The majority of chemicals the world relies on today are derived from petroleum. Since fossil fuels are non-renewable resources that cannot be sustainably relied upon in the long-term, it is of interest to explore new ways to synthesize commodity chemicals using alternative starting materials. Herein, this work will describe how polymer waste and bio-based precursors can be applied to create chemicals typically derived from virgin petroleum feedstock. In the past century, the world has produced over 7.5 billion metric tonnes of plastics which weigh more than one billion elephants, but 76% of these materials have been discarded into landfills or mismanaged, causing negative externalities such as environmental damage, deleterious health effects, and global economic loss. The research presented demonstrates how multiple types of polyethylene (PE), a frequently used plastic that comprises 36% of all polymers created, can be chemically upgraded using two routes. First, tandem catalytic conversion by platinum supported on gamma-alumina under mild conditions (280 °C without solvent or additives) upcycles PE into high yields (up to 80 wt%) of lubricant grade valuable long-chain alkylaromatics and alkylnaphthenes. Second, a simple, three step sequence of bromination, dehydrobromination, and olefin metathesis reactions, each with respectable yields (86-97%), transforms PE into value-added α,ω-divinyl-functionalized oligomers with shorter, tunable chain lengths that can be used in the synthesis of lubricants and new commodity polymers, with preliminary technoeconomic analyses that demonstrate this three-step process could be economically viable on an industrial scale. Transitioning to renewable bio-based resources to generate energy can be a sustainable method to counter the negative environmental impacts of extracting non-renewable oil from the Earth. Using 1-octen-3-ol, an alcohol that can be derived from nature, high-performance C16H32 diesel was created in three steps with mostly high yields and conversions: (1) dehydration [58% yield], (2) Diels-Alder cyclodimerization [92% conversion], and (3) hydrogenation [95% yield]. With a high gravimetric net heat of combustion of 43.41 MJ/L and a cetane number of 71 which are greater than those for diesel fuel, this high-quality biofuel transcends the performance of diesels used today.

Catalytic hydrosilylation is an efficient method for making organosilicon compounds and one of the most widely used reactions in silicon chemistry. Metal-catalyzed hydrosilylation of carbonyl compounds is an atom-economical methodology to access synthetically useful silyl ethers. Considering the heightened interest in hydrosilylation catalyzed by high-valent pincer oxo-rhenium complexes and the current lack of detailed mechanistic understanding, catalytic hydrosilylation of various carbonyl compounds, including biomass-derived carbonyl molecules, using oxo rhenium(V) pincer complex [Re(O)2(PNN)][OTf] (OTf = CF3SO3⎻) with organosilanes is described in this work. Direct reductive deoxygenation can be accomplished at moderate temperature (80 ℃). Both the isolation of the potential intermediate metal hydride and stoichiometric deuterium scrambling experiment reveal that the rhenium hydride is not the active catalyst, hydride transfer results from additional silane in the system. An alternative nonhydride Lewis acid catalysis pathway is proposed with the formation of frustrated Lewis pair between metal center and silane. In-situ 1H NMR experiments were conducted to address the kinetics of benzaldehyde hydrosilylation in a rhenium pincer system. The rate of reaction is determined to be independent of substrate concentration but first-order with respect to silane and catalyst, suggesting silane activation is the rate-determining step.

Increasing greenhouse gas emissions and petroleum depletion have motivated the development of renewable energy sources. Nonfood lignocellulosic biomass is a promising renewable source for making liquid fuels, valuable chemicals, and materials due to its high energy content. However, the efficient utilization of biomass has been significantly hindered by its recalcitrant nature. Herein, we describe the use of genetically modified high-syringol (high-S) poplar lignin to produce 4-propyl-2,6-dimethoxyphenol (DMPP). Various lignin extraction methods and catalyst preparations were studied to optimize depolymerization yields. The produced monomer, DMPP, is then upgraded to the multi-functional compound propylpyrogallol (DMPPO) by a catalytic reaction using Nb2O5 in water or hydrobromic acid (HBr). Epoxies are used in various applications due to their excellent mechanical properties, chemical resistance, and thermal stability. Up to 90% of epoxy thermosets are made from petroleum-based bisphenol A (BPA), but interest in BPA alternatives is rapidly increasing due to toxicity concerns. The resulting DMPPO can be converted to a novel tri-epoxide by epichlorohydrin. Epoxy thermoset polymers using the two different epoxide preparations are synthesized, characterized, and contrasted. The performance of renewable lignin-based DMPPO epoxy thermosets, in terms of thermal and mechanical properties, opens avenues for the direct utilization of biorefinery products in the fabrication of bio-based polymers and offers a sustainable alternative to petroleum-based polymer materials.

