Ni_(x)Cu_(y)-B_(24)N_(28)催化CO_(2)氧化C_(3)H_(8)速控步骤的反应机理研究北大核心CSCD

采用密度泛函理论(DFT)研究了C_(3)H_(8)和CO_(2)在Ni_(x)Cu_(y)-B_(24)N_(28)(x+y=4,x=1、2、3、4)表面吸附及速控步骤反应机理.计算了C_(3)H_(8)、CO_(2)和相应中间体在Ni_(x)Cu_(y)-B_(24)N_(28)表面的吸附能以及6条可能路径下的反应热和活化能.计算结果表明,C_(3)H_(8)和CO_(2)在Ni_(x)Cu_(y)-B_(24)N_(28)表面是物理吸附,C_(3)H_(8)+CO_(2)→CH_(3)CHCH_(3)+OCOH是最有利的路径,其在不同催化剂表面的活化能顺序是NiCu_(3)-B_(24)N_(28)(1.42 eV)、Ni_(2)Cu_(2)-B_(24)N_(28)(1.57 eV)、Ni_(3)Cu-B_(24)N_(28)(1.62 eV)、Ni_(4)-B_(24)N_(28)(1.75 eV).由此可知,在Ni_(x)Cu_(y)-B_(24)N_(28)催化CO_(2)氧化C_(3)H_(8)的体系中,Cu含量直接影响其催化活性,即NiCu_(3)-B_(24)N_(28)用于催化CO_(2)氧化C_(3)H_(8)有一定优势.     

《化学进展》2002年度作者索引

BBalder Eliasson14 ( 6 ) ,45 6C蔡文生 14 ( 1) ,0 37陈　嵘 14 ( 4 ) ,2 5 7陈惠麟 14 ( 6 ) ,446陈绘丽 14 ( 2 ) ,13314 ( 4 ) ,2 39陈晋阳 14 ( 6 ) ,40 9陈令新 14 ( 1) ,0 6 8陈晓峰 14 ( 6 ) ,477陈拥军 14 ( 5 ) ,40 5陈志春 14 ( 3) ,2 12陈瓞延 14 ( 2 ) ,0 81程　鹏 14 ( 1) ,0 47程代云 14 ( 5 ) ,36 0崔晓莉 14 ( 5 ) ,32 5D戴迎春 14 ( 2 ) ,12 1代　斌 14 ( 3) ,2 2 5代　燕 14 ( 1) ,0 47党鸿辛 14 ( 3) ,15 9邓云度 14 ( 3) ,182丁永生 14 ( 5 ) ,332董绍俊 14 ( 5 ) ,374杜灿屏 14 ( 2 ) ,15 614 ( 5 ) ,40 5杜会枝 1…     

β分子筛中Brønsted酸分布及酸性强度的量子化学ONIOM 理论计算研究

基于量子化学ONIOM [B3LYP/6-31G(d,p):UFF]计算方法, 研究了β分子筛中Brønsted酸的落位及其酸性强度. 计算采用22T簇模型, 得到了不同酸性位的(Al, H)/Si替代能和质子亲和势. 研究结果表明, Brønsted酸最有可能落位在Al(8)-O(11)-Si(4), Al(8)-O(4)-Si(1), Al(7)-O(7)-Si(2)和Al(9)-O(6)-Si(3)位置. 根据去质化能的计算, Al(7)-O(7)-Si(2)位置的酸性最强, Al(8)-O(11)-Si(4)的酸性最弱. 酸性的强弱顺序为Al(7)-O(7)-Si(2)＞Al(9)-O(6)-Si(3)＞Al(8)-O(4)-Si(1)＞Al(8)-O(11)-Si(4).     

混酸体系中31种金属离子的浮选行为

在总浓度为0.17～3.4N的HCl-HNO_3(〔HCl〕:〔HNO_3〕=2.4:1)体系中,以(18～60)×10~(-5)M的CPC为捕集剂,对(2.755～28.69)×10~(-5)M的31种金属离子进行了浮选,表明Ir(Ⅳ)、Pt(Ⅳ)、Ge(Ⅳ)、Sn(Ⅳ)、Bi(Ⅲ)、Au(Ⅲ)、T1(Ⅱ)、Pd(Ⅱ)、Sn(Ⅱ)可浮选95％以上,而Cr(Ⅵ)、Ti (Ⅳ)、Zr(Ⅳ)、Ga(Ⅲ)、In(Ⅲ)、Fe(Ⅲ)、Sb(Ⅲ)、Al(Ⅲ)、Mn(Ⅱ)、Fe(Ⅱ)、Co(Ⅱ)、Ni(Ⅱ)、Cu(Ⅱ)、Zn(Ⅱ)、Cd(Ⅱ)、Pb(Ⅱ)浮选率低于20％或几乎不浮选,Ru(Ⅱ)、Rh(Ⅱ)、Ir(Ⅱ)、Hg(Ⅱ)、Ag(Ⅰ)、TI(Ⅰ)部分被浮选。与HCl体系的浮选结果进行了比较,发现贵金属的浮选率和选择性在HCl-HNO_3体系中更好。进行了Au(Ⅲ)、Pt(Ⅳ)、Pd(Ⅱ)与Zn(Ⅱ)、Cd(Ⅱ)、Hg(Ⅱ)、Sb (Ⅲ)的分离试验,结果令人满意。     

