Effect of preparation methods on Pt/alumina catalysts for the hydrogen iodide catalytic decomposition

Three kinds of Pt/alumina catalysts were prepared by impregnation-hydrogen reduction,impregnation-hydrazine reduction and electroless plating methods.Their differences in the structures,specific areas and particle sizes were characterized by XRD,BET and TEM,respectively.Furthermore,their catalytic activities for the hydrogen iodide(HI)decomposition were evaluated in a fixed bed reactor.The results show that the catalyst 5%Pt/Al_2O_3 prepared by the electroless plating has the optimum catalytic properties...     

Conductance studies of some ammonium and alkali metal salts in propylene carbonate

Conductance data are reported for NaI, KI, RbI, CsI, NH₄I, NaClO₄, and KClO₄ in propylene carbonate at 25°C in the concentration range 1×10^–4 –8.3×10^–3M. Analysis of the data with the current conductance theories indicates negligible ion-association, strong cation-solvent and weak anion-solvent interactions.     

CuI-catalyzed Coupling Reactions of Aryl Iodides with Amides Using L-Proline and KF/Al2O3

An efficient experimentally simple and inexpensive catalyst system for the selective amidation of aryl iodides using 15 mol% of CuI as catalyst, 15 mol% of L-proline as ligand and KF/Al2O3 as a base in toluene is described.     

Thermodynamics analysis of indium iodide polycrystal synthesis

According to the thermodynamics analysis, the molar enthalpy change, the molar entropy increase, the Gibbs free energy change and the balance constant of indium iodide polycrystal synthesis reaction were calculated in order to evaluate the feasibility of reaction temperature on 653 K. After the temperature 653 K was applied in the synthesis experiment, indium iodide polycrystal was successfully obtained by the two‐zone vapor transporting method. The result of X‐ray diffraction analysis indicates the temperature 653K can be used for indium iodide polycrystal synthesis.     

Desulfinylative Pd-catalyzed coupling reaction of arenediazonium salt with aryl sulfinates to give unsymmetrical biaryls

An efficient route for the synthesis of unsymmetrical biaryls was developed via palladium catalyzed reaction of arenediazonium salts and aryl sulfinates under inert atmosphere. This synthesis involves cascade processes. Tetrabutylammonium iodide was used as an iodide source for in situ formation of aryl iodide, followed by desulfinylative cross-coupling reaction between aryl sulfinates and aryl iodides. A wide range of biaryls were selectively prepared in one pot from simple substrates in good to excellent yields.     

CuI mediated synthesis of heterocyclic flavone-benzofuran fused derivatives

An efficient synthetic method of heterocyclic flavone benzofuran fused derivatives is reported in good to excellent yield (75–90%) via Ullmann type coupling reaction. The protocol involves catalytic amount of CuI (10 mol%) and K₂CO₃ base for the intramolecular CO bond formation under mild reaction conditions.     

On the behaviour of Eu oxo-species in molten NaBr–NaI (0.77:0.23) mixture at 973 K

The interaction of Eu₂O₃ with molten NaBr–NaI (0.77:0.23) mixture at 973 K was studied by sequential addition method with the use of YSZ membrane oxygen electrode for controlling of course of the process. The Red-Ox process is accompanied with formation of EuO in the melt. The total solubility of EuO (sum of concentration of Eu²⁺, O^2–, non-dissociated EuO) in the molten NaBr–NaI at 973 K (mole fraction 2.7 × 10^–4) is considerably lower than in pure NaI melt (4.2 × 10^–4), which can be explained using the ‘hole’ model by reduction of a number of holes of comparable with EuO particle size because of addition of smaller bromide ion to the iodide melt.

The solubility of EuO is appreciably affected by its dispersity and the value of surface energy causing these solubility changes is estimated as 37 J m^–2.     

An N-protection free ligation of the peptide thioester and the peptide with an N-alkoxy- or N-aryloxyamino group at its N-terminus

Peptides with an N-alkoxy or N-aryloxy amino acid at their N-terminus were synthesized and successfully ligated with a peptide thioester by silver ion activation under a slightly acidic condition without requiring protection of the side chain amino groups. The N-methoxy group was easily cleaved by the SmI₂ reduction in CH₃OH aq. to obtain the desired peptide with a native peptide bond. This method was successfully applied to the synthesis of the human atrial natriuretic peptide showing the efficiency of the novel ligation.     

