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You searched for +publisher:"University of New Mexico" +contributor:("Challa, Sivakumar"). Showing records 1 – 2 of 2 total matches.

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University of New Mexico

1. Jones, John. Trapping Platinum on Ceria: Role of Surface Facets.

Degree: Nanoscience and Microsystems, 2016, University of New Mexico

Supported platinum catalysts are used in the automotive industry for the oxidation of CO, hydrocarbons, and NOx. Dispersed Pt provides active sites for these reactions to occur. During the use of these catalyst, high temperatures will cause Pt to become volatile and sinter, forming large particles which will lead to a loss of catalytic activity. The study of Pt sintering has been of high priority for the automotive industry along with mechanisms that will reduce the effect of sintering. Developing an understanding of how supports can hinder sintering of Pt will lead to the preparation of more robust catalysts. A promising support for Pt is CeO2. Altering the synthesis of CeO2 can allow for different nanoshapes to be formed which lead to different surface facets being exposed. The three types of nanoshaped CeO2 synthesized for the catalyst are polyhedra, rods, and cubes, which expose different surface facets. The polyhedra produced expose primarily the (111) and (100) facet while rods expose (111) and cubes expose the (100). These three CeO2 nanoshapes will be tested to discover if one surface facet is able to trap Pt in a dispersed form after aging at high temperature. Powder catalysts containing CeO2 were produced to simulate diesel oxidation catalysts. A first set of catalysts was prepared using an incipient wetness technique of La-Al2O3 with chloroplatinic acid producing Pt/La-Al2O3. This product was then mixed with each of the CeO2 nanoshapes and aged at 800 °C. The resulting products were analyzed to determine if the volatile Pt had sintered or had transferred from the La-Al2O3 support and become trapped on the CeO2 support. A second set of catalysts was prepared using an incipient wetness technique of each of the CeO2 nanoshapes with chloroplatinic acid, producing Pt/CeO2. These catalysts were then aged at 800 °C and analyzed to determine the effectiveness of the different exposed surface facets at keeping Pt in a dispersed phase. Dispersion of Pt after aging at high temperature was shown to have been greatly affected by the type of CeO2 support used. In both parts of this research, it was found that the CeO2 cubes, exposing primarily the (100) facet, were not able to keep Pt highly dispersed, allowing for the growth of large Pt particles. The catalysts containing either the CeO2 polyhedra or rods, which exposed the (111) facet, were shown to trap Pt in an atomically dispersed state. This allowed for high catalytic reactivity to be maintained even after aging at high temperature. Advisors/Committee Members: Datye, Abhaya, Datye, Abhaya, Challa, Sivakumar, Fernando, Garzon.

Subjects/Keywords: Platinum; Ceria; Sintering; Trapping; CO oxidation; TEM; X-ray diffraction; CeO2

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APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6th Edition):

Jones, J. (2016). Trapping Platinum on Ceria: Role of Surface Facets. (Masters Thesis). University of New Mexico. Retrieved from http://hdl.handle.net/1928/31672

Chicago Manual of Style (16th Edition):

Jones, John. “Trapping Platinum on Ceria: Role of Surface Facets.” 2016. Masters Thesis, University of New Mexico. Accessed October 22, 2020. http://hdl.handle.net/1928/31672.

MLA Handbook (7th Edition):

Jones, John. “Trapping Platinum on Ceria: Role of Surface Facets.” 2016. Web. 22 Oct 2020.

Vancouver:

Jones J. Trapping Platinum on Ceria: Role of Surface Facets. [Internet] [Masters thesis]. University of New Mexico; 2016. [cited 2020 Oct 22]. Available from: http://hdl.handle.net/1928/31672.

Council of Science Editors:

Jones J. Trapping Platinum on Ceria: Role of Surface Facets. [Masters Thesis]. University of New Mexico; 2016. Available from: http://hdl.handle.net/1928/31672


University of New Mexico

2. Benavidez, Angelica. The Nucleation and Growth of Nanoparticles for Heterogeneous Catalysis.

Degree: Chemical and Biological Engineering, 2015, University of New Mexico

These studies investigate the nucleation and growth of nanoparticles and how their interaction with a support affects their reactivity as a heterogeneous catalyst. As capabilities in both synthesis methods and characterization methods advance, the use of nanoparticles and sub-nanometer species are more commonly used. These small particles introduce new factors that can cause differences in reactivity. Various catalyst synthesis methods are employed to deposit mono-dispersed particles on different oxide and carbon supports. Electron microscopy is used to study nanoparticle sintering and the careful tracking of individual particles gives insight into growth mechanisms. X-ray absorption spectroscopy measurements are used to characterize catalysts and elucidate the reasons for a support effect in both hydrogenation and oxidations reactions. This investigation aims to produce a more active catalyst by exploring different aspects that play a role in reactivity and selectivity. Understanding the growth mechanisms that commonly to lead deactivation gets us one step closer to creating a sinter resistant catalyst. These studies also show that changing a catalyst support can increase its activity. The exploration of the fundamentals of nanoparticle structure and interaction with its surroundings leads to a more efficient catalyst. Advisors/Committee Members: Datye, Abhaya, Loehman, Ronald, Karim, Ayman, Challa, Sivakumar.

Subjects/Keywords: heterogeneous catalysis; nucleation

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APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6th Edition):

Benavidez, A. (2015). The Nucleation and Growth of Nanoparticles for Heterogeneous Catalysis. (Doctoral Dissertation). University of New Mexico. Retrieved from http://hdl.handle.net/1928/27761

Chicago Manual of Style (16th Edition):

Benavidez, Angelica. “The Nucleation and Growth of Nanoparticles for Heterogeneous Catalysis.” 2015. Doctoral Dissertation, University of New Mexico. Accessed October 22, 2020. http://hdl.handle.net/1928/27761.

MLA Handbook (7th Edition):

Benavidez, Angelica. “The Nucleation and Growth of Nanoparticles for Heterogeneous Catalysis.” 2015. Web. 22 Oct 2020.

Vancouver:

Benavidez A. The Nucleation and Growth of Nanoparticles for Heterogeneous Catalysis. [Internet] [Doctoral dissertation]. University of New Mexico; 2015. [cited 2020 Oct 22]. Available from: http://hdl.handle.net/1928/27761.

Council of Science Editors:

Benavidez A. The Nucleation and Growth of Nanoparticles for Heterogeneous Catalysis. [Doctoral Dissertation]. University of New Mexico; 2015. Available from: http://hdl.handle.net/1928/27761

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