Thesis (Sc.D.) Massachusetts Institute of Technology. Dept. of Chemical Engineering, 1948. / Vita. Appendix contains numerous pamphlets. / Bibliography: leaves 548-551. / by Arch Chilton Scurlock. / Sc.D.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Chemical Engineering, 2010. / Cataloged from PDF version of thesis. / Includes bibliographical references. / The focus of this work was on developing a novel scalable size based separation technology for nonmagnetic particles in the submicron size range utilizing magnetophoretic forces. When a nonmagnetic particle is immersed in a magnetic fluid and subjected to magnetic field gradients, it behaves like a magnetic hole and experiences magnetic buoyancy forces proportional to its volume. This size dependence of magnetic buoyancy forces can be exploited to selectively focus larger nonmagnetic particles from a mixture and thus we can fractionate nonmagnetic particles on the basis of size. We designed a separation system composed of a regular array of iron obstacle posts which utilized magnetic buoyancy forces to perform size based separations. A Lagrangian particle tracking model was developed which could describe the behavior of a nonmagnetic particle in regions of inhomogeneous magnetic field gradients. Particle trajectories were simulated for a number of obstacle array geometries and over a range of operating conditions in order to understand the nature of the magnetic buoyancy force and aid in separation system design. Based on the results of the trajectory simulations, an experimental set up was conceptualized and built to demonstrate capture and separation of nonmagnetic particles using magnetic buoyancy forces. Capture visualization experiments were performed utilizing fluorescence microscopy which showed visual evidence of focusing and preferential capture of larger nonmagnetic particles. Experiments also yielded results qualitatively consistent with the Lagrangian trajectory model. Pulse chromatography experiments were also performed in order to quantitatively understand the capture and separation behavior. The results obtained showed quantitative evidence of preferential capture of larger particles. Particle capture efficiencies were compared with predictions from simulations and were found to be qualitatively consistent. Finally, the potential of this separation technology was demonstrated by performing proof-of-concept separation experiments with a mixture of 840 nm and 240 nm particles. / by V. N. Ravikanth Annavarapu. / Ph.D.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Chemical Engineering, 2003. / Includes bibliographical references. / The feasibility of using high gradient magnetic separation (HGMS) to separate the Fe₃0₄ nanoparticles was studied in this work. We present a general model for nanoparticle capture based on calculating the limit of static nanoparticle buildup around the collection wires in an HGMS column. Model predictions were compared successfully with experimental results from a bench-scale HGMS column. Permanent capture of individual nanoparticles is limited by diffusion away from the wires; however, 60-125 nm aggregates of particles can be captured permanently in the bench-scale column. The model provided estimates of the minimum particle size for permanent capture of individual nanoparticles and nanoparticle aggregates. / This focus of this thesis is a novel class of water-based magnetic fluids that are specifically tailored to extract soluble organic compounds from water. Magnetic fluids are colloidal dispersions of magnetic nanoparticles that do not settle in gravitational or moderate magnetic fields due to their small size and do not aggregate because of their surface coatings. These materials offer several potential advantages over traditional methods of organic separation, such as activated carbon adsorption. For example, magnetic fluids possess a large surface area for separation while avoiding porous structures that introduce a high mass transfer resistance. The magnetic fluids were prepared by precipitation and consist of a suspension of [approximately]7.5 nm diameter magnetite (Fe₃0₄) nanoparticles coated with a [approsimately]9 nm thick bifunctional polymer layer comprised of an outer hydrophilic polyethylene oxide (PEO) region for colloidal stability, and an inner hydrophobic polypropylene oxide (PPO) region for solubilization of organic compounds. Characterization of these materials revealed the particle dimensions and magnetic properties. In addition, we examined the colloidal stability of the magnetic fluids over a broad range of conditions. The structure of the polymer shell, which was examined with neutron scattering and lattice calculations, shows some evidence of segregation of the PEO and PPO chains. The magnetic fluids exhibit a high capacity for organic solutes, with partition coefficients between the polymer coating and water on the order of 10³ to 10⁵, which is consistent with values reported for solubilization of these organics in PEO-PPO-PEO block copolymer (Pluronic) micelles. / by Geoffrey D. Moeser. / Ph.D.

Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Chemical Engineering, 1999. / Includes bibliographical references (leaves 122-128). / by Timothy George Benish. / Ph.D.

