Browsing by Subject "Polycyclic aromatic hydrocarbons"

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    Expanded Aromatic Monomers for Functional Porous Polymers
    (2017-05) Karunathilake, Arosha Aruni Kumari
    Porous materials have attracted immense attention in the scientific community due to their excellent performance in a variety of applications such as gas adsorption, separation and catalysis. In the last few years utilizing expanded aromatic monomers for porous polymers has emerged as a method of designing and synthesizing functional porous polymers. As described in Chapter 1, expanded aromatic scaffolds such as hexaphenylbenzene (HEX), hexabenzocoronene (HBC) and corannulene have unique chemical structures and electronic properties that could be used to improve the performance of porous materials for applications in energy storage. Their unique symmetry and shape can be used to introduce novel topologies and conjugated π systems to porous polymers which provides improved gas binding ability. Chapter 2 describes a series of novel corannulene based porous organic polymers (BB-POPs) that retain the inherit redox activity of corannulene when incorporated into the porous system. These materials are the first reported POPs based on corannulene. Chapter 3 describes the synthesis and characterization of novel HEX and HBC based POPs (HEX-POP-93 and HBC-POP-98) for volatile organic compounds (VOCs) adsorption. Interestingly, while both POPs have moderate BET surface areas (687 and 548 m2 g-1 respectively), they both show an excellent selectivity for organic vapors over water, with a high benzene adsorption capacity of 99.9 wt.% for HEX-POP-93. Presented in Chapter 4 is the bottom-up synthesis of nanographene based porous organic polymers. Nanographenes (NGs) such as HBC are observed to readily adopt π-stacked arrangements. As such, stable π-stacked conformations between the HBC units are likely a major directing force for the POP structure. Since these interactions cause the π-surfaces within the polymer to be blocked, they limit the gas and VOCs adsorption capability. Thus, pre-synthesized HEX based POPs were post-synthetically cyclodehydrogenated to obtained NG based POPs with good surface areas and high CO2 binding ability (22 wt. %). The overall findings presented in this dissertation suggest that the expanded aromatic structures introduce novel properties to porous materials while the careful design will enhance the ultimate properties.
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    LES/PDF approach for turbulent reacting flows
    (2012-12) Donde, Pratik Prakash; Raman, Venkat; Clemens, Noel; Ezekoye, Ofodike; Goldstein, David; Moser, Robert
    The probability density function (PDF) approach is a powerful technique for large eddy simulation (LES) based modeling of turbulent reacting flows. In this approach, the joint-PDF of all reacting scalars is estimated by solving a PDF transport equation, thus providing detailed information about small-scale correlations between these quantities. The objective of this work is to further develop the LES/PDF approach for studying flame stabilization in supersonic combustors, and for soot modeling in turbulent flames. Supersonic combustors are characterized by strong shock-turbulence interactions which preclude the application of conventional Lagrangian stochastic methods for solving the PDF transport equation. A viable alternative is provided by quadrature based methods which are deterministic and Eulerian. In this work, it is first demonstrated that the numerical errors associated with LES require special care in the development of PDF solution algorithms. The direct quadrature method of moments (DQMOM) is one quadrature-based approach developed for supersonic combustion modeling. This approach is shown to generate inconsistent evolution of the scalar moments. Further, gradient-based source terms that appear in the DQMOM transport equations are severely underpredicted in LES leading to artificial mixing of fuel and oxidizer. To overcome these numerical issues, a new approach called semi-discrete quadrature method of moments (SeQMOM) is formulated. The performance of the new technique is compared with the DQMOM approach in canonical flow configurations as well as a three-dimensional supersonic cavity stabilized flame configuration. The SeQMOM approach is shown to predict subfilter statistics accurately compared to the DQMOM approach. For soot modeling in turbulent flows, an LES/PDF approach is integrated with detailed models for soot formation and growth. The PDF approach directly evolves the joint statistics of the gas-phase scalars and a set of moments of the soot number density function. This LES/PDF approach is then used to simulate a turbulent natural gas flame. A Lagrangian method formulated in cylindrical coordinates solves the high dimensional PDF transport equation and is coupled to an Eulerian LES solver. The LES/PDF simulations show that soot formation is highly intermittent and is always restricted to the fuel-rich region of the flow. The PDF of soot moments has a wide spread leading to a large subfilter variance. Further, the conditional statistics of soot moments conditioned on mixture fraction and reaction progress variable show strong correlation between the gas phase composition and soot moments.
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    On the use of hydrophobic biopolymers and hydrophobic biopolymer-coated sands for the removal of naphthalene, phenanthrene, and pyrene from contaminated sediments
    (2010-12) Sitzes, Ryan Ziegler; Reible, Danny D.; Lawler, Desmond F.
    The overall objective of the present study was to evaluate the effectiveness of using a variety of hydrophobic biopolymers and hydrophobic biopolymer-coated sands as technically and economically feasible in-situ sediment amendments or alternative capping materials on a laboratory scale. Cutin from tomato peels, cellulolytic enzyme lignin from sitka spruce chips, and keratin azure from commercially dyed sheeps wool were isolated, prepared, tested, and evaluated as feasible hydrophobic biopolymers for the removal of selected Polycyclic Aromatic Hydrocarbons (PAHs). Testing included chemical and physical characterization, as well as the measurement of kinetics and equilibrium sorption parameters for the sorbates naphthalene, phenanthrene, and pyrene as model hydrophobic organic contaminants. Tomato peel cutin exhibited the largest overall affinity for PAHs, however, keratin azure was selected for further evaluation as the most feasible material due to its low preparation cost. Amendment of industrial sand with a stable, uniform, cross-linked keratin azure derivative was achieved to produce hydrophobic biopolymer-coated sand products containing zero, moderate, and high mass fractions of sand. Chemical and physical material parameters, as well as kinetics and equilibrium sorption parameters for the sorbates naphthalene, phenanthrene, and pyrene, were then obtained for the coated sand products. This allowed simple finite difference modeling of PAH fate and transport through a thin cap comprised of the same, insight into the specific sorption mechanisms involved, and information which could prove useful in predicting potential of keratin products to provide a suitable capping material. Conclusions and recommendations for future research focus on the technical and economical feasibility of the prepared hydrophobic biopolymers and hydrophobic biopolymer-coated sand products as capping or in-situ sediment amendments.