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Modeling and simulation of heterogeneous catalytic reactions : from the molecular process to the technical system
The Nobel Prize in Chemistry 2007 awarded to Gerhard Ertl for his groundbreaking studies in surface chemistry highlighted the importance of heterogeneous catalysis not only for modern chemical industry but also for environmental protection.
eBook
Fundamental concepts in heterogeneous catalysis
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
eBook
Computational modeling of homogeneous catalysis
Traditionally, the application of computational chemistry to homogeneous catalysis had been limited because of the size and complexity of the molecules involved. However, recent progress in both computer power and theoretical methods have led to a new scenario where calculations can have a significant impact in both the understanding and the optimization of catalytic cycles. As a result, computational modelling is now an essential tool for the characterization and understanding of the reaction mechanisms at play in homogeneous catalysis. Computational Modelling of Homogeneous Catalysis is an extensive collection of recent results on a wide array of catalytic processes. The chapters are, in most cases, authored by the researchers who have performed the calculations. The book illustrates the importance of computational modelling in homogeneous catalysis by providing up-to-date reviews of its application to a variety of reactions of industrial interest, including: + olefin polymerization; + hydrogenation; + alkene/alkyne isomerization; + hydroformylation; + hydroboration; hydrosylation; + dihydroxylation; + benzannulation; + epoxidation; + N-N triple bond activation. This book facilit.
eBook
Combinatorial development of solid catalytic materials
The book provides a comprehensive treatment of combinatorial development of heterogeneous catalysts. In particular, two computer-aided approaches that have played a key role in combinatorial catalysis and high-throughput experimentation during the last decade — evolutionary optimization and artificial neural networks — are described. The book is unique in that it describes evolutionary optimization in a broader context of methods of searching for optimal catalytic materials, including statistical design of experiments, as well as presents neural networks in a broader context of data analysis. It is the first book that demystifies the attractiveness of artificial neural networks, explaining its rational fundamental — their universal approximation capability. At the same time, it shows the limitations of that capability and describes two methods for how it can be improved. The book is also the first that presents two other important topics pertaining to evolutionary optimization and artificial neural networks: automatic generating of problem-tailored genetic algorithms, and tuning evolutionary algorithms with neural networks. Both are not only theoretically explained, but also well illustrated through detailed case studies.
eBook
Active sites for CO₂ hydrogenation to methanol on Cu/ZnO catalysts
The active sites over commercial copper/zinc oxide/aluminum oxide (Cu/ZnO/Al₂O₃) catalysts for carbon dioxide (CO₂) hydrogenation to methanol, the Zn-Cu bimetallic sites or ZnO-Cu interfacial sites, have recently been the subject of intense debate. We report a direct comparison between the activity of ZnCu and ZnO/Cu model catalysts for methanol synthesis. By combining x-ray photoemission spectroscopy, density functional theory, and kinetic Monte Carlo simulations, we can identify and characterize the reactivity of each catalyst. Both experimental and theoretical results agree that ZnCu undergoes surface oxidation under the reaction conditions so that surface Zn transforms into ZnO and allows ZnCu to reach the activity of ZnO/Cu with the same Zn coverage. Our results highlight a synergy of Cu and ZnO at the interface that facilitates methanol synthesis via formate intermediates.
Journal Article
Practical quantum advantage in quantum simulation
The development of quantum computing across several technologies and platforms has reached the point of having an advantage over classical computers for an artificial problem, a point known as ‘quantum advantage’. As a next step along the development of this technology, it is now important to discuss ‘practical quantum advantage’, the point at which quantum devices will solve problems of practical interest that are not tractable for traditional supercomputers. Many of the most promising short-term applications of quantum computers fall under the umbrella of quantum simulation: modelling the quantum properties of microscopic particles that are directly relevant to modern materials science, high-energy physics and quantum chemistry. This would impact several important real-world applications, such as developing materials for batteries, industrial catalysis or nitrogen fixing. Much as aerodynamics can be studied either through simulations on a digital computer or in a wind tunnel, quantum simulation can be performed not only on future fault-tolerant digital quantum computers but also already today through special-purpose analogue quantum simulators. Here we overview the state of the art and future perspectives for quantum simulation, arguing that a first practical quantum advantage already exists in the case of specialized applications of analogue devices, and that fully digital devices open a full range of applications but require further development of fault-tolerant hardware. Hybrid digital–analogue devices that exist today already promise substantial flexibility in near-term applications.
