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Abstract: The beneficial feature of the application of natural gas in the automotive industry is the lowest carbon content of any fossil fuel, which results in the lowest CO2 emissions. On the other hand, the concern of atmospheric pollution due to methane emissions from natural-gas vehicles (NGV) engines evokes the stringent regulations of vehicular pollution from NGVs, and specific considerations in designing the catalytic converters with expensive and scarce noble metal catalysts. Pd is conventionally used for the catalytic combustion of methane but its activity is inhibited by water, and a considerable work needs to be done to increase its stability. Adding a co-metal like Pt in order to produce a bimetallic alloy catalyst or adding a metal-oxide promoter is desirable to stabilize the catalytic conversion. However, the chemical states of Pd in bimetallic catalysts is expected to be completely different from that of the mono Pd under the reaction conditions. Therefore, an in situ X-ray absorption spectroscopy (XAS) study can also be a viable investigation to shed light on the effect of Pt on Pd/PdOx distribution in bimetallic Pd-Pt catalysts under reaction conditions at low temperatures (200-550ºC) with or without the presence of water as a catalytic poison. Furthermore, loss of activity can be avoided by choosing a SnO2 promoter as a non-noble metal oxide support material with a low metal-oxygen bond. This thesis develops an understanding of the effect of the addition of Pt in bimetallic Pd-Pt/Al2O3 catalysts and also the benefits of using SnO2 as a support for Pd-based catalysts encountering the effect of water in a low-temperature methane combustion reaction. The synthesis method of controlled-size nanoparticles via a colloidal solution technique and evaluating the effect of different synthesis parameters helps to control interactions between catalytic phases in bimetallic catalysts, and also assures the existence of intrinsic bimetallicity to get desired activity and stability in order to study the structure-property relationship and understand not only the role of Pt as a secondary catalytic phase, but also SnO2 as a metal-oxide promoter in methane combustion reactions. Besides, in situ XAS studies demonstrate the effect of Pt on the state of the active Pd surface under low-temperature, dry and wet lean methane combustion conditions. Pt addition promotes Pd reduction even in a reactive oxidizing environment with a significantly lower activity in a dry condition as compared with the oxidized Pd. However, the presence of water leads to the increased fraction of metallic Pd due to the lack of surface oxygen, resulting in Pt atoms available for methane dissociation, which does not occur in the dry methane-lean feed in which oxygen poisons Pt. Evaluation of the effect of the Pd:Pt ratio on the stability of the bimetallic Pd-Pt/Al2O3 catalysts during and after 40-hour in-situ hydrothermal ageing at 400-550ºC with 5% water in a low-temperature lean methane combustion revealed that the ratio of Pd/Pt had the governing effect, not the catalyst preparation method. The Pd:Pt 1:1 (atomic) ratio catalyst was found to provide the most optimal combination of activity and stability. Significant structural changes also occurred in-situ regardless of the preparation method. Finally, as a potential replacement of Pt in catalytic converters for NGVs, the beneficial role of SnO2 as a metal oxide support was also studied. SnO2 enhanced the activity of PdO sites by providing oxygen, and overrode the Pt-promoting role in bimetallic Pd-Pt/Al2O3 catalysts.

This research topic aims to design and simulate a reduced order model of a physics based three way catalyst (TWC) in automotive systems. A catalytic converter carries out a chemical redox reactions of pollutant gases in order to convert them to less harmful gases before emission through the vehicle exhaust. The thermal and oxygen storage dynamics of a TWC are described using a set of partial differential equations (PDE) which are coupled and non-linear in nature along the spatial axis of the catalyst. Computing the solution for a PDE based system of equations is arduous since the state of the system is distributed in an infinite domain along the spatial axis. Hence a model order reduction needs to be carried out in order to observe the behavior of PDE based systems using only a finite number of states. In order to solve for such systems, the PDEs need to be transformed into ordinary differential equations (ODE) which result in a finite, but still a large, number of states. This transformation from a set of PDEs with infinite states to an ODE system with a finite number of states is carried out using the Galerkin's projection method. Since we are dealing with a non-linear PDE, the resulting ODEs are time dependent non-linear system of equations. The model order reduction of the ODE based system is achieved using Proper Orthogonal Decomposition (POD). The POD method uses a basis representation of the system variable, and these basis functions are derived from a matrix containing the values of the variable at different instants over time and space obtained through real time measurement or simulation. The basis functions are extracted from the data matrix by performing Singular Value Decomposition (SVD). SVD computes the eigen values of the system and stores them in a matrix arranging them from the most dominant modes to the least. The number of eigen values selected represents the number of basis functions for the system. An energy estimation criterion is selected to limit the number of basis functions that will capture the entire system dynamics. Therefore we end up with a reduced number of modes that describe the order of the ODE based system. The accuracy of the reduced order model will be calculated for different number of basis functions and a selection of an optimal model order will be determined by computing the root-mean-square error (RMSE) for each of these modes. The reduced model will be developed over the Federal Test Protocol (FTP) driving cycle and the results will be validated alongside the measurement values over the US06 driving cycle.

Abstract: In this work the Computational Fluid Dynamics modeling of the Automotive Catalytic Converter is comprehensively performed, including the study of the Flow Field distribution and the Temperature distribution under cold, non-reacting flow for six different monolith properties. A sensitivity study of some key lengths values was also performed. Later, the effect of the reactions is included by using an example reaction of Ammonia oxidation, which by the use of the multi-scale lookup tables technique allows to model the sub-grid effects of diffusion into the washcoat, that otherwise would be impossible to consider properly with alternatives modeling approaches.

