Matching Items (7)
Filtering by
- Creators: Arizona State University
- Creators: Muhich, Christopher
Description
This honors thesis is focused on two separate catalysis projects conducted under the mentorship of Dr. Javier Pérez-Ramírez at ETH Zürich. The first project explored ethylene oxychlorination over supported europium oxychloride catalysts. The second project investigated alkyne semihydrogenation over nickel phosphide catalysts. This work is the subject of a publication of which I am a co-author, as cited below.
Project 1 Abstract: Ethylene Oxychlorination
The current two-step process for the industrial process of vinyl chloride production involves CuCl2 catalyzed ethylene oxychlorination to ethylene dichloride followed by thermal cracking of the latter to vinyl chloride. To date, no industrial application of a one-step process is available. To close this gap, this work evaluates a wide range of self-prepared supported CeO2 and EuOCl catalysts for one-step production of vinyl chloride from ethylene in a fixed-bed reactor at 623 773 K and 1 bar using feed ratios of C2H4:HCl:O2:Ar:He = 3:3 6:1.5 6:3:82 89.5. Among all studied systems, CeO2/ZrO2 and CeO2/Zeolite MS show the highest activity but suffer from severe combustion of ethylene, forming COx, while 20 wt.% EuOCl/γ-Al2O3 leads to the best vinyl chloride selectivity of 87% at 15.6% C2H4 conversion with complete suppression of CO2 formation and only 4% selectivity to CO conversion for over 100 h on stream. Characterization by XRD and EDX mapping reveals that much of the Eu is present in non-active phases such as Al2Eu or EuAl4, indicating that alternative synthesis methods could be employed to better utilize the metal. A linear relationship between conversion and metal loading is found for this catalyst, indicating that always part of the used Eu is available as EuOCl, while the rest forms inactive europium aluminate species. Zeolite-supported EuOCl slightly outperforms EuOCl/γ Al2O3 in terms of total yield, but is prone to significant coking and is unstable. Even though a lot of Eu seems locked in inactive species on EuOCl/γ Al2O3, these results indicate possible savings of nearly 16,000 USD per kg of catalyst compared to a bulk EuOCl catalyst. These very promising findings constitute a crucial step for process intensification of polyvinyl chloride production and exploring the potential of supported EuOCl catalysts in industrially-relevant reactions.
Project 2 Abstract: Alkyne Semihydrogenation
Despite strongly suffering from poor noble metal utilization and a highly toxic selectivity modifier (Pb), the archetypal catalyst applied for the three-phase alkyne semihydrogenation, the Pb-doped Pd/CaCO3 (Lindlar catalyst), is still being utilized at industrial level. Inspired by the very recent strategies involving the modification of Pd with p-block elements (i.e., S), this work extrapolates the concept by preparing crystalline metal phosphides with controlled stoichiometry. To develop an affordable and environmentally-friendly alternative to traditional hydrogenation catalysts, nickel, a metal belonging to the same group as Pd and capable of splitting molecular hydrogen has been selected. Herein, a simple two-step synthesis procedure involving nontoxic precursors was used to synthesize bulk nickel phosphides with different stoichiometries (Ni2P, Ni5P4, and Ni12P5) by controlling the P:Ni ratios. To uncover structural and surface features, this catalyst family is characterized with an array of methods including X-ray diffraction (XRD), 31P magic-angle nuclear magnetic resonance (MAS-NMR) spectroscopy, and X-ray photoelectron spectroscopy (XPS). Bulk-sensitive techniques prove the successful preparation of pure phases while XPS analysis unravels the facile passivation occurring at the NixPy surface that persists even after reductive treatment. To assess the characteristic surface fingerprints of these materials, Ar sputtering was carried out at different penetration depths, reveling the presence of Ni+ and P-species. Continuous-flow three-phase hydrogenations of short-chain acetylenic compounds display that the oxidized layer covering the surface is reduced under reaction conditions, as evidenced by the induction period before reaching the steady state performance. To assess the impact of the phosphidation treatment on catalytic performance, the catalysts were benchmarked against a commercial Ni/SiO2-Al2O3 sample. While Ni/SiO2-Al2O3 presents very low selectivity to the alkene (the selectivity is about 10% at full conversion) attributed to the well-known tendency of naked nickel nanoparticles to form hydrides, the performance of nickel phosphides is highly selective and independent of P:Ni ratio. In line with previous findings on PdxS, kinetic tests indicate the occurrence of a dual-site mechanism where the alkyne and hydrogen do not compete for the same site.
