(6iq) Rational Design of Catalytic and Hydrocarbon Trapping Materials to Meet Automotive Emissions Regulations

Rational Design of Catalytic and Hydrocarbon Trapping
Materials to meet Automotive Emissions Regulations

As
the emission legislation for vehicle pollutants is becoming more stringent
worldwide due to increasing concerns of the impact of air pollution on both the
environment and public health, much opportunity is created in the fields of
catalysis and catalytic materials. 
Several challenges for which I am particularly well-positioned to make
important advancements include the following: 
(i) Developing catalytic materials that are active for the oxidation of
diesel at temperatures as low as 150 ^oC,
(ii) Studying and understanding the function of hydrocarbon (HC) trapping
materials, such as ion-exchanged zeolites with different metals, for both
fundamental and applied purposes, (iii) Investigating the direct conversion of
methane (natural gas) to ethanol, where ethanol blends (e.g. E85) are provided
by most gas station in the US.  To-date,
availability of direct conversion of methane to ethanol and higher alcohols is
still limited.  Data such as these will
lead to the development of catalysts and processes for more energy efficient
vehicles and lower automotive exhaust emissions.

My
Ph.D. thesis at the University of South Carolina focused on developing a fundamental
understanding of the synthesis of dendrimer-stabilized nanoparticles in
solution and on oxide supports.  Most
researchers had focused on the final catalytic material, and left untouched the
interactions of dendrimers with the metal ions in
solution.  Our goal was to investigate the
complexation between dendrimer templates and metal ions and increase the metal
uptake by the dendrimers by varying the experimental
conditions.  By doing so, I developed a
new synthetic procedure towards the formation of dendrimer-stabilized
Au/Rh nanoparticles and the subsequent synthesis of cost-effective supported
metal catalysts.  The major novelty of
this synthetic route is that pH control helps to regulate the size of Au/Rh nanoparticles
formed, when a dendrimer route is used.  This
project was funded by Toyota Motor Engineer and Manufacturing of North America,
Inc. and I have participated in the design and writing of 3 annual proposals
that were successfully funded.  Diverging
from this project ? in conjunction with Dr. Michael Amiridis
and Dr. John Regalbuto, I also became interested in
different synthetic routes of nearly uniform and highly dispersed nanoparticles
on high surface area oxide supports.  To
this end, I synthesized a series of Ag heterogeneous catalysts using the Strong
Electrostatic Adsorption (SEA) technique, previously unexplored in the
literature, in which the metal nanoscale size is manipulated by altering the
experimental conditions. 

In
my postdoctoral research in Oak Ridge National Laboratory, I developed a method
to treat automobile exhausts for the regulated hydrocarbon (HC) emissions
resulting from cold-starting engines. 
The most effective solution is to employ suitable materials which can
trap HCs temporarily, such as ZSM-5 and β-zeolites.  The silver exchanged ZSM-5 and
β-zeolites, exhibited an increased propylene adsorption/desorption in the
absence of both H₂O and CO₂.  Combination
of synthesis and evaluation of such materials gives me tools to better
elucidate fundamental understanding in the adsorption of HCs in the automotive
exhaust emissions before they pass to the catalytic converter.  Recently I have initiated a project for the design
of Pd based catalytic materials supported on a ZrO₂-SiO₂
mixed oxide support, aiming to enhanced low-temperature oxidation performance.  Under certain conditions, Pd/ZrO₂-SiO₂
outperformed a Pd/Pt commercial diesel oxidation
catalyst.  The rigorous synthesis of
catalytic materials was new for my research group in ORNL.  As a result, I
now have experience in starting up an academic research lab including designing
and constructing laboratory process equipment necessary for my research.

Apparently,
catalytic materials with enhanced low-temperature oxidation performance are
necessary, with significant attention being paid to their stability under harsh
reaction environments, typical to automotive emissions control due to
hydrothermal aging and poisoning.  Furthermore, HC porous trapping materials for the treatment
of automobile exhausts resulting from cold-starting engines need to be
developed, ensuring temporary retention of HCs until automotive emission
control catalysts are lit off.  After
resolving those issues, future work will build upon my expertise in
catalyst synthesis and HC trapping materials to develop fundamental
understanding of structure-activity relationships for the formation of useful
materials that will provide a basis for lowering the automotive emissions.  Since this is an emerging field, I anticipate
this type of studies to extent into the future and I seek to undertake them as
a tenure track faculty.