K.T. Venkateswara Rao

Solvent-free hydration of alkynes over a heterogeneous silver exchanged silicotungstic acid catalyst

Silver exchanged silicotungstic acid (AgSTA) catalysts were prepared and characterized by X-ray diffraction, FT-IR spectroscopy, laser Raman, temperature programmed desorption of ammonia, FT-IR pyridine adsorption and X-ray photo electron spectroscopy. The activity of the catalysts was evaluated for the hydration of non-activated alkynes to corresponding carbonyl compounds without addition of any acid co-catalyst under solvent-free conditions. The highest catalytic activity was obtained for the catalyst with partially silver exchanged STA. This catalytic system provides one of the most straight forward syntheses of carbonyl compounds from terminal alkynes with Markovnikov-type regioselectivity. The catalyst can be recovered by simple filtration and is reusable without loss of activity and selectivity. A plausible reaction mechanism for the AgSTA catalyzed hydration of alkynes is proposed.

Vapor-phase selective aerobic oxidation of benzylamine to dibenzylimine over silica-supported vanadium-substituted tungstophosphoric acid catalyst

Silica-supported vanadium-substituted tungstophosphoric acid (TPAVx, x = 0–3) catalysts were prepared by an impregnation method and their physico-chemical properties derived from different spectroscopic techniques. The characterization results confirmed the incorporation of vanadium into the framework of heteropoly tungstate anion and the Keggin structure remained intact on SiO2. Vapor-phase aerobic oxidation of benzylamine was evaluated over these catalysts and dibenzylimine was obtained as the selective oxidative condensation product. Under optimized reaction conditions, 90% conversion of benzylamine with 95% selectivity to dibenzylimine was achieved over 20 wt% TPAV1/SiO2 catalyst. The catalyst showed constant activity, after an initial decrease by about 10%, during the time on stream analysis. Controllable acidity and redox properties of the catalyst were accountable for high catalytic activity and selectivity. A plausible reaction mechanism is also elucidated.

Role of vanadium in Keggin heteropoly molybdate supported on titania catalysts for oxidation reactions

Abstract.Vanadium-incorporated molybdophosporic acid catalysts supported on titania were prepared and characterized by FT-IR, X-ray diffraction and laser Raman spectroscopy. Characterization data reveals the incorporation of vanadium into the primary structure of Keggin ion of MPA. Catalysts activities were evaluated for oxidation of 1,2 benzenedimethanol using H2O2 and O2 as oxidants. Vanadium-containing catalysts showed high activity compared to their parent heteropoly acids. Oxidation ability depended on the number of V atoms present in Keggin heteropoly molybdate. Effect of reaction parameters on the oxidation ability was also evaluated. ᅟAn efficient synthesis of phthalide over vanadium incorporated molybdophosporic acid catalysts supported on titania were prepared and characterized by FT-IR, X-ray diffraction and Laser Raman spectroscopy. The oxidation ability depended on the number of V atoms in the Keggin molybdophosporic acid.

Targeted Renal Nerve Deactivation by Neurotropic Agents

Renal denervation through catheter-based ablation of renal nerves appears to be a promising therapy to treat resistant hypertension. Currently, there are several approaches in development to achieve ablation. These include energy-based approaches using radiofrequency (RF), ultrasound (intravascular and extra-vascular), beta-radiation and cryoablation [1–8]. All energy-based approaches are untargeted and have the potential to damage the vascular wall and surrounding tissue. Moreover, OCT findings have shown that RF probes damage the endothelial layer and cause thrombus formation on the intraluminal side [9]. Late stenosis in renal arteries have also been reported in a limited number of cases with RF ablation [10, 11]. In addition, energy-based approaches are not suitable for treating stented areas of the renal arteries [12].

Vanadium-Substituted Tungstophosphoric Acid Supported on Titania: A Heterogeneous Catalyst for Selective Oxidative Cleavage of Olefins to Carbonyl Compounds at Room Temperature

A series of vanadium-incorporated tungstophosphoric acid catalysts supported on titania were prepared and characterised by FT-infrared, X-ray diffraction, laser Raman spectroscopy, X-ray photoelectron spectroscopy and temperature-programmed reduction techniques. The characterisation data reveals the incorporation of vanadium into Keggin unit of TPA and its subsequent dispersion on titania. The catalytic activity of these catalysts was evaluated for oxidative cleavage of olefins to corresponding carbonyl compounds using H2O2 as oxidant at room temperature. Influence of vanadium presence in primary as well as secondary structure of tungstophosphoric acid on catalytic activity was also studied. Different parameters such as H2O2 to substrate mole ratio, solvent effect and temperature on activity and selectivity were also evaluated. The preparation of the catalyst is simple, easily recoverable and reusable many times without loss of activity and selectivity. The catalyst is also active even for oxidative cleavage of aliphatic olefins.