Nov. 20, 1951 M. MANCON 2,575,722 PROCESS FOR PRODUCTION OF LOWER ALIPHATIC ESTERS Filed Nov, l, 1948

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INVENTOR. MAurice N1A Ncon. BY A-6-6-6-4 44-g ATTOfFVE4S. Patented Nov. 20, 1951 2,575,722 UNITED STATES PATENT OFFICE 2,575,722 PROCESS FOR PRODUCTION OF LOWER ALPHIATIC ESTERS Maurice Maingon, Wendin le Vieil, France, as signor to Les Usines de Melle (Societe Anon yme), Saint-Leger-les-Melle, France, a corpo ration of France Application November 1, 1948, Serial No. 57,744 In France November 3, 1947 10 Claims. (Cl. 260-488) 1. 2 This invention relates to a process of manu taining a total quantity of ester that is far facture of lower aliphatic esters and particularly greater than that which corresponds to the feed to a continuous process for producing saturated ing with acid and alcohol, and often a quantity and unsaturated lower aliphatic esters. Of alcohol that is likewise considerable. These Several processes for continuous manufacture products, uselessly removed from the bath, are of esters are based on the following principle: returned to it, a procedure which represents, into a bath composed of acid, alcohol, catalyst economically Speaking, a useless expenditure of (generally sulfuric acid), and products of the calories. reaction (esters and water) is fed continuously The principal object of the present invention, an equimolecular mixture of acid and alcohol. 0 accordingly, is to produce an efficient and eco The bath so fed is heated in such a manner that, nomical process for the production of such esters in a given time, the ester and the water, cor and to overcome at least some of the disadvan responding to the input during that time, are tages of the prior processes. eliminated from the bath in the form of vapors. The invention accordingly comprises the novel The vapors emitted by the esterification bath 5 process and steps of processes, specific embodi contain in all cases the four volatile constituents ments of which are described hereinafter by of the bath (alcohol, acid, ester and water), the way of example and in accordance with which composition of the vapors depending upon the I now prefer to practice the invention. relative volatilities of the constituents and upon I have found in accordance with my inven the quantitative composition of the bath. 20 tion that lower aliphatic esters having 2 to 5 In all cases also, in order to keep the compo carbon atoms can be prepared from the corre sition of the bath constant, which is a condition sponding lower aliphatic acid and lower aliphatic of the continuity of the above-described oper alcohol by a process which includes continu ation, one treats the emitted vapors to separate ously feeding the alcohol and acid into a catalytic their constituents; the acid and the alcohol bath in proportion to produce the ester, the bath which they contain are sent back into the bath, containing an esterification catalyst, water in as well as a portion of that one of the products the proportion of at least 50% by weight, and the of the reaction (water or ester) which has been acid and alcohol mentioned. The proportion of found to be extracted in the vapors in a quan alcohol in the bath Should be lower than the tity greater than the quantity produced. Con 30 proportion of acid. The bath is heated to cause sequently, in a given time, one draws from the esterification and ester, alcohol, Water and acid aggregate of the equipment a number of mole are continuously distilled from the bath, the cules of water and of ester that is exactly equal heating being regulated so that the formed ester to that of the molecules of acid and alcohol and water added are substantially entirely vapor introduced during the same time. 35 ized in proportion to their presence in the bath. In the special case of the lower aliphatic I then continuously wash the distillate with a esters, such as methyl, ethyl, propyl, isopropyl, liquid in order to remove acid therefrom Sub and allyl formate, methyl, ethyl, and ispropyl stantially without removing the ester. The acid acetate, and methyl propionate, the vapor ten so removed is then returned to the bath. The sion of the esters and of the alcohols is much 40 Washing may be effected by washing the distillate greater than that of the water; on the other with a small quantity of reflux insufficient to hand the quantity of water that is produced is form an azeotropic mixture of ester and