Engineering Commons^™

Fundamental Studies Of Flame Propagation In Lean-Burn Natural Gas Engines, Zhiyan Wang

Open Access Dissertations

Lean-burn natural gas engines offer enhanced thermal efficiencies and reduced soot and NOx emissions. However, cycle-to-cycle variability in combustion that can result from unreliable ignition, variability in equivalence ratio and quenching is a challenge. Reliability of ignition can be improved by employing a dual-fuel ignition strategy in which a small quantity of diesel fuel is injected to initiate ignition. Computational studies of n-heptane/methane-air mixing layers are performed to provide insight into the fundamental physics of dual-fuel ignition. The results show that the characteristic time required for steady premixed flame propagation has three components: time for autoignition to occur, time for …

Enabling A Sustainable Economy Through Energy Systems Modeling: Solar-Centric, Efficient, Integrated And Continuous Process Synthesis And Optimization, Emre Gencer

Open Access Dissertations

The expected increase in food, energy and water demand due to increase in population and change in consumption habits in conjunction with diminishing fossil fuel reserves and increasing greenhouse gas emissions urge the development and implementation of alternative energy conversion techniques using renewable energy for a sustainable economy. Among renewable energy sources, solar energy is prominent due to its abundance. A sustainable economy can be created by producing building blocks foundational to meeting all basic human needs of daily existence. However, intermittencies and limitations on land area dedicated to harness solar energy are the major obstacles on widespread implementation of …

Mechanical Dispersion Of Semi-Solid Binders In High-Shear Granulation, Nathan J. Davis

Open Access Dissertations

Granulation is an important industrial process used to produce many foods, medicines, consumer products, and industrial intermediate products. This thesis focuses on high shear wet granulation with the specific case study of detergent manufacture using a high shear pin mixer. The key rate process in detergent manufacturing was determined to be the mechanical dispersion of the semi-solid surfactant binder. The pin mixer and mechanical dispersion utilized experiments, population balance models, and discrete element method (DEM) models.

The mechanical dispersion of the surfactant binder was studied using a lab scale 6 liter pin mixer. An experimental method was developed to isolate …

Mechanism And Kinetics Of Homogeneous Catalysis, Silei Xiong

Open Access Dissertations

A model-based approach using a diverse set of data including monomer consumption, evolution of molecular weight, and end-group analysis was employed to determine each of the reaction specific rate constants involved in 1-hexene polymerization process catalyzed by a family of group IV single-site catalysts. The primary set of elementary reaction steps included initiation, normal propagation, misinsertion, recovery from misinsertion, monomer independent and dependent chain transfer. Robust determination of kinetic constants and reaction mechanisms for a series of Group IV amine bis-phenolate complexes led to the development of several structure−activity relationships.^ For some of the catalysts of the bis-phenolate family the …

Effect Of Maleic Acid On The Selectivity Of Glucose And Fructose Dehydration And Degradation, Ximing Zhang

Open Access Dissertations

5-Hydroxymethyfurfural (HMF), a platform chemical can upgrade to a variety of fuels and polymers, can be manufactured from lignocellulose. This study focuses on the Lewis and Brønsted acid effect on hexose dehydration for HMF production. We report the positive effect of maleic acid, a dicarboxylic acid used as Brønsted acid, on the selectivity of hexose dehydration to 5-hydroxymethyfurfural (HMF), and subsequent hydrolysis to levulinic and formic acids. We also describe the kinetic analysis of a Lewis acid (AlCl ₃) alone and in combination with HCl or maleic acid to catalyze the isomerization of glucose to fructose, dehydration of fructose …

Experimental And Modeling Investigation Of Cellulose Nanocrystals Polymer Composite Fibers, Si Chen

