Metal Oxide Nanofiber Catalysis
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Metal Oxide Nanofiber Catalysis
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Author : Daniel Patrick Noon
language : en
Publisher:
Release Date : 2015
Metal Oxide Nanofiber Catalysis written by Daniel Patrick Noon and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2015 with categories.
The synthesis of solids with finely turned nanostructures that offer superior catalytic performance is a major challenge in heterogeneous catalysis for gas phase reactions. Industrial catalysts are almost universally composed of quasi-spherical nanoparticles, or powders plagued with particle agglomeration, migration and sintering problems that lead to deactivation. In this work, quasi-cylindrical nanofibers are electrospun and extensively utilized for the oxidative coupling of methane (OCM), as well as for propylene epoxidation and the catalytic partial oxidation (CPO) of methane. Electrospun nanofibers of metal oxides may be tuned to have high surface areas but typically possess no internal porosity, reducing diffusion limitations that would lengthen the exposure of target intermediate oxidation products to unselective catalysis. Additionally, experiments and density functional theory (DFT) studies have previously shown that pentagonal Ag nanowires exhibit higher selectivity than conventional particles in ethylene epoxidation since their surfaces are terminated mainly by the (100) surface facet rather than the lowest energy (111) facet that dominates particles. Hence, nanofibers may elevate catalytic performance in broad range of partial oxidation reaction schemes. Research into the oxidative coupling of methane, or, the catalytic conversion of methane to ethane and ethylene by molecular oxygen, almost exclusively utilized powders and failed to result in viable catalyst despite four decades of intense, global efforts. Accordingly, the use of catalytic nanofibers provides a potentially fruitful path towards a solution. Here, nanofiber fabrics of La2O3-CeO2 were electrospun and used in fixed bed OCM reactors to achieve 70% selectivity and 16% yield for C2+ hydrocarbons at a CH4/O2 feed ratio of 7 and remarkably low feed temperature of 470 ?C. Powders of La2O3-CeO2 documented in the literature exhibit similar selectivity and yield, but with the feed at 715 ?C. The electrospun fabrics used in this research were found to have dense nanofibers of diameters typically within the 20 - 200 nm range and, accordingly, surface areas of 10 - 20 m2/g as well as thinner fibers tending towards both higher C2+ selectivity and CH4 conversion. While performing reaction engineering studies using the aforementioned fabrics, it was found that designing reactors comprising dual catalytic La2O3-CeO2 fabric beds with inter-stage O2 injection and cooling pushes yields to 21%. Moreover, a novel in-situ microprobe sampling technique for acquiring spatial temperature and concentration profiles within these OCM reactors was developed, providing a means to formulate and validate detailed chemical kinetic mechanisms. This has led to the discovery of prompt H2 formation in OCM, a feature previously unidentified that may break ground in mechanism refinement. Additionally, spatial concentration and temperature profiles were acquired in fixed bed reactors comprising La2O3-CeO2 fabrics doped with varying levels of Ir and fed CH4/O2 mixtures to gain insight into the transition from OCM to the catalytic partial oxidation of methane. It was found that, in general, OCM and CPO appear to occur both in parallel and sequentially in a fixed bed, evidenced by the temporary rise and subsequent destruction of C2+ hydrocarbons when the catalyst is doped with 0.05 wt% Ir. Clearly, this sampling technique has broad applicability in catalysis research over a limitless number of reactions for the acquisition of comprehensive data sets potentially useful for formulating and refining detailed chemical kinetic mechanisms (DCKM), thus furthering a fundamental understanding of the catalysis and advancing faster towards the development of higher performing materials.
Metal Oxide Nanofibers As Filters Catalyst And Catalyst Support Structures
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Author : Sneha Swaminathan
language : en
Publisher:
Release Date : 2010
Metal Oxide Nanofibers As Filters Catalyst And Catalyst Support Structures written by Sneha Swaminathan and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2010 with Automobiles categories.
