Paraffin Dehydrocyclization: Isotope Effect and Competitive Conversion of Alkane/Naphthene Mixture with a Pt–Mg(Al) Oxide Catalyst
✍ Scribed by Yuguo Wang; Buchang Shi; Robert D. Guthrie; Burtron H. Davis
- Book ID
- 102578054
- Publisher
- Elsevier Science
- Year
- 1997
- Tongue
- English
- Weight
- 147 KB
- Volume
- 170
- Category
- Article
- ISSN
- 0021-9517
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✦ Synopsis
The kinetic isotope effect and the lack of deuterium-hydrogen exchange in the unconverted reactants show that chemisorption of the reactant is the slow step of the dehydrocyclization mechanism with a Pt-SiO 2 catalyst. While the chemisorption was nearly irreversible for a Pt-SiO 2 catalyst, this was not the case for a Pt-Sn-SiO 2 and Pt-Mg(Al)O catalysts. Data from the competitive conversion of a mixture of n-C 8 H 18 and n-C 8 D 18 show that there is a kinetic isotope effect for the dehydrocyclization reaction and that the magnitude of the effect for Pt-Mg(Al)O (∼2.0) falls between those of Pt-SiO 2 and Pt-Sn-SiO 2 . The slight reversibility of the chemisorption step indicates that the Mg(Al)O support interacts with Pt but not to the extent that tin does in a silica-supported catalyst with a Pt : Sn = 1 : 1 ratio. The kinetic isotope effect for Pt-Mg(Al)O is about 2 and is comparable to the one obtained with a Pt-Sn-SiO 2 catalyst but is considerably lower than the value of 3.5 obtained with a Pt-SiO 2 catalyst.