This work is the subject of a publication of which I am a co-author, as cited below.
D. Albani; K. Karajovic; B. Tata; Q. Li; S. Mitchell; N. López; J. Pérez-Ramírez. Ensemble Design in Nickel Phosphide Catalysts for Alkyne Semi-Hydrogenation. ChemCatChem 2019. doi.org/10.1002/cctc.201801430
Project 1 Abstract: Ethylene Oxychlorination
The current two-step process for the industrial process of vinyl chloride production involves CuCl2 catalyzed ethylene oxychlorination to ethylene dichloride followed by thermal cracking of the latter to vinyl chloride. To date, no industrial application of a one-step process is available. To close this gap, this work evaluates a wide range of self-prepared supported CeO2 and EuOCl catalysts for one-step production of vinyl chloride from ethylene in a fixed-bed reactor at 623 773 K and 1 bar using feed ratios of C2H4:HCl:O2:Ar:He = 3:3 6:1.5 6:3:82 89.5. Among all studied systems, CeO2/ZrO2 and CeO2/Zeolite MS show the highest activity but suffer from severe combustion of ethylene, forming COx, while 20 wt.% EuOCl/γ-Al2O3 leads to the best vinyl chloride selectivity of 87% at 15.6% C2H4 conversion with complete suppression of CO2 formation and only 4% selectivity to CO conversion for over 100 h on stream. Characterization by XRD and EDX mapping reveals that much of the Eu is present in non-active phases such as Al2Eu or EuAl4, indicating that alternative synthesis methods could be employed to better utilize the metal. A linear relationship between conversion and metal loading is found for this catalyst, indicating that always part of the used Eu is available as EuOCl, while the rest forms inactive europium aluminate species. Zeolite-supported EuOCl slightly outperforms EuOCl/γ Al2O3 in terms of total yield, but is prone to significant coking and is unstable. Even though a lot of Eu seems locked in inactive species on EuOCl/γ Al2O3, these results indicate possible savings of nearly 16,000 USD per kg of catalyst compared to a bulk EuOCl catalyst. These very promising findings constitute a crucial step for process intensification of polyvinyl chloride production and exploring the potential of supported EuOCl catalysts in industrially-relevant reactions.
Project 2 Abstract: Alkyne Semihydrogenation
Despite strongly suffering from poor noble metal utilization and a highly toxic selectivity modifier (Pb), the archetypal catalyst applied for the three-phase alkyne semihydrogenation, the Pb-doped Pd/CaCO3 (Lindlar catalyst), is still being utilized at industrial level. Inspired by the very recent strategies involving the modification of Pd with p-block elements (i.e., S), this work extrapolates the concept by preparing crystalline metal phosphides with controlled stoichiometry. To develop an affordable and environmentally-friendly alternative to traditional hydrogenation catalysts, nickel, a metal belonging to the same group as Pd and capable of splitting molecular hydrogen has been selected. Herein, a simple two-step synthesis procedure involving nontoxic precursors was used to synthesize bulk nickel phosphides with different stoichiometries (Ni2P, Ni5P4, and Ni12P5) by controlling the P:Ni ratios. To uncover structural and surface features, this catalyst family is characterized with an array of methods including X-ray diffraction (XRD), 31P magic-angle nuclear magnetic resonance (MAS-NMR) spectroscopy, and X-ray photoelectron spectroscopy (XPS). Bulk-sensitive techniques prove the successful preparation of pure phases while XPS analysis unravels the facile passivation occurring at the NixPy surface that persists even after reductive treatment. To assess the characteristic surface fingerprints of these materials, Ar sputtering was carried out at different penetration depths, reveling the presence of Ni+ and P-species. Continuous-flow three-phase hydrogenations of short-chain acetylenic compounds display that the oxidized layer covering the surface is reduced under reaction conditions, as evidenced by the induction period before reaching the steady state performance. To assess the impact of the phosphidation treatment on catalytic performance, the catalysts were benchmarked against a commercial Ni/SiO2-Al2O3 sample. While Ni/SiO2-Al2O3 presents very low selectivity to the alkene (the selectivity is about 10% at full conversion) attributed to the well-known tendency of naked nickel nanoparticles to form hydrides, the performance of nickel phosphides is highly selective and independent of P:Ni ratio. In line with previous findings on PdxS, kinetic tests indicate the occurrence of a dual-site mechanism where the alkyne and hydrogen do not compete for the same site.