Open Access Dissertations

Cellulose nanocrystals (CNCs) are a class of newly developed and sustainable nanomaterial derived from cellulose-based materials such as wood. There have been substantial research efforts to utilize these materials as reinforcing agents. However, in order to develop CNC nanocomposites with industrial applications, it is necessary to understand how addition of CNCs affect the properties of the polymer nanocomposite. In the present work, several approaches, experimental and theoretical, are presented in an effort to characterize and understand the effect of CNCs on the properties of polymer CNC fibers. ^ Two experimental methods were used to develop cellulose acetate (CA) and CNC …

Modeling, Optimization, And Sensitivity Analysis Of A Continuous Multi-Segment Crystallizer For Production Of Active Pharmaceutical Ingredients, Bradley James Ridder

Open Access Dissertations

We have investigated the simulation-based, steady-state optimization of a new type of crystallizer for the production of pharmaceuticals. The multi-segment, multi-addition plug-flow crystallizer (MSMA-PFC) offers better control over supersaturation in one dimension compared to a batch or stirred-tank crystallizer. Through use of a population balance framework, we have written the governing model equations of population balance and mass balance on the crystallizer segments. The solution of these equations was accomplished through either the method of moments or the finite volume method. The goal was to optimize the performance of the crystallizer with respect to certain quantities, such as maximizing the …

Structure-Activity Relationships For The Water-Gas Shift Reaction Over Supported Metal Catalysts, Kaiwalya D. Sabnis

Open Access Dissertations

The Water-Gas Shift (WGS) reaction (CO + H₂O → CO₂ + H₂) is an important chemical process for industrial hydrogen production. The overall goal of this project is to use kinetic experiments and in situ characterization techniques in tandem, in order to derive structure-activity relationships for various catalytic systems. These relationships facilitate the rational catalyst design by identification of catalyst descriptors. In order to establish such relationships, various studies were undertaken, such as (i) effect of transition admetals on the WGS catalysis by molybdenum carbide (ii) effect of residual oxygen content on the performance of …

Kesterite Thin-Film Solar Cell Absorbers Derived Using Inhomogeneous Czts Nanoparticles, Wei-Chang D. Yang

Open Access Dissertations

My doctoral research focuses on understanding the structure-property-processing relationship of the kesterite materials to improve their device performance. It is recognized in both my own work and the recent literature that the structural and compositional integrities of CZTSSe are crucial to derive the solar cell grade kesterite thin-films. Analytical electron microscopy (AEM) allows me to demonstrate the structural and compositional inhomogeneity of the CZTS nanoparticles and CZTSSe thin-films at the nanoscale. For example, the observed forbidden reflections in TED patterns and FFT diffractograms corresponding to HRTEM images indicate that cation disorder leads to stacking faults in CZTS nanoparticles. Probe-corrected STEM …

Investigation And Modeling Of Uranium Polarization For The Electrorefining Of Scrap U-Mo Foils, Melissa Rose

Open Access Dissertations

A uranium molybdenum alloy fuel has been proposed to convert research and test reactors from highly enriched uranium to low enriched uranium to increase the proliferation resistance at such reactors. Pyroprocessing has been selected to recover uranium from the scrap produced in the manufacture of this novel fuel type. Electrorefining, the main separation process of pyroprocessing, is modeled through a novel approach using corrosion theory. To use corrosion theory, knowledge of uranium polarization and kinetic parameters such as Tafel constant, transfer coefficient and exchange current density are required. Uranium polarization was investigated at five temperatures and three scan rates in …

Structure And Activity Relationships Of Bimetallic Catalysts For Aqueous Phase Reforming And The Water-Gas Shift Reaction, Fred Gerald Sollberger

Open Access Dissertations

As the existing deposits of petroleum and non-renewable energy resources are exhausted, become more difficult to extract, and remain in politically unstable regions of the world, the search for long term alternatives for fuels and chemicals from renewable sources such as biomass continues. One promising process for the production of renewable hydrogen to use in conversion of biomass to fuels and chemicals is aqueous phase reforming (APR) of cellulose-derived carbohydrates. In the first study Pt/MWCNT catalysts have been promoted by addition of transition metal promoters Cu, Ni, Co, Fe, Mn, Mo, W, and Re in Pt:M 1:1 atomic ratios to …

