Isolation And Characterization Of Biomass Components Base On Ionic Liquid Complete Dissolution System

Ionic liquid is a new type of environmentally friend "green solvents". It has excellent dissolving capacity, high thermal stability and chemical stability. Ammonia ismild base. It can partially break the chemical bond between lignin and polysaccharide. This article was focused on the isolation of cellulose, hemicellulose andlignin from larch ball-milled powder based on complete dissolution in ionic liquid system and ammonia hydrothermal system. The isolated cellulose, hemicellulose andlignin were characterized using neutral sugars analysis, FT-IR spectra, X-ray diffractometry, CP/MAS 13C-NMR and SEM. The results were as follows.(1) The sugar analysis showed that the isolated hemicellulosic fractions weremainly composed of glucose (81.39-90.18%), and little amount of galatose(1.98-9.79%), xylose (1.72-2.88%), mannose (4.19-5.76%) and rhamnose(0.10-0.22%) were also observed, respectively.(2) The crystalline structure of ball-milled powder transformed from type I to type II. The crystallinityslightly increased compared with the ball-milled samples.(3) The FT-IR spectrum showed that these lignin fractions were mainly composed of guaiacyl units with small amounts of syringyl units. The lignin-carbohydrates complexes (LCC) exhibited the absorption peak of lignin, which demonstrated that these fractions represented the structure of lignin to some extent.(4)The results showed that the smaller molecular size and more branched of hemicelluloses were extracted by the ammonia treatment.Interestingly, the content of xylosein the hemicelluloses increased with the time in ammonia biomass of ammonias-system realization, while that of arabinose decreased.(5)Further studies from NMR showed thatthe lignin fractions isolated from ammonia hydrothermal system were mainly composed of guaiacyl units with noticeable amounts ofsyringyl units and fewer p-hydroxyphenyl units.The 2D HSQC spectrum indicated that the molar ratioof guaiacyl units to syringyl units (G/S) was 0.69 based on the integration of the finger contours. Inaddition, these lignin preparations consisted mainly of?-O-4 (75.55%)ether bonds combined with small quantities of?-?'(12.19%) and?-5'(7.39%)carbon-carbon linkages. Furthermore, minor amounts of hydroxycinnamyl alcohol end groups (4.88%) were also detected in these lignin fractions.