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Investigation Of Active Site Structure And Formation On Boron Based Oxidative Dehydrogenation Catalysts
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Book Synopsis Investigation of Active Site Structure and Formation on Boron-based Oxidative Dehydrogenation Catalysts by : Melissa Cendejas
Download or read book Investigation of Active Site Structure and Formation on Boron-based Oxidative Dehydrogenation Catalysts written by Melissa Cendejas and published by . This book was released on 2021 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Light olefins such as propylene and ethylene are the two most important building blocks in the chemical industry, and their production is energetically costly. Oxidative dehydrogenation (ODH) of light alkanes has been studied as a lower energy alternative method to produce light olefins. Despite decades of research, there has yet to be a catalyst that is selective and productive enough for industrial implementation. Boron containing materials have recently been identified as highly selective catalysts for the ODH of light alkanes to olefins. These materials, such as hexagonal boron nitride (h-BN), exhibit higher propylene selectivity compared to the previous state-of-the-art supported vanadium oxide catalysts (90% propylene selectivity for h-BN vs. 70% for V/SiO2 at 4% propane conversion). Our group's previous work on these catalysts revealed that the reaction proceeds via a gas-phase radical mechanism, presumably initiated by the surface, and that dynamic boron oxy/hydroxy layer is responsible for catalytic activity. The dynamic nature of the active surface prevents the precise definition of an active site using ex situ techniques. In this work, I describe the use of controlled synthesis and detailed solid state NMR characterization to probe the requirements for active site formation on the catalyst surface. I also describe the first set of in situ/operando X-ray spectroscopy studies of propane ODH over hBN. Operando X-ray Raman spectroscopy is used to show the changes that occur to the catalyst on a bulk scale, while in situ near ambient pressure X-ray photoelectron spectroscopy reveals the near-surface of the catalyst during propane ODH. The X-ray spectroscopy measurements described set the foundation for future studies of the working catalyst.
Book Synopsis Mechanistic Insights on the Oxidative Dehydrogenation of Light Alkanes Catalyzed by Boron-based Catalysts by : Juan Mauricio Venegas
Download or read book Mechanistic Insights on the Oxidative Dehydrogenation of Light Alkanes Catalyzed by Boron-based Catalysts written by Juan Mauricio Venegas and published by . This book was released on 2019 with total page 120 pages. Available in PDF, EPUB and Kindle. Book excerpt: Light olefins such as ethylene and propylene form the foundation of the modern chemical industry, with yearly production volumes well into the hundreds of millions of metric tons. Currently, these light olefins are mainly produced via energy-intensive steam cracking. Alternatively, oxidative dehydrogenation (ODH) of light alkanes to produce olefins allows for lower operation temperatures and extended catalyst lifetimes, providing valuable process efficiencies. This route has led to significant research interest due to the wide availability of natural gas from shale deposits. Advances in this area have still not yielded catalysts that are sufficiently selective to olefins for industrial implementation, and ODH still remains a holy grail of selective alkane oxidation research. Research into selective heterogeneous catalysts for the ODH of propane has led to the extensive use of vanadium oxide-based catalysts, and studies on the surface mechanism involved have been used to improve the catalytic activity of the material. Despite decades of research, however, selectivity towards propylene has not proven satisfactory at industrially-relevant conversions. In this thesis, I will present the serendipitous discovery and subsequent development of hexagonal boron nitride (hBN) and other boron-containing catalysts as selective ODH catalysts. Specifically, I will illustrate the evolution of our understanding of the chemical origin of the reactivity of these materials, which until our initial discovery were deemed chemically inert. By combining reactivity studies with spectroscopic characterization highlighted a unique interaction between boron and oxiygen that differs from that of metal oxides. This methodical characterization of catalytic activity and structural changes of hBN during ODH prompted us to zero in on oxidized boron species, not hBN itself, as the true catalyst of alkane oxidation. In turn, this discovery led us to describe a whole class of B-containing materials that share (and often improve upon) the catalytic performance of hBN. At this point, we decided to step away from material studies and instead improve our understanding on how the catalytic performance of hBN is affected by reactor operating parameters. In particular, we investigated the role of heat and mass transfer on catalytic performance. Unexpectedly, we were once again surprised by hBN when various experimental results during these efforts suggested the significance of gas phase chemistry on ODH performance. For example, we observed that upon dilution of hBN with an inert thermal conductor (to mitigate hotspot formation), the observed reactivity scales with total bed volume rather than hBN mass. Up until these studies, we expected all reactivity to stem from oxidized boron species, but these may be only a part of a more complex surface-gas phase reaction network. The final portion of this thesis presents our latest efforts to understand the role of each reactant on surface and gas phase reaction pathways. Within this work, we incorporate water into our reaction feeds to assess its influence as a source of gas phase radical species to carry out propane activation. Indeed, we observe significant rate enhancements by addition of water. This reactivity enhancement likely involves influencing reactive species concentrations primarily in the gas phase and, to a lesser extent, altering the surface composition during ODH. Overall, this thesis expands our understanding of B-based materials as ODH catalysts and highlights the importance of considering gas phase radical chemistry in future process development.
