Catalytic Oxidation of Toluene on Hydrothermally Prepared Ceria Nanocrystals

Ceria nanocrystals were prepared hydrothermally and tested as potential catalysts for oxidation of volatile organic compounds using toluene as a model compound. Pure ceria with a crystallite size of 4 nm, determined by the Scherrer method from XRD pattern has been obtained. The specific surface area of the prepared nanoparticles determined by BET analysis yielded 201 m2 g–1, while the band gap of 3.2 eV was estimated from DRS spectrum via Tauc’s plot. Catalytic tests were performed on calcined ceria (500 °C) with increased crystallite size (9 nm) caused by thermal treatment. The tests showed good activities for the toluene oxidation with T50 temperatures, corresponding to 50 % toluene conversion, observed at 250 °C and even lower temperatures depending on the total flow rate of the gas mixture. The one-dimensional pseudo-homogeneous model of the fixed bed reactor was proposed to describe the reactor performance and the appropriate kinetic parameters were estimated. Good agreement between experimental data and the proposed model was observed. This work is licensed under a Creative Commons Attribution 4.0 International License

Studies in the Propiothiolactone Series. II.* Preparation of DL-α-Succinimido- and L-α-(p-Toluenesulfonamido)-β-propiothiolactone

The compounds mentioned in the title were prepared via debenzylation and subsequent cyclization of α-succinimido- and α-(p-toluenesulfonamido)-β-benzylthiopropionyl chlorides with aluminum bromide in benzene at room temperature

Studies in the Propiothiolactone Series. II.* Preparation of DL-α-Succinimido- and L-α-(p-Toluenesulfonamido)-β-propiothiolactone

The compounds mentioned in the title were prepared via debenzylation and subsequent cyclization of α-succinimido- and α-(p-toluenesulfonamido)-β-benzylthiopropionyl chlorides with aluminum bromide in benzene at room temperature

Spektroskopski studij sintetskog forsterita dobivenog iz zeolitnih prekursora

Important ceramics materials are prepared from aluminosilicate based precursors using novel methods, offering at the same time a better control over many important properties. Forsterite, due to its good refractoriness with melting point at 2163 K, excellent electrical insulation properties even at high temperatures, low dielectric permittivity, thermal expansion and chemical stability, is a material of interest to engineers and designers especially as an active medium for tuneable laser and is also a material of interest to SOFC (Solid oxide fuel cells) manufacturers. The aim of this study is to investigate the synthesis of crystalline forsterite using different zeolite precursors previously activated by ball milling. Synthetic forsterite was synthesized from different zeolite precursors and MgO combining highenergy ball milling and thermal treatment of the mixture under determined conditions of time and temperature for each operation. In this research are studied the solid-state phase transformations taking place at temperatures below 1273 K. The obtained products were characterized using different spectroscopy techniques in comparison with surface analysis method and X-ray diffraction.Važni keramički materijali pripremljeni su iz alumosilikatnih prekursora, pri čemu su primijenjene novije metode, koje istodobno daju mogućnost intervencije u procese nastajanja i kontrolu nad mnogim svojstvima. Forsterit je silikatni materijal posebno interesantan inženjerima i konstruktorima procesne opreme, osobito u laserskoj tehnici i području gorivih čvrstih oksidnih ćelija (SOFC), zbog svoje kemijske stabilnosti, dobrih vatrostalnih karakteristika, tališta od 2163 K, izvrsnih električkih izolacijskih svojstava, male električne permitivnosti i slabog termičkog širenja. Cilj ovog rada je istraživanje na području sinteze kristalnog forsterita uz upotrebu različitih zeolitnih prekursora koji su prethodno aktivirani mljevenjem kugličnim mlinom. Sintetski forsterit dobiven je iz smjese MgO i različitih zeolitnih prekursora, kombinirajući visoko energijsko mljevenje i termičku obradu u kontroliranim vremenskim i temperaturnin uvjetima. U ovom istraživanju studirane su fazne transformacije čvrstog stanja koje se odvijaju na temperaturama ispod 1273 K. Dobiveni proizvod je opisan pomoću različitih spektroskopskih tehnika, analizom specifične površine i rendgenskom difrakcijom

Mechanochemical stability of hydrogen titanate nanostructures

Structural stability of nanostructured titanates was investigated for further processing and possible applications. With the aim to investigate their mechanochemical stability we applied highenergy ball milling and studied induced phase transitions. Hydrogen titanates having two different morfologies, microcrystals and nanotubes, were taken into consideration. During mechanochemical treatment of both morphologies, we observed the phase transition from hydrogen titanate to TiO2 anatase and then to TiO2 rutile. Anatase to rutile phase transition occurred without appearance of intermediate high pressure TiO2 II typically observed in the case of mechanochemical treatment of TiO2. In the case of microcrystals, phase transition from hydrogen titanate to anatase starts after longer milling time than in the case of nanotubes, which is explained by larger particles sizes of crystalline powder. On the contrary, further phase transition from anatase to rutile was occurred faster in crystalline powder than in the case of nanotubes. The sequence of phase transitions was studied by Raman spectroscopy and X-ray powder diffraction, while morphology and crystal structure at nanoscale were analyzed by high resolution electron microscopy

