锕系元素在熔盐体系中的电化学及萃取特性研究进展

熔融盐是一类非水溶剂,分为高温熔盐、室温熔盐和低温熔盐。 作为反应介质和电解介质,因其优良性能,可以溶解很多难溶于水的活泼金属。 近年来,该领域的研究热点是将熔盐作为干法后处理的电解质分离和回收锕系元素。 本文综述了锕系元素在高温熔盐中的电化学行为、热力学等物理特性,介绍了近几年室温离子液体(RTILs)的研究进展及锕系元素在RTILs中萃取特性的最新研究成果,展望了熔盐体系未来的研究方向。     

镧系和锕系元素在离子液体中电化学行为研究进展

在核燃料后处理中,离子液体作为"新一代绿色溶剂"可以替代强腐蚀性的高温熔盐用于干法后处理电解回收金属离子。本文总结了近年来国内外在离子液体中锕系和镧系元素的电化学行为。通过对比各研究结论的异同,评述了几类离子液体作为电解液电沉积金属及合金薄膜的优劣势;展望了离子液体作为电解液用于镧系和锕系元素分离实现提取铀和钚的研究前景和目前需要解决的问题。     

镧系和锕系元素在离子液体中电化学行为研究进展

在核燃料后处理中,离子液体作为“新一代绿色溶剂”可以替代强腐蚀性的高温熔盐用于干法后处理电解回收金属离子。本文总结了近年来国内外在离子液体中锕系和镧系元素的电化学行为。通过对比各研究结论的异同,评述了几类离子液体作为电解液电沉积金属及合金薄膜的优劣势。展望了离子液体作为电解液进行镧锕分离实现提取铀和钚的研究前景和目前需要解决的问题。     

国外核燃料后处理化学分离技术的研究进展及考察

后处理技术可分为使用水溶液的湿法和不使用水溶液的干法。湿法主要有溶剂萃取法(液液萃取法)、离子交换法和沉淀法等。以TBP(磷酸三丁酯)为萃取剂的PUREX法是当今后处理的主流技术。通过PUREX流程,可回收乏燃料中约99.5%的铀和钚,但由于长寿命次锕系元素(MA: Np、Am、Cm)以及Tc等得不到有效的分离回收,放射性废物的放射毒性仅降低一个量级。并且该技术本身存在萃取工艺流程复杂,设备规模大,产生大量的难处理有机废液等问题。多年来世界核能主要国家都在致力于改良PUREX流程的同时,开展更先进的湿法后处理技术研发。干法后处理采用熔盐或液态金属作为介质,主要有电解精炼法、金属还原萃取法、沉淀分离法和氟化物挥发法等。具有装置规模较小,耐辐照性强,临界安全性高等优点。但分离性能较低,且由于操作温度高(数百摄氏度),材料耐用性以及操作可靠性尚待解决。近年来干法作为金属燃料后处理以及超铀元素嬗变燃料处理的分离技术,重新受到重视。本文概括介绍了国外先进湿法和干法后处理技术的研究动向,并对分离技术中的主要化学问题进行了分析和考察。     

La和Nd在其氯化物熔体中的电化学腐蚀

稀土金属在其氯化物熔盐中的自腐蚀是导致电解制备稀土金属时电流效率降低的一个重要原因。但由于实验技术上的困难,有关这方面的研究报道不多。本文将在水溶液体系中常用的电化学弱极化测量腐蚀速度及电化学参数的方法用之于La、Nd在其氯化物熔盐体系中的腐蚀,表明同样适用。     

熔盐电化学低碳冶金新技术研究

本文重点介绍“氯化物熔盐体系电解还原固态氧化物冶金过程的高效化”和“氯化物熔盐体系电裂解硫化物及熔融碳酸盐与熔融氧化物体系电分解氧化物无温室气体排放冶金”的研究进展,结合武汉大学的部分代表性工作阐述了相关技术的原理,以期揭示熔盐电解技术在节能减排和资源高效利用上的优势及其发展前景,为发展短流程、低碳高效的电化学冶金工业提供理论和技术支持。     

化学计量学在锕系元素分析中的应用

锕系元素的化学性质相似,各元素的分离和分析都很困难,用传统的数据解析手段,难以实现各元素的同时、快速分析。化学计量学是一种高效、功能强大的数据解析方法,对于样品复杂,基体干扰严重以及多组分样品的分析具有独特优势。将化学计量学应用于锕系元素的分析中,利用数学分离代替化学分离,可直接对样品进行测定。化学计量学方法也可用来指导试样的科学采集,进行实验设计、仪器分析操作条件选择等。从吸收光谱、ICP–AES及放射性测量3个方面综述了化学计量学在锕系元素分析中的应用,阐明了化学计量学在锕系元素分析中的应用难点及发展前景。     

