Lignin is the second most abundant biopolymer on Earth, right after cellulose, with a highly complex chemical structure that hinders its possible utilizations. Applications that utilize lignin in different manners are of great interest, due to its inexpensive nature. Present work is based on the notion of converting lignin into different biofuels that have only a few, however important, advantages over lignin as a direct energy source. The first part of current work (pyrolysis) details the analysis of lignin from a relatively new lignin isolation process called LignoBoost. It is obtained from the pulp and paper industry via CO₂ precipitation of lignin from black liquor (BL). This method is environment friendly, results lignin with minimal oxidation, eliminates the main bottleneck of the Kraft cycle (recovery boiler capacity), and yet leaves enough lignin in the process stream to recover pulping chemicals and generate energy for the pulp mill. Pyrolysis had converted this lignin into bio-oil with high aliphatic content and low oxidation level, all advantageous for application as liquid fuel. The second part of this dissertation proved the theory that lignin degradation and lipid accumulation metabolic pathways can be interconnected. Gram-positive Rhodococcus opacus species, DSM 1069 and PD630 were used to evaluate lignin to lipid bioconversion, starting with ethanol organosolv and Kraft lignin. This conversion is a first step in a multistep process towards biodiesel production, which includes transesterification, after lipids are extracted from the cells. Results clearly indicated that the lignin to lipid bioconversion pathway is viable, by cells gaining up to 4 % of their weight in lipids, while growing solely on lignin as a carbon and energy source.

Soil organic N (SON) comprises 90% of all N in surface soils, yet as much as half remains in forms which are chemically unknown or, at best, poorly understood. Analytical methods such has pyrolysis field-ionization mass spectrometry (Py-FIMS) and 15N cross polarization magic-angle spinning nuclear magnetic resonance (CPMAS-NMR) spectroscopy are widely used for the characterization of SON; however, these methods have limitations which contribute to the gaps in our understanding of SON chemistry. For example, Py-FIMS may produce heat-induced secondary compounds, and 15N-NMR may lack sensitivity and resolution for experiments at natural 15N abundance. X-ray absorption near edge structure (XANES) spectroscopy probes the bonding environment of individual elements. The application of this technique to complex environmental samples such as soil is still in its infancy, but early studies suggest that this technique may help resolve SON molecular structure. This dissertation sought to develop and apply synchrotron-based N and C K-edge XANES spectroscopy to the study of soil and soil extracts to determine the structures in which SON is bound. In these studies, Py-FIMS was coupled with XANES as a corroboratory technique.<p> Initial methodological development resulted in a calibration method whereby N2 gas generated in ammonium-containing salts was used to calibrate a soft X-ray beamline at the N K-edge. Although XANES can produce secondary compound artifacts, contrary to early assertions that it is a non-destructive technique, it was shown in a second study that beam-induced decomposition can be minimized by moving the beam to a fresh spot between scans.<p> Three applied studies exploring SON composition were conducted. These studies followed a spatial gradient ranging from the landscape scale, through a rhizosphere study, and ended with a study of glomalin-related soil protein (GRSP). Glomalin-related soil protein is a persistent soil glycoprotein of arbuscular mycorrhizal origin (AMF) implicated in aggregation and long-term C and N storage. Nitrogen and C K-edge XANES and Py-FIMS were used in all studies, and GRSP was further characterized using proteomics techniques.<p> Soil organic N composition was largely controlled by topographic position, and to a lesser degree, by cultivation. Divergent (i.e., water shedding) positions were enriched in carbohydrates and low molecular weight lignins, whereas convergent, depressional and level positions showed enrichment in lipid-type compounds. These differences were attributed to tillage-induced redistribution of soil, and water movement from upper to lower slope positions. Nitrogen XANES revealed a unique form of organic N, identified as N-bonded aromatics, particularly in the divergent positions.<p> Rhizosphere soil was enriched in higher molecular weight lipid-type materials and depleted in low molecular weight polar compounds. This was attributed to increased input of fresh plant material and higher microbial turnover in the rhizosphere. Nitrogen-bonded aromatics also were detected in the rhizosphere.<p> The GRSP extracts were characterized as mostly proteinaceous, but also contained many co-extracted, non-protein compounds. Despite being previously described as a glycoprotein, only weak carbohydrate signals were observed. Proteomics-based assessment of GRSP showed no homology to any proteins of AMF origin, instead showing homology with thioredoxin and with heat-stable soil proteins. This may be because protein databases do not yet contain glomalin-related sequences, or that glomalin is homologous to non-AMF soil proteins.<p> This dissertation demonstrated that N XANES is a sensitive and novel method for characterizing SON, and can be used complementarily with other analytical techniques such as Py-FIMS and proteomics. The continued development of XANES will provide a useful tool for SOM research into the future.

