Pyrolytic alkylation-gas chromatography-mass spectrometry of model polymers Further insights into the mechanism and scope of the technique

The mechanism of the high-temperature hydrolysis and alkylation with tetraalkylammonium hydroxides of bio- and geopolymers has been approached mainly by studying the behaviour of single standard compounds. In the present work, we have applied this technique to three polymers of known structure, i.e. suberin, polycitraconic acid (PCA) and a lignin dehydrogenase polymer (DHP), related respectively to natural polyesters, fulvic acids and lignins, in order to get new insight into the reaction mechanisms. As further application of the technique, the case study of the lignin signature during the coalification process has been analyzed by pyrolysis-butylation of humic acids extracted from two peat and lignite samples.     

Evidence of char formation during wood heat treatment by mild pyrolysis

The behaviour of wood polymers during heat treatment carried out under inert atmosphere at 240 °C has been reinvestigated to understand the important decrease of the O/C ratio observed in a previous study using X-ray photoelectron spectroscopy (XPS). Heat treatment was performed not only on beech sawdust but also on its lignin and holocellulose fractions obtained after acidic hydrolysis of polysaccharides or delignification with sodium chlorite. CP/MAS ¹³C NMR spectra indicate as previously reported an important degradation of hemicelluloses after thermal treatment. However, assignments of the signals appearing in the range of 125-135 ppm and 35 ppm attributed up to now to thermal crosslinking of lignin and formation of methylene bridges should be reconsidered. Indeed, heat treatment of the holocellulose fraction indicates quite similar signals showing that these latter are not due to lignin modification. According to the literature, these new signals have been attributed to the beginning of char formation. Determination of Klason lignin and HPLC analysis of the sugars contained in the hydrolysate support the hypothesis of formation of carbonaceous materials within the wood structure during heat treatment by mild pyrolysis.     

硅铝催化剂催化有机溶剂木质素的解聚

E cient conversion of lignin to fine chemicals and biofuel become more and more attractive in biorefinery. In this work, we used a series of silica-alumina catalysts (i.e., SiO₂-Al₂O₃, HY, Hβ, and HZSM-5) to degrade lignin into arenes and phenols. The relationship between the catalyst structure and lignin depolymerization performance was investigated. The results showed that both acidity and pore size of the catalyst could in uence the conversion of lignin. In the volatilizable product, phenols were identified as the main phenolic monomers via gas chromatography-mass spectrometer. SiO₂-Al₂O₃ was the most effcient catalyst, giving 90.96% degree of conversion, 12.91% yield of phenols, and 2.41% yield of arenes in ethanol at 280℃ for 4 h. The Fourier transform infrared spectroscopy and ¹H nuclear magnetic resonance spectroscopy analysis demonstrated that deoxygenation and alkylation occurred in this process. The effect of solvents was also investigated and the results showed that ethanol was the most effcient solvent.     

Sisal chemically modified with lignins: Correlation between fibers and phenolic composites properties

Sisal fibers have been chemically modified by reaction with lignins, extracted from sugarcane bagasse and Pinus-type wood and then hydroxymethylated, to increase adhesion in resol-type phenolic thermoset matrices. Inverse gas chromatography (IGC) results showed that acidic sites predominate for unmodified/modified sisal fibers and for phenolic thermoset, indicating that the phenolic matrix has properties that favor the interaction with sisal fibers. The IGC results also showed that the phenolic thermoset has a dispersive component closer to those of the modified fibers suggesting that thermoset interactions with the less polar modified fibers are favored. Surface SEM images of the modified fibers showed that the fiber bundle deaggregation increased after the treatment, making the interfibrillar structure less dense in comparison with that of unmodified fibers, which increased the contact area and encouraged microbial biodegradation in simulated soil. Water diffusion was observed to be faster for composites reinforced with modified fibers, since the phenolic resin penetrated better into modified fibers, thereby blocking water passage through their channels. Overall, composites' properties showed that modified fibers promote a significant reduction in the hydrophilic character, and consequently of the reinforced composite without a major effect on impact strength and with increased storage modulus.     

Lignin-Phenylhydrazone as a Corrosion Inhibitor of API X52 Carbon Steel in 3.5% NaCl and 0.1 mol/L HCl Medium

The best alternative to fight against corrosion is the use of an inhibitor, the purpose of this work is the formulation of a new biomass-based molecule against corrosion of carbon steel. Lignin was extracted using the Kraft process and phenylhydrazine molecules have been scratched. The influence of the lignin-phenylhydrazone(LP) on the corrosion of carbon steel in salt and the acidic medium was studied by the polarization resistance, the potentiodynamic polarization, and the electrochemical impedance spectroscopy. The results of these tests reveal that the behavior of the inhi-bitor is a mixed type. The adsorption mechanism of the inhibitor follows the Langmuir isothermal model. Gibbs energy shows that the process of inhibition of carbon steel is spontaneous. The SEM confirms that the inhibitor reduces the corrosion of the steel and stops the corrosion pitting phenomenon. The modified lignin shown as a good corrosion inhibitor in acid medium is highly saline with an efficiency> 96%.     

