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Thermal analysis and EPR study of copper species in mordenites prepared by conventional and microwave-assisted methods

Authors
  • Shelyapina, Marina1
  • Zvereva, Irina1
  • Yafarova, Liliya1
  • Bogdanov, Dmitrii1
  • Sukharzhevskii, Stanislav1
  • Zhukov, Yurii1
  • Petranovskii, Vitalii2
  • 1 Saint Petersburg State University, 7/9 Universitetskaya nab., St. Petersburg, 199034, Russia , St. Petersburg (Russia)
  • 2 Universidad Nacional Autónoma de México, Centro de Nanociencias y Nanotecnología de la, Ensenada, Baja California, 22860, Mexico , Ensenada (Mexico)
Type
Published Article
Journal
Journal of Thermal Analysis and Calorimetry
Publisher
Springer Netherlands
Publication Date
Feb 01, 2018
Volume
134
Issue
1
Pages
71–79
Identifiers
DOI: 10.1007/s10973-018-7016-2
Source
Springer Nature
Keywords
License
Yellow

Abstract

Copper-exchanged mordenites prepared by different methods, conventional and microwave assisted, have been investigated by TG, DSC, temperature-programmed reduction (TPR), and EPR methods. TPR study of hydrated and annealed at 573 and 973 K samples revealed that the copper reduction occurs directly from Cu2+ to Cu0, and Cu2+ ions are in different local environments. The microwave-assisted treatment leads to formation of [Cu–O–Cu]2+ species in the main mordenite channels. The most easily recoverable copper in the fully hydrated samples corresponds to the individual Cu2+ ions coordinated by H2O molecules, and the number of these [Cu(H2O)n]2+ complexes does not depend on the preparation method and the total copper content. According to the EPR study, upon sample dehydration, [Cu(H2O)n]2+ species lose water and approach the wall of the zeolite forming a bond with reversible charge transfer from a framework oxygen to Cu2+.

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