用以分解氟里昂-12的新型催化剂WO_3/Al_2O_3

氟里昂(CFCs)是破坏大气臭氧层的元凶,是仅次于CO2的第二大类温室气体;此外,它作为一类含氯挥发性有机物,对人体有一定潜在危害.为了禁止氟里昂的生产和使用,1987年签署了“蒙特利尔协定”,至今已有包括中国在内的163个缔约方.然而各国还存有几百万吨氟里昂,为此,探索分解氟里昂的技术已成当务之急.氟里昂能通过多种技术销毁,如:等离子体分解法、UV射线分解法、高能射线分解法、焚烧法、电化学分解法、超临界水法、超声辐照法等,而催化分解是最被看好的方法之一.所谓催化分解,即在催化剂的作用下,氟里昂与水蒸气反应生成CO2、HF和HCl,…     

NO分解催化剂的研究进展

本文对用于NO直接催化分解的贵金属、金属氧化物、钙钛矿型复合金属氧化物、分子筛和碳氮化合物5种代表性催化材料上NO的催化分解性能及反应机理进行了综述.介绍了各种催化材料在用于NO分解反应中所取得的成就和存在的问题.此外,也对计算机模拟技术在NO催化分解中的应用进行了简单介绍,说明计算机技术是一种重要的实验研究辅助手段,有助于对实验现象的理解并为开发新型催化材料提供理论指导.     

双金属催化剂体系催化过氧化氢分解反应

研究了双金属催化剂体系催化过氧化氢分解反应,测量了不同催化剂体系的活化能.结果表明,双金属催化剂对过氧化氢分解反应具有良好的催化性能,且双金属催化剂存在协同催化作用;而酸性环境对过氧化氢催化分解有明显的抑制作用.     

单质铜与过氧化氢溶液反应的研究*

针对单质铜能否与过氧化氢发生反应,以及用硫酸酸化反应液能否加快铜离子催化过氧化氢分解反应速率的疑惑,设计了单质铜与过氧化氢溶液反应和铜离子催化过氧化氢分解反应的实验。认为单质铜能被过氧化氢氧化生成氧化铜和氧化亚铜,加热反应液能明显增大铜离子催化过氧化氢分解反应的速率,用硫酸酸化反应液能明显减小铜离子催化过氧化氢分解反应的速率。     

Co-B非晶态合金催化PH_3分解制备高纯磷(英文)

用化学还原法合成了Co-B非晶态合金,用ICP、DSC、SEM、BET、SAED和XRD技术对样品的组成和结构性质进行了表征.研究了Co-B非晶态合金的新应用-用于催化PH3分解制备高纯磷,考察了催化分解反应条件对分解率的影响.实验结果表明Co-B非晶态合金对PH3分解具有很好的催化效果, 390℃时分解率达84.7%, 420℃达90.2%, 450℃时99.8%.     

室温催化分解空气中臭氧污染物

臭氧污染是我国目前面临的突出环境问题,臭氧及其室内反应形成的二次污染物危害着人体健康。室温催化分解是避免空气臭氧污染的有效方法,本文首先总结了碳、沸石、贵金属与过渡金属氧化物等材料的臭氧催化分解性能;然后聚焦锰氧化物,比较分析了不同锰氧化物的臭氧催化活性,阐述了锰氧化物催化分解臭氧机理的研究进展。水蒸气导致的失活是当前臭氧催化剂研发面临的主要挑战,对臭氧催化分解与失活机理的深入认识是指导高效抗湿臭氧催化材料研发的关键。     

二氧化锰催化分解室内空气中甲醛的研究

甲醛作为室内空气中的主要污染物,具有来源广泛、释放周期长和致癌等特点。二氧化锰因其较高的低温催化活性和低毒廉价优势,被应用于甲醛的催化分解。本文从二氧化锰负载贵金属、二氧化锰结构调控、二氧化锰与其他非贵金属材料复合三方面,综述了二氧化锰催化分解甲醛的研究进展,探讨分析了负载贵金属、晶型与形貌、层间/隧道内阳离子、表面缺陷、原子掺杂以及与其他材料复合等结构调控策略对二氧化锰催化分解甲醛性能的影响,并总结了贵金属与非贵金属催化分解甲醛机理的区别。最后,分析了现阶段室内甲醛净化面临的问题和挑战,展望了二氧化锰催化分解甲醛的主要研究方向和发展趋势。     