Book Synopsis Synthesis and Investigation of Boron and Vanadium Based Catalysts for the Oxidative Dehydrogenation of Light Alkanes to Olefins by : Natalie Raquel Altvater
Download or read book Synthesis and Investigation of Boron and Vanadium Based Catalysts for the Oxidative Dehydrogenation of Light Alkanes to Olefins written by Natalie Raquel Altvater and published by . This book was released on 2023 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Light olefins like ethylene and propylene are important building blocks for the chemical industry. Production of these chemicals exceeds 100 million metric tons each year, and they are used in all areas of society including automotive, medical, textile, and food packaging. These light olefins are traditionally produced via steam cracking which is an energy intensive process. The increasing availability of natural gas in the present chemical industry has shifted the feedstock for refinery processes and impacted the production volume of certain olefins, particularly propylene. As a result, there is a growing need for on-purpose propylene production methods to meet the market demands. Oxidative dehydrogenation (ODH) of propane to propylene is one potential pathway for increasing propylene production. Propane ODH offers lower temperature operation and does not suffer from catalyst deactivation from coke. This process still suffers from over oxidation of products and does not achieve propylene yields required for industrial implementation. Propane ODH has been studied extensively for vanadium oxide catalysts and more recently for boron-based catalysts. Despite the wealth of literature on these ODH catalyst there are still several open questions on the catalyst structure and reaction mechanisms that continue to motivate research to improve the catalytic systems. The understanding on the mechanism and structural features of boron-based has been significantly developed in recent years. This work serves to build on this knowledge and improve current knowledge on structure activity relationships for this system. Vanadium oxide catalysts have been the center of propane ODH for much longer than boron, and while literature agrees generally on the surface mechanism description of this system, there are open questions on different pathways in the mechanism and their influence on performance. The goal of this work is to show how synthesis spectroscopy, reaction engineering, and computation work combine to further the understanding of boron and vanadium oxide catalyst for propane ODH.
Book Synopsis Nanostructured Catalysts by : Susannah L. Scott
Download or read book Nanostructured Catalysts written by Susannah L. Scott and published by Springer Science & Business Media. This book was released on 2008-04-06 with total page 341 pages. Available in PDF, EPUB and Kindle. Book excerpt: With the recent advent of nanotechnology, research and development in the area of nanostructured materials has gained unprecedented prominence. Novel materials with potentially exciting new applications are being discovered at a much higher rate than ever before. Innovative tools to fabricate, manipulate, characterize and evaluate such materials are being developed and expanded. To keep pace with this extremely rapid growth, it is necessary to take a breath from time to time, to critically assess the current knowledge and provide thoughts for future developments. This book represents one of these moments, as a number of prominent scientists in nanostructured materials join forces to provide insightful reviews of their areas of expertise, thus offering an overall picture of the state-- the art of the field. Nanostructured materials designate an increasing number of materials with designed shapes, surfaces, structures, pore systems, etc. Nanostructured materials with modified surfaces include those whose surfaces have been altered via such techniques as grafting and tethering of organic or organometallic species, or through various deposition procedures including electro, electroless and vapor deposition, or simple adsorption. These materials find important applications in catalysis, separation and environmental remediation. Materials with patterned surfaces, which are essential for the optoelectronics industry, constitute another important class of surface-modified nanostructured materials. Other materials are considered nanostructured because of their composition and internal organization.
