分子氧/醛/过渡金属盐体系选择性氧化二苯硫醚的研究(英文)

在温和的反应条件和三氧化二铁或三氧化二钴存在下 ,结合使用分子氧和正戊醛以及采用“一步法”的方式 ,可有效和选择性地发生二苯硫醚氧化成相应的亚砜或砜的反应。与传统的氧化剂相比 ,此方法更安全和简便。     

Ti-MWW分子筛催化叔丁基过氧化氢氧化脱硫

以Ti-MWW为催化剂,考察了不同氧化剂对分别含有苯并噻吩、二苯并噻吩和4,6-二甲基二苯并噻吩等有机硫化物模拟油品氧化反应的影响,结果表明,叔丁基过氧化氢对有机含硫化合物的氧化活性明显高于过氧化氢水溶液。以叔丁基过氧化氢为氧化剂,三种噻吩类含硫化合物氧化的难易顺序为二苯并噻吩> 4, 6-二甲基二苯并噻吩> 苯并噻吩,其氧化活性顺序与含硫化合物中硫原子的电子云密度和空间位阻有关。考察了Ti-MWW/叔丁基过氧化氢催化氧化体系对成品柴油的催化氧化脱硫,结果表明,成品柴油中的含硫化合物可被有效地氧化脱除,在优化的反应条件下,经过两次氧化、萃取后,成品柴油中的总硫含量从1015μg/mL降低至11μg/mL,总脱硫率达到99%。     

CeO2/NaY催化剂的氧合及其催化氧化脱硫性能

采用等体积浸渍法制备了一系列CeO₂/NaY催化剂,重点考察了焙烧温度和铈负载量对催化剂活性组分结构及性能的影响。通过拉曼（Raman）光谱、X射线衍射（XRD）、低温N₂吸附-脱附（BET）、高分辨透射电子显微镜（HR-TEM）以及氢气程序升温还原（H₂-TPR）等技术对催化剂的结构、形貌和化学性能进行了表征分析。结果表明,焙烧温度与铈负载量对于铈物种在分子筛载体表面及孔道内的分散形态和与载体的相互作用有着重要影响,进而影响催化剂中铈物种的氧合性能与氧化脱硫性能。在常温常压下的氧合性能测试,催化剂最大储氧量为每克催化剂1.44 mmol O₂。在反应温度100 ℃,催化剂用量0.20 g,以正辛烷为溶剂二苯并噻吩初始浓度为500 μg·g^-1的模拟油样20 mL,氧气流量为50 mL·min^-1的条件下,反应240 min二苯并噻吩转化率可达90.10%,二苯并噻吩被氧化为二苯并噻吩砜。因此,发展稀土改性分子筛催化剂,应用于以分子氧为氧化剂的油品氧化深度脱硫,对探究绿色高效的油品氧化脱硫技术具有积极意义。     

模拟油品氧化脱硫及反应动力学研究

在H₂O₂/WO₃/ZrO₂氧化体系中对以甲苯为溶剂、二苯并噻吩(DBT)为模型含硫化合物的模拟油品(硫的质量分数为1540×10^-6)进行了氧化脱硫研究,考察了反应温度、反应时间、氧化剂加入量、催化剂用量对DBT转化率的影响。实验结果表明,在反应温度50℃,反应时间90min,氧化剂加入量油/H₂O₂的体积比为20∶1和催化剂用量0.02g/mL的适宜氧化脱硫条件下,96%以上的DBT氧化为容易分离脱除的二苯并噻吩砜(DBTOs);同时研究了DBT氧化反应动力学,得知DBT氧化反应为一级反应,表观活化能E_a为55.37kJ/mol,指前因子A为3.35×10⁷min^-1。     

