Influence of heating on the solid acidity of montmorillonite: A combined study by DRIFT and Hammett indicators

Liu, Dong; Yuan, Peng; Liu, Hongmei; Cai, Jingong; Qin, Zhan-Fen; Tan, Daoyong; Zhou, Qing; He, Hongping; Zhu, Jianxi

doi:10.1016/j.clay.2011.03.016

Cited by 68 publications

(50 citation statements)

References 52 publications

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Section: Introductionmentioning

confidence: 99%

“…The Hammett indicators technique (Walling 1950;Benesi 1957;Adams and McCabe 2006;Liu et al 2011), n-butylamine back titration (Reddy et al 2005), and microcalorimetry (Breen 1991a, b;Hart and Brown 2004;Jerónimo et al 2007) have been used to determine the number of acid sites. 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).…”

Section: Introductionmentioning

confidence: 99%

“…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%

“…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). However, the solid acidity of montmorillonite is difficult to compare directly between different studies because both the samples used and the applied measurement methods are not uniform.…”

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%

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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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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

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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Graphene Oxide Catalyzed Dehydration of Fructose into 5‐Hydroxymethylfurfural with Isopropanol as Cosolvent

et al. 2014

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The design of green heterogeneous catalysts for the efficient conversion of biomass into platform molecules is a key aim of sustainable chemistry. Graphene oxide prepared from Hummers oxidation of graphite was proven to be a green and efficient carbocatalyst for the dehydration of fructose into 5‐hydroxymethylfurfural (HMF) in some three‐carbon and four‐carbon alcohol mediated solvent systems. HMF was obtained in up to 87 % yield in 90 vol % isopropanol‐mediated DMSO solvent. Some control experiments and analytical data showed that a small number of sulfonic groups and abundance of oxygen‐containing groups (alcohols, epoxides, carboxylates) have an important synergic effect in maintaining the high performance of graphene oxide.

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Thermal transport and chemical effects of fillers on free‐radical frontal polymerization

Gary

Bynum

Thompson

et al. 2020

Journal of Polymer Science

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Frontal polymerization (FP) is a process in which a front propagates in a localized reaction zone, converting monomer into polymer through the coupling of thermal diffusion with the Arrhenius kinetics of an exothermic reaction. Fillers are added to control the rheological properties of the formulation and to enhance the mechanical properties of the product. However, the thermal and chemical effects of these fillers on the front propagation have not been thoroughly explored. Herein we report the thermal and chemical effects of fillers on free‐radical frontal polymerization. It was found that fillers with high thermal diffusivities, such as milled carbon fiber and boron nitride increased the front velocity. Despite their high thermal diffusivities, fillers such as aluminum and alumina decreased the front velocity. This is likely due to the radical‐scavenging ability of aluminum oxide, which was explored with clay minerals. It was found that the presence of water within clay fillers can also decrease the front velocity. To probe the chemical effects, acid‐activated clay minerals were utilized. The results demonstrate that some fillers can increase front velocity through their high thermal diffusivities while others decrease it by acting as radical scavengers.

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Influence of heating on the solid acidity of montmorillonite: A combined study by DRIFT and Hammett indicators

Cited by 68 publications

References 52 publications

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

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

Graphene Oxide Catalyzed Dehydration of Fructose into 5‐Hydroxymethylfurfural with Isopropanol as Cosolvent

Thermal transport and chemical effects of fillers on free‐radical frontal polymerization

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