Doctor of Philosophy (PhD), Ohio University, 2020, Chemical Engineering (Engineering and Technology)

Growing renewable energy technologies is not only essential to reduce carbon emissions and mitigate climate change, but also critical to boost global energy security and support a sustainable basis for economic development. Prioritizing new technologies that promote the transition from fossil fuels to renewable energy technologies is critical to address future global energy demands and prevent global warming. Lignin is a major renewable and non-fossil source of aromatic compounds that can be used to generate sustainable fuels, fine chemicals, additives, and resins. The application of lignin, however, as a source of aromatic compounds has been largely undeveloped due to the lack of an efficient depolymerization process. Among various methods that have been developed so far for lignin depolymerization, electrochemical conversion is a promising approach for industrial application because it occurs at room temperature and ambient pressure. Nickel-based and lead dioxide-based materials are among the most common electrocatalysts for lignin oxidation, as both are inexpensive and stable in highly alkaline electrolytes, and possess high catalytic activities for lignin oxidation. In this Ph.D. project, several nickel-based alloys were developed through co-electrodeposition of nickel and cobalt; and nickel and tin, to enhance the properties of the nickel catalysts for lignin depolymerization. Incorporation of cobalt to nickel reduces the onset potential for lignin oxidation due to the enhanced properties resulting from doping cobalt to nickel. Electrochemical oxidation of lignin on nickel-cobalt alloys with a higher cobalt content leads to lower energy requirements for lignin depolymerization and higher rates of formation of the functionalized aromatic compounds. Nickel-tin alloys provide higher surface areas and better stabilities for long term lignin oxidation. Lignin depolymerization is the dominant reaction at the low cell voltages when the oxygen evolution faradaic effici (open full item for complete abstract)

Committee: John Staser (Advisor); Rebecca Barlag (Committee Member); Sarah Davis (Committee Member); Kevin Crist (Committee Member); Marc Singer (Committee Member) Subjects: Chemical Engineering

Master of Science (MS), Ohio University, 2019, Chemical Engineering (Engineering and Technology)

The aim of this study is to first develop a non-precious metal oxide electrocatalyst for selective electrochemical oxidation of lignin. Next, the metal oxide electrocatalyst along with a modified metal electrocatalyst, previously developed in our research group are studied for the lignin electrolysis process in an anion exchange membrane (AEM) electrolysis cell. To that aim, four β-PbO2/MWNTs nanocomposites were developed via a wet-chemistry procedure and studied in a three electrode cell configuration. Product stream analysis was conducted by gas chromatography-mass spectroscopy (GS-MS). In addition, cyclic voltammetry (CV), linear sweep voltammetry (LSV) and potentiostatic measurements were carried out to evaluate electrocatalyst performance. The 33.3 wt% β-PbO2 nanocomposite possessed the highest electro-catalytic activity and stability for oxidation of lignin. Also, GC-MS results revealed that the β-PbO2/MWNTs nanocomposite is likely a selective electrocatalyst for conversion of lignin into low molecular weight aromatic (LMWA) compounds. The 33.3 wt% β-PbO2 nanocomposite and a modified bimetallic Ni-Co supported on TiO2 were used as the anodic catalyst in an AEM system to quantify H2 production and energy consumption rates of this system and compare them with recent efforts for water and lignin electrolysis in the literature. From the results, it was demonstrated that the β-PbO2/MWNTs nanocomposite is a stable and active electrocatalyst that can fasten the anodic lignin oxidation rate and therefore increase the cathodic reaction rate which is H2 evolution. At the end, our results showed that using β-PbO2/MWNTs as the anodic catalyst can lead to high hydrogen evolution rates (~45.6 mL/h) and increase energy efficiency by 20%, compared to a well-established and commercial alkaline water electrolyzer.

Committee: John A. Staser (Advisor); Kevin Crist (Committee Member); Marc Singer (Committee Member); Marcia Kieliszewski (Committee Member) Subjects: Chemical Engineering; Chemistry

Doctor of Philosophy (PhD), Ohio University, 2020, Chemical Engineering (Engineering and Technology)

Lignin is one of the main byproducts of pulp and paper industry and biorefineries. Depolymerization of lignin can lead to producing valuable low molecular weight compounds with different functional groups, which are mainly achieved from crude oil sources. Lignin electrolysis could address issues of other lignin depolymerization methods such as complexity, lignin combustion, and low selectivity. On the other hand, lignin electrolysis can occur at significantly lower overpotentials than those required for water electrolysis, which leads to lower-voltage electrolyzer operation and as a result lower energy consumption for hydrogen production. This study includes research and experimental works on developing a continuous electrochemical process for both lignin electrolysis and hydrogen production in an electrolyzer. At the first step of this project, high surface area TiO2 or carbon-supported NiCo electrocatalysts were synthesized and applied for lignin depolymerization at room temperature and pressure. The electrocatalysts were characterized by Brunauer-Emmett-Teller (BET), X-Ray Diffraction (XRD), Scanning Electron Microscopy (SEM), and Energy-dispersive X-ray spectroscopy (EDS) techniques. In addition, a three-electrode rotating disc electrode (RDE) system was used to test the performance and durability of 6 electrocatalysts individually and among them 1:3NiCo/TiO2 was selected as the most effective catalyst for lignin depolymerization. In the second step, a continuous electrochemical cell with 10 cm2 electrodes, separated by an anion exchange membrane (AEM), was applied for lignin electrolysis in the anode and hydrogen generation in the cathode. The effects of temperature, lignin concentration, cell voltage, and electrolysis time on hydrogen production, oxygen evolution, lignin conversion, products with different functional groups, and energy efficiency of the electrochemical reactor were investigated. Although applying high cell voltages increases the rate of electr (open full item for complete abstract)

