Using a surface-sensitive chemical probe and a bulk structure technique to monitor the γ- to θ-Al2O3 phase transformation

Journal Article · Thu Jun 30 04:00:00 EDT 2011 · Journal of Physical Chemistry C, 115(25):12575–12579

DOI:https://doi.org/10.1021/jp203541a· OSTI ID:1018125

Kwak, Ja Hun; Peden, Charles HF; Szanyi, Janos

In this work, we investigated the phase transformation of γ Al2O3 to θ Al2O3 by ethanol TPD and XRD. Ethanol TPD showed remarkable sensitivity toward the surface structures of the aluminas studied. Maximum desorption rates for the primary product of ethanol adsorption, ethylene, were observed at 225°C, 245°C and 320°C over γ-, θ-, and α-Al2O3, respectively. Ethanol TPD over a γ Al2O3 sample calcined at 800 °C clearly show that the surface of the resulting material possesses θ-alumina characteristics, even though only the γ-alumina phase was detected by XRD. These results strongly suggest that the γ-to-θ phase transformation of alumina initiates at oxide particle surfaces. The results obtained are also consistent with our previous finding that the presence of penta-coordinated Al3+ sites, formed on the (100) facets of the alumina surface, are strongly correlated with the thermal stability of γ-alumina.

• Research Organization: Pacific Northwest National Laboratory (PNNL), Richland, WA (US), Environmental Molecular Sciences Laboratory (EMSL)
• Sponsoring Organization: USDOE
• DOE Contract Number: AC05-76RL01830
• OSTI ID: 1018125
• Report Number(s): PNNL-SA-79213; 35599; VT0401000
• Journal Information: Journal of Physical Chemistry C, 115(25):12575–12579, Journal Name: Journal of Physical Chemistry C, 115(25):12575–12579 Journal Issue: 25 Vol. 115; ISSN 1932-7447
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
ADSORPTION
DESORPTION
ETHANOL
ETHYLENE
Environmental Molecular Sciences Laboratory
Ethanol TPD
MONITORS
OXIDES
PHASE TRANSFORMATIONS
PROBES
SENSITIVITY
STABILITY
X-RAY DIFFRACTION
alumina phase transformation