water. relatively greater than with the higher esters The catalytic bath that is initially established (18 grams to 60 grams in the case of methyl comprises essentially water, acid, and alcohol formate; 18 grams to 88 grams in the case of 45 that are to be combined and an esterification ethyl acetate). catalyst, for example sulfuric acid. It is ad It follows therefrom that with the esterifica vantageous to make the alcohol figure in it in tion baths generally used prior to my invention, a proportion lower than that of the acid and, and which are rich in alcohol or in acid, but poor in fact, as small as is possible without unfavor in water, the ratio between the water and the 50 ably affecting the speed of reaction between the ester contained in the vapors emitted by the acid and the alcohol. The most advantageous bath is much lower than the ratio in which they concentrations, in practice, are those of about are formed, and in order to arrive at removing 5 to 20% of alcohol in the bath, concentrations in the form of vapor all the water that is formed, lower than 10% being generally preferable. one must distill a large volume of vapors con 55 For practising the invention, one proceeds 2,575,722 3 4. preferably in the following manner: One heats In the examples which follow one may secure the catalytic bath while at the same time feeding an expression in figures of the relative yields it continuously with acid and alcohol in the rel of all the fluids. ative proportions calculated for the production The accompanying drawing forming part of of the ester that is desired; one regulates the this application shows one form of apparatus in heating so that the ester is vaporized practically which the process of the invention may be car in its entirety in proportion to its formation and ried out. SO that in this way its proportion in the bath The single figure is a diagram of apparatus remains very low; and finally one effects con Suitable for carrying out the process. tinuously an introduction of acid and alcohol 19 . An esterification boiler or kettle comprises a into the bath in order to offset the losses by heating device 2, such as an immersed coil, and evaporation and to maintain the constancy or a pipe for egress of vapors 4, terminating at the quasi-constancy of the proportion of these con lower part of a plate column 3. From the foot stituents in the bath and of the volume of the of the latter there issues a pipe 5 for return of latter. As a general rule, the process is oper s liquid, terminating at the kettle . ated So that the concentration of the ester in Above the column 3 there is mounted a con the bath does not appreciably exceed 5%, Any denser 6 supplied with vapors coming from the water added is also substantially entirely vapor column 3 by way of a pipe ' which has a reg ized by such regulated heating in proportion to ulating cock and which is connected to the pipe its presence in the bath. - 20 for egress of vapors 7; at 8 there is indicated '. To compensate losses by evaporation it is evi a pipe for return passage of condensed liquid. dently advantageous to recover, from the vapors To the pipe there is likewise connected a produced, the total or a portion of one or more pipe 9, equipped with a cock and terminating of the constituents other than the ester and at a separation apparatus 3, of any type (for the water; nevertheless all or a portion of the 25 example, a distillation installation preceded by water may be introduced into the bath as a a decanter), in which the alcohol, ester and substance accompanying the alcohol and/or acid Water are separated from each other. supplied, which are thus introduced in the form A pipe passing from the apparatus 3 to of aqueous solutions. the boiler makes it possible to return to it This recovery of evaporated constituents may 30 the alcohol that is recovered. At and 2 there be effected in any separation apparatus or in are indicated the feed pipes for input of acid stallation of well-known type, and, in many and of alcohol. cases, it may be limited to the alcohol in consider The following are given as examples. The ation of the fact that the acid is, after the water, invention is not to be considered as limited the least volatile constituent of the bath and 35 thereto except as indicated in the appended that, in consequence, the losses of acid by evapo claims. ration are relatively not very considerable. Eacample 1.