Ti-HMS催化氧化脱除模拟燃料中的硫化物

 将噻吩、苯并噻吩、二苯并噻吩和4,6-二甲基二苯并噻吩(DMDBT)分别溶于正辛烷配成模拟燃料,以Ti-HMS为催化剂,以H2O2为氧化剂,对模拟燃料的氧化脱硫进行了研究,考察了Ti-HMS的催化活性及硅/钛比和结晶度对催化剂活性的影响. 结果表明,在Ti-HMS上硫化物氧化的难易顺序是由噻吩环上硫原子的电子云密度和硫化物分子的空间位阻共同决定的; 氧化反应发生在分子筛孔道内,骨架钛原子为活性中心; DMDBT在Ti-HMS上的氧化脱除效果比在TS-1,Ti-β或Ti-MCM-41上好. 随着Ti-HMS中硅/钛比的增大,DMDBT的脱除率降低; 随着Ti-HMS分子筛结晶度的升高,DMDBT的脱除率升高.     

MoO3/介孔Al2O3催化氧化脱除模拟油中的硫

以环己烷为溶剂,二苯并噻吩（DBT）、苯并噻吩（BT）、4,6-二甲基二苯并噻吩（4,6-DMDBT）、噻吩（Th）作为模型含硫化合物配制成模拟油,在MoO3/介孔Al2O3-H2O2体系中对模拟油催化氧化脱硫进行了研究. 考察了MoO3负载量、氧化剂用量、催化剂用量、氧化反应温度及反应时间对DBT脱除效果的影响. 实验结果表明：在MoO3负载量为20%,催化剂用量为1.5%,氧化剂H2O2与模拟油中硫的摩尔比为4,反应温度为60℃,反应时间为40分钟时DBT脱除率最高,达99.4%,几乎可以被完全脱除;在此条件下模型化合物的氧化反应活性顺序为：DBT > 4,6-DMDBT >BT>Th.     

过氧化氢选择性氧化硫醚的研究进展

亚砜和砜类化合物具有广谱生物活性而有广泛的应用前景,同时作为有机合成的重要中间体广泛应用于碳-碳键形成、分子重组反应中.硫醚直接氧化是制备亚砜和砜的主要方法之一.在众多关于硫醚选择性氧化反应的研究中,过氧化氢作为清洁氧化剂备受关注.鉴于此,就过氧化氢选择性氧化硫醚反应中的重要金属催化体系和一些非金属催化体系的研究状况作一综述,简要介绍各类催化氧化体系的催化效果.     

Ti-MWW催化氧化脱除轻油中苯并噻吩和二苯并噻吩

 以Ti-MWW为催化剂,研究了轻油中的有机硫模型化合物苯并噻吩和二苯并噻吩的氧化脱除. 结果表明,在343 K和乙腈为溶剂的条件下,苯并噻吩的转化率可达100%, 二苯并噻吩的转化率可达95%以上. 溶剂对苯并噻吩的氧化有很大影响,在相同的反应条件下,三种溶剂中苯并噻吩的转化率为乙腈＞甲醇＞水. 讨论了Ti-MWW催化氧化苯并噻吩的反应历程和溶剂效应.     

N-氟代双苯磺酰胺作为氧化剂制备二硫化合物的研究（英文）

建立了一种以N-氟代双苯磺酰胺(NFSI)为氧化剂合成二硫化合物的新方法.该方法反应温和、操作简便、反应时间短并无过度氧化的副产物(亚砜或砜类化合物)生成.     

