Chemical Engineering Commons^™

Closing A Synthetic Carbon Cycle: Carbon Dioxide Conversion To Carbon Monoxide For Liquid Fuels Synthesis, Yolanda Andreina Daza

USF Tampa Graduate Theses and Dissertations

CO₂ global emissions exceed 30 Giga tonnes (Gt) per year, and the high atmospheric concentrations are detrimental to the environment. In spite of efforts to decrease emissions by sequestration (carbon capture and storage) and repurposing (use in fine chemicals synthesis and oil extraction), more than 98% of CO₂ generated is released to the atmosphere. With emissions expected to increase, transforming CO₂ to chemicals of high demand could be an alternative to decrease its atmospheric concentration. Transportation fuels represent 26% of the global energy consumption, making it an ideal end product that could match the scale of CO …

Conversion Of Landfill Gas To Liquid Hydrocarbon Fuels: Design And Feasibility Study, Ryan Alexander Kent

USF Tampa Graduate Theses and Dissertations

This paper will discuss the conversion of gas produced from biomass into liquid fuel through the combination of naturally occurring processes, which occur in landfills and anaerobic digesters, and a gas-to-liquids (GTL) facility. Landfills and anaerobic digesters produce gases (LFG) that can be converted into syngas via a Tri-reforming process and then synthesized into man-made hydrocarbon mixtures using Fischer-Tropsch synthesis. Further processing allows for the separation into liquid hydrocarbon fuels such as diesel and gasoline, as well as other middle distillate fuels. Conversion of landfill gas into liquid fuels increases their energy density, ease of storage, and open market potential …

Modified Yttrium Hydroxide/Mc Nylon Nanocomposites And Scaling Effects In Multilayer Polyethylene Films, Jia Chen

USF Tampa Graduate Theses and Dissertations

In this thesis, monomer casting (MC) nylon was synthesized. MC nylon could replace nonferrous metals in certain applications, including gears, wheels, and other moving parts. However, compared with metals, MC nylon products have poor strength and stiffness, and crack easily, especially at low temperatures. In addition, the dimensional stability of MC nylon is poor, especially in the large casting nylon products, causing significant internal stresses due to shrinkage. Thus, MC nylon cracks easily when cast and molded. The yttrium hydroxide particles were modified by stearic acid and dispersed in the caprolactam. The polymerization time was short due to fast anionic …

Feasibility Of Cathodic Protection In Grouted Post Tensioned Tendons - Exploratory Model Calculations, Jacob Dharma Bumgardner

USF Tampa Graduate Theses and Dissertations

Recent corrosion related failures of grouted post tensioned tendons, even after the introduction of improved grouts, have led to renewed interest in supplemental or backup means of corrosion control for these systems. A finite element model is presented to explore feasibility of impressed current cathodic protection of strand in grouted tendons. The model examines polarization evolution as function of service time and includes consideration of anode placement and size, grout porosity, pore water alkalinity, electrochemical species diffusivity and applied voltage on the polarization efficacy and durability of such a system. The exploratory model projections suggested that, within the context of …

Interplays Of Co2, Subnanometer Metal Clusters, And Tio2: Implications For Catalysis And Co2 Photoreduction, Chi-Ta Yang

USF Tampa Graduate Theses and Dissertations

This research is motivated by two significant challenges facing the planet: reducing the emission of CO₂ to the atmosphere and production of sustainable fuels by harnessing solar energy. The main objective of this work is the study of promising photocatalysts for CO₂ reduction. DFT modeling of CO₂, subnanometer Ag&Pt clusters, and anatase TiO2 (101) surface is employed to gain fundamental understanding of the catalytic process, followed by validation using a guided experimental endeavor. The binding mechanism of CO₂ on the surface is investigated in detail to gain insights into the catalytic activity and to assist …

An Investigation On The Band Gap And Band Edge Of Semi-Conducting Lanthanum Transition Metal Perovskites For Photocatalytic Applications, Divya Suresh

USF Tampa Graduate Theses and Dissertations

For the past few decades, a frenzy of attention has been given towards the development of an assortment of photocatalysts as a solution for various environmental problems. TiO2 is the most widely used photocatalyst. TiO2 is biocompatible, chemically and thermally stable but TiO2 and a vast majority other photocatalysts have large band gaps, and hence they find applicability only in the UV region of the solar spectrum. These large band gap photocatalysts suffer a severe limitation with regard to their overall process efficiency as the UV region contributes to about 3 to 4 % of the solar spectrum in terms …

