乙酰化处理对碱木质素在四氢呋喃中微结构的影响

通过对比碱木质素(AL)和乙酰化碱木质素(ACAL)在四氢呋喃(THF)中溶液行为和物理化学性质的差异, 揭示了乙酰化处理对碱木质素在THF中微结构的影响. 分别采用动态光散射、凝胶渗透色谱(GPC)、透射电子显微镜(TEM)、特性粘度、荧光光谱仪、耗散型石英晶体微天平(QCM-D)和自组装技术等研究了AL和ACAL在聚集形态、聚集机理以及吸附特性等方面的特征. 研究发现, 乙酰化处理会降低碱木质素在THF中的分子间和分子内聚集程度. AL在THF中以单分子和聚集体的形式共同存在, 分子较为蜷曲; ACAL在THF中则更多地是以单分子形式存在而几乎不存在大聚集体, 分子较为伸展, 其流体力学半径要比相同绝对分子量的AL更大.THF中的AL聚集体会在液固界面上发生强烈的吸附, 但ACAL由于与溶剂间的相互作用较强而几乎不会吸附在液固界面上. 由于AL分子在THF中较为蜷曲且吸附能力较强, 因此利用以THF为流动相的GPC直接测量AL的分子量时所得结果并不准确, 为保证GPC的测量结果更加全面可靠, 需要在测量前对碱木质素进行乙酰化处理.     

温度对碱木质素在溶液中微结构及物理化学性质的影响

研究了温度对碱木质素(AL)的微结构及物理化学性质的影响. 在20-60 ℃范围内, 采用表面电荷仪、动态光散射、zeta 电位仪、粘度计、表面张力仪、石英晶体微天平、紫外和荧光等仪器, 研究了AL在碱性溶液中的分子聚集形态、表面带电情况、亲疏水特性、溶液特性粘度以及AL在气液和液固界面上的吸附等性质. 结果表明, AL溶液的特性粘度、表面张力以及分子的表面电荷密度都会随温度上升明显降低, 而分子内和分子间聚集作用、分子的疏水性以及在液固界面上的吸附量会随温度上升逐渐增大, zeta 电位绝对值则呈现出先降低后上升然后再降低的趋势. 分析认为, 温度上升会同时降低AL中弱酸性基团的电离程度和AL与水分子间的氢键作用, 这两个因素的变化直接导致了AL微结构和物理化学性质的改变. 温度升高时, 水由AL的良溶剂逐渐变为不良溶剂, 尽管AL通常被视为阴离子表面活性剂, 但其受温度影响时所呈现出的变化规律却更类似于非离子表面活性剂.     

Electrochemical Reduction and Oxidation of Six Natural 2′‐Deoxynucleosides at a Pyrolytic Graphite Electrode in the Presence or Absence of Ambient Oxygen

Recently we have demonstrated that pyrolytic graphite electrodes (PGE) offer a broad analytically useful potential window, ranging from about ?2.0 V to +1.6 V vs. Ag|AgCl|3 M KCl, which enables to use the PGE not only for anodic measurements, but also for direct reduction of nucleobases in DNA oligonucleotides. In this follow‐up study, we have focused on the electrochemical behavior of four 2′‐deoxynucleosides derived from adenine, guanine, cytosine, thymine, uracil, and 5‐methyl cytosine on the PGE. On one hand we have obtained analogous primary redox responses as previously with the oligonucleotides. On the other hand, significant differences were observed, particularly when considering secondary responses involving products of the primary conversions, suggesting involvement of different mechanisms. Further we have found that presence of the ambient oxygen in the electrolyte does not dramatically affect the redox signals of the nucleosides. This finding is in contrast with DNA responses measured at the mercury‐based electrodes, where deaeration prior to the measurements was necessary. We demonstrate that all studied nucleosides can be analyzed using a simple ex situ (medium exchange) procedure.     

A comparative study of the electrospray ionization response of β‐O‐4′ lignin model compounds

Electrospray ionization mass spectrometry has recently become the technique of choice for rapid characterization of lignin degradation products. However, the fundamental question of the relationship between lignin structure and ionization efficiency has not been explored. In this work, we studied the electrospray ionization response of five structurally similar β‐O‐4′ model lignin compounds using lithium cationization in the positive electrospray ionization mode. The studied compounds have the same β‐O‐4′ backbone structure but differ at the α‐position by increasing nonpolar side chains. Our results show a correlation between the ionization response and the length of the nonpolar side chain, with analytes having the longest side chain recording the highest ESI response in the full scan mode. Factors affecting the formation of analyte ions and analyte cluster ions were also studied. We have shown for the first time in this work that the introduction of a nonpolar group onto a β‐O‐4′ lignin compound can increase the lithium cationization ESI response in the positive ion mode.     

Extraction of male steroids and progesterone from water by vegetable oil gels and their determination by partial filling capillary micellar electrokinetic chromatography

Microemulsion gels were synthetized from macadamia, linseed, olive, walnut, rapeseed, sesame, and coconut oils and frying oil made from sunflower, palm, and rapeseed oils. The gels were similar as polyacrylamide–based gels with exception of replacing dodecyl sulfate with vegetable oils. The gels were modified with celluloses, cotton, or lignin to make the emulsions sustainable for water purification. They were used to compare sorption properties when they were used as solid‐phase adsorbents in isolation of steroids from water. Hydrophobicity features of the gels were compared by detecting adsorption and extraction efficiency of nonpolar androstenedione, testosterone, and progesterone, which exist in wastewater and drinking water. Quantification was done with partial filling–micellar electrokinetic chromatography with 29.5 mM sodium dodecyl sulfate–3.4 mM sodium taurocholate as the micelle and 20 mM ammonium acetate (pH 9.68) as the electrolyte. UV‐detection was used. Methanol was the best eluent for extraction of steroids from gels. The highest recoveries were from frying oil and rapeseed oil gels modified with celluloses. They also possessed the best floating properties on water surface. Lignin modified gels were too hydrophilic, when in touch with water they filled up with water. They also had the lowest capacity.     

