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

Doctor of Philosophy, The Ohio State University, 2022, Chemical Engineering

Chemical looping uses a metal oxide oxygen carrier to provide the necessary oxygen for the partial or complete combustion of fuel. Chemical looping systems can be configured to produce sequestration ready CO2, high purity syngas, high purity hydrogen, or any combination of the three. The uniqueness of the moving bed reducer reactor pioneered at The Ohio State University (OSU) is the basis of the systems presented here. The work presented in this dissertation aims to determine process improvements and applications for which chemical looping provides an efficient alternative to traditional processing methods for the reduction in emissions and potential cost savings. The use of biomass fuel in a moving bed reducer chemical looping system was investigated on a bench scale reactor system, known as Biomass-to-Syngas (BTS). Tars, which are known to cause operational issues, were measured at the outlet of the system. A reduction in these tars from traditional gasification of the order of 1g/m3 to a concentration of 0.3g/m3 was observed, due to the unique catalytic cracking ability of the Iron-Titanium Composite Metal Oxide (ITCMO) used in this study.1,2 This reduction in present tars shows just one area where the use of a chemical looping system increases the quality of syngas produced from biomass fuels. Additional improvements to the BTS process were investigated, to reduce the amount of steam input and determine reactor length characteristics. Experimental trials found that the reducer reactor length was a critical factor, as a continued increase in reactor length results in a decrease in syngas purity. This decrease is attributed to water-gas-shift (WGS) occurring in the lower portion of the reducer, increasing the amount of CO2 undesirably. The amount of steam injected to the system, typically done to tune the H2:CO ratio and to increase gasification kinetics, was studied to determine process efficiency. It was found that for a hardwood biomass, only 5% steam (fed b (open full item for complete abstract)

Committee: Andrew Tong (Advisor); Jeffery Chalmers (Committee Member); Joel Paulson (Committee Member); Harpreet Singh (Committee Member) Subjects: Chemical Engineering; Energy; Engineering

Doctor of Philosophy, The Ohio State University, 2022, Chemical Engineering

Chemical looping partial oxidation is a process technology with the potential to enable clean, sustainable, and cost-effective valorization of hydrocarbon feedstocks to an array of chemical products. In the process scheme, the partial oxidation reaction is partitioned into separate reduction and oxidation reactions facilitated by an oxygen carrying chemical intermediate, referred to here as an oxygen carrier. By utilizing lattice oxygen donation from a metal oxide oxygen carrier in lieu of molecular oxygen, the hydrocarbon fuel can be efficiently converted to high purity syngas. The benefits and impacts of improving the efficiency of syngas generation are propagated through to downstream fuel and chemical synthesis processes. In this study, the chemical looping partial oxidation process for the thermochemical conversion of methane to syngas is investigated at the sub-pilot scale. Performance of the process and identification of viable operating conditions based on thermodynamic criteria is explored through process simulation. The design, construction, commissioning, and operation of a 15 kWth sub-pilot is detailed. In the unit, methane conversion of 99.64% and syngas purity of 97.13% are obtained with a product H2/CO ratio of 1.96. Co-reforming of methane with steam and CO2 is demonstrated, where net CO2 utilization is exhibited and flexible product H2/CO ratio of between 1.19 to 2.50 with high syngas purity is achieved. Finally, considerations for the design of the reactors during scale-up is discussed. The partial oxidation of biomass feedstocks towards the production of liquid fuels is investigated. Gasification of woody biomass and corncob biomass is studied at the sub-pilot scale where 89% carbon conversion and H2/CO ratio between 0.87 to 1.88 is demonstrated. Steam is shown to assist in the conversion of char in the moving bed reducer and suggestions toward commercial design are given. Adiabatic process simulation of the integration of the biomass to syngas pr (open full item for complete abstract)

Committee: Andrew Tong (Advisor); Andre Palmer (Committee Member); Jeffrey Chalmers (Committee Member); Heather Allen (Committee Member) Subjects: Chemical Engineering; Energy; Engineering

Master of Science in Polymer Engineering, University of Akron, 2020, Polymer Engineering

In the competitive market of plastic fillers, inexpensive and reliable materials are always sought after. Using a method of thermal conversion, called pyrolysis, a potential contender was created from a plant biomass known as soybean hulls (SBH). The SBH are a byproduct of the soybean farming industry and represent an abundant and inexpensive feedstock. Thermal conversion of the SBH material gives rise to a lightweight carbon-rich filler called pyrolyzed soybean hulls (PSBH). Two separate lots, lot A and lot B, were created with lot A corresponding to SBH pyrolyzed at 450°C (PSBH-A) and lot B corresponding to SBH pyrolyzed at 500°C (PSBH-B). Both lots of PSBH were also milled to reduce their particle size and tested against the as-received PSBH fillers. These milled materials were designated as ground soybean hulls (GSBH). Two different polyolefins, linear low-density polyethylene (LLDPE) and polypropylene (PP), were used for this study. The PSBH fillers were added to the polyolefins in weight percentages of 10, 20, 30, 40, and 50 percent with the resulting plastic/PSBH composites being tested for their mechanical, thermal, and water absorption properties. In general, the addition of filler increased the maximum stress of LLDPE/PSBH composites while reducing maximum stress of PP/PSBH composites. The strain at maximum stress was reduced with increasing amounts of PSBH filler for all composites. Modulus of elasticity generally increased with increasing filler amount. For thermal properties, the addition of PSBH filler increases the heat distortion temperature, increases the thermal decomposition temperature, and reduces the heat of fusion of the composites compared to the neat polyolefins. The liquid absorption and thickness swelling in the materials were small overall but did increase with increasing amounts of PSBH filler and with the time spent submerged in liquid. Milling the PSBH material into GSBH generally had small effects on the various material properties (open full item for complete abstract)

