Fraction of platinum surface covered with carbonaceous species following hydrogenolysis of hexane on platinum alumina catalysts
Catalytic naphtha reforming plays a major role in satisfying the demand for unleaded, high octane gasoline. Hydrogen containing carbonaceous deposits (coke) accumulation on the surface of the catalysts during reforming operation. This study investigated the following question: what is the fraction of the platinum surface covered with the deposits following a typical reforming reaction. These observations prompted us to prepare a platinum-alumina catalyst with a high metal content (5%) to enhance the sensitivity of experiments designed to examine the platinum surface following hexane hydrogenolysis. The reaction was selected because it is a good model reaction for catalytic reforming and it was also studied by the Somorjai group in the higher temperature range of their work. Hydrogenolysis of hexane was carried out in a flow system for 3 h at 713 K, at atmospheric pressure, and around 0.1 total conversion. The catalyst was cooled down to room temperature in the reactant mixture, and the fraction of surface platinum atoms exposed was measured in situ by four independent methods: titration of adsorbed oxygen by dihydrogen, chemisorption of carbon monoxide, infra-red spectroscopy of carbon monoxide bonded to platinum, and rate of ethylene hydrogenation. Independent gravimetric studies showed that coke deposits of around 1% by weight were formed on the same catalyst during hydrogenolysis of hexane under similar conditions. Each of the four methods indicate that approximately 50% of the platinum surface remains exposed under the conditions.
- Research Organization:
- Stanford Univ., CA (USA)
- OSTI ID:
- 6913331
- Resource Relation:
- Other Information: Thesis (Ph. D.)
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
CATALYSTS
POISONING
SURFACE PROPERTIES
NAPHTHA
CATALYTIC REFORMING
CARBONACEOUS MATERIALS
CHEMISORPTION
COMPARATIVE EVALUATIONS
DEPOSITION
DEPOSITS
HEXANE
HYDROGENATION
INFRARED SPECTRA
MEASURING METHODS
PLATINUM
ALKANES
CHEMICAL REACTIONS
COAL TAR OILS
DISTILLATES
ELEMENTS
ENERGY SOURCES
FOSSIL FUELS
FUELS
HYDROCARBONS
MATERIALS
METALS
OILS
ORGANIC COMPOUNDS
OTHER ORGANIC COMPOUNDS
PETROLEUM
PETROLEUM DISTILLATES
PETROLEUM FRACTIONS
PLATINUM METALS
REFORMER PROCESSES
SEPARATION PROCESSES
SORPTION
SPECTRA
TRANSITION ELEMENTS
020400* - Petroleum- Processing