金属材料分析方法的选择和施行——第六讲 金属材料中稀土元素的测定（续）

2.3.4在稀土共存时钍的螯合滴定稀土矿石常有少量钍、钇或钪共存,例如以包头矿源为原料的一些含稀土元素的金属材料常同时含有一定量的钍,例如在稀土-硅-镁-铁合金中常含有微量钍,在此类金属材料的分析中,钍的测定不容忽视。钍的测定可采用光度法,也可用螯合滴定法,有关光度法测定钍将在以后论述。本节中只讨论钍的螯合滴定的有关问题。钍属锕系元素,仅有正四价一种稳定的原子价状态,其配位数为8,与EDTA或CyDTA能形成稳定的螯合物,lgK值达23.2,用上述滴定剂可进行螯合滴定。钍与稀土共存时,可进行钍和稀土的连续滴定,但如用XO作指示剂,…     

白云鄂博矿云母型矿石中钍的赋存状态及分布规律研究EI北大核心CSCD

利用化学检测分析、自动矿物分析、扫描电镜、微区能谱分析探讨了白云鄂博主、东矿云母型矿石中钍的赋存状态和分布规律。结果表明:主矿云母型矿石中含有一定量钍的独立矿物(钍石、铁钍石),东矿钍的独立矿物极少,钍主要以独立矿物的形式和类质同象的形式赋存于钍石、铁钍石和氟碳铈矿、独居石中;主、东矿云母型矿石中氟碳铈矿中Th O_2的平均含量比约为4∶1,独居石中Th O_2的平均含量比约为10∶1;查明主矿云母型矿石中77.79%的Th O_2分布于钍石、铁钍石、氟碳铈矿和独居石中,东矿云母型矿石中63%的Th O_2分布于氟碳铈矿和独居石中。     

白云鄂博矿云母型矿石中钍的赋存状态及分布规律研究

利用化学检测分析、自动矿物分析、扫描电镜、微区能谱分析探讨了白云鄂博主、东矿云母型矿石中钍的赋存状态和分布规律。结果表明:主矿云母型矿石中含有一定量钍的独立矿物(钍石、铁钍石),东矿钍的独立矿物极少,钍主要以独立矿物的形式和类质同象的形式赋存于钍石、铁钍石和氟碳铈矿、独居石中;主、东矿云母型矿石中氟碳铈矿中Th O_2的平均含量比约为4∶1,独居石中Th O_2的平均含量比约为10∶1;查明主矿云母型矿石中77.79%的Th O_2分布于钍石、铁钍石、氟碳铈矿和独居石中,东矿云母型矿石中63%的Th O_2分布于氟碳铈矿和独居石中。     

矿石中微量钍的萃取比色测定——偶氮氯膦Ⅲ-十六烷基三甲基溴化铵分光光度法

目前,偶氮氯膦Ⅲ主要用于钍、铀等元素的分光光度法测定。偶氮氯膦Ⅲ同这些元素形成的络合物十分稳定,显色反应灵敏度很高,与四价钍生成有络色合物的克分子吸收系数达1.22×10~6。目前,矿石中钍的测定多用偶氮胂Ⅲ和钍试剂钍色法。本文提出利用长链铵,使偶氮氯膦Ⅲ与钍在其作用下,生成的紫蓝色三元络合物,用异戊醇-苯混合有机溶剂萃取该络合物,作钍的分光光度测定,试剂空白值小,灵敏度较高。同时制定了简易、快速的测定矿物岩石中微量钍的分析方法。     

土壤对外源钍的吸附行为表征

外源钍对土壤的污染风险和程度取决于钍在土壤中的吸附行为. 以包头稀土工业区土壤样品和土壤环境矿物组分为研究对象, 通过静态吸附方法研究外源钍在土壤样品和环境矿物组分(高岭土、蒙脱土、碳酸钙、水合氧化铁/锰和腐殖酸)上的吸附, 并对吸附行为进行了表征. 结果表明, 土壤样品对外源钍有很强的吸附能力, 对加入的外源钍(10^-4 mol/L)吸附率在97%以上; 土壤环境矿物组分对加入的外源钍(1 g/L)吸附率在28%～46%之间. 通过扫描电镜-能谱(SEM-EDS)分析可知, 外源钍进入土壤后与矿物组分发生相互作用, 可能形成了稳定化钙质钍碳酸盐和钍磷酸盐; 傅里叶变换红外光谱(FTIR)分析表明, 钍是与土壤环境矿物组分上的活性吸附位点发生相互作用而吸附并保持在土壤中, 是物理吸附和化学吸附共同作用的过程; X射线衍射分析(XRD)表明, 土壤在吸附钍前后, 其矿物组分基本相同, 而矿物晶体相态发生明显变化. 由于不同土壤矿物组分对钍的吸附方式不同, 导致吸附的钍以不同形态存在于土壤中.     

