ZnO·WO3悬浮水溶液中SO2的光催化氧化

本文考察了ZnO·WO₃悬浮水溶液中污染物SO₂的可见光催化氧化并建议通空气处理较高浓度的SO₃^2-扩水溶液。含0.15mol/LSO₃^2-水溶液可见光照2h可将SO₃^2-基本上光催化氧化成SO₄^2-。对这光助SO₃^2-自发氧化反应中可能平行存在的自发、多相催化、光化学和光催化等反应进行实验对比;筛选出克分子比0.5ZnO·WO为最佳掺杂配比;考察了光催化剂热处理、空气流量、pH对光催化活性的影响,得出pH7.5为最佳值;太阳光催化SO₃^2-氧化速率比室内实验更快,展现了利用太阳能于环保的应用前景,对所有实验结果都给以理论解释,并提出一个较详细的反应机理。     

过渡金属酸盐在催化反应中的应用

过渡金属酸盐因其催化性能优良、价格低廉、容易获得、毒性低、稳定性良好等特点,成为广受关注的一类催化剂。金属酸盐是指一类含有配合物阴离子的离子型化合物,其配合物阴离子包括中心金属和与其相配位的多个配体基团:中心金属为过渡金属元素,配体为氧离子(金属氧酸盐,如WO₄^2-, PMo₁₂O₄₀^3- 等)、硫离子(硫代金属酸盐,如MoS₄^2- 等)或卤素离子(卤代金属酸盐,如PtCl₆^2-, TiF₆^2-等)。通过改变中心过渡金属元素和抗衡阳离子的组成,可在分子水平上对金属酸盐进行性能调控。但过渡金属酸盐在催化领域中的研究多集中于金属氧酸盐,本综述则涵盖了包括金属氧酸盐、硫代金属酸盐、氰基金属酸盐和卤代金属酸盐等多种过渡金属酸盐作为催化剂在催化反应中的应用。另外,本文还着重介绍了过渡金属酸盐催化剂与离子液体结合使用,从而实现其循环使用的研究。     

大黄素的电化学氧化还原机理研究

本文利用循环伏安法(CV)、红外光谱循环伏吸法(CVA)和导数循环伏吸法(DCVA)研究大黄素(Q)在乙腈溶剂中的电子转移机理.Q的还原过程中阴离子自由基Q^?-会结合中性分子Q生成二聚物Q₂^?-.Q₂^?-在更负的电位下进一步还原为Q₂^2-.当扫描范围为-0.2 ~ -2.0 V时,经过一个循环伏安过程,在扫描结束物质并没有回到反应物Q,而是Q₂^2-. Q₂^2-会继续发生电化学反应,经历两步一电子过程,分别生成Q₂^3-. 和Q₂^4-.,对应CV图中峰C₃和C₄.当扫描范围扩大至1.0~-2.0 V时,在更正的电位下,观察到两个新的氧化峰A₁和A₂,该范围内的三圈扫描结果表明,在扫描结束物质重新氧化回到Q.当扫描范围缩小至0.3 ~ -1.4 V,A2峰随着扫描圈数的增加而增大,与A2峰对应的氧化产物Q₂^?-在溶液中不断积累.A1峰对应于Q₂^?-氧化回到Q.     

基于硫酸根自由基的先进氧化活化方法及其在有机污染物降解上的应用

基于硫酸根自由基(SO₄^.-)的先进(高级)氧化法(AOPs)因其对新型有机污染物的高降解能力和高适应性而受到越来越多的关注。相比羟基自由基(·OH),SO₄^.-的选择性更好、还原电位更高、半衰期更长、pH范围更宽且成本更低,因而能更有效的降解污染物。SO₄^.-可由过一硫酸盐(PMS)或过二硫酸盐(PDS)等过硫酸盐(PS)通过热、机械化学、过渡金属、碳质材料、碱、紫外(UV)或电化学等方法活化产生。本文分析了不同活化方法的优缺点及其应用于有机污染物降解上的研究进展,总结了SO₄^.-降解含不同官能团污染物的三种机理(加成作用、夺氢作用和直接电子转移),并综述了SO₄^.-降解持久性有机污染物(POPs)、“伪持久性有机污染物”——药物和个人护理品(PPCPs)及有机染料三大类有机污染物的降解途径、降解产物及其研究进展,最后展望了该技术未来的研究方向。     

