Download or read book In Situ Polarization Modulation Infrared Reflection Absorption Spectroscopic and Kinetic Investigations of Heterogeneous Catalytic Reactions written by Yun Cai and published by . This book was released on 2010 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: A molecular-level understanding of a heterogeneous catalytic reaction is the key goal of heterogeneous catalysis. A surface science approach enables the realization of this goal. However, the working conditions (ultrahigh vacuum (UHV) conditions) of traditional surface science techniques restrict the investigations of heterogeneous catalysis system under industrial working conditions (atmospheric pressures). Polarization Modulation Infrared Reflection-Absorption Spectroscopy (PM-IRAS) can be operated in both UHV and atmospheric pressure conditions with a wide temperature span while providing high resolution (4 cm-1 is used in this dissertation) spectra. In this dissertation, PM-IRAS has been employed as a major technique to: 1) obtain both electronic and chemical information of catalysts from UHV to elevated pressure conditions; 2) explore reaction mechanisms by in situ monitoring surface species with concurrent kinetic measurements. In this dissertation, NO adsorption and dissociation on Rh(111) have been studied. Our PM-IRAS spectra show a transition of NO adsorption on three-fold hollow sites to atop sites occurs at low temperatures (

Download or read book In situ Characterization of Heterogeneous Catalysts written by José A. Rodriguez and published by John Wiley & Sons. This book was released on 2013-06-10 with total page 500 pages. Available in PDF, EPUB and Kindle. Book excerpt: HELPS RESEARCHERS DEVELOP NEW CATALYSTS FOR SUSTAINABLE FUEL AND CHEMICAL PRODUCTION Reviewing the latest developments in the field, this book explores the in-situ characterization of heterogeneous catalysts, enabling readers to take full advantage of the sophisticated techniques used to study heterogeneous catalysts and reaction mechanisms. In using these techniques, readers can learn to improve the selectivity and the performance of catalysts and how to prepare catalysts as efficiently as possible, with minimum waste. In-situ Characterization of Heterogeneous Catalysts features contributions from leading experts in the field of catalysis. It begins with an introduction to the fundamentals and then covers: Characterization of electronic and structural properties of catalysts using X-ray absorption fine structure spectroscopy Techniques for structural characterization based on X-ray diffraction, neutron scattering, and pair distribution function analysis Microscopy and morphological studies Techniques for studying the interaction of adsorbates with catalyst surfaces, including infrared spectroscopy, Raman spectroscopy, EPR, and moderate pressure XPS Integration of techniques that provide information on the structural properties of catalysts with techniques that facilitate the study of surface reactions Throughout the book, detailed examples illustrate how techniques for studying catalysts and reaction mechanisms can be applied to solve a broad range of problems in heterogeneous catalysis. Detailed figures help readers better understand how and why the techniques discussed in the book work. At the end of each chapter, an extensive set of references leads to the primary literature in the field. By explaining step by step modern techniques for the in-situ characterization of heterogeneous catalysts, this book enables chemical scientists and engineers to better understand catalyst behavior and design new catalysts for green, sustainable fuel and chemical production.