For environmental protection, the suppression of automotive exhausts such as nitrogen oxides (NOx) and carbon monoxide (CO) is very important. These gases are potential health hazards and green house gases. Burning of hydrocarbon (HC) ideally leads to the formation of water and carbon dioxide; however, due to incomplete combustion and temperatures fluctuations reached in the combustion chamber, the exhaust contains significant amounts of pollutants which need to be transformed into harmless compounds. Hence this concern triggered the need for stringent environmental regulations which resulted in the introduction of catalytic devices in automobiles. Traditionally, the catalyst is impregnated onto a porous substrate. The limitation of this method is the difficulty involved in controlling the catalyst particle size during the sintering or reduction steps that result in high temperature agglomeration effects. In the present work, a novel approach has been developed wherein the noble metal nanocatalysts have been incorporated on ceramic nanofibers by the electrospinning process. The catalysts on ceramic nanofibers increase the overall exposed catalyst area and simultaneously immobilize the catalyst to minimize catalyst loss. A small amount of the catalyst incorporated into ceramic nanofibers was mixed with microfibers to fabricate a filter disk by vacuum molding technique. This filter disk termed as 'catalytic filter' is a combination of catalytic elements and filter. The catalyzed ceramic nanofiber augmented microfiber filter media can be used for two applications: reduction of NOx and oxidation of CO and for enhanced particulate removal. This filter would include advantages such as light weight structure, optimization of precious metals, high capture efficiency, high surface area, highly interconnected network of pores and high permeability. The key aspects in this dissertation can be divided into six parts: fabrication of catalytic filters and their optimization, fabrication of three-way catalysts and oxygen storage catalysts, crosslinking of nanofibers as an intermediate step to ceramic nanofiber manufacture, comparison of catalytic filter with the traditional methods and conventional catalytic converter, particle size reduction and studying the deactivation using water and H2S. All the types of catalytic filter which were fabricated were successful in reducing NO and oxidizing CO completely. The degradation temperature of NO and CO depended on the type, amount and loading of the catalyst nanoparticles on the alumina nanofiber.
Electrospun Nanofiber Metal Oxides For Reactive Sorption And Catalysis
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Author : Faisal Alshafei
language : en
Publisher:
Release Date : 2018
Electrospun Nanofiber Metal Oxides For Reactive Sorption And Catalysis written by Faisal Alshafei and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2018 with categories.
Electrospun metal oxides is a new class of materials that have demonstrated auspicious potential and have been used in a wide range of applications. In this work, various smooth, continuous, and defect-controlled metal-polymer nanofibers were synthesized via electrospinning with diameters ranging from approximately 50 to 600 nm, and subsequently thermally treated to decompose the polymer (PVP or PEO) and form highly porous, fibrous metal (Cu-, Ni-, Mg-, and Ca-) oxide nanostructures. In the first part of this thesis, parameters that influence the electrospinning process were systematically investigated for PVP-Cu(NO3)2 systems. Both solution properties (polymer/metal concentration, polymer molecular weight, and solvent identity) and processing conditions (applied voltage, tip-of-needle to collector distance, extrusion rate, and humidity) were varied to probe the effect of these electrospinning factors on fiber quality prior to thermal treatment. The data collected demonstrated that factors that do not directly and strongly influence viscosity, conductivity and solvent evaporation (e.g., applied voltage, extrusion rate, and tip-of-needle to collecting plate distance) do not have substantial effects on fiber diameter and morphology. Subsequent thermal treatment of the electrospun nanofibers and choice of metal, however, were found to markedly impact the morphology of the formed fiber oxides (e.g., string-like structures or segmented particles). In the second part of this thesis, electrospun fiber metal oxide materials were tested in two main applications (high temperature CO2 removal and low-temperature H2S removal) and their performance was compared to materials prepared via traditional synthesis