EXAMPLES 17 to 20 The procedure was the same as that for Examples 1 to 4, except that the overall working pressure was reduced to 5 atmospheres. No substantial changes in selectivity and conversion were experienced.

Claims

1. A process for producing an ester of a carboxylic acid, which process comprises reacting a compound containing at least one ethylenic centre of unsaturation with a carboxylic acid and oxygen in the presence 5 of a catalytic system comprising a compound of tin or cerium, in the presence of iodine or a compound capable of liberating iodine during the reaction.

2. A process according to Claim 1, wherein the reaction is conducted at a temperature over 80°C. 10

3. A process according to Claim 2, wherein the reaction is carried out at a temperature in the range from 100°C to 180°C.

4. A process accordinq to Claim 1 or 2, wherein the reaction is carried out at a pressure below 50 atmospheres absolute.

5. A process accordinq to any precedinq claim, wherein the reaction 15 is carried out with an excess of oxyqen relative to the compound containinq at least one ethylenic centre of unsaturation.

6. A process accordinq to any precedinq claim, wherein the compound containing at least one ethylenic centre of unsaturation is ethylene, propylene, but-2-ene or allyl alcohol.