Hydrocarbon catalysis over platinum single crystal surfaces: the role of adsorbed carbon deposits and other chemical additives

Technical Report · Thu Oct 01 04:00:00 EDT 1981

OSTI ID:5679132

Davis, S M

The role of strongly adsorbed hydrocarbon deposits in reforming catalysis over platinum single crystal surfaces at atmospheric pressure and temperatures between 300 and 700/sup 0/K has been established and a model developed for the working structure and composition of the active catalyst surface. For this purpose a sensitive counting system for carbon-14 radiotracer studies was developed and utilized to investigate the kinetics of hydrocarbon rehydrogenation and intermolecular hydrogen transfer reactions. Quantitative hydrogen thermal desorption methods were developed to determine the composition of adsorbed hydrocarbon species and the energetics of elementary, sequential C-H bond breaking processes. Carbon-monoxide adsorption-thermal desorption studies were used to titrate uncovered platinum surface sites before and after reaction rate studies. The dynamics of the metal-hydrocarbon interaction, including minimum surface residence times for dissociatively chemisorbed intermediates (10/sup -2/ - 10/sup -1/ sec) were revealed from simultaneous studies of the reaction kinetics for hydrocarbon-deuterium exchange and skeletal rearrangement. Restart reaction studies were used to investigate the catalytic activity and selectivity of carbon covered platinum. These studies together with deactivation kinetics derived from reaction rate studies over initially clean platinum surfaces have clearly demonstrated that the primary role of the disordered, polymeric carbonaceous deposit is very simply that of a non-selective poison. The structure sensitivity of n-butane, isobutane, neopentane, and n-hexane skeletal rearrangement catalyzed at atmospheric pressure and 530 to 700/sup 0/K was investigated on a series of platinum single crystal surfaces with variable terrace, step, and kink structure. Only aromatization and bond-shift isomerization displayed structure sensitive reaction kinetics.

• Research Organization: Lawrence Berkeley Lab., CA (USA)
• DOE Contract Number: W-7405-ENG-48
• OSTI ID: 5679132
• Report Number(s): LBL-13051; ON: DE82010296
• Country of Publication: United States
• Language: English

Related Subjects

2-2-DIMETHYLPROPANE
2-METHYLPROPANE
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400201 -- Chemical & Physicochemical Properties
400301* -- Organic Chemistry-- Chemical & Physicochemical Properties-- (-1987)
400302 -- Organic Chemistry-- Isotope Effects-- (-1987)
ADSORPTION
ALKANES
ATMOSPHERIC PRESSURE
BETA DECAY RADIOISOTOPES
BETA-MINUS DECAY RADIOISOTOPES
BUTANE
CARBON
CARBON 14
CARBON ISOTOPES
CATALYTIC EFFECTS
CHEMICAL REACTION KINETICS
CHEMICAL REACTIONS
DATA
DECOMPOSITION
DEUTERIUM
ELEMENTS
EVEN-EVEN NUCLEI
EXPERIMENTAL DATA
HEXANE
HIGH TEMPERATURE
HYDROCARBONS
HYDROGEN ISOTOPES
HYDROGENATION
INFORMATION
ISOMERIZATION
ISOTOPE APPLICATIONS
ISOTOPE EFFECTS
ISOTOPES
KINETICS
LIGHT NUCLEI
MEDIUM TEMPERATURE
METALS
NONMETALS
NUCLEI
NUMERICAL DATA
ODD-ODD NUCLEI
ORGANIC COMPOUNDS
PLATINUM
PLATINUM METALS
POISONING
RADIOISOTOPES
REACTION INTERMEDIATES
REACTION KINETICS
SORPTION
SORPTIVE PROPERTIES
STABLE ISOTOPES
SURFACE PROPERTIES
TRACER TECHNIQUES
TRANSITION ELEMENTS
YEARS LIVING RADIOISOTOPES