Dy_(2)O_(3),Cu_(2)O在LiF-DyF_(3)熔盐体系的溶解度研究EI北大核心CSCD

以LiF-DyF_(3)为熔盐,电解Dy_(2)O_(3),Cu_(2)O制备Dy-Cu合金过程中,明确Dy_(2)O_(3),Cu_(2)O溶解度是制定合理加料制度、提高电解效率的关键。采用等温饱和法研究了Dy_(2)O_(3),Cu_(2)O溶解平衡时间,考察了温度、DyF_(3)浓度对单一氧化物(Dy_(2)O_(3)或Cu_(2)O)及混合氧化物(Dy_(2)O_(3)与Cu_(2)O)溶解度的影响,通过最小二乘法对溶解度数据进行了拟合,建立了温度、DyF_(3)浓度与Dy_(2)O_(3),Cu_(2)O溶解度之间的数学回归方程。研究结果表明,Dy_(2)O_(3),Cu_(2)O在LiF-DyF_(3)熔盐中溶解平衡的时间分别为110,120 min,溶解反应为吸热反应。相同温度下,随熔盐中DyF_(3)浓度增大,Dy_(2)O_(3)的溶解度逐渐增大,Cu_(2)O溶解度变化较小;在温度为910~1030℃,熔盐中DyF_(3)浓度为15%~40%(摩尔分数)时,Dy_(2)O_(3),Cu_(2)O溶解度分别为0.55%~3.45%,0.39%~0.52%。     

《化学进展》2004年度作者索引

A艾晓莉 16 ( 4) ,6 54安　燕 16 ( 4) ,6 6 0B白　亮 16 ( 2 ) ,2 56白春礼 16 ( 3) ,376白东鲁 16 ( 5) ,791C蔡汝秀 16 ( 6 ) ,96 2蔡卫权 16 ( 3) ,4 0 6蔡亚岐 16 ( 5) ,70 8蔡政亭 16 ( 5) ,785曹　斌 16 ( 2 ) ,2 91曹　怡 16 ( 3) ,4 6 3曹　镛 16 ( 1) ,0 99柴立和 16 ( 2 ) ,16 9晁自胜 16 ( 1) ,0 6 1陈　彬 16 ( 3) ,38616 ( 6 ) ,86 3陈　东 16 ( 4) ,4 92陈　静 16 ( 6 ) ,989陈　琳 16 ( 5) ,758陈　涛 16 ( 5) ,797陈　楠 16 ( 6 ) ,94 0陈丰秋 16 ( 6 ) ,954陈洪杰 16 ( 5) ,6 82陈惠麟 16 ( 4) ,574陈继涛 16 ( 3) ,335…     

Keyword Index Vol.12,2001

Ab initio (0215) Ab initio calculation (0727) Ab initio calculation (0833) 9(1020)-Abeo-7b,10b,11,15-tetra-hydroxy-8,11,13- abietatrien-12-O-b-D-glucopyranoside (0145) 11(15-1)-Abeotaxoids (0063) Abietane diterpenoid (0429) Abietanoid (0145) Absorption (1113) Absorption heat (0803) Abstraction reaction (0727) 3-Acetamidotropolone (0103) Acetic acid production (0125) 12-Acetyl-aspergillol (0435) Acid (0933) Acrylamide (0411) 2-Acrylamido-2-methyl-1-propane sulfonic acid (0411) Acrylic aci…     

