Brazilian Mineral Clays: Classification, Acid Activation and Application as Catalysts for Methyl Esterification Reactions

Dill, Laís Pastre; Kochepka, Débora Merediane; Lima, Larissa Lavorato; Leitão, Alexandre A.; Cordeiro, Claudiney Soares

doi:10.21577/0103-5053.20200164

Cited by 5 publications

(6 citation statements)

References 2 publications

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“…The presence of the Brønsted acidic sites is fundamental until 280 • C, when esterification reactions between APP and PER start to occur. The conclusions of [33] corroborates the results obtained in our previous study [29].…”

Section: Introductionsupporting

confidence: 91%

“…Despite having a distribution of moderate strength sites similar to that of AH5, the presence of those strong sites represents a disadvantage for the esterification reactions. A possible explanation is that the coordination of the Lewis sites is more affected by steric hindrance, decreasing the esterification kinetics rate, as suggested in [33].…”

Section: Cone Calorimetry (Cc)mentioning

confidence: 95%

“…Nevertheless, only few works investigated the influence of the acidity of aluminosilicates on the flame-retarding properties of intumescent composites [23,[25][26][27][28][29]. Montmorillonites are well-known catalysts for esterification reactions in organic liquid media and many works try to correlate a better catalytic performance to the presence of Brønsted acidic sites [30][31][32][33]. Furthermore, montmorillonite (Mt) presents some favorable features: it exhibits swelling properties, cation exchange capacity [34], and its surface acidity can be modified through an acidic activation [35].…”

Section: Introductionmentioning

confidence: 99%

“…Furthermore, montmorillonite (Mt) presents some favorable features: it exhibits swelling properties, cation exchange capacity [34], and its surface acidity can be modified through an acidic activation [35]. Methyl esterification reactions between methanol and carboxylic acids (acetic and lauric acids) were performed, catalyzed by acid-activated smectites with a high content of Mt [33]. It was found that the higher the ratio of Brønsted/Lewis acidic sites, the higher the esterification conversion achieved.…”

Section: Introductionmentioning

confidence: 99%

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Flame-Retarding Properties of Injected and 3D-Printed Intumescent Bio-Based PLA Composites: The Influence of Brønsted and Lewis Acidity of Montmorillonite

et al. 2022

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The influence of processing intumescent bio-based poly(lactic acid) (PLA) composites by injection and fused filament fabrication (FFF) was evaluated. A raw (ANa) and two acidic-activated (AH2 and AH5) montmorillonites were added to the intumescent formulation, composed by lignin and ammonium polyphosphate, in order to evaluate the influence of the strength and the nature (Brønsted or Lewis) of their acidic sites on the fire behavior of the composites. The thermal stability and the volatile thermal degradation products of the composites were assessed. The injected and 3D-printed composites were submitted to cone calorimeter (CC), limit oxygen index (LOI), and UL-94 flammability tests. A similar tendency was observed for the injected and 3D-printed samples. The high density of strong Lewis sites in AH2 showed to be detrimental to the fire-retarding properties. For the CC test, the addition of the intumescent composite reduced the peak of heat released (pHRR) in approximately 49% when compared to neat PLA, while the composites containing ANa and AH5 presented a reduction of at least 54%. However, the addition of AH2 caused a pHRR reduction of around 47%, close to the one of the composite without clay (49%). In the LOI tests, the composites containing ANa and AH5 achieved the best results: 39% and 35%, respectively, for the injected samples, and 35 and 38% for the 3D-printed samples. For the composite containing AH2 the LOI values were 34% and 32% for injected and 3D-printed samples, respectively. Overall, the best performance in the flammability tests was achieved by the composites containing clays with only weak and moderate strength acidic sites (ANa and AH5).

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Section: Introductionsupporting

confidence: 91%

Section: Cone Calorimetry (Cc)mentioning

confidence: 95%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Flame-Retarding Properties of Injected and 3D-Printed Intumescent Bio-Based PLA Composites: The Influence of Brønsted and Lewis Acidity of Montmorillonite

et al. 2022

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“…The decreases in MgO and Al 2 O 3 after the acid treatment indicate that parts of the octahedral sheets were dissolved during activation. Many acid sites (Lewis and Brønsted) are created in montmorillonite through acid activation (Yang et al, 2020;Dill et al, 2021). The CaO, K 2 O and Fe 2 O 3 contents of the natural samples also decreased, indicating the impact of acid treatment on accessory minerals in the bentonite.…”

Section: Xrf Analysis Of the Bentonite Samplesmentioning

confidence: 99%