Chemical Groups and Structural Characterization of Lignin via Thiol-Mediated Demethylation

A new approach to increase the reactivity of lignin by thiol-mediated demethylation was investigated in this study. Demethylated lignin was characterized by the changes in its hydroxyl and methoxyl groups, molecular weight, and other properties using titration and spectroscopy methods including FT-IR, ¹H NMR, UV, and GPC. The total, phenolic, and aliphatic hydroxyl contents in lignin increased while the methoxyl content decreased after demethylation reaction, which indicated the occurrence of demethylation reaction. The results from FT-IR and UV analysis also indicated that the kraft lignin in this study contains mainly guaiacyl moiety and demethylated lignin has a higher guaiacyl content than original lignin. The average molecular weight of lignin decreased after demethylation reaction due to the cleavage of ether linkages in lignin macromolecules. No severe degradation of lignin was observed during the demethylation reaction.     

玉米秸秆木质素的去甲基化/羟乙基化复合改性研究

利用亚硫酸钠和乙二醛对玉米秸秆木质素进行去甲基化/羟乙基化复合改性,以提高木质素的羟基含量和反应活性。通过FT-IR、TG、DSC以及乙酰化滴定等技术研究了木质素复合改性效果。结果表明:经过去甲基化/羟乙基化复合改性后的玉米秸秆木质素具有优异的活性,其总羟基质量分数较原料木质素提升了88.33%,酚羟基提升了14.70%,反应活性得到明显增强。FT-IR表征发现:复合改性从多方面提升了木质素的羟基含量,对羟基含量的增加有着较为显著的效果。热重和DSC表征发现:复合改性木质素(G-DL)相较于原料木质素降解得更加彻底,其放热峰出现在77℃,放热量达459.82 J/g,反应活性较去甲基化木质素(DL)和原料木质素更高。     

Nitration anodique

Anodic oxidation of aromatic hydrocarbons and olefins in acetonitrile containing silver nitrite, has been studied.With aromatic hydrocarbons the better yields in mononitro compounds were obtained with anthracene and methoxybenzene. The orientation is discussed: the site of substitution is the unsubstituted position with most important spin density in the radical cation (from substrate oxidation).Diphenyl ethylene and paramethoxystyrene yields nitroolefins; the 2-phenylpropene produce a mixture of nitroolefin and nitro alcohol. Trans stilbene gave a mixture of 1,2 addition products containing the nitrato group. In order to explain the formation of the products we proposed a mechanism consistent with the ambidentate character of the nitrite ion.     

芳基甲基醚去甲基化反应

文章综述了芳基甲基醚去甲基化反应所采用的试剂和反应条件。对该类反应的研究现状作出总结,离子液体催化是该类反应的发展方向。     

Reactivity of Lignin and Lignin Models Towards UV-Assisted Peroxide

The comparative reactivities of a series of guaiacyl and syringyl lignin model compounds and their methylated analogues towards alkaline peroxide and UV-alkaline peroxide were investigated. The overall reaction was followed by monitoring the reduction of the substrate as a function of time, and in every case, the reaction showed pseudo-first-order kinetics. The reaction rates of most lignin models having identical sidechains with alkaline peroxide and with UV-alkaline peroxide were in the order syringyl > guaiacyl > 3,4,5-trimethoxyphenyl > veratryl. Thus phenols react faster than their methyl ethers, and an extra ortho methoxyl group promotes the reaction. Lignin models possessing electron-donating side-chains had generally higher reaction rates than those with electron-withdrawing sidechains. The reaction rates of the series of benzoic acids were 2–4 times higher at pH 11 than at pH 5. UV-peroxide degradation of a eucalypt kraft lignin was faster than that of a pine kraft lignin, and degradation was 1.4–1.6 times faster at pH 11 than at pH 5. The data are consistent with the formation of higher amounts of reactive radicals under alkaline conditions, and aromatic rings with greater electronegativities promoting reactions with the radicals.     

