The Progress of Ageing of Lignin-containing Paper Induced by Light and its Relation to Chemiluminescence – Temperature Runs

Lignin-containing papers from different sources and of different age were irradiated by the visible light and the progress of the degradation reaction was followed by non-isothermal chemiluminescence method. Kinetic data obtained for papers degraded in oxygen were compared with double fold endurance test and carbonyl groups concentration. The effect of lignin on degradation of cellulose after deacidification treatment of the paper by methoxymagnesium methylcarbonate (MMMC) was ascertained and a mechanism of co-oxidation of lignin and cellulose in originally alkaline conditions was outlined.     

木质素:一种有潜力的生物质基催化剂来源

木质素是自然界中储量丰富的唯一含芳环生物质可再生资源,但复杂的结构使其难以高效利用,目前大部分被废弃。除通过氧化还原等过程可将其转化为石油化工产品的替代品外,木质素结构中丰富的含氧官能团及制浆过程引入的硫元素等均可提供有效位点,为其作为催化剂基质提供了丰富的可行性。本文从木质素资源的来源和结构分析出发,根据不同催化反应的机理和制备催化剂过程中的结构改性类型,综述了具有不同结构特征的木质素基催化剂分别在生物质平台化合物水解等酸碱催化反应、电催化反应和负载金属纳米粒子催化氧化还原反应等过程中的应用,讨论了木质素类型、制备或活化改性条件对催化材料性能的影响,也指出了当前木质素基催化剂的开发研究难点和未来发展方向。     

Lignin: its functions and successive flow

Phenolic lignin-based polymers with structure-variable function have originally been designed, and a process has been developed for synthesizing them directly from native lignins. The key point of the process is to set up two different solvents, which are immiscible each other, for selective modification and separation of lignin and carbohydrates: hydrophobic solvent for hydrophobic lignin and hydrophilic solvent for hydrophilic carbohydrates. The native lignins, three dimensional network polymers, are subjected to selective modifications at the interface between both phases to give linear type polymers (lignophenols) composed mainly of 1,1-bis(aryl)propane type units, almost quantitatively. The process provides a new system for successively utilizing lignocellulosics in the molecular level.     

木素碱性硝基苯氧化产物的高效液相色谱分析

- hydroxybenzaldehyde,vanillin and syringaldehyde etc. were separated on a Novapak C18 column (5μ 3. 9mm i. d.× 150mm) and eluted with MeOH-H2O (25:75, V/V) at a flow rate of 0. 6mL/min and detected at 254nm. Quantitative analysis was performed with piperonal instead of synthetic product . m-meconin,as the internal standard. Recoveries are 95%-98% and CV≤1%. The method is simple,rapid and reliable.     

Lignin-Derived Syringol and Acetosyringone from Palm Bunch Using Heterogeneous Oxidative Depolymerization over Mixed Metal Oxide Catalysts under Microwave Heating

Biomass valorization to building block chemicals in food and pharmaceutical industries has tremendously gained attention. To produce monophenolic compounds from palm empty fruit bunch (EFB), EFB was subjected to alkaline hydrothermal extraction using NaOH or K₂CO₃ as a promotor. Subsequently, EFB-derived lignin was subjected to an oxidative depolymerization using Cu(II) and Fe(III) mixed metal oxides catalyst supported on γ-Al₂O₃ or SiO₂ as the catalyst in the presence of hydrogen peroxide. The highest percentage of total phenolic compounds of 63.87 wt% was obtained from microwave-induced oxidative degradation of K₂CO₃ extracted lignin catalyzed by Cu-Fe/SiO₂ catalyst. Main products from the aforementioned condition included 27.29 wt% of 2,4-di-tert-butylphenol, 19.21 wt% of syringol, 9.36 wt% of acetosyringone, 3.69 wt% of acetovanillone, 2.16 wt% of syringaldehyde, and 2.16 wt% of vanillin. Although the total phenolic compound from Cu-Fe/Al₂O₃ catalyst was lower (49.52 wt%) compared with that from Cu-Fe/SiO₂ catalyst (63.87 wt%), Cu-Fe/Al₂O₃ catalyst provided the greater selectivity of main two value-added products, syringol and acetosyrigone, at 54.64% and 23.65%, respectively (78.29% total selectivity of two products) from the NaOH extracted lignin. The findings suggested a promising method for syringol and acetosyringone production from the oxidative heterogeneous lignin depolymerization under low power intensity microwave heating within a short reaction time of 30 min.     

Lignosulfonate/silica hybrid nanoparticles as a novel biobased filler in polybenzoxazine matrix

Lignin is an abundant and sustainable resource that exhibits numerous attractive functional properties as a reinforcing agent for benzoxazine-based composites, due to its stiffness, thermal stability, and high carbon content. However, the low quality of lignin particles dispersions associated with the weak particles-matrix interactions reduces the reinforcement capability. In this work, hybrid lignin/silica (NaLS/SiO₂) nanoparticles were obtained from sodium lignosulfonate (NaLS) and tetraethylorthosilicate (TEOS) under basic conditions. The particles were characterized by transmission electron microscopy (TEM) confirming their spherical morphology and narrow nanometric-size distributions. The hybrid particles were incorporated into conventional benzoxazine (BA-a) and a difuran biobased benzoxazine (SA-dfda) to prepare nanocomposites with different mass compositions (3, 5, and 10 wt%). Morphological, mechanical, dynamo-mechanical, and thermal properties of the obtained composites were assessed. All the materials exhibited a homogenous filler dispersion that contributed to improve the reinforcement properties. Hybrid nanoparticles proved to be an interesting alternative as a filler in the benzoxazine matrix to prepare high-performance thermosetting composites.     

Novel Synthetic Strategy for the Production of Fully Bio-Based Binders Using 2,5-Diformylfuran

In this work, resol based binders were prepared with lignin, resorcinol and the bio-based aldehydic platform chemicals 5-hydroxymethylfurfural (HMF) and 2,5-diformylfuran (DFF). In preliminary studies, the solubility and stability of DFF in aqueous-alkaline conditions was investigated. Various binders were prepared to investigate the influence of the HMF-DFF ratio and the influence of the aldehyde concentration on the molar mass, rheological properties and curing characteristics of the final binders. It is shown that significantly higher molecular weights and viscosities are obtained by using DFF instead of HMF. The properties of the final binder could also be affected by the precise choice of DFF concentration, as this resulted in higher levels of crosslinking. This work offers a novel type of fully bio-based binder that consists of non-toxic components and is therefore less hazardous than some conventional binders.     

Near‐IR surface‐enhanced Raman spectrum of lignin

Compacted powders of commercially available nano‐ and microparticles of silver were used to successfully induce the surface‐enhanced Raman scattering (SERS) effect in spruce milled‐wood lignin (MWL). For the two silver particle sizes used in this investigation, the spectra were mostly similar. Some general characteristics of the lignin SERS spectrum are described. The SERS technique was found to be sensitive for detecting lignin. Significant spectral changes were present between the SERS and normal Raman spectra of MWL. The SERS spectrum was assigned on the basis of literature‐reported vibrational assignments of lignin and its models. Based on significant changes in Raman features, we propose that the lignin is strongly adsorbed on silver. To determine whether SERS of lignin can be obtained directly from wood without its isolation, Wiley‐milled spruce wood (WMW) adsorbed on silver was studied. The results indicated that not only the surface‐enhancement effect was successfully induced in the WMW, but that its spectrum was similar to MWL SERS. Moreover, for WMW, no signals from the carbohydrate components were observed, and therefore, lignin was detected selectively. This nano‐ and microparticle‐based molecularly specific method is expected to make a significant contribution in identifying and investigating lignin in various lignin‐containing materials. Published in 2009 by John Wiley & Sons, Ltd.