古海洋环境演化对富钴结壳稀土元素富集的制约

为了探讨古海洋环境演化对海山富钴结壳稀土元素富集的制约,本次选取西太平洋Lamont海山具有多层结构富钻结壳L1作为研究对象,逐层取样分析研究,认为古海洋环境演化以及磷酸盐化作用对不同稀土元素的影响不同:Ce含量受海洋生产力水平的制约,与形成时古海洋生产力水平呈正相关关系,但受磷酸盐化影响并不显著;而磷酸盐化对富钻结壳中其他稀土元素影响存在明显差异:导致老壳层中稀土元素相对较少,而重稀土元素则相对增加.另外富钴结壳壳层在生成后可能仍然继续与周边海水发生稀土元素交换,导致壳层生成得越早,其重稀土元素相对于其他稀土元素越富集,而Eu则越亏损.     

岩溶地下河系统中表层土壤稀土元素含量及分布特征

以桂林寨底地下河系统中表层土壤为研究对象,采用激光剥蚀电感耦合等离子体质谱(LA-ICP-MS)进行稀土元素测试分析,开展了稀土元素地球化学研究,研究结果表明:研究区内土壤稀土元素总量∑REE分布范围为117.82~451.98μg·g~(-1),平均为312.30μg·g~(-1),变化范围属中等分异型,高于中国大陆的土壤稀土元素总量背景值。轻稀土总量LREE高于中国大陆土壤LREE背景值,重稀土总量HREE略低于中国大陆土壤HREE背景值。LREE/HREE平均值为7.86,与北美页岩LREE/HREE值7.47相接近。土壤样品的北美页岩标准化曲线具有略轻稀土富集的右倾特征,Ce和Eu均表现出微弱的负异常特征,与研究区内成土母岩有一定的关系。虽然成土母岩决定着土壤中稀土元素的初始含量,但最终含量还受到其他因素的影响。     

川西凹陷雷口坡组稀土元素特征及其意义

对川西凹陷丰卤1井雷口坡组岩屑样品进行了稀土元素(REE)的分析.结果表明,通过REE参数∑REE、LREE、HREE、w(LREE)/w(HREE)、w(LaN)/w(YbN)、δ Ce和δ Eu的比较,雷口坡组∑REE与LREE和HREE的变化呈正相关,LREE占∑REE的74%,对∑REE的变化起主要影响作用;R...     

麦哲伦海山群富钴结壳铈富集的控制因素

利用ICP-OES和ICP-MS,分析了麦哲伦海山群西北端MK海山2170 m水深的MKD23B-3号富钴结壳样品,获得了其剖面上Ce,Co和P2O5含量数据.结果显示,该样品未磷酸盐化壳层的过剩Ce(Cexs)与Co含量之间呈明显的正相关关系,相关系数R2高达0.7893;与生长速率呈负相关关系,相关系数R2高达0.7211,表明壳层生长速率是制约结壳Ce含量的主因,高的Ce含量是低的生长速率造成的.在假设海水pH,Mn2+等条件不变的前提下,结壳生长速率正相关于Fe,Mn的沉积通量,而Fe,Mn的沉积通量正相关于海水中溶解氧含量.因此,在海水pH,Mn2+等条件不变的前提下,Cexs负相关于海水中溶解氧含量,海水溶解氧含量只是制约结壳Ce含量的间接因素,纠正了"结壳高Ce异常指示其形成时海水中高溶解氧含量"的认识.     

电感耦合等离子体质谱测定富钴结壳中的稀土元素

采用封闭压力酸溶(HF+HNO3)消解样品,以Rh为内标,用电感耦合等离子体质谱测定富钴结壳中的稀土元素。用此方法对3个国家一级标准物质富钴结壳标样(GSMC-1,GSMC-2,GSMC-3)进行了多次测定,结果稀土元素的测定值与标准值相符,多次测定结果的相对标准偏差(RSD,n=5)在0.36%～4.0%之间,加标回收率为90%～106%。基于此方法,对6个富钴结壳样品进行了测定,显示富钴结壳样品中稀土元素的配分曲线与标准物质中稀土元素的配分模式一致。方法适用于富钴结壳样品的批量分析。     

