CdS修饰TiO2纳米带制备及光催化降解有毒有机污染物

以硫酸钛为原料,在210℃低温下,水热制备TiO₂纳米带.通过沉淀法用CdS修饰TiO₂纳米带表面,制得TiO₂@CdS复合光催化剂,采用XRD、TEM和反射紫外对其结构及光化学特性进行初步表征.以可见光(λ≥450 nm)光催化降解罗丹明B(Rhodamine B,RhB)、水杨酸(Salicylic Acid,SA)及2,4-二氯苯酚(2,4-Dichlorophenol,2,4-DCP)为探针反应,研究反应温度、介质和负载CdS对TiO₂@CdS结构性能的影响.结果表明,所制备的TiO₂纳米带分散性好.复合粉末由锐钛矿相TiO₂和立方相CdS组成.常温25℃中性介质中用CdS修饰的TiO₂的活性,在可见光照射下,为单纯TiO₂纳米带的29倍.同时,TiO₂也促进了CdS可见光光催化活性的提高.通过跟踪降解体系紫外-可见光谱(UV-vis)、红外光谱(FTIR)和总有机碳(TOC)测定,结果发现TiO₂@CdS/vis体系在pH 7.0时,对SA的降解率较TiO₂纳米带有显著地提高,反应15 h和21 h后,RhB和2,4-DCP的矿化率分别可达到47.8%和30.8%.     

Hg掺杂CdS的制备及可见光降解有毒有机污染物

采用镉硫共沉淀方法制备了Hg掺杂CdS(Hg_xCd_1-xS)光催化剂,运用X射线衍射法(XRD)、X射线光电子能谱(XPS)、透射电镜(TEM)和紫外-可见吸收光谱对所制备的催化剂进行了表征;利用可见光催化降解罗丹明B(Rhodi-amine B,RhB)和2,4-二氯苯酚(2,4-dichlorophenol,2,4-DCP)为探针反应,对Hg_xCd_1-xS可见光催化活性进行了研究,通过跟踪RhB降解过程中吸收光谱的变化和总有机碳(TOC),评价了Hg_xCd_1-xS对有机物的氧化降解及深度矿化能力.结果表明:Hg_xCd_1-xS催化剂为立方晶型,Hg的最佳掺杂量为5%,其禁带宽度约为2.15 eV,对RhB和2,4-DCP均有较好的降解效果,实验条件下30 min RhB褪色率为100%,RhB的30 h矿化率为45.5%,2,4-DCP的16 h降解率达55%.Hg_xCd_1-xS可见光光催化降解RhB具有较高的稳定性,Hg的掺杂能有效降低CdS光腐蚀问题.通过ESR跟踪测定光催化反应过程中产生的自由基,表明降解过程涉及·OH机理.     

铕掺杂TiO2的制备及其可见光光催化性能研究

采用溶胶-凝胶法制备了不同铕(Eu)掺杂量的TiO₂纳米颗粒(Eu-TiO₂),利用透射电镜(TEM),X射线光电子能谱(XPS),X射线衍射(XRD)及紫外可见漫反射(UV-Vis DRS)等方法对Eu-TiO₂进行了物理特性的初步表征.结果表明:与未掺杂纳米TiO₂比较,Eu-TiO₂禁带宽度变窄,具有可见光光催化活性.在可见光下(λ≥420 nm)照射下,以光催化降解染料罗丹明B(Rhodamine B,RhB)为目标反应,探讨了Eu-TiO₂不同制备条件对RhB降解光催化活性的影响,优化得到制备高活性Eu-TiO₂最佳pH为3、掺杂比例(n_Eu/n_Ti)为0.05%、煅烧温度为500 ℃.研究了可见光照射下Eu-TiO₂降解RhB和无色有机小分子水杨酸(SA)光催化反应条件及降解特性,RhB的12 h深度氧化矿化率为60.2%,SA的8 h降解率达到100%.通过跟踪测定可见光下Eu-TiO₂光催化反应过程中氧化物种的变化,研究了可见光激发Eu-TiO₂光催化反应机理,表明其光催化反应主要涉及羟基自由基(·OH)历程.     