Book Synopsis Fundamental Studies on the Structure of Surface Oxide Sites on Supported Oxidative Dehydrogenation Catalysts by : Alyssa Marie Love
Download or read book Fundamental Studies on the Structure of Surface Oxide Sites on Supported Oxidative Dehydrogenation Catalysts written by Alyssa Marie Love and published by . This book was released on 2018 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: The structure of metal oxide sites on supported metal oxide catalysts has a significant impact on the performance of the catalyst. For example, silica-supported vanadium oxide-a catalyst widely studied for the oxidative dehydrogenation of propane (ODHP) to propene-has a higher selectivity towards propene when the catalyst surface is comprised of primarily dispersed VOx surface species. Conversely, as the loading of vanadium oxide is increased beyond the monolayer coverage threshold, three-dimensional V2O5 particles begin to form which lower the catalyst selectivity towards propene (at higher propane conversions) in favor of COx combustion products. For this catalytic application and for other supported metal oxides, understanding the variables that maximize the dispersion of two-dimensional metal oxide species on a support surface is invaluable information to improve the preparation of these catalysts. This thesis describes the synthesis and detailed characterization of supported oxide catalysts for the oxidative dehydrogenation of catalysts. In this work, vapor-phase grafting techniques were used to investigate the chemical reactions that occur during the synthesis of silica-supported vanadium oxide ODH catalysts. By depositing the neat vanadium precursor, VO(OiPr)3, onto silica dehydrated at 700 degrees C (called V/SiO2(700)), the complexity of variables in the synthesis was significantly decreased (compared to incipient wetness). Key anchoring and restructuring reactions during the formation of vanadium oxide sites on silica were characterized with a combination of infrared (IR), Raman, solid-state nuclear magnetic resonance (NMR), and X-Ray absorption spectroscopic studies, in addition to thermogravimetric analysis-differential scanning calorimetry-mass spectrometry (TGA-DSC-MS), inductively coupled plasma (ICP) elemental analysis, etc. Afterwards, key synthesis variables (i.e., isopropanol solvent, H-bonded silanols and Na+ ions on the support surface) were incorporated into this grafting system to develop a more comprehensive model for the dispersion of vanadium oxide under wet impregnation conditions. Efforts to improve Raman sensitivity towards metal oxide surface sites with shell-isolated nanoparticle-enhanced Raman spectroscopy (SHINERS) are also addressed in this work. The methodology and characterization approach presented for the study of supported vanadium oxide catalysts was also applied to the study of promising new ODHP catalysts, including hexagonal boron nitride and silica-supported boron oxide catalysts.
Book Synopsis Development and Characterization of Oxyfunctionalized Boron Nitride Catalysts for the Oxidative Dehydrogenation of Light Alkanes to Olefins by : Theodore Agbi
Download or read book Development and Characterization of Oxyfunctionalized Boron Nitride Catalysts for the Oxidative Dehydrogenation of Light Alkanes to Olefins written by Theodore Agbi and published by . This book was released on 2022 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Light olefins like ethylene and propylene are platform chemicals integral to the chemical industry. Production of polymers, oxygenates, and other important chemical intermediates demand global production volumes that top 100 million metric tons per year. Production of these light olefins, traditionally through steam cracking, is one of the most energy intensive processes in petrochemical sector. Changing refinery feedstocks (i.e. increased availability of natural gas) have created both necessity and opportunity for 'On-Purpose' propylene technologies to meet propylene demands. The oxidative dehydrogenation of propane to propylene (ODHP) is an attractive alternative process to produce propylene. ODHP enables lower process temperatures and avoids coke deactivation of the catalyst, and has the potential to significantly ease energy, capital, and material intensities of industrial propylene production. To-date, metal oxide ODHP catalysts like vanadia-based catalysts-the previous state of the art ODHP catalyst-do not achieve competitive propylene yields to make them industrially viable. The pioneering work of our research group has identified BN-a material renowned for its chemical inertness-as a highly reactive, selective, and stable ODHP catalyst. Since