Identification of different tetrapropylammonium cations occluded in ZSM-5 zeolite by combined thermal analysis (t.g.-d.t.a.) and 13C-n.m.r. spectroscopy
✍ Scribed by J. El Hage-Al Asswad; N. Dewaele; J.B. Nagy; R.A. Hubert; Z. Gabelica; E.G. Derouane; F. Crea; R. Aiello; A. Nastro
- Publisher
- Elsevier Science
- Year
- 1988
- Tongue
- English
- Weight
- 464 KB
- Volume
- 8
- Category
- Article
- ISSN
- 0144-2449
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✦ Synopsis
The combined use of thermal analysis (t.g.-d.t.a.) and 13C-n.m.r. spectroscopy allows one to identify four different structural environments for TPA + ions occluded in the ZSM-5 channels. A first low-temperature (ca. 380°C) d.t.a, peak is assigned to less strongly held or outer shell "strained" TPA + ions (type I), while a large intermediate temperature (ca. 425°C) peak C1 is attributed to inner-strained TPA + ions (type II). Both TPA ÷ species neutralize the SiO-defect groups. The high-temperature (ca. 475°C) peak is attributed to two different TPA + ions: those neutralizing the framework (Si-O-AI)negative centers (type III) (for high AI content samples), and those in the relaxed form that also neutralize SiO-defect groups (type IV) (for both high-and low-At-content samples). Types I-III all show the same 13C-n.m.r. spectra (splitting of the CH3-n.m.r. line), while type IV exhibits only one nlm.r, line for the CH3groups.