Patented Feb. 10, 1953
`
`2,628,249
`
`STATES PTENT v@FFICIE
`
`2,628,249
`ESTERIFICATION PROCESS
`Anthony J. Bruno, Jr., Pittsburgh, Pa., assignor
`to Pittsburgh Coke & Chemical Company, Pitts
`burgh, Pa., a corporation of Pennsylvania
`No Drawing. Application January 3, 1951,
`Serial No. 204,285
`(Cl. 260-475)
`12 Claims.
`
`10
`
`2
`(3) The provision of new esteri?cation catalysts
`which increase the speed of reaction to such an
`extent that the tendency to produce color-form
`ing bodies is greatly reduced.
`Still further objects and the entire scope of
`applicability of the present invention will be
`come apparent from the detailed description
`given hereinafter; it should be understood, how
`ever, that the detailed description and speci?c
`examples, while indicating preferred embodi
`ments of the invention, are given by way of illus
`tration only, since various changes and modi?ca
`tions Within the spirit and scope of the invention
`will become apparent to those skilled in the art
`1 from this ‘detailed description.
`GENERAL DESCRIPTION
`These objects are accomplished according to
`the present invention by the production of esters
`through the condensation of a carboxylic acid
`with an alcohol in liquid phase contact with a
`catalyst comprising a mixture of (1) a sulfur
`containing acid from the group consisting of sul
`furic and sulfonic acids, and (2) activated carbon.
`Sufficient of the catalytic mixture is used to have
`a catalytic effect upon the condensation of the
`alcohol and the acid.
`‘
`The success of the present invention is due pri
`marily to the unique discovery that a mixture of
`activated carbon with sulfuric acid or an aryl
`sulfonic acid can serve as a catalyst in esteri?ca
`tlon procedures and that, when this catalytic
`mixture is employed, the resulting esters possess
`unpredictably high degrees of purity and lack
`of discoloration and are obtained in surprisingly
`This is in contrast to the results
`‘ high yields.
`obtained when the aryl sulfonic acids, sulfuric
`acid, or activated carbon per se are used as
`esteri?cation catalysts which, in the case of the
`acids, result in the formation of discolored esters
`and which generally require longer periods of
`time for completion.
`
`1
`This invention relates to new improvements in
`esteri?cation processes and is particularly con
`cerned with the production of discoloration-free
`esters of high molecular weight and low vapor
`pressure from the corresponding alcohol and acid.
`FIELD OF‘ INVENTION
`Large quantities of esters are consumed each
`year as plasticizers in the formation of plastic
`compositions, coating compositions, ?lms, ?la
`ments, and the like. One of the prime considera
`tions given to any ester for use in such manner
`re the purity of the product, i. e., the lack of con
`taminating materials giving the product unde-_
`sirable color characteristics or acidic or similar
`properties, which may cause the ester or- the ma
`terials with which they are mixed to be unstable
`or cause the products to be unusable for many
`purposes. Accordingly, an extensive amount of
`work has been carried out in an e?ort to devise
`improvements in the existing procedures for ester
`production, so as to produce products having the
`highest possible degree of purity and freedom
`from discoloration.
`.
`In this regard, it has been known that certain
`materials, such as mineral acids, sulfonic acids,
`ion exchange resins, or the like, can be used as
`catalysts in esterifications. However, such mate
`rials, as the ion exchange resins, are costly and
`difficulty of recovery from the reaction mixture
`and bulkiness make them generally unattractive.
`On the other hand, the mineral acids and aryl
`sulfonic acids possess the disadvantage that they.
`discolor the resulting esters. Although the such
`discolored ester can be rendered colorfree, the
`treatments required are most involved and quite
`costly. Consequently, the trade has been at
`tempting for some time to ?nd new and better
`esteri?cation catalysts and methods which do not
`possess the detracting disadvantages referred to.
`OBJECTS
`A principal object of this invention is the pro
`EXAMPLES
`vision of new improvements in esteri?cation pro
`cedures, particularly, the methods used to form
`.A more complete understanding of the pro
`high molecular weight esters. Further objects
`cedures of this invention may be had by refer
`ence to the following illustrative examples of
`include:
`1
`actual operations in accordance with the inven
`(1) The provision of new methods for forming
`plasticizer-type esters in very high yields, which
`tion, wherein all parts are by weight.