Download or read book Unraveling Mechanisms and Quantifying Active Sites by Using In situ and Ex situ Infrared Spectroscopy written by Shao-Chun Wang (Ph.D.) and published by . This book was released on 2022 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: The molecular-level understanding of surface sites and reaction mechanisms is key for the development of the field of heterogeneous catalysis. Infrared spectroscopy, studying molecular vibrations, is widely used to investigate the structures of surface-bound species in heterogeneous catalysts. Heterogeneous catalytic reactions proceed via adsorption of the reagent(s), surface reaction, and desorption of the product(s), leading to complex in-situ or operando IR spectra. However, the information of active species is usually concealed by spectator species which do not participate in the catalytic cycle. Modulation excitation spectroscopy serves as a tool to increase the signal-to-noise level and to differentiate between the active species and spectator species during a catalytic reaction. In Chapter 2, we report on the use of diffuse reflectance FT-IR spectroscopy (DRIFTS) with a modulation excitation (ME) approach followed by mass spectrometry (MS) to investigate the reaction of ethanol to n-butanol over hydroxyapatite (HAP). The approach allows for a vibrational characterization of the active surface species and the formulation of a consistent mechanism. Based on our experimental observations, Ca2+/OH- can be put forward as the main active site for the aldol condensation. POH/OH- acid-base pair is proposed as the active site for the Meerwein-Ponndorf-Verley (MPV) direct hydrogen transfer for the n-butanol formation.In Chapter 3, we describe the use of NO as a probe molecule in low-temperature IR spectroscopy to identify and quantify copper species in the state-of-the-art commercial NOx abatement catalyst, Cu ion-exchanged chabazite zeolite. While bulk analysis can reveal the total concentration of copper in the catalyst, the amount of ion-exchanged copper is more difficult to determine due to the appearance of non-exchanged Cu species, CuOx. Molecules such as carbon monoxide (CO) and nitric oxide (NO) are routinely used as a probe to investigate the copper speciation in order to draw structure-activity correlations. However, NO is easy to decompose and reacts with copper species at ambient temperature, causing complexity in IR spectra. Here, we develop NO adsorption IR spectroscopy at cryogenic conditions to avoid the undesired reactions. The observed IR peaks for Cu+(NO)2 and Cu2+(NO) species can be used to quantify the amount of exchanged copper species in a broad range of samples, including a commercial wash-coated honeycomb. Calibration curves for Cu+(NO)2 and Cu2+(NO) are determined for copper loadings up to 3.99 wt% with silica to alumina ratio of 16-22 and quantitative agreement with complementary hydrogen temperature-programmed reduction (H2-TPR) results is established. Our methodology allows us to identify different Cu species in Cu-CHA, such as Z2Cu(II), Z1Cu(II)OH and Cu dimers, based on their distinct IR signatures. In addition, the perturbed T-O-T framework vibration - characterized at 400 oC - can also be used as a complementary method to quantify Z2Cu(II) species. This work demonstrates that cryogenic NO-IR is a facile technique to identify and quantify the exchanged copper species in Cu-CHA to accelerate catalyst development. In chapter 4, we extend the NO-IR method to characterize the ion-exchanged species in Cu-ZSM-5 and Fe-CHA. The adsorbed NO shows distinct IR characteristics for exchanged copper species at 1914 cm-1 and the calibration curve for Cu2+ species for estimating high Cu-loading Cu-ZSM-5 is determined. In the case of Fe-CHA, the NO-IR is not efficient due to the formation of NO monomer and trimer on copper species, causing complexity in the IR spectra. Carbon monoxide (CO) is then applied as an alternative probe molecule. The results of CO-IR for Fe-CHA showed more defined IR features for Fe2+(CO) than in NO-IR. With this toolbox in hand, the calibration curve for the concentration of Fe2+ in Fe-CHA by CO-IR is then established. Perspectives for future research are outlined in Chapter 5, the preliminary results for a Cu-Ga binary catalyst for methanol production from CO2 hydrogenation was tested by using the DRIFTS cell with ambient pressure. However, due to thermodynamic limitation, the reaction favors reverse water gas shift under ambient pressure. The newly designed operando DRIFTS cell allows to minimize the exchange time of concentration modulation and have the capability of holding at high pressure (> 25 bar) and high temperature (> 250 oC) which is suitable for investigating the heterogeneous catalysts for CO2 hydrogenation. With the well-establish tool, we will be able to investigate surface-bound species and reaction mechanisms under working conditions by IR spectroscopy. Not only can gas phase catalytic reactions be studied by DRIFTS, but heterogeneous catalytic reactions in liquid phase can also be investigated by attenuation total reflection IR spectroscopy (ATR-IR). Competitive adsorption with reactants and solvents is especially important in the case of (micro-) porous catalysts where the composition inside the pores can be very different from the bulk due to size exclusion and confinement effects. ATR-IR with the ME approach can shed light on mechanistic insights for liquid phase reactions. Lastly, with the success of low temperature NO and CO-IR method development, characterizing different metal ion-exchanged zeolites for various applications such as methane to methanol, syngas to dimethyl ether, and NOx abatement is crucial for structure-reactivity correlation. Ultimately, low temperature NO and CO-IR can be established as facile techniques to identify and quantify metal ion species located in different types of zeolites.