Committee: John Staser (Advisor) Subjects: Chemical Engineering; Chemistry; Engineering; Environmental Engineering; Wood Sciences

Master of Science (MS), Ohio University, 2019, Chemical Engineering (Engineering and Technology)

The aim of this study is to first develop a non-precious metal oxide electrocatalyst for selective electrochemical oxidation of lignin. Next, the metal oxide electrocatalyst along with a modified metal electrocatalyst, previously developed in our research group are studied for the lignin electrolysis process in an anion exchange membrane (AEM) electrolysis cell. To that aim, four β-PbO2/MWNTs nanocomposites were developed via a wet-chemistry procedure and studied in a three electrode cell configuration. Product stream analysis was conducted by gas chromatography-mass spectroscopy (GS-MS). In addition, cyclic voltammetry (CV), linear sweep voltammetry (LSV) and potentiostatic measurements were carried out to evaluate electrocatalyst performance. The 33.3 wt% β-PbO2 nanocomposite possessed the highest electro-catalytic activity and stability for oxidation of lignin. Also, GC-MS results revealed that the β-PbO2/MWNTs nanocomposite is likely a selective electrocatalyst for conversion of lignin into low molecular weight aromatic (LMWA) compounds. The 33.3 wt% β-PbO2 nanocomposite and a modified bimetallic Ni-Co supported on TiO2 were used as the anodic catalyst in an AEM system to quantify H2 production and energy consumption rates of this system and compare them with recent efforts for water and lignin electrolysis in the literature. From the results, it was demonstrated that the β-PbO2/MWNTs nanocomposite is a stable and active electrocatalyst that can fasten the anodic lignin oxidation rate and therefore increase the cathodic reaction rate which is H2 evolution. At the end, our results showed that using β-PbO2/MWNTs as the anodic catalyst can lead to high hydrogen evolution rates (~45.6 mL/h) and increase energy efficiency by 20%, compared to a well-established and commercial alkaline water electrolyzer.

Committee: John A. Staser (Advisor); Kevin Crist (Committee Member); Marc Singer (Committee Member); Marcia Kieliszewski (Committee Member) Subjects: Chemical Engineering; Chemistry

PhD, University of Cincinnati, 2020, Engineering and Applied Science: Chemical Engineering

Biofuels, derived from lignocelluloses, is an attractive supplement to fuel produced from non-renewable resources. Various pretreatment methods have been developed to overcome the recalcitrance of lignocelluloses to provide highly digestible substrates for enzymatic hydrolysis. Organosolv pretreatment with ethanol is a promising method for increasing cellulose accessibility, releasing sugars from hemicellulose, and recovering relatively pure lignin as a by-product. The use of other short-chain aliphatic alcohols in the organosolv pretreatment, such as methanol and propanol, was considered to have high-efficiency delignification. The following step of biochemical conversion is enzymatic hydrolysis, by which cellulose and hemicellulose are converted into fermentable sugars. The high cost of enzymes is one of the major bottlenecks in biochemical conversion. In this work, methanol, ethanol, and propanol organosolv lignins from poplar, eucalyptus, aspen, Loblolly pine, and kenaf have been evaluated for their effects on enzymatic hydrolysis of lignocelluloses. Two dimension heteronuclear single quantum coherence spectroscopy (2D-HSQC), heteronuclear single quantum coherence-total correlated spectroscopy (HSQC-TOCSY), and heteronuclear multiple bond correlation spectroscopy (HMBC) have been used to characterize the structure changes of lignins before and after organosolv pretreatment. The spectra of HSQC, HSQC-TOCSY, and HMBC revealed that the alkylation (e.g., methylation, ethylation and propylation) of hydroxyl groups took place not only at Ca, but also at Cß and C?, and potentially also at the phenolic hydroxyl group of lignin. These results showed that propanol organosolv lignins (POLs) from poplar and aspen had higher stimulatory effects than the ethanol and methanol organosolv lignins (EOLs and MOLs) on the enzymatic hydrolysis of Avicel. The alkylation degree will affect the hydrophobicity of resulting organosolv lignins, which in turn will control their positive (open full item for complete abstract)

Committee: Maobing Tu Ph.D. (Committee Chair); Mingming Lu Ph.D. (Committee Member); Yoonjee Park Ph.D. (Committee Member); Jingjie Wu Ph.D. (Committee Member); Wei Yuan Ph.D. (Committee Member) Subjects: Agricultural Engineering