Applications Of Optical Properties From Nanomaterials For Enhanced Activity Of A Titania Photocatalyst Under Solar Radiation, Jon W. Pickering

USF Tampa Graduate Theses and Dissertations

In recent years, employing advanced oxidation processes (AOPs) as a means of wastewater remediation has emerged as a promising route towards maintaining a sustainable global water management program. The heterogeneous photocatalytic oxidation process has been of particular interest due to the prospective of utilizing solar radiation as the driving force behind the degradation of pollutants. Of the photocatalyst studied to date, TiO2 remains the most attractive material for environmental applications due to its affordability, stability, biocompatibility and high quantum yield. A key draw back however is roughly only 5% of solar radiation incident on earth can provide the energy required …

Topographical Enhancement Of Cell Adhesion On Poorly Adhesive Materials, Maritza Muniz Maisonet

USF Tampa Graduate Theses and Dissertations

The overall thrust of this dissertation is to gain a fundamental understanding of the synergistic effects between surface topography and chemical functionality of poorly adhesive materials on enhancing the adhesion of mouse embryonic fibroblasts. Cellular response to surface topography and chemical functionality have been extensively studied on their own providing valuable information that helps in the design of new and improved biomaterials for tissue engineering applications. However, there is a lack of understanding of the synergistic effect of microscale and nanoscale topography with chemical functionality and the relative impact and contribution of each in modulating cellular behavior. By understanding the …

Fabrication Of Tissue Precursors Induced By Shape-Changing Hydrogels, Olukemi O. Akintewe

USF Tampa Graduate Theses and Dissertations

Scaffold based tissue reconstruction inherently limits regenerative capacity due to inflammatory response and limited cell migration. In contrast, scaffold-free methods promise formation of functional tissues with both reduced adverse host reactions and enhanced integration. Cell-sheet engineering is a well-known bottom-up tissue engineering approach that allows the release of intact cell sheet from a temperature responsive polymer such as poly-N-isopropylacrylamide (pNIPAAm). pNIPAAm is an ideal template for culturing cell sheets because it undergoes a sharp volume-phase transition owing to the hydrophilic and hydrophobic interaction around its lower critical solution temperature (LCST) of 32°C, a temperature close to physiological temperature. Compared to …

Additives For Heat Transfer Enhancement In High Temperature Thermal Energy Storage Media: Selection And Characterization, Philip D. Myers Jr.

USF Tampa Graduate Theses and Dissertations

Inorganic salts are very promising as high-temperature heat transfer fluids and thermal storage media in solar thermal power production. The dual-tank molten salt storage system, for example, has been demonstrated to be effective for continuous operation in solar power tower plants. In this particular storage regime, however, much of the thermal storage potential of the salts is ignored. Most inorganic salts are characterized by high heats of fusion, so their use as phase-change materials (PCMs) allows for substantially higher energy storage density than their use as sensible heat storage alone. For instance, use of molten sodium-potassium eutectic salt over a …

Metallic Encapsulation For High Temperature (>500 °C) Thermal Energy Storage Applications, Abhinav Bhardwaj

USF Tampa Graduate Theses and Dissertations

Deployment of high temperature (>500 °C) thermal energy storage in solar power plants will make solar power more cost competitive and pave the way towards a sustainable future. In this research, a unique metallic encapsulation has been presented for thermal energy storage at high temperatures, capable of operation in aerobic conditions. This goal was achieved by employing low cost materials like carbon steel. The research work presents the unique encapsulation procedure adopted, as well as various coatings evaluated and optimized for corrosion protection. Experimental testing favored the use of 150 μm of nickel on carbon steel for corrosion protection …

Silicone Elastomer-Based Combinatorial Biomaterial Gradients For High Throughput Screening Of Cell-Substrate Interactions, Greeshma Mohan

USF Tampa Graduate Theses and Dissertations

Biomaterials have evolved over the years from the passive role of mere biocompatibility to an increasingly active role of presenting instructive cues to elicit precise responses at the molecular and cellular levels. Various characteristics common to synthetic biomaterials in vitro and extracellular matrices in vivo, such as immobilized functional or peptide groups, mechanical stiffness, bulk physical properties and topographical features, are key players that regulate cell response. The dynamics in the cell microenvironment and at the cell adhesive interface trigger a web of cell-material and cell-cell information exchanges that have a profound impact in directing the ultimate cell fate …

