Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Chemical Engineering, 2008. / This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections. / Includes bibliographical references (p. 195-202). / Over the past decade the synthesis of colloidal semiconductor nanocrystals of diverse shapes and sizes has sparked tremendous interest in both the industrial and scientific communities. Much of the work thus far has been done by extensive trial-and-error optimization of the chemistry to produce the desired nanocrystalline product. However, despite a tremendous effort in developing adaptable chemistries, the underlying mechanisms leading to nucleation and crystal growth in these systems are still not well understood. This thesis aims to address this challenge by utilizing first principles calculations and mathematical modeling to study the formation of cadmium selenide nanocrystals, the most frequently studied and best characterized nanocrystal system. In the first part of this thesis we investigate the elementary reaction steps that occur in the organic medium during early stages of particle nucleation. In particular, using density functional theory calculations, we probe the mechanism of formation of active growth species and small molecular clusters. We further explore the effect of ligand stabilization on cluster formation. In the second part, we explore reactions occurring on various surfaces of CdSe at later stages of crystal growth using periodic density functional theory calculations. Homoepitaxy and heteroepitaxy reactions on several relaxed and reconstructed wurtzite CdSe surfaces are investigated. Furthermore, the effect of ligand binding on crystal growth is examined using several model ligands. We show that ligands exhibit a range of affinities and selectivities for different facets of CdSe. We relate our findings to experimental observations, in particular, nanocrystal morphology and shape anisotropy. Finally, utilizing experimental and computational insights, we develop a mathematical model that explains both nucleation and growth in the formation of nanocrystals. / (cont.) Cluster formation is modeled using a population balance approach combining discrete and continuous Fokker-Planck rate equations for small and large-sized clusters, respectively. The model explores the relative importance of factors such as temperature, additives, and reaction versus diffusion control on the formation of nanocrystals. / by Jane Yevgeniya Rempel. / Ph.D.

Thesis (B.S.)--Massachusetts Institute of Technology, Dept. of Chemical Engineering, 1958. / MIT copy bound with: Distribution of residence times in packed beds / Kenneth A. Smith. 1958. / Includes bibliographical references (leaf 27). / by Walter Wiechmann. / B.S.

Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Chemical Engineering, 2002. / Includes bibliographical references. / Linear-dendritic diblock copolymers combine the properties of dendritic macromolecules with the morphology of block copolymers, making it possible to create nanostructured materials which self assemble in the bulk state to form ordered thin films, and in solution to form highly functional micellar systems. The linear-dendritic system described here consists of 2000 molecular weight linear polyethylene oxide (PEO) with a polyamidoamine (PAMAM) dendron covalently bonded to one chain end. Specular neutron reflectivity has been used to investigate the structure of monolayers formed at an air-water interface. The dendritic end groups were functionalized with deuterated stearic acid to make the dendritic block hydrophobic, resulting in a macroamphiphile. Results indicate that stable monolayers are formed with PEO resting on the subphase and stearate groups extending into the air. Surface concentration and dendrimer generation were both found to impact monolayer formation. / (cont.) EM, SAXS and DSC have been used to characterize bulk morphology in PEO-PAMAM. A segregated melt state with elongated globular PAMAM domains is observed for generations 2.0 through 4.0 at temperatures above the PEO melting point. Below the PEO melting point the morphology is disrupted by PEO crystallinity with the extent of disruption depending on generation. Stearate functionalized PEO-PAMAM diblocks also exhibit a segregated melt state at elevated temperatures. Crystallization of the stearate groups creates hard confinement with PEO crystallization inside lamellar domains observed for all generations at room temperature. A free energy model is presented for microphase segregation of linear-dendritic diblock copolymers with an amorphous linear block. This model combines expressions for the stretching free energy of linear chains and interfacial energy with a static model for dendritic branching in order to predict a phase diagram for microphase segregation. Results indicate that surface tension and repulsion in the dendrimer block each have strong impact on phase boundaries. Finally, metallic gold nanoclusters were formed in aqueous solution in conjunction with PEO-PAMAM. Particle formation involved the reduction of HAuC14 with excess NaBH4. Particles were formed both above and below the critical micelle concentration (CMC) for PEO-PAMAM. TEM images indicate that particle sizes ranged from 50 to 100 A with smaller, more uniform particles formed at higher PAMAM generations. / by Mark Alan Johnson. / Ph.D.

