Study On Application Of Biomass Pre-Extraction On Bamboo Apmp And Its Mechanism

In order to deal with the global resources and energy crisis, the research of biomass technology has been set off worldwide. Biomass resource has been paid great attention because it is renewable and the environment friendly. Bamboo is an excellent resource due to its high fiber quality, and widely distributed in GX. However, bamboo high-yield pulp has poor optical properties, such as brightness and brightness stability of bleached pulp, which seriously limits the usage scale of high-yield bamboo pulp. This essay studies the effect of succus bambusae pre-extraction, pressurized hot water and alkaline hydrogen peroxide, on bambusa chungii APMP pulping, and the dynamics characteristics of sacharide dissolution during the process of bamboo alkaline hydrogen peroxide pre-extraction bamboo. Then the dynamics model of sacharide dissolution was built. The results were showed as follow:(1) In the succus bambusae, several components with large amounts including toluene77.88%, xylene0.98%, hydroquinone0.41%, hexamethyl cyclotrisiloxane0.48%, glyceryl monostearate0.44%and methyl stearate2.07%, were detected by GC-MS analysis. Amony those components, toluene, xylene and hydroquinone had great influence on the brightness of APMP pulp. After adding hydroquinone, toluene and xylene, XPS analysis results showed that the groups of C=O、O-C-O and O=C-O on the fiber surface increased, and the increasing rate of peak area of C1was almost the same, and the peak area of C3and O1increased mostly after adding the hydroquinone, then toluene and xylene as follow. However, After the bamboo were pressed and pre-extracted succus bambusae by60%ethanol, the brightness of original APMP pulp was higher than those without pre-extraction, which was3.5%ISO, as well as the bleached pulp brightness, which was5.9%ISO, and the PC was lower56%, and the PFI milling decreased about23%, but the physical index had deceased a little.(2) The optimum conditions for hot water pre-extraction of bamboo hemicellulose were:the temperature rose to120℃in50min, then to maximum temperature of170℃in35min, and holding time was2hours, liquor-to-wood ratio was1:5. Under the optimum conditions the extraction yields of hemicellulose and bamboo were high of43.48%and86.84%separately, and the PFI milling reduced about20%, but the bamboo yield was low generally, as well as the color and the strength of pulp was decreased. In addition, the influence of holding time at maximum temperature and liquor-to-wood ratio on the extraction yield of hemicelluloses and bamboo was greater than the maximum temperature. The pH value of extracted liquid was between3.5-4.5. In addition, the structure changes of milled wood lignin were analyzed by FTIR, the results showed that after pre-extracting the groups of carbonyl C=O, aromatic ring, C-C, C-O, the C-H of benzene ring, lilac type lignin, and guaiacyl lignin and condensed guaiacyl lignin all increased. Using13C-NMR analysis, the groups of C2or C6in phenol acetylation syringyl, Ca and Cy in β-O-4, C1in etherified guaiacyl, Cp in pinoresinol, C2/C6in hydroxyphenyl, C1in β-5, C2in guaiacyl, Cy in pinoresinol, methyl in methylene and acetyl all increased a lot, but the C3/C4in syringyl, Ca in P-(3and methoxy decreased. By the analysis of chromophore’s content, it was found that the bamboo material contained more etherification of carbonyl and o-phenol structure. After pre-extracting, the content of conjugated carbonyl、o-phenol and o-quinone in bamboo materials、 unbleached pulp and bleached pulp all increased.(3) The optimum conditions for alkaline hydrogen peroxide pre-extraction of bamboo hemicellulose were:H2O2dosage of1.5%, liquor-to-wood ratio of1:8, the temperature rose to maximum temperature of90℃in30min, and holding time was2hours. In this process, both hemicellulose extraction and bamboo yield were ideally, for1.68%and96.21%respectively. However, compared to hot water pre-extraction, the hemicellulose extraction yield was lower, while the bamboo yield was remained high, and the color of pre-extracted bamboo was lighter. The liquor-to-wood ratio had the greatest impact on the extraction of hemicellulose and the bamboo yield, followed by the holding time at maximum temperature, next reaction temperature, and the last H2O2dosage. The pH value of extracted liquid was dropped, but it still be alkaline. The APMP pulp yield after pre-extracting was good, and the brightness increased5%ISO-7%ISO, and the PFI milling dropped45%significantly, but the tear index and folding ability of pulp decreased. The pre-extraction of alkaline hydrogen peroxide was very beneficial to the dissolution of1%sodium hydroxide and alcohol benzene extractives, while it had little influence on the content of ash and acid-insoluble lignin. The intensification of pre-extraction conditions had a certain effect on the dissolution of holocellulose, poly pentose and acid soluble lignin. Holding time at maximum temperature and liquor-to-wood ratio had greater effect on the dissolution of holocellulose than the other pre-extraction conditions.FTIR analysis of milled wood lignin showed that after alkaline hydrogen peroxide pre-extraction the groups of aromatic, C-C, C-O, ester carbonyl C=O, C-H benzene bond in guaiacyl and HGS type lignin had reduced. After pre-extracting, the groups of-COO-, Cβ in cinnamic aldehyde, acetylated guaiacyl, guaiacyl, β-O-4lignin in raw bamboo materials; the groups of etherified guaiacyl, guaiacyl, etherified β-aryl ether, β-O-4lignin in unbleached APMP pulp; the groups of C=O in phenolic acid, C6(α-OR) in guaiacyl and C5(α-OAC) in etherified β-aryl ether in bleached pulp all decreased. Chromophore content analysis indicated after pre-extracting the content of conjugated carbonyl, adjacent phenol and o-quinone was lower than those without pretreatment in the raw materials, unbleached pulp and bleached pulp, especially the content of etherified carbonyl in pretreated pulp and the content of o-quinone in unbleched pulp.(4) HPAEC analysis results showed that the dissolution rate of sacharide (glucose, arabinose, galactose and xyloseand) and the content of solids in the extract liquid were increased with the holding time extended and temperature rose. The gains of varieties of sugars’dissolution all reached to the maximum when the holding time was extended to1hour. The maximum temperature had the greatest impact on sugar’s dissolution, especially when temperature increased from80℃to90℃. The dissolution rate of xylose was very low, less than1%, while the arabinose and galactose were higher,7%and12%respectively. The dynamic model of carbohydrate dissolution druing alkaline hydrogen peroxide pre-extracting bamboo process could be expressed by the second law of Fick’s, the dynamic model was, the diffusion was the major controlling step during pre-extraction process. When the temperature was90℃, the ln[C∞/(C∞-C)] of glucose, arabinose, galactose and xyloseand had a good linear relationship with time, and the dynamic equations of these sacharides were y=0.747x, y=0.7524x, y=0.8414x, y=2.0562x respectively, and the dynamic model and equations could forecast well to the sacharide dissolution during alkaline peroxide pretrement process.