Analysis Of Advanced Supercritical Carbon Dioxide Power Cycles For Concentrated Solar Power Applications, Saeb Mostaghim Besarati

USF Tampa Graduate Theses and Dissertations

Solar power tower technology can achieve higher temperatures than the most common commercial technology using parabolic troughs. In order to take advantage of higher temperatures, new power cycles are needed for generating power at higher efficiencies. Supercritical carbon dioxide (S-CO₂) power cycle is one of the alternatives that have been proposed for the future concentrated solar power (CSP) plants due to its high efficiency. On the other hand, carbon dioxide can also be a replacement for current heat transfer fluids (HTFs), i.e. oil, molten salt, and steam. The main disadvantages of the current HTFs are maximum operating temperature …

Photonic Crystal-Based Flow Cytometry, Justin William Stewart

USF Tampa Graduate Theses and Dissertations

Photonic crystals serve as powerful building blocks for the development of lab-on-chip devices. Currently they are used for a wide range of miniaturized optical components such as extremely compact waveguides to refractive-index based optical sensors. Here we propose a new technique for analyzing and characterizing cells through the design of a micro-flow cytometer using photonic crystals. While lab scale flow cytometers have been critical to many developments in cellular biology they are not portable, difficult to use and relatively expensive. By making a miniature sensor capable of replicating the same functionality as the large scale units with photonic crystals, we …

Investigation Of Enhanced Titanium And Zinc Oxide Semiconductors For The Photodegradation Of Aqueous Organic Compounds, Innocent Udom

USF Tampa Graduate Theses and Dissertations

Growing demand and shortages of potable water sources due to industrialization have become a great concern worldwide. Various approaches and solutions have been adopted to provide cleaner and quality water. In a preliminary study, a method of treating wastewater was investigated in which algae were used to remove nutrients (nitrogen and phosphorous) from wastewater and then the algae were harvested for use as a biofuel. The results from this investigation are included in the Appendix B. Employing traditional oxidants, such as hydrogen peroxide, chlorine, and ozone, for treatment of recalcitrant organic compounds have achieved less promising results. However, photocatalysis, an …

Insights Into The Epitaxial Relationships Between One-Dimensional Nanomaterials And Metal Catalyst Surfaces Using Density Functional Theory Calculations, Debosruti Dutta

USF Tampa Graduate Theses and Dissertations

This dissertation involves the study of epitaxial behavior of one-dimensional nanomaterials like single-walled carbon nanotubes and Indium Arsenide nanowires grown on metallic catalyst surfaces. It has been previously observed in our novel microplasma based CVD growth of SWCNTs on Ni-Fe bimetallic nanoparticles that changes in the metal catalyst composition was accompanied by variations in the average metal-metal bond lengths of the nanoparticle and that in turn, affected nanotube chirality distributions. In this dissertation, we have developed a very simplistic model of the metal catalyst in order to explain the nanotube growth of specific nanotube chiralities on various Ni-Fe catalyst surfaces. …

Homochiral Metal-Organic Materials: Design, Synthetic And Enantioseletive Separation, Shi-Yuan Zhang

USF Tampa Graduate Theses and Dissertations

Owing to the growing demand for enantiopurity in biological and chemical processes, tremendous efforts have been devoted to the synthesis of homochiral metal-organic materials (MOMs) because of their potential applications in chiral separation and asymmetric catalysis. In this dissertation, the synthetic strategies for homochiral MOMs are discussed keeping the focus on their applications. Two distinct approaches have been taken to synthesize chiral structures with different topologies and accessible cavities. The chiral MOMs have been utilized in enantioselective separation of racemates.

Chiral variants of the prototypal metal-organic framework MOF-5, δ-CMOF-5 and [lambda]-CMOF-5, have been synthesized by preparing MOF-5 in the presence …

Investigation Of Tio2 And Invo4-Tio2 Semiconductors For The Photocatalytic Degradation Of Aqueous Organics, Sandra L. Pettit

USF Tampa Graduate Theses and Dissertations

Water is a vital natural resource. To develop more sustainable water systems, we must focus efforts on the removal of persistent contaminants. Aqueous organic contaminants include azo dyes, halogenated organics (e.g. pesticides), and algal and bacterial metabolites. The latter are common to surface waters and freshwater aquaculture systems and can cause taste and odor problems. Two of the principal organoleptic compounds are geosmin and 2-methylisoborneol (MIB). Traditional oxidation treatment methods, utilizing chlorine, hydrogen peroxide, and potassium permanganate, have been employed with varying levels of efficacy for removal of these and other organic contaminants. Advanced Oxidation Processes (AOPs) have greater potential …

