Патент USA US2411567код для вставки
2,411,567 Patented Nov. 26, 11946 um'reo smug ' PATENT . _' 2,411,567 oi'rica MANUFACTURE or cannoxrmo ACID ANHYDRIDES James Wotherspoon Fisher, Spondon, near Derby, England, assignor' to British Celanese Limited, London, England, a company oi’ Great Britain . _ Nu Drawing. Application July 13, 1944, Serial No.‘ ' 544,823. In Great Britain August 23, 1943 9 Claims. 1 (01. 260-413) '_ ' Y Y , a2 . boxylic acid; moreover the constant boiling" mix- . ture which ‘it forms with acetic acid should con tain a substantial proportion; for example at ‘ This invention relates to the manufacture of , anhydrides of carboxylic acids. _ In one method of making anhydrides ‘of car- . least 10% and preferably 20% or more, of acetic acid. Examples of suitable azeotroping agents are toluene, ethyl benzene and tetrachlorethyl boxylic acids, which is useful in a great number of instances, the carboxylic acid is caused to re act with acetic anhydride, wherebythe carboxylic acid is dehydrated to its anhydride and the acetic anhydride is hydrated to acetic acid. The usual method of carrying out this reaction is to enee In preparing carboxylic acid anhydrides by the process of the invention a mixture of the car 10 boxylic acid, the azeotroping agent, and acetic anhydride may be heated to boiling in a reaction vessel under a fractionating column which is maintained at- a temperature such that the con anhydride is made by passing acetic anhydride , pass acetic anhydride vapour through the car boxylic acid at a temperature above the boiling point of acetic anhydride. For example stearic vapour through molten stearic acid. _ stant boiling mixture of the azeotroping agent‘ and acetic acid isv distilled oil’ while any acetic‘ V The reaction may be represented for a mono anhydride or carboxylic acid vapour that may _ carboxylic acid by the equation, , also be present is condensed and returned to the reaction vessel. Heating may be continued un til no more acetic acid is evolved, as indicated by B being any suitable organic‘radicle, Thus in‘ 20 a rise in the temperature at the top of the frac 2R.COOH+ (CH3.CO) 20+ . ' . ‘ _ (3.00) 20+2CH3.COOH tionating column. above the boiling point of the theory one molecular proportion of acetic anhy dride should convert two molecular proportions constant boiling mixture. The remainder of the _ azeotroping agent may then be removed, pref [of the carboxylic acid into the corresponding an- , erably by distillation under reduced‘ pressure, hydride. vIn practice this is very far from being _ leaving the carboxylic acid anhydride in the reac so, and it. is found necessary to pass through the 25 ' carboxylic acid an amount of acetic anhydride ‘ many times greater than the theoretical quantity ' . if good yields of the anhydride are to be obtained. ‘tion vessel. The acetic acid and azeotroping agent may subsequently be separated, for ex ample by extracting the acetic acid with water, and the azeotroping agent dried and re-used. 'As an example, when making stearicanhydride The new process i‘s‘of particular value in the the amount of acetic anhydride necessary for a 30 manufacture of the anhydrides of saturated acids ‘ substantially complete conversion of the stearic acid may be as high as ?fty times the theoretical quantity. This is a serious drawback, for even if this acetic anhydride is for the most part re ' covered, its vapourisation requires the expendi ture of a large amount of heat. ' ‘containing six or more carbon atoms in. the acid ' molecule, including both straight chain com pounds such for example as stearic acid, palmiticv 35 acid, and lauricacid, and branched chain com- ‘ . According to the present invention carboxylic} acids are converted into their anhydrides by heating themwith liquid acetic anhydride in the presence of an organic liquid which does not en ter chemically into reaction with the carboxylic acid or its anhydride or ‘with the acetic anhy _ dride, and which forms with acetic acid a con. stant boiling mixture of minimum boiling point, I and as the reaction proceeds removing the acetic 45 acid produced thereby from the reaction zone by distilling it oil as a constant boiling mixture. pounds such for example as 2-ethylhexoic acid. It may however also be used to make the anhy drides of a great number of other carboxylic ‘ acids, including the anhydrides 'oiother'homo logues of acetic acid, e. g. propionic and n-bu tyric anhydridesyanhydrides of aliphatic dibasic ‘acids, e. g. succinic anhydride and ethyl‘suc cinic anhydride, and aromatic acid anhydrides, e. g. benzoic anhydride. ' The invention is illustratedby the following I examples; -, name, 1 By this means it is possible to secure very good .1360 parts by weight of commercial stearic' yields of the carboxylic acid anhydrides using much less- acetic anhydride than has previously 50 acid were dissolved in 1730 parts of toluene (which been required, for example less than 11.5 times - the theoretical quantity. ‘ 4 ~ had been dried by distilling oil water as its con stant-boiling mixture'with toluene) in a reaction vessel ?tted with a fracti'onating ‘column, and The organic liquid (hereinafter referred to as 302 parts 01' 95% acetic anhydride was added‘ to the azeotroping agent) which is used to assist the reaction is preferably a solvent tor the car 55 the solution. The mixture was heated under at 1 . v 3 ,g - - mospheric pressure to v120° C. At this temperature a temperature reaction takes of about"; place, and stearic anhydride and acetic acid are formed. The constant boiling mixture of'acetic acid and‘ » - v 4 s 3. Process for the manufacture of the anhy dride ofa saturated fattynacid containing at least 6 carbon atoms in the acid molecule, which com prises heating the fatty‘ acid with'liquid acetic toluene, boiling at about 105° C., was allowed to distil on, any vapourised acetic anhydride being condensed and returned to‘ the reaction ‘vessel. Towards the end of the reaction the temperature . of the liquid in the reaction vessel began to rise, until when the reaction‘ was substantially com-=1. 