this discovery, we have worked to understand the fundamental reaction mechanisms present and identify structure-performance relationships that may further develop this class of catalyst. To-date, we have developed extensive spectroscopic characterization capabilities to identify the oxyfunctionalized boron layer formed in situ which contains highly dynamic active species responsible for the high reactivity and selectivity observed. Understanding the activation of molecular O2 and functionality of the oxyfunctionalized layer has been a highly collaborative process requiring a myriad of complimentary spectroscopic and reaction studies to develop fundamental insights. As such, I will provide a comprehensive context of our evolving knowledge in this collaborative project that have since been published where possible and will focus mainly on the recent insights made in this work. The work presented in this dissertation characterizes and probes the reactivity of the highly dynamic oxyfunctionalized surface layer that has been correlated with the reactivity and selectivity observed on this catalyst. Herein, the coordination environment of B and extent of oxyfunctionalization were analyzed via X-ray Photoelectron Spectroscopy (XPS), X-ray Absorption Spectroscopy (XAS), and Attenuated Total Reflectance IR (ATR-IR) as a function of the reaction progress. Corresponding reaction studies show direct correlation between the development of tri-coordinated oxygenated B networks and the increasing reactivity and selectivity of the reaction during the catalyst's activation period. The significance of a set of reaction parameters was then examined to identify process levers conducive to oxyfunctionalization quantified by XPS. The acid-base activity of these surface tri-coordnated B networks in the oxyfunctionalized layer are examined via two prototypical reactions: (1) isopropanol decomposition and (2) formic acid decomposition. Catalytic reaction via flow through reactor and temperature programmed decomposition (TPD) studies using Diffuse Reflectance Infrared Fourier Transform IR spectroscopy (DRIFTs) and Mass Spectrometry (MS) are used to extract insights for the adsorption modes of alkoxides and formates their decomposition pathways. Observed surface reactions of isopropoxy intermediates under these conditions are used to understand possible surface reaction pathways available under ODHP conditions. The role of O2 in specific homogeneous pathways of the mixed hetero-homogeneous mechanism previously proposed by us and for supported boron oxide materials are examined. A simplified model for the surface-initiated radical oxidation chemistry pathways, was then used to probe a selectivity descriptor based on the different reactivities of propyl radicals. Using this knowledge, we design, and test model 3D printed BN based monoliths that optimize homogeneous reaction pathways. These catalysts are shown to be highly active and selective and stable for ~2.5wks. The results also suggest that oxygenates may be relevant products from homogeneous reactions. "The Boron Project," as we so lovingly called it, has seen several PhD students matriculate as we contributed diligently to uncovering the behavior of this material. The goal of this work is to highlight new avenues through which we can further understand surface reactivity, new tools through which we can probe gas phase radical chemistries, and new catalyst design approaches.
Book Synopsis Kinetics of Chemical Processes by : Michel Boudart
Download or read book Kinetics of Chemical Processes written by Michel Boudart and published by Elsevier. This book was released on 2014-05-16 with total page 263 pages. Available in PDF, EPUB and Kindle. Book excerpt: Kinetics of Chemical Processes details the concepts associated with the kinetic study of the chemical processes. The book is comprised of 10 chapters that present information relevant to applied research. The text first covers the elementary chemical kinetics of elementary steps, and then proceeds to discussing catalysis. The next chapter tackles simplified kinetics of sequences at the steady state. Chapter 5 deals with coupled sequences in reaction networks, while Chapter 6 talks about autocatalysis and inhibition. The seventh chapter describes the irreducible transport phenomena in chemical kinetics. The next two chapters discuss the correlations in homogenous kinetics and heterogeneous catalysis, respectively. The last chapter covers the analysis of reaction networks. The book will be of great use to students, researchers, and practitioners of scientific disciplines that deal with chemical reaction, particularly chemistry and chemical engineering.
