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Browsing by Author "Szilvási, Tibor"

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    Kinetic Investigations into Selective Partial Oxidation Reactions over Transition Metal Catalysts
    (University of Alabama Libraries, 2025) Minne, Alexander; Harris, James W.
    Oxidations comprise 30% of the reactions in the chemical industry. However, significant challenges exist in controlling the selectivity of oxidation reactions. Selective oxidation by a heterogeneous catalyst is a direct route to the production of alcohols, aldehydes, ketones, and epoxides. The design and development of efficient selective oxidation catalysts enable understanding of structure–reactivity correlations and improve the viability of green chemistry techniques. This work investigates the kinetics of two selective oxidation reactions: oxidative cross-coupling of methanol and dimethylamine (DMA), and methane oxychlorination (MOC). The oxidative cross-coupling of methanol and DMA forms a C–N bond and results in dimethylformamide (DMF) formation. Through the partial oxidation of methanol, formaldehyde forms as an intermediate that acts as an electrophile and undergoes nucleophilic attack by DMA. This reaction is enabled by Au-based bimetallic alloy catalysts. Au can be alloyed with more reactive metals such as Ag or Pd, which accelerate the dissociative adsorption of O₂ on the catalyst surface. The resultant reactive surface oxygen "spills over" onto nearby Au atoms where selective partial oxidation of methanol can occur while avoiding total oxidation to CO₂. The kinetics of this reaction were investigated using a continuous flow packed-bed reactor. Within this work, bimetallic Au-based alloy combinations, metal ratio, particle size, and the effects of alkali doping were explored using the coupling of methanol and DMA as a probe reaction. In the latter half of the dissertation, methane oxychlorination was investigated over supported Pd nanoparticles. Although vast methane resources exist globally, they are often off-gassed or flared due to the economic challenges of transporting CH₄. A proposed route for upgrading is the catalytic functionalization of CH4 with halogens in the presence of oxygen—known as oxyhalogenation. This work focuses on oxychlorination kinetics over Pd/SiO₂ catalysts of different weight loading and nanoparticle size. Pd nanoparticles were also encapsulated in small-pore zeolites to explore the influence of size and shape selectivity by the porous structures. Together, these kinetic studies demonstrate the meticulous considerations needed to design efficient oxidation catalysts capable of converting carbon resources into valuable chemicals while minimizing harmful emissions.
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    Simulated Properties of Multivalent Ionic Liquids and Their Performance in Gas Capture and Separation
    (University of Alabama Libraries, 2022) Liu, Xiaoyang; Turner, Christoffer H.; University of Alabama Tuscaloosa
    Due to their tunable thermophysical properties, ionic liquids (ILs) have emerged as potential candidates for gas capture and separation. However, the underlying mechanisms for gas solvation and separation are still not clear. In order to provide more insight, we use multi-scale simulations to investigate the properties of ILs and their performance in gas capture and separation. We primarily focus on the physiochemical nature of the solute-solvent interactions, especially the electrostatic potential (ESP) surface properties of individual cations and anions, as well as that of the gas solutes. With our simulations, we isolate the role of two primary effects that contribute to gas solubilities in ILs: the free volume effect and the anion effect. The free volume effect can be quantified by the fractional free volume, which is found to be correlated to the cation and anion ionic polarity index, which is a newly proposed parameter based on an analysis of the molecular ESP surface. The anion effect can be quantified by the solvation affinity index (SAI), which is also a newly proposed parameter based on an analysis of the anion ESP surface. Based on these fundamental interactions, we design a new framework for prescreening IL pairs for achieving high gas capture and separation performance that we refer to as the solvation affinity index matrix. The SAI matrix is applicable to different gas solutes, as well as to a wide range of different anions.