Date of Award

2017

Document Type

Open Access Dissertation

Department

Chemical Engineering

Sub-Department

College of Engineering and Computing

First Advisor

Jochen Lauterbach

Abstract

The development of economy strongly related with increased consumption of fossil fuels, which causes severe air pollution issue. With more and more strict environmental regulations implemented all over the world, robust and efficient emission control technologies need to be innovated and applied to overcome the pollution challenge. This dissertation focuses on utilizing heterogeneous catalysis to eliminate carbon monoxide (CO), hydrocarbons (CHx) and nitric oxides (NOx) emissions produced from fossil fuel combustion.

The first type of catalyst is Pd supported on Mn-Ce solid solution. It achieves 100% CO conversion at room temperature. The high activity is attributed to superior lattice oxygen transfer interaction between Pd and support, which is discovered by multiple in situ and ex situ characterizations. When tested under practical simulated diesel exhaust condition, including extra water, CHx and NOx, the CO light-off temperature increased to 170oC due to competitive adsorption of CHx and NOx. The comparison of structure characterization before and after hydrothermal aging shows that the Pd is attempting to aggregate and solid solution support is tending to segregate. However, such minor change is not significant enough to change catalysts activity. Doping additional Sn into MC support can improve sulfur resistance of catalysts for low temperature CO oxidation.

The second type of catalyst is Pd supported on shape and surface facet controlled Fe and Mn-Fe nanorods. Mn can be successfully doped into Fe nanorod and form solid solution. The Pd/Mn-Fe catalyst shows over 90% CO conversion at 50oC which is much higher than the inactive Pd/Fe catalyst. The Pd structure and reactivity change on doped oxide surface with controlled facet will be elucidated. The goal of this study is to provide new fundamental insight on metal-support interaction and active sites design approach.

The third type is SSZ-13 zeolite based catalyst, which has small pore structure and excellent hydrothermal stability. By ion exchange method, metal cations can be introduced into the zeolite pores and function as active sites. The active sites can be used in the ammonia selective catalytic reduction (NH3-SCR) of NOx, which is a major NOx reduction technology in heavy duty trucks and coal power plants. Cu-SSZ-13 zeolite catalysts show the best NO conversion (over 95%) from 150-450oC when compared with Fe and Ce based SSZ-13. Moreover, in the presence of SO2 and H2O, which usually can poison SCR catalysts, Cu-SSZ-13 still keeps a relatively high sulfur resistance at temperatures between 250-450oC.

Available for download on Monday, November 06, 2017

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