Engineering Commons^™

Insights Into Supported Metal Catalyst Sintering And Their Application For Bio-Oil And Crude Oil Upgradation, Md Fakhruddin Patwary

Theses and Dissertations

Typical heterogeneous catalysts consist of transition metal nanoparticles anchored against sintering on an inert, porous, high temperature stable support. The synthesis of supported catalyst involves pretreatment (drying, reduction) of deposited, ionic metal precursor complexes to form metal nanoparticles. In the first part of this work, we aim to understand the influence of pretreatment (reduction temperature, heating rate, moisture content) on final particle size. Supported nanoparticles of Pt and Pd were synthesized by strong electrostatic adsorption (SEA) and dry impregnation (DI). Reduced samples were characterized by in-situ and ex-situ XRD and STEM. The DI-derived samples generally showed an expected increase of …

Polybenzimidazole Membranes For Electrochemical Applications With Harsh Operating Conditions, Kris Likit-Anurak

Theses and Dissertations

Polybenzimidazole (PBI) membranes are high temperature proton exchange membranes (PEMs) which have advantages such as being able to operate in high temperatures, strong acid environments, and have no need for external humidity during operation. PBI membranes have been demonstrated to work effectively in multiple electrochemical devices, including fuel cells, hydrogen separation pumps, redox flow batteries, and a hybrid sulfur electrolyzer. In this work, para-PBI and densified para-PBI membrane have been used to improve electrochemical performance in harsh operating conditions that are both high temperature (≥120 ̊C) and high acid concentration (≥ 5M). First, we demonstrated the use of para-PBI membranes …

Engineering Hybrid Colloidal Systems Formed By Charge-Driven Assembly Between Spherical Soft Nanoparticles And Discotic Nanoplatelets, Gelareh Rezvan

Theses and Dissertations

Soft matter, a fascinating class of materials, holds a paramount significance in the realm of material design and engineering. Within this broad category, colloidal gels with their unique characteristics have drawn tremendous attention in a variety of applications, spanning from biomedical engineering to oil and gas recovery. Meeting the specific requirements and criteria of these diverse fields necessitates the development of colloidal gels with highly tunable properties to optimize their performance for a wide range of applications. Hence, both scientific and industrial advancement call for more control over the gel properties by exploring novel practical parameters. This dissertation describes an …

Heterogeneous Catalyst Design For Biomass Conversion, Dia Sahsah

Theses and Dissertations

Catalytic upgrading of bio-based feedstocks to commodity chemicals and fuels is pivotal to a more sustainable, renewable, and environmentally benign chemical economy. However, due to the high oxygen content, high water solubility, excessive reactivity, and thermal instability, typical and well-developed catalytic material and reactor processes reliably utilized in conventional petrochemical industry are, in general, not suitable for the processing of biomass feedstocks. Therefore, the development of novel heterogeneous catalysts is necessary in order to design new high-performance catalytic reactor systems. However, rational catalyst design is a multifaceted problem, and a myriad of factors influencing the catalytic performance at the reactor …

Catalytic Hydrogenation Of Dimethyl Oxalate To Ethylene Glycol Using Silver Based Catalysts On Sba-15, Nicolas Edouard Gleason-Boure

Theses and Dissertations

Ethylene glycol (EG) is an important industrial chemical in the manufacturing of certain plastics. There is growing industrial interest in the production of dimethyl oxalate (DMO) from syngas, which can be hydrogenated to produce EG. Many studies have focused on the catalytic reduction of DMO using copper-based catalysts on silica supports, but fewer studies have been done on the effects of silver for this reaction. This work presents an in-depth study of silver catalysts prepared via various methods including incipient wetness impregnation, charge enhanced dry impregnation, and the use of various organic solvents. Reaction studies show that using pure methanol …

Structure Property Performance Of Ti3c2 Mxene/Polyelectrolyte Hybrids For Electronic And Electromagnetic Applications, Farivash Gholamirad

Theses and Dissertations

Hybrid materials based on transition metal carbide MXene (Ti3C2Tx) nanosheets have great potential for electronic, electromagnetic interference (EMI) shielding, and environmental applications due to the unique combination of considerable electrical conductivity of 4000 to 15000 S.cm-1, abundant surface functional groups (OH, O, F, Cl), and suitable mechanical properties. However, the performance of final products depends not only on the properties of constituent components but also on the morphology of the assembly. The strong repulsive electrical double layer forces among MXene nanosheets make control over their assembly morphology and final properties challenging. To address this challenge, this dissertation focuses on applying …

