一氧化碳低温氧化催化剂的研究

在矿井生产中，为防止ＣＯ中毒，一般的防护方法采用自救器、压缩氧和氧气发生器。自救器具有体积小和携带方便等优点仍广泛用于矿井ＣＯ的救护。但由于ＣＯ催化剂催化反应放热大，使工人佩戴时感觉不适，容易造成摘掉自救器而发生危险的情况。研究低温下使ＣＯ高效转化的...     

氧化镍中非化学计量氧在乙烷氧化脱氢中的作用

以纯ＮｉＯ为模型催化剂考察了乙烷氧化脱氢（ＯＤＨＥ）性能，发现非化学计量氧的存在与反应的活性及选择性密切相关．ＴＧＡ研究结果表明，５００℃制备的样品具有ｘ≈６％的非化学计量氧．Ｈ２ＴＰＲ结果表明，非化学计量氧与晶格氧的可还原性明显不同；Ｏ２ＴＰＤＭＳ又把非化学计量氧区分为两个氧物种，Ｏ－２和Ｏ－（或Ｏ２－２）．脉冲试验结果表明，非化学计量氧对ＯＤＨＥ制乙烯是选择性反应的活性氧物种，晶格氧是完全氧化反应的活性氧物种．一旦催化剂中非化学计量氧耗尽并动用晶格氧时，催化剂便有Ｎｉ０生成，表现出自催化性能，使反应活性迅速提高，但产物均为ＣＯ２，ＣＯ，ＣＨ４等完全燃烧或裂解产物．为保持有较高的乙烯收率，反应处于稳态时Ｎｉ必须处于高价态．电导测定结果表明，优良的ＯＤＨＥ催化剂应有Ｐ型半导性．     

钙钛矿型稀土—过渡金属复合氧化物系催化剂的稳定性及XPS研究

在以钙钛矿型稀土—过渡金属复合氧化物为催化剂的研究中,非化学计量氧和点缺陷是很重要的.王承宪等对钙钛矿型催化剂Ca_xLa_(1-x)MnO_(3+λ)(0≤X≤1)中的缺陷及其在氨氧化中的作用进行了研究,发现非计量氧(λ)为x值的函数,催化剂的活性可以用非计量氧或不同的缺陷来说明.但是由于氧的活泼性及其状态的复杂性,致使人们较少地考察非化学计量氧的问题.     

胶束增稳室温燐光法中化学除氧技术的研究

简便、快速的Na_2SO_3化学除氧技术改善了胶束增稳室温燐光法(MS-RTP)通氮除氧过程费时、繁冗的操作。本文对化学除氧MS-RTP的各种影响条件做了较详细的研究。实验表明,除了SDS、TINO_3、Na_2SO_3用量及温度等因素外,pH对RTP强度和除氧时间也有显著的影响。本文对前人工作作了补充和完善,并对化学除氧机理提出了不同的认识。文中对国产SDS进行了提纯。在荧光光度计上建立了化学除氧MS-RTP法。     

适宜氧空位诱导α-MnO2高效催化消除碳烟研究

柴油机排放的碳烟颗粒对人类和自然产生了严重的威胁,开发高活性低成本的碳烟燃烧催化剂是解决这一问题的关键。本文采用不同煅烧气氛（空气、真空和氮气）成功制备了含有不同浓度氧空位的α-MnO2催化剂（记为M-Air-500,M-Va-500,M-N-500,M-N-450）。M-Va-500和M-N-500催化剂在500 ℃煅烧会失去过多晶格氧,导致晶相结构发生改变,出现Mn3O4相,这与XRD和HRTEM结果一致。XPS和Soot-TPR的结果说明,适量的表面氧空位能够吸附并活化氧气分子,催化剂表面的化学吸附氧提高了催化剂的催化性能。H2-TPR结果说明适量的氧空位能够加快晶格氧的迁移,提高可移动氧物种丰度,增强催化剂的氧化能力。结合催化活性测试结果可以得出：在保持α-MnO2晶相结构的前提下,氧空位越多,催化剂表面的化学吸附氧越多,催化活性越好。     

La2NiO4+δ的非化学计量与氧渗透性能

采用质量损失法、碘量滴守法和正电子湮没寿命谱研究了Ｌａ２ＮｉＯ４＋δ透氧膜的非化学计量,并表征了该材料的氧渗透性能,探讨了Ｌａ２ＮｉＯ４＋δ的非化学计量缺陷与氧渗透性能之间的关系。研究结果表明,Ｌａ２ＮｉＯ４＋δ的氧渗透通量随δ的增大而增大。     

