Preparation Of Lignin-based Carbon Nanofibers And Its Functional Application

With the increasing shortage of fossil resources,fossil-based raw materials shortage ensued.Using bio-materials to supplement fossil raw materials is becoming increasingly important.Using crop straw,grasses to produce cellulosic ethanol is an effective way.Cellulosic ethanol produced through hydrolysis and enzymatic hydrolysis the sugar of biomass raw materials,packed in a lot of residue generated in production.However the use of residues is mainly to combustion heat recovery,the less cost-effective.Lignin with higher carbon content,renewable,low cost,is based on the aromatic ring,so it can be used as raw materials of carbon fiber.Residues mainly composed of lignin,so in this paper,lignin derived from residues was used as raw materials to produce lignin-based nanofibers,which provided a way for efficient utilization of the residues.Electrospinning is a technology that can produce nanofiber continuously.In this study,lignin was extracted from cellulose ethanol residues and it was used as raw materials to manufacture lignin-based nanofibers/Lignin was extracted by NaOH solution.The IR spectral indicated that the constitutional units of lignin mainly was S type.DSC analysis suggested that the glass transition temperature was 97℃。When spinning,the DMF was used as solvent and PEO was used as auxiliary agent.The spinning performance of pure lignin and lignin/PEO hybrid spinning solution was investigated.It was found that pure lignin spinning solution couldn’t be spun until the concentration of the solution was up to 50%.Even so,it was the fibers with bead.However,the lignin/PEO hybrid presented good spinning performance.After oxidation and carbonization,the fibers seen to broken,and the yields of carbonized fibers had nothing to do with the amount of PEO.The pyrolysis kinetics of precursor fibers showed the reaction process of 3-order.The carbonized fibers was activated to manufacture lignin-based activated carbon fibers.The fibers with highest surface area was produced under the condition where the activation temperature was 800℃ and the ration of fibers to KOH was 1:6.The results of adsorption isotherm and adsorption kinetics indicated that the chemisorption was rate-limit step of the adsorption of MB and phenol onto fibers.To manufacture Ni-lignin based composite catalyst,the nickel nitrate was added into spinning solution.It was found that the addition of nickel nitrate contributed to formation of thinner fibers.The Ni was still loaded after oxidation and carbonization.The catalyst affected the lignin depolymerization of lignin,but the regularity of the distribution of products was not clear.