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"Catalytic Microreactors for Portable Power Generation” addresses a problem of high relevance and increased complexity in energy technology. This thesis outlines an investigation into catalytic and gas-phase combustion characteristics in channel-flow, platinum-coated microreactors. The emphasis of the study is on microreactor/microturbine concepts for portable power generation and the fuels of interest are methane and propane. The author carefully describes numerical and experimental techniques, providing a new insight into the complex interactions between chemical kinetics and molecular transport processes, as well as giving the first detailed report of hetero-/homogeneous chemical reaction mechanisms for catalytic propane combustion. The outcome of this work will be widely applied to the industrial design of micro- and mesoscale combustors.
Recent advances in microfabrication technologies have enabled the development of entirely new classes of small-scale devices with applications in fields ranging from biomedicine, to wireless communication and computing, to reconnaissance, and to augmentation of human function. In many cases, however, what these devices can actually accomplish is limited by the low energy density of their energy storage and conversion systems. This breakthrough book brings together in one place the information necessary to develop the high energy density combustion-based power sources that will enable many of these devices to realize their full potential. Engineers and scientists working in energy-related fields will find: • An overview of the fundamental physics and phenomena of microscale combustion; • Presentations of the latest modeling and simulation techniques for gasphase and catalytic micro-reactors; • The latest results from experiments in small-scale liquid film, microtube, and porous combustors, micro-thrusters, and micro heat engines; • An assessment of the additional research necessary to develop compact and high energy density energy conversion systems that are truly practical.
The shift towards biomass and lower quality fossil fuel feedstocks will require new conversion approaches. Catalysis will be critical in the processing of these new feedstocks. By studying catalysis at industrially relevant conditions, it may be possible to reduce the time and cost of developing new catalyst systems. Microreactors enable the study of multiphase catalyst systems at pressures that were previously difficult to attain on the laboratory scale. The reduced length scales, characteristic of microchemical systems, provide additional benefits such as enhanced heat and mass transfer and a reduction of hazardous waste. The improved heat and mass transfer allow for kinetics to be probed at isothermal conditions in the absence of complicating mass transfer effects. A high-pressure microreactor system for catalyst study was designed, fabricated, and tested. The system allows for the multiphase study of homogenously and heterogeneously catalyzed systems, with a unique reactor designed for each application. A multicomponent gas phase is delivered simultaneously with a liquid stream, resulting in regular segmented (slug) flow. The isobaric system is operated at pressures of up to 100 bar. Gas and liquid flow rates, and therefore residence time, are specified independently of pressure. The system is capable of being operated at temperatures of up to 350°C and residence times of up to 15 minutes. Inline analysis, using an attenuated total reflection FTIR flow cell, and sample collection for offline analysis can be performed simultaneously. Both homogeneous and heterogeneous catalysis were demonstrated in the high-pressure system. A kinetic expression was derived for the homogeneous hydroformylation of terminal alkenes, catalyzed by Wilkinson's catalyst. The empirical reaction orders for the dependence on catalyst, hydrogen, and carbon monoxide were determined, along with the activation energy and pre-exponential factor. These results were then reconciled with a mechanistic model. The hydrogenation of cyclohexene over platinum catalysts was chosen to demonstrate the performance of the heterogeneous reactor. This reaction proceeded rapidly allowing mass transfer to be characterized in the microreactor. Observed mass transfer rates were two orders of magnitude higher than in traditional systems.
Heterogeneous catalysis and mathematical modeling are essential components of the continuing search for better utilization of raw materials and energy, with reduced impact on the environment. Numerical modeling of chemical systems has progressed rapidly due to increases in computer power, and is used extensively for analysis, design and development of catalytic reactors and processes. This book presents reviews of the state-of-the-art in modeling of heterogeneous catalytic reactors and processes. Reviews by leading authorities in the respective areas Up-to-date reviews of latest techniques in modeling of catalytic processes Mix of US and European authors, as well as academic/industrial/research institute perspectives Connections between computation and experimental methods in some of the chapters
In this thesis, on-chip microreactors for catalytic combustion of methanol-air mixture were designed, fabricated and characterized. Using standard optical lithography, deep reactive-ion etching (DRIE) and other fabrication techniques, microreactors with integrated micropillars having four different types of designs, viz., square and staggered pillar arrangements along with axial and diagonal flow configurations were generated. The diameter and height of the micropillars are both 100 um and the available internal surface area of the reactor is 629.77 mm^2. Such microfabricated microreactors have a high surface-area-to-volume-ratio in the order of 27.80 mm^-1. A wash-coating procedure was adopted to deposit Pt on Al2O3 catalyst onto the reactor surfaces. After a preheating procedure, by introducing methanol-air mixture into the reactors, an autonomous and stable on-chip catalytic combustion could be sustained. This work shows that apart from the catalyst, fuel type, fuel and air flow rates, the geometric configuration of the microreactor plays a significant role in terms of achieving highest on-chip temperature. It was found that the on-chip microreactor with squared pillar arrangement coupled with diagonal flow configuration provided the best performance for the catalytic combustion of methanol-air mixture. It was also demonstrated that the well-known transition from heterogeneous catalytic combustion to a mixed heterogeneous-catalytic-and-homogeneous-gas-phase combustion exists during the combustion process in these on-chip microreactors. Such sustained catalytic combustion can be utilized as future heat source for direct thermal-to-electric energy conversion platform where the on-chip microreactors can be packaged with commercial thermoelectric modules to achieve power generation on-chip.