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Chemical Engineering, 1951. / Includes bibliographical references (leaves 92-93). / by S.T. Demetriades. / M.S.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Chemical Engineering, February 2013. / Cataloged from PDF version of thesis. "September 2012." / Includes bibliographical references. / Monoclonal antibodies and proteins derived from them are an emerging class of anticancer therapeutics that have shown efficacy in a range of blood and solid tumors. Antibodies targeting solid tumors face considerable transport barriers in vivo, including blood clearance, extravasation, diffusion within the tumor interstitium, binding to antigen, endocytosis, and degradation. The unique pathology of the blood supply to solid tumors only serves to exacerbate these problems. A consequence of poor delivery of antibodies to solid tumors is a characteristic perivascular distribution of antibodies around tumor blood vessels. Often, antibodies bind only cells within a few cell layers of blood vessels, leaving large areas of tumor cells farther from perfused vessels completely untargeted. This phenomenon has been observed in multiple studies involving different antibodies, antigens, and tumor types, both in animal models and in clinical settings. In this thesis, the perivascular localization of antibodies is explored as a function of quantitative parameters of the antibody and associated antigen. A novel experimental system to quantitatively determine bound antibody levels, antigen levels, and blood vessel localization on a microscopic scale throughout entire tumor cross sections has been developed. This system has been used to quantitatively measure antibody and antigen distribution in tumor tissue under a variety of conditions. Effects of varying antibody dose, antibody affinity, and tumor type and site have been explored and quantitated using this model. To guide experimental design, we have developed a simplified mathematical model of the tumor vasculature. This model offers insights into the effects of antigen and antibody parameters, including dose, affinity, antigen density, and endocytosis rates, which are measurable in vivo and affect antibody penetration into tumor tissue. A simple scaling analysis further allows the quantitative determination of the minimum antibody dose required to saturate a tumor given the antigen turnover rate and density. Together, the mathematical model and quantitative experimental analysis allow conclusions to be made regarding antibody design and antigen selection for improved tumor penetration of therapeutic antibodies. / by John J. Rhoden. / Ph.D.

Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Chemical Engineering, 1999. / Includes bibliographical references. / Fullerenes are molecules comprised entirely of sp2-bonded carbon atoms arranged in pentagonal and hexagonal rings to form a hollow, closed-cage structure. Fullerenes, such as C60 and C70, are single-shell molecules, while carbon nanostructures--a larger class of structures that includes fullerenes as a subset--typically contain many shells and hundreds or thousands of carbon atoms. C60 and C70, first discovered in 1985, were isolated macroscopically in 1991 from soot produced in laminar low pressure premixed benzene/oxygen/argon flames operated at fuel-rich conditions. Studies of these flames indicated that fullerene yields depend on adjustable parameters like temperature, pressure, atomic carbon/oxygen ratio, and residence time. In addition, high resolution transmission electron microscopy (HRTEM) showed that benzene flame soot also contains carbon nanostructures, including fullerene onions and nanotubes. Although some conditions under which fullerenes form in flames have been identified, little is known about the formation mechanisms of either fullerenes or carbon nanostructures. One possible mechanism involves a molecular weight growth process analogous to soot formation including 1) the stepwise addition of acetylene to curved precursor molecules and 2) the coagulation of aromatic precursor molecules, followed by bond rearrangement to form the closed-cage structure. Polycyclic aromatic hydrocarbons (P AH), which participate in soot nucleation and growth, are potential precursors in these mechanisms. Carbon nanostructures may form by a similar molecular weight growth process or by the rearrangement of carbon material in the condensed soot. Understanding these mechanisms and modeling the formation kinetics is important if combustion is to be used as a process for the synthesis of fullerenes and carbon nanostructures. Therefore, this work focuses on 1) developing a detailed understanding of the fullerenes formation mechanisms in premixed benzene/oxygen/argon flames by measuring concentration profiles for fullerenes (C60, C70, C76, C7s, and C84)., PAH, and light gas species and using the data to evaluate kinetic models consistent with proposed mechanisms and 2) understanding how carbon nanostructures form and evolve in premixed benzene/oxygen/ argon flames by using HRTEM to observe changes in soot and nanostructures with residence time in the flame. A laminar premixed benzene/oxygen/argon flat flame was operated at the following conditions: fuel equivalence ratio, 2.4 (atomic C/0 ratio, 0.96); cold gas velocity at the burner, 25 emfs; pressure, 40 torr; and fraction of argon in fuel mixture, 10 mol%. Concentrations of C6o, C10, C16, C1s, and C84 and 14 P AH were measured at different axial distances (residence times) in the flame, and an additional 16 PAH were identified without quantitation, by sampling condensible flame material through a quartz probe and analyzing the samples by high performance liquid chromatography (HPLC) and gas chromatography/mass spectrometry (GC/MS). The fullerenes concentration profiles show two regions of fullerenes formation and conswnption. The first region, at short residence times in the flame, coincides with the onset of soot formation and immediately follows the maximwn P AH concentration in this flame. The rate of conswnption of P AH is more than sufficient to account for the rate of formation offullerenes in this region of the flame, consistent with the view that reactive coagulation of P AH could be the dominant pathway for fullerenes formation. The second region, at longer residence times, shows significantly higher fullerenes concentrations and occurs in a part of the flame where the concentration of P AH is below the detection limit but where the concentration of acetylene remains high enough for acetylene to be the main reactant in this region of fullerenes formation. The observed rate of conswnption of acetylene through this region is more than sufficient to account for the observed rate of formation of fullerenes. The decrease in fullerenes concentration in the downstream part of both regions appears to be a result of competition between formation and conswnption reactions. Calculations show that neither oxidation nor pyrolysis alone can account for the observed conswnption of fullerenes, but reactions with soot may explain the observed conswnption. The fullerenes may be incorporated into the soot as surface growth species, and conswnption dominates when the concentration of PAH o; acetylene, which are the reactants for fullerenes formation, is lowered sufficiently. A study of changes in soot and carbon nanostructures with residence time in the same premixed benzene/oxygen/argon flame was conducted. Samples were taken by three different methods: scraping solids from surfaces inside the combustion chamber, collecting material from different vertical positions in the flame through a quartz probe, and collecting condensible material on an electron microscope grid at different vertical positions in the flame with a thermophoretic sampler. HRTEM imaging of all samples showed soot particles composed to some extent of amorphous and fullerenic carbon (i.e., curved layers, spiral shells, ,and fullerene molecule-sized closed-shell structures). Qualitative and quantitative analyses ofresidence time-resolved samples showed that the carbon layers increase in length and decrease in radius with increasing residence time in the flame and that the nwnber of closed-shell structures, possibly fullerene molecules, increases with residence time in the flame. This observation is consistent with fullerenes concentration increasing with residence time and with a consumption pathway in which fullerenes react with soot. Overall, the data suggest that the formation of amorphous and fullerenic carbon occurs in milliseconds, with the fullerenic carbon becoming more curved as a soot particle traverses the length of the flame. This formation process is consistent with the heterogeneous reaction of gas phase P AH or light hydrocarbons with carbon layers in the solid phase soot. Conversely, the formation of carbon nanostructures, such as nanotubes and fullerene onions, appears to require much longer residence times, perhaps seconds or minutes. This is consistent with the internal rearrangement of carbon layers in the solid phase which appears to occur while the soot is exposed to the high temperature flame environment for extended periods of time. / by William Joseph Grieco. / Ph.D.

