Premium
Aluminium Coordinations in Zeolite Mordenite By 27 Al Multiple Quantum MAS NMR Spectroscopy
Author(s) -
Chen TieHong,
Wouters Bart H.,
Grobet Piet J.
Publication year - 2000
Publication title -
european journal of inorganic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.667
H-Index - 136
eISSN - 1099-0682
pISSN - 1434-1948
DOI - 10.1002/(sici)1099-0682(200002)2000:2<281::aid-ejic281>3.0.co;2-i
Subject(s) - calcination , mordenite , chemistry , zeolite , nuclear magnetic resonance spectroscopy , spectroscopy , solid state nuclear magnetic resonance , quadrupole , analytical chemistry (journal) , crystallography , nuclear magnetic resonance , stereochemistry , catalysis , organic chemistry , atomic physics , physics , quantum mechanics
27Al 3Q MAS NMR spectroscopy has been applied to study the coordination state of the species giving the 30 ppm Al NMR signal in the 27 Al MAS NMR spectrum of activated mordenite materials. From the 27 Al 3Q MAS NMR measurements it is evident that the broad peak at 30 ppm in the 27 Al NMR spectrum of the mordenite calcined at temperatures up to 600 °C comes mainly from the distorted four‐coordinated Al. By simulation a quadrupolar coupling constant of 5.8 MHz was estimated for the distorted tetrahedral Al. For samples calcined at 650 and 700 °C, a small amount of pentacoordinated Al emerges. The majority of the signal, however, arises from distorted tetrahedral Al. A two‐step calcination results in a significant contribution of the pentacoordinated Al to the signal at 30 ppm. From the simulated line‐shape, a quadrupole coupling constant of 6.2 MHz is obtained for the latter signal. These data show that during the calcination of the mordenite, the coordination environment at the Al centre gradually becomes distorted to give rise to the shoulder at 30 ppm. With the increase of the calcination temperature, pentacoordinated Al species form