<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><div lang="EN-US" link="blue" vlink="purple"><div class="WordSection1"><p class="MsoNormal"><o:p> </o:p></p><p class="MsoNormal" align="center" style="text-align:center;line-height:150%;background:white"><b><span style="font-size:14.0pt;line-height:150%;color:black">PhD DEFENSE STUDENT: </span></b><span style="font-size:14.0pt;line-height:150%;color:black">Monique Shauntá Wilburn<o:p></o:p></span></p><p class="MsoNormal" align="center" style="text-align:center;line-height:150%;background:white"><b id="yui_3_16_0_ym19_1_1479700940765_266030"><span style="font-size:14.0pt;line-height:150%;color:black">DATE: </span></b><span style="font-size:14.0pt;line-height:150%;color:black">Thursday, December 1, 2016<o:p></o:p></span></p><p class="MsoNormal" align="center" style="text-align:center;line-height:150%;background:white"><b id="yui_3_16_0_ym19_1_1479700940765_266034"><span style="font-size:14.0pt;line-height:150%;color:black">TIME: </span></b><span style="font-size:14.0pt;line-height:150%;color:black">10:00 AM<o:p></o:p></span></p><p class="MsoNormal" align="center" style="text-align:center;line-height:150%;background:white"><b id="yui_3_16_0_ym19_1_1479700940765_266039"><span style="font-size:14.0pt;line-height:150%;color:black">PLACE:</span></b><span style="font-size:14.0pt;line-height:150%;color:black"> Large Mechanical Engineering Conference Room<o:p></o:p></span></p><p class="MsoNormal" align="center" style="text-align:center;line-height:150%;background:white"><b id="yui_3_16_0_ym19_1_1479700940765_266044"><span style="font-size:14.0pt;line-height:150%;color:black">DISSERTATION CHAIR:
</span></b><span style="font-size:14.0pt;line-height:150%;color:black">Dr. Jeffrey Rimer<o:p></o:p></span></p><div class="MsoNormal" align="center" style="text-align:center;line-height:150%;background:white"><span style="color:black"><hr size="2" width="100%" align="center"></span></div><p class="MsoNormal" align="center" style="text-align:center;line-height:150%;background:white"><b id="yui_3_16_0_ym19_1_1479700940765_266049"><span style="font-size:14.0pt;line-height:150%;color:black">TITLE: <o:p></o:p></span></b></p><p class="MsoNormal" align="center" style="text-align:center;line-height:150%;background:white"><b><span style="font-size:14.0pt;line-height:150%;color:black">Methane Oxidation over, and Sulfur Interactions with, Pd/Pt Bimetallic Catalysts<o:p></o:p></span></b></p><p class="MsoNormal" style="line-height:18.0pt;background:white"><span style="color:black"> <o:p></o:p></span></p><p class="MsoNormal" style="text-align:justify;line-height:150%;background:white"><span style="color:black"> Since meeting the legislation regarding vehicle exhaust emissions is becoming more challenging, and there is growing concern over energy independence, alternative fuels are being investigated. Natural gas is one such, and is typically
viewed as a lower emission producing fuel in comparison to gasoline and diesel. Natural gas primarily consists of methane (CH<sub id="yui_3_16_0_ym19_1_1479700940765_266069">4</sub>) and contains trace sulfur species, making complete combustion on natural
gas challenging under lean-burn operation conditions. If incomplete CH<sub id="yui_3_16_0_ym19_1_1479700940765_266070">4 </sub>combustion occurs, the remaining CH<sub id="yui_3_16_0_ym19_1_1479700940765_266071">4</sub> can be emitted in the vehicle exhaust
thereby increasing the total hydrocarbon emissions. With the goal of designing and characterizing a Pd:Pt catalyst which is best suited for use in a natural gas vehicle aftertreatment system, the focus of this research effort was placed on understanding how