分解反应自催化性质快速鉴别的实验方法

许多物质的分解都具有自催化特性,常用的自催化鉴别方法是利用差示扫描量热仪(DSC)、微量量热仪(C80)等进行等温实验判定(简称"等温法").但等温法的温度选择较为困难,因此很有必要从实验角度找到一种简便有效的自催化鉴定方法.本文基于Roduit理论模拟的结果,从实验角度提出了分解反应自催化特性的判定方法(简称"中断回扫法"),并利用该法以及等温法对4种样品(硝酸异辛酯(EHN)、2,4-二硝基甲苯(2,4-DNT)、过氧化二异丙苯(DCP)以及过氧化氢异丙苯(CHP))的分解特性进行判定.结果表明:EHN以及DCP的分解符合n级分解规律,而2,4-DNT以及CHP的分解符合自催化分解规律;中断回扫法可以快速、有效地用于鉴别物质分解是否具有自催化特性.     

分解反应自催化性质快速鉴别的实验方法

许多物质的分解都具有自催化特性,常用的自催化鉴别方法是利用差示扫描量热仪（DSC）、微量量热仪（C80）等进行等温实验判定（简称“等温法”）. 但等温法的温度选择较为困难,因此很有必要从实验角度找到一种简便有效的自催化鉴定方法. 本文基于Roduit理论模拟的结果,从实验角度提出了分解反应自催化特性的判定方法（简称“中断回扫法”）,并利用该法以及等温法对4种样品（硝酸异辛酯（EHN）、2,4-二硝基甲苯（2,4-DNT）、过氧化二异丙苯（DCP）以及过氧化氢异丙苯（CHP））的分解特性进行判定. 结果表明：EHN以及DCP的分解符合n级分解规律,而2,4-DNT以及CHP的分解符合自催化分解规律;中断回扫法可以快速、有效地用于鉴别物质分解是否具有自催化特性.     

Guggenheim法处理过氧化氢催化分解反应动力学数据

采用Guggenheim法处理过氧化氢催化分解反应动力学数据,不用测定过氧化氢完全分解时氧气的体积V∞,即可求出反应速率常数k。该方法既节省实验时间,又减少了实验误差,数据处理结果表明,该方法适用于过氧化氢催化分解反应动力学数据处理。     

WO3/ZrO2 Strong Acid as a Catalyst for the Decomposition of Chlorofluorocarbon (CFC-12)

IntroductionChlorofluorocarbons(CFCs) diffusing to the stratosphere isa major reason forozone de-pletion[1 ] .Also CFCshasbeen claimed to be notoriousforitsgreenhouseeffect[2 ] .So,recent-ly it has become very important to eliminate CFCs as far as protecting the ozone layer sur-rounding the earth is concerned.Among various kinds of approaches to do destruction toCFCs,the catalytic decomposition seems to be the most practical and energetically favorableone,especially for treating small amo…     

CFC and Halon replacements in the environment

Substitute fluorocarbons may have direct environmental impact, for example as greenhouse gases, or indirect impacts through the products of their decomposition in the environment. The mechanisms of that atmospheric decomposition are reviewed here and shown to be well established now. The end products are halogen acids and trifluoroacetic acid, all of which pre-exist in the environment in quantities greater than are expected to arise from fluorocarbon use and emissions. Furthermore, the growth in use of fluorocarbon replacements has been shown to be far less than the fall in CFC and Halon production. Hydrochlorofluorocarbons (HCFCs) have replaced less than one third of CFCs and are, themselves, ozone depleting substances that will be phased out under the Montreal Protocol. The growth in hydrofluorocarbons (HFCs) amounts to about 10% of the fall in CFCs. It is likely that the impact of new fluorocarbons on climate change will be a very small fraction of the total impact, which comes mainly from the accumulation of carbon dioxide in the atmosphere.     

