木质素活化及在木材胶粘剂中的应用进展

木质素是相对分子量较高的天然聚合物,由于具有苯酚结构利于制备木材胶粘剂,但是木质素本身反应活性低,一般都将其活化后再利用.而且,除了以往利用最多的造纸工业产生的木质素外,研究发现木材经过褐腐菌降解后残留主要成分是结构部分发生变化的木质素,这种可再生生物质资源以其自身的结构特点在合成胶粘剂上也有很大的优势,本文结合木质素胶粘剂应用中的问题,重点概述了活化木质素的各种方法及褐腐木质素在木材胶粘剂中的应用.     

Adsorption properties of amine modified lignin-hydrogel composite for uranyl ions: Theoretical and experimental insights

A new modified material was synthesized and characterized as ethylene diamine modified (EA) Polyacrylamide (PAA)-Lignin (L). The adsorption features of EA modified PAA-L were studied for uranyl ions. The characterization experiments were evaluated by FT-IR spectroscopic techniques, scanning electron microscopy (SEM), and PZC analysis. Adsorption of UO₂²⁺ ions as a function of concentration, pH, temperature, and time of adsorption were studied. The adsorption phenomenon of UO₂²⁺ ions onto PAA-L-EA from aqueous medium was successfully evaluated by various equilibrium models such as Langmuir, Freundlich, and Dubinin-Radushkevich (DR). The (Qe) maximum adsorption capacity values for Langmuir model was calculated as 0.792 kg mol^?1 by using experimental data. The constant values of thermodynamic parameters such as (ΔG°), (ΔH°) and (ΔS°) were calculated and it has observed that the mechanism of adsorption was found compatible with endothermic and spontaneous owing to increasing disorderliness at solution/solid system. The adsorption mechanism is compatible with Elovich and intraparticle diffusion models. The power of the interaction between modified lignin and uranyl ?on was explained in the light of Hard and Soft Acid-Base Principle.     

Lignin nanoparticles as a novel carrier for efficacious delivery of toll like receptor 7/8 agonist: Physicochemical and in-vitro evaluation

Imidazoquinolinone (IMDQ) derivatives are known TLR7/8 agonists and are approved by the FDA for antiviral and skin cancer treatment. Their use as innate immune system activating molecules has been limited by poor pharmacokinetic properties and toxicities associated with systemic administration. In the present study, an IMDQ derivative, 1-(3-(aminomethyl) benzyl)-2-butyl-1H-imidazo[4,5-c] quinolin-4-amine (meta-aminomethyl BBIQ, 4), was encapsulated in biopolymer lignin nanoparticles (LNPs) to develop slow-release delivery system and to enhance its immune activating properties. A co-precipitation method was used to synthesize LNPs of alkali lignin. Characterization studies demonstrated the formation of spherical shaped nanoparticles of ∼150 nm size. The encapsulation efficiency and loading capacity for meta-aminomethyl BBIQ in LNPs was found to be 99% and 70%, respectively. In-vitro release studies showed 78% release over 24 h at pH 7.4 followed by sustained release. Kinetic modelling studies showed the release profile followed Weibull order kinetics with β value ≤ 0.75 corresponding to Fickian diffusion. Moreover, blank as well as meta-aminomethyl BBIQ-loaded LNPs were non-hemolytic and did not show significant cytotoxicity in RAW 264.7 and MDA-MB-23 cells at all tested concentrations. This study confirms the potential to use LNPs as a drug delivery system for immune modulators or vaccine adjuvants.     

生物质基酸性低共熔溶剂用于高效溶解木质素及溶解机理

设计能高效溶解木质素的溶剂对木质素的高值化利用具有重要意义。本文中设计了基于氯化胆碱、甜菜碱和左旋肉碱作为氢键受体(HBA)和四种氢键供体(HBD)的生物质衍生的酸性低共熔溶剂(DESs),可以溶解包括碱木质素(AL)、脱碱木质素(DAL)、酶解木质素(EHL)和硫酸盐木质素(KL)在内的不同类型的木质素。在大多数所设计的DESs中,EHL比AL、KL和DAL更容易溶解,而不同木质素中羟基的含量对木质素的溶解有显著影响,但是并非在所有DESs中木质素的溶解情况都符合上述规则。氯化胆碱是构建DESs的首选HBA,具有良好的性能并适应于不同类型木质素的溶解,而合适的酸度使苯甲酸和没食子酸乙酯成为对木质素溶解有利的HBDs。研究表明能有效溶解木质素的DESs应具有强的氢键酸度(α值> 0.95)以及与溶解的木质素匹配的合适极性。此外,HBD的pK_a值和DESs的酸度也是评价酸性DESs溶解木质素性能的有效指标。通常具有适中pK_a值的HBDs能够用于构建具有高效的木质素溶解性能的DESs。DESs的粘度对木质素溶解也有一定影响,较低的粘度有助于木质素溶解。     

木质素接枝偶氮苯液晶聚合物的合成与表征及光响应性能研究

以天然高分子木质素为原料,通过亲核取代反应将木质素改性成为大分子引发剂,引发偶氮苯单体的原子转移自由基聚合(ATRP),得到一系列木质素基光响应聚合物.接枝后的木质素的热稳定性明显改善,且平均接枝率达到72.8%时才能表现出液晶行为.小角X射线散射和偏光显微镜的结果表明所形成的液晶相为近晶C型,层间距为3.21nm.在此基础上,用紫外-可见吸收光谱(UV-Vis)对木质素基液晶聚合物的光响应性进行研究,发现溶液中的光响应性比膜状态的光响应速率快.在紫外光的辐照下,木质素基液晶聚合物表现出快速的光致液晶-各向同性相变行为.     

