【作者】 李红斌；

【导师】 房桂干；

【作者基本信息】 中国林业科学研究院 ， 林产化学加工工程， 2008， 博士

【摘要】 本文对麦草原料制备化学机械浆高白度漂白化学机械浆主要的制浆性能进行了对比研究,比较了三种不同的化学药品用于预浸渍阶段（碱性过氧化氢预处理、果胶酶/碱性过氧化氢预处理、中性亚硫酸钠预处理）对未漂白浆的光学和物理性能的影响,包括成浆白度、成浆强度指标、纤维筛分级分,而且也比较了磨浆的比能耗和废水污染负荷。研究结果表明:麦草原料经过碱性H₂O₂ （1.5%用量H₂O₂,2.0%用量NaOH,0.4%用量DTPA）预处理,制得的纸浆具有较高的白度和良好的物理强度。且磨浆废水污染负荷较低。纸浆的碱性过氧化氢可漂性较好。选用过氧化氢（P）、过氧乙酸（Pa）和硼氢化钠（B）等不同类型的漂白药剂经过筛选试验,并分别优化了各自单段漂白的适宜条件。并对P/Pa/B进行了不同组合序列的漂白效果进行了研究。研究结果表明,过氧乙酸与过氧化氢最佳组合方式为PaP₁P₂ （过氧乙酸用量1.0%,两段H₂O₂用量皆为5%）,这种漂白方式漂后麦草化机浆白度可以达到72.83%ISO;经过P₁P₂B （两段5.0%用量H₂O₂漂白,后续1.0%用量的NaBH₄还原）三段漂白后,漂白麦草化学机械浆的白度可达73.98%ISO。对比研究了新鲜麦草和储存麦草化机浆的漂白性能发现,麦草原料经过一段时间贮存后,对所制得的纸浆的后续漂白会带来负面影响,试验结果表明:麦草原料经过12个月时间的贮存,制得的麦草化学机械浆以相同的漂白工艺,即PaP₁P₂和P₁P₂B的工艺漂白后,成浆白度分别为67.09%ISO,70.83%ISO,因此原料的新鲜程度对于禾草类原料的化学机械浆的漂白性能影响十分显著。漂白废液的研究结果表明:麦草化学机械浆纸浆P₁P₂B漂白工艺三段漂白废水BOD与COD总发生量分别为149.06kg/t浆和384.24kg/t浆,均低于PaP₁P₂漂白工艺三段漂白废水BOD与COD总发生量;从漂白废液气相色谱/质谱分析检测结果可以看出:两种漂白废液的主要污染物质成分构成较为相近,均含有芳香族化合物和脂肪族化合物,但是Pa漂白废液中酯类有机物和4, 4`-二羟基二苯丙烷的相对含量明显高于NaBH₄漂白废液的相对含量。这可以用来解释Pa漂白废液的污染负荷高于NaBH₄漂白废液污染负荷的现象。麦草化学机械浆经过H₂O₂（用量4%、6%、8%、10%）漂白,纸浆酸化前后成浆白度（%ISO）存在明显差异,纸浆酸化后白度增值最小的为9.85个百分点,增值最大的16.12个百分点,同时酸化后成浆b*值也明显减小（趋向蓝色）。纸浆返黄试验的结果表明:麦草化学机械浆经过PaP₁P₂、P₁P₂B处理与单独使用H₂O₂漂白相比,纸张白度稳定性明显提高;相比之下,硼氢化钠处理后,纸浆白度稳定性比过氧乙酸的处理效果明显,这主要是硼氢化钠处理纸浆以后,木质素结构中羰基数量的减少,从而增加了成浆白度稳定性。通过对木质素碱性硝基苯氧化产物以及1H-NMR谱图分析的结果可以看出,麦草化学机械浆纸浆经过碱性H₂O₂漂白,以及后续NaBH₄还原处理以后,其中,香草醛约占40%～48%,紫丁香醛约占41%～53.10%,对羟苯甲醛约占6%～9%,说明麦草原料以及化机浆漂白后木质素属G-S-H型木质素。麦草化学机械浆纸浆经过碱性H₂O₂漂白,木质素中酚羟基含量（0.29个/C9）略高于原料中的酚羟基含量（0.28个/C9）,说明H₂O₂漂白不能有效地减少木质素中酚羟基这类助色基团的数量。麦草化机浆H₂O₂漂白后,总的羰基含量由原料木质素中的0.1063个/C9减少到0.0782个/C9,减少了26.43%;而后续使用NaBH₄还原处理纸浆木质素中共轭羰基数量由H₂O₂漂白后的0.0782个/C9下降到0.0235个/C9,减少了69.95%,这是由于NaBH₄还原处理后,与苯环的共轭结构,被还原成Cα-OH结构;破坏了木质素中共轭发色基团,提高了成浆白度及其白度稳定性。更多还原

