Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Chemical Engineering, 2001. / Includes bibliographical references (p. 323-339). / In many commercial applications involving surfactants, the desired properties are controlled by both the equilibrium and the dynamic interfacial behavior. In particular, surfactant adsorption at air-water interfaces causes the surface tension to decrease, which, for example, can control the spreading properties of a liquid, and hence, is important in practical applications involving the use of paints and pesticides, as well as in the manufacturing of photographic films. Similarly, surfactant adsorption at oil-water interfaces causes the interfacial tension to decrease, which, for example, can enhance the ability of surfactant solutions to remove oily soil from dirty surfaces (fabric, hair, skin, etc.) during cleaning applications. A predictive, molecular-thermodynamic theory capable of modeling the behavior of surfactants at solution interfaces would help minimize the need for costly and time-consuming experimentation associated with the development of surfactant products based on a trial-and-error approach. Furthermore, this theory should encompass mixtures of surfactants, since their use in industrial applications is widespread, whether intentionally, to take advantage of synergism between the surfactant components in a mixture, or simply because it is too costly to mass produce a single, pure surfactant. With this as motivation, a molecularly-based theoretical framework to model both the equilibrium and the dynamic adsorption of surfactant mixtures at both the air-water interface and the oil-water interface has been developed. The equilibrium air-water surface equation of state is based on a two-dimensional, nonideal gas-like monolayer model of the adsorbed surfactant molecules. For non-ionic surfactants, two types of interactions were accounted for: / (cont.) (i) repulsive, steric interactions, which were modeled using a hard-disk treatment, and (ii) attractive, van der Waals interactions, which were modeled using a virial expansion, truncated to second order in surfactant surface concentration. Since both the hard-disk size and the second-order virial coefficients characterizing these interactions can be deduced from the known molecular structures of the surfactants, this surface equation of state contains no experimentally determined parameters. This nonionic surface equation of state was subsequently modified to incorporate electrostatic effects associated with charged surfactants. For mixtures that contain only a single ionic surfactant species, the electrostatic contribution to the surface equation of state was computed using a Gouy-Chapman based approach, which also included a Stern layer of counterion exclusion. This electrostatic description assumes that all of the electrostatic charge on the adsorbed surfactant molecules is located on a single two-dimensional charge layer. The Gouy-Chapman model was then extended to mixtures that contain multiple ionic surfactants, or surfactants that contain multiple charged groups (such as zwitterionic surfactants) by treating the case of multiple, two-dimensional charge layers at the interface. This extended theoretical framework is capable of treating any number of surfactant components containing any number of charged groups ... / by Michael Mulqueen. / Ph.D.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Chemical Engineering, 1991. / Includes bibliographical references (leaves 278-282). / by Shin-Gyoo Kang. / Ph.D.

Thesis (B.S.)--Massachusetts Institute of Technology, Dept. of Chemical Engineering, 1980. / MIT copy bound with: Surgical Appliance Industries, Inc. / Charles Francis Albright, Jr. [1980] jlh / Includes bibliographical references (leaves [56]-[57]). / by John Peter Banevicius. / B.S.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Chemical Engineering, 2011. / Cataloged from PDF version of thesis. / Includes bibliographical references (p. 273-287). / Integrated gasification combined cycle (IGCC) technology has attracted interest as a cleaner alternative to conventional coal-fired power generation processes. While a number of pilot projects have been launched to experimentally test IGCC technologies, mathematical simulation remains a central part of the ongoing research efforts. A major challenge in modeling an IGCC power plant is the lack of real experience and reliable data. It is critical to properly understand the state of knowledge and evaluate the impact of uncertainty in every phase of the R&D process. A rigorous investigation of the effect of uncertainty on IGCC system requires accurate quantification of input uncertainty and efficient propagation of uncertainty through system models. This thesis proposes several uncertainty quantification methods which expand the sources of information that can be used for parameter estimation. Key features of these methods include the use of entropy maximization to translate subjective opinions to probability distribution functions, and a more flexible probability model that easily captures anomaly associated with small sample data. In addition, Bayesian estimation is extended to dynamic models. Aided by a computationally efficient algorithm, termed sequential Monte Carlo method, the Bayesian approach is shown to be an effective way to estimate time-variant parameters. Uncertainty propagation is performed using the deterministic equivalent modeling method (DEMM) which is based on polynomial chaos representation of random variables and probabilistic