Induced catalytic activity of fluorided alumina in the reactions of isobutane
- Univ. of Pittsburgh, PA (United States)
The reaction chemistry for the conversion of isobutane on pure and fluorided aluminas was compared to continuous flow experiments. Catalysts with 0, 2.6, 4.5, and 6.5% F were pretreated in flowing oxygen either at 500 or 650{degrees}C. Only the products of dehydrogenation and demethanation were obtained on pure alumina; the rate of reaction was about one order of magnitude higher when the catalyst was pretreated at 650{degrees}C than when it was pretreated at 500{degrees}C. Paraffins, including neopentane, were also produced over fluorided aluminas; on catalysts pretreated at 650{degrees}C while dehydrogenation and demethanation decreased, paraffin formation increased with time on stream (TOS). Over the catalysts with 4.5 and 6.5% F the rate of hydride transfer-producing paraffins exceeded that of initiation (H{sub 2} + CH{sub 4} formation) by a factor of from 2 to 3. All of the catalysts were more active than silica-alumina for isobutane conversion. IR spectra from pyridine adsorbed on catalysts with 0-4.5% F and pretreated either at 500 or 650{degrees}C showed no evidence of a band of 1540-50 cm{sup -1} assignable to pyridinium ion formed by interaction between pyridine and Bronsted acid sites. On the catalyst with 6.5% F this band appeared when the catalyst was pretreated at either 500 or 650{degrees}C. Isobutane can be dehydrogenated and demethanated over the dual acid-base pair sites of the alumina. The increasing paraffin formation with TOS may result from new and additional Bronsted sites introduced during dehydrogenation. 22 refs., 7 figs., 4 tabs.
- OSTI ID:
- 224043
- Journal Information:
- Journal of Catalysis, Journal Name: Journal of Catalysis Journal Issue: 2 Vol. 157; ISSN 0021-9517; ISSN JCTLA5
- Country of Publication:
- United States
- Language:
- English
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