-Manufacture of methyl acetate Where it is desired to recover the evaporated acid, one subjects the vapors originating from The kettle , of a capacity of 2500 liters, is the bath to a washing by means of liquid pro- : charged with an initial filling comprising: duced by the condensation of previously distilled Water ------800 kgs, or 53% vapors, in a proportion sufficiently great to con Acetic acid------430 kgs., or 29% stitute a barrier with respect to the vapors of Methyl alcohol------255 kgs., or 17% acid, but insufficiently great to permit the forma Sulfuric acid------15 kgS., or 1% tion of the azeotropic mixture of water and ester which would be too rich in ester. Through the pipes if and 2 one introduces, It is thus convenient to effect this washing respectively, 400 kilograms of glacial acetic acid by bubbling the vapors through liquid on the and 25 kilograms of pure methyl alcohol per plates of a column which column is surmounted hour. by a vapor condenser, but the method is not 50 One heats, by means of the coil 2, in such limited to such operation. fashion that a total weight of 965 kilograms of As a variant form, one may use as washing vapors escape from the bath per hour'; these liquid, for example in a plate column or a vapors have the following composition: sprinkling or trickling tower, etc., pure ester Per cent Originating, for example, from the apparatus or Methyl acetate------61. installation for treatment of the vapors, or even Water ------24 water. Methyl alcohol------11 In all cases it is expedient not to promote the Acetic acid------4. formation of the binary mixture of ester and The proportion of methyl acetate in the bath water and not to fall into the faults of the usual 60 is maintained at about 15 kilograms or about 1% proceSSes which, by an excess of refining, bring of the weight of the bath. Into the condenser about excessive expenditures of calories and a 6 One directS 250 kilograms of vapors per hour, diminution of the capacity of the baths. In which are condensed therein, and the correspond accordance with the invention, the proportion ing liquid is conducted back by way of the pipe of Washing liquid is preferably comprised between 65 8 to column 3. In this way, the vapors eScap 0.2 and 0.5 times the weight of the vapors es ing through the pipe 9 have the following com caping from the bath. position: One ascertains that the high hourly produc Per cent. tion of ester, coupled with the considerable re Methyl acetate ------69 duction of the expenditure of calories and with O the diminution of the size of apparatus for Water ------17, . treatment of the vapors (which results by re Methyl alcohol------14. ducing the volume of vapors escaping from the Acetic acid ------0.1. bath) produces an efficient economical process The separator f3 Separates the constituents of which is an object of the invention. s the vapors, the ester passing out through pipe Resease 5 4 and the alcohol passing into pipe fo. The ;By regulation of the valve in pipe. , 650 kilo Separated Water is discarded. grams per hour of vapors passing from the top By way of the pipe 9 one returns into the of ColuErin 3 pass into the condenser 6 and then bath 100 kilograms of recovered methyl alcohol the condensed liquid is returned through pipe 8 per hour. into the column 3. The Vapors passing through By the above amount of feed through pipes the pipe 9 have the following composition: 0, it? and f2, the volume and the composition Of the bath are kept constant and in perfect Per cent equilibrium indefinitely, the production of ester Ethyl acetate------61 Water a sawwaawasses as as was a sa-aw we has renes as an w--- 18 being 500 kilograms per hour, through pipe 4. Acetic acid.------0.8 Eacample 2. Manufacture of ethylformatite Ethyl alcohol.------are as rews.as--- 202 The bath introduced into the kettle is as foll So, i26 kilograms of ethyl alcohol. 96.5% (by OWS: Volume) pass through the pipe 9 per hour and, Water ------a - r - - - 1050 kgs, or 70% 5 after separation at 3 as heretofore, are returned Formic acid------a -a a ra a 330 kgs, or 22% to the kettle by way of pipe O. Under these Ethyl alcohol------105 kgs, or 7% conditions, 420 kilograms of pure ethyl acetate Sulfuric acid.------15 kgs, or 1% are produced per hour. The proportion of ethyl One introduces into this bath, per hour, 470 acetate in the bath is maintained at about 44 kilograms of 80% technical formic acid and 390 O kilograms. kilograms of alcohol of 96.5% (by volumes), cor Eacample 4.