Deependra Tripathi

Visible light driven photocatalytic oxidation of thiols to disulfides using iron phthalocyanine immobilized on graphene oxide as a catalyst under alkali free conditions

The present paper describes the synthesis of graphene oxide immobilized iron phthalocyanine (FePc) for the photocatalytic oxidation of thiols to disulfides under alkaline free conditions. Iron phthalocyanine tetrasulfonamide was immobilized on carboxylated graphene oxide supports via covalent attachment. The loading of FePc on GO nanosheets was confirmed by FTIR, Raman, ICP-AES, UV-Vis and elemental analyses. The synthesized catalyst was found to be highly efficient for the photo-oxidation of thiols to disulfides in aqueous medium using molecular oxygen as oxidant under visible light irradiation. The identification of photo-oxidation products and their quantitative determination was done using GC-MS. After completion of the reaction, the catalyst was easily recovered by filtration and reused for several runs without loss in activity and no leaching was observed during the reaction.

Preparation of silver–tungsten nanostructure materials for selective oxidation of toluene to benzaldehyde with hydrogen peroxide

We have developed a facile one-pot synthetic strategy to prepare Ag/WO3 nanostructure materials with different morphologies using a cationic surfactant, cetyltrimethylammonium bromide. These materials were employed as catalysts in the direct synthesis of toluene to benzaldehyde using H2O2. The morphology of the Ag/WO3 materials can be varied by changing the synthesis parameters. The size and shape of the Ag/WO3 nanostructure catalyst has direct influence on the toluene conversion and benzaldehyde selectivity. The effect of different reaction parameters like reaction temperature, H2O2 to toluene molar ratio, reaction time, and so forth have been studied in detail. The Ag/WO3 catalyst with ∼7 nm silver nanoparticles on the WO3 nanorod with a diameter ∼60 nm showed the best catalytic activity of 42% toluene conversion with 93% benzaldehyde selectivity. The catalyst did not show any leaching up to four reuses, showing the true heterogeneity of the catalyst.

Thiourea dioxide with TBHP: a fruitful and greener recipe for the catalytic oxidation of alcohols

Thiourea dioxide, owing to its hydrogen bonding ability, has been established as an exceptional, widely applicable organocatalyst. In the present paper, thiourea dioxide, an organocatalyst, in combination with t-butyl hydroperoxide (TBHP), a non-toxic and environmentally benign oxidant, serves to be a greener and more fruitful approach for the oxidation of alcohols to corresponding carbonyl compounds in excellent yields under mild reaction conditions.

Characterization and Identification of Polycyclic Aromatic Hydrocarbons in Diesel Particulate Matter

Emission of toxic exhaust from diesel engines is one of the major problems associated with the use of petroleum fuels. Particulate matter emission is perceived as a major pollutant, detrimental to the human health and environment, and has led to considerable study. Vehicular emissions comprise toxic pollutants that include unburnt hydrocarbons, polycyclic aromatic hydrocarbons, dioxins, and others. In this study, experiments have been carried out with the objective of determining overall particulate matter chemical composition and size. Electron microscopic images of the emitted soot were studied for average particle size distribution. More than 50 percent of the particles were in the range of 25 to 35 nanometers. Approximately 7, 9, 16, and 5 percent of the measured particles were from 35 to 40, 40 to 45, 45 to 50, and 50 to 55 nanometers, respectively. Determined elements were Al, Ba, Ca, K, Mg, Ti, Zn, and Zr at concentrations of 727, 53, 1100, 701, 1145, 638, 177, and 800 micrograms per milliliter respectively. Fifteen polycyclic aromatic hydrocarbons were detected in the extracts of filters and their concentrations were estimated. This investigation allows the comparison of particulate matter from different fuels and their blends.

Room Temperature Selective Epoxidation of Cyclooctene Over Ag nanoparticles Supported on Tungsten Oxide with H2O2

We have prepared silver nanoparticles (AgNPs) supported on tungsten oxide (WO3) in presence of cetyltrimethyl ammonium bromide (CTAB), a catinic surfactant. The catalyst was characterized by XRD, ICP-AES, FT-IR, SEM and TEM. The catalyst was highly active for selective oxidation of cyclooctene to cyclooctene oxide at room temperature with H2O2. The reusability of the catalyst which is a prerequisite for practical applications was performed and it was found that the catalyst exhibits no significant changes in its catalytic activity even after three reuses. A cyclooctene conversion of 55% with cyclooctene oxide selectivity of ~99% was achieved over this catalyst