Meizhen Lu

Zhejiang University of Technology, Hang-hsien, Zhejiang Sheng, China

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Publications (9)28.04 Total impact

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    ABSTRACT: This work described a general strategy to enhance a typical organic–aqueous heterogeneous green oxidation reaction by introducing surface tunable magnetic nanoparticles into liquids to form a controllable Pickering emulsion. We synthesized cross-linked polystyrene (PS)-covered Fe3O4 nanoparticles grafted with different N-alkyl imidazoles and systematically discussed the effect of surface properties on the formation of emulsions. By loading such particles, the dichloromethane–water-based 2,2,6,6-tetramethylpiperidine-1-oxyl-mediated Montanari oxidation system was converted from the unstable millimeter-scale dispersion into a stable micrometer-scale emulsion, which significantly reduced the reactant transfer distance and resulted in a significantly high overall reaction rate. This reaction efficiency is elucidated in terms of unique properties inherent in an emulsion, including the self-assembly of Fe3O4/PS and Fe3O4/PS[im-Cn]Cl (n=1, 4, 6, and 10) nanoparticles, well ensuring a large specific surface area of the water–oil interface.
    ChemCatChem 01/2015; DOI:10.1002/cctc.201402856 · 5.18 Impact Factor
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    ABSTRACT: The microchannel liquid-flow focusing and cryo-polymerization is an efficient method for the preparation of cryogel beads with a narrow diameter distribution. In order to prepare cryogel beads with expected diameters, it is necessary to get insights in the liquid-liquid immiscible flow characteristics of the flow-focusing fluid and the monomer solution in microchannels. In this work, the slug flow behaviors of two immiscible liquids regarding the preparation of poly(2-hydroxyethylmethacrylate) (pHEMA) cryogel beads in a rectangular cross-junction microchannel were investigated experimentally by the high-speed imaging method. Correlations of the immiscible liquid-liquid slug flow parameters like the aqueous slug velocity and length, the aqueous slug nose and tail lengths, the water-immiscible slug length as well as the aqueous droplet size were obtained. The pHEMA cryogel beads were prepared under certain flow conditions and the bead sizes were measured by laser particle size analyzer. The obtained correlations were then employed to estimate the bead sizes and compared with those obtained experimentally. The results showed that the present correlations gave reasonable estimations of the mean bead diameters at various conditions and thus, could be useful and helpful in the preparation of cryogel beads with expected size distributions in rectangular microchannels.
    Chemical Engineering Research and Design 11/2014; DOI:10.1016/j.cherd.2014.01.012 · 1.93 Impact Factor
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    ABSTRACT: In this work, the role of Brønsted acid for furfural production in biomass pyrolysis on supported sulfates catalysts was investigated. The introduction of Brønsted acid was shown to improve the degradation of polysaccharides to intermediates for furfural, which did not work well when only Lewis acids were used in the process. Experimental results showed that CuSO4/HZSM-5 catalyst exhibited the best performance for furfural (28% yield), which was much higher than individual HZSM-5 (5%) and CuSO4 (6%). The optimum reaction conditions called for the mass ratio of CuSO4/HZSM-5 to be 0.4 and the catalyst/biomass mass ratio to be 0.5. The recycled catalyst exhibited low productivity (9%). Analysis of the catalysts by Py-IR revealed that the CuSO4/HZSM-5 owned a stronger Brønsted acid intensity than HZSM-5 or the recycled CuSO4/HZSM-5. Therefore, the existence of Brønsted acid is necessary to achieve a more productive degradation of biomass for furfural.
