缺碳型介孔空心球状WC制备及其对甲醇氧化的电化学行为

采用喷雾干燥法制得空心球状结构偏钨酸铵, 通过固定床气固反应, 以CO/H₂为还原碳化气氛在700～900 ℃下制备了介孔结构空心球状碳化钨(WC). 经XRD, SEM及EDS测试表明, WC粉末样品在保持了单相WC的前提下, 样品存在一个微量缺碳的原子比例, 其W/C＞1, 且在高氢环境中WC球体表面有部分纳米颗粒依附于片状碳化钨基体上. 将制备得到的WC粉末样品制成微电极, 采用电化学测试技术研究了WC在硫酸介质中对甲醇的电催化氧化反应. 结果表明, 缺碳的介孔结构空心球状WC催化剂对甲醇氧化有着良好的电催化活性, 并对动力学参数进行了研究, 结果显示其反应的表观活化能为105.06 kJ/mol, 且其在微电极中的氧化行为受扩散控制.     

WxC-MCM-48催化剂的合成、表征及加氢脱硫催化性能

以正硅酸乙酯(TEOS)为硅源，十六烷基三甲基溴化铵(CTAB)为表面活性剂，仲钨酸铵为钨源，采用水热晶化法一步合成了不同钨含量(以Si、W物质的量比n_Si/n_W表示)的WO₃-MCM-48，然后经甲烷/氢气(V/V=1/4)混和气体程序升温还原碳化(TPC)，制备出了W_xC-MCM-48(x=1、2)催化剂，采用XRD、N₂吸附-脱附和NH₃-TPD对样品的结构进行了表征，用噻吩作为模型化合物，对W_xC-MCM-48催化剂的加氢脱硫催化活性进行了评价。结果表明，在一定钨含量的条件下，WO₃-MCM-48和W_xC-MCM-48样品仍然保持MCM-48的三维立方有序介孔结构，n_Si/n_W=30～15时，碳化钨的物相为W₂C；n_Si/n_W=7.5时，碳化钨为W₂C和WC物相，W_xC-MCM-48催化剂表现出了良好的加氢脱硫催化性能。     

碳化钨/碳化二钨核壳结构纳米复合材料的制备及电化学性能

以偏钨酸铵为钨源, 铁黄(FeOOH)为载体, 将表面包覆法与原位还原碳化技术相结合, 制备出了具有核壳结构的碳化钨(WC)/碳化二钨(W₂C)纳米复合材料; 应用X射线衍射(XRD)分析、透射电子显微镜(TEM)和X射线能量散射谱(EDS)等手段对不同阶段样品的晶相、形貌、微结构和化学组成等特征进行了表征. 结果表明, 负载体经煅烧后, 载体及包裹层的物相均发生了变化, 形貌也相应地发生了改变; 经盐酸处理及还原碳化后, 样品由WC和W₂C纳米颗粒构成, 并构成了以W₂C为壳, 以WC为核的典型核壳结构; 结合表征结果对核壳结构的形成机理进行了探讨. 采用三电极体系循环伏安法测试了样品在酸性、中性和碱性溶液中对甲醇的电催化氧化活性. 结果表明, 与颗粒状碳化钨和介孔空心球状碳化钨相比, 样品的电催化活性有了明显的提高. 这说明W₂C与WC构成核壳结构纳米复合材料后, 其电化学性能有了明显的提升, 核壳结构纳米复合材料是提高碳化钨催化材料活性的有效途径之一.     

简易模板剂法制备多级介孔TiO2微球及其在染料敏化太阳能电池中的性能

采用模板剂法一步合成分级结构的介孔TiO₂微球, 考察了烷基胺类模板剂中烷基链长度对介孔TiO₂微球合成及性能影响. 将其应用于染料敏化太阳能电池的光阳极半导体薄膜中, 得到了9.5%-10.1%的高能量转换效率. X射线衍射(XRD)、物理吸附仪(BET)、扫描电镜(SEM)等的分析结果表明: 分级结构介孔TiO₂微球的晶相为纯锐钛矿型; 介孔TiO₂微球表面粗糙, 的纳米粒子堆积形成, 使微球具有介孔性质和较适宜的比表面积. 介孔TiO₂微球堆积形成了利于物质扩散的通道并具有良好的光散射效果; 同时微球介孔粗糙表面保证了染料的大量吸附, 从而提高了电池的光电流. 通过电化学阻抗分析结果验证了分等级结构介孔TiO₂微球光阳极有利于电解液的传输和物质扩散的优异性能.     

表面活性剂-模板化法制备多级孔β沸石及其四氢萘加氢裂化制苯、甲苯、二甲苯的催化性能

采用表面活性剂-模板化法,分别以β-60和β-150为母体,选用十六烷基三甲基溴化铵(CTAB)作为表面活性剂,以一步和两步法制备了2种多级孔β沸石。以X射线衍射(XRD)、扫描电镜(SEM)、透射电镜(TEM)、N₂吸附-脱附测试和NH₃程序升温脱附(NH₃-TPD)测试对多级孔β沸石的物化性质进行分析。采用等体积浸渍法负载25%的WO₃制备成加氢裂化催化剂,考察其在四氢萘加氢裂化制备苯(B)、甲苯(T)和二甲苯(X)的催化性能。结果表明：相比于母体,一步制备样品的介孔孔容提高3倍以上,两步制备样品的介孔孔容提高1倍以上。另外,以β-60为母体,一步和两步制备样品的介孔均是无序的。一步制备样品的最高BTX收率是53%,两步制备样品的最高BTX收率是51%;然而,以β-150为母体,一步制备样品的介孔是无序的,而两步制备样品的介孔是有序的。一步制备样品的最高BTX收率是46%,两步制备样品的最高BTX收率是50%。因此,多级孔β沸石制备的加氢裂化催化剂的催化性能是由介孔的含量和有序度共同决定的。     