`are substantially free of discoloration and which
`Example I
`possess an extremely high degree of purity.
`5%)
`This example illustrates the preparation of
`(2) The provision of new catalysts for use in
`dibutyl phthalate.
`esteri?cation reactions which may be employed
`200 parts of phthalic anhydride, 200 parts of
`in place of prior known csteri?cation catalysts
`without causing discoloration of desired products,v
`butyl alcohol, one part of 95% sulfuric acid and
`C)! in
`- 2.5 parts of activated carbon are charged into a
`
`20
`
`2:
`
`30
`
`4-3
`
`_
`
`.
`
`and, ,
`
`.
`
`Petitioners' Exhibit 1013, Page 1 of 4
`
`

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`2,628,249
`
`suitable reaction vessel ?tted with a re?ux con
`denser, a re?ux water separator, and an efficient
`stirrer. With the contents of the vessel thor
`oughly agitated, they are heated up to a con
`trolled re?ux temperature of 145° to 150° C. and
`retained there for ?ve hours. During this period,
`water of reaction is removed and 90 parts of butyl
`alcohol are added in 10 part portions to compen
`sate for loss of alcohol dissolved in the removed
`water.
`At the end of ?ve hours, the reflux condenser
`is shut oil‘ and the excess alcohol is allowed to
`distill off from the reaction vessel. The dibutyl
`phthalate contained in the reaction vessel iswith
`drawn and passed to a mixing vessel where su?i
`cient caustic soda is added to just neutralize the
`tree mineral acid. The ester is then washed'with
`an excess of water, after which it is passed
`through ?lters and collected. It is then blown
`with steam to insure complete removal of vola
`tiles, dried and ?ltered.
`35a parts of dibutyl phthalate having the fol
`lowing speci?cations are obtained:
`
`10
`
`20
`
`Percent ester _________________ _._' ____ __ 99.5%
`Percent acid (as phthalic acid) ______ __~_ 0.003%
`Color API-IA scale ___________________ __ 10 to 15
`Speci?c gravity 20°/20° ___________ __'__'_ 1.0474
`Percent water ______________________ __ 0.05
`Refractive index nD25 ________________ __ 1.4910
`Example II
`The reaction of Example I is carried out in an
`identical manner, except that 50 parts of benzene
`are added to the reaction mixture as an- azeotropic
`agent in order to eiiect a controlled temperature
`of 145° to 150° C. and obtain an efficient separa
`tion of water. The resulting product has the
`same speci?cations as the product of Examplel.
`Example III
`The reaction of Example I is carried out in an
`identical manner, except that the activated car
`bon is omitted. The resulting ester has an APHA
`color of about 200.
`-
`
`DETAILED DESCRIPTION
`One of the important reactants for use in
`these new procedures is activated carbon which
`may be derived from a number of di?erent
`sources. The exact form in which the activated
`carbon is used in the reaction is not critical, but
`most effective results are obtained when the car
`bon is used in an extremely ?nely divided form,
`e. g., a size where 85 to 95% will pass a 325 mesh
`standard sieve. Most activated carbons appear
`to be more or less generally useful for this pur
`pose, but equally desirable results are not ob
`tained with all activated carbons. It has been
`discovered that activated decolorizing carbons
`are most desirable.
`The other component of the catalytic mixture
`for use with these new procedures is a sulfur
`containing acid, which may be either sulfuric
`acid‘ or a‘ sulfonic acid. Examples of suitable
`aryl sulfonic acids include benzene, toluene,
`naphthalene, or‘ para-butylphenol sulfonic acids.
`Also alkane sulfonic acids, such as petroleum oil
`sulfonic acids, may be used. Sulfuric acid is the
`preferred material, and it is desirable to employ
`a substantially concentrated sulfuric acid, such
`as the commercial 95% acid. However, less con
`centrated acid may be used.
`The relative proportions of carbon to acid
`in the catalytic mixture may be varied. However,
`for best results, it has been found that mixtures
`containing about one part of the sulfur-contain
`ing acid for each one to 20 parts of activated
`carbon give the best esters with the greatest
`speed.