NdCl3-BaCl2-LiCl三元体系相图的研究

研究熔盐体系的各种物理化学性质及电解制备金属, 相图是非常必要的。由于稀土元素分离提纯及实验时测定相图的困难, 至今只能见到某些稀土氯化物的二元相图, 而含稀土的三元氯化物体系相图的报导甚少, NdCl3-BaCl2-LiCl三元相图尚未见到文献报导, 本文测定了该三元体系的相     

LnCl_3-KCl-NaCl体系粘度的研究

目前关于熔盐体系粘度的研究报道甚少,这是由于熔体粘度的测量,技术上难度较大,尤其是当温度超过773K以后。稀土金属及其合金的生产,国内外多采用KCl-LnCl_3熔盐电解法。近年来,科学工作者系统地研究了LnCl_3-KCl-NaCl(Ln=La、Ce、Pr、Nd、Sm)熔盐体系。这一体系在生产中可以降低电解温度,减少材料腐蚀,降低电解质的挥发损失。因此研究该体系的物理化学性质,将有重要的意义。本工作是通过对熔体粘度的研究,为稀土熔盐化学和生产实践提供基础数据。     

熔盐电解法制备镁稀土合金的现状及展望

熔盐电解法是一种高效制备镁稀土合金的方法,工艺流程简便易于连续生产,而且制备的镁稀土合金成分均匀,不偏析。 不同稀土元素的熔盐体系也有所区别,重稀土元素一般采用氧化物电解法,而轻稀土元素则采用氯化物电解法。 针对以上不同的电解方法,本文从电解原料、电解槽结构、电极过程、电解工艺、尾气处理等多方面详细阐述了制备镁稀土合金的现状,并对电解法制备镁稀土合金的未来提出发展方向。     

二氧化碳和丙烯直接合成甲基丙烯酸的NiPMo/TiO2催化剂的研究

用溶胶-凝胶法以磷钼酸(MPA)的镍盐溶液水解钛酸四丁酯制备了NiPMo/TiO2催化剂.使用ICP、 XRD、 TG-DTA、 IR、 TPD-MS和微反应技术研究了催化剂的化学组成、热稳定性、化学吸附性质和催化反应性能.杂多钼酸盐与TiO2通过O2-在TiO2表面发生了键合.在623 K下,杂多阴离子仍保持原有的Keggin结构.CO2在Lewis酸位Ni(Ⅱ)和Lewis碱位Ni-O-Mo的桥氧协同作用下生成CO2卧式吸附态Ni(Ⅱ)←O-(CO)←(O--Ni).丙烯有多种吸附态在催化剂上吸附.在563 K、 1 MPa和空速1500 h-1的反应条件下,丙烯的摩尔转化率为3.2%,产物MAA选择性为95%.     

Synthesis of 1-benzyloxypyrazin-2(1H)-one derivatives

Different approaches for the synthesis of 1-benzyloxypyrazin-2(1H)-one derivatives from simple amino acids have been investigated. A library of 33 precursors for the preparation of N-hydroxy pyrazinones was obtained in moderate to good yields.     

α-Amino acid derived enaminones and their application in the synthesis of N-protected methyl 5-substituted-4-hydroxypyrrole-3-carboxylates and other heterocycles

A new and simple synthesis of novel N-protected methyl 5-substituted-4-hydroxypyrrole-3-carboxylates, which exist in equilibrium with their 4-oxo tautomers, has been developed in two steps starting from N-protected α-amino acids. The key intermediates are enaminones, which can also be isolated, characterized, and used for the construction of other functionalized heterocycles, before they spontaneously decompose to pyrrole products. 4-Hydroxypyrroles are prone to partial aerial oxidation but can be efficiently alkylated or reduced to stable polysubstituted pyrrolidine derivatives.     

Specific intramolecular aromatic CH insertion of diazosulfonamides

The chemoselectivity in the intramolecular CH insertion of various diazosulfonamides has been experimentally studied. The results reveal that the aliphatic 1,4-, 1,5-, or 1,6-C(sp³)?H insertions of diazosulfonamides are not accessible, while the aromatic 1,5-C(sp²)?H insertion can be realized specifically by adjusting the diazo-adjacent group. In addition, the general chemoselectivities in the intramolecular CH insertions of diazosulfonyl compounds are summarized. Generally, diazosulfones undergo both aromatic 1,5-C(sp²)?H and aliphatic 1,5- and 1,6-C(sp³)?H insertions, while diazosulfonates undergo aliphatic 1,5- and 1,6-C(sp³)?H insertions. However, diazosulfonamides only undergo aromatic 1,5-C(sp²)?H insertion.     