This work is the subject of a publication of which I am a co-author, as cited below.
D. Albani; K. Karajovic; B. Tata; Q. Li; S. Mitchell; N. López; J. Pérez-Ramírez. Ensemble Design in Nickel Phosphide Catalysts for Alkyne Semi-Hydrogenation. ChemCatChem 2019. doi.org/10.1002/cctc.201801430
ContributorsTata, Bharath (Author) / Deng, Shuguang (Thesis director) / Muhich, Christopher (Committee member) / Chemical Engineering Program (Contributor, Contributor) / School of Sustainability (Contributor) / Barrett, The Honors College (Contributor)
Created2019-05
Description
Neurotoxicology has historically focused on substances that directly damage nervous tissue. Behavioral assays that test sensory, cognitive, or motor function are used to identify neurotoxins. But, the outcomes of behavioral assays may also be influenced by the physiological status of non-neural organs. Therefore, toxin induced damage to non- neural organs may contribute to behavioral modifications. Heavy metals and metalloids are persistent environmental pollutants and induce neurological deficits in multiple organisms. However, in the honey bee, an important insect pollinator, little is known about the sublethal effects of heavy metal and metalloid toxicity though they are exposed to these toxins chronically in some environments. In this thesis I investigate the sublethal effects of copper, cadmium, lead, and selenium on honey bee behavior and identify potential mechanisms mediating the behavioral modifications. I explore the honey bees’ ability to detect these toxins, their sensory perception of sucrose following toxin exposure, and the effects of toxin ingestion on performance during learning and memory tasks. The effects depend on the specific metal. Honey bees detect and reject copper containing solutions, but readily consume those contaminated with cadmium and lead. And, exposure to lead may alter the sensory perception of sucrose. I also demonstrate that acute selenium exposure impairs learning and long-term memory formation or recall. Localizing selenium accumulation following chronic exposure reveals that damage to non-neural organs and peripheral sensory structures is more likely than direct neurotoxicity. Probable mechanisms include gut microbiome alterations, gut lining
damage, immune system activation, impaired protein function, or aberrant DNA methylation. In the case of DNA methylation, I demonstrate that inhibiting DNA methylation dynamics can impair long-term memory formation, while the nurse-to- forager transition is not altered. These experiments could serve as the bases for and reference groups of studies testing the effects of metal or metalloid toxicity on DNA methylation. Each potential mechanism provides an avenue for investigating how neural function is influenced by the physiological status of non-neural organs. And from an ecological perspective, my results highlight the need for environmental policy to consider sublethal effects in determining safe environmental toxin loads for honey bees and other insect pollinators.
damage, immune system activation, impaired protein function, or aberrant DNA methylation. In the case of DNA methylation, I demonstrate that inhibiting DNA methylation dynamics can impair long-term memory formation, while the nurse-to- forager transition is not altered. These experiments could serve as the bases for and reference groups of studies testing the effects of metal or metalloid toxicity on DNA methylation. Each potential mechanism provides an avenue for investigating how neural function is influenced by the physiological status of non-neural organs. And from an ecological perspective, my results highlight the need for environmental policy to consider sublethal effects in determining safe environmental toxin loads for honey bees and other insect pollinators.
