Lignin Degradation And Its Products' Relevant Applications In One-step Synthesis Of Au-mesoporous Carbon Materials

With the continuous consumption of fossil resources,the demand for renewable resources is becoming more and more urgent.Lignin,one of the most abundant renewable aromatic hydrocarbon materials in nature,has great potential as a suitable substitute for the petroleum-derived aromatic hydrocarbons.Owing to structural complexity and bonding diversity,more than 90%of lignin did not been effectively utilized and was discharged directly into rivers as waste from paper pulping,causing serious environmental pollution.In this context,how to utilize lignin effectively has high economic/practical value.Based on previous research of our group,a series of heteropolyacid-functionalized ionic liquids were synthesized to degrade lignin and then vanillyl alcohol,one of degradation products,was selected as a substitute for phenol to fabricate Au nanoparticles?AuNPs?imbedded mesoporous carbons via a one-step process.The main contents discussed in this dissertation were as follows:?1?Six heteropolyacid-functionalized ionic liquids were synthesized and characterized by ¹H NMR and FT-IR.It was found that allyl imidazolium phosphotungstate[Amim]H₂PW₁₂O₄₀ exhibits the best performance in alkali lignin degradation.Under optimal degradation conditions?90?mol of catalyst,80 mg of alkali lignin,20 mL of water,90°C,6 h?,the degradation rate and total phenolic yield are 21.50%and1.72%,respectively,and the catalyst can be reused for 5 times.Moreover,the processes of[Amim]H₂PW₁₂O₄₀-mediated degradation were investigated,and it was found that the catalyst can effectively interrupt the carbon-carbon bonds and ether bonds in alkali lignin.?2?A series of vanillyl alcohol-based AuNPs-imbedded mesoporous carbons were synthesized and characterized by XRD,N₂adsorption-desorption,TEM,ICP-AES and Raman.The catalyst of Au-C-3wt%-S-?1:30?-700-water-HF with⁵.1 nm AuNPs-imbedded worm-like mesostructure?BET surface area and pore volume being 251m²/g and 0.15 cm³/g,respectively?showed the best performance in selective oxidation of benzyl alcohol.Under optimal reaction conditions?25 mg of catalyst,1 mmol of benzyl alcohol,2 mmol of K₂CO₃,5 mL of water,100 ^oC,6 h?,the conversion of benzyl alcohol and the selectivity to benzoic acid are 98.4%and 98.0%,respectively,meanwhile,the TOF value is as high as 321 h^-1.In addition,the catalyst can be reused for 4times without significant loss of catalytic activity.