Download or read book In situ Spectroscopy in Heterogeneous Catalysis written by James F. Haw and published by Wiley-VCH Verlag GmbH. This book was released on 2002 with total page 296 pages. Available in PDF, EPUB and Kindle. Book excerpt: "Not using in-situ methods to examine catalytic processes is like studying a life with access only to the prenatal and postmortem states." This quote from the world renowned specialist in the field of in situ methods, Gabor A. Somorjai, clearly emphasizes the importance of these techniques in understanding heterogeneous catalysis - a type of chemical reaction used nowadays for most chemically produced supplies and fuels. Yet the fundamental mechanisms are often still not completely understood. Many of the leading scientists in the field have contributed to this book which provides an overview of the most varied spectroscopic and related methods for studying catalytic structures and their functions during a chemical reaction. While primarily written for users of these methods, this is also a valuable aid to interpreting the phenomena observed. Indispensable for everyone working in the field.

Download or read book Design and Construction of a Polarization Modulated Infrared Reflection Absorption Spectrometer and Validation with Carbon Monoxide Adsorption on a Platinum 100 Surface written by and published by . This book was released on 2009 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: A polarization modulated infrared reflection absorption spectroscopy (PM-IRRAS) instrument was designed, constructed, and validated with CO adsorption on a Pt(100) surface. The instrument is attached to a reaction chamber which can accommodate pressures from 1*10 -9 Torr up to 760 Torr, to allow the study of model catalysts under a wide range of pressures, to cross the 'pressure gap' between most surface science methods and more common catalytic conditions. The system works as designed, with a signal to noise ratio slightly lower than the previous IRRAS system. It allows for studies at the same UHV conditions as previous literature, as well as conducting studies of the same model catalyst under significantly higher pressures. The Pt(100)/CO studies agree with previous literature at low pressures, and find no significant change at higher pressures. Increased pressure leads to a higher surface concentration, determined from a blue shift in the location of the CO atop peak from 2080 cm -1 to 2090 cm -1, but no new bands were observed.

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

Download or read book Nanoalloys written by Damien Alloyeau and published by Springer Science & Business Media. This book was released on 2012-07-13 with total page 415 pages. Available in PDF, EPUB and Kindle. Book excerpt: Bimetallic nanoparticles, also called nanoalloys, are at the heart of nanoscience because of their ability to tune together composition and size for specific purposes. By approaching both their physical and chemical properties, Nanoalloys: Synthesis, Structure & Properties provides a comprehensive reference to this research field in nanoscience by addressing the subject from both experimental and theoretical points of view, providing chapters across three main topics: Growth and structural properties Thermodynamics and electronic structure of nanoalloys Magnetic, optic and catalytic properties The growth and elaboration processes which are the necessary and crucial part of any experimental approach are detailed in the first chapter. Three chapters are focused on the widely used characterization techniques sensitive to both the structural arrangements and chemistry of nanoalloys. The electronic structure of nanoalloys is described as a guide of useful concepts and theoretical tools. Chapters covering thermodynamics begin with bulk alloys, going to nanoalloys via surfaces in order to describe chemical order/disorder, segregation and phase transitions in reduced dimension. Finally, the optical, magnetic and catalytic properties are discussed by focusing on nanoparticles formed with one element to track the modifications which occur when forming nanoalloys. The range and detail of Nanoalloys: Synthesis, Structure & Properties makes it an ideal resource for postgraduates and researchers working in the field of nanoscience looking to expand and support their knowledge of nanoalloys.

Download or read book Polarization Modulation Infrared Reflection Absorption Spectroscopy on Pd Model Catalysts at Elevated Pressure written by Marta Borasio and published by . This book was released on 2006 with total page 148 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Development of Combined Operando Diagnostics written by Lisa Rämisch and published by . This book was released on 2024 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: With the aim to bridge the pressure gap between traditional surface science and industrial applications, heterogeneous catalytic reactions on model catalysts are increasingly studied at near-ambient pressures. Under those conditions, the gas phase has been shown to play an important role during the interaction at the gas-surface interface making it complex to study. This complexity can be captured by simultaneously measuring different properties of the gas-surface interaction operando while the reaction takes place. Since each diagnostic tool offers unique information, combining them provides a fuller understanding of the reaction. This thesis presents a combination of three laser- and optical-based operando techniques that have been combined in a versatile in-house setup. We have shown that planar laser-induced fluorescence (PLIF), two dimensional-surface optical reflectance (2D-SOR) and polarization modulation-infrared reflection absorption spectroscopy (PM-IRRAS) can be combined, either simultaneously or in various configurations, to study CO oxidation on different Pd-based model catalysts. Thereby, chemical and structural information about the surface and chemical information about the gas phase can be obtained in space and temporally resolved. Moreover, some of the in-house optical techniques are combined with synchrotron-based techniques to extract more chemical and structural information than can be obtained from one measurement. This is demonstrated with simultaneous measurements combining PM-IRRAS and ambient pressure X-ray photoelectron spectroscopy (AP-XPS) for different gas-phase catalysis reactions and 2D-SOR with High Energy Surface X-ray Diffraction (HESXRD) for electrochemical studies.

