Catalytic Properties of Fullerene Materials

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Catalytic Properties of Fullerene Materials

• Ripudaman Malhotra, Al Hirschon, Don McMillen
• SRI International, Menlo Park, CA
• and
• Bill Bell, TDA Corporation,
• Wheat Ridge, CO

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Outline

• FULLERENES
• Range of Fullerene Materials
• WHY FULLERENES?
• HYDROGEN-TRANSFER REACTIONS
• Dealkylation
• Reduction (hydrogenation)
• METHANE ACTIVATION
• Thermal Background and Fullerene-Soot Catalysis
• Comparison of Fullerene Soot with Other Carbons
• Effect of Various Pretreatments/Doping of
  Fullerene Soot
• OTHER CATALYTIC APPLICATIONS
• Selective Reductions
• Hydroformylation

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Fullerenes

• A newly discovered form of carbon
• Structure consists of cages made of carbon atoms
• Cages formed by including pentagons in a lattice
  of hexagons

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Range of Fullerene Materials

• Soluble Fullerenes C60, C70, C84, ...
• Insoluble Soot, metallized soot
• Fullerene Derivatives
• Functionalized
• Endohedrals
• Nanotubes, nanoparticles, encapsulates

COMMON DENOMINATOR Pentagon surrounded by
hexagons
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Pentagon imparts...

• Electrophilicity and an ability to stabilize
  radicals

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Krotos Suggestion A good model for Fullerene
Soot
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Fullerenes catalyze coupling and transalkylation
reactions
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Fullerenes Catalyze Cleavage of Dinanphthylmethane
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Systems to probe H-transfer reactions
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Dealkylation of less reactive aromatic nuclei
-1
Dimethylnaphthalene Dealkylation Rate Constant,
sec
-6
X 10
Carbon Type
Fullerene soots are more effective than either
acetylene black or activated carbons.
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Dealkylation of more reactive polynuclear
aromatics
-1
sec
Methylpyrene Dealkylation Rate Constant,
-6
X 10
Carbon Type
Dealkylation is rapid in the presence of all
carbons tested
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Transfer Hydrogenations
Carbon Type
Fully active NiMo sulfide is counterproductive
for this purpose
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Dehydrogenation of Tetralin
Percent Tetralin Dehydrogenation
Carbon Type
Fullerene soots are more effective than other
carbons
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Hydrogenation of Anthracene
Metal loaded fullerene soots are very effective
with gas phase H2
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Dealkylation under H2 pressure
Fullerene soots are more effective under H2
pressure even without metal loading
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Schemes for Methane Conversion
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Fullerene soot shows higher conversion despite
lower surface area
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Yield of higher hydrocarbons not limited by
conversion

• Only gases and char observed during soot
  catalysis no tars
• Increased C production with increasing flow-rate
  in the soot-catalyzed case indicates competing
  secondary reactions

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SALI Evidence for Chemisorption of Methane on
Fullerene Soot
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Doping with K or Mn increases the selectivity to
C2 and higher hydrocarbons
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Fullerenes as Ligands

• Hydroformylation Studies (Claridge et al., J.
  Mol. Catal. 89, 113,1994)
• C60 displaces PPh3 ligands from RuH(CO)(PPh3)3
  fluxional ligand
• Turnover frequency unchanged for ethene
• TO frequency for propene hydroformylation
  significantly reduced by C60, as is the
  n/iso-ratio

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Regioselective Reductions
-
Planeix and coworkers, 1994
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Conclusions

• Wide range of fullerene materials
• Fullerenes, including fullerene soots, catalyze
  H-transfer reactions.
• Their ability to catalyze hydrodealkylations
  makes them potentially useful for petroleum
  upgrading
• Fullerene soot is very effective in converting
  methane into higher hydrocarbons
• Selectivity to C2 increased by doping with K or
  Mn
• Fullerene materials are promising candidates for
  catalyst supports

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Acknowledgment

• Initial finding ACT project from NEDO
• Methane Activation US-DOE, PETC

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Flow Apparatus for Methane Conversion

• About 1.0 g soot supported on alumina frit
• Preheater set at 600C
• Temperature in reactor varied between 600 and
  1000C
• Upward gas flow through the catalyst bed
• Product gases quencehed and analyzed by on-line GC