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The acidity of trivalent cation-exchanged montmorillonite. Temperature-Programmed desorption and infrared studies of pyridine and n-butylamine

Published online by Cambridge University Press:  09 July 2018

C. Breen
Affiliation:
School of Chemical Sciences, National Institute for Higher Education, Glasnevin, Dublin 9, Eire
A. T. Deane
Affiliation:
School of Chemical Sciences, National Institute for Higher Education, Glasnevin, Dublin 9, Eire
J. J. Flynn
Affiliation:
School of Chemical Sciences, National Institute for Higher Education, Glasnevin, Dublin 9, Eire

Abstract

Temperature-programmed desorption (TPD) and IR spectroscopy were used to characterize the number and strength of acid sites in Al3+-, Cr3+- and Fe3+-exchanged montmorillonite. The bases pyridine and n-butylamine occupied three different sites in the interlamellar space: (i) physisorbed base, (ii) base bound to Lewis acid sites, and (iii) protonated base. TPD profiles for pyridine were characterized by maxima at 40°, 150° and 340°C, whilst those for n-butylamine occurred at 30°, 200° and 410°C. The Al3+- and Cr3+-exchanged forms were stable up to pretreatment temperatures of 300°C, but the Fe3+-form required > 3 day exposure to base vapour to re-establish the high-temperature desorption peak. Variable-temperature IR studies showed that the number of Brönsted-bound pyridine molecules increased with increased outgassing temperature.

Information

Type
Research Article
Copyright
Copyright © The Mineralogical Society of Great Britain and Ireland 1987

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