Catalyst Acidit Distributions Using Visible and Fluorescent Indicators.

Drushel, Harry V.; Sommers, A. L.

doi:10.1021/ac60244a023

Cited by 41 publications

(12 citation statements)

References 20 publications

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“…As in the case of dicinnamalacetone, (Figure 4(C)),the interaction between the molecule and the Lewis acid sites might lead to the appearance of an absorption band between 400 nm and 500 nm, which is responsible for the orange color. 68 Although surface acidity of a solid can be determined by simple titration with Hammett indicators, the problem existed since both Lewis acid sites and Brønsted acid sites had the capability to modify the color of the Hammett indicator solution without any distinction. Therefore, pyridine adsorption probed by FT-IR spectroscopy was used as an additional method to investigate the difference between Lewis acid sites and Brønsted acid sites.…”

Section: Dicinnamalacetone Yellowmentioning

confidence: 99%

Iron-Modified Mesoporous Silica as an Efficient Solid Lewis Acid Catalyst for the Mukaiyama Aldol Reaction

Ollevier

Kleitz

2018

ACS Catal.

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Fe-MCM-41 and Fe-SBA-15, two different iron-containing mesoporous silicas were successfully synthesized by a straightforward and versatile method using iron acetylacetonate as a metal precursor. pH adjustment with ammonia during the synthesis was found to be an efficient way to improve the iron content. Physicochemical parameters of the iron-containing mesoporous silicas were obtained by nitrogen physisorption measurements, and the coordination environment of iron elements was validated by UV-vis diffuse reflectance spectroscopy and X-ray photoelectron spectroscopy. The surface acidity was tested by using a series of Hammett indicators. To further distinguish the Lewis acid sites on the surface, pyridine adsorption FT-IR method was implemented. These prepared nanoporous catalysts were screened in the Mukaiyama aldol reaction as a model reaction catalyzed by a Lewis acid. The Lewis acid catalytic activity of the materials was fine-tuned, and the corresponding aldol products were obtained in good yield and selectivity. More importantly, the solid catalysts were very stable and could be reused at least nine times while maintaining the same catalytic activity.

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Section: Dicinnamalacetone Yellowmentioning

confidence: 99%

Iron-Modified Mesoporous Silica as an Efficient Solid Lewis Acid Catalyst for the Mukaiyama Aldol Reaction

Ollevier

Kleitz

2018

ACS Catal.

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“…As far back as the 1960s, 1-aminobutane dissolved in isohexane was directly titrated on clay suspensions in isohexane using bromothymol blue and bromcresol green as indicators [28]. In this study, 1-aminobutane, pkb = 10.9; kb = 1.26 × 10 −11 moll −1 , was used as a base to determine the total acidity of the differently activated clay powders from Uganda clays.…”

Section: Surface Aciditymentioning

confidence: 99%

Distinguishing Kaolinites and Smectite Clays from Central and Eastern Uganda Using Acidity, pH, Colour and Composition

Mukasa-Tebandeke¹,

Ssebuwufu²,

Nyanzi³

et al. 2015

AJAC

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The Langmuir isotherms of 1-aminobutane in isohexane slurries showed increase in clay acidity with increase in concentration of mineral acid used to leach the clay as well as the temperature at which the clay was thermally activated prior to experimentation involving adsorption of 1-aminobutane. The values of acidity for Central Uganda were low ranging from 0.07 mol/g to 0.32 mol/g yet those for clays from Eastern Uganda were high ranging from 0.1 mol/g to 1.85 mol/g. Based on acidity, pH, elemental and mineral compositions, the clays from Central Uganda were found to be kaolinites or halloysites, yet Eastern Uganda clays were resolved to contain nontronite and kaolinite.

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“…The titration procedure was as described by Drushel and Sommers (1966). Ten to twenty mg of the samples in iso-octane suspension were titrated with 0-005 N nbutylamine in iso-octane solution.…”

Section: Apparatus and Proceduresmentioning

confidence: 99%

Surface Acidity of Montmorillonites

Frenkel

1974

Clays and clay miner.

120

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Abstract--Surface acidity of almost homoionic montmorillonites was measured by titrating selected Hammett indicators adsorbed on the clay with n-butylamine.As expected, the acidity is strongly affected by the exchangeable cations and the degree of hydration of the clay. Greater polarizing ability of the interlayer cations increases both the strength and number of acid sites per H 0 value. The acidity of 'activated' or heated H-montmorillonite does not exceed that of untreated H-montmorillonite. The origin of the negative charge in the montmorillonite appears to affect the acidity of the clay.It is concluded that the very high acidities reported in the literature (Ho < -5-6) are apparent only and are due to physisorption of the indicator.

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Catalyst Acidit Distributions Using Visible and Fluorescent Indicators.

Cited by 41 publications

References 20 publications

Iron-Modified Mesoporous Silica as an Efficient Solid Lewis Acid Catalyst for the Mukaiyama Aldol Reaction

Iron-Modified Mesoporous Silica as an Efficient Solid Lewis Acid Catalyst for the Mukaiyama Aldol Reaction

Distinguishing Kaolinites and Smectite Clays from Central and Eastern Uganda Using Acidity, pH, Colour and Composition

Surface Acidity of Montmorillonites

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