(548c) Bimetallic Cu/Pd Nanoparticles As Low Temperature Sulfur-Tolerant WGS Catalysts

Bimetallic
Cu/Pd nanoparticles as low temperature sulfur-tolerant
WGS catalysts

SeongUk Yun and Vadim V. Guliants

Chemical
Engineering, University of Cincinnati, Cincinnati OH 45221

The global interest in the water-gas shift (WGS) reaction as
a method of making hydrogen from coal-gasification products increased
significantly in recent years. However, typical low
temperature WGS catalysts are easily deactivated by sulfur compounds present in
coal-derived syngas. According to recent theoretical predictions, Cu and
Pd are expected to be promising sulfur-tolerant WGS catalysts.
In addition, bimetallic Cu/Pd nanoparticles
exhibiting bulk alloy, surface alloy, and core-shell structures are expected to
show differences not only in the WGS activity, but also tolerance to sulfur.

Several bimetallic Cu/Pd catalysts
were synthesized in our laboratory and characterized by scanning electron
microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction
(XRD), thermogravimetric analysis (TGA), physi/chemisorption, and temperature-programmed reduction
(TPR) in H₂. The TPR analysis showed that the presence of Cu
facilitated the reduction of active metals at lower temperatures. The TGA
analysis revealed a strong interaction between Cu, Pd and oxide support suggesting solid alloy information.
The XRD indicated that the size of these metallic nanoparticles was in the
15-20 nm range depending on the Cu/Pd
ratio. The size and shape of supported Cu/Pd
nanoparticles were determined by TEM. The WGS catalytic activity of catalysts
have been evaluated in the WGS reaction at 398-723 K under atmospheric pressure
in a fixed-bed microreactor employing the feed of 10%
CO and 20% H₂O (balance He). Significant improvement in the WGS
catalytic activity was observed by optimizing the Cu/Pd
ratio. These novel bimetallic catalysts showed improved sulfur resistance
during WGS reaction.