Author: Publisher:
ISBN:
Category :
Languages : en
Pages : 249
Book Description
Implication of Defects in the Bulk Structure of Heterogeneous Catalysts for Structure Activity Relationships
Author: Structure-activity and Selectivity Relationships in Heterogeneous Catalysis
Author: Heterogeneous Catalysis of Mixed Oxides
Author: Makoto MisonoPublisher: Elsevier Inc. Chapters
ISBN: 0128081090
Category : Science
Languages : en
Pages : 87
Book Description
The chemistry of metal oxides, both single and mixed metal oxides, relevant to heterogeneous catalysis such as relationships among the composition, structure, and chemical properties of mixed oxides, is provided in perspective. The important chemical properties in heterogeneous catalysis are acid–base and reduction–oxidation (redox) properties, where ionic radii, electronegativity, valency, and tendency to form covalent bond of constituent elements are most influential. Structural factors such as lattice defects and nonstoichiometry are also relevant. Although the surface of metal oxides is different from the solid bulk and changes depending on various factors, the surface reflects more or less the solid bulk and the knowledge of bulk properties is useful to understand the catalysis of mixed oxides. In some cases, the solid bulk actually takes part in catalysis. Other fundamental features of metal oxide catalysis like synergistic effects of more than two different active sites (acid and base, acid and oxidation, etc.) are also discussed.
Structure-Activity and Selectivity Relationships in Heterogeneous Catalysis
Author: R.K. GrasselliPublisher: Elsevier
ISBN: 0080887198
Category : Science
Languages : en
Pages : 375
Book Description
Structure plays an important role in heterogeneous catalysis. It provides a framework for the arrangement and stragetic placement of key catalytic elements, hosting them in a prescribed manner so that their respective electronic properties can exhibit their desired catalytic functions and mutual interactions. Under reaction conditions these framework structures and their catalytic guests undergo dynamic processes becoming active participants of the overall catalytic process. They are not mere static geometric forms. The dynamics of catalytic structures are particularly vivid in selective oxidation catalysis where the lattice of a given catalytic solid partakes as a whole, not only its surface, in the redox processes of the reaction. The catalyst becomes actually a participating reagent. By proper choice of key catalytic elements and their host structures, preferred catalytic pathways can be selected over less desired ones. However, not only in selective redox catalysis does structure play an important role, its importance is also well documented, among others, in shape selective zeolite catalysis, enantioselective hydrogenation and hydrodesulfurization. The contributions presented in this book address the dynamic character of the solid state under catalytic reaction conditions. By relating structure to activity and selectivity in heterogeneous catalysis our understanding of such correlations has been significantly enhanced through the use of sophisticated spectroscopic means, surface science and modeling.
Structure-activity Relationships in Heterogeneous Catalysts for Hydrocarbon Conversions
Author: Maricruz Sanchez SanchezPublisher:
ISBN:
Category :
Languages : en
Pages :
Book Description
Characterization of Catalytic Materials
Author: Israel E. WachsPublisher: Momentum Press
ISBN: 1606501844
Category : Science
Languages : en
Pages : 220
Book Description
Heterogeneous catalysis has undergone a revolutionary change in the past two decades due to the development of sophisticated characterization methods that provide fundamental information about the catalyst bulk structures, surfaces, and their properties. For the first time, these characterization methods have allowed researchers to "see" the surfaces of catalytic materials, their bulk structures (crystalline as well as amorphous phases), the influence of the process conditions on the catalytic material, as well as the effect of different synthesis methods. This new information has tremendously advanced our understanding of catalytic materials and their properties. These characterization methods have become our "eyes" and are indispensible in the development of new catalytic materials. It is hard to conceive of a modern heterogeneous catalysis activity, be it research or manufacturing, without the aid of these new characterization techniques.
Heterogeneous Catalysis
Author: Abdullah A. ShaikhPublisher: Walter de Gruyter GmbH & Co KG
ISBN: 3110624931
Category : Science
Languages : en
Pages : 216
Book Description
This textbook is a perfect introduction to heterogeneous catalysis focusing on the industrial implementation. It is written in a comprehensible manner using language that is easy accessible and provides problems to practice.
