Abstract
Molecular scale modifications were achieved by spontaneous polarization which is favored in enhancements of β-crystallization phase inside polyvinylidene fluoride (PVDF) nanofibers (NFs). These improvements were much more effective in nano and submicron fibers compared to fibers with relatively larger diameters. Metallic nanoparticles (NPs) supported by nanofibrous membranes opened new vistas in filtration, catalysis, and serving as most reliable resources in numerous other industrial applications. In this research, hydrogenation of phenol was studied as a model to test the effectiveness of polarized PVDF nanofiber support embedded with agglomerated palladium (Pd) metallic nanoparticle diameters ranging from 5–50 nm supported on polymeric PVDF NFs with ~200 nm in cross-sectional diameters. Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM), Atomic Force Microscopy (AFM), Energy Dispersive X-Ray Spectroscopy (EDX), Fourier Transform Infrared Spectroscopy (FTIR) and other analytical analysis revealed both molecular and surface morphological changes associated with polarization treatment. The results showed that the fibers mats heated to their curie temperature (150 °C) increased the catalytic activity and decreased the selectivity by yielding substantial amounts of undesired product (cyclohexanol) alongside with the desired product (cyclohexanone). Over 95% phenol conversion with excellent cyclohexanone selectivity was obtained less than nine hours of reaction using the polarized PVDF nanofibers as catalytic support structures.
Highlights
Metal and metal oxide (M/MO) nanoparticles (NPs) have excellent catalytic properties [1,2,3,4,5].M/MO NPs cause high-pressure drop in fixed-bed systems
Microscopy (TEM), Atomic Force Microscopy (AFM), Energy Dispersive X-Ray Spectroscopy (EDX), Fourier Transform Infrared Spectroscopy (FTIR) and other analytical analysis revealed both molecular and surface morphological changes associated with polarization treatment
EDX analysis was used to identify Pd catalytic particles composition dispersed on the polyvinylidene fluoride (PVDF) fibers, X-ray spot probe was placed on top of the location of interest for 30 s
Summary
Metal and metal oxide (M/MO) nanoparticles (NPs) have excellent catalytic properties [1,2,3,4,5]. Catalysts fabricated from M/MO NPs supported on polymers (M/MO NPs-Polymer) combine the excellent properties of both NPs and polymers Different factors such as the type of functional groups and surface properties of the polymeric support, size and concentration of the NPs, and the fabrication technique control the final catalytic properties of the M/MO NPs-Polymer [9]. NFs possess many excellent properties such as small fiber diameter, high aspect ratio (length to diameter ratio), huge surface area to volume ratio or mass ratio, high and controllable porosity, small pore size and great mechanical stiffness, and tensile strength along the fibers which make them excellent materials for different engineering applications [18,19,20,21,22,23]. The catalytic performance of the prepared polarized catalysts were tested in the phenol hydrogenation reaction and compared to non-polarized catalysts
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