Hydroisomerization and hydrocracking of alkanes. 7. Influence of the balance between acid and hydrogenating functions on the transformation of n-decane on PtHY catalysts
- Instituto Superior Tecnico, Lisboa Codex (Portugal)
- Universite de Poitiers (France)
The transformation of n-decane was studied at 473 K, 101 kPa and pH{sub 2}/p{sub n-decane} = 9 on a series of PtHY catalysts containing from 0.02 to 1.5 wt% platinum and with Si/Al atomic ratios of 3, 9, or 35. The ratio between the number of accessible Pt atoms and the number of acid sites on which the heat of ammonia adsorption is greater than 100 kJ mol{sup -1} (n{sub Pt}/n{sub A}) was chosen for characterizing the balance between the hydrogenating and the acid functions. The activities, stabilities, and selectivities of the catalysts are definitely governed by this balance. For low values of N{sub Pt}/n{sub A} (<0.03), the activity per acid site is low, the deactivation is rapid and n-decane leads directly to all the isomerization and cracking products. For high values ({ge}0.17) the activity per acid sites is maximal, the deactivation is very slow and n-decane transforms successively into monobranched isomers, dibranched isomers, and tribranched isomers plus cracking products. In this latter case the catalyst can be considered as an ideal bifunctional catalyst, namely a catalyst on which only one transformation of the alkene intermediates on the acid sites can occur during their diffusion from the platinum sites on which they are generated to those on which they are hydrogenated. Therefore the reaction scheme of n-decane transformation matches the reaction scheme of olefinic intermediates. From the product distribution established on ideal catalysts the mechanism of the transformation of olefinic intermediates can be deduced. Branching isomerization occurs through protonated cyclopropane and cyclobutane intermediates. 29 refs., 9 figs., 5 tabs.
- OSTI ID:
- 494269
- Journal Information:
- Journal of Catalysis, Journal Name: Journal of Catalysis Journal Issue: 2 Vol. 162; ISSN 0021-9517; ISSN JCTLA5
- Country of Publication:
- United States
- Language:
- English
Similar Records
Hydroisomerization and hydrocracking of n-heptane on Pt/SAPO-5 and Pt/SAPO-11 catalysts
Impact of catalyst metal-acid balance in n-hexadecane hydroisomerization and hydrocracking