Preparation and characterization of activated carbons from impregnation pitch by ZnCl2

Using an impregnation pitch from bituminous coal tar (OP) supplied by Industrias Químicas del Nalon Company as raw material, two phases (isotropic and anisotropic) have been obtained. The latter was used as precursor for the preparation of activated carbons. First, a chemical activation process was carried out with ZnCl₂ as activating agent. The process was conducted at different concentrations and temperatures and by means of impregnation with solid zinc chloride. Optimal values were obtained for samples prepared by using a ZnCl₂:pitch ratio equal to 3:1 (sample AZn3). Next, this sample was thermally treated at two different temperatures, i.e., 700 and 800 °C. A lose of specific surface area, microporosity and mesoporosity was observed with respect to sample AZn3, such a lose being more remarkable as temperature increased. Moreover, impregnation of the anisotropic phase of the original pitch with an aqueous solution of ZnCl₂ followed by thermal treatment resulted in a poorly developed surface area and porous texture, probably due to the presence of Zn complexes, which interfere with the activation process.     

气密性碳涂覆光纤筛选强度与电阻关系研究

通过实验分析确立了把光纤电阻作为衡量气密性碳涂覆光纤通过２％应变筛选的过渡标准。要拉制２％应变筛选的碳涂覆光纤，其电阻值应小于３０ｋΩ／ｃｍ。     

Gas transport through homogeneous and asymmetric polyethersulfone membranes

Both homogeneous and asymmetric polyethersulfone (PES) membranes were prepared by solvent casting. The sorption and permeation behavior of CO₂, O₂, and N₂ using these two kinds of cast PES membranes and commercially available homogeneous PES film was investigated to extract the pressure dependence of gas permeability and the permselectivity for CO₂ relative to N₂, and to confirm the validity of the working assumption that a skin layer in an asymmetric membrane can be essentially replaced by a thick homogeneous dense membrane. The pressure dependence of the mean permeability coefficient to CO₂ in homogeneous membranes obeys the dual-mode mobility model. The ideal separation factor for CO₂ relative to N₂ at an upstream pressure of 0.5 MPa attains ca. 40, while the permeability to CO₂ is about 2.7 Barrer at the same upstream pressure. The same separation factor in asymmetric membranes amounts to 35. The diffusion behavior for the skin layer in an asymmetric membrane with a thin skin layer can be simulated approximately by that in a homogeneous dense membrane. © 1993 John Wiley & Sons, Inc.     

Electroanalytical and chromatographic determination of pentachlorophenol and related molecules in a contaminated soil: a real case example

Electroanalytical and chromatographic methodologies have been applied for the determination of pentachlorophenol (PCP) and some of its derivatives in real soil samples contaminated by industrial discharge. The analytes were extracted with hexane from soil samples collected at different points of the site and mixed to produce a representative sample. Square wave voltammetry (SWV) experiments were carried out on either a boron-doped diamond (BDD) electrode or a gold ultramicroelectrode (Au-UME) in an analyte composed by the Britton-Robinson (B-R) buffer at pH 5.5 with the direct addition of proper amounts of the extract. The voltammetric responses revealed an irreversible anodic peak at approximately 0.80 V vs. Ag/AgCl with a peak current showing a linear dependence on PCP concentration. This linear relationship yielded a detection limit (DL) of 2×10⁻⁸ mol l⁻¹ (or 5.5 μg l⁻¹) for the BDD electrode and 6.9×10⁻⁸ mol l⁻¹ (18.4 μg l⁻¹) for the Au-UME, while the independently measured HPLC detection limit was 1.1×10⁻⁸ mol l⁻¹ (3.0 μg l⁻¹). The application of electroanalytical and chromatographic methodologies in the analysis of soil extracts revealed, besides the PCP responses, signals for some related molecules such as o-tetrachlorobenzoquinone (o-chloranil), hexachlorobenzene and tetrachlorophenol. Recovering experiments for PCP showed a concentration of 27.5 mg kg⁻¹ for the electroanalytical determinations and 26.8 mg kg⁻¹ for the HPLC analysis, values exceedingly high if considering that the maximum residue limit established for natural waters by the Brazilian Environmental Agency is 10 μg l⁻¹.     

活性炭酸处理对CuO／C催化剂上NO还原反应的影响

４种国产活性炭被用于ＮＯ还原反应，其中，山楂核炭和山桃核炭具有较高的ＮＯ还原转化率。实验发现，表面含氧基团－ＣＯＯ－对活性炭自身的还原性和对ＮＯ的还原活性有很重要的影响。对表面富－ＣＯＯ－基团的活性炭，稀盐酸处理使表面－ＣＯＯ－显著分解。     

助剂改性活性炭担载Pt催化剂催化硝基苯加氢制对氨基苯酚

以改性活性炭担载的Pt为催化剂催化硝基苯经加氢重排一步合成对氨基苯酚，收率54．70％，选择性可达91.40%。     

Carbon deposition on a Ni/α-Al2O3 catalyst

The kinetics of carbon deposition over a Ni/α-Al₂O₃ commercial catalyst, has been studied using CH₄−H₂ gas mixtures in the range of 748–873 K. A Hougen-Watson type model gives good agreement with the experimental rates.     

碳原子簇的结构与质谱的关联（Ⅱ）

根据出现在质谱中的各种大小的碳原子簇的相对丰度,分析了由激光产生的碳原子簇离子的统计分布,研究了这些统计分布与碳原子簇结构的关联。研究结果表明：相同构型的原子簇的相对丰度可以由同一条对数正态分布曲线来描述,由此能够获得碳原子簇构型的变化情况。质谱中分布曲线的数目对应于具有不同构型或不同结构稳定性的原子簇的数目。如果某些簇离子的谱峰明显地高出分布曲线,它们的结构应特别稳定,其成簇原子数就是所谓的“奇幻数”（ｍａｇｉｃｎｕｍｂｅｒ）,例如在石墨质谱中的Ｃ＿（６０）就属于这种情况。原子簇的统计分布还与它们的生成过程有关,由此可能揭示出原子簇的产生机理。     

聚丙烯基纳米碳纤维复合材料结晶行为研究

采用示差扫描量热法(DSC)研究了纳米碳纤维对PP／CNF复合材料中PP结晶行为的影响。结果表明：纳米碳纤雏可提高PP的结晶温度，但略降低其结晶速率和结晶度。提高纳米碳纤雏含量或减小纳米碳纤雏直径，PP结晶行为的上述变化更为明显，但结晶速率随纳米碳纤维含量出现先减小后增大的趋势。