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91.
Cathryn G. Conner Anka N. Veleva Vesselin N. Paunov Simeon D. Stoyanov Orlin D. Velev 《Particle & Particle Systems Characterization》2020,37(7):2000122
A highly controllable and scalable process for fabrication of large amounts of concentrated lignin nanoparticles (LNPs) is reported. These lignin core nanoparticles are formed through flash nanoprecipitation, however, scaling up of the fabrication process requires fundamental understanding of their operational formation mechanism and surface properties. It is shown how a semicontinuous synthesis system with a recirculation loop makes it possible to produce flash precipitated lignin nanoparticles in large amounts for practical applications. The roles of the process parameters, including flow rates and lignin concentration, are investigated and analyzed. The results indicate that the LNPs are formed by a process of continuous burst nucleation at the point of mixing without diffusive growth, which yields nanoparticles of highly uniform size following a modified LaMer nucleation and growth mechanism. This mechanism makes possible facile process control and scale-up. Effective control of the resulting nanoparticle size is achieved through the initial concentration of lignin in the injected solution. The impressive capability to produce suspensions of any predesigned multimodal distribution is demonstrated. The resulting nanofabrication technique can produce large volumes of concentrated LNP suspensions of high stability and tightly controlled size distributions for biological or agricultural applications. 相似文献
92.
Tibo De Saegher Dr. Jeroen Lauwaert Prof. Joeri Vercammen Prof. Kevin M. Van Geem Prof. Jeriffa De Clercq Prof. An Verberckmoes 《ChemistryOpen》2021,10(8):740-747
Lignin valorization and particularly its depolymerization into bio-aromatics, has emerged as an important research topic within green chemistry. However, screening of catalysts and reaction conditions within this field is strongly constrained by the lack of analytical techniques that allow for fast and detailed mapping of the product pools. This analytical gap results from the inherent product pool complexity and the focus of the state-of-the-art on monomers and dimers, overlooking the larger oligomers. In this work, this gap is bridged through the development of a quasi-orthogonal GPC-HPLC-UV/VIS method that is able to separate the bio-aromatics according to molecular weight (hydrodynamic volume) and polarity. The method is evaluated using model compounds and real lignin depolymerization samples. The resulting color plots provide a powerful graphical tool to rapidly assess differences in reaction selectivity towards monomers and dimers as well as to identify differences in the oligomers. 相似文献
93.
研究了在超临界乙醇中、氢气存在下,一系列金属-酸双功能催化剂的酸性、孔径大小、负载的金属对热解木质素加氢裂解过程的影响.制备并采用N2等温吸附和BET比表面、X射线衍射、NH3-程序升温脱附技术对催化剂进行表征.实验结果表明催化剂酸性增强可促进热解木质素的缩聚反应,从而产生大量的焦炭和水,导致其液化效率降低.微孔催化剂比介孔催化剂孔径小,与强酸共同作用会导致热解木质素裂解生成更多的小分子气体.在催化剂上负载金属Ru可有效地抑制热解木质素的缩聚反应,促进其裂解液化. 相似文献
94.
95.
分别制备了不同磺酸基含量的磺化碱木质素(SAL)、不同交联度和分子量的磺化碱木质素聚氧乙烯醚(SAL-PEG),采用动态光散射(DLS)法分别研究磺酸基含量和PEG非离子长链对SAL和SAL-PEG溶液行为的影响规律.结果表明,不同磺酸基含量(1.28~2.09 mmol/g)的SAL在1.0 g/L的水溶液中存在聚集行为,磺酸基含量的增加使SAL的分子舒展程度增加,聚集程度越弱;Na Cl的加入使SAL的分子舒展程度减小,聚集体发生解聚.不同PEG含量的SAL-PEG在1.0 g/L的水溶液中主要以单分子状态存在,聚集行为较弱,分子的流体动力学半径与其分子量和交联度成正比;Na Cl的加入使SAL-PEG的PEG非离子长链却被严重压缩,分子流体动力学半径显著减小,减小程度与其分子量和交联度成正比,但SAL-PEG的聚集程度仍然较弱. 相似文献
96.