Understanding The Corrosion And Discharge Behaviour Of Zinc Anodes In Primary Alkaline Batteries, Brian James Lenhart

Theses and Dissertations

Primary zinc alkaline batteries power a wide array of everyday use electronic devices such as remote controls, calculators, cameras, and flashlights and will own an appreciable share of the battery market for the foreseeable future. Primary alkaline batteries generally utilize carbon, gas diffusion air, or manganese dioxide cathode but always coupled with a slurry zinc anode. There are several issues with this primary alkaline platform, largely emphasized by the performance of the zinc anode, such as a gassing phenomenon which leads to battery rupture and under certain circumstances, low material utilization leading to low energy density. The gassing and material …

Revisiting The Volumetric Swing Frequency Response Method For The Determination Of Limiting Mass Transfer Mechanisms Of N2 And O2 In Carbon Molecular Sieve 3k172, Adam Marshall Burke

Theses and Dissertations

Adsorption-based separations processes, along with the adsorbents that enable them, have benefited from a greater particular focus in recent years, following a desire to improve process energy efficiencies and cost economics. One such adsorbent, carbon molecular sieves (CMS), have likewise been a greater focus. CMS materials offer several key practical uses, such as the separation of nitrogen and oxygen, and the removal of carbon dioxide from methane process streams. In order to effectively design and implement an industrial scale process using a CMS material, the behavior of these gases on the chosen material must be known, including the limiting mass …

New Perspectives And Insights Into Direct Epoxidation Of C3H6 Using O2 And Ag Based Catalysts And Measurement Of Active Ag Site Concentration Of Promoted Ag Catalyst For C2H4 Epoxidation By H2 Pulse Titration Over Oxygen Pre-Covered Surface, Md Masudur Rahman

Theses and Dissertations

Direct epoxidation of C₃H₆ using molecular O₂ and Ag catalysts to produce propylene oxide (PO) selectively is a long-sought goal in the field of heterogeneous catalysis. In the early 1990’s Scientists at ARCO reported promising results of 58 – 59% selectivity to PO at 3.2% conversion of C₃H₆ over an unusual composition of 54.0 wt% Ag, 2.0 wt% K⁺, 0.5 wt% Mo and balance CaCO₃. Feed additives of ethyl chloride (EtCl), nitric oxide (NO) and CO₂ were stated necessary to achieve the claimed high PO selectivities. The roles …

Mathematical Analysis Of Electrochemical Systems, Shiv Krishna Reddy Madi Reddy

Theses and Dissertations

A solid electrolyte interphase (SEI) growth model is developed in a mixed modethat contains solvent diffusion through the SEI layer and corresponding solvent reduction kinetics at the SEI/electrode interface. The governing equations are solved by the Landau transformation, which makes the moving layer fixed to predict the open circuit potential, SEI layer thickness, and capacity loss. The estimated parameters fitted with experimental data from the literature are computed using COMSOL and MATLAB. Results show that the mixed mode model predicts lower capacity loss and thinner SEI layer due to its growth under open circuit conditions than previously reported by others. …

Supported Metal Bifunctional And Bimetallic Catalysts With Precisely Controlled Structures And Properties, Anhua Dong

Theses and Dissertations

In heterogenous catalysis, metallic nanomaterials play vital roles in numerous chemical processes. However, monofunctional catalysts are greatly impeded in their applications especially in the systems including tandem and/or sequential reaction steps. Besides, the catalytic performance can also be greatly influenced by the particle size, morphology, and geometry of the surface metal atoms.

The goal of this work is to synthesize bifunctional or bimetallic nanoparticles with high metal dispersion and homogenous alloys by rational synthetic strategies to facilitate the catalyst function. Strong electrostatic adsorption (SEA) is an effective and facile methodology to produce well dispersed and uniform nanoparticles. Metal-acid bifunctional catalysts …

Durability Enhancement Of Anion Exchange Membrane Based Fuel Cells (Aemfcs) And Water Electrolyzers (Aemels) By Understanding Degradation Mechanisms, Noor Ui Hassan

Theses and Dissertations

The past several years have seen remarkable progress in renewable energy sources such as solar and wind, showing excellent efficiency and significant cost reduction. The intermittent nature of renewable resources requires them to be integrated with energy storage systems that can hold or convert this excess energy into other forms. Though batteries have been the most popular, it is also possible to store the energy as chemicals and fuels, such as hydrogen (H₂). Hydrogen generation from water electrolysis has been receiving significant attention in recent years. Among the existing water electrolysis technologies, anion exchange membrane electrolyzers (AEMELs) are …

