土壤发育过程中稀土元素的地球化学指示意义

研究了海南岛北部不同时期喷发的玄武岩上发育土壤中稀土元素的地球化学特征和行为,探讨成土元素的分异及其对土壤发育程序的指示作用。ＲＥＥ总量与成土年龄呈显著正相关,是指示土壤发育程序的良好指标。同时,随土壤发育程度的加深,ＲＥＥ出现分异,土壤中轻稀土逐渐富集,重稀土亏损,伴随的进一步发育,Ｃｅ逐渐向正异常而Ｅｕ向负异常方向演化。     

天津沿海排污河中稀土元素的地球化学特征

选择天津沿海的南、北排污河为对象，研究了城市排污河中稀土元素的某些地球化学特征。结果表明，在排污河水体中溶解态稀土含量仍很低，但与其他天然大河相比，Eu和重稀土溶解态含量明显偏高。原水中稀土元素含量较高，以悬浮态为主。轻稀土的溶解态与悬浮态分布模式随原子序递增有相反的变化趋势。沉积物与悬浮物中的稀土含量明显低于其他天然河流，而悬浮物中的稀土含量又明显低于沉积物。沉积物与悬浮物中的稀土分布模式相似，均为轻稀土富集、重稀土亏损、Eu正异常型。这种分布模式与其他天然河流不同，而与本地区含有机质丰富的土壤相似，表明其外源为附近土壤。排污河稀土元素地球化学特性与天然河流的差异可能主要由于其水体中含有大量有机污染物造成的。     

山西省兴县铝土矿稀土元素地球化学特征及其地质意义

兴县铝土矿是山西霍西—河东铝土矿成矿带的典型代表,为喀斯特型铝土矿。为进一步研究兴县铝土矿成因,以兴县铝土矿样品为研究对象,分析了稀土元素REE含量和地球化学特征。通过研究发现:兴县铝土矿稀土元素总量较高,轻稀土富集,重稀土呈现不同程度的亏损。稀土元素分布模式及Eu异常分析,认为兴县铝土矿主要物质可能来源于下部奥陶系灰岩,同时混入了其他少量的铝硅酸盐矿物;从本区铝土矿稀土元素中Ce异常和La/Y比值情况显示,铝土矿形成于偏氧化性—碱性的海陆过渡相环境;另外通过比对一些国内外的喀斯特型铝土矿,发现兴县铝土矿稀土元素含量非常高,具有巨大的潜在经济价值。     

内蒙古中部渣尔泰山群微量元素地球化学特征

通过对内蒙古中部渣尔泰山群各层位岩石采样,对该山群中共43个微量元素（含稀土元素）与地壳丰度进行了对比分析,总结了该山群微量元素的地球化学特征。研究表明,该山群富集W、Re、Cu、Pb、Co等元素,而In、V、Cr、Ni等元素亏损较严重;微量元素在板岩和云母石英片岩中相对含量较高,在灰岩中相对贫化;此外,该山群稀土元素地球化学特征表现为轻稀土富集,重稀土亏损;具有明显的Eu的负异常,Ce的弱正异常。     

煤矿区地下水稀土元素地球化学特征:以皖北许疃矿为例

为了解煤矿区地下水稀土元素地球化学特征,采集了许疃煤矿3个含水层水样,进行常规离子和稀土元素测试,探讨了稀土组成及元素异常特征,结果表明:许疃矿3个含水层呈碱性,pH值平均为8.7,地下水中阴离子以HCO_3~-为主,阳离子以K~++Na~+为主。Ca~(2+)和Mg~(2+)含量在灰岩水中最大,Na~++K~+浓度在煤系水中最高。地下水中稀土总量偏低(∑REE=0.023~0.251μg·L~(-1)),经后太古宙平均页岩标准化,表现为轻稀土亏损,重稀土富集,所有样品均表现为明显的Eu正异常,多数样品表现为Ce和Y负异常;这些特征受到多种因素控制,其中Ce负异常受到地下水pH值影响,而Eu异常受长石类矿物溶解的影响,Y负异常和较低的Y/Ho值与Ca~(2+)浓度密切相关,受到围岩作用的影响。这些特征及影响因素表明利用稀土元素特征进行矿井水源识别具有一定的可行性。     

