Insights Into Active Site Structures for Pd-based Bimetallic Heterogeneous Catalysts
Title | Insights Into Active Site Structures for Pd-based Bimetallic Heterogeneous Catalysts PDF eBook |
Author | Madelyn Rose Baltus Ball |
Publisher | |
Pages | 136 |
Release | 2019 |
Genre | |
ISBN |
Catalytic reactions play a large role in the production of energy and products used in our modern society. In order to improve the efficiency of existing processes and make the conversion of new feedstocks, such as biomass and natural gas, possible, there exists the need for improved catalytic materials. Many active catalysts have complex active sites containing multiple components; therefore, fundamental understanding of active sites and structure-performance relationships is needed to rationally design new catalysts. The work in this dissertation is focused on catalytic synthesis of well-controlled bimetallic catalysts in order to develop structure-activity and structure-selectivity relations for different chemical transformations. A controlled surface reaction synthesis approach is used to deposit Pd onto Au, Ag, or Cu parent catalysts. These Pd bimetallic catalysts are then studied for reactions where selectivity is a main challenge, and the selective Pd structure is identified. First, AuPd/TiO2 catalysts are studied for the gas phase amination of 1-hexanol using ammonia. It was determined that there are no monometallic Pd structures on the catalysts. The Pd atoms are well diluted in the Au nanoparticles at low loadings and as the Pd loading increases, more contiguous Pd sites are formed. From reactivity studies, it is determined that both the Au and Pd contribute to the overall hexanol conversion, however the activity in enhanced for the bimetallic catalysts compared to the monometallic catalysts. This rate improvement is attributed to a geometric effect where surface intermediates are not stabilized by hydrogen bonding to adsorbed ammonia in close proximity. Furthermore, the selectivity to primary amines is increased as the loading of Pd increases in the AuPd catalysts, while lower Pd loadings favor more substituted products. The selectivity trends are hypothesized to be related to both geometric and electronic effects present in the AuPd catalyst system. Next, AgPd catalysts were studied for the hydrodechlorination of 1,2-dichloroethane. The role of the support in the formation of well-controlled bimetallic nanoparticles was investigated and it was determined that well-mixed AgPd particles were formed on a TiO2 support, while some monometallic Pd particles were also formed on C and SiO2 supports. Again, using chemisorption, XAS, and CO-FTIR, it was determined that isolated Pd atoms within the Ag nanoparticles are formed on the TiO2 support at low loadings. On the SiO2 supported catalysts, contiguous Pd species are formed. The isolated Pd species are highly selective to ethylene while the contiguous Pd species are selective to the undesired ethane. Thus, the support was determined to play an important role in tuning the AgPd structure and the resulting selectivity for hydrodechlorination. The rate of 1,2-dichloroethane conversion was determined to be related to the selectivity, with the ethylene selective catalysts exhibiting the highest turnover frequencies. Finally, AgPd and CuPd catalysts were investigated for the selective hydrogenation of acetylene. Both TiO2 and SiO2 supported catalysts were studied, and it was determined by EDS analysis that the CuPd nanoparticle composition distribution was more uniform on the SiO2 support than on the TiO2 support. IR spectra of the catalyst surface after being exposed to reaction conditions indicate the presence of numerous spectator species and it is determined that there are less sites covered by spectators for the bimetallic catalysts compared to a monometallic Pd catalyst. On the TiO2 support, the bimetallic catalysts exhibit the highest rates per gram of Pd and high ethylene selectivites above 99%. The monometallic catalysts are less than 95% selective to ethane, indicating that the alloy formation improves the ethylene selectivity; the enhanced selectivity is attributed to electronic effects in the bimetallic nanoparticles. This work enabled the development of detailed active site hypotheses for different Pd based bimetallic catalysts and provided insights into the desired structures to inform rational catalyst design. The controlled surface reaction synthesis approach and general characterization methodology can be applied to a broad range of catalyst and reaction systems to improve chemical transformations for improved production of chemicals and fuels for modern society.
Bimetallic Catalysts
Title | Bimetallic Catalysts PDF eBook |
Author | John H. Sinfelt |
Publisher | Wiley-Interscience |
Pages | 190 |
Release | 1983-09-29 |
Genre | Science |
ISBN |
Presents an account of the research on bimetallic catalysts. Focuses attention on the possibility of influencing the selectivity of chemical transformations on metal surfaces and preparing metal alloys in a highly dispersed state. Covers the validation and elucidation of the bimetallic cluster concept. Includes figures and tables.
Design of Heterogeneous Catalysts
Title | Design of Heterogeneous Catalysts PDF eBook |
Author | Umit S. Ozkan |
Publisher | John Wiley & Sons |
Pages | 340 |
Release | 2009-02-11 |
Genre | Science |
ISBN | 352762533X |
This long-awaited reference source is the first book to focus on this important and hot topic. As such, it provides examples from a wide array of fields where catalyst design has been based on new insights and understanding, presenting such modern and important topics as self-assembly, nature-inspired catalysis, nano-scale architecture of surfaces and theoretical methods. With its inclusion of all the useful and powerful tools for the rational design of catalysts, this is a true "must have" book for every researcher in the field.