TiO2的低温制备及其对有毒有机污染物的降解

溶胶水热法制备了TiO₂粉末,用X射线衍射仪(XRD)、比表面积及孔径分析仪(BET)和透射电镜(TEM)对TiO₂进行了初步表征,结果显示:纳米TiO₂主要为锐钛矿相(含板钛矿相(121)),比表面积为106.2 m²/g.在紫外光(λ≤387 nm)照射条件下,以有机染料罗丹明B(Rhodamine B,RhB)和无色小分子2,4-二氯苯酚(2,4-dichlorophenol,2,4-DCP)的紫外光(λ≤387 nm)光催化降解试验为探针反应,低温(50℃)下制备的TiO₂粉末具有较高光催化活性,对RhB和2,4-DCP有较好的降解效果.通过分析紫外-可见光谱(UV-Vis)、红外光谱(FTIR)和总有机碳(TOC)测定,发现TiO₂/UV体系能使RhB和2,4-DCP发生有效的降解,反应5 h后RhB和7 h后2,4-DCP的矿化率分别达到81.2%和86.8%.同时,采用辣根过氧化物酶(POD)、N,N-二乙基对苯二胺(DPD)分光光度法和苯甲酸荧光光度法分别测定了在降解过程中H₂O₂和羟基自由基(.OH)的变化,表明TiO₂光催化机理涉及到.OH历程.     

g-C3N4/Fe3O4/BiOI磁性材料的制备及其可见光助芬顿催化性能

采用共沉淀-回流法制成g-C₃N₄/Fe₃O₄/BiOI磁性复合材料作为异相光助芬顿(Fenton)催化剂。运用扫描电镜(SEM)、透射电镜(TEM)、X-射线衍射(XRD)、振动样品磁强计(VSM)和N₂吸附-脱附等手段分别对催化剂的形貌、结构、组成、磁性和比表面积等进行了表征，并以罗丹明B(RhB)为模型污染物考察了材料的可见光催化性能。实验结果表明，当BiOI的负载质量为50%时，在可见光照射下，复合材料具有最好的光催化性能，180 min内对RhB的降解效率可达到99.20%。较高的光催化性能归因于所制备材料对RhB较强的吸附、强烈的可见光响应以及异质结构促进了光生载流子的分离。进一步在光催化体系中加入适量的H₂O₂后，可极大提高三元复合材料可见光助Fenton降解RhB的效率，30 min内即可达到98.44%,这得益于体系中发生Fenton反应产生较多具有强氧化性的羟基自由基，同时光生电子可加速Fe³⁺     

可见光/Fenton光催化降解有机染料

采用Fenton试剂(Fe³⁺/H₂O₂)在可见光条件下(λ＞450nm)光催化降解目标染料化合物罗丹明B(RhodamineB,RhB).在pH＜3.0体系中用可见光照射,能使RhB染料在光敏化作用下有效降解,反应160min后矿化率达到71.8%.采用ESR和溴甲酚绿(Bromocresolgreen,BCG)法跟踪测定活性氧化物种,通过对RhB降解过程的紫外-可见光谱、红外光谱分析及总有机碳量(TOC)跟踪测定,结果表明,Fe³⁺/H₂O₂/RhB体系在可见光照射下主要的活性氧化物种为羟基自由基,能有效地降解RhB.     

异相Fenton光催化对有毒有机污染物的降解

以蒙脱石-K10(Montmorillonite K10)作为Fe3 的载体制备异相Fenton催化剂(Mot-Fe),并用此催化剂在可见光(λ>420 nm)照射下研究其降解染料罗丹明B(Rhoda-mine B,RhB)和2,4-二氯苯酚(2,4-Dichlorophenol,DCP)。研究表明,选定的Mot-Fe/H2O2体系能有效地降解RhB,反应300 min脱色完全,总有机碳(TOC)去除率达85.2%,反应过程中主要涉及到.OH自由基的产生和参与。可见光照射下,对DCP/Mot-Fe/H2O2体系,TOC的去除率达到51.6%。催化剂具有比较好的稳定性,能够重复使用。     