A general and convenient synthesis of 4-(tosylmethyl)semicarbazones and their use in amidoalkylation of hydrogen,heteroatom, and carbon nucleophiles

A general synthesis of previously unknown semicarbazone-based α-amidoalkylating reagents, 4-(tosylmethyl)semicarbazones, has been developed. The synthesis involved three-component condensation of semicarbazones of aliphatic or aromatic aldehydes with the same or other aldehydes and p-toluenesulfinic acid. The scope and limitations of this reaction were investigated. The compounds obtained were demonstrated to be an efficient α-(4-semicarbazono)alkylating agents. They were reacted with H- (sodium borohydride), O- (sodium methylate), S- (sodium phenylthiolate), N- (pyrrolidine, sodium succinimide), P- (trialkyl phosphites), and C-nucleophiles (sodium diethyl malonate) to give the corresponding products of the tosyl group substitution, 4-substituted semicarbazones, including analogues of nitrofurazone. Among the prepared compounds tested in vitro for antibacterial and antifungal activity, three nitrofuryl-containing semicarbazones exhibited high biological activities with minimum inhibitory concentration (MIC) values of 8–32 μg/mL.     

Toward new camptothecins. Part 6: Synthesis of crucial ketones and their use in Friedländer reaction

In the context of the preparation of camptothecin and luotonin A analogs, the synthesis of some key keto-precursors and their use in Friedländer condensation are described. This paper also focuses on the stability of these keto intermediates and emphasizes the major differences between indolizinones and pyrroloquinazolinones series. Noteworthy is also the report of some original structures isolated as by-products of some experiments.     

Synthesis of novel chiral bidentate hydroxyalkyl-N-heterocyclic carbene ligands and their application in palladium-catalyzed Mizoroki–Heck couplings and asymmetric addition of diethylzinc to benzaldehyde

A small library of new chiral bidentate hydroxyalkyl-imidazolium salts 1 is conveniently synthesized on multi-gram scale from inexpensive and commercially available chiral pool amino acids. The corresponding carbenes, generated by deprotonation of imidazolium salts 1, in combination with palladium(II) chloride were tested in the Mizoroki–Heck coupling reaction. The most significant results in terms of yields and reactivities were achieved with low catalyst loading. The catalytic activities of these imidazolium salts were also investigated in the asymmetric addition of diethylzinc to benzaldehyde. The use of MgO nanoparticles as an additive in conjunction with these ligands played a crucial role in increasing the efficiency of these reactions.     

N-Heterocyclic carbene-palladacyclic complexes: synthesis,characterization and their applications in the C-N coupling and α-arylation of ketones using aryl chlorides

N-Heterocyclic carbene-palladacyclic complexes 3 were successfully achieved in a one-pot procedure under mild conditions. The structure of 3a was unambiguously confirmed by X-ray single crystal diffraction and it was an active catalyst in the Buchwald-Hartwig amination and α-arylation of ketones even at very low catalyst loadings (0.01?mol%).     

Iodine-mediated oxidative Pictet-Spengler reaction using terminal alkyne as the 2-oxoaldehyde surrogate for the synthesis of 1-aroyl-β-carbolines and fused-nitrogen heterocycles

An efficient iodine-mediated oxidative Pictet-Spengler reaction in dimethyl sulphoxide (DMSO) using terminal alkynes as the 2-oxoaldehyde surrogate for the synthesis of aryl (9H-pyrido[3,4-b]indol-1-yl)methanones is described. The scope of the protocol includes the total synthesis of Fascaplysin, Eudistomins Y₁ and Y₂. The methodology is extended for preparing pyrrolo[1,2-a]-quinoxaline and indolo[1,5-a]quinoxaline derivatives. The utility of 1-aroyl-β-carbolines was demonstrated by performing palladium-catalyzed β-carboline directed ortho-C(sp2)-H functionalization of the phenyl ring with thiomethyl (SMe) group using DMSO as source and for accessing 4-aryl-canthin-6-ones.     

Facile synthesis of bicyclic 1-arylpyrazol-5-ones

In this Letter, we described a facile method for constructing fused bicyclic 1-arylpyrazol-5-one ring system. We employed various methylene-containing carboxylic acids as the substrates and proved that the pyrazolone ring closure requires activated methylene group in intermediate II. Accordingly, a series of structurally diversified, fused bicyclic 1-arylpyrazol-5-ones was prepared in moderate to high yields using the requisite substrates.