ContributorsBurden, Christina Marie (Author) / Amdam, Gro (Thesis advisor) / Smith, Brian H. (Thesis advisor) / Gallitano-Mendel, Amelia (Committee member) / Harrison, Jon (Committee member) / Vu, Eric (Committee member) / Arizona State University (Publisher)
Created2016
Description
Cannabis use is increasing both medically and recreationally. Over the last decade studies have investigated sex differences associated with Parkinson’s disease (PD) diagnosis and degenerative symptoms. Previous research has shown that cannabis use has had either a beneficial or deleterious effect on PD symptoms. This research will examine whether sex differences exist among the positive or negative effects of cannabis use in PD. In this paper, an analysis of sex-based differences between male and female cohorts categorized across 2,700 participants is completed under the Fox Insight data set. Each cohort will be compared to 14 nonmotor symptoms and 8 motor symptoms commonly associated with PD. In each cohort mean age, cannabis intake, cannabis dose, cannabis type, and PD diagnosis are analyzed within groups. Each symptom (motor and nonmotor) was analyzed between cohort responses to indicate if there was beneficial or worsening effect within cannabis. Results indicated that the designated female cohort reported both beneficial and worsening effects of cannabis use regarding both motor and nonmotor symptoms. The positive symptoms primarily consisted of individual motor functioning (e.g. dyskinesia, stiffness, back pain, etc.) while the worsening symptoms primarily consisted of nonmotor functioning (e.g. anxiety and apathy). Meanwhile, the male cohort only reported beneficial effects towards nonmotor symptoms (e.g. dystonia, muscle cramps, heart rate). These findings suggest the need for further examination of nigrostriatal pathways and hypothalamic integrity in PD, as it may provide more information into the effects of cannabis use based on sex differences.
ContributorsHooten, Madeline Loraine (Author) / Ofori, Edward (Thesis advisor) / Daniulaityte, Raminta (Committee member) / Peterson, Daniel (Committee member) / Arizona State University (Publisher)
Created2022
Description
Acetylcholinesterase (AChE) inhibition by chemical toxicants such as organophosphates, nerve agents, and carbamates can lead to a series of adverse health outcomes including seizures, coma, and death. An adverse outcome pathway (AOP) is a framework that describes a series of biologically measurable key events (KEs) leading from some molecular initiating event (MIE) to an adverse outcome (AO) of regulatory significance, all developed and hosted in the AOP Wiki. A quantitative AOP (qAOP) is a mathematical model that predicts how perturbations in the MIE affect KEs based on the key event relationships (KERs) that define the AOP. The purpose of this thesis was to expand upon the KERs that define the AOP for AChE inhibition leading to neurodegeneration in order to better understand the effects of AChE inhibitors and the risks they pose to ecosystems, wildlife, and human health. In order to reduce the resources and time spent for chemical toxicity testing, a qAOP was developed based on the available quantitative data and models that supported the AOP. A literature review for the collection of qualitative evidence and quantitative data in support of the AOP was performed resulting in further expansion of the relationships between key events (KERs) through construction of additional KER description pages. A model evaluation was performed by comparing the qAOP model predictions with experimental data, with a subsequent sensitivity analysis of unknown parameters. The qAOP model simulates the MIE through its fifth KE (KE 5) and KE 7. Model predictions compared to experimentally measured data either under- or overpredicting multiple KEs warranting additional refinement such as a formal parameter optimization. Overall, more data amenable to qAOP model development are needed. To aid qAOP model development, the presentation of data in the AOPWiki may be improved by presenting the quantitative data in the AOP Wiki in a tabular format and allowing for the hosting of mathematical models or raw data. With these recommendations in mind, and through continued AOP construction in the AOP Wiki, new qAOP models will be developed, ultimately supporting chemical risk assessment and the mitigation of effects upon exposed individuals and wildlife populations.