拉曼光谱法研究Na+, Mg2+//SO42-, Cl-, H2O四元体系中SO42-离子缔合结构特征及其变化规律

复杂水盐体系存在稳态和介稳固液相平衡以及复杂的成盐规律。为了解固液平衡状态下液相的结构特征,本文采用拉曼光谱技术并结合高斯-洛伦兹去卷积分峰拟合程序对Na⁺, Mg²⁺//SO₄^2-, Cl^-, H₂O四元体系及其二元和三元子体系中ν₁-SO₄^2-的离子缔合结构特征进行了分析。研究结果表明:SO₄^2-在Na₂SO₄-H₂O体系存在自由态SO₄^2-和SO₄^2-离子簇两种结构,在MgSO₄-H₂O, MgSO₄-MgCl₂-H₂O及Na⁺, Mg²⁺//SO₄^2-, Cl^-, H₂O等含镁体系中,还有Mg²⁺-H₂O-SO₄^2-和Mg²⁺-OSO₃^2-两种缔合结构。在二元和三元体系中ν₁-SO₄^2-的离子缔合结构以自由态SO₄^2-为主,随着SO₄^2-离子总浓度的变化,上述四种结构所占比例会发生规律性变化。Na⁺, Mg²⁺//SO₄^2-, Cl^-, H₂O四元体系在NaCl减少及等温蒸发过程中,自由态SO₄^2-结构比例逐步降低, Mg²⁺和SO₄^2-相结合形成Mg²⁺-H₂O-SO₄^2-或Mg²⁺-OSO₃^2-结构的机会增多,在复盐区还会形成SO₄^2-离子簇结构。由此判断溶液结构的适应性变化是导致介稳现象的重要原因。进一步的相关分析表明:SO₄^2-的浓度和耶涅克指数J与ν₁-SO₄^2-峰的峰强度和峰面积存在正相关关系, Mg²⁺浓度是影响ν₁-SO₄^2-峰中四种缔合结构的比例发生变化的主要因素。     

湿法脱硫浆液中Hg2+的还原机制研究

针对燃煤电厂湿法脱硫浆液中Hg²⁺易被还原的特性,研究Hg²⁺在模拟湿法脱硫系统中的迁移机制,考察了浆液温度、pH值以及SO₃^2-、Cl^-、Ca²⁺、Mg²⁺浓度等因素对Hg²⁺还原性能的影响。结果表明,Hg²⁺还原率随着浆液中SO₃^2-浓度的增大而降低;pH值对Hg²⁺的还原呈先增加后降低的趋势,在pH值为5.5时还原率最高;温度的升高不利于浆液中稳定的二价汞盐络合物存在,导致Hg²⁺还原率增加;Ca²⁺、Mg²⁺以及Cl^-浓度的增加有利于形成稳定化合物,从而抑制Hg²⁺的还原。     

Improved electrochemical properties in the Li3Fe2(PO4)3 by titanium and vanadium doping

Ti⁴⁺ ions were introduced to the VO₄^3- substituted Li₃Fe₂(PO₄)₃ by sol-gel method. Simultaneous substitution of Ti⁴⁺ for Fe³⁺ and VO₄^3- for PO₄^3- in the Li₃Fe₂(PO₄)₃ resulted in a net improvement in the rate capability and cycling performance, as compared with the single Ti⁴⁺ or VO₄^3- substituted compound.     