Molecular Theoretical Model For Lipid Bilayers: Adsorption Of Lipidated Proteins On Lipid Bilayers As A Function Of Bilayer Composition And Curvature, Shauna Celeste Kennard

Theses and Dissertations

Protein localization on biological membranes is motivated by either highly selective recognition of specific target membrane components or nonspecific attraction to general physical properties of the membrane, such as charge, lipid heterogeneity, and curvature. Here we discuss the interaction between lipidated proteins and lipid bilayer membranes from a comprehensive examination of how features of the membrane and its lipid constituents, including lipid composition, headgroup size, degree of tail saturation, tail length (bilayer thickness), and membrane geometry, affect the adsorption ability of the proteins. Of key importance is the strong interconnection among these compositional and morphological elements of the membrane in …

Highly Active And Stable Low-Pgm And Pgm-Free Catalysts For Anion Exchange Membrane Fuel Cells, Horie Adabi Firouzjaie

Theses and Dissertations

Anion exchange membrane fuel cells (AEMFCs) have recently seen significant growth in interest as their achievable current density, peak power density, and longevity have been dramatically improved. Though these advances in performance have been important for demonstrating the feasibility of the technology, nearly all AEMFCs reported in the literature have required a relatively high loading of platinum group metal (PGM)- based catalysts at both the anode and cathode electrodes. However, to take command of the low-temperature fuel cell market, AEMFCs cannot simply reach the same performance as incumbent proton exchange membrane fuel cells (PEMFCs), which have had decades of development …

First-Principles Based Heterogeneous Catalyst Design For Energy Conversion And Plastics Upcycling Processes, Kyung-Eun You

Theses and Dissertations

Replacing scarce and expensive Pt-group metals (Pt, Pd, Ir, Rh, and Ru) commonly used in heterogeneous catalysis with earth-abundant and inexpensive materials is an important challenge to achieve sustainability

The main focus of the first project is to develop highly selective non-precious metal catalysts for the hydrodeoxygenation (HDO) of biomass-derived polyols and we chose to examine the HDO of glycerol and its deoxygenated reaction products (1,2- and 1,3- propanediol) over Cu modified Mo₂C (Cu/Mo₂C) catalysts. In this study, we combined experimental and density functional theory (DFT) results to reveal that the Cu modifier can significantly reduce …

Fundamentals Of Adsorption And Large Scale Pressure Swing Adsorption (Psa) Process Design, Huan Jiang

Theses and Dissertations

This work focused on both fundamental of adsorption and large-scale PSA design. Chapter 1 and 2 addressed the analysis of conditions for formation of adsorption azeotropes in binary systems. Chapter 1 theoretically assessed the necessary and sufficient conditions for the formation of an adsorption azeotrope in a binary gas mixture when this mixture exhibits either intersecting or non-intersecting single gas isotherms. Chapter 2 confirmed theoretically whether adsorption azeotropes can form in a binary mixture at a pressure below the intersection pressure of the corresponding single gas isotherms. Analytical expressions derived for both general and dual thermodynamically consistent process Langmuir (DPL) …

Synthesis, Characterization And Evaluation Of Dilute Limit Alloy Bimetallic Catalysts For Bio-Oil Upgrading, Leandro Tagum De Castro

Theses and Dissertations

Well-defined single-atom catalytic sites with unique geometric and electronic properties are at the forefront of catalyst research. One type of SAC is a so-called dilute limit alloy (DLA), where single metal atom sites are supported on (or in) the surface of a second metal. This category of well-dispersed atoms alloyed on a metal surface has shown to be effective in reactions like selective hydrogenation of alkynes and dienes to alkenes, ethanol dehydrogenation, and the Ullmann reaction of aryl chlorides. In biomass conversion, this type of catalyst may find its way to address and improve conversion and yield that are crucial …

Catalytic Cracking Of Oxygenated Polymer Waste Via Zeolite Catalysts, Andrew Jaeschke

Theses and Dissertations

Plastic recycling has been a prevalent issue since the commercialization of plastics due to lack of adoption and insufficient technology. There are many different types of plastics used in modern day society; however, majority of recycling efforts are focused solely on polyethylene terephthalate (PET) and polyethylene plastics. Some of these overlooked plastics include polyols and polyurethanes, which can be found in a variety of applications including furniture stuffing, adhesives, and insulation foams. Recently, plastic research has turned to catalytic cracking units as a means of plastic recyclability. Catalytic cracking of hydrocarbons is a field dominated by zeolites catalysts, especially ZSM-5. …

Observing And Modeling Water Electrolysis Performance Limitations Attributed To Gas Generation And Porous Media Properties, Joseph S. Lopata

Theses and Dissertations

Water electrolysis has been a simple method of hydrogen production for over two centuries, but the exploration of its nuances is still accelerating. This work compiles numerous mechanisms via which electrolysis efficiency is influenced by phenomena that occur within, adjacent to, and nearby functional porous media. Computational and experimental methods are applied to electrolysis systems to quantify the impact of twophase flow patterns and porous media properties on energy losses, primarily those linked directly to the presence of the gas phase.

