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排序方式: 共有576条查询结果,搜索用时 46 毫秒
81.
Stefania Garzoli Mijat Božović Anna Baldisserotto Manuela Sabatino Stefania Cesa Federico Pepi 《Natural product research》2018,32(11):1254-1259
A comprehensive study on essential oil samples of Foeniculum vulgare Miller from Tarquinia (Italy) is reported. A 24-h systematic steam distillation was performed on different harvested samples applying different extraction times. The GC-MS analysis of the residue outcome showed o-cymene, α-phellandrene, α-pinene and estragole as the major constituents. The predominance and continued presence of o-cymene makes this fennel oil a rather unique chemotype. An evident correlation between the antifungal activity and phenological stage is demonstrated. The most active fractions were particularly rich in estragole, as well as a significant amount of fenchone that possibly exerts some additive effect in the expression of overall antifungal potency. Pre-fruiting material produced oil particularly rich in o-cymene. With reference to the duration of the extraction, the maximum amount of oil was released within the first 3 h, whereas the reproductive phase material needed at least 6 h for the extraction. 相似文献
82.
Stoyan Stoyanov Georgi Yordanov Ceco Dushkin 《Reaction Kinetics and Catalysis Letters》2008,94(2):227-232
The effect of Ni loading on the catalytic activity of Ni/ZrO2 catalyst for methane steam reforming was investigated. The sample containing 15 wt.% Ni exhibited the highest activity as
well as stability at 600°C.
An erratum to this article is available at . 相似文献
83.
Reaction parameters influence on the catalytic performance of copper-silica aerogel in the methanol steam reforming 《燃料化学学报》2016,44(1):84-90
Steam reforming of methanol was carried out on the copper-silica aerogel catalyst.The effects of reaction temperature,feed rate,water to methanol molar ratio and carrier gas flowrate on the H_2 production rate and CO selectivity were investigated.M ethanol conversion was increased considerably in the range of about 240-300,after which it increased at a slightly lower rate.The used feed flowrate,steam to methanol molar ratio and carrier gas flowwere 1.2-9.0 m L/h,1.2-5.0 and 20-80 m L/min,respectively.Reducing the feed flowrate increased the H_2 production rate.It was found that an increase in the water to methanol ratio and decreasing the carrier gas flowrate slightly increases the H2production rate.Increasing the water to methanol ratio causes the lowest temperature in which CO formation was observed to rise,so that for the ratio of 5.0 no CO formation was detected in temperatures lower than 375℃.In all conditions,by approaching the complete conversion,increasing the main product concentration,increasing the temperature and contact time,and decreasing the steam to methanol ratio,the CO selectivity was increased.These results suggested that CO was formed as a secondary product through reverse water-gas shift reaction and did not participate in the methanol steam reforming reaction mechanism. 相似文献
84.
《Comptes Rendus Chimie》2016,19(4):433-440
In this study, an experimental plasma-chemical reactor equipped with an arc discharge water steam plasma torch was used for biomass conversion to hydrogen-rich synthesis fuels. Glycerol and crushed wood were used as biomass sources. The effects of different conversion parameters including the water steam flow rate, treated material flow rate, and plasma torch power were studied. The experimentally obtained results were compared with the model based on the thermodynamic equilibrium. Additionally, the quantification of the plasma conversion system in terms of energy efficiency and specific energy requirement was performed. It has been found that the synthesis gas can be effectively produced from the biomass using water steam plasma. 相似文献
85.
透平转子的可靠性设计 总被引:3,自引:0,他引:3
介绍透平转子的可靠性设计方法。该方法以传统的转子强度和振动的设计方法为基础,把透平转子的静应力、材料静强度、应力幅、尺寸系数、表面加工系数、应力集中系数、材料疲劳极限、热疲劳累积损伤程度、材料低周疲劳程度、蠕变寿命、固有频率、激振力频率、不平衡响应等处理为随机变量,使用机械概率设计法确定转子设计的可靠度。文中给出了透平转子静强度、疲劳强度、热疲劳、蠕变寿命、避开弯曲共振、避开扭转共振和限制不平稳响 相似文献
86.
87.
88.
Hongsheng Wang Bingzheng Wang Sean-Thomas B. Lundin Hui Kong Bosheng Su Jian Wang 《Molecules (Basel, Switzerland)》2021,26(22)
To efficiently convert and utilize intermittent solar energy, a novel solar-driven ethanol steam reforming (ESR) system integrated with a membrane reactor is proposed. It has the potential to convert low-grade solar thermal energy into high energy level chemical energy. Driven by chemical potential, hydrogen permeation membranes (HPM) can separate the generated hydrogen and shift the ESR equilibrium forward to increase conversion and thermodynamic efficiency. The thermodynamic and environmental performances are analyzed via numerical simulation under a reaction temperature range of 100–400 °C with permeate pressures of 0.01–0.75 bar. The highest theoretical conversion rate is 98.3% at 100 °C and 0.01 bar, while the highest first-law efficiency, solar-to-fuel efficiency, and exergy efficiency are 82.3%, 45.3%, and 70.4% at 215 °C and 0.20 bar. The standard coal saving rate (SCSR) and carbon dioxide reduction rate (CDRR) are maximums of 101 g·m−2·h−1 and 247 g·m−2·h−1 at 200 °C and 0.20 bar with a hydrogen generation rate of 22.4 mol·m−2·h−1. This study illustrates the feasibility of solar-driven ESR integrated with a membrane reactor and distinguishes a novel approach for distributed hydrogen generation and solar energy utilization and upgradation. 相似文献
89.
Cu/ZrO2催化剂上乙醇水蒸气重整反应的研究Ⅱ反应条件的影响 总被引:3,自引:1,他引:2
采用沉淀法或醇凝胶法、浸渍法制备Cu/ZrO2催化剂,在常压微型固定床石英管反应器上进行乙醇水蒸气重整反应,采用程序升温还原(TPR)技术表征催化剂的还原特性。考察了催化剂还原温度、反应温度、水醇比、空速等对反应的影响以及催化剂的稳定性。结果表明,在300℃~500℃,随反应温度升高,乙醇转化率增大,H2选择性下降。不同还原温度对转化率的影响不是很大,对于H2选择性,300℃、400℃还原的催化剂优于500℃还原的催化剂。高水醇比有利于提高转化率和H2选择性。随空速增大,转化率和H2选择性呈现下降的趋势。8%Cu/ZrO2催化剂在400℃或450℃反应22h显示出良好的稳定性。 相似文献
90.
An environmentally friendly method for extracting sulfonamides(SAs) residues from animal feed was described and applied. The method used online microwave-assisted steam extraction coupled with solid phase extraction(MASE-SPE), which was followed by the analysis using high performance liquid chromatography-mass spectrometry(HPLC-MS/MS). The SAs residues were extracted successively with water steam under microwave irradiation, and thus directly introduced into an SPE column containing cation-exchange resin. The SAs were then eluted with methanol-ammonia(90:10, volume ratio) from the SPE column and followed by HPLC-MS/MS. The limits of detection(LODs) for the analytes ranged from 0.24 ng/g to 0.49 ng/g. The limits of quantification(LOQs) ranged from 0.82 ng/g to 1.63 ng/g. Average recoveries of SAs were 76.3%-92.1%. The developed method was a reliable and environmentally friendly alternative to previous methods with respect to time, solvent and labor consumption for the analysis of SAs in animal foodstuffs. 相似文献