routes (e.g., sol-gel, co-precipitation, hydrothermal treatment, etc.) In the first application, CaO-based materials were tested as potential sorbents in sorption enhanced steam methane reforming (SE-SMR) to capture CO2 and shift the reaction towards producing more hydrogen. The electrospun CaO-nanofibers, when reacted with CO2, achieved complete conversion to CaCO3 and had an initial CO2 sorption capacity of 0.79gCO2/gsorbent at 873 K and 923 K (highest of all materials tested), as the macro-porosity imparted by the electrospinning process improved the CO2 diffusion through the CaCO3 product layers. Furthermore, when these electrospun sorbents were added to a commercial catalyst and tested in SE-SMR conditions, they had three to four times longer breakthrough times than CaO sorbents derived from natural sources (e.g., CaO-marble). To further improve the stability of CaO-based sorbents, chemical doping of Ca-supports with Mg, Al, Y, La, Zn, Er, Ga, Li, Nd, In, and Co was combined with electrospinning to yield mixed oxide materials with high sorption capacities (~0.4-0.7 gCO2/gsorbent) and improved durability (up to 17 cycles). It was demonstrated that metals that have high Tammann temperatures were effective at reducing sintering and CaO particle agglomeration by acting as spacers, thus, retaining the sorbent's initial sorption capacity upon repeated cycling. In the second application, CuO nanofibers with varying diameters (~70-650 nm) were prepared from two polymers (PEO and PVP) and reacted with H2S at ambient conditions to form CuS. The results from this study demonstrated that the sulfur removal capacity of CuO materials, whether prepared via electrospinning, hydrothermal treatment, sol-gel or co-precipitation, was strongly dependent on crystallite size (a linear relationship was established between CuO removal capacity and crystallite size and held true for all CuO materials with crystallites between 5-26 nm) and CuO purity (i.e., presence of residual carbon on the surface of the oxide). Indeed, properties such as surface area, pore volume and morphology (e.g., flowerlike, fiber-like, belt-like, etc.) were found to have an insignificant impact on removal capacity. This work offers fundamental insights into the design of multifunctional and highly porous metal oxide nanofibers for sorptive and catalytic applications.
Metal Oxide Based Nanofibers And Their Applications
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Author : Vincenzo Esposito
language : en
Publisher: Elsevier
Release Date : 2021-10-25
Metal Oxide Based Nanofibers And Their Applications written by Vincenzo Esposito and has been published by Elsevier this book supported file pdf, txt, epub, kindle and other format this book has been release on 2021-10-25 with Technology & Engineering categories.
Metal Oxide-based Nanofibers and their Applications provides an in-depth overview on developments surrounding the synthesis, characterization properties, and applications achieved by scientific leaders in the area. Sections deal with the theoretical and experimental aspects of the synthesis and methodologies to control microstructure, composition and shape of the nanofibrous metal oxides, review the applications of metal oxide nanofibers in diverse technologies, with special focus on the relation between the structural, morphological and compositional features of the nanofibers, cover applications of metal oxide nanofibers in the fields of sensing (biosensing, gas sensing), and consider biomedical and cleaning technologies. Lastly, a final section covers their application in energy generation and storage technologies (e. g. piezoelectric, solar cells, solid oxide fuel cells, lithium-ion batteries, supercapacitors, and hydrogen storage are reviewed. Reviews electrospinning methods for the synthesis and design of nanocomposites and hybrid metal oxide nanofibers Discusses applications of metal oxide nanofibers in sensing, biomedical fields, cleaning technologies, and energy Emphasizes the structural, morphological and compositional properties of nanofibers and their effect on device performance
Catalysis For C1 Chemistry Oxidative Coupling Of Methane Using Nanofiber Catalysts And Discovery Of Catalysts For Atmospheric Reduction Of Co2 To Methanol
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Author : Bahman Zohour
language : en
Publisher:
Release Date : 2017
Catalysis For C1 Chemistry Oxidative Coupling Of Methane Using Nanofiber Catalysts And Discovery Of Catalysts For Atmospheric Reduction Of Co2 To Methanol written by Bahman Zohour and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2017 with categories.
