The effects of Te on the performance of Mo-V catalysts prepared by hydrothermal synthesis

Some Mo-V-Te-La catalysts with varied component were prepared by hydrothermal synthesis and dried with microwave method. The component of the catalyst were greatly affected the crystal structure and Raman spectrum. The phase in the catalysts was different when the Mo, V, and Te content varied. When the catalyst containing the same Mo, V content, due to the effect of dopant of Te element (V0.07 Mo0.93)5O14 became the main phase in the catalyst. The catalyst also showed good activity for the reaction of selective oxidation propane to acrolein and acrylic acid.     

Vesicles prepared by β-cyclodextrins Inclusion complexes based on switching supramolecular interaction models induced by mixed solvents

Vesicles, based on two-head inclusion model (2:1) and one-head inclusion model (1:1) of carboxymethyl-β-cyclodextrin (CM-β-CD) with N,N′-bis (ferrocenylmethylene) diaminohexane (BFD) were prepared in water as well as in mixed solvents (water/methanol, water/ethanol, water/isopropanol, water/tert-butanol and water/glycerol). Morphologies and sizes of the aggregates in water and mixed solvents were observed by TEM and confirmed by DLS. A gradual change was shown with increasing proportion of the organic component in the mixed solvents. The polarities and steric hindrances of the mixed solvents would play key roles in the morphological changes of aggregates. Moreover, two possible formation mechanisms in different solvents were proposed based on UV, CV and ¹H-NMR data. The work in this paper may extend the applications of vesicles in biosimulation, drug-delivery and smart materials.     

Effect of nickel and cobalt ions on low temperature synthesis of mullite by sol–gel technique

Synthesis of mullite has been achieved at a low temperature of 600 °C by sol–gel technique in presence of nickel and cobalt ions. Samples were characterized by DTA, XRD, FESEM and FTIR spectroscopy. Mullite formation was found to depend on the concentration of the ions to a certain extent. Highly crystalline spherical mullite particles of dimension 35 nm were obtained at 0.02 M nickel or cobalt concentration.     

Electrochemical characterization of sodium and potassium doped lanthanum–titanium mixed oxides prepared by sol–gel method

Varying amounts of Na and K doped lanthanum–titanium oxides were synthesized by gel entrapment technique. These ceramics were characterized by X-ray diffraction. Microstructural investigations revealed grain growth in the doped material compared to undoped sample. Dielectric relaxations of these compounds were investigated in the temperature range 250–900 °C. A high degree of dispersion of the permittivity of un-doped lanthanum–titanium oxide and K and Na doped lanthanum–titanium oxide was observed in the frequency range <100 kHz which was attributed to oxygen vacancies. An increase in the permittivity values were observed with 1 % Na and K doped samples. The permittivity values further deteriorated with the dopant concentration. Using the Cole–Cole model, an analysis of the dielectric loss with frequency was performed, assuming a distribution of relaxation time. The dielectric loss was found to decrease by doping K in lanthanum–titanium oxide matrix. The dc conductivity studies showed that a temperature dependent hopping type mechanism is responsible for electrical conduction in the system.     

Studies of the ligand effect on the synthesis of dialuminoxanes by various β-diketiminato ligands

Reactions of LH (L = HC[C(Me)N(2,6-Me(2)C(6)H(3))](2)) with Me(n)AlCl(3-n) in diethyl ether afforded the adducts LH·AlMe(n)(Cl)(3-n) (n = 2, 3; 1, 4; 0, 5) in good yields. Treatment of 3 at elevated temperatures in toluene resulted in LAlMeCl (2) by intramolecular elimination of methane. The controlled hydrolysis of LAlMeCl (2) with equimolar amounts of water in the presence of N-heterocyclic carbene (NHC) gave a mixture of [LAl(Me)](2)(μ-O) (7) and dimeric [LAlMe(μ-OH)](2) (8). A convenient route for the preparation of [LAlMe(μ-OH)](2) (8) was the NHC-assisted controlled hydrolysis of LAlMeI (9). Stepwise hydrolysis of LAlH(2) (11) gave dialuminoxane hydride [LAl(H)](2)(μ-O) (12) and dialuminoxane hydroxide [LAl(OH)](2)(μ-O) (13), respectively. Anhydrous treatment of LAlCl(2) (1) or LAlMeCl (2) with Ag(2)O afforded chlorinated dialuminoxane [LAl(Cl)](2)(μ-O) (14) and [LAl(Me)](2)(μ-O) (7), respectively.     

Propane oxidative dehydrogenation over V-containing mixed oxides derived from decavanadate-exchanged ZnAl–layered double hydroxides prepared by a sol–gel method

The catalytic properties of ZnAlVO mixed oxides derived from decavanadate-exchanged ZnAl–layered double hydroxide (LDH) precursors prepared by a sol–gel method (ZnAlVO–LDHx,y) were investigated in the oxidative dehydrogenation of propane and compared with those of supported catalysts obtained by conventional impregnation of NH₄VO₃ on ZnO (ZnVO-I,y) and ZnAlO mixed oxide (ZnAlVO-I,y) supports. The effects of composition and calcination time on the catalytic behavior were particularly examined. Higher propane conversions were achieved at higher vanadium content and calcination time of the precursors. The LDH-derived catalysts were the most active ones in all the temperature range studied (300–425 °C). The order of activity for propane conversion for the different catalyst families varies as ZnAlVO–LDHx,y > ZnAlVO-I > ZnVO-I and follows the strength of the Lewis and Brønsted acid sites determined by monitoring of pyridine adsorption by Fourier transform infrared spectroscopy, whereas the propene selectivities are close together in agreement with the similar densities of basic sites determined by CO₂–temperature-programmed desorption measurements. It was indeed established that the acidity, rather than the nature of the crystalline phases, the reducibility, or the specific surface area of the samples, governs the catalytic activity.     

Enhanced visible light photoelectrochemical performance of β-Bi2O3-TiO2/ITO thin films prepared by aqueous sol-gel

Journal of Solid State Electrochemistry - Semiconductor heterojunction of β-Bi2O3-TiO2/ITO thin films was prepared by aqueous sol-gel and their photoelectrochemical and photoelectrocatalytic...     

Studies on the synthesis of orthogonally protected azalanthionines,and of routes towards β-methyl azalanthionines,by ring opening of N-activated aziridine-2-carboxylates

Orthogonally protected azalanthionines were successfully synthesised by the ring-opening of N-activated aziridine-2-carboxylates with protected diaminopropanoic acids (DAPs). The required DAPs were also prepared by ring-opening of N-activated aziridine-2-carboxylates with para-methoxybenzylamine, but it was found that the choice of aziridine protecting groups dictated both the success of the reaction as well as the regioselectivity of the isolated products. Attempts to extend the methodology to the preparation of the more sterically demanding β-methyl azalanthionines have, so far, been unsuccessful.     

A new synthesis of β,γ-unsaturated esters and allenic esters with construction of a carbon-carbon bond between α- and β-positions by the reaction of magnesium alkylidene carbenoids with lithium ester enolates

Treatment of lithium ester enolates with magnesium alkylidene carbenoids, generated from 1-chlorovinyl p-tolyl sulfoxides with isopropylmagnesium chloride via the sulfoxide-magnesium exchange reaction, gave β,γ-unsaturated esters in moderate to good yields. When this reaction was conducted with the lithium ester enolates of α-chlorocarboxylic acid esters, allenic esters were obtained. This procedure provides an unprecedented way for the synthesis of β,γ-unsaturated esters and allenic esters from ketones with the construction of a carbon-carbon bond between α- and β-positions.