添加磷钨酸的离子液体萃取催化氧化脱硫研究

研究了以3-辛基-1-甲基咪唑四氟硼酸盐离子液体(C_8mimBF_4)为萃取剂,磷钨酸(H_3PW_(12)O_(40))为催化剂,质量分数为30%的过氧化氢(H_2O_2)为氧化剂,将模拟油中的特征硫化物苯并噻吩(BT)氧化成相应砜类物质的萃取催化氧化脱硫(ECODS)过程。通过正交试验确定其最佳反应条件:反应温度40℃、氧硫摩尔比8:1、H_3PW_(12)O_(40)与硫摩尔比8:100、萃取剂与模拟油体积比1:10、反应时间60min,在此条件下BT模拟油的脱硫率可达95.72%。同时在最佳反应条件下考察了该ECODS体系对其他类型硫化物为底物的模拟油的脱硫性能,实验结果表明几乎可以完全除去二苯并噻吩(DBT)和4,6-二甲基二苯并噻吩(4,6-DMDBT)。由正交试验极差可知,各因素对BT模拟油ECODS影响的优先顺序为:催化剂用量反应时间反应温度氧硫摩尔比剂油比。动力学实验结果表明BT氧化符合拟一级动力学模型,并计算了反应速率常数和半衰期。     

Photocatalytic reduction of nitrite to dinitrogen in aqueous suspensions of metal-loaded titanium(IV) oxide in the presence of a hole scavenger: an ensemble effect of silver and palladium co-catalysts

Nitrite (NO(2)(-)) was photocatalytically reduced to dinitrogen (N(2)) in an aqueous suspension of two kinds of titanium(iv) oxide particles loaded with palladium and silver (Pd-TiO(2) and Ag-TiO(2)) at pH 8 under irradiation of UV light in the presence of sodium oxalate as a hole scavenger. The two metal-loaded TiO(2) photocatalysts had different roles in conversion of NO(2)(-) to N(2) and worked in an effective ensemble without conflict: (1) Pd-TiO(2) induced photocatalytic disproportionation of NO(2)(-) to N(2) and nitrate (NO(3)(-)) and (2) Ag-TiO(2) selectively reduced the thus-formed NO(3)(-) back to NO(2)(-) (partially to N(2)) with oxalate acting as a hole scavenger. When Pd-TiO(2) was used alone for NO(3)(-) reduction in the presence of sodium oxalate, Pd-TiO(2) induced fruitless photocatalytic decomposition of oxalate to carbon dioxide and dihydrogen. The presence of Ag-TiO(2) suppressed the fruitless decomposition of oxalate by Pd-TiO(2) because Ag-TiO(2) continuously provided NO(2)(-) in the reaction system using oxalate as a hole scavenger and Pd-TiO(2) therefore only worked as a photocatalyst for disproportionation of NO(2)(-) to N(2) and NO(3)(-) as it did when used alone.     

Monolayers (Langmuir films) behavior of multi-component systems composed of a bile acid with different sterols and with their 1:1 mixtures

Different physicochemical properties of Langmuir films (monolayers) composed of 10 mixed systems of a bile acid, deoxycholic acid (DC) with various plant sterols, such as stigmasterol (Stig), beta-sitosterol (Sito) and campesterol (Camp) and a stanol, cholestanol (Chsta) in addition to an animal sterol, cholesterol (Ch) [these sterols and Chsta are abbreviated as St] and DC with 1:1 St mixtures; (Ch+Chsta), (Ch+Stig), (Stig+Chsta), (Ch+Sito) and (Ch+Camp) on the substrate of 5M aqueous NaCl solution (pH 1.2) at 25 degrees C, were investigated in terms of mean surface area per molecule (A(m)), the partial molecular area (PMA), surface excess Gibbs energy (DeltaG((ex))), interaction parameter (I(p)) as well as activity coefficients (f(1) and f(2)) in 2-D phase of each binary (or ternary) component system and elasticity (Cs(-1)) of formed films; these were analyzed on the basis of the respective surface pressure (pi) versus A(m) isotherms as a function of mole fraction of Sts (X(st)) in the DC/St(s) mixtures at discrete surface pressures. Notable findings are: (i) all the binary component systems did form patched film type monolayers consisting of (a) DC-dominant film solubilizing a trace amount of St molecules and (b) St dominant film dissolving a small amount of DC molecules, (ii) DC in 2-D phase exhibited a transition from LE film to LC film at a constant pressure (pi(C)(1)) accompanied by compression and (iii) DeltaG((ex)) as well as I(p) was found to be greatly dependent on (a) the combinations of DC with different St species and (b) to be markedly varied by a difference in mixing ratio of DC to Sts. Compressibility (or elasticity) analyses and fluorescence microscopy images could support the above findings as well as interpretation.     