Partially bio‐based poly(amide imide)s by polycondensation of aromatic diacylhydrazides based on lignin‐derived phenolic acids and aromatic dianhydrides: Synthesis,characterization, and computational studies 下载免费PDF全文
Sachin S. Kuhire Pragati Sharma Suman Chakrabarty Prakash P. Wadgaonkar 《Journal of polymer science. Part A, Polymer chemistry》2017,55(21):3636-3645
Two new bio‐based diacylhydrazide monomers, namely, 4,4′‐(propane‐1,3‐diylbis(oxy))bis(3‐methoxybenzohydrazide) and 4,4′‐(propane‐1,3‐diylbis(oxy))bis(3,5‐dimethoxybenzohydrazide) were synthesized starting from lignin‐derived phenolic acids, namely, vanillic acid and syringic acid. A series of poly(amide imide)s was synthesized by polycondensation of these diacylhydrazide monomers with commercially available aromatic dianhydrides. Poly(amide imide)s showed inherent viscosity in the range 0.44–0.56 dL g?1 and exhibited good solubility in organic solvents. Poly(amide imide)s could be cast into transparent, flexible, and tough films from their N ,N‐dimethylacetamide solutions. Poly(amide imide)s showed 10% weight loss in the temperature range 340–364 °C indicating their good thermal stability. Glass transition temperature (T g) of poly(amide imides)s were measured by DSC and DMA which were in the range 201–223 °C and 214–248 °C, respectively. The T g values of poly(amide imide)s were dependent on the number methoxy substituents on aromatic rings of diacylhydrazide monomers. Molecular dynamics simulation studies revealed that chain rigidity is the dominant factor for observed trends in T g. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55 , 3636–3645 相似文献
97.
Peracetic Acid Depolymerization of Biorefinery Lignin for Production of Selective Monomeric Phenolic Compounds 下载免费PDF全文
Ruoshui Ma Mond Guo Kuan‐ting Lin Prof. Dr. Vincent R. Hebert Prof. Dr. Jinwen Zhang Prof. Dr. Michael P. Wolcott Melissa Quintero Dr. Karthikeyan K. Ramasamy Dr. Xiaowen Chen Prof. Dr. Xiao Zhang 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(31):10884-10891
Lignin is the largest source of renewable material with an aromatic skeleton. However, due to the recalcitrant and heterogeneous nature of the lignin polymer, it has been a challenge to effectively depolymerize lignin and produce high‐value chemicals with high selectivity. In this study, a highly efficient lignin‐to‐monomeric phenolic compounds (MPC) conversion method based on peracetic acid (PAA) treatment was reported. PAA treatment of two biorefinery lignin samples, diluted acid pretreated corn stover lignin (DACSL) and steam exploded spruce lignin (SESPL), led to complete solubilization and production of selective hydroxylated monomeric phenolic compounds (MPC‐H) and monomeric phenolic acid compounds (MPC‐A) including 4‐hydroxy‐2‐methoxyphenol, p‐hydroxybenzoic acid, vanillic acid, syringic acid, and 3,4‐dihydroxybenzoic acid. The maximized MPC yields obtained were 18 and 22 % based on the initial weight of the lignin in SESPL and DACSL, respectively. However, we found that the addition of niobium pentoxide catalyst to PAA treatment of lignin can significantly improve the MPC yields up to 47 %. The key reaction steps and main mechanisms involved in this new lignin‐to‐MPC valorization pathway were investigated and elucidated. 相似文献
98.
GUO Xiu-juan WANG Shu-rong WANG Kai-ge LUO Zhong-yang State Key Laboratory of Clean Energy Utilization Zhejiang University Hangzhou P. R. China 《高等学校化学研究》2011,(3):426-430
The structure of milled wood lignin(MWL), isolated via the Bjrkman procedure, was studied by means of 1H NMR spectroscopy and Fourier transform infrared spectroscopy, and then its pyrolytic product distribution was investigated on a pyrolysis device. MWL obtained from Manchurian Ash(MA) contained more methoxyl and free phenolic hydroxyl groups per C9 unit than MWL from Mongolian Pine(MP) due to the existence of both guaiacyl and syringyl units, which have a major influence on the pyrolysis behavior of lign... 相似文献
99.
采用溶胶-凝胶法合成了一系列镨掺杂的铁酸钙氧化物(Ca1-xPrxFeO3, 简称CPF-x), 优化了其焙烧机制, 研究了其对甘蔗渣木质素(BL)的催化热解作用, 考察了其再生性能. 研究结果表明, CPF-x适宜的合成及焙烧参数分别为: x=0.5, 焙烧温度为800 ℃, 焙烧时间为6 h, 在该条件下得到的CPF-0.5-800-6呈立方晶相, 为疏松多孔结构; 掺杂Pr后, 其比表面积提高了近3倍. CPF-0.5-800-6对BL催化热解最佳工艺参数为: m(CPF-0.5-800-6)∶m(BL)=1∶3, 热解温度为650 ℃, 液相收率最大可达20.73%, 其中主要产物为紫丁香酚类、 苯酚类及愈创木酚类, 其总选择性为63.21%. 以CPF-0.5-800-6为催化剂, 紫丁香酚类化合物选择性由20.60%增大到29.59%, 实现了提高BL催化热解中某种单酚化合物的选择性. CPF-0.5-800-6经5次催化热解-再生循环反应后, 仍具有良好的反应活性和结构稳定性. 相似文献
100.