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    30 May 2019, Volume 53 Issue 3 Previous Issue    Next Issue
    Research Report
    Preparation of Silver Ion-loaded Mesoporous SBA-15 Adsorbent and Its Application in Adsorption of Fatty Acids Methyl Ester
    Bo CHEN,Yuanbo HUANG,Peiyan WANG,Shouqing LIU,Delu NING,Zhifeng ZHENG
    2019, 53 (3):  1-7.  doi: 10.3969/j.issn.1673-5854.2019.03.001
    Abstract ( 455 )   HTML ( 803 )   PDF (4360KB) ( 523 )   Save

    The mesoporous Ag+-APTS/SBA-15 adsorbent was prepared by surface modification of 3-aminopropyltriethoxysilane (APTS) and loading silver ion with the mesoporous molecular sieve SBA-15 as support. The adsorbent was characterized by nitrogen adsorption-desorption, X-ray diffraction(XRD), Fourier transform infrared spectroscopy(FT-IR), transmission electron microscopy(TEM), and scanning electron microscopy-energy spectrum(SEM-EDS). The adsorbent was applied to separating the mixed fatty acid methyl esters to investigate its adsorption properties. The results of nitrogen adsorption-desorption, XRD and TEM showed that the adsorbent had regular ordered pore structure; FT-IR data showed that the surface of mesoporous SBA-15 was successfully modified by APTS; SEM-EDS results showed that silver ion was successfully loaded onto the support SBA-15. The adsorbent had good adsorptive effect on unsaturated fatty acid methyl esters(UFAMEs), with the increase of loading amount of silver ion and the double-bond number of UFAMEs, the adsorption capacity of adsorbent increased gradually for the UFAMEs. When the silver ion loading amount was 25%, the adsorption rate of methyl linolenate on the adsorbent got to 53.47%.

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    Preparation and Characterizations of Polyvinyl Alcohol-microcrystalline Cellulose-hexagonal Boron Nitride Composite Membrane
    Xin GE,Houfu CHENG,Sentao HUANG,Jingwen CHEN,Fuxiu FU,Xunjun CHEN,Jianfang GE
    2019, 53 (3):  8-14.  doi: 10.3969/j.issn.1673-5854.2019.03.002
    Abstract ( 518 )   HTML ( 874 )   PDF (5421KB) ( 599 )   Save

    Microcrystalline cellulose(MCC) was extracted from pineapple leaf fibrous by means of pre-acid immersion, alkaline extraction and acid hydrolysis and the influences of mass fraction of sulfuric acid solution, temperature and reaction time on the reaction were discussed. The results showed that the optimum preparation conditions of MCC were mass fraction of sulfuric acid 64%, reaction temperature 45 ℃ and reaction time 90 min. Hexagonal boron nitride(h-BN) was used to modified MCC in order to gain h-BN-MCC composite powder. The products were mainly characterized by Fourier transform infrared spectroscopy(FT-IR), scanning electron microscopy(SEM) and thermogravimetic analysis(TG). The results showed that the infrared spectrogram characteristic peaks were consistent with the reference and the mass loss of cellulose microcrystalline was 97% when the temperature raised to 700 ℃. The whisker lengths were about several to twenty microns and the diameters were 2-3 μm.Then the composite powder was dispersed in polyvinyl alcohol(PVA) to prepare h-BN-MCC-PVA composite membrane. Tensile strength and contact angle test were used to characterize the membrane. MCC could assist h-BN to compound with PVA well and tensile strength and elongation at break of h-BN-MCC-PVA composite membrane could be increased by 15.1% and 122.0% respectively. And the composite powder could enhance the hydrophobicity of the film and the contact angle could increase from 34.91° to 52.28°.

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    Preparation of Yb(OTf)3 Immobilized on Mesoporous Silica and Its Catalytic Activity for Lactic Acid Productionfrom Glucose
    Shiwei WANG,Qibao WANG
    2019, 53 (3):  15-23.  doi: 10.3969/j.issn.1673-5854.2019.03.003
    Abstract ( 456 )   HTML ( 151 )   PDF (3289KB) ( 575 )   Save

    Two kinds of SBA-15 and MCM-41 mesoporous silica were prepared by solvent and calcination method, and they were used as the carrier of the supported ytterbium triflate(Yb(OTf)3) catalysts. The carriers and catalysts were characterized by small angle X-ray diffraction(SAXD), nitrogen adsorption/desorption, 29Si solid state nuclear magnetic resonance spectroscopy(NMR), transmission electron microscope(TEM) and thermogravimetric analysis(TG), and the catalytic performances of these catalysts in the preparation of lactic acid from glucose were evaluated. The experimental results showed that the amount of hydroxyl group of mesoporous silica by solvent method was higher than that of mesoporous silica by calcination method, so its catalytic activity was higher. The average pore size of SBA-15 was about 3 nm larger than that of MCM-41, which led to better mass transfer performance of SBA-15 and better catalytic performance of Yb(OTf)2-SBA-15. The yield of lactic acid could reach 42.35% when it reacted at 2 MPa N2 pressure and 190 ℃ for 60 min with Yb(OTf)2-SBA-15-S as catalyst.