《化学进展》2001年度作者索引

B白东鲁 13 (5 ) ,3 5 1包信和 13 (2 ) ,12 8C蔡开勇 13 (1) ,5 6陈　荣 13 (3 ) ,2 3 9陈建波 13 (5 ) ,3 76陈凯先 13 (4) ,2 83陈朗星 13 (3 ) ,2 0 9陈晓波 13 (5 ) ,3 92陈小平 13 (3 ) ,2 2 4陈新滋 13 (1) ,3 3成　峰 13 (4) ,2 83成　弘 13 (4) ,3 15储　伟 13 (2 ) ,12 8崔俊儒 13 (5 ) ,3 76D戴　瑛 13 (3 ) ,167戴立信 13 (2 ) ,15 6代　星 13 (3 ) ,183党　志 13 (4) ,3 10董炎明 13 (5 ) ,3 4 3杜灿屏 13 (4) ,3 2 313 (4) ,3 2 813 (5 ) ,41013 (5 ) ,411F范崇政 13 (2 ) ,94范星河 13 (4) ,2 5 1封麟先 13 (2 ) ,10 8冯长…     

硫酸铵-锌试剂-Tween 80体系萃取分离铜(Ⅱ)、钴(Ⅱ)、镍(Ⅱ)、锌(Ⅱ)、镉(Ⅱ)、锰(Ⅱ)

研究了(H4)2SO4-Zincon(锌试剂)-Tween 80体系萃取分离金属离子Cu(Ⅱ)、Co(Ⅱ)、Ni(Ⅱ)、Zn(Ⅱ)、Cd(Ⅱ)、Mn(Ⅱ)的行为.试验表明,Cu(Ⅱ)、Co(Ⅱ)、Ni(Ⅱ)在pH 6～9范围内,与Zincon形成的螯合物可被Tween 80相完全萃取,而Zn(Ⅱ)、Cd(Ⅱ)、Mn(Ⅱ)基本不被萃取,进而实现了Cu(Ⅱ)、Co(Ⅱ)、Ni(Ⅱ)与Zn(Ⅱ)、Cd(Ⅱ)、Mn(Ⅱ)混合离子的定量萃取分离.     

Intramolecular Induction of Asymmetric Darzen's Condensation of Aldehydes with Chiral α-Chloroacetates

Inconvergentwithourinterestintheasymmetricsynthesisofnaturalproducts,intramolecularinductionofasymmetricDarzen'scondensationlofaldehydeswithQchloroacetatesofchiralalcoholswasstudies,asshowninScheme1.Scheme1.R*OH CICH,COCI~CICH,COOR*i(-)-menthol(450%)3( )-Jsomenthoi(i56%)5(-)-8-phenylmenthoi(74%)2( )-neomenthol(147%)4( )-f6nchol(478%)6(-)-8-11-naphthylmenthoi(99%)I-henumbersintileparenthesisilldicatedthece%oftilecorrcspondillgmethy13-pllcn}lgl}'cidatcobtainedh\'trallscstcrltiationBenza…     

Speciation of Volatile Selenium Species in Plants Using Gas Chromatography/Inductively Coupled Plasma Mass Spectrometry

 Gas chromatography/inductively coupled plasma mass spectrometry (GC/ICP MS) coupled with solid phase micro extraction can provide a simple, extremely selective and sensitive technique for the analysis of volatile sulfur and selenium compounds in the hea     

电感耦合等离子体质谱（ICP-MS）法与氢化物发生-原子吸收光谱（HG-AAS）法测定土壤中硒含量的对比研究

基于氢化物发生器与原子吸收光谱联用(HG-AAS),测定土壤样品中硒的含量,并与电感耦合等离子体质谱(ICP-MS)法测定值进行了对比。在两种仪器的最佳工作条件下,测定土壤硒的含量,实验结果表明:ICP-MS法和HG-AAS法对土壤硒含量测定的线性范围分别为0.85~100.00μg/L和0.08~16.00μg/L,检出限分别为0.25μg/L和0.02μg/L,精密度分别为1.3%和2.1%;用加标回收实验和测定国家标准土壤样品(GSS-7)对这两种方法的准确性进行了验证,ICP-MS法和HG-AAS法的加标回收率分别为96.7%~99.4%和94.9%~99.5%,GSS-7标准土样的结果均在标准值范围内,说明这两种测定土壤中硒含量的方法是准确可靠的。HG-AAS法测定线性范围窄,部分样品需要稀释,而且氢化物发生系统是手动进样,导致操作复杂,分析周期长;ICP-MS法仪器测定快速,但是仪器昂贵。     

Sequential hydride generation/pneumatic nebulisation inductively coupled plasma mass spectrometry for the fractionation of arsenic and selenium species