Tools For Efficient Design Of Multicomponent Separation Processes, Joshua Lee Huff

Open Access Dissertations

Separations account for as much as 85% of plant operating costs in chemical production; it is therefore important that they be designed with energy efficiency in mind. This can only be achieved if two things are achieved: the complete space of design options is known, and an accurate way is developed to compare all possible design options. For both membrane separation cascades and multicomponent distillation configurations, this dissertation explores methods for designing energy efficient separations.^ The operating cost of membranes used in production of nitrogen gas from air is largely driven by the compressors required to maintain a pressure differential. …

Fundamental Studies On Copper Zeolites For Catalytic No X Abatement, Anuj Arun Verma

Open Access Dissertations

Stringent regulations in mobile NOx emissions have resulted in the development of Standard Selective Catalytic Reduction (SCR) as the dominant NOx abatement technology in lean burn diesel engines. Standard SCR is a reaction of nitric oxide (NO) with ammonia (NH₃), in the presence of oxygen (O ₂) to form nitrogen (N₂) and water (H₂O). Copper containing zeolites show commercially viable SCR performance. Cu-SSZ-13 (CHA framework), a member of this family, is a preferred catalyst for SCR applications because it shows exceptional hydrothermal stability in addition to commercially viable SCR performance. Our work focuses …

Lab-Scale Fast-Hydropyrolysis And Vapor-Phase Catalytic Hydrodeoxygenation For Producing Liquid Fuel Range Hydrocarbons From Intact Biomass, Vinod Kumar Venkatakrishnan

Open Access Dissertations

Liquid transportation fuels are primarily produced from petroleum-based non-renewable carbon sources. Sustainably available lignocellulosic biomass, as a renewable form of atmospheric carbon, could be utilized to produce hydrocarbon-based fuels with high energy density. One of the process options for this conversion is the H2Bioil process, where biomass is rapidly heated in a hydrogen environment to produce fast-hydropyrolysis vapors that are catalytically upgraded in downstream hydrodeoxygenation (HDO) to produce hydrocarbons. This process has been modeled to have high carbon and energy efficiencies of ~70% and ~75%, respectively.

This dissertation presents the results of a lab-scale experimental proof-of-concept for the H2Bioil process …

Atomic Level Study Of Water-Gas Shift Catalysts Via Transmission Electron Microscopy And X-Ray Spectroscopy, Mehmed Cem Akatay

Open Access Dissertations

Water-gas shift (WGS), CO + H₂ O [Special characters omitted.] CO₂ + H₂ (ΔH° = -41 kJ mol ^-1 ), is an industrially important reaction for the production of high purity hydrogen. Commercial Cu/ZnO/Al₂ O₃ catalystsare employed to accelerate this reaction, yet these catalysts suffer from certain drawbacks, including costly regeneration processes and sulfur poisoning. Extensive research is focused on developing new catalysts to replace the current technology. Supported noble metals stand out as promising candidates, yet comprise intricate nanostructures complicating the understanding of their working mechanism.

In this study, the structure of the supported …

Spectroscopic And Kinetic Study Of Copper-Exchanged Zeolites For The Selective Catalytic Reduction Of Nox With Ammonia, Shane Adam Bates

Open Access Dissertations

The recent application of metal-exchanged, small-pore zeolites for use in the selective catalytic reduction (SCR) of NO_x with ammonia NH₃ for automotive deNO_x applications has been a great stride in achieving emission standard goals. Copper-exchanged SSZ-13 (Cu-SSZ-13), the small-pore zeolite in this study, has been shown to be very hydrothermally stable and active under conditions presented in the exhaust of the lean-burn diesel engine. In this work, detailed studies were performed to identify many aspects of the active site(s) in Cu-SSZ-13 in order to learn about the standard SCR mechanism.

