Characterisation of Al coordination at the outer surface of dealuminated mordenites by X-ray photoelectron spectroscopy

Remy, M.; Genet, Mj.; Notte, Pp.; Lardinois, Pf.; Poncelet, Georges

doi:10.1016/0927-6513(93)80057-2

Cited by 27 publications

(21 citation statements)

References 17 publications

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“…Both Al VI and Al IV could be discriminated in the support calcined at 500 °C, with α‘ values of 1462.4 eV for Al VI (BE of Al 2p = 74.4 eV, fwhm = 1.97 eV) and 1461.4 eV for Al IV (BE of Al 2p = 73.2, fwhm = 2.01 eV). These values are close to those established for zeolites. − No good fit with the experimental curve was obtained when the Al VI /Al IV ratio determined from the 27 Al MAS NMR measurement (4.5:1) was imposed for the Al 2p and Al KLL peak decomposition. A good fit was only obtained for a ratio of 1.5:1, thus indicating a greater proportion of Al IV in the surface than in the bulk.…”

Section: Discussionsupporting

confidence: 74%

α-Alumina-Supported Nickel Catalysts Prepared with Nickel Acetylacetonate. 2. A Study of the Thermolysis of the Metal Precursor

Molina

Poncelet

1999

J. Phys. Chem. B

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The thermolysis of nickel acetylacetonate supported on α-alumina has been investigated by thermal methods (TGA-DTG-DTA), infrared spectroscopy (FTIR), and X-ray photoelectron spectroscopy (XPS). At 250 °C and in static air atmosphere, decomposition of the metal ligands is nearly complete. Higher temperatures are needed in an inert atmosphere or in a vacuum. The variation of XPS peak parameters of samples heated at various temperatures between 120 and 900 °C has been interpreted as a change of the distribution of the Ni species between the octahedral and tetrahedral aluminum sites of the support, and a progressive formation of a nickel aluminate-like species, in agreement with temperature-programmed reduction features.

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Section: Discussionsupporting

confidence: 74%

α-Alumina-Supported Nickel Catalysts Prepared with Nickel Acetylacetonate. 2. A Study of the Thermolysis of the Metal Precursor

Molina

Poncelet

1999

J. Phys. Chem. B

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“…Similar values have also been found using classical pillaring methods. 7 Although these values are intermediate between those of octahedral and tetrahedral aluminum of well-characterized aluminosilicates, 26 they cannot be unambiguously ascribed to a determinate aluminum environment, 27 particularly when different coordination sites of aluminum may be present. 28 31 P MAS-NMR spectra of representative samples at rt and calcined at 673 K are shown in Figure 5.…”

Section: Resultsmentioning

confidence: 96%

Preparation and Properties of Fluorinated Alumina-Pillared α-Zirconium Phosphate Materials

et al. 1996

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A polyoxyaluminum cluster, larger than the tridecamer ion [AlO 4 Al 12 (OH) 24 (H 2 O) 12 ] 7+ , was intercalated into R-zirconium phosphate using an oligomeric solution aged at 368 K and conducting the intercalation reaction, first at reflux and then with hydrothermal treatment, in the presence of F -. Different intercalation compounds were prepared by varying the Al 3+ /phosphate ratio, but a unique single phase material with basal spacing of 21.3 Å was obtained. As revealed by chemical analysis and X-ray photoelectron spectroscopy (XPS), F -is incorporated into the intercalated oligomer where it partially substitutes OH -ions. The XPS technique was also a helpful tool to determine the Al 3+ concentration from which other Al 3+ compounds are precipitated outside of the phosphate interlayer. Thermal treatment caused a continuous and gradual interlayer contraction up to 973 K, but no evidence of layer collapse or segregation of alumina was found, at least up to 1273 K. 31 P and 27 Al solid state NMR spectroscopies were used to investigate the mechanism of interaction between the phosphate layer and the aluminum species. Because of this interaction, the 31 P signal shifts toward higher field, at ≈20 ppm, while the 27 Al NMR spectra display the characteristic signal of octahedrally coordinated Al and of a new resonance between 44.8 and 49.8 ppm, which is related to the existence of Al-O-P bonds. An increase of the relative intensity of this signal was observed upon calcination of the materials at 673 K. The presence of F -in the interlayer aluminum oxide produced an enhancement of the thermal stability and porosity of the pillared materials. Studies of thermal-programmed desorption of NH 3 , pyridine adsorption, and decomposition of isopropyl alcohol have revealed the acid nature of fluorinated alumina-pillared R-ZrP materials. The acid sites catalyze the dehydration reaction of isopropyl alcohol with a selectivity of practically 100%.

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“…Dealumination of small-port mordenite is a process in which the access to the porous network is enhanced by the removal of (extra)framework Al species, at the expense of active site density. 44,52 Therefore, the distribution of active sites imaged using pyridine as a molecular probe results from a complex interplay between the accessibility and the actual concentration of Brønsted acid sites. Regions with a well-preserved small-port behavior or, on the contrary, extensively dealuminated will both give rise to a weak Raman signal, complicating thus the interpretation of the SRS images alone.…”

Section: ■ Results and Discussionmentioning

confidence: 99%

“…This treatment enhances the molecular accessibility (large-port behavior) while largely retaining the structural integrity and showing the typical MOR X-ray diffraction pattern (Figure S1). Nevertheless, this comes at the expense of about 50% of the acid sites related to the framework aluminum . The mesoporosity introduced by the dealumination is evidenced in the N 2 isotherm by the hysteresis loop at relative pressures above 0.4 (Figure S2).…”

Section: Resultsmentioning

confidence: 99%

Correlating Acid Site Distribution and Catalytic Activity in Dealuminated Mordenite at the Single-Particle Level

Fleury

Roeffaers

2020

ACS Catal.

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Researchers widely use bulk scale measurements to rationalize catalyst performances and construct structure−activity relationships. Such ensemble-averaged information neglects the complexity of the catalytic process, where spatial variations in molecular transport and catalytic site availability strongly influence the overall performance. However, understanding the interplay between the molecular processes and the local catalyst properties at the scale of individual particles requires the correlation of information obtained from different microscopy techniques. In this contribution, we directly reveal the nontrivial nanoscale correlation between the acid site distribution and the local catalytic performance of dealuminated mordenite zeolite particles by sequentially applying advanced Raman microspectroscopy, scanning electron microscopy, and fluorescence microscopy. In addition to the intra-and interparticle heterogeneities, the nonstraightforward correlation between acidity and activity at the pixel-to-pixel level highlights the complex impact of postsynthetic treatments on zeolites.

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Characterisation of Al coordination at the outer surface of dealuminated mordenites by X-ray photoelectron spectroscopy

Cited by 27 publications

References 17 publications

α-Alumina-Supported Nickel Catalysts Prepared with Nickel Acetylacetonate. 2. A Study of the Thermolysis of the Metal Precursor

α-Alumina-Supported Nickel Catalysts Prepared with Nickel Acetylacetonate. 2. A Study of the Thermolysis of the Metal Precursor

Preparation and Properties of Fluorinated Alumina-Pillared α-Zirconium Phosphate Materials

Correlating Acid Site Distribution and Catalytic Activity in Dealuminated Mordenite at the Single-Particle Level

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