Book Synopsis Discovery and Development of Heterogeneous Catalysts for the Oxidative Dehydrogenation of Alkanes by : Joseph Grant
Download or read book Discovery and Development of Heterogeneous Catalysts for the Oxidative Dehydrogenation of Alkanes written by Joseph Grant and published by . This book was released on 2018 with total page 108 pages. Available in PDF, EPUB and Kindle. Book excerpt: The recent surge in shale gas resources creates new opportunities to improve process efficiencies for the production of important chemical building blocks. Non-oxidative dehydrogenation of propane (PDH), the primary "on-purpose" propylene technology used worldwide today, has process inefficiencies that may be improved by co-feeding oxygen and propane to drive the oxidative dehydrogenation (ODH) of propane reaction. However, after decades of catalyst research for ODH of propane this reaction has yet to be commercialized due to the difficulty of controlling this partial oxidation to selectively yield propylene rather than the more-thermodynamically stable CO and CO2 (COx) products. This thesis explores the reactivity and properties of two very different classes of catalysts for the ODH of alkanes: 1) supported vanadia and 2) boron-containing catalysts. Supported vanadia catalysts, the most-studied catalyst for this transformation in the literature, show markedly higher selectivity to propylene when existing as dispersed two-dimensional metal oxide surface species. By introducing a small amount of Na+ to the surface of SiO2, the maximum two-dimensional surface density can be dramatically enhanced. This effect is proved using spectroscopic characterization, as well as the ODH of propane used as a probe reaction. Boron-containing compounds, especially boron nitride (BN) materials, were previously overlooked as catalysts for the ODH of alkanes, and rather deemed to be inert. On the contrary, these B-containing catalysts are now considered to be among the most-selective catalysts for the ODH of alkanes as a method to form their corresponding olefins. The rate of alkane consumption is dependent on oxygen adsorption to the catalyst surface, and shows second-order dependence in the concentration of the alkane. At these temperatures (400-500°C) oxygen adsorption to the B-containing catalyst only occurs when exposed to the ODH reaction (not only air or a combination of air and steam), and is verified with numerous spectroscopic techniques including X-ray Photoelectron Spectroscopy (XPS), and Attenuated Total Reflectance Infrared (ATR-IR). Recent work with X-ray Absorption Spectroscopy (XAS) and 11B MAS NMR dismisses the possibility that a potential B2O3 surface layer acts as the active site by revealing that B2O3 is not present on spent catalysts.
Book Synopsis Chemical Process Technology by : Jacob A. Moulijn
Download or read book Chemical Process Technology written by Jacob A. Moulijn and published by John Wiley & Sons. This book was released on 2013-03-21 with total page 691 pages. Available in PDF, EPUB and Kindle. Book excerpt: With a focus on actual industrial processes, e.g. the production of light alkenes, synthesis gas, fine chemicals, polyethene, it encourages the reader to think “out of the box” and invent and develop novel unit operations and processes. Reflecting today’s emphasis on sustainability, this edition contains new coverage of biomass as an alternative to fossil fuels, and process intensification. The second edition includes: New chapters on Process Intensification and Processes for the Conversion of Biomass Updated and expanded chapters throughout with 35% new material overall Text boxes containing case studies and examples from various different industries, e.g. synthesis loop designs, Sasol I Plant, Kaminsky catalysts, production of Ibuprofen, click chemistry, ammonia synthesis, fluid catalytic cracking Questions throughout to stimulate debate and keep students awake! Richly illustrated chapters with improved figures and flow diagrams Chemical Process Technology, Second Edition is a comprehensive introduction, linking the fundamental theory and concepts to the applied nature of the subject. It will be invaluable to students of chemical engineering, biotechnology and industrial chemistry, as well as practising chemical engineers. From reviews of the first edition: “The authors have blended process technology, chemistry and thermodynamics in an elegant manner... Overall this is a welcome addition to books on chemical technology.” – The Chemist “Impressively wide-ranging and comprehensive... an excellent textbook for students, with a combination of fundamental knowledge and technology.” – Chemistry in Britain (now Chemistry World)
Book Synopsis Development of Boron-based Catalysts for the Oxidation of Light Alkanes to Olefins by : William Peter McDermott
Download or read book Development of Boron-based Catalysts for the Oxidation of Light Alkanes to Olefins written by William Peter McDermott and published by . This book was released on 2021 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: The production of light olefins, such as ethylene and propylene, is a key pillar of the chemical industry as they can be transformed into oxygenates, polymers, and other specialty chemicals. Traditionally, these light olefins have been produced through the steam cracking of petroleum-derived feedstocks. In recent years, the wide availability of natural gas has made light olefin production from light alkanes economically advantageous. However, the current routes to light olefins from natural gas are inefficient, with both steam cracking and non-oxidative alkane dehydrogenation suffering from high reaction temperatures and coke deposition. This has driven academic