Spektroskopski studij sintetskog forsterita dobivenog iz zeolitnih prekursora

Important ceramics materials are prepared from aluminosilicate based precursors using novel methods, offering at the same time a better control over many important properties. Forsterite, due to its good refractoriness with melting point at 2163 K, excellent electrical insulation properties even at high temperatures, low dielectric permittivity, thermal expansion and chemical stability, is a material of interest to engineers and designers especially as an active medium for tuneable laser and is also a material of interest to SOFC (Solid oxide fuel cells) manufacturers. The aim of this study is to investigate the synthesis of crystalline forsterite using different zeolite precursors previously activated by ball milling. Synthetic forsterite was synthesized from different zeolite precursors and MgO combining highenergy ball milling and thermal treatment of the mixture under determined conditions of time and temperature for each operation. In this research are studied the solid-state phase transformations taking place at temperatures below 1273 K. The obtained products were characterized using different spectroscopy techniques in comparison with surface analysis method and X-ray diffraction.Važni keramički materijali pripremljeni su iz alumosilikatnih prekursora, pri čemu su primijenjene novije metode, koje istodobno daju mogućnost intervencije u procese nastajanja i kontrolu nad mnogim svojstvima. Forsterit je silikatni materijal posebno interesantan inženjerima i konstruktorima procesne opreme, osobito u laserskoj tehnici i području gorivih čvrstih oksidnih ćelija (SOFC), zbog svoje kemijske stabilnosti, dobrih vatrostalnih karakteristika, tališta od 2163 K, izvrsnih električkih izolacijskih svojstava, male električne permitivnosti i slabog termičkog širenja. Cilj ovog rada je istraživanje na području sinteze kristalnog forsterita uz upotrebu različitih zeolitnih prekursora koji su prethodno aktivirani mljevenjem kugličnim mlinom. Sintetski forsterit dobiven je iz smjese MgO i različitih zeolitnih prekursora, kombinirajući visoko energijsko mljevenje i termičku obradu u kontroliranim vremenskim i temperaturnin uvjetima. U ovom istraživanju studirane su fazne transformacije čvrstog stanja koje se odvijaju na temperaturama ispod 1273 K. Dobiveni proizvod je opisan pomoću različitih spektroskopskih tehnika, analizom specifične površine i rendgenskom difrakcijom

Proliferative advantage of specific aneuploid cells drives evolution of tumor karyotypes

Most tumors have abnormal karyotypes, which arise from mistakes during mitotic division of healthy euploid cells and evolve through numerous complex mechanisms. In a recent mouse model with increased chromosome missegregation, chromosome gains dominate over losses both in pretumor and tumor tissues, whereas T-cell lymphomas are characterized by gains of chromosomes 14 and 15. However, the quantitative understanding of clonal selection leading to tumor karyotype evolution remains unknown. Here we show, by introducing a mathematical model based on a concept of a macro-karyotype, that tumor karyotypes can be explained by proliferation-driven evolution of aneuploid cells. In pretumor cells, increased apoptosis and slower proliferation of cells with monosomies lead to predominant chromosome gains over losses. Tumor karyotypes with gain of one chromosome can be explained by karyotype-dependent proliferation, whereas, for those with two chromosomes, an interplay with karyotype-dependent apoptosis is an additional possible pathway. Thus, evolution of tumor-specific karyotypes requires proliferative advantage of specific aneuploid karyotypes

18-crown-6-sodium cholate complex: thermochemistry, structure and stability

18-crown-6, one of the most relevant crown ethers, and sodium cholate, steroidal surfactant classified as natural bile salt, are components of novel, synthesized coordination complex ; 18-crown-6-sodium cholate (18C6•NaCh). Like crown ethers, bile salts act as building blocks in supramolecular chemistry in order to design new functionalized materials with a desired structure and properties. In order to obtain thermal behavior of this 1:1 coordination complex, thermogravimetry and differential thermal analysis were used, as well as microscopic observations and differential scanning calorimetry. Temperature dependent infrared spectroscopy (IR) gave a detailed view into phase transitions. The structures during thermal treatment were observed with powder X-ray diffraction, and molecular models of the phases are made. Hard, glassy, colorless compound 18C6•NaCh goes through crystalline – crystalline polymorphic phase transitions at higher temperatures. The room temperature phase is indexed to a triclinic lattice, while in the high temperature phases molecules take randomly one of the two different configurations in the unit cell, resulting in the 2-fold symmetry. The formation of cholesteric liquid crystalline phase occurs simultaneously with partial decomposition, followed by the isotropisation with simultaneous and complete decomposition at much higher temperature, as obtained by IR. The results provide valuable information about the relationship between molecular structure, thermal properties, and stability of the complex, indicating the importance of an appropriate choice of cation, amphiphilic, and crown ether unit in order to synthesize compounds with desired behavior