次烟煤与木质素共热溶物的液化及其Ni-Mo-S/Al2O3催化剂循环利用性能

对神府次烟煤与木质素共热溶得到的四种具有不同热溶产率的热溶物进行元素分析、红外光谱、同步荧光光谱等表征,对四种热溶物和神府原煤的加氢液化性能进行比较,并进行了催化剂在热溶物液化过程的循环利用性能研究。结果表明,神府煤热溶物较同一温度得到的神府煤与木质素共热溶物具有更多的芳香组分和四环及其以上的多环芳烃。热溶物较神府原煤在液化时具有更高的转化率和油收率。在催化剂Ni-Mo-S/Al₂O₃作用下,热溶物在液化过程中几乎全部转化,并具有很高的油收率,且神府煤与木质素共热溶物较神府煤热溶物具有更高的油收率。在神府煤与木质素共热溶物的液化过程中,催化剂Ni-Mo-S/Al₂O₃表现出优异的可循环利用性能,经过四次循环利用后没有观察到催化剂表面的炭沉积现象。     

高沸醇溶剂法提取胡萝卜木质素

以乙二醇水溶液为溶剂,采用高沸醇溶剂法（high boiling solvent,HBS）从胡萝卜中提取木质素。 结果表明,将胡萝卜干粉投入到质量分数为80%的乙二醇中,在210 ℃、料液质量比为1∶6的条件下蒸煮2 h,木质素收率最高（17.79%）。 采用红外光谱（FTIR）、紫外光谱(UV)和核磁共振(1H NMR)等测试技术对其结构进行了表征。 结果表明,高沸醇法提取的胡萝卜木质素具有木质素类化合物的典型结构特征。 通过元素分析和甲氧基含量的测定,得到胡萝卜木质素的C9结构模型为C9H9.62O1.99(OCH3)0.96。 利用Fenton反应产生羟基自由基·OH,研究了胡萝卜木质素对羟基自由基的抑制效率。 结果表明,胡萝卜木质素在较低的浓度（50 mg/L）下对羟基自由基就具有较强的抑制效果,抑制率最高可达64.9%。     

木质素二聚体模型物裂解历程的理论研究

木质素作为生物质的主要成分之一, 是生物油的重要组分, 在工业生产中有着重要的应用. 生物质高温裂解液化制备生物油的过程伴随着木质素的裂解, 因此研究木质素高温裂解历程, 对生物油的制备有很大的帮助. 利用密度泛函方法对木质素在高温条件下的裂解历程进行理论研究, 并通过对各步反应的热力学焓变计算, 确定了初次裂解的路径为Cα—Cβ和β-O-4热裂解路径. 根据进一步的研究预测了裂解反应的主要产物.     

The Structural,Molecular and Functional Properties of Lignin-Containing Beechwood Glucuronoxylan

The samples of 4-O-methyl-D-glucurono-D-xylan (GX) with different lignin and uronic acid (MeUA) contents were prepared from beechwood by various procedures. The re-dissolution process of the partially water-soluble GX-2 lyophilizate in aqueous medium depended on the content and distribution of MeUA. In contrast to the supernatant after ultracentrifugation, the sediment had a significantly lower MeUA content and showed mainly high-molecular mass components. A part of lignin degradation products is separable by repeated dissolution and precipitation of GX in acidic and alkaline 80% ethanolic media with assistance of ultrasound. Irradiation in acidic ethanol (GX-3/ac) showed no effect on the distribution of the UV₂₅₄-absorbing component. GX-3 sonicated in neutral and alkaline media (GX-3/ne, GX-3/alk) lost water solubility. The lignin-rich GX samples showed remarkable emulsifying efficiency and protein foam stabilization effect. In addition, the presence of phenolics provided antioxidant properties to these xylan preparations indicating their potential as polymeric radical scavengers.     

Fractionated Lignosulfonates for Laccase-Catalyzed Oxygen-Scavenging Films and Coatings

Lignin derivatives have potential as antioxidants in advanced packaging materials through their ability to scavenge oxygen in reactions catalyzed by phenol-oxidizing enzymes, such as laccase. The effects of size fractionation of lignosulfonates on laccase-catalyzed reactions were investigated in experiments with aqueous solutions, films, and coated paperboard. Four industrial lignosulfonate preparations were compared: Feed (unfractionated), Prod (5–60 kDa enriched), Conc (≥60 kDa enriched), and Perm (≤60 kDa enriched). Extraction of lignosulfonates from films showed that the enzymic reaction increased the average molecular weight from <10,000 to up to 66,000. The enzymatic reaction resulted in an increase in the water contact angle of the films from the range 25–49° to 56–81°. The four preparations showed relatively small differences with regard to their ability to scavenge oxygen in aqueous solution and in experiments with coated paperboards in sealed chambers. Coatings with lignosulfonates where the contents of low-molecular weight material had been reduced (i.e., Prod and Conc) showed improved water resistance after the enzymic reaction. Thus, in both aqueous and solid media, fractionation of lignosulfonates had little effect on oxygen scavenging, but fractionation was beneficial for other reasons, such as improved cross-linking resulting in higher molecular weight and superior water resistance.