| Lignocellulose is a renewable natural resource from photosynthesis of plant,and primarily consists of cellulose,hemicelluloses and ligninin plant cell wall.Cellulose is a polysaccharide containing many glucose units in parallel chains.Hemicelluloses are a heterogeneous group of polysaccharides including xyloglucans,xylans,mannans and glucomannans.Lignin is an irregular polyphenolic polymer containing guaiacyl(G),syringyl(S)and p-hydroxyphenyl(H)structures.The biorefinery process offers good answers to the approaching oil crisis by producing biofuels,functional materials and chemical using renewable lignocellulose.However,different from petroleum,lignocellulose is a solid,heterogeneous,In order to overcome these inherent obstacles,we have developed p-toluenesulfonic acid(p-Ts OH)flow through fractionation technology.We hope to achieve the goal of rapid and non-destructive dissociation by degrading poplar cell wall chemical components through p-Ts OH.Studies have shown that the flow extraction of p-Ts OH can realize the separation of poplar wood chemical components.It has the advantages of reducing the degradation of lignin and carbohydrates and maintaining the lignin structure and using of high value of vegetarian.It is believed that the experimental results and theoretical findings of this study have practical guiding significance for the utilization of poplar resources.By dissociating poplar wood with p-Ts OH and analyzing the composition of the water insoluble solid residues(WIS)and hydrolysate,we have concluded that p-Ts OH treatment has the advantages preserving lignin structure and preventing of carbohydrates form degradaiton.About 82.3% of xylan is dissolved,while 93.5% of glucan is retained in WIS.Flow fractionation can retain the carbohydrates of poplar to the maximum,and 77.7% xylan in the hydrolysate can be recovered in the form of xylose.Formation of soluble lignin,xylose and acetic acid are time dependent.Deacetylation is faster than xylan hydrolysis,lignin dissolves quickly and occurs at the earliest stage of fractionation.There is a correlation between the yield of water-insoluble lignin(AHL)and the color of lignin obtained from the flow fractionation of wood.The results of gel permeation chromatography showed that the molecular weight distribution of AHL was wider than that of MWL,and the dispersibility was higher than that of MWL.The polydispersity of AHL under different processing conditions was at a narrow range.The 2D NMR analysis results show that the amount of ?-O-4 in AHL is slightly lower than that in MWL,but is much higher than the amount of ?-O-4 in conventional technical lignins.AHL has reduced thermal stability compared to natural lignin MWL.In subsequent aging tests,as the aging conditions become stronger,the lignin was further condensed and the ?-O-4 content was reduced.In addition,the reaction mechanism of ?-O-4 lignin model(GG)in p-Ts OH was successfully proposed.Two steps method was proposed to dissociate wood using aquouse p-Ts OH with different concentration,namely wood is subjected to acidic hydrolysis to remove hemicellulose and lignin sequentially.The results showed that hemicellulose with a mass fraction of 7.7% was dissolved.Delignification reached 83.7% in the sectond setp of fractionation.The retention of ?-O-4 was very high.The crystallinity of cellulose Crl reached 73.3%.Briefly,fractionation of lignocellulose biomass using p-Ts OH have the advantages of good recovery of carbohydrate and well-preserved structure and bright color of lignin.However,challenges still exist to be overcome for the future study,especially the separation of p-Ts OH,sugar and lignin in the liquid fractionation products. |
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