乙酰糖基金属卟啉的合成及其对烷烃温和氧化的选择性催化作用

由吡咯和葡萄糖取代苯甲醛直接缩合制备了两种葡萄糖取代卟吩,四(邻位乙酰葡萄糖氧代苯基)卟吩和四(间位乙酰葡萄糖氧代苯基)卟吩,它们进一步金属化合成了四种葡萄糖金属卟啉,氯化四(邻位乙酰葡萄糖氧代苯基)卟吩合铁、氯化四(间位乙酰葡萄糖氧代苯基)卟吩合铁、氯化四(邻位四乙酰葡萄糖氧代苯基)卟吩合锰和氯化四(间位乙酰葡萄糖氧代苯基)卟吩合锰。它们的结构由紫外-可见光谱、元素分析和核磁共振证实。研究了这些葡萄糖取代金属卟啉对亚碘酰苯常温常压下氧化异戊烷反应的选择性催化作用。研究表明,糖基金属卟啉催化异戊烷端基碳氢键的氧化,对一级碳氢键表现出专一性催化作用。非糖基金属卟啉催化异戊烷二级和三级碳氢键的氧化。与非糖基金属卟啉比较,糖基金属卟啉对烷烃羟基化反应的催化行为更接近细胞色素P-450单充氧酶。     

基于生物炭的高级氧化技术去除水中化学品类新污染物研究进展

化学品类新污染物种类繁多,对自然生态环境和人类健康存在严重风险,是新污染物治理的主要对象。由于常规水处理工艺对新污染物的去除能力有限,如何发展绿色、经济、高效和安全稳定的净水技术成为新污染物管控的重要课题。生物炭因其丰富的表面结构与性质,具有优异的吸附和催化能力。近年来,众多科研工作者开展了基于生物炭的高级氧化技术(AOPs)去除新污染物的效能和机制研究。本文聚焦主要的化学品类新污染物,分析了生物炭结构与去除新污染物功能间的关系,综述了近年来生物炭在光催化氧化、类芬顿氧化和过硫酸盐催化氧化中的应用,并探讨了水环境条件(如pH值、阴离子和有机物等)对反应体系的影响,最后对未来相关研究中值得关注和深入探索的问题进行了总结与展望。     

甲醛低温催化氧化动力学研究: Ⅰ 本征动力学

甲醛是室内空气污染的主要物种之一[1]。甲醛被吸入人体后,破坏人体的DNA结构,从而引起基因突变,产生潜在的致癌性。因此,脱除甲醛具有一定的现实意义。甲醛的脱除方法主要有催化氧化法、热氧化法、吸附法、生物脱除法等。催化氧化法由于具有很高的脱除效率,是研究较多的脱除甲     

Chemical‐surface modification of polymers using atmospheric pressure nonequilibrium plasmas and comparisons with vacuum plasmas

We demonstrate that stable microwave‐coupled atmospheric pressure nonequilibrium plasmas (APNEPs) can be formed under a wide variety of gas and flow‐rate conditions. Furthermore, these plasmas can be effectively used to remove surface contamination and chemically modify polymer surfaces. These chemical changes, generally oxidation and crosslinking, enhance the surface properties of the materials such as surface energy. Comparisons between vacuum plasma and atmospheric plasma treatment strongly indicate that much of the vacuum‐plasma literature is pertinent to APNEP, thereby providing assistance with understanding the nature of APNEP‐induced reactions. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 40: 95–109, 2002     

Fe2O3/CNT催化湿法H2O2氧化苯酚

通过化学沉积法和热处理得到多壁碳纳米管负载Fe2O3催化剂 Fe2O3/CNT, Fe2O3的负载质量分数约为15.1%,XRD表征显示,负载的Fe2O3存在α和γ这2种晶型。考察了Fe2O3/CNT催化湿式H2O2氧化去除废水中苯酚催化性能,通过苯酚的去除率及反应过程中催化剂活性组分的溶出总量,研究了催化剂制备过程中添加聚乙烯醇对催化剂性能的影响。在苯酚和H2O2初始浓度分别为350和1 500 mg/L、催化剂投加量为1.0 g/L、温度80 ℃条件下,经过240 min的反应,苯酚去除率达100％,COD去除率为86.1％。     

