微量Fe3+对过氧化氢异丙苯热稳定性影响研究

为研究微量铁离子（Fe³⁺）对过氧化氢异丙苯（CHP）热稳定性的影响,采用绝热加速量热仪（ARC）对CHP及含4种不同浓度Fe3+的CHP进行了绝热分解测试,测试分析了5个样品在绝热条件下的起始分解温度（To,s）、绝热温升（ΔTad,s）、最大温升速率（mm,s）和最大温升速率到达时间（θm,s）等参数,并利用热惰性因子Φ对实验数据进行了修正。研究结果表明:在绝热条件下,微量Fe3+的存在对CHP分解的To,s,ΔTad,s,mm,s和θm,s均有较大影响,且浓度不同对各参数的影响不一样;Fe³⁺的存在增加了CHP分解的剧烈程度,且浓度越大,CHP分解越剧烈,其热分解失控可能性越大,危险性越高;储存运输CHP时要避免与高浓度的Fe³⁺接触。研究结果可为CHP的热稳定性安全提供一定参考。     

Acid-catalyzed heterogeneous reaction of 3-methyl-2-buten-1-ol with hydrogen peroxide

Acid-catalyzed heterogeneous oxidation with hydrogen peroxide(H2O2) has been suggested to be a potential pathway for secondary organic aerosol(SOA) formation from isoprene and its oxidation products. However, knowledge of the chemical mechanism and kinetics for this process is still incomplete. 3-Methyl-2-buten-1-ol(MBO321), an aliphatic alcohol structurally similar to isoprene, is emitted by pine forests and widely used in the manufacturing industries. Herein the uptake of MBO321 into H2SO4–H2O2mixed solution was investigated using a flow-tube reactor coupled to a mass spectrometer. The reactive uptake coefficients(γ) were acquired for the first time and were found to increase rapidly with increasing acid concentration. Corresponding aqueous-phase reactions were performed to further study the mechanism of this acid-catalyzed reaction. MBO321 could convert to 2-methyl-3-buten-2-ol(MBO232) and yield isoprene in acidic media. Organic hydroperoxides(ROOHs) were found to be generated through the acid-catalyzed route,which could undergo a rearrangement reaction and result in the formation of acetone and acetaldehyde. Organosulfates, which have been proposed to be SOA tracer compounds in the atmosphere, were also produced during the oxidation process. These results suggest that the heterogeneous acid-catalyzed reaction of MBO321 with H2O2 may contribute to SOA mass under certain atmospheric conditions.     

两种海藻中MAAs抗氧化活性的研究

对两种海藻(紫菜、江蓠)中MAAs化合物(mycosporine-like amino acicds)的抗氧化活性进行了研究,并利用高效液相色谱法对MAAs化合物中抗氧化活性因子进行了定量解析。结果表明:紫菜和江蓠中的MAAs化合物对羟基自由基和超氧阴离子的生成都有一定的抑制作用,且紫菜抽提物中的MAAs化合物有较好的自由基活性。紫菜中的MAAs化合物对卵磷脂的氧化也具有抑制作用,其作用强度随着浓度的增大而增大,而江蓠抽提物对卵磷脂氧化抑制作用不明显。高效液相色谱检测分析结果显示紫菜MAAs化合物中起抗脂质氧化作用的主要活性成分为porphyra-334,江蓠抗氧化抑制作用不明显的原因为抽提物MAAs化合物中porphyra-334含量过少所致。     

Modeling of the venting of an untempered system under runaway conditions

The prediction of the consequences of a runaway reaction in terms of temperature and pressure evolution in a reactor requires the knowledge of the reaction kinetics, thermodynamics and fluid dynamics inside the vessel during venting. Such phenomena and their interaction are complex and yet to be fully understood, especially reactions where the pressure generation is totally or partially due to the production of permanent gases (gassy or hybrid systems). Moreover, these phenomena cannot be easily determined by laboratory scale experiments. In this paper, a dynamic model developed to simulate the behavior of an untempered reacting mixture during venting is presented. The model provides the temperature, pressure and mass inventory profiles before and during venting. A sensitivity study of the model was performed. This modeling work provides some insight regarding the interpretation of the data obtained from untempered system venting experiments. The outcome of this work contribute to improving the design of emergency relief systems for hybrid and gassy systems, where significant progress is still to be made in the experimental and modeling areas.     

Thermal risk analysis of cumene hydroperoxide in the presence of alkaline catalysts

Many studies have been performed to clarify the basic thermal runaway hazards and kinetics of cumene hydroperoxide (CHP) decomposition. However, materials that are incompatible with CHP have not been clearly identified. Alkaline solutions have been used as a catalyst to form dimethylphenyl carbinol (DMPC) and dicumyl peroxide (DCPO); however, these solutions also affect the reaction and storage temperature of CHP. In this study, thermal calorimeters, differential scanning calorimetry (DSC) and vent sizing package 2 (VSP2), were used to compare the effects of various bases on the decomposition of CHP in cumene. Specifically, the exothermic onset temperature, change in pressure over time, self-heating rate and heat of decomposition were evaluated. Moreover, to appraise the degree of hazard associated with the use of CHP, the compatibility of CHP with various substances was analyzed, and a risk matrix for thermal runaway reactions was obtained. The results of the present study could be used to design safety procedures for the production of CHP and its derivatives.     

过氧化氢异丙苯热稳定性与热安全性研究

为研究过氧化氢异丙苯(CHP)的热稳定性和热安全性,利用C80微量量热仪对CHP在空气中的热分解进行试验研究。利用热分析技术研究CHP的热分解,得到了升温速率对CHP热分解的影响,CHP热分解的活化能,绝热条件下最大反应速率到达时间Tmrad和不同包装下的自加速分解温度。结果表明:随着升温速率的增加,CHP的起始放热温度和最大放热温度随之升高;CHP热分解的活化能范围为52～91 kJ/mol;Tmrad为1,8,24,50和100 h时对应的起始温度分别为118.08,75.41,55.83,44.83和34.52℃;CHP的储罐内径越大,其对应的自加速分解温度越低。     

Agrobacterium-mediated transformation of Nicotiana attenuata, a model ecological expression system

Summary. Research into the genetic basis of the ecological sophistication of plants is hampered by the availability of transformable systems with a wealth of well-described ecological interactions. We present an Agrobacterium-mediated transformation system for the model ecological expression system, Nicotiana attenuata, a native tobacco that occupies the post-fire niche in the Great Basin Desert of North America. We describe a transformation vector and a transformation procedure that differs from the standard cultivated tobacco transformation protocols in its use of selectable markers, explants, media and cultivation conditions. We illustrate its utility in the transformations with genes coding for key enzymes in the oxylipin cascade (lipoxygenase, allene oxide synthase, hydroperoxide lyase) in antisense orientations and present high-throughput screens useful for the detection of altered phenotypes for the oxylipin cascade (green leaf volatiles and jasmonic acid after wounding). Received 14 March 2002; accepted 10 May 2002