Doctor of Philosophy (PhD)
Cain Department of Chemical Engineering
Many heterogeneous catalysts contain more than one type of active site. These sites may cooperate to steer a reaction toward desired pathways. However, the inter-site communication has been less studied. This is mainly due to the lack of fabrication methods for well-defined catalytic architectures with spatially separated active sites, where different reactants can be activated separately. In order to better understand the site cooperation effect, we proposed a novel catalytic architecture, where two sites are spatially separated by a partition layer, which allows selective permeation of certain reactants (e.g., H2). The study was focused on hydrogen and oxygen spillover effects.
Two candidate reactions were selected to study the hydrogen spillover effect: 1) semihydrogenation of acetylene and butadiene; 2) selective hydrogenation of oxygen into hydrogen peroxide. We fabricated the desired catalytic architecture by covering an oxide overcoat layer on a Pd catalyst. H2 molecule is able to permeate through the oxide overcoat and dissociates on the Pd surface, then undergoes spillover to reach the external surface where hydrogenation of alkyne/diene/O2 takes place.
In addition to the widely studied hydrogen spillover behavior, oxygen spillover has also been proposed in several oxidation reactions including the oxidative coupling of methane. MnOx-Na2WO4/SiO2 is among the best catalysts for the oxidative coupling of methane. Since methane and oxygen have equal access to all active sites in conventional catalysts, combustion cannot be easily inhibited. The proposed catalytic architecture – two active sites (WOx and MnOx) separated by a partition layer – is expected to decouple the activation of methane and oxygen and improve the selectivity toward C2 compounds by oxygen spillover from MnOx to WOx.
Aireddy, Divakar Reddy, "Understanding and Manipulating the Spillover Effects in Heterogeneous Catalysis" (2023). LSU Doctoral Dissertations. 6122.
Available for download on Wednesday, April 03, 2030