可见光催化条件下乙腈参与的烯烃双官能团化反应

烯烃双官能团化反应可将烯烃转化为多种重要的化合物,是一类十分重要的有机反应。实现了室温条件下光催化活化乙腈α位碳氢键,引发分子内官能团迁移的未活化烯烃双官能团化反应。以过氧化十二酰(LPO)为氢原子转移试剂,室温下经可见光催化,实现了乙腈转变为氰自由基,通过该自由基引发苯并噻唑基团的分子内迁移,实现了烯烃的双官能团化反应,将氰基和苯并噻唑同时引入未活化的烯烃末端双键的两端。采用核磁共振和质谱等波谱技术对目标产物进行了相应的表征,并对产物的特征核磁共振谱信号及可能的反应机理进行了分析。     

硫酸根自由基的活化生成方法研究进展

综述了光活化、超声波活化等7种过硫酸盐活化方法,以及国内外过硫酸盐活化方法的研究进展,通过反应机理、研究现状和优缺点三个方面来研究不同活化过硫酸盐方法。活化过硫酸盐的氧化工艺拥有良好的应用前景,但该技术仍有局限性。在过硫酸盐活化过程中,针对现阶段活化技术仍处于单影响因素的模拟实验环境,以及可能产生有毒有害的副产物等问题,提出了对应的解决方案,并对以硫酸根自由基为主要自由基的氧化技术发展进行了展望。     

改性活化过硫酸盐应用及机理研究进展

生物炭(BC)由于活化性能良好、成本低且绿色环保,已广泛应用于活化过硫酸盐(PS)去除水中难降解有机污染物.不同的改性修饰方法可以丰富BC表面活性位点,进一步增强BC的理化性质,提高活化性能与稳定性.首先,综述了BC应用于活化PS的改性方法;其次,总结了BC活化PS的反应活性位点,PS活化的自由基与非自由基途径及其差异;接着,分析了改性以及生物质原料对两种不同活化途径之间的转化影响;最后,展望了BC活化PS应用及机理研究的发展方向.     

改性生物炭活化过硫酸盐应用及机理研究进展

生物炭（BC）由于活化性能良好、成本低且绿色环保，广泛应用于活化过硫酸盐（PS）去除水中难降解有机污染物。不同的改性修饰方法可以丰富BC表面活性位点，进一步增强BC的理化性质，提高活化性能与稳定性。首先，综述了生物炭应用于活化PS的改性方法；其次，总结了BC激活PS的反应活性位点，PS活化的自由基与非自由基途径及其差异；接着，分析了改性以及生物质原料对两种不同活化途径之间的转化影响；最后，展望了BC活化PS应用及机理研究的发展方向。     

不同方式活化过硫酸盐处理含油污泥及机理探究

为了有效降解含油污泥中的原油,在热活化的基础上考察不同活化方式对原油去除率的影响,并探究其活化机理。结果表明,与单一热活化相比,复合活化方式均可以提高过硫酸盐的氧化效果,其中Fe3O4的活化效果最佳,其原油的去除率为45. 87%。通过进一步分析可知,活化过硫酸盐可产生硫酸根自由基(SO4-·)和羟基自由基(·OH),这些强氧化性基团可以降解大部分石油类污染物。在此基础上测定了pH在实验过程中的变化,探究pH变化与降解机理的关系。目前,活化过硫酸盐氧化技术主要用于水和土壤方面的处理,对含油污泥的研究相对薄弱,因此活化过硫酸盐氧化法修复含油污泥具有良好的发展前景。     

过硫酸盐高级氧化降解水体中有机污染物研究进展

基于硫酸根自由基（sulfate radical,SO₄ ^-·）氧化原理的活化过硫酸盐（persulfate,PS）氧化法是近年来高级氧化工艺（advanced oxidation process,AOP）的研究热点,以经济、高效、环境友好、安全稳定的优势在水处理、环境保护等领域开辟了新的思路。此前,学者们发现过硫酸盐高级氧化根据活化反应条件（如温度、光照、pH、过渡金属及催化剂等）的不同,会产生不同的自由基参与氧化反应,对降解结果也会产生不同程度的影响。本文根据相关自由基氧化机理,从产生硫酸根自由基的单一氧化、复杂活化体系硫酸根自由基与其他自由基复合氧化以及强化降解等方面,分析了近几年国内外学者对过硫酸盐降解典型有机污染物的研究及在催化剂开发方面所做的工作,指出了许多新颖的过硫酸盐活化手段及其降解效果与不足,并就未来的发展进行了展望,以期为过硫酸盐氧化法未来更好地发展和应用探索出路。     

基于亚硫酸盐的高级氧化活化方法最新进展

在基于硫酸根自由基（SO4·-）的高级氧化水处理技术中,SO4·-的来源主要集中于过硫酸盐,关于亚硫酸盐〔S（Ⅳ）〕的报道较少。对比分析了S（Ⅳ）和过硫酸盐（PS）产生自由基的特点,总结了由S（Ⅳ）活化产生SO4·-降解有机物的机理,介绍了过渡金属活化、光活化、电活化以及多种方式联合活化等方法活化S（Ⅳ）并用于废水处理...     