`'
`The quantity of the catalytic mixture of acti
`vated carbon and acid relative to the amounts of
`acid and alcohol used in the esteri?cation reac
`tion can" be‘ varied and will be dependent to some
`extent upon the particular acid and alcohol used
`in the process; Broadly, su?icient of the cata
`lytic mixture is employed to produce a catalytic
`effect upon the condensation on the alcohol and
`acid to form the ester. However, best results
`have been obtained using between 0.1 and 5% by
`' weight of the catalytic mixture in the esteri?ca
`tion, 1. e., between about 0.05 and 2.5% H2804 and
`about 0.05 and 4.5% activated carbon.
`The ability of the new catalytic mixtures of
`this invention to vform esters of high purity and
`freedom'from discoloration seems to be general
`for all esteri?cation procedures, which form im
`pure or discolored esters when mineral acids, such
`as sulfuric or 'ary‘l sulfonic acids, are used as the
`catalysts. However, the invention is most use
`fully applied in the formation of high molecular
`weight esters, such as those formed from poly
`carboxylic acids, of molecular weight greater
`than 105 to give esters having a molecular weight
`between 120 and 400.
`A large variety of di?'erent types of alcohols
`maybe successfully used in carrying out the pro
`cedures of this invention. Examples of useful
`alcohols ‘include:
`(a) ‘Monohydric alkyl ‘alcohols, e. g., methanol;
`ethanol; 11- or sec-propanol; n-. sec.-, or tertiary
`butanol; 11-, sec.-, or isoamyl alcohol; isooctyl al
`cohol; 2-ethy1hexyl alcohol; nonyl alcohol; lau~
`ryl ‘alcohol; s'tearyl alcohol and dodccanol;
`(b) Dihydr'ic alkyl alcohols, .e. g., glycol; .1-3
`propylene glycol; 1,4-butylene glycol; 1,6-hexa
`methylene glycol, ‘and 1,,8-octandiol;
`"(0) Higher polyhydric alkyl alcohols, e. g., glyc
`erol; 1,3,4-‘butantri'ol; 1,2,,6-hexantrio1; penta
`ery'thritol; pentaglycerol and sucrose;
`(6) ‘Phenols, e. 'g., ‘phenol; cresols; chloro
`
`Example IV
`This example illustrates the preparation of di
`2-ethylhexy1 sebacate.
`The following ingredients are charged into a
`reaction vessel equipped with stirrer, re?ux con
`denser, and re?ux water separator:
`606 parts sebacic acid
`859 parts 2-ethylhexano1
`200 parts benzene
`1.5 parts sulfuric acid (95 %)
`15 parts activated carbon
`The materials are heated to 125° to 130° C. with
`controlled re?ux and simultaneous removal of
`condensed water. The reaction is carried out for
`six hours when re?uxing is discontinuedand the
`excess alcohol and benzene are allowed to distill
`o?. Su?icient caustic soda is then added to
`neutralize free acid and the resulting ester is
`washed with water. ‘The product is vthen blown
`with steam to completely remove volatiles, dryed
`and ?ltered. Without further treatment, 1190
`parts of 2-ethylhexyl sebacate, having the follow
`ing properties, are obtained:
`
`Percent ester ___________ _'_ __________ __ 99.3%
`Percent acid (as sebacic acid) ________ .__ 0.016%
`Color APHA scale ___________________ .._ 50 1:060
`Speci?c gravity 25° /25° ______ r. _______ -_ ‘Q9119
`Percent water ______ _>_-__-__ir _________ . 0.083%
`Refractive index 11.525 _________ W4---” 1.4496 '
`
`60
`
`75
`
`Petitioners' Exhibit 1013, Page 2 of 4
`
`

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`,
`
`6 .