Synergism of sweeping frequency ultrasound and deep eutectic solvents pretreatment for fractionation of sugarcane bagasse and enhancing enzymatic hydrolysis

Sugarcane bagasse (SCB) is an abundant agricultural waste in China and the conversion of the waste into plethora of useful resources is very vital. To achieve this, fractionation of the waste is highly important in the biomass biorefinery. The present study aims at investigating the synergistic role of deep eutectic solvents (DES) with sweeping frequency ultrasound (SFUS) and fixed frequency ultrasound (FFUS) in the fractionation of SCB to enhance the enzymatic saccharification process. Therefore, the effects of ultrasound (US) and DES conditions on the pretreatment efficiency were investigated. Under optimum SCB pretreatment conditions, FFUS (40 kHz, 60 min) + DES (choline chloride (ChCl)-lactic acid (LA), 120 °C, 3 h) and SFUS (40 kHz, 60 min) + DES (ChCl-LA, 120 °C, 3 h), the lignin removal rates were 80.13 and 85.62%, respectively. The hemicellulose removal rates were 78.08 and 90.46%, respectively; and the contents of glucose, xylose and arabinose in the liquid fractions after FFUS + DES pretreatment were 7.07, 17.95 and 3.01%, respectively. However, the yield of glucose, xylose, and cellobiose after enzymatic hydrolysis of the SFUS + DES pretreated SCB were 86.76, 38.68, and 20.76%. Analytical studies revealed that the SFUS + DES pretreatment can effectively destroy the ultrastructure of SCB and reduce the crystallinity of cellulose. Furthermore, the mechanism of pretreatment with SFUS + DES was proposed, which confirmed the excellent performance of SFUS + DES. Thus, the application of SFUS + DES pretreatment was able to improve the removal of lignin and hemicellulose from SCBs.     

木质素活化改性制备酚醛树脂胶黏剂研究进展

木质素由于化学结构与苯酚相似,通过活化改性可部分替代苯酚制备木质素改性酚醛树脂胶黏剂。既可降低成本、达到生物质资源高效利用的目的,并且制备的木质素改性酚醛树脂胶黏剂有毒残余较低,具有环保意义,是合成制备生物质高分子材料的重要途径。本文综述了国内外研究人员在木质素活化改性制备酚醛树脂胶黏剂研究领域的最新进展,重点介绍了化学改性、物理改性、生物改性等木质素活化改性方法,比较了不同改性产物制备酚醛树脂胶黏剂的性能,并对影响木质素活化改性制备酚醛树脂胶黏剂实现工业化应用的主要因素进行了分析。     

Formation and characterization of mechanochemically generated free lignin radicals from olive seeds

In this study, formation and quantification of mechanochemically generated free radicals of lignin were evaluated after the extraction of lignin from olive seeds and detailed lignin characterization was performed. Lignin was extracted from crushed olive seeds as an insoluble solid using Klason method. Isolated lignin was mechanochemically grinded under cryo conditions using Cryomill and particlesizes were determined by using Zeta Sizer, structural changes were followed by XRD and FTIR-ATR; thermal stabilities were tracked by TGA and DSC. In order to enable solubility demanding studies (such as ¹H‑NMR and GPC), acylation of lignin was accomplished. ESR measurements were completed to prove the nature of the radicals. Free radicals cavenging activity of olive seed lignin was determined and quantified using 2-diphenyl-1-picrylhydrazyl (DPPH) method. Number of created mechanoradicals (per gram of olive seed lignin) was calculated from the corresponding UV‑Vis spectra. Finally, morphological changes of the lignin over cryomilling was evaluated using SEM.     

木质素增强丁苯橡胶复合材料研究

采用木材水解木质素为原料,均匀溶解在碱性溶液中,与天然橡胶复合形成互穿网络结构,再通过共沉淀法制得一种木质素/天然橡胶复合物。采用该复合物部分代替商用橡胶补强剂——白炭黑,通过三段混炼法对丁苯橡胶进行混炼。结果表明,这种木质素/天然橡胶复合物对丁苯橡胶具有一定的补强作用,其拉伸强度及断裂伸长率均得到一定改善;而热机械性能研究发现,该复合物部分代替白炭黑后,橡胶材料的滚动阻力及耐寒性均得到改善,但抗湿滑性能有一定程度下降。