Syntéza nových dvojrozměrných zeolitů a jejich postsyntetické modifikace

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...Význam udržitelných chemických technologií a snižování ekologické náročnosti chemických procesů neustále roste. Ačkoli je známa řada různých metod výroby epoxidů, sulfoxidů a sulfonů, přímá selektivní oxidace výchozích látek s využitím jednoduchého oxidačního činidla je velmi žádoucí z pohledu ekonomického i ekologického. Hlavním cílem této práce je design a příprava nových zeolitů s obsahem titanu, schopných katalyzovat selektivní oxidaci objemných organických látek s využitím peroxidu vodíku jako oxidačního činidla. Studována byla zejména epoxidace cyklických olefinů a terpenů a oxidace objemných thioetherů na příslušné sulfoxidy a sulfony. V rámci této práce byla připravena dvojice nových titanosilikátů s extra velkými póry (Ti-CFI, Ti-UTL). Titanosilikáty Ti-CON, Ti-AFI, Ti-IFR byly připraveny deboronací a následnou impregnací roztokem titanového prekursoru. Dále byly připraveny dvě skupiny dvojrozměrných titanosilikátů na bázi modifikovaného vrstevnatého TS-1 a vrstevnatého prekursoru Ti-IPC-1P, který vzniká "top-down" modifikací Ti-UTL. V neposlední řadě byl Ti-UTL přeměněn na dvojici nových materiálů Ti-IPC-2 (struktura OKO) a Ti-IPC-4 (struktura PCR) s menšími póry ve smyslu "ADOR" přeměny. Toto je první příklad "ADOR" přeměny titanosilikátů. Zejména materiály připravené pilířováním...Department of Physical and Macromolecular ChemistryKatedra fyzikální a makromol. chemieFaculty of SciencePřírodovědecká fakult

Synthesis and Post-synthesis Modification of Novel 2-Dimensional Zeolites

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..

Fluoride etching opens the structure and strengthens the active sites of the layered ZSM-5 zeolite

International audienc

Fluoride etching opens the structure and strengthens the active sites of the layered ZSM-5 zeolite

International audienceThe NH4F etching is a chemical approach for the preparation of hierarchical zeolites without substantial modification of their framework composition and acidic properties. We employed this approach to modify the 2-dimensional form of ZSM-5 and obtain a catalyst for bulky molecules conversion. The etching conditions were varied in order to obtain hierarchical ZSM-5 with different level of dissolution. Thus, obtained derivatives of 2-dimensional ZSM-5 were thoroughly studied in order to get deep insights into the effect of fluoride treatment. The 2-dimensional ZSM-5 was found unexpectedly stable under etching conditions, which is a consequence of the high quality of zeolite crystals containing a limited number of defect zones and misoriented crystalline domains, in contrast to conventional ZSM-5. Fluoride etching was also used to de-pillar 2-dimensional ZSM-5. The morphology and textural properties of the de-pillared ZSM-5 were very similar to those of the parent layered ZSM-5. Accordingly, amorphous and extra-framework species were dissolved first, resulting in the complete removal of extra-framework Al, thereby strengthening the active sites. In summary, the fluoride etching opens the structure of layered ZSM-5 and strengthens its acid sites when combined with dealumination during calcination

Catalytic activity of advanced titanosilicate zeolites in hydrogen peroxide S-oxidation of methyl(phenyl)sulfide

