"Patentedxjan’. 7,1947 ; vf 3 ‘ ' 2,413,889 _ 3g" "PRODUCTION 2,413,889 or ACRYLIC acn) a . V ’ _ I " Chess'ie E. Itehberg, Glenside', snatched” n.‘ a ,Fisher, Abinz'ton, Pm, assignorsmtoeUnlted . States of-America as represented by‘ the Score-1 , ‘ , ‘.L'tary ‘of Agriculture .} No Drawing; Application November ‘11, 1944, _ : ‘SerialNo. 563,047 scalar. ‘ , (Granted - (01, 260——526)_ > " i ‘ _ ‘a _ , under the act ‘cf-March 3,1883, as ‘f ‘amended April 30, 1928: 370 0. G. 757) ‘ This application made ‘,under the ‘act "of product, methyl Iormate, was then slowly with; March 3,, 1883, as amended by the, act of,April drawn as formed until its production ceased (8 to 10 hours). The excess methyl acrylate was 30, 1928, andthe. invention herein described, if ' ' patented, may, be manufactured and used by or ' then distilled at a pressure of 140 mm., after for theGovernme'nt -oi' the United States oi America for governmental purposes without the payment to us of any royalty thereon. ‘ which the formed acrylic acid was distilled at 56° ‘C. (25 mm.). The yield was 231 g. (80 per ‘ 1 cent of the theoretical based on the formic acid used). Over 91 percent 01' the methyl acrylate saturated acids by‘the acidolysis ofv unsaturated put into the reaction mixture was either recov esters, and particularly to the~production of 10 ered or converted into acrylic acid. acrylic acid by the reaction of an ester of acrylic When acetic acid and unsubstituted methyl This invention relates to the production of un-w acid with, an organicacid other thanthe acid to‘be formed, in particular, with a saturated ali acrylate were reacted in a similar manner, acrylic ' ‘ phatic acid such as formic acid or acetic acid. acid was obtained, although the rate of acid- olysis was slower. ; Y The preparation of dry acrylic acid in high 415 The process is not limited to the speci?c re yields in accordance with the‘ present ‘known agents and conditions given above. Other ‘min methods is di?icultt Hydrolysis of methyl acry eral acid catalysts maybe used instead of the late or ethyl acrylate yields various side products sulfuric acid, and various polymerization inhib in addition to the desired acrylic acid, and the itors may be substituted for the hydroquinone. acrylic acid produced is contaminated with war-y 20 Entraining agents may be used to facilitate the distillation oi’ the various fractions. Various This invention has among its vobjects the prep-, other. acids, such as butyric acid, benzoic acid, aration of dry acrylic'acid' under essentially an‘ boric acid, and lactic acid may be used instead , hydrous conditions in high yields by acidolysis of the formic acid or the acetic acid, and other of esters of acrylic acid with anhydrous organic 25 esters of acrylic acid, particularly alkyl acrylates, acid other than the acrylicv acids prepared; and may be used in place of the ,methy1 acrylate. such other objects as willlbe apparent from the Also, other estersv of higher series may be used, following description and claims.‘v . . 3 such as esters of crotonic acid, to produce cro In accordance with the invention, dry acrylic tonic acid, although preferably, for purposes of ter. ‘ I , , , _. acid is preferably produced by reacting by mix, ing and heating a suitable ester of acrylic acid 30 fractional distillation, the reacting acids and es- . ters should be so selected that the produced by product ester boils at the lowest boiling point, with an anhydrous saturated aliphatic acid in ‘ , the presence of a mineral acid esteriflcation cat alyst and a polymerization'_ inhibitor, and'remov ing the by-product ester, which is produced by replacement of the hydrogen oftthe carboxylic group of the saturated aliphatic acid employed with the acrylic ester group, as the by-product ' the excess reacting ester boils next, and the ,iormed unsaturated acid boils at the highest 35 point. ' , . Either continuous or batch operation may be used, but'it is preferred that the formed by product ester be removed continuously in the "ester is formed. For example, when methyl manner indicated. , ' acrylate and anhydrous formic acid are reacted, the by-product, methylformate, is distilled until 40 Having thus described the invention, what is the reaction'is complete, and‘the‘formed acrylic acid'isthen recti?ed._ " ‘g , ‘ , , ' > The process is exhibited by the following ex ample: . ' r 7 Four moles (184 " "*‘ Example g.)’ of formic ‘acid,’ 12’ moles‘ (1032 g.) of unsubstituted methyl‘ acrylate (an" excess of the-amount required for the reaction), claimed-is: ‘ 1. A process of preparing dry acrylic acid com " prising mixing and heating an ester of acrylic acid with a saturated aliphatic acid under an hydrous conditions in the presence of a mineral - acid ,esteriilcation catalyst and a. polymerization inhibitor, and removing‘ the by-product ester which is produced as it is formed. 2.‘ A process of preparing dry acrylic acid com 30 g. ‘of hydroquinone as a-polymerization 'in prising mixing and heating an alkyl acrylate hibitor, and‘2 ml. of sulfuric acid‘ as a‘catalyst with a saturated aliphatic acid under anhydrous were mixed‘ and re?uxed in a still having a 3 conditions in the presence of a mineral acid es i’oot column and a; variable take-off head; ‘The - terification catalyst, and a polymerization inhib , still was operated wlth‘total reflux until the tem-' itor, and removing the lay-product ester which perature at the still-head fell to 32° C. The by 55 is produced as it is formed. . 9,418,889 ' 4 . 3 . 8. A process otjpreparing-dry acrylic acid c0m-~ erltlv acid esteriiication catalyst and a polymeri-I prising mixlng'and heatingmethylacrylate with ‘ zation inhibitor, removing'the by-product ester a'saturated aliphaticacid under'anhydrous oon-, , which is produced‘as- it is formed, and then frac tionally distilling the reaction mass to separate theexcess alkyl acrylate from the formed acrylic ditions in the presence; or a- mineral lacid es teri?cation catalyst and a polymerisation inhib. itor. and removing the try-product ester which’ is produced as it is tor-med; 6. A process of preparing dry acrylic acid com ‘ prising mixing and heating an excess of methyl acrylate with formic acid under anhydrous con formic acid under anhydrous conditions in the‘ 10 tions in the presence of a mineral acid esteri? cation catalyst and a polymerization inhibitor, presence of a mineral acidv esteri?cation catalyst 4. A process 01' preparing dryacrylic acidicom- ’ prising mixing and'heating-methylacrylate with ' and a polymerization-inhibitor. and removing- the by-product, methyl tormateras it is formed. 5. A process of preparing dry acrylic acidcom prising mixing and heating an excess of an al kyl acrylate having a lower boilingpoint than acrylic acid with a saturated aliphatic acid under anhydrous conditions in the presence of} min- _ removing the by-product, methyl tormate, as it is formed, and then fractlonally distilling the reaction mass to separate the excess methyl acry 15 late from the formed acrylic acid. CHESSIE E. REHBERG. CHARLES H. FISHER.