Vanillin Coupling Reaction And Chitosan Degradation Reaction

Environmental pollution and energy crisis have drawn worldwide attention,while consequent exploration and development of green renewable energy systems gradually are becoming a mainstream research direction in recent years.Biomass,as a substitute of fossil fuels,is expected to be the renewable resource of the future due to the vast number of chemical products that can be potentially manufactured from it.Therefore,conversion of biomass and its platform compounds to fuels or chemicals are important objectives for the development of future sustainable energy system.In this paper,the development of lignocellulose derivative to high value-added chemicals was enriched by using vanillin as raw materials.Simultaneously,a high-efficiency dehydration of chitosan to 5-hydroxymethylfurfural via hydrothermal conversion was explored and the mechanism of the dehydration reaction was studied,which provided the proof-of-principle for the tran,sformation of chitosan into energy compounds.This dissertation mainly focus on the study as follows:Firstly,six kinds of thiazole ionic liquids with different functional groups have been designed and synthesized based on the structural design of ionic liquids.And their structures have been characterized.These thiazole ionic liquids were used as catalysts for benzoin condensation reaction.Furthermore,the effects of reaction temperature,time and amount of catalysts were also investigated.Secondly,we protected hydroxyl group of vanillin with the benzylation,sulfonylation and acetylation in order to improve the efficiency of the reaction.The C₁₄ intermediate was obtained by benzoin condensation reaction,and the mechanism of benzoin condensation reaction was deduced.The experiment results showed that hydroxyl protection is very necessary,which could greatly improve the reaction efficiency and thus throw new light on future industrial application.Thirdly,we synthesized a series of Br???nsted-Lewis acidic ionic liquids which efficiently catalyzed the degradation of chitosan to HMF and can be recycled by simple separation.And their structures and stability were characterized by ¹H NMR,FT-IR and TGA.Fourthly,the catalytic effect of different Br???nsted-and Lewis-acidic sites and the molar fraction of Lewis-acidic sites were investigated in detail.It was found that Br???nsted-Lewis acidic ionic liquids?[Hmim][HSO₄]-0.5 FeCl₂?exhibited good catalytic performance.A high HMF yield of 44.11%was obtained starting from 50 mg of chitosan.Furthermore,the effects of reaction temperature,time,and amount of catalyst were also investigated.The optimal reaction conditions were obtained for a 1.25 wt%aqueous solution of the catalyst under hydrothermal conditions?180 ? for 4h?.