多金属结核/结壳中稀土元素的富集特征及其资源效应

多金属结核/结壳是海洋中最重要的固体沉积矿产之一,蕴藏丰富的铁、锰、铜、钴、镍等金属元素,也是稀土元素的富集体.利用等离子质谱仪/光谱仪对太平洋、大西洋、印度洋及南海北部海多金属结核/结壳11个样品25份试样的稀土含量进行了分析,多金属结核/结壳中稀土平均含量为1265 57×10-6,其中结核平均含量为1096.96×10-6,结壳平均含量1623.88×10-6,人人超过地壳和玑积岩的平均含量.稀土元素的富集主要受控于结核/结壳中铁、锰氧化物及粘土矿物对海水和沉积物中稀土元素的吸附作用,Ce元素高度富集,使其成为多金属结核/结壳矿产开发中可能最先利用的稀土元素之一.     

稀土元素在植物中的分异机制 (I) 小麦不同器官中的稀土元素分异模式及形成机制

以小麦为植物材料，利用外源稀土添加、营养液培养等人工控制手段，研究了稀土元素在植物体内的分异效应，并探讨了分异效应产生的机制。结果表明，稀土元素在小麦不同器官中出现显著分异。根系出现中稀土(MREE)富集特征和“M”型四重效应，分析是由稀土元素与PO4^3-的选择性沉淀造成。小麦地上部分稀土元素分布出现“W”型四重效应，分析也是由根部磷沉淀造成。与此同时，小麦茎部相对富集轻稀土(LREE)，叶中相对富集重稀土(HREE)。运用VMINTEQ程序计算了木质部溶液中稀土元素的结合形态主要有LnEDTA^-和Ln^3 (Ln指稀土元素)，但仅有LnEDTA^-表现出HREE相对富集特征，其他形态则表现出LREE相对富集特征。分析叶部LREE／HREE分异是吸收LnEDTA^-造成，而茎部LREE／HREE分异则是吸收Ln^3 和其他形态稀土的结果。细胞壁对Ln^3 的吸附也是导致以上分异特征的重要因素。     

激光剥蚀-电感耦合等离子体质谱研究富钴结壳生长环带的元素分布

建立了以Ti为内标,富钴结壳标准物质GSMC-1为外标,193nmArF准分子激光剥蚀ICP-MS方法研究富钴结壳不同结壳层中元素组成及分布。所建立的定量方法用于GSMC-2和GSMC-3的测定,分析结果的相对标准偏差和相对误差均小于10%;各分析元素的检出限为3.2～191ng/g(除Si外),可以满足富钴结壳原位微区分析的要求。对取自西太平洋麦哲伦海山区富钴结壳样品MDD-42,从核心到最外结壳层以0.5mm的微间距剥蚀并采集140个样品点,不同生长环带的微区分析结果表明,成矿元素和伴生元素在不同结壳层中呈现不同的分布特性,直接反映了结壳形成时期的地质作用和古海洋沉积环境。     

南方离子型稀土矿区马尾松稀土元素的分布与富集

为探讨南方离子型稀土矿区马尾松地上部分各器官稀土元素的分布与富集特征,采集福建省长汀县濯田镇马尾松下的土壤样品和地上部分各器官(树皮、树干、树枝和树叶)样品,测定其稀土元素。结果表明:马尾松下的土壤稀土元素含量平均值为275.15 mg·kg~(-1),轻重稀土元素分异明显, Ce元素富集明显, Eu元素相对亏损;马尾松地上部分各器官稀土元素含量普遍较低, LREE高于HREE,轻重稀土元素分异。马尾松地上部分各器官稀土元素球粒陨石分布模式中, Ce元素和Eu元素明显正异常,马尾松树干、树叶重稀土元素标准化后明显波动分布,呈锯齿状,马尾松树皮和树枝波动幅度小;其δCe(δEu)均大于1, Ce和Eu元素明显富集。马尾松地上部分各器官稀土元素的吸收系数均较小,该地区稀土元素由土壤到植物的迁移程度低,马尾松地上部分各器官对稀土元素的富集能力弱,但其生物量和提取稀土元素的能力不容忽视,可尝试将植物提取技术运用于该地区的稀土净化。     