钝化芳环的硝化反应

研究了一系列含有不同钝化基团的芳环化合物的硝化方法,考察了三氟甲基苯、对苯二甲酸二甲酯和对苯二甲酸用混酸直接硝化,收率分别为82．6％、79．8％和92．8％。对影响反应的因素,如硫酸的浓度和用量、反应温度和不同钝化基团的影响等进行了分析。     

氯苯清洁硝化

硝基氯苯是重要的化工原料,广泛用于精细化学品的合成.传统硝硫混酸硝化工艺存在副反应多、设备腐蚀、环境污染等缺陷.文章综述固体酸、离子液体、稀土盐/氟两相、氮氧化物、微反应器应用于氯苯硝化研究的最新进展,展望其发展方向.     

Specifics of Silicon Nitration

The sequence of formation of silicon nitride phases inside the volume of an initial silicon grain heated in a gaseous nitrogen medium is studied. Technologies for making ceramics articles based on silicon nitride are proposed.     

4-氯喹啉的硝化

研究了4-氯喹啉的5-位和8-位的硝化反应。利用发烟硝酸和浓硫酸的混酸体系,在4-氯喹啉的5-位或者8-位引入1个硝基,从而方便地合成8-硝基-4-氯喹啉和5-硝基-4-氯喹啉。反应总收率达75%以上。在该反应中,不同的投料顺序可以影响8-硝基-4-氯喹啉和5-硝基-4-氯喹啉的产出比例。以4-氯喹啉缓慢加入混酸体系的投料方式,有助于提高5-硝基-4-氯喹啉的收率。     

3-氟甲苯的硝化反应

以3-氟甲苯为原料，用三种不同硝化反应制备了5-氟-2-硝基甲苯。采用混酸硝化(在溶剂中，36.2ml浓硝酸、14.8ml浓硫酸、0℃～5℃、90g3-氟甲苯)，5-氟-2-硝基甲苯的选择性为59.8％；68%，的浓硝酸／多聚磷酸硝化(28.0ml 68％硝酸、0℃～5℃、35g多聚磷酸、16．5g3-氟甲苯)5-氟-2-硝基甲苯的选择性为80.0％；浓硝酸硝化(96.5ml浓硝酸、200g3-氟甲苯、50℃～55℃、8小时、真空蒸馏)5-氟-2-硝基甲苯的选择性为79.9％，应用H-MR和IR对产品进行了表征。     

木质素及其改性树脂羟值的测定

选用合适的复合酰化体系,通过电位滴定,测定了工业碱木质素及其改性树脂的羟值。该方法简便快捷,精确性及重复性较好,易于实际应用。     

Nitration of the Acetanilide-type Compounds

Some aromatic compounds containing the imino group (NH) were nitrated in acetic acid or anhydride, and the ortho/para ratios were measured. N-Methyl derivatives of the aforementioned compounds are much less reactive when nitrated under comparable conditions and give significantly lower o/p ratios. These results along with the literature data support the hypothesis that the acetanilide-type compounds are nitrated via N-nitro intermediates.     

绿色硝化反应研究进展

介绍了磺酸镧系盐催化硝化、氮氧化物硝化、固体酸催化硝化、液相负载硝化和气相硝化等绿色硝化反应,评述了它们的优缺点,提出了固体氧化物和全氟烷磺酸协同催化NO2／O2绿色硝化反应,有望成为一种有前途的绿色硝化方法。     

间甲基苯腈的硝化及产物的结构表征

以浓硝酸为硝化剂硝化间甲基苯腈得到3种硝基间甲基苯腈的异构体。在n(间甲基苯腈)∶n(发烟硝酸)=1∶10,反应时间2 h,反应温度18~20℃的条件下,冰浴中将浓硝酸缓慢滴加到间甲基苯腈中,得3种硝基间甲基苯腈异构体,粗品总收率92%。经柱层析和重结晶,从粗产物中分离出3种纯异构体,分别为3-甲基-4-硝基苯腈、3-甲基-6-硝基苯腈和3-甲基-2-硝基苯腈,以间甲基苯腈计,收率分别为43%、37%和12%。应用核磁共振、红外和气质联用技术,表征了3种纯异构体的结构,对硝化反应的位置选择性进行了初步分析。     

