Byproduct identification in the terephthalic acid production process and possible mechanisms of their formation

Roffia, P.; Calini, Pierangelo; Motta, Luigi; Tonti, S.

doi:10.1021/i300016a024

Cited by 26 publications

(30 citation statements)

References 5 publications

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“…Besides 4-CBA and pTOL, BZ and HMB (peaks labeled as 5 and 2, respectively) are readily identified in the electropherogram. Minor impurities (peaks 6, 7 and 8) observed in the previous condition ( Figure 2B), decreased considerably and are not seen in the electropherogram due 3,2004 to sample dilution. By decreasing the base width of the terephthalic acid peak, sample dilution affects the migration time of all other sample components.…”

Section: Resultsmentioning

confidence: 77%

“…They comprise the derivatives of benzoic acid, phenol, terephthalic acid, diphenyl, fluorenone and anthraquinone as well as a variety of esters. 3 The presence of these impurities in terephthalic acid used in the production of polyester, for instance, is undesirable because they can slow down the polymerization process and also impart coloration to the polymer due to thermal instability. This effect is caused by the presence of monoprotic acids, such p-toluic acid (pTOL), benzoic acid (BZ) and 4-carboxybenzaldehyde (4-CBA).…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Analysis of impurities in crude and highly-purified terephthalic acid by capillary electrophoresis

Moraes¹,

Rubim²,

Realpozo³

et al. 2004

J. Braz. Chem. Soc.

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Neste trabalho, foi desenvolvido um método simples e rápido, utilizando eletroforese capilar (CE), para a análise simultânea de 4-carboxibenzaldeído (4-CBA), ácido p-toluóico (pTOL) e ácido benzóico (BZ), em lotes industriais de ácido tereftálico cru (CTA) e purificado (PTA). As condições eletroforéticas de análise foram: tampão tetraborato a 20 mmol L -1 (pH 9), injeção hidrodinâmica (5 s, 17 kPa), tensão aplicada de +30 kV e detecção direta em 200 nm.Foram analisados cinco lotes de CTA e quatro lotes de PTA nos teores de 4-CBA e pTOL pela metodologia proposta e as metodologias utilizadas na empresa Tereftalatos Mexicanos S.A. (TEMEX), que são cromatografia gasosa para pTOL e polarografia para 4-CBA, mostrando concordância entre os valores encontrados. Os níveis de BZ foram determinados apenas pela metodologia CE, apresentando no CTA, valores compreendidos entre 60 e 300 ppm, enquanto que no PTA, 5 a 7 ppm. Várias impurezas derivadas da oxidação incompleta do p-xileno foram investigadas, constatando-se a presença do ácido 4-hidroximetilbenzóico por comparação com padrões.In this work, a simple and fast capillary electrophoresis method for the simultaneous analysis of 4-carboxybenzaldehyde (4-CBA), p-toluic acid (pTOL) and benzoic acid (BZ) in industrial batches of crude (CTA) and highly-purified (PTA) terephthalic acid was developed. The electrophoretic conditions comprise: 20 mmol L -1 tetraborate buffer at pH 9, hydrodynamic injection (5 s/17 kPa), applied voltage of +30 kV and direct UV detection at 200 nm.The concentrations of 4-CBA and pTOL in five batches of CTA and four batches of PTA as determined by the proposed CE methodology were in agreement with the results from gas chromatography and polarography methods in current use in Tereftalatos Mexicanos S.A. (TEMEX). Levels of BZ were determined only by the CE methodology and ranged from 60 -300 ppm in CTA and 5 -7 ppm in PTA. Several impurities deriving from the incomplete oxidation of p-xylene were investigated. So far the positive identification of 4-hydroxymethylbenzoic acid was accomplished by comparison with pure standards.

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Section: Resultsmentioning

confidence: 77%

Section: Introductionmentioning

confidence: 99%

Analysis of impurities in crude and highly-purified terephthalic acid by capillary electrophoresis

Moraes¹,

Rubim²,

Realpozo³

et al. 2004

J. Braz. Chem. Soc.

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“…process. Further, the presence of the p-TA and BPTA in the solid TPA product from the stirred reactor implies oxygen starvation in the liquid phase [39]. At all conditions investigated, the spray reactor produces similar TPA yield as a stirred reactor with a carbon balance closure of above 94% for each experiment but significantly better solid TPA product that conforms to polymer-grade purity.…”

Section: Product Analysismentioning

confidence: 93%

“…In addition to the intermediates shown in Figure 1.3, there are many other byproducts formed in the pX oxidation process to TPA. These impurities can be grouped into the derivatives of benzoic acid, phenol, terephthalic acid, diphenyl, fluorenone, benzophenone, anthraquinone, aromatic esters and bromine-substituted intermediates [39]. The formation of these compounds is due to the side reactions, radical and/or ionic, occurring among pX, the oxidation intermediates, reaction solvent, and the catalytic system.…”

Section: Px Oxidationmentioning

confidence: 99%

A spray reactor concept for catalytic oxidation of p-xylene to produce high-purity terephthalic acid

Niu

Zuo

et al. 2013

Chemical Engineering Science

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“…In addition, the solid also contains trace amounts of yellow colored by-products such as the derivatives of fluorenone and anthraquinone that can affect the quality of polymers. 21 The presence of these compounds is detected by the optical density at 340 nm. 15 The lower that optical density, the lesser the amounts of these yellow colored by-products.…”

Section: Semi-continuous Oxidation Of P-xylenementioning

confidence: 99%

Liquid phase oxidation of p-xylene to terephthalic acid at medium-high temperatures: multiple benefits of CO2-expanded liquids

et al. 2010

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The Co/Mn/Br catalyzed oxidation of p-xylene to terephthalic acid (TPA) is demonstrated in CO 2 -expanded solvents at temperatures lower than those of the traditional Mid-Century (MC) process. As compared with the traditional air (N 2 /O 2 ) oxidation system, the reaction with CO 2 /O 2 mixture at 160• C and using an additional inert gas (N 2 or CO 2 ) pressure of 100 bar increases both the yield of TPA and the purity of solid TPA via a more efficient conversion of the intermediates, 4-carboxybenzaldehyde and p-toluic acid. At the same time, the amount of yellow colored by-products in the solid TPA product is also lessened, as determined by spectroscopic analysis. Equally important, the decomposition or burning of the solvent, acetic acid, monitored in terms of the yield of the gaseous products, CO and CO 2 , is reduced by ca. 20% based on labeled CO 2 experiments. These findings broaden the versatility of this new class of reaction media in homogeneous catalytic oxidations by maximizing the utilization of feedstock carbon for desired products while simultaneously reducing carbon emissions.

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Byproduct identification in the terephthalic acid production process and possible mechanisms of their formation

Cited by 26 publications

References 5 publications

Analysis of impurities in crude and highly-purified terephthalic acid by capillary electrophoresis

Analysis of impurities in crude and highly-purified terephthalic acid by capillary electrophoresis

A spray reactor concept for catalytic oxidation of p-xylene to produce high-purity terephthalic acid

Liquid phase oxidation of p-xylene to terephthalic acid at medium-high temperatures: multiple benefits of CO2-expanded liquids

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