10 plete (as indicated by a rise in the temperature _ ‘ at the top of ‘the fractionating column to the‘ boiling point of toluene) it had reached 160° C._ anhydride in the presence of an organic solvent for the fatty acid which'does not enter chemi cally into reactionwith the fatty acid or its an hydride and which forms with acetic acid a con stant boiling mixture of minimum boiling point containing at‘ least 20% of acetic acid, and re- ' moving the acetic acid produced from the reac tion zone as the reaction proceeds by distilling it off as a constant boiling mixture with the or ganic solvent. At this point the fractionating colunm was cut . out and, while the temperature of the liquid was. 15 ‘ 4. Process forv the manufacture of stearic an held at 160° 0., the pressure was steadily reduced -, hydride, which comprises heating stearic acid until substantially all the remaining toluene had ' _with liquid. acetic anhydride in the presence of been removed, a small current of alrbeing passed an organic solvent for stearic acid which does not through the liquid meanwhile. When all the ' enter' chemically into reaction with stearic acid, ' toluene had been removed, there remained in the 20 stearic anhydride or acetic‘ anhydride and which reaction vessel stearic anhydride of purity above forms with acetic acid a'constant boiling mixture 90%. ' of ‘minimum boiling .point, and removing the The distillate,- comprising toluene and aceticv ‘acetic acid producedgby the reaction from the re action zone as the reaction proceeds by distilling acid, was extracted with apsmall quantity of wa ter to remove the acetic acid; the toluene was 25 it off as a constant boiling mixture with the or dried by distilling oi! the ?rst 2-3% of its bulk, ganic solvent. and was then available for re-use. . ' I 5. Process for the manufacture of ethyl-hexoic The anhydrides of lauric acid and palmitic anhydride, which comprises heating ethyl¢hexoic acids- are made in a similar way, employing the- I same molecular proportions of the reactants. Example 2 ’ acid with liquid acetic anhydride in the presence 30 of an'organic solvent for ethyl-hexoic acid which does not enter chemically into reaction with ethyl-hexoic acid, ethyl-hexoic anhydride or ace-1 tic anhydride and which forms with acetic acid ' dissolved in 3700 parts of toluene, and 600 parts a constant boiling mixture of minimum boiling _ of acetic anhydride were added to the solution. 36 point. and removing the acetic acid produced by 1000 parts by weight of 2-ethylhexoic acid were The mixture was heated under a fractionating ., column, as described in Example 1, until ‘the temperature of the liquid reached 150° C. thereaction from the reaction zone as thereac tion proceeds by distilling it off as a constant The : boiling mixture. with the organic solvent. reaction was .then substantially-complete. The 6. Process for the manufacture of lauric an fractionating column was now out out and the 40 hydride, which comprises heating lauric acid with temperature of the liquid allowed to fall to ‘125° liquid acetic anhydride in the presence of anor C., and maintained at. this level while the re ganic solvent for lauric acid which does not enter maining toluene was distilled off under increas- ’ chemically into reaction with lauric acid, lauric , ingly low pressure. When substantially all the ‘ anhydride or acetic anhydride and which forms toluene had been removed, the residue contained 45 with acetic acid-a‘constant boiling mixture of 85-90% of 2'-ethy1hexoic anhydride.’ minimum boiling point, and removing the acetic Having'described my invention, what I- desire acid produced by the reaction from the reaction to secure by Letters Patent is: ' ' zone asthe reaction proceeds by distilling it oil‘ 1. Process for the manufacture of the anhy as a constant boiling‘ mixture ‘with the organic _ dride of a carboxylic acid, which comprises heat 50 solvent. ’ ‘ ing a carboxylic acid with liquid acetic anhydride I '7. Process for. the manufacture of stearic an- - in the presence of an organic liquid which does not enter chemically into reaction with’ the car hydride which comprises heating to boiling a mixture of stearic acid, acetic anhydride and to] uene, and removing the acetic acid produced by - boxylic acid or its anhydride or the ‘acetic an‘ hydride and which forms with acetic acid a con 55 stant boiling mixture of minimum boiling point, » and removing the ‘acetic acid produced by the ing mixture with the toluene.v reaction from‘ the reaction zone-as vthe reaction proceedsby distilling. it off as a constant boiling mixture. . . 60 which does'not enter chemically into reaction anhydride and ‘which forms with acetic acid a 70 the reaction from the reaction zone as the reac tion proceeds by distilling it off‘ as a constant , ‘ boiling mixture. constant boiling mixture with the toluene. 9. Process for the manufacture of lauric an hydride which comprises heating to boiling a mix-~ ture of lauric acid, acetic anhydride and toluene, and removing the acetic acid produced by the re ' with the fatty acid or its anhydride or the acetic id produced by mixture of ethyl-hexoic acid, acetic anhydride and toluene, and removing'the acetic acid pro duced by the reaction from the reaction zone as the reaction‘proceeds by‘ distilling it off as a anhydride in the. presence of an‘organic liquid 65 point, and removing the acetic ‘ 8. Process for the manufacture of‘ethyl-hexoic anhydride which comprises heating to boiling a 2. Process for the manufacture of ‘the anhy dride ‘of a‘ saturated fatty acid containing at least six carbon atoms in the acid molecule, which comprises heating the fatty acid with liquid acetic constant boiling mixture of minimum boiling the reaction from the reaction zone as the_reac tion proceeds by distilling it oil! as a constant boil action from the reaction zone as the reaction proceeds by distilling it of! as a constant boiling mixture with the toluene. ' - JAMES WO'I'HERSPOON FISHER.