Liu, Yiyun;
(2021)
Study of Cu-Exchanged CHA Catalysts for the Selective Catalytic Reduction (SCR) Reaction.
Doctoral thesis (Ph.D), UCL (University College London).
Preview |
Text
PhD Thesis_Yiyun Liu_v2.5.3_submit.pdf - Accepted Version Download (7MB) | Preview |
Abstract
Eliminating the harmful NOx, which is the major pollutant in the exhaust gas of diesel engines, has long been the pursue of scientists. Cu-chabazite (Cu-CHA) zeolites system developed in 2008 is shown to be an efficient and thermal stable catalyst in the deNOx NH3-SCR reaction and has received intense study since then. Aiming to further improve its catalytic activity, a wide range of characterization techniques has been developed and applied to study the well-defined structures and catalysis. Study of SCR reaction over the Cu-CHA catalysts demands the understanding of active Cu sites, for which loading-dependent behaviour is first studied with UV-Vis spectroscopy and ex-situ EPR spectroscopy together with the reaction evaluation. To further investigate different Cu species, the combination of H2-TPR, NH3-TPD and EPR spectroscopy were applied to quantify the Cu speciation in the catalysts, from which the sequential domination of 2AlCu, 1AlCu and CuO species with increasing Cu loadings was observed. Subsequent study of dehydration and hydrothermal aging processes with EPR also reveals the transformation of Cu species from 1AlCu to 2AlCu through the formation of hydrated complexes and the decomposition of CuOx clusters. On the other hand, the interaction between Cu-CHA catalysts and SCR reactants was studied with in situ FTIR and operando NEXAFS, showing the adsorption of NO and NH3 molecules respectively. Aiming to uncover the key species in the SCR reaction and reveal the origin of different reactivity for 1AlCu and 2AlCu sites, the samples with different Cu distribution was studied with operando X-ray spectroscopy under SCR conditions. With the combination of HERFD-XANES, vtc-XES and time-resolved XAS at transient states, key intermediate CuNOx species is observed to be preferentially formed on the 1AlCu sites, while a framework coordinated CuI(NH3)xOfw species is identified to be the real species causing NH3 inhibition effect, hindering the re-oxidation of CuI especially at 2AlCu sites.
| Type: | Thesis (Doctoral) |
|---|---|
| Qualification: | Ph.D |
| Title: | Study of Cu-Exchanged CHA Catalysts for the Selective Catalytic Reduction (SCR) Reaction |
| Event: | UCL (University College London) |
| Open access status: | An open access version is available from UCL Discovery |
| Language: | English |
| Additional information: | Copyright © The Author 2021. Original content in this thesis is licensed under the terms of the Creative Commons Attribution-NonCommercial 4.0 International (CC BY-NC 4.0) Licence (https://creativecommons.org/licenses/by-nc/4.0/). Any third-party copyright material present remains the property of its respective owner(s) and is licensed under its existing terms. Access may initially be restricted at the author’s request. |
| UCL classification: | UCL UCL > Provost and Vice Provost Offices > UCL BEAMS UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Engineering Science UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Engineering Science > Dept of Chemical Engineering |
| URI: | https://discovery.ucl.ac.uk/id/eprint/10136256 |
Loading...
Loading...Loading...Loading...Archive Staff Only
 |
View Item |
