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Synthesis of novel zeolite materials and their application in catalysis
Veselý, Ondřej ; Přech, Jan (advisor) ; Zima, Vítězslav (referee) ; Hronec, Mlan (referee)
Zeolites are crystalline microporous tectosilicates with acidic properties. The pore sizes of molecular dimensions restrict molecules from entering/exiting the pores based on the molecule size and geometry, or formation of certain (bulky) transition states within the pores. Accordingly, zeolites have become vital industrial catalysts, adsorbents and ion-exchangers. Zeolites are commonly synthesised by hydrothermal crystallization. However, this method provides only limited control over their crystal structure, morphology, or location of active sites within the framework. Some of these limitations can be overcome using an alternative synthetic method; the Assembly-Disassembly-Organisation- Reassembly (ADOR). The ADOR transforms a parent (germanosilicate) zeolite into a layered precursor and subsequently uses the layers as building blocks for a new zeolite framework. We aimed to develop methodology to control the crystal morphology of germanosilicate zeolite UTL (Assembly), determine the mechanism of the UTL hydrolysis (Disassembly), and to reconstruct the parent UTL zeolite from the ICP-1P layered material (Organisation and Reassembly) since the traditional ADOR yields zeolites of smaller channel size but the parent UTL. We found the UTL crystal morphology progressively varies the Si/Ge molar ratio...
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Labile elementosilicates as intermediates for design of novel materials
Yue, Qiudi ; Opanasenko, Maksym (advisor) ; Hronec, Mlan (referee) ; Zima, Vítězslav (referee)
Zeolites are crystalline microporous materials with three-dimensional frameworks built from corner-sharing TO4 tetrahedra. Traditionally, zeolites are defined as aluminosilicates (T = Si and Al). Nowadays, the skeleton atoms have been expanded to other tri-/tetra-valent elements, including B, Ga, Ge, Ti, etc., due to the chemical flexibility of zeolites. Resulting materials are termed as elementosilicates for respective element-containing zeolites. Such materials exhibit fascinating properties due to the different nature of elements in the framework, e.g. structural flexibility and tunable acidity. Taking advantage of the unique properties of elementosilicate zeolites, their applications as the starting solids for the synthesis of new materials and as adsorbents for gas separation have made great progress. However, the complexity of the factors affecting the zeolite synthesis limits the possibility to control the key parameters of zeolites formation, e.g. crystallization mechanism, crystal growth rate, and phase selectivity. From the another side, for particular zeolite systems being perspective for gas separation, correlation between the chemical composition of designed structures and their adsorption performance is elusive. Considering the above statements, this thesis was focused on the design...
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Design of sustainable catalysts by post-synthesis modification of germanosilicate zeolites
Zhang, Jin ; Shamzhy, Mariya (advisor) ; Hronec, Mlan (referee) ; Kubička, David (referee)
1 Abstract Due to the presence of small structural units (e.g., D4R, D3R), the frameworks of germanosilicate zeolites are generally characterized by high pore volumes and multidimensional/extra-large pore systems, making them especially suitable in processing bulky molecules (in particular, involved in biomass-derived compounds valorization). However, weak acidity, low hydrothermal stability and high cost of Ge significantly limit the practical use of Ge-containing zeolites. This thesis is aimed at design of sustainable germanosilicate zeolite-based catalysts of modifiable chemical composition and tunable porosity for relevant acid-catalyzed reactions, such as ketalization of polyols, epoxidation of olefins, Baeyer-Villiger oxidation of cyclic ketones and Meerwein-Ponndorf-Verley reduction of aldehydes. Germanosilicate zeolites of different structures, including medium-pore ITH, large pore IWW, extra-large pore UTL and *CTH, were thoroughly characterized using a combination of techniques (i.e., XRD, physisorption, electron microscopy, chemical analysis, among others) and subjected to different post-synthesis modifications to address synthesis-structure-activity relationships in the designed germanosilicate-zeolite based catalysts. In ketalization of glycerol to solketal, weak acid centers of IWW and UTL...
