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(11) EP 1 912 929 B1

(12) EUROPEAN PATENT SPECIFICATION

(45) Date of publication and mention (51) Int Cl.: of the grant of the patent: B01J 31/04 (2006.01) C07C 67/08 (2006.01) 08.01.2014 Bulletin 2014/02 (86) International application number: (21) Application number: 06788502.0 PCT/US2006/028942

(22) Date of filing: 26.07.2006 (87) International publication number: WO 2007/021475 (22.02.2007 Gazette 2007/08)

(54) PRODUCTION OF DI-(2-ETHYLHEXYL) TEREPHTHALATE HERSTELLUNG VON DI-(2-ETHYLHEXYL)-TEREPHTHALAT PRODUCTION DE DI-(2-ETHYLHEXYLE) TEREPHTHALATE

(84) Designated Contracting States: (56) References cited: AT BE BG CH CY CZ DE DK EE ES FI FR GB GR • DATABASE WPI Week 200142 Derwent HU IE IS IT LI LT LU LV MC NL PL PT RO SE SI Publications Ltd., London, GB; AN 2001-392553 SK TR XP002413852 & JP 2001 031794 A (HOKOKU SEIYU KK) 6 February 2001 (2001-02-06) (30) Priority: 12.08.2005 US 202975 • DATABASECA [Online] CHEMICAL ABSTRACTS SERVICE, COLUMBUS, OHIO, US; ZENG, (43) Date of publication of application: CHONGYU: "Study on esterification rule in DOTP 23.04.2008 Bulletin 2008/17 preparation" XP002413815 retrieved from STN Databaseaccession no. 1995: 468078& "Studyon (73) Proprietor: EASTMAN CHEMICAL COMPANY esterification rule in DOTP preparation" Kingsport TN 37660 (US) NANJING HUAGONG XUEYUAN XUEBAO , 1 CODEN: NAXUEI; ISSN: 1000-5994, vol. 16, no. 4, (72) Inventors: 1994, pages 69-72, • COOK, Steven, Leroy • DATABASECA [Online] CHEMICAL ABSTRACTS Kingsport, TN 37660 (US) SERVICE, COLUMBUS, OHIO, US; JIANG, • TOMLIN, Christopher, Fletcher PINPING: "Synthesis of DOTP by Kingsport, TN 37660-5630 (US) esterification" XP002413816 retrieved from STN • TURNER, Philip, Wayne Database accession no. 1995:454573 & Blountville, TN 37617 (US) "Synthesis of DOTP plasticizer by esterification" HUAXUE SHIJIE , CODEN: HUAKAB; ISSN: (74) Representative: Brown, Fraser Gregory James et 0367-6358, vol. 35, no. 8, 1994, pages 411-415, al • DATABASE WPI Week 200003 Derwent Cleveland Publications Ltd., London, GB; AN 2000-036530 10 Fetter Lane XP002413844 & RU 2 114 100 C1 (KHIMPLAST London EC4A 1BR (GB) STOCK CO) 27 June 1998 (1998-06-27)

Note: Within nine months of the publication of the mention of the grant of the European patent in the European Patent Bulletin, any person may give notice to the European Patent Office of opposition to that patent, in accordance with the Implementing Regulations. Notice of opposition shall not be deemed to have been filed until the opposition fee has been paid. (Art. 99(1) European Patent Convention). EP 1 912 929 B1

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Description DETAILED DESCRIPTION

