Montmorillonite Clay-Promoted, Solvent-Free Cross-Aldol Condensations under Focused Microwave Irradiation

Rocchi, Damiano; González, Juan Francisco; Menéndez, J. Carlos

doi:10.3390/molecules19067317

Cited by 35 publications

(27 citation statements)

References 39 publications

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“…This hypothesis is consistent with the documented ability of clay minerals to catalyze condensation and polymerization reactions from a variety of substrates. [35][36][37] This effect is of particular importance, since the low-molecular weight degradation products have been shown to have a mutagenic potential 38 .At pyrolysis temperatures of 450 °C -550 °C, the 13 C NMR signal is very similar in all the materials being centered at ~ 130 pm as see in Figure 2 (g-l). The primary species produced at these temperatures have an aromatic carbon structure, in addition to some phenolic and carboxylic species observed at ~150-160 ppm and 165-180 ppm, respectively.…”

Section: Infiltrationmentioning

confidence: 73%

Mineral–Biochar Composites: Molecular Structure and Porosity

Rawal¹,

Joseph²,

Hook³

et al. 2016

Environ. Sci. Technol.

163

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Dramatic changes in molecular structure, degradation pathway, and porosity of biochar are observed at pyrolysis temperatures ranging from 250 to 550 °C when bamboo biomass is pretreated by iron-sulfate-clay slurries (iron-clay biochar), as compared to untreated bamboo biochar. Electron microscopy analysis of the biochar reveals the infusion of mineral species into the pores of the biochar and the formation of mineral nanostructures. Quantitative 13C nuclear magnetic resonance (NMR) spectroscopy shows that the presence of the iron clay prevents degradation of the cellulosic fraction at pyrolysis temperatures of 250 °C, whereas at higher temperatures (350-550 °C), the clay promotes biomass degradation, resulting in an increase in both the concentrations of condensed aromatic, acidic, and phenolic carbon species. The porosity of the biochar, as measured by NMR cryoporosimetry, is altered by the iron-clay pretreatment. In the presence of the clay, at lower pyrolysis temperatures, the biochar develops a higher pore volume, while at higher temperature, the presence of clay causes a reduction in the biochar pore volume. The most dramatic reduction in pore volume is observed in the kaolinite-infiltrated biochar at 550 °C, which is attributed to the blocking of the mesopores (2-50 nm pore) by the nonporous metakaolinite formed from kaolinite. Disciplines Engineering | Physical Sciences and Mathematics

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Section: Infiltrationmentioning

confidence: 73%

Mineral–Biochar Composites: Molecular Structure and Porosity

Rawal¹,

Joseph²,

Hook³

et al. 2016

Environ. Sci. Technol.

163

View full text Add to dashboard Cite

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“…The literature contains many examples of self-dual Leonard pairs. For instance (i ated with an irreducible module for the Terwilliger algebra of the hypercube (see [4, C Leonard pair of Krawtchouk type (see [10, De nition 6.1]); (iii) the Leonard pair assoc module for the Terwilliger algebra of a distance-regular graph that has a spin model bra (see [1,Theorem], [3,Theorems 4.1, 5.5]); (iv) an appropriately normalized tota (see [11,Lemma 14.8]); (v) the Leonard pair consisting of any two of a modular Leon De nition 1.4]); (vi) the Leonard pair consisting of a pair of opposite generators fo bra, acting on an evaluation module (see [5,Proposition 9.2]). The example (i) is a sp examples (iii), (iv) are special cases of (v).…”

Section: Introductionmentioning

confidence: 99%

Volcanic ash as reusable catalyst in the green synthesis of 3H-1,5-benzodiazepines

Muñoz

Pasquale

Sathicq

et al. 2019

Green Processing and Synthesis

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The volcanic ash from the Andes mountain range (Puyehue-Cordon Caulle volcanic complex situated in western South America on the Argentinean-Chilean border) was used as heterogeneous acid catalyst in the suitable synthesis of 3H-1,5-benzodiazepines. The natural ashes were classified according to their particle size to generate the different catalytic materials. The catalysts were characterized by powder X-ray diffraction (XRD), scanning electron microscopy (SEM) with energy dispersive spectroscopy (EDS), vibrational spectroscopies (FT-IR and Raman), and textural properties were determined by N2 adsorption (SBET). Potentiometric titration with n-butylamine was used to determine the acidic properties of the catalytic materials. Several 3H-1,5-benzodiazepines were obtained by reaction of o-phenylenediamine and substituted 1,3-diphenyl-1,3-propanedione in solvent-free conditions, giving good to excellent yields of a variety benzodiazepines. The method was carried out in environmentally friendly conditions and it was operationally simple. The volcanic ash resulted in a safe and recyclable catalyst.

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“…H‐form zeolites are typical solid acids containing both Brønsted and Lewis acid sites . Montmorillonite K10 primarily contains strong Lewis acid sites . CeO 2 has both basic and acidic properties .…”

Section: Resultsmentioning

confidence: 99%

“…[33][34][35][36][37][38][39] Montmorillonite K10 primarily contains strong Lewis acid sites. [40][41][42] CeO 2 has both basic and acidic properties. 43,44 MgO and CaO are basic oxides.…”

Section: Catalyst Screeningmentioning

confidence: 99%

Selective removal of 1,2‐propanediol and 1,2‐butanediol from bio‐ethylene glycol by catalytic reaction

Jiang

Yang

et al. 2017

AIChE Journal

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Ethylene glycol (EG), synthesized from biomass, frequently contains refractory 1,2‐propanediol (PDO) and 1,2‐butanediol (BDO). Selective removal of PDO and BDO was realized herein by catalytic dehydration to form volatile aldehydes, ketones, and acetals. Various acidic and basic catalysts were screened under a range of conditions for the conversion of a mixture containing 73 wt % EG, 20 wt % PDO, and 7 wt % BDO. Over H‐Beta 26 zeolite, the most selective catalyst among tested, PDO and BDO conversions reached 99.1 and 99.3%, respectively, after 4 h reaction at 453 K, with separation factors over 2. The activation energies for EG, PDO, and BDO dehydration were ca. 99.3, 69.9, and 54.0 kJ/mol, respectively, accounting for the high reactivity of PDO and BDO. The dehydration largely proceeded in the micropores of H‐Beta and depended on the number of strong Brønsted acid sites, but excessively strong acid sites enhanced the polymerization of EG. © 2017 American Institute of Chemical Engineers AIChE J, 63: 4032–4042, 2017

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Montmorillonite Clay-Promoted, Solvent-Free Cross-Aldol Condensations under Focused Microwave Irradiation

Cited by 35 publications

References 39 publications

Mineral–Biochar Composites: Molecular Structure and Porosity

Mineral–Biochar Composites: Molecular Structure and Porosity

Volcanic ash as reusable catalyst in the green synthesis of 3H-1,5-benzodiazepines

Selective removal of 1,2‐propanediol and 1,2‐butanediol from bio‐ethylene glycol by catalytic reaction

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