Download or read book Simultaneous i in Situ i Monitoring of Surface and Gas Species and Surface Properties by Modulation Excitation Polarization modulation Infrared Reflection absorption Spectroscopy CO Oxidation Over Pt Film written by and published by . This book was released on with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Encyclopedia of Interfacial Chemistry written by and published by Elsevier. This book was released on 2018-03-29 with total page 5276 pages. Available in PDF, EPUB and Kindle. Book excerpt: Encyclopedia of Interfacial Chemistry: Surface Science and Electrochemistry, Seven Volume Set summarizes current, fundamental knowledge of interfacial chemistry, bringing readers the latest developments in the field. As the chemical and physical properties and processes at solid and liquid interfaces are the scientific basis of so many technologies which enhance our lives and create new opportunities, its important to highlight how these technologies enable the design and optimization of functional materials for heterogeneous and electro-catalysts in food production, pollution control, energy conversion and storage, medical applications requiring biocompatibility, drug delivery, and more. This book provides an interdisciplinary view that lies at the intersection of these fields. Presents fundamental knowledge of interfacial chemistry, surface science and electrochemistry and provides cutting-edge research from academics and practitioners across various fields and global regions

Download or read book Spectroscopic Signatures of Pressurized Carbon Dioxide in Diffuse Reflectance Infrared Spectroscopy of Heterogeneous Catalysts written by Samuel M. Fehr and published by . This book was released on 2020 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Abstract: Using diffuse reflectance infrared Fourier transform (DRIFT) spectroscopy to study surface species of reaction intermediates on heterogeneous catalysts requires particular precautions, when assigning IR bands to intermediates apparently resulting from the reaction of H2, CO, and CO2. In accordance with earlier work, it is shown that in the investigation of the heterogeneous methanol synthesis, several gas phase bands of CO2 were misassigned in previous studies as adsorbates on the catalyst surface. Thus, several combination bands and overtones of CO2 in the 2200–750 cm−1 range – notably those at 2130, 2112, 2107, 2094, 2077, ∼2056, 1933, ∼1920, ∼1079, ∼1050, ∼973, and ∼948 cm−1 – were already misinterpreted as adsorbates/intermediates. Some of these bands exhibit similar (low) intensities as surface species and are in the range of typical adsorbed CO or methoxy/methanol vibrations. Higher pressures and temperatures, which are necessary to study industrial catalysts by in situ IR spectroscopy, even amplify this effect. In addition, due to a Fermi resonance at a CO2 partial pressure above ∼10 bar, two further bands appear at 1388 and 1285 cm−1. This is also within the range typically associated with surface adsorbates. In order to avoid misassignments of IR bands for in situ or operando DRIFT spectroscopy, those occurring at CO2 pressures up to 30 bar in the widely used Praying Mantis TM High Temperature Reaction Chamber are presented here and assigned to their origin as combination bands and overtones of gaseous CO2

Download or read book Development of Infrared Spectroscopy Techniques for Monitoring Heterogeneous Catalytic Systems Under in Situ and Operando Conditions written by Cecilia Mondelli and published by . This book was released on 2007 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book In Situ Studies of Promoted Catalytic Surfaces and Redox Active Mineral Surfaces written by Alexander David Gordon and published by . This book was released on 2011 with total page 193 pages. Available in PDF, EPUB and Kindle. Book excerpt: In this dissertation the in situ technique, attenuated total reflection-Fourier transform infrared spectroscopy, will be utilized to probe reaction chemistry on two sets of surfaces; the first, a silicon-copper alloy surface where copper acts as a catalyst in the synthesis of methylchlorosilanes, and the second, a redox active iron-sulfur surface. Spectroscopic information obtained in situ will be combined with kinetic batch reaction results to elucidate details of the reaction mechanism that gives information regarding product formation in real time under real experimental conditions, without the need for modifying the experimental conditions to fit the analysis as is the case in traditional surface science techniques.

