Performance of Ceria Supported Monometallic and Bimetallic Single-atom Catalysts in Carbon Monoxide Oxidation PDF Download
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Author: Nicholas A. Pantelis
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Book Description
Research into atomically-dispersed metal catalysts on metal-oxide supports like ceria and alumina has grown significantly due to these catalysts' increased performance relative to bulk, nanoparticle, and sub-nanometer metal catalysts. Atomically dispersed, single atom catalysts have been shown to increase the specific activity of metal catalysts on metal-oxide supports. This study mainly focuses on difference in kinetic behavior of single-atom palladium, platinum, and nickel adatoms supported on ceria support during the oxidation of carbon monoxide. The relationship between metal weight-loading on a ceria support, reactor temperature, and reaction order was described. Bimetallic single atom catalysts of palladium and platinum on ceria were studied to compare to monometallic systems in terms of activity. Catalysts were characterized using ICP and CO-DRIFTS analysis, and a differential packed-bed reactor was used carry out the oxidation reaction; the effluent stream was analyzed using a GC to determine reaction kinetics. It was determined that CO binds most strongly to Pt, followed by Pd, and then Ni. The transition from single atom to sub-nanometer nanoparticles or nanoparticles shows a decrease in specific activity with increasing weight loading. At relatively larger weight loadings, for each metal, the order in CO transitions from above 1 to 0 (or slightly negative), while the order in O2 transitions from slightly negative or 0 to above 1. Pd, Pt, and Ni, at similar nominal weight loadings, have similar activities in different temperature ranges; this observation shows CO poisons the metal site but does not explain why at low weight loadings the order in CO increases above 1. Binding energies between metals and ceria as well as metal and CO may explain this observation. Bimetallic Pd/Pt catalysts seem to show apparent synergy due to the fact that the activation energy decreases well below the activation energy of monometallic systems of Pd and Pt.
Author: Nicholas A. Pantelis
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Book Description
Research into atomically-dispersed metal catalysts on metal-oxide supports like ceria and alumina has grown significantly due to these catalysts' increased performance relative to bulk, nanoparticle, and sub-nanometer metal catalysts. Atomically dispersed, single atom catalysts have been shown to increase the specific activity of metal catalysts on metal-oxide supports. This study mainly focuses on difference in kinetic behavior of single-atom palladium, platinum, and nickel adatoms supported on ceria support during the oxidation of carbon monoxide. The relationship between metal weight-loading on a ceria support, reactor temperature, and reaction order was described. Bimetallic single atom catalysts of palladium and platinum on ceria were studied to compare to monometallic systems in terms of activity. Catalysts were characterized using ICP and CO-DRIFTS analysis, and a differential packed-bed reactor was used carry out the oxidation reaction; the effluent stream was analyzed using a GC to determine reaction kinetics. It was determined that CO binds most strongly to Pt, followed by Pd, and then Ni. The transition from single atom to sub-nanometer nanoparticles or nanoparticles shows a decrease in specific activity with increasing weight loading. At relatively larger weight loadings, for each metal, the order in CO transitions from above 1 to 0 (or slightly negative), while the order in O2 transitions from slightly negative or 0 to above 1. Pd, Pt, and Ni, at similar nominal weight loadings, have similar activities in different temperature ranges; this observation shows CO poisons the metal site but does not explain why at low weight loadings the order in CO increases above 1. Binding energies between metals and ceria as well as metal and CO may explain this observation. Bimetallic Pd/Pt catalysts seem to show apparent synergy due to the fact that the activation energy decreases well below the activation energy of monometallic systems of Pd and Pt.
Author: Xavier Isidro Pereira Hernandez
Publisher:
ISBN:
Category : Automobiles
Languages : en
Pages : 268
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Book Description
Ceria-supported Pt catalysts have great potential for oxidation reactions and industrial applications such as vehicle emission control. These applications can be greatly benefited by tailoring this catalyst to meet their specific requirements. Single-atom catalysts have the highest atom efficiency and can have superior reactivity and selectivity. The synthesis of a ceria-supported Pt single-atom catalyst by methods that can be used in an industrial setup and scale is very important. This dissertation reports the synthesis of a thermally stable ceria-supported Pt single-atom catalyst by high-temperature calcination. Moreover, the limits in the amount of Pt that can be stabilized as single atoms and the anchoring sites for Pt single atoms are also discussed. Activation of the ceria-supported Pt single-atom catalyst to achieve high activity at low temperature for CO oxidation is presented and the catalyst characteristics affecting the activity are also discussed. Finally, a synthesis method is presented to stabilize Pt as single atoms on ceria which can remain stable at high temperature not only under oxidizing conditions but also reducing conditions while still exhibiting high activity for low-temperature CO oxidation.
