Download or read book Laser Diagnostics and Modeling of the Coupling Between Heterogeneous Catalytic and Gas phase Oxidation of Hydrogen written by Michael Försth and published by . This book was released on 1998 with total page 78 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 Laser Diagnostics and Modeling of Combustion written by Kazuo Iinuma and published by Springer. This book was released on 1987 with total page 386 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Modeling and Laser Diagnostic Experiments in Laser assisted Chemical Vapor Deposition written by David Clinton Skouby and published by . This book was released on 1989 with total page 332 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Scientific and Technical Aerospace Reports written by and published by . This book was released on 1992 with total page 1556 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Relationships Between Gas Phase Ionization Energies and Solution Phase Oxidation Potentials Applications to the Electrocatalytic Production of Hydrogen from Weak Acids written by Takahiro Sakamoto and published by . This book was released on 2010 with total page 596 pages. Available in PDF, EPUB and Kindle. Book excerpt: The transfer of electrons to and from a molecule is one of the more fundamental and important chemical processes. One such important example is the reduction-oxidation (redox) cycles in catalysts and enzymes. In the hydrogenase enzymes, adding and removing electrons is one of the key processes for generating H2 from water molecules. Finding a direct free energy relation between the vertical ionization energies (IEV) measured spectroscopically by gas-phase photoelectron spectroscopy and the oxidation potentials (E1/2) measured thermodynamically in solution by cyclic voltammetry (CV) for molecules is an important aspect for developing effective catalysts. In this study, a series of organometallic compounds such as metallocenes were used for investigating the free energy relationships and catalysts inspired by the active sites of [FeFe]-hydrogenases enzymes were evaluated for their ability to produce H2 from electrocatalytic reduction of weak acids. The first part of the dissertation explores metallocenes of the form (ç5 C5H5)2M (M= Fe, Ru, Os, Co, Ni) as the model for developing the free energy relation between gas phase ionization energies (IEV) and solution oxidation potentials (E1/2). It was found that computing the electronic properties of Cp2Fe, Cp2Ru, and Cp2Os using VWN-Stoll and OPBE density functional theory (DFT) functional was successful with root mean square deviation (RMSD) of 0.02 eV between the experimental and calculated ionization energies. However, calculated ionization energies of Cp2Co and Cp2Ni were less successful with RMSD of 0.3 eV between the experimental and calculated ionization energies. Introduction of the B3LYP or M06 hybrid DFT functionals yielded much improved results (0.1 eV) over the previous combinations of DFT functional for Cp2Co and Cp2Ni. The energy relation between the two experimental measurements was established and further computational studies revealed that the solvation energy was the largest energy contribution between IEV and E1/2 in the five studied metallocenes. The RMSD of the calculated oxidation potentials, after adjusting for the error in gas phase ionization energies, was 0.09 V. The second part of the dissertation explores a series of catalysts inspired by the active sites of [FeFe]-hydrogenase enzymes; ì-(2,3-pyrazinedithiolato)diironhexacarbonyl (PzDT-cat), Fe2(ì-X2C5H8O)(CO)6 (where X = S, Se, Te), and Fe2(ì-1,3-SC3H6X)(CO)6 (where X = Se and Te) for their ability to produce H2 from weak acids utilizing the computational techniques and knowledge gained from the metallocene study. Even though the overall electronic perturbation from ì-(1,2-benzenedithiolato)diironhexacarbonyl (BDT-cat) to ì-(2,3-pyridinedithiolato)diironhexacarbonyl (PyDT-cat) to PzDT-cat is found to be small, the reduction potential of PzDT-cat was found to be 0.15 V less negative than that of BDT-cat resulting in less energy required for initiating electrocatalytic H2 production over the BDT-cat and PyDT-cat. Lower reorganization energy has been achieved by substitutions of larger chalcogens at the Fe2S2 core. However, the electrocatalytic production of H2 from acetic acid in acetonitrile was found to be diminished upon going from analogous S to Se to Te species. This is ascribed to the increase in the Fe-Fe bond distance with a corresponding increase in the size of the chalcogen atoms from S to Se to Te, disfavoring the formation of a carbonyl-bridged structure in the anion which is thought to be critical to the mechanism of H2 production.