collocation algorithm. One major issue often overlooked in the analysis of IGCC models is to represent correlation in the input parameters. This thesis proposes the use of principal component analysis (PCA) to represent correlated random variables. The resulting formulation is the same as the truncated Karhunen-Lodve expansions. Explicit incorporation of correlation not only improves accuracy of the approximation but also reduces the overall computational time. A comprehensive study of the MIT-BP IGCC model is carried out to determine uncertainties of the key measures of performance and cost, including energy output, thermal efficiency, CO 2 emission, plant capital cost, and cost of electricity. Whenever possible, the probability distributions of input parameters are estimated based on realistic data. Experts' judgments are solicited if data acquisition is infeasible. Uncertainty analysis is conducted in a three-step approach. First, technology-related input parameters are taken into account to determine uncertainties of plant performance. Second, cost uncertainties are determined with only economic inputs in order to identify important economic parameters. Finally, the plant model is integrated with cost model and they are evaluated with the key technical and economic inputs identified in the previous steps. Our study indicates the property of coal feed has a substantial impact on the energy production of the IGCC plant, and subsequently on the cost of electricity. Immature technologies such as gasification and gas turbine have important bearing on model performance hence need to be addressed in future research. / by Bo Gong. / Ph.D.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Chemical Engineering, 1988. / Includes bibliographical references (p. 240-244). / by David Shu Chung Lee. / Ph.D.

Thesis (B.S.)--Massachusetts Institute of Technology, Dept. of Chemical Engineering, 1980. / Includes bibliographical references (leaf 35). / by John Francis Dolan / B.S.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Chemical Engineering, 1993. / Includes bibliographical references (leaves 232-240). / by Dawn Reneé Orton. / Ph.D.

Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Chemical Engineering, 1999. / Includes bibliographical references (leaves 141-144). / by Scott Travis Johnston. / Ph.D.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Chemical Engineering, 2004. / Includes bibliographical references (leaves 160-166). / The thesis that follows consists of a collection of work supporting and extending a novel reformulation of fluid mechanics, wherein the linear momentum per unit mass in a fluid continuum, m, is supposed equal to the volume velocity v[sub]v. The latter differs from the barycentric velocity V[sub]m by the vector field j[sub]v, where j[sub]v = v[sub]v - v[sub]m represents the heretofore largely ignored diffusive transport of volume. We will begin by giving a motivating discussion containing example problems which point to the possible need for a change in the constitutive choice for in. This will be followed by a brief outline of the kinematic concepts necessary to understand and utilize volume transport, including a general expression for j[sub]v. We will conclude by presenting the modified governing equations that result from the constitutive choice m = v[sub]v. Upon completing the required overview of existing ideas, a detailed linear irreversible thermodynamic study of the modified governing equations which result from the choice m = v[sub]v is presented. This analysis yields, inter alia, an expression for the entropy production per unit volume in the fluid which requires that the deviatoric stress tensor be expressed in terms of the volume velocity. Furthermore, an expression for the diffusive flux of internal energy is derived that differs from classical results by a term proportional to the diffusive flux of volume. This change in the internal energy flux stems from the explicit recognition of a diffusive volume flux, and precedes any specific choice of constitutive expression for the molecular flux of heat or species. / (cont.) The remainder of the thesis, which constitutes the bulk of the work performed, focuses on testing the proposed equation set against known experimental data. Each of the physically measurable phenomena treated herein was previously believed outside the realm of classical continuum fluid dynamics. We begin by considering the thermophoretic and diffusiophoretic motion of particles suspended in gases or liquids. We continue by studying the thermo-molecular pressure drop which results from applying a temperature gradient across the ends of a closed capillary. We conclude by presenting a hydrodynamic/Brownian motion model of thermal diffusion in liquids, wherein theoretical predictions for the Soret coefficient in a binary liquid system are presented that may be evaluated from readily available physicochemical data. It is shown, in each case, that the predictions of our modified theory are in agreement with experimental data. The final chapter of this dissertation is dedicated to utilizing the results derived in the previous chapters to comment on the veracity of the claim that the specific linear momentum in a fluid is given by the volume, rather than the barycentric, velocity. General arguments supporting this claim are presented and then followed by a list of questions which remain to be answered. Finally, a list of proposed experiments are detailed which could further test the predictions made herein. / by James R. Bielenberg. / Ph.D.