Thesis: Sc. D., Massachusetts Institute of Technology, Department of Chemical Engineering, 2014. / Cataloged from PDF version of thesis. / Includes bibliographical references. / Microreactors have been demonstrated to provide many advantages over conventional process technologies for the synthesis of chemical compounds and kinetic studies at the laboratory scale. High heat and mass transfer rates, rapid mixing, and higher selectivities and conversions can be achieved in these microdevices thanks to the small characteristic dimensions, enabling the synthesis of compounds that cannot be synthesized in conventional reactors. In the past years, efforts have been directed towards the application of microreactor technology for production purposes, especially in the pharmaceutical and fine chemicals industry. The challenge is how to get benefit of the transport rates inherent to microreactors while increasing the throughput for production applications. Two approaches to increase production rate are possible: a) scale-out by parallelization of units; b) scale-up by increase in channel size and flow rates. Scale-out would require thousands of units to achieve kg/min of production rates and development of very expensive and complex control systems to ensure identical operating conditions in each unit for a perfect and predictable overall reactor performance. On the other hand, scale-up by increase in channel size risks losing mass and heat transfer performance. The Advanced-Flow Reactor (AFR) manufactured by Corning Inc. combines both approaches being able to yield production rates of 10 - 300 g/min per module. If the AFR is demonstrated to perform efficiently and to be easily scalable, it may become an alternative for process intensification and transition from batch to continuous in the pharmaceutical and fine chemicals industry. Additional advantages include shorter process development times thanks to the scalability of the reactor modules, higher selectivities and yields, greener production processes, and possibility of introducing new chemistries. In this context, fundamental understanding of the hydrodynamics for multiphase systems is essential and critical for process development and scale-up purposes. The objective of this thesis is to study both experimentally and through computational fluid dynamic simulations the hydrodynamic characteristics of the AFR to demonstrate the capabilities of this technology using non-reactive (hexane/water) and reactive systems (carbon dioxide/water, ozone/alkene) at ambient conditions. / by María José Nieves Remacha. / Sc. D.

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Chemical Engineering, 1968. / Bibliography: leaves 83-87. / by George Berbeco. / M.S.

