超声喷雾共沉淀法制备纳米氧化锡粉体及其气敏性研究

采用超声波喷雾技术,以SnCl4·5H2O和CO(NH2)2为前驱体原料制备了氧化锡以及Ce稀土离子掺杂纳米粉体.详细地研究了超声喷雾条件、反应时间以及化学组分对纳米SnO2粉体的形貌和尺寸的影响规律,以及前驱体沉淀物脱水化学处理的条件.用XRD,TEM研究了所获纳米粒子的晶相和形貌.结果表明,制备的SnO2纳米粒子呈球状,尺寸在10～20 nm,纳米颗粒均匀,分散性好.以该粉体为基础制备了相应的气敏元件,测定了气体灵敏度与温度和稀土元素掺杂的关系.研究测试表明,纳米SnO2半导体气敏元件对NO2气体有着良好的响应-恢复特性,并且具有较高的灵敏度和较低的工作温度.稀土元素铈的掺杂能明显提高纳米SnO2粉体的气敏性能.     

钕改性钛基SnO2/Sb电催化电极的制备及表征

为改善钛基SnO2／Sb电极的电催化性能,采用浸渍法制备了Nd改性钛基SnO2／Sb电极。以活性艳红X-3B为目标有机物,考察电极的电催化性能,对制备温度和Nd掺杂量进行了研究,确定了适宜的制备条件为：热处理温度550℃,Nd掺杂量1.0％。采用SEN,EDS,XRD及XPS等分析方法对所制备电极的表面形貌、元素组成及结构进行分析,发现掺杂Nd可使SnO2粒径变小,有利于电极电催化性能的改善,同时Nd元素的引入可使杂质元素sb,Nd在电极表面涂层富集。Nd改性钛基SnO2／Sb电极表面主要是四方相金红石结构的SnO2晶体,掺杂的sb和Nd分别以Sb^5＋和Nd^3＋的形式存在。电极动电位扫描测试结果表明,Nd改性钛基SnO2／Sb电极具有较高的阳极析氧电位,有利于有机物的阳极氧化降解。     

基于半导体纳米SnO_2构建的气敏传感器的应用研究进展

SnO2是传统的气敏材料,由于其具有间隙锡离子和氧空位的特性,使得气体更容易吸附在材料表面,从而显示出更好的气敏性质.通过把SnO2进行贵金属附载掺杂和多种气敏性半导体氧化物的复合,探讨了一系列性能良好的气敏传感器,阐述了SnO2气敏传感的最新进展.     

SnO_2-SiO_2负载Cu、Ni催化剂的CO_2加氢反应性能

采用表面反应改性法制备了SnO2 SiO2 (SnSiO)表面复合物载体 ,用等体积浸渍法制备了SnSiO担载的Cu Ni双金属催化剂。借助BET、XRD、TPR、IR和微反等技术研究了SnSiO及其负载的Ni、Cu双金属催化剂的表面构造、化学吸附及CO2 加氢反应性能。结果表明 :SnSiO是SnO2 单分子层价联于SiO2 表面的复合氧化物 ,仍保持类似SiO2载体的孔结构和比表面 ;SnO2 引入SiO2 表面后可以有效地促进CuO、NiO的还原 ,还原后成为负载在SnSiO载体表面的Cu Ni合金 ;CO2 在负载型Cu Ni合金表面Cu或表面Ni位上发生化学吸附 ,形成线式和剪式吸附态 ;CO2 在催化剂上的加氢反应产物主要是CH3 OH、CH4 、CO和H2 O ,生成CH3 OH的选择性与催化剂组成及反应条件密切相关。Cu Ni催化剂 ,在 0 5MPa ,170℃ ,H2 /CO2 (mol/mol)为 3的条件下 ,CH3 OH的选择性达到 84 6 %。     