Thermal decomposition and burning behavior of cellulose treated with ethyl ester phosphoramidates: Effect of alkyl substituent on nitrogen atom

This research explores the structural effect of phosphoramidates as flame retardants (FRs) for cotton cellulose. Flame retardant (FR) and thermal decomposition actions of phosphate such as triethyl phosphate (TEP), primary phosphoramidate such as diethyl phosphoramidate (DEPA) and secondary phosphoramidates such as phosphoramidic acid, N(2-hydroxy ethyl) diethylester (PAHEDE), diethyl ethyl phosphoramidate (DEEP) and diethyl 2-methoxyethylphosphoramidate (DEMEP) on cotton cellulose were investigated. Limiting oxygen index (LOI) of treated cotton cellulose showed that all phosphoramidates exhibited better flame retardant properties as compared to TEP. Secondary phosphoramidate PAHEDE had better flame retardant properties as compared to DEMEP and DEEP which indicate that flame retardancy of secondary phosphoramidates is structure related. Test performed on pyrolysis combustion flow calorimeter (PCFC) for treated cellulose showed higher reduction in heat of combustion for efficient FRs (PAHEDE, DEPA). Evolved gas analysis using thermogravimetric analyzer-Fourier transform infrared spectroscopy (TGA-FTIR) and thermogravimetric analyzer-mass spectrometer (TGA-MS) of treated cellulose showed that phosphoramidates could catalyze the dehydration and char formation of cellulose at a lower temperature. The enhanced flame retardant action of phosphoramidate may be due to the catalytic thermal decomposition of the phosphoramidate structure to produce acidic intermediates which could react with cellulose to alter its thermal decomposition.     

Photodissociation of propargyl bromide and photoionization of the propargyl radical

Velocity map imaging was used to study the 193 nm photodissociation of propargyl bromide C(3)H(3)Br as well as the photoionization dynamics of the resulting propargyl radical C(3)H(3). Images were recorded by using single-photon vacuum ultraviolet ionization of the propargyl radical and by using two-photon resonant, three-photon ionization of the ground state Br((2)P(32)) and spin-orbit excited Br(*)((2)P(12)) atoms. Analysis of these data allowed the determination of the branching ratio Br:Br(*) as well as the photofragment angular distributions. Images of C(3)H(3) produced by the photodissociation of both C(3)H(3)Br and C(3)H(3)Cl were recorded at several energies between 8.97 and 9.12 eV, as well as at 9.86 eV, and showed no obvious internal energy dependence of the relative photoionization cross sections.     

Orbital phase control of the preferential branching of chain molecules.

The orbital phase theory was applied to the stabilities of the branched isomers (1) of E(4)H(10) (E = C, Si, Ge, Sn) relative to the normal ones (2). The orbital phase prediction was confirmed by ab initio molecular orbital (MO) and density functional theory (DFT) calculations as well as by some experimental results. Further applications to the relative stabilities of other alkane and alkene isomers lead to the preference of the branched to the normal isomers, the neopentane-type to isobutane-type branching, the terminal to inner methyl branching, and the methyl to ethyl inner substitution in the longer alkanes, as well as the preference of isobutene to 2-butene moieties. The preferential stabilization of the branched isomers was shown to be general and controlled by the orbital phase.     

