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991.
固体强酸催化剂Pd/WO3-ZrO2的制备及其对正庚烷异构化反应的催化性能 总被引:5,自引:1,他引:5
采用共沉淀方法制备了固体酸载体WO3-ZrO2,考察了W含量和焙烧温度等对WO3-ZrO2酸性和物相结构的影响,并且考察了Pd/WO3-ZrO2催化剂对正庚烷异构化反应的催化性能. 结果表明,Pd/WO3-ZrO2催化剂的催化性能与固体强酸的W含量及晶相结构密切相关. 在w(W)=13.2%~15.8%时,经700~800 ℃焙烧,WO3在ZrO2表面达到单层分散,且大部分ZrO2以四方晶相存在,所制备的0.5%Pd/WO3-ZrO2对正庚烷异构化反应的催化活性可达到70.4%,选择性可达到81.0%. 相似文献
992.
993.
994.
Yuanbo Li Fengshou Dong Xingang Liu Jun Xu Wuying Chen Li Cheng Ping Ning Jing Li Yunhao Wang Yongquan Zheng 《Journal of separation science》2010,33(13):1973-1979
A simple enantioselective HPLC method was developed for measuring carfentrazone‐ethyl enantiomers. The separation and determination was accomplished on an amylose tris[(S)‐α‐methylbenzylcarbamate] (Chiralpak AS) column using n‐hexane/ethanol (98:2, v/v) as mobile phase at a flow rate of 1.0 mL/min with UV detection at 248 nm. The effects of mobile‐phase composition and column temperature on the enantioseparation were discussed. The accuracy, precision, linearity, LODs, and LOQ of the method were also investigated. LOD was 0.001 mg/kg in water, 0.015 mg/kg in soil and wheat, with an LOQ of 0.0025 mg/kg in water and 0.05 mg/kg in soil and wheat for each enantiomer of carfentrazone‐ethyl. SPE was used for the enrichment and cleanup of soil, water, and wheat samples. Recoveries for two enantiomers were 88.4–106.7% with RSDr of 4.2–9.8% at 0.1, 0.5, and 1 mg/kg levels from soil, 85.8–99.5% with the RSDr of 4.4?9.6% at 0.005, 0.025, and 0.05 mg/kg levels from water, and from wheat the recoveries were 86.3?91.3% with RSDr below 5.0% at 0.2, 0.5, and 1 mg/kg levels. This method could be used to identify and quantify the carfentrazone‐ethyl enantiomers in food and environment. 相似文献
995.
Nafion‐coated antimony film electrode (NCAFE) was prepared in situ by simultaneously plated antimony with analytes, and applied to the determination of trace Pb(II) and Cd(II) in non‐deaerated solutions by differential pulse anodic stripping voltammetry (DPASV). Various experimental parameters, which influenced the response of the NCAFE to those metals, were thoroughly optimized and discussed. The results indicated that the sensitivity and resistance to surfactants at the NCAFE were remarkably improved with relative to the antimony film electrode (AFE). In the presence of 5 mg·L?1 gelatin, the peak heights at the NCAFE showed 4‐fold enhancement for Pb and a 9‐fold enhancement for Cd over a bare AFE. Reproducibility of the sensor was satisfactory, and the relative standard deviations were 4.8% for 20 μg·L?1 Pb and 3.2% for 25 μg·L?1 Cd (n=15) with preconcentration time of 180 s. The determination limits (S/N=3) of this sensor were determined to be 0.15 μg·L?1 for Pb and 0.30 μg·L?1 for Cd with accumulation time of 300 s. The NCAFE was successfully applied to determining Pb(II) and Cd(II) in vegetable and water samples with satisfactory results. 相似文献
996.
P-Phos [2,2′6,6′-四甲氧基吡啶-4,4′-二(二苯基膦)-3,3′-联吡啶]是一类对空气稳定的杂环磷配体。本文以较简单的方法合成了rac-P-Phos配体,并用IR、1H NMR、13C NMR和元素分析等方法进行了表征。首次将P-Phos配体用于催化卤代芳烃和胺的偶联反应中。通过对碱、溶剂和催化剂用量等的筛选,确立了最优化的反应条件。配体对溴代芳烃的催化效果很好,对具有吸电子存在的氯代芳烃,特别是氯代吡啶同样得到了令人满意的结果,分离产率高达97%。催化剂对水和空气的稳定性很好,对胺偶联反应的催化效果很理想,因此是一种有应用前景的催化剂。 相似文献
997.
Myriam E. Rodriguez Ping Zhang Kashif Azizuddin Grace B. Delos Santos Song-mao Chiu Liang-yan Xue Jeffery C. Berlin Xinzhan Peng Hongqiao Wu Minh Lam Anna-Liisa Nieminen Malcolm E. Kenney Nancy L. Oleinick 《Photochemistry and photobiology》2009,85(5):1189-1200
The phthalocyanine photosensitizer Pc 4 has been shown to bind preferentially to mitochondrial and endoplasmic reticulum membranes. Upon photoirradiation of Pc 4-loaded cells, membrane components, especially Bcl-2, are photodamaged and apoptosis, as indicated by activation of caspase-3 and cleavage of poly(ADP-ribose) polymerase, is triggered. A series of analogs of Pc 4 were synthesized, and the results demonstrate that Pcs with the aminopropylsiloxy ligand of Pc 4 or a similar one on one side of the Pc ring and a second large axial ligand on the other side of the ring have unexpected properties, including enhanced cell uptake, greater monomerization resulting in greater intracellular fluorescence and three-fold higher affinity constants for liposomes. The hydroxyl-bearing axial ligands tend to reduce aggregation of the Pc and direct it to lysosomes, resulting in four to six times more killing of cells, as defined by loss of clonogenicity, than with Pc 4. Whereas Pc 4-PDT photodamages Bcl-2 and Bcl-xL, Pc 181-PDT causes much less photodamage to Bcl-2 over the same dose–response range relative to cell killing, with earlier cleavage of Bid and slower caspase-3-dependent apoptosis. Therefore, within this series of photosensitizers, these hydroxyl-bearing axial ligands are less aggregated than is Pc 4, tend to localize to lysosomes and are more effective in overall cell killing than is Pc 4, but induce apoptosis more slowly and by a modified pathway. 相似文献
998.
基于支持向量机方法的HERG钾离子通道抑制剂分类模型 总被引:1,自引:0,他引:1
对human ether-a-gō-gō related genes(HERG)钾离子通道(钾通道)抑制剂,计算了表征分子组成、电荷分布、拓扑、几何结构及物理化学性质等特征的1559个分子描述符.采用Fischer Score(F-Score)排序过滤和Monte Carlo模拟退火法相结合从中筛选与HERG钾通道抑制剂分类相关的分子描述符.采用支持向量机(SVM)方法,分别以IC50=1.0、10.0μmol·L-1为分类标准,建立了三个分类预测模型.对367个训练集分子,用五重交叉验证.得到正、负样本的平均预测精度分别为84.8%-96.6%、80.7%-97.7%,其总的平均预测精度为87.1%-97.2%,优于其它文献报道结果.对97个外部测试集分子,所建三个模型的总样本预测精度在67.0%-90.1%之间,接近或优于其它文献报道结果. 相似文献
999.
1000.