Solid acid catalysts from clays

Trombetta, Marcella; Busca, Guido; Lenarda, Maurizio; Storaro, Loretta; Ganzerla, Renzo; Piovesan, Luca; López, Antonio Jiménez; Alcántara-Rodrı́guez, M.; Rodríguez‐Castellón, Enrique

doi:10.1016/s0926-860x(99)00413-5

Cited by 69 publications

(24 citation statements)

References 24 publications

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“…The obtained acidity is thought to have a minor contribution to the total acidity if the hydrogen is tightly bound. [28] Moreover, the Brønsted acidity is widely believed to be associated with dissociated water molecules in the hydration sphere of the interlayered protons. [19a,29] After treating HNb 3 O 8 ·H 2 O at a higher temperature under vacuum, anhydrous HNb 3 O 8 is prepared, [30] and the interlayered protons move near the surface of the Nb 3 O 8 -slabs (Fig.…”

Section: Brønsted Acidity Of Layered Niobic Acidmentioning

confidence: 99%

Density Functional Theoretical Studies on Polyaniline/HNb₃O₈ Layered Nanocomposites

Yang¹,

Hou²,

Feng³

et al. 2007

Adv Funct Materials

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A theoretical study of polyaniline (PANI)/HNb3O8 layered nanocomposites has been performed based on ab initio calculations and experimental data. The Brønsted acidity of the layered niobic acid, and the interaction between the interlayered polyaniline molecules and the inorganic slabs in PANI/HNb3O8 nanocomposites, have been investigated. For the intercalation process of organic species into layered niobic acid, it is important to clarify whether the source of Brønsted acidity arises from the interlayered or hydrated protons. Thus, three inorganic layer structures, KNb3O8, HNb3O8, and HNb3O8·H2O, are evaluated, and the results show that there is only a minor contribution to the total acidity if the hydrogen is tightly bound by the inorganic slab. After the interlayered aniline monomers are polymerized within the acidic inorganic layers, two orientated structures of PANI molecules are calculated in which the interlayered C6 rings are perpendicular and parallel to the inorganic slabs, respectively, based on the experimental results. In comparison, PANI molecules in the latter orientation are placed in a relatively narrower interlayer space, and the hydrated proton cannot simultaneously form two effective hydrogen bonds with the O atom of Nb3O8– and an N atom of the PANI molecule because of the orientation requirement of the hydrogen bond. The interlayered hydrated proton cannot effectively transfer electrons between the PANI molecule and the inorganic slab. A similar conclusion is also reached from a detailed analysis of band structure and density of states (DOS). The calculated results are in good agreement with the experimental fact that a relatively higher conductivity is apparent in the former rather than in the latter.

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Section: Brønsted Acidity Of Layered Niobic Acidmentioning

confidence: 99%

Density Functional Theoretical Studies on Polyaniline/HNb₃O₈ Layered Nanocomposites

Yang¹,

Hou²,

Feng³

et al. 2007

Adv Funct Materials

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“…Another widely used method to study the surface acidity of a solid catalyst is through the product distribution analysis of some model catalyzed reactions [11]. Isomerisation, catalytic dehydration, and dehydrogenation are the most common typical model reactions used for investigating the acid-base properties of heterogeneous catalyst systems [12,13].…”

Section: Introductionmentioning

confidence: 99%

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

et al. 2009

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“…It is well known that surface acidity of a solid is essential for heterogeneously catalyzed reactions, as well as for adsorption and ion-exchange processes (Adams and McCabe, 2006;Trombetta et al, 2000). Surface acidity of clay minerals characterizes their ability to donate a proton or an electron pair.…”

Section: Introductionmentioning

confidence: 99%

“…Probe molecule is adsorbed on the surface and studied then by different physico-chemical methods, i.e. titration and spectroscopic techniques such as FTIR, XPS, NMR (Blanco et al, 1988;Sun Kou et al, 2000), along with temperature programmed desorption (TPD) of NH 3 and CO 2 (Okada et al, 2006;Trombetta, M., 2000;Ertl et al, 1997, Matsuhashi et al, 1994), microcalorimetry (Ravichandran and Sivasankar, 1997), thermal…”

Section: Introductionmentioning

confidence: 99%

“…On the other hand, application of catalytic reactions is based on the reactivity of a probe molecule and its ability to characterize surface sites. The most known catalytic test reactions are isopropanol conversion (Trombetta et al, 2000), dehydration of alcohols, cracking of cumene (Ravichandran et al, 1996) and benzene benzylation (Pushpaletha et al, 2005). Each of the techniques has its advantages and disadvantages.…”

mentioning

confidence: 99%

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Characterization of surface acidity and catalytic ability of natural clay minerals by means of test catalytic reaction

Novikova¹,

Belchinskaya

Roessner

et al. 2013

Acta Geodynamica Et Geomaterialia

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Catalytic test reaction of methylbutynol (MBOH) conversion was applied to investigation of natural clays and non-clay minerals from Jordanian (bentonite, kaolinite, diatomite, zeolite) and Russian (palygorskite, kaolinite, hydromica) deposits as well as H-ZSM-5. Palygorskite and kaolinite containing samples have shown the highest catalytic activity. Conversion over Jordanian clay minerals decreased in the order: zeolite > bentonite > red kaolinite > white kaolinite > diatomite that agreed to change of acidity, surface area of samples. Sufficient deactivation was observed for H-ZSM-5, kaolinite and hydromica due to adsorption of secondary product in micropores of raw minerals. Products of both acidic and basic pathways of test reaction were formed indicating the presence of acid and basic sites on clays surface, apart from acidic catalyst H-ZSM-5. The yield ratio of acidic to basic products was above the unity for zeolite, bentonite, red kaolinite, and palygorskite; equal to unity for diatomite and hydromica, and less then unity for white kaolinite. It was observed for kaolinite containing sample that high activation temperature increased conversion of MBOH owing to formation of additional basic sites as a result of mineral dehydroxylation. Rise of montmorillonite content from 30 to 80 % provided 91-97 % of MBOH conversion.

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Solid acid catalysts from clays

Cited by 69 publications

References 24 publications

Density Functional Theoretical Studies on Polyaniline/HNb₃O₈ Layered Nanocomposites

Density Functional Theoretical Studies on Polyaniline/HNb₃O₈ Layered Nanocomposites

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

Characterization of surface acidity and catalytic ability of natural clay minerals by means of test catalytic reaction

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Solid acid catalysts from clays

Cited by 69 publications

References 24 publications

Density Functional Theoretical Studies on Polyaniline/HNb3O8 Layered Nanocomposites

Density Functional Theoretical Studies on Polyaniline/HNb3O8 Layered Nanocomposites

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

Characterization of surface acidity and catalytic ability of natural clay minerals by means of test catalytic reaction

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Product

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Density Functional Theoretical Studies on Polyaniline/HNb₃O₈ Layered Nanocomposites

Density Functional Theoretical Studies on Polyaniline/HNb₃O₈ Layered Nanocomposites