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</o:shapelayout></xml><![endif]--></head><body lang=EN-US link=blue vlink=purple><div class=WordSection1><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal><span style='font-size:9.0pt;color:gray'><o:p> </o:p></span></p><p class=MsoNormal align=center style='text-align:center;page-break-after:avoid'><b><span style='font-size:16.0pt;font-family:"Tahoma","sans-serif"'>PhD Dissertation Defense<o:p></o:p></span></b></p><p class=MsoNormal align=center style='text-align:center;page-break-after:avoid'><b><span style='font-size:16.0pt;font-family:"Tahoma","sans-serif"'><o:p> </o:p></span></b></p><p class=MsoNormal align=center style='text-align:center'><b><span style='font-size:14.0pt;font-family:"Tahoma","sans-serif";text-transform:uppercase'>EXPERIMENTAL STUDIES OF nO<sub>X </sub>STORAGE AND REDUCTION ON LEAN nO<sub>X </sub>TRAPS<o:p></o:p></span></b></p><p class=MsoNormal><b><span style='font-size:14.0pt;font-family:"Tahoma","sans-serif"'><o:p> </o:p></span></b></p><p class=MsoNormal align=center style='text-align:center'><b><span style='font-size:14.0pt;font-family:"Tahoma","sans-serif"'>Prasanna Dasari<o:p></o:p></span></b></p><p class=MsoNormal align=center style='text-align:center'><b><span style='font-size:12.0pt'><o:p> </o:p></span></b></p><p class=MsoNormal align=center style='text-align:center'><b><span style='font-size:12.0pt'>Date: Friday, Aug. 2<sup>nd</sup>, <sup> </sup>2013<o:p></o:p></span></b></p><p class=MsoNormal align=center style='text-align:center'><b><span style='font-size:12.0pt'><o:p> </o:p></span></b></p><p class=MsoNormal align=center style='text-align:center'><b><span style='font-size:12.0pt'>Location:</span></b> <span style='font-size:12.0pt'>Chemical Engineering Conference Room <o:p></o:p></span></p><p class=MsoNormal align=center style='text-align:center'><b><span style='font-size:12.0pt'>Time: 11:00 AM<o:p></o:p></span></b></p><p class=MsoNormal align=center style='text-align:center'><b><span style='font-size:12.0pt'><o:p> </o:p></span></b></p><p class=MsoNormal align=center style='text-align:center'><b><span style='font-size:12.0pt'>Committee Chair: <o:p></o:p></span></b></p><p class=MsoNormal align=center style='text-align:center'><span style='font-size:12.0pt'>Dr. Michael Harold<b><o:p></o:p></b></span></p><p class=MsoNormal><span style='font-size:12.0pt'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:12.0pt'><o:p> </o:p></span></p><p class=MsoNormal>Stricter emission standards have driven the research and development of several emission aftertreatment technologies like selective catalytic reduction (NH<sub>3</sub>-SCR) and lean NO<sub>X</sub> trap (LNT) technology. On an NH<sub>3</sub>-SCR catalyst, NH<sub>3</sub> is injected into the exhaust, which then selectively reduces NOx to N<sub>2</sub>. During the LNT process, NO<sub>X</sub> is stored on an alkali earth oxide during the lean phase, forming surface nitrite/nitrate species, which are then reduced to N<sub>2</sub> over precious metals during periodic ¡°rich¡± operation. A combined LNT-SCR hybrid system promises to be more cost-effective and operates by utilizing NH<sub>3</sub> formed during the rich phase operation of LNT to reduce NOx that breakthroughs LNT on the SCR catalyst downstream.<o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>An experimental set-up was built to monitor the transient reactor temperatures and effluent gas concentrations. This work systematically investigated the production of NH<sub>3</sub> on typical Pt-Rh/BaO/Al<sub>2</sub>O<sub>3</sub> LNT monolithic catalysts during the reduction of NOx by CO in the presence of excess water without any molecular H<sub>2</sub> being fed to the system; under both steady-state and cyclic operation conditions. The objective was to determine the effect of various operating parameters and the involvement of intermediate species on the mechanism leading to NH<sub>3</sub> formation and NOx reduction. Under steady-state conditions, H<sub>2</sub> formed by wgs reaction plays a dominant role in reducing NOx to NH<sub>3</sub>. However, under cyclic operation conditions, hydrolysis of intermediate isocyanate species is shown to be the leading route to NH<sub>3</sub> formation.<o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>An extensive study of the NO<sub>X</sub> storage mechanism and the impact of CO<sub>2</sub> were conduced at low temperatures (< 300 ¢ªC). It was determined that the local minima in NOx conversion observed at 200 ¢ªC, during the reduction of NOx by H<sub>2</sub> in the presence of CO<sub>2</sub> was a result of the competition posed by CO<sub>2</sub> for the two kinds of storage sites involved. Also, at 200 ¢ªC carbonates are relatively more stable on the Ba sites located far from Pt and were hard to replace by nitrates due to diffusion limitations. SpaciMS was employed to investigate NOx reduction mechanism by C<sub>3</sub>H<sub>6</sub> in LNT systems. Spatial and temporal profiles of species concentrations and temperatures were developed along the catalyst length.<o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal><o:p> </o:p></p></div></body></html>