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 (p. 253-267). / Natural gas supply chain planning and optimization is important to ensure security and reliability of natural gas supply. However, it is challenging due to the distinctive features of natural gas supply chains. These features arise from the low volumetric energy density of natural gas and the significance of gas quality and pressure in supply chain operations. Contracts play a central role in the entire supply chain due to high capital cost, specificity and investment risks associated with gas infrastructure. An upstream production planning framework is crucial for supply-side optimization and scenario evaluation in the natural gas supply chain. The technical features of upstream systems imply that the most efficient mode of operation is by single entity central control of the system, while their economics favor involvement of multiple parties in ownership. To resolve this conflict, upstream systems are generally operated by a single operator on the basis of governing rules that stem from agreements between the upstream operator, multiple stakeholders and consumer facilities. These agreements govern production sharing, operational strategy and gas sales in the upstream system. A short-term operational planning framework (with a 2-12 weeks planning horizon) for upstream natural gas systems is presented that can help to maximize production infrastructure utilization and aid in its management, minimize costs and meet production targets while simultaneously satisfying governing rules. Its requirements are inspired by the Sarawak Gas Production System (SGPS), an offshore gas production system in the South China Sea, which supplies the liquefied natural gas (LNG) plant complex at Bintulu in East Malaysia. This is the first attempt to formulate a comprehensive modeling framework for an upstream gas production system that includes a production infrastructure model and a methodology to incorporate governing rules. / (cont.) The model has two components: the infrastructure model is a model of the physical system, i.e., of wells, trunkline network and facilities while the contractual model is a mathematical representation of the governing rules, e.g., production-sharing contracts (PSC), customer specifications and operational rules. The model formulation and objectives are from the perspective of the upstream operator. The infrastructure model incorporates the capability to track multiple qualities of gas throughout the network and determine the optimal routing and blending of gas such that the quality specifications are satisfied at the demand nodes. Nonlinear pressure-flowrate relationships in wells and the network are included for predicting a sufficiently accurate pressure-flowrate profile thereby facilitating implementation of the production strategy on the network. Modeling of complex platform configurations with reversible lines, lines that can be shut-off in normal operation and compression facilities, further improve the realistic representation of the network. A simplified prediction of natural gas liquids (NGL) production is included to maximize NGL revenue. The contractual model represents the framework for modeling the governing rules that are central to the operation of upstream systems. Modeling of productionsharing contracts is a two-fold challenge: accounting for gas volumes and converting the logical rules as stated in the system operations manual to binary constraints. A PSC network representation is proposed to account for gas volumes as well as interactions between different PSC. PSC rules are expressed as logical expressions in terms of availability, priority and transfer Boolean-states, and converted to binary constraints. Additional logical constraints are required to model the inference and intent of the rules. Operational rules can be modeled within the same framework. / (cont.) The resulting mathematical program is a mixed-integer nonlinear program (MINLP) with nonconvex functions and can be solved with the current state-of-the-art global optimization approaches, provided careful attention is paid to the model formulation.A hierarchical multi-objective approach is proposed to address multiple objectives when operating upstream systems, by optimizing a lower priority objective over the multiple optimal solutions of a program with a higher priority objective to obtain a win-win scenario. A reproducible case study that captures all the features of natural gas upstream systems is constructed to facilitate future work in algorithm development for such problems. A preliminary comparison with the existing approach indicates that substantial benefits may be possible by using the proposed approach for short-term planning. The application of a reduced-space global optimization approach to planning in upstream gas networks has also been demonstrated, which can significantly lower the number of variables in the branch-and-bound algorithm. The lower bounding problem is implemented using McCormick (convex) relaxations of computer evaluated functions and solved by implementing a nonsmooth bundle solver as a linearization tool to obtain a linear programming relaxation. The upper bounding problem is implemented using automatic differentiation and a local NLP solver. Branch-and-bound with reduction heuristics and linearization propagation is used for global optimization.This approach has been found to be competitive with current state-of-the-art global optimization algorithms for upstream planning problems. / by Ajay Selot. / Ph.D.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Chemical Engineering, 2001. / Includes bibliographical references (p. 193-207). / A successful mammalian cell culture process depends on sufficient expression and correct glycosylation of the recombinant product. Low product titer and inconsistent protein glycosylation constitute two major problems frequently encountered in biopharmaceutical production. Using Chinese Hamster Ovary (CHO) cells expressing recombinant human interferon-gamma (IFN-y) as the model system, this thesis investigated strategies that can potentially enhance heterologous protein expression or control the extent of protein glycosylation. There has been considerable interest in developing culture strategies to improve productivity in mammalian cell lines by limiting the cellular growth rate. An initial investigation demonstrated the difficulty in obtaining growth-arrested cells that are robust and productive. In the following study, a method to rapidly generate and isolate CHO cells that exhibit enhanced potential for use in proliferation-controlled bioprocesses was developed. By combining bicistronic retroviral technology with an appropriate selection strategy, a subpopulation was isolated from a heterogeneous cell population. To evaluate the effectiveness of this screening process, the performance of this selected subpopulation was compared with that of the original population under identical growth-arresting conditions. Important differences were observed: by contrast to the original population, the selected cells maintained consistently high viabilities and continued to stably express recombinant proteins after being growth-arrested for two weeks. Asparagine-linked (N-linked) glycosylation can significantly impact critical properties of human therapeutic proteins. / (cont.) An essential step in N-linked glycosylation is the transfer of an oligosaccharide from dolichol phosphate (Dol-P) to a potential glycosylation site on a polypeptide. Variability in the success of this reaction affects the extent of glycosylation on proteins. Radiolabeling studies showed that over the course of CHO batch culture, glycosylation precursor concentrations remained within a two-fold range, and overall protein glycosylation increased by 15-25%. Given the key role of Dol-P in glycosylation, its availability was postulated to limit glycosylation by controlling the abundance of glycosylation precursors. To test this hypothesis, the impact of Dol-P feeding on CHO cells was investigated. Although exogenous Dol-P was incorporated by CHO cells and processed into glycosylation precursors in a dose-dependent manner, Dol-P supplementation had no marked effects on the level of glycosylation precursors or on the extent of glycosylation. / by Inn Huam Yvonne Yuk. / Ph.D.