Theoretical Studies Of Co Based Catalysts On Co Hydrogenation And Oxidation, Nianthrini Balakrishnan

USF Tampa Graduate Theses and Dissertations

CO hydrogenation and CO oxidation are two important processes addressing the energy and environmental issues of great interest. Both processes are carried out using metallic catalysts. The objective of this dissertation is to study the catalytic processes that govern these two reactions from a molecular perspective using quantum mechanical calculations. Density Functional Theory (DFT) has proven to be a valuable tool to study adsorption, dissociation, chain growth, reaction pathways etc., on well-defined surfaces. DFT was used to study the CO reduction reactions on promoted cobalt catalyst surfaces and CO oxidation mechanisms on cobalt surfaces.

CO hydrogenation via Fischer-Tropsch Synthesis (FTS) …

Application And Characterization Of Self-Assembled Monolayers In Hybrid Electronic Systems, Michael Enoch Celesin

USF Tampa Graduate Theses and Dissertations

In this study, we explore ultra-thin insulators of organic and inorganic composition and their potential role as high-speed rectifiers. Typical applications for these structures include IR sensing, chemical detection, high speed logic circuits, and MEMS enhancements. While there are many elements in the functional group required to create a rectifying antenna (rectenna), the primary thrust of this work is on the rectifier element itself.

To achieve these research goals, a very good understanding of quantum tunneling was required to model the underlying phenomenon of charge conduction. The development of a multi-variable optimization routine for tunneling prediction was required. MATLAB was …

Development Of Catalytic Technology For Producing Sustainable Energy, Syed Ali Z Gardezi

USF Tampa Graduate Theses and Dissertations

This dissertation explores catalyst technology for the production of renewable liquid fuels via thermo-chemical conversion of biomass derived syngas. Fischer-Tropsch synthesis is a process for converting syngas, i.e. a mixture of CO and H2, into energy rich long chain hydrocarbons and oxygenated compounds. This synthesis process involves a number of elementary reactions leading to an array of polymeric products. The economic operation of an FTS process lie in the interplay of both catalyst and reactor design. In relation to catalysis, the nature of chemisorbed species, and the fractional availability of active metal sites determines rate, conversion and yield. Similarly, reactor …

Kelvin Probe Electrode For Contactless Potential Measurement On Concrete-Properties And Applications, Michael Thomas Walsh

USF Tampa Graduate Theses and Dissertations

The practical feasibility of using a Kelvin Probe as a novel reference electrode in the measurement of both potential and polarization pulse response of reinforcing steel in concrete is demonstrated. Potential values measured using a KP reflect greater stability and repeatability than can typically be attained with conventional reference electrodes. Duplicate reinforced concrete beam test specimens with well-differentiated centrally corroding rebar segments were analyzed using both the Kelvin Probe (KP) and a conventional Saturated Calomel Electrode (SCE). Potential profile maps were developed using potential values recorded under static conditions with both the SCE and the KP. Nominal polarization resistance was …

Structured Materials For Catalytic And Sensing Applications, Selma Hokenek

USF Tampa Graduate Theses and Dissertations

The optical and chemical properties of the materials used in catalytic and sensing applications directly determine the characteristics of the resultant catalyst or sensor. It is well known that a catalyst needs to have high activity, selectivity, and stability to be viable in an industrial setting. The hydrogenation activity of palladium catalysts is known to be excellent, but the industrial applications are limited by the cost of obtaining catalyst in amounts large enough to make their use economical. As a result, alloying palladium with a cheaper, more widely available metal while maintaining the high catalytic activity seen in monometallic catalysts …

Model Pt- And Pd-Based Electrocatalysts For Low Temperature Fuel Cells Applications, Selasi Ofoe Blavo

USF Tampa Graduate Theses and Dissertations

In the search for alternative energy technologies, low temperature fuel cells continue to feature as technologies with the most promise for mass commercialization. Among the low temperature fuel cells, alkaline and proton exchange membrane fuel cells are the most popular. Alkaline fuel cells have typically been used for water generation as well as auxiliary power for space shuttles. Their bulkiness however makes them undesirable for other applications, especially in automobiles, where there is a great demand for alternative technologies to internal combustion engines. Proton exchange membrane fuel cells on the other hand possess numerous qualities including their compact size, high …

Synthesis Of Titanium Dioxide Photocatalyst With The Aid Of Supercritical Fluids, Haitao Li

USF Tampa Graduate Theses and Dissertations

Titanium Dioxide (TiO2) emerged as one of the most popular photocatalysts since 1970's. However, its photocatalytic activity requires UV irradiation due to its large band gap unless further functionalization or modifications are performed. Furthermore, recovery issue has always been a major drawback, if the more effective form nano particles are utilized.