Master of Science (M.S.), University of Dayton, 2020, Chemical Engineering

The use of cost-effective bio-based materials, such as lignin, offers the potential to replace commercially available, expensive synthetic petroleum materials which are currently used in the production of fibers and plastics. Many lignin-based nano-scale fibers have the potential to be used in a vast range of applications, ranging from automobiles to the electronics industry. These nanofibers can also be used in chemical separations and adsorption technologies. Unfortunately, lignin possesses a low molecular weight, and therefore polymer blends are used for the production of lignin-based nanofibers. Hence there is a need to optimize and understand polymer-polymer interactions of lignin and a carrier polymer to ultimately generate nanofibers with desired characteristics. In this study, two types of lignin, low sulfonate (LSL) and alkali, kraft lignin (AL) were investigated and combined with polyacrylonitrile-co-methyl acrylate (PAN-MA) for the fabrication of nanofibers using electrospinning techniques. The polymers were solubilized in N,N dimethylformamide (DMF) and prepared at different PAN-MA:lignin ratios ranging from 100:0 to 50:50 at varying total polymer concentrations ranging from 10 wt % to 20 wt %. Using solvent evaporation, PAN-MA/lignin films were obtained and the polymer arrangements, phase separation, and morphology were studied via polarized optical microscope (POM) and scanning electron microscopy (SEM). AL blends showed good miscibility with PAN-MA at higher concentrations wherein LSL blends found to have phase separation. Rheological characterization of LSL and AL in PAN-MA polymer solutions included flow sweep, frequency sweep, and amplitude sweep tests, which were used to gain insights into the effects of lignin type and ratios in the polymer solutions. Electrospinning of various PAN-MA/lignin solutions proceeded at an operating voltage of 15 kV with currents varying between 0-2 µA and at a 0.003 ml/min constant flow rate. Thermal and chem (open full item for complete abstract)

Committee: Erick Vasquez Dr. (Committee Chair); Donald Klosterman Dr. (Committee Member); Kenya Crosson Dr. (Committee Member) Subjects: Automotive Engineering; Chemical Engineering; Chemistry; Environmental Engineering; Materials Science; Nanotechnology; Polymers; Sustainability

MS, University of Cincinnati, 2010, Engineering and Applied Science: Environmental Engineering

Manganese peroxidase, lignin peroxidase, and laccases have shown promise for efficient removal of lignin fraction within the biomass which is resistant to biomass-to-ethanol process. This thesis research study focused on the effectiveness of ligninases, formations of delignification products and optimal experiment conditions for delignification. Another widely used and studied biomass pretreatment method, dilute acid pretreatment was tested in this study. Four types of biomass were tested. Author focused the studies of kinetic rate, activation energy and pretreated biomass weight model for every model biomass. Additional, this thesis research conducted a carbon and hydrogen elements analysis for the four model biomass to calculate the mass balance for this dilute acid pretreatment experiment.

Committee: Timothy Keener PhD (Committee Chair); Mingming Lu PhD (Committee Member); Joo Youp Lee PhD (Committee Member) Subjects: Environmental Engineering

Doctor of Philosophy, University of Akron, 2024, Polymer Engineering

In this work, High Density Polyethylene (HDPE) composites were made using Torrefied Soybean Hulls (TSBH) and Carbon Black (CB) to study the interactions affiliated with the TSBH content for as-received as well as size-reduced particles. The Milled TSBH (MTSBH) was shown to integrate well at low loadings, but showed signs of favoring filler-filler interactions over filler-matrix interactions, reducing the overall effectiveness as the loadings increased. Rheological testing showed that the higher-loaded MTSBH composites behaved similar to composites with larger particles as the loading increased, indicating that clusters had formed. Unmilled TSBH (UTSBH) showed good mechanical strength, but the particle size was shown to limit its ability to integrate into the material, even at low loadings. The addition of CB was shown to have the most impact on the low loading MTSBH composites, where the MTSBH-CB interactions were shown to influence the filler network in electrical resistance testing where a nonlinear trend was observed in the composite resistivity with the addition of MTSBH. In UTSBH composites, there were less signs of CB-UTSBH interactions due to the relatively large particle size. To contrast the hydrophilic matrix behavior of HDPE, Nylon-6 (PA6) was used as a matrix for the TSBH composites. In cases where either TSBH filler was used, the composite performance was shown to improve to a greater degree than in the case of HDPE due to the hydrophilic groups contained in the PA6 backbone. Similar to the HDPE composites, the TSBH particles showed a lack of effectiveness at higher filler loadings, though MTSBH showed more effective integration which indicates that this is a result of particle size. The CB and MTSBH showed synergistic effects with high CB and low MTSBH loading during cyclic tension testing, where the increase in strain energy density required for a test was less when the CB was present that when it was not. This effect was seen throughout the mono (open full item for complete abstract)

Committee: Erol Sancaktar (Advisor); Kevin Cavicchi (Committee Chair); Wieslaw Binienda (Committee Member); Steven Chuang (Committee Member); James Eagan (Committee Member) Subjects: Chemical Engineering; Materials Science; Mechanics; Plastics