and industrial research into oxidative alternatives such as the oxidative dehydrogenation (ODH) of alkanes to olefins. Catalysts such as supported vanadium oxides have been studied for the ODH of propane where kinetic and mechanistic studies have led to improvements in this system. However, despite decades of research, work in this area has still not delivered a catalyst with sufficient light olefin selectivity for industrial use.This thesis presents the discovery and development of hexagonal boron nitride (hBN) as a selective catalyst for the ODH of propane and other light alkanes. This material offers superior light olefin selectivity and reduced CO and CO2 selectivity when compared to previously studied metal oxide catalysts. Through kinetic insights, I will show that hBN activates oxygen and alkanes in a manner that is fundamentally different than metal oxides. Spectroscopic characterization shows that the surface of hBN oxidizes to form a BOx layer after exposure to reaction conditions. It is this discovery that led to the establishing of a new class of selective ODH catalysts: elemental boron and inorganic borides. The investigation of the reactivity and structure of these materials offers additional information concerning the origin of activity of boron-containing catalysts. Alongside evaluating the origin of reactivity of these promising ODH catalysts, attention was given to the oxidative cracking of hydrocarbons. Within our initial studies of hBN, we had observed that low PO2 conditions enhanced the selectivity to light olefins. However, these conditions also lead to low alkane conversions. Using n-butane as a model substrate, we optimized the reaction conditions to enhance conversion and light olefin selectivity. Here, we demonstrate that this system is one of the most selective for oxidative cracking. This study also offers further insight into the role of O2 and provides evidence for a surface-initiated gas phase radical mechanism. This thesis culminates with the latest findings in probing the gas phase reactivity of boron-based ODH catalysts. We observe enhanced rates with the dilution of catalyst, providing further evidence for a gas phase mechanism. Alongside these reactivity studies, spectroscopic insights reveal the role of agglomerated BOx formation in ODH reactivity. Also presented here is an outlook on the future study of boron-based catalysts for alkane oxidations and the targeted studies required for continued development of this promising system.
Book Synopsis Insights Into Active Site Structures for Pd-based Bimetallic Heterogeneous Catalysts by : Madelyn Rose Baltus Ball
Download or read book Insights Into Active Site Structures for Pd-based Bimetallic Heterogeneous Catalysts written by Madelyn Rose Baltus Ball and published by . This book was released on 2019 with total page 136 pages. Available in PDF, EPUB and Kindle. Book excerpt: Catalytic reactions play a large role in the production of energy and products used in our modern society. In order to improve the efficiency of existing processes and make the conversion of new feedstocks, such as biomass and natural gas, possible, there exists the need for improved catalytic materials. Many active catalysts have complex active sites containing multiple components; therefore, fundamental understanding of active sites and structure-performance relationships is needed to rationally design new catalysts. The work in this dissertation is focused on catalytic synthesis of well-controlled bimetallic catalysts in order to develop structure-activity and structure-selectivity relations for different chemical transformations. A controlled surface reaction synthesis approach is used to deposit Pd onto Au, Ag, or Cu parent catalysts. These Pd bimetallic catalysts are then studied for reactions where selectivity is a main challenge, and the selective Pd structure is identified. First, AuPd/TiO2 catalysts are studied for the gas phase amination of 1-hexanol using ammonia. It was determined that there are no monometallic Pd structures on the catalysts. The Pd atoms are well diluted in the Au nanoparticles at low loadings and as the Pd loading increases, more contiguous Pd sites are formed. From reactivity studies, it is determined that both the Au and Pd contribute to the overall hexanol conversion, however the activity in enhanced for the bimetallic catalysts compared to the monometallic catalysts. This rate improvement is attributed to a geometric effect where surface intermediates are not stabilized by hydrogen bonding to adsorbed ammonia in close proximity. Furthermore, the selectivity to primary amines is increased as the loading of Pd increases in the AuPd catalysts, while lower Pd loadings favor more substituted products. The selectivity trends are hypothesized to be related to both geometric and electronic effects present in the AuPd catalyst system. Next, AgPd catalysts were studied for the hydrodechlorination of 1,2-dichloroethane. The role of the support in the formation of well-controlled bimetallic nanoparticles was investigated and it was determined that well-mixed AgPd particles were formed on a TiO2 support, while some monometallic Pd particles were also formed on C and SiO2 supports. Again, using chemisorption, XAS, and CO-FTIR, it was determined that isolated Pd atoms within the Ag nanoparticles are formed on the TiO2 support at low loadings. On the SiO2 supported catalysts, contiguous Pd species are formed. The isolated Pd species are highly selective to ethylene while the contiguous Pd species are selective to the undesired ethane. Thus, the support was determined to play an important role in tuning the AgPd structure and the resulting selectivity for hydrodechlorination. The