Study On Metal Nanoparticles Supported By Lignin-based Phenolic Nanospheres And Their Catalytic Performance

With rising awareness of global energy crisis and increasingly serious environmental pollution,the exploitation and utilization of new clean and environmental-friendly energy resources has a profound impact on the development of human economy and society.Biorenewable polymers such as lignocelluloses are showing the tremendous potential replacing traditional synthetic materials,which can not only reduce human dependence on petrochemical resources,but also benefit the concept of sustainable development.Lignin,as the most abundant aromatic biopolymer in nature,has great potential as a sustainable replacement for phenol-formaldehyde(PF)resin synthesis,which has been considered as one of the most promising options for lignin valorization.In this study,lignin and its derivatives were used as reducing agent and stabilizing agent of noble metal nanoparticles to prepare composite catalysts in the field of catalysis.The results are as follows:Novel hetero-structure nanocomposite catalyst comprised of lignin-based phenolic resin(LPF)nanosphere support and Ag NPs was prepared using a simple hydrothermal curing and subsequent in-situ reduction method.It was found that lignin in this nanocomposite exhibited a series of benign functions:?)amphiphilic lignin as a surfactant reduced the diameter of spherical support from microscale to nanoscale;?)part of the lignin(uncombined lignin)acted as a role of sacrificial template to increase the roughness of nano sphere surface;?)lignin was used as the green reducing agent for reducing Ag+to Ag;?)for the catalytic reduction of methylene blue,lignin could adsorb the cationic dye by electrostatic interactions and form a synergetic effect of adsorption and catalysis.Owing to the multifunctionality of lignin,the LPF@Ag nanocomposites demonstrated significantly higher aqueous dispersion stability,catalytic capacity and good recyclability compared to the lignin-free PF@Ag microcomposites.Novel lignin-based phenol-formaldehyde(LPF)nanosphere stabilized Pd NPs were synthesized and tested for the catalytic reduction of hexavalent chromium.The 40%replacement of phenol by lignin resulted in a significant decrease of the nanosphere size and enhancement of the nanosphere surface roughness,which increased the specific surface area of LPF nanosphere accordingly.Owing to the enhanced specific surface area and the excellent reducing activity of lignin,the as-prepared LPF nanosphere had considerably higher Pd NP loading amount compared with the lignin-free PF support.Therefore,the nanocomposite catalyst Pd@LPF showed highly efficient reduction activity of Cr(?),which was superior compared to most other catalyst materials reported.In addition,the Pd@LPF nanocomposites exhibited excellent reusability in the reduction of Cr(?)owing to the stable loading of Pd NPs on the lignin-based support.Sodium lignosulfonate modified phenolic resin spheres(LPF)were prepared by a simple hydrothermal method.When introduced to the synthesis system,sodium lignosulfonate functioned as a surfactant and LPF composite spheres became considerably rough and the average size significantly shrank with the addition of SL.Moreover,the introduction of sodium lignosulfonate can effectively prevent Ag nanoparticles from aggregating on the modified-phenolic resin spheres surface,thus resulting high density and small-sized Ag nanoparticles on its surfaces.Furthermore,the as-prepared composites showed enhanced catalytic performance and good recyclability for the reduction of 4-nitrophenol in the presence of NaBH4.