THE CHARACTERIZATION OF SOME METHACRYLATE AND ACRYLATE HOMOPOLYMERS, COPOLYMERS AND FIBERS VIA DIRECT PYROLYSIS MASS SPECTROSCOPY &Ouml / zlem G&uuml / ndogdu, Suriye Ph.D., Department of Polymer Science and Technology Supervisor: Prof. Dr. Jale Hacaloglu December 2012, 177 pages Poly(methyl methacrylate) possesses many desirable properties and is used in various areas. However, the relatively low glass transition temperature limits its applications in textile and optical-electronic industries. Monomers containing isobornyl, benzyl and butyl groups as the side chain are chosen to copolymerize with MMA to increase Tg and to obtain fibers with PMMA. In this work, thermal degradation characteristics, degradation products and mechanisms of methacrylate homopolymers, poly(methyl methacrylate), poly(butyl methacrylate), poly(isobornyl methacrylate) and poly(benzyl methacrylate), acrylate homopolymers, poly(n-butyl acrylate), poly(t-butyl acrylate), poly(isobornyl acrylate), two, three and four component copolymers of MMA and fibers are analyzed via direct pyrolysis mass spectrometry. The effects of substituents on the main and side chains, the components present in the copolymers and fiber formation on thermal stability, degradation characteristics and degradation mechanisms are investigated. According to the results obtained, the depolymerization mechanism yielding mainly the monomer is the main thermal decomposition route for the methacrylate polymers, acrylate polymers degradation occurs by H-transfer reactions from the main chain to the carbonyl groups. However, when the alkoxy group involves

Intentional amendment of soil with charcoal (called biochar) is a promising new approach to sequester atmospheric carbon dioxide and increase soil fertility. However, the environmental properties of biochars can vary with production conditions, making it challenging to engineer biochars that are simultaneously optimized for carbon sequestration, nutrient storage, and water-holding capacity. For this reason, I have undertaken a systematic study to (a) determine the pyrolysis conditions that lead to biochars with desired chemical and physical properties, and (b) find how these properties affect the water-holding capacity and nutrient adsorption in biochar-soil mixtures. First, a library of biochars was produced in a custom-built pyrolysis reactor under precisely controlled conditions. The chemical and physical structures of the produced biochars were characterized with various analytical techniques including 13C NMR, XPS, EA and BET pore surface analysis. My results suggest that the chemical composition and pore structure of biochars are determined not just by the maximum heat treatment temperature, but also by several other factors that include the pyrolysis heating rate, treatment time at the maximum temperature and particle size. I also tested a new approach that combines thermogravimetric reactivity measurements, diffusion-reaction theory and structural models to achieve a better characterization of the complicated multi-scale pore structure of biochars. The structural models treat biochars as porous solids having micro- and macropores of different shapes and exhibiting widely ranging pore-size distributions. Simulations results are then compared to experimental data to identify the presence of ordered or random pore networks and test their size distributions and connectivity. I then developed a multi-solid one-dimensional model that can use experimentally determined biochar properties to predict their field performance in beds packed with soil/biochar mixtures. The model used a system of coupled partial differential equations to describe the dynamic adsorption/elution of ammonium nitrate, a model fertilizer, in columns packed with biochar/soil mixtures and perfused with aqueous solutions of the fertilizer. The PDE system was solved using orthogonal collocation on finite elements. My chromatographic model accounted for all the important processes occurring in this system, including external mass transfer between the fluid phase and the solid particles, as well as intraparticle diffusion and adsorption of the solute on the pore surface area of the sorbents. To our knowledge, this is the first chromatographic model that accounted explicitly for the presence of two solid phases with widely different pore structures and adsorption capacities. A systematic parametric study was carried out to determine the importance of each system parameter. The adsorption equilibrium parameters and the intraparticle effective diffusivity of ammonium had the most significant effect on environmental performance. To complete the theoretical analysis, I also developed a model to describe the saturation and drainage of water from the packed column. The model accounted for all the important processes occurring in this system: (a) water exchange between the interstitial pore region and two different smaller pore regions and (b) water flow inside the larger pore region and the two different smaller pore regions. The transient mass balances led to a system of partial differential equations that was solved using block centered finite difference.

