Study On The Effects Of The Hemicellulose Pre-Extraction On The Structure Of Bamboo MWL And LCC

Based on preliminary findings, the color of the bambusa chungii bamboo that was pre-extracted hemicellulose by hot water was deepened, and the preparation APMP pulp with pre-extracted bamboo was also difficult to bleach. But after the alkaline hydrogen peroxide (AHP) pre-extraction, the bamboo’s color became shallow, and the brightness of APMP pulp was increased greatly. In this paper, we studied the structure changes before and after pretreated milled wood lignin (MWL), lignin carbohydrate (LCC) and water soluble lignin (LCC-AcOH), using infrared spectroscopy (FT-IR) and nuclear magnetic resonance spectroscopy (13C-NMR).And in order to further understand the effect of pretreatment on MWL and LCC, we extracted MWL and LCC from bamboo, and degradated them by imitated pre-extraction process. Through above researches, the cause of brightness changes of the bamboo and APMP pulp after hot water and AHP pre-extraction can been analyzed. And these researches will also provide a theoretical basis for the combination of biomass refining and pulp and paper. The results are as follows:1. The color of bamboo was deepened after hot-water pre-extraction, the pulp brightness was greatly reduced, the PC number of bleached pulp also been increased. After the AHP pre-extraction, the brightness of both APMP and its bleached pulp were increased obviously, the brightness of unbleached pulp was increased about5%ISO, the bleached pulp was increased about7%ISO, and the PC number decreased more than double.At the same time, AHP pre-extraction has little impact on the yield of bleached pulp.2. After hot-water pre-extraction, in MWL structure the content of hydroxyl and C-H of aliphatic was reduced. The content of the C=O, syringyl lignin, aromatic ring, C-H ring structure, as well as the C6(α-OR) of guaiac wood, etherification of beta aryl ether C5(a-OAC) all were increased, so the chromophore content increased in MWL structure, and the color of the pre-extracted bamboo was deepened. After the MWL pre extracted by hot-water, the content of aliphatic and hydroxyl C-H, O-H and-CH3reduced. And the content of non conjugated C=O, aromatic ring, violet Ding Xiangji, condensation guaiac wood, guaiac wood, C-C, C-O and C=O increased.3. In the raw materials LCC and LCC-AcOH after hot-water pre extracted, the content of hydroxyl, non conjugated C=O, aromatic ring, ester carbonyl, aromatic ring structure, guaiac wood lignin and syringyl lignin increased. And this tell us the content of lignin structure increased in LCC. After the hot-water pre extraction, the content of the Cα、Cβ、Cγ in β-0-4, C3/C4、C2in xylan, Cγ in pinoresinol, C3、C4、C5in β-glucose, C3、C5in β-xylose, Cγof α-0-4, C6in α-、β-mannose, C6in α-、β-glucose, C6in α-galactose reduced. The chromophore content increased, the color of the pre extracted bamboo deepened.After LCC is pre extracted by hot-water, the content of hydroxyl, non conjugated C=O, aromatic ring, ester carbonyl, aromatic ring structure increased. β-O-4, β-glucose, pinoresinol, β-glucose,β-xylose, α-0-4, α-、β-mannose, α-、β-glucose, α-galactose reduced. The β-0-4link bond split,and carbohydrate hydrolysis and dissolution, the lignin structure be free.4. After AHP pre extraction, the content of the C=O, C-C, C-O, C-H, aromatic ring structure cinnamic acid, pinoresinol, guaiac wood methoxy, guaiac wood lignin and syringyl lignin in raw MWL reduced. This is because of the oxidation of hydrogen peroxide. The hydrogen peroxide can oxidative removal of part of lignin in in alkaline conditions, and the content of chromophoric groups decreased, raw material color shallowed, bleachability increased.After the MWL is pre extracted by AHP, the aromatic ring, violet Ding Xiangji, condensation guaiac wood, guaiac wood,C-C,C-O and C=O in MWL has reduced in some extent. The cinnamic acid and pinoresinol decreased, and the content of chromophore in pretreated raw material reduced, so the bamboo pale. 5. After AHP pre extraction, the content of hydroxyl and aliphatic C-H, ester carbonyl aromatic ring, ester carbonyl, aromatic ring structure in the LCC and LCC-AcOH reduced. The content of the acyl, cinnamic acid, benzoic acid and cinnamic acid is reduced. And the content of the Cα、Cβ、Cγinβ-O-4, C3/C4、C2in xylan, Cγin pinoresinol, C3、C4、C5inβ-glucose, C3、C5in β-xylose, Cγ of α-O-4, C6in α-、β-mannose, C6in α-、β-glucose, C6in α-galactose reduced.After the LCC is pre extracted by AHP, the content of hydroxyl and aliphatic C-H, non conjugated C=O, ester carbonyl aromatic ring, syringyl, guaiacyl and condensation of guaiacol guaiac wood lignin reduced. Pinoresinol, xylan, glucose, mannose, galactose and other sugar components has some degradation. The decline of β-0-4structure content, and the certain degradation of guaiacyl and syringyl lignin, made the chromophore content in raw material decrease. And the bleachability increase.