A New Member of the Graphene Family: Graphene Acid

A new member of the family of graphene derivatives, namely, graphene acid with a composition close to C₁(COOH)₁, was prepared by oxidation of graphene oxide. The synthetic procedure is based on repeated oxidation of graphite with potassium permanganate in an acidic environment. The oxidation process was studied in detail after each step. The multiple oxidations led to oxidative removal of other oxygen functional groups formed in the first oxidation step. Detailed chemical analysis showed only a minor amount of other oxygen‐containing functional groups such as hydroxyl and the dominant presence of carboxyl groups in a concentration of about 30 wt %. Further oxidation led to complete decomposition of graphene acid. The obtained material exhibits unique sorption capacity towards metal ions and carbon dioxide. The highly hydrophilic nature of graphene acid allowed the assembly of ultrathin free‐standing membranes with high transparency.     

羟基自由基引发的邻二甲苯大气氧化机理

采用量子化学、过渡态理论和单分子反应理论计算,研究了由羟基(OH)自由基引发的邻二甲苯(oX)大气氧化降解机理.在M06-2X/6-311++G(2df, 2p)水平上优化了反应物、过渡态和产物的结构,在ROCBSQB3水平上计算了反应势能面.采用过渡态理论计算了各个可能反应步骤的速率常数和反应通道的分支比,同时还采用单分子反应理论(RRKM-ME)计算探讨了反应的压力效应.计算发现,在大气中,邻二甲苯与OH的反应以苯环加成为主,首先形成两个加和物oX-1-OH (R1)和oX-3-OH (R3),它们随后与大气中的氧气发生反应.R1和R3与O₂可直接发生不可逆直接夺氢生成二甲基苯酚,或和O₂的可逆加成,生成双环自由基中间体.双环自由基将与大气中的氧气结合,形成双环过氧自由基,接着与NO或HO₂反应生成有机硝酸酯或有机过氧化氢化合物,或被还原为双环烷氧自由基,并最终生成产物,包括丁二酮、丁烯二醛、甲基乙二醛、4-氧-2-戊烯醛、2, 3-环氧丁二醛以及少量的乙二醛.这些产物中有机过氧化氢和甲基乙二醛被认为对二次气溶胶有较大的贡献.结合理论计算和文献报道的实验结果,提出了新的oX大气氧化机理,预测了在高NO浓度条件下可能产物的分支比,并与文献报道结果相比较.最后还讨论了温度对反应机理的影响.     

氮杂冠醚取代单Schiff碱过渡金属配合物催化氧化对二甲苯研究

本文将苯并-10-氮杂-15-冠-5或吗啉基取代的单Schiff碱过渡配合物作为催化剂,在常压和120℃条件下,以空气为氧源,研究了对二甲苯催化氧化反应。实验探讨了Schiff碱配合物中心金属离子、Schiff碱配体中挂接的氮杂冠醚环、配体芳环上取代基和反应时间等对对二甲苯催化氧化反应的影响。实验结果表明:Schiff碱配合物中氮杂冠醚的存在能显著缩短反应诱导期,提高催化反应活性和产物选择性;Schiff碱Mn(III)配合物比Schiff碱Co(II)具有更高的催化反应活性;氮杂冠醚Schiff碱Mn(III)配合物对于二甲苯的催化氧化反应转化率大于60%,对甲苯甲酸产物的选择性均高于70%。     

Atmospheric oxidation mechanism of bromoethane

A mechanism for the atmospheric oxidation of bromoethane is proposed from an ab initio study. Using CCSD(T)/6-311++G(2df,2p)//MP2/6-31G(d) level of theory, the structure and energetics of the 35 species and transition states involved in the atmospheric oxidation of bromoethane are examined. From these calculations, reaction enthalpies and activation energies to characterize the potential energy surface of the proposed mechanism for the complete atmospheric degradation of bromoethane are determined. The studies revealed that the hydrogen abstraction from the alpha carbon has the lowest activation energy barrier of all the possible abstractions, making this pathway the most energetically favored pathway for the atmospheric oxidation process. The brominated species that result from the oxidation at the alpha carbon are BrC(O)CH(3) and BrC(O)H. Other species resulting from oxidation initiated at the beta carbon are also identified.     

