Silicone glue coated stainless steel wire for solid phase microextraction

A new solid phase microextraction (SPME) fiber based on high-temperature silicone glue coated on a stainless steel wire is presented. The fiber coating can be prepared easily in a few minutes, it is mechanically stable and exhibits relatively high thermal stability (up to 260 °C). The extraction properties of the fiber to benzene, toluene, ethylbenzene, and xylenes (BTEX) were examined using both direct and headspace SPME modes coupled to gas chromatography-flame ionization detection. The effects of the extraction and desorption parameters including extraction and desorption time, sampling and desorption temperature, and ionic strength on the extraction/desorption efficiency have been studied. For both headspace and direct SPME the calibration graphs were linear in the concentration range from 0.5 μg L⁻¹ to 10 mg L⁻¹ (R² > 0.996) and detection limits ranged from 0.07 to 0.24 μg L⁻¹. Single fiber repeatability and fiber-to-fiber reproducibility were less than 6.8 and 21.5%, respectively. Finally, headspace SPME was applied to determine BTEX in petrol station waste waters with spiked recoveries in the range of 89.7-105.2%.     

Cu_xCo_(1-x)/Al_2O_3/FeCrAl整体式催化剂上甲苯催化燃烧(英文)

以FeCrAl合金薄片为基底,Al2O3浆料为过渡胶体,不同摩尔比的Cu、Co为催化活性组分,制备了一系列CuxCo1-x/Al2O3/FeCrAl(x=0-1)新型整体式催化剂.采用X射线粉末衍射(XRD),扫描电子显微镜(SEM),X光电子能谱(XPS)和程序升温还原(TPR)等手段对催化剂的结构进行了表征.在微型固定床反应器上评价了催化剂的催化甲苯燃烧性能.研究结果表明:在所制备的整体式催化剂上,当Cu含量比较低时,形成了Cu-Co-O固溶体;当Cu含量比较高时,可以测得CuO的衍射峰.催化剂表面颗粒大小和形貌与Cu、Co摩尔比密切相关.在催化剂表面,Co以Co2+和Co3+价态存在,而Cu主要以Cu2+价态存在.催化剂中的Cu可以改善Co的氧化还原性,从而有利于催化剂活性的提高.在所制备的催化剂中,Cu0.5Co0.5/Al2O3/FeCrAl催化剂具有最好的活性,甲苯在374oC可以完全催化燃烧消除.     

Bentone-34／0V-1毛细管柱的研制及其分离性能

自行研制了Bentone-34／0V-1高效石英毛细管气相色谱柱，并利用该柱分别对二甲苯、二氯苯和二氯甲苯异构体3种体系进行分析。在选用的色谱条件下，难分离物喷对二甲苯和间二甲苯分离度达3；间二氯苯和对二氯苯分离度达137结果表明该柱具有分离效果好，分析速度快的优点。     

Intersystem crossing at singlet conical intersections

The energy of the lowest triplet state of organic molecules is intermediate between the ground state and the first excited singlet. At the S₁/S₀ conical intersection, the two singlet states are degenerate. It is shown that for some molecules (ethylene, benzene, toluene and pyrrole) the T₁ state is also degenerate with the two singlet states. Moreover, the spin orbit coupling matrix element at this structure is necessarily large, so that intersystem crossing can be quite efficient. If the lowest triplet state is repulsive (as in the studied molecules) it may significantly contribute to the dissociation yield under certain experimental conditions.     

Effect of temperature on the volumetric properties of (cyclohexanone + an aromatic hydrocarbon)

The excess molar volume of (cyclohexanone + benzene, or toluene, or ethylbenzene, or styrene) were obtained from the densities measured by means of a vibrating-tube densimeter over the whole composition range at temperatures (293.15, 303.15, 313.15, 323.15, 333.15, 343.15, 353.15) K and atmospheric pressure. The excess molar volume provide the temperature dependence of in the temperature range of (293 to 353) K. The results were correlated using the fourth-order Redlich-Kister equation, with the maximum likelihood principle being applied for the determination of the adjustable parameters. It was found that the in the systems studied increase with rising temperature.     

Toluene methylation on AlPO4-Al2O3 catalysts (5–15 wt.% Al2O3)

The alkylation of toluene with methanol over AlPO₄-Al₂O₃ (5–15 wt.% Al₂O₃) catalysts produces a mixture of xylenes (XYL) although trimethylbenzenes (TMB) were also found. The TMB selectivity increased with temperature at the expense of XYL selectivity. Isomer distribution was approximately 48, 24 and 27 mol% foro-, m- andp-XYL, and 74, 26 and 0 mol% for 1,2,3-, 1,2,4- and 1,3,5-TMB, both quite different from the equilibrium isomer composition. The catalytic activity increased with alumina content, however, it decreased on increasing the calcination temperature in the 923–1273 K range. Good correlations between catalytic activity and the increase in acidic properties with Al₂O₃ loading (as determined by base chemisorption, in the gas phase,versus pyridine and 2,6-dimethylpyridine) have been obtained.     

