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Hydrogenation properties of mechanically milled Mg2Ni0.8Cr0.2-CoO/Al2O3 composites
WANG Xiu-li, TU Jiang-ping, CHEN Chang-pin, ZHANG Xiao-bin, ZHAO Xin-bing
Journal of Zhejiang University-SCIENCE B (Biomedicine & Biotechnology), 2005, 6(3): 10-.
https://doi.org/10.1631/jzus.2005.B0208
Mg2Ni0.8Cr0.2-x wt.% CoO/Al2O3 (x=0.5, 1, 2 and 3) composites were prepared by mechanically milling sintered Mg2Ni0.8Cr0.2 alloy and CoO/Al2O3 compound for 45 h. The addition of CoO/Al2O3 compound resulted in the good kinetics properties of hydriding/dehydriding reaction of the composites. The composite with 1.0 wt.% CoO/Al2O3 catalyst could reach the maximum hydrogen absorption capacity (2.9 wt.%) within 5 min at 393 K under H2 pressure of 4 MPa, and can desorb rapidly at 493 K. The decomposition and synthesis of hydrogen molecule on Mg2Ni0.8Cr0.2 alloy surface was promoted by addition of CoO/Al2O3 catalyst. In addition, the formation of metallic Ni particles, strain and defects during the ball milling process also resulted in the improved hydrogenation performance of Mg2Ni-based alloys.
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Effect of polyoxypropylene chain length on the critical micelle concentration of propylene oxide-ethylene oxide block copolymers
ZHANG Zhi-guo, YIN Hong
Journal of Zhejiang University-SCIENCE B (Biomedicine & Biotechnology), 2005, 6(3): 12-.
https://doi.org/10.1631/jzus.2005.B0219
In this work, the surface activity of block copolymer nonionic surfactants (RPE) has been determined, i.e., critical micelle concentration (CMC), surface excess concentration (|£), surface area demand per molecule (A), surface tension at CMC (|?CMC). A linear decrease of ln[CMC] vs number of oxypropylene units in copolymer molecule was observed. The change in the work of cohesion per oxypropylene group when passing from molecular into micellar state, calculated from the Shinoda equation, was 0.43kT for the studied compounds.
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Prediction of valid acidity in intact apples with Fourier transform near infrared spectroscopy
LIU Yan-de, YING Yi-bin, FU Xia-ping
Journal of Zhejiang University-SCIENCE B (Biomedicine & Biotechnology), 2005, 6(3): 158-164.
https://doi.org/10.1631/jzus.2005.B0158
To develop nondestructive acidity prediction for intact Fuji apples, the potential of Fourier transform near infrared (FT-NIR) method with fiber optics in interactance mode was investigated. Interactance in the 800 nm to 2619 nm region was measured for intact apples, harvested from early to late maturity stages. Spectral data were analyzed by two multivariate calibration techniques including partial least squares (PLS) and principal component regression (PCR) methods. A total of 120 Fuji apples were tested and 80 of them were used to form a calibration data set. The influences of different data preprocessing and spectra treatments were also quantified. Calibration models based on smoothing spectra were slightly worse than that based on derivative spectra, and the best result was obtained when the segment length was 5 nm and the gap size was 10 points. Depending on data preprocessing and PLS method, the best prediction model yielded correlation coefficient of determination (γ2) of 0.759, low root mean square error of prediction (RMSEP) of 0.0677, low root mean square error of calibration (RMSEC) of 0.0562. The results indicated the feasibility of FT-NIR spectral analysis for predicting apple valid acidity in a nondestructive way.
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Optimization of technological conditions for one-pot synthesis of (S)-α-cyano-3-phenoxybenzyl acetate in organic media
ZHANG Ting-zhou, YANG Li-rong, ZHU Zi-qiang
Journal of Zhejiang University-SCIENCE B (Biomedicine & Biotechnology), 2005, 6(3): 175-181.
https://doi.org/10.1631/jzus.2005.B0175
Optically active form of α-cyano-3-phenoxybenzyl (CPB) alcohol, building block of pyrethroid insecticides, was synthesized as its acetate by the combination of anion-exchange resin (D301)-catalyzed transcyanation between m-phenoxybenzaldehyde (m-PBA) and acetone cyanohydrin (AC), and lipase (from Alcaligenes sp.)-catalyzed enantioselective transesterification of the resulting cyanohydrin with vinyl acetate. Through optimizing technological conditions, the catalyzing efficiency was improved considerably compared to methods previously reported. Concentrations of CPB acetate were determined by gas chromatograph. The enantio excess (e.e.) values of CPB acetate were measured by NMR (nuclear magnetic resonance) method. Effects of solvents and temperatures on this reaction were studied. Cyclohexane was shown to be the best solvent among the three tested solvents. 55 °C was the optimal temperature for higher degree of conversion. External diffusion limitation was excluded by raising the rotational speed to 220 r/min. However, internal diffusion could not be ignored, since the catalyst (lipase) was an immobilized enzyme and its particle dimension was not made small enough. The reaction rate was substantially accelerated when the reactant (m-PBA) concentration was as high as 249 mmol/L, but decreased when the initial concentration of m-PBA reached to 277 mmol/L. It was also found that the catalyzing capability of recovered lipase was high enough to use several batches. Study of the mole ratio of AC to m-PBA showed that 2:1 was the best choice. The strategy of adding base catalyst D301 was found to be an important factor in improving the degree of conversion of the reaction from 20% to 80%. The highest degree of conversion of the reaction has reached up to 80%.
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Reductive denitrification of nitrate by scrap iron filings
HAO Zhi-wei, XU Xin-hua, WANG Da-hui
Journal of Zhejiang University-SCIENCE B (Biomedicine & Biotechnology), 2005, 6(3): 182-186.
https://doi.org/10.1631/jzus.2005.B0182
Reduction of nitrate by zero-valent iron is a highly exergonic reaction that has long been known to occur. Use of scrap iron filings (SIF) as the PRB (Permeable Reactive Barrier) material can be used to recycle certain by-products, and identify cheaper replacements for expensive conventional PRB materials, especially pure metallic iron. The feasibility of reductive denitrification of nitrate by SIF was studied by batch experiments. Operational parameters such as pH value, SIF dosage and initial concentration of nitrate were investigated. The removal efficiency of nitrate reached 80% under the conditions of pH of 2.5, nitrate initial concentration of 45 mg/L and SIF dosage of 100 g/L within 4 h. Results indicated that nitrate removal is inversely related to pH. Low pH value condition favors for the nitrate transformation. Different from the results of others who studied nitrate reduction using iron powder, we found that there was a lag time before nitrate reduction occurs, even at low pH. Finally, the possible mechanism of nitrate reduction by Fe0 is discussed.
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13 articles
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