共查询到20条相似文献,搜索用时 15 毫秒
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Carina A. Esteves Costa Carlos A. Vega-Aguilar Alírio E. Rodrigues 《Molecules (Basel, Switzerland)》2021,26(15)
Lignin is the second most abundant component, next to cellulose, in lignocellulosic biomass. Large amounts of this polymer are produced annually in the pulp and paper industries as a coproduct from the cooking process—most of it burned as fuel for energy. Strategies regarding lignin valorization have attracted significant attention over the recent decades due to lignin’s aromatic structure. Oxidative depolymerization allows converting lignin into added-value compounds, as phenolic monomers and/or dicarboxylic acids, which could be an excellent alternative to aromatic petrochemicals. However, the major challenge is to enhance the reactivity and selectivity of the lignin structure towards depolymerization and prevent condensation reactions. This review includes a comprehensive overview of the main contributions of lignin valorization through oxidative depolymerization to produce added-value compounds (vanillin and syringaldehyde) that have been developed over the recent decades in the LSRE group. An evaluation of the valuable products obtained from oxidation in an alkaline medium with oxygen of lignins and liquors from different sources and delignification processes is also provided. A review of C4 dicarboxylic acids obtained from lignin oxidation is also included, emphasizing catalytic conversion by O2 or H2O2 oxidation. 相似文献
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- 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. 相似文献
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V.E. Tarabanko Yu.V. Hendogina D.V. Petuhov E.P. Pervishina 《Reaction Kinetics and Catalysis Letters》2000,69(2):361-368
Kinetics and selectivity of the retroaldol reaction of vanillideneacetone in the alkaline media were studied. The reaction is of first order with respect to substrate and alkali concentration. The pH dependencies of the rates of vanillin formation in the processes of lignosulfonates and vanillideneacetone oxidation agree almost quantitatively. This indicates that the retroaldol reaction plays an important role in the alkaline oxidative destruction of lignins. 相似文献
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V. E. Taraban'ko N. V. Koropatchinskaya A. V. Kudryashev B. N. Kuznetsov 《Russian Chemical Bulletin》1995,44(2):367-371
The oxidation of a number of lignin species by molecular oxygen was studied. The selectivity of the process was found to be close to that of the oxidation with nitrobenzene. The influence of lignin origin on the yields of vanillin and syringaldehyde as well as the correlation between the rates of wood delignification and the aldehydes formation are discussed.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 2, pp. 375–379, February, 1995. 相似文献
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WANG Dong SU Lian-jiang CHENG Xiu-li SUN Er-jun SHI Tong-shun. College of Chemistry Jilin University Changchun P. R. China . Department of Chemistry Daqing Teachers College Daqing P. R. China 《高等学校化学研究》2007,23(2):135-137
IntroductionPorphyrins are important substances which are es-sential for sustaining life, and extensively existin vivo,possess the key structure of important substances, suchas chlorophyll, hemachrome, vitamin B12, hemoglo-bin,etc. They are widely used in… 相似文献
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《Analytical letters》2012,45(17):2635-2656