缺碳型介孔空心球状碳化钨制备及其对甲醇氧化的电化学行为

采用喷雾干燥法制得空心球状结构偏钨酸铵,通过固定床气固反应,以CO/H2为还原碳化气氛在700～900℃下制备了介孔结构空心球状碳化钨(WC).经XRD,SEM及EDS测试表明,WC粉末样品在保持了单相WC的前提下,样品存在一个微量缺碳的原子比例,其W/C1,且在高氢环境中WC球体表面有部分纳米颗粒依附于片状碳化钨基体上.将制备得到的WC粉末样品制成微电极,采用电化学测试技术研究了WC在硫酸介质中对甲醇的电催化氧化反应.结果表明,缺碳的介孔结构空心球状WC催化剂对甲醇氧化有着良好的电催化活性,并对动力学参数进行了研究,结果显示其反应的表观活化能为105.06kJ/mol,且其在微电极中的氧化行为受扩散控制.     

制备参数对高比表面积介孔催化剂La-Co-Zr-O结构与性能的影响

采用双表面活性剂模板(十六烷基三甲基溴化铵和聚乙二醇辛基苯基醚的混合物)分解法制备了不同原子比(n_La+n_Co)/(n_La+n_Co+n_Zr)和不同温度焙烧的系列介孔混合氧化物催化剂La-Co-Zr-O。运用XRD、N₂吸附/脱附、XPS和H₂-TPR等技术对催化剂进行了表征，并以CO和C₃H₈氧化为模型反应，考察了组分配比和焙烧温度等参数对催化剂催化性能的影响。比表面积和孔径测试结果表明，样品具有很高的比表面积(108～266 m²·g^-1)和分布集中的孔径(3.4～3.9 nm)，Zr含量较高的样品比表面积较大。XRD结果表明，样品中的活性组分钴物种主要以Co₃O₄形式存在；XPS和H₂-TPR结果表明，样品中可还原的晶格氧的数量、活动度以及表面钴原子浓度均与催化剂对CO和C₃H₈的氧化性能密切相关。原子比为0.5的样品中，较多的晶格氧易于在相对低温下还原；而原子比为0.7的样品表面钴原子浓度较高，这使得两样品均表现出较高的催化活性。经650 ℃焙烧的样品仍保持较高的比表面积(108 m²·g^-1)和分布集中的介孔孔径(最可几孔径约3.8 nm)，且催化活性下降幅度也很小，表明该系列介孔催化剂具有优良的抗烧结能力和介孔热稳定性。     

纳米镍钴铁氧体空心微球的制备与性能

以乙二醇为溶剂,氯化铁、氯化钴、氯化镍和醋酸铵为反应试剂,采用溶剂热法制备纳米Ni_xCo_1-xFe₂O₄(x=0、0.3、0.5、0.7、1)铁氧体空心微球,研究镍含量对铁氧体空心球的磁性与吸波性能的影响。借助X-射线衍射仪(XRD)、扫描电子显微镜(SEM)、透射电子显微镜(TEM)、振动样品磁强计(VSM)和网络分析仪对试样的物相组成、微观形貌和电磁特性进行表征。结果表明制备的镍钴铁氧体为尖晶石结构,且形貌为空心球,粒径在200 nm左右。当x=0时,镍钴铁氧体空心球饱和磁化强度最大为81.7 emu·g^-1,反射损耗在1 658.8 MHz有最小值为-16.9 dB。     

纳米镍钴铁氧体空心微球的制备与性能

以乙二醇为溶剂,氯化铁、氯化钴、氯化镍和醋酸铵为反应试剂,采用溶剂热法制备纳米Ni_xCo_1-xFe₂O₄(x=0、0.3、0.5、0.7、1)铁氧体空心微球,研究镍含量对铁氧体空心球的磁性与吸波性能的影响。借助X射线衍射仪(XRD)、扫描电子显微镜(SEM)、透射电子显微镜(TEM)、振动样品磁强计(VSM)和网络分析仪对试样的物相组成、微观形貌和电磁特性进行表征。结果表明制备的镍钴铁氧体为尖晶石结构,且形貌为空心球,粒径在200nm左右。当x=0时,镍钴铁氧体空心球饱和磁化强度最大为81.7emu·g^-1,反射损耗在1658.8MHz有最小值为-16.9dB。     

高度分散的Pt/TiO2的制备及光催化活性

用柠檬酸作为空穴捕获剂和分散剂, 在温和条件下用光催化还原法将3 nm金属铂沉积在7 nm的锐钛矿相及介孔二氧化钛纳米晶表面. TEM观察显示铂的负载量为w＝1.0%时, 多数二氧化钛纳米晶表面沉积了岛状的铂团簇, XPS和电子衍射结果表明铂以游离态存在. 负载w＝1.0%～2.0%铂的TiO₂在苯酚光氧化反应中活性显著提高. Pt/TiO₂在氨气中经550 ℃氮化, 可制得氮掺杂的Pt/TiO₂可见光光催化剂, 氮化过程中铂团簇没有烧结和显著长大.     

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.