在FTO导电玻璃上电化学沉积高效可见光光电化学分解水Cu2O/g-C3N4异质结膜

近几十年来,光电化学分解水制氢作为一种洁净的、能持续利用太阳能的技术受到极大关注.在众多光催化材料中,p型半导体氧化亚铜(Cu2O)被认为是最有前途的可见光光电分解水材料之一.理论上,它的光能转换为氢能的效率可达到18.7%.然而,目前所报道的Cu2O光转换效率远远低于此值;同时,纯Cu2O在光照条件下的稳定性较差.研究表明,Cu2O与其它半导体复合可以增强其光电转换效率和提高稳定性.如Cu2O和能带匹配的石墨相氮化碳(g-C3N4)复合后,光催化性能和稳定性都有较大提高.但目前所报道的Cu2O/g-C3N4复合物几乎都是粉末状催化剂,不便于回收和重复使用.本文首先采用电化学方法在FTO导电玻璃上沉积Cu2O薄膜,采用溶胶凝胶法制备g-C3N4纳米颗粒材料,然后采用电化学法在Cu2O薄膜表面沉积一层g-C3N4纳米颗粒,得到了Cu2O/g-C3N4异质结膜.分别利用X射线粉末衍射(XRD)、高分辨透射电子显微镜(HRTEM)、扫描电子显微镜(SEM)、紫外可见光谱(UV-Vis)和光电化学分解水实验分析了Cu2O/g-C3N4异质结的组成结构、表面形貌、光吸收性能及催化剂活性和稳定性.XRD和HRTEM表征显示,本文成功合成了Cu2O/g-C3N4异质结材料,SEM图表明g-C3N4纳米颗粒在Cu2O表面分布均匀,大小均一.可见光光电化学分解水结果显示,异质结薄膜的光电化学性能比纯的Cu2O和g-C3N4薄膜材料有极大提高.当在Cu2O表面沉积g-C3N4的时间为15 s时,得到样品Cu2O/g-C3N4-15异质结膜,其在–0.4 V和可见光照射条件下,光电流密度达到了–1.38 mA/cm2,分别是纯Cu2O和g-C3N4薄膜材料的19.7和6.3倍.产氢速率也达到了0.48 mL h–1 cm–2,且产氢和产氧的速率之比约为2,说明此异质结材料在可见光作用下能全分解水.经过三次循环实验,光电化学分解水的效率仅降低10.8%,表明该材料具有良好的稳定性.根据UV-Vis表征和光电化学性能对比,Cu2O/g-C3N4-15的光电性能最好,但其光吸收性能并不是最好,说明光电化学性能与光吸收不是成正比关系,主要是由于Cu2O和g-C3N4两个半导体相互起到了协同作用.机理分析表明,Cu2O/g-C3N4异质结薄膜在光照下,由于两者能带匹配,Cu2O的光生电子从其导带转移到g-C3N4的导带上,g-C3N4价带上的空隙转移到Cu2O的价带上,从而降低了光生电子和空隙的复合,提高了其光催化性能.由于g-C3N4的导带位置高于H2O(或H+)还原为H2的电势,Cu2O的价带位置低于H2O(或OH–)还原为O2的电势,所以在外加–0.4 V偏压和可见光照射条件下,Cu2O/g-C3N4能全分解水,光生载流子越多,光电化学分解水的速率越大.综上所述,在Cu2O薄膜上沉积g-C3N4后得到的异质结薄膜具有高效的光能转换为氢能性能.     

KI与无机铵盐催化CO2与环氧丙烷合成碳酸丙烯酯

以无毒、合成简单、廉价的无机铵盐(氨基甲酸铵、碳酸氢铵、碳酸铵等)为助催化剂,研究其对卤化钾(KCl、KBr、KI)催化CO2与环氧丙烷合成碳酸丙烯酯(PC)的影响.结果表明,卤化钾与无机铵盐显示出很好的协同催化效应.其中以氨基甲酸铵为助催化剂,KI为主催化剂时,催化合成PC的效果最好.同时考察了催化剂用量、反应温度、CO2初始压力、PC的预加入量、反应时间等因素对反应的影响.在优化条件下,PC收率大于99%.