`
`CONCLUSIONS
`
`20
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`25
`
`35
`
`40
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`2,628,249
`5
`phenol; amylphenol; polychlorophenol; ‘pr-hy
`irclate; ethylhexyl picolinate and biphenyl furo
`droxy biphenyl; betahydroxy naphthalene; 2
`a e;
`chloro-3-methyl phenyl; paranitrophenol and
`(g) Glycol derivative esters, e. g., ethylene gly
`salicyl alcohol;
`col dlpropionate; diethylene glycol diacetate; tri~
`ethylene glycol di-2-ethylbutyrate; polyethylene
`(c) Alicyclic alcohols, e. g., cyclohexanol, inosi
`glycol sebacate; tetraethylene glycol di-ethyl
`tal; hydroxy benzene hexachloride; 2-methyl
`cyclohexanol; cycloheptanol, and benzyl alcohol;
`hexoate; diethylene glycol ricino'leate; polyeth
`ylene glycol dilevulinate; ethylene glycol adipate;
`(I) Heterocyclic alcohols, e. g';, furfuryl alco
`tetraethylene glycol azelate; tri-(ethylene glycol
`hol; tetrahydroiurfuryl alcohol; alpha, beta, or
`gamma-pyridone and carbostyril;
`monoethyl ether) citrate; and ethylene glycol
`monoamyl ether ricinoleate.
`(g) Ether alcohols, e. g., diethylene glycol; di
`ethylene glycol monomethyl ether; ethylene gly
`The reaction conditions used in carrying out
`col monoethyl ether; tetraethylene glycol; bu
`esteri?cations with my new catalytic mixtures
`toxyethanol; pentanoxymethanol and butylene
`can be varied and are primarily dependent upon
`glycol monobutyl ether.
`the particular esters being formed. Thus, the
`temperatures will vary and depend primarily upon
`A large Variety of carboxylic acids may be
`used in the esteri?cation procedures of this in
`the alcohols used, but in any case, a temperature
`vention. Examples of usable acids include:
`suf?cient to cause the esteri?cation to proceed
`in the presence of the catalytic mixtures should
`(a) Aliphatic monocarboxylic acids, e. g., ace~
`tic; propionic; butyric; caproic; lauric; myristic;
`be used. Generally, temperatures between 50 and
`palmitic; stearic; pelargonic; ethyl butyric; ethyl
`200° C. will be employed.
`No speci?c type of apparatus is required, and
`hexanoic; and oleic acids.
`the general type of equipment normally used
`(1)) Aliphatic dicarboxylic acids, e. g., succinic;
`oxalic; suberic; azelaic; adipic; sebacic; maleic;
`in esteri?cation reactions can be utilized. Like
`wise, general information and knowledge regard~
`glutaric and fumaric acids;
`ing esteri?cation reactions can be applied by those
`(0) Higher aliphatic polycarboxylic acids, e. g.,
`skilled in the art in carrying out the operations
`citric; aconitic and tricarballylic;
`in accordance with this invention.
`(d) Aryl carboxylic acids; e. g., benzoic; phen
`ylacetic; salicylate; ll-chlorobenzoic; 0-, m-, or
`p-toluic; phthalic; naphthoic; Z-nitrobenzoic
`and pyromellitic acids;
`(6) Alicyclic carboxylic acids, e. g., cyclohex
`anoie; Z-methyl cyclohexanoic; a-cyclohexyl bu
`tyric; 2-methyl cyclohexyl acetic; cyclohexyl
`succinic and benzene hexachloride acetic acids;
`(1‘) Heterocyclic carboxylic acids, e. g., iuroic;
`picolinic; nicotinic; lutidinic; cinchomeronic;
`and 2-methyl furoic acids;
`(g) Miscellaneous acids, e. g., chloroacetic;
`abietic; tartaric; glycolic; levalinic and ricinoleic
`acids.
`Where it is desired, the anhydride, if available,
`of any of these acids may be employed in place of
`the acid per se.
