Development of a Bio-Inspired Dual Catalytic System for Alkane Dehydrogenation

The alkene is a central functional group in organic synthesis. While myriad reliable methods exist to access this moiety from other functionalities, acceptorless dehydrogenation, or the direct synthesis of alkenes from alkanes with hydrogen gas as the sole byproduct, remains a challenging, albeit highly desirable, transformation. This essay provides an account of our recent efforts toward accessing this difficult reaction class, with particular attention paid to the diverse precedents that informed our explorations. This report highlights the benefits of maintaining a broad range of interests, and we hope that it illustrates the vast connectivity between chemical disciplines.     

异甘草素合成工艺优化及其清除自由基活性研究

对异甘草素的合成工艺进行优化和体外清除自由基活性进行研究。通过间苯二酚、冰醋酸、对羟基苯甲酸合成异甘草素,考察物料比、温度、反应时间对产率的影响,通过紫外分光度法对其清除自由基活性进行研究。酚与酸物料比1∶2.5,240 W微波辐射3 min,2,4-二羟基苯乙酮产率最高为65.75%;当醛酮物质的量比为3∶1,温度控制在120~130℃,回流6 h,异甘草素产率最高为28.10%;反应时间控制20 min,异甘草素加入量为1.00 m L清除DPPH自由基能力最强,为66.4%。异甘草素具有一定的抗自由基活性。     

H_2O_2辅助氧化石墨烯光降解罗丹明B

采用传统Hummer法制备氧化石墨烯(GO),以罗丹明B作为目标污染物,研究GO的光降解性能。研究结果表明,GO表现出优异的光降解罗丹明B性能,在GO投加质量浓度为0.15 g/L,罗丹明B质量浓度为10 mg/L(200 m L),300 W氙灯光照120 min后,对其降解率达到86.99%;加入1.0 m L H_2O_2,120 min后光降解率可达到96.14%;羟基自由基捕获实验证明H_2O_2/GO光催化罗丹明B主要遵循羟基自由基氧化机制。在GO投加质量浓度为0.15 g/L,H_2O_2用量为2.0 m L,罗丹明B质量浓度10 mg/L,pH为3,光照10 min降解率达到98%。     

电化学处理废水过程中羟基自由基的测定

采用三维电极-电Fenton耦合法降解模拟苯酚废水,验证模拟苯酚废水降解过程中羟基自由基的存在,考察不同电压、起始p H值、铁粉加入量、曝气等因素对羟基自由基生成量的影响,实验结果表明:当溶液的p H为6.86(原溶液),加入3.0 g/300 m L Fe粉,5 V电压下1.5 L·min-1的曝气下电解30 min后,苯酚降解过程中羟基自由基的生成量最大。     

Photocatalytic degradation of gaseous perchloroethylene in continuous flow reactors: Rate enhancement by chlorine radicals

The degradation of perchloroethylene (PCE) by UV/TiO₂ photocatalysis in gas phase was studied. The degradation efficiency has been compared in different continuous flow reactors: a photocatalytic tangential reactor (PTR) where the air flows tangentially over the catalytic medium and two photocatalytic filtering reactors (PFR) where the air flows through the porous catalytic medium. The degradation rate shows a linear dependence with the concentration of pollutants (up to 350 mg PCE/N m³) for the PTR, but the degradation was negligible for the PFR. The degradation rate was enhanced by accelerating the chlorine radicals’ formation (by adding HCl in catalytic quantity in the air flow or by PCE over-heating). In these conditions, the oxidation rate constant of PCE in the PFR was about five times higher than that in the PTR, although the mass of catalyst involved in the PFR was about 10 times lower and the contact time was about a 1000 times shorter than that of the PTR. Thus, the catalyst is globally more efficiently used in the PFR, as the mass transfer is not limiting. As a result, a degradation mechanism of PCE, involving the generation of free chlorine radicals, as the first limiting step, has been confirmed.     

Heterogeneous chain propagation in low-pressure flames

An analysis of papers on hydrogen combustion at low pressures is performed, which refines the contribution of the catalytic reactions on the reactor wall to the gas-phase part of the process. A new model for the heterogeneous loss of active reaction centers was proposed and tested experimentally to explain inconsistencies that occur in some papers. In this model, the diffusion region of chain termination is formed under standard experimental conditions in vacuum oxyhydrogen flames at a reactor gas pressure a thousand times lower than the boundary pressure postulated by the previous models as the pressure below which the diffusion region of chain termination cannot be formed. __________ Translated from Fizika Goreniya i Vzryva, Vol. 42, No. 2, pp. 10–18, March–April, 2006.     

Oxidative radical generation via nitrogen dioxide dimer conversions induced by amide groups of macromolecules

The features of initiation of free radical reactions in polymers by dimers of nitrogen dioxide are considered. The conversion of planar dimers into nitrosyl nitrate in the presence of amide groups of macromolecules has been revealed. Nitrosyl nitrate initiates radical reactions in oxidative primary process of electron transfer with formation of intermediate radical cations and nitric oxide. As a result of subsequent reactions, nitrogen‐containing radicals are produced. The dimer conversion has been exhibited by estimation of the oxyaminoxyl radical yield in characteristic reaction of p‐benzoquinone with nitrogen dioxide on addition of aromatic polyamide and polyvinylpyrrolidone to reacting system. The isomerization of planar dimers is efficient in their complexes with amide groups, as confirmed by ab initio calculations. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Fenton氧化法去除酱油生产废水中焦糖色素的研究

着重考察了Fenton试剂对水中焦糖色素降解的影响因素.从试验中得出,这些影响因素包括pH、催化剂的投加方式、催化剂与氧化剂的化学计量数以及反应时间等.Fenton反应中,pH4的条件下处理效果最好,反应进行40min时去除率达到90%.     

The Nature of the Mental Representation of Radicals in Chinese: A Priming Study.

Using a priming procedure, 4 experiments were carried out to investigate the effects of a short preexposure of a prime that was a radical or contained radicals identical to the target. Significant facilitation was found when the target contained the prime as a radical, although only for low-frequency targets which did not arise merely as a result of graphical similarity. Facilitation also occurred when the prime and target shared a radical in the same position but not when in different positions. When the prime and target had exactly the same radicals but in different positions, however, the priming effect was inhibitory. This set of results suggests that simple characters (radicals) and complex characters are represented at a different level. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effect of temperature on methyl radical generation over Sr/La2O3 catalysts

The role of gas phase CH₃ radicals in the oxidative coupling of CH₄ over 1 wt% Sr/La₂O₃ is supported by the observations that (i) this is a very effective catalyst for the generation of CH₃ · radicals and (ii) the concentration of CH₃ · radicals increases with temperature over the range of 450 °C–800 °C.