The Nobel Prize in Chemistry 2007 awarded to Gerhard Ertl for his groundbreaking studies in surface chemistry highlighted the importance of heterogeneous catalysis not only for modern chemical industry but also for environmental protection. Heterogeneous catalysis is seen as one of the key technologies which could solve the challenges associated with the increasing diversification of raw materials and energy sources. It is the decisive step in most chemical industry processes, a major method of reducing pollutant emissions from mobile sources and is present in fuel cells to produce electricity. The increasing power of computers over the last decades has led to modeling and numerical simulation becoming valuable tools in heterogeneous catalysis. This book covers many aspects, from the state-of-the-art in modeling and simulations of heterogeneous catalytic reactions on a molecular level to heterogeneous catalytic reactions from an engineering perspective. This first book on the topic conveys expert knowledge from surface science to both chemists and engineers interested in heterogeneous catalysis. The well-known and international authors comprehensively present many aspects of the wide bridge between surface science and catalytic technologies, including DFT calculations, reaction dynamics on surfaces, Monte Carlo simulations, heterogeneous reaction rates, reactions in porous media, electro-catalytic reactions, technical reactors, and perspectives of chemical and automobile industry on modeling heterogeneous catalysis. The result is a one-stop reference for theoretical and physical chemists, catalysis researchers, materials scientists, chemical engineers, and chemists in industry who would like to broaden their horizon and get a substantial overview on the different aspects of modeling and simulation of heterogeneous catalytic reactions.
This compendium reports fundamental science and engineering advances of the US Army Research Labratory (ARL) within the area of Energy and Power technologies. Although, in general, ARL's Materials Research encompasses a broad range of materials technologies (e.g.: Photonics, Electronics, Biological and Bio-inspired Materials, Structural Materials, High Strain and Ballistic Materials, and Manufacturing Science), this publication specifically addresses selected energy and power material related work at ARL. While this work includes electrochemical energy storage (batteries and capacitors) and electrochemical energy conversion (fuel cells, photoelectrochemistry, and photochemistry), special emphasis is given on electrochemical energy storage: • Micro Electro-Mechanical Systems (MEMS): Power density, efficiency, and robustness of motors, generators, and actuators while also reducing their life cycle costs. • Energy Storage: Electrical and electrochemical energy storage devices to decrease device size, weight, and cost as well as increase their capabilities in extreme temperatures and operating conditions. • Power Control and Distribution: Tactical, deployable power systems using conventional fuels, alternative fuels, and energy harvested from renewable/ambient sources. • Power Generation/Energy Conversion: Smart energy networks for platforms, forward operating bases, and facilities using modeling and simulation tools as well as new, greater capability and efficiency components. • Thermal Transport and Control: Heat and higher power density systems, advanced components, system modeling, and adaptive or hybrid-cycle technologies. Keywords: Electrochemical Energy Storage, Batteries, Capacitors, Electrochemical Energy Conversion, Fuel Cells, Photoelectrochemistry, Photochemistry, High Voltage Electrolytes, Li-ion Batteries, Li-ion Chemistry, Lithium–Sulphur Batteries, Nuclear Metastables, Pyroelectric Energy Conversion, Charged Quantum Dots, High-Efficiency Photovoltaics, IR Sensing, GaN Power Schottky Diodes, Threshold-Voltage Instability, Reliability Testing, SiC MOSFETs, Power Electronics Packaging, High Voltage 4H-SiC GTOs, Silicon Carbide, Avalanche Breakdown Diode, SiC PiN Diodes, Thyristor Protection, Compact DC-DC Battery Chargers
This proceedings volume comprises the invited plenary lectures, contributed and poster papers presented at a symposium organised to mark the successful inauguration of the world's first commercial plant for production of gasoline from natural gas, based on the Mobil methanol-to-gasoline process. The objectives of the Symposium were to present both fundamental research and engineering aspects of the development and commercialization of gas-to-gasoline processes. These include steam reforming, methanol synthesis and methanol-to-gasoline. Possible alternative processes e.g. MOGD, Fischer-Tropsch synthesis of hydrocarbons, and the direct conversion of methane to higher hydrocarbons were also considered.The papers in this volume provide a valuable and extremely wide-ranging overview of current research into the various options for natural gas conversion, giving a detailed description of the gas-to-gasoline process and plant. Together, they represent a unique combination of fundamental surface chemistry catalyst characterization, reaction chemistry and engineering scale-up and commercialization.