Au纳米粒子在有机溶剂中的电导行为

采用化学方法制备出粒径约10nm的Au纳米粒子,分别用十二、十四和十六烷基硫醇对Au粒子表面进行修饰,再溶入不同有机溶剂中,制备得到Au纳米粒子/氯仿和Au纳米粒子/甲苯溶液.测试了不同溶液的电导率随溶质浓度的变化规律,发现在整个浓度范围内存在一个临界浓度值.当溶质浓度低于临界浓度值时,溶液的电导率随溶质浓度的增加而迅速增加;而当溶质浓度超过临界浓度值时,溶液电导率的增加缓慢.在本文测试的浓度范围内,当Au纳米粒子分别被十二、十四和十六烷基硫醇修饰时,Au纳米粒子/氯仿溶液的临界浓度值分别约为11.22,7.96和5.47g/L.在相同浓度下,Au纳米粒子外面包裹的烷基硫醇的链长越短,其溶液的电导率越大.在整个浓度范围内,Au纳米粒子/氯仿溶液的电导率均高于Au纳米粒子/甲苯溶液的电导率.     

Mesoporous carbon-supported cobalt catalyst for selective oxidation of toluene and degradation of water contaminants

Mesoporous carbon-supported cobalt (Co-MC) catalysts are widely applied as electrode materials for batteries. Conversely, the development of Co-MC as bifunctional catalysts for application in organic catalytic reactions and degradation of water contaminants is slower. Herein, the catalyst displayed high activity in the selective oxidation of toluene to benzaldehyde under mild conditions, attaining a high selectivity of 92.3%. Factors influencing the catalytic reaction performance were also investigated. Additionally, Co-MC displayed remarkable catalytic activity in degrading dyes relative to the pure metal counterpart. Moreover, the catalyst exhibited excellent reusability, as determined by the cyclic catalytic experiments. The paper demonstrates the potential of Co-MC as a bifunctional catalyst for both toluene selective oxidation and water contaminant degradation.     

Photocatalytic performance of TiO2/V2O5 nanocomposite powder prepared by DC arc plasma

TiO₂/V₂O₅ nanocomposite powder was synthesized by the DC arc plasma, and its photocatalytic activity was examined by decompositions of Rhodamine B solution and toluene gas. In the synthesis of TiO₂/V₂O₅ nanocomposite powder, TiCl₄ and VOCl₃ precursors were introduced into thermal plasma flame with argon carrier gases through separated two gas bubblers. They were decomposed by Ar–N₂ thermal plasma generating Ti and V vapors, followed by the formation of oxides with the injection of additional oxygen into a plasma reactor. Nanocomposite composed of relatively small size V₂O₅ nanoparticles on a spherical TiO₂ nanoparticle which was about 250 nm in diameter was identified by X-ray diffractometry, electronic microscopy, and energy dispersive spectroscopy when the ratio of carrier gas flow rates for TiCl₄ to VOCl₃ was 1:4 or 1:5. In ultraviolet–visible absorption spectroscopy, the absorbed wavelength of light for synthesized TiO₂/V₂O₅ nanocomposite powder was wider than that for commercially available TiO₂ nanopowder. Therefore, Rhodamine B solution exposed to visible light was decomposed by TiO₂/V₂O₅ nanocomposite, whereas it was not decomposed by TiO₂ nanopowder. In addition, toluene decomposition in a dielectric barrier discharge reactor was carried out with nano-sized photocatalysts of TiO₂ nanopowder and TiO₂/V₂O₅ nanocomposite. Relatively higher removal rate of toluene was found in the case of TiO₂/V₂O₅ nanocomposite in virtue of improved photocatalytic performance.     

木质素催化转化制取苯、甲苯和二甲苯

对HZSM-5、HY和MCM-22三种催化剂进行了比较, 其中HZSM-5催化裂解木质素制备苯、甲苯和二甲苯(BTX)的结果最优．确定了木质素催化裂解的最佳反应条件,包括反应温度、载气流速、催化剂/木质素配比．当反应温度为550～600 oC,载气流速为300 mL/min,催化剂/木质素配比为2时,使用HZSM-5催化裂解制备BTX的最高C产率和芳香选择性分别可达25.3%和90.9%。