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预提取对竹片理化性质及半纤维素糖组分降解的影响

Effect of Pre-extraction on the Physicochemical Properties and Hemicellulose Composition Degradation of Bamboo Chips

【作者】 黄凯

【导师】 宋雪萍;

【作者基本信息】 广西大学 , 轻工技术与工程(专业学位), 2014, 硕士

【摘要】 本文以南方特有的粉单竹为研究对象,采用热水预提取(HWP)和碱性过氧化氢预提取(AHPP)两种方法预提取竹片中的半纤维素,从半纤维素的提取对竹片纤维理化性质的影响角度,分析预提取前后竹片化学组分、纤维表面官能团含量、纤维素的结晶度和孔隙度的变化;研究不同预提取方法对纤维形态、磨浆能耗、制浆得率、光学性能及纸张物理强度的影响,综合分析预提取对APMP制浆性能的影响。最后,模拟竹子中天然存在的半纤维素糖组分(葡聚糖和木聚糖)的含量,基于高效液相色谱分析技术,研究不同降解条件下这些糖组分的热降解行为。得到的主要结论如下:1、HWP竹片后,制备APMP,发现磨浆能耗降低,竹片颜色加深,白度显著下降,且纸浆物理性能下降较大。AHPP后白度提高,且纸浆物理性能得到较好的保持。HWP后竹片除了纤维素和抽出物含量有所上升,其他化学组分含量下降;AHPP后,纤维素含量略微增大,其它化学组分均不同程度降低。2、HWP后竹片新增孔洞增多,破损组织及不规则排列的纤维束增多。通过BET分析知道,HWP后竹片的孔容和比表面积都得到显著的增大;AHPP后竹片的孔容和比表面积也都得到显著的增大,但增幅不及HWP,说明AHPP对木素和半纤维素的溶出作用不及HWP。HWP和AHPP预提取后竹片纤维素结晶度分和X—射线结晶指数分别升高。3、FTIR分析发现,AHPP主要是使木素中β-O-4、α-O-4以及C=C键断裂,从而有利于后续的制浆漂白;HWP主要是使竹片中的C-C、C-O、C=O、芳香环上的C—H、酯羰基C=O和愈创木基上的C—H苯环键增多,从而影响到竹片中发色基团含量的增多,对后续的制浆漂白造成困难。4、竹片纤维表面主要含有C、H、O元素,及少量的N元素。HWP后纤维表面的氨基(—NH2)或者酰胺基(O-C-NH,又称肽键)被除去,且由O/C值大小知道,HWP比AHPP使纤维表面暴露出更多的纤维素。与HWP对比,AHPP去除了纤维表面部分的氨基(—NH2)或者酰胺基(O=C-NH)基团,木素及抽出物含量减少明显,但纤维表面暴露出一些新的-C=O,O-C-O基团。5、HWP后W(1)、L(1)和Fines(1)减小,但L(n)有所增加,且纤维长宽比下降。HWP后APMP中细小纤维重量百分含量显著增大,但其它目数下的纤维重量百分含量均不同程度降低,说明HWP使得制浆过程中的长纤维易被切断;AHPP后的H2O2补充漂白前后的纤维长度分布变化不大。6、在HW过程中,温度升高至190℃后,葡聚糖开始生成葡单糖,且在这个温度下随着时间的延长葡单糖降解生成HMF的速率越快。170℃时木聚糖从1.5h左右开始降解为木糖。在AHP过程中,木聚糖降解生成木糖的温度始于90℃,随着温度的进一步升高,反应速率加快,相同时间生成木单糖的含量增多,且整个AHP降解反应中,没有发现葡萄糖单糖、HMF和糠醛的生成。