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Stabilization of metal nanoparticles in MWW zeolite for catalytic applications
Molitorisová, Sidónia ; Shamzhy, Mariya (advisor) ; Hronec, Mlan (referee)
Controlling both size of metal nanoparticles (MNPs) and acidobasic characteristics of the zeolite support is highly desirable for preparation of stable and active bifunctional catalysts. 2D-3D transformation of layered zeolite precursor into three-dimensional zeolite coupled with metal encapsulation is one of the most efficient synthetic strategies so far to achieve the appropriate metal dispersion and aggregative stability of MNPs within zeolite matrix. Nevertheless, the effect of support acidic characteristics on the properties of thus prepared metal@zeolite catalyst remained unrevealed, while the synthetic strategy itself requires further optimization to minimize the loss of metal component. This work addresses the influence of chemical composition of zeolite layered precursor on physical-chemical and catalytic properties of metal@zeolite catalysts prepared via 2D-3D transformation strategy, taken Pd@MCM-222D-3D system as a representative example. Both Si/Al ratio of MCM-22P layered precursor (e.g., Si/Al = 15, 20, 30) and Pd loading (e.g., 0.1, 0.3, 0.8 wt.%) were varied resulting in a set of nine Pd@MCM-222D-3D catalysts. In addition, three Pd@MCM-22impreg catalysts with the same metal loading (0.1 wt.%), but different Si/Al ratios of a support were synthesized via conventional impregnation...
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Chemistry of the Interlamellar Space of Two-dimensional Zeolites
Mazur, Michal ; Čejka, Jiří (advisor) ; Zima, Vítězslav (referee) ; Hronec, Mlan (referee)
The presented PhD thesis is focused on the synthesis, characterization, and modifications of zeolites and zeolitic materials. The main interests are two-dimensional (2D) zeolites and modification of their interlamellar space. Presented work was performed at the Department of Synthesis and Catalysis at J. Heyrovský Institute of Physical Chemistry in Prague, Czech Republic under the supervision of Prof. Jiří Čejka. Zeolites are inorganic crystalline solids with a microporous framework structure. They are widely used as catalysts, sorbents, and ion-exchangers. Conventional zeolites have been recognized as three-dimensional (3D) tetrahedrally-connected frameworks. However, some of them are also known to exist in various layered forms (2D zeolites). Recently, the transformation of 3D germanosilicate UTL into layers (IPC-1P) has started a new branch in 2D zeolites chemistry. This chemically selective degradation of UTL framework was performed via acid hydrolysis. In the structure of this germanosilicate, Ge atoms are preferentially located in specific building units, double-four-rings (D4R), which connect dense silica layers. Modifications of the layered precursor IPC-1P led to discovery of the two novel 3D zeolites: IPC-4 (PCR) and IPC-2 (OKO). This novel approach in the zeolite synthesis, called ADOR...
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Synthesis and Post-synthesis Modification of Novel 2-Dimensional Zeolites
Přech, Jan ; Čejka, Jiří (advisor) ; Bulánek, Roman (referee) ; Hronec, Mlan (referee)
Development of sustainable and environmentally friendly chemical processes is of vital importance nowadays. Although there is a palette of different synthetic methods for the formation of epoxides, sulphoxides and sulphones, from both economic and environmental points of view, a direct oxidation with a simple oxidant is highly appreciated. The main goals of the thesis were design and synthesis of novel titanium containing zeolitic materials with the ability to catalyse selective oxidation of sterically demanding organic compounds, particularly epoxidation of cyclic olefins and terpenes and oxidation of bulky thioethers to corresponding sulphoxides and sulphones with hydrogen peroxide as the oxidant. Two novel extra-large pore titanosilicates were prepared by means of hydrothermal synthesis (Ti-CFI, Ti-UTL), three large-pore titanosilicates (Ti-CON, Ti-AFI, Ti-IFR) were prepared using two step deboronation - liquid phase titanium impregnation procedure and two groups of lamellar materials were prepared. One group was based on modified nanosheet TS-1; the other was prepared from Ti-IPC- 1P lamellar precursor, which was prepared by means of top-down transformation of Ti-UTL. Last but not least, the Ti-UTL was transformed into new titanosilicates Ti-IPC-2 (OKO structure) and Ti-IPC-4 (PCR structure) by...
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