FIELD OF THE INVENTION [0004] The esterification process of the present inven- tion is carried out in a reaction zone comprising a pres- [0001] This invention pertains to the preparation of 5 sure vessel while maintaining the EH:TPA mole ratio at di-(2-ethylhexyl) terephthalate from 2:1 to 2.5:1 The pressure and temperature within the re- (TPA). More specifically, this invention pertains to a proc- action zone are maintained at 100 to 400 kPa gauge (1 ess for the preparation of di-(2-ethylhexyl) terephthalate to 4 bar gauge (barg)) and 180 to 270°C. Preferred pres- by the esterification of TPA with 2-ethylhexanol (EH) at sure and temperature ranges are 200 to 350 kPa gauge elevated temperature and pressure while removing the 10 (2 to 3.5 barg) and 180 to 260°C. water of reaction from the reaction mixture. [0005] An important feature of the present invention is the removal of water of reaction along with EH during the BACKGROUND OF THE INVENTION esterification process. The maintenance of the EH:TPA mole ratio at 2:1 to 2.5:1 requires the addition of EH to [0002] Di-(2-ethylhexyl) terephthalate, also known as 15 the reaction vessel during the process. The EH/water dioctyl terephthalate or DOTP, is used as a plasticizer in mixture or azeotrope removed from the reaction zone a variety of polymeric materials such as polyvinyl chlo- may beallowed toseparate into an EH- richorganic phase ride. DOTP can be prepared by the titanate-catalyzed and an aqueous phase and the EH-rich organic phase transesterification of (DMT) with can be returned to the reaction zone. Alternatively, the EH. Direct esterifications of TPA with EH under condi- 20 EH:TPA mole ratio may be maintained at 2:1 to 2.5: by tions similar to those used for the transesterification of the addition of fresh EH. DMT have produced slow reaction rates and sporadic [0006] The removal of water of reaction from the reac- problems with foaming. US-2002028963-A1 discloses tion zone is assisted by passing an inert gas through the an esterification process wherein water is removed by TPA/EH reaction mixture in the reaction zone. Nitrogen azeotropic distillation together with an alcohol. JP-25 is the least expensive and thus is the preferred inert gas. 60004151-A (JP-03004052-B) discloses the reaction of The inert gas typically is fed below the surface of the TPA and EH under elevated pressures and tempera- TPA/EH reaction mixture by means of a conventional tures. JP-2001031794-A discloses the preparation of conduit or via a gas sparging device. While the inert gas terephthalic acid esters by reacting at least one of C9- C may be fed intermittently or discontinuously, it preferably 18 monohydric alcohol and 2-ethylhexanol with tereph- 30 is fed continuously at the commencement of the esteri- thalic acid. Water formed during the reaction was re- fication reaction. The amount of gas passed through the moved and the alcohol was separated and recirculated TPA/EH reaction mixture may vary significantly but typ- to the system. Finally, US-5,532,495 discloses a multi- ically is in the range of 2 to 5 volumes of gas per volume step esterification process that includes removing water of reaction mixture per hour. and a portion of the alcohol reactant from the reaction 35 [0007] The titanium catalyst may be any titanium com- mixture. pound soluble in the reaction mixture, i.e., soluble in EH and the di-(2-ethylhexyl) terephthalate product. An ex- BRIEF SUMMARY OF THE INVENTION ample of suitable titanium compounds include titanium tetraalkoxides having the formula Ti(OR)4 wherein R is [0003] We have developed a process for the prepara- 40 an alkyl group of 1 to 8 carbon atoms. The catalytically- tion of di-(2- ethylhexyl) terephthalate by the esterification effective amount of the titanium compound generally is of TPA with EH at elevated pressure and temperature an amount which provides a titanium [Ti] concentration wherein the water of reaction and some of the EH is re- of 50 to 200 parts per million by weight in the reaction moved during the esterification process. The present mixture. The process of the present invention may be invention therefore provides a process 45 carried out in a batch, semi-continuous or continuous for the preparation of di-(2-ethylhexyl) terephthalate mode. In the batch mode, an agitated pressure vessel is which comprises contacting TPA with EH in the presence charged with TPA, EH and catalyst, heated and pressu- of a titanium catalyst in a reaction zone wherein the total rized and the esterification is carried out while passing pressure is maintained at 100 to 400 kPa gauge (1 to 4 an inert gas through the reaction mixture. An EH/water bar gauge), the temperature is maintained at 180° to50 mixture is removed and EH is fed to the reaction vessel 270°C, the EH: TPA mole ratio is maintained at 2: 1 to 2.5: over the course of the process. At the conclusion of the 1, and an inert gas is passed through the TPA/EH reac- process, the di-(2- ethylhexyl) terephthalate product is re- tion mixture in the reaction zone to cause a mixture of covered from the vessel and purified according to con- water and EH to be removed from the reaction zone dur- ventional procedures. Continuous operation involves ing the preparation of di-(2- ethylhexyl) terephthalate. Our 55 continuously or intermittently feeding TPA, EH and cat- novel process provides the desired diester product at alyst to and continuously or intermittently removing EH, good reaction rates with high conversions of the TPA water and product-containing reaction mixture from a reactant with no observable foaming problems. pressure vessel maintained at a predetermined temper-