The toxicity of certain elements is known to be related to their organic substituents and/or oxidation states. As such, total elemental determinations do not always yield sufficient information for accurate risk assessments and therefore speciation or fractionation data are required. In order to obtain fractionation data for trace levels of arsenic and selenium, a novel sequential pneumatic nebulisation (PN)/hydride generation (HG) inductively coupled plasma mass spectrometry (ICP-MS) method was developed. The method offers the advantage of sample introduction via either PN or HG by simply rotating a 4-way switching valve while the system is in operation. In PN mode, the liquid sample is aspirated into ICP, allowing for the determination of the total amount of each element, whilst in HG mode only the arsenic and selenium species that form volatile hydrides are determined. Conveniently, in the case of arsenic, this allows for differentiation between the four most toxic arsenic species (arsenate, arsenite, monomethylarsonic acid and dimethylarsinic acid), which form volatile hydrides, and the virtually non-toxic forms (arsenobetaine, arsenosugars, etc.), which do not. This allows for the rapid estimation of the amounts of toxic and non-toxic arsenic species present in a sample. For arsenic, the technique gave detection limits of 36 ng l⁻¹ in PN mode and 1 ng l⁻¹ in HG mode. For selenium, detection limits of 150 ng l⁻¹ were achieved in PN mode and 220 ng l⁻¹ in HG mode. The technique also gave good long- and short-term stabilities of under 6% RSD for both elements. A variety of samples, including water and urine standard reference materials, were analysed in both modes, and the precision and accuracy of the results for total arsenic and selenium levels were assessed. Using the technique in both modes also allowed for the fractionation of As and Se species into their volatile hydride-forming and non-hydride-forming species. This was particularly informative, with respect to As species present, in the case of a kelp powder extract. Digested tobacco samples were only analysed for their total As levels, in which case results obtained via both sample introduction modes showed good agreement.     

Fluorine-induced chemiluminescence detection of biologically methylated tellurium,selenium, and sulfur compounds

Summary The sensitive detection of volatile, methylated selenium and tellurium compounds based on capillary gas chromatography coupled to fluorine-induced chemiluminescence detection is described. The method requires no sample derivatization, and the detection limits for selenides and tellurides (low pg range) are the lowest reported to date. This technique can resolve and speciate complex mixtures of methylated tellurium, selenium, and sulfur gases and is useful for analysis of selenium and tellurium gases in environmental samples that also contain usually interfering reduced sulfur gases. Applications of the technique for analysis of bacterial and fungal headspace samples are presented.     

A study of antimony complexed to soil-derived humic acids and inorganic antimony species along a Massachusetts highway

Antimony is a toxic metalloid and is often present in inorganic forms such as more toxic Sb(III) and less toxic Sb(V). Auto brake linings are major contributors to antimony emissions along heavily traveled highways. In this study the distribution of water extractable Sb(III) and Sb(V) species along a Massachusetts highway was investigated. Antimony complexed to roadside soil-derived humic acids was studied by ion chromatography (IC) and size exclusion chromatography (SEC) coupled to inductively coupled plasma-mass spectrometry (ICP-MS). Thirty surface soil and soil core samples along route 116 in western Massachusetts were collected. Two soil-derived humic acids were extracted from the roadside soils. Elevated levels of nitric acid-extractable Sb (range: 2.9-24.9 µg/kg) and Pb (range: 10.4-2420 mg/kg) were found in the soil along the road and correlated well with highway traffic patterns. Sb(V) was the dominant species present in both surface and soil core samples, and is mostly confined to the top 20-cm layer of soil. HA mediated Sb(III) to Sb(V) oxidation was relatively fast and demonstrated pseudo-first order kinetics, where pseudo rate constant k is 3.033 h^-1. Antimony bound to soil-derived humic acid molar mass fractions was identified.     

Chromatographic speciation of anionic and neutral selenium compounds in Se-accumulating Brassica juncea (Indian mustard) and in selenized yeast

Selenium-accumulating plants such as Brassica juncea (Indian mustard) concentrate the element in plant shoots and roots. Such behavior may provide a cost-effective technology to clean up contaminated soils and waters that pose major environmental and human health problems (phytoremediation). Such ability to transform selenium into bioactive compounds has important implications for human nutrition and health. Element selective characterization of B. juncea grown in the presence of inorganic selenium under hydroponic conditions provides valuable information to better understand selenium metabolism in plants. The present work determines both previously observed organoselenium species such as selenomethionine and Se-methylselenocysteine and for the first time detects the newly characterized S-(methylseleno)cysteine in plant shoots and roots when grown in the presence of selenate or selenite as the only selenium source. A key feature of this study is the complementary role of selenium and sulfur specific chromatographic detection by HPLC with interfaced inductively coupled plasma mass spectrometry (ICP-MS) detection and by derivatization GC with interfaced atomic spectral emission. HPLC-ICP-MS limits of detection for such species were in the range 5-50 ng Se mL(-1) in the injected extracts. Speciation profiles are compared with those of selenium-enriched yeast by both HPLC-ICP-MS and GC-AED.     