The goal of this research is to explore novel catalytic material and systems for effective conversion of C1 feed. Catalysis of C1 chemistry is of critical importance for the clean production of fuels and chemicals and future energy sustainability. Herein, two processes were studied: In the first section, a comprehensive study of oxidative coupling of methane (OCM) using novel nanofiber catalysts of mixed metal oxides was undertaken and in the second section, direct catalytic conversion of carbon dioxide (CO2) to methanol was studied, which resulted in discovery of a superior catalytic system for CO2 hydrogenation to methanol. Section 1: Utilization of natural gas as an alternate chemical feedstock to petroleum has been a highly desirable but difficult goal in industrial catalysis. Accordingly, there has been a substantial interest in the oxidative coupling of methane (OCM), which allows for the direct catalytic conversion of methane into economically valuable C2+ hydrocarbons. OCM is a complex reaction process involving heterogeneous catalysis intricately coupled with gas phase reactions; hence, despite decades' worth of research, it has yet to be commercialized. The lack of progress in OCM is primarily due to the following reasons: 1. The absence of a highly active and robust catalyst that can operate at lower temperatures; and 2. Our inadequate understanding of the underlying detailed chemical kinetics mechanism (DCKM) of the OCM process, which impedes the undertaking of quantitative simulations of novel reactor configurations and/or operating strategies. To address these issues, we undertook the following program of studies: 1. Further improved the synthesis of novel nanofiber catalysts by electrospinning, building on the early discovery that La2O3-CeO2 nanofibers were highly active and robust OCM catalysts; 2. Applied our novel microprobe sampling system to OCM reactors for the acquisition of spatially resolved species concentration and temperatures profiles within the catalytic zone. Our novel sampling approach led to the important discovery that H2 is produced very early in the OCM catalytic zone, an observation that was completely missed in all prior studies. The application of our novel microprobe system to a dual-bed OCM reactor also demonstrated the feasibility to significantly improve C2+ product yields to 21% (from 16% for single bed) which we plan to further improve by considering more sequential beds; 3. Outlined development and validation of new generation of DCKM for the OCM process using the high-information content of spatial concentration profiles obtained in part 2. Most importantly, to improve the current DCKM literature by considering surface reactions that result in early H2 formation. Validated DCKM represent highly valuable numerical tools that allow for the prediction of the OCM performance of different reactor configurations operating under a broad range of conditions, e.g. high pressures, porous wall reactors etc. Consequently, this new generation of comprehensive DCKM based on the sampling profiles, detailed in this report, will be of considerable use in improving the yields of useful products in the OCM process; 4. Explore novel conditions that include oxygen-feed distributed packed bed OCM reactors and coupled catalytic and non-thermal plasma OCM reactors, again to further push the yields for useful C2+ products. The details of the proposed approach for implementing such reactor configurations and development of a new generation of DCKM for the OCM process is outlined in the future work, Chapter 4, of section 1 of the report. Section 2: Direct catalytic conversion of carbon dioxide to liquid fuels and basic chemicals, such as methanol, using solar-derived hydrogen at or near ambient pressure is a highly desirable goal in heterogeneous catalysis. When realized, this technology will pave the way for a sustainable society together with decentralized power generation. Here we report a novel class of holmium (Ho) containing multi-metal oxide Cu catalysts discovered through the application of high-throughput methods. In particular, ternary systems of Cu-GaOx-HoOy > Cu-CeOx-HoOy ~ Cu-LaOx-HoOy supported on -Al2O3 exhibited superior methanol production (10x) with less CO formation than previously reported catalysts at atmospheric pressure. Holmium was shown to be highly dispersed as few-atom clusters, suggesting that the formation of tri-metallic sites could be the key for the promotion of methanol synthesis by Ho.