    Bioresource Technology 07/2014; 169. DOI:10.1016/j.biortech.2014.07.053 · 5.04 Impact Factor
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    ABSTRACT: This study demonstrated the use of a magnetic superhydrophobic polymer nanosphere cage derived from a Pickering emulsion as a framework for miceller catalysis in biphasic media. We designed this system through the covalent stabilisation of active site (2,2,6,6-tetramethylpiperidine 1-oxyl)-grafted amphiphiles onto the magnetic hydrophobic core to form a micelle-like architecture and used it as a Pickering emulsifier to develop a new kind of micelle-catalysed biphasic system. The catalysis results reveal that these fixed micelle-tethered 2,2,6,6-tetramethylpiperidine 1-oxyl catalysts demonstrate much higher activity than their soluble counterparts in the biphasic Montanari oxidation of alcohols, which could be due to the unique properties of Pickering emulsion and miceller catalysis. In addition, the excellent magnetic response ensures the efficient recycling of the catalyst by magnetic decantation. The catalyst can be recycled at least 10 times without significant loss of activity or degradation of magnetic susceptibility. Moreover, this study demonstrates that this new Pickering emulsion-based and micelle-catalysed biphasic system is technically simple and practically applicable.
    ChemCatChem 05/2014; 6(6). DOI:10.1002/cctc.201400009 · 5.18 Impact Factor
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    ABSTRACT: Nitrogen source is one of the important factors that affect the microalgae growth and lipid accumulation. We studied the effects of various nitrogen sources (i.e. NaNO3, CO(NH2)2, NH4Cl and CH3COONH4) and amount on the growth density, lipid yield, and eicosapentaenoic acid (EPA) content of Nannochloropsis oculata by single factor experimental method. The results show that N. oculata preferred NH4+ as nitrogen source rather than NO3- and CO(NH2)2. NH4+ could promote the growth and lipid accumulation of N. oculata. With the increase of nitrogen concentration, the biomass and the content of polyunsaturated fatty acid (PUFA) increased, but the content of lipid decreased. CH3COONH4 was the most suitable for growth, accumulation of lipid and EPA of N. oculata among the four investigated nitrogen sources. The optimal concentration was 5.29 mmol/L.
    Sheng wu gong cheng xue bao = Chinese journal of biotechnology 12/2013; 29(12):1865-9.
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    ABSTRACT: The technology of packed bed dielectric barrier discharge (DBD) plasma followed by a chemical absorption has been developed and was found to be an efficient way for decomposition treatment of sulfuryl fluoride (SO2F2) in simulated residual fumigant. The effects of energy density, initial SO2F2 concentration and residence time on the removal efficiency of SO2F2 for the DBD plasma treatment alone were investigated. It was found that the SO2F2 could be removed completely when initial volume concentration, energy density and residence time were 0.5%, 33.9 kJ/L and 5.1 s, respectively. The removal mechanism of SO2F2 in the packed bed DBD reactor was discussed. Based on the detailed analysis of SO2F2 molecular stability and its exhaust products in the DBD plasma reactor, it was concluded that the energetic electrons generated in the packed bed DBD reactor played a key role on the removal of SO2F2, and the major decomposition products of SO2F2 detected were SO2, SiF4 and S (Sulfur). Among these products, SiF4 was formed by the F atom reacted with the filler-quartz glass beads (SiO2) in the packed bed DBD reactor. Aqueous NaOH solution was used as the chemical absorbent for the gaseous products of SO2F2 after plasma pretreatment. It was found that the gaseous products in the plasma exhaust could be absorbed and fixed by the subsequent aqueous NaOH solution.
