混晶TiO2光催化剂的制备及机理研究

本文总结了混晶TiO₂光催化剂的各种制备方法,并将其分为两大类：一类是原位生成混晶,如水热法、溶剂热法、溶胶-凝胶法、微乳液-水热联用方法等;另一类是对两种晶型TiO₂材料进行物理混合或对锐钛矿进行高温煅烧,如溶剂混合-煅烧法、高温煅烧法等。其中,后者操作简单易行、对设备要求不高,但获得的混晶TiO₂易产生硬团聚,严重影响其光催化性能;在实际应用中前者制备的TiO₂材料更具优势。同时,本文还对混晶TiO₂光催化机理的研究历程进行了总结,并对其中存在的争议进行了评述。最后,展望了混晶TiO₂光催化剂在环境和能源领域中的应用。     

纳米二氧化钛/碳纳米管复合催化剂光催化性能及碳纳米管组分的作用

运用溶胶-凝胶及低温水热法合成纳米TiO₂/碳纳米管复合催化剂, 以甲基橙为目标降解物考察复合物的光催化活性. 运用X光衍射、透射电镜、Brunauer-Emmett-Teller低温氮气吸附、差热-热重分析及紫外-可见漫反射吸收光谱等表征催化剂. 结果表明, 与单纯纳米TiO₂相比, 溶胶-凝胶法制备的复合催化剂的光催化活性显著提高, 实验条件下复合的碳纳米管最适含量为3%(碳纳米管/TiO₂, 重量百分比), 复合催化剂经在缓和氧化气氛中焙烧处理可在保持碳纳米管热稳定前提下获得纳米TiO₂的充分晶化. 观察到了低温水热合成的复合催化剂的甲基橙降解活性的进一步提升, 复合催化剂中纳米TiO₂在碳纳米管表面分散均匀, TiO₂和碳纳米管组分间的紧密和充分键合及低温水热条件下催化剂的大比表面积、超细粒径以及碳纳米管的热稳定等有利于复合催化剂的光催化活性. 进一步地, 探讨了复合催化剂中适量碳纳米管组分的光活性促活机制.     

贵金属对TiO2悬浮液光照过程中H2O2形成的促进作用

众所周知,TiO₂是一种能进行光能-化学能转换的半导体材料.70年代初期,日本的Fujishima等人[1]发现TiO₂电极能利用光能将水分解为氢气和氧气.从此,TiO₂作为光能转换材料,在太阳能利用,环境保护,卫生医疗等许多领域逐渐引起研究人员的注目并相继在许多基础和应用方面得到了大量的研究^[2～5].     

均一、单分散二氧化钛系列球形胶体颗粒的可控制备研究

TiO₂作为一种重要的半导体材料,具有光催化活性高、化学性质稳定、折射率高等特性,因而在光催化、陶瓷、涂料、化妆品及光电子器件等领域有着十分广泛的应用前景.尤其是近年来,核-壳结构的复合颗粒以及空心和介孔TiO₂胶体颗粒的出现,使TiO₂材料增添了许多独特的优异性能,相应研究成为热点.     

TiO2-SiO2复合氧化物的制备及在液相氧化中应用的研究进展

TiO₂-SiO₂复合氧化物是一种新型催化剂,因其在液相氧化方面有着高效的催化能力,而逐渐受到广泛关注。本文详细介绍了近年来国内外TiO₂-SiO₂复合氧化物的制备方法（如化学沉淀法,溶胶-凝胶法,非水解溶胶-凝胶法和水热法）及其对复合氧化物材料孔结构,元素分布均匀程度影响的研究进展。同时总结了近年来TiO₂-SiO₂复合氧化物在催化氧化方面的应用,并提出了TiO₂-SiO₂复合氧化物今后研究需关注的问题。     

二氧化钛多孔材料及其性能研究进展

二氧化钛(TiO₂)多孔材料由于具有优异的物理化学性质,在催化、能源、传感等领域展现了重要的研究价值和应用潜力。 TiO₂的多孔结构特别在一些涉及异相反应的应用(如异相催化、气敏等)中具有重要的优势,如丰富的传质通道和表面活性位点、可调变的孔尺寸等。 目前,多孔TiO₂功能材料的开发和优化研究正在不断推进其工业化应用的进程。 本文围绕多孔TiO₂的几个优势应用领域(光催化、光生电子存储和气敏)的研究进展,从结构和缺陷设计出发介绍和讨论性能调控策略。 本文还特别介绍了本课题组通过光诱导合成法开发的一系列多孔TiO₂基功能材料,并对相关性能研究领域的关键问题进行了分析和展望。     

锂离子电池二氧化钛负极材料

锂离子电池是一种能量密度高、安全稳定和使用寿命长的储能器件,已广泛应用于移动电子设备和电动汽车等领域。二氧化钛(TiO₂)具有无毒害、价格低廉、储量大和化学结构稳定等优点,是一种具有应用前景的负极材料。然而,TiO₂的实际应用受限于自身较低电子电导率和锂离子(Li⁺)扩散系数。本文总结了TiO₂三种常见晶型的储锂机制(锐钛矿TiO₂两相固溶储锂机制、TiO₂(B)本征赝电容储锂机制和金红石TiO₂电位控制相变过程);针对其电子传导和Li⁺扩散能力的不足,详细综述了纳米结构维度设计、本征/非本征电子结构调控(元素掺杂、Ti³⁺自掺杂和高导电材料修饰)和异相结优化改性三方面的研究进展。最后展望了TiO₂材料在锂离子电池及其他二次电池领域的发展趋势和应用前景。     