Carbon And Oxide Nanostructures
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Author : Noorhana Yahya
language : en
Publisher: Springer Science & Business Media
Release Date : 2011-01-12
Carbon And Oxide Nanostructures written by Noorhana Yahya and has been published by Springer Science & Business Media this book supported file pdf, txt, epub, kindle and other format this book has been release on 2011-01-12 with Technology & Engineering categories.
This volume covers all aspects of carbon and oxide based nanostructured materials. The topics include synthesis, characterization and application of carbon-based namely carbon nanotubes, carbon nanofibres, fullerenes, carbon filled composites etc. In addition, metal oxides namely, ZnO, TiO2, Fe2O3, ferrites, garnets etc., for various applications like sensors, solar cells, transformers, antennas, catalysts, batteries, lubricants, are presented. The book also includes the modeling of oxide and carbon based nanomaterials. The book covers the topics: Synthesis, characterization and application of carbon nanotubes, carbon nanofibres, fullerenes Synthesis, characterization and application of oxide based nanomaterials. Nanostructured magnetic and electric materials and their applications. Nanostructured materials for petro-chemical industry. Oxide and carbon based thin films for electronics and sustainable energy. Theory, calculations and modeling of nanostructured materials.
Metal Oxide Nanostructures From Electrospun Carbon Templates
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Author : Dickson Andala
language : en
Publisher: LAP Lambert Academic Publishing
Release Date : 2012-03
Metal Oxide Nanostructures From Electrospun Carbon Templates written by Dickson Andala and has been published by LAP Lambert Academic Publishing this book supported file pdf, txt, epub, kindle and other format this book has been release on 2012-03 with categories.
The work covered herein discusses for the first time various techniques used in the fabrication of metal oxide nanofibers and nanotubes from eletrospun carbon fibers as templates. The nanofibers were prepared by electrospinning metal oxide precursor inside a polymer matrix. The metal oxide tubes were by tubes by fiber templating. This was followed by calcination to yield the nanofibers and nanotubes. Their morphological, structural, optoelectronic and catalytic properties are also discussed. Among key applications they have found utilization as catalyst supports. Palladium nanoparticles have been supported on Titanium dioxide nanofibers and applied in Heck-coupling reactions. Similarly, included is the effect of impurities on the metal oxide tubes properties done by doping with metal ions. In addition, photocatalytic behavior of metal oxides nanofibers have also been discussed.
Metal Oxide Carbon Hybrid Materials
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Author : Muhammad Akram Chaudhry
language : en
Publisher: Elsevier
Release Date : 2022-03-20
Metal Oxide Carbon Hybrid Materials written by Muhammad Akram Chaudhry and has been published by Elsevier this book supported file pdf, txt, epub, kindle and other format this book has been release on 2022-03-20 with Technology & Engineering categories.
Metal Oxide–Carbon Hybrid Materials: Synthesis, Properties and Applications reviews the advances in the fabrication and application of metal oxide–carbon-based nanocomposite materials. Their unique properties make them ideal materials for gas-sensing, photonics, catalysis, opto-electronic, and energy-storage applications. In the first section, the historical background to the hybrid materials based on metal oxide–carbon and the hybridized metal oxide composites is provided. It also highlights several popular methods for the preparation of metal oxide–carbon composites through solid-state or solution-phase reactions, and extensively discusses the materials’ properties. Fossil fuels and renewable energy sources cannot meet the ever-increasing energy demands of an industrialized and technology-driven global society. Therefore, the role of metal oxide–carbon composites in energy generation, hydrogen production, and storage devices, such as rechargeable batteries and supercapacitors, is of extreme importance. These problems are discussed in in the second section of the book. Rapid industrialization has resulted in serious environmental issues which in turn have caused serious health problems that require the immediate attention of researchers. In the third section, the use of metal oxide–carbon composites in water purification, photodegradation of industrial contaminants, and biomedical applications that can help to clean the environment and provide better healthcare solutions is described. The final section is devoted to the consideration of problems associated with the development of sensors for various applications. Numerous studies performed in this area have shown that the use of composites can significantly improve the operating parameters of such devices. Metal Oxide–Carbon Hybrid Materials: Synthesis, Properties and Applications presents a comprehensive review of the science related to metal oxide–carbon composites and how researchers are utilizing these materials to provide solutions to a large array of problems. Reviews the fundamental properties and fabrication methods of metal-oxide–carbon composites Discusses applications in energy, including energy generation, hydrogen production and storage, rechargeable batteries, and supercapacitors Includes current and emerging applications in environmental remediation and sensing
Electrospun Nanofibers
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Author : Santosh Kumar Tiwari
language : en
Publisher: Springer Nature
Release Date : 2021-09-14
Electrospun Nanofibers written by Santosh Kumar Tiwari and has been published by Springer Nature this book supported file pdf, txt, epub, kindle and other format this book has been release on 2021-09-14 with Science categories.