alumina-supported Pd:Pt catalysts perform during simulated natural gas engine aftertreatment system oxidation (combustion) and deactivate due to aging or poisoning effects.<o:p></o:p></span></p><p class="MsoNormal" style="text-align:justify;line-height:150%;background:white"><span style="color:black"> Using Pt/Pd/Al<sub id="yui_3_16_0_ym19_1_1479700940765_266074">2</sub>O<sub id="yui_3_16_0_ym19_1_1479700940765_266075">3</sub> catalysts, the effect of Pd:Pt ratio, and H<sub id="yui_3_16_0_ym19_1_1479700940765_266076">2</sub>O
and SO<sub id="yui_3_16_0_ym19_1_1479700940765_266077">2</sub> exposure on complete CH<sub id="yui_3_16_0_ym19_1_1479700940765_266078">4</sub> oxidation was studied. Small substitutions of Pt for Pd moles resulted in an increased CH<sub id="yui_3_16_0_ym19_1_1479700940765_266079">4</sub> oxidation
activity in comparison to monometallic Pd. Greater substitutions led to decreased activity. In terms of sulfur poisoning, DRIFTS and TPD studies show that SO<sub id="yui_3_16_0_ym19_1_1479700940765_266080">2 </sub>sorption characteristics depend on both precious
metal crystallite particle size and Pd:Pt mole ratio. Catalysts with a small particle size or high Pd content tended to form more aluminum sulfate species, which decomposed at high temperatures. Large particle size or low-Pd content catalysts tended to form
a more low-temperature decomposing and desorbing species, such as molecular SO<sub id="yui_3_16_0_ym19_1_1479700940765_266081">2</sub> and aluminum surface sulfite. It was found that the amount of SO<sub id="yui_3_16_0_ym19_1_1479700940765_266082">2</sub> adsorbed
and later desorbed during TPD decreased with increasing particle size or Pt content in the bimetallic Pd-Pt/Al<sub id="yui_3_16_0_ym19_1_1479700940765_266083">2</sub>O<sub id="yui_3_16_0_ym19_1_1479700940765_266084">3</sub> catalysts.<o:p></o:p></span></p><p class="MsoNormal" style="text-align:justify;line-height:150%;background:white"><span style="color:black"> To decouple particle size and mole ratio aspects during CH<sub id="yui_3_16_0_ym19_1_1479700940765_266089">4</sub> oxidation experiments, catalysts with various metal compositions but similar particle sizes were compared.
CO and SO<sub id="yui_3_16_0_ym19_1_1479700940765_266090">2</sub> adsorption DRIFTS studies were used to identify sites impacted by SO<sub id="yui_3_16_0_ym19_1_1479700940765_266091">2</sub> exposure and evaluate the Pd:Pt mole ratio effect on sulfur surface
species formation. Temperature-programmed oxidation, desorption, and reduction processes were used to evaluate sulfur species decomposition and performance regeneration effectiveness. At low temperatures, Pd-based catalysts with little to no Pt substitution
tended to form aluminum sulfate species, which could be removed at high temperatures to recover catalytic activity, but Pd-based catalysts with higher Pt substitution were less effective at sulfate formation at low temperatures. In this case, molecular SO<sub id="yui_3_16_0_ym19_1_1479700940765_266092">2</sub> and
aluminum surface sulfite species inhibited the CH<sub id="yui_3_16_0_ym19_1_1479700940765_266093">4</sub> oxidation reaction over a broader temperature range. In general, the effectiveness of SO<sub id="yui_3_16_0_ym19_1_1479700940765_266094">2</sub> regeneration
methods decreased with increasing Pt content. For bimetallic catalysts containing more Pt moles than Pd moles, sulfur decays CH<sub id="yui_3_16_0_ym19_1_1479700940765_266095">4</sub> oxidation activity to a lesser degree than the high-temperature regeneration
methods due to the associated sintering effects. In terms of H<sub id="yui_3_16_0_ym19_1_1479700940765_266096">2</sub>O impact, although the CH<sub id="yui_3_16_0_ym19_1_1479700940765_266097">4</sub> oxidation reaction was inhibited in the presence of H<sub id="yui_3_16_0_ym19_1_1479700940765_266098">2</sub>O
for catalysts containing Pd, only low-Pd content catalysts decayed due to H<sub id="yui_3_16_0_ym19_1_1479700940765_266099">2</sub>O exposure.<o:p></o:p></span></p></div></div></div></span><style><!--
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