离子液体［bmim］HSO4中合成的苯胺与环氧丙烷共聚物的电催化性能

 采用恒电流电解法,在1-丁基-3-甲基咪唑硫酸氢盐(［bmim］HSO4)离子液体中合成了苯胺与环氧丙烷共聚物(PAN-PPO). 扫描电镜观察表明, PAN-PPO由直径小于80 nm的纳米纤维组成. PAN-PPO对草酸氧化具有较好的电催化活性. 采用电化学原位红外光谱技术对草酸的电催化氧化进行了简单的分析.     

一种新型的甲酸/铁离子燃料电池

以甲酸为燃料、 Fe³⁺为氧化剂组成了一种新型的甲酸/铁离子燃料电池, 阳极催化剂为多壁碳纳米管(MWCNT)或β-环糊精修饰的MWCNT(β-CD-MWCNT)负载的金属钯或钯锡纳米颗粒: PdSn/MWCNT, Pd/β-CD-MWCNT和PdSn/β-CD-MWCNT. 运用循环伏安(CV)和计时电流(CA)等技术研究了各催化剂在碱性条件下对甲酸氧化反应的电催化活性. 结果表明, 加入适量的金属锡能促进钯对甲酸的电催化氧化, 甲酸氧化电位提前, 电流密度增加; 环糊精的改性对催化剂电催化活性有一定提升. 将上述催化剂制成电池阳极片, 碳粉制成电极阴极片, 组成甲酸/铁离子燃料电池并测试其放电性能. 结果表明, 电池的开路电压在0.981.20 V之间; 以PdSn/β-CD-MWCNT为阳极时, 其最大放电电流密度达50 mA/cm², 最大功率密度达12.6 mW/cm², 远优于以Pd/C为阳极的电池性能.     

碳化钨和Vulcan XC-72炭黑载钯催化剂对甲酸氧化的电催化性能

研究了碳化钨(WC)和Vulcan XC-72炭黑(XC)作混合载体的Pd/WC-XC催化剂对甲酸氧化的电催化性能.发现Pd/WC-XC催化剂对甲酸氧化的电催化性能优于Pd/XC催化剂.而且,Pd/WC-XC催化剂的电催化性能与WC和XC的质量比有关,当质量比为3:1时,催化剂对甲酸氧化的电催化活性最好,当质量比为2:1时,催化剂对甲酸氧化的电催化稳定性性最好.     

一种提高铂电催化氧化甲酸性能的简单方法

在离子液体1-乙基咪唑三氟乙酸盐(HElmTfa)中,采用循环伏安法在铂电极表面修饰聚吡咯(PPY),制得PPy-HEImTfa/Pt,并研究了其对甲酸的电催化氧化性能.与相同条件下的铂基底电极相比,PPy-HEImTfa/Pt对甲酸的电催化氧化性能有很大的提高.原位红外光谱表明,PPy-HElmTfa能降低中间体CO等对铂电极的毒化作用,促进甲酸直接氧化生成CO_2.     

Pd/PVP-MWCNTs电极对甲酸氧化的电催化性能

用聚乙烯吡咯烷酮（PVP）修饰的多壁碳纳米管（MWCNTs）作为Pd纳米粒子的载体,制得了Pd/PVP-MWCNTs催化剂并研究了其对甲酸氧化的电催化性能. 红外光谱仪（FTIR）和透射电镜（TEM）观测结果表明,Pd/PVP-MWCNTs催化剂中的Pd纳米粒子平均粒径小、分散性好. 因此,Pd/PVP-MWCNTs催化剂对甲酸电氧化有很好的电催化性能.     