Committee: Erol Sancaktar (Advisor); Kevin Cavicchi (Committee Member); James Eagan (Committee Member) Subjects: Plastics; Polymer Chemistry; Polymers

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, The Ohio State University, 2019, Chemical Engineering

The importance of increasing the sustainability of chemical production processes has become a top priority for chemical manufacturing companies. Some of the target areas that are key to achieving more sustainable processes are the following: utilizing renewable carbon feedstocks, decreasing energy costs, decreasing waste via selective catalysis, and utilizing environmentally benign solvents. Heterogeneous catalyst design has the potential to address several of these target areas. The main focus of this work involves conducting rational design of heterogeneous catalysts that incorporate solvent-like molecules to perform selective biomass conversion and C-C bond reactions in more sustainable solvents. Sustainable conversion of biomass remains a challenge, including fructose dehydration to 5-hydroxymethylfurfural (HMF). Fructose can be selectively dehydrated to HMF in dimethyl sulfoxide (DMSO) without addition of an acid catalyst. The role of DMSO is examined starting with either fructose or HMF in DMSO/water. With increasing DMSO content, it is observed that fructose conversion, HMF selectivity, and post-reaction solution acidity increase. While DMSO degradation to sulfuric acid is a potential source of acidity and reactivity, a barium chloride precipitation test demonstrates that sulfate ions are not detectable after reaction. Additionally, an adsorption test in presence of a basic polymer determined that methane sulfonic acid, another DMSO degradation product, is also not detectable post reaction suggesting that DMSO is stable during reaction at 120°C and 150°C with oxygen present. Instead, the majority of the acidic species produced are formic acid, levulinic acid, and humins. These acids have a minimal effect on fructose conversion in DMSO. These results suggest that DMSO promotes fructose conversion mainly through solvation effects and not as an origin of acid catalysis. For HMF stabilization, the optimal molar fraction of DMSO in water is 0.20 to 0.43. Overall (open full item for complete abstract)

Committee: Nicholas Brunelli (Advisor); Umit Ozkan (Committee Member); Li-Chiang Lin (Committee Member); Andrew Michel (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

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

Inorganic content in coal is high and co-firing coal with biomass at power plants to mitigate hazardous pollutants has been implemented at the expense of energy content and density partitioning. Co-Hydrothermal Carbonization (Co-HTC) is a thermochemical process, where coal and biomass were treated simultaneously in subcritical water, resulting in bulk-homogenous hydrochar that is carbon-rich and a hydrophobic solid fuel with combustion characteristics like coal and can serve as a viable upgrade to standard co-firing fuel. The main goal of this work was to evaluate the synergistic effects of miscanthus on coal during Co-HTC through two objectives: (1) Evaluate the solid biofuel properties of the Co-HTC hydrochar and characterize the inorganic content of the process liquid (2) Examine the process economics of scaled-up Co-HTC hydrochar production. Fuel quality was assessed for all hydrochars by evaluating mass yields, energy content, ultimate analysis, and proximate analysis. Calculation of combustion parameters showed experimental ignition and burnout indices of Co-HTC 260 °C hydrochar were 29.0% and 26.5 % lower than theoretical, non-interacting indices, respectively. Hydrochars shared the benefits of low sulfur and low ash content of miscanthus but maintaining higher energy content of coal. Hydrochars produced at 260 °C had energy contents as high as coal (27.3 ± 0.6 MJ kg-1) and 73% less ash content and 74% less sulfur than raw coal as a result of the more acidic environment produced by miscanthus decomposition. Furthermore, hydrochars were homogeneous as miscanthus-derived hydrochar was formed on coal surface according to SEM imaging and verified by the reduced pore width from nitrogen adsorption. A technoeconomic analysis of Co-HTC was performed for a scaled-up Co-HTC plant that produces fuel for 110 MWe coal-fired power plant using Clarion coal #4a and miscanthus as starting feedstocks. With precise mass and energy balance of the Co-HTC process, sizing (open full item for complete abstract)

Committee: Toufiq Reza (Advisor) Subjects: Chemical Engineering; Energy; Mechanical Engineering