氮杂冠醚取代非对称双Schiff碱配合物催化氧化对二甲苯研究

将一系列苯并-10-氮杂-15-冠-5或吗啉基取代的不对称双Schiff碱配合物作为催化剂,在常压和120℃条件下用于催化氧化对二甲苯研究。探讨了Schiff配合物中心金属离子、Schiff碱配体中挂接的氮杂冠醚环、配体芳环上取代基等对催化氧化对二甲苯反应活性及其氧化产物选择性的影响。实验结果表明:配合物中氮杂冠醚的存在能显著缩短反应诱导期、提高催化活性和选择性;Schiff碱Mn(Ⅲ)配合物比Schiff碱Co(Ⅱ)和Schiff碱Cu(Ⅱ)具有更高的催化活性;氮杂冠醚Schiff碱Mn(Ⅲ)配合物催化氧化二甲苯的转化率和产物选择性分别达75%和90%。     

Preparation of Anode Material for Lithium Ion Battery by Chemical Oxidation

Sincetheoilcrisisinthe60'sand70's,ithasbeenrealizedthatthenaturalresourcesareveryimportantandtheresearchoflithiumsecondarybatterywasthenbegun.Recently,theurgentdemandofmicroelectronicsforsecondarybatterywithhighenergydensityandlightweighthasgreatlystimulatedthedevelopmentoflithiumsecondarybattery.Onlyintheearly90's,didthiskindofbatterybecomecommercialwhenitwasfoundthatgraphitecansubstitUtelithiumorlithiumalloysandsolvetheproblemsofsafetyandcyclelife.However,thesynthesisconditionforgraphiteiscr…     

Oxidized Xanthan Gum Crosslinked NOCC: Hydrogel System and Their Biological Stability from Oxidation Levels of the Polymer

Dynamic hydrogel systems from N,O-carboxymethyl chitosan (NOCC) are investigated in the past years, which has facilitated their widespread use in many biomedical engineering applications. However, the influence of the polymer's oxidation levels on the hydrogel biological properties is not fully investigated. In this study, chitosan is converted into NOCC and introduced to react spontaneously with oxidized xanthan gum (OXG) to form several injectable hydrogels with controlled degradability. Different oxidation levels of xanthan gum, as well as NOCC/OXG volume ratios, are trialed. The infrared spectroscopy spectra verify chemical modification on OXG and successful crosslinking. With increasing oxidation levels, more dialdehyde groups are introduced into the OXG, resulting in changes in physical properties including gelation, swelling, and self-healing efficiency. Under different volume ratios, the hydrogel shows a stable structure and rigidity with higher mechanical properties, and a slower degradation rate. The shear-thinning and self-healing properties of the hydrogels are confirmed. In vitro assays with L929 cells show the biocompatibility of all formulations although the use of a high amount of OXG15 and OXG25 limited the cell proliferation capacity. Findings in this study suggested a suitable amount of OXG at different oxidation levels in NOCC hydrogel systems for tissue engineering applications.     

CeO2/NaY催化剂的氧合及其催化氧化脱硫性能

采用等体积浸渍法制备了一系列CeO₂/NaY催化剂,重点考察了焙烧温度和铈负载量对催化剂活性组分结构及性能的影响。通过拉曼（Raman）光谱、X射线衍射（XRD）、低温N₂吸附-脱附（BET）、高分辨透射电子显微镜（HR-TEM）以及氢气程序升温还原（H₂-TPR）等技术对催化剂的结构、形貌和化学性能进行了表征分析。结果表明,焙烧温度与铈负载量对于铈物种在分子筛载体表面及孔道内的分散形态和与载体的相互作用有着重要影响,进而影响催化剂中铈物种的氧合性能与氧化脱硫性能。在常温常压下的氧合性能测试,催化剂最大储氧量为每克催化剂1.44 mmol O₂。在反应温度100 ℃,催化剂用量0.20 g,以正辛烷为溶剂二苯并噻吩初始浓度为500 μg·g^-1的模拟油样20 mL,氧气流量为50 mL·min^-1的条件下,反应240 min二苯并噻吩转化率可达90.10%,二苯并噻吩被氧化为二苯并噻吩砜。因此,发展稀土改性分子筛催化剂,应用于以分子氧为氧化剂的油品氧化深度脱硫,对探究绿色高效的油品氧化脱硫技术具有积极意义。     