A series of seven Cu-SSZ-13 samples were …

Spectroscopic And Kinetic Characterization Of Catalytic Materials For The Conversion Of Biomass-Derived Compounds, Paul James Dietrich

Open Access Dissertations

As economies look to transition away from petroleum for social, economic, and political reasons, biomass will continue to attract attention as a renewable feedstock for the fuels and chemicals industry. In order to turn biomass into end use fuels and chemicals, the oxygen content must be lowered significantly, requiring large hydrogen inputs. For these processes to be completely renewable, the hydrogen must come from biomass or biomass-derived compounds. In this work, catalysts for the aqueous phase reforming (APR) of biomass-derived sugars were characterized by a combination of reaction kinetics, X-ray spectroscopy, electron microscopy, and theoretical computation to determine the active …

The Effect Of Composition On The Linear And Nonlinear Mechanical Properties Of Particulate Filled Elastomers, Oluwaseyi Ogebule

Open Access Dissertations

Engineering elastomers are materials capable of undergoing large deformation upon load application and recovering upon load removal. From car tires to building vibration isolator systems, elastomers are the most versatile of engineering materials. The inclusion of particulate fillers into elastomers enhances their mechanical properties (modulus, tensile strength, toughness, tear resistance, etc) thereby extending their applicability to more demanding functions. The automotive, healthcare, construction, adhesives and consumer products are some of the many industries that produce finished goods containing elastomeric parts.

Despite the various concepts on reinforcement in filled elastomers, a complete understanding of their linear viscoelastic properties and the nonlinear …

Elucidation Of Chiral Recognition Mechanisms Of Solutes By Amylose Tris[(S)-Alpha-Methylbenzylcarbamate] Sorbent, Hung-Wei Tsui

Open Access Dissertations

Enantioselective separations of chiral molecules are important in various chemical fields, such as pharmaceuticals and agrochemicals industries. Polysaccharide-based sorbents have been widely used in chiral liquid chromatography. The recognition mechanisms which determine their enantioselectivities are not completely understood.

In this dissertation, the chiral recognition mechanisms of a widely used commercial sorbent, amylose tris[(S)-alpha-methylbenzylcarbamate], for benzoin (B) enantiomers were first studied. The HPLC data for benzoin with pure n-hexane as the mobile phase have been obtained. The behavior of sorbent-solute-hexane systems can be interpreted by considering only sorbent solute two-component interactions. Infrared (IR) spectra showed evidence of substantial hydrogen bonding (H-bonding) …

Design And Assembly Of Nanostructured Complex Metal Oxide Materials For The Construction Of Batteries And Thermoelectric Devices, Gautam Ganapati Yadav

Open Access Dissertations

Thermoelectric devices and lithium-ion batteries are among the fastest growing energy technologies. Thermoelectric devices generate energy from waste heat, whereas lithium-ion batteries store energy for use in commercial applications. Two different topics are bound with a common thread in this thesis - nanotechnology! In fact, nanostructuring is a more preferred term for the approach I have taken herein. Another commonality between these two topics is the material system I have used to prove my hypotheses - complex metal oxides.

Complex metal oxides can be used for both energy generation and storage as they are stable at high temperatures, are benign …

Development Of Quantitative Ft- Ir Methods For Analyzing The Cure Kinetics Of Epoxy Resins, Sang Ha Son

Open Access Dissertations

Epoxy thermosets are important engineering materials with applications in coating, adhesives, packaging and as structural components in a variety of advanced engineering products. The ultimate performance of polymer critically depends upon the details of the cure chemistry used to produce the thermoset. In order to better understand and monitor the cure chemistry, quantitative analysis of the FT-IR response has been developed for describing the epoxy-amine curing reaction as well as monitoring the hydrogen bonding that occurs in these systems The FT-IR analysis includes (i) quantitative deconvolution of complex peaks into individual spectral contributions, (ii) peak identification via DFT analysis and …