Bimetallic Nanostructures
Title | Bimetallic Nanostructures PDF eBook |
Author | Ya-Wen Zhang |
Publisher | John Wiley & Sons |
Pages | 738 |
Release | 2018-05-16 |
Genre | Science |
ISBN | 1119214629 |
Systematically summarizes the current status and recent advances in bimetallic structures, their shape-controlled synthesis, properties, and applications Intensive researches are currently being carried out on bimetallic nanostructures, focusing on a number of fundamental, physical, and chemical questions regarding their synthesis and properties. This book presents a systematic and comprehensive summary of the current status and recent advances in this field, supporting readers in the synthesis of model bimetallic nanoparticles, and the exploration and interpretation of their properties. Bimetallic Nanostructures: Shape-Controlled Synthesis for Catalysis, Plasmonics and Sensing Applications is divided into three parts. Part 1 introduces basic chemical and physical knowledge of bimetallic structures, including fundamentals, computational models, and in situ characterization techniques. Part 2 summarizes recent developments in synthetic methods, characterization, and properties of bimetallic structures from the perspective of morphology effect, including zero-dimensional nanomaterials, one-dimensional nanomaterials, and two-dimensional nanomaterials. Part 3 discusses applications in electrocatalysis, heterogeneous catalysis, plasmonics and sensing. Comprehensive reference for an important multidisciplinary research field Thoroughly summarizes the present state and latest developments in bimetallic structures Helps researchers find optimal synthetic methods and explore new phenomena in surface science and synthetic chemistry of bimetallic nanostructures Bimetallic Nanostructures: Shape-Controlled Synthesis for Catalysis, Plasmonics and Sensing Applications is an excellent source or reference for researchers and advanced students. Academic researchers in nanoscience, nanocatalysis, and surface plasmonics, and those working in industry in areas involving nanotechnology, catalysis and optoelectronics, will find this book of interest.
Catalytic Chemistry of Pd-Au Bimetallic Surfaces
Title | Catalytic Chemistry of Pd-Au Bimetallic Surfaces PDF eBook |
Author | Wen-Yueh Yu |
Publisher | |
Pages | 396 |
Release | 2015 |
Genre | |
ISBN |
Catalyst development is important to the contemporary world as suitable catalysts can allow chemical processes to proceed with reduced energy consumption and waste production. In order to design catalysts with improved performance, the fundamental studies that correlate catalytic properties with surface structures are essential as they can provide mechanistic insights into the reaction mechanism. Pd-Au bimetallic catalysts have shown exceptional performance for a number of chemical reactions, however, the interplay between the reactive species and surface properties are still unclear at the molecular level. In this dissertation, the catalytic chemistry of Pd-Au surfaces was investigated via model catalyst studies under ultrahigh vacuum conditions. A range of Pd-Au model surfaces were generated by annealing Pd/Au(111) surfaces and characterized/tested by surface science techniques. The findings in this dissertation may prove useful to enhance the fundamental understanding of structure-reactivity relation of Pd-Au catalysts in associated reactions.
Electron Microscopy in Heterogeneous Catalysis
Title | Electron Microscopy in Heterogeneous Catalysis PDF eBook |
Author | P.L Gai |
Publisher | CRC Press |
Pages | 243 |
Release | 2003-01-14 |
Genre | Science |
ISBN | 1420034413 |
Catalysis is one of the most important technologies in the industrial world, controlling more than 90% of industrial chemical processes and essential for large-scale production of plastics and fuel. Exploring the most common type of catalysis used in industry, Electron Microscopy in Heterogeneous Catalysis provides a coherent account of heterogeneo
Heterogeneous Catalysis and Fine Chemicals IV
Title | Heterogeneous Catalysis and Fine Chemicals IV PDF eBook |
Author | H.U. Blaser |
Publisher | Elsevier |
Pages | 693 |
Release | 1997-06-19 |
Genre | Technology & Engineering |
ISBN | 0080533930 |
After three meetings in Poitiers, France, the 4th International Symposium on Heterogeneous Catalysis and Fine Chemicals was held under the auspices of the New Swiss Chemical Society in Basel, Switzerland. Fundamental as well as applied contributions on the use of heterogeneous catalysis for the preparation of fine chemicals were presented and discussed.The program consisted of 4 plenary lectures, 28 oral contributions and around 90 posters covering a broad range of reactions and catalytic aspects. 82 of these contributions are collected in the present proceedings, grouped into the following 8 topical areas:- Industrial and engineering problems (7 contributions)- Alkylation and acylation reactions (11 contributions)- Enantio- and diastereoselective hydrogenation reactions (9 contributions)- Chemoselective hydrogenation reactions (12 contributions)- Oxidation reactions (14 contributions)- Immobilized and encapsulated complex catalysts (12 contributions)- Zeolite and clay catalysts (12 contributions)- Miscellaneous topics (5 contributions)