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HC-SCR of NO\(_x\) emissions over Ag-AL\(_2\)O\(_3\) catalysts using diesel fuel as a reductant

Sitshebo, Simbarashe Wilson Timothy (2011)
Ph.D. thesis, University of Birmingham.

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Abstract

Hydrocarbon selective catalytic reduction (HC-SCR) of nitrogen oxides (NO\(_x\)) over silver-alumina (Ag-Al\(_2\)O\(_3\)) catalysts, in diesel exhaust gas, has been investigated and presented in this research thesis. The work involved the use of H\(_2\) to activate diesel-type HC reductants. Numerous HC-SCR studies have been conducted (to date) by various authors and research groups in an effort to improve the low temperature (< 350 \(^\circ\)C) NO\(_x\) reduction activity of the catalyst, but mainly at laboratory scale, using simulated diesel exhaust gases and the pelletized form of the catalyst. Conversely, the work presented and discussed herein is based on Ag-Al\(_2\)O\(_3\) coated monolith substrates for the examination of the NO\(_x\) reduction efficiency when utilizing the full diesel exhaust gas. The activity of the pelletized form of the catalyst and that of a coated monolith substrate could vary according to various characteristics, such as, the chemical (reaction kinetics) and physical (mass transfer, species filtration) processes. These effects were examined under ‘passive’ and ‘active’ operation of the respective catalysts. Diesel oxidation catalysts (DOCs) and unique prototype catalysts were also utilized in order to reduce possible poisoning species, which can lead to the deactivation of the Ag-based catalyst. Furthermore, variations in exhaust gas temperature and composition, by continually changing engine load and speed, were explored and the effects on catalyst activity presented. It was suspected that the fluctuating temperature profiles of the exhaust gas could limit the amount of poison species accumulation onto the catalyst active surface and, as a result, could slow down the deactivation mechanisms. Finally, fuel reforming of conventional diesel, RME and GTL fuels was conducted for the production of hydrogen (H\(_2\)). The produced H\(_2\) could then be utilized in the combustion process itself or in a HC-SCR reactor, for reduced engine out or tailpipe emissions.

Type of Work:Ph.D. thesis.
Supervisor(s):Tsolakis, Athanasios and Wyszynski, Miroslaw L.
School/Faculty:Colleges (2008 onwards) > College of Engineering & Physical Sciences
Department:School of Mechanical Engineering
Subjects:TJ Mechanical engineering and machinery
Institution:University of Birmingham
ID Code:1338
This unpublished thesis/dissertation is copyright of the author and/or third parties. The intellectual property rights of the author or third parties in respect of this work are as defined by The Copyright Designs and Patents Act 1988 or as modified by any successor legislation. Any use made of information contained in this thesis/dissertation must be in accordance with that legislation and must be properly acknowledged. Further distribution or reproduction in any format is prohibited without the permission of the copyright holder.
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