The mitigation and tuning of the niobic acid (NBO) acidity has been successful pursued by addition of K+, Ba2+ and Nd3+ dopant species in amounts from 1 to 15 atom•nm-2. The characterization of the intrinsic acid properties of the samples was performed by adsorption of NH3 in a volumetric-microcalorimetric coupled line and by temperature programmed desorption (TPD) of 2-phenylethylamine in a thermogravimetric apparatus. The K-dopant was more effective in decreasing the acidity of niobic acid than the Ba- and Nd-dopants. Complementary measurements of effective acidity of the samples in water by base titrations with 2-phenylethylamine completed the study. A different picture of the effect of the three dopants on the NBO acidity was observed in water. All the results indicated that the K-species doped more selectively the Brønsted acid sites, acting as an ion-exchanger, while Ba- and Nd-species had prevalent action on the Lewis acid sites of the NBO surface.

Modulation of the acidity of niobic acid by ion-doping : Effects of nature and amount of the dopant-ions / P. Carniti, A. Gervasini, M. Marzo, A. Auroux. - In: THERMOCHIMICA ACTA. - ISSN 0040-6031. - 567(2013), pp. 51-56. [Epub ahead of print]

Modulation of the acidity of niobic acid by ion-doping : Effects of nature and amount of the dopant-ions

P. Carniti
Primo
;
A. Gervasini
Secondo
;
2013

Abstract

The mitigation and tuning of the niobic acid (NBO) acidity has been successful pursued by addition of K+, Ba2+ and Nd3+ dopant species in amounts from 1 to 15 atom•nm-2. The characterization of the intrinsic acid properties of the samples was performed by adsorption of NH3 in a volumetric-microcalorimetric coupled line and by temperature programmed desorption (TPD) of 2-phenylethylamine in a thermogravimetric apparatus. The K-dopant was more effective in decreasing the acidity of niobic acid than the Ba- and Nd-dopants. Complementary measurements of effective acidity of the samples in water by base titrations with 2-phenylethylamine completed the study. A different picture of the effect of the three dopants on the NBO acidity was observed in water. All the results indicated that the K-species doped more selectively the Brønsted acid sites, acting as an ion-exchanger, while Ba- and Nd-species had prevalent action on the Lewis acid sites of the NBO surface.
Niobic acid catalyst ; Ion doping ; Intrinsic and effective acidity ; Adsorption microcalorimetry ; Thermal programmed desorption
Settore CHIM/02 - Chimica Fisica
2013
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/2434/220715
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