2 3 EP 1 912 929 B1 4 ature, pressure and liquid level. The product-containing with the recycled EH to facilitate removal of water. Total reaction mixture may be fed to one or more secondary reaction time was 10.5 hours at a maximum temperature reaction vessels wherein conversion of TPA and/or TPA of 260°C and a maximum autoclave pressure of approx- half-ester to the diester product is completed. imately 300 kPa gauge (3 barg). Unreacted TPA (14 g) [0008] In the simplest embodiment, the reaction vessel 5 was recovered by filtration. The crude product then was may be fitted with one inlet for EH reactant return and a neutralized with 2.5% aqueous NaOH, washed with wa- control valve to remove volatiles in lieu of a fractionation ter and filtered. Excess EH was stripped off at reduced column. The reactor is charged with terephthalic acid, pressure and the residue then steam stripped. The excess 2-ethylhexanol, and a catalytic amount of a tita- stripped product was treated with activated carbon at nium catalyst such as titanium tetraisopropoxide (TIPT). 10 90°C for one hour then filtered through a filter aid to give Heating and stirring of the mixture results in both an in- 136.6 g of product ∼ (80% conversion). Analysis (Gas crease in pressure and esterification of the TPA to DOTP Chromatography, area percentages): 0.04% EH; 0.07% and the release of volatiles including EH and water. The di-(2-ethylhexyl) , 0.13% methyl (2-ethylhexyl) volatile components consist primarily of the water of re- terephthalate; 0.02% unknown; 99.42% DOTP. Color action and unreacted EH. These components can be 15 (PCS): 20. swept out of the reactor with the aid of an inert gas purge, [0012] A comparative experiment was performed at at- condensed and the 2-ethylhexanol separated from the mospheric pressure. To a liter, 2- round-bottom flask water and returned to the autoclave via a pump. The prod- equipped with overhead stirrer, thermometer, heating uct of this reaction typically is refined by filtering out un- mantel and vapor decanter was added 350 g (2.107 mol) reacted TPA for recycle. The crude product (filtrate) is 20 of TPA, 687 g (5.28 mol) of EH and 0.208 g (200 ppm) then neutralized with 2.5 weight percent aqueous NaOH, of TIPT. Upon heating, the reaction began at∼ 180°C. washed with water and filtered. Excess 2-ethylhexanol The temperature slowly reached 189°C in 6 hours. A tem- is stripped off at reduced pressure and the residue is then perature of 202°C was achieved after 10 hours reaction steam stripped. The stripped product is treated with ac- time. The temperature was held at 205°C until ∼14 hours tivated carbon for one hour then filtered through a filter 25 of reaction time were completed. The temperature then aid to give the final product. reached 210°C at 15 hours, 222°C at 18 hours and the [0009] In a preferred embodiment, the process may be final temperature was 230°C, where it was held for 2 practiced in a continuous mode by adding the TPA to a hours. A reaction time of 21.5 hours was therefore re- suitable reaction vessel by means of a screw feeder and quired before water evolution slowed to the point that the the EH/catalyst as a pump- fed mixture to a stirred, pres- 30 reaction was discontinued. A total of 73.5 g of water- surizedreaction vesselequipped with a reflux condenser/ containing distillate was collected out of a theoretical decanter combination such that the water of reaction can amount of 75.8 g. The crude product was stripped of vol- be removed and the unreacted EH returned to the reac- atiles, giving a total of 125.3 g. The residue weighed tor. The effluent from this reactor can be passed to a 733.7 g for a yield of 88.9%. Analysis (Gas Chromatog- chain of one or more polishing reactors wherein the con- 35 raphy, area percentages): 0.04% EH; 0.04% di-(2- ethyl- version to DOTP with removal of water is continued. The hexyl) phthalate, 0.36% DOTP Isomer; 99.39% DOTP. product of this reaction can be further processed and Color (PCS): 40. refined by steps that are compatible with those listed for the batch example. 40 Claims EXAMPLES 1. Process for the preparation of di-(2-ethylhexyl) [0010] The process provided by the present invention terephthalate which comprises contacting tereph- is further illustrated by the following examples wherein thalic acid (TPA) with 2-ethylhexanol (EH) in the all percentages given are by weight unless specified oth- 45 presence of a titanium catalyst in a reaction zone erwise. wherein, the temperature is maintained at 180° to [0011] A 500 milliliter autoclave was charged with 270°C, the EH:TPA mole ratio is maintained at 2:1 137.9 g (0.83 mole) TPA, 250 g (1.92 moles) EH and 125 to 2.5:1, characterized in that the total pressure in ppm (0.048 g) TIPT catalyst. The autoclave was the reaction zone is maintained at 100 to 400 kPa equipped with a stirrer, a conduit for feeding EH and ni- 50 gauge (1 to 4 bar gauge (barg)) and an inert gas is trogen below the surface of the TPA/EH catalyst mixture, passed through the TPA/EH reaction mixture in the a pressure relief conduit and a conduit fitted with a control reaction zone to cause a mixture of water and EH to valve (backpressure regulator) for the removal of water be removed from the reaction zone during the prep- and EH. The autoclave then was sealed and heated to aration of di-(2-ethylhexyl) terephthalate. approximately 180°C to generate a pressure of 100 kPa 55 gauge (1 barg) within the autoclave. As the reaction pro- 2. Process according to Claim I wherein the inert gas ceeded, a mixture of water and EH was removed and the is passed through the TPA/EH reaction mixture at a EH was pumped back to the autoclave. Nitrogen was fed rate of 2 to 5 volumes of gas per volume of reaction