无金属催化芳基乙烯的C-H三氟甲基化反应

以CF₃SO₂Na为三氟甲基源、NaBrO₃作为氧化剂，通过一锅反应合成了β-三氟甲基取代苯乙烯类化合物，开发了一种简便、直接的芳基乙烯的碳氢键活化三氟甲基化的方法。机理研究表明，反应经历了自由加成消除的过程。在NaBrO₃的氧化作用下，生成三氟甲基自由基，进而对双键加成，形成苄位自由基。NaBrO₂夺取自由基的电子，生成相应的碳正离子，进一步脱去质子生成相应的转化产物。     

含有芝麻酚-二苯甲酮结构光引发剂的合成及应用

本文合成了一种单组份的夺氢型自由基光引发剂5-(4’-苯甲酰苯基)氧基)-1,3-苯并二氧戊烷(BPBDO),通过1H、13C及MS表征并确定了其化学结构;通过ESR、LFP实验研究了BPBDO的光引发机理;通过甲基丙烯酸甲酯的聚合反应研究了BPBDO引发单体进行光聚合性质。最终结果显示BPBDO的引发过程是通过自身夺氢-供氢过程,能够产生活性自由基,并引发单体聚合,其引发活性比BP/BDO引发体系更高,并且在整个使用过程中可以减少甚至不需加入叔胺助引发剂。     

辐射引发聚合反应研究进展

文章综述了辐射聚合的机理、辐射引发传统自由基聚合及活性自由基聚合、辐射改性聚合物等,着重讨论了辐射接枝改性聚合物、辐射交联改性聚合物、辐射降解聚合物及辐射法制备复合材料。     

基于Py-GC/MS研究热解反应中自由基的捕获反应

在500℃下对类煤模型化合物1-萘甲醇与同位素示踪剂的共热解进行了机理研究。利用Py-GC/MS进行快速产物检测,同时联合自由基捕获剂来推断自由基的反应过程。结果表明,在500℃和0.2 min的条件下,1-萘甲醇的热解产物相对单一,但是自由基反应的引发、交换和湮灭极其快速,现有检测方法是对某一时间节点的平衡反应结果的分析。通过D₂O和H₂¹⁸O同位素示踪,成功捕获到了自由基交换后的D取代产物和¹⁸O取代产物。揭示了1-萘甲醇经过1-萘甲基自由基转化为1-萘甲醛的转化过程,发现萘环上的取代基在1-萘甲醇的热解过程中起着重要作用。同时对自由基及产物进行了定性和半定量分析,发现在加入自由基捕获剂后产物的丰度较之前降低了一个数量级,说明了自由基捕获剂抑制了产物的生成。     

纤维板用胶粘剂及其甲醛释放量的研究新进展

介绍了醛类胶粘剂型、低/无甲醛胶粘剂型、无胶粘剂型纤维板的研究状况;重点阐述了改性脲醛树脂胶在纤维板中的应用、游离甲醛的产生机理及检测方法、减少纤维板中游离甲醛释放量的有效方法.     

小分子烃类蒸汽热裂解自由基机理模型研究方法的探讨

由于热裂解存在反应时间短、自由基数量多、浓度小,且不同原料产生的不同自由基之间、反应深度较大时管壁处于高温和停留时间所生成的不同自由基与主流体间的相互作用会随时改变反应路径,并影响到产物分布,因此造成了用实验方法研究单体烃热裂解反应机理的困难。将Materials Studio软件与Aspen Plus软件相结合来研究单体烃热裂解的自由基反应机理,并通过对乙烷热裂解一次反应机理、乙烷和丙烷混合热裂解相互作用机理、动力学数据准确性对比及正已烷空间位阻的影响,对研究方法进行了论述。结果表明,数值模拟的理论方法与实验方法相比,可以深入了解实验研究不可能达到的一些机理细节问题,如果将实验研究和模拟研究相结合,可避免目前动力学模型研究中的各种假设,提高机理模型研究的准确性,为工业生产预测提供高精度的机理模型。     

Decay of free radicals in irradiated PMMA at high pressures studied by ESR

The decay of free radicals in irradiated PMMA subjected to high pressures has been studied by the method of ESR. The rate constants and activation energies has been determined for the decay of free radicals at the pressures of 5000 and 10,000 atm over the temperature range of 100–170°C. It has been found that the rate of decay was reduced essentially by the effect of high pressure. The mechanism of the decay of free radicals in solid polymers is being discussed. The important influence of the motion of macromolecule segments on the course of radical reactions in solid phase is printed out.     