Evaluation of a purge-and-trap injection system for capillary gas chromatography-microwave induced plasma-atomic emission spectrometry for the determination of volatile selenium compounds in water

A method is presented for the selective determination of the volatile selenium species dimethylselenide and dimethyldiselenide, using a commercially available purge-and-trap injection system coupled to capillary gas chromatography-microwave induced plasma-atomic emission spectrometry. The efficiency of the purging step was evaluated and the parameters affecting the purge and trap processes were optimized. The method was applied to the determination of volatile selenium compounds in lake water. Relative detection limits of 2ng/l for dimethylselenide and dimethyldiselenide, corresponding to an absolute detection limit of 10 pg, were achieved.     

Preliminary studies on selenium-containing proteins in Brassica juncea by size exclusion chromatography and fast protein liquid chromatography coupled to ICP-MS

An approach for screening and resolving selenium-containing plant proteins was developed based on the combination of sample preparation and multi-dimensional liquid chromatography coupled to ICP-MS. Different protein extraction protocols were investigated. A 24 h dodecylsulfate-mediated protein extraction in a sonication bath followed by acetone precipitation was found to be optimal. The use of different protein precipitate solubilizing agents (sodium dodecyl sulfate media and Tris-HCl buffer) demonstrates possible fractionation of the selenium-containing proteins. Selenium-containing protein screening and fractionation were carried out by means of SEC-ICP-MS. High molecular weight selenium containing proteins were solubilized with a sodium dodecyl sulfate-containing buffer, whereas the low molecular weight compounds were released into a Tris-HCl buffer. Size exclusion chromatography-fast protein liquid chromatography coupled to ICP-MS allowed separation and detection of several selenium-containing proteins in Se-supplemented wild type Brassica juncea plant, a fast growing selenium accumulator.     

Speciation of Selenium in Enriched Garlic Sprouts by High-Performance Liquid Chromatography Coupled with Inductively Coupled Plasma-Mass Spectrometry

Selenium species in enriched garlic (Allium Sativum L) sprouts were determined by high-performance liquid chromatography coupled with inductively coupled plasma-mass spectrometry (HPLC-ICP-MS). The garlic was grown in a 10 mg/L selenite nutrient solution, and the total selenium accumulated by the sprouts was 250 µg/g. Three mobile phase systems were investigated and a buffer of 20 mmol/L ammonium acetate/5% methanol was chosen for subsequent analysis. Comparative experiments were performed to determine the selenium species in the garlic sprouts with four extraction solutions: 0.1 mol/L HCl, 0.1 mol/L NaOH, 20 mmol/L ammonium acetate/5% methanol and protease XIV. The most suitable results were obtained using 0.1 mol/L HCl as the extracting solution. Validation was performed; all selenium compounds had recoveries of 102.5% to total selenium, with good linearity and precision. The major compound accumulated in the garlic sprouts was methylselenocysteine, which accounted for 65.01% of the selenium.     

Trace analysis of hetero aromatic compounds (NSO) in water and polluted groundwater by Solid phase micro-extraction (SPME)

By using Solid Phase Micro-Extraction (SPME) and Capillary Gas Chromatography (CGC) a method was developed to analyze hetero aromatic compounds (NSO) in water. Compounds with nitrogen, sulfur, or oxygen in the aromatic ring system are found in creosotecontaminated groundwater. NSO are highly water-soluble, toxic, and have adverse organoleptic characteristics. SPME is a fast, simple, and solvent-free sample preparation technique that involves exposing a polymer coated fiber to a sample to extract contaminants. Different fiber coatings were tested, and polyacrylate was found to extract NSO in the highest amounts and to be most versatile. Extraction was strongly enhanced by salting. The optimized SPME method combined with CGC coupled to an ion trap mass spectrometer (ITMS) has detection limits of 20–40 ng/L for the semi-volatile and 1–10 μg/L for the volatile NSO, response linear with respect to concentrations over three orders of magnitude, and precision of 3–14% relative standard deviation. The method was evaluated using real creosote-contaminated groundwater samples and feasibility was demonstrated. SPME-CGC/ITMS allows an unequivocal identification and quantification at a low NSO level in environmental samples.