Use of pyrrole as an IR spectroscopic molecular probe in a surface basicity study of metal oxides

Binet, Claude; Jadi, A.; Lamotte, J.; Lavalley, Jean‐Claude

doi:10.1039/ft9969200123

Cited by 42 publications

(39 citation statements)

References 11 publications

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“…Infrared spectroscopy has been extensively used to characterize CeO2 surfaces and their modification after exposure to H2 or D2 [8,22,26,38,47,48,[81][82][83][84][85][86][87][88]. Studies by Lamotte et al [81] and Binet et al [82] supported the hypothesis that the coordination of methoxy and OH species occurred via one-(I), two-(II), or three-fold (III) binding through a single oxygen to surface cerium atoms [81,82].…”

Section: Characterization Of Hydrogen Species By Infrared and Raman S...mentioning

confidence: 98%

A review of the interactions between ceria and H2 and the applications to selective hydrogenation of alkynes

Kammert

Moon

2020

Chinese Journal of Catalysis

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Section: Characterization Of Hydrogen Species By Infrared and Raman S...mentioning

confidence: 98%

A review of the interactions between ceria and H2 and the applications to selective hydrogenation of alkynes

Kammert

Moon

2020

Chinese Journal of Catalysis

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“…The determination of surface basicity is more complex as the probe molecules, such as carbon dioxide (CO 2 ) [23], may dissociate or give rise to complex surface reactions. Adsorption of pyrrole (C 4 NH 5 ) as a probe molecule to detect the basic sites on the surface of metal oxides and to estimate their basic strength has been studied by IR [24,25] and nuclear magnetic resonance (NMR) [26][27][28] spectroscopies, and will be considered here from a theoretical point of view.…”

Section: Introductionmentioning

confidence: 99%

Characterization of Acid and Basic Sites on Zirconia Surfaces and Nanoparticles by Adsorbed Probe Molecules: A Theoretical Study

Maleki

Pacchioni

2020

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Acid and basic sites on monoclinic and tetragonal zirconia were investigated at the DFT level by computing IR and NMR properties of adsorbed probe molecules. Regular and stepped ZrO 2 surfaces as well as stoichiometric zirconia nanoparticles have been considered. Acidity and basicity were probed by the adsorption of carbon monoxide and pyrrole, respectively. CO adsorption shows a positive shift of the CO stretching frequency in IR spectra while the C atom of CO is shielded and 13 C chemical shifts moves to higher field as a function of the strength of the acid site. For the study of basic sites we used a pyrrole molecule, but the interaction between the pyrrole ring and the surface leads to adsorption modes that cannot be used to titrate the surface basicity. On the other hand, at high coverage the molecule assumes an upright position and the formation of a hydrogen bond of the pyrrole NH group with the oxygen atoms of the surfaces provides a proxy of the basic properties of these sites. In particular, we focus on changes of the N-H IR frequency, 1 H, 15 N, and 17 O NMR chemical shifts and their correlations with the surface basicity. Among the correlations found, that between the N-H stretching frequency of adsorbed pyrrole and the 17 O NMR chemical shift of the O ion where the molecule is bound show a nice linear correlation. These two properties can provide useful information about the basic character of various O sites on the surface of zirconia.

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“…The Keggin ion in pure calcined MPA sample shows FT-IR bands at 1060 cm −1 , 960 cm −1 , 870 cm −1 , and 750 cm −1 corresponds to P-O i , Mo-O t , Mo-O c -Mo, and Mo-O e -Mo bonds, respectively [18]. All the FT-IR bands corresponding to Keggin ion appeared in La x MPA samples, and also a shift in the peak position of Mo-O e -Mo stretching mode was observed in these samples.…”

Section: Resultsmentioning

confidence: 99%

“…It is well known that incorporated foreign metal ion in the Keggin structure could induce variations in the FT-IR spectra of samples [19]. It was previously reported that incorporated metal ion reduced the symmetry of [PO 4 ] 3− ion, which resulted in a split in the P-O stretching band [18]. The FT-IR spectra of La x TPA and La x MPA materials did not exhibit any peaks at 1080 cm −1 or 1060 cm −1 after La exchange.…”

Section: Resultsmentioning

confidence: 99%

Lanthanum Exchanged Keggin Structured Heteropoly Compounds for Biodiesel Production

2019

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La-exchanged 12-tungstophosphoric acid (La x TPA) and 12-molybdophosphoric acid (La x MPA) salts (x = 0.25, 0.50, 0.75 and 1.00) were prepared via an ion exchange method. The physico-chemical characteristics of the materials were analyzed by using elemental analysis, X-ray diffraction (XRD), Fourier transformed infrared (FT-IR) spectroscopy, scanning electron microscopy (SEM), N 2 -physical adsorption, X-ray photoelectron spectroscopy (XPS), and acidity-basicity measurements. The results indicated that La was introduced into the secondary structure of heteropolyacid (HPA) and have not influenced the primary structure, which effectively improved the surface area and pore size. Acidity-basicity studies indicated that incorporation of La resulted in a decrease in the number of acid sites and an increase in the number of basic sites. The catalytic activity of samples was studied in transesterification of glyceryl tributyrate with methanol and La x TPA samples which exhibited high activity compared to La x MPA samples due to having more active basic sites and a larger surface area. Calcined La x TPA samples showed excellent stability, outstanding recyclability, and high activity for one pot transesterification and esterification processes. This outcome was attributed to the presence of balanced acidic and basic sites.

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Use of pyrrole as an IR spectroscopic molecular probe in a surface basicity study of metal oxides

Cited by 42 publications

References 11 publications

A review of the interactions between ceria and H2 and the applications to selective hydrogenation of alkynes

A review of the interactions between ceria and H2 and the applications to selective hydrogenation of alkynes

Characterization of Acid and Basic Sites on Zirconia Surfaces and Nanoparticles by Adsorbed Probe Molecules: A Theoretical Study

Lanthanum Exchanged Keggin Structured Heteropoly Compounds for Biodiesel Production

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