A routine gas chromatographic method for the analysis of chlorofluorocarbons in aerosol cans

Summary A gas chromatographic (GC) method for the routine analysis of fully halogenated chlorofluorocarbons (CFCs) in aerosol cans is described. The identification of CFCs by GC was found to be in full agreement with those by GC-mass-spectrometery. The method has been applied to the analysis of CFCs in 448 aerosol products. The most commonly used fully halogenated CFC propellants in aerosol cans were found to be CFC11, CFC12 and CFC114.     

Comparative Study on Decomposition of CFCl<Subscript>3</Subscript> in Thermal and Cold Plasma

Decomposition of CFCl₃ was investigated in an RF inductively coupled thermal reactor in neutral, oxidative and reductive conditions, and in a silent electric discharge (cold plasma) in neutral and oxidative conditions, respectively. In RF thermal plasma reactor, in neutral conditions, mainly gaseous products and minor amount of solid soot was formed. About 50% the soot could be extracted by toluene. Both the gas phase and the extract contained a wide range of aliphatic and aromatic compounds including chlorine and fluorine containing polyaromatic hydrocarbons (PAHs). In oxidative conditions much less soot was formed as compared to the neutral case. The solid product contained about 45% extractable fraction even in oxidative conditions. However, the extract contained less PAHs than in neutral conditions. In reducing atmosphere the soot yield was similar to the neutral case, but the soot contained 29% extractable fraction only. The extract consisted of polyhalogenated aromatic and polyaromatic hydrocarbons as main components. In neutral conditions different chlorofluorocarbons (CFCs) and chlorine were detected as gaseous products in cold plasma. In oxidative conditions, as final products of decomposition CO₂, CFCs and Cl₃ were formed.     

Catalytic hydrolysis of CFC-12 over solid acid Ti(SO_4)_2

Due to increasing enthusiasm for environmental preservation, the synthesis ofchlorofluorocarbons (CFCs) alternatives and the decomposition of existing CFCs havebeen two hot topics since the production and utilization of CFCs are banned by manycountries. The former has been well carried out while the latter was rarely reported inChina. Among a dozen of decomposition approaches. catalytic hydrolysis is verypromising because of simple processes, requiring mild conditions, dioxins free and the…     

Interference of chlorofluorocarbon (CFC)‐containing inhalers with measurements of volatile compounds using selected ion flow tube mass spectrometry

Selected ion flow tube mass spectrometry (SIFT-MS) is a sensitive technique capable of measuring volatile compounds (VCs) in complex gas mixtures in real time; it is now being applied to breath analysis. We investigated the effect of inhalers containing chlorofluorocarbons (CFCs) on the detection and measurement of haloamines in human breath. SIFT-MS mass scans (MS) and selected ion monitoring (SIM) scans were performed on three healthy non-smoking volunteers before and after inhalation of the following medications: Combivent™ metered-dose inhaler (MDI) (CFC-containing); Ventolin™ MDI (CFC-free); Atrovent™ MDI (CFC-free), Beclazone™ MDI (CFC-containing); Duolin™ nebuliser. In addition, the duration of the persistence of the mass/charge ratios was measured for 20 h. Inhalers containing CFCs generated large peaks at m/z 85, 87, 101, 103 and 105 in vitro and in vivo, consistent with the predicted product ions of CFCs 12, 114 and 11. No such peaks were seen with Duolin™ via nebuliser, or CFC-free MDIs. We conclude that measurement of VCs, such as haloamines, with product ions of similar m/z values to the ions found for CFCs would be significantly affected by the presence of CFCs in inhalers. This issue needs to be accounted for prior to the measurement of VCs in breath in people using inhalers containing CFCs. Copyright © 2009 John Wiley & Sons, Ltd.     

Fluorocarbons in the global environment: a review of the important interactions with atmospheric chemistry and physics

Fluorocarbon impact on ozone depletion is reviewed together with the efficacy of the Montreal Protocol in acting to correct the imbalance between stratospheric ozone production and destruction. The Protocol is also helping to reduce global warming: CFCs are shown to be currently the largest fluorocarbon contributors to climate change. Relative contributions to climate change from CFCs and their HFC substitutes are discussed, together with the consequences of control of minor greenhouse gases on an environmental impact which is dominated by carbon dioxide emissions. Both the potencies of the materials for environmental change and their concentrations in the atmosphere are important and are considered here.Trifluoroacetic acid, a minor product of atmospheric decomposition of some HCFCs and HFCs and of the pyrolysis of fluoropolymers, has been shown to be uniformly distributed in seawater to a depth of over 4000 m and so is natural, although the actual source has yet to be identified.The Montreal Protocol is only one example of action to reduce undesirable impact from fluorocarbons. Other, less universal, actions include abatement of fluoroform greenhouse gas emissions from HCFC manufacturing, process changes to eliminate trifluoromethylsulfur pentafluoride emissions from electrochemical fluorination and ceasing manufacture of perfluorooctanyl sulfonate compounds due to their persistence in human tissue.     