The book provides an up-to-date account of the various techniques of fabrication & functionalization of electrospun nanofibers as well as recent advancements. An overview of the advanced applications of such techniques in different areas is also presented. Both experimental and theoretical approaches related to electrospun nanofibers are covered along with a discussion on the inherent properties of electrospun nanofibers. Therefore, this book provides a unique resource not only to established researchers but also newcomers starting out in this field.
Carbon Nanofibers
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Author : Chang-Seop Lee
language : en
Publisher:
Release Date : 2018
Carbon Nanofibers written by Chang-Seop Lee and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2018 with Carbon nanofibers categories.
This book is divided into two sections. Section One covers the authors' work on the synthesis and characteristics of the various carbon nanofibers and microcoils using chemical vapor deposition and electrospun technologies. This section includes Chapters One through Four. Chapter One is an introductory chapter which presents synthesis, properties and analysis of carbon nanofibers and microcoils prepared by chemical vapor deposition and electrospun technologies. Chapter Two introduces information for approaching electrospun carbon nanofibers (ECNFs) with superior mechanical strength from aligned and stretched polyacrylonitrile (PAN) copolymer nanofibers possessing high degrees of morphological and structural perfection. Chapter Three investigates the in-situ and ex-situ processes for the formation of geometrically controlled carbon microcoils and the practical application of carbon microcoils to the various nano/micro electronic or mechanical devices. Chapter Four discusses the synthesis and various characterizations of carbon nanofibers synthesized by catalytic chemical vapor deposition of halogenated hydrocarbons. Section Two deals with the recent advances in materials synthesis and characterization of carbon nanofibers and their applications such as Li secondary batteries, supercapacitors and heavy metal remediation in ground and wastewater. This section includes chapter Five through Ten. Chapter Five presents preparation and characterization of carbon nanofibers (CNFs), CNFs-Si, and CNFs-(PC)Si composites synthesized by the Chemical Vapor Deposition (CVD) method using transition metal catalysts and applications to anode materials of Li secondary batteries. Chapter Six introduces a synthesis and characterization of carbon nanofibers and Si/carbon nanofiber composites based on Ni and Mo catalysts prepared for the anode material of Li secondary batteries. Chapter Seven discusses the electrophoretic deposition of Ni and Cu catalysts on C-fiber textiles for the growth of carbon nanofibers and coating of silica by the hydrolysis of tetraethyl orthosilicate on carbon nanofibers, and finally applications to the anode materials for Li secondary batteries. Chapter Eight presents synthesis and characterization of transition metal coated carbon nanofibers on Ni foam via CVD followed by a dipping method and electrochemical performance as anode materials for Li secondary batteries. Chapter Nine introduces a design of hierarchical porous carbon materials containing various metal oxides as an electrode material for high-performance supercapacitors. Chapter Ten discusses an innovative carbon nanofibrous composite material prepared by the electrospun method and its application for efficient heavy metal pollutant remediation in contaminated groundwater as well as in wastewater treatment.