TiO 2 fibers were prepared through electrospinning of poly methyl methacrylate (PMMA) and titanium isopropoxide (TIP) solution followed by calcination of fibers in air at 500 ∘ C. Cetyltrimethylammonium bromide (CTAB) protected palladium nanoparticles (Pd NPs) prepared through reduction method were successfully adsorbed on the TiO 2 nanofibers (NF). Combined studies of X-ray diffraction (XRD), scanning electron microscope (SEM), and transmission electron microscope (TEM) indicated that the synthesized Pd/TiO 2 had anatase. BET indicated that the synthesized TiO 2 and Pd/TiO 2 had a surface area of 53.4 and 43.4 m 2 /g, respectively. The activity and selectivity of 1 mol% Pd/TiO 2 in the Heck reaction have been investigated towards the Mizoroki-Heck carbon-carbon cross-coupling of bromobenzene (ArBr) and styrene. Temperature, time, solvent, and base were optimized and catalyst was recycled thrice.1 H NMR and 13 C NMR indicated that stilbene, a known compound from literature, was obtained in various Heck reactions at temperatures between 100 ∘ C and 140 ∘ C but the recyclability was limited due to some palladium leaching and catalyst poisoning which probably arose from some residual carbon from the polymer. The catalyst was found to be highly active under air atmosphere with reaction temperatures up to 140 ∘ C. Optimized reaction condition resulted in 89.7% conversions with a TON of 1993.4 and TOF value of 332.2 hr −1 .
Background: Electrospinning is a technique for producing nanofibers, useful in many fields of nanotechnology. The size and morphology of the nanofibers obtained depends on the polymer solution properties, the parameters of the equipment and the conditions of the surrounding. In almost all reported electrospinning set ups, a pump ,which regulates the flow of the polymer solution, has been included as one of the requirements. In this study, the effects of solution concentration, viscosity, voltage and the distance from the tip of the syringe to the aluminum collector on the morphology and diameters of poly(methyl methacrylate)(PMMA) fibers were investigated, using a pump-free electrospinning set up. Methods: Varied PMMA concentration (50 -120 mg/mL), voltage (10-18 kV) and distance (5 – 18 cm) of electrospinning were studied and the optimum electrospinning conditions identified. PMMA/ titanium isopropoxide solution of ratio 1:2 was prepared, electrospun at optimized conditions (15 kV, 18 cm, Dichloromethane/Dimethylformamide 60:40) and the fibers obtained analyzed using a scanning electron microscope. Results: Solutions of PMMA whose concentrations were less than 50 mg/mL, produced beads on fibers, whereas those at ~ 100 mg/mL formed the best bead-free fibers of diameter 350±50 nm. The results showed a direct dependence of fiber diameter on the solution viscosity. Fibers of larger diameters were obtained when the distance from the tip of the syringe to the aluminum collector and voltage were increased but at higher distances (>18 kV) fewer fibers were collected. When the voltage was steadily increased, the fibers broadened and the diameters were non-uniform due to splaying and splitting. Increasing the distance between the pipette-tip and the collector from 10 to 18 cm resulted in reduced electric field which in turn yielded fewer fibers. Conclusions: The results obtained in a pump free set-up were comparable to those eletrospun in the presence of a pump.
TiO2 fibers were prepared through electrospinning of polymethyl methacrylate (PMMA) and Titanium isopropoxide (TIP) solution followed by calcination of fibers in air at 500 ºC. CTAB protected Palladium nanoparticles prepared through reduction method were successfully adsorbed on the TiO2 nanofibers. Combined studies of X-ray diffraction (XRD), Scanning electron microscope (SEM) and Transmission electron microscope (TEM), indicated that the synthesized Pd/TiO2 was anatase phase. BET indicated that the synthesized TiO2 and Pd/TiO2 had a surface area of 53.4672 and 43.4 m 2 /g, respectively. The activity and selectivity of 1 mol % Pd /TiO2 in the Heck reaction has been investigated towards the Mizoroki-Heck carbon-carbon cross coupling of bromobenzene and styrene. Temperature, time, solvent and base were optimized and catalyst recycled twice. 1 H NMR and 13 C NMR indicated that stilbene, a known compound from literature was obtained in various Heck reactions at temperatures between 100 ºC and 140 ºC. but the recyclability was limited due to some palladium leaching and catalyst poisoning which probably arose from some residual carbon from the polymer. The catalyst was found to be highly active under air atmosphere with reaction temperatures up to 140 ºC. Optimized reaction condition resulted into 89.7 % conversions with a TON of 1993.4 and TOF value of 332.2 hr -1 .
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