【Abstract】 In this paper, the Pink Sheets bamboo in South China was investigated, treated by both Hot Water Pre-extraction (HWP) and Alkaline Hydrogen Peroxide Pre-extraction (AHPP) methods to extract hemicellulose from bamboo. The physico-chemical properties including chemical compositions, the content of functional groups on fibre surface, cellulose crystallinity, porosity, etc. were characterized before and after pre-extraction. Besides, the pulping properties including fiber morphology, refining energy, pulp yield, optical properties and physical strength of pulp were also analyzed so as to evaluate the impacts of different pre-extraction methods to the APMP process comprehensively. Moreover, the thermal degradation behavior of glucan and xylan under different conditions, based on high-performance liquid chromatography analysis technique, were investigated so as to unveil the degradation regularities of polysaccharides. It is expected, in this work, that improving sugar yield and minimizing the generation of toxic by-products could be achieved by controlling the pre-extraction conditions.The main conclusions are as follows:1. On the preparation of APMP process with bamboo as material, it was improved that, after HWP method, refiner energy consumption reduced whereas Bamboo chips color was deepened with significant decrease of the whiteness. Moreover, HWP method also has a negative effect on the most physical properties of the pulp relative to nonextracted. By contrast, APMP with AHPP increase the whiteness, keeping the performance of pulp bleaching significantly. The analysis of chemical composition indicates that the cellulose and extractives content of bamboo chips increased for various degrees after HWP. After AHPP, the cellulose content of bamboo chips increased slightly, but other chemical components declined inordinately.2. The porosity of bamboo rised after HWP. There are increasing proportion of damaged tissue and uncrystallized fibers found in the samples of electron micrographs. BET data elucidated, compared with non-extracted bamboo, bamboo, after HWP, both the pore volume and surface area had increased significantly, respectively. In terms of AHPP, the pore volume and specific surface area of treated bamboo had also increased significantly respectively, which were smaller than those of HWP. After both HWP and AHPP, cellulose crystallinity and X-ray crystallography indices of bamboo increased respectively.3. The spectra of FT-IR indicated that AHPP mainly led to the cleavage of lignin in the P-O-4, α-O-4, and C=C bonds and the degradation, even removal, partial lignin and extractives in the bamboo, which would be positive to the subsequent bleaching of the pulp. As for HWP, it tended to raise the contents of the C-C, C-C-O, C=O, C-H bond on the aromatic ring, the C=O bond on ester carbonyl group and H-benzene bonds on the guaiacyl, impeding the subsequent pulp bleaching via increasing the content of chromophore in the bamboo.4. XPS data demonstrated that bamboo fiber surface almost consisted of hydrogen, carbon, oxygen and a slight amount of nitrogen. The surface amino (-NH2) or an amide group (O=C-NH) of fibre was removed after HWP. According to the change of the O/C value, it was believed that HWP exposed more fiber surface cellulose than that of AHPP. Contrast with HWP, AHPP only removed partial amino (-NH2) or an amide group (O=C-NH, also known as peptide bonds) group on the surface of fibre. Besides, the contents of lignin and extractives were reduced significantly. However, a number of -C=O and O-C-O groups would generate on the surface of fibre.5. W (1), L (1) and Fines (1) were reduced after HWP. However the L (n) increased and the fiber aspect ratio decreased. A significant increase was observed in fines percentage by weight of APMP after HWP but the weight percentage of the fiber under all mesh class reduced to varying degrees, suggesting that the long fibers would be cut easily during pulping process after HWP. Compared with the former, AHPP long fiber content significantly increased. The distribution of fibre length in the bleaching APMP distribution changed a little with the addition of peroxide.6. In the HW process, the dextran started generating glucosamine monosaccharides at 190℃.Moreover monosaccharide glucosamine degraded of HMF speed became faster among with temperature and time riesd. At 170℃ with 1.5h, xylan started degradated to xylose. In the AHP process, temperature of xylan degradated to xylose started at 90℃, reaction rate accelerated within temperature increased, and the yield of xylose increased within same time. It was interesting that the generation of glucose, HMF and furfural did not observed during the entire AHP reaction process.

  • 【网络出版投稿人】 广西大学
  • 【网络出版年期】2016年 03期
  • 【分类号】TS711
  • 【被引频次】2
  • 【下载频次】197
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