Author: Wenchi Liu
Publisher:
ISBN:
Category :
Languages : en
Pages : 93
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Book Description
Catalysis is of vital importance in a wide range of areas including energy processing and chemical production. Catalytic conversion of C1 sources such as carbon monoxide and methane to make hydrocarbon fuels and oxygenated products has far reaching implications especially in the context of the gradual depletion of crude oil resource and the potential surge in the natural gas production in the coming decades. The control over reaction activity and selectivity for the conversion CO and CH4 in the Fischer–Tropsch synthesis and oxidative coupling of methane (OCM) have received tremendous attention and have been proved challenging. This dissertation focuses on the catalytic conversion of CO (Fischer–Tropsch synthesis) using supported cobalt based bimetallic nanoparticle model catalysts and the oxidative coupling of methane with noble metal promoted metal oxide catalysts. Using colloidal synthesis, a series of cobalt based bimetallic nanoparticles Co–M (M = Mn, Ru, Rh, and Re) with well-defined sizes, shapes, and compositions were obtained. Detailed synthesis procedures were presented and key synthetic parameters were discussed. The as-synthesized nanoparticles were subjected to extensive in-situ X-ray spectroscopy studies using ambient pressure X-ray photoelectron spectroscopy (AP-XPS) and X-ray absorption spectroscopy (XAS) under catalytic relevant conditions. Composition wise, the results indicate the surface concentration of Co on the as-synthesized Co–M bimetallic particles is slightly less than the bulk atomic Co %. While oxidation treatment led to a slight increase of the surface Co, major effect was seen after the reduction treatment where surface segregation of the second metal resulted in a drastic decrease of the surface Co content. The effect is more pronounced at elevated reduction temperatures. Under reaction conditions, the surface compositions remained similar to those after the reduction treatment at high temperatures. Among the bimetallics tested, the Co–Mn system is relatively less susceptible to surface reconstructions induced by oxidation and reduction treatments. In addition, the reducibility of Co was also shown to be modified depending on the second metal present and Re was proved to be most efficient in leading to a facile reduction of Co. Catalytic performance of the bimetallic catalysts supported on mesoporous silica MCF–17 indicates a positive effect in the catalytic activity for Co–Rh and Co–Mn systems, while Co–Re and Co–Cu showed decreased activity. Less pronounced promotion effect of the second metal on the product distribution was observed with only a slight increase in the selectivity towards C5+ products. The selectivities for CH4 and C5+ of the various Co–M bimetallic catalysts generally resemble those of pure Co catalysts. Although in extremely low selectivity, alcohols were also formed with Co–Rh and Co–Cu bimetallic catalysts. The appearance of longer chain alcohol such as propanol, which was not present for pure Co catalysts, is an evidence for potential synergistic promotion. For oxidative coupling of methane (OCM), the promotion effect of noble metals (Pt, Ir, and Rh) on the performance of MnxOy-Na2WO4/MCF–17 catalysts was investigated. The introduction of noble metals had little effect on the surface area and phase composition of the original catalyst but led to a more reduced nature of the surface oxide species. Catalytic study revealed an enhanced selectivity towards both C2 and C3 hydrocarbons as compared to the undoped MnxOy-Na2WO4/MCF–17 catalyst in the order of Rh-doped > Ir-doped > Pt-doped samples together with a lower olefin to paraffin ratio. A more optimized strength of interaction between the carbon intermediates and the catalyst surface was suggested, which in combination with the improved reducibility of Mn and W species are believed to be responsible for the improved performance. In addition, monodispersed leaf-like manganese–tungsten–oxide (Mn–W–Ox) nanoparticles and hydroxylated hexagonal boron nitride (h-BN) were synthesized and used as novel catalysts in OCM reaction. Preliminary results indicate that the MCF–17 supported Mn–W–Ox nanoparticle catalyst showed a CH4 conversion of 5.4% and C2 selectivity of 42% with good stability over time. On the other hand, hydroxylated h-BN exhibited good activity (~20% CH4 conversion) with moderate selectivity towards C2 hydrocarbons (20%–30%). However, the hydroxylated h-BN catalysts faced serious deactivation, which was not eliminated by lowering the reaction temperature or the oxygen concentration in the reaction gas feed.