SnO2的表面酸性及其催化臭氧氧化活性的研究

以SnO2催化臭氧化降解高浓度糖蜜酒精废水为探针反应,研究SnO2催化臭氧氧化降解糖蜜酒精废水的活性,并采用吸附吡啶的红外光谱研究SnO2及金属氧化物改性的SnO2催化剂表面的酸性.催化剂吸附吡啶的红外光谱表明:吡啶分子在SnO2表面吸附时,形成六元环振动峰1 449 cm-1,说明SnO2表面存在Lewis酸中心.掺入第二组分对SnO2进行酸性调变后,酸类型和酸中心发生了变化.CuO-SnO2催化剂表面仅存在L酸,NiO-SnO2,Fe2O3-SnO2及CoO-SnO2等的表面不仅存在L酸,还存在不同强度的B酸,且Fe2O3-SnO2与CoO-SnO2存在与SnO2不同的第二类L酸.水的存在使得NiO-SnO2,Fe2O3-SnO2及CoO-SnO2催化剂表面的L酸减弱,B酸强度增强;而CuO-SnO2表面出现了弱的B酸.将催化剂的酸类型与催化臭氧氧化活性进行关联,发现B酸的存在是造成催化剂活性降低的一个原因.     

SnO2—SiO2负载Cu,Ni催化剂的CO2加氢反应性能

采用表面反应改性法制备了SnO2-SiO2(SnSIO)表面复合物载体,用等体积浸渍法制备了SnSiO担载的Cu-Ni双金属催化剂,借助BFT,XRD,TPR,IR和微反等技术研究了SnSiO及其负载的Ni,Cu双金属催化剂的表面构造,化学吸附及CO2加氢反应性能,结果表明：SnSiO是SnO2单分子层价联于SiO2表面的复合氧化物,仍保持类似SiO2载体的孔结构和比表面;SnO2引入SiO2表面后可以有效地促进CuO,NiO的还原,还原后成为负载在SnSiO载体表面的Cu-Ni合金,CO2在负载型Cu-Ni合金表面Cu或表面Ni位 发生化学吸附,形成线式和剪式吸附;CO2在催化剂上的加氢反应产物主要是CH3OH,CH4,CO和H2O,生成CH3OH的选择性与催化剂组成及反应条件密切相关,Cu-Ni催化剂,在0．5MPa,170度,H2。CO2（mol/mol)为3 的条件下,CH3OH的选择性达到84．6％。     

CO为还原剂同时还原SO2和NO的SnO2-TiO2固溶体催化剂Ⅱ.催化剂的物理化学性质

 用XRD, XPS, CO-TPR, NH3-TPD, SO2-TPD和IR等方法表征了SnO2-TiO2固溶体催化剂的物理化学性质. 不同配比的SnO2和TiO2均可形成均一的具有金红石结构的连续固溶体,其晶粒度比单纯的SnO2或TiO2的晶粒度小. SnO2-TiO2固溶体的比表面积随SnO2含量的增大呈火山形变化,说明在SnO2-TiO2固溶体中SnO2可阻止TiO2由锐钛矿型变为金红石型过程中比表面积的减小,而TiO2则提供了维持大表面的结构框架. SnO2倾向于在固溶体表面偏析,固溶体的表面氧含量高于单纯SnO2的表面氧含量而低于单纯TiO2的表面氧含量. SnO2, TiO2和SnO2-TiO2表面含有能被CO还原的吸附氧和晶格氧,被还原的SnO2, TiO2和SnO2-TiO2的表面晶格氧的数量仅占所有晶格氧的0.001%, 说明CO只使部分晶格氧还原并生成氧阴离子空穴. TiO2表面没有酸性, SnO2和SnO2-TiO2呈微弱酸性. 经CO还原的SnO2-TiO2上存在大量的强碱中心,说明SnO2和TiO2之间发生了协同作用. SnO2-TiO2固溶体的这些物化性质均十分有利于SO2+NO+CO的氧化还原反应.     