My dissertation addresses how engineers, scientists, and bureaucrats generated knowledge about pollution, crafted an institution for environmental protection, and constructed a collective identity for themselves. I show an important shift in regulators\' priorities, from stringent health-based standards to flexible technology-based ones through the development of end-of-pipeline pollution control devices, which contributed to the emergence of economic incentives and voluntary management programs. Drawing on findings from archival documents, published sources, and oral history interviews, I examine the first decade of the EPA amid constant organizational changes that shaped the technological and managerial character of environmental policy in the United States. Exploring the EPA\'s internal research and development processes and their relationship with scientific and engineering communities sheds light on how the new fields of environmental engineering and policy were co-produced in the 1970s. I argue that two competing approaches for environmental management, a community health approach and a control technology approach, developed from EPA\'s responses to bureaucratic, geographical, and epistemic challenges. I focus on researchers and managers from the Office of Research and Development at Research Triangle Park, North Carolina, as they were engaged in (1) controversy about integrated aerometry and epidemiology research intended to correlate air pollution and health, (2) intra-agency debate about the government\'s responsibility for introducing catalytic converters for tailpipe emissions reduction and responding to the potential environmental and social consequences, and (3) inter-agency activities for the demonstration of scrubbers for smokestack emissions and further application of the control technology approach in energy-related environmental problems. My principal conceptual contribution is "regulatory engineering." I define regulatory engineering as an approach to sociotechnical problems in which engineering practices are incorporated into regulatory and organizational changes, which in turn influences technical knowledge and identity formation. As EPA activities became closely associated with energy and economic issues toward the end of the 1970s, I argue that engineers took the initiative in demonstrating and evaluating control technologies for pollution abatement and energy development, scientists carefully studied environmental and health effects of these technologies, and regulators set up pollution standards and attainment deadlines accordingly. Studying the co-production of knowledge, institution, and identity through the lens of regulatory engineering helps us to understand technoscientific and managerial aspects of environmental governance beyond the 1970s EPA where technical feasibility considerations, economic incentives, and cooperative management expanded into legislation and regulation.

Abstract: Global kinetic model for a Pt-Pd diesel oxidation catalyst (DOC) is proposed and validated. Experimental data was obtained using different concentrations of the artificial gas mixtures which were passed over a bimetallic catalyst. Previous works of Voltz [1], Pandya [2], Sola [3] and many others were used to propose a new model, which was validated using a MATLAB based solver and optimizer. A reasonable match between the experimental data and predicted values was seen for all experimental conditions except for the runs with CO, H2, C3H6 and NO. Some fundamental observations were made in this case but further investigations are necessary to improve the model.

The life cycle analysis compares the environmental impacts of catalytic converters and the effects of not using these devices. To environmentally evaluate the catalytic converter, the emissions during extraction, processing, use of the product are considered. All relevant materials and energy supplies are evaluated for the catalytic converter. The goal of this life cycle is to compare the pollutants of a car with and without a catalytic converter. Pollutants examined are carbon monoxide (CO), carbon dioxide (CO2), hydrocarbons (HC), and nitrogen oxides (NOx). The main finding is that even considering materials and processing, a catalytic converter decreases the CO, HC and NOx pollutant emissions. The CO2 emissions are increased with a catalytic converter, but this increase is small relative to the overall CO2 emissions. The majority of catalytic converter pollutants are caused by the use phase, not extraction or processing. The life cycle analysis indicates that a catalytic converter decreases damage to human health by almost half, and the ecosystem quality damage is decreased by more than half. There is no damage to resources without a converter, as there are no materials or energy required; the damages with a converter are so small that they are not a significant factor. Overall, catalytic converters can be seen as worthwhile environmental products when considering short term effects like human health effects of smog, which are their design intent. If broader environmental perspectives that include climate change are considered, then the benefits depend on the weighting of these different environmental impacts.

Abstract: In this thesis, the development and use of a transient heterogeneous 2D model for monolithic catalytic converter is presented. Study on the cold flow hydrodynamics, temperature effect and CO conversion and light off behaviour of different models is developed. Different models are studied based on different parameters such as monolith brick CPSI configuration, size of the converter, inlet cone sizing and inlet velocity of the converter. The results for both steady state and transient modes are presented in detail. It is shown that monolith brick CPSI has a significant effect on pressure drop and light-off behaviour of the converter. Also, converter size has a major effect on the performance of a converter. Inlet cone sizing showed to have a significant effect on the hydrodynamics of the converter but it did not have a major effect on light-off behaviour of the converter.

The objective of this study was to evaluate the practical limits of EPA's NONROAD 2005 to accurately simulate Central Florida conditions, especially with regard to lawn and garden equipment. In particular we investigated a NONROAD emission inventory using default inputs and then created a locally specific emission inventory. These emission inventories were prepared for Orange, Osceola, and Seminole county and focused only on the VOC and NOx emissions caused by lawn and garden equipment. The model was manipulated to assess its ability to represent this specific category of nonroad equipment for a given airshed first by running a base case scenario using default data and then by developing a locally-specific scenario through administration of a survey. The primary purpose of the survey was to evaluate local values for equipment population, equipment characteristics, activity estimates, and other relevant information. To develop these local input estimates, data were collected concerning population and usage statistics in the Central Florida area and were combined with emission factors, load factors, allocation factors, and other needed values that have been previously established by the U.S. EPA. The results of the NONROAD model were compared with the resulting emission estimates calculated from locally derived inputs, and as a result of the analysis an accurate emission estimate was calculated. In addition, several possible air quality action steps were further assessed according to feasibility, cost, and predicted emission benefit. These potential management projects were further investigated by assessing the success of other similar projects in other cities in an effort to establish specific costs and emission benefits as they relate to the tri-county area.