<html><head></head><body style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space; color: rgb(0, 0, 0); font-size: 14px; font-family: Calibri, sans-serif; "><div><br></div><span id="OLK_SRC_BODY_SECTION"><div xmlns:v="urn:schemas-microsoft-com:vml" xmlns:o="urn:schemas-microsoft-com:office:office" xmlns:w="urn:schemas-microsoft-com:office:word" xmlns:m="http://schemas.microsoft.com/office/2004/12/omml" xmlns="http://www.w3.org/TR/REC-html40"><div lang="EN-US" link="blue" vlink="purple"><div class="WordSection1"><p class="MsoNormal" align="center" style="mso-margin-top-alt:auto;margin-bottom:6.0pt;text-align:center;text-indent:0in;line-height:18.0pt"><b><span style="font-size:14.0pt;color:black">PhD DEFENSE: </span></b><span style="font-size:14.0pt;color:black">Sachi Shrestha</span><span style="color:black"><o:p></o:p></span></p><p class="MsoNormal" align="center" style="mso-margin-top-alt:auto;margin-bottom:6.0pt;text-align:center;text-indent:0in;line-height:18.0pt"><b><span style="font-size:14.0pt;color:black">DATE: </span></b><span style="font-size:14.0pt;color:black">August 3, 2015</span><span style="font-size:11.0pt;color:black"><o:p></o:p></span></p><p class="MsoNormal" align="center" style="mso-margin-top-alt:auto;margin-bottom:6.0pt;text-align:center;text-indent:0in;line-height:18.0pt"><b><span style="font-size:14.0pt;color:black">TIME: </span></b><span style="font-size:14.0pt;color:black">3:00 PM</span><span style="font-size:11.0pt;color:black"><o:p></o:p></span></p><p class="MsoNormal" align="center" style="mso-margin-top-alt:auto;margin-bottom:6.0pt;text-align:center;text-indent:0in;line-height:18.0pt"><b><span style="font-size:14.0pt;color:black">PLACE: </span></b><span style="font-size:14.0pt;color:black">Chemical Engineering Conference Room</span><span style="font-size:11.0pt;color:black"><o:p></o:p></span></p><p class="MsoNormal" align="center" style="mso-margin-top-alt:auto;margin-bottom:6.0pt;text-align:center;text-indent:0in;line-height:18.0pt"><b><span style="font-size:14.0pt;color:black">DISSERTATION CHAIR: </span></b><span style="font-size:14.0pt;color:black">Dr. Michael Harold</span><span style="font-size:11.0pt;color:black"><o:p></o:p></span></p><div class="MsoNormal" align="center" style="margin-top:0in;text-align:center;text-indent:0in;line-height:24.0pt"><b><span style="font-size:14.0pt;color:black"><hr size="2" width="100%" align="center"></span></b></div><p class="MsoNormal" align="center" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto;text-align:center;text-indent:0in;line-height:normal"><b><span style="font-size:14.0pt;color:black">TITLE:<o:p></o:p></span></b></p><p class="MsoNormal" align="center" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto;text-align:center;text-indent:0in;line-height:22.5pt"><b><span style="font-size:14.0pt">Understanding the Behavior of Bi-Functional Catalyst in Selective Catalytic Oxidation of Ammonia to Nitrogen<o:p></o:p></span></b></p><p class="MsoNormal" align="center" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto;text-align:center;text-indent:0in;line-height:22.5pt"><b><span style="font-size:14.0pt"><o:p> </o:p></span></b></p><p class="MsoNormal">Comprehensive steady-state experimental and modeling study of the selective oxidation of ammonia on washcoated multi-functional Pt/<span style="">g</span>-Al<sub>2</sub>O<sub>3</sub>+metal-exchanged zeolite monolith is
reported. The catalysts are compared in terms of their activity and selectivity for a range of temperature, catalyst architecture, catalyst composition, space velocity, and feed compositions (NH<sub>3</sub> + O<sub>2</sub>; NH<sub>3</sub> + NO+ O<sub>2</sub>)