Download or read book In Situ Infared i e Infrared Studies of Catalytic Partial Oxidation written by Chundi Cao and published by . This book was released on 2008 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Catalytic partial oxidation (CPO) has received considerable interest recently both as a way to utilize remote natural gas resources and to provide H[subscript]2 for a fuel cell. Studies on the reactions at lower temperatures and transient conditions were performed, which can provide insights on the mechanism of CPO at high reactions, particularly on the role of the chemical and physical state of the noble metal catalyst. In this work, ignition of methane CPO on Pt/Al[subscript]2O[subscript]3 and Rh/Al[subscript]2O[subscript]3 catalysts and methanol CPO on Pt/Al[subscript]2O[subscript]3 catalysts were studied using in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS). The ignition mechanism study of CH4 on Pt/Al[subscript]2O[subscript]3 showed that oxygen mainly covers the surface until ignition. Competition between the two reactants is assumed. The heat of adsorption of oxygen is a key factor for ignition of the methane partial oxidation reaction on Pt/Al[subscript]2O[subscript]3. The ignition mechanism on Rh/Al[subscript]2O[subscript]3 was found to be different from Pt/Al[subscript]2O[subscript]3. The oxidation state of the catalyst changed significantly as the temperature was raised towards the ignition. An oxidized rhodium state, Rh[superscript]n+, progressively formed as the temperature was increased while Rh[superscript]0 decreased. In addition, a greater amount of Rh[supercript]n+ was found when the oxygen concentration in the feed was higher. From these results, it is hypothesized that ignition of methane CPO on Rh/Al[subscript]2O[subscript]3 is related to the accumulation of the Rh[superscript]n+ state. Dissociation adsorption of methanol occurs on both Al2O3 and Pt/Al[subscript]2O[subscript]3. It is suggested that formate was one of the important intermediates in the reaction pathway. Oxygen species play a key role in the formation of formate on the catalysts, and it also affects the product composition. Formate mainly decomposed into CO, which is the dominant source for CO[subscript]2 production in the reactions at higher temperatures.

Download or read book Adsorption and Reactions of COx and NOx Molecules on Heterogeneous Catalysts Reactivity and in Situ FTIR Spectroscopy Studies written by Jian Zheng and published by . This book was released on 2014 with total page 120 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book In situ Characterization of Heterogeneous Catalysts written by José A. Rodriguez and published by John Wiley & Sons. This book was released on 2013-04-17 with total page 488 pages. Available in PDF, EPUB and Kindle. Book excerpt: Helps researchers develop new catalysts for sustainable fueland chemical production Reviewing the latest developments in the field, this bookexplores the in-situ characterization of heterogeneous catalysts,enabling readers to take full advantage of the sophisticatedtechniques used to study heterogeneous catalysts and reactionmechanisms. In using these techniques, readers can learn to improvethe selectivity and the performance of catalysts and how to preparecatalysts as efficiently as possible, with minimum waste. In-situ Characterization of Heterogeneous Catalysts featurescontributions from leading experts in the field of catalysis. Itbegins with an introduction to the fundamentals and thencovers: Characterization of electronic and structural properties ofcatalysts using X-ray absorption fine structure spectroscopy Techniques for structural characterization based on X-raydiffraction, neutron scattering, and pair distribution functionanalysis Microscopy and morphological studies Techniques for studying the interaction of adsorbates withcatalyst surfaces, including infrared spectroscopy, Ramanspectroscopy, EPR, and moderate pressure XPS Integration of techniques that provide information on thestructural properties of catalysts with techniques that facilitatethe study of surface reactions Throughout the book, detailed examples illustrate how techniquesfor studying catalysts and reaction mechanisms can be applied tosolve a broad range of problems in heterogeneous catalysis.Detailed figures help readers better understand how and why thetechniques discussed in the book work. At the end of each chapter,an extensive set of references leads to the primary literature inthe field. By explaining step by step modern techniques for the in-situcharacterization of heterogeneous catalysts, this book enableschemical scientists and engineers to better understand catalystbehavior and design new catalysts for green, sustainable fuel andchemical production.