Isolation And Application Of Hemicellulose From Residues Of Hybrid Poplar

Hemicellulose could be used for the production of high-value materials, chemicals toreplace decreasing petrochemical-based feedstocks. However, they are still under-utilizedtoday. Hemicelluloses were extracted from residues of hybrid poplar, partily delignified usingalkaline-ethanol aided with ultrasound. The effects of alkaline concentration, temperature andtime on the yield during the extraction of hemicellulose from hybrid poplar residues wereoptimized using orthogonal design method. The hemicelluloses obtained under the optimumextraction conditions were recovered by precipitation and structurally characterized. The filmcasted from the mixture of the hemicellulose and nanocellulose was investigated. All theresults are as follows:(1) Compared with deligninfications using alkaline-ethanol treatment and water onecoupled with ultrasound, alkaline-ethanol treatment aided with ultrasound caused the mostsignificant destruction in the sample microstructures. And the maxium yield of hemicellulosewas obtained after the alkaline-ethanol treatment. The obtained hemicelluloses were morehomogeneous in sugar components and the greatest in the xylose ratio.(2) The optimal extraction conditions using the orthogonal design method: NaOHconcentration of8%, reaction temperature of90℃, and extraction time of12h. Thehemicellulose yield was87.2%under the conditions. The obtained hemicellulose wascharacterized using the Fourier transform infrared spectrometry, Nuclear Magnetic ResonanceSpectrum and component analysis. The results showed that the hybrid poplar hemicelluloseconsisted of4-O-methyl-D-glucurono-D-xylan and a little number of glucosyl mannan, andsome lignin in them.(3) The hemicelluloses obtained under the optimal extraction conditions were recoveredby neutralization and ethanol-precipitation consecutively. About37%(HA) of hemicellulosein dewaxed sample was obtained after the neutralization of the alkaline extract, and about50%(HB) of them was obtained using the ethanol-precipitation from the neutralized extractafter the recovery of HA. The obtained hemicelluloses were characterized using the Fouriertransform infrared spectrometry, Nuclear Magnetic Resonance Spectrum, component analysis,molecular mass distribution, z-average size and zata potential. The results showed that2-O-(4-OMe-α-D-GlcpA)(1â†'4)-β-D-Xylp was main component in HA and HB. And HB hadmore negative charge than HA did. Both TGA and DTG curves showed the hemicellulosicfraction HA with higher molecular weight and higher lignin content and higher thermalstability than HB.(4) The obtained hemicellulose/nanocellulose composite films with or without theadding glycerol were casted. Their structure was uniform. Their equilibrium moisture and their solubility decreased with the increase in the amount of nanocellulose, but their elongation rateat breaking increased. The equilibrium moisture and elongation rate of composite filmsincreased with the increase in the amount of glycerol, but their solubility decreased. Theresults of thermal analysis showed that the stability of composite films enhanced with increasein the amount of nanocellulose, but decreased with the increase in amount of glycerol andhemicellulose. The composite films were laminated architecturally, but the lamination wasweakened by the addition of glycerol and the increase in the amount of hemicellulose.