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Selective Catalytic Reduction of Nitric Oxide by Hydrocarbons over Dendrimer-Stabilized Supported Bimetallic NanoparticlesEPA Grant Number: F5B71266
Title: Selective Catalytic Reduction of Nitric Oxide by Hydrocarbons over Dendrimer-Stabilized Supported Bimetallic Nanoparticles
Investigators: Deutsch, David S.
Institution: University of South Carolina at Columbia
EPA Project Officer: Zambrana, Jose
Project Period: July 1, 2005 through June 1, 2007
Project Amount: $43,455
RFA: GRO Fellowships for Graduate Environmental Study (2005) RFA Text | Recipients Lists
Research Category: Academic Fellowships
To develop mono- and bimetallic nanoparticles with finely tuned particle sizes and compositions for use in HC-SCR catalysts
The use of dendrimers, a family of hyper-branched, spherical polymers, may offer a unique path to rational design and synthesis of nanostructured bimetallic heterogeneous catalysts through the control of size, stability, and composition of nanoparticles in solution. In particular, poly(amido)amine (PAMAM) dendrimers can exchange metal ions into their branches, and subsequent reduction in solution yields dendrimer-stabilized metallic nanoparticles. After deposition of these dendrimer-metal nanocomposites onto a porous support, thermal decomposition of the dendrimer renders the active metal phase of the catalyst accessible for reaction. Using this method of catalyst synthesis, it may be possible to discover a stable supported bimetallic catalyst of known composition, morphology, and particle size that will achieve superior activity for the selective catalytic reduction of nitric oxide in the presence of propylene.
In order to properly prepare and activate these nanostructured materials, it is important to understand the method in which the dendrimer decomposes and desorbs from the surface of supported metal catalysts. This process will be monitored under inert, reducing, and oxidizing environments in-situ via Fourier-Transform Infrared (FTIR) spectroscopy. Furthermore, FTIR spectroscopy of adsorbed CO will be used to investigate the accessibility of the active metal sites after various oxidation and reduction treatments. These experiments, along with transmission electron microscopy, XPS, and EXAFS measurements, will supplement results obtained from kinetic studies in bench-scale chemical reactors.
Nanostructured bimetallic catalysts are among the most promising classes of catalytically active materials today. It has been shown that the active phase of supported metal catalysts loses its bulk chemical properties as the particle size decreases to approximately 1-2 nm, while possibly gaining and entirely new set of characteristics on the nanoscale level. It is expected that supported bimetallic catalysts such as Pt-Rh or Pt-Ru will not only show different NO reduction kinetics compared to their monometallic counterparts, but these samples may also exhibit activity dissimilar to Pt-Rh or Pt-Ru catalysts synthesized via traditional incipient-wetness techniques, thus highlighting the potential benefits of employing dendrimers as nanoparticle stabilizers.