脱硫脱硝一体化催化剂SnO2-TiO2的程序升温还原及脱附研究

对以CO为还原剂同时还原SO2，NO为S和N2的反应。SnO2和TiO2(锐钛矿)没有催化活性。但它们组合成固溶体后，显示出很高的活性，说明它们之间存在协同效应．我们采用CO—TPR和NO—TPD证实SnO2和TiO2之间的协同效应表现为几何效应即TiO2使SnO2良好分散在TiO2的内孔表面和电子效应即TiO2促进SnO2表面晶格氧的还原和削弱NO的吸附能力．CO—TPR研究证明SnO2或SnO2-TiO2中被CO还原的晶格氧数只是总晶格氧数的10^-5，说明这部分晶格氧为表面晶格氧。这是在CO存在下SnO2或SnO2-TiO具有催化氧化还原活性的前提．     

SnO2-TiO2薄膜载体对Au-Pt纳米颗粒电化学性能的影响

采用真空镀膜法在玻碳(GC)电极表面修饰SnO2-TiO2薄膜, 在SnO2-TiO2/GC复合电极表面组装Au-Pt双金属纳米颗粒, 制得Au-Pt/SnO2-TiO2/GC复合电极. 通过循环伏安法(CV)研究了SnO2-TiO2薄膜载体对Au-Pt双金属纳米颗粒电化学性能的影响; 采用扫描电镜(SEM)及X射线光电子能谱(XPS)对Au-Pt在SnO2-TiO2薄膜沉积的形貌及结构进行了表征. 研究结果表明, 10 nm的Au-Pt双金属纳米颗粒均匀地组装于SnO2-TiO2薄膜表面; SnO2-TiO2薄膜载体改善了复合电极抗CO中毒能力; Au-Pt双金属合金的形成提高了Pt 对甲醇氧化的电催化能力, SnO2-TiO2薄膜载体又使Pt纳米粒子d空轨道增多, 提高了Au-Pt双金属纳米颗粒的稳定性和催化性能.     

纳米薄膜光催化剂的制备与表面态研究

利用溶胶-凝胶提拉成膜法制备了TiO2,SnO2,Ag/SnO2,Ag/SnO2/TiO2纳米薄膜半导体催化剂.采用粉末电导法初步研究了纳米半导体薄膜催化剂的表面结构,测定了表面态能级相对于半导体导带边的位置.实验表明:四种催化剂在不同的表面能级位置都存在表面态:TiO2具有两类表面态,其能量分别为0.75eV和0.58eV.Ag/SnO2/TiO2由于Ag的担载,出现更负的表面态能级(0.33eV).这将会显著提高导带电子密度,加速光催化反应速率.     

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%.     

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.     

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.     

A general and convenient synthesis of 4-(tosylmethyl)semicarbazones and their use in amidoalkylation of hydrogen,heteroatom, and carbon nucleophiles

A general synthesis of previously unknown semicarbazone-based α-amidoalkylating reagents, 4-(tosylmethyl)semicarbazones, has been developed. The synthesis involved three-component condensation of semicarbazones of aliphatic or aromatic aldehydes with the same or other aldehydes and p-toluenesulfinic acid. The scope and limitations of this reaction were investigated. The compounds obtained were demonstrated to be an efficient α-(4-semicarbazono)alkylating agents. They were reacted with H- (sodium borohydride), O- (sodium methylate), S- (sodium phenylthiolate), N- (pyrrolidine, sodium succinimide), P- (trialkyl phosphites), and C-nucleophiles (sodium diethyl malonate) to give the corresponding products of the tosyl group substitution, 4-substituted semicarbazones, including analogues of nitrofurazone. Among the prepared compounds tested in vitro for antibacterial and antifungal activity, three nitrofuryl-containing semicarbazones exhibited high biological activities with minimum inhibitory concentration (MIC) values of 8–32 μg/mL.     

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.     

Synthesis of novel chiral bidentate hydroxyalkyl-N-heterocyclic carbene ligands and their application in palladium-catalyzed Mizoroki–Heck couplings and asymmetric addition of diethylzinc to benzaldehyde

A small library of new chiral bidentate hydroxyalkyl-imidazolium salts 1 is conveniently synthesized on multi-gram scale from inexpensive and commercially available chiral pool amino acids. The corresponding carbenes, generated by deprotonation of imidazolium salts 1, in combination with palladium(II) chloride were tested in the Mizoroki–Heck coupling reaction. The most significant results in terms of yields and reactivities were achieved with low catalyst loading. The catalytic activities of these imidazolium salts were also investigated in the asymmetric addition of diethylzinc to benzaldehyde. The use of MgO nanoparticles as an additive in conjunction with these ligands played a crucial role in increasing the efficiency of these reactions.