TiO2光催化还原CO2

光催化还原CO₂技术在CO₂的治理与利用方面有着潜在的应用价值和良好的开发前景。该文简要综述了近年来用于光催化还原CO₂反应的TiO₂光催化剂材料,包括纯TiO₂催化剂、负载型TiO₂催化剂、金属改性TiO₂催化剂、半导体复合TiO₂催化剂和有机光敏化TiO₂催化剂等,并介绍了各类催化剂光催化还原CO₂的反应性能。     

粉末状和薄膜状TiO2对敌敌畏的光催化降解

在光照条件下,光催化剂TiO₂有很强的氧化能力,能有效降解水中的有机污染物^[1],因而日益受到人们的关注.目前,研究最多的胶体溶液和颗粒悬浮体系因其难于分离、回收而限制了实际应用,因此催化剂固定问题急需解决.近年来,国内外对TiO₂薄膜催化剂做了许多探索^[2,3],取得了一些进展.本文用溶胶-凝胶法制备了一种粉末状TiO₂光催化剂和两种薄膜型TiO₂光催化剂,并进行了结构和形貌的表征,对敌敌畏稀释液做了光催化降解实验,并与粉末状TiO₂进行对比.结果表明:薄膜TiO₂催化剂优于粉末TiO₂催化剂.     

无铅卤系钙钛矿纳米晶:新一代光催化材料

由于TiO₂光催化材料具有反应速度快、稳定性好、不产生二次污染等优点,常被应用于污染物降解、CO₂还原、制氢等领域,然而TiO₂可见光利用率低,限制了其进一步广泛应用。近年来,无铅卤系钙钛矿纳米晶由于其带隙可调、可见光吸收能力强等优势在光催化领域显示出巨大的潜力。相关研究表明:无铅卤系钙钛矿纳米晶可成功应用于CO₂还原、有机污染物降解等领域,效果显著。基于此,本文首先阐述了无铅卤系钙钛矿纳米晶的制备方法,并系统地总结了其在CO₂还原、制氢、污染物降解、NO去除等领域的应用研究进展,最后就现阶段无铅卤系钙钛矿纳米晶光催化材料研究中存在的问题及今后的研究方向进行了分析和展望。     

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.     

α-Amino acid derived enaminones and their application in the synthesis of N-protected methyl 5-substituted-4-hydroxypyrrole-3-carboxylates and other heterocycles

A new and simple synthesis of novel N-protected methyl 5-substituted-4-hydroxypyrrole-3-carboxylates, which exist in equilibrium with their 4-oxo tautomers, has been developed in two steps starting from N-protected α-amino acids. The key intermediates are enaminones, which can also be isolated, characterized, and used for the construction of other functionalized heterocycles, before they spontaneously decompose to pyrrole products. 4-Hydroxypyrroles are prone to partial aerial oxidation but can be efficiently alkylated or reduced to stable polysubstituted pyrrolidine derivatives.     

Specific intramolecular aromatic CH insertion of diazosulfonamides

The chemoselectivity in the intramolecular CH insertion of various diazosulfonamides has been experimentally studied. The results reveal that the aliphatic 1,4-, 1,5-, or 1,6-C(sp³)?H insertions of diazosulfonamides are not accessible, while the aromatic 1,5-C(sp²)?H insertion can be realized specifically by adjusting the diazo-adjacent group. In addition, the general chemoselectivities in the intramolecular CH insertions of diazosulfonyl compounds are summarized. Generally, diazosulfones undergo both aromatic 1,5-C(sp²)?H and aliphatic 1,5- and 1,6-C(sp³)?H insertions, while diazosulfonates undergo aliphatic 1,5- and 1,6-C(sp³)?H insertions. However, diazosulfonamides only undergo aromatic 1,5-C(sp²)?H insertion.     

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.     

N-Heterocyclic carbene-palladacyclic complexes: synthesis,characterization and their applications in the C-N coupling and α-arylation of ketones using aryl chlorides

N-Heterocyclic carbene-palladacyclic complexes 3 were successfully achieved in a one-pot procedure under mild conditions. The structure of 3a was unambiguously confirmed by X-ray single crystal diffraction and it was an active catalyst in the Buchwald-Hartwig amination and α-arylation of ketones even at very low catalyst loadings (0.01?mol%).     

Iodine-mediated oxidative Pictet-Spengler reaction using terminal alkyne as the 2-oxoaldehyde surrogate for the synthesis of 1-aroyl-β-carbolines and fused-nitrogen heterocycles

An efficient iodine-mediated oxidative Pictet-Spengler reaction in dimethyl sulphoxide (DMSO) using terminal alkynes as the 2-oxoaldehyde surrogate for the synthesis of aryl (9H-pyrido[3,4-b]indol-1-yl)methanones is described. The scope of the protocol includes the total synthesis of Fascaplysin, Eudistomins Y₁ and Y₂. The methodology is extended for preparing pyrrolo[1,2-a]-quinoxaline and indolo[1,5-a]quinoxaline derivatives. The utility of 1-aroyl-β-carbolines was demonstrated by performing palladium-catalyzed β-carboline directed ortho-C(sp2)-H functionalization of the phenyl ring with thiomethyl (SMe) group using DMSO as source and for accessing 4-aryl-canthin-6-ones.