聚天冬氨酸-2-甲氧基苯氧基乙胺的合成及阻垢性能研究

环境友好型水处理剂是目前水处理剂研究的热点方向。以2-甲氧基苯氧基乙胺在水溶液中对聚琥珀酰亚胺(PSI)进行开环聚合制备了一种新型绿色高效的水处理剂聚天冬氨酸-2-甲氧基苯氧基乙胺聚合物(PASP-MPEA),利用红外光谱和核磁共振对其进行了表征。采用静态阻垢法评价了PASP-MPEA的阻垢性能。结果表明,该聚合物的阻垢性能较PASP显著提高,浓度为10 mg/L时,阻CaCO₃垢效率较PASP提高35%;4 mg/L时,阻CaSO₄垢效率接近100%。基于量子化学计算研究可知,其阻垢机理是该聚合物中富裕的电子给予体能与Ca²⁺络合,大大降低Ca²⁺与CO₃^2-和SO₄^2-等阴离子结合的几率,从而显示优异的阻垢性能。     

照相明胶与化学增感剂相互作用的XPS研究

本文采用X射线光电子能谱技术研究了两种照相明胶与化学增感剂相互作用的机理.当两种照相明胶样品在HAuCl₄溶液中反应5min后,明胶中的蛋氨酸、蛋氨酸亚砜均被氧化为蛋氨酸砜.与此同时,明胶吸附的大部分Au³⁺被还原为Au⁺,并且Au⁺以络合形态存在于明胶之中.根据与AuCl₃反应之后明胶中Au³⁺与Au⁺的比例,法国明胶的还原性略高于包头明胶.添加到明胶中的Na₂S₂O₃能将明胶大分子所含的蛋氨酸亚砜全部还原为蛋氨酸.S₂O₃^2-、蛋氨酸和蛋氨酸砜可以稳定共存于明胶体系之中,外加的S₂O₃^2-的还原性高于明胶中蛋氨酸、蛋氨酸亚砜的还原性.添加Na₂S₂O₃后的两种照相明胶均可以将其溶胀吸附的Au³⁺全部还原为胶态金.此时,参与氧化还原反应的主要基团是S₂O₃^2-而非明胶中的蛋氨酸残基.由于Na₂S₂O₃的添加,照相明胶对AuCl₃的还原能力增强.     

基于零价铝的氧化/还原技术在水处理中的应用

利用零价金属(ZVMs)处理环境污染物一直是环境治理领域的研究热点,其中以零价铁(ZVI)的研究最为广泛。近年来,零价铝(ZVAl)因其具有比ZVI更低的氧化还原电位(E⁰(Al³⁺/Al⁰)=-1.662 V, E⁰(Fe²⁺/Fe⁰)=-0.44 V)及其两性性质(反应pH可以拓展到碱性)而开始受到关注。目前环境领域关于ZVAl的研究主要集中于两类:以零价铝/氧/酸(ZVAl/O₂/H⁺)体系为核心的氧化体系和以零价铝/无氧(ZVAl/anaerobic)体系为核心的还原体系,其中前者因原位产生过氧化氢构成类Fenton氧化体系而备受关注。研究已发现,基于ZVAl的氧化/还原技术可有效去除酚类、偶氮染料、有机卤化物等有机污染物和Cr(Ⅵ)、As(Ⅲ)等无机污染物,且超声、微波、外加多金属氧酸盐(POM)、Fe²⁺等辅助手段对该技术有一定辅助效果。本文分别就基于ZVAl的氧化体系和还原体系,对其反应机理及去除水中污染物的国内外最新研究进展进行了综述和展望,以期促进ZVAl水处理技术的发展。铝作为地壳中最丰富的金属元素,ZVAl不存在像ZVI高pH值时产生沉淀的问题,相信随着ZVAl表面氧化膜这一制约因素的逐渐解决,其在水处理领域将有更广泛的应用。     

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.     

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.     

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.     

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.