Synthesis and characterization of aerogel-derived cation-substituted hexaaluminates
- Univ. of Michigan, Ann Arbor, MI (United States). Dept. of Chemical Engineering
New methods have been developed for the synthesis of high surface area cation-substituted hexaaluminates. These materials were prepared by calcining high temperature (ethanol extraction) or low temperature (CO{sub 2} extraction) aerogels at temperatures up to 1,600 C. Cation-substituted hexaaluminates have emerged as promising catalysts for use in high temperature catalytic combustion. In comparing unsubstituted and cation-substituted hexaaluminates, the authors found that the phase transformations were much cleaner for the cation-substituted materials. BaCO{sub 3} and BaAl{sub 2}O{sub 4} were intermediates during transformation of the unsubstituted materials, while the cation-substituted materials transformed directly from an amorphous phase to crystalline hexaaluminate. Moreover, the presence of substitution cations caused the transformation to occur at lower temperatures. Mn seems to be a better substitution cation than Co since the Mn-substituted materials exhibited higher surface areas and better heat resistances than the Co-substituted materials. The low temperature aerogel-derived materials possessed quite different characteristics from the high temperature aerogel-derived materials. For example, phase transformation pathways were different.
- OSTI ID:
- 522344
- Report Number(s):
- CONF-961202--; ISBN 1-55899-361-4
- Country of Publication:
- United States
- Language:
- English
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