Stability of fluorinated surfactants in advanced oxidation processes--A follow up of degradation products using flow injection-mass spectrometry, liquid chromatography-mass spectrometry and liquid chromatography-multiple stage mass spectrometry

The advanced oxidation process (AOP) reagents ozone (O3), O3/UV, O3/H2O2, and H2O2/Fe2+ (Fenton's reagent) were applied to the anionic and the non-ionic fluorinated surfactants perfluorooctanesulfonate (PFOS) and N-ethyl-N-(perfluoroalkyl)-sulfonyl-glycinic acid (HFOSA-glycinic acid) or N-ethyl-N-perfluoroalkyl sulfonylamido-2-ethanol polyethoxylates (NEtFASE-PEG), their methyl ethers (NEtFASE-PEG methyl ether) and partly fluorinated alkyl-ethoxylates (FAEO) dissolved in ultrapure water. To monitor the efficiencies of destruction samples were taken during the treatment period of 120 min. After sample concentration by C18-solid phase extraction (SPE) and desorption MS, coupled with atmospheric pressure chemical ionisation (APCI) or electrospray interface (ESI) was applied for detection. No elimination of PFOS was observed while HFOSA-glycinic acid and AOP treated non-ionic surfactants were eliminated by oxidation. Degradation products could be detected and identified. So PFOS was observed during HFOSA-glycinic acid oxidation. Polyethylene glycols (PEG) and PEG methyl ethers were generated from non-ionic fluorinated surfactants beside their oxidation products--aldehydes and acids--all identified by tandem (MS-MS) or multiple stage mass spectrometry (MSn). AOP treatment of FAEO blend resulted in a mixture of partly fluorinated alcohols, separated and identified using GC-MS.     

Stable radicals formation in coals undergoing weathering: effect of coal rank

Once coal is excavated it comes into contact with atmospheric oxygen and begins to undergo low temperature oxidation. The mechanism by which the molecular oxygen interacts with the coal macromolecule is suggested to occur in several steps. These steps primarily involve O(2) diffusion to the surface where physical adsorption followed by chemical adsorption takes place. The chemical adsorption forms several types of oxides that can subsequently react to form several products, primarily CO(2). It has also been suggested that some of these oxidation mechanisms might involve radical reactions. As the previous studies were conducted under conditions where significant structural changes occur it is possible that in the low temperature range (T < 100 °C) the oxidation mechanism is different. Several different rank (lignite-subbituminous-bituminous) coals were isothermally heated at 95 °C in an air atmosphere for a period of up to 6 months and samples were collected at two week intervals. The radical concentration of each sample was measured by Continuous Wave Electron Paramagnetic Resonance (CW-EPR). It is apparent that there are distinct differences between the lower rank (lignite) and the higher rank (subbituminous, bituminous) coals. The lower rank coals exhibited only carbon centered radicals with an adjacent oxygen atom and the higher rank coals exhibited only carbon centered radicals. Interestingly, the lower rank coals exhibited no change in radical concentration due to the long term oxidation treatment while the higher rank coals showed a distinct increase in the radical concentration. These findings shed new light on the complex heterogeneous low temperature oxidation reactions occurring at the coal surface.     

