Creation of acid sites by La-ions in L zeolite

The creation of strong acid sites in alkaline K-L-zeolites on ion-exchanging with La-ions is reported. Acidity measurements have been carried out by temperature programmed desorption of adsorbed ammonia. Reaction data which confirm the creation of acid sites are also reported.

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Enhanced Adsorption Capacity and Photo-Catalytic Oxidative Activity of Dyes in Aqueous Medium by Hydrothermally Treated Titania Pillared Clay

Titania pillared montmorillonite clay was prepared by two different routes viz. 1) conventional ion exchange method and 2) modified method wherein the post hydrothermal treatment after ion-exchange was employed. The influence of the post hydrothermal treatment on the textural properties of titania-pillared clays was studied. The calcined clay was characterized by different physico-chemical techniques such as XRD, EDX, low temperature (77 K) nitrogen adsorption and UV-Vis diffuse reflectance spectroscopy. The content of pillared titania remained unchanged irrespective of the method of preparation. The method of preparation and severity of the conditions employed for the hydrothermal treatment resulted in alteration of the crystallinity and crystallite size of the anatase. The changes in the average pore diameter was found to comensurate with the changes in crystallite size of anatase phase. The increase in total pore volume as a function of the severity of the post hydrothermal treatment resulted in the decrease in micropore volume. The severity of the post hydrothermal treatment governed the extent of the blue shift in UV-Vis DRS spectra.The behaviour of titania pillared clays in adsorptive capacity and in photo-catalytic oxidation of methylene blue and victoria pure blue in aqueous medium was studied as a function of their physico-chemical characteristics. The titania pillared clays prepared by post hydrothermal route has shown enhanced adsorption capacity and photo-catalytic oxidation.     

Synthesis and characterization of gallosilicate pentasil (MFI) framework zeolites

Crystalline gallosilicates with a pentasil (MFI) framework containing Ga³⁺ in lattice positions were synthesised. The kinetic features of the hydrothermal system containing triethyl-n-butylammonium cations (TEBA)⁺ as template in the gel system have been investigated. The gallosilicate products were characterized by XRD, framework-IR, TG/DTA,²⁹Si and⁷¹Ga MASNMR and sorption measurements using standard techniques.

Sustainable routes to amines in recyclable water using ppm Pd catalysis

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N2Phos – an easily made,highly effective ligand designed for ppm level Pd-catalyzed Suzuki–Miyaura cross couplings in water

A new biaryl phosphine-containing ligand from an active palladium catalyst for ppm level Suzuki–Miyaura couplings, enabled by an aqueous micellar reaction medium. A wide array of functionalized substrates including aryl/heteroaryl bromides are amenable, as are, notably, chlorides. The catalytic system is both general and highly effective at low palladium loadings (1000–2500 ppm or 0.10–0.25 mol%). Density functional theory calculations suggest that greater steric congestion in N₂Phos induces increased steric crowding around the Pd center, helping to destabilize the 2 : 1 ligand–Pd(0) complex more for N₂Phos than for EvanPhos (and less bulky ligands), and thereby favoring formation of the 1 : 1 ligand–Pd^o complex that is more reactive in oxidative addition to aryl chlorides.

A new, biaryl phosphine-containing ligand, N₂Phos, forms a 1 : 1 complex with Pd resulting in an active catalyst at the ppm level for Suzuki–Miyaura couplings in water, enabled by an aqueous micellar medium. Notably, aryl chlorides are shown to be amenable substrates.     

Nano-TiO2-Induced Apoptosis by Oxidative Stress-Mediated DNA Damage and Activation of p53 in Human Embryonic Kidney Cells

The aim of the present study is to explore the mechanism of cytotoxic and genotoxic effects of TiO₂ nanoparticles on human embryonic kidney (HEK-293) cells. Toxicity was evaluated using changes in various cellular parameters of HEK-293 cells like morphology, viability, metabolic activity, oxidative stress and apoptosis. Oxidative stress was measured by the level of reactive oxygen species (ROS), lipid peroxidation, superoxide dismutase, catalase and glutathione peroxidase. Apoptosis induced by nano-TiO₂ was characterized by PI staining and DNA ladder assay. Furthermore, apoptotic proteins such as p53 and Bax were analysed by western blot. Our results indicate that nano-TiO₂ induces cytotoxicity in a time- and dose-dependent manner. Oxidative stress and apoptosis were induced by exposure to nano-TiO₂. Moreover, the expression of p53, Bax and caspase-3 were increased in a dose-dependent pattern. In conclusion, ROS-mediated oxidative stress, the activation of p53, Bax, caspase-3 and oxidative DNA damage are involved in the mechanistic pathways of nano-TiO₂-induced apoptosis in HEK-293 cells.     

Role of micro-structure and interfacial properties in the higher photocatalytic activity of TiO2-supported nanogold for methanol-assisted visible-light-induced splitting of water

This paper deals with the textural, microstructural and interfacial properties of Au/TiO(2) nanocomposites, in relation to their photocatalytic activity for splitting of water. TiO(2) samples of two different morphologies were employed for dispersing different cocatalysts, such as: Au, Pt, Ag or Cu, for the sake of comparison. The samples were characterized using powder XRD, XPS, UV-visible, thermoluminescence, SEM, HRTEM and SAED techniques. Compared to other metal/TiO(2) photocatalysts, Au/TiO(2) with an optimum gold loading of 1 wt% was found to exhibit considerably higher activity for visible light induced production of H(2) from splitting water in the presence of methanol. Further, the sol-gel prepared TiO(2) (s.TiO(2)), having spherical grains of 10-15 nm size, displayed better photoactivity than a Degussa P25 catalyst. The electron microscopy investigations on s.TiO(2) revealed significant heterogeneity in grain morphology of individual TiO(2) particles, exposure of the lattice planes, metal dispersion, and the interfacial metal/TiO(2) contacts. The gold particles were found to be in a better dispersed state. O(2) TPD experiments revealed that the gold nanoparticles and Au/TiO(2) interfaces may serve as distinct binding sites for adsorbate molecules. At the same time, our thermoluminescence measurements provide an insight into Au-induced new defect states that may facilitate the semiconductor-to-metal charge transfer transition. In conclusion, the superior photocatalytic activity of Au/TiO(2) may relate to the grain morphology of TiO(2), dispersion of gold particles, and the peculiar architecture of metal/oxide heterojunctions; giving rise in turn to augmented adsorption of reactant molecules and their interaction with the photo-generated e(-)/h(+) pair. The role played by methanol as a sacrificial reagent in photocatalytic splitting of water is discussed.     

Synthesis and Characterization of Transition Metal (Cu,Co, Fe) Complexes of 6-Methyl-5-arylhydrazono-2-thio-4-oxo-pyrimidine Ligand

The article deals with a study to synthesize transition metal complexes of copper, cobalt, and iron with the ligand 6-methyl-5-arylhydrazono-2-thio-4-oxo-pyrimidine (MATOPyr). The synthesized ligand and all metal complexes were characterized by elemental analysis, XRD, SEM, FTIR, ¹HNMR, UV-VIS, magnetic spectral studies, and Mössbauer measurements. The morphology of the ligand along with the complexes of all three metals was also deduced.     

Influence of physico-chemical parameters on n-hexane dehydrocyclization over Pt/LTL zeolites

The influence of different physico-chemical parameters such as crystallite size, nature of framework and extra-framework cations of the zeolite LTL and the extent of platinum loading on the catalytic performance of Pt/LTL catalysts in n-hexane dehydrocyclization reaction is reported.