rate of 1,2-dichloroethane conversion was determined to be related to the selectivity, with the ethylene selective catalysts exhibiting the highest turnover frequencies. Finally, AgPd and CuPd catalysts were investigated for the selective hydrogenation of acetylene. Both TiO2 and SiO2 supported catalysts were studied, and it was determined by EDS analysis that the CuPd nanoparticle composition distribution was more uniform on the SiO2 support than on the TiO2 support. IR spectra of the catalyst surface after being exposed to reaction conditions indicate the presence of numerous spectator species and it is determined that there are less sites covered by spectators for the bimetallic catalysts compared to a monometallic Pd catalyst. On the TiO2 support, the bimetallic catalysts exhibit the highest rates per gram of Pd and high ethylene selectivites above 99%. The monometallic catalysts are less than 95% selective to ethane, indicating that the alloy formation improves the ethylene selectivity; the enhanced selectivity is attributed to electronic effects in the bimetallic nanoparticles. This work enabled the development of detailed active site hypotheses for different Pd based bimetallic catalysts and provided insights into the desired structures to inform rational catalyst design. The controlled surface reaction synthesis approach and general characterization methodology can be applied to a broad range of catalyst and reaction systems to improve chemical transformations for improved production of chemicals and fuels for modern society.
Book Synopsis NMR Techniques in Catalysis by : Alexis T. Bell
Download or read book NMR Techniques in Catalysis written by Alexis T. Bell and published by CRC Press. This book was released on 1994-02-25 with total page 450 pages. Available in PDF, EPUB and Kindle. Book excerpt: This volume provides an overview of the applications of modern solid-state nuclear magnetic resonance (NMR) techniques to the study of catalysts, catalytic processes, species adsorbed on catalysts and systems relevant to heterogeneous catalysis. It characterizes the structure of catalytic materials and surfaces.
Book Synopsis Strong Metal-support Interactions by : R. T. K. Baker
Download or read book Strong Metal-support Interactions written by R. T. K. Baker and published by . This book was released on 1986 with total page 258 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Boron Nitride Catalyst for Partial Oxidation of Hydrocarbons by : Leonardo David Garro Mena
Download or read book Boron Nitride Catalyst for Partial Oxidation of Hydrocarbons written by Leonardo David Garro Mena and published by . This book was released on 2021 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: The catalytic activity of hexagonal boron nitride (hBN) is not yet well understood but it seems to be related to hBN hydroxylated sites. A good understanding of those sites and how they are produced is a key step to reveal the true nature of hBN catalytic activity. Here, we report a set of thermal treatments to produce a diversity of hydroxylated sites, as well as a method to remove the boric acid produced by hBN decomposition. We found that some of the boric acid dehydrates on the surface of hBN to produce a borated hBN (hBNO) characterized by an FTIR peak at 1090 cm−1 and an XRD shift due to the variation in the planar distance. When characterizing the thermally treated hBN, the storage of the sample changed the borate's hydration degree and modified both the XRD pattern and the FTIR spectrum. When stored in a humid environment, boric acid peaks are visible; but when stored in a dry place they are absent. The methods established here are a solid basis for the manufacture, purification and characterization of hBN by thermal treatments, showing how the process can be designed to generate various functional groups on its surface. The thermally treated hBN was also evaluated as a support for Pt during partial oxidation of methane (POM) for the production of syngas. POM is a promising alternative to steam reforming of methane (SRM). POM is an exothermic reaction that requires lower temperatures and less energy than the endothermic SRM. The weaker interaction between Pt and hBN leads to a higher reducibility of Pt, which makes it more active than, for example, Pt/Al2O3. In this work we synthesized several Pt catalysts on thermally treated hBN and tested its activity for POM. We discovered that Pt/hBN is more active than Pt/Al2O3. The most active catalysts are those where boric acid is present on the surface of hBN before the Pt impregnation. The catalysts prepared this way feature Pt particles on a borated hBN, which makes the Pt-support interaction even weaker, increasing its catalytic activity. Finally, the oxidative dehydrogenation (ODH) of ethane was evaluated on thermally treated hBN. The catalytic activity of hBN using the ODH reaction was evaluated on hBN heated with an O2/C2H6/N2 stream (activated hBN) vs a 100% N2 stream (non-activated hBN: hBN*). hBN* catalyzed the catalytic dehydrogenation (CDH) of ethane when the temperature was higher than 160 °C. At 160 °C or below, hBN* was activated and the ODH reaction took place. The catalytic activity of hBN for the ODH reaction increased significantly when the thermal treatment was followed by a sonication step and a separation by centrifugation (labeled as hBNO). This sample showed a borated layer characterized by an FTIR vibration at =1190 cm−1. We concluded that there are several active sites on hBN catalyzing the ODH reaction, all of them involve oxygen and requires activation or preparation of the catalyst. Future work is needed to explore the nature of these active sites for the design of hBN based catalysts.
