Studies of the Electronic Structure of Cu/SiO2 and Cu/ZSM-5 Catalysts PDF Download
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Author: Stephen M. Ouellette
Publisher:
ISBN:
Category : Copper catalysts
Languages : en
Pages : 32
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Author: Stephen M. Ouellette
Publisher:
ISBN:
Category : Copper catalysts
Languages : en
Pages : 32
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Author:
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Author: Pascal Granger
Publisher: Elsevier
ISBN: 0080554059
Category : Technology & Engineering
Languages : en
Pages : 419
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This book offers an overview of the state of the art in the field of DeNOx catalysis in order to focus novel orientations, new technological developments, from laboratory to industrial scale. A particular attention has been paid towards the implementation of catalytic processes for minimising NOx emissions either from stationary or mobile sources under lean condition to meet future standard regulations of NOx emissions. In the first part of this book, critical aspects reported in the literature which usually make difficult the achievement of efficient catalytic technologies in those conditions are summarised and analysed in order two separate new perspectives. The second part deals with fundamental aspects at molecular level. A better understanding of the reactions involved under unsteady-state conditions is probably a pre-requisite step for improving the performances of the actual processes or developing original ones. The development of powerful in situ spectroscopic techniques is of fundamental interest for kinetic modelling. Correlations between spectroscopic and kinetic data with those obtained from theoretical calculations are reported. Some illustrations emphasise the fact that these comparisons may help in determining the nature of the catalytic active sites and building predictive tools for simulations under running conditions. The latter part of this book will be illustrated by different practical approaches covering various aspects related to the catalysts preparation and the development of alternative technologies which include industrial considerations.- New technological developments for investigating catalytic reactions in transient conditions (in situ and operando spectroscopic techniques)- Concerted approaches in DeNOx catalysis - How academic aspects (kinetic, in situ spectroscopic measurements) can provide useful information for practical applications- Comparison of different approaches provided by academic and industrial partners
Author: Bryan Roger Goodman
Publisher:
ISBN:
Category :
Languages : en
Pages : 258
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Author: Albert F. Carley
Publisher: Springer Science & Business Media
ISBN: 9780306473937
Category : Science
Languages : en
Pages : 404
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Exciting results are still emerging from the many research groups working in this fertile area and the book is an excellent stimulus to researchers at the start of the 21st century."--BOOK JACKET.
Author: Hongyu Shang
Publisher:
ISBN:
Category : Chemistry
Languages : en
Pages : 49
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In separate studies, Fe-Ni oxide has been tested as a catalyst for electrochemical CO2 reduction. Developing efficient methods to reduce CO2 to a high-energy-density fuel or other value-added products is important to solve pressing issues related to energy conversion and storage. Developing more active catalysts to improve the slow cathode kinetics is essential to improve the conversion efficiency of CO2 reduction. Cu is the only metal showing high selectivity for C-C bond coupling during electrochemical CO2 reduction, and few studies have investigated the use of mixed metal oxides for this reaction. In our group, we have demonstrated that CuFeO2 has the ability to convert CO2 to acetate with high selectivity. To further understand this reaction, we now investigate modified catalysts where Cu has been replaced by Ni. These catalysts are prepared by the same electrodeposition method followed by thermal annealing as previously reported for CuFeO2 catalysts. XRD shows that the catalyst adopts the spinel NiFe2O4 phase compared to the delafossite phase, CuFeO2. Electrolysis is performed to study catalyst performance, and results show that Ni-Fe oxide catalysts produce a comparable or even higher acetate yield compared to CuFeO2. Further XUV spectroscopy experiments are planned to investigate how the electronic structure influences the selectivity and efficiency of the catalyst.
Author: Elizabeth Anne Fugate
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Energy conversion and storage technologies are often limited by the stability and selectivity of catalysts. One reaction of great importance in the energy conversion process is CO2 reduction. For CO2 reduction, selectivity is often influenced by the structure of the catalyst material. Also, catalysts need to be selective for CO2 reduction over the hydrogen evolution reaction. Recent studies have shown that the selectivity of catalysts to high energy dense products is dependent on the band gap of the catalyst materials. This approach has also shown potential to be used to outcompete the hydrogen evolution process. Earth abundant metal oxides have narrow band gaps that would be energetically favorable for this process. These materials such as CuFeO2 and Cu2O have narrow band gaps (Eg) and Fermi levels (EF) that are suitable for reducing CO2 as well as the oxidation of water. By investigating the electronic structure of these catalysts, we can better understand how electron transfer impacts the selectivity of different products. To this end catalysts that are selective to high energy density products can be produced. Thus by investigating metal oxides of varying electronic structure, we can elucidate trends in product selectivity. We have produced Fe2O3, CuO, and CuFeO2 catalysts by electrodeposition to investigate the photoelectrocatalysis of CO2 reduction. Only the CuFeO2 mixed phase catalyst produced selective photocurrent under CO2 reduction conditions. Our CuFeO2 was able to produce acetate at approximately 70% faradaic efficiency as confirmed by standard addition method using Ion Chromatography and Nuclear Magnetic Resonance Spectroscopy. By looking at the structure using X-ray Photoelectron Spectroscopy, we conclude that our catalyst has an iron rich surface that we believe to be responsible for this high selectivity under CO2 reduction conditions. We believe there is a metal to metal charge transfer from the Fe to the Cu where the hole is localized to Cu 3d orbitals in the valence band and the electron is localized to Fe 3d orbitals in the conduction band. This state results in a long-lived Fe2+ excited state that we hypothesize is responsible for the reduction of CO2. In the near future, we plan to probe charge transfer dynamics of this material via soft X-ray transient absorption spectroscopy, which is oxidation state and element specific. Additionally, we have produced NiOx, CoOx, and MnOx catalysts. Cyclic voltammetry was used to investigate trends in the overpotential for the water oxidation reaction at pH 7 and pH 13. Both NiOx and CoOx have significantly lower overpotentials than any of the other oxides with the overpotential corresponding to 3d orbital occupancy. Additionally, nickel doping of Fe2O3 lowers the overpotential significantly, with a 10% nickel molar ratio in the electrolyte being optimal. By investigating the ground and excited state x-ray spectra of these oxides, we can determine how electronic structure and the band gap of these materials correlate with the overpotential for water oxidation.