非水溶性席夫碱铁疏水异相光催化降解有毒有机污染物

通过化学方法合成了疏水性金属有机复合物双（水杨醛）邻苯二胺席夫碱铁（Fe-Bis-Schiff-base- salicylaldehyde-o-Phenylenediamine,Fe-SPA）。在水溶性介质体系中,以Fe-SPA疏水特性作为异相光催化剂降解有毒有机污染物,在pH 7.2介质,可见光（λ>420nm）照射下,通过Fe-SPA活化H2O2降解有毒有机污染物罗丹明B（Rhodamine B,RhB）、亚甲基蓝（Methylene Blue trihydrate,MB）和2,4-二氯苯酚（2,4-Dichlorophenol,2,4-DCP）,研究了Fe-SPA的光催化特性。在实验条件下,反应150min RhB褪色完全,反应300min MB 褪色完全,反应10h DCP降解率达到65%。采用ESR（电子顺磁共振）跟踪测定活性氧化物种,检测到催化体系中产生了高氧化活性羟基自由基。通过RhB体系降解过程中的紫外-可见光谱和红外光谱分析,表明目标底物有效降解且最终转化为胺类和羧酸类小分子。在水溶性介质体系中,Fe-SPA以疏水特性作为异相光催化剂具有良好的稳定性,循环使用5次,光催化活性基本稳定。     

共沉淀法制备Ag/AgCl-TiO2空心复合纳米微球及其光催化性能

通过甲基丙烯酸与苯乙烯聚合制备了表面负电性的聚苯乙烯(PSt)纳米乳胶粒. 在乙醇与水的混合溶剂中, 用硅烷偶联剂乙烯基三甲氧基硅烷对其进行表面改性后加入钛酸四丁酯、 氯化钠和硝酸银, 以PSt乳胶粒为模板采用共沉淀法制备了PSt-AgCl-TiO₂复合微球. 在180 ℃对其进行液相预处理及煅烧去除PSt模板后制备了Ag/AgCl-TiO₂空心复合粒子. 对各阶段产物的形貌、 晶体结构和比表面积等进行了表征. 结果表明, 所得产物为Ag/AgCl与锐钛矿型TiO₂复合的空心粒子, 其比表面远大于商品TiO₂(P25). 考察了Ag/AgCl-TiO₂复合粒子在紫外光与可见光下对罗丹明B(RhB)降解的催化活性. 结果表明, 在紫外光下n(Ag)/n(Ti)=0.1%的Ag/AgCl-TiO₂复合粒子活性最高, 30 min时对RhB的降解率比不含Ag/AgCl的TiO₂空心微球提高了13%; 虽然Ag/AgCl-TiO₂在可见光下的催化活性远比紫外光下低, 但与纯TiO₂空心纳米微球相比其催化活性仍明显增强. n(Ag)/n(Ti)=2.0%的Ag/AgCl-TiO₂复合粒子催化活性最高, 120 min时对RhB的降解率比不含Ag/AgCl的TiO₂空心微球提高了38%.     

Keggin型铬取代的磷钨杂多阴离子/二氧化钛纳米膜光催化剂的制备及可见光催化性能

以钛酸四丁酯Ti(OC₄H₉)₄为TiO₂前驱体,Keggin型铬取代的杂多阴离子PW₁₁Cr为可见光活性组分,采用溶胶-凝胶提拉法在玻片表面制备了PW₁₁Cr/TiO₂纳米膜光催化剂,并用UV-Vis DRS、IR、XRD、SEM和TEM等技术手段对催化剂的光吸收性质、化学组成、晶相和表面结构形貌等进行了表征;讨论了膜中PW₁₁Cr和TiO₂相互作用的方式;以染料模型污染物RhB的可见光催化降解为探针,评估了PW₁₁Cr/TiO₂光催化剂的可见光催化活性,讨论了光催化反应机理,并与TiO₂的光催化反应机理进行了比较;考察了焙烧温度、PW₁₁Cr剂量和溶液pH值对光催化活性的影响;最后用RhB的循环降解实验评估了催化剂的光催化稳定性。 实验结果表明,PW₁₁Cr/TiO₂光催化剂对可见光有明显吸收,较低焙烧温度(100 ℃)下得到的膜为无定形结构,而较高焙烧温度(500 ℃)为纳晶结构;前者的光催化活性较高,在200 W金卤灯照射下降解10 μmol/L RhB,120 min的降解率为95%,4 h的COD去除率为72%;羟基自由基是导致RhB降解的主要氧活性物质;低的膜处理温度,高的PW₁₁Cr负载量和溶液酸性有利于提高PW₁₁Cr/TiO₂膜的光催化活性;经循环重复使用10次,PW₁₁Cr/TiO₂膜的光催化活性仅有较少损失。     

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.