Preparation Of Mesoporous Silica Supported Ruthenium Oxides And The Application And Kinetic Study In The Catalysis Of Water Oxidation, Yang Zhang

Open Access Dissertations

Photo-induced water splitting of water into H2 and O2 has been a major focus in the development of clean and renewable energy. The development of viable and efficient catalysts that facilitates O2 production remains the major challenge in the study of the corresponding half-reaction of water oxidation. There are plenty of metal oxides reported active in the catalysis of water oxidation. However, several important performance bench marks of those materials, such as the non-stoichiometric production of O2, slow reaction rate and/or low quantum efficiency, remain to be improved.

Ruthenium oxide (RuO2) has long been known as one of the most …

High-Pressure Vapor-Phase Catalytic Hydrodeoxygenation Of Lignin-Derived Compounds To Hydrocarbons On Bimetallic Catalysts In The Range Of 0.2-2.4 Mpa., Sara Lynn Yohe

Open Access Dissertations

Biomass, as the only renewable source of carbon, presents a sustainable alternative to liquid fossil fuels for the production of renewable transportation fuels and chemicals. The lignin portion of biomass poses a significant challenge in the upgrading and conversion of lignocellulosic biomass to fuels and chemicals, and in many current biorefineries is not utilized. However, the lignin fraction is a valuable feedstock due to its aromatic structure, lower O:C ratio than cellulose and hemicellulose, and high energy content (up to 40%) and weight fraction (average 25 wt%) of biomass. Several processes (including fast-pyrolysis, fast-hydropyrolysis, and liquid phase processing) are able …

Comprehensive Computational Modeling Of Hypergolic Propellant Ignition, Swanand Vijay Sardeshmukh

Open Access Dissertations

Ignition and combustion of hypergolic propellants mono-methyl hydrazine (MMH) and red fuming nitric acid (RFNA) is investigated computationally. A hierarchical approach is chosen to study parametric behavior of isolated processes and complex interactions thereof, in this transient phenomenon. Starting with a homogeneous reactor, performance of three reduced kinetic mechanisms is assessed first, followed by the study of auto-ignition delay as a function of initial composition and thermal state of the mixture. Macroscopic features as well as the structure of opposed diffusion flame are studied next, followed by the study of opposed liquid jets and the gas layer at the interface. …

Energy Systems Analysis For A Solar Economy, Dharik Sanchan Mallapragada

Open Access Dissertations

The use of solar energy for human needs faces challenges owing to its relatively low energy intensity and intermittent availability, coupled with the constrained availability of renewable carbon and land resources. This study uses systems analysis tools to identify carbon and energy efficient transformations of solar energy for different purposes, including transportation fuels and grid-scale energy storage. These efforts have been complemented with a feasibility analysis of existing fossil-energy and other hybrid pathways.

In an era of limited fossil resources, liquid fuels from sustainably available (SA) biomass could meet the energy needs of the transportation sector. We present a method …

An Analysis Of The Impact Of Storage Temperature, Moisture Content & Duration Upon The Chemical Components & Bioprocessing Of Lignocellulosic Biomass, Arun Athmanathan

Open Access Dissertations

The successful utilization of lignocellulosic biomass as a feedstock for fuels and chemicals necessitates storage for 2-6 months. It is correspondingly important to understand the impact of storage parameters - moisture concentration, temperature and duration - on biomass quality.

As aerobic storage is the most viable large-scale solution, aerobic storage experiments were carried out with three projected bioenergy feedstocks - sweet sorghum (Sorghum bicolor) bagasse, corn (Zea mays) stover and switchgrass (Panicum virgatum). Stored samples of each were examined for dry matter loss and composition change to develop a material balance around carbohydrates and lignin.

A mean dry matter loss …