HEH/EHP萃取剂中钍的反萃性能研究

研究了含钍HEH/EHP(2-乙基己基膦酸单-2-乙基己基脂)萃取剂中钍的反萃性能。采用HCl,HNO3和H2SO4三种矿物酸分别对钍进行了反萃试验研究,结果表明,当反萃酸浓度为[H+]=6 mol.L-1时,HCl和HNO3反钍率小于1%,而硫酸的反钍率接近69%,表明H2SO4是钍的有效反萃剂。以H2SO4作为反萃剂,研究了相比、反萃酸浓度、酸用量、萃取剂浓度及钍负载量对钍的反萃性能的影响。在此基础上,对钍的逆流反萃过程进行了研究,当起始酸浓度为7 mol.L-1时,分别采用1∶1和4∶1的相比进行3级逆流反萃,反萃率分别为92.10%和53.29%。     

P507-H_2SO_4体系萃取色层分离铀、钍、锆、钛的研究

本文用P507-二甲苯作固定相,以硅烷化硅胶作载体,系统地研究了铀(V1)、钍(1V),锆(1V),钛(1V)的萃取色层行为。测定了铀、钍络合物的组成,探讨了铀、钍的萃取机理。提出了连续萃取色层分离铀、钍、锆钛的途径,拟定了矿石中少量铀和钍连续测定的方法。     

钍含量对Co/HMS催化剂结构和费托合成的影响

详细研究了钍含量对15% Co/HMS催化剂结构、费托合成CO转化率和烃分布的影响, 结果表明: 钍助剂的添加降低了催化剂的钴还原度, 并可使催化剂钴晶粒减小, 且存在钍物种对钴物种的覆盖; 钴晶粒的减小、较高钍含量时催化剂里钍物种对钴物种的覆盖和钴物种还原性能的降低, 使催化剂存在最优的钍含量, 此时催化剂表面暴露的金属钴原子最多, 较好地解释了钍含量达到1.5 wt%时, 催化剂CO转化率最高的实验现象. 烃分布研究表明: 反应温度较低时钍助剂将促进产物链的增长和高碳烃选择性的增加, 但反应温度较高时难以促进产物链的增长.     

钪、铀、钍、锆、稀土元素的极谱吸附催化波研究——Ⅳ.钍的催化波及其在矿石分析中的应用

前言为测定岩石矿物中痕量的钍,我们在氯化铵-亚硝基苯胲胺铵盐中加入少量二苯胍,使钍的灵敏度比文献中测钍的灵敏度提高几十至几百倍。为防止钍的水解,我们还在溶液中加入少量的草酸铵。在此底液中钍的浓度在0.0005—0.04微克/毫升间呈直线关系。本文还试验了测钍的底液条件,并采用共沉淀和PMBP萃取方法将钍和其他伴生元素分离。用此法测定了岩石中痕量的钍,结果满意。     

稀有元素矿物系统全分析中的铀、钍、稀土元素的纸色层分离和测定

本文用纸色层法分离铀、钍、稀土等元素,用国产色层纸(23×13厘米),用上行法进行条件试验。试验结果表明,试液以硝酸介质,用丁酮-甲基异丁基酮-硝酸-水(45∶45∶5∶5(体积比))作展开剂,分离铀、钍、钪和稀土元素结果良好,Rf值分别为:铀(近于1),钍(0.5),钪(0.16),稀土(0)。温度10—30℃,展开时间2—3小时,铀,钍,稀土元素Rf值变化不大。从20毫克稀土元素中定量分离微克量钍和铀;从4毫克钍中定量分离微克量稀土元素和铀;从10毫克铀中定量分离微克量钍及稀土。解决了铀、钍和稀土元素中大量元素分离微量元素的问题。将分离后的铀、钍、稀土元素色带剪下,视其含量用容量法或比色法测定,相对误差5％左右。拟订了细晶石、褐钇钶矿、黄绿石、黑稀金矿等稀有元素矿物系统全分析中的铀、钍和稀土元素的测定方法。经几年的生产实践和大批样品的分析,结果甚佳。从而简化了稀有元素矿物全分析中铀、钍和稀土元素的分离和测定手续,提高了测定它们的准确度,并缩短分析时间,降低成本。     

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.     

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.     

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.     

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.     

CoFe2O4自形成磁性液体场致结构化对磁化的影响

The Langevin paramagnetic theory can’t describe the relation between magnetization of ferrofluids and applied magnetic field. The structuralization of ferrofluids, which is considered the main influence factor of the magnetization, is regarded. The part of magnetization works is deposited when the structure is forming. This action influences the magnetization of ferrofluids directly or indirectly. On the base of the “compressing” model, the Langevin function that usually describes the magnetization of ferrofluid is modified, and a well-fitted curve is obtained. An equation of the relation between the equivalent volume fraction after being “compressed” and the intensity of magnetic field is discovered, which approximately describes the process of magnetization. The relation between the approximate initial susceptibility and the volume fraction can be obtained from modified formula.