Brønsted and Lewis acidity of modified montmorillonite clay catalysts determined by FT-IR spectroscopy

Reddy, C. Ravindra; Bhat, Y. S.; Nagendrappa, Gopalpur; Prakash, B. S. Jai

doi:10.1016/j.cattod.2008.04.004

Cited by 142 publications

(102 citation statements)

References 26 publications

(22 reference statements)

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“…0.5 g was dried in an oven for 1 hour at 100 ºC, then 0.1 cm 3 of pyridine was exposed to the samples overnight. The samples were redried at 120 ºC for one hour to remove the physisorbed pyridine [14]. The Brønsted and Lewis acids were determined by FTIR using the KBr pellet.…”

Section: Modification and Characterization Of M-mmt K10mentioning

confidence: 99%

“…Cation exchanged MMT has been used for esterification of short to medium chain carboxylic acids such as succinic acid [13], propionic acid [14], ethanoic acid, butanoic acid, hexanoic acid, octanoic acid and decanoic acid [15]. The production of fatty acid ester from steric acid using untreated MMT K10 as catalyst has been reported previously [16].…”

Section: Introductionmentioning

confidence: 99%

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Esterification of oleic acid with alcohols over Cu-MMT K10 and Fe-MMT K10 as acid catalysts

Harun

Jihadi

Ramli

et al. 2018

AIP Conference Proceedings

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Abstract. The esterification of free fatty acids with alcohols using montmorillonite (MMT) clay as heterogeneous catalyst is one of the methods to produce fatty acid alkyl ester that can be used as alternative renewable biofuels. However, the unmodified MMT gives low conversion of free fatty due to the limitation of acid sites in the clay structure. This work focuses on preparation of an environmental friendly catalyst from montmorillonite K10 (MMT K10) clay catalyst for the esterification of oleic acid with various alcohols. Esterification of oleic acid with alcohols has been carried out in the presence of metal exchanged MMT K10 (M-MMT K10; M = Fe 3+ and Cu 2+ ). The concentrations of both Fe 3+ and Cu 2+ precursors were varied at 1 M and 4 M. The effect of different alcohols used, molar ratio of reactants and catalyst loading on the esterification reaction was investigated. Among the exchanged clay catalysts, 4 M Fe-MMT K10 was found to be more active for the esterification of oleic acid with methanol. The maximum oleic acid conversion (ca. 68.5%) was achieved after 3 hours of reaction at the reaction temperature of 60 o C with molar ratio of methanol to oleic acid of 10:1 and catalyst loading of 5 wt% relative to the mass of oleic acid. The catalytic activity was found to be directly related to the amount of cation used in the modification step and Brønsted acidity of metal exchanged MMT K10 clay catalyst.

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Section: Modification and Characterization Of M-mmt K10mentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Esterification of oleic acid with alcohols over Cu-MMT K10 and Fe-MMT K10 as acid catalysts

Harun

Jihadi

Ramli

et al. 2018

AIP Conference Proceedings

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“…The temperature-programmed desorption of basic gas molecules (Arena et al 1998;Breen et al 1987; Adams and McCabe 2006;Singh et al 2007) and Hammett indicators (Walling 1950;Benesi 1957;Liu et al 2011) have been used to evaluate the strength of acid sites. In addition, Brønsted and Lewis acid sites can be distinguished by differentiating vibrational bands of the adsorbed basic probe molecules using Fourier transform infrared spectroscopy (FTIR) (Akçay 2005;Billingham et al 1996;Brown and Rhodes 1997;Cseri et al 1995;Flessner et al 2001;Liu et al 2011;Reddy et al 2009;Reddy et al 2007;Singh et al 2007;Tyagi et al 2006). Based on these investigations, the number of acid sites in montmorillonite obtained from different sources has been found to range from 0.09 to 0.60 mmol/g (Flessner et al 2001;Hart and Brown 2004;Liu et al 2011;Walling 1950).…”