Thesis: Ph. D., Massachusetts Institute of Technology, Department of Chemical Engineering, 2017. / Cataloged from PDF version of thesis. / Includes bibliographical references (pages 147-155). / Phosphoric acid is the primary ingredient for almost all the phosphorous based fertilizer used in agriculture around the world. During the production of phosphoric acid, phosphate rock is reacted with sulfuric acid producing gypsum as the byproduct that is separated from the phosphoric acid by filtration. The efficiency of filtration depends strongly on the crystal size distribution (CSD) and shape. Undesired gypsum CSD and shape not only prolong the filtration and bottleneck the plant's overall production, but also decrease the phosphate recovery from the wet cake. To optimize the process, a first-principle process model is developed for the reactor-crystallizer to predict CSD and shape, and subsequently the filtration rate. This thesis presents a multidimensional population balance model (PBM) framework that models CSD with two independent characteristic lengths or 2D PBM. Compare with the 1D PBM, the extra characteristic length in the 2D PBM provides enough degrees of freedom to model needle-, plate-, and rod-like crystals that exhibits varying aspect ratio. The applicability of the 2D PBM for continuous crystallization is made possible by introducing growth rate dispersion mechanism that accounts for the broadening of the size distribution from the measured 2D CSD. Computationally efficient and highly resolved numerical methods are developed for solving both dynamic and steady-state 2D PBM that consists of integro-partial differential equation. Maximum likelihood estimation method is used for the first time to estimate crystal kinetics from the measured 2D CSD and shows much more accurate estimation than the established moment approach. The supersaturation in the multicomponents aqueous solution is defined based on chemical potential and is modeled by a speciation based mixed-solvent-electrolyte thermodynamic model. The effect of metal ion impurity on crystal growth rate and nucleation rate is modeled based on the crystal kinetics determined for the crystallizing system without impurity. All individual model components developed are validated and integrated to predict the effect of temperature, residence time, acid composition, and metal ion impurity concentration on the CSD and shape. The predicted CSD and shape are used as input for the filtration model that quantifies cake filterability. Finally, steady-state process optimization is formulated for maximum phosphoric acid production rate. / by Zhilong Zhu. / Ph. D.

Thesis (M.S.)--Massachusetts Institute of Technology. Dept. of Chemical Engineering, 1947. / Includes bibliographical references (leaves 118-119). / by Samuel Gusman. / M.S.

Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Chemical Engineering, 2000. / Includes bibliographical references (p. 273-277). / This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections. / Chemical process engineering activities such as design, optimization, analysis, control, scheduling, diagnosis, and training all rely on mathematical models for solution of some engineering problem. Likewise, most of the undergraduate chemical engineering curricula are model-based. However, the lack of formalization and systematization associated with model development leads most students and engineers to view modeling as an art, not as a science. Consequently, model development in practice is usually left to specialized modeling experts. This work seeks to address this issue through development of a framework that raises the level of model development from procedural computations and mathematical equations to the fundamental concepts of chemical engineering science. This framework, suitable for implementation in a computer-aided environment, encompasses a phenomena-based modeling language and logical operators. The modeling language, which represents chemical processes interms of interacting physicochemical phenomena, provides a high-level vocabulary for describing the topological and hierarchical structure of lumped or spatially distributed systems, mechanistic characterization of relevant phenomena (e.g., reactions, equilibria, heat and mass transport), and thermodynamic and physical characterization of process materials. Thelogical operators systematize the modeling process by explicitly capturing procedural and declarative aspects of the model ingactivity. / (cont.) This enables a computer to provide assistance for analyzing and constructing phenomena-based models, detect model inconsistencies and incompleteness, and automatically derive and explain the resulting model equations from chemical engineering first principles. In order to provide an experimental apparatus suitable for evaluating this framework, the phenomena-based language and logical operators have been implemented in a computer-aided modeling environment, named MODEL.LA. MODEL.LA enables phenomena-based modeling of dynamic systems of arbitrary structure and spatial distribution, hierarchical levels of detail, and multicontext depictions. Additional components allow incorporation of thermodynamic and physical property data, integration of control structures, operational task scheduling, and external models,and assistance for specification and solution of the resulting mathematical model. Application of this environment to several modeling examples, as well as its classroom and industrial deployment, demonstrate the potential benefits of rapid, reliable, and documented chemical process modeling that may be realized from this high-level phenomena-based approach. / by Jerry Bieszczad. / Ph.D.

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Chemical Engineering, 2004. / Includes bibliographical references (leaves 39-41). / (cont.) to determine the CO₂ uptake rates and PHB production rates of strains engineered for enhanced CO₂ fixation and PHB production respectively. / The metabolism of Synechocystis PCC6803 cells has been investigated using full-genome DNA micro-arrays and C14 tracer techniques. Full-genome (3169 genes) DNA micro-arrays were used to probe transcript levels of Synechocystis cells grown under a variety of medium conditions. Canonical discriminant analysis was used to identify transcript levels that allowed discrimination between growth media conditions, and allowed predictions of polyhydroxybutyrate (PHB) levels. Phosphate-related genes were found to alter in response to phosphate limitation and were found to include differentially regulated multi-gene families. Nitrogen-related genes were not found to be substantially reflective of nitrogen limitation under the conditions studied. Finally, transcription of PHA biosynthetic pathway genes were found to reflect the media conditions of greatest PHB accumulation, suggesting that constitutive over-expression of the PHA biosynthetic genes may lead to greater PHB accumulation levels. A methodology using C14 tracers was developed for the accurate measurement of CO₂ uptake rates and the partitioning of the fixed carbon into different biosynthetic fractions. These techniques were applied to the characterization of WT Synechocystis cells in late exponential phase. A stoichiometric model of Synechocystis metabolism was used to determine constraints between the measurements. A balance on C14 counts was obtained and significant levels of secreted compounds were not detected. The measured carbon fixation rates were found to be consistent with the observed growth rates, but inconsistent with measurements of oxygen evolution in the light and uptake in the dark made using a Clarke Electrode apparatus. These techniques may be used in future studies / by Saliya Sudharshana Silva. / S.M.