Titanium-containing zeolite-based catalysts have been synthesized and investigated as catalysts in methyl (phenyl)sulfide oxidation with hydrogen peroxide. A hierarchical TS-1 prepared by the secondary templating and a layered TS-1 without and with silica and silica-titania pillars have been studied. Conventional TS-1 was a benchmarking material. The study focuses on observation of the different catalytic performance with regard to textural properties; presence and volume of mesopores and different diffusion characteristics. Thus, a deficiency and excess of the oxidizing agent were used in the catalysed reactions and the progress of reaction and selectivity to products were studied. All tested catalysts have shown after 240 min almost total conversion of methyl (phenyl)sulfide with different selectivity (substrate/catalyst mass ratio 10). It was observed that the reactants ratio hydrogen peroxide/ methyl(phenyl)sulfide influences the selectivity to sulfoxide or sulfone over a particular catalyst. In the case of hydrogen peroxide deficiency experiments (H2O2/sulfide = 0.5 mol/mol) the catalysts exhibited different distributions of products. Lamellar catalyst provided 100% selectivity to sulfoxide, the others in range of 90-65% selectivity to sulfoxide; however, the selectivity was independent on the reaction time and substrate conversion. In the case of the excess of the oxidant, except for Ti-pillared TS-1, all the catalysts showed stabile selectivity of 65% towards methyl(phenyl)sulfoxide being independent of the catalyst. The Ti-pillared TS-1 has shown, during the reaction progress, a decrease in the selectivity to sulfoxide from initial 60% to final 20% of sulfoxide at almost total conversion. The only case when higher selectivity to sulfone was achieved was gradual dosing of hydrogen peroxide.Web of Science32415314

Quantification of Lewis acid sites in 3D and 2D TS-1 zeolites: FTIR spectroscopic study

International audienc

Složitý svět jedním číslem aneb Česko v indexech

Publikace přináší přehled nejznámějších indexů, pomocí nichž hodnotí pokroky v nejrůznějších oblastech lidské činnosti ve světle dosahování udržitelnosti ve všech jejích pilířích – v environmentálním, sociálním i ekonomickém. Stav a vývoj v Česku je ukázán jednak pomocí skóre patnácti vybraných indexů a porovnáním s žádoucím stavem, tak i v rámci zemí Evropské unie a celého světa. Cílem knihy je najít odpovědi na otázky, jak Česko čelí komplexním výzvám nejen v oblasti životního prostředí, ale i v kontextu sociálně-ekonomickém. Jinými slovy, jaká je kvalita života či ekonomický vývoj, jelikož lidská společnost, její ekonomika a přírodní sféra fungují jako ucelený a propojený systém vzájemných interakcí. Jako nástroj pro mapování situace využívá hodnocení pomocí indexů, protože je u nich výrazná snaha o komplexní propojení nejrůznějších témat, která spolu zdánlivě nesouvisí, ve skutečnosti se však navzájem výrazně ovlivňují. Pořadí Česka se v mezinárodním srovnání u jednotlivých indexů liší v závislosti na zvoleném tématu, metodě výpočtu a vstupních datech. Jejich pochopení napomáhá uvedení silných a slabých stránek indexu a popisu, jak jsou jednotlivé indexy konstruovány – které indikátory a vstupní data do jejich výpočtu vstupují i popis metodiky výpočtu

Titanosilicates enhance carbon dioxide photocatalytic reduction

In this study, we aimed to correlate the structural properties of mesoporous zeolites with their photo catalytic performance. We prepared three types of titanosilicate zeolite photocatalysts and characterized them in detail. Titanosilicate photocatalysts showed significantly higher selectivity to CO2 reduction products, i.e., CH4 and CO, than a commercial TiO2, P25. Among them, the photocatalysts TS-1-V and Lam-TS 1, which consist of unit-cell-thick nanosheets with MFI zeolite topology, had the highest photoreduction quantum efficiency. The TPD-CO2 results showed that Lam-TS-1 and TS-1-V samples have stronger interactions with both CO2 and H2O than TS-1-C. Furthermore, the amount of CO2 chemisorbed/ desorbed on Lam-TS-1 and TS-1-V was higher, indicating a higher number of interaction sites. Therefore, the key factors in photocatalytic CO2 reduction with titanosilicate catalysts are not only the strength and number of CO2 adsorption sites but also the hydrophilicity of the photocatalysts, which strongly affects their efficiency and selectivity.Web of Science26art. no. 10139