3 5 EP 1 912 929 B1 6

mixture per hour. Revendications

3. Process according to Claim 2 wherein the titanium 1. Procédé pour la préparation de di-(2-éthylhexyl) té- catalyst is a titanium tetraalkoxide having the formula réphtalate qui comprend la mise en contact d’acide 5 Ti(OR)4 wherein R is an alkyl group of I to 8 carbon téréphtalique (TPA) avec du 2-éthylhexanol (EH) en atoms. présence d’un catalyseur au titane dans une zone de réaction, dans lequel la température est mainte- 4. Process according to Claim 3 wherein the total pres- nue de 180°C à 270°C, le rapport molaire EH:TPA sure is maintained at 200 to 350 kPa gauge (2 to 3.5 est maintenu de 2:1 à 2,5:1, caractérisé en ce que bar gauge (barg)), the temperature is maintained at 10 la pression totale dans la zone de réaction est main- 180° to 260°C. tenue de 100 à 400 kPa effectifs (1 à 4 bars effectifs (barg)) et un gaz inerte est passé à travers le mé- 5. Process according to Claim 3 or Claim 4 wherein the lange réactionnel TPA/EH dans la zone de réaction concentration of the catalyst in the reaction mixture pour faire en sorte qu’un mélange d’eau et d’EH soit is an amount which provides a titanium [Ti] concen- 15 éliminé de la zone de réaction durant la préparation tration of 50 to 200 parts per million by weight. du di-(2-éthylhexyl) téréphtalate.

2. Procédé selon la revendication 1, dans lequel le gaz Patentansprüche inerte est passé à travers le mélange réactionnel 20 TPA/EH à un débit de 2 à 5 volumes de gaz par 1. Verfahren zur Herstellung von Di-(2-ethylhexyl)ter- volume de mélange réactionnel par heure. ephthalat, das das Kontaktieren von Terephthalsäu- re (TPA) mit 2- Ethylhexanol (EH)in Gegenwart eines 3. Procédé selon la revendication 2, dans lequel le ca- Titankatalysators in einer Reaktionszone umfasst, talyseur au titane est un tétra-alcoxyde de titane de 25 wobei die Temperatur bei 180° bis 270°C gehalten formule Ti(OR)4 dans laquelle R est un groupe alkyle wird und das EH:TPA-Molverhältnis bei 2:1 bis 2,5: de 1 à 8 atomes de carbone. 1gehalten wird, dadurchgekennzeichnet dass der Gesamtdruck in der Reaktionszone bei 100 bis 400 4. Procédé selon la revendication 3, dans lequel la kPa gauge [Relativdruck] (1 bis 4 bar gauge (barg)) pression totale est maintenue de 200 à 350 kPa ef- gehalten wird und ein Edelgas durch das TPA/EH- 30 fectifs (2 à 3,5 bars effectifs (barg)), la température Reaktionsgemisch in der Reaktionszone geleitet est maintenue de 180°C à 260°C. wird, um ein Gemisch aus Wasser und EH zu erzeu- gen, das während der Herstellung von Di-(2-ethyl- 5. Procédé selon la revendication 3 ou la revendication hexyl)terephthalat aus der Reaktionszone entfernt 4, dans lequel la concentration du catalyseur dans wird. 35 le mélange réactionnel est une quantité qui fournit une concentration en titane [Ti] de 50 à 200 parties 2. Verfahren nach Anspruch 1, wobei das Edelgas mit par million en poids. einer Rate von 2 bis 5 Volumen Gas pro Volumen Reaktionsgemisch pro Stunde durch das TPA/EH- Reaktionsgemisch geleitet wird. 40

3. Verfahren nach Anspruch 2, wobei der Titankataly-

sator ein Titantetraalkoxid mit der Formel Ti(OR)4 ist, worin R eine Alkylgruppe mit 1 bis 8 Kohlenstoffa- tomen ist. 45

4. Verfahren nach Anspruch 3, wobei der Gesamtdruck bei 200 bis 350 kPa gauge (2 bis 3,5 bar gauge (barg)) gehalten wird und die Temperatur bei 180° bis 260°C gehalten wird. 50

5. Verfahren nach Anspruch 3 oder Anspruch 4, wobei die Konzentration des Katalysators im Reaktionsge- misch ein Betrag ist, der eine Titan [Ti]-Konzentrati- on von 50 bis 200 ppm an Gewicht vorsieht. 55

4 EP 1 912 929 B1

REFERENCES CITED IN THE DESCRIPTION

This list of references cited by the applicant is for the reader’s convenience only. It does not form part of the European patent document. Even though great care has been taken in compiling the references, errors or omissions cannot be excluded and the EPO disclaims all liability in this regard.

Patent documents cited in the description

• US 2002028963 A1 [0002] • JP 2001031794 A [0002] • JP 60004151 A [0002] • US 5532495 A [0002] • JP 03004052 B [0002]

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