Studies On Preparation And Application Of Nanofiber Supported Catalyst

Rare-metals, such as palladium, nickel, possess high catalytic activity have been widely used in the field of energy, chemical engineering, environment, biotechnology, etc. Nanoparticles of rare-metals can reduce the amount of use and significantly increase the catalytic activity and catalytic efficiency of these rare metals because these metals are really expensive. However, the nanoparticles are quite difficult to reclaim from the reaction solution because of small size. The waste solution poses a great pollution on the environment without reclamation of rare-metals. Supported catalysts have attracted more and more attention because they can provide high catalytic activity and a way to reclaim the catalyst. The nanoparticles on catalyst support have a fine dispersion in the solution, and subsequently enhance the catalytic efficiency. Electrospinning as an effective and universal method can prepares nanofibers and makes the nanofiber a promising and attractive candidcate for catalyst support. In this study, the supported catalysts of silica-supported palladium (Pd/SiO2) nanofiber and silica-supported nickel (Ni/SiO2) nanofibers were fabricated by electrospinning and their catalytic performances of hydrogenation and CO2 reforming of methane were investigated. The main contents of this paper are as follows:(1) Pd/SiO2 nanofibers were prepared by a combination of sol-gel and electrospinning, followed by the calcination of PdCl2/PVP/TEOS nanofibers at a high temperature and the reduction of PdO/SiO2 nanofibers in a H2 atmosphere. The surface morphologies,structure and catalytic performances of Pd/SiO2 nanofibers were characterized with scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), nuclear magnetic resonance (NMR) measurements etc. The results indicated that the SiO2-supported catalyst nanofibers showed a diameter of about 500 nm, and the Pd nanoparticles with a size of 20-30 nm were evenly and firmly attached on the surface of the SiO2 nanofibers. The specific surface area of the Pd/SiO2 nanofibers was as high as 350-400 m2/g. The degree of hydrogenation (93.48%) for acrylic acid catalyzed by the Pd/SiO2 nanofibers was higher than that for acrylic acid catalyzed by Pd powder(89.01%) at the same catalyst content.(2) Ni/SiO2 nanofibers have been successfully synthesized by a combination of sol-gel and electrospinning technique, followed by the calcination of Ni(NO3)2/PVP/SiO2 nanofibers at a high temperature and the reduction of NiO/SiO2 nanofibers in a H2 atmosphere. The surface morphologies,structure and catalytic performances of Ni/SiO2 nanofibers were systematically characterized with SEM, TEM, XRD,N2 sorption measurements etc. The results indicated that SiO2-supported catalyst nanofibers showed a diameter of 200-500 nm and most of the Ni nanoparticles were confined inside SiO2 nanofibres with average particle size of 8.1 nm. Compared with the Ni/SiO2 catalyst conventionally prepared via incipient impregnation method using commercial SiO2 powder as the support, the electrospun Ni/SiO2 catalyst exhibits improved metal dispersion and enhanced interaction between nickel spices and SiO2, leading to slightly higher activity, much better stability and higher resistance to carbon deposition in carbon dioxide (CO2) reforming of methane.