Chitosan is one of the most abundant natural polysaccharide in nature. Due to its unique properties, chitosan has fascinated the scientific community since its discovery. When modified with other materials and combined with magnetic particles, the resulting composite material, a magnetic chitosan derivative, is provided with three significant characteristics. First, chitosan has excellent properties for preconcentration/extraction, such as adsorption and chelating effects, low cost, and nontoxicity. Second, new functional groups have enhanced the properties of chitosan that include water solubility, stability, recyclability, and enhanced adsorption capacity. Finally, due to the efficient and fast adsorption processes, as well as simple and convenient magnetic separation, the magnetic adsorbents greatly reduce the time of sample handling. In this article, recent synthesis and modification methods of magnetic chitosan derivatives are reviewed along with some applications in analytical separations. 相似文献
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Shuyan Chen Shicheng Shen Xiang Yan Jie Mi Gehua Wang 《Journal of Dispersion Science and Technology》2016,37(11):1574-1580
With the cheap and abundant resource of alkali lignin as feedstock, surfactants for enhanced oil recovery were synthesized by amination and alkylation reaction of lignosulfonate. The effects of amination conditions, including the ratio of raw materials, amination reagent, temperature, and reaction time, on nitrogen contents and surface tension of the surfactants were investigated. The results showed that ethylenediamine was more suitable for amination, and the molar ratio of alkali lignin, ethylenediamine, and formaldehyde was 1:2:1.5 at 80°C for 5 hours. The structure of synthesized products was characterized by Fourier transform infrared spectrometry. The HLB value of synthesized product was 10. The interfacial tension between Daqing crude oil and synthetic water could be decreased to 10?2 mN/m with synthesized surfactant and NaOH at 45°C. Moreover, the effects of molecular weight of surfactants on interfacial tension were also studied. The synthesized surfactant (Mw > 10,000) showed a better interfacial activity on Daqing crude oil. 相似文献
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电控离子膜(Electrically Switched Ion Membrane, ESIM)分离是近年来发展起来的一种新型离子选择性高效分离技术,已被用于多种金属阳离子及阴离子的选择性分离与回收。电控膜分离源于电控离子交换(Electrically Switched Ion Exchange, ESIX)技术,其高效运行依赖于具有离子交换功能的电活性材料(Electroactive Ion Exchange Material, EIXM)。EIXM既能传递电子又能传递离子,通过调节其氧化/还原电位可以控制离子的可逆置入/释放,同时实现目标离子的高效分离和EIXM的再生,因而不产生二次污染。本文从EIXM简介、结构设计与可控合成、各种电控离子选择性分离机制的研究进展以及新型ESIX-ESIM膜组件开发和应用几个方面,分析总结了从最初的ESIX技术到基于ESIX原理的电控离子选择渗透膜(Electrically Switched Ion Permselective Membrane, ESIPM)分离的发展历程。展望未来ESIM分离技术,应针对目标离子的选择性分离要求,设计合成新型结构ESIM材料和研发相关膜组件系统,可望最终实现ESIM技术的工业应用。 相似文献
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采用碱提法从生态入侵植物水葫芦中提取木质素,利用傅立叶红外光谱(FT-IR)和扫描电镜(SEM)等手段对所获得的木质素进行表征,研究了水葫芦木质素对水中苯胺的吸附性能,考察了溶液p H值、吸附时间、初始浓度等因素对水葫芦木质素吸附苯胺的影响。当Na OH溶液浓度0.1 mol/L,提取时间4 h,温度100℃,料液比1∶20时,水葫芦木质素的收率最大为6.81%。红外图谱显示,在1 456~1 656 cm-1处存在木质素的芳香环骨架振动吸收峰;扫描电镜显示,木质素呈大量细小的颗粒,木质素颗粒表面存在许多微小的孔状结构,有利于吸附作用的发生。在室温下,溶液p H 6.0,苯胺初始浓度为150 mg/L,吸附剂用量为5 mg,吸附时间120 min时,水葫芦木质素对苯胺的最大吸附容量为12.2 mg/g。苯胺吸附实验数据拟合符合准二级动力学模型以及Langmuir吸附等温模型。水葫芦木质素对苯胺的吸附以单分子层化学吸附为主,属于优惠吸附。相同吸附条件下,水葫芦木质素对湖泊水样中苯胺的吸附与实验模拟水样的吸附效果相近。水葫芦木质素可作为富集分离材料用于分析样品制备以及水中污染物的吸附。 相似文献
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G. N. Dalimova 《Chemistry of Natural Compounds》2005,41(1):85-87
The functional composition and structural porosity of hydrolyzed lignin from cotton-seed husks was altered by oxidation with hydrogen peroxide.__________Translated from Khimiya Prirodnykh Soedinenii, No. 1, pp. 69–70, January–February, 2005. 相似文献
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Cecilia Sáenz Barrio Elena Romero Melgosa Jesús Sanz Asensio Javier Galbán Bernal 《Mikrochimica acta》1996,122(3-4):267-277