Download or read book Catalysis written by James Spivey and published by Royal Society of Chemistry. This book was released on 2020-02-05 with total page 246 pages. Available in PDF, EPUB and Kindle. Book excerpt: Catalysts are required for a variety of applications and researchers are increasingly challenged to find cost effective and environmentally benign catalysts to use. This volume looks at modern approaches to catalysis and reviews the extensive literature. Chapters highlight reactions active under oxidative coupling of methane conditions and how they are interlinked, heterogeneous nickel catalysts and their use in laboratory and industry, the reaction mechanism of heterogeneous catalysis with the surface science probe, the concepts of electroless deposition (ED) methods for preparation of true bimetallic catalysts, the general subject of metal-support interactions occurring over ruthenium-based catalysts and benzene as the target volatile organic compound (VOC). Appealing broadly to researchers in academia and industry, these illustrative chapters bridge the gap from academic studies in the laboratory to practical applications in industry not only for catalysis field but also for environmental protection. The book will be of great benefit to any researcher wanting a succinct reference on developments in this area now and looking to the future.
Book Synopsis Springer Handbook of Advanced Catalyst Characterization by : Israel E. Wachs
Download or read book Springer Handbook of Advanced Catalyst Characterization written by Israel E. Wachs and published by Springer Nature. This book was released on 2023-06-12 with total page 1109 pages. Available in PDF, EPUB and Kindle. Book excerpt: Co-edited by world-renowned scientists in the field of catalysis, this book contains the cutting-edge in situ and operando spectroscopy characterization techniques operating under reaction conditions to determine a materials’ bulk, surface, and solution complex and their applications in the field of catalysis with emphasis on solid catalysts in powder form since such catalyst are relevant for industrial applications. The handbook covers from widely-used to cutting-edge techniques. The handbook is written for a broad audience of students and professionals who want to pursue the full capabilities available by the current state-of-the-art in characterization to fully understand how their catalysts really operate and guide the rational design of advanced catalysts. Individuals involved in catalysis research will be interested in this handbook because it contains a catalogue of cutting-edge methods employed in characterization of catalysts. These techniques find wide use in applications such as petroleum refining, chemical manufacture, natural gas conversion, pollution control, transportation, power generation, pharmaceuticals and food processing. fdsfds
Book Synopsis Sustainable Catalytic Processes by : Basudeb Saha
Download or read book Sustainable Catalytic Processes written by Basudeb Saha and published by Newnes. This book was released on 2015-06-11 with total page 219 pages. Available in PDF, EPUB and Kindle. Book excerpt: The development of catalysts is the most sophisticated art in chemical sciences. It can be read like a story book when the critical scientific contents are presented in a chronological manner with short and simple sentences. This book will meets these criteria. To address the sustainability issues of existing chemical manufacturing processes or producing new chemicals, researchers are developing alternate catalysts to eliminate toxic chemicals use and by-products formation. Sustainable Catalytic Processes presents critical discussions of the progress of such catalytic development. This book of contemporary research results in sustainable catalysis area will benefit scientists in both industries and academia, and students to learn recent catalysts/process development. Reports the most recent developments in catalysis with a focus on environmentally friendly commercial processes, such as waste water treatment, alternate energy, etc Bridges the theory, necessary for the development of environmentally friendly processes, and their implementation through pilot plant and large scale Contains mainly laboratory scale data and encourages industrial scientists to test these processes on a pilot scale Includes work examples featuring the development of the new catalysts/processes using bio-renewable feedstock satisfactorily addressing environmental concerns Includes one chapter demonstrating real industrial examples motivating the industrial and academic researchers to pursue similar research
