C h a p t e r 16
Silica-Alumina Ratio Effects on Zeolite Crystallization in the Presence of Trioctylamine Downloaded by UNIV OF CALIFORNIA SAN DIEGO on March 28, 2016 | http://pubs.acs.org Publication Date: May 27, 1988 | doi: 10.1021/bk-1988-0368.ch016
IR
and NMR Characterization
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M . L. Occelli , G. P. Ritz , P. S. Iyer , and J . V.
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Sanders
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Science and Technology Division, Unocal Corporation, P.O. Box 76, Brea, CA 92621 Division of Material Science and Technology, Commonwealth Scientific and Industrial Research Organisation, Clayton, Victoria 3168, Australia
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X-ray and NMR analyses of several Si-rich (Na, K, TOA)-mordenites and Al-rich (Na,K,TOA)-pentasils did not reveal the presence of significant amounts of amorphous material or occluded reactants. Phase impurities (feldspar) are believed responsible for the appearance of a relatively strong band at about 585 cm in the MID-IR spectra of (Na,K,TOA)-mordenites. Shifts to lower frequencies in the T-O band region correlates well with the presence of faults in several of the mordenite crystals studied. Aluminum-27 MAS NMR spectra show a single resonance at 50-53 ppm typical of Al(IV) in these zeolites. IR spectra indicate that after calcination, the pentasils exhibit bands only at 3733 and ~3588 cm . After NH-exchange and calcination at 500°C, all the samples examined showed an aluminum-27 NMR resonance near 0 ppm typical of Al(VI) indicating dealumination of the crystal lattice. This is accompanied by IR bands appearing at 3630-3635 cm in the OH-stretching region. Only when in their H-form, do the pentasils show an IR band at ~3635cm which, on the basis of Al-NMR results, is attributed to stretching vibrations of Al-OH groups resulting from extra lattice aluminum generated during zeolite activation. -1
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A l u m i n a - r i c h z e o l i t e s o f the p e n t a s i l f a m i l y and s i l i c e o u s m o r d e n i t e c r y s t a l s can be s y n t h e s i z e d from near s t o i c h i o m e t r i c h y d r o g e l s o f c o m p o s i t i o n A l 0 ~ : x S i 0 : l . 5 N a 0 : 2 . 2 K 0 : 2 5 0 rLO c o n t a i n i n g f o u r moles o f t r i o c t y famine (TOA) peT mole Α Ί 0 (V). G e l s w i t h χ
