Study On The Dissociation Of Poplar Components In Ethanol/Water System And Its High Value Conversion And Utilization

With the continuous development of biorefining technology and biomass science,more and more attention has been paid to the conversion and utilization of agricultural and forestry biomass resources.In this paper,poplar wood was separated by ethanol/water system,which was transformed into liquid hemicellulose and lignin products and solid cellulose products,and further transformed into high-quality chemicals.The major research contents are summarized as follows:In this paper,acids and bases were used to catalyze the treatment of poplar powder in ethanol/water system.And the dissolution law of cellulose,hemicellulose and lignin was explored by adjusting the type and amount of catalyst.Furfural was prepared from hemicellulose component in the hydrolysate.The results showed that acid-base assisted ethanol/water system had selective solubility for lignin and hemicellulose.The highest dissolution rate of lignin was 93%in acid(2%sulfamic acid)assisted ethanol/water system,and 85%in alkali(2%lithium hydroxide)assisted ethanol/water system.With the increase of acid and alkali dosage,the lignin first delignification efficiency(LFDE)increased.In addition,the acid environment is more suitable for the production of functional xylooligosaccharides and furfural products.Based on the above research,ethanol was prepared from cellulose rich residue by enzymatic hydrolysis and fermentation.The results showed that the cellulose skeleton of poplar wood pretreated by ethanol/water system remained intact.The surface morphology of poplar wood changed from granular to fluffy,and the fiber surface appeared wrinkles and cracks.After pretreatment,the crystallinity and crystallite size of poplar cellulose increased from 62.7 nm and 2.50 nm to 76.6 nm and 3.56 nm,respectively.And the enzymolysis efficiency of poplar increased by 10 times,up to 94.4%,and the ethanol yield increased by 4.5 times,up to 82.6%.The organosolv lignin was extracted from ethanol/water treatment solution by acid precipitation.It was found that the lignin yield was 81%and the purity was 98%in the sulfamic acid assisted ethanol/water system.Combined with infrared spectroscopy,scanning electron microscopy and gel permeation chromatography(GPC),the structure characteristics of lignin isolated from poplar wood by enzymatic/mild acidolysis lignin(EMAL)and ethanol/water system were compared and analyzed.It was found that the chemical structure of lignin in ethanol/water system was relatively complete(with typical GSH type lignin structure),and its molecular weight was lower and homogeneous(M_W1550?4240 g/mol,PDI 1.67?2.51),showing micro-nano morphology(300?7000 nm).The total phenol content(TPC)and free radical scavenging ability of lignin were determined by ³¹P-NMR,Folin ciocalteu method and DPPH radical scavenging method.The results showed that the higher the phenolic hydroxyl content in lignin,the stronger its antioxidant capacity.The radical scavenging index(RSI)of lignin in ethanol/water system was 152%and 143%higher than that of commercial antioxidants(BHT)and EMAL,respectively.In addition,Na BH₄ and Ru/C catalysts were used to degrade lignin in ethanol/water system to prepare phenolic chemicals.The results showed that Na BH₄and Ru/C could catalyse lignin conversion and the conversion rate of lignin monomer can reach 56.1%at 240?for 1 h.