【作者】 袁成强；

【导师】 陈嘉川；

【作者基本信息】 山东轻工业学院 ， 制浆造纸工程， 2008， 硕士

【摘要】 近年来,虽然通过增加木浆比例和提高废纸资源的利用率来调整制浆造纸原料结构,但非木材原料(尤其是麦草)仍是我国重要的纤维资源。因此研究麦草在制浆及漂白过程中木素结构的变化对发展我国造纸工业具有举足轻重的作用。本文系统地研究了酶用量对酶解-弱酸解两段法提取麦草浆残余木素的影响,结果表明,当酶用量为3 mL/g绝干浆时,所得残余木素的得率和纯度较高,能很好地反应木素的原本结构。采用酶解-弱酸解两段法分别从麦草原料、蒸煮各个阶段纸浆及OQP漂白纸浆中分离出原料木素和纸浆残余木素试样。采用酸析法得到粗的黑液溶出木素试样,并用弱酸解法进行提纯,得到纯度较高的溶出木素试样。通过凝胶渗透色谱对所有木素试样进行了木素分子质量分布的研究。结果表明,麦草在烧碱-蒽醌法蒸煮过程中,随着蒸煮的加深,残余木素的平均分子质量先增大后减小,升温后期和保温初期,是造成木素大分子降解的主要阶段;黑液溶出木素的平均分子质量逐渐增大;在OQP漂白中,木素分子的平均分子质量都在减小。与过氧化氢漂白相比,氧脱木素过程中木素平均分子质量减小幅度较大。麦草在蒸煮和漂白各个阶段,纸浆残余木素平均分子质量均大于溶出木素,但木素多分散性基本没有变化。利用红外光谱和磷谱核磁共振技术,对木素结构中功能基团进行了定性和定量分析。通过31P-NMR谱图系统地分析了麦草在烧碱-蒽醌法蒸煮及OQP漂白过程中木素结构中功能基团含量的变化规律。在烧碱-蒽醌法蒸煮中,麦草残余木素在升温初期,脂肪族含量略有增加,羧基增加,总酚羟基下降,随着蒸煮的进行,脂肪族羟基迅速下降,羧基含量基本不变,总酚羟基含量增加,缩合酚羟基和紫丁香基含量逐渐增加,愈疮木基和脱甲基酚羟基、对酚羟基含量逐渐降低。在烧碱-蒽醌蒸煮过程中,随着蒸煮的加深,溶出木素中脂肪族羟基开始降低很快,后来基本保持不变;总酚羟基含量增加,其中紫丁香基酚羟基和缩合酚羟基含量增加,愈疮木基酚羟基和对酚羟基的含量变化幅度较小。在蒸煮初期产生了大量的羧基,但随着蒸煮程度的加深,羧基含量有所减少。在氧脱木素中,纸浆残余木素中脂肪羟基和羧基含量增加,总酚羟基含量基本不变;废液中溶出木素脂肪羟基比未漂浆残余木素中含量低,但总酚羟基和羧基含量较高;纸浆残余木素中,缩合酚羟基、紫丁香基酚羟基、愈疮木基酚羟基、对酚羟基含量变化不大,但废液溶出木素各酚羟基含量均高于残余木素。过氧化氢漂白后,纸浆残余木素中脂肪羟基和羧基含量增加,总酚羟基及各酚羟基含量明显降低,木素结构单元间的连接没有明显断裂,但木素结构单元发生了开环反应。更多还原

【Abstract】 Although the structure of raw materials has being adjusted through increasing the proportion of wood pulp and by effectively utilizing the waste paper, non-wood species (especially the wheat straw) will still play an important part. So it is significant for Chinese paper industry to study the changes of lignin structure during cooking and bleaching of wheat straw.The effect of enzyme dosage on the two-stage method of enzyme-mild acidic hydrolysis solution to extract residual lignin from wheat straw pulp was studied in this paper. The result showed that the yield and purity of lignin is highest when the dosage is 3 mL/g (dry slurry). The sample of isolated lignin by the two-stage method was representative, and can represent the protolignin well.The wheat straw lignin and residual lignin samples were isolated from wheat straw, pulps from all stages and OQP pulps, by the two-stage method: enzyme-mild acidic hydrolysis methods. The crude lignin isolated from black liquor by acidic precipitation was purified by mild acidic hydrolysis and dissolved lignin samples with high purity and yield were obtained.The lignin molecular weight distribution was studied through GPC analysis. The results indicated that: during the NaOH-AQ cooking process of wheat straw, the average molecular weight of residual lignin increased at first and then decreased with the deepening of the cooking, and the molecular weight decreasing mainly happened at the last stage of rising temperature and the first stage of keeping temperature. The average molecular weights of dissolved lignin increased gradually and had a rapid increased at the last time. The average molecular weight of residual lignin decreased during OQP bleaching. Compared with hydrogen peroxide bleaching, oxygen delignification is the main factor to decrease the molecular weight. The molecular weight of residual lignin is much larger than the dissolved at each stage of cooking and bleaching, but the dispersivity of lignin keeps at the similar level.The functional groups in all lignin samples in the cooking and OQP bleaching were qualitative and quantitatively analyzed with infrared spectroscopy and 31P-NMR techniques, and were compared to one another.At the first stage of increasing temperature of NaOH-AQ cooking, the contents of aliphaticOH (A-OH) and COOH increase, but the content of total phenolic OH (T-OH) decreases. With the deepening of cooking,the content of A-OH decrease rapidly, and the content of COOH had almost unchanged, while the content of T-OH increased a lot. The contents of condensed phenolic OH (C-OH) and syringyl phenolic (S-OH) increased, but guaiacyl and dementhylated OH (G-OH) and p-hydroxy-phenyl OH (p-OH) decreased in the residual lignin.In NaOH-AQ cooking process, the content of A-OH decreases rapidly during the initial stage of cooking, and then changed a little. At the first stage of cooking, a large number of COOH was generated, as the deepening of cooking, the content was reduced. Along with the deepening of cooking, the content of T-OH、S-OH and C-OH increased, while the contents of G-OH and p-OH were not changed so much in the dissolved lignin.After oxygen delignification lignin, the content of A-OH and COOH increased, while the content of T-OH had almost unchanged in the residual lignin. Compared with unbleached pulp, the contents of A-OH in dissolved lignin were lower, and the contents of T-OH and COOH were higher. The contents of C-OH、S-OH、G-OH and p-OH changes a little in the residual lignin, and the contents of all kind phenolic hydroxyl groups in dissolved lignin were higher than residual lignin.After hydrogen peroxide bleaching, the content of total phenolic hydroxyl and other phenolic hydroxyl were significantly decreased, while the contents of aliphatic hydroxyl and carboxyl increased a little in the residual Lignin.更多还原