-Manufacture of isopropyl acetate responding to 374 kilograms of pure formic acid One Operates with a bath having the following and 374 kilograms of pure ethyl alcohol. equilibrium composition: One distills 1310 kilograms of vapors per hour, the vapors evolving from the bath having the 2. Water ------750 kgs., or 50% following composition: Acetic acid------525 kgs., or 35% Per cent Esopropyl alcohol------165 kgs., or 11% Ethyl formate ------53 Isopropyl acetate------45 kgs, or 3% Water ------305 Sulfuric acid------15 kgs., or 1% Ethyl alcohol------2 3) Oneintroduces into this bath, per hour, while Formic acid.------4.5 heating, 210 kilograms of pure acetic acid Having isolated the condenser 6 by the closing through pipe and, through pipe 2, 180 kilo of the cock of the pipe 7', one returns 300 kilo grams of aqueous isopropyl alcohol containing grams per hour of anhydrous ethyl formate at 35 88% (by weight) isopropyl alcohol, which con the top of the column 3, for example by way of position corresponds to the binary azeotropic a pipe 5 going from the apparatus 3 to the mixture of water and isopropyl alcohol. pipe 8. The proportion of ethyl formate in the One distills 1175 kilograms of vapors per hour, bath is maintained at about 15 kilograms. the vapors evolving from the bath having the In the Vapors escaping through the pipe 9 and following composition: which have the following composition: Per cent Isopropyl acetate------45 Per cent Water ------35 Ethyl formate------59 Acetic acid------12 Ethyl alcohol------5 Isopropyl alcohol------8 Water ------26 : The vapors in pipe 7, which have the following there are 150 kilograms of alcohol per hour, composition: Which, after separation from the other elements Per cent, composing these vapors, separation being effected Isopropyl acetate------59.5 at 3 as heretofore indicated, are returned to the kettle by Way of the pipe 9. In this way 50 Water ------17 one produces 600 kilograms of pure ethyl formate Isopropyl alcohol------22.5 per hour, the composition of the bath remain Acetic acid ------ing constant. are divided into two equal parts, one of which is...directed into the condenser 6 through pipe 7', Eacample 3.-Manufacture of ethyl acetate and the other is passed into the pipe 9. In the The bath introduced into the kettle is as foll Separating device 3, there are separated per lows: hour 350 kgs, of pure isopropyl acetate, 83 kgs. of Water and 4 kgS. of acetic acid, with water Water ------870 kgs, or 58% and acid are discarded, and 150 kgs. of aqueous Acetic acid------540 kgs., or 36% isopropyl alcohol containing 88% isopropyl al Ethyl alcohol------68 kgs, or 4.5% cohol and which return to the kettle via pipe Sulfuric acid------22 kgs, or 1.5% 0. One introduces into this bath 288 kilograms EEG imple 5-Manufacture of allyl formate of 99% acetic acid through pipe and 225 kilo One Operates with a bath having the follow grams of ethyl alcohol of 96.5% (by volume) ing equilibrium composition: through pipe 2 per hour. Water ------930 kgs, or 62% One distills 1300 kilograms of vapors per hour Formic acid------360 kgS., or 24% into column 3, which vapors have the following Allyl alcohol------150 kgs, or 10% composition: Allyl formate------Per cent 30 kgs, or 2% Ethyl acetate ------44 Benzene-Sulfonic acid------30 kgs, or 2% Water ------or r s - - was se - - 30 One heats the bath and one introduces into Acetic acid------0 it, per hour, 340 kilograms of allyl alcohol and Ethyl alcohol------16 75 270 kilograms of formic acid. The vapors which 2,573,722 7. 8 evolve from the bath have the following com the formed ester and water added are substan position: . . . . . is is tially entirely vaporized in proportion to their - Percent presence in the bath, and continuously Washing Water ------88 the distillate with a small quantity of reflux Allyl formate------51 inSufficient to form an azeotropic mixture of Formic acid------5 ester and water in order to remove acid from Allyl alcohol------6 the distillate. One distills per hour 1004 kilograms of Vapors, 3. A process for making lower aliphatic esters of which 300 kilograms are directed into the having 2 to 5 carbon atoms from the correspond condenser 6 through pipe 7', and the remaining ing lower aliphatic acid and lower aliphatic al 704 kilograms are directed into the pipe 9. The cohol, which comprises, continuously feeding said vapours passing through said pipe 9 have the alcohol and acid into a catalytic bath in pro following Composition: . - portion to produce ester, said bath containing . . . . . Fer cent an esterification catalyst, water in the propor 5 tion of at least 50% by weight, and such acid Allyl formate------71 and alcohol, the proportion of alcohol in the Water ------15 bath being lower than the proportion of acid, Allyl alcohol------. 