Author: Michael S. Schneider
Publisher:
ISBN:
Category :
Languages : en
Pages : 152

Get Book Here

Book Description

Author: Walter Leitner
Publisher: Springer Science & Business Media
ISBN: 3540710744
Category : Science
Languages : en
Pages : 214

Get Book Here

Book Description
Multiphase catalysis is a key technology for the competitive and sustainable production of fine chemicals in coming decades. A joint academic and industry consortium has developed tools for considering complex chemical and process-based requirements when setting up a catalytic system. This book shows how the resulting competence covers such supercritical fluid (SCF) technology in catalysis, ionic liquids (Il), ligand design for SFCs and Ils, thermomorphic solvent systems, reactor design and more.

Author: Shao-Chun Wang (Ph.D.)
Publisher:
ISBN:
Category :
Languages : en
Pages : 0

Get Book Here

Book Description
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.

Author: James F. Haw
Publisher: Wiley-VCH Verlag GmbH
ISBN:
Category : Science
Languages : en
Pages : 296

Get Book Here

Book Description
"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.

Author: J. W. Niemantsverdriet
Publisher: John Wiley & Sons
ISBN: 3527611355
Category : Science
Languages : en
Pages : 344

Get Book Here

Book Description
Superbly organized and of great pedagogic value, 'Spectroscopy in Catalysis' describes the most important modern analytical techniques used to investigate catalytic surfaces. These include electron, ion, and vibrational spectroscopy, mass spectrometry, temperature-programmed techniques, diffraction, and microscopy. With the focus on practical use, rather than theory, each chapter presents current applications to illustrate the type of information that the technique provides and evaluates its possibilities and limitations, allowing selection of the best catalyst and the correct technique to solve a given problem. This third edition includes significant new developments and case studies, with all the chapters updated by way of recent examples and relevant new literature. For students and for everyone who wants a digestible introduction to catalyst characterization. From reviews of the previous editions: 'This is a truly valuable book ... very useful for industrial practitioners who need to be aware of the type of information that can be obtained from modern surface spectroscopies .... The book has a superb pedagogic value...' Journal of Catalysis '... this is an excellent text on spectroscopies in catalysis and I highly recommend it for ... introductory courses on heterogeneous catalysis or as a general introductory monograph.' Journal of the American Chemical Society

Author:
Publisher:
ISBN:
Category : Dissertations, Academic
Languages : en
Pages : 396

Get Book Here

Book Description

Author: Rubén Duque
Publisher:
ISBN:
Category : Carbon dioxide
Languages : en
Pages : 215

Get Book Here

Book Description

Author: Daniel J. Dwyer
Publisher:
ISBN: 9780841221895
Category : Catalyse - Congrès
Languages : en
Pages : 0

Get Book Here

Book Description

Author:
Publisher:
ISBN:
Category : Power resources
Languages : en
Pages : 782

Get Book Here

Book Description

Author: Rasmus Fehrmann
Publisher: John Wiley & Sons
ISBN: 3527324291
Category : Science
Languages : en
Pages : 498

Get Book Here

Book Description
This unique book gives a timely overview about the fundamentals and applications of supported ionic liquids in modern organic synthesis. It introduces the concept and synthesis of SILP materials and presents important applications in the field of catalysis (e.g. hydroformylation, hydrogenation, coupling reactions, fine chemical synthesis) as well as energy technology and gas separation. Written by pioneers in the field, this book is an invaluable reference book for organic chemists in academia or industry.