【Abstract】 The pulping properties of wheat straw materials by chemi-mechanical pulping process were investigated and compared in this thesis. Investigations on influences of impregnation using three kinds of pretreatments process（alkaline peroxide pretreatment, pectinase /alkaline peroxide pretreatment, neutral sodium sulfite pretreatment ） on unbleached chemimechanical pulps including optical and physical properties, were carried, such as coarse pulp brightness, coarse pulp strength, results of fiber screen classified parts , and specific energy consumption of refing process and COD load of effluent generated by pulping process were also contrasted. Results shows that higher pulp brightness, lower pollution load of effluent generated by refining process, better pulp strength and bleaching performance can be gathered through chemi-mechanical pulping process.Therefore, alkaline hydrogen peroxide pretreatment is a feasible method for wheat straw chemical mechanical pulping process.High brightness of wheat straw chemi-mechanical pulp bleached by peracetic acid and sodium borohydride combined with alkaline peroxide was gained. The final pulp brightness could be 72.38% ISO under the Pa optimal condition（peracetic acid dosage 1.0%, bleaching time 120min, pH 5, pulp consistency 20%）, associated with two stage 5.0% H₂O₂ for multi-stage bleaching （PaP₁P₂ bleaching process）of wheat straw chemical mechanical pulp; The final brightness of wheat straw chemi-mechanical pulp bleached by NaBH₄ （NaBH₄ dosage 1.0%, bleaching time 60min, pH 10-11, pulp consistency 10%）associated with two stage 5.0% H₂O₂ could be 73.98%ISO. After storage for period of time, the appearance color of wheat straw becomes darker and deeper due to the changes of lignin from wheat straw materials, which adding the bleaching difficuty. The brightness of pulp made by wheat straw material storaged for 12 months could only be achieved at 67.09%ISO and 70.83%ISO respectively, using the same bleaching process（PaP₁P₂, P₁P₂B1.0 ）, Results shows that the short storage-time material is important to wheat straw chemi-mechanical bleaching.The research on effluent from bleached pulp indicated that both COD value and BOD value of bleaching effluent from wheat straw chemi-mechanical pulp P₁P₂B bleaching stages are lower than that of PaP₁P₂, which are 149.06 kg/t pulp and 384.24 kg/t pulp respectively. The molecular structures of pollutant in these two kinds of effluent are similar, both contain aromatic compounds and aliphatic compounds, which can be determined by chromatography and mass spectrometry. The content of esters organic compounds and 4,4`-（1-methylethylidene） bis- organicas from Pa bleaching effluent is obviously higher than the content of organicas from NaBH₄ bleaching effuent. This could be one of the reasons which result in the pollution load of Pa bleaching effluent is higher than that of NaBH₄ bleaching effluent.There is an obvious difference for wheat straw chemi-mechanical brightness of pulp bleached by H₂O（24%、6%、8%、10% dosage）after acidfication, the pulp least brightness gain can be reached by 9.85 % ISO, the maximal brightness gain can be reached by 16.12 % ISO, and b* value decreased after acidficationPulp yellowing experiment results show that wheat straw chemi-mechanical pulp brightness stabilization is significantly improved using 1.0% peracetic acid or 1.0% NaBH₄ compared with H₂O₂ bleaching results; in contrast, the treatment efficiency for pulp brightness stabilization treated by 1.0% NaBH₄ is more obvious than the pulp stabilization treated by 1.0% peracetic acid. Improvement of brightness stabilization can be judged by quantity of carboxyl, because of the quantity of carboxyl of lignin from pulp treated by NaBH₄ decreasing, the pulp brightness stabilization is improved.Determination of nitrobenzene oxidation products of lignin by GC and spectra analysis for ¹H-NMR show that the lignin of wheat straw materials, chemi-mechanical pulps ,pulp bleached by alkaline H₂O₂ and pulps treated by H₂O₂/NaBH₄ is a G-S-H type lignin （the proportion of guaiacylpropane units 40%～48%, syringylpropane units is about 41%～53.10%, and p-hydroxyphenylpropane units is about 6%～9%）.Amount of auxochrome phenolic hydroxyl（0.29 unit/C9）in lignin from H₂O₂ bleaching chemi-mechanical pulp is slightly higher than one of material（0.28 unit/C9）, so amount of auxochrome phenolic hydroxyl can not be effectively decreased by alkaline peroxide bleaching process. Conjugated carbonyl content in lignin from H₂O₂ bleaching chemi-mechanical pulp decreases by 26.43% from 0.1063 unit/C9 to 0.0782 unit/C9, the content of conjugated carbonyl in lignin from pulp reduced by NaBH₄ decreases further by 69.95% from 0.0782 unit/C9 to 0.0235 unit/C9. Conjugated carbonyl in lignin from wheat straw chemi-mechanical pulp was reduced from Cα=O structure to Cα-OH structure by NaBH₄ reducing process after H₂O₂ bleaching process, this is the reason for pulp brightness improvement and pulp brightness stablilization increase.更多还原