乙醇浓度对桉木片醇水抽提预处理液成分的影响

采用回转式密封炉在醇水体系下对桉木片进行抽提预处理,分别采用3种不同浓度(醇/水比1/4、1/2、1/1)的混合液制备了不同的抽提物。对过滤后的抽提液首先进行糖分测定;其次将抽提液经冷冻干燥、苯/甲醇溶解、风干处理后,进行亲脂性化合物的测定;着重考察了乙醇/水体系中乙醇的浓度对预处理抽提液成分相对含量的影响。结果表明,抽提液中总含糖量分别为1.597mg/L、1.641mg/L、1.679mg/L,占物料总质量比例分别为5.39%、5.54%、5.66%,其中木糖的含量最高,三种样品均在78%以上;定性测得的预处理实验中抽提液亲脂性化合物为烷烃类、酯类和胶质类化合物,并且分子量大;主要的化合物为2,4’,5-三甲基二苯甲烷,2,6,11-三甲基-十五烷,十七烷,2,6,10,14-四甲基-十六烷,十九烷,槲皮素,二十六烷。     

4种常见木质素有机溶剂法分级的研究进展

随着对木质素基生物质材料开发和研究的逐渐深入,进一步提高木质素基生物质材料的性能,需对木质素原料进行结构分级。有机溶剂法分级是一种可以获得具有特定理化性质木质素的简单可行的分级方法。本文总结了近年来采用有机溶剂法,对硫酸盐木质素、有机溶剂木质素、碱木质素和酶解木质素4种常见木质素进行分级,且分级效果较好的研究成果,利用分子质量及分子质量分布,以及醇羟基、酚羟基、甲氧基等官能团含量作为分级评价指标,比较了不同分级策略所使用的单一或多种有机溶剂的分级特点和优缺点,并对木质素分级研究作简要总结和展望。     

Energetic analysis of gasification of biomass by partial oxidation in supercritical water

Partial oxidation gasification in supercritical water could produce fuel gases (such as H2, CO and CH4) and signif-icantly reduce the energy consumption. In this work, an energetic model was developed ...     

超临界乙醇体系中苯酚催化加氢的降解规律

目前,液化的生物油与石油粗油成分接近,通常环类化合物含量高,如煤焦油中酚及其衍生物含量占40%以上,急需加氢升级技术。超临界乙醇（243.1℃,6.38MPa）温度、压力条件低,具有良好的传质性能,且为绿色、可再生溶剂。在超临界乙醇体系下的催化加氢是一种油升级有效方式。本文以苯酚为生物油中环类化合物典型模型,在300～400℃、Pt/C催化剂下,探讨超临界乙醇体系下苯酚催化加氢过程。研究分析了超临界乙醇中温度、氢气压力和反应时间对苯酚催化加氢降解规律的影响,并建立了能很好地描述过程中苯酚转化率的动力学模型（R2 = 0.989）。实验表明：该体系下的苯酚催化加氢降解反应的级数为二级,反应的活化能为51.7kJ/mol;尽管升高温度和氢气压力均能提高苯酚的转化率,但温度对转化率的影响更为显著。本研究将为更好地控制反应过程和提高超临界乙醇体系中苯酚的转化率提供参考。     

杨木APMP及其白水中纤维的形态分析

随着白水封闭循环程度的不断提高,白水中纤维和细小纤维的回用必然会对纸机运行和纸页性质产生一定的影响。本文分析研究了杨木APMP及其白水中纤维与细小纤维的形态。结果表明,APMP纤维的平均长度比自水纤维的长,但白水中细小纤维的含量明显比浆料的高,而且细小纤维的平均面积也更大。     

磷酸溶液处理对对位芳纶纤维结构的影响

用黏度法、X射线衍射（XRD）、光学显微镜及扫描电镜（SEM）等测试手段对磷酸溶液处理前后对位芳纶纤维的相对分子质量、聚集态结构、形态结构进行了研究,探讨了磷酸溶液处理对对位芳纶纤维不同层次结构的影响。结果显示：未处理对位芳纶纤维的黏均相对分子质量为2．70万,用50％磷酸溶液处理4h后,其相对分子质量降低为2．38万;而其处理前后结晶度分别为58．24％、59．58％,变化不大。未处理对位芳纶纤维的表面光滑,经磷酸溶液处理后纤维原纤化作用明显,表面可观察到大量的微细纤维。     

