Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Chemical Engineering, 1994. / Includes bibliographical references (p. 423-441). / by Timothy Joseph Dalton. / Ph.D.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Chemical Engineering, 1991. / Includes bibliographical references (leaves 328-338). / by Karl Allen Graham. / Ph.D.

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Chemical Engineering, 1940. / Includes bibliographical references (leaves 64-66). / by William A. Merritt. / M.S.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Chemical Engineering, 1983. / MICROFICHE COPY AVAILABLE IN ARCHIVES AND SCIENCE / Bibliography: leaves 327-337. / by Julian Obdulio Villalba. / Ph.D.

Thesis (Sc. D.)--Massachusetts Institute of Technology, Dept. of Chemical Engineering, 1991. / Includes bibliographical references. / by Christopher John Nagel. / Sc.D.

Thesis: Ph. D., Massachusetts Institute of Technology, Department of Chemical Engineering, 2018. / Cataloged from PDF version of thesis. / Includes bibliographical references (pages [383]-406). / Over the last century there have been countless experimental measurements of the overall reaction kinetics of gas-phase radicals, often with the aid of lasers. In more recent decades, ab initio predictions of product branching using quantum chemical calculations combined with modem rate theories have become common. However, there are few experimental measurements against which to validate predicted product branching, even for an important reaction system such as hydroxyl radical addition to acetylene that is critical to oxidation chemistry both in the atmosphere and in combustion. As a result, many of the kinetic parameters that appear in commonly used combustion mechanisms are based purely on predictions. The few experiments that do attempt to quantify product branching generally fall into two categories, each with unique advantages/disadvantages: crossed molecular beams (CMB) that simulate single collision conditions, or end-product analysis of a complex, thermalized process, such as pyrolysis. Laser flash photolysis (LFP) with molecular beam mass spectrometry (MBMS) offers a compromise between CMB and end-product experiments: the reaction conditions are thermalized but still simple enough that primary products can be quantified with confidence. This thesis describes a unique apparatus, and the improvements made to it, that combines LFP and MBMS for primary product branching quantification, as well as multiple-pass laser absorbance spectrometry (LAS) for accurate measurements of overall kinetics. The full capability of this LFP/MBMS/LAS apparatus is demonstrated for the chemically interesting phenyl radical + propene reaction system, which has been implicated as a potential source of second aromatic ring formation under combustion conditions. Overall kinetic measurements are also reported in this work either for systems that involve a newly discovered reactive species (various cycloaddition reactions of the simplest Criegee Intermediate formed in atmospheric ozonolysis) or that was disputed in the literature (vinyl radical + 1,3-butadiene, which has been implicated as a potential source of benzene in combustion). Finally, this thesis shows how detailed chemical insights made either experimentally or theoretically can be translated into applications via the Reaction Mechanism Generator (R4G). The application discussed is natural gas high temperature pyrolysis for the production of C2 commodity chemicals. / by Zachary J. Buras. / Ph. D.

Thesis (B.S.)--Massachusetts Institute of Technology, Dept. of Chemical Engineering, 1922. / Includes bibliographical references (leaf 24). / by Fred Chase Koch. / B.S.

Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Chemical Engineering, 2001. / "February 2001." / Includes bibliographical references. / Retrofitting is the redesign of an operating chemical plant to find new configurations and optimal operating conditions. In the chemical industry, 60% of new capital investments in plants and equipment are retrofitting projects, while only 10% goes to building new plants. Investment in retrofitting amounted to $26 billion in 2000. Despite the importance of retrofitting, there are few methodologies for finding improved economic and environmental performance for continuous processes. This work proposes a systematic framework for the understanding of retrofitting of continuous chemical processes and develops a new methodology to support decision making in solving this problem. Successful retrofitting solutions derive from a balance of operational experience in the plant and the rigor of mathematical analysis. This balance is accomplished by proposing tools and algorithms that in the problem formulation, the analysis of the flowsheet, the synthesis of retrofitting options and the final decision, allow the decision maker to handle the complexity of the problem and focus on the truly critical aspects of the flowsheet. The proposed methodology structures the problem by defining a broad range of retrofitting objectives and alternatives. The initial step is the formulation of retrofitting as an optimization problem. This includes defining retrofitting goals and translating them into objective functions. A parameter optimization of the base case design determines the incentives and constraints for retrofitting. The analysis continues through a network optimization analogy. The representation of the flowsheet as a multicommodity network allows the use of a graph based algorithm to determine the cycles in the process and apply flow decomposition by techniques developed in this study. Flow decomposition determines the path and cycles by which commodities (chemicals) flow through the network. The focus on chemicals and their paths rather than unit operations avoids the distinction of process subsystems providing an integrated view of the flowsheet. The objective function is evaluated in terms of path and cycle flows. Using graphical and mathematical programming (sensitivity analysis) approaches, the synthesis stage identifies retrofitting opportunities that increase the favorable and limit the unfavorable paths and cycles. Once a set of appropriate retrofitting alternatives is identified. the decision stage proceeds through a systematic construction of the superstructure and the corresponding MINLP model. The procedure takes into account the implicit logic of the retrofit alternatives to reduce the space of decision variables. The methodology is completed with a framework to implement the outer approximation algorithm taking into account the characteristics of the retrofitting problem. Case studies illustrate the benefits of the different stages of the proposed retrofitting methodology: efficient solution algorithms, systematic ways to analyze and generate alternative plant configurations and ease in finding optimal designs and investment decisions. The new methodology is compatible with existing flowsheet simulation tools and optimization packages and can easily be applied to a wide range of practical problems. / Ernique A. Guinand. / Ph.D.

Thesis (Sc. D.)--Massachusetts Institute of Technology, Dept. of Chemical Engineering, 1993. / Vita. / Includes bibliographical references (leaves 168-182). / Xinjin Zhao. / Sc.D.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Chemical Engineering, 2008. / Includes bibliographical references (p. 173-181). / To unravel the complexity of cellular systems, protein prefractionation tools can be used to reduce cell lysate complexity and increase assay sensitivity. Rapid free flow isoelectric focusing (FF-IEF) is achieved in a microfluidic device by isolating the electrodes from the focusing region with porous buffer regions. Moving the electrodes enables the use of large electric fields without the detrimental effects of bubble formation in the focusing region of the device. The anode and cathode porous buffer regions, which are formed by acrylamide functionalized with immobilized pH groups, allow ion transport while providing buffering capacity. Thermo-electric cooling mitigates the effects of Joule heating on sample focusing at high field strengths (-500V/cm). This localized cooling was observed to increase device performance. Rapid focusing of low molecular weight isoelectric point markers proteins and protein complexes demonstrate the versatility of the technique. Simulations provide insight into and predict device performance based on a well-defined sample composition. This thesis also presents the first implementation of cascaded stages for a microfabricated free-flow isoelectric focusing device. Both analytical and computational models for IEF suggest device performance will be improved by utilizing multiple stages to reduce device residence time. These predictions are shown to be valid by using focusing of small IEF markers as a demonstration. We also show focusing of fluorescently tagged proteins under different channel geometries, with the most efficient focusing occurring in the cascaded design, as predicted by theory. An additional aim of this work is to demonstrate the compatibility of cascaded FF-IEF with common bioanalytical tools. As an example, outlet fractions from cascaded FF-IEF were analyzed by SDS-PAGE. Processing of whole cell lysate followed by immunoblotting for cell signaling markers demonstrates the reduction of albumin from samples, as well as the enrichment of apoptotic markers. Commercial FF-IEF equipment requires multiple inlets to approximate the linear pH gradient commonly used in IEF. These inlets require many premixed pH buffers and a dedicated pumping system, increasing system cost and complexity. / (cont.) As an alternative approach, a preparative scale FF-IEF microfluidic device is also designed and tested. The advantages of the divergent IEF design versus a rectangular design are demonstrated using pH indicators to visualize the formation of pH gradients within the devices. Theoretical and experimental observations indicate that using a divergent channel circumvents many of the difficulties associated with preparative FF-IEF equipment. Protein pI markers are used to demonstrate the devices ability to fractionate samples, even in the presence of salt levels too high for conventional IEF techniques. The devices process complex biological samples, fractionating whole cell lysate at a rate of 2mL/hr. The device performance is further analyzed by 2-D gels of the fractionated outlets to show that cell lysate can be enriched based on pI. These findings underscore the promise of small, inexpensive, and disposable FF-IEF devices in proteomics and systems biology research. / by Jacob William Albrecht. / Ph.D.