Pd/TiC-C催化剂对甲酸氧化的电催化性能

研究了TiC和C作混合载体的Pd(Pd/TiC-C)催化剂对甲酸氧化的电催化性能。发现Pd/TiC-C催化剂对直接甲酸燃料电池(DFAFC)中甲酸氧化的电催化性能要优于Pd/C催化剂。而且,Pd/TiC-C催化剂的电催化性能与C和TiC的质量比有关,当质量比为2时,Pd/TiC-C催化剂对甲酸氧化的电催化活性和稳定性最好,甲酸在C和TiC的质量比为2的Pd/TiC-C催化剂电极上的氧化峰峰电位为0.164 V,比在Pd/C催化剂电极上负移12 mV,峰电流密度为23.08 mA/cm2,比在Pd/C催化剂电极上高约42％。     

Pt/C催化剂对甲酸电催化氧化的粒径效应

在甲醇溶剂中,利用SnCl2作为还原剂,通过控制反应条件制备了具有不同粒径Pt粒子的炭载Pt(Pt/C)催化剂.X射线衍射(XRD)和透射电子显微镜(TEM)的结果表明,Pt/C催化剂中Pt粒子具有高度的均一性和良好的分散度.电化学研究结果显示,对于甲酸的电催化氧化,Pt/C催化剂存在着明显的粒径效应.当Pt粒子粒径为3.2 nm时,Pt/C催化剂对甲酸的电催化氧化活性最佳.Pt/C催化剂对甲酸氧化的粒径效应与其表面含氧基团含量、Pt粒子的比表面积及相对结晶度相关.     

不同状态Au对甲酸在Pd催化剂上电催化性能的影响

合成并比较了碳载Au(Au/C)、碳载Pd(Pd/C)、碳载高合金化Pd-Au(Pd-Au/C-T)和碳载非合金化Pd-Au(Pd-Au/C-H)催化剂对甲酸氧化的电催化活性和稳定性.结果表明,Au/C对甲酸氧化基本没有电催化活性,而Pd/C对甲酸氧化有较好的电催化性能,Au的加入能进一步提高Pd催化剂对甲酸氧化的电催化活性和稳定性,特别是Pd-Au/C-T对甲酸氧化的电催化活性和稳定性要好于Pd-Au/C-H,更远好于Pd/C催化剂.相关反应机理有待进一步揭示.     

Pt电极上甲酸电催化氧化机理研究进展

本文综述了甲酸在铂电极上电催化氧化机理的实验和理论研究进展. 铂电极甲酸的电化学氧化主要有两种途径：1）间接途径,甲酸经由CO中间物氧化为最终产物CO₂,室温下该途径对总电流贡献不超过1%;2）直接途径,甲酸直接氧化生成CO₂. 作者课题组对文献中桥式吸附甲酸根是否是甲酸氧化反应直接途径的反应中间物的争论进行了详细的分析和探讨,认为桥式吸附的甲酸根不是间接途径中生成CO的前驱体,也不是甲酸直接氧化途径的中间物. 作者课题组还指出了支持甲酸根是甲酸直接氧化途径的反应中间物的推论的问题所在.     

电解液对炭载Pd催化剂对甲酸氧化的电催化性能的影响

为了了解(NH4)2SO4,K2SO4和H2SO4电解液对炭载Pd(Pd/C)催化剂对甲酸氧化的电催化性能的影响和机理,用电化学方法测量了Pd/C催化剂在不同电解液中对甲酸氧化的电催化性能。发现在不同电解液中,Pd/C催化剂对甲酸氧化的电催化活性和稳定性按(NH4)2SO4>K2SO4>H2SO4的次序降低。由于在含甲酸的电解液中,不同电解液的pH值差别较小,电解液的pH值只有较小的影响。其次,电解液的电导率对甲酸氧化峰峰电位有一定的影响。最后,由于NH4+起着特殊作用,它能降低CO在Pd/C催化剂电极上的吸附量,因此,在(NH4)2SO4电解液中,Pd/C催化剂对甲酸氧化的电催化性能最好。     

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%.     

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.     

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.     

Facile synthesis of bicyclic 1-arylpyrazol-5-ones

In this Letter, we described a facile method for constructing fused bicyclic 1-arylpyrazol-5-one ring system. We employed various methylene-containing carboxylic acids as the substrates and proved that the pyrazolone ring closure requires activated methylene group in intermediate II. Accordingly, a series of structurally diversified, fused bicyclic 1-arylpyrazol-5-ones was prepared in moderate to high yields using the requisite substrates.     

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.     

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.