Although different approaches for the reduction of NOx species have been widely investigated in the literature, there are a number of drawbacks to the current industrial processes. In addition, increasingly stringent legislation ensures continued interest in improving these methods. An opportunity to utilise the H2 produced during biomass gasification to treat the subsequent exhaust emissions was identified and a number of novel catalyst systems were prepared and explored in a variety of different deNOx processes, and their performance compared to typical ‘standard’ catalysts.Measurements conducted on a pilot scale gasifier confirmed the presence of between 10 – 17 % H2, depending on the conditions in the gasifier, and validated the approach of this work. An experimental set–up consisting of a 15 mm i.d. stainless steel reactor housed within an electric furnace was constructed and commissioned, and an analytical method for the detection of eight potential deNOx reaction species was developed utilising a Quadrupole Mass Spectrometer (QMS). All of the catalysts explored in this study (o.d. = 14 mm, length = 10 mm) were prepared through impregnation of supplied samples of cordierite substrate monoliths coated with a γ–Al2O3 washcoat. Results of catalytic studies make up the bulk of this thesis, and two such processes were explored:(a) Selective Catalytic Reduction (SCR) – Pt/Al2O3 has already been widely explored for this process and Ag/Al2O3 was also prepared as a potential novel material. Although the Ag/Al2O3 catalyst displayed some conversion of NO at higher temperatures (e.g. 17 – 21 % at ≥ 350 ᵒC), apparent selectivity to the formation of N2 was poor (e.g. 40 – 41 %).(b) NOx Storage and Reduction (NSR) – Ba/Pt/Al2O3 is considered the standard catalyst for this process and was compared to two novel materials: Ba/Ag/Al2O3 and K/Ag/Al2O3. With respect to the standard catalyst, the novel systems demonstrated comparable, and in some cases improved performance depending on the NSR conditions at 400 ᵒC. Ba/Ag/Al2O3 demonstrated a capacity to store 11 – 15 % of the supplied NO and subsequently reduce 6 – 77 % of the stored species to N2. K/Ag/Al2O3 demonstrated a capacity to store 23 – 72 % of the supplied NO and subsequently reduce 60 – 92 % of the stored species to N2.
|Date of Award||24 Jan 2014|
|Supervisor||Stan Kolaczkowski (Supervisor), Kieran Molloy (Supervisor) & Serpil Awdry (Supervisor)|