Master of Science (M.S.), University of Dayton, 2022, Chemical Engineering

Nanoparticle additives increase the thermal conductivity of conventional heat transfer fluids like water at low concentrations, which could lead to improved heat transfer fluids and processes. In this study, lignin-based Fe₃O₄ nanoparticles (lignin@Fe₃O₄ ) are investigated as a novel bio-based magnetic nanoparticle additive to enhance the thermal conductivity of aqueous-based fluids. Kraft lignin was used to encapsulate the Fe₃O₄ nanoparticles to increase the dispersion rate and prevent agglomeration and oxidation of the magnetic nanoparticles. Lignin@Fe₃O₄ nanoparticles were prepared using a co-precipitation method and characterized by various experimental techniques, including Transmission Electron Microscopy (TEM) and Vibrating Sampling Magnetometry (VSM). Once fully characterized, lignin@Fe₃O₄ nanoparticles were dispersed in aqueous 0.1 % w/v agar-water solutions at five low concentrations: 0.001 %w/v, 0.002 %w/v, 0.003 %w/v,0.004 %w/v and 0.005 %w/v. Thermal conductivity was measured using METER Group's KD-3 Tempos and the transient line heat source method was used at five different temperature conditions: 25 °C, 30 °C, 35 °C, 40 °C, and 45 °C. Additionally, at room temperature, the thermal conductivity of aqueous-based lignin@Fe₃O₄ suspensions was characterized at the following magnetic fields of 0 Gauss, 100 Gauss, 200 Gauss, 300 Gauss, and 400 Gauss. This study shows an increment of thermal conductivity by about 10% in the highest concentrations and temperature conditions. Additionally, the study also demonstrated the increment of thermal conductivity up to 5% in 200 Gauss magnetic field strength in the highest concentrations at a constant room temperature of 21 °C. This work establishes that lignin-based Fe₃O₄ nanosuspension increases the thermal conductivity of aqueous-based fluids and has the potential to enhance the thermal conductivity of conventional heat transfer fluids.

Committee: Eric Vasquez Ph.D (Committee Chair); Soubantika Palchoudhury Ph.D (Committee Member); Kevin Myers D.Sc (Committee Member) Subjects: Chemical Engineering; Materials Science; Nanoscience

Doctor of Philosophy, University of Akron, 2022, Polymer Science

Photoelectrochemical (PEC) conversion of biomass (e.g., lignin) to hydrogen, a carbon-negative emission technology, is characterized by four key processes: (i) photo-generated electron-hole pairs, (ii) electron transport from the anode to the cathode, (iii) hydrogen generation at the cathode and (iv) biomass oxidation by photogenerated holes in the valence band. Overall performance of the photoelectrochemical cell is governed by step (i), electron-hole generation, followed by step (iv), charge transfer at the semiconductor/electrolyte interface. This dissertation will discuss the development of an in situ infrared spectroscopic (IR) approach to study charge dynamics during PEC reactions. Accumulated photogenerated electrons on the semiconductor surface in PEC reactions exhibit a structureless, and featureless spectrum centered around 2000 cm-1. The intensity and rate of the IR profile of photogenerated electrons at this wavenumber correlates to the charge transport in the PEC process, qualitatively characterizing the efficiency of the catalyst. Electron accumulation can also be observed under dark conditions with negative voltage bias. Adsorbed water on the semiconductor surface serves as a hole scavenger and shields the catalyst surface from oxygen, preventing electron-hole recombination, while simultaneously promoting the formation of a double layer of electrons and protons on the semiconductor surface. The effect of voltage on the performance of the PEC cell is investigated through the analysis of the IR profile (i.e., relative concentration) of photogenerated electrons. The results of charge dynamics shed a light on the PEC mechanism and provide a scientific basis for devising novel approaches to enhance the PEC efficiency. The observations of the dynamics of accumulated electrons and water coverage in PEC reactions revealed the applicability of the in situ IR approach to electro-swing CO2 capture in liquid monoethanolamine (MEA). CO2 reacts with amines (open full item for complete abstract)

Committee: Steven S.C. Chuang (Advisor); Toshikazu Miyoshi (Committee Member); Zhenmeng Peng (Committee Member); Mesfin Tsige (Committee Member); Yu Zhu (Committee Member) Subjects: Alternative Energy; Analytical Chemistry; Polymers

Doctor of Philosophy, University of Toledo, 2021, Biology (Ecology)