First, an introduction to the chemistry and operating principle of water electrolysis is presented and relevant works from the …

Rational Synthesis Of Ultra-Small And Durable Platinum-Based Catalysts For Renewable Energy Applications, Fahim Bin Abdur Rahman

Theses and Dissertations

Ultrasmall supported platinum nanoparticles (Pt NPs) are often used in two promising renewable energy production technologies – hybrid-sulfur water splitting for actively catalyzing H2SO4 decomposition and in fuel cells for the oxygen reduction reaction (ORR). However, the stability of Pt NPs under reaction conditions is the ultimate challenge for these processes. Two prevalent ways to overcome this challenge are improving stability by anchoring Pt onto a secondary metal or doping heteroatoms into the support. This dissertation covers the rational design, synthesis, and stabilization of Pt-based catalysts in these two ways to achieve durable catalytic performance with desired activity and selectivity. …

Fine Points For Broad Bumps: The Extension Of Rietveld Refinement For Benchtop Powder Xrd Analysis Of Ultra-Small Supported Nanoparticles, Jeremiah W. Lipp

Theses and Dissertations

The goal of this work is to demonstrate the capabilities of benchtop Bragg diffraction in characterizing ultra-small (< 2nm) nanoparticles. To this end we have established a method for accurately separating the background, adjusting for relevant intensity effects, and analyzing the results with Rietveld refinement. This method is applied to the characterization of six silica-supported “noble” metals under ambient conditions: Pt, Pd, Ir, Rh, Ru, and Au. Surprisingly, Bragg diffraction is capable of shining light on this difficult-to-characterize size region – revealing the propensity of these metal nanoparticles to oxidize at room temperature. Preliminary findings for future work are also discussed: extending our method to crystalline supports and fluorescent samples.

Hydrodeoxygenation Of Biomass Derived Sugar Alcohols To Platform Chemicals Using Heterogeneous Catalysts, Blake Macqueen

Theses and Dissertations

This work set out to investigate biomass derived sugar alcohol upgrading via the removal of oxygen and hydroxyl groups via the hydrodeoxygenation reaction utilizing heterogeneous catalysts. The importance of reaction conditions, catalyst meal loadings, catalyst structure and properties were probed using techniques such as design of experiments, and spectroscopic techniques including Raman and DRIFTS. The state of the art simultaneous hydrodeoxygenation (S-HDO) catalyst ReO_x-Pd/CeO₂ was investigated and optimized for various sugar alcohol substrates. The kinetics and associated mass transfer were also investigated to give further insight into the reaction over the ReO_xPd/CeO₂ catalyst.

First, …

Development Of A Multi-Scale Mechano-Electrochemical Battery Model, Drew J. Pereira

Theses and Dissertations

As the automotive industry moves towards large format electric vehicles, such as trucks and SUVs, the need for highly efficient, energy-dense electrodes rapidly increases. Several promising active materials have been studied and proposed, however, many of these materials undergo significant volume change upon lithiation and de-lithiation. Cell and pack designers struggle to understand and predict how active material volume change at the particle scale will affect mechano-electrochemical behavior on the electrode, cell, and pack scales. Additionally, many of these active materials suffer in their cycle life due to a mechanically-driven degradation of the electrode matrix. Therefore, the focus of this …

Recent Advances In Catalytic Ethylene Epoxidation: Synthesis, Characterization, And Evaluation, Benjamin Thomas Egelske

Theses and Dissertations

First synthesized in 1859 by French chemist Charles-Adolphe Wurtz, ethylene oxide (EO) is produced from the direct epoxidation of ethylene and molecular oxygen over a low surface area α-Al₂O₃ supported silver (Ag) catalyst [1-6]. With a production capacity over 35 Mt/year, EO is the largest chemical by volume synthesized from a heterogeneously catalyzed process and is used in the production of ethylene glycol, ethoxylates, and ethanolamines [6, 7]. State-of-the-art catalyst formulations contain high loadings of Ag, typically 12-30wt%, required to recover activity in the presence of promoter elements which increase EO selectivity from ~75% for unsupported Ag to 80% for …