    Environmental Science & Technology 06/2013; 47(14). DOI:10.1021/es400786p · 5.48 Impact Factor
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    ABSTRACT: Effects of carbon sources (Na2CO3, NaHCO3 and glucose) and concentration of NaHCO3 on the growth density and lipid contents of Nannochloropsis oculata were studied. N. oculata preferred inorganic carbon to glucose, the growth density and lipid content of algae cultured with NaHCO3 were higher than that with glucose. The effects of concentration of NaHCO3 on growth density and lipid content were related to inoculation density and nitrogen level. In high nitrogen level, the concentration of NaHCO3 had little effect on the growth density, but in low nitrogen level, the growth density increased at first, and then decreased with the increase of concentration of NaHCO3. Based on the results we suggest that an optimum ratio of carbon to nitrogen was existed. Furthermore, we found the optimum ratio was changed with inoculation density. The optimum ratio of carbon to nitrogen was 3 when inoculation density was OD440 of 0.10, the optimum ratio increased to 5 with OD440 of 0.70. Concentration of NaHCO3 and ratio of carbon to nitrogen had significant effects on the lipid content and productivity. Lipid content reached the highest value when the ratio of carbon to nitrogen was 1 with experimental range of nitrogen level and inoculation density. The lipid productivity was 56.7 mg/(L.d) , and the EPA productivity was 6.5 mg/(L.d) at optimum cultivation condition with NaHCO3 as carbon source, the ratio of carbon to nitrogen at 1, the concentration of NaNO3 at 0.225 g/L, and the inoculation density with OD440 of 0.70.
    Sheng wu gong cheng xue bao = Chinese journal of biotechnology 03/2013; 29(3):358-69.
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    ABSTRACT: Sweet sorghum is a high-yielding energy crop that leaves a large amount of lignocellulosic residues after the sugar fraction fermented to ethanol. Here, we developed a biphasic kinetic model for the dilute sulfuric acid-catalyzed hemicellulose hydrolysis of sweet sorghum bagasse at temperatures of 110–150 °C, and we then calculated the kinetic parameters for xylose production and furfural decomposition. The results indicated that elevated reaction temperatures promote the hydrolysis of hemicellulose and the degradation of xylose. The xylose yield increased in proportion to reaction time in the initial stages and then declined due to the degradation of xylose to furfural. The pre-exponential factors for the ‘easy-to-hydrolyze’ fraction, the ‘hard-to-hydrolyze’ fraction of hemicellulose and xylose degradation were 3.53 × 106, 1.80 × 105 and 0.62 min−1, respectively, and the activation energies were 60.7, 58.1 and 14.5 kJ/mol, respectively. The ideal hydrolysis condition for xylose production was 140 °C for 50 min, under which the xylose yield reached 60% of hemicellulose weight. This xylose can be used to form bioethanol and produce further downstream products.
    Industrial Crops and Products 07/2012; 38:81–86. DOI:10.1016/j.indcrop.2012.01.013 · 3.21 Impact Factor
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    ABSTRACT: Lignocellulose and other carbohydrates are being studied extensively as potential renewable carbon sources for liquid biofuels and other valuable chemicals. In the present study, a simple, sensitive, selective, and reliable HPLC method using a photodiode array (PDA) detector and an evaporative light scattering detector (ELSD) was developed for the simultaneous determination of important sugars (D(+)-cellobiose, glucose, xylose, and arabinose), furfural and 5-hydroxymethylfurfural (5-HMF) in lignocellulose hydrolysate. The analysis was carried out on an Aminex HPX-87H column (250 mm × 4.6 mm, 5 μm particle size). Ultra-pure water with 0.00035 M H(2)SO(4) was used as the mobile phase with a flow rate of 0.6 mL/min. The temperature of the ELSD drift tube was kept at 50 °C, the carrier gas pressure was 350 kPa, and the gain was set at 7. Furfural and 5-HMF were quantified on a PDA detector at 275 nm and 284 nm, respectively. The sugar concentrations were determined by ELSD. This method was validated for accuracy and precision. The regression equation revealed a good linear relationship (r(2) = 0.9986 ± 0.0012) within the test ranges. The method showed good reproducibility for the quantification of six analytes in corncob hydrolysate, with intra- and inter-day variations less than 1.12%. This method is also convenient because it allows the rapid analysis of the primary products of biomass hydrolysis and carbohydrate degradation.
    Carbohydrate research 04/2012; 353:111-4. DOI:10.1016/j.carres.2012.03.029 · 2.03 Impact Factor