Soil organic N (SON) comprises 90% of all N in surface soils, yet as much as half remains in forms which are chemically unknown or, at best, poorly understood. Analytical methods such has pyrolysis field-ionization mass spectrometry (Py-FIMS) and 15N cross polarization magic-angle spinning nuclear magnetic resonance (CPMAS-NMR) spectroscopy are widely used for the characterization of SON; however, these methods have limitations which contribute to the gaps in our understanding of SON chemistry. For example, Py-FIMS may produce heat-induced secondary compounds, and 15N-NMR may lack sensitivity and resolution for experiments at natural 15N abundance. X-ray absorption near edge structure (XANES) spectroscopy probes the bonding environment of individual elements. The application of this technique to complex environmental samples such as soil is still in its infancy, but early studies suggest that this technique may help resolve SON molecular structure. This dissertation sought to develop and apply synchrotron-based N and C K-edge XANES spectroscopy to the study of soil and soil extracts to determine the structures in which SON is bound. In these studies, Py-FIMS was coupled with XANES as a corroboratory technique.<p> Initial methodological development resulted in a calibration method whereby N2 gas generated in ammonium-containing salts was used to calibrate a soft X-ray beamline at the N K-edge. Although XANES can produce secondary compound artifacts, contrary to early assertions that it is a non-destructive technique, it was shown in a second study that beam-induced decomposition can be minimized by moving the beam to a fresh spot between scans.<p> Three applied studies exploring SON composition were conducted. These studies followed a spatial gradient ranging from the landscape scale, through a rhizosphere study, and ended with a study of glomalin-related soil protein (GRSP). Glomalin-related soil protein is a persistent soil glycoprotein of arbuscular mycorrhizal origin (AMF) implicated in aggregation and long-term C and N storage. Nitrogen and C K-edge XANES and Py-FIMS were used in all studies, and GRSP was further characterized using proteomics techniques.<p> Soil organic N composition was largely controlled by topographic position, and to a lesser degree, by cultivation. Divergent (i.e., water shedding) positions were enriched in carbohydrates and low molecular weight lignins, whereas convergent, depressional and level positions showed enrichment in lipid-type compounds. These differences were attributed to tillage-induced redistribution of soil, and water movement from upper to lower slope positions. Nitrogen XANES revealed a unique form of organic N, identified as N-bonded aromatics, particularly in the divergent positions.<p> Rhizosphere soil was enriched in higher molecular weight lipid-type materials and depleted in low molecular weight polar compounds. This was attributed to increased input of fresh plant material and higher microbial turnover in the rhizosphere. Nitrogen-bonded aromatics also were detected in the rhizosphere.<p> The GRSP extracts were characterized as mostly proteinaceous, but also contained many co-extracted, non-protein compounds. Despite being previously described as a glycoprotein, only weak carbohydrate signals were observed. Proteomics-based assessment of GRSP showed no homology to any proteins of AMF origin, instead showing homology with thioredoxin and with heat-stable soil proteins. This may be because protein databases do not yet contain glomalin-related sequences, or that glomalin is homologous to non-AMF soil proteins.<p> This dissertation demonstrated that N XANES is a sensitive and novel method for characterizing SON, and can be used complementarily with other analytical techniques such as Py-FIMS and proteomics. The continued development of XANES will provide a useful tool for SOM research into the future.