Massachusetts Institute of Technology. Dept. of Chemical Engineering. Thesis. 1965. Sc.D. / Sc.D.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Chemical Engineering, 2005. / Includes bibliographical references. / Polycyclic aromatic molecules, including polycyclic aromatic hydrocarbons (PAHs) have attracted considerable attention in the past few decades. They are formed during the incomplete combustion of hydrocarbon fuels and are precursors of soot. Some PAHs are known carcinogens, and control of their emissions is an important issue. These molecules are found in many materials, including coal, fuel oils, lubricants, and carbon black. They are also implicated in the formation of fullerenes, one of the most. chemically versatile class of molecules known. Clearly, models that provide predictive capability for their formation and growth are highly desirable. Thlermochemical properties of the species in the model are often the most important parameter, particularly for high temperature processes such as the formation of PAH and other aromatic molecules. Thermodynamic consistency requires that reverse rate constants be calculated from the forward rate constants and from the equilibrium constants. The later are obtained from the thermochemical properties of reactants and products. The predictive ability of current kinetic models is significantly limited by the scarcity of available thermochemical data. / (cont.) In this work we present the development of a Bond-Centered Group Additivity method for the estimation of the thermochemical properties of polycyclic aromatic molecules, including PAHs, molecules with the furan substructure, molecules with triple bonds, substituted PAHs, and radicals. This method is based on thermochemical values of about two hundred polycyclic aromatic molecules and radicals obtained from quantum chemical calculations at the B3LYP/6-31G(d) level. A consistent set of homodesmic reactions has been developed to accurately calculate the heat of formation from the absolute energy. The entropies calculated from the B3LYP/6-31G(d) vibrational frequencies are shown to be at least as reliable as the few available experimental values. This new Bond-Centered Group Additivity method predicts the thermochemistry of C₆₀ and C₇₀ fullerenes, as well as smaller aromatic molecules, with accuracy comparable to both experiments and the best quantum calculations. This Bond-Centered Group Additivity method is shown to extrapolate reasonably to infinite graphene sheets. / (cont.) The Bond-Centered Group Additivity method has been implemented into a computer code within the automatic Reaction Mechanism Generation software (RMG) developed in our group. The database has been organized as a tree structure, making its maintenance and possible extension very straightforward. This computer code allows the fast and easy use of this estimation method by non-expert users. Moreover, since it is incorporated into RMG, it will allow users to generate reaction mechanisms that include aromatic molecules whose thermochemical properties are calculated using the Bond-Centered Group Additivity method. Exploratory equilibrium studies were performed (l. Equilibrium concentrations of individual species depend strongly on the thermochemistry of the individual species, emphasizing the importance of consistent thermochemistry for all the species involved in the calculations. Equilibrium calculations can provide many interesting insights into the relationship between PAH and fullerenes in combustion. / by Joanna Yu. / Ph.D.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Chemical Engineering, 2009. / This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections. / Includes bibliographical references. / The purpose of this research was to study the various factors affecting the economic and technical feasibility of Engineered Geothermal Systems, with a special emphasis on advanced drilling technologies. The first part of the thesis was devoted to modeling and analysis of the technologies used to develop EGS projects. Since the cost of completing wells is a major factor in determining the economic feasibility of EGS projects, it is vital to be able to accurately predict in determining the economic feasibility of EGS projects, it is vital to be able to accurately predict their costs. Historic well cost data was analyzed to identify trends, and a drilling cost index for updating historic geothermal well costs to present day costs was developed. The effects of different advanced drilling technologies on drilling costs were estimated and incorporated into a techno-economic model to estimate their impact, as well as the impact of advanced reservoir stimulation technologies, on EGS levelized electricity costs. A technical analysis of geothermal binary Rankine cycle surface power plants was also performed to determine the effect of novel working fluids on plant efficiency for both sub- and supercritical binary cycles. The objective of the second part of the thesis was the application of thermal spallation drilling to deep boreholes. Thermal spallation is the fragmentation of a brittle solid into small, disc-like flakes by rapidly heating a confined fraction of the rock. It was proposed that the necessary temperatures and heat fluxes needed to induce thermal spallation in the high pressure, high density deep borehole environment could be achieved using hydrothermal flame technologies. An autoclave reaction system was designed and constructed to create flame jets in water at a pressure of 250 bar. The temperatures of these flames were measured, and attempts were made to use the flames to spall small rock samples. The experimental system was modified to study the centerline temperature decay of supercritical water jets injected at temperatures up to 525 °C into ambient temperature water. A device for measuring the heat flux from these jets was designed, constructed, and used to determine the heat transfer coefficients of the jets impinging against a flat surface. Together, these studies indicate that the necessary temperatures and heat fluxes required to induce thermal spallation in rocks can be achieved in a deep borehole. / by Chad R. Augustine. / Ph.D.

Thesis (Sc. D.)--Massachusetts Institute of Technology, Dept. of Chemical Engineering, 1936. / Vita. / Includes bibliographical references (leaf 76). / by Charles Norton Henshaw. / Sc.D.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Chemical Engineering, 1991. / Includes bibliographical references (leaves 134-139). / by Simone Marco Paolo Arizzi. / Ph.D.