Thesis: Ph. D., Massachusetts Institute of Technology, Department of Chemical Engineering, 2014. / Cataloged from PDF version of thesis. / Includes bibliographical references. / There is an ever increasing need for clean, portable energy devices, such as fuel cells and high energy batteries to replace or reduce the world's dependence on fossil fuels. The continued development of thin-film solid polymer electrolytes with improved mechanical and ion transport properties is critical for the further advancement of such electrochemical energy devices. For hydrogen and methanol fuel cells, the proton exchange membrane (PEM) has to have high protonic conductivity, low fuel crossover, and be mechanically and chemically stable. In particular, for direct methanol fuel cells and for high temperature (>100 °C), low relative humidity (< 60% RH) hydrogen fuel cells, the current industrial standard PEM, Nafion®, does not have all the required attributes. Layer-by-Layer (LbL) assembly allows for the controlled deposition of alternating polyelectrolytes at the nanometer scale. This technique can be used with highly proton conductive water soluble polymers as well as doped polymers. In addition, LbL assembly can be used to coat a variety of substrates of various shapes and sizes. An LbL system composed of poly(diallyl dimethyl ammonium chloride) (PDAC) and sulfonated poly(2,6-dimethyl 1,4- phenylene oxide) (sPPO) has shown to have relatively high proton conductivity and very low methanol permeability compared to that of Nafion@, but lacking in mechanical strength when hydrated and losing significant proton conductivity at lower RH conditions. Herein this thesis work describes the selection, optimization, and utilization of multilayer systems and system composites as the PEM in hydrogen and methanol fuel cells, focusing on improving and understanding the improvements to the properties of layer-by-layer films and composite membranes for fuel cell applications by targeting two main areas: the mechanical properties and the conductive properties. In addition, characterization and film analysis work was done to correlate and explain how the changing of the LbL system and fabrication techniques impacted the membrane's mechanical and conductive properties. First, the mechanical strength and stability were greatly improved by spray-assembling the films on an electrospun fiber mat to form a composite membrane. Spray-LbL assembly was performed both with and without vacuum assistance, which had complementary effects on the film properties. By combining these techniques, composite membranes with methanol permeability twenty times lower than Nafion® and through-plane proton selectivity five times greater than Nafion@ were fabricated. In addition, the planar swelling of the composite membranes in water was significantly reduced. This large reduction in swelling is hypothesized to be due to the electrostatic interaction of the LbL system with the underlying electrospun fibers and would not occur in a typical polymer blend. Second, to improve the conductivity of the LbL films overall and specifically at lower RH conditions, two approaches were used. In the first approach, divalent salts were added to the polyanion solution to provide a stronger shielding effect than monovalent salts. The divalent salts allowed for ion bridging and increased both the number and the mobility of protons associated with sulfonic acid groups in the LbL film; thus increasing the film's conductivity. Through optimization of salt type and concentration, the protonic conductivity of PDAC/sPPO films was increased fourfold, and the humidity dependence of the conductivity was decreased. In the second approach, PDAC was replaced with a phosphoric-acid-doped polymer, poly(2- vinyl pyridine) (P2VP). The phosphoric acid concentration in the LbL film and the number of free sulfonic acid groups could be controlled post film fabrication by changing the concentration of the phosphoric acid dopant. The resulting P2VP/sPPO films exhibited greater conductivity than similarly doped P2VP films and under stronger doping conditions (0.4 M - 1.0 M phosphoric acid), the film's conductivity increases seventy-fivefold (110 mS/cm at 50% RH at room temperature), resulting in a conductivity an order of magnitude greater than Nafion®. The large increases in conductivity, particularly at low RH conditions further support a recently reported and very promising proton transport mechanism that utilizes both phosphoric and sulfonic acid groups. / by David ShinRen Liu. / Ph. D.