Lignocellulose Biomass Dissolution In Ionic Liquids And Structures And Properties Of Regenerated Materials

As the most abundant renewable resources in nature,lignocellulose biomass has advantages such as biodegradability,green environmental protection and low price,which is a potential substitute for fossil resources.But the complex structures of the lignocellulose biomass greatly limit their further utilization.As a new type of solvents,ionic liquids（ILs）can be well applied in the dissolution of lignocellulose on account of their unique properties such as low melting point,less volatile,non-detectable vapor pressures,high stability and solubility,and so on.In this paper,the corncob and willow were dissolved in the biological derivative choline butyrate solution system to prepare lignocellulosic aerogel,and then were applied in the adsorption of dyes in the simulated sewage.At the same time,the novel tetrabutylammonium propionate/Nmethylimidazole（MIM）was designed,and then the solubility of cellulose in this solvent were determined.We studied the effect of the mass ratio of MIM to tetrabutylammonium propionate on the solubility of cellulose and the possible dissolution mechanism.Meanwhile,the effects of preparation conditions and preparation process on the morphology of cellulose were investigated.The main contents are as follows:1.A series of lignocellulosic aerogels were prepared by modulating the concentration of the original lignocelluloses（the corncob and willow）in the biological derivative choline butyrate ILs and preparation conditions.The results showed that the morphology and structure of the lignocelluosic aerogel mainly depended on the concentration of lignocellulose solution.With increasing lignocellulose concentration,the pore diameters of lignocellulosic aerogels were reduced,but the thickness of the pore wall gradually increased.At the same time,it was found that the preparation conditions（lignocellulose solution prefrozen,frozen in liquid nitrogen and freezingthawing cycles）had no effect on the morphology and structures of lignocellulosic aerogels.Moreover,the aerogels prepared under these conditions were similar to those directly prepared from lignocellulose solutions.This study provides a new route for the preparation of lignocellulosic aerogels by a simple and easy pathway.2.The adsorption efficiency of corncob aerogel on the methylene blue in simulated sewage methylene blue solution was studied.The results showed that the decolorization efficiency of the aerogel prepared from 0.5% corncob solution was advantageous over the original corncob and those prepared from the other corncob solutions.Moreover,the decolorization efficiency was very fast at the beginning,and then achieved adsorption saturation after two hours.The aerogel had the best efficiency for the removal of the methylene blue at 40 oC.This study has important reference value for the effective use of the low-cost renewable original lignocellulose to control environmental pollution.3.The novel tetrabutylammonium propionate/N-methylimidazole（MIM）solvents were designed,and the solubility of cellulose in this solvent was determined.We systematically studied the effect of the mass ratio of MIM to tetrabutylammonium propionate on the solubility of cellulose and the dissolution mechanism of cellulose in this solvent.Meanwhile,the effects of preparation conditions and processes on the morphology and properties of regenerated cellulose materials were estimated.At 25 °C,tetrabutylammonium propionate was solid,and MIM didn’t dissolve cellulose.However,the tetrabutylammonium propionate/MIM solvents had a good solubility for cellulose.In the tetrabutylammonium propionate/MIM solvents,MIM mainly disassociated the tetrabutylammonium propionate（[（CH₃CH₂CH₂CH₂）₄N][CH₃CH₂COO]）into [（CH₃CH₂CH₂CH₂）₄N]+ cations and [CH₃CH₂COO]-anions.The [CH₃CH₂COO]-in the solvent played a leading role in the dissolution of cellulose.The dissolution mechanism of cellulose in tetrabutylammonium propionate/MIM solvents may be the interaction between [CH₃CH₂COO]-anion and hydroxyl hydrogen in cellulose,which opened the hydrogen bonds of cellulose,and then cellulose was dissolved.In addition,the porous and dense cellulose materials were obtained by modulating the preparation conditions and processes.The crystal form of the regenerated cellulose material was cellulose II.Moreover,in the process of cellulose dissolution,the chemical structure of cellulose hardly changed,and no chemical reaction took place between the solvent and cellulose.