Download or read book Laser Aided Diagnostics of Plasmas and Gases written by K Muraoka and published by CRC Press. This book was released on 2016-04-19 with total page 307 pages. Available in PDF, EPUB and Kindle. Book excerpt: Updated and expanded from the original Japanese edition, Laser-Aided Diagnostics of Gases and Plasmas takes a unique approach in treating laser-aided diagnostics. The book unifies the subject by joining applications instead of describing each application as a totally separate system. In taking this approach, it highlights the relative strengths of

Download or read book Laser Diagnostics for Combustion Temperature and Species written by Alan C. Eckbreth and published by CRC Press. This book was released on 1996-10-10 with total page 636 pages. Available in PDF, EPUB and Kindle. Book excerpt: Focusing on spectroscopically-based, spatially-precise, laser techniques for temperature and chemical composition measurements in reacting and non-reacting flows, this book makes these powerful and important new tools in combustion research

Download or read book Bimodal Oxidation written by Robert Bakhtchadjian and published by CRC Press. This book was released on 2019-11-15 with total page 302 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book is devoted to the problems of oxidation chemical reactions and addresses bimodal reaction sequences. Chemical reactions of oxidation, occurring under certain conditions and in multicomponent systems are complex processes. The process of the oxidation essentially changes in the presence and contact of the solid substances with reactants. The role of solid substances and the appearance of this phenomenon in oxidation reaction are discussed. The reader will understand the "driving forces" of this phenomenon and apply it in practice. Written for chemists, physicists, biologists and engineers working in the domain of oxidation reactions. Key Selling Features: Covers the historical background, modern state of the art, and perspectives in investigations of the coupling between heterogeneous and homogeneous reactions Discusses the feasible pathways of the coupling of heterogeneous and homogeneous reactions in oxidation in man-made and natural chemical systems Addresses the abundance, peculiarities and mechanisms of the bimodal reaction sequences in oxidation with dioxygen in recent decades Discusses the existence of the bimodal reaction sequences in chemical systems investigations in atmospheric chemistry and heterogeneous photocatalysis Presented in a simple concise style, accessible for both specialists and non-specialists

Download or read book Scientific and Technical Aerospace Reports written by and published by . This book was released on 1982 with total page 1284 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Industrial Applications of Laser Diagnostics written by Yoshihiro Deguchi and published by Taylor & Francis. This book was released on 2016-04-19 with total page 301 pages. Available in PDF, EPUB and Kindle. Book excerpt: Tighter regulations of harmful substances such as NOx, CO, heavy metals, particles, emissions from commercial plants and automobiles reflect a growing demand for lowering the anthropogenic burdens on the environment. It is equally important to monitor controlling factors to improve the operation of industrial machinery and plants. Among the many me

Download or read book Catalytic Recombination of Hydrogen and Oxygen written by J. V. Gaven and published by . This book was released on 1955 with total page 36 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Laser Diagnostics of Materials and Chemistry written by and published by . This book was released on 1984 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Several examples are given of the ability of laser-based diagnostic techniques to make noninvasive measurements in hostile environments. Using coherent anti-Stokes Raman scattering both majority and minority species concentrations, as well as temperature, have been measured in the hot, high-pressure, particle-laden stream of a coal gasifier. In addition, numerous toxic and corrosive elements in the gasifier stream have been identified, but not yet quantified. In addition to providing the capability for making analytical determinations, laser techniques have been extensively employed to measure the rates of elementary chemical reactions. Recently, the temperature regime over which such meaurements are possible has been expanded. Although much of the laser diagnostic activity to date has involved investigations of the gas phase, significant information concerning heterogeneous phenomena can still be inferred. For instance, gas-solid reactions can manifest themselves as changes in vapor phase composition. Furthermore, in the future we expect expanded studies involving reactions of refractory metals (both atoms and clusters) and additional investigations of processes occurring at interfaces and on surfaces.