Author: John H. Sinfelt
Publisher: Wiley-Interscience
ISBN:
Category : Science
Languages : en
Pages : 190
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Book Description
Presents an account of the research on bimetallic catalysts. Focuses attention on the possibility of influencing the selectivity of chemical transformations on metal surfaces and preparing metal alloys in a highly dispersed state. Covers the validation and elucidation of the bimetallic cluster concept. Includes figures and tables.
Author: Prashanth W. Menezes
Publisher: Elsevier
ISBN: 0323952380
Category : Technology & Engineering
Languages : en
Pages : 270
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Book Description
Single Atom Catalysts: Design, Synthesis, Characterization, and Applications in Energy focuses on the synthesis, design and advanced characterization techniques for single atom catalyst materials and their direct energy conversion and storage applications. This book reviews emerging applications of single atom catalysts in fuel cells, batteries, water splitting, carbon dioxide reduction, and nitrogen fixation. Both noble metal and non-noble metal single atom catalysts (SACs) are discussed as noble metal-based SACs are highly efficient and non-noble metal-based SACs might have lower associated costs. There is an emphasis on materials design focused on improving performance of catalysts based on overall catalytic activity, selectivity and stability. Specific parameters that impact this performance are emphasized throughout the book, including single metal atom stabilization, metal-support interactions and the coordination environment. - Discusses the different intricate design and synthesis methods pertaining to various noble and non-noble metal-based SACs - Provides in-depth understanding about the structural, morphological, and physicochemical characterization techniques of synthesized SACs with data analysis and interpretation - Describes state-of-the-art applications of SACs in renewable energy generation and their conversion, storage, and associated challenges
Author: R. T. K. Baker
Publisher:
ISBN:
Category : Science
Languages : en
Pages : 258
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Book Description
Author: Elson Longo
Publisher: Springer
ISBN: 3319538985
Category : Technology & Engineering
Languages : en
Pages : 450
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Book Description
In this book we explore new approaches to understanding the physical and chemical properties of emergent complex functional materials, revealing a close relationship between their structures and properties at the molecular level. The primary focus of this book is on the ability to synthesize materials with a controlled chemical composition, a crystallographic structure, and a well-defined morphology. Special attention is also given to the interplay of theory, simulation and experimental results, in order to interconnect theoretical knowledge and experimental approaches, which can reveal new scientific and technological directions in several fields, expanding the versatility to yield a variety of new complex materials with desirable applications and functions. Some of the challenges and opportunities in this field are also discussed, targeting the development of new emergent complex functional materials with tailored properties to solve problems related to renewable energy, health, and environmental sustainability. A more fundamental understanding of the physical and chemical properties of new emergent complex functional materials is essential to achieving more substantial progress in a number of technological fields. With this goal in mind, the editors invited acknowledged specialists to contribute chapters covering a broad range of disciplines.