The key objectives of this research were synthesizing new TiO2 based photocatalyst systems that are effective with both the UV and the visible light while utilizing novel superior environmentally friendly techniques enabling development of nano-structured photocatalysts that can be easily recovered. In this dissertation research, highly porous nano-structured TiO2/WO3/Fe3+ …

One Dimensional Stochastic Coating Growth Kinetics Of Peg 3400 Onto Ammonium Nitrate In A Fluidized Bed, Brandon Smeltzer

USF Tampa Graduate Theses and Dissertations

Fluidized beds represent a cost effective, scalable technology invaluable to the chemical processing community as part of the global scheme of particle design. However, despite wide spread use and multiple approaches (empirical and mechanistic) to modeling a fluidized bed coating process, operations must be done at different scales due to changes within the balance of phenomenological forces (e.g. gravity, buoyancy, drag, surface tension, viscosity, kinetic energy).

Ammonium nitrate is synthetic compound that has multiple applications such as fertilizer, rocket fuel, and self-cooling applications. Ammonium nitrate has five temperature dependent crystal structures that are accompanied by a change in density. The …

Modeling And Design Of Photocatalytic Reactors For Air Purification, Yangyang Zhang

USF Tampa Graduate Theses and Dissertations

Photocatalysis is a promising technique for the remediation of indoor air pollution. Photocatalysis utilizes semiconductor photocatalysts (such as TiO₂ or ZnO) and appropriate light to produce strong oxidizing agents (OH*) that are able to break down organic compounds and inactivate bacteria and viruses. The overall goal of the research is to develop an efficient photocatalytic reactor based on mass transfer for indoor air purification. This study has focused on the enhancement of the effectiveness of the photocatalytic process by the introduction of artificial roughness on the reactor catalyst surface. The major effect of artificial roughness elements on the catalytic …

Innovative Desalination Systems Using Low-Grade Heat, Chennan Li

USF Tampa Graduate Theses and Dissertations

Water and energy crises have forced researchers to seek alternative water and energy sources. Seawater desalination can contribute towards meeting the increasing demand for fresh water using alternative energy sources like low-grade heat. Industrial waste heat, geothermal, solar thermal, could help to ease the energy crisis.

Unfortunately, the efficiency of the conventional power cycle becomes

uneconomically low with low-grade heat sources, while, at the same time, seawater desalination requires more energy than a conventional water treatment process. However, heat discarded from low-grade heat power cycles could be used as part of desalination energy sources with seawater being used as coolant …

Fermentation And Supercritical Extraction Studies Of Açaí Berry, Rosanna Iris Ayala

USF Tampa Graduate Theses and Dissertations

The açaí berry has grown in popularity for dieters and the health conscious. The berry contains high levels of antioxidants. The main anthocyanins are cyanidin-3-rutinoside and cyanidin-3-glucoside. The berries also contain vitamins and nutrients that help boost energy and alertness, and fatty acids that help maintain normal cholesterol levels. As a result of the health benefits of the constituents, the berries are chosen for obtaining the active ingredients by extraction.

The solids left over after extraction still contain nutrients and useful components. There is a possibility of fermenting this residual and creating an açaí berry wine. Açaí berry wine is …

Investigation And Synthesis Of Novel Graphene-Based Nanocomposites For Hydrogen Storage, Anthony Joseph D'Angelo

USF Tampa Graduate Theses and Dissertations

It is of great interest to develop and utilize a high surface area material with optimized hydrogen sorption properties. The need for a renewable energy source to replace automobile gasoline has become more critical in the past decade. Hydrogen is a viable fuel source for automobile usage; however, the question of how hydrogen will be safely and efficiently stored still remains. Critical factors for optimum hydrogen storage include ambient conditions and low activation temperature for adsorption and desorption phenomena. In order for optimum hydrogen adsorption to be achieved, the properties of (1) high surface area, (2) optimum hydrogen adsorption energy, …