双相致密透氧膜

混合导体透氧材料由于在高温下具有氧离子导电特性,在纯氧制备、膜反应器及富氧燃烧等方面显示出广阔的应用前景。单相混合导体材料用作透氧材料时存在稳定性不足、机械性能差等问题,限制了其在生产中的实际应用。在离子导体相中掺入电子导体相形成双相导体膜可以提高透氧材料在高温下和高氧浓度梯度下的工作稳定性和化学稳定性。本文详细论述了双相透氧材料的透氧机理和研究进展,包括氧离子导体/贵金属电子导体和氧离子导体/氧化物电子导体和氧离子导体/混合导体等的复合形式。重点分析了材料的组成、结构以及两相之间的化学相容性和混合比例对材料透氧率和工作稳定性的影响。介绍了双相材料在甲烷部分氧化制合成气(POM)膜反应过程及富氧燃烧中的应用,分析了目前有待解决的问题并提出了今后的研究方向。     

催化分子氧环氧化烯烃的研究进展

环氧化合物是一类十分有用的合成中间体 ,广泛应用于石油化工、精细化工和有机合成 .但至今为止 ,工业上除用分子氧直接氧化乙烯制环氧乙烷外 ,其它所有 C2 以上的环氧化合物还不能用分子氧直接氧化相应的烯烃制得 .国外生产环氧丙烷和环氧氯丙烷的主要方法有卤醇法、Halcon法 ,而国内则以卤醇法为主 .另外 ,过酸法常用于精细产品的合成中 ,以 H2 O2 、Na Cl O等为氧源的环氧化研究 ,近年来也已取得了较大的进展 .卤醇法较早应用于生产 ,但存在严重的设备腐蚀和环境污染问题 ;Halcon法利用 ROOH为氧源 ,有联产品 ,生产过程较复杂 ,基本…     

La_2NiO_(4 δ)的非化学计量与氧渗透性能

采用质量损失法、碘量滴定法和正电子湮没寿命谱研究了 La_2NiO_(4＋δ)透氧膜的非化学计量,并表征了该材料的氧渗透性能,探讨了 La_2NiO_(4＋δ)的非化学计量缺陷与氧渗透性能之间的关系。研究结果表明, La_2NiO_(4＋δ)的氧渗透通量随δ的增大而增大。     

基于晶格氧的甲烷化学链重整制合成气

利用氧载体中的晶格氧代替分子氧进行的甲烷化学链重整制合成气,是一种新颖的甲烷制合成气技术,具有较高经济效益和环境效应。它具有省却纯氧设备、能自热、合适的氢碳比、有用的副产物以及过程易于工业化等优点,因此受到国内外研究者的普遍关注。本文介绍了化学链重整技术的基本原理及其特点;重点总结了用于甲烷化学链重整的单金属氧载体和复合金属氧载体的研究进展;同时,探讨了几种具有典型代表的甲烷化学链重整反应装置,并指出串行流化床反应器是实现化学链重整技术工业化最有效的装置;最后对化学链重整技术的拓展应用以及与其他技术交叉运用等发展趋势进行了展望。     

Oxygen scavengers and sensitizers for reduced oxygen inhibition in radical photopolymerization

Oxygen inhibition in the free‐radical photopolymerization of (meth)acrylates is one of the most challenging problems in thin film application. Apart from the utilization of an inert gas atmosphere, additives reducing oxygen inhibition due to production of new propagating centers are used. In the present study, a more straightforward approach to reduce oxygen inhibition by photosensitized generation of singlet oxygen and subsequent scavenging of these species by selective singlet oxygen trappers was investigated. The potential of 1,2‐dions conventionally used as type‐II photoinitiators for visible light polymerization to function as singlet oxygen generators was verified in sensitized steady state photooxidation experiments in solution. A set of furan and anthracene derivatives were tested as oxygen scavengers and their corresponding relative reaction rates were determined. The ability of these sensitizer/scavenger systems to reduce oxygen inhibition in practical applications was studied in photo‐DSC‐experiments. In thin film polymerization (investigated by ATR‐FTIR), the formation of insufficiently cured surfaces could be prevented by the usage of singlet oxygen trappers. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 6916–6927, 2008     