Effect of the rutile content on the photovoltaic performance of the dye-sensitized solar cells composed of mixed-phase TiO2 photoelectrodes

The effect of the rutile content on the photovoltaic performance of dye-sensitized solar cells (DSSCs) composed of mixed-phase TiO(2) photoelectrode has been investigated. The mixed-phase TiO(2) particles with varied amounts of rutile, relative to anatase phase, are synthesized by an in situ method where the concentration of sulfate ion is used as a phase-controlling parameter in the formation of TiO(2) using TiCl(4) hydrolysis. The surface area (S(BET)) varies from 33 (pure rutile) to 165 (pure anatase) m(2) g(-1). Generally, both the current density (J(sc)) and photo-conversion efficiency (η) decrease as the rutile content increases. The incorporation of rod-shaped rutile particles causes low uptake of dye due to the reduced surface area, as well as slow electron transport in less efficiently-stacked structure. However, maximum J(sc) (14.63 mA cm(-2)) and η (8.69%) appear when relatively low rutile content (16%) is employed. The reported synergistic effect by the efficient interparticle electron transport from rutile to anatase seems to overbalance the decrease of surface area when small amount of rutile particles is incorporated.     

柏子养心丸的毛细管电泳指纹图谱

建立了柏子养心丸(Baizi Yangxin Wan, BZYXW)毛细管区带电泳指纹图谱(CEFP)。采用三棱柱优化法优化背景电解质(BGE),以色谱指纹图谱分离量指数(RF)为实验条件优化的目标函数,最终确定BGE为50 mmol/L硼砂-50 mmol/L磷酸氢二钠-200 mmol/L硼酸-150 mmol/L碳酸氢钠(体积比为7:7:1:1,含4%乙腈,pH 9.70)。在其他优化的毛细管电泳条件为紫外检测波长228 nm,运行电压12 kV,重力进样25 s (高度14 cm)条件下,采用未涂层石英毛细管(70 cm(有效分离长度57 cm)×75 μm)分离,以阿魏酸峰为参照,确定了17个共有指纹峰。对样品聚类分析后用其中9批生成对照CEFP(RCEFP),以其为标准,用系统指纹定量法鉴别出12批BZYXW质量为: 3批好,1批良好,3批中,1批一般,4批劣。三棱柱优化法为BGE选择提供了重要参考,建立的BZYXW-CEFP精密度好、重现性高,可用于BZYXW的质量控制。     

Transformations of mercury species in the presence of Elbe river bacteria

The influence of Elbe river bacteria isolated from suspended particulate matter (SPM) on dynamic species transformation of mercury was investigated. Experiments were carried out in the presence of bacteria (batch cultures) and in sterile tapwater as a control. For the methylation of inorganic mercury ions by bacteria several cofactors are under discussion. In this work, methylcobalamin, methyl iodide and S-adenosylmethionine were tested as biogenic methyl donors and trimethyl-lead chloride, trimethyltin chloride and dimethylarsenic acid as abiotic methyl donors. Transmethylation reactions as examples of abiotic methyl transfers have higher effectiveness in the formation of methylmercury (CH₃Hg⁺) than methylation with biogenic compounds. This result was observed in batch cultures as well as in sterile water. SPM-bacteria inhibit methyl transfer to mercury(II) ions. This is not only due to passive adsorption processes of mercury(II) to bacterial cell walls; methylmercury is also decomposed very rapidly by SPM-bacteria and is immobilized as mercury(II) by the cells.     

The use of organometallic transition metal complexes in the synthesis of shaped carbon nanomaterials

A review of the use of organometallic complexes in the synthesis of shaped carbon nanomaterials (SCNMs), in particular carbon nanotubes (CNTs) has been undertaken. This review reveals that a limited number of organometallic complexes have been used as catalysts (typically ferrocene, Fe(CO)₅) to make carbon materials that have distinctive shapes. Depending on the reaction conditions employed, ferrocene can be used to synthesize single walled (SWCNTs), double walled (DWCNTs) and multiwalled nanotubes (MWCNTs) as well as fibres and other SCNMs. The type of reactor used as well as the reaction conditions (temperature, pressure, gas flow rates, etc.) and the presence of hydrogen and heteroatoms (N, O, S, P, etc.) also play a role in determining the final carbon types (and their sizes) that have been synthesized. The influence of the various chemical and physical factors on the carbons produced are discussed. The current mechanism used to explain the formation of CNTs is described.