烃类选择氧化过程中自由基的调控策略与工业氧化应用研究进展

催化烃类氧化是提供合成树脂、合成纤维和合成橡胶等大宗化学品以及各类精细化学品的基本工艺,在化学工业中具有重要的地位。目前工业上的烃类氧化工艺普遍需要高温高压条件,苛刻条件可以使氧气活化及碳氢键断裂产生自由基。本文从均相催化、非均相催化、仿生催化等方面对近年来催化氧化反应的研究进展进行了回顾,梳理了催化氧化中的自由基机理。总结了仿生催化体系中自由基稳定性和定向性调控机制等方面的研究现状,提出了高效催化剂的设计、自由基的传递及调控机制等方面将是催化氧化领域的重要研究方向。     

The effect of HMMM in a hybrid polymerization comprising free radical polymerization

Compositions of hexamethoxymethylmelamine (HMMM)-ether polyol and acrylate can be cured by a hybrid polymerization composed of condensation polymerization and free radical polymerization at higher temperatures in the presence of a latent acid catalyst, but without a free radical initiator. The initiating radicals of the free radical polymerization come from the decomposition of adventitious peroxides. It has been proved that HMMM plays a very important role in this hybrid polymerization. HMMM is not only a crosslinking agent of polyol, bill also acts as a catalyst of formation and decomposition of the peroxides of the active methylene groups of ethyl polyol. The hybrid polymerization system provides a synergetic effect on the curing reaction, partly ascribed to the thermochemistry complementary between endothermic condensation polymerization and exothermic free radical polymerization. This paper presents a review of this research.     

超氧阴离子自由基荧光探针的研究进展

超氧阴离子自由基(O 2-.)是生物体内重要的自由基之一,也是所有活性氧自由基的前体,可以转化为其它的活性氧自由基。近年来大量文献报道超氧阴离子自由基与生物体发生的炎症、衰老及癌症等重大疾病有密切关系,因此对其检测具有非常重要的科学意义。本文综述了有关超氧阴离子自由基荧光探针的设计、合成及其分析检测。     

Biomimetic Thiyl Radical Chemistry by γ-Irradiation of Micelles and Vesicles Containing Unsaturated Fatty Acids

Different types of lipid aggregations, such as micelles and liposomes, can be used as biomimetic models. The uses of γ-irradiation as a valid methodology for simulating the biological generation of thiyl radicals in these models are summarized and, in particular, thiyl radical catalyzed cis trans isomerization of unsaturated lipids is underlined. The efficiency of antioxidants against lipid isomerization assayed by biomimetic models and the importance of trans lipids as novel biomarkers of radical stress are also described.     

Free radicals in coals and coal conversion. 4. Investigation of the free radicals in selected macerals upon liquefaction

This study of the nature and role of free radicals in coals and coal conversion considers free radicals from selected macerals in the liquefaction process. High-purity macerals were liquefied to different extents at high temperature (425–480 °C) in the presence of naphthalene or tetralin and hydrogen or nitrogen. The initial concentrations of free radicals as well as the residual concentrations have been measured. The dependence of free radical concentrations on solvents, gases, and temperature is reported. Resinites show the least number of free radicals. They also liquefy almost completely under all conditions used. Fusinites have the highest concentration of residual free radicals and they are unaffected by solvent, gas or temperature changes: The vitrinites show intermediate free radical concentrations that depend very strongly on the solvent used, and on the temperature, but they are unaffected by the gas used. A correlation has been established between free radical concentration and degree of conversion.     

受生物启发模拟合成生物矿物材料及其作用机制探讨

在自然界中,生物矿化是生物体自身重要的晶体设计过程。而随着时代的发展,如何对生物矿化方法进行模拟,以合成各种功能化材料为人们所应用,也开始受到人们越来越多的关注。就目前的实际情况来看,多种不同的生物矿物材料,例如碳酸钙等在生物和地质体系中广泛存在,并对生物体的特异功能发挥出十分重要的作用。对生物矿化与仿生合成的内涵进行介绍,研究生物矿物的结构及形成机理,并对生物启发模拟合成生物矿物材料的相关方法进行重点研究。     

Radikalische Additionen an ungesättigte Fettstoffe

Free Radical Additions to Unsaturated Fatty Acids Unsaturated fatty acids e.g. oleic acid are 1,2-dialkyl substituted alkenes with an electron-rich C,C-double bond. Elektrophilic free radicals can be added to the double bond to give functionalized and branched fatty acids. The electrophilic free radicals have been generated a) by oxidation of enolizable compounds by manganese (III) acetate prepared in situ by addition of potassium permanganate to catalytic amounts of manganese (II) acetate; b) with di-tert.-butylperoxide as initiator. Free radical addition of the radical to methyl oleate occurs to give an adduct radical which can be stabilized by hydrogen transfer or by oxidative elimination with copper (II) acetate. We have been able to add also alkanes e.g. cyclohexane to methyl oleate. A review of free radical additions to oleic acid is given.     

