(4ec) Development, Optimization, and Functionalization of Nanostructured Catalysts for the Production of Valuable Hydrocarbons Via Fischer-Tropsch Synthesis

Fischer-Tropsch Synthesis (FTS) has gained prominence for utilizing synthesis gas (syngas) as a chemical building block to produce transportation fuels and synthetic oils. The development of coal gasification technologies has catapulted interest in maximizing syngas utilization due to its cost-effectiveness and exceptional performance metrics. Syngas, a mixture of carbon monoxide (CO) and hydrogen (H₂), is a product of the thermochemical conversion of coal but can also be obtained from methane (CH₄) and other carbonaceous feedstocks, such as petroleum residue and biomass. FTS comprises a series of complex chemical reactions involving the cleavage of C≡O bonds to obtain hydrocarbons via surface polymerization. The primary products depend on many factors, with the product mixture typically consisting of linear paraffins and α-olefins. The complexity and high variability of FTS have made its optimization challenging. Controlling the product mixture is strategically relevant, as hydrocarbon products with varying carbon chain lengths serve distinct purposes. Maximizing the C₅₊ selectivity remains a crucial challenge for FTS, as several parameters have been shown to influence it, including reactor type, catalyst type and composition, and operating conditions such as pressure, temperature, and H₂/CO ratio in the feed.

As part of this doctoral work in chemical engineering at the University of Utah, extensive work has been done on the design and optimization of catalysts to push FTS to the forefront of syngas maximization. The research objective is to synthesize and characterize state-of-the-art Fischer-Tropsch catalysts and measure their performance. By amalgamating contemporary concepts in nanotechnology, materials science, and electrochemistry with traditional techniques in heterogeneous catalysis, a thorough research program has been developed and conducted to maximize CO conversion and enable potential tunable hydrocarbon selectivity. This work aims to deepen our understanding of FTS and its complex behavior by designing contemporary catalysts based on pioneering ideas to investigate and develop structure-function relationships. This research is segmented into three main sections, tackling different aspects of catalyst design and optimization.

The first section involves additive manufacturing (3D printing) and electrochemical methods to design and synthesize nanostructured catalysts. Cylindrical Ti-6Al-4V (Ti64) alloy structures were 3D-printed via direct metal laser melting (DMLM). They were used as substrates to grow self-organizing titanium dioxide (TiO₂) nanotube arrays (TNAs) to serve as catalytic supports. Such TiO₂-based nanomaterials have been highlighted for their ability to enhance the movement of molecules by controlling properties such as porosity and surface geometry. This research explores electrochemical anodization for growing TNAs on 3D-printed titanium structures and thermal annealing as an optimization technique. By impregnating TNAs with a bimetallic FeCo active phase, this study introduces catalysts that have not been explored for FTS applications before. These systems have shown comparable performance to wrought TiO₂-based catalysts, displaying a promising outcome for an emerging technology in catalysis, such as 3D printing.The second section investigates the design and synthesis of bifunctional catalysts for FTS. These systems have gained traction in recent years for catalytic applications, as they combine functionalities by facilitating different processes within a single catalyst, thus making them attractive for highly complex processes like FTS. These bifunctional catalysts can successfully combine hydrocarbon formation with their upgrading into more complex gasoline or diesel-range products within a single system. This research explores the enhancement of TiO₂ as a support in Fischer-Tropsch catalysts via acid functionalization, which is presumed to be highly desirable by sustaining hydrocarbon growth and isomerization reactions. The study reveals that structural modifications of the support by introducing Brønsted and Lewis acid sites in its architecture are highly impactful in the resulting morphology and FTS reaction performance of the catalysts. This work represents a pioneering effort in catalyst design by elucidating active phase-support relationships and the importance of support architecture and composition in FTS performance. The third section uses a monometallic active phase of ruthenium (Ru) nanoparticles (RuNPs) supported on acid-functionalized TiO₂. The metal nanoparticles are bound to organic ligands to explore a method for optimizing FTS product distribution. The influence of three ligands, triphenylphosphine (TPP), triphenylmethyl mercaptan (TPMT), and 1,1-Bis(diphenylphosphino)methane (DPPM), are evaluated for their electron-donating and withdrawing effects. This bifunctional catalyst design has yet to be reported for a Ru active phase, further elucidating some pivotal metal-support interactions and the effects of these optimization methods compared to traditional unpromoted counterparts.

Research Interests

My research interests are rooted in the design, synthesis, characterization, and evaluation of leading-edge nanostructured materials for application in heterogenous catalysis, emphasizing applications for Fischer-Tropsch Synthesis (FTS) and other relevant chemical processes. As a member of the Nanointerface Engineering Laboratory, my areas of study involve techniques including additive manufacturing, wet impregnation, electrochemical anodization, and acid-functionalization, with a focus on optimizing support materials and enhancing catalytic active phases. For characterization purposes, traditional methods are of interest, including field-emission scanning electron microscopy (FESEM), energy dispersive X-ray spectroscopy (EDXS), X-ray diffraction (XRD), X-ray fluorescence (XRF), volumetric titration, gas chromatography-mass spectroscopy (GC-MS), scanning transmission electron microscopy (STEM), Fourier transform infrared spectroscopy (FTIR), and X-ray photoelectron spectroscopy (XPS). Developing and evaluating such synthesis methods and testing catalysts' morphology, surface chemistry, stability, activity, and chemical composition represent pioneering efforts in pushing the boundaries of traditional catalysis for industrially relevant chemical reactions.