氮中二氧化硫标准气体定值方法的研究

介绍用脉冲荧光分析仪对氮中二氧化硫标准气体定值的分析方法,对方法的精密度、准确度及定值的不确定度进行了考察。该方法的定值结果与重量法的配制值相一致。用该法对荷兰国家计量院制备的氮中二氧化硫标准气体进行比对试验,取得了良好的等效性。     

二氧化硫的电化学氧化过程：Ⅲ.SO2在聚钴卟啉电极上的氧化机理

采用循环伏安法，稳态法，计时电位法等研究了ＳＯ２在聚钴卟啉膜电极上的电化学氧化过程，并和ＳＯ２在贵金属电极上的行为进行了比较。     

纳米金催化剂的抗水性能和抗硫中毒性能

与Au/Al2O3相比,复合载体负载的Au/FeOx/Al2O3具有更高的催化CO氧化的低温活性和稳定性,且表现出湿度增强效果,水分压为550~1 600 Pa时催化剂活性较高.在完全无水的环境中,催化剂发生快速不可逆失活;在饱和水汽的环境中,催化剂发生缓慢可逆失活.在水汽作用下的失活与纳米金粒子的粒径长大有关.助剂对催化剂抗水性能影响不大,但对抗硫中毒性能的影响较大.Au/CeO2/Al2O3催化剂显示有最佳的抗硫中毒性能.催化剂表面硫化物和硫酸盐的生成是导致催化剂不可逆硫中毒失活的主要原因.     

负载型贵金属催化剂的硫中毒机理——载体的酸碱性与催化剂抗硫性能的关系

以H_2S为毒物,H_2-O_2反应为催化模型反应,制备并考察了一系列不同酸碱性的负载型钯催化剂。以NH_3和吡啶为探针分子,用程序升温脱附(TPD)或红外光谱法测定了催化剂的酸碱性。用交替脉冲微反色谱技术评价了催化剂的活性和耐硫中毒性,并对催化剂的耐硫性能和载体酸碱性进行关联和解释。在以上研究基础上,指出了提高催化剂抗硫性能的途径。     

聚电解质──壳聚糖浓溶液流变学性质研究：浓度、温度、溶剂pH值和外加盐对粘度及流动性的影响

本工作用日本岩本ＲＰＸ－７０５多功能流变仪测定了在不同浓度、温度、溶剂ｐＨ值和外加盐浓度对壳聚糖在甲酸水溶液中其浓溶液粘度η随剪切速率γ的变化关系．讨论了浓度、温度等对溶液粘度、流动活化能Ｅ_γ和流动指数ｎ的影响．发现溶剂ｐＨ值减小或溶液中外加盐浓度增加，溶液粘度变小，ｎ增大，表明非牛顿流动性减弱，并且进一步讨论了零剪切粘度η_０和外加盐浓度Ｃ_ｓ的依赖关系．     

Catalytic Asymmetric[2,3]-Sigmatropic Rearrangement of Sulfur Ylides Generated from Carbenoids and Allenic 2-Methylphenyl Sulfide

The first investigation on catalytic asymmetric [2, 3]-sigmatrop-ic rearrangement of sulfur ylides generated from carbenoids andallenic phenyl sulfide was carried out. Up to 55% ee value wasobtained.     

Study of clinker dopped with P and S compounds

The sintering and the structure of clinkers, modified by the introduction of different ionic forms of sulfur and phosphorus into the raw mix, were examined. One reference synthetic mixture and 25 modified mixtures were prepared by mixing the reference sample with 0.5, 1.0, 1.5, 2.0 and 2.5%w/w of chemical grade CaSO₄, CaS, Ca₃(PO₄)₂, CaHPO₄ and Ca(H₂PO₄)₂. Free lime content in all samples was measured. The sintering reactions in samples were recorded by means of differential thermal analysis. The texture of the clinkers was examined using a scanning electron microscope and EDX. It is concluded that, despite of their relatively low doping concentration in the raw mix, P and S affect considerably its reactivity and the texture of the clinker. The various ionic forms of the same element (SO₄ ^2-, S^2- for S, PO₄ ^3-, HPO₄ ^2- and H₂PO₄ ^- for P) exhibit a different and unequivocal effect on the reactivity of the synthetic raw mix and on the texture of the corresponding clinkers. S (in both forms) and P (added as HPO₄ ^2-) are mainly dissolved in the melt and they have a positive effect on the burnability of the raw mix. P (added as PO₄ ^3- or H₂PO^4-) is preferentially accumulated in belite. In this case further stabilization of β-C₂S occurs and the binding of the free lime is hindered. This revised version was published online in August 2006 with corrections to the Cover Date.     

Chalcogenide Exchange Reaction of [RGa(μ3-Te)]4 with Elemental Sulfur and Selenium: A Density Functional Theory Study

Thermodynamic and mechanistic features of the chalcogen exchange reaction between [RGa( ₃-Te)]₄ and elemental sulfur or selenium have been studied employing density functional theory (DFT) calculations using the BL3YP basis set and Stuttgart pseudopotentials. For [MeGa( ₃-E)]₄ (E=S, Se, Te) the correlation between the calculated parameters and diffraction data for their isolable analogs is greater than 98%. Each step of the conversion of [MeGa( ₃-Te)]₄ to [MeGa( ₃-E)]₄ via [Me₄Ga₄( ₃-Te)_4–x ( ₃-E) _x ] (E=S, Se) is predicted to occur as a series of isolated reactions. The entropy change for each chalcogen exchange is small in magnitude and corresponds to the degree of cage distortion within the cubane molecules. Calculations performed on [MeGa( ₃-Te)]₄...S₈ and [MeGa( ₃-Te)]₄-S suggest that an increase in electrophilicity of the gallium next to a surface bound tellurium may result in nucleophilic cage opening for which intermediate structures are calculated.     

Conformational studies of 1,2,3-trichloro- and 1,2,3-tribromopropane by nuclear magnetic resonance spectroscopy: attractive parallel (1:3) halogen-hydr

Analysis of the NMR spectra of 1,2,3-trichloropropane and 1,2,3-tribromopropane in various media shows the most stable conformer to be AG_-. The populations of several conformera have been estimated by using pure trans and gauche coupling constants obtained from closely similar molecules. The calculated populations found in non-polar solvents agree well with those obtained by electron diffraction studies in the gas phase. It is suggested that the AG_- form is stabilised relative to AG₊ by the former having two parallel (1:3) halogen-hydrogen attractions against one in the AG₊ form. Comparison is made to related molecules where the most stable conformers also have the greatest number of parallel (1:3) halogen-hydrogen interactions.