Studies on the oxygen stoichiometry in superconducting cuprates by thermoanalytical methods

Thermoanalytical methods provide important means for studying oxygen stoichiometries in highT _c superconducting cuprates. The optimum annealing temperature for a desired oxygen content in the superconducting product or in related materials can be established by thermogravimetric measurements. By performing the final annealing in a thermobalance the amount of the incorporated or released oxygen can be conveniently both controlled and determined. Furthermore, the absolute oxygen content in the end product can be analyzed by the thermogravimetric reduction method. Finally, the stability of the oxygen content under various atmospheres can be checked utilizing either thermogravimetric or differential thermal analysis techniques. The potential and applications of thermal analysis within the above themes of cuprate superconductor research are reviewed and discussed using illustrative examples from the authors' own experimental works as well as from the literature.Financial support provided by the Mitsubishi Foundation is gratefully acknowledged.     

Taming of Singlet Oxygen: Towards Artificial Oxygen Carriers Based on 1,4-Dialkylnaphthalenes

Naphthalene endoperoxides are known as convenient sources of singlet oxygen (O₂, ¹Δ_g), which is the major product of endoperoxide cycloreversion reaction. However, their potential as carriers of ground-state molecular oxygen (O₂, ³Σ_g) similar to artificial oxygen carriers remains largely unexplored. This is due to the extreme reactivity and cytotoxic effects of the released singlet oxygen. We now report that a compound with a bimodular design, which incorporates an endoperoxide and an efficient physical quencher of singlet oxygen, 1,4-diazabicyclo[2.2.2]octane (DABCO), produces exclusively ground-state molecular oxygen. This result, coupled with the fact that oxygen release rates from endoperoxides are highly amenable to fine-tuning in a very broad range, and open to targeting by ligand attachment, raises the potential of these compounds far above any comparable chemical, or even biochemical sources. In cell culture experiments, we showed that the addition of the endoperoxide-quencher conjugate can enhance and sustain cell proliferation.     

Synthesis and characterization of new porphyrin/4-quinolone conjugates

New porphyrin/4-quinolone conjugates were synthesized from the Suzuki-Miyaura coupling reaction of a β-borylated porphyrin with bromo-4-quinolones containing N-ethyl and N-d-ribofuranosyl substituents. The use of electrospray ionization tandem mass spectrometry showed important information about the fragmentation pathways of the new compounds. It was possible to distinguish between those compounds with the porphyrin moiety linked at the 6-position of the quinolone unit from their 7-substituted isomers. The new compounds showed to be good singlet oxygen generators.     

Enhancement of singlet oxygen generation based on incorporation of oxoporphyrinogen (OxP) into microporous solids

Singlet oxygen, ¹O₂, generating compounds are highly useful for photodynamic therapy or organic oxidative transformations. In this work, the synthesis and photochemical performances for singlet oxygen generation of a range of oxoporphyrinogen-containing porous coordination polymers (OxP-PCPs) are reported. Oxoporphyrinogens, a previously unreported class of singlet oxygen generators derived from the oxidation of the antioxidant-substituted porphyrin tetrakis(3,5-di-tert-butyl-4-hydroxyphenyl)porphyrin, were converted to molecular tectons by the introduction of oligophenylene-carboxylate linkers and incorporated into porous coordination polymers using well-known oxo-Zr(IV)₆ cluster chemistry. Their structures and textural properties were analyzed revealing substantial surface areas up to 650 m² g^?1 for the optimum linker length (biphenylyl). The oxoporphyrinogen precursors exhibit good quantum yields of singlet oxygen generation (up to Φ = 0.37), and a high level of activity is maintained in the resulting coordination polymers, which appear to be superior for singlet oxygen generation to the precursors and to a reported reference material. These OxP-PCP materials were applied for the selective oxidation of sulfides to sulfoxides. This work demonstrates that the excellent singlet oxygen generator oxoporphyrinogens can be successfully incorporated as porous solids and conveniently applied in heterogeneous oxidative transformations.     

