Preparation Of Ultra Thin-Fibrous Catalyst And Their Uses For The Catalytic Hydrogenation

The diameter of elctrospun fiber is in the range of nanometer to micrometer, and its length can reach several kilometers, so it has high length-diameter ratio and can offer large surface in the application. Fiberous composite carrying a nano particle can be reached via electrospinning method.Ultra thin fiberous catalyst was prepared via electrospun technology, which containing palladium or nickel, supported by polyacrylonitrile, polystyrene-acrylonitrile, polyvinylpyrrolidone and chitosan derivative, and their catalytic performance for hydrogenation was discussed in the paper. The prepared supported palladium catalyst with ultra thin fiber morphology can hydrogenate olefin and nitrobenzene hydrogenation in high efficiency. The loss of noble metal was reduced and the quality of the product was improved for formation of chemical bond between metal and polymer.The relation of system parameter and process parameter to electrospun fiber morphology were studied during the electrospun process, and the ultra thin fiber hydrogenation catalyst were sucessfully prepared by adjusting the parameters. The catalysts were characterized by SEM, TEM, IR, and XRD, respectively. The results showed that fiber diameter was in the range from nanometer to micrometer and metal particles were in a nano scale.In polyacrylonitrile supported nano-palladium catalyst, fiber diameter was in a range of 70～220nm and palladium agglomerate was in a range of 15～50nm. The catalytic behavior was studied by the hydrogenation ofα-octene at room temperature. The catalyst with smaller palladium particles and thinner fiber show better catalytic performance.The catalyst of poly(styrene-co-acrylonitrile) supported with palladium bearing a nano-fibrous morphology has high activity and good recycle for hydrogenation ofα-olefm at room temperature under 1 atm. hydrogen pressure. Moreover, it was found that the hydrogenation reaction ofα-hexene was accompanied with a isomerization reaction. The experiment results show that the yield of hexane catalyzed by the nano-fibrous catalyst was 4.7 times higher than that of PdCl₂/γ-Al₂O₃ catalyst. The hydrogenation ofα-tetradecylene, cyclohexene, nitrobenzol and styrene by the nano-fibrous catalyst was also studied, the selectivity to primary products of the hydrogenation of cyclohexene, nitrobenzol and styrene was 100%.The nano-fibrous polyvinylpyrrolidone supported palladium catalyst were prepared via electrospinning and heat cross-linking technique, the diameter of palladium (Pd) nanoparticles was under 15 nm. The catalytic property was tested by hydrogenation ofα-octene, cyclohexene and nitrobenzene in ethanol, octane and cyclohexane were prepared at normal temperature and under hydrogen pressure in a 100% yield, respectively.The catalyst, palladium supported with chitosan condensated with salicylaldehyde, was studied in hydrogenation ofα-octene, nitrobenzene, 4-nitrophenol and m-dinitrobenzene, it was active and good selectivity forα-octene and nitrobenzene, when the activation time is 90 min, the catalyst showed the best hydrogenation active.The catalyst, chitosan grafting acrylic acid copolymer supported palladium was prepared with a diameter of nanofiber in 70-200 nm, and the metals particles size in a range of 10-40 nm, the palladium particles dispersed on nanofibers homogeneously. The catalyst was applied to hydrogenateα-octene in normal temperature and pressure, the conversion ofα-octene was 98.6%, and the yield of octane was 63.1% by the bimetallic catalyst. While the conversion ofα-octene was 81.7%, and the yield of octane was 43.4% by single metal catalyst. The results showed that bimetallic catalyst has more reactivity and selectivity than single-metal catalyst.