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Polycyclic aromatic hydrocarbon (PAH) formation and growth from cyclopentadiene (CPD) moieties have been investigated using a laminar flow reactor and molecular modeling. The resonance-stabilized cyclopentadienyl radical is readily formed in flames and can participate in PAH growth to soot by reaction with the ??onds of aromatic species. Both CPD pyrolysis and computational results indicate that formation of indene and benzene is favored at low temperatures (below 750oC) and formation of naphthalene is favored at high temperatures. Reaction pathways from CPD have further been extended to PAH formation from the reaction of CPD and aromatic compounds with different types of ??onds. Results indicate that, while the major products from the pyrolysis of CPD, acenaphthylene, styrene and phenanthrene mixtures are from the reaction of CPD to itself rather than to these aromatic compounds with different ??onds, CPD does add to these compounds to produce larger PAH. Polychlorinated naphthalene (PCN) formation from chlorinated phenols has also been studied. In combustion exhaust gas, chlorinated phenols can produce dioxin as well as PCNs. PCN and polychlorinated dibenzofuran (PCDF) congener product distributions were consistent with proposed pathways involving phenoxy radical coupling at unchlorinated ortho-carbon sites. Tautomerization of the phenoxy radical coupling and subsequent fusion via H2O loss results in PCDF formation. Competing with this reaction pathway, CO elimination and subsequent fusion via hydrogen and/or chlorine loss was found to produce PCNs. PCDF isomer distributions were found to be weakly dependent to temperature, whereas PCN isomer distributions were found to be more temperature sensitive with selectivity to particular isomers decreasing with increasing temperature. Results of this research contribute to a better understanding of chemical mechanisms involved in the formation of toxic byproducts and soot in combustion systems.

Carbon molecular sieve (CMS) membranes represent the most attractive pure component materials to compete against polymer membranes for high performance gas separations. CMS membranes are formed from the thermal decomposition of polymer precursors and can therefore be formed into continuous defect free membranes with excellent gas separation performance. Over the last 20 years, CMS membranes have been produced in a variety of geometries and have a wide range of separation performance applicable to several important gas separations. Though research into CMS membrane formation is quite extensive, the relationship between synthesis factors and separation performance is still not well understood. The goal of this study was to elucidate the effect of two different synthesis factors on the separation performance of CMS membranes to allow more control over separation performance. The foci of this study were to clarify (1) the effect of pyrolysis atmosphere and (2) the effect of polymer precursor composition. Dense flat CMS membranes were synthesized from 6FDA:BPDA-DAM precursor at 550 oC using several pyrolysis atmospheres including vacuum pyrolysis (<0.05 torr), helium and argon flowing at atmospheric pressure, and helium and argon flowing at reduced pressures. The separation performance of CMS membranes produced under different pyrolysis atmospheres suggests that the amount of oxygen available during pyrolysis has a significant affect on the microstructure of membrane. CMS membranes were produced from 6FDA:BPDA(1:1)-DAM and 6FDA:BPDA(1:1)-DAM under identical pyrolysis conditions to determine the utility of polymer precursor composition as an engineering tool to fine-tune the performance of CMS membranes. In a second study utilizing 6FDA-6FpDA and 6FDA-6FmDA precursors, the separation performance of CMS membranes was shown to be dependent on the intrinsic precursor free volume. These studies have shown that two factors to be considered when choosing a polymer precursor are the intrinsic free volume of the polymer and the composition of the by-products evolved during pyrolysis.