Herein, I present two main ideas that aim to utilize two different waste feedstocks, lignocellulosic biomass and produced water. While they are fundamentally different, they both offer an opportunity to take advantage of a waste product for environmentally relevant study.Aromatic molecules are essential to many mass-produced polymers, like polystyrene, epoxy resins, and poly(ethyleneterephthalate) (PET). The monomer precursors for these polymers are largely sourced from petroleum. Chemicals like benzene, toluene, and xylene are common products of refineries and critical to polymer synthesis. Herein, I present lignin, a component of lignocellulosic biomass, and a naturally occurring aromatic macromolecule as a viable feedstock for aromatic monomers. I will introduce novel renewable polyesters and bio-derived thermosets from the lignin-derived molecule isoeugenol. Thermal properties of these renewable polyesters are tunable to those of industrially relevant polyesters like PET. Further, a bio-derived epoxide was synthesized, and the polyester active esters were utilized to create crosslinked thermoset networks that give predictable thermal and mechanical properties. I will also discuss the potential use of produced water, a waste stream from the oil and gas industry, as a lithium source. With the need for energy storage rising, lithium is a resource that will continue to be in high demand. I will introduce two different membrane systems, and the synthesis of several ion selective ligands for each system. The incorporation of 12-crown-4 ether into the membrane framework was thought to selectively bind lithium, yet we saw reverse LiCl/NaCl permeability selectivity from the expected results. This gave insights into the fundamental relationship between Li+ and 12-crown-4 ether in aqueous environments. Building on that result, more ligands were synthesized to investigate both crown ether size and linker length on the ion transport properties of the membranes.

Increasing greenhouse gas emissions as well as a series of environmental issues caused by fossil fuels combustion have motivated the development of renewable energy sources. Nonfood lignocellulosic biomass is a promising renewable source for making liquid fuels and valuable chemicals, due to its high energy content stored by the biosphere. However, the efficient utilization of biomass has been significantly hindered by its recalcitrant nature. Herein, we have investigated the use of Ni/C for the catalytic depolymerization of native lignin in Miscanthus, a grassy biomass. Under optimized conditions, over 69% yield of select aromatic products were obtained from lignin. Carbohydrates remaining after lignin removal were recovered as a solid residue, which upon treatment with iron chloride produced useful platform chemicals (furfurals and levulinic acid). Understanding bond connectivity in biomass (between lignin and carbohydrates) advances the development and commercialization of more efficient catalytic methods for biomass utilization. To achieve this goal, Dynamic Nuclear Polarization (DNP) Enhance Solid State NMR (ssNMR) was used to probe the atomic level structure of biomass pre- and post- lignin treatment. Our results revealed an increase in the relative ratio of crystalline cellulose upon the catalytic depolymerization of lignin (CDL) using Ni/C catalyst. In parallel with direct catalysis of native lignin in raw biomass, organosolv pretreatment was used to produce sulfur-free technical lignin in high purity. Our study investigated the effect of biomass substrate and organosolv pretreatment methods on the isolated lignin towards further upgrading over a Ni/C catalyst. By comparing different solvents (acetic acid/formic acid, acetone and methanol) applied for lignin extraction, methanol was revealed to minimize the undesirable re-condensation of organosolv lignin.

