Doctoral theses
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 compound valorization). However, the weak acidity, low hydrothermal stability and high cost of Ge significantly limited the practical use of Ge-containing zeolites.
This thesis 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.
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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. 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. This thesis was focused on the design of a series of elementosilicate zeolites with tunable properties (in particular, morphology, porosity, or acidity) either through controlling the crystallization mechanism or by manipulation with the zeolite structure and chemical composition.
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Zeolites are crystalline aluminosilicates and environmentally friendly solid acid catalysts thanks to their non-toxicity, large surface area, excellent (hydro)thermal stability, and tunable acidity. Traditionally, zeolite catalysts are applied in industrial processes related to petrochemistry, but several studies have recently shown their high potential in fine chemicals production and volatile organic compounds (VOCs) elimination. Advanced materials based on newly developed layered and nanosized zeolites have exhibited further fascinating properties, e.g., a short diffusion pathway, tunable structure and morphology. However, the limited correlation between key parameters of zeolite synthesis and their properties (structural, textural, acidic) and catalytic performance, especially for new layered and nanosized zeolites, hinders the development and application of zeolite catalysts.
This thesis was focused on the preparation of several sets of specific zeolite catalysts to gain further insights into the relationship between key properties of zeolites (structure, morphology, chemical composition, accessibility to acid sites or other functional groups, and organization of layers, among others) and their performance as catalysts, supports for other active phases or nanosized components of colloidal system
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This PhD thesis focuses on modification of the structure and textural properties of germanosilicates using different ways of post-synthesis treatment: the ADOR (Assembly –Disassembly – Organization – Reassembly) transformation and post-synthesis degermanation and alumination.
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Zeolites with encapsulated metal nanoparticles have attracted a wide attention in
heterogeneous catalysis due to their high catalytic activity, selectivity, and stability. The PhD
thesis was focused on design and synthesis of metal@zeolite catalysts with small and
uniformly distributed metal nanoparticles.
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The use of germanium in zeolite synthesis has significantly expanded their structural diversity. Incorporating Ge has enabled the creation of numerous unique frameworks with large and extra-large pores. Furthermore, leveraging the hydrolytic instability of Ge–O bonds, germanosilicates have been used for: i) the top-down synthesis of new zeolite structures via the Assembly–Disassembly–Organization–Reassembly (ADOR) approach, and ii) isomorphous substitution with elements like Al, Ga, Ti, and Sn to introduce various acid functionalities into the framework.
In theory, the ADOR strategy offers broad applicability across structurally and chemically diverse zeolites. In practice, however, it has only been successfully applied to a limited number of germanosilicates, including Ti- or Al-containing UTL-type zeolites. This restricts the catalytic potential of ADORable zeolites and limits the range of reactions they can effectively catalyze.
The thesis aims to expand the ADOR synthetic method towards the preparation of ADORable Lewis acid zeolites with new structures and, to investigate their structure-property-activity relationship.
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Master theses
Recent research in zeolite science is focused on designing strategies for preparation of
hierarchical micro-mesoporous or micro-macroporous zeolites, with the purpose of replacing
toxic and environmentally unfriendly homogeneous catalysts used for different reactions,
involving bulky reagents and/or products. A one-pot three-component Prins-Friedel-Crafts
reaction of an aldehyde, homoallylic alcohol, and aromatic compound is one of the processes
demanding such intensification for efficient production of valuable heterocyclic compounds
containing the 4-aryltetrahydropyran moiety. This work provides a detailed catalytic
evaluation of specially synthesized Al- and Ga- substituted zeolites with the same topology
but variable crystal morphology to address the acidic and textural characteristics of a
heterogeneous acid catalyst, which are crucial for attaining high activity and selectivity in the
PFC reaction of butyraldehyde, 3-buten-1-ol and anisole.
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Zeolites are important industrial catalysts because of their porous structure, tunable acidobasic properties and toleration to environment. Zeolites containing tetravalent elements in the framework imposing Lewis acidity are highly active and selective catalyst of oxidation reactions involving hydrogen peroxide as “green” oxidant. This diploma thesis was aimed at characterization of acidobasic properties of Ti-, Sn- and Ge-substituted zeolites using FTIR spectroscopy of adsorbed pyridine and acetonitrile-d3. The concentration and strength of Lewis acid sites in the catalysts will be related to their activity in epoxidation reaction.
Electron diffraction (ED) is a powerful technique for determining the structure of crystalline materials, offering an alternative to single-crystal X-ray diffraction (SCXRD), which is often limited by crystal size. ED enables analysis at the nanoscale, making it especially valuable for samples with crystals too small for conventional methods. Using a transmission electron microscope (TEM), ED collects diffraction patterns that can be used to determine unit cell parameters, lattice type, and even full crystal structures. However, traditional ED requires significant expertise and is time-consuming.
Recent advances aim to streamline and automate both data collection and analysis. Notably, continuous rotation electron diffraction (cRED) enables rapid data acquisition in just a few minutes, allowing structure determination within a single day. This work demonstrates the application of the cRED method for the structural characterization of zeolites.
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Bachelor theses
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.
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Recently, post-synthesis degermanation/metallation approach opened the way to zeolite materials with new structures and variable functionalities promising for catalytic applications. However, the influence of the chemical composition of parent germanosilicate on the physicochemical characteristics of thus prepared Al-, Ti-, Sn-substituted zeolites has not been studied yet.
In this work, a series of Al-, Ti- and Sn-substituted zeolites were prepared using degermanation/metallation of IWW and ITH zeolites with variable Si/Ge ratios, while their physicochemical properties were studied using a set of characterization techniques, such as XRD, nitrogen physisorption, ICP-MS, UV-vis spectroscopy, and FTIR spectroscopy of adsorbed probe molecules.
The results of this B.Sc. thesis evidence that a variation in the Si/Ge ratio may result in modification of the crystal size and shape of germanosilicate zeolites and affect the state of metal atoms incorporated into zeolite by a degermanation/metallation approach.
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Zeolites are porous aluminosilicates widely used in acid catalysis due to their properties, such as Brønsted and Lewis acidity, thermal stability, and defined pore structure providing shape selectivity. Zeolites can be synthesized as nanolayered crystals that can be further modified by pillaring. These architectures are more open, thus can lead to novel applications of zeolites in catalysis. One of the acid-catalyzed reactions where 3D standard zeolites were shown to be active catalysts is cyclization of pseudoionone. This reaction is used for the synthesis of α-, β- , and γ-ionones, important organic compounds used in medicine and fragrance industries mainly as violet fragrances. Up to date, there are no reports on the catalytic activity of layered zeolites in ionone synthesis, however, these open structures have a potential to be utilized in such reactions due to the improved reactant diffusion through the catalyst. In this work, catalytic performance of the materials based on MFI zeolite layers was investigated in the conversion of pseudoionone-to-ionones.
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Heterogeneous catalysts for the Meerwein–Ponndorf–Verley (MPV) reduction of ketones and aldehydes are of interest due to the water sensitivity and separation challenges associated with homogeneous catalysts. In the MPV reaction, a hydrogen atom is transferred from a sacrificial alcohol to the carbonyl group, producing the corresponding alcohol. Tin- and zirconium-containing zeolites are effective catalysts for this hydrogen transfer. However, conventional 3D zeolites often pose diffusion limitations when reducing bulky molecules, such as terpenoids, due to restricted access to active sites. This study explores the use of 2D pillared zeolite catalysts as a solution to these diffusion constraints in MPV reductions.
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