Author: Shaikh Tofazzel Hossain
Publisher:
ISBN:
Category : Carbon monoxide
Languages : en
Pages : 422
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Shape- and size-controlled CeO2 and SiO2 have been used in many catalysis applications. This research focused on the low-temperature CO oxidation for the automotive exhaust system. After starting a car, it needs to increase the temperature of catalytic converter to achieve full CO conversion. Toxic gas from the car pollutes the environment till the car reaches the required temperature. Thus, the preparation of efficient catalyst is much needed to lower the CO conversion temperature. This work especially focused on the correlation of the effect of catalyst supports' kind and morphology with their catalytic activity. Copper nitrate and copper carbonate precursors for wet impregnation method and copper nitrate for thermal decomposition method have been used to impregnate CuO onto hydrothermally prepared CeO2 nanorods. Several characterization techniques, such as X-ray diffraction (XRD), Raman spectroscopy, transmission electron microscopy (TEM) and hydrogen temperature programmed reduction (H2-TPR) have confirmed the presence of three different copper species interacting with CeO2 nanorods while forming oxygen vacancies in CeO2 lattice by compensating the charges between copper and cerium. Cu-O-Ce solid solutions and CuO impregnated on CeO2 nanorods catalysts (CuO/CeO2) with various compositions have been prepared using thermal decomposition and hydrothermal methods, to understand the distribution effect of copper species on low temperature CO oxidation. A series of temperature programmed reduction-temperature programmed oxidation (TPR-TPO) thermal cycling studies have been conducted to understand the interactions between three assigned copper species with CeO2 support and the corresponding catalytic performance of the catalysts. The effect of support reducibility and reduction treatment has been studied in SiO2 nanospheres and CeO2 nanorods supported CuO[subscript x] catalysts on CO oxidation. CuO nanoparticles have been impregnated on SiO2 nanospheres and CeO2 nanorods using thermal decomposition method and then the samples have been oxidized in air at different temperatures (400-600 °C). The sample oxidized at 400 °C has also been further reduced under hydrogen atmosphere to compare the effect of thermal treatment (oxidation vs. reduction treatments) on the catalytic activity. In comparison to SiO2 nanospheres supported CuO[subscript x] catalysts, both CuO/CeO2 and reduced CuO[subscript x]/CeO2 catalysts exhibited superior catalytic performance in terms of CO conversion and low-temperature hydrogen consumption. The enhanced activity of CeO2 nanorods supported CuO[subscript x] catalysts has been correlated strongly to the surface defects on CeO2 nanorods and interfacial structures. In addition, in a novel design of co-supported scaffold structure catalyst, CeO2 nanorods and SiO2 nanospheres have been mixed in various ratios and 10 wt% CuO nanoparticles have been impregnated onto CeO2-SiO2 composite support using thermal decomposition method. Agglomeration of CeO2 nanorods have been stopped by introducing SiO2 nanospheres in the catalyst system, and this design can increase the chance to expose more CeO2 surface to CuO nanoparticles in order to form higher amount of surface defects (incorporation of Cu ions and oxygen vacancies) and lead to higher synergistic interaction between CuO and CeO2. H2 TPR and CO oxidation experiments suggested an enhanced low-temperature catalytic performance for 1:1 ratio mixture of CeO2 and SiO2 due to a strong interfacial interaction among SiO2-CeO2-CuO. For kinetic study, 5%CO-95%He and O2 gases have been used to reduce and oxidize CuO/CeO2 catalyst respectively at a constant temperature of 400 °C (isothermal process). Mathematical formulas for power law, diffusion, nucleation and contraction models have been used to compare with the experimental data collected during the reduction and oxidation process of the catalyst to determine the best fitted reaction mechanism.
Author: Jan Connerton
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Author: Tetsuro Seiyama
Publisher: Elsevier
ISBN: 0080954340
Category : Technology & Engineering
Languages : en
Pages : 803
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New Horizons in Catalysis: Part 7B. Proceedings of the 7th International Congress on Catalysis, Tokyo, 30 June-4 July 1980 (Studies in Surface Science and Catalysis)