The global production of plant biomass waste is in the order of 140 Gt per year which offers a promising alternative to petroleum and a sustainable resource to produce fuels and chemicals. Inspired by innovative advancement in biomass valorization, two catalytic processes have been developed to produce chlorine dioxide and polar aprotic solvents from non-edible biomass residues. The application of chlorine dioxide (ClO2) in water treatment is growing because of its superior antimicrobial properties and lower tendency to generate harmful chlorinated organic by-products. Most of the previously investigated catalysts for the one electron oxidation of chlorite to ClO2 are based on manganese or iron porphyrin complexes which suffer from expensive ligand and catalyst syntheses as well as the catalyst instability in oxidative environment. Chlorine dioxide chemistry and its catalytic production are explained in depth in chapter 1. Second chapter describes a novel catalyst design based on molecules that can be derived from lignin for catalytic production of ClO2 in water. A lignin-derived ligand bis(2-hydroxy-3-methoxy-5-propylbenzyl) glycine, (DHEG) was synthesized from 2-methoxy-4-propylphenol (dihydroeugenol (DHE)) and the amino acid glycine. Two mononuclear iron and manganese complexes of DHEG were prepared, characterized, and employed for the oxidation of chlorite to chlorine dioxide in aqueous solution. Peroxyacetic acid (PAA) was used as a ‘green’ oxidant in the redox reactions for the catalyst activation generating high valent Fe and Mn(IV)-OH intermediates. EPR studies verified the formation of a high valent MnIV species. Both Fe and Mn activated complexes catalyzed chlorite oxidation with bimolecular rate constants of 32 and 144 M-1 s-1, respectively, at pH 4.0 and 25 °C. The Mn complex was found to be more efficient for chlorite oxidation with a turnover frequency of 17 h-1 and remained active during subsequent additions of PAA. The rate of ClO2 formation with PAA/Mn-DHEG was first-order in PAA and showed acidic pH dependence. A mechanism that accounts for all observations is presented. Chapter 3 highlights the need of more environmentally benign polar aprotic solvents (PAS) from sustainable resources. Of particular interest for this work is the catalytic conversion of cellulose to short chain polyols and the coupling of these polyols with N,N-dimethylurea (DMU) to produce cyclic PAS. Detailed chemistry background for this transformation are presented within this chapter. In the final chapter, a green and catalytic process is described for the synthesis of N,N'-dimethylimidazolidinone (DMI) and 1,3,4-trimethylimidazolidin-2-one (TMI) from cellulose, the most abundant and non-edible component of biomass. The physical and chemical properties of DMI and TMI including high boiling point, remarkable chemical stability, and being more eco-friendly than DMF make them appealing for use in the pharmaceutical industry. Cellulose depolymerization and reaction of intermediate products with N,N-dimethylurea (DMU) to produce PAS have been investigated in a one-pot, two-step process at elevated temperature. Ru/C is an effective multifunctional catalyst for both C-C bond cleavage of cellulose and subsequent hydrogenation of the unsaturated products in the second step; the catalyst also promotes the condensation hydroxy ketone intermediates with DMU to create cyclic PAS concurrently. Such tandem reactions are challenging to achieve particularly when incompatible conditions are required for each step. Solvent selection is also challenging with the low solubility of cellulose in most common organic solvents. Herein, the overall 85% selectivity for PAS was achieved from the reactions of cellulose or sugar with DMU over Ru/C in DMI (the product) as a solvent. The optimized conditions for coupling of 1,2-propylene glycol with DMU was used in a mechanistic study for the production of PAS with both homogeneous and heterogenous Ru catalysts. Catalytic oxidation of 1,2-PG to hydroxy acetone is the key step to produce TMI with a higher yield obtained using electron-donating phosphine ligands on Ru.

Lignocellulosic biomass is composed of lignin, cellulose, and hemicellulose. Lignin is naturally formed renewable aromatic biopolymer; the cellulose and hemicellulose are polysaccharides. By far, the “second generation” biorefineries mainly use the value of cellulose pulp in paper industries or in making low-value chemicals such as ethanol while more than 98% of lignin is discarded into direct combustion. The valorizations of lignin and polysaccharides are still under development. Herein, we have studied the heterogeneous catalytic conversion of lignin monomers and polysaccharides with Ru/C catalyst with different metal oxides for making a variety of value-added chemicals. For instance, we developed a Ru/C and Nb2O5 co-catalyst system to funnel different lignin monomers into C9 hydrocarbons which could potentially be used as drop-in fuels. We also investigated the Ru/C and WOx co-catalysts to convert the polysaccharides into diols and polyols. By performing the isotopic reactions and time programmed sampling, our study disclosed the mechanisms and kinetics of the catalytic reactions. To achieve the goal of biomass valorization, we also developed a purification method to avoid catalyst poisoning by the contaminations from raw biomass and thus facilitated the sustainable utilization of native lignin into valuable chemicals.

In attempts to develop tandem catalysis of alkane dehydrogenation and polyol deoxydehydration, the reactivity of a (tBuPCP)IrH2/H4 (PCP=[κ3-2,6-C6H3(CH2PtBu2)2]) and methyltrioxorhenium was explored. The resulting bimetallic complex, [(tBuPCP)Ir(ReO3)(H)], which was stable at low-temperature, quickly turned into [(tBuPCP)Ir(ReO4)(H)] at room temperature. The reactivity of these highly oxophillic bimetallic complexes was studied. With NMR and DFT studies, the pathway of bimetallic formation was elucidated.

Ethylene/1-hexene copolymerization by a single-site hafnium salan-type catalyst activated by B(C6F5)3 produced high 1-hexene-incorporated copolymers. The composition dependence on monomer concentrations and reaction time was explored. Deuterium labeling experiments revealed that primary sites decreased as secondary sites increased over the course of the reaction. The secondary sites showed no reactivity towards the polymerization of ethylene and 1-hexene. High 1-hexene concentration suppressed catalyst deactivation. In-situ NMR demonstrated a positive comonomer effect, where higher kobs of ethylene and 1-hexene were achieved with increased [1-hexene]0.

