자료유형  

 학위논문

Control Number  

0017160796

International Standard Book Number  

9798382716961

Dewey Decimal Classification Number  

540

Main Entry-Personal Name  

An, Suming.

Publication, Distribution, etc. (Imprint  

[S.l.] : University of Colorado at Boulder., 2024

Publication, Distribution, etc. (Imprint  

Ann Arbor : ProQuest Dissertations & Theses, 2024

Physical Description  

125 p.

General Note  

Source: Dissertations Abstracts International, Volume: 85-11, Section: B.

General Note  

Advisor: Skodje, Rex.

Dissertation Note  

Thesis (Ph.D.)--University of Colorado at Boulder, 2024.

Summary, Etc.  

요약Understanding single molecule catalysis kinetics is critical for interpreting complex catalytic mechanisms at their most fundamental level. Such insights not only provide a better understanding of catalytic reactions but also open the door to designing highly efficient and tailored catalysts with unprecedented precision, thereby driving innovation in fields ranging from sustainable energy production to pharmaceutical synthesis. In this thesis, a theoretical approach for the study of supported atom catalysis is developed based on recent advances in the study of single molecule kinetics. This perspective is particularly valuable for elucidating the role of disorder in single atom and single site catalysts on amorphous supports. The distribution of passage times (or waiting times) through a complex catalytic network originating from a set of coupled active sites is described using a probability distribution function, f(t), which reflects the local environment of the reaction center. An efficient algorithm based on linear algebra of the Markov transition matrix is devised to generate f(t) or its moments.The kinetics of the hydrogenation reaction of styrene on an organovanadium (III) catalyst supported on amorphous silica are then investigated. The kinetic model consists of three intertwined catalytic cycles emanating from three chemically distinct active sites to describe the chemistry. Density functional theory (DFT) calculations help determine the free energy barriers of the reactions, aiding in constructing the rate coefficient matrix. The disorder induced by the amorphous support material is categorized into a low-dimensional short-range component reflecting the covalent structures near the reaction center and a weaker long-range component modeling the bulk randomness. The results are analyzed across a wide range of concentration values and disorder scenarios, uncovering unusual structures in the f(t) probability distribution function (PDF) for certain cases, revealing the contribution of multiple catalytic pathways acting in concert.Furthermore, catalysis from single active sites is analyzed using methods developed from single molecule kinetics. Employing a stochastic Markov state description, the observable properties of general catalytic networks of reactions are expressed using an eigenvalue decomposition of the transition matrix for the Markov process. Through sensitivity analysis, the necessary eigenvalues and eigenvectors are related to the energies of controlling barriers and wells located along the reaction routes. The energetic span theory is generalized, allowing computation of the eigenvalues from several activation energies corresponding to distinct barrier-well pairings. The formalism is demonstrated for model problems and a physically realistic mechanism for an alkene hydrogenation reaction on a single atom catalyst. Spectral analysis allows identification of a hierarchy of timescales from the single molecule signal, corresponding to specific relaxation modes in the network.Moreover, a theory-based optimization strategy based on density functional theory (DFT) determination of the transition states and intermediates is presented for a low-dimensional coordinate representation of the heterogeneity of the active sites. This approach is applied to a vanadium catalyst on an amorphous SiO2 support, involving a large kinetic network described using a full-chemistry model. Without assuming a priori scaling relations or mechanism reduction, the optimal state of heterogeneity is found at atomic configurations where the activation energies for two distinct key chemical processes are equal. A posteriori, it is found that the system's behavior is consistent with linear free energy scaling relations in the randomness parameters. Energetic span theory proves useful in reducing the full chemistry model to a small number of key reactions. Combining a nonlinear optimization algorithm with energetic span theory significantly simplifies treating disordered systems.

Subject Added Entry-Topical Term  

Chemistry.

Subject Added Entry-Topical Term  

Energy.

Subject Added Entry-Topical Term  

Physical chemistry.

Subject Added Entry-Topical Term  

Inorganic chemistry.

Index Term-Uncontrolled  

Density functional theory

Index Term-Uncontrolled  

Hydrogenation reaction

Index Term-Uncontrolled  

Probability distribution function

Index Term-Uncontrolled  

Markov process

Index Term-Uncontrolled  

Vanadium catalyst

Added Entry-Corporate Name  

University of Colorado at Boulder Chemistry

Host Item Entry  

Dissertations Abstracts International. 85-11B.

Electronic Location and Access  

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Control Number  

joongbu:656629