Structure-activity Relationships for Carbonaceous Heterogeneous Single-site Catalysts Using Ab-initio Simulations
Author: Nina Michelle SackersFundamental Concepts in Heterogeneous Catalysis
Author: Jens K. NørskovPublisher: John Wiley & Sons
ISBN: 1118888952
Category : Technology & Engineering
Languages : en
Pages : 228
Book Description
This book is based on a graduate course and suitable as a primer for any newcomer to the field, this book is a detailed introduction to the experimental and computational methods that are used to study how solid surfaces act as catalysts. Features include: First comprehensive description of modern theory of heterogeneous catalysis Basis for understanding and designing experiments in the field Allows reader to understand catalyst design principles Introduction to important elements of energy transformation technology Test driven at Stanford University over several semesters
Computational Modeling of the Structure and Catalytic Behavior of Graphene-supported Pt and PtRu Nanoparticles
Author: Raymond GasperPublisher:
ISBN:
Category :
Languages : en
Pages :
Book Description
Computer modeling has the potential to revolutionize the search for new catalysts for specific applications primarily via high-throughput methodologies that allow researchers to scan through thousands or millions of potential catalysts in search of an optimal candidate. To date, the bulk of the literature on computational studies of heterogeneous catalysis has focused on idealized systems with near-perfect crystalline surfaces that are representative of macroscopic catalysts. Advancing the frontier to nanoscale catalysis, in particular, heterogeneous catalysis on nanoclusters, requires consideration of low-symmetry nanoparticles with realistic structures including the attendant complexity arising from under-coordination of catalyst atoms and dynamic fluxionality of clusters. In this thesis, we focus on understanding structure - property - function relationships of Platinum and Platinum-Ruthenium alloy nanoclusters on defective graphene supports, which are highly effective catalysts for methanol fuel cells. In particular, we focus on understanding the interplay between support defects and the electronic structure of supported nanoclusters, and the consequent impact on the thermodynamics and kinetics of the methanol decomposition reaction (MDR), a reaction of interest for renewable energy technologies such as direct-methanol fuel cells. Using density functional theory (DFT) modeling, we first investigate the adsorption and reaction thermodynamics of MDR intermediates on defective graphene-supported Pt13 nanoclusters with realistic, low-symmetry morphologies. We find that the support-induced shifts in catalyst electronic structure correlate well with an overall change in adsorption behavior of MDR intermediates. The reaction thermodynamics are modified by the support interaction to more favorable reaction free energies, suggesting greater catalytic activity. We also show that adsorption energy predictors established for traditional heterogeneous catalysis studies of MDR on macroscopic crystalline facets are equally valid on catalyst nanoclusters (supported or otherwise) with irregular, low-symmetry surface morphologies. To understand the kinetics of MDR on graphene-supported Pt13 clusters, we implement and apply a microkinetic model within a batch reactor setup. The microkinetic model predicts high activity for the MDR over nanoparticles that interact strongly with support defects, in comparison to larger nanoparticles that are only weakly influenced by the support which exhibit much lower activity; these results agree with fuel-cell level experimental results. We also find that the support effect induces changes in the most favorable reaction pathway, and in the populations of dominant surface species under realistic reaction conditions. Our studies provide molecular-level insights into experimental observations of enhanced catalytic activity of graphene-supported Pt nanoclusters for MDR and suggest promising avenues for further tuning of catalytic activity through computer-aided-engineering of catalyst-support interactions. An associated problem with modeling supported nanoclusters involves being able to generate, at the outset, realistic structures of nanoparticles. Using an empirical-potential-based genetic algorithm (developed by my colleague Dr. Hongbo Shi) and DFT modeling, we identify low-energy structures of Pt nanoparticles over the range of 10-100 atoms. We then show that there exists a size window (40-70 atoms) over which Pt nanoclusters bind CO weakly, the binding energies being comparable to those on Pt(111) or Pt(100) facets. The size-dependent adsorption energy trends are, however, distinctly non-monotonic and are not readily captured using traditional descriptors such as d-band energies or (generalized) coordination numbers of the Pt binding sites. Instead, by applying machine-learning algorithms (collaborative work with Dr. Hongbo Shi), we show that multiple descriptors, broadly categorized as structural and electronic descriptors, are essential for qualitatively capturing the CO adsorption trends. Our approach allows for building quantitatively predictive models of site-specific adsorbate binding on realistic, low-symmetry nanostructures, which is an important step in modeling reaction networks as well as for rational catalyst design in general. We also extend the Pt-C empirical potential to the Pt-Ru-C system that will allow for future studies of supported Pt-Ru nanoclusters that are among the best known catalysts for MDR. Developing the Pt-Ru-C empirical potential was based on previously established potentials for the Pt-C and Ru-C system. Achieving an accurate Pt-Ru-C potential required careful benchmarking against experimental and DFT data, resulting in targeted adjustment of the Pt-Ru and Ru-C bond parameters.