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911.
912.
用超临界流体干燥法制备出大孔高比表面高分散态Fe/ZrO_2气凝胶超细粒子催化剂,研究了在其制备过程中织构性质、颗粒大小、体相和表面结构的变化,并与普通浸渍法制备的Fe/ZrO_2催化剂作了对比。对几种Fe/ZrO_2催化剂的F-T反应性能考察表明,Fe/ZeO_2气凝胶超细催化剂显示出高的反应活性;随载体ZrO_2颗粒尺寸减小,活性组分铁的分散度变大,其颗粒尺寸变小,催化剂比表面积增大,反应活性增大,甲烷和低碳烃生成量增加,重质组分减少,认为产物烃分布主要受催化剂活性相颗粒尺寸效应制约。 相似文献
913.
氢化物发生石墨炉原位富集直接测定高温镍基合金中碲 总被引:5,自引:0,他引:5
通过选择碲的氢化物发生条件,克服了高含量镍对碲的干扰,把氢化物富集在涂钯石墨管里,然后再原子化,成功地测定了高温镍基合金中碲。 相似文献
914.
915.
工业废水中微量铜(Ⅱ)和氰化物的流动注射光度分析 总被引:2,自引:0,他引:2
采用FIA技术,以光度比色法为基础,建立了工业废水中微量Cu^2+和CN^-的顺序自动分析方法和装置。其对二种离子的测定频率为60样/h,相对标准偏差<1.0%,工作曲线的r值≥0.999,各项分析技术指标均优于手工法操作。 相似文献
916.
Peng He Hui Liu Yanfeng Li Jiqin Zhu Shiping Huang Zhigang Lei Peng Wang Huiping Tian 《Adsorption》2012,18(1):31-42
The GCMC (grand canonical Monte Carlo) simulation technique was used to predict the competition adsorption characteristics
of benzene and propene in different pore systems of MCM-22. The nine-site model of benzene was used, which proved to be effective
and efficient. The zeolite was divided into three adsorption sites following a simulated annealing method. It is found that
benzene and propene have the same preferential adsorption site and a similar adsorption order in different sites. Moreover,
the pure and mixture isotherms of the three sites are drawn. From the isotherms, we obtained a selectivity reversal of the
mixture isotherms of benzene and propene in different sites. It is also noted that the competition adsorption in the three
adsorption sites for the two adsorbates can fall into three successive steps and the adsorption order of propene in mixture
in these three sites is S3→S1→S2. A new model is presented to predict the benzene and propene adsorption equilibrium in MCM-22.
This approach yields better multicomponent equilibrium predictions than ideal adsorbed solution theory (IAST). Isotherms at
different mole fraction of benzene in gas phase indicate an advantage to increase the feed radio of benzene and propene. Thus,
this work is helpful for a better understanding of the adsorption mechanism of benzene and propene in MCM-22 and hence the
relation of the catalytic properties of the zeolite to its structure. 相似文献
917.
918.
采用非水毛细管电泳方法对2’-AMP、3’-AMP和5’-AMP 3种单磷酸腺苷进行分离研究,考察了电泳溶液pH*值、非水介质、缓冲溶液对分离的影响。以含50%乙腈的Tris-H3BO3体系为缓冲溶液,在pH*10.0、压差进样(50 mbar,5 s)、柱温25℃、25 kV恒压下进行分离,在波长260 nm处负极检测,各组分可达到基线分离。在质量浓度为1~100 mg/L范围内,3种单磷酸腺苷的线性关系良好,平均回收率为88%~106%,RSD小于4%。该方法应用于核苷样品的测定,结果满意。 相似文献
919.
Efficient basic hydrotalcite (HT)-supported gold nanoparticle (AuNP) catalysts have been developed for the aerobic oxidative tandem synthesis of methyl esters and imines from primary alcohols catalyzed under mild and soluble-base-free conditions. The catalytic performance can be fine-tuned for these cascade reactions by simple adjustment of the Mg/Al atomic ratio of the HT support. The one-pot synthesis of methyl esters benefits from high basicity (Mg/Al=5), whereas moderate basicity greatly improves imine selectivity (Mg/Al=2). These catalysts outperform previously reported AuNP catalysts by far. Kinetic studies show a cooperative enhancement between AuNP and the surface basic sites, which not only benefits the oxidation of the starting alcohol but also the subsequent steps of the tandem reactions. To the best of our knowledge, this is the first time that straightforward control of the composition of the support has been shown to yield optimum AuNP catalysts for different tandem reactions. 相似文献
920.
Allylated biphenol neolignans contain a variety of chemopreventive entities that have been used as anti-tumor drug leads. Herein, 37 allylated biphenols were evaluated for anti-proliferative activity by the MTT assay and inhibitory effect on the migration and tube formation of HUVECs featuring anti-angiogenic properties. 3-(2-Methylbut-3-en-2-yl)-3′,5′-bis(trifluoromethyl)-[1,1′-biphenyl]-4-ol (5c) exerted an inhibitory effect on HUVECs compared to honokiol (IC?? = 47.0 vs. 52.6 μM) and showed significant blocking effects on the proliferation of C26, Hela, K562, A549, and HepG2 (IC?? = 15.0, 25.0, 21.2, 29.5, and 13.0 μM, respectively), superior to those of honokiol (IC?? = 65.1, 62.0, 42.0, 75.0, and 55.4 μM, respectively). Importantly, compound 5c inhibited the migration and capillary-like tube formation of HUVECs in vitro. 相似文献