Derivatization-independent cholesterol analysis in crude lipid extracts by liquid chromatography/mass spectrometry: applications to a rabbit model for atherosclerosis

Direct measurement of various sterols in crude lipid extracts in a single experiment from limited biological samples is challenging. Current mass spectrometry (MS) based approaches usually require chemical derivatization before subjecting to MS analysis. Here, we present a derivatization-independent method for analyzing various sterols, including cholesterol and its congeners, using liquid chromatography and atmospheric pressure chemical ionization mass spectrometry. Based on the specific tandem mass spectrometry pattern of cholesterol, multiple reaction monitoring (MRM) transitions were used to quantify free cholesterol and its fatty acyl esters. Several cholesterol oxidation products could also be measured using the upfront liquid chromatography separation and specific MRM transitions. The method was validated alongside established enzymatic assays in measuring total cholesterol. As a proof of concept, we analyzed plasma sterols in rabbits administrated with a high cholesterol diet (HCD) which is a classical atherosclerotic model. Free cholesterol, cholesterol esters, 7-hydroxycholesterol, and 7-ketocholesterol were elevated in plasma of rabbits on HCD. This method could also serve as an excellent tool for quantitative analysis of other sterols such as ergosterol and sitosterol in other organisms beside mammalian. In Saccharomyces cerevisiae, our results indicated dramatic increases of the ratio of ergosterol esters to free ergosterol in both yeh2Δ and tgl1Δ cells, which are consistent with the function of the respective enzymes.     

Surface characterization of functional iron–gallium alloys annealed under different conditions

Fe–Ga alloys are functional magnetostrictive materials, which are promising for application in actuators and sensors. Because surface properties of these alloys such as corrosion resistance are important in technological applications, it is required to characterize the chemical composition and state of the surface of these alloys, which depend on annealing conditions. In this study, X-ray absorption spectroscopy (XAS) and secondary ion mass spectrometry (SIMS) were used to characterize surface layers formed on the Fe–Ga alloys annealed under different atmospheric conditions. The XAS spectra of the annealed sample showed that the amount of gallium in the surface layers increased due to annealing, whereas the XAS spectra of the as-polished alloys revealed that the amounts of iron and gallium arise from the bulk composition. The XAS spectra of the alloys annealed in argon–hydrogen with residual oxygen showed that gallium is increased for its preferential oxidation. SIMS depth profile also showed the enrichment of gallium on the surface and the inhomogeneous distribution of iron on the surface layers.     

常压下Pt-Bi双金属催化剂上甘油选择性氧化(英文)

制备了一系列活性碳(AC)负载的Pt-Bi双金属催化剂,考察了催化剂中Bi含量对其催化甘油选择性氧化反应性能的影响.结果表明,适量Bi的添加可以改善催化剂中Pt的氧化还原性能,从而有利于催化剂活性的提高和二羟基丙酮(DIHA)产物的生成.当Bi的含量为5%时,该催化剂的活性最高,甘油转化率和DIHA选择性分别达到91.5%和49.0%.表征结果显示,Pt-Bi颗粒的平均粒径为3.8nm,且高度分散在催化剂表面,这是该催化剂具有较高活性的主要原因.     

Observation of methanol behavior in fuel cells in situ by NMR spectroscopy

The chemical conversion of methanol in direct methanol fuel cells was followed in situ by NMR spectroscopy. Comparing data of the methanol oxidation on Pt and PtRu anode catalysts allowed the role of Ru in both Faradaic and non-Faradaic reactions to be investigated. The spatial distributions of chemicals could also be determined. (Picture: T1-T4=inlet and outlet tubes.).     

电化学氧化和臭氧化预处理酸性化工废水的效能研究

保持一定酸度条件下对比了电化学氧化和臭氧氧化预处理酸性化工废水的效能（废水原pH 0.85）. 结果表明,在废水中添加2 g·L^-1 NaCl电化学氧化预处理效果较佳,30 mA·cm^-2条件下电解20 min后水样的CODCr（化学需氧量）去除率达43.4%,BOD₅/COD_Cr（生化需氧量与化学需氧量的比值）值从原来的0.034上升至0.14,可生化性明显提高. 单独臭氧化仅在pH 7.0才能取得一定的预处理效能. Ti(Ⅳ)/O₃/H₂O₂高级氧化体系在pH 2.85条件下亦有较好的预处理效果,16 min后水样COD_Cr去除率达22.9%,BOD₅/COD_Cr值则提高至0.072.