木质素基环氧丙烯酸酯的合成及紫外光固化

正木质素是地球上一种储量十分丰富的可再生资源,可生物降解[1,2].木质素结构中含有大量羟基,主要以酚羟基和醇羟基形式存在,可与许多化合物发生化学反应制得木质素基环保材料,是最有前途的生物质资源之一[3].但工业木质素纯度较低,对其利用多为直接混合,如水泥减水剂等低端领域.环氧丙烯酸酯(EA)作为紫外光固化的预聚体,在紫外光照射下可快速固化,其黏接性高,耐化学药品性能优异,应用广泛[4,5].因此降低EA的成本,对其进行改性是近年来该领域的研究热点[6].本文以工     

Ultra‐high performance supercritical fluid chromatography of lignin‐derived phenols from alkaline cupric oxide oxidation

Traditional chromatographic methods for the analysis of lignin‐derived phenolic compounds in environmental samples are generally time consuming. In this work, an ultra‐high performance supercritical fluid chromatography method with a diode array detector for the analysis of major lignin‐derived phenolic compounds produced by alkaline cupric oxide oxidation was developed. In an analysis of a collection of 11 representative monomeric lignin phenolic compounds, all compounds were clearly separated within 6 min with excellent peak shapes, with a limit of detection of 0.5–2.5 μM, a limit of quantification of 2.5–5.0 μM, and a dynamic range of 5.0–2.0 mM (R² > 0.997). The new ultra‐high performance supercritical fluid chromatography method was also applied for the qualitative and quantitative analysis of lignin‐derived phenolic compounds obtained upon alkaline cupric oxide oxidation of a commercial humic acid. Ten out of the previous eleven model compounds could be quantified in the oxidized humic acid sample. The high separation power and short analysis time obtained demonstrate for the first time that supercritical fluid chromatography is a fast and reliable technique for the analysis of lignin‐derived phenols in complex environmental samples.     

Pretreatment processes for lignocellulosic biomass conversion to biofuels and bioproducts

Lignocellulosic materials, such as forestry, agricultural and agroindustrial residues, are among the most important sources of biomass for the production of fuels, chemicals and materials. However there are physical and chemical barriers in the lignin–carbohydrate supramolecular structure that render most plant cell wall components almost completely unavailable for conversion into commercial products. Thus successful conversion strategies must lead to the disruption of this structure and result in partial or total separation of the lignocellulosic components, increasing the accessibility of cellulose, hemicelluloses and lignins. It must also minimize the formation of by-products. Each pretreatment technology has its own characteristics and is usually applied to a specific source of carbohydrates and lignins. A general overview of the most important pretreatment methods for the production of platform chemicals and fermentable sugars are given in this paper.     

Flame-retardant effect of a functional DOPO-based compound on lignin-based epoxy resins

A simple and environmentally benign synthetic route to lignin-based epoxy resins is highly desirable. Alkali lignin and glyoxal are promising renewable and sustainable alternatives to phenol and formaldehyde, respectively. Their use is demonstrated to produce lignin-phenol-glyoxal novolac epoxy resins (LPG-NERs) through a simple one-pot synthesis. Flame retardancy of LPG-NERs was improved by functionalization with a N, S modified 9, 10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO) material (termed DBS) obtained via nucleophilic reaction between DOPO and a N, S containing intermediate. FTIR and ¹H NMR analyses confirmed the successful fabrication of LPG-NERs and SBD. The introduction of lignin and SBD reduced crosslinking of the epoxy network, weakening mechanical properties, but conferred excellent flame retardancy (including vapor and condensed phases) as determined by LOI (34.5%), UL-94 (V-0 rating), and cone calorimetry tests (lower heat release and smoke production, and higher char formation). The SBD structure imparted a desirable vapor mechanism (blowing out phenomenon caused by the fire quenching effect of PO?/PO₂? radicals and dilution effect from non-condensable gases such as NH₃, N₂, SO₂), while lignin (a natural biochar precursor) in synergy with SBD imparted superior charring performance.     

Selective Utilization of the Methoxy Group in Lignin to Produce Acetic Acid

Selective transformation of lignin into a valuable chemical is of great importance and challenge owing to its complex structure. Herein, we propose a strategy for the transformation of methoxy group (‐OCH₃) which is abundant in lignin into pure highly valuable chemicals. As an example to apply this strategy, a route to produce acetic acid with high selectivity by conversion of methoxy group of lignin was developed. It was demonstrated that the methoxy group in lignin could react with CO and water to generate acetic acid over RhCl₃ in the presence of a promoter. The conversions of methoxy group in the kraft lignin and organosolv lignin reached 87.5 % and 80.4 %, respectively, and no by‐product was generated. This work opens the way to produce pure chemicals using lignin as the feedstock.