Supramolecular Control of Singlet Oxygen Generation

Singlet oxygen (¹O₂) is the excited state electronic isomer and a reactive form of molecular oxygen, which is most efficiently produced through the photosensitized excitation of ambient triplet oxygen. Photochemical singlet oxygen generation (SOG) has received tremendous attention historically, both for its practical application as well as for the fundamental aspects of its reactivity. Applications of singlet oxygen in medicine, wastewater treatment, microbial disinfection, and synthetic chemistry are the direct results of active past research into this reaction. Such advancements were achieved through design factors focused predominantly on the photosensitizer (PS), whose photoactivity is relegated to self-regulated structure and energetics in ground and excited states. However, the relatively new supramolecular approach of dictating molecular structure through non-bonding interactions has allowed photochemists to render otherwise inactive or less effective PSs as efficient ¹O₂ generators. This concise and first of its kind review aims to compile progress in SOG research achieved through supramolecular photochemistry in an effort to serve as a reference for future research in this direction. The aim of this review is to highlight the value in the supramolecular photochemistry approach to tapping the unexploited technological potential within this historic reaction.     

Electroreduction of molecular oxygen on dispersed copper in an ion-exchange matrix

Electrochemical reduction of molecular oxygen was studied on a [dispersed copper]-[macroporous KU-23 15/100S sulfocation exchanger with various metal concentrations] composite electrode. It was found that a high proton concentration in the ion-exchange matrix causes a decrease in the oxygen reaction overvoltage. The nanostructured state of copper particles causes stabilization of the intermediate product, i.e., hydrogen peroxide. Using the rotating disk electrode method, it was detected that the process is limited by external diffusion of oxygen to composite grains. The oxygen reaction is mostly concentrated on the grain surface and surface layers; oxygen is reduced in the bulk due to dispersed copper oxidation.     

细胞色素P-450的化学模拟——酞菁铁(Ⅱ)光催化吖啶氮氧化物氧转移反应

在光的作用下,酞菁铁(Ⅱ)可催化吖啶氮氧化物的氧转移反应,将环己烯氧化成环氧化产物,成功地模拟了细胞色素P-450的选择性氧化烯烃的反应。观察到酞菁铁(Ⅱ)与吖啶氮氧化物形成配合物的紫外可见吸收。这是具有氧化性能的活泼中间体。比较了取代基性质对吖啶氮氧化物氧转移所生成的产物分布的影响,讨论了光催化氧转移反应机制。     

Ce-Fe-Zr-O/MgO整体型氧载体用于化学链部分氧化甲烷制合成气

以MgO为载体,采用球磨法制备了Ce-Fe-Zr-O/MgO粉末状氧载体,进而采用挤压成型法制备了整体型氧载体。研究了两种氧载体化学链部分氧化甲烷制合成气的性能,并通过XRD、H₂-TPR对氧载体进行表征。结果表明,粉末状氧载体中的储氧组分以Ce-Fe-Zr-O固溶体形式存在,而整体型氧载体的制备过程会导致Zr、Fe游离氧化物的形成。粉末状氧载体和整体型氧载体上均存在表面晶格氧和体相晶格氧,其中,体相晶格氧具有高选择性氧化甲烷的性能,可以将甲烷转化成CO和H₂。粉末状氧载体与甲烷反应活性较高,但其存在高含量的表面氧,易导致甲烷的完全氧化。整体型氧载体上体相晶格氧占据优势,可将甲烷选择性氧化为CO和H₂。氧化还原循环实验表明,粉末状氧载体在还原反应发生短时间内容易引起甲烷裂解导致产物气中的H₂/CO物质的量比显著大于2.0,同时产生大量积炭,制约了其循环性能。而整体型氧载体经10次循环实验后,全程反应过程中合成气H₂/CO物质的量比一直维持在2.0附近,显示了较高的循环稳定性能。     

Soluble polymers with pendant thionine groups: Synthesis and evaluation as singlet oxygen photosensitizers

Thionine ( 1 ) has been covalently bound to linear copoly(styrene-p-vinylbenzyl chloride) and to linear copoly(acrylic acid-2-ethylhexyl acrylate). The resulting polymeric dyes, purified by ultrafiltration, present quantum yields of singlet oxygen generation in dimethylformamide solution lower than their corresponding low-molecular-weight models thionine hydrochloride ( 1.HCl ) and N(3)-acetylthionine ( Ac-1 ), the decrease being more pronounced in the case of the polystyrene-dye photosensitizer. High chromophore concentrations within the volume encompassed by each macromolecule in the solution can explain this fall in efficiency. The free dyes thionine hydrochloride and its hydrolysis products thionoline ( 2 ) and thionol ( 3 ) behave as good singlet oxygen generators, with quantum yields of 0.71, 0.62, and 0.63, respectively. © 1993 John Wiley & Sons, Inc.