N-羟基-N-苯基-2-吡啶甲酰胺钴配合物的合成及均相催化乙苯的氧化反应

近年来,在催化氧化反应领域,人们一直试图用价廉易得的氧作氧化剂,在较温和的条件下催化烃类氧化,以得到价值更高的含氧化合物．研究新的活化分子氧的高活性催化剂成为化学家追求的重要目标之一［１～４］．在各类催化剂中,金属卟啉类［５,６］和金属席夫碱类［...     

超临界水的分子动力学模拟

采用分子动力学(MD)模拟的方法对超临界条件下水的结构及扩散性质进行了研究.模拟结果表明超临界条件下水分子之间的氢键作用明显减弱,分子极性大大降低.扩散性质与常温下相比,其大小约上升了两个数量级.     

TiNi合金表面原位热氧化膜的结构与光电性能的研究

采用AFM、XRD和EDS等手段,对TiNi合金在空气中、400—800℃下形成的氧化膜组织结构进行了分析,并对TiNi合金表面原位热氧化膜的光电性能进行了研究.结果表明,TiNi合金在空气中氧化原位形成的氧化膜的结构主要为金红石型二氧化钛,不同温度下生长的氧化膜存在择优取向;随着氧化温度的升高,所制备的TiO2/TiNi电极的稳态光电流和开路光电压随氧化温度的升高先增大后减小,在700℃所制备的TiO2/TiNi电极的稳态光电流最大.     

TiO2薄膜光催化还原Hg2+的研究

采用溶胶法制备出TiO2、SO42-/TiO2、CdS/TiO2薄膜光催化剂,研究了TiO2薄膜光催化还原Hg2+的最佳实验条件以及SO42-/TiO2、CdS/TiO2薄膜与TiO2薄膜、TiO2粉体与薄膜之间的光催化活性差异.结果表明:当pH=5.34时,经30 min紫外光照射,Hg2+的还原率达到最大;Hg2+初始浓度越高,光致还原量越低;光源波长越短,Hg2+的还原率越高;当甲醇添加量达到15%(体积比)时,反应30 min后,Hg2+的还原率即达100%;CdS改性薄膜的光催化活性高于未改性薄膜;CdS/TiO2薄膜的光催化活性略高于粉体.     

Electrochemical determination of iodide on a vanadium oxide-polypropylene carbonate coated glassy carbon electrode

A vanadium oxide-modified glassy carbon electrode was simply and conveniently fabricated by casting vanadium tri(isoproxide) oxide (VO(OC₃H₇)₃) and poly(propylene carbonate) (PPC) onto the glassy carbon electrode surface. The electrochemical properties of iodide at the VO(OC₃H₇)₃-PPC film-modified glassy carbon electrode were investigated by cyclic voltammetry, and an anodic peak was observed at approximately +0.71 V (vs. SCE). Based on this, a sensitive and convenient electrochemical method was proposed for the determination of iodide. Flow injection amperometry (FIA) exhibited a good linear relationship with the concentration of iodide in the range of 5 × 10⁻⁷ mol L⁻¹ and 1 × 10⁻³ mol L⁻¹, and the detection limit was 1 × 10⁻⁷ mol L⁻¹. Quantitative recovery of iodide in synthetic samples has been obtained and the interferences from different cations and anions have been studied. The method has been successfully applied to the determination of iodide in dry edible seaweed. The concentrations of iodide measured by this method are in good agreement with those obtained by spectrophotometric method.     

Electrocatalytic oxidation and detection of hydrazine at gold electrode modified with iron phthalocyanine complex linked to mercaptopyridine self-assembled monolayer

Electrocatalytic oxidation and detection of hydrazine in pH 7.0 conditions were studied by using gold electrode modified with self-assembled monolayer (SAM) films of iron phthalocyanine (FePc) complex axially ligated to a preformed 4-mercaptopyridine SAMs. The anodic oxidation of hydrazine in neutral pH conditions with FePc-linked-mercaptopyridine-SAM-modified gold electrode occurred at low overpotential (0.35 V versus Ag|AgCl) and the treatment of the voltammetric data showed that it was a pure diffusion-controlled reaction with the involvement of one electron in the rate-determining step. The mechanism for the interaction of hydrazine with the FePc-SAM is proposed to involve the Fe^(III)Pc/Fe^(II)Pc redox process. Using cyclic voltammetry (CV) and Osteryoung square wave voltammetry (OSWV), hydrazine was detected over a linear concentration range of 1.3 × 10⁻⁵ to 9.2 × 10⁻⁵ mol/L with low limits of detection (ca. 5 and 11 μM for OSWV and CV, respectively). At concentrations higher than 1.2 × 10⁻⁴ mol/L the anodic peak potential shifted to 0.40 V (versus Ag|AgCl), and this was interpreted to be due to kinetic limitations resulting from the saturation of hydrazine and its oxidation products onto the redox-active monolayer film. This type of metallophthalocyanine-SAM-based electrode is a highly promising electrochemical sensor given its ease of fabrication, good catalytic activity, stability, sensitivity and simplicity.     

负载型La0.8Sr0.2MnO3燃烧催化剂的载体效应

Combustion catalysts La0.8Sr0.2MnO3 supported on γ-Al2O3, α-Al2O3, cordierite (2MgO•2Al2O3•5SiO2) and ZrO2 were compared. Further investigation was focused on LSM/ γ-Al2O3 catalyst. It was observed that LSM/γ－Al2O3 catalyst loaded with 20% (mass fraction) LSM (La0.8Sr0.2MnO3 or corresponding oxides), heated at 750℃ or above, perovskite-type oxides were found by XRD examination, whereas, the same catalyst loaded with 10% or less LSM, perovskite oxides were absent, calcination temperature about 750℃ is necessary for the formation of perovskite structure in LSM/γ-Al2O3 catalysts. High activity of complete oxidation of xylen will be obtained when perovskite-type oxides.
Investigation of TPR showed that neat LSM or LSM/γ-Al2O3(20%) was reduced by H2-N2 mixed gas. Two degradation processes took place. In the first, reduced temperature peak was about 350 - 450℃. If reduction ended at 400℃, perovskite structure was retained, which may be due to the reduction of Mn3+to Mn2+ on the surface of LSM only. In the second process, perovskite structure was destroied, and La2O3, Mn2O3, Mn - Sr - O oxides could be obtained, which took place in the temperature range 685 - 750℃ and ended at 800℃. This was proved by TPR experiments (Fig. 3, 5) and XRD patterns (Fig. 4)
Catalysts LSM/γ-Al2O3(10% or 20%) heated at 500℃ have only one TPR peak, i. e. lower temperature peak. This is due to the absence of perovskite-type oxides in the catalysts. However, neat LSM or LSM/γ-Al2O3(20%) heated 750℃ or above, not only the first low temperature TPR peak but also the second peak, which is contributed by the perovskite-type oxides in these catalysts appeared. Therefore, the second TPR peak, i. e. the higher temperatue peak is a characteristic peak for perovskite-type oxides in the reduced process. When LSM/ γ-Al2O3 (10%) catalys is heated at 750℃, no perovskite-type oxides were detected by XRD, and the second reduction peak was absent also in TPR process. \
The order of the second reduction peak temperature(characteristic peak of perovskite - type ox- ides) is: neat LSM(750℃）> LSM/γ-Al2O3 20% (685-698℃) -deposited LSM/γ-Al2O3 (698℃) > LSM/γ-Al2O3 15% (677 - 680℃) >(LSM/γ-AL2O3 10% 620 - 630℃, for Mn - Al - O medium oxides on surface). It is correleted with the increasing of the effect of support sequentially.
When LSM/γ-Al2O3 catalysts were heated at 900℃, more stable phase, spinel MnAl2O4 appeared, which could be proved by TPR of model catalyst MnAl2O4/γ-Al2O3.     

Meso位直结型稳定双卟啉的合成及性质

利用氧化法成功地合成了同核meso位直结型稳定卟啉二聚体锌络合物,收率接近理论值;无论是碱式还是金属络合物都显示出卟啉环间成平面正交的电子吸收光谱;在循环伏安图谱中都显示出卟啉环间再氧化还原过程中较强烈的库仑作用;每个卟啉环的一电子氧化或还原均为可逆过程。     

Co/ZrO2催化剂的结构及TPR性能研究

采用XRD和TPR技术研究了CoZrO体系催化剂的物相结构及还原性能,并以CO氧化反应为探针考察了催化剂的氧化活性.结果表明,钴的存在会阻止tZrO₂→混合相→mZrO₂的转变和ZrO₂颗粒的增长;高温焙烧后,部分钴氧化物与载体ZrO₂形成固溶体.Co/ZrO₂催化剂中的钴以Co₃O₄的形式存在,钴锆之间的相互作用有利于钴的分散.随着Co负载量增加,催化剂的CO氧化活性提高.     

CeO2对CuO／Al2O3分散状态及催化性能的影响

用色谱－液反流动法技术,考察了ＣｕＯ催化剂对ＣＯ的性及添加ＣｅＯ２对催化活性的影响,并运用ＸＲＤ,ＴＰＲ和ＸＰＳ技术,研究了催化剂的物相结构和还原牧场 生。实验结果表明,ＣｅＯ２的添加增加了ＣｕＯ的分散性,使ＣｕＯ的特征衍射峰消失,从而改善了催化剂的氧化活性。