治理铬渣的两个关键

铬渣中存在的酸溶性六价铬是解毒效果能否持久的关键，而铬渣中游离氧化镁消化是利用铬渣作建筑材料时必须高度重视的问题，论述了湿法解毒、高温解毒和非熔融的综合利用法等方法，对铬盐行业的铬渣治理有指导作用。     

贫燃条件下汽车尾气净化催化技术的发展与展望

本文介绍了用于贫燃发动机尾气，柴油机尾气净化催化技术的发展状况，对各种催化剂及其载体材料的性能进行了比较，提出了开发贫燃条件汽车尾气净化催化技术尚需解决的问题。     

相转移催化还原法制备5—氯—2—氧化吲哚

报道了５－氯吲哚醌在聚乙二醇或二缩乙二醇相转移催化下的Ｗｏｌｆｆ－Ｋｉｓｈｎｅｒ还原制备５－氯－２－氧化吲哚的方法，在最佳反应条件下产率９２％，产物结构经ＩＲ和＾１ＨＮＭＲ确证。     

防止过拟合的属性约简

近年来,机器学习的过拟合问题备受关注,尤其在属性约简中。为解决这一难题,提出一种融合集成策略和去除操作的算法。首先将训练模型数据平分为◢M份;然后将其中M◣-1份采用集成策略进行潜在约简计算;最后将剩余的一份进行提前测试,一旦发生过拟合则将刚加入的属性从潜在约简集中去除。利用提前测试潜在属性约简的方法来防止过拟合现象的发生,几组UCI数据的实验结果说明了新算法的有效性,同时为丰富和发展属性约简提供了一种新的方向。     

温度对还原增感立方体氯化银乳剂中光电子衰减的影响

利用微波介电检测技术,测得还原增感立方体氯化银乳剂中自由光电子与浅束缚光电子衰减行为随还原增感温度的变化。实验发现还原增感温度变化会引起增感中心陷阱作用的变化:当还原增感温度较低时,增感中心起空穴陷阱作用,延缓光电子衰减;还原增感温度较高时,增感中心起深电子陷阱作用,加速光电子衰减。由此,我们得到了确定最佳增感温度的依据。     

Self-assembled monolayers of a disulphide-derivatised cobalt-porphyrin on gold

A self-assembled monolayer (SAM) of a novel cobalt(II)porphyrin disulphide derivative was prepared on flat gold(1 1 1) electrode. Evidence for surface modification was provided by electrochemical reductive desorption of the monolayer and ellipsometry, consistent with a coverage of 2.5 × 10⁻¹⁰ mol cm⁻² and a thickness of 13 Å, respectively. Both results support the presence of SAMs where the molecules share an intermediate position between perpendicular and flat orientation. Scanning tunnelling microscopy have also proven the formation of CoPSS SAMs, however high-resolution images could only be obtained when the CoPSS molecules were diluted in an hexanethiol SAM. The electrocatalytic activity of the surface confined Co-porphyrin was evaluated for the oxygen reduction. Voltammetric data indicate that reaction involves two electrons consistent with the formation of hydrogen peroxide. Under similar experimental conditions the data obtained for an iron-porphyrin analogue points for a full reduction of dioxygen to water.     

Oxygen reduction activity of Pt and Pt-Mn-Co electrocatalysts sputtered on nano-structured thin film support

We report on extensive measurements of oxygen reduction activity of Pt and Pt-Co-Mn electrocatalysts using the rotating ring-disk electrode (RRDE) method. The electrocatalysts were prepared by sputtering from Pt or Pt, Co and Mn targets onto 3M's nano-structured thin film support (NSTF) structures. The area specific activity of Pt/NSTF, measured in 0.1 M HClO₄ and at room temperature, is similar to that of bulk Pt. The area specific measurements show a 20 mV reduction in the Pt-Co-Mn/NSTF overpotential compared to Pt/NSTF. The corresponding kinetic gain in the area specific activity of the ternary alloy is about a factor of two. This ORR enhancement factor observed in the ternary Pt-Co-Mn/NSTF by RRDE measurements is similar to the results obtained in 50 cm² H₂/air fuel cells.     

Decomposition of nitric oxide over perovskite oxide catalysts: effect of CO2, H2O and CH4

Direct nitric oxide decomposition over perovskites is fairly slow and complex, its mechanism changing dramatically with temperature. Previous kinetic study for three representative compositions (La_0.87Sr_0.13Mn_0.2Ni_0.8O_3−δ, La_0.66Sr_0.34Ni_0.3Co_0.7O_3−δ and La_0.8Sr_0.2Cu_0.15Fe_0.85O_3−δ) has shown that depending on the temperature range, the inhibition effect of oxygen either increases or decreases with temperature. This paper deals with the effect of CO₂, H₂O and CH₄ on the nitric oxide decomposition over the same perovskites studied at a steady-state in a plug-flow reactor with 1 g catalyst and total flowrates of 50 or 100 ml/min of 2 or 5% NO. The effect of carbon dioxide (0.5–10%) was evaluated between 873 and 923 K, whereas that of H₂O vapor (1.6 or 2.5%) from 723 to 923 K. Both CO₂ and H₂O inhibit the NO decomposition, but inhibition by CO₂ is considerably stronger. For all three catalysts, these effects increase with temperature. Kinetic parameters for the inhibiting effects of CO₂ and H₂O over the three perovskites were determined. Addition of methane to the feed (NO/CH₄=4) increases conversion of NO to N₂ about two to four times, depending on the initial NO concentration and on temperature. This, however, is still much too low for practical applications. Furthermore, the rates of methane oxidation by nitric oxide over perovskites are substantially slower than those of methane oxidation by oxygen. Thus, perovskites do not seem to be suitable for catalytic selective NO reduction with methane.     

The CH4/NO/O2 “Lean-deNOx” Reaction on Mesoporous Mn-Based Mixed Oxides

High surface area Mn-based porous oxides (MANPO) containing additives like Ce, Sr and La were found to be very active and selective materials under 0.67% CH₄/0.2% NO/5% O₂ lean-deNO _x conditions in the 200–300°C low-temperature range. These materials perform also impressively in the presence of 4% H₂O in the feed stream, where a N₂ selectivity of 98% and an excellent stability over 24 h on stream have been observed. The MANPO materials can be considered serious competitors of noble metals for low-temperature lean-deNO _x applications.     

Charge reduction and regeneration in K+, Na+, Mg2+, Ni2+ and Co2+-exchanged Wyoming Bentonite

Controlled calcination of ion-exchanged Wyoming Bentonite in the presence and absence of ammonia leads to layer charge reductions. Detailed chemical analyses of both unexchangeable and exchangeable species lead to the conclusion that in no case is there migration of the original interlamellar cations into the octahedral region of the layers although, in terms of ionic radius alone, Mg²⁺, Ni²⁺ and, possibly Co²⁺, might be expected to do so. The production of unexchangeable Mg, Ni or Co, is identified as resulting from high temperature hydrolysis leading to hydroxide or oxide formation.