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Full-Text Articles in Engineering
Computational Study Of The Reactions Of Heteroatomic Compounds On Ceo2, Suman Bhasker Ranganath
Computational Study Of The Reactions Of Heteroatomic Compounds On Ceo2, Suman Bhasker Ranganath
LSU Doctoral Dissertations
The mechanisms of ambient-temperature reactions of heteroatomic compounds catalyzed by ceria (CeO2), an archetypical reducible oxide, for enzyme mimetics, environmental protection, and chemical synthesis are investigated in this dissertation using theoretical methods. CeO2 is modeled with thermodynamically stable low-index surfaces exposed by commonly studied ceria thin films and nano particles. To understand phosphatase-like dephosphorylation activity, stable adsorption states and surface reactions of model phosphates are examined. Binding of the central P-atom to surface lattice oxygen (Olatt) supplemented by phosphoryl O-Ce interaction is the only stable adsorption state for the un-dissociated molecule. Deprotonation of phosphate monoesters, …
Engineering Dopant Position In Structure-Controlled Ceo2-Zro2 Catalysts, Behnam Safavinia
Engineering Dopant Position In Structure-Controlled Ceo2-Zro2 Catalysts, Behnam Safavinia
LSU Master's Theses
CeO2-ZrO2 (CZO) nanoparticles (NPs) have application in many catalytic reactions, such as methane reformation, due to their oxygen cycling ability. Ni doping has been shown to improve the catalytic activity and acts as an active site for the decomposition of methane. In this work, Ni:CZO NPs were synthesized via a two-step co-precipitation/molten salt synthesis to compare Ni distribution, oxygen vacancy concentration, and catalytic activity relative to a reference state-of-the-art catalyst. To better understand the effects of Ni position and dispersion, and oxygen vacancy formation in these materials, the Ni concentration, reaction time, and deposition methods were varied. …
First-Principles Study On The Catalytic Role Of Cerium Dioxide In The Conversion Of Organic Compounds, Chuanlin Zhao
First-Principles Study On The Catalytic Role Of Cerium Dioxide In The Conversion Of Organic Compounds, Chuanlin Zhao
LSU Doctoral Dissertations
Ceria is an earth-abundant material that has been widely used in heterogeneous catalysis, environmental catalysis, and energy applications thanks for its ability to readily convert between different oxidation states. The objective of this study is to theoretically elucidate the reaction mechanisms for the conversion of model organic compounds on ceria, in order to gain insights for the design of cost-effective and selective ceria-based catalysts. Acetaldehyde, acetic acid, and para-nitrophenyl phosphate monoester were selected as the model compounds to probe ceria surfaces. Density functional theory calculations can provide accurate predictions of adsorption and reaction energetics, which can be used to …
Synthesis, Characterization, And Testing Of Atomically-Precise Au Clusters Supported On Tio₂ For Co Oxidation, Sarthak Gaur
Synthesis, Characterization, And Testing Of Atomically-Precise Au Clusters Supported On Tio₂ For Co Oxidation, Sarthak Gaur
LSU Doctoral Dissertations
Supported Au catalysts have been studied extensively for CO oxidation. These catalysts are known to catalyze this reaction even at sub-ambient temperatures. While recent literature demonstrates catalytic activity of gold nanoparticles <2 nm, the next stage in fine tuning this catalysis process is to develop gold clusters prepared with atomic precision. Such atomically precise gold catalysts supported on TiO2 hitherto have not been investigated for CO oxidation. The main objective of this work is to synthesize atomically-precise Au38 clusters in a flask-based method using principles of wet chemistry, to characterize these clusters using various advanced spectroscopic techniques, and to test these clusters as potential catalytic materials for CO oxidation. Furthermore, we have tested TiO2-supported Au38 clusters and a commercially purchased Au/TiO2 catalyst for CO oxidation at 30 °C and 60 °C, and used DRIFTS as a probe spectroscopic technique to correlate kinetics with the mechanism occurring on the surface of both catalysts in order to device the mechanistic pathways for CO oxidation. The work reported in this dissertation is the first spectroscopic observation of the phenomena where sulfur may have beneficial effect on the catalytic activity of Au/TiO2 catalysts. Such an interesting observation where sulfur has beneficial effect on catalytic activity of Au/TiO2 catalysts has never been observed in the past. We have also synthesized and tested Fe3O4@Au core-shell nanoparticles supported on TiO2 for CO oxidation. We show for the first time that, core-shell type nanogold catalysts are better suited compared to pure gold nanoparticles for heterogeneous gas phase catalysis of CO oxidation. By conducting comprehensive experiments towards understanding CO oxidation catalysis using X-ray photoelectron spectroscopy, infrared spectroscopy, and temperature programmed reduction, we show that the enhanced catalytic activity is due to a combination of factors ranging from synergistic interaction between Au and Fe, complete removal of organic capping ligands and the presence of metallic gold (Au0) in the active catalyst.
X-Ray Absorption Spectroscopy Applied To Mixed-Metal Iron-Based Fischer-Tropsch Catalysts, Andrew Allen Campos
X-Ray Absorption Spectroscopy Applied To Mixed-Metal Iron-Based Fischer-Tropsch Catalysts, Andrew Allen Campos
LSU Doctoral Dissertations
Synthetic fuels derived from methane, coal or biomass are essential in addressing future transportation fuel demands which are expected to exceed petroleum-derived capacities. The Fischer-Tropsch synthesis (FTS) is the most studied technique for the conversion of coal or biomass-derived syngas into transportation fuels. Fe-based catalysts are typically used for the FTS of biomass and/or coal-derived syngas due to: the relatively low cost of iron, water-gas shift activity, and low methane selectivity at industrial FTS conditions. Fe/Cu/SiO2 Fischer-Tropsch catalysts promoted with Cr, Mn, Mo, W, or Zr were studied in-situ, using Fe K-edge TPR XANES (temperature programmed reduction X-ray absorption near-edge …