Herein we developed two mathematical models of microbial enzyme-driven, plant litter decomposition: (1) a two-substrate cellulose (C2) and lignin (C3) model including cellulolytic (E2) and ligninolytic enzymes (E3) and (2) a three-substrate organic nitrogen (C1), cellulose (C2), and lignin (C3) model including nitrogen-acquiring (E1), cellulolytic (E2), and ligninolytic (E3) enzymes. For the lignocellulose model, we set observed first-order decay rates equal to reverse Michaelis-Menten (RMM) equations to estimate relative enzyme activities associated with observed patterns of hollocellulose (C2) and lignin (C3) decay. Results were consistent with empirical studies, showing a negative relationship of E2/(E2+E3) to litter lignin content, C3/(C2+C3), above a minimum threshold of 40% lignin, at which lignin begins to decay. For the three-pool model, we solved for the allocation of each enzyme pool as functions of litter lignocellulose index (LCI), microbial and litter C:N stoichiometry, and constraints on total enzyme production, again setting observed decay rates equal to RMM equations. To our knowledge, the lignocellulose model is the first mechanistic explanation of microbial allocation of cellulolytic and ligninolytic enzymes as a function of the lignin concentration of the lignocellulose complex. It was consistent with observations but raised questions about factors controlling the threshold for lignin decay. The three-pool model provides the first practical solution for analytically allocating microbial C- and N-acquiring enzymes as functions of both litter C-quality and C:N stoichiometry but insufficient data exist to reconcile these underlying controls with observed patterns of enzyme allocation and C and N dynamics during long-term litter decay.

Committee: Daryl Moorhead (Advisor); Jon Bossenbroek (Committee Member); Michael Weintraub (Committee Member); Robert Sinsabaugh (Committee Member); Gwenaëlle Lashermes (Committee Member) Subjects: Ecology

PhD, University of Cincinnati, 2021, Arts and Sciences: Chemistry

Abstract This dissertation focuses on biomass conversion, including the investigation of the effects of lignin structure on enzymatic hydrolysis, and lignin valorization to valuable chemicals under mild conditions. In this work, four different types of lignin model polymers have been synthesized and employed in enzymatic hydrolysis to understand their effects on glucose release. A cobalt-based catalytic system has also been developed to cleave the ether C–O bonds in lignin model compounds and organosolv lignin. The lignin structure is complicated to allow in-depth studies of structure-reactivity relationships. Thus, the use of lignin model systems can simplify the analysis, representing a viable strategy in this research field. On the other hand, overly simplified lignin model compounds may not necessarily reflect how real lignin behaves. Herein four lignin model polymers bearing ß-O-4 and/or ß-ß linkages and guaiacyl and/or syringyl units have been synthesized, which involves polymerization, further derivatization, and polymer purification. With medium complexity in structures, these polymers are expected to bridge the gap between overly simplified lignin model compounds and real lignin in terms of understanding the biomass conversion. Lignin model polymers I and IV contain ß-O-4 linkages with syringyl and guaiacyl units, respectively. Lignin model polymer II is composed of ß-O-4 and ß-ß with the syringyl unit only. Lignin model polymer III is composed of ß-O-4 and ß-ß with both syringyl and guaiacyl units. The complexity in lignin structure plays a crucial, yet not well-understood, role in sugar production from biomass via enzymatic hydrolysis. To understand the well-defined lignin structure's influence, the aforementioned four lignin model polymers were employed in enzymatic hydrolysis. Lignin model polymers I and IV increase the glucose yield by 6% and 11%, while lignin model polymers II and III decrease the glucose yield by 3% and 2%, respe (open full item for complete abstract)

Committee: Hairong Guan Ph.D. (Committee Chair); Allan Pinhas Ph.D. (Committee Member); Maobing Tu Ph.D. (Committee Member); Peng Zhang Ph.D. (Committee Member) Subjects: Chemistry

Master of Science (M.S.), University of Dayton, 2021, Chemical Engineering

Emulsions are used for many biological, pharmaceutical, and food purposes and require a non-toxic, eco-friendly emulsifier to keep them stabilized over time. Iron oxide nanoparticles (IONPs) have been thoroughly studied and used as an additive in emulsions to form Pickering emulsions. In this study, Kraft lignin, a type of biopolymer obtained from Kraft pulp, was used as a coating for the IONPs to prevent agglomeration and oxidation. Specifically, lignin@Fe3O4 nanoparticles were synthesized using a co-precipitation bottom-up approach and were characterized using multiple techniques, such as Fourier-Transform Infrared Spectroscopy (FT-IR), Thermogravimetric Analysis (TGA), Dynamic Light Scattering (DLS), and Vibrating-Sample Magnetometer (VSM). After confirming the formation of lignin@Fe3O4, these nanoparticles were used to prepare Pickering emulsions with castor oil/sudan red G dye and pure water. Five different oil/water ratios were tested (10/90, 30/70, 50/50, 70/30, and 90/10), along with three nanoparticle concentrations (0.1, 0.5, and 1.0 w/v%) and 5 magnetic fields (540, 370, 100, 5, and 0 mT). The emulsion stability without a magnetic field was determined by measuring droplet sizes using microscopy techniques as a function of time. The Pickering emulsions, stabilized by lignin@Fe3O4, can also undergo a demulsification process using external magnetic fields, successfully separating the oil and the aqueous phase. Also, this study shows that an aqueous lignin@Fe3O4 nanoparticle solution and 1-pentanol adsorb at the oil/water interface and can be used to herd spilled oil on water, exemplifying the adsorptive properties of IONPs. The successful Pickering emulsions then had their magnetorheological properties tested on a rheometer. Flow, amplitude, and frequency sweep tests were run at 0 mT and 60 mT and proved that applying a magnetic field can change the emulsions' rheological behavior, from liquid-like to solid-like, as nanoparticle concentration increased. Over (open full item for complete abstract)

