Hydrocarbon reforming for hydrogen fuel cells. Annual report, 1 October 1979 to 30 September 1980
The mechanism of carbon formation on nickel autothermal steam reforming catalysts has been studied by temperature-programming, thermogravimetric and electron microscopic techniques. Temperature programmed surface reaction (TPSR) studies of carbon deposited on nickel reforming catalysts by the decomposition of ethylene exhibit seven forms of carbon that are distinguished by their characteristic reactivity with H/sub 2/ and 3.0 vol% H/sub 2/O/He. The relative population of the different carbon states depends primarily on the temperature during deposition. The reactivity of the carbon states are not altered by exposure to steam in C/sub 2/H/sub 4/-H/sub 2/O mixtures, but the amount of carbon deposited decreases to zero as the H/sub 2/O/C increases past a critical ratio. Critical steam-to-carbon ratios have been measured in the presence of C/sub 2/H/sub 4/-H/sub 2/O mixtures so as to establish the carbon formation boundary for several alumina-supported nickel, Ni-Rh, and Ni-Ir alloy catalysts. The critical H/sub 2/O/C ratio measured with a gravimetric balance decreased from approx. 30 at 773/sup 0/K to approx. 1 at 1073/sup 0/K for all the catalysts studied. The very rapid rate of C/sub 2/H/sub 4/ reforming over this temperature range caused mass transport gradients, which in turn lowered the apparent critical H/sub 2/O/C ratios. Carbon deposited on a 17 wt% Ni/Al/sub 2/O/sub 3/ catalyst at 875/sup 0/K and 1073/sup 0/K was examined by transmission (TEM) and scanning (SEM) electron microscopy. Results are reported and discussed.
- Research Organization:
- SRI International, Menlo Park, CA (USA)
- DOE Contract Number:
- AC21-79MC11323
- OSTI ID:
- 6778207
- Report Number(s):
- DOE/MC/11323-T1
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
08 HYDROGEN
AUTOTHERMAL REFORMER PROCESSES
CATALYSTS
HYDROGEN FUEL CELLS
HYDROGEN GENERATORS
HYDROGEN PRODUCTION
CARBON
DEPOSITS
ELECTRON MICROSCOPY
ETHYLENE
IRIDIUM
IRIDIUM ALLOYS
MORPHOLOGY
NAPHTHA
NICKEL
NICKEL ALLOYS
QUANTITY RATIO
RHODIUM
RHODIUM ALLOYS
SCANNING ELECTRON MICROSCOPY
STEAM
THERMAL GRAVIMETRIC ANALYSIS
ALKENES
ALLOYS
CHEMICAL ANALYSIS
CHEMICAL REACTIONS
COAL TAR OILS
DIRECT ENERGY CONVERTERS
DISTILLATES
ELECTROCHEMICAL CELLS
ELEMENTS
ENERGY SOURCES
FOSSIL FUELS
FUEL CELLS
FUELS
GAS GENERATORS
GRAVIMETRIC ANALYSIS
HYDROCARBONS
METALS
MICROSCOPY
NONMETALS
OILS
ORGANIC COMPOUNDS
OTHER ORGANIC COMPOUNDS
PETROLEUM
PETROLEUM DISTILLATES
PETROLEUM FRACTIONS
PLATINUM METAL ALLOYS
PLATINUM METALS
QUANTITATIVE CHEMICAL ANALYSIS
REFORMER PROCESSES
REFRACTORY METALS
THERMAL ANALYSIS
TRANSITION ELEMENTS
300503* - Fuel Cells- Materials
Components
& Auxiliaries
080103 - Hydrogen- Production- Steam Reformer Processes