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Sreshtha Ph.D. Dissertation- Final.pdf (22.63 MB)

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Catalytic Reduction of Nitrogen Oxide Emissions with Lower Hydrocarbons for Natural gas-fired Lean-burn Engines

Sinha Majumdar, Sreshtha
http://orcid.org/0000-0002-0394-2672
http://rave.ohiolink.edu/etdc/view?acc_num=osu1471602998

Abstract Details

2016, Doctor of Philosophy, Ohio State University, Chemical Engineering.
A hydrothermally stable dual-catalyst aftertreatment system for emission control of nitrogen oxides (NOx) with lower hydrocarbons (CHx) has been developed for natural gas-fired stationary lean-burn engines. The dual-catalyst system consists of a physical mixture of a reduction catalyst, palladium supported on sulfated zirconia (Pd/SZ) and an oxidation catalyst, cobalt oxide supported on ceria, CoOx/CeO2. The multifunctional aftertreatment system oxidizes nitric oxide (NO) to nitrogen dioxide (NO2), reduces NO2 to nitrogen (N2), and oxidizes carbon monoxide (CO) and the unutilized hydrocarbons. For practical applications in environmental catalysis, the catalytically active powder catalyst needs to be wash-coated onto a monolith core. To prevent permanent loss of activity due to physical separation of the wash-coat from the walls of the monolith core, adhesivity enhancing materials (binders) are added to the wash-coat. A novel method of incorporating binder to the active catalyst in situ during sol-gel synthesis is presented in this work. Alumina binder incorporated into Pd/SZ in situ during sol-gel synthesis was chosen for further development of a catalytically active washcoat based on activity tests under simulated engine-exhaust conditions. The alumina binder-incorporated Pd/SZ catalyst slurry controlled at pH 1 and calcined at 700oC demonstrated the most promising NOx reduction and CH4 oxidation activity. Cyclic thermal shock tests demonstrated enhanced adhesive properties of the wash-coat to the walls of the cordierite monolith core. Thus, a catalytically active wash-coat with superior adhesive properties was developed for practical application in a real-world aftertreatment unit. The effect of in situ incorporation of alumina to Pd/SZ during sol-gel synthesis on the structural, textural and chemical properties of the resulting catalyst was investigated as these properties significantly influence the catalytic activity of the resulting catalyst. The formation of a zirconia-alumina mixed oxide with predominantly metastable tetragonal phase of the zirconia in the support was suggested. Results from N2 adsorption experiments at 77 K, 27Al magic angle spinning nuclear magnetic resonance (MAS NMR), laser Raman spectroscopy and X-ray photoelectron spectroscopy (XPS) provide further indication of the formation of a zirconia-alumina mixed oxide. Enhanced strength of the acid sites at higher temperatures was shown by strong interaction of pyridine probe molecule with the alumina-incorporated Pd/SZ catalyst. Cationic Pd species in the catalyst sample were evidenced using electron paramagnetic resonance (EPR). These results were significant as the structural, textural and chemical properties of the Pd/SZ catalyst strongly influence the catalytic properties for NOx reduction under lean conditions. Sulfur tolerance and hydrothermal stability tests on alumina-incorporated Pd/SZ containing dual-catalyst bed demonstrated superior sulfur tolerance and hydrothermal stability under wet SO2 feed conditions when compared to the alumina-free Pd/SZ containing dual-catalyst bed. Increasing the reaction temperature from 450oC to 500oC improved the CH4 conversions and maintained very stable NOx conversions under wet SO2 exhaust conditions. XPS on catalyst samples ex-situ poisoned with SO2 show that sulfates are deposited on the surface of the reduction catalysts while a combination of sulfates and sulfites are deposited on the surface of the oxidation catalyst. Alumina incorporation into Pd/SZ protects the support and increased its tolerance to poisoning.
Umit Ozkan, PhD (Advisor)
Andre Palmer, PhD (Committee Member)
Kurt Koelling, PhD (Committee Member)
249 p.
Chemical Engineering
NOx reduction, lean-burn, sulfated zirconia, alumina binder, wash-coat, sol-gel, sulfur tolerance, hydrothermal stability, palladium, XPS, 27Al MAS NMR, in situ XRD, DRIFTS

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Citations

  • Sinha Majumdar, S. (2016). Catalytic Reduction of Nitrogen Oxide Emissions with Lower Hydrocarbons for Natural gas-fired Lean-burn Engines [Doctoral dissertation, Ohio State University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=osu1471602998

    APA Style (7th edition)

  • Sinha Majumdar, Sreshtha. Catalytic Reduction of Nitrogen Oxide Emissions with Lower Hydrocarbons for Natural gas-fired Lean-burn Engines. 2016. Ohio State University, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=osu1471602998.

    MLA Style (8th edition)

  • Sinha Majumdar, Sreshtha. "Catalytic Reduction of Nitrogen Oxide Emissions with Lower Hydrocarbons for Natural gas-fired Lean-burn Engines." Doctoral dissertation, Ohio State University, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=osu1471602998

    Chicago Manual of Style (17th edition)

osu1471602998
76
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