Section: Introductionmentioning

confidence: 99%

“…Therefore, a complete evaluation of the solid acidity of montmorillonite, including the types and origins of solid acid sites, the acid amount, and the distribution of acid strength, is necessary. The solid acidity of montmorillonite is greatly influenced by heating and cation-exchange processes (Billingham et al 1996;Brown and Rhodes 1997;Heller-Kallai 2006;Liu et al 2011;Noyan et al 2006;Reddy et al 2009;Reddy et al 2007). However, most investigations have focused on acidactivated montmorillonite due to its high acidity and excellent performance in catalytic reactions, such as Friedel-Crafts alkylation and the polymerization of unsaturated hydrocarbons.…”

Section: Introductionmentioning

confidence: 99%

Studies on the solid acidity of heated and cation-exchanged montmorillonite using n-butylamine titration in non-aqueous system and diffuse reflectance Fourier transform infrared (DRIFT) spectroscopy

Liu

Yuan

et al. 2013

Phys Chem Minerals

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The effects of heating and cation exchange on the solid acidity of montmorillonite were investigated using n-butylamine titration in non-aqueous system and diffuse reflectance Fourier transform infrared spectroscopy. The number of total, Brønsted, and Lewis acid sites showed the same modulation tendency with increasing heating temperature, reaching a maximum at 120°C and subsequently decreasing until it reaches a minimum at 600°C. The Lewis acid sites result from unsaturated Al 3? cations, and their number increased with the heating temperature due to the dehydration and dehydroxylation of montmorillonite. The generation and evolution of Brønsted acidity were mainly related to interlayer-polarized water molecules. Water adsorbed on the unsaturated Al 3? ions also acted as a Brønsted acid. The acid strength of the Brønsted acid sites was dependent on the polarization ability of the exchangeable cation, the amount of interlayer water, and the degree of dissociation of the interlayer water coordinated to exchangeable cations. All cation-exchanged montmorillonites exhibited different numbers of acid sites and various distributions of acid strength. Brønsted acidity was predominant in Al 3? -exchanged montmorillonite, whereas the Na ? -and K ? -exchanged montmorillonites showed predominantly Lewis acidity. Moreover, Mg 2? -and Li ? -exchanged montmorillonites exhibited approximately equal numbers of Brønsted and Lewis acid sites. The Brønsted acidity of cation-exchanged montmorillonite was positively correlated with the charge-to-radius ratios of the cations, whereas the Lewis acidity was highly dependent on the electronegativity of the cations. The acid strengths of Al 3? -and Mg 2? -exchanged montmorillonites were remarkably higher than those of monovalent cationexchanged montmorillonites, showing the highest acid strength (H 0 B -3.0). Li ? -and Na ? -exchanged montmorillonites exhibited an acid strength distribution of -3.0 \ H 0 B 4.8, with the acid strength ranging primarily from 1.5 to 3.3 in Li ? -exchanged montmorillonite, whereas only weaker-strength acid sites (1.5 \ H 0 B 4.8) were present in K ? -exchanged montmorillonite. The results of the catalysis experiments indicated that montmorillonite promoted the thermal decomposition of the model organic. The catalytic activity showed a positive correlation with the solid acidity of montmorillonite and was affected by cation exchange, which occurs naturally in geological processes.

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“…, 1452 cm À1 and 1446 (1441) cm À1 are assigned to pyridine adsorbed on Lewis sites of alumina (or magnesia) [26]. The lack of bands at 1640 and 1545-1540 cm À1 for both solids indicates the absence of Brö nsted acidity or that these acid sites are not strong enough to interact with pyridine and generate the pyridinium ions [26].…”

mentioning

confidence: 98%

Ethanol steam reforming over rhodium and cobalt-based catalysts: Effect of the support

Moura

Souza

Bellido

et al. 2012

International Journal of Hydrogen Energy

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Brønsted and Lewis acidity of modified montmorillonite clay catalysts determined by FT-IR spectroscopy

Cited by 142 publications

References 26 publications

Esterification of oleic acid with alcohols over Cu-MMT K10 and Fe-MMT K10 as acid catalysts

Esterification of oleic acid with alcohols over Cu-MMT K10 and Fe-MMT K10 as acid catalysts

Studies on the solid acidity of heated and cation-exchanged montmorillonite using n-butylamine titration in non-aqueous system and diffuse reflectance Fourier transform infrared (DRIFT) spectroscopy

Ethanol steam reforming over rhodium and cobalt-based catalysts: Effect of the support

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