Thesis (B.S.)--Massachusetts Institute of Technology, Dept. of Chemical Engineering, 1928. / by Joseph A. Jamison, Benjamin F. Miller, Edmund L. Welcyng. / B.S.

Thesis: Ph. D., Massachusetts Institute of Technology, Department of Chemical Engineering, 2017. / Cataloged from PDF version of thesis. / Includes bibliographical references. / Lignocellulosic biomass is an attractive renewable source for fuels and chemicals. Of the many conversion alternatives, catalytic fast pyrolysis has emerged as an attractive technology to convert biomass into fuel additives and value-added chemicals. Current pyrolysis oils or bio-oils are incompatible with refinery streams due to their high acid, water, and water content. The key roadblock in its commercial exploitation is development of catalytic platforms for selective deoxygenation along with minimum hydrogen consumption and carbon loss. Current catalytic solutions including zeolites, and conventional hydrotreating catalysts employ high hydrogen pressures, leading to aromatic ring hydrogenation, and hydrogen consumption. This thesis focusses on developing fundamental catalytic understanding on cheaper and earth-abundant reducible transition metal oxide catalysts for selective hydrodeoxygenation (HDO) of bio-oil derived model compounds using reactivity, computation and characterization studies. The first section focuses on developing structure-reactivity relationships on bulk and supported MoO₃ catalysts for the HDO of lignin-derived model compounds. Characterization reveals that MoO₃ undergoes reduction to catalytically inactive MoO₂ at a temperature of 673 K, and stabilization of partially reduced MoO₃ surface through its partial carburization to oxycarbide phase (MoOxCyHz) at temperatures < 623 K. Thereafter, TiO₂ and ZrO₂ supports prevent the reduction of dispersed oligomeric MoOx species to catalytically inactive species, enhancing their stability. In addition, the overall catalyst reactivity inversely correlates to the maximum hydrogen consumption temperature during hydrogen temperature programmed reduction (H₂-TPR). Furthermore, a near-monolayer oligomeric MoOx dispersion on ZrO₂ support was found to be optimum for HDO reactivity. The second section focuses on developing mechanistic insights into the HDO on bulk and supported MoO₃ with the aid of density functional theory (DFT) computations and kinetic studies. DFT computations were carried out on the elementary steps for HDO of acetone-a model compound on pristine [alpha]-MoO₃ (010) surface to reveal dissociative H₂ adsorption on the (010) surface to be the rate-limiting step. Kinetic studies on MoO₃ supported on ZrO₂ reveal the differences in reaction mechanism and the nature of active sites for HDO on MoO₃/ZrO₂ as compared to bulk MoO₃. The third section focuses on generalizing the low-temperature (< 523 K) selective HDO on other reducible base metal oxides, specifically cobalt oxide and demonstrates oxides to have significantly higher reactivity than base metals for HDO. Finally, lanthanum strontium cobaltite (La₀.₈Sr₀.₂CoO₃), a perovskite oxide, was demonstrated as a novel HDO catalyst at < 523 K. Overall, this thesis provides a toolkit for developing structure-reactivity relationships on reducible metal oxides for their use as HDO catalysts. / by Manish Shetty. / Ph. D.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Chemical Engineering, 1995. / Includes bibliographical references (p. 408-415). / by Timothy J. Resch. / Ph.D.