in the presence and absence of H<sub>2</sub>O and CO<sub>2</sub>. SCR functions used in this thesis are Cu-ZSM-5, Fe-ZSM-5 and Cu-SSZ-13. The Pt loading of the monolith used are in the range of 0.7 – 10 g/ft<sup>3</sup> of monolith.<o:p></o:p></p><p class="MsoNormal">A single component Pt/Al<sub>2</sub>O<sub>3</sub> catalyst, at the lower space velocity (66k hr<sup>-1</sup>) light-off was characterized by decrease in the light-off temperature of ammonia oxidation with increase in Pt loading from 0.7
to 10 g Pt/ft<sup>3</sup> monolith and, in general, the selectivity to N<sub>2</sub> decreased while that of N<sub>2</sub>O and NO<sub>x</sub> increased. In absence of feed NO, a dual-layer ASC resulted in higher selectivity to N<sub>2,
</sub>due to selective reaction in the Fe-zeolite layer between NH<sub>3</sub> from the bulk and counter-diffusing NO<sub>x</sub> formed in the underlying Pt/Al<sub>2</sub>O<sub>3</sub>. Even with feed NO, the dual layer catalyst showed low NO<sub>x</sub> yield
and high N<sub>2</sub> yield due to SCR of NO by NH<sub>3</sub>. When Fe-ZSM-5 and Pt/Al<sub>2</sub>O<sub>3</sub> particles were mixed and washcoated as a single layer, this led to an increase in NH<sub>3</sub> conversion at high space velocity due to a decrease
in the diffusion barrier, however, the N<sub>2</sub> yield was lower due to Pt-catalyzed NH<sub>3</sub> oxidation, compared to the dual-layer ASC. The mixed catalyst out-performed the dual-layer catalyst at low temperature by exhibiting lower N<sub>2</sub>O
and higher N<sub>2</sub> yield which was attributed to NO migration and reduction on the SCR.
<o:p></o:p></p><p class="MsoNormal">Most of the trends were predicted by a 1+1 D reactor model that includes the Pt/Al<sub>2</sub>O<sub>3</sub> ammonia oxidation and Fe-ZSM-5 kinetics and the relevant transport processes. Kinetic parameters are estimated from single catalytic
component experiments while the reacting species effective diffusivity in the alumina and zeolite layers are estimated from the simulation of multi-layer experiments in which inert top layers of
<span style="">g</span>-Al<sub>2</sub>O<sub>3</sub> and Na-exchanged ZSM-5 were added to an underlying Pt/<span style=""> g</span>-Al<sub>2</sub>O<sub>3</sub> layer.<o:p></o:p></p><p class="MsoNormal">ASC comprising Cu-SSZ-13+Pt/Al<sub>2</sub>O<sub>3</sub> showed conversion and selectivity trends similar to that of Fe-ZSM-5+Pt/Al<sub>2</sub>O<sub>3</sub>. In absence of feed NO, NH<sub>3</sub> conversion decreased while N<sub>2</sub>
selectivity increased as Cu-SSZ-13 loading was increased. In presence of feed NO, both NH<sub>3</sub> and NO<sub>x</sub> conversion of the dual-layer catalyst increased with an increase in the Cu-SSZ-13 washcoat loading (thickness). We also demonstrated that
a hybrid catalyst having dual-layer and mixed catalyst attributes exhibits good performance by exploiting the beneficial effects of both catalyst types.<o:p></o:p></p><p class="MsoNormal">Finally, experimental and modeling study of CO oxidation on a Pt/Al<sub>2</sub>O<sub>3</sub> revealed a shift from kinetic to mixed washcoat diffusion with increasing temperature. Experiments conducted on the Pt/Al<sub>2</sub>O<sub>3</sub>
layer coated with £^-Al<sub>2</sub>O<sub>3</sub> layer of different thicknesses were used to estimate the effective diffusivity of CO in the £^-Al<sub>2</sub>O<sub>3</sub>.<o:p></o:p></p></div></div></div></span><style><!--
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