Polymerization and chelating behavior of N-acryloyl,N-phenylthiourea

Summary The title monomer has been prepared for the first time. It has been polymerized by a free radical mechanism in different solvents. Only oligomers were obtained so far. The dependence of the rate of polymerization on monomer and initiator concentrations has been measured and was found to follow the usual free radical scheme. The overall activation energy of polymerization has been measured in two solvents and was found to be 21.2 and 15.03 K.Cal/mol in tetrahydrofuran (THF) and N,N-dimethyl formamide (DMF) respectively. The prepared monomer has excellent chelating ability with different metal cations. The stability constant of the monomer with copper (II) ions has been measured in acetone as well as in dioxane. The complexes have no tendency for free radical polymerization.     

温室气体二氧化碳化学转化与利用的方法学

二氧化碳既是温室气体的主要组成又是储量丰富的碳资源,研究二氧化碳的化学转化和利用有着重要的意义。基于二氧化碳与催化剂的弱相互作用以及催化活化原理,通过采用环境友好的反应介质（如超临界二氧化碳、聚乙二醇和离子液体等）及催化剂的设计、分离和循环利用策略,设计各类单组分双功能或双组分双功能的高效催化剂用于合成有机碳酸酯和嗯唑啉酮类化合物,建立具有重要工业应用背景的碳酸酯、嗯唑啉酮和羧酸酯合成新方法以及环境友好的新工艺。超临界二氧化碳既作为一种反应物（可再生资源）,又作为环境友好、性质可调的反应介质。在高密度二氧化碳体系中的聚乙二醇自由基化学是一个环境友好的氧化体系。在一定的条件下,聚乙二醇通过氧化降解产生的自由基能应用于脂肪醇的甲酰化、苄醇的氧化、C—H键的活化等氧化反应。     

Some Biochemical Processes Induced by Radiation as Studied by Pulse Radiolysis

The main types of biochemically important electron transfer substances can be made to undergo reactions under irradiation which in some ways mimic those which occur in nature. In the case of NAD⁺, pulse radiolysis shows that electrons add to the pyridine ring forming an NAD· radical with a characteristic absorption in the visible range which is capable of transferring its electron to oxygen. Using simpler pyridinyl compounds it has been found that, as well as the absorptions in the visible range, the radicals exhibit absorptions in the infrared range which correlate well with transitions which may be deduced from the known charge-transfer bands of the parent compound. The NAD· radical can be made by one-electron oxidation of NADH as well as by reduction of NAD⁺, and the reaction with oxygen enables NADH to be converted into NAD⁺ by an unambiguous free radical route. Cytochrome-c can be reduced either by hydrated electrons or CO₂^?. In solution buffered to neutral pH, the reduction gives rise immediately to normal reduced cytochrome-c, but in mildly alkaline solution, an unstable reduced form appears whose conformation changes over a fraction of a second to that of normal reduced cytochrome-c. As well as the hydrated electron and CO₂^?, the superoxide anion radical O₂^? has also been found to reduce cytochrome-c. This reaction is very slow (k ～ 10⁵ M^?1 sec^?1).     

Chlorination of poly(vinyl chloride) model compounds in radical‐complexing solvents

A potential route to the preparation of poly(1,2‐dichloroethylene) by the selective chlorination of poly(vinyl chloride) (PVC) was explored. During free‐radical chlorinations with Cl₂, certain solvents play the very important role of forming complexes with the free chlorine atom that lead to changes in the pattern of chlorine substitution. In our work, the photochlorination of three model compounds for PVC, namely, 2,4‐dichloropentane, 3‐chloropentane, and 4‐chloroheptane, was carried out with molecular chlorine in the absence or presence of complexing solvents. The effects of these solvents on the chlorination selectivity were determined. During the conventional chlorination of sec‐alkyl chlorides with molecular chlorine, bridged‐radical intermediates are believed to be involved. They lead to vicinal dichlorides as the major products. However, we found that complexing solvents significantly increased the yields of geminal dichlorides instead. Such solvents also are well known to decrease reactivity in free‐radical chlorinations with Cl₂. Thus, for both of these reasons, the chlorination of PVC with Cl₂ in complexing solvents is unlikely to be useful for the preparation of poly(1,2‐dichloroethylene). J. VINYL ADDIT. TECHNOL., 22:405–409, 2016. © 2015 Society of Plastics Engineers     