黎塘富含铁锰结核土壤区碳酸盐岩稀土元素特征及其形成环境

为掌握黎塘富含铁锰结核土壤区碳酸盐岩稀土元素特征,对研究区岩石样品进行了采样分析,并对其形成环境进行了讨论。结果表明:研究区碎屑岩岩石样品远高于碳酸盐岩,碳酸盐岩不同地层具有一定差异,碳酸盐岩轻稀土元素之间、重稀土元素之间分馏不明显,而碎屑岩具有一定分馏特征。碳酸盐岩Y/Ho的比值以及Ce以负异常为主,表明碳酸盐岩应为海相-氧化环境,δCe与LaN/SmN、DyN/SmN的相关性表明经过了后期成岩的改造作用。碎屑岩Y/Ho的比值以及Ce基本无异常,表明碎屑岩应为湖相成因,当时沉积水体氧化还原条件基本无变化。碳酸盐岩不同地层δCe的差异,说明了氧化性随地质时期的变化,这种变化推断为后期土壤铁锰结核的形成起到了重要的作用。     

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%.     

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.     

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.     

Highly regioselective Buchwald–Hartwig amination at C-2 of 2,4-dichloropyridine enabling a novel approach to 2,4-bisanilinopyridine (BAPyd) libraries

The highly regioselective Buchwald–Hartwig amination at C-2 of the cheap and readily accessible reagent, 2,4-dichloropyridine with a range of anilines and heterocyclic amines is described. This new methodology is robust and provides a facile access to 4-chloro-N-phenylpyridin-2-amines on 0.25 mol scale. These intermediates undergo a further Buchwald–Hartwig amination at higher temperature to enable rapid exploration of the chemical space at C-4 and to provide a library of 2,4-bisaminopyridines.     

KMnO4-mediated oxidative CN bond cleavage of tertiary amines: Synthesis of amides and sulfonamides

KMnO₄-mediated oxidative CN bond cleavage of tertiary amines producing secondary amine was introduced, which was trapped by electrophiles (acyl chloride and sulfonyl chloride) to form amides and sulfonamides. The reaction could take place at mild condition, tolerating a wide range of function groups and affording products in moderate to excellent yields.     

Chemistry of heterocyclic compounds at the A. E. Favorsky Irkutsk Institute of Chemistry, Siberian Branch of the Russian Academy of Sciences, over 50 years (Review)

The review contains a concise historical account and information on the most significant researches undertaken by the staff at the A. E. Favorsky Irkutsk Institute of Chemistry, Siberian Branch of the Russian Academy of Sciences on the Chemistry of Heterocyclic Compounds. Dedicated to Academician of the Russian Academy of Sciences B. A. Trofimov on his 70th jubilee. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 10, pp. 1443–1502, October, 2008.     

Sulfur-directed metal-free and regiospecific methyl C(sp3)–H imidation of thioanisoles

Regiospecific and direct imidation of the methyl C(sp³)–H bond of thioanisoles is realized under mild and metal-free conditions with N-fluorobis(benzenesulfonyl)imide as an oxidant and nitrogen source. Proposed mechanism suggests that thionium ion intermediates and a Pummerer-type reaction are involved. The imidation has advantages such as high step-economy, excellent functionality tolerance, and regiospecificity, giving structurally diverse imidation products.     

Selective syntheses of 2H-1,3-oxazines and 1H-pyrrol-3(2H)-ones via temperature-dependent Rh(II)-carbenoid-mediated 2H-azirine-ring expansion

The Rh(II)-catalyzed reaction of 2-carbonyl-substituted 2H-azirines with ethyl 2-cyano-2-diazoacetate or 2-diazo-3,3,3-trifluoropropionate provides an easy access to 2H-1,3-oxazines and 1H-pyrrol-3(2H)-ones. These compounds can be selectively prepared from the same starting material using temperature as the only varied parameter. The 2-azabuta-1,3-diene intermediate, a common precursor for both heterocyclic products, isomerizes into 2H-1,3-oxazine under kinetic control, while 1H-pyrrol-3(2H)-one is the sole product of the reaction at elevated temperatures. According to DFT-calculations a one-atom oxazine ring contraction involving ring-opening to a 2-azabuta-1,3-diene intermediate, followed by a 1,5- and 1,2-prototropic shift leads to the consecutive formation of imidoylketene and azomethine ylide, which then further undergo cyclization to the pyrrole derivative.     

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.