Committee: Erick Vasquez Ph.D (Advisor); Kevin Myers D. Sc. (Committee Member); Li Cao Ph.D. (Committee Member) Subjects: Chemical Engineering; Chemistry; Materials Science; Nanoscience; Sustainability

Master of Science (M.S.), University of Dayton, 2019, Chemical Engineering

Ethanol extraction from aqueous solutions, such as biofuel fermentation broths, is a highly energy-intensive process with high operational costs. Currently, unit operations such as distillation, dehydration by vacuum distillation, and extractive distillation are used to obtain ethanol at a high purity level from aqueous streams, which is challenging due to the azeotrope formation. Alternative technologies using ionic liquids in liquid-liquid extraction have been proposed for ethanol extraction processes; however, these liquids are not environmentally friendly, have high toxicity, and possess complex structures. Hence, the utilization of other solvents in liquid-liquid extraction could become a more attractive process for ethanol extraction from aqueous solutions. Vegetable oils, fatty esters, hydrocarbons, and fatty alcohols have been proposed as green solvents and as the extract phase based on separation factors and distribution coefficients and due to their inherent low-cost. For instance, as compared to many other green solvents, a high distribution coefficient for castor oil in ethanol extraction from water has been found, suggesting a high capacity of this solvent in ethanol separation processes. Nonetheless, few studies focus on understanding the fundamental principles of extraction and phase equilibria for extract solvents. In this study, a liquid-liquid equilibrium study of the ternary system comprised of castor oil, water, and ethanol is obtained experimentally for the first time using a gas chromatograph system equipped with a headspace autosampler. In addition to obtaining the ternary diagram for castor oil/water/ethanol mixtures, this study analyzes the use of bio-based lignin magnetic nanoparticles to increase the extract phase ethanol separation efficiency. Lignin is an underutilized renewable resource that has high adsorptive properties, which combined with magnetic nanoparticles, could aid significantly in many liquid-liquid extraction processes due (open full item for complete abstract)

Committee: Erick Vasquez Ph. D (Advisor); Kevin Myers D. Sc., P.E (Committee Member); Christopher Muratore Ph. D (Committee Member) Subjects: Chemical Engineering; Chemistry; Materials Science; Nanoscience; Sustainability

Master of Science, The Ohio State University, 2018, Horticulture and Crop Science

Alfalfa (Medicago sativa L.) is grown worldwide and used fundamentally to meet the nutritional requirements by primarily ruminant livestock. However, nutritive value of alfalfa is severely limited by indigestible cell wall constituents, such as lignin. There have been many efforts to improve alfalfa digestibility by down regulating enzymes in lignin pathways to develop alfalfa with reduced lignin (RL) content. In 2015, RL cultivars were released for commercial use. The purpose of this research was to: 1) compare forage nutritive value and yield of a RL cultivar (HarvXtra) to non-RL cultivars and 2) to determine if a recalibration of the predictive equations for alfalfa quality (PEAQ) was necessary for adequate neutral detergent fiber (NDF) predictions for RL alfalfa. This research was established in six states across the USA in 2015 and continued until spring of 2017 for Objective one. Plant sampling for Objective two occurred in Ohio and Wisconsin in 2016. The experimental design was a randomized complete-block with a split plot restriction on treatment randomization, where harvest intervals (28-, 33-, and 38-day) were the whole plot factor and cultivar was the sub plot factor. For Objective one, the overall linear model for cultivar response to harvest intervals was significant and all cultivars responded similarly across harvest intervals and events. Reduced lignin alfalfa, `HarvXtra-008' always had higher nutritive value than non-RL cultivars. Neutral detergent fiber digestibility (NDFD) for `HarvXtra-008' was greater (P<0.05) by 4.0 to 10.4% (21 to 49 g kg-1 actual NDFD units) than non-RL cultivars. The NDF was lower (P<0.05) for `HarvXtra-008' by 5.4 to 8.3% units than `P54R02'. Differences in yield at individual harvests among cultivars and across harvest intervals were non-significant; however, `HarvXtra-008' lower (P<0.05) in annual total dry matter yield than non-RL cultivars. For Objective two, the PEAQ NDF prediction was calculated from the stage of th (open full item for complete abstract)

Committee: R. Mark Sulc (Advisor); David Barker (Committee Member); Maurice Eastridge (Committee Member); Edzard van Santen (Committee Member) Subjects: Agronomy