HAZOP技术及其在左旋多巴产品脱甲基反应上的应用

介绍了HAZOP(危险过程可操作性分析)的核心技术,即节点的划分和偏差的确定。将其应用到左旋多巴生产工艺过程中:分析工艺流程,,选取脱甲基反应作为HAZOP分析的节点,找出所有可能发生的事故,给出相应的措施。分析表明,HAZOP分析较其他定性分析更为全面,从而为安全生产提供一定的保障。     

Lignin for Bioeconomy: The Present and Future Role of Technical Lignin

Lignin, the term commonly used in literature, represents a group of heterogeneous aromatic compounds of plant origin. Protolignin or lignin in the cell wall is entirely different from the commercially available technical lignin due to changes during the delignification process. In this paper, we assess the status of lignin valorization in terms of commercial products. We start with existing knowledge of the lignin/protolignin structure in its native form and move to the technical lignin from various sources. Special attention is given to the patents and lignin-based commercial products. We observed that the technical lignin-based commercial products utilize coarse properties of the technical lignin in marketed formulations. Additionally, the general principles of polymers chemistry and self-assembly are difficult to apply in lignin-based nanotechnology, and lignin-centric investigations must be carried out. The alternate upcoming approach is to develop lignin-centric or lignin first bio-refineries for high-value applications; however, that brings its own technological challenges. The assessment of the gap between lab-scale applications and lignin-based commercial products delineates the challenges lignin nanoparticles-based technologies must meet to be a commercially viable alternative.     

绿色硝化研究进展

叙述了绿色硝化目前现状,指出新技术如氟两相、微波及超声波应用在硝化反应中的重要作用,特别指出N2O5-离子液体体系在硝化反应中的应用,尤其是在胺类硝化中,对促进硝化反应绿色化有重要意义.附参考文献71篇.     

Nitration of Condensed Polycyclic Aromatic Ketones

Nitration of three isomeric dibenzanthrones, 13H-dibenzo[a,de]-anthracene-13-one(3), 7H-benzo[hi]chrysene-7-one(4), and 7H-dibenzo[a,kl]anthracene-7-one(5), with concentrated nitric acid was studied under various conditions. The nitration of (3) at 15 °C in 1,1,2,2-tetrachloroethane gave the 5-nitro derivative. The nitration of (4) in boiling acetic acid produced the 9-nitro derivative. The nitration of (5) at 70 °C in acetic acid gave the 5-nitro derivative. These nitro compounds are very useful in synthesizing undecacyclic aromatic hydrocarbons.     

Nitration procedures using electrogenerated reagents

Oxidation of dinitrogen tetroxide at a platinum electrode permits the generation of nitronium tetrafluoroborate in acetonitrile containing lithium tetrafluoroborate. Using other electrolytes nitronium hexafluorophosphate can be similarly generated in nitromethane and dinitrogen pentoxide in dichloromethane. The three nitrating agents efficiently nitrate a range of organic substrates including aromatics, alkenes, dienes and trialkyl silylenol ethers.     

甲苯区域选择性硝化的研究进展

综述近20多年来国内外提高甲苯硝化反应区域选择性的各种方法的新进展。通过对各种硝化剂和催化剂的讨论和分析,提出通过提高甲苯硝化产物中对位异构体的比例,可进一步提高甲苯硝化产物的区域选择性,避免大量邻硝基甲苯的产生,改善了硝化反应环境,减少环境污染。将各种分子筛用于甲苯的区域选择性硝化,具有节约能源及原材料、无废酸废水产生、无腐蚀等特点。硝化产物转化率大幅度提高,硝化产物区域选择性好。