The current status and future perspectives for quantum simulation are overviewed, and the potential for practical quantum computational advantage is analysed by comparing classical numerical methods with analogue and digital quantum simulators.
Journal Article
Influence of atomic site-specific strain on catalytic activity of supported nanoparticles
Heterogeneous catalysis is an enabling technology that utilises transition metal nanoparticles (NPs) supported on oxides to promote chemical reactions. Structural mismatch at the NP–support interface generates lattice strain that could affect catalytic properties. However, detailed knowledge about strain in supported NPs remains elusive. We experimentally measure the strain at interfaces, surfaces and defects in Pt NPs supported on alumina and ceria with atomic resolution using high-precision scanning transmission electron microscopy. The largest strains are observed at the interfaces and are predominantly compressive. Atomic models of Pt NPs with experimentally measured strain distributions are used for first-principles kinetic Monte Carlo simulations of the CO oxidation reaction. The presence of only a fraction of strained surface atoms is found to affect the turnover frequency. These results provide a quantitative understanding of the relationship between strain and catalytic function and demonstrate that strain engineering can potentially be used for catalyst design.
Detailed knowledge of how strain influences catalytic reactions remains elusive. Here, the authors experimentally measure the strain in supported Pt nanoparticles on alumina and ceria with atomic resolution and computationally explore how the strain affects the CO oxidation reaction.
Journal Article
Enzyme-catalysed 6+4 cycloadditions in the biosynthesis of natural products
Pericyclic reactions are powerful transformations for the construction of carbon–carbon and carbon–heteroatom bonds in organic synthesis. Their role in biosynthesis is increasingly apparent, and mechanisms by which pericyclases can catalyse reactions are of major interest
1
. [4+2] cycloadditions (Diels–Alder reactions) have been widely used in organic synthesis
2
for the formation of six-membered rings and are now well-established in biosynthesis
3
–
6
. [6+4] and other ‘higher-order’ cycloadditions were predicted
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in 1965, and are now increasingly common in the laboratory despite challenges arising from the generation of a highly strained ten-membered ring system
8
,
9
. However, although enzyme-catalysed [6+4] cycloadditions have been proposed
10
–
12
, they have not been proven to occur. Here we demonstrate a group of enzymes that catalyse a pericyclic [6+4] cycloaddition, which is a crucial step in the biosynthesis of streptoseomycin-type natural products. This type of pericyclase catalyses [6+4] and [4+2] cycloadditions through a single ambimodal transition state, which is consistent with previous proposals
11
,
12
. The [6+4] product is transformed to a less stable [4+2] adduct via a facile Cope rearrangement, and the [4+2] adduct is converted into the natural product enzymatically. Crystal structures of three pericyclases, computational simulations of potential energies and molecular dynamics, and site-directed mutagenesis establish the mechanism of this transformation. This work shows how enzymes are able to catalyse concerted pericyclic reactions involving ambimodal transition states.
Enzymatic catalysis of pericyclic [6+4] cycloaddition reactions to form ten-membered rings is observed during biosynthesis of the macrocyclic antibiotic streptoseomycin, and the mechanism of these transformations is established.
Journal Article
Kinetic pathways of crystallization at the nanoscale
Nucleation and growth are universally important in systems from the atomic to the micrometre scale as they dictate structural and functional attributes of crystals. However, at the nanoscale, the pathways towards crystallization have been largely unexplored owing to the challenge of resolving the motion of individual building blocks in a liquid medium. Here we address this gap by directly imaging the full transition of dispersed gold nanoprisms to a superlattice at the single-particle level. We utilize liquid-phase transmission electron microscopy at low dose rates to control nanoparticle interactions without affecting their motions. Combining particle tracking with Monte Carlo simulations, we reveal that positional ordering of the superlattice emerges from orientational disorder. This method allows us to measure parameters such as line tension and phase coordinates, charting the nonclassical nucleation pathway involving a dense, amorphous intermediate. We demonstrate the versatility of our approach via crystallization of different nanoparticles, pointing the way to more general applications.
Low-dose liquid-phase transmission electron microscopy, particle tracking and numerical simulations are used to characterize the crystallization kinetics and pathways of gold nanoprisms at the single-particle level.
Journal Article