Download or read book Quantitative Laser Diagnostics of Gas phase Potassium Species in Biomass Combustion and Gasification written by Emil Thorin and published by . This book was released on 2023 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Laser Diagnostics and Chemical Modeling of Combustion and Catalytic Processes written by Michael Försth and published by . This book was released on 2001 with total page 96 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Application of Laser based Diagnostics for Nanomaterials Synthesis written by Xiaofei Liu and published by . This book was released on 2009 with total page 220 pages. Available in PDF, EPUB and Kindle. Book excerpt: Spectroscopic laser-based diagnostics are applied in the gas-phase synthesis of nanostructrued materials to make non-intrusive, in-situ, spatially-precise measurements of gas-phase temperatures and relevant chemical species. For the nanomaterials themselves, a novel application of Raman spectroscopy is developed to characterize nanoparticles in-situ, during flame and plasma synthesis. As result, the local conditions for gas-phase synthesis can be determined for a given nanomaterial property, so that fundamental mechanisms can be revealed and process conditions can be optimized. The synthesis configurations investigated in this work are (i) the inverse co-flow diffusion flame (IDF), (ii) the counter-flow diffusion flame (CDF), (iii) the low-pressure burner-stabilized premixed stagnation-point flame, and (iv) the inductively-coupled plasma (ICP) impinging on a cold substrate. Spontaneous Raman spectroscopy (SRS) is used to measure local gas-phase conditions in the 2-D axi-symmetric IDF and the quasi 1-D CDF, where nanomaterials are grown on inserted substrates of various compositions. Nitrogen-diluted methane-air flames are examined. Carbon nanotubes (CNTs) are grown catalytically on metal-alloy substrates, and their morphologies are correlated with the local gas-phase temperature and the concentrations of carbon-based precursor species (e.g. C2H2, CO). Zinc oxide (ZnO) nanostructures are grown directly on zinc-plated steel substrates, and their morphologies are correlated with the local gas-phase temperature and the concentrations of oxidative (e.g. O2, H2O, and CO2) and reducing (e.g. H2) species. Computational simulations in 1-D, involving detailed chemical kinetics and transport properties, and in 2-D, using simplified kinetics and transport, are used to validate and improve the measurements. Laser-induced fluorescence (LIF) is employed to measure the gas-phase temperature profile and OH radical species concentration distribution in a low-pressure, premixed, nitrogen-diluted hydrogen-oxygen, burner-stabilized, stagnation-point flame. Titania nanoparticles are synthesized using a metalorganic precursor. The LIF measurements are compared with computational simulations with detailed chemical kinetics and transport, to affirm the quasi 1-D flow field, as well as to investigate the effects of precursor addition and uniform electric-field application. SRS is utilized to characterize in-situ the composition and crystallinity of nanoparticles, in aerosol form, produced in the aforementioned low-pressure premixed flame and in the ICP synthesis setup. The Stokes spectra are identified for crystalline phases of TiO2 (and Al2O3 in a different flame setup) and c-BN based on ex-situ-taken spectra from the literature. The in-situ technique is able to delineate the phase conversion of nanoparticles (including amorphous to crystalline) as they evolve in the flow field.

Download or read book Heterogeneous Catalysis with Lasers written by Thomas F. George and published by . This book was released on 1986 with total page 14 pages. Available in PDF, EPUB and Kindle. Book excerpt: Theoretical techniques have been developed to describe a variety of laser-induced molecular rate processes occurring at solid surfaces which are involved in heterogeneous catalysis. Such processes include adsorption, migration, chemical reactions and desorption. The role of surface phonons in laser-selective processes and laser heating has been analyzed. The importance of electronic degrees of freedom has been considered for semiconductor and metal substrates, with special emphasis on the laser excitation of surface states. Surface-modified photochemistry has also been investigated, where the effect of a metal surface on the resonance fluorescence spectrum of a laser-driven atom/molecule has been assessed by means of surface-dressed optical Bloch equations. It is seen that the spectrum can be significantly different from the gas-phase case. Two related gas-surface collision processes have also been studied. First, the feasibility of the formation of the electron-hole pairs in a semiconductor by vibrationally excited molecules has been explored. Second, charge transfer in ion-surface collisions has been examined for both one-electron and two-electron transfer processes. Work has been initiated on microstructures and rough structures, including clusters and surface gratings. Keywords: Energy transfer; Quantum optics; Reaction kinetics; Proton neutralization; Ion neutralization; Ion formation.