Optimization of simultaneous thermal analysis for fast screening of polycondensation catalysts

El-Toufaili, Faissal-Ali; Wiegner, Jens-Peter; Feix, Gunter; Reichert, Karl‐Heinz

doi:10.1016/j.tca.2005.04.009

Cited by 18 publications

(20 citation statements)

References 3 publications

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“…Hydrotalcite was shown to be more active than antimony in polycondensation of BHET. [4][5][6][8][9][10] In a previous paper, [11] the effects of HT properties on its activity as a BHET polycondensation catalyst were studied. It was found that the hydroxide groups of HT are necessary for its catalytic activity.…”

Section: àmentioning

confidence: 99%

“…[8][9][10]12] When the polycondensation reaction starts, EG is set free as a condensate by-product and is carried away from the reaction medium by inert-gas purging. This leads to mass loss that is recorded as a function of time and temperature.…”

Section: Materials Characterizationmentioning

confidence: 99%

“…The polycondensation is considered irreversible as the EG removal is efficient and mass-transfer limitations in the melt as well as on the melt-gas interface are absent under the applied conditions. [8] The reaction order of HT-catalyzed polycondensation was determined by the method of integration. As the polycondensation was carried out under dynamic conditions, the relation between concentration of hydroxyl end group, time, and temperature was studied instead of the relation between the concentration of hydroxyl end groups and time.…”

Section: Kineticsmentioning

confidence: 99%

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Kinetics and Mechanistic Investigation of Hydrotalcite‐Catalyzed Melt Synthesis of Poly(ethylene terephthalate)

El-Toufaili¹,

Feix²,

Reichert³

2006

Macro Materials & Eng

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Summary: Hydrotalcite‐catalyzed polycondensation of BHET was studied by thermogravimetry to elucidate the kinetics. The reaction was found to follow second‐order kinetics with respect to hydroxyl end groups. The overall activation energy of the polycondensation was found to decrease with increasing catalyst concentration before it leveled out to the value of 93 kJ · mol−1 at high catalyst concentration. This is a result of the uncatalyzed reaction that takes place parallel to the catalyzed one. The activation energy of the uncatalyzed path was found to be 156 kJ · mol−1. IR spectroscopy and XRD showed that the monomer intercalates between the layers of hydrotalcite at the beginning of the reaction enabling the complexation of oxygen‐containing functional groups with the hydroxide groups of the catalyst. Based on these findings a polycondensation mechanism is proposed. One end group of the monomer is activated in the form of alkoxide that counterbalances the positive charge of the hydrotalcite layer. This alkoxide group attacks an ester carbonyl group fixed close to it, generating a new ester bond and a glycoxide species. The role of hydrotalcite is to activate the reactants, rendering the attacking hydroxyl group more nucleophilic and the ester carbonyl group more electrophilic, and at the same time fixing the reactant together in a favorable geometry.Intercalation of BHET in the gallery of HT layers in a twisted alkoxide form.magnified imageIntercalation of BHET in the gallery of HT layers in a twisted alkoxide form.

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Section: àmentioning

confidence: 99%

Section: Materials Characterizationmentioning

confidence: 99%

Section: Kineticsmentioning

confidence: 99%

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Kinetics and Mechanistic Investigation of Hydrotalcite‐Catalyzed Melt Synthesis of Poly(ethylene terephthalate)

El-Toufaili¹,

Feix²,

Reichert³

2006

Macro Materials & Eng

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“…Comprehensive description of the screening method and determining of the catalytic activity can be found in the literature. [7,8] The method is very sensitive and the results are reproducible within 1.5% uncertainty.…”

Section: Catalyst Screeningmentioning

confidence: 99%

“…In previous studies [4,5,[7][8][9] , it was shown that HT is more active than antimony in catalyzing polycondensation of BHET into PET. In the current work, the activity of HT was tuned by modification of the ratio of aluminum to magnesium in its composition and/or by its pretreatment such as calcination and exchanging of carbonate by other anions.…”

Section: Introductionmentioning

confidence: 99%

Studies on Hydrotalcite‐Catalyzed Synthesis of Poly(ethylene terephthalate)

El-Toufaili

Ahmadniana

Dinse

et al. 2006

Macro Materials & Eng

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Summary: The hydrotalcite‐catalyzed synthesis of PET was studied to clarify the effect of hydrotalcite properties on its catalytic activity. Hydrotalcite was modified by various treatments to tune its activity as a polycondensation catalyst. Hydrotalcite activity was found to decrease upon calcination. However, rehydration of the calcinated hydrotalcite resumed the catalytic activity. The hydrotalcite activity depends on the ratio of magnesium to aluminum cations in its composition, and highest activity occurs at a molar ratio of 2:1. Replacement of the carbonate anions of hydrotalcite by more nucleophilic ones like hydroxide and alkoxide groups resulted in improved catalytic activity. Hydrotalcite has two assembly orders: primary lamination of sheets into plates and secondary agglomeration of plates into particles. Hydrotalcite with larger sheet size showed lower activity. On the other hand, milling of hydrotalcite particles did not affect its activity as it probably enters the reaction on a plate level, which is not affected by milling. Polycondensation resulted in expansion of the hydrotalcite sheets under the effect of formed polymer. Reuse of hydrotalcite after polycondensation followed by depolycondensation resulted in a large activity enhancement.High‐resolution SEM micrograph of calcinated HT after rehydration.magnified imageHigh‐resolution SEM micrograph of calcinated HT after rehydration.

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Attapulgite‐supported aluminum oxide hydroxide catalyst for synthesis of poly(ethylene terephthalate)

Lin

Chen

2013

J of Applied Polymer Sci

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A novel nanocomposite catalyst was prepared from immobilization of aluminum oxide hydroxide onto the attapulgite. Characterizations with scanning electron microscopy (SEM) and wide angle X-ray diffraction (XRD) of the as-prepared catalyst revealed that AlO(OH) nanoparticles were distributed on the attapulgite. Thermogravimetric analysis-infrared spectrometry (TGA-IR) of the mixture prepared by mixing of bishydroxy ethylene terephthalate (BHET) and the catalyst indicated that attapulgite-supported aluminum oxide hydroxide catalyst can catalyze BHET polycondensation under the applied conditions. A kinetic model for determining the activation energy has been applied to evaluate the catalyst activity. The catalyst activity was examined through comparative experiments, and the results showed that the new catalyst exhibited higher activity for BHET polycondensation under identical reaction conditions, and the viscosity-average molecular weight of poly(ethylene terephthalate) (PET) product obtained was increased about 2000 g/mol.

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Optimization of simultaneous thermal analysis for fast screening of polycondensation catalysts

Cited by 18 publications

References 3 publications

Kinetics and Mechanistic Investigation of Hydrotalcite‐Catalyzed Melt Synthesis of Poly(ethylene terephthalate)

Kinetics and Mechanistic Investigation of Hydrotalcite‐Catalyzed Melt Synthesis of Poly(ethylene terephthalate)

Studies on Hydrotalcite‐Catalyzed Synthesis of Poly(ethylene terephthalate)

Attapulgite‐supported aluminum oxide hydroxide catalyst for synthesis of poly(ethylene terephthalate)

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