Sumita N. Rao

Bio: Sumita N. Rao is an academic researcher from Techno India. The author has contributed to research in topics: Catalysis & Schiff base. The author has an hindex of 5, co-authored 9 publications receiving 233 citations. Previous affiliations of Sumita N. Rao include Rani Durgavati University & Rashtrasant Tukadoji Maharaj Nagpur University.

Catalytic oxidation of styrene using cis-MoO2(L)(solv) [L=salicylidene salicyloyl hydrazine) and its zeolite composite as catalysts in the presence of molecular oxygen

Abstract: The catalytic oxidation of styrene using cis -MoO 2 (L)(solv) [L=Salicylidene Salicyloyl Hydrazine) and its zeolite-Y composite as catalysts in the presence of molecular oxygen and in the temperature range 50–70°C is studied. The oxidation products are found to be styrene epoxide and phenyl acetaldehyde. Phenyl acetaldehyde is observed to form only in homogeneous catalytic system towards the end of a 5-h reaction period. A 77% conversion of styrene into products (styrene epoxide: phenyl acetaldehyde ratio=85:15) is obtained under homogeneous catalytic conditions, whereas use of complex zeolite composite resulted in 68% conversion of styrene into styrene epoxide selectively. Styrene epoxide is formed with a turnover of 9/mol Mo in catalyst at 60°C in homogeneous catalytic system. The turnover increased to 64 when encapsulated complex is used. The rate of styrene oxidation showed first-order dependence with respect to catalyst and substrate concentration. A mechanism for oxidation of styrene with cis -MoO 2 (L)(solv) is proposed and reasons for selective conversion of styrene into corresponding epoxide is presented.

Catalytic air oxidation of cyclooctene using cis-[MoO2(SAL-SH)(DMF)] (SAL-SH=salcylidene salicyloyl hydrazinato-) and its zeolite-Y encapsulated composite

Abstract: Oxidation of cyclooctene to cyclooctene epoxide using cis -MoO 2 (SAL-SH)(DMF) and its zeolite-Y encapsulated composite as catalysts is reported. The percent conversion into epoxide was 68% at 60°C under 0.1 mmol of cis -MoO 2 (SAL-SH)(DMF), 0.3 mmol of cyclooctene and under oxygen saturated conditions. The turnover with respect to Mo in the complex is eight. The percent conversion improved to 75% and the turnover increased nine times when complex-NaY composite is used under the same conditions. The oxidation reaction showed first order dependence with respect to the concentrations of catalyst and cyclooctene. The reaction is endothermic with an activation energy of 25.8 kcal mol −1 . A reaction scheme for oxidation of cyclooctene using cis -MoO 2 (SAL-SH)(DMF) is proposed and the higher activity observed with complex-NaY composite is attributed to absence of μ-oxo dimer formation in this case. The intermediate Mo(IV)O complex reacts with O 2 , regenerating the parent Mo(VI)O 2 complex, which participates cyclically in the reaction.

Pickling Waste as an Inexpensive Iron Source for Fenton Oxidation of Synthetic Dye Bath Waste

Abstract: A simple, low cost, highly effective, and useful Fenton oxidation treatment of synthetic dye bath waste with pickling liquor as a source of iron (Fe2+ catalyst) is reported. Optimizations of contact time, Fe2+ and H2O2 doses are carried out. Oxidative de-colorization and degradation of Reactive Blue 4 and Reactive Orange 16 was measured in terms of decrease in absorbance at their wavelength of maximum absorption (RB4, 599 nm; and RO16, 493 nm) and also as reduction in chemical oxygen demand (COD). Approximately, 62% COD was removed in 2 h at optimized doses of Fe2+ (8.95 mM) and H2O2 (61.8 mM) by using pickling waste as a source of Fe2+ catalyst. Similar performance efficiency was observed when neat FeSO4 was used as a source of Fe2+, indicating that pickling liquor can be a low cost source of Fe2+ to treat synthetic dye bath waste by Fenton method.

Synthesis and antioxidant activities of Schiff bases and their complexes: a review

Abstract: Schiff bases, named after Hugo Schiff, are aldehyde- or ketone-like compounds in which the carbonyl group is replaced by imine or azomethine group. They are widely used for industrial purposes and also have a broad range of applications as antioxidants. An overview of antioxidant applications of Schiff bases and their complexes is discussed in this review. A brief history of the synthesis and reactivity of Schiff bases and their complexes is presented. Factors of antioxidants are illustrated and discussed. Copyright © 2016 John Wiley & Sons, Ltd.

Polymer supported vanadium and molybdenum complexes as potential catalysts for the oxidation and oxidative bromination of organic substrates.

Abstract: The Schiff base (H2fsal-ohyba) derived from 3-formylsalicylic acid and o-hydroxybenzylamine has been covalently bonded to chloromethylated polystyrene cross-linked with 5% divinylbenzene (abbreviated as PS-H(2)fsal-ohyba, I). Treatment of [VO(acac)2] with PS-H2fsal-ohyba in dimethylformamide (DMF) gave the oxovanadium(iv) complex PS-[VO(fsal-ohyba).DMF] (1). Complex 1 can be oxidized into the dioxovanadium(v) species, PS-K[VO2(fsal-ohyba)] (2) on aerial oxidation in the presence of KOH or into the oxoperoxo species, PS-K[VO(O2)(fsal-ohyba)] (3) in the presence of H2O2 and KOH in DMF suspension. Similarly, PS-[MoO(2)(fsal-ohyba).DMF] (4) has been isolated by the reaction of [MoO2(acac)2] with PS-H2fsal-ohyba. All these complexes have been characterised by various techniques. These complexes catalyse the oxidation of styrene, ethylbenzene and phenol efficiently. Styrene gives five reaction products namely styrene oxide, benzaldehyde, 1-phenylethane-1,2-diol, benzoic acid and phenylacetaldehyde, while ethylbenzene gives benzaldehyde, phenyl acetic acid, styrene and 1-phenylethane-1,2-diol. The oxidation products of phenol are catechol and p-hydroquinone. These catalysts are also able to catalyse the oxidative bromination of salicylaldehyde to 5-bromosalicylaldehyde with ca. 80% selectively in the presence of aqueous 30% H2O2/KBr, a reaction similar to that exhibited by vanadate-dependent haloperoxidases. Their corresponding neat complexes have also been prepared and their catalytic activities have been compared.