Author: Tomas Ramirez Reina
Publisher: John Wiley & Sons
ISBN: 3527346392
Category : Technology & Engineering
Languages : en
Pages : 498
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Book Description
A comprehensive guide that offers a review of the current technologies that tackle CO2 emissions The race to reduce CO2 emissions continues to be an urgent global challenge. "Engineering Solutions for CO2 Conversion" offers a thorough guide to the most current technologies designed to mitigate CO2 emissions ranging from CO2 capture to CO2 utilization approaches. With contributions from an international panel representing a wide range of expertise, this book contains a multidisciplinary toolkit that covers the myriad aspects of CO2 conversion strategies. Comprehensive in scope, it explores the chemical, physical, engineering and economical facets of CO2 conversion. "Engineering Solutions for CO2 Conversion" explores a broad range of topics including linking CFD and process simulations, membranes technologies for efficient CO2 capture-conversion, biogas sweetening technologies, plasma-assisted conversion of CO2, and much more. This important resource: * Addresses a pressing concern of global environmental damage, caused by the greenhouse gases emissions from fossil fuels * Contains a review of the most current developments on the various aspects of CO2 capture and utilization strategies * Incldues information on chemical, physical, engineering and economical facets of CO2 capture and utilization * Offers in-depth insight into materials design, processing characterization, and computer modeling with respect to CO2 capture and conversion Written for catalytic chemists, electrochemists, process engineers, chemical engineers, chemists in industry, photochemists, environmental chemists, theoretical chemists, environmental officers, "Engineering Solutions for CO2 Conversion" provides the most current and expert information on the many aspects and challenges of CO2 conversion.
Author: Maarten Antoon Jan Campman
Publisher:
ISBN: 9789038600888
Category :
Languages : en
Pages : 131
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Book Description
Author: Jonathan Leon Snider
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Book Description
As human population and industrialization grows, so too do our global demands for fuels and chemicals. Increasing consumption of fossil fuels has led to rising CO2 levels in the atmosphere, a major challenge due to the role of CO2 as a significant greenhouse gas contributing to climate change. To address anthropogenic CO2 production, new processes to capture, sequester, and utilize carbon dioxide are needed. CO2 utilization in particular is an attractive approach as it also creates a value-added product. This utilization could take the form of direct CO2 hydrogenation or a two-step process whereby the CO2 is first converted to CO via the water-gas shift reaction. To enable these processes, the discovery and development of efficient catalysts that can selectively reduce CO and CO2 to high value, oxygenated products is necessary. Towards this goal, the investigation of new catalyst formulations is crucial. Furthermore, the characterization of these materials is necessary to understand the drivers of catalyst performance and predict future targets for study. In Chapter 3, we begin with an investigation into the design of Co-Cu catalysts for CO hydrogenation to higher alcohols. To improve control over particle properties, a liquid phase nanoparticle synthesis based on the polyol method was selected to synthesize Co2.5Cu particles, which were then supported onto a variety of metal oxide supports. The results show alloyed phases were obtained using the polyol method, resulting in selectivity towards higher alcohols, as high as 11.3% when supported on alumina. However, segregation of cobalt and the formation of cobalt carbide were observed in the catalysts after catalytic testing, which limit performance compared to the desired alloy phase. In Chapter 4, our focus shifts towards understanding the surface properties of a newly discovered Ni5Ga3 catalyst for CO2 hydrogenation to methanol. Results revealed that upon air exposure Ga migrates from the subsurface region to the surface of the nanoparticles forming a Ga-oxide shell surrounding a metallic core. Reduction of this shell results in a surface enrichment of Ga. By varying reduction temperatures, it was found that partial reductions gave low CO uptakes but high methanol activity, indicating a promotional effect of the oxide phase. In Chapter 5, the investigation into the role of metal oxides in methanol synthesis continues with a study of In-Pd catalysts. We present the promotional effect of Pd on In2O3 catalysts and investigate structure-performance relationships therein. Catalysts were synthesized with varying In:Pd ratios, and it was found that In2Pd/SiO2 showed the highest activity (5.1 umol MeOH/gInPd/sec) and selectivity toward methanol (61%). Based on microkinetic modeling, operando X-ray absorption spectroscopy and ex situ characterization, the active phase is proposed to be a bimetallic In-Pd particle with a Pd-rich core and a surface In2O3 phase. A non-precious metal containing In-Ni system was also developed and displayed similar composition-activity trends to the In-Pd system. Both palladium and nickel were found to form a bimetallic catalyst with enhanced methanol activity and selectivity relative to indium oxide. Overall, this dissertation presents catalyst syntheses, advanced characterizations, and catalytic hydrogenation experiments which led to fundamental insights into the activity and selectivity of heterogeneous, bimetallic catalysts for alcohols synthesis. This work provides key understanding towards the development of catalyst theory and materials for the hydrogenation of CO and CO2.