Structure And Stability Of Ag-Ir Bimetallic Catalysts Prepared By Electroless Deposition And Synthesis And Performance Of High Selectivity Movnbsbteox Mixed Oxides For Oxidative Dehydrogenation Of Ethane, Mozhdeh Parizad

Theses and Dissertations

Improvements in industrial thermal conversions can be realized through comprehensive catalytic studies, where enhanced catalyst stability and activity are desired. Catalyst performance can be greatly affected by structural changes at high temperatures. In the case of supported Ag-Ir particles, the surface free energy (SFE) can determine preferred arrangement of the component metals. The well-established methods of strong electrostatic adsorption (SEA) and electroless deposition (ED) have been used to synthesize highly-dispersed Ag/Ir on different alumina supports (δ,θ-Al2O3 and γ-Al2O3). Surface thermodynamics dictate that the Ir-Ag system should conform to minimize free energy resulting in a low SFE Ag layer localized on …

Preparation, Characterization And Evaluation Of Rationally Designed Catalysts By Electroless Deposition, Wen Xiong

Theses and Dissertations

In heterogeneous catalysis, it is a proven factor that the surface-specific activity and the catalyst selectivity strongly depends on the active sites which are determined by the composition, size, and shape of the particle. For structure-sensitive reactions favored by specific surface sites, such as corners, steps, or edges, TOF and selectivity can be greatly changed by the size of catalyst particles since the active site distribution will change with the size of the catalysts. Usually, metal particles are synthesized by two methods in industry, namely precipitation and impregnation, which often exhibit a broad size distribution. The grand challenge of colloidal …

Catalytic And Non-Catalytic Methods For Hydrocarbon Upgrading, Valorization, And Pollutant Control, Michael Morgan Royko

Theses and Dissertations

This work investigates catalytic and non-catalytic oxidative chemical upgrading and pollutant remediation techniques to responsibly utilize hydrocarbon feedstocks with existing infrastructure as the transition to more renewable and cleaner feedstocks for energy generation are developed. These technologies include oxidative dehydrogenation of ethane, development of magnetically separable catalysts to reduce carbon monoxide emissions during biomass upgrading as well as the subsequent use of the upgraded biomass for partial coal replacement, and electrochemical treatment of a washcoat free wire mesh supported catalyst to reduce carbon monoxide emissions in combustion exhaust.

First, doping of secondary metals in M1/M2 catalysts for oxidative dehydrogenation of …

From The Surface To The Reactor: Identifying The Active Sites For Propane Dehydrogenation On Platinum-Based Catalysts Through Density Functional Theory, Experimental Data, And Uncertainty Quantification, Charles Henry Fricke

Theses and Dissertations

Propane dehydrogenation is a critical process of producing propylene, an important feedstock for the chemical industrial. There are multiple key processes to produce propylene in this manner, but one of the largest processes involves non-oxidative dehydrogenation on a platinum-tin alloy based catalyst. In general, these reactions and catalytic particles are complex, with many dehydrogenation, cracking, and reforming reactions taking place during these processes on multiple surfaces. With this in mind, ab initio computational catalysis models are used to generate further insight into these catalytic processes. In this dissertation, there are three aims to be solved: identifying the most likely active …

Insights Into Rational Catalysts Synthesis, Abolfazl Shakouri

Theses and Dissertations

Atomically distributed metal centers with maximized atom utilization efficiency called single-atom catalysts (SACs) have attracted significant attention in catalysis. SACs with the advantages of both homogeneous and heterogeneous catalysts have been rising as a new frontier in the field of catalysis. New catalytic technologies are ever-growing, considering 90% of all chemical processes employ catalysts, securing modern society’s sustainable future. A classical field in catalysis has been dedicated to catalysis by supported metals. Recently, a vast effort has been devoted to smaller catalyst particles where size is restricted to a single atom on a surface. Single atoms supported or embedded on …

Mathematical Model For Sei Growth Under Open-Circuit Conditions, Wei Shang

Theses and Dissertations

An irreversible capacity loss will take place in lithium ions batteries due to the solid electrolyte interface (SEI) creating, which consumes the active lithium and reduces solvent. SEI is either good since it can prevent further electrolyte decomposition or bad for lessening batteries' lifetime. Mathematical modeling of SEI formation is done within a porous electrode to model an empirical battery in the x-direction.A solid electrolyte interphase (SEI) growth model is developed in a mixed-mode which contains solvent diffusion through the SEI layer and its corresponding kinetics of solvent reduction at the electrode surface. The governing equations are numerically solved by …