黄山景观流域溶解态稀土元素地球化学特征

对黄山景观流域径流中溶解态稀土元素进行了研究,以探讨其地球化学特征与物质来源。结果表明,其主要来源为岩石化学风化,其次为大气输入。稀土元素含量枯水期高于丰水期,与蒸发富集效应有关。流域源头稀土元素含量高、重稀土相对富集,中下游稀土含量低、轻稀土相对富集,反映了源头花岗岩到中下游沉积岩对其相应控制。流域水体中Ce为负异常,表现出对流经原岩如花岗岩的继承;Eu为正异常,归因于花岗岩中斜长石/钾长石等矿物的优先风化释放。Y/Ho比值在空间上存在分异,主要为流经岩性不同所致,季节性分异则受到了水/粒相互作用的影响。研究表明,黄山景观流域溶解态稀土元素来源与迁移受流经岩性尤其花岗岩的影响显著。     

高岭土吸附稀土元素的实验研究

为更好了解粘土矿物对稀土元素(REE)的吸附及其控制因素,进行了不同溶液介质条件(平衡时间、REE含量、pH＝3～6.5) 1 g·L-1高岭土对REE吸附的系列实验.结果表明: 稀土在较短时间内(24 h)吸附/解吸过程达到平衡;Langmuir吸附等温线能模拟REE在高岭土上的吸附,总的趋势是REE含量越高,分馏越不明显;此外,pH对REE吸附和分馏有很大影响,REE分配系数随pH值增加而增加,且在pH近中性时,出现了明显的重稀土比轻稀土更多的被吸附.     

深海富稀土沉积研究的若干问题

深海富稀土沉积是指稀土元素含量(包含Y)≥400×10~(-6)的一类深海沉积物,以中-重稀土富集、与钙十字沸石紧密共生而区别于其他深海沉积类型。深海富稀土沉积在太平洋和印度洋广泛分布,其稀土氧化物资源量可达1000亿t,其中重稀土资源量约为325亿t,引起了国际学术界的普遍关注。在系统总结深海富稀土沉积的调查研究历史和现状基础上,对其分布特征和规律、地球化学特征、载体矿物、富集机制、物质来源等研究进展进行了阐述,并指出了目前在稀土元素富集机制研究方面存在的几个重要问题:稀土元素的物质来源;沉积物孔隙水对于稀土元素富集的作用;钙十字沸石等共生矿物的成矿指示意义。     

厦门西海域表层沉积物中稀土元素分布特征

以厦门西海域表层沉积物为对象,研究了沉积物中稀土元素(REE)的分布特征.结果表明:厦门西海域沉积物中REE含量为125.71～206.02 μg·g-1,西部港湾区的8号和九龙江口的2号采样点REE含量较高,且轻稀土占绝对优势.REE含量随沉积物粒级呈有规律的变化,REE含量最高的是＜63μm的粒级,最低的是250 μm的粒级;沉积物经球粒陨石标准化后,各粒级REE总体配分曲线相近,均表现为明显的Eu亏损和Ce亏损,且＜63μm粒级亏损尤为严重.Eu与Ce异常平均值均小于黄河流域和长江流域沉积物;＜63μm粒级的沉积物中轻重稀土分馏程度最高,但在其他三种粒级沉积物中由粗到细分馏程度逐渐降低.分馏现象表明细粒级沉积物轻重分馏较粗粒级明显.与当地土壤稀土元素背景值比较,沉积物主要来自厦门西海域本地的土壤.     

河台金矿中稀土元素在韧性剪切过程中迁移行为的研究

通过对两类糜棱岩及其原岩的稀土元素含量的分析研究，结果表明稀土元素在韧性剪切过程中发生有规律的成分变异。在云母石英片岩及混合岩形成糜棱岩、超糜棱岩过程中，即随着变形强度的增强，单个稀土元素、轻稀土、重稀土和稀土总量均出现有规律的增加或减少，而稀土元素配分模式不变。通过对构造岩变形前后的等比分析，认为两类不同的糜棱岩类中稀土元素的成分变异极少，但存在少量稀土元素的迁入迁出，变化的原因是在岩石变形过程中发生了体积的改变和大量的流体作用影响，并导致轻稀土相对富集、重稀土相对亏损的分异作用。     

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.