`Using the above acids and alcohols in this in
`vention, examples of esters of high molecular
`weight with substantial freedom from discolora
`tion or presence of impurities which can be pre
`pared include:
`(a) Aliphatic monocarboxylic acid esters, e. g.,
`butyl laurate; amyl laurate; glycerol monolau
`rate; butyl oleate; ethylhexyl oleate; benzyl
`stearate; cyclohexyl stearate; lauryl butyrate;
`glycerol tributyrate; dodecyl acetate; nonyl ethyl
`hexanoate; sucrose octoacetate and tetrahydro
`furfuryl oleate;
`(b) Aliphatic dicarboxylic acid esters, e. g., di
`isooctyl adipate; dinonyl adipate; dinonyl azel
`ate; diisooctyl sebacate; diethyl adipate; di
`methoxymethyl adipate; bis-(methyloyclohexyl)
`adipate; dibenzyl sebacate; dibutyl succinate and
`dilauryl oxalate;
`(0) Higher aliphatic polycarboxylic acid esters,
`e. g., triethyl citrate; tributyl tricarballylate; tri
`amyl aconitate; and triphenyl citrate;
`(d) Aryl, carboxylic acid esters, e. g., lauryl
`benzoate; nonyl phenylacetate; ctyl naphtho
`ate; cliethyl phthalate; tetraethyl pyromellitate
`and diamyl phthalate;
`(e) Alicyclic carboxylic acid derivatives, e. g.,
`lauryl 2-methylcyclohexanoate; tetrahydrofur
`i'uryl cyclohexanoate; diamyl cyolohexylsuccinate
`and naphthyl cyclohexan'oate;
`(j) Heterocyclic carboxylic acid esters, e. g.,
`lauryl furoate; phenyl nicctinate; myristyl picol
`
`This present invention provides new catalytic
`mixtures for use in the liquid phase esteri?ca
`tion of carboxylic acids with alcohols to form
`esters. The new catalysts which are used in the
`liquid phase with the reactants are generallyr
`applicable to the formation of all esters, but they
`are most effectively employed in the formation
`of esters of high molecular weight which gen
`erally produce discolored products when formed
`using mineral acids or sulfonic acids as the ester“
`i?cation catalysts. The usefulness of the new
`catalytic mixtures of this invention is primarily
`due to their ability to form esters at relatively
`high reaction rates, which are of very high purity
`and do not contain discolorizing ingredients.
`I claim:
`1. In the process for the production of esters,
`the step which comprises condensing a material
`from the group consisting of carboxylic acids and
`anhydrides thereof with an alcohol in the pres—
`ence of between 0.1 and 5% by weight of a mix
`ture of (1) a sulfur-containing acid from the
`group consisting of sulfuric and sulfonic acids,
`and (2) activated carbon.
`2. A process for the production of substantially
`colorless low vapor pressure esters of carboxylic
`acids, which comprises adding between 0.05 and
`2.5% by weight of H2804 and between 0.05 and
`4.5% by weight of activated carbon to an esteri
`?cation mixture, ‘subjecting the mixture to a
`temperature su?icient to cause esteriflcation and
`recovering an ester from the reaction mixture.
`3. In the process for the production of high
`tmolecular weight esters having very good color
`characteristics, the improvement comprising car~
`65
`rying out the esteri?cation using a mixture of
`sulfuric acid and activated carbon as the esteri
`?cation catalyst.
`4. A process as claimed in claim 3, wherein
`said mixture comprises one to 20 parts of acti~
`vated canbon for each part of sulfuric acid.
`5. A process as claimed in claim 1 wherein
`the condensation is carried out at a temperature
`between 50 and 200° C.
`6. A process as claimed in claim 1, wherein said
`
`50
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`55
`
`60
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`75
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`Petitioners' Exhibit 1013, Page 3 of 4
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`

`
`2,628,249
`
`7
`material is a dica-rboxy‘lic acid of ‘the general
`formula:
`
`8
`11. A process as claimed in claim 1, wherein a
`mixture of alcohols is used.
`12. In the process for the production of esters,
`HOOC(CH2)¢COOH
`the step ‘which comprises condensing a material
`‘margin :8 is an integer from 2 to m‘
`7. A process as claimed in claim 1, wherein 5 from the group conslspmg of carboxyiw fff'clds and
`said alcohol is a saturated monohydric a-lkyl alco-
`anhydndes thereof Wlth aim. alcohol. “1 “he pres"
`1101 having between one and 18 carbon atoms.
`ence of a‘ cat???“ cmPpmmg a mlxture of .(1)
`a sulfur-containing acid from the group consist
`8. A process as claimed in claim 1, wherein said
`.
`.
`i
`.- ~
`.
`‘lgiegfciliéfglglc and sulfonic acids, and (2) acti
`material is an aryl dicarboxylic acid
`9. A process as claimed in claim 8, wherein said 10
`'
`'
`'
`,
`material is phthalic anhydride.
`ANTHONX J‘ BRUNO’ J“
`10. A process as claimed in claim 1, wherein
`No references cited.
`said carbon is of such ?neness that at least 85
`to 95% will pass a 325 mesh standard sieve.
`
`Petitioners' Exhibit 1013, Page 4 of 4