ContributorsSinitsyn, Dennis (Author) / Watanabe, Karen (Thesis advisor) / Vinas, Natalia (Committee member) / Wirkus, Stephen (Committee member) / Arizona State University (Publisher)
Created2023
Description
Glyphosate is the most heavily used herbicide worldwide and recent reports indicate that it may have deleterious neurological and neurodegenerative effects on human health. Here I demonstrate that glyphosate can infiltrate the brain in a dose-dependent manner in mice sub-acutely exposed to 125, 250, or 500 mg/kg/day. I also establish that glyphosate elicits a neuroinflammatory response in both the cortex and hippocampus, marked by elevation of tumor necrosis factor α (TNFα), and causes transcriptomic dysregulation of key genes involved in oligodendrocyte proliferation, maturation, and myelination. Given that both the hippocampus and the cortex are critical for learning and memory, and are affected in Alzheimer’s disease (AD), I investigate how 50 or 500 mg/kg chronic glyphosate exposure influences locomotion, anxiety-like behavior, and cognition in the APP/PS1 mouse model of AD. Results show that while glyphosate did not influence weight, appearance, locomotion, or anxiety-like behavior, learning acquisition is impaired in the place preference and reaction time tasks following 500mg/kg chronic exposure. Additionally, I report a strong increase in water consumption in glyphosate-exposed mice, demonstrating that chronic glyphosate exposure induces polydipsia. To ascertain whether glyphosate influences AD pathogenesis, I examine neuropathological changes following chronic daily oral exposure to 50 or 500 mg/kg glyphosate. Post-mortem analysis of amyloid-beta (Aβ) in APP/PS1 hippocampal and cortical tissue show that 50 or 500 mg/kg of glyphosate elevates soluble and insoluble Aβ1-40 and Aβ1-42 in both sexes, with females showing higher levels. Further analysis of cortical TNFα levels in chronically exposed APP/PS1 mice and littermate controls confirms a neuroinflammatory response. I report no differences in amyloid precursor protein (APP) processing pathway components, CA1 NeuN+ neuronal number, relative density of Iba1+ microglia in the hippocampus, or relative density of MBP+ oligodendrocytes in the fimbria. I also show that 50mg/kg chronic glyphosate exposure elevates hemoglobin A1c levels, indicating disruptions in glucose metabolism that may be tied to polydipsia. Collectively, these results indicate that glyphosate crosses the blood-brain barrier, induces a neuroinflammatory response, and exacerbates amyloid pathology. Ultimately, these findings provide important insight into the concerns surrounding the neurological implications of glyphosate exposure.
ContributorsWinstone, Joanna (Author) / Velazquez, Ramon (Thesis advisor) / Newbern, Jason M (Committee member) / Huentelman, Matthew J (Committee member) / Leung, Maxwell (Committee member) / Coleman, Paul D (Committee member) / Arizona State University (Publisher)
Created2023
Description
Two-dimensional quantum materials have garnered increasing interest in a wide
variety of applications due to their promising optical and electronic properties. These
quantum materials are highly anticipated to make transformative quantum sensors and
biosensors. Biosensors are currently considered among one of the most promising
solutions to a wide variety of biomedical and environmental problems including highly
sensitive and selective detection of difficult pathogens, toxins, and biomolecules.
However, scientists face enormous challenges in achieving these goals with current
technologies. Quantum biosensors can have detection with extraordinary sensitivity and
selectivity through manipulation of their quantum states, offering extraordinary properties
that cannot be attained with traditional materials. These quantum materials are anticipated
to make significant impact in the detection, diagnosis, and treatment of many diseases.
