Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Chemical Engineering, 2010. / Cataloged from PDF version of thesis. / Includes bibliographical references. / In the light of increasing fears about climate change, greenhouse gas mitigation technologies have assumed growing importance. In the United States, energy related CO₂ emissions accounted for 98% of the total emissions in 2007 with electricity generation accounting for 40% of the total'. Carbon capture and sequestration (CCS) is one of the options that can enable the utilization of fossil fuels with lower CO₂ emissions. Of the different technologies for CO₂ capture, capture of CO₂ by chemical absorption is the technology that is closest to commercialization. While a number of different solvents for use in chemical absorption of CO₂ have been proposed, a systematic comparison of performance of different solvents has not been performed and claims on the performance of different solvents vary widely. This thesis focuses on developing a consistent framework for an objective comparison of the performance of different solvents. This framework has been applied to evaluate the performance of three different solvents - monoethanolamine, potassium carbonate and chilled ammonia. In this thesis, comprehensive flow-sheet models have been built for each of the solvent systems, using ASPEN Plus as the modeling tool. In order to ensure an objective and consistent comparison of the performance of different solvent systems, the representation of physical properties, thermodynamics and kinetics had to be verified and corrected as required in ASPEN Plus. The ASPEN RateSep module was used to facilitate the computation of mass transfer characteristics of the system for sizing calculations. For each solvent system, many parametric simulations were performed to identify the effect on energy consumption in the system. The overall energy consumption in the CO₂ capture and compression system was calculated and an evaluation of the required equipment size for critical equipment in the system was performed. The degradation characteristics and environmental impact of the solvents were also investigated. In addition, different flow-sheet configurations were explored to optimize the energy recuperation for each system. Monoethanolamine (MEA) was evaluated as the base case system in this thesis. Simulations showed the energy penalty for CO₂ capture from flue gas from coal-fired power plants to be 0.01572 kWh/gmol CO₂ . The energy penalty from CO₂ regeneration accounted for 60% of the energy penalty while the compression work accounted for 30%. The process flexibility in the MEA system was limited by degradation reactions. It was found that different flow-sheet configurations for energy recuperation in the MEA system did not improve energy efficiency significantly. Chilled ammonia was explored as an alternative to MEA for use in new coal-fired power plants as well as for retrofitting existing power plants. The overall energy penalty for CO₂ capture in chilled ammonia was found to be higher than in the MEA system, though energy requirements for CO₂ regeneration were found to be lower. The energy penalty for 85% capture of CO₂ in the chilled ammonia system was estimated to be 0.021 kWh/gmol CO₂. As compared to the MEA system, the breakdown of the energy requirements was different with refrigeration in the absorber accounting for 44% of the energy penalty. This illustrates the need to perform a systemwide comparison of different solvents in order to evaluate the performance of various solvent systems. The use of potassium carbonate as a solvent for CO₂ capture was evaluated for use in Integrated Reforming Combined Cycle (IRCC) system. With potassium carbonate, a high partial pressure of CO₂ in the flue gas is required. Different schemes for energy recuperation in the system were investigated and the energy consumption was reduced by 22% over the base case. An optimized version of the potassium carbonate flowsheet was developed for an IRCC application with a reboiler duty of 1980 kJ/kg. In conclusion, a framework for the comparison of the performance of different solvents for CO₂ capture has been developed and the performance of monoethanolamine, chilled ammonia and potassium carbonate has been compared. From the standpoint of energy consumption, for existing power plants the use of MEA is found to be the best choice while for future design of power plants, potassium carbonate appears to be an attractive alternative. An economic analysis based on the technical findings in this thesis will help in identifying the optimal choices for various large, stationary sources of CO₂. / by Anusha Kothandaraman. / Ph.D.

