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The role of boron oxide in oxidative dehydrogenation of hydrocarbons
Stoklasa, Jan ; Rubeš, Miroslav (advisor) ; Grajciar, Lukáš (referee)
Hexagonal boron nitride appears to be a suitable catalyst for the oxidative dehydrogenation of hydrocarbons. With its high selectivity towards alkenes and low production of carbon monoxide and dioxide, this catalyst emerges as an ideal candidate for this process. Literature references indicates that a radical mechanism seems probable, as evidenced by the dependence on the reactor shape and catalytic volume. The exact mechanism is still under investigation, and the focus of this study is to describe the initial steps of the reaction and investigate poorly defined boron oxide (BOx) species. It has been found that during the reaction of the catalyst surface model with the O2H radical, two types of complexes are observed - dispersive and covalently bound. By monitoring the interaction energies, it was discovered that both types are energetically very close to each other, with a low barrier for transition between them. When the surface interacts with the propyl radical, only dispersive complexes were observed.
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The role of topology and chemical composition of zeolites on their biomedical characteristics
Nováková, Denisa ; Grajciar, Lukáš (advisor) ; Rubeš, Miroslav (referee)
7 Abstract Zeolites are traditionally used materials in the petrochemical and chemical industry that have recently drawn attention for their possible utilization in biomedicine as drug and gene carriers, materials in bone tissue engineering, or adsorbents for detoxifying human organisms. Zeolites offer a possible solution for removing protein-binding uremic toxins, such as p-cresol, that are unremovable during classical hemodialysis. This bachelor's thesis focuses on analyzing the motion of water within zeolite with CAN framework topology using molecular dynamics simulations with neural network potentials. The obtained data is used to calculate the self-diffusion coefficients and analyze the effect of water loading, aluminum content, and the distribution of aluminum atoms on water diffusion and degree of deprotonation of Brønsted acid sites (BASs). In addition, the thoroughly tested water-loaded CAN models are used for evaluation of the interaction between the zeolite framework and water molecules and p-cresol in the context of potential application of zeolites for dialysis. Key words zeolites, machine learning, biomedicine, p-cresol, CAN
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Theoretical insights into encapsulated noble metals
Hou, Dianwei ; Heard, Christopher James (advisor) ; Logsdail, Andrew (referee) ; Rubeš, Miroslav (referee)
Noble metals are widely used in industry due to their excellent catalytic and optical properties. Because of limited reserves and high prices, it is desired to make effective use of every atom. It has been possible in recent years to produce subnanometer clusters or even isolated atoms, despite their low resistance against sintering. Furthermore, it has been recently established that the encapsulation of single atoms and subnanometer noble metal clusters can be achieved via trapping at metal oxides, ranging from two-dimensional layered materials to the void space within the pores of zeolites. However, neither the atomistic mechanisms of atom/cluster trapping, nor the means by which they may be optimized are known. Furthermore, the relationship between the physical and electronic state of trapped atoms/clusters and their reactive properties in catalysis are currently only weakly understood. In this thesis, we used theoretical methods ranging from global structure optimization to kinetic Monte Carlo to identify the roles of cluster size, charge state, and the present and type of common adsorbents on the stability, catalytic and optical properties of subnanometre-sized noble metal clusters trapped at metal oxides. This thesis takes the form of three sections: (1) Structure, stability, and migration...
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A novel approach for description of non-covalent intermolecular interactions
Rubeš, Miroslav ; Bludský, Ota (advisor) ; Fišer, Jiří (referee) ; Jurečka, Petr (referee)
Charles University in Prague Faculty of Science Department of Modeling of Chemical Properties of Bio- and Nanostructures A novel approach for description of non-covalent intermolecular interactions Dissertation Thesis Abstract Mgr. Miroslav Rubeš Supervisor: RNDr. Ota Bludský, CSc. Institute of Organic Chemistry and Biochemistry AS CR Center for Biomolecules and Complex Molecular Systems Prague 2010 Introduction Non-covalent interactions play a major role in many important physical, chemical, and biological processes that include, for instance, inter-molecular interactions between biomolecules, adsorption and separation, self-assembly in supra-molecular chemistry, and catalytic activity. To gain a deeper understanding of such processes at the atomistic level it is often necessary to investigate these systems theoretically. Due to the complex character of relevant systems, realistic models include hundreds of atoms and, thus, the computational investigation must rely on rather approximate methods. An accurate description of these systems still represents a major challenge for theoretical chemists. Methods based on density functionals (density functional theory, DFT) are currently among the most popular approaches for computational treatment of large systems. Unfortunately, the non-covalent interactions...
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