CFC phase-out: have we met the challenge?

In 1974 Nobel prize winners Rowland and Molina proposed that chlorofluorocarbons (CFCs) were stable enough to reach the stratosphere, where, under intense solar radiation they released Cl atoms that could destroy stratospheric ozone protecting the earth’s surface from UV rays. The CFC industry funded both scientific studies to test the Rowland and Molina hypothesis and programmes to identify potential replacements, from which the HFCs emerged as likely candidates. After 5 years it was concluded, on the best scientific evidence available, that stratospheric ozone was being depleted at ∼3% per decade, but sufficient time was available for an orderly phase-out. Although the USA and a few other countries stopped the use of CFCs in aerosols little further work was done until 1985 when the CFC debate was renewed following the discovery of stratospheric ozone depletion over the Antarctic during its spring. Manufacturers restarted their R&D programmes; governments negotiated the Montreal Protocol in 1987 agreeing the partial phase-out of the CFCs. As a result of subsequent amendments CFCs have now been phased-out in the developed world and HCFCs will follow over the next two decades. This paper reviews what has been achieved and what remains to be done. Has the world-wide effort been successful in protecting the ozone layer? Have “acceptable” alternatives been found for the CFCs/HCFCs in their various applications?     

Permeation properties to hydrocarbons,perfluorocarbons and chlorofluorocarbons of cross-linked membranes of polymethacrylates with poly(ethylene oxide) and perfluorononyl moieties

Two kinds of cross-linked polymer membranes were prepared by photo polymerization. One of them (PEO membrane) is a co-polymer of methoxy-terminated poly(ethylene glycol) methacrylate (MEMA) and poly(ethylene glycol) dimethacrylate (EDMA) in feed ratio of 70/30 in wt%. The other (PF/PEO membrane) is a co-polymer of 1H,1H,9H-hexadecafluorononyl methacrylate and EDMA in feed ratio of 70/30 in wt%. The block lengths of poly(ethylene oxide) (PEO) are 9 and 14 for MEMA and EDMA, respectively. Permeation properties of inorganic gases, hydrocarbons, perfluorocarbons and chlorofluorocarbons (CFCs) were investigated for these membranes compared with a silicone rubber (SR) membrane. The PF/PEO membrane is inferior to the SR membrane as for CFCs/N₂ separation because the former has lower permeabilities. The PEO membrane has good performance for separation of hydrocarbons and CFCs from N₂ or perfluorocarbons.     

Enhancements in dissociative electron attachment to CF4, chlorofluorocarbons and hydrochlorofluorocarbons adsorbed on H2O ice

We report that the absolute cross sections for dissociative attachment of approximately 0 eV electrons to chlorofluorocarbons (CFCs) and hydrochlorofluorocarbons (HCFCs) are strongly enhanced by the presence of H2O ice. The absolute cross sections for CFCl3, CHF2Cl, and CH3CF2Cl on water ice are measured to be approximately 8.9 x 10(-14), approximately 5.1 x 10(-15), and approximately 4.9 x 10(-15) cm2 at approximately 0 eV, respectively. The former value is about 1 order of magnitude higher than that in the gas phase, while the latter two are 3-4 orders higher. In contrast, the resonances at electron energies > or = 2.0 eV are strongly suppressed either for CFCs and HCFCs or for CF4 adsorbed on H2O ice. The cross-section enhancement is interpreted to be due to electron transfer from precursor states of the solvated electron in ice to an unfilled molecular orbital of CFCs or HCFCs followed by its dissociation. This study indicates that electron-induced dissociation is a significant process leading to CFC and HCFC fragmentation on ice surfaces.