Download or read book Diffuse Reflectance Infrared Fourier Transform Spectroscopy drifts of Molecules Adsorbed on Nickel Rhodium and Ruthenium Catalysts written by Lawrence Nwankwo Orji and published by . This book was released on 1986 with total page 616 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Dissertation Abstracts International written by and published by . This book was released on 1989 with total page 822 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Comprehensive Dissertation Index written by and published by . This book was released on 1989 with total page 754 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book American Doctoral Dissertations written by and published by . This book was released on 1985 with total page 696 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book American Chemical Society Directory of Graduate Research 1987 written by American Chemical Society, Committee on Professional Training Staff and published by . This book was released on 1987 with total page 1390 pages. Available in PDF, EPUB and Kindle. Book excerpt:

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 Process and Chemical Engineering written by and published by . This book was released on 1999-07 with total page 76 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Plasma Catalysis written by Annemie Bogaerts and published by MDPI. This book was released on 2019-04-02 with total page 248 pages. Available in PDF, EPUB and Kindle. Book excerpt: Plasma catalysis is gaining increasing interest for various gas conversion applications, such as CO2 conversion into value-added chemicals and fuels, N2 fixation for the synthesis of NH3 or NOx, methane conversion into higher hydrocarbons or oxygenates. It is also widely used for air pollution control (e.g., VOC remediation). Plasma catalysis allows thermodynamically difficult reactions to proceed at ambient pressure and temperature, due to activation of the gas molecules by energetic electrons created in the plasma. However, plasma is very reactive but not selective, and thus a catalyst is needed to improve the selectivity. In spite of the growing interest in plasma catalysis, the underlying mechanisms of the (possible) synergy between plasma and catalyst are not yet fully understood. Indeed, plasma catalysis is quite complicated, as the plasma will affect the catalyst and vice versa. Moreover, due to the reactive plasma environment, the most suitable catalysts will probably be different from thermal catalysts. More research is needed to better understand the plasma–catalyst interactions, in order to further improve the applications.

Download or read book A Diffuse Reflectance Fourier Transform Infrared Study of the Adsorption and Decomposition of Dimethyl Methylphosphonate on Copper Oxide Supported Y alumina written by Enid Nyakarura Gatimu and published by . This book was released on 2004 with total page 194 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Diffuse Reflectance Infrared Fourier Transform Spectra of Selected Organic Compounds written by and published by . This book was released on 1982 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Diffuse reflectance infrared spectra of a variety of different organic compounds have been determined. Profiles of the spectra along with the location and relative intensity of the principal bands have been included for each compound studied. In addition both diffuse reflectance and transmittance infrared spectra were obtained for the same samples, and the spectral results were compared. Although some minor variations are observed between a diffuse reflectance spectrum and the corresponding transmittance spectrum, the diffuse reflectance is quite useful and may be a superior technique for the study of many samples because it possesses an inherently higher signal-to-noise response, requires less sample preparation and allows a very wide range of samples (solids, liquids of low volatility, neat sample, or sample diluted in a reflecting medium) to be studied under very similar conditions.

Download or read book Time resolved Fourier Transform Infrared Spectroscopy Investigation of Methanol Decomposition on Nickel 100 written by John Stephan Huberty and published by . This book was released on 1995 with total page 562 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book In Situ Fourier Transform Infrared Spectroscopy of Adsorbed Species on Mixed Metal Oxide Catalysts for Higher Alcohol Synthesis written by Ahmet Baysar and published by . This book was released on 1985 with total page 404 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Reflection Absorption Infrared Spectroscopy of Molecular Adsorption and Catalysis on the Silver 111 Surface written by Wee Sun Sim and published by . This book was released on 1996 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Diffuse Reflectance Fourier Transform Infrared Spectroscopic Study of Chemical Bonding and Hydrothermal Stability of an Amino Silane on Metal Oxide Surfaces written by Somsak Naviroj and published by . This book was released on 1982 with total page 42 pages. Available in PDF, EPUB and Kindle. Book excerpt: Fourier transform infrared spectroscopy is used to study the metal oxide/silane interface. Structures of gamma-aminopropyldimethylethoxysilane (gamma-APDMES) coupling agent on the surface of metal oxide powders are proposed. The structure depends on the surface characteristics of the substrate. The amine group of the silane molecule forms a hydrogen bond with the silica surface. The enhanced intensity of the amine band around 1/71600 C indicates that amine group forms a complex on the titanium and aluminum oxide surfaces as well as hydrogen bond. By using the diffuse reflectance infrared technique, the Al-O-Si and Ti-O-Si antisymmetric frequencies are detected at 963 and 1/950 cm, respectively, which agree favorably with the calculated frequencies. When the treated metal oxide powders are immersed in 80 degrees C water, the desorption of silance is more rapid when aluminum powder, rather than titanium powder, is the substrate. Silica powder, however, forms a more hydrophobic surface. The rate of silane desorption decreased in the order of aluminum oxide, titanium oxide, and silicon oxide. (Author).

Download or read book Reflection Absorption Infrared Spectroscopy of Molecules Adsorbed on Metal Surfaces written by Shamsal Haq and published by . This book was released on 1993 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Infrared Absorption Spectroscopy of Carbon Monoxide on Nickel Films written by and published by . This book was released on 1978 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Sensitive vibrational spectra of carbon monoxide molecules adsorbed on evaporated nickel films have been measured by attaching a thermometer to the sample, cooling the assembly to liquid helium temperatures, and recording the temperature changes which occur when infrared radiation is absorbed. The measurements are made in an ultrahigh vacuum chamber in which the sample surface can be cleaned, heated, exposed to gas molecules and cooled to 1.6 K for the infrared measurements. The spectra of chemisorbed CO molecules are interpreted in terms of the linear and bridge adsorption sites on the nickel surface, and they show how the distribution of molecules among these sites changes when the CO coverage increases and intermolecular forces become important. The spectra of physically adsorbed molecules in both monolayer and multilayer films are also reported. Absorptions as small as five parts in 105 of the incident radiation can presently be detected in spectra covering broad bands of infrared frequencies with a resolution of 2 cm−1. This high sensitivity is attributable to the low noise and reduced background signal of the thermal detection scheme, to the stability of the rapid scan Fourier transform infrared spectrometer, and to the automated computerized data acquisition electronics. Better performance is expected in future experiments on single crystal samples as well as evaporated films. This will make it possible to study molecules with weaker absorptions than CO and to look for evidence of chemical reactions between different adsorbed molecules.

Download or read book Multiple Internal Reflection Fourier Transform Infrared Spectroscopy Studies of Thiocyanate Adsorption on Silver and Gold written by Diane B. Parry and published by . This book was released on 1989 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: