Electrooxidation Mechanism of Methanol at Pt-Ru Catalyst Modified GC Electrode in Electrolytes with Different pH Using Electrochemical and SERS Techniques

The electrochemical and in-situ surface-enhanced Raman spectroscopy （SERS） techniques were used to investigate the electrooxidation behavior of methanol in acidic, neutral and alkaline media at a Pt-Ru nanoparticle modified glassy carbon （Pt-Ru/GC） electrode. The results showed that methanol could be dissociated spontaneously at the Pt-Ru/GC electrode to produce a strongly adsorbed intermediate, CO. It was found that CO could be oxidized more easily in the alkaline medium than in the acidic and neutral media. The peak potential of methanol oxidation was shifted from 0.663 and 0.708 V in the acidic and neutral media to -0.030 V in the alkaline medium, which is due to that the adsorption strength of CO on the Pt surface in the alkaline medium is weaker than that in the acidic and neutral media. The final product of the methanol oxidation is CO2. However, in the alkaline medium, CO2 produced would form CO3^2- and HCO3^- resulting in the decrease in the alkaline concentration and then in the decrease in the performance of DMFC. Therefore, the performance of the alkaline DMFC is not Stable.     

正庚烷在超稳Y沸石(USY)负载超强酸催化剂上加氢异构化

The Pt-bearing SO₄^2-/ZrO₂ superacid catalysts supported on ultra stable Y (USY) zeolite were prepared by impregnation and characterized by X-ray diffraction, nitrogen adsorption and Hammett indicators. Their catalytic activities were evaluated in the hydroisomerization of n-heptane with an atmospheric fixed-bed reactor. The catalysts possessed a high surface area, superacidity and well maintained pore structure of USY support. The supported catalysts with a suitable SO₄^2-/ZrO₂ loading exhibited a higher catalytic activity and selectivity than the unsupported SO₄^2-/ZrO₂ catalyst or the Pt supported on USY catalyst without superacid. At the reaction temperature of 220 ℃, over the catalyst with a Pt loading of 0.8wt% and ZrO₂ loading of 10wt%, the conversion of n-heptane could be as high as 35.2% with a selectivity of 87.9% for isomerization products.     

钴的光度分析方法进展

综述了近十多年来国内外钴的光度分析方法,包括分光光度法、催化光度法、原子吸收光度法等。     

Determination of Partial Molar Volumes of EPA and DHA Ethyl Esters in Supercritical Carbon Dioxide

The use of supercritical fluids (SCFs) as solvents has been attracting widespread interest in the research and commercial applications. The study of partial molar volumes of solutes at infinite dilution in the near-critical region is of considerable fundamental importance, as these data reflects the interactions occurring between the solute and the solvent. Experimental measurements of partial molar volumes may be divided into two categories: direct and indirect methods. The direct methods…     

Distribution of Helium Isotopes in Western Pacific Upper Layer

3He/4He ratios in samples of sea water obtained at depths from surface to 300 m in the upper layer of the Western Pacific Ocean were measured by a mass spectrometer VG5400. The lateral and vertical distribution of He isotopes in the studied area was discussed in detail on the basis of 3He/4He ratios. Excess and depleted 3He. in relation to δ3He value of surface water in equilibrium with air has been discussed in the area, which may be mainly attributed to the incorporation of the North Pacific Intermediate Water with the Equatorial Upwelling and the exchange of water masses between the South China Sea and the Western Pacific, respectively. The present work in Western Pacific has also indicated that He isotopes may be used as a tracer for mixing processes of water masses and oceanic circulation.     

薄层色谱法在香兰素合成中的应用

应用薄层色谱法对愈创木酚、3－甲氧基－4－羟基扁桃酸和香兰素进行了分析，以硅胶GF254作为吸附剂，从几种溶剂系统中选出氯仿：乙酸乙酯：正丙醇：冰乙酸：水＝20：1：1：1：2溶液作为展开剂。建立了 香兰素的薄层扫描定量分析方法，测定波长为500nm，参比波长为570nm，线性范围为0．31－6．2μg。     

单核锌双卟啉配合物构象平衡的理论研究及光谱分析

合成了一系列以不同长度柔韧链相连的p/p型单核锌双卟啉配合物。选用Tripos力场,利用分子动力学模拟退火和分子力学构象搜索相结合的方法对该系列双卟啉进行了能量优化和构象分析。理论计算结果表明:该类双卟啉稳定存在的最低能量构象为叠合式,最高能量构象为伸展式,并存在一系列的中间能量构象;双卟啉分子内π-π作用和能量转移与双卟啉存在的两种主要构象密切相关;分析了分子内π-π作用的本质。运用不同光谱测试手段验证了理论计算结果: 利用可见和相应二阶导数吸收光谱研究了双卟啉主要存在的叠合式和伸展式构象,通过红外光谱观察了对双卟啉构象和卟啉环间π-π作用较为敏感的吸收谱带;利用荧光光谱计算了双卟啉的分子内能量转移效率。     

相转移催化应用于催化裂化汽油氧化脱硫的研究

随着人们环境保护意识的增强及原油硫含量的增大, 生产满足环境保护要求的清洁燃料是全球炼油工业的发展趋势, 燃料油脱硫显得越来越重要. 在众多的脱硫方法中, 选择性氧化脱硫技术以其工艺条件温和, 脱硫效果明显等特点, 受到了炼油行业的极大关注[1~3], 但脱硫率偏低(30％), 其关键是水相氧化剂与含硫化合物的有效混合. 本文将相转移催化应用于催化裂化(FCC)汽油的氧化脱硫中, 并对脱硫的工艺和机理进行了研究.     

非晶聚对苯二甲酸乙二醇酯薄片在低温退火过程中的声发射现象

Acoustic emission during sub-Tg annealing fort amorphous polyethylene terephthalate (PET) sheet quenched from melt has been observed. The mechanical properties, texture and glass transition of annealed specimens have been studied. It is shown that some of PET chains change from non-equilibrium state to equilibrium state during sub-Tg annealing, which leads to stress concentration in specimen. When the level of internal stress approaches to the limit, the acoustic waves are emitted due to sudden releasing of stress and the micro-defects are for-med. This is one of the important reasons,the causes the loss of mechanical properties to an-nealed specimens.     

Y掺杂对氢氧化镍电极高温性能的影响

合成了内掺稀土元素Y的β-Ni(OH)2和α-Ni(OH)2材料, 并通过XRD、TEM、CV 和充放电测试等方法研究了Y元素对这两种晶型活性材料的结构、形貌以及高温电化学性能方面的影响, 发现Y元素可显著提高β-Ni(OH)2和α-Ni(OH)2材料的高温性能, 且作用机理相同, 均是通过提高析氧过电位来改善镍电极的高温充电效率. 但是α-Ni(OH)2在高温下的相稳定性仍有待提高.