Thesis: Ph. D., Massachusetts Institute of Technology, Department of Chemical Engineering, February 2014. / Cataloged from PDF version of thesis. / Includes bibliographical references. / Carbon materials are important in electrochemistry. The often cited advantages of carbonaceous materials for electrochemical applications include wide potential working windows, tunable electrocatalytic activity for a variety of redox species, and ease of modifications either by covalent or by noncovalent functionalization. My thesis aims at elucidating the structure-property relationships of carbon-based electrochemical systems, to realize several important applications including electrochemical sensing, catalysis, and energy storage. Specifically, I have examined two classes of carbon-based electrochemical systems: electrospun carbon nanofibers (ECNFs) and redox polymer/carbon hybrid systems. For the first type of material system, I have studied the effects of synthesis condition, architecture design, and post-treatment of ECNFs on their electrochemical properties, and explored the applications of ECNFs in electrochemical sensing and energy storage. I have studied the effects of the carbonization condition of ECNFs on their densities of electronic states (DOS) and electrochemical activities for a wide range of redox-active molecules. Additionally, I have demonstrated ultrawide-range electrochemical sensing using substratesupported continuous high-DOS ECNFs. Furthermore, I have examined microwave-assisted controlled oxidation of high-DOS ECNFs for tailoring their electrocapacitive performance. For the second type of material system, I have investigated the assembly methods and structural manipulation of redox polymer/carbon hybrid systems, and explored their applications in energy storage and catalysis. I have demonstrated that a redox-responsive polymer, polyvinylferrocene (PVF), is useful for noncovalent dispersion and redox-controlled precipitation of pristine carbon nanotubes (CNTs) in nonaqueous media. Moreover, using the stable PVF/CNT dispersion, I have demonstrated solution-based fabrication of PVF/CNT hybrids with controlled nanostructures for supercapacitor applications. Furthermore, I have 'demonstrated local oxidation-induced deposition of PVF onto a carbon fiber matrix for electrochemical control over heterogeneous catalysis. / by Xianwen Mao. / Ph. D.

Thesis (Sc. D.)--Massachusetts Institute of Technology, Dept. of Chemical Engineering, 1941. / Vita. / Includes bibliographical references (leaves 142-147). / by Morgan Chuan-yuan Sze. / Sc.D.

Thesis: Ph. D., Massachusetts Institute of Technology, Department of Chemical Engineering, 2016. / This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections. / Cataloged from PDF version of thesis. / Includes bibliographical references. / Biomass can serve as a renewable alternative to the inevitably depleting fossil fuel resources and provide feedstocks for the production of fuels and chemicals. Mono- and dicarboxylic acids and esters are key intermediates to chemical products, especially for biodegradable polymers. This thesis has addressed the challenges in chemocatalytic synthesis of mono- and dicarboxylic acids and esters, including gluconic acid, succinic acid, itaconic acid and their esters, from biomass-derived molecules. Gold (Au) catalysts have been rarely investigated for the oxidation of glucose in the absence of a base. These conditions are critical, however, to enable the sequential one-pot combination of cellulose hydrolysis and glucose oxidation. The study provides insights into the deactivation of the catalysts caused by leaching and hydrothermal sintering of Au nanoparticles, as well as by adsorption of reaction species. We found that lowering the surface density of Au on metal oxides decreases the sintering rate of the Au nanoparticles and hence enhances the stability and activity of the catalyst. Levulinate derivatives are an attractive platform for the production of renewable chemicals. We report on the oxidation of methyl levulinate into dimethyl succinate with peroxides under mild conditions using Bronsted and Lewis acid catalysts and focuses on the reaction selectivity control. While the molecular structure (i.e., carbon chain length and branching around the C=O group) and the oxidant type affect the product distribution, solvent choice has the strongest impact on changing the location of oxygen insertion into the carbon backbone. In contrast to Brønsted acids, for water-tolerant Lewis acidic triflate salts, the reaction selectivity is affected by the size of the metal cation. We have developed a novel approach to synthesize unsaturated dicarboxylic acid esters via aldol condensation of keto esters catalyzed by Lewis acidic zeolites. Hafnium-containing BEA (Hf- BEA) zeolites are highly active, selective and stable for the condensation of ethyl pyruvate into itaconic acid ester analogues. Analysis of the dynamic behavior of Hf-BEA under flow conditions and studies with Na-exchanged zeolites suggest that Hf(IV) open sites possess dual functionality for Lewis and Bronsted acid catalysis. / by Yuran Wang. / Ph. D.

Thesis (Sc.D.)--Massachusetts Institute of Technology, Dept. of Chemical Engineering, 1984. / MICROFICHE COPY AVAILABLE IN ARCHIVES AND SCIENCE. / Bibliography: leaves 284-287. / by Majed A. Toqan. / Sc.D.