Doctor of Philosophy, University of Toledo, 2016, Chemical Engineering

Declining nonrenewable petroleum resources combined with political and environmental concerns over fossil fuels have necessitated the search for alternate energy sources. Plant (lignocellulosic) biomass, which includes the fibrous, woody, and generally inedible portion of plant matter, is an abundant, inexpensive, and sustainable source of organic carbon that can be processed to produce fuel ethanol and a variety of other chemicals. The biological conversion of cellulosic biomass to ethanol could offer high yields at low costs, but only if more improvement is seen in technology for releasing simple sugars from recalcitrant biomass. Lignocellulosic biomass is composed of three major components- cellulose, hemicellulose, and lignin. The cellulose and hemicellulose portions when hydrolyzed into glucose and pentose sugars, can be fermented to produce fuel. The pretreatment of biomass is a crucial step, and in recent years, ionic liquids (ILs) have been gaining recognition as environmentally benign solvents for biomass pretreatment, owing to their favorable properties Although a promising route, IL pretreatment still harbors several critical aspects that require further investigation, and the goal of this dissertation is to address these concerns. A key aspect that influences the economic viability of the ionic liquid pretreatment technique is the recovery and reuse of ILs. The extent of recovery of the IL under investigation, 1-ethyl-3-methylimidazolium acetate (EMIM-Ac), is investigated and the results are presented in chapter 3. It is shown that the ionic liquid does not irreversibly adsorb onto the biomass and can be recovered in the displacement solvent (water is used as antisolvent for separating ionic liquid from the biomass after pretreatment) at different biomass loadings. Nearly complete recovery of IL in wash solutions is achieved and no appreciable loss in its effectiveness for subsequent pretreatment is observed for over 9 recycle stages. However, the water (open full item for complete abstract)

Committee: Sasidhar Varanasi (Committee Chair); Jared Anderson (Committee Member); Bryant Hanson (Committee Member); Glenn Lipscomb (Committee Member); Constance Schall (Committee Member) Subjects: Chemical Engineering

Doctor of Philosophy, University of Toledo, 2016, Biology (Cell-Molecular Biology)

ZmMYB31 and ZmMYB42 are R2R3 MYB regulatory factors implicated in the regulation of phenylpropanoid genes in maize (Fornale, Sonbol et al. 2006, Fornale, Shi et al. 2010). Here we tested the hypothesis that the regulatory functions of MYB31 and MYB42 are conserved in other monocots specifically sorghum and rice. The expression profile of syntelogs of MYB31 and MYB42 and of four phenylpropanoid genes, caffeic acid O-methyltransferase (Comt), 4-coumarate-CoA ligase (4CL), ferulate-5-hydroxylase (F5H), and caffeoyl shikimate esterase (Cse), was determined and found to vary along the developmental gradient of young seedling leaves. There was a general trend towards reduced expression of these phenylpropanoid genes in mature leaf tip tissues as compared to the basal leaf tissues. Specific antisera were developed and used to demonstrate, by chromatin immunoprecipitation (ChIP), that Comt is also a target of MYB31 and MYB42 in the mature leaf tissues, not only of maize but also in sorghum and rice. In addition, 4CL2, F5H, and Cse were discovered to be regulatory targets of MYB31 and/ or MYB42 in seedling leaves of all three species but their binding profile differed between species. A survey of promoter occupancy revealed 9 out of 54 instances of common tissue specific regulation by MYB31 or MYB42 across 2 or more species and two (CSE and MYB31) that occur in all three species. In two instances enriched promoter occupancy by these regulators paralleled reduced expression of the target genes (Comt and 4CL2). The Cse gene is targeted by MYB42 in all three species and may represent a conserved regulatory module that functions early in the phenylpropanoid pathway. Similarly the MYB31 regulatory gene was a common target of MYB42 in the leaf tip of all three species and evidence is provided of cross regulation and MYB42 autoregulation. In summary, it was found that apart from a few instances of conserved regulatory patterns, the functions of MYB31 and MYB42 syntelogs ap (open full item for complete abstract)

Committee: John Gray Dr. (Advisor); Lirim Shemshedini Dr. (Committee Member); Erich Grotewold Dr. (Committee Member); Scott Leisner Dr. (Committee Member); Alexei Federov Dr. (Committee Member) Subjects: Biology; Botany; Molecular Biology; Plant Biology; Plant Sciences

Doctor of Philosophy, Case Western Reserve University, 2015, Macromolecular Science and Engineering

Aerogels are an interesting class of materials that possess many exotic and extreme properties. These properties are developed as the gel network is produced from solution. As the gel develops, it builds a hierarchical structure, possessing architectures at different size scales through molecular and macro-scale interactions. Once the solvent is removed, and the resultant aerogel is produced, the hierarchical nature of the material produces many desirable properties including: extremely high porosities (greater than 90% pore volume)[1], extremely low thermal conductivities (10-30 mW/m-k)[1], very low densities (as low as 0.002 g/cm3)[2], low refractive indices (as low as 1.01),[3] low dielectric constants (between 1.0 and 1.5),[4] high surface areas,[5,6] and the slowest speed of sound through a solid material. The first chapter of this thesis deals with the structure/property relationships of polymer/clay aerogels interfused with uniformly distributed air bubbles were examined. Through the incorporation of a polyelectrolyte in a montmorillonite (MMT) clay solution, the viscosity was systematically changed by the addition of ions with different charges. The bubbles were achieved via high speed mixing and were stabilized through the use of the surfactant sodium dodecyl sulfate (SDS). As the charge of the ion increased from +1 (Na+ ions) to +2 (Ca2+ ions) to finally +3 (Al3+ ions), the modulus of the resultant aerogels increased. The foamed polymer/clay aerogels showed a reduction in thermal conductivity while retaining similar mechanical properties to unfoamed polymer/clay aerogels. The most promising composition was one which contained 5% MMT clay/5% poly(vinyl alcohol)/0.5% xanthum gum/0.5% SDS/0.2% Al2(SO4)3·6(H2O) possessing a density of 0.083 g/cm3, an average modulus of 3.0 MPa, and a thermal conductivity of 41 mW/m·K. The second project investigated the feasibility of incorporating ground recycled polyurethane (PU) foam into clay/polymer aerog (open full item for complete abstract)