Reduction of cathodic delamination rates of anticorrosive coatings using free radical scavengers

Cathodic delamination is one of the major modes of failure for anticorrosive coatings subjected to a physical damage and immersed in seawater. The cause of cathodic delamination has been reported to be the result of a chemical attack at the coating–steel interface by free radicals and peroxides formed as intermediates in the cathodic reaction during the corrosion process. In this study, antioxidants (i.e., free radical scavengers and peroxide decomposers) have been incorporated into various generic types of coatings to investigate the effect of antioxidants on the rate of cathodic delamination of epoxy coatings on cold rolled steel. The addition of <5 wt% free radical scavengers to epoxy coatings improved the resistance toward cathodic delamination by up to 50% during seawater immersion, while peroxide decomposers had a limited effect. Testing using substrates prepared from stainless steel, copper, aluminum, galvanized steel, and brass also showed a reduction in the rate of cathodic delamination when the coating was modified with a free radical scavenger. The protective mechanism of free radical scavengers investigated for the primers are similar to that of antioxidants used for protection against photochemical degradation by UV-radiation of top coatings. Both substrate corrosion and degradation of a coating exposed to UV-radiation lead to the formation of free radicals as reactive intermediates.     

Free Radical Scavenging and Cellular Antioxidant Properties of Astaxanthin

Astaxanthin is a coloring agent which is used as a feed additive in aquaculture nutrition. Recently, potential health benefits of astaxanthin have been discussed which may be partly related to its free radical scavenging and antioxidant properties. Our electron spin resonance (ESR) and spin trapping data suggest that synthetic astaxanthin is a potent free radical scavenger in terms of diphenylpicryl-hydrazyl (DPPH) and galvinoxyl free radicals. Furthermore, astaxanthin dose-dependently quenched singlet oxygen as determined by photon counting. In addition to free radical scavenging and singlet oxygen quenching properties, astaxanthin induced the antioxidant enzyme paroxoanase-1, enhanced glutathione concentrations and prevented lipid peroxidation in cultured hepatocytes. Present results suggest that, beyond its coloring properties, synthetic astaxanthin exhibits free radical scavenging, singlet oxygen quenching, and antioxidant activities which could probably positively affect animal and human health.     

Polymerization reactor: The influence of “gel effect” in batch and continuous solution polymerization of methyl methacrylate

This article describes the influence of gel effect in the free radical polymerization of methyl methacrylate. A mathematical model has been developed which tries to predict the performance of batch and continuous polymerization reactors under dynamic and steady-state conditions. The influence of diffusion phenomena on the process kinetics (gel effect) is very important. The autoacceleration in the polymerization rate of the batch reactor and the mulitple steady state for the continuous stirred tank reactor (CSTR) are connected with the attainment of critical conditions in the system. Such a model is useful for the design of the reactor and the choice of the control system.     

混合表面活性剂水溶液自组装特性研究

在以表面活性剂为模板的仿生合成中,模板的自组装特性是关键环节。由于混合胶团的存在,两种表面活性剂的水溶液体系的效能高于单一表面活性剂溶液;利用试验优选合适的混合表面活性剂用于仿生合成,耗费时间长,成本高。本文从热力角度出发,分析了混合成胶自由能的影响,建立了离子 非离子混合表面活性剂的自组装模型,利用该模型模拟考察了混合表面活性剂的混合临界胶团浓度和胶团组成等参数,得到了其影响因素及作用规律,并进行了部分试验验证,二者吻合得较好。     

