火焰原子吸收分光光度法测定改性粘土催化剂中的铜

以无机天然粘土或用金属离子交换处理粘土制备的改性粘土作为固体酸催化剂 ,因其具有选择性好、廉价、易再生及无环境污染等特点 ,正成为目前绿色化学研究的热点 ,特别是经离子交换制备的改性粘土应用于芳烃的选择性硝化反应的研究 ,已取得较大的进展。该改性固体酸催化剂中改性元素的含量常影响催化剂的性能 ,但对改性粘土催化剂中改性元素的含量的测定却未见报道。微量铜的测定常采用紫外可见分光光度法 [1] 和原子吸收分光光度法 [2 ]。本文对经铜元素改性的粘土催化剂进行处理 ,采用了火焰原子吸收分光光度法 ,直接测定了铜元素的含量[3…     

灰化前处理-电感耦合等离子体原子发射光谱法测定阿那曲唑中钯的残留量

阿那曲唑商品名为瑞婷、瑞宁得,为强效非甾体类芳香化酶抑制剂,可降低血浆雌激素水平,产生抑制乳腺肿瘤生长的作用,临床上广泛用于绝经后妇女的晚期乳腺癌治疗[1-2]。由于阿那曲唑在制备过程中要用到钯作催化剂,其残留会对人体健康带来一定的危害,所以必须对钯的残留量做准确的测定[3]。微量钯的测定多采用分光光度法[4]或原子吸收光谱法[5-6],也有关于电感耦合等离子体原子发射     

火焰原子吸收光谱法测定废水中金和银

当今工业企业都被要求实施清洁生产,以及减量化、再利用、再循环的循环经济3R原则[1],尤其是对电镀废水中重金属的排放监测和针对金、银等贵金属的回收再利用的分析检测,已经成为环境监测和工业分析的重要内容。对于金和银的测定,目前已有分光光度法[2-3]、电化学法[4]、原子发射光谱     

贵金属离子非酶法生物还原机理初探

在微生物湿法冶金回收贵金属的研究工作中,掌握金属非酶法生物还原的作用过程及本质是优化浸出工艺条件,设计高效,经济的生物加收技术的关键,因此有关细菌固定金属的作用机制的研究一直为人们所关注,冻干的海藻（Chlorella vulgaris)和四氯金（Ⅲ）酸盐[AuCl4]-相互作用,Au3＋快速被还原为Au ,继而缓慢地被还原成Au[1],厌氧的脱硫弧菌属（Desulfovibrio desulfuricans)的休止细胞能将溶液中的钯离子还原为金属钯,用丙酮酸钠,甲酸钠或氢气作为电子供体[2],我们试图从失活细菌与金属离子的界面出发,利用谱学技术,考察细菌与金属离子之间的相互作用本质,为开发利用生物体作为吸附剂进行废水处理,回收贵重或有害金属以及制备高分散度负载型金属催化剂[3]提供理论依据。     

3,5-二氯-PADAT萃取光度法测定钯

3,5-二氯-PADAT作为显色剂已用于水相光度法测定钯,但萃取光度法测定钯尚未见报导。本文参考文献[2]研究了该试剂与钯在强酸性介质中形成络合物的萃取性能及萃取光度法测定钯的实用条件。实验证明,3.5-二氯-PADAT钯形成的紫红色络合物可被异戊醇萃取,钯量在6微克/5毫升异戊醇内服从比尔定律,萃取后的络合物相当稳定。方法应用于工业废水和催化剂中钯的测定,获良好结果。     

原子吸收光谱法测定催化剂中高含量镍

加氢催化剂在我国炼油工业中一直起着十分重要的作用。其主要成分有硅、铝、钼、镍、磷等元素 ,这些金属元素在催化剂中大多以金属氧化物形式存在 ,该催化剂过去通常用硫酸溶解试样 ,光度法分析其中金属元素含量。但使用该溶样方法 ,无法进行原子吸收光谱法测定。本法在聚四氟乙烯压力溶弹内 ,用王水作溶剂溶解样品 ,具有试剂用量少 ,免受污染等优点。目前应用较为广泛的测定镍的方法有分光光度法[1] 、石墨炉原子吸收光谱法[2 ] 、电感耦合等离子体发射光谱法[3] 。分光光度法需较长时间 ,操作复杂 ,所用试剂比较多 ;石墨炉原子吸收光谱法…     

钼体系催化剂中钼的光度测定

钼体系催化剂是一类重要的催化剂。催化剂中钼的含量对催化剂的活性起着重要作用,快速准确地测定其中钼的含量对于催化剂的研究是很必要的。硫氢酸盐光度法是测定钼常用的方法,具有操作简便、结果准确之优点。由于该催化剂只能在氮气保护下溶于汽油,遇到空气和水时钼即析出,故不能直接用文献[1]介绍的方法测定钼体系催化剂中钼。本文对汽油在无水乙醇中的溶解情况进行试验,表明催化剂的汽油溶液能溶于无水乙醇,而且稳定,从而解决了试样的稀释、分取和储存等问题。本法将钼的硫氰酸盐光度法应用到钼体系催化剂中钼的测定,得到了满意的结果。仪器与试剂 72型分光光度计;50％硫氰酸钾溶     

蒙脱士负载钯催化芳基溴化物脱溴性能研究

芳基溴化物催化脱溴 ,无论在有机合成 ,还是消除芳基溴化物对环境的污染方面均具有重要意义 .催化脱卤已有许多研究报道 [1] .常用的负载催化剂为 Pd/C[2 ] ,这种催化剂催化活性较高 ,但对不同卤素的选择性较差 ,贵金属钯损失较大 .用功能化的蒙脱土负载钯催化剂 [3 ]催化芳基溴化物的脱溴 ,有较好的脱溴性能 ,但脱溴时间较长 ,且催化剂制备困难 .我们用胺为吸附质 ,将钯负载在廉价的蒙脱土上制成蒙脱土负载钯催化剂 ,并将其用于催化有机卤化物脱卤 .结果表明 ,该负载钯催化剂对芳基溴化物脱溴具有显著的催化活性和选择性 ,且催化剂易于制…     

马来酸-苯乙烯共聚物-钯络合物催化剂在加氢反应中的变化及钯的回收利用

马来酸-苯乙烯共聚物-钯络合物在催化加氢过程中,络合在高分子配体上的钯离子易被还原为Pd(0),而部分地脱落下来,这可从XPS及电镜分析证实。催化活性中心可能是高分子络合(或隔离保护)的Pd(0)微粒。本文研究了高分子钯催化剂在硝基苯加氢过程中,钯的用量范围,溶剂对催化活性的影响,催化剂的回收与其活性及金属钯的回收与再利用。此外还测定了硝基苯催化加氢的活化能。     

电感耦合等离子体质谱法测定汽车尾气净化催化剂中铂、钯、铑含量

汽车尾气净化催化剂样品经过氧化钠熔融,用热水浸出,加入盐酸酸化后,分取部分试液用电感耦合等离子体质谱法测定其中铂、钯、铑的含量。选择镉(~(111)Cd)和铊(~(203)Tl)作为内标元素。铂、钯、铑的检出限(3s)分别为0.048,0.056,0.019μg·g~(-1)。方法用于5件催化剂样品的分析,测定结果与光度法测定结果相一致。铂、钯、铑的平均回收率分别为100.0%,100.0%,99.8%;相对标准偏差(n=12)分别为1.3%,1.0%,1.6%。     

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.