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Date of Award
Chemical Engineering and Materials Science
Eranda . Nikolla
This thesis focuses on developing high performance heterogeneous catalytic structures for chemical and fuel production processes. This thesis work proposes to achieve enhanced catalytic performance by tuning the 3D environment of catalytically active sites. Two approaches toward development of enhanced catalytic structures are demonstrated.
The first approach involves tuning the 3D environment of active sites via the construction of the “inverted” structures, where metal core NPs are coated with a porous oxide layer. A facile, room-temperature method is utilized to synthesize the probe system, inverted Pd@TiO2 catalyst, with control over the oxide film and NPs structure. The “inverted” structures with different porosity and crystal structure of the TiO2 film are synthesized by tuning synthesis parameters, such as solvent, nature of the hydrolysis initiator, pH, and the amount of interfacial surfactant on the Pd NPs. The “inverted” catalyst exhibits significant enhancement in HDO selectivity of aromatic alcohols/aldehydes, while maintaining high catalytic activity, due to the extent of interaction between the metal and metal oxide, and favorable adsorption orientations of the aromatics on the active sites induced by the pores.
The second approach involves tuning the 3D environment of metal sites through the surface bound ligands. Two examples are utilized to illustrate this concept. One involves employing organic acid layers on the support (Al2O3) to create Bronsted acid sites at the interface of Pt and acid coated Al2O3 to achieve better activity and selectivity for HDO of biomass-derived oxygenates. Controlling the molecular structure of the organic ligands can manipulate the strength of the Brønsted acid sites to achieve a balance between activity, selectivity and stability. The other example is employing different surface ligands on Pd NPs to enhance catalytic performance for low temperature H2O2 synthesis. A ligand exchange method is proposed to vary the type of ligands bound to the surface of Pd NPs, which eliminates artifacts in the particle architecture induced by synthesis approaches using various ligands. Surface ligands with hydroxyl functionality are found to induce enhanced performance (activity/selectivity to H2O2 production) by favoring H2O2 formation and desorption, as opposed to H2O2 over-hydrogenation and decomposition pathways.
Wang, Bingwen, "Controlling The Three-Dimensional Environment Of Catalytic Active Sites For Selective Heterogeneous Catalysis" (2019). Wayne State University Dissertations. 2374.