Despite the exciting promise of these cutting-edge technologies, it is largely
unknown what the inherent toxicity and biocompatibility of two-dimensional (2D)
materials are. Studies are greatly needed to lay the foundation for understanding the
interactions between quantum materials and biosystems. This work introduces a new
method to continuously monitor the cell proliferation and toxicity behavior of 2D
materials. The cell viability and toxicity measurements coupled with Live/Dead
fluorescence imaging suggest the biocompatibility of crystalline MoS2 and MoSSe
monolayers and the significantly-reduced cellular growth of defected MoTe2 thin films
and exfoliated MoS2 nanosheets. Results show the exciting potential of incorporating
kinetic cell viability data of 2D materials with other assay tools to further fundamental
understanding of 2D material biocompatibility.
variety of applications due to their promising optical and electronic properties. These
quantum materials are highly anticipated to make transformative quantum sensors and
biosensors. Biosensors are currently considered among one of the most promising
solutions to a wide variety of biomedical and environmental problems including highly
sensitive and selective detection of difficult pathogens, toxins, and biomolecules.
However, scientists face enormous challenges in achieving these goals with current
technologies. Quantum biosensors can have detection with extraordinary sensitivity and
selectivity through manipulation of their quantum states, offering extraordinary properties
that cannot be attained with traditional materials. These quantum materials are anticipated
to make significant impact in the detection, diagnosis, and treatment of many diseases.
Despite the exciting promise of these cutting-edge technologies, it is largely
unknown what the inherent toxicity and biocompatibility of two-dimensional (2D)
materials are. Studies are greatly needed to lay the foundation for understanding the
interactions between quantum materials and biosystems. This work introduces a new
method to continuously monitor the cell proliferation and toxicity behavior of 2D
materials. The cell viability and toxicity measurements coupled with Live/Dead
fluorescence imaging suggest the biocompatibility of crystalline MoS2 and MoSSe
monolayers and the significantly-reduced cellular growth of defected MoTe2 thin films
and exfoliated MoS2 nanosheets. Results show the exciting potential of incorporating
kinetic cell viability data of 2D materials with other assay tools to further fundamental
understanding of 2D material biocompatibility.
ContributorsTran, Michael, Ph.D (Author) / Tongay, Sefaattin (Thesis advisor) / Green, Matthew (Thesis advisor) / Muhich, Christopher (Committee member) / Arizona State University (Publisher)
Created2019
Description
Human impact alters the natural environment via multiple pathways, including contamination from pollutants. This human activity may adversely impact an organism’s ability to respond to environmental change. Using Bisphenol-A (BPA), a common environmental contaminant, I examined how exposure affected behavioral strategies critical for survival in a changing environment. BPA is used during plastic manufacturing, and it enters aquatic systems from wastewater streams; however, it is an endocrine-disruptor that has broad health effects from metabolism to behavior at a wide exposure range. In this study, I specifically tested whether environmentally relevant concentrations of BPA impact maximum metabolic rate and boldness in zebrafish, Danio rerio. I also examined activity level, optomotor response, body mass, and standard length to see if I can mechanistically explain any underlying changes caused by BPA. I treated groups of adult zebrafish for 7 days and exposed them to either 0.1% dimethyl sulfoxide (DMSO, control), a low environmentally relevant concentration of BPA (0.02 mg/L), or a 1-fold higher BPA concentration (0.2 mg/L). I found that the low exposure group experienced a decrease in maximum metabolic rate and the high exposure group showed a decrease in boldness. In other words, these changes in metabolism were not dosage dependent while the boldness results were dosage dependent. BPA had no effects on optomotor response, body mass, standard length or activity level. These results suggest that no level of BPA is safe, environmentally relevant concentrations are having an effect on adult organisms’ behavior and health that could affect their survival.
ContributorsLopez, Melissa (Author) / Martins, Emilia P (Thesis advisor) / Suriyampola, Piyumika S (Thesis advisor) / Conroy-Ben, Otakuye (Committee member) / Arizona State University (Publisher)
Created2021