Bio-cathode materials evaluation in microbial fuel cells: A comparison of graphite felt,carbon paper and stainless steel mesh materials

The choice of the cathode material is crucial for every bio-cathode microbial fuel cell (MFC) setup. The commonly used biocathode materials, Graphite felt (GF), carbon paper (CP) and stainless steel mesh (SSM) were compared and evaluated in terms of current density, power density, and polarization. The maximum current density and power density of the MFC with GF-biocathode achieved 350 mA m⁻² and 109.5 mW m⁻², which were higher than that of the MFC with CP-biocathode (210 mA m⁻² and 32.7 mW m⁻²) and the MFC with SSM-biocathode (18 mA m⁻² and 3.1 mW m⁻²). The polarization indicated that the biocathode was the limiting factor for the three MFC reactors. Moreover, cyclic voltammetry (CV) showed that the microorganisms on the biocathode played a major role in oxygen reduction reaction (ORR) for GF- and CP-biocathode but SSM-biocathode. Electrochemical impedance spectroscopy suggested that GF biocathode performed better catalytic activity toward ORR than that of CP- and SSM-biocathode, also supported by CV test. Additionally, the MFC with GF-biocathode had the highest Coulombic Efficiency. The results of this study demonstrated GF was the most suitable biocathode for MFCs application among the three types of materials when using anaerobic sludge as inoculums.     

Manganese dioxide-coated carbon nanotubes as an improved cathodic catalyst for oxygen reduction in a microbial fuel cell

To develop an efficient and cost-effective cathodic electrocatalyst for microbial fuel cells (MFCs), carbon nanotubes (CNTs) coated with manganese dioxide using an in situ hydrothermal method (in situ MnO₂/CNTs) have been investigated for electrochemical oxygen reduction reaction (ORR). Examination by transmission electron microscopy shows that MnO₂ is sufficiently and uniformly dispersed over the surfaces of the CNTs. Using linear sweep voltammetry, we determine that the in situ MnO₂/CNTs are a better catalyst for the ORR than CNTs that are simply mechanically mixed with MnO₂ powder, suggesting that the surface coating of MnO₂ onto CNTs enhances their catalytic activity. Additionally, a maximum power density of 210 mW m⁻² produced from the MFC with in situ MnO₂/CNTs cathode is 2.3 times of that produced from the MFC using mechanically mixed MnO₂/CNTs (93 mW m⁻²), and comparable to that of the MFC with a conventional Pt/C cathode (229 mW m⁻²). Electrochemical impedance spectroscopy analysis indicates that the uniform surface dispersion of MnO₂ on the CNTs enhanced electron transfer of the ORR, resulting in higher MFC power output. The results of this study demonstrate that CNTs are an ideal catalyst support for MnO₂ and that in situ MnO₂/CNTs offer a good alternative to Pt/C for practical MFC applications.     

Laccase and alkali treatments of cellulose fibre: Surface lignin and its influences on fibre surface properties and interfacial behaviour of sisal fibre/phenolic resin composites

This paper is an attempt to investigate the influences of enzyme (laccase) and alkali treatments on the surface lignin of single cellulose fibre. The fibre surface characteristics and the interfacial behaviour of the sisal fibre/phenolic resin composites were also studied by SEM, AFM, XPS. The surface lignin greatly affected the surface physical and chemical properties of single cellulose fibres. The surface lignin concentration was up to 35% for the raw fibre without any treatment, and then it decreased to 24%, 20% and 18% for the fibres with laccase treatment, alkali treatment and laccase/alkali treatment, respectively. The removal of lignin from fibre surface could enhance the interfacial strength of composites, and thus increase the tensile strength and internal bonding strength by 43% and 51%, respectively, for the composites obtained from laccase/alkali treated fibres.