Committee: David Schiraldi Ph.D. (Advisor); Mary Ann Meador Ph.D. (Advisor); Gary Wnek Ph.D. (Committee Member); Eric Baer Ph.D. (Committee Member) Subjects: Aerospace Materials; Automotive Materials; Chemistry; Engineering; Experiments; Inorganic Chemistry; Materials Science; Organic Chemistry; Polymer Chemistry; Polymers

Master of Science, The Ohio State University, 2014, Food, Agricultural and Biological Engineering

Anaerobic digestion may provide an attractive alternative for producing clean, affordable transportation fuels. This technology is currently being used for biogas production and some researchers are investigating the opportunity to upgrade biogas to liquid transportation fuels using the Fischer-Tropsch process. One of the primary concerns is creating and sustaining feedstock supply capable of meeting the commercial scale system demands. Current plans include sourcing biomass from municipal yard waste, agricultural residue (corn stover) and dedicated energy crops (miscanthus). This study is focused on the harvest, storage and densification characteristics of biomass feedstocks intended for anaerobic digestion, specifically, the selective harvest of corn stover. Investigations were designed to: 1) assess functionality of traditional harvesting methods to alter the relative components of cellulose, hemicellulose, lignin and extractives in corn stover; 2) determine the level of dry matter loss (DML) and the relative quantities of volatile solids (VS) for corn stover stored under varying levels of outdoor exposure; and 3) determine the limiting fraction affecting the densification of baled corn stover and develop recommendations as to the ideal biomass fraction for densification. Corn stover was baled at the Farm Science Review site in London, Ohio using three collection strategies (two cut heights and material other than grain) to determine if components changed significantly to effect biogas yield. It was determined that it is possible to significantly (p<0.05) increase hemicellulose level by up to 2.32%, while reducing lignin and ash content by 1.14% and 2.79%, respectively, when increasing the stover cut height from 2.5 cm to MOG harvesting height of 30 cm. However, bales with MOG harvested at 30 cm lack structure due to larger particle size because the MOG material was not chopped before baling and lack of stalk material in the bale. This can be alleviated by (open full item for complete abstract)

Committee: Scott Shearer PhD (Advisor); Yebo Li PhD (Committee Member); Ajay Shah PhD (Committee Member) Subjects: Agricultural Engineering; Engineering; Environmental Engineering

Doctor of Philosophy, The Ohio State University, 2014, Horticulture and Crop Science

The genetic diversity in the crop landraces and crop wild relatives (CWRs) of the world is the `biological cornerstone' of food security—we must ensure that it is conserved. Two important steps that could assist the in-situ conservation of this germplasm are: 1) determining how natural selection has shaped the distribution of functional genetic diversity across the landscape; and 2) identifying potential threats to this diversity. In addition, the former could assist landrace farmers in securing germplasm capable of withstanding future biotic and abiotic shifts by producing information on the locations of pertinent genetic diversity. In this body of work we provide examples of each of these steps—one from the maize landraces of Chiapas, Mexico (step 1) and the other from the sunflower system of the US (step 2). First, we sought understanding of how natural selection has shaped functional genetic diversity in Zea mays ssp. mays (maize) landraces grown along an elevational cline in Chiapas, Mexico by using RNA-seq approaches. We collected maize landraces from three elevational zones (highland, ~2100 m; midland, ~1550 m; and lowland, ~600 m) and planted them in a midland common garden. RNA-seq was performed on young leaf tissue. Weighted gene co-expression network analysis was used to identify co-expressed gene modules among landraces. Association analysis was then performed between landrace module expression values and environmental parameters of landrace origin. We identified an apparent tradeoff between an ABA dependent abiotic stress response in the lowland landraces and a possible plasma membrane repair/signaling response in the highland landraces. We then used the RNA-seq dataset to find signals of genetic differentiation in phenylpropanoid, flavonoid, and lignin biosynthesis between highland and lowland maize landraces. Genes differentially expressed between highland and lowland landraces were compared to a list of known and predicted genes involv (open full item for complete abstract)

Committee: Kristin Mercer Dr. (Advisor); Erich Grotewold Dr. (Committee Member); Leah McHale Dr. (Committee Member); Andrew Michel Dr. (Committee Member) Subjects: Agriculture; Biology; Conservation; Ecology; Horticulture; Molecular Biology; Plant Biology; Plant Sciences; Sustainability