Alkane transformations on supported platinum catalysts. Part 3: The stability of Pt/Al{sub 2}O{sub 3} (EUROPT-3) and of PtRe/Al{sub 2}O{sub 3} (EUROPT-4) during the hydrogenolysis of alkanes
- Brunel Univ., Uxbridge (United Kingdom)
The hydrogenolysis of ethane, propane and n-butane has been studied on Pt/Al{sub 2}O{sub 3} (EUROPT-3) and PtRe/Al{sub 2}O{sub 3} (EUROPT-4) catalysts between 520 and 660 K by a thermal cycling technique using a 10-fold excess of H{sub 2}. Analogous catalysts having higher metal concentrations have also been examined. With neither ethane nor propane does any progressive deactivation result from repeated thermal cycles, but with n-butane on Pt/Al{sub 2}O{sub 3} catalysts initial loss of activity alters product selectivities, specifically by decreasing the probability of breaking the internal C-C bond. After this, they behave reproducibly. With PtRe/Al{sub 2}O{sub 3} catalysts, product selectivities shown by n-butane are very different from those given by the Pt/Al{sub 2}O{sub 3} catalysts but are unaltered by the somewhat greater initial deactivation; they show some sample-to-sample variation, which is attributed to differences in surface Re concentrations. These results are explained by a model in which in which sites on low-index planes in very small Pt particles are those that are first inactivated through the formation of strongly held dehydrogenated species; when Re atoms are present they preferentially occupy these sites and the operation of bimetallic centres explains why deeper hydrogenolysis occurs in this case. Reproducible rates of n-butane hydrogenolysis are obtained with Pt/Al{sub 2}O{sub 3} below about 600 K, but not with PtRe/Al{sub 2}O{sub 3}; use of short (1 min) reaction pulses overcomes this difficulty. Partially deactivated catalysts can, however, be studied in the continuous-flow mode. 18 refs., 6 figs., 4 tabs.
- OSTI ID:
- 501843
- Journal Information:
- Journal of Catalysis, Vol. 163, Issue 2; Other Information: PBD: Oct 1996
- Country of Publication:
- United States
- Language:
- English
Similar Records
Alkane transformations on supported platinum catalysts. Part 1: Reactions of ethane, propane, and n-butane on 6. 3% platinum/silica (EUROPT-1)
Alkane transformations on supported platinum catalysts. Part 2: Reactions of propane and of n-butane on EUROPT-1 modified by titania and by alumina