Three different extraction procedures for eight pesticides (chlorfenvinphos, diazinon, ethyl parathion, ethiofencarb, fenitrothion, malathion, metalaxyl, pirimicarb) in water samples are compared. The extraction procedures are: liquid-liquid extraction (LLE), solid-phase extraction (SPE) and microextraction (ME). For each procedure the most suitable conditions were obtained experimentally, with special remarks on ME, in which the effects of different mixtures of Kaltron with other solvents were tested. A preconcentration factor (PF) was used to rank the methods; the best results were observed for ME, (PF 15–45, whereas PF < 10 for SPE, and PF 13 for LLE). In all cases, the determination was performed by gas chromatography, using a nitrogen phosphorus detector and the internal standard method (methyl parathion) as the quantification procedure. 相似文献
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Radial Basis Function Neural Networks-Based Modeling of the Membrane Separation Process: Hydrogen Recovery from Refinery Gases 总被引:1,自引:0,他引:1 下载免费PDF全文
Lei Wang Cheng Shao Hai Wang Hong Wu 《天然气化学杂志》2006,15(3):230-234
Membrane technology has found wide applications in the petrochemical industry, mainly in the purification and recovery of the hydrogen resources. Accurate prediction of the membrane separation performance plays an important role in carrying out advanced process control (APC). For the first time, a soft-sensor model for the membrane separation process has been established based on the radial basis function (RBF) neural networks. The main performance parameters, i.e, permeate hydrogen concentration, permeate gas flux, and residue hydrogen concentration, are estimated quantitatively by measuring the operating temperature, feed-side pressure, permeate-side pressure, residue-side pressure, feed-gas flux, and feed-hydrogen concentration excluding flow structure, membrane parameters, and other compositions. The predicted results can gain the desired effects. The effectiveness of this novel approach lays a foundation for integrating control technology and optimizing the operation of the gas membrane separation process. 相似文献
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在木质纤维素制取乙醇过程中,合理高效地分离出木质素并加以利用,可以提升纤维乙醇整体工艺的经济性。 以杨木粉为原料,从木质素产率和改性程度的角度出发,分析对比了3种预处理方法所提取的木质素。 结果表明,磷酸丙酮法所得木质素产率达到15%~25%,碱法蒸煮法和有机溶剂所得木质素仅占到9.58%和13.47%。 红外吸收光谱结果表明,磷酸丙酮木质素在1608、1507和1463 cm-1等处具有相对最强的吸收信号,在1650 cm-1处也有共轭羰基吸收峰,因此磷酸丙酮木质素的改性程度相对较小,核磁共振氢谱表征也同时验证了这一结果,这种木质素适于进一步的开发利用。 低压常温下的磷酸丙酮预处理方法可以有效提升纤维乙醇工艺的经济性。 相似文献
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油菜籽中主要硫甙的分离提纯 总被引:6,自引:0,他引:6
用柱色谱方法从甘蓝型油菜籽中分离提纯了1-硫[(1Z)-3-羟基-1-[(磺酸基)亚氨基]-4-戊烯基]-1-硫代-β-D-葡萄糖钾盐(progoitrin)。用甲醇溶液提取菜籽中的硫甙,得到粗提物;粗提物经酸性氧化铝色谱柱与反相C18硅胶柱进一步分离提纯,得到纯品。对纯品进行紫外光谱、红外光谱、核磁共振氢谱、质谱和元素分析,测得的数据与文献值相符。用高效液相色谱测得硫甙提取物的纯度为99%。该方法操作简便,得到的硫甙样品纯度高,是一种有价值的硫甙提取方法,具有良好的应用前景。 相似文献
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解读纳滤:一种具有纳米尺度效应的分子分离操作 总被引:1,自引:0,他引:1
纳滤膜是20世纪80年代末期发展起来的一种广泛用于液体分离的新型分离膜。早期研究中,先后提出的基于筛分效应的细孔模型,基于静电效应的电荷模型,以及同时考虑上述两种效应的静电位阻模型和道南位阻模型等为人们更好地理解纳滤膜分离机理和指导纳滤膜过程应用发挥了十分重要的作用。然而由于这些具有“疏松型反渗透膜”特点的纳滤膜没有相应的膜性能预测评价软件,使得针对具体应用过程的纳滤膜的大规模标准化应用受到了一定的制约。为此,结合上述模型,根据一些特定实验拟合确定混合盐体系同号离子间的竞争作用和异号离子间的调节作用,提出了一个适于混合盐体系的纳滤膜分离性能评价模型,促进了纳滤膜技术在水处理过程的大规模推广。最近,根据纳滤膜对离子选择性分离性能及其伴随的动电性质的细致而深入的实验研究,发现仅考虑筛分效应和静电效应并不能完全合理地解释纳滤膜的分离性能,且在动电性质的解析上也存在一定缺陷,进而对纳滤膜纳米级孔径引起的特殊效应和溶液体系中复杂相互作用引起的荷电性质变化有了更为深刻的认识和理解,提出并定量分析了离子透过纳滤膜时存在的介电排斥效应。 相似文献
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An influential subject of research is the use of lignin for effective removal of hazardous dyes from wastewater effluents utilizing green techniques. Lignin makes up to 10–25% of lignocellulosic biomass. In this study, a solvent evaporation approach was employed to construct a novel chitosan lignin membrane, which was then used to remove the methylene blue (MB) dye from water. The physicochemical, thermal, and morphological attributes were characterized by SEM, XRD, FTIR ATR, and TGA DSC. With higher lignin content in the membrane, its tensile strength was reduced. The dye was removed 95% of the time by the membrane, and the adsorption followed the Langmuir isotherm. The membranes could be recycled up to five times. 相似文献