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  • Author or Editor: Wenxiang Zhang x
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A two-dimensional thin-layer chromatographic fingerprint has been developed on a polyamide plate for the quality control of Helleborus thibetanus Franch. The investigated sample was separated by chloroform-ethyl acetate-methanol (3.0:8.0:4.4, v/v) in the first dimension and isooctane-n-propyl alcohol-water (10:2.5:1.0, v/v) adding 0.28 mol L−1 sodium dodecyl sulfate, a reversed micelle, in the second dimension. The plate was dried in the air at room temperature and examined in ultraviolet (UV) light at λ = 365 nm after development. The two developments were carried out over a distance of 70 mm. The two-dimensional thin-layer chromatographic method was validated in terms of repeatability, stability, and robustness. For fingerprint analysis, nine spots were identified as common spots. Statistical method (canonical correlation analysis) was first used to calculate the degree of similarity between the two-dimensional chromatograms. The proposed method was novel and accurate for the identification and quality evaluation of H. thibetanus Franch.

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Abstract  

The catalytic properties of supported Cu/SBA-15 catalysts prepared by the ion-exchange method were investigated for the hydrogenolysis of glycerol in a fixed-bed tubular reactor. The Cu/SBA-15 catalyst performed higher selectivity to 1,2-propanediol and high stability. We propose that the larger specific surface area and the ordered mesoporous channels of SBA-15 may play important roles in stabilizing highly dispersed copper species, and forming an active and durable catalyst for the title reaction.

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Reaction Kinetics, Mechanisms and Catalysis
Authors: Lixia Wang, Wanchun Zhu, Dafang Zheng, Xue Yu, Jing Cui, Mingjun Jia, Wenxiang Zhang, and Zhenlu Wang

Abstract  

The reaction of direct transformation of ethanol to ethyl acetate was investigated on reduced Cu/ZrO2 catalysts prepared by a co-precipitation procedure. The catalytic performances of these Cu–Zr mixed oxides were considerably influenced by changing the molar ratio of Cu to Zr. The highest selectivity to ethyl acetate was found over Cu/ZrO2(1) catalyst (molar ratio of Cu to Zr was 1). A variety of characterization techniques, such as N2 adsorption, XRD, XPS, TPR and NH3-TPD were carried out on the catalysts. The results revealed that the presence of a certain amount of Cu+ species may play very important role in improving the selectivity to ethyl acetate of the Cu/ZrO2 catalysts.

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