Kinetics and mechanism of Pechmann condensation reaction over sulphated zirconia-supported zinc oxide

El-Dafrawy, Shady; Hassan, Shawky M.; Farag, Mervat

doi:10.1016/j.jmrt.2019.09.063

Cited by 8 publications

(8 citation statements)

References 64 publications

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“…Figure shows the results of reusing the catalyst four times. With the increase in the number of usages of the 50%Fe:50%Co-MOF nanocatalyst, its catalytic activity is slightly decreased from 93.40, 86.10, and 82.40, to 76.80 for the first, second, third, and fourth use, respectively, because of the gradual loss of the catalyst weight during filtration and washing. , …”

Section: Resultsmentioning

confidence: 99%

Fe/Co-MOF Nanocatalysts: Greener Chemistry Approach for the Removal of Toxic Metals and Catalytic Applications

2022

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This study describes the preparation of new bimetallic (Fe/Co)–organic framework (Bi-MOF) nanocatalysts with different percentages of iron/cobalt for their use and reuse in adsorption, antibacterial, antioxidant, and catalytic applications following the principles of green chemistry. The prepared catalysts were characterized using several techniques, including X-ray powder diffraction, Fourier transform infrared spectroscopy, transmission electron microscopy, and scanning electron microscopy. These techniques proved the formation of MOFs, and the average crystallite sizes were 25.3–53.1, 27.6–67.2, 3.0–18.9, 3.0–12.9, and 3.0–23.6 nm for the Fe-MOF, Co-MOF, 10%Fe:90%Co-MOF, 50%Fe:50%Co-MOF, and 90%Fe:10%Co-MOF samples, respectively. The nanoscale (Fe/Co) Bi-MOF catalysts as efficient heterogeneous solid catalysts showed high catalytic activity with excellent yields and short reaction times in the catalytic reactions of quinoxaline and dibenzoxanthene compounds, in addition to their antioxidant and antibacterial activities. Furthermore, the nanoscale (Fe/Co) Bi-MOF catalysts efficiently removed toxic metal pollutants (Pb 2+ , Hg 2+ , Cd 2+ , and Cu 2+ ) from aqueous solutions with high adsorption capacity.

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Section: Resultsmentioning

confidence: 99%

Fe/Co-MOF Nanocatalysts: Greener Chemistry Approach for the Removal of Toxic Metals and Catalytic Applications

2022

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“…Although the herein-discussed studies corroborated with the observed intermediate II and the proposed electrophilic aromatic substitution as the first step under the evaluated reaction conditions, the Pechmann condensation mechanism is still controversial. For instance, EL-Dafrawy and coauthors 37 investigated the kinetic parameters of the Pechmann condensation between resorcinol (1b) and ethyl acetoacetate (2a) under reflux conditions and in the presence of the zinc oxide supported on sulfated zirconia as catalyst. The experimental results showed that the transesterification step is the rate-determining step.…”

Section: Resultsmentioning

confidence: 99%

Synthesis of C4-substituted coumarins via Pechmann condensation catalyzed by sulfamic acid. Insights into the reaction mechanism by HRMS analysis

Barcellos¹,

Moraes²,

Lenardão³

2021

Arkivoc

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A series of functionalized C4-substituted coumarins were synthesized by exploring the reaction of activated and non-activated phenols and β-ketoesters under solvent-free conditions in the presence of sulfamic acid as a Br∅nsted acid catalyst. Fifteen examples were prepared with moderate to excellent yields (50% to 90%) using 10 mol % of the catalyst. Furthermore, it was possible from the proposed methodology to scale up the synthesis of coumarins to obtain up to 11 g of product. This work also provides a preliminary insight into the reaction mechanism using high-resolution mass spectrometry analysis. The key cinnamic acid derivative intermediate was detected, implying that under the evaluated conditions, the mechanistic pathway starts with an aromatic electrophilic substitution followed by dehydration reaction and intramolecular transesterification.

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“…Despite the fact that no a general agreement on the structure of ZS has not been achieved, it has been well established that acidic SO 3 with an adjacent Brønsted site is the acidic active site [48]. Therefore, sulfated metal oxides such as ZrO 2 , have both Brønsted acid sites arising from the existing sulfate groups at the surface of the catalyst and Lewis acid sites derived from the metal oxides [49]. In our particular case of the ZS material, Lewis acidity could be inherent to Zr 4+ sites.…”

Section: Discussionmentioning

confidence: 99%

Comparative Study of Different Acidic Surface Structures in Solid Catalysts Applied for the Isobutene Dimerization Reaction

et al. 2020

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Dimerization of isobutene (IBE) to C8s olefins was evaluated over a range of solid acid catalysts of diverse nature, in a fixed bed reactor working in a continuous mode. All catalytic materials were studied in the title reaction performed between 50–250 °C, being the reaction feed a mixture of IBE/helium (4:1 molar ratio). In all materials, both conversion and selectivity increased with increasing reaction temperature and at 180 °C the best performance was recorded. Herein, we used thermogravimetry analysis (TGA) and temperature programmed desorption of adsorbed ammonia (NH3-TPD) for catalysts characterization. We place emphasis on the nature of acid sites that affect the catalytic performance. High selectivity to C8s was achieved with all catalysts. Nicely, the catalyst with higher loading of Brønsted sites displayed brilliant catalytic performance in the course of the reaction (high IBE conversion). However, optimum selectivity towards C8 compounds led to low catalyst stability, this being attributed to the combined effect between the nature of acidic sites and structural characteristics of the catalytic materials used. Therefore, this study would foment more research in the optimization of the activity and the selectivity for IBE dimerization reactions.

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Kinetics and mechanism of Pechmann condensation reaction over sulphated zirconia-supported zinc oxide

Cited by 8 publications

References 64 publications

Fe/Co-MOF Nanocatalysts: Greener Chemistry Approach for the Removal of Toxic Metals and Catalytic Applications

Fe/Co-MOF Nanocatalysts: Greener Chemistry Approach for the Removal of Toxic Metals and Catalytic Applications

Synthesis of C4-substituted coumarins via Pechmann condensation catalyzed by sulfamic acid. Insights into the reaction mechanism by HRMS analysis

Comparative Study of Different Acidic Surface Structures in Solid Catalysts Applied for the Isobutene Dimerization Reaction

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