ESR study of pressure dependence of the peroxy radical decay in irradiated isotactic polypropylene

By the use of gamma radiation the free radicals were generated in isotactic polypropylene. The polymer was exposed to the action of atmospheric oxygen and the peroxy radicals were formed. Then the decay of peroxy radicals was investigated at varying temperatures as a function of pressure. The rate constants of the free radical decay were determined, and the corresponding activation volumes were calculated. The kinetic characteristics imply that the peroxy radicals predominantly occured in amorphous region the polymer. The results suggest that useful information on molecular mechanism of radical reactions in the solid phase may be obtained from the determination of activation volumes.     

Thermal degradation of poly(methyl methacrylate) at 50°C to 125°C

Small but significant numbers of chain scissions occur in a commercial poly(methyl methacrylate) sheet exposed to temperatures between 50 and 125°C. The scission rate is initially high and then levels off to a constant rate. The short-time rate of chain scissions is temperature dependent, while the long-time rate of chain scissions appears to be temperature independent. Four possible sources of random chain scission initiation were considered: (1) the presence of unreacted initiators of polymerization, (2) free radicals generated from additives in the commercial film, (3) weak links in the polymer chain, and (4) free radicals generated from the thermal decomposition of an oxidation product of methyl methacrylate (MMA) monomer. The source most consistent with our results is the one involving free radicals generated from the oxidation product of MMA monomer.     

Facile and flexible fabrication of structured array surfaces on binderless tungsten carbide by using electrical discharge machining with a novel self-assembly ball electrode

Electrical discharge machining (EDM) method is an innovative method for the fabrication of structured array surfaces on binderless tungsten carbide (WC) which is a typical embossing mold material, compared to traditional machining methods. To improve the convenience of electrode replacement and the fabrication efficiency of the structured array, a novel self-assembly ball electrode is innovatively developed. The feasibility of machining binderless WC with a self-assembly ball electrode was studied and its effect on profile deviation analyzed. Furthermore, the discharge condition's effect on surface roughness, material removal rate (MRR), and tool wear ratio (TWR) was investigated. The microstructure, phase structure, and element distribution of binderless WC caused by EDM were characterized by Raman spectroscopy, scanning electron microscopy, and energy dispersive x-ray spectroscopy. The results indicated that the maximum profile deviation of the different random structured arrays was about 3.7 μm. The surface roughness of all structured arrays was below 1 μm. The maximum TWR was about 0.008 mm³/min. Besides, the binderless WC surface after EDM presented strong D and G carbon peaks, which means the precipitation and transformation of the WC phase during the discharge process. Finally, different kinds of self-assembly ball electrodes are developed and used to fabricate the lens array structures on binderless WC. The fast fabrication of the micro-lens array surfaces in different arrangements sheds some light on the design and manufacturing of other functional structured surfaces.     

Binderless granulation of pharmaceutical lactose powders

With a binderless fluidized bed granulation method (Pressure Swing Granulation, PSG), jet-milled lactose particles were successfully agglomerated into narrow and spherical granules. This should be the first achievement of binderless granulation from an organic powder indicating the high potential of PSG application to pharmaceutical processes. With a decrease in the mean diameter of primary particles, the granules' mean diameter decreased, and the compression strength of a single granule increased.The size of product lactose granules predicted by the Iwadate–Horio [Powder Technol. 100 (1998) 223] model was in good agreement with the experimental results obtained by sieve analysis.     

Studies on the initiation mechanism of persulfate/aliphatic secondary amine system in vinyl polymerization

Persulfate/aliphatic secondary amine initiation systems were studied. Secondary amines were discovered to be excellent accelerators for the polymerization of acrylic monomers in aqueous solution initiated by persulfate. The rate of acrylamide polymerization and the overall activation energies were determined respectively. The active intermediates of the secondary amine species formed during the initiation reaction were detected by ESR technique to be dialkylamino radicals(R₂N·). From the results the initiation mechanism was proposed.     

褐煤无黏结剂成型理论的粉体工程分析

在分析多种褐煤无黏结剂成型假说的基础上,提出了影响褐煤成型特性的其他内因。介绍了褐煤无黏结剂成型的粉体力学模型,同时对无桥、液桥、固桥3种黏结类型下的平均颗粒抗拉强度的计算公式进行了推导。探讨了在褐煤成型过程中,不同阶段相应的主要黏结力,并得出褐煤型煤最终产品的强度取决于颗粒间形成的固桥黏结力。研究表明:确定合理的外部条件,使颗粒间形成合适的固桥黏结力,即可满足褐煤运输和加工利用所需强度。