14 heating said hath to cause esterification, con In the separating device f3, there are separated tinuously distilling ester, alcohol, water and acid per hour 500 kgs., of pure ally formate, 104 kgS. 20 from the bath, the heating being regulated so of Water which are discarded and 100 kgs, of that the formed ester and Water added are Sub allyl alcohol which are returned to the kettle. stantially entirely vaporized in proportion to via pipe 0...... their presence in the bath, continuously washing In all of the examples except Example 2 above the distillate with a liquid in order to remove the valve in the pipe 5 is closed during the 25 acid therefrom Substantially without removing carrying out of the process. the ester, and returning the acid so washed out ... Neither the foregoing examples nor the dia to the bath. gram of equipment are intended to be of a limit 4. A process in accordance with claim 1 in ing character. Thus, for example, the column which the content of alcohol in the bath is about 3 and the boiler may be grouped one above 30 5 to 20% by weight. the other in a single piece of apparatus. 5. A process in accordance with claim 1 in What I claim is: . . which the heating is regulated so that the pro 1. A process for making lower aliphatic esters portion of ester in the bath is not substantially having 2 to 5 carbon atoms from the correspond greater than 5% by weight. ing lower aliphatic acid and lower aliphatic 35 6. A process according to claim 3 in which the alcohol, which comprises, continuously feeding liquid employed for washing is a condensate of said alcohol and acid into a catalytic bath in the distillate used in Sufficient amount to re proportion to produce ester, said bath contain move the acid but insufficient to form an azeo ing an esterification catalyst, and Water if the tropic mixture of water and ester. proportion of at least 50% by weight of the bath, 40 7. A process in accordance with claim 3 in and such acid and alcohol, the proportion of which the proportion of Wash liquid is in the alcohol in the bath being lower than the pro range of 0.2 to 0.5 times the weight of the dis portion of acid, heating said bath to cause ester tillate from the bath. ification, continuously distilling ester, alcohol, 8. A process in accordance with claim 1 in water and acid from the bath, the heating being 45 which the acid is acetic acid and the alcohol is regulated so that the formed ester and water methyl alcohol for forning the ester. added are substantially entirely vaporized in 9. A process in accordance with claim 1 in proportion to their presence in the bath, con which the acid is formic acid and the alcohol tinuously washing the distillate with a liquid is ethyl alcohol for forming the ester. substantially without removing ester from the 50 10. A process in accordance with claim 1 in distillate, and regulating said feed of alcohol and which the acid is acetic acid and the alcohol is acid into the bath to compensate for evaporation ethyl alcohol for forming the ester. losses and to maintain substantially constant the composition and volume of the bath. MAURICE MAINCON. 2. A process for making lower aliphatic esters 55 having 2 to 5 carbon atoms from the correspond REFERENCES CITED ing lower aliphatic acid and lower aliphatic al The following references are of record in the cohol, which comprises, continuously feeding-said file of this patent: alcohol and acid into a catalytic bath in pro portion to produce ester, said bath containing an UNITED STATES PATENTS esterification catalyst, water in the proportion Number Name Date of at least 50% by weight, and such acid and 1,260,977 Helbronner ------Mar. 26, 1918 alcohol, the proportion of alcohol in the bath 1,400,849 Backhaus ------Dec. 20, 1921 being lower than the proportion of acid, heating 1770,779 Horsley ------July 15, 1930 said bath to cause esterification, continuously us 2,095,496 Gerg ------Oct. 12, 1937 distilling ester, alcohol, water and acid from 2,147,341 Harrington ------Feb. 14, 1939 the bath, the heating being regulated so that 2,208,770 McKeon ------July 25, 1940