New methods (in-situ NMR with high-pressure NMR cell and batch reactor with Auto-Sampler) for quantitative kinetic study of selective ethylene tri/tetra-merization by chromium N-phosphinoamidine were developed. The monomer consumption and 1-hexene versus 1-octene product formation in real-time was reported for various catalysts.

Biorenewable material has gained a greater focus in research to produce chemicals, fuels, plastics, and energy because of their abundance, diversity, and unique properties. Biorenewable materials include mainly terrestrial based plants that grow throughout the world. From the plant, there are constructed of three biopolymers, and in this study the biopolymer of interest is called lignin. Lignin is the second most abundant biopolymer and is known as the most abundant source of phenolic structures known to mankind. Current research focuses on utilizing lignin’s aromatic monomers as replacements for phenolic monomers derived from nonrenewable resources. The key problem in accomplishing this idea is the recalcitrant structure of lignin. The functional properties of technical lignin must be characterized in more detail in order for it to become a renewable raw material for the chemical industries. Herein, we have investigated the structure dependent properties of lignin from samples of fountain grass, walnut shell, and poplar. These samples were analyzed before and after successive organic solvent extractions. The lignin samples were fractionated according to their molar mass by these optimized organosolv extractions. Utilizing Ni/C for catalytic depolymerization achieved 50% aromatic products from fountain grass and walnut shell, respectively. Previously in our laboratory, we utilized Ni/C for catalytic depolymerization of Poplar lignin and achieved reported yields of 69%. Stemming from this idea, we wanted to approach the depolymerization of lignin with the removal of metal catalysts. Herein, we describe lignin hydrogenolysis/depolymerization of organosolv poplar lignin in ethanol/isopropanol solvent in the absence of added catalysts. Heating Organosolv Poplar Lignin (OPL) at 270 °C for 4 h in 50:50 (v:v) EtOH/i-PrOH in a closed pressure vessel gave an overall oil yield of 70 wt%, of which about 48% consisted of the monomers (E)-4-propenyl syringol and isoeugenol. Notably, these catalyst-free reactions in ethanol/ isopropanol media show monomer yields comparable to those reported for lignin depolymerization using precious metal catalysts and dihydrogen, which suggests unexpectedly favorable H-donor ability of this mixed alcohol medium. With the advancements in discovering a mixture to utilize an alcohol mixture to depolymerize lignin, we wanted to finish by connecting the bridge gap between utilizing lignin aromatic monomers straight to materials such as thermosets and thermoplastics. We report novel methodology on the extraction, isolation, and depolymerization of different biomass towards monomeric compounds of interest in the goal of further utilizing them into material networks.

The escalating accumulation of plastic waste in landfills as well as the environment has raised many concerns regarding pollution, toxicity and resource depletion. Polyolefins, comprising of polyethylene (PE) and polypropylene (PP), contribute to about half of plastic waste production. Despite their inherent chemical inertness that makes recycling especially challenging, waste polyolefins are also a potential resource for the production of chemicals and new materials. The work presented demonstrates the transformation of polyethylene into value-added alkylaromatics via tandem hydrocracking/aromatization using bifunctional catalysts. By replacing a more acidic Pt/F-Al2O3 over a previously reported Pt/Al2O3 catalyst, 70 wt% PE was converted to liquid products containing surfactant-range alkylaromatics at 280 °C in 8 h. Moreover, a 5-fold enhancement in the carbon-carbon bond scission rate and doubling in the molar yields of alkylaromatics were achieved. Mechanistic studies revealed that the Pt site(s), responsible for hydrogenation/dehydrogenation, work synergistically with Brønsted acid sites, which facilitate C-C bond scission, isomerization, and aromatization.While alkylbenzenes are used for manufacturing anionic surfactants, they are present in a complex mixture of liquid hydrocarbons in the described reactions. A two-step/one-pot reactive separation process was envisaged and demonstrated using silica sulfuric acid to sulfonate long-chain alkylaromatics, followed by neutralization with sodium hydroxide. This simple process effectively turns the complex liquid hydrocarbons mixture into two valuable and easily separable products, sodium alkylbenzene sulfonates and lubricant-range saturated hydrocarbons. Overall, a PE-derived surfactant was synthesized using polymer waste as a feedstock, providing a potential route to displacing alkylbenzene production from petroleum resources.