THE INFLUENCE OF RHENIUM SUPPORTED CATALYSTS FOR DRY REFORMING Sean Mueller

1
THE INFLUENCE OF RHENIUM SUPPORTED CATALYSTS FOR
DRY REFORMINGSean Mueller Dr. Susan
WilliamsNational Science Foundation Research
Experience for UndergraduatesChemical and
Petroleum EngineeringThe University of Kansas
Background A mixture of hydrogen and carbon
monoxide, known as synthesis gas, is widely used
in industry to produce a variety of chemical
compounds. Dry reforming, steam reforming, and
partial oxidation are used to produce synthesis
gas. Rhenium is known to improve catalyst
stability with a slight decrease in activity
however, the interactions between rhenium and the
metal, as well as the support, are not well
understood. Dry Reforming of CH4 with CO2 CH4
CO2 ? 2 CO 2 H2 Advantages - CH4 and CO2
are widely available at low cost - 11 H2 to
CO ratio is preferred for producing oxygenated
compounds - Synthesis gas product ratios can
be varied by combining other reactions Disadvanta
ges - Reaction is limited by equilibrium at
low temperatures - Catalysts deactivate due
to carbon deposition at high temperatures Dry
Reforming Mechanism on Platinum Zirconia The
simplified dry reforming reaction,

from above, actually proceeds through
two
independent pathways, CH4
decomposition
and CO2 dissociation.
An undesired
reverse water gas
shift
(RWGS) can also occur.

Experimental Results Reaction Studies of Activity
Results Continued Conclusions
Reaction Conditions Temperature 800C, CH4CO2
11, PtRe 14, Pt 0.1
wt. All catalysts were reduced at 400C for
one hour prior to reaction.
1. CO2 conversion exceeded CH4 conversion
indicating the presence of the RWGS reaction. 2.
Promotion of the support with Ce results in
increased activity of the catalyst. 3. Promotion
of the Pt metal with Re results in a slightly
decreased activity of the catalyst.
CO desorption from Pt/ZrO2 occurs around 400 C,
Pt/CeZrO2 around 200 C, Pt-Re/CeZrO2 around 150
C, and Pt-Re/ZrO2 around 300 C For all catalysts,
the carbonate region decreases in intensity with
increasing temperature
Fourier Transform Infared Spectroscopy

• Analysis Conditions
• Fresh catalystKBr 11
• Reduce in H2 for 1 hour at 400
• Flush in He until no further change
• 3. In He, cool to room temperature taking scans
  every 50 C
• 4. Expose to CO until no further changes
• 5. Flush in He until no further change
• 6. In He, heat to 400 C taking scans every 50 C

Conclusions There is a debate as to whether a
Pt-Re alloy exists in reforming catalysts. Some
studies conclude that Re and Pt are in the
metallic state and have a strong bimetallic
interaction (alloy) others have found that Re
exists in the cationic state and has a strong
effect on the support. Recent studies3 have
proposed that most of the Re is in the metallic
state and alloyed with Pt, and that there is a
small amount of cationic Re that interacts
strongly with the support. Based on my results,
I propose that Re does have a strong interaction
with Pt and also the support. The Pt-Re
interaction degrades over time, but the Re
interaction with the support is stable. In fact,
it is the Re-support interaction that eventually
yields increasing activity even while the Pt-Re
interaction degrades. In the Ce promoted
supports, Re is prevented from strongly
interacting with the oxygen in the support the
difference in activities between Pt-Re/ZrO2 and
Pt-Re/CeZrO2 help support this hypothesis. To
confirm this hypothesis, I propose further
studies using pre and post reaction TPR, TPO,
Extended X-ray Absorption Fine Structure (EXAFS)
analysis, and further FTIR (post reaction) and
reaction activity analysis.

• CO2 adsorbed 2300-2400
• Ce promoted supports have a much more intense
  carbonate region 1000-1600
• 3. CO adsorbed on terrace Pt 2075
• 4. CO adsorbed on step Pt 2085
• 5. Pt-Re catalysts, regardless of the presence of
  Ce, show decreased CO adsorption

a) Structure of the ZrO2 support 1
b) Reaction mechanism on a catalyst particle 2
Metal and Support Promotion The addition of Ce
cations to the zirconia support increases the
thermal stability and surface area of the
support, retards Pt particle growth, thus
maintaining a high surface area of exposed Pt
sites, and increases oxygen transfer between the
metal and the support thereby decreasing carbon
deposition on the metal. Metal promoters, such as
Rhenium (Re), are known to reduce the CH4
dissociation that is the main cause of carbon
deposition. Re also inhibits the agglomeration
of Pt particles. In this study, the affect of the
addition of Re to Pt supported on ZrO2 and
Ce-ZrO2 was investigated.
Acknowledgements The University of Kansas REU
Program and the National Science Foundation,
David Slade, Wei Wang, Abhishek Jain, Andy
Arthur, Kate Wilbanks, Jose Ortega, Sagar Sarsani,

• References
• Jung, C., Ito, Y., Endou, A., Kubo, M., Imamura,
  A., Selvam, P., Miyamoto, A., Catalysis Today.
  87. (2003).
• Wei, J., Iglesia, E., Journal of Catalysis. 224.
  (2004).
• Xiao, J., Puddephatt, R.J., Coordination
  Chemistry Reviews. 143. (1995).

Gas phase CO disappears at RT and the Pt-CO bond
disappears as temperature increases. CO2
adsorption increases with temperature.