Penta-coordinated Al3+ ions as preferential nucleation sites for BaO on γ-Al2O3: an ultra-high magnetic field 27Al MAS NMR study
In this paper, we report the first observation of preferential anchoring of an impregnated catalytic phase onto penta-coordinated Al3+ sites on the surface of γ Al2O3. The interaction of barium oxide with a γ alumina support was investigated by high resolution solid state 27Al magic angle spinning NMR at an ultra-high magnetic field of 21.1T and at sample spinning rates of up to 23 kHz. Under these experimental conditions, a peak in the NMR spectrum at ~ 23 ppm with relatively low intensity, assigned to 5-coordinated Al3+ ions, is clearly distinguished from the two other peaks representing Al3+ ions in tetra-, and octahedral coordination sites. Spin-lattice 27Al relaxation time measurements clearly show that these penta-coordinated Al3+ sites are located on the surface of the γ alumina support. BaO deposition onto this γ alumina sample resulted in the loss of intensity of the 23 ppm peak. The intensity loss observed was linearly proportional to the amount of BaO deposited. The results of this study strongly suggest that, at least for BaO, these penta-coordinated Al3+ ions are the nucleation sites.
- Research Organization:
- Pacific Northwest National Lab. (PNNL), Richland, WA (United States). Environmental Molecular Sciences Lab. (EMSL)
- Sponsoring Organization:
- USDOE
- DOE Contract Number:
- AC05-76RL01830
- OSTI ID:
- 920521
- Report Number(s):
- PNNL-SA-54213; JCTLA5; 19800; 9103a; KC0302010; TRN: US200818%%616
- Journal Information:
- Journal of Catalysis, 251(2):189-194, Vol. 251, Issue 1; ISSN 0021-9517
- Country of Publication:
- United States
- Language:
- English
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