高效液相色谱法分析十溴二苯乙烷产品

采用Zorbax C18色谱柱(5 μm,150 mm×4.6 mm)于40 ℃下分离十溴二苯乙烷产品,以甲醇-四氢呋喃(体积比为70∶30)为流动相,在230 nm波长下检测。实验结果显示,在十溴二苯乙烷的质量浓度为0.001～0.100 g/L时,其浓度与峰面积有较好的线性关系。该方法对十溴二苯乙烷的回收率大于96%,相对标准偏差为4.0%,可替代热分析法分析十溴二苯乙烷,且能满足工业生产检测的要求。     

Photocatalytic Synthesis of Hydrocarbon Oxygenates from C2H6 and CO2 over Pd-MoO3/SiO2 Catalyst

Pd-MoO3/SiO2 catalyst has been prepared using the method of incipient wetness impregnation. The photo absorbing behaviors and chemisorbing properties of the catalyst have been characterized by UV-vis spectra and TPD-MS experiments. The results indicated that metal Pd loaded on MoOe/SiO2 has a significant effect on the photo absorbing performance of MoO3/SiO2, and an obvious blue shift of the absorption edge is produced. Under UV irradiation, the chemisorption state of CO2 undergoes decomposing process to form CO at 481 K, and a two-site adsorption state of ethane can be formed at around 496 K. Photo-oxidation of ethane using carbon dioxide can mainly produce propanal, ethanol and acetaldehyde in the temperature range of 353-423 K. The presence of metal Pd improves the catalytic activity remarkably.     

Supported ZnO catalysts for the conversion of alkanes:About the metamorphosis of a heterogeneous catalyst

ZnO could be a suitable catalyst for the oxidative conversion of CH4,C2H6 and C3H8.However,the main drawback is its thermal instability.Therefore,ZnO supported on ZrO 2,TiO2,γ-Al2O and SiO2 was investigated for the oxidative dehydrogenation of propane and ethane,and the oxidative coupling of methane.The stability of the supported ZnO is partially improved,but ZnO reacts with the support material,forming new compounds (Zn-zirconates,-titanates,-aluminates and-silicates),which already occurs below reaction temperature.This might also be the case for many other heterogeneous catalysts.     

Chromium(III) determination without sample treatment by batch and flow injection potentiometry

A new and easy device for direct detection of chromium(III) in batch and flow analysis without previous oxidation/reduction or preconcentration steps of samples is designed and evaluated. For this purpose a potentiometric sensor with solid state membrane based on carbon paste matrix is developed. The sensor is modified with di(2-hydroxyphenylimino)ethane and the principal analytical parameters of the potentiometric response in batch and flow analysis are optimized and calculated. Optimal detection limits (1.4 × 10⁻⁷ M in static mode and 5.4 × 10⁻⁷ M in on-line analysis) and selectivity to trivalent chromium are obtained in both analysis modes. The use of this device to direct detection of chromium(III) in real samples is tested using a sediment Certified Reference Material. Chromium(III) determination is also carried out with successful results in environmental samples such as extracts from soils used as barriers in landfills and industrial samples such as waste waters from electroplating industries.     

Pesticides in water and the performance of the liquid-phase microextraction based techniques. A review

The control of pesticides in surface, drinking and groundwater is nowadays a real necessity. In the European Community, their concentration must comply with the established parametric and environmental quality standards (EQSs). Regarding the new legislation, this article updates the information concerning the monitoring of pesticides and the technical specifications for their measurement in water samples where ultra-sensitive analytical methods are required. For some compounds, like pesticides, there is still a need to improve the performance of the existing methods. High sensitive techniques like gas chromatography tandem mass spectrometry (GC–MS/MS) and liquid chromatography coupled with mass spectrometry (LC–MS) have been developed. However, for most of the substances present at trace and ultra-trace levels the extraction and preconcentration steps are so far essential for their detection. Advances at a micro scale have been made and different types of microextractions are being developed. Liquid-phase microextraction (LPME) is an example. The study of this technique has increased in the last years and some innovations have been recently reported for pesticides water analysis. This article reviews the new developed LPME-based techniques and compares its performance with the analytical specifications established for pesticides water monitoring. The results show that LPME-based techniques can be a promising tool to improve the nowadays performance of methods used in pesticides water control.     

乙烷／丙烷混合工质流动沸腾传热研究

对乙烷、丙烷纯质及三种不同浓度比例的乙烷／丙烷二元混合物在内径为8mm的水平管内进行了饱和流动沸腾传热特性的实验研究,重点分析了热流密度、质量流量的变化对二元混合工质传热系数的影响。选用了4种专用于计算混合物流动换热的关联式,并与实验数据进行了比较,其中Gungor—Winterton and Thome关联式和Zou...     

Spin-crossover phenomena of the assembled iron complexes by enclathrating an organic molecule

Assembled complex, Fe(bpa)₂(NCX)₂ (bpa=1,2-bis(4-pyridyl)ethane; X=S, Se, BH₃) enclathrated diphenylmethane. The skeletons were interpenetrating structures for NCS and NCSe complexes, while 2D grid structure was obtained for NCBH₃ complex. The assembled iron complexes showed spin-crossover phenomena by enclathrating diphenylmethane. The ratio of spin transition and the transition temperature depended on the assembled structure.     

乙烷部分氧化超细Fe－Mo－O催化剂的研究

采用溶胶-凝胶法制备了Fe－Mo－O催化剂，用XRD、TEM、BET、IR、TPR、TPD和微反等技术研究了催化剂晶体结构、表面构造、晶格氧活泼性、化学吸附和乙烷部分氧化反应性能。Fe－Mo－O复合氧化物催化剂是由超细微粒组成，微粒粒径约10 nm～20 nm，比表面积为48.1 m2/g。催化剂表面由Lewis碱位（Mo=O键的端氧和Fe－O－Mo键中的桥氧）及Lewis酸位构成。乙烷能以甲基中的H原子吸附在催化剂表面Lewis碱位Mo=O的端氧上形成分子吸附态，其部分氧化产物主要是C2H4和少量的CH3CHO。