Selective Catalytic Reduction of NOx by NH3 (NH3-SCR) in Small Pore Cu-exchanged Chabazite (CHA) Catalysts
| dc.contributor.advisor | Epling, William S. | |
| dc.contributor.committeeMember | Harold, Michael P. | |
| dc.contributor.committeeMember | Rimer, Jeffrey D. | |
| dc.contributor.committeeMember | Chellam, Shankar | |
| dc.contributor.committeeMember | Kamasamudram, Krishna | |
| dc.creator | Wang, Di | |
| dc.date.accessioned | 2017-07-26T18:44:50Z | |
| dc.date.available | 2017-07-26T18:44:50Z | |
| dc.date.created | May 2014 | |
| dc.date.issued | 2014-05 | |
| dc.date.submitted | May 2014 | |
| dc.date.updated | 2017-07-26T18:44:51Z | |
| dc.description.abstract | Nitrogen oxides, NOx (NO+NO2), are considered significant air pollutants. Selective catalytic reduction of NOx with NH3 (NH3-SCR) is a leading technology candidate for NOx emissions control for diesel engine vehicles. Recently, the Cu-exchanged chabazite framework type zeolite with small pores, such as SAPO-34 and SSZ-13, has received a great deal of attention due to exceptional hydrothermal durability and enhanced SCR activity. I have carried out a systematic study over both Cu-SAPO-34 and Cu-SSZ-13 catalysts to elucidate the reaction mechanisms, acid properties, Cu structures, active centers and deactivation modes. First, the intrinsic mechanism of the SCR reaction over a Cu-exchanged SAPO-34 catalyst at low temperature was studied by in-situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS), coupled with a mass spectrometer to measure inlet and outlet gas concentrations. The evolution of the surface intermediates, as well as the reactivity of NH3 with surface NOx species and NOx with surface NH3 species, was evaluated. Second, a series of SAPO-34 catalysts with various Cu loadings (ranging 0.7-3.0 wt%) was prepared by a solid state ion exchange method (SSIE). The acid properties as well as the Cu structures were characterized by XRD, NH3-TPD, UV-vis, DRIFTS and H2-TPR. Third, a SSIE method was developed to synthesize Cu-SSZ-13 catalysts with excellent NH3-SCR performance and durable hydrothermal stability. After the SSIE process, the SSZ framework structure and surface area was maintained. DRIFTS and NH3-TPD experiments provide evidence that Cu ions were successfully exchanged with Brønsted acid protons in the pores. Fourth, the hydrothermal stability of Cu-SAPO-34 and Cu-SSZ-13 was studied. Their different evolutions of zeolite framework, acidity and Cu structure during the hydrothermal aging were probed by XRD, DRIFTS and NH3-TPD. The results suggest that Cu-SAPO-34 is more resistant to hydrothermal aging in comparison to Cu-SSZ-13. Last, the SO2 poisoning effect over Cu-SAPO-34 catalyst was investigated by using in-situ DRIFTS combined with temperature programmed desorption (TPD) experiments. It was found that the low temperature deactivation mechanism involved the formation of ammonium sulfate species as well as the competitive adsorption SO2 with NOx. | |
| dc.description.department | Chemical and Biomolecular Engineering, Department of | |
| dc.format.digitalOrigin | born digital | |
| dc.format.mimetype | application/pdf | |
| dc.identifier.citation | Portions of this document appear in: Zhang, Li, Di Wang, Yong Liu, Krishna Kamasamudram, Junhui Li, and William Epling. "SO 2 poisoning impact on the NH 3-SCR reaction over a commercial Cu-SAPO-34 SCR catalyst." Applied Catalysis B: Environmental 156 (2014): 371-377. https://doi.org/10.1016/j.apcatb.2014.03.030. And in: Wang, Di, Li Zhang, Krishna Kamasamudram, and William S. Epling. "In situ-DRIFTS study of selective catalytic reduction of NO x by NH3 over Cu-exchanged SAPO-34." Acs Catalysis 3, no. 5 (2013): 871-881. DOI: 10.1021/cs300843k. And in: Wang, Di, Feng Gao, Charles HF Peden, Junhui Li, Krishna Kamasamudram, and William S. Epling. "Selective Catalytic Reduction of NOx with NH3 over a Cu‐SSZ‐13 Catalyst Prepared by a Solid‐State Ion‐Exchange Method." ChemCatChem 6, no. 6 (2014): 1579-1583. DOI: 10.1002/cctc.201402010. And in: Wang, Di, Li Zhang, Junhui Li, Krishna Kamasamudram, and William S. Epling. "NH 3-SCR over Cu/SAPO-34–zeolite acidity and Cu structure changes as a function of Cu loading." Catalysis Today 231 (2014): 64-74. https://doi.org/10.1016/j.cattod.2013.11.040. | |
| dc.identifier.uri | http://hdl.handle.net/10657/1948 | |
| dc.language.iso | eng | |
| dc.rights | The author of this work is the copyright owner. UH Libraries and the Texas Digital Library have their permission to store and provide access to this work. UH Libraries has secured permission to reproduce any and all previously published materials contained in the work. Further transmission, reproduction, or presentation of this work is prohibited except with permission of the author(s). | |
| dc.subject | NH3-SCR | |
| dc.subject | Small pore zeolite | |
| dc.title | Selective Catalytic Reduction of NOx by NH3 (NH3-SCR) in Small Pore Cu-exchanged Chabazite (CHA) Catalysts | |
| dc.type.dcmi | text | |
| dc.type.genre | Thesis | |
| thesis.degree.college | Cullen College of Engineering | |
| thesis.degree.department | Chemical and Biomolecular Engineering, Department of | |
| thesis.degree.discipline | Chemical Engineering | |
| thesis.degree.grantor | University of Houston | |
| thesis.degree.level | Doctoral | |
| thesis.degree.name | Doctor of Philosophy |