Strategies for maximizing free‐radical grafting reaction yields

It is very challenging to obtain very large amounts of vinyl monomers grafted onto polymer backbones in the melt through a free‐radical mechanism. The objective of this study was to develop strategies that would allow one to maximize the amount of 3‐isopropenyl‐α,α‐dimethylbenzene isocyanate (TMI) grafted onto polypropylene (PP) by reactive extrusion processes. For that purpose, an internal batch mixer was used to simulate potential reactive extrusion processes. Two strategies were studied: The first one was to apply the comonomer concept developed in previous studies. More specifically, styrene (St) was used as a comonomer to control the grafting yield and the molar mass of TMI‐grafted PP. The second strategy delt with the feeding mode of the reactants. Two feeding modes were investigated: (a) one‐pot feeding, that is, the total amount of TMI, St, and a peroxide were premixed with PP and the whole mixture was then charged to the reactor at once; (b) stepwise feeding, that is, the total amount of TMI, St, and the peroxide was divided in several equal fractions. The first fraction of the mixture was premixed with PP and then charged to the reactor. After a certain reaction time, the other fractions were charged to the reactor one after another in certain time intervals. Both strategies were shown to be very good at maximizing free‐radical grafting reaction yields. They can be easily adopted if free‐radical grafting is to be carried out by reactive extrusion in a screw extruder. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 1799–1807, 2003     

The reaction of hydrogen atoms with methionine residues: A model of reductive radical stress causing tandem protein-lipid damage

The occurrence of tandem damage, due to reductive radical stress involving proteins and lipids, is shown by using a biomimetic model. It is made of unsaturated lipid vesicle suspensions in phosphate buffer in the presence of methionine, either as a single amino acid or as part of a protein such as RNase A, which contains four methionine residues. The radical process starts with the formation of H(.) atoms by reaction of solvated electrons with dihydrogen phosphate anions, which selectively attack the thioether function of methionine. The modification of methionine to alpha-aminobutyric acid is accompanied by the formation of thiyl radicals, which in turn cause the isomerization of the cis fatty acid residues to the trans isomers. The relationship between methionine modification and lipid damage and some details of the reductive radical stress obtained by proteomic analysis of irradiated RNase A are presented.     

Free radical polymerization and lipid binding of lysozyme reacted with peroxidizing linoleic acid

Insolubilization and polymerization of proteins exposed to peroxidizing lipids may be due either to cross-linking with incorporation of fragments of the lipid oxidation products, or to free radical transfer from lipid to protein and subsequent free radical polymerization of protein. The second mechanism which has been proposed was inferred from measurements of electron spin resonance signals in proteins. In this study, uniformly labeled linoleic acid, [¹⁴C(U)] LA, was reacted with lysozyme. Volatile oxidation products of LA were also used in some experiments. Incubation was done in the absence of water. Oligomers of lysozyme, as well as the monomer, were isolated after incubation, and the [¹⁴C] label incorporated into each fraction was determined. The results show that the dominant mechanism of protein polymerization after exposure to peroxidizing linoleic acid is the transfer of free radical from lipid to protein, and subsequent free radical polymerization.     

石油热解过程中自由基调控反应机理的构建与应用

石油热解是生产高品质气液燃料和化学品的重要步骤,不仅涉及非催化过程,也涉及催化过程。石油热解过程反应机理不仅为解析不同类型的热解反应过程、构建反应动力学模型以及定向调控和强化,而且对于工艺条件优化、反应调控和强化、催化剂开发和优化以及反应装备技术开发和强化等均能指明方向和提供依据,但现有热裂解自由基链式反应机理和催化裂化正碳离子反应机理均存在实验现象尚未能合理解释。本文提出了石油热解过程的化学反应主体均由受热离解的自由基主导的观点,创建了石油热解过程自由基调控反应机理,不同热解工艺区别主要在于二次自由基调控,自由基复合产物以及稳定产物形成了特定热解过程的产物分布。按照初始自由基产生、二次自由基调控和自由基复合3个阶段的反应机理,合理解析石油催化裂化过程各种应用现象,有效指导了劣质重油快速催化热解-气化耦合技术和原油直接分级气相毫秒催化裂解制化学品技术的开发,证实了石油热解过程自由基调控反应机理的普适性,为工艺条件优化、反应调控和强化、催化剂优化提升和反应装备技术强化等均能指明方向和提供依据。     

Free‐radical solution polymerization of styrene in a tubular reactor—effects of recycling

The styrene free‐radical solution polymerization reaction in a tubular loop reactor is studied here both experimentally and through simulation. An attempt is made to compare the performances of tubular loop reactors when the recycle ratio is varied, based on steady‐state and dynamic responses and on the quality of the polymer produced at different conditions. It is shown here that steady‐state responses of loop reactors and traditional tubular reactors are very similar as far as the quality of the polymer obtained is concerned. Therefore, the recycle ratio cannot be used as a fundamental operation parameter for grade transitions at plant site. However, it is also shown that the recycling of polymer material is very important to accelerate the attainment of the final steady‐state in tubular reactor configurations, because recirculation of material homogenizes the distorted radial profiles of the axial flow velocities.