Thesis (Sc.D.)--Massachusetts Institute of Technology, Dept. of Chemical Engineering, 1983. / MICROFICHE COPY AVAILABLE IN ARCHIVES AND SCIENCE / Includes bibliographical references. / by James Nathaniel Michaels. / Sc.D.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Chemical Engineering, 2007. / Includes bibliographical references. / There is large and growing interest in making a wide variety of materials and surfaces antimicrobial. Initiated chemical vapor deposition (iCVD), a solventless low-temperature process, is used to form thin films of polymers on fragile substrates. To improve research efficiency, a new combinatorial iCVD system was fabricated and used to efficiently determine the deposition kinetics for two new polymeric thin films, poly(diethylaminoethylacrylate) (PDEAEA) and poly(dimethylaminomethylstyrene) (PDMAMS), both candidates for antimicrobial coatings. Fourier transform infrared (FTIR) spectroscopy shows that functional groups are retained in iCVD of PDMAMS and PDEAEA, whereas essentially all fine chemical structure of the material is destroyed in plasma-enhanced CVD. It was found that the combinatorial system in all cases provided agreement, within experimental certainty, with results of blanket iCVD depositions, thus validating the use of the combinatorial system for future iCVD studies. Finished nylon fabric was subsequently coated with PDMAMS by iCVD with no affect on the color or feel of the fabric. Coatings PDMAMS of up to 540 gg/cm2 were deposited on fabric. / (cont.) A coating of 40 gpg/cm2 of fabric was found to be very effective against gram-negative E. coli, with over a 99.9999%, or 6 log, reduction in viable bacteria in one hour. A coating of 120 gg/cm2 was most effective against the gram-positive B. subtilis. Further tests confirmed that the iCVD polymer did not leach off the fabric. Type-II photoinitiation was utilized to perform vapor phase deposition of covalently-bound polymer coatings of the polymer PDMAMS. The durability was improved so that 80 wt% of the fabric coating was retained after extended antimicrobial testing and three rounds of ultrasonication. The coating was effective, killing 99.9% of E. coli in one hour. The gCVD process was then further explored using the less-UV-sensitive monomer DEAEA for deposition onto spun cast PMMA thin films. Durable films up to 54 nm thick retained 94% of their thickness after 10 rounds of ultrasonication. Gel Permeation Chromatography (GPC) and Variable Angle Spectroscopic Ellipsometry (VASE) swelling cell measurements gave estimated ranges of 72-156 kDa for the molecular weight and 0.1-0.24 chains/nm2 for the graft density. / by Tyler P. Martin. / Ph.D.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Chemical Engineering, 2001. / Page 313 blank. / Includes bibliographical references. / Cellular physiology is a combination of many different functions that have to be accurately probed individually and then precisely correlated to each other, in order to reveal the language used by the cell to communicate changes from the environment to gene expression and vice versa. Genes are transcribed to proteins, which catalyze metabolic pathways, whose activity may in return affect gene expression. DNA microarrays allowed the measurement of the full gene expression profile under a particular set of environmental conditions and genetic backgrounds. To understand, however, the correlation between gene expression and the actual metabolic state of the cell, the latter needs to be also determined with high accuracy. This requires that a comprehensive set of variables is defined to describe metabolic activity and reliable methodologies are developed for the accurate determination of such variables. Defining flux as the rate at which material is processed through a metabolic pathway, the fluxes of a metabolic bioreaction network can be employed to provide an overall measure of metabolic activity. A complete and accurate flux map is the phenotypic equivalent of the gene expression profile. In addition, metabolic fluxes, and especially their changes in response to genetic or environmental perturbations, provide insightful information about the distribution of kinetic and regulatory controls in metabolism. / (cont.) In this context, my Ph.D. thesis focused in the development of methods for high-resolution metabolic flux determination using stable isotopes, mass spectrometry and bioreaction network analysis. Metabolic fluxes cannot be measured directly, but they are rather estimated from measurements of extracellular metabolite consumption and production rates along with data of isotopic-tracer distribution at various network metabolites after the introduction of labeled substrates. This indirect estimation is possible because the unknown fluxes are mapped into the measurements through mass and isotopomer balances. I applied observability analysis techniques into metabolic systems to determine which is the maximum resolution of the in vivo metabolic flux network that can be obtained from potential or provided experimental data. My research focused primarily in examining whether mass spectrometric measurements can be used as sensors of the metabolic fluxes. An experimental protocol for the acquisition of mass spectrometric measuremets of biomass hydrolysates using GC-(ion-trap) MS was developed. Finally, the developed computational and experimental methodology for flux quantification was applied in the elucidation of lysine biosynthesis flux network of Corynebacterium glutamicum under glucose limitation. / by Maria Ioanni Klapa. / Ph.D.

Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Chemical Engineering, 2000. / Includes bibliographical references (leaves 275-280). / The need to predict the interactions between the microstructure of polymeric fluids and the macroscopic flow field in polymer processing operations has lead to the development of many numerical methods for the simulation of viscoelastic flows. The two main obstacles to the use of these tools in the quantitative analysis of polymer processing operations are the need for accurate constitutive equations and the computational efficiency of the numerical methods. The goal of the first part of this thesis is to develop constitutive equations appropriate for modeling nonisothermal viscoelastic flows and to examine the influence of temperature variations on the stress in the fluid. The pseudotime method developed by Crochet and Naghdi (1978) and by Sarti (1977) is used to obtain thermodynamically consistent constitutive equations for the internal energy, the stress, and the heat flux vector. Fourier"s Jaw is assumed for the thermal conductivity, and the internal energy is chosen to depend only on the temperature of the fluid. The non isothermal analog to the Giesekus constitutive equation for the polymer contribution to the stress is then de1ived with the pseudotime approach. The constitutive equations are combined with conservation equations for mass. momentum, and energy to model the nonisothermal viscoelastic extrudate swell problem. For contraction-shaped dies, the final thickness of the extrudate is shown to depend on both the thermal and the strain histories of the fluid emerging, at the die exit. In this thesis second part of this thesis, efficient time integration algorithms are developed within the framework of examining the linear stability of isothermal viscoelastic two dimensional steady flows in complex geometries to three-dimensional perturbations. In this approach, a steady base state is found by discretizing in two dimensions with the discrete elastic-viscous split stress gradient (DEVSS-G) finite element formulation of the momentum-continuity pair combined with either the streamwise upwind Petrov-Galerkin (SUPG) or discontinuous Galerkin (DG) finite element discretization of the hyperbolic constitutive equation for the polymer contribution to the stress tensor. The resulting set of nonlinear algebraic equations is solved by using the Newton-Raphson method. The stability of these states is determinined by time integration of the evolution equations for infinitessimal perturbations governed by the equations of motion and the constitutive equation for the stress linearized about the base state. Two time integration methods are investigated: the {}-method operator splitting scheme and a fourth-order Runge-Kutta method. Both schemes reduce to a solution to a modified Stokes problem and an evaluation of the time-dependent constitutive equation. The overall efficiency of both methods is extremely high, as is the potential for implementation on parallel computers. An algorithm also is presented for calculating eigenvalues with the largest real parts that combines time integration of the linearized equations with a Krylov subspace method to accelerate the calculation of the eigenvalues. Although this method does not dramatically reduce the computational cost over time integration alone. it does provide a more complete analysis of the eigenspectrum. The linear stability of the flow of an Oldroyd-B model is analyzed with both the time integration methods and the hybrid time integration/Krylov algorithm for flow through several model geometries. First, the circular Couette problem is examined to benchmark the methods, and the stability results presented here are in good agreement with those obtained by other methods of analysis. The second model geometry is flow around an isolated cylinder confined in a channel. This investigation is motivated by the observation that the flow of a Boger fluid in this geometry undergoes a transition from a two-dimensional flow to a three-dimensional flow at a critical value of the Weissenberg number (Mc Kinley, 1993 ). Contrary to experimental observations, the flow with the Oldroyd-B model is predicted to be stable for all values of the Weissenberg number investigated. We</=0. 75. The flow of the Oldroyd-B model around a closely spaced linear array of cylinders is predicted to undergo a transition from a two-dimensional steady state to a three-dimensional state at a value of the Weissenberg number that is in good agreement with the experimental observations of Liu ( 1997) for a Boger fluid. An energy analysis of the interactions between the long-time perturbations and the base state flow indicates that the mechanism for this instability is similar to the mechanism proposed by Joo and Shaqfeh ( 1994) for the non-axisymmetric transition observed in the viscoelastic circular Couette flow. / by Mark Davis Smith. / Ph.D.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Chemical Engineering, 1989. / Includes bibliographical references (leaves 152-159). / by Timothy Joseph Donnelly. / Ph.D.

Thesis (Sc. D.)--Massachusetts Institute of Technology, Dept. of Chemical Engineering, 1986. / MICROFICHE COPY AVAILABLE IN ARCHIVES AND SCIENCE / Vita. / Includes bibliographies. / by Richard K. Helling. / Sc.D.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Chemical Engineering, 1997. / Vita. / Includes bibliographical references. / by Premnath Venugopalan. / Ph.D.

Thesis: Ph. D., Massachusetts Institute of Technology, Department of Chemical Engineering, 2017. / Cataloged from PDF version of thesis. / Includes bibliographical references. / Due to the forthcoming shortage of natural resources, the demand for more efficient and ecofriendly chemical processes for the conversion of energy and matter, especially with respect to carbon management, is growing rapidly. Therefore, a search for high-performance solar energy conversion systems to end the current carbon economy era is of paramount importance in both academic and industrial sectors. In this regard, we have studied organic photovoltaics and solar water splitting by using oCVD (Oxidative Chemical Vapor Deposition) polymers and doping-treated bismuth vanadate (BiVO 4), respectively. oCVD is a solvent-free conformal vacuum-based technique to enable thin-film fabrication of insoluble polymers at moderate vacuum (~ 0.1 Torr) and low temperature (25 150 °C). Moreover, oCVD carries the well-cited processing benefits of vacuum processing, such as parallel and sequential deposition, well-defined thickness control, large-area uniformity, and inline integration with other standard vacuum processes (e.g., vacuum thermal evaporation). Based on the above-mentioned technical advantages from oCVD, polyselenophene and poly(3,4- dimethoxythiophene) have been successfully applied to organic photovoltaics. Cost-effective solar hydrogen production requires catalytic materials that have earth-abundant element composition, suitable photoelectrochemical properties, and broad technological applicability. To create this versatile catalytic material, controlling the catalyst's atomic structure is of primary importance since their functionalities (e.g., electronic band structure, catalytic activity, chemical stability, etc.) are governed by its atomic structure. According to the strategy, BiVO 4's atomic structure has been engineered via phosphorus, indium and molybdenum doping. The improved photocatalytic behavior of doping-treated BiVO4 has been studied within experimental and computational domains. / by Won Jun Jo. / Ph. D.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Chemical Engineering, 1994. / Includes bibliographical references (leaves 231-240). / by William Gabriel Worley. / Ph.D.