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    Extraction and Relative Molecular Mass Distribution of Corncob Xylan
    Hongyu FAN,Min WEI,Jian ZHAO,Jianchun JIANG
    2019, 53 (3):  24-32.  doi: 10.3969/j.issn.1673-5854.2019.03.004
    Abstract ( 683 )   HTML ( 260 )   PDF (1125KB) ( 771 )   Save

    A graded ethanol precipitation technique was employed to obtain xylan from the alkaline hydrogen peroxide-extracted corncob liquid. The results of single factor test showed that in the alkaline hydrogen peroxide solution of 1% H2O2 and 5% NaOH with the reaction temperature of 50℃, reaction time of 16 h, and liquid-solid ratio of 20:1(mL:g), the yield of xylan could reach 83.15%. And the effects of vacuum freezing and drying methods on the properties of xylan were investigated. Hemicellulose monosaccharide composition was determined by high performance ion chromatography, and hemicellulose was analyzed and characterized by FT-IR, TG, 1H NMR, 13C NMR and GPC. The results showed that all fractions were composed of xylose, glucose, arabinose, etc., mainly composed of L-arabinose-(4-O-methyl-D-glucuronic acid) xylan; the degrees of branching(w(arabinose)/w(xylose)) were 0.17 to 0.52, and it increased as the volume fraction of ethanol increased. The drying method had a great influence on the relative molecular weight of the product. The weight average molecular weights(Mw) of vacuum freeze-dried xylan were 108 533 to 197 752, and the vacuum dried Mw were 41 231 to 47 242.Among the 12 fractions obtained by the two kinds of drying method, the dispersion coefficients were 1.172 to 1.517, and 11 of them had the dispersion coefficient of less than 1.5, which were uniformly distributed low-dispersion xylan.

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    Molecular Dynamics Simulation of Effect of Heat Treatment on Structure and Mechanical Properties of Lignocellulose Iβ
    Wei WANG,Yunting WANG,Xinning LI
    2019, 53 (3):  33-38.  doi: 10.3969/j.issn.1673-5854.2019.03.005
    Abstract ( 484 )   HTML ( 85 )   PDF (3218KB) ( 672 )   Save

    Molecular dynamics(MD) simulation method was used to study the structure and mechanical properties of cellulose Iβ, the main component of wood, in heat treatment environment. A 3×3×3 cellulose supercell model for simulation was established. The volume, density, and hydrogen bond change diagrams of 350-550 K were obtained. Changes in the microstructure of cellulose were analyzed and the mechanical properties were calculated. The results showed that the unit cell volume increased gradually with the temperature increase, from 11.99 nm3 at 350 K to 12.26 nm3 at 550 K, and the density of model was 1.581-1.617 g/cm3, which was consistent with the experimental results. The total number of hydrogen bonds decreased by 24%, and the hydrogen bonds in the molecular chain were partially broken to form new interchain hydrogen bonds. The ratio of hydrogen bonds in the chain to hydrogen bonds between chains changed from 2.1:1 to 1:1.5, which in turn affected its mechanical properties. As the temperature increased, the Young's modulus gradually decreased, and the rate of change was about 13%. Shear modulus and bulk modulus were less affected by temperature compared with Young's modulus and there were no significant changing trend.

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    Preparation and Property Characterization of Polyvinyl Alcohol Hydrogel with Anisotropic Structure
    Lin ZHANG,Huiliang WANG
    2019, 53 (3):  39-45.  doi: 10.3969/j.issn.1673-5854.2019.03.006
    Abstract ( 691 )   HTML ( 318 )   PDF (4640KB) ( 632 )   Save

    Polyvinyl alcohol(PVA) hydrogels with anisotropic microstructures were firstly prepared by directional freezing-thawing(DFT) of PVA aqueous solution, and then they were crosslinked with 60Co γ-rays irradiation to improve their thermal stability and mechanical properties. Scanning electron microscopy(SEM) showed that original anisotropic microstructures of PVA hydrogels could be maintained after radiation-induced crosslinking. Long aligned channels were found along the parallel direction, pores with similar sizes were found along the perpendicular direction. The thermal stability tests showed that the PVA hydrogels prepared with one directional freezing-thawing cycle and irradiated with 30-70 kGy 60Co γ-rays could maintain their original gel states in 60℃ water for more than 10 h. Tensile mechanical testing showed that the radiation crosslinked PVA hydrogels(DFT-RC-3-10) maintained their anisotropic tensile properties, moreover, the tensile strengths and elastic moduli of the radiation crosslinked PVA hydrogels(DFT-RC-3-10) were enhanced, for the PVA gel samples prepared with three directional freezing-thawing cycles and irradiated with 10 kGy 60Co γ-ray, the tensile strength and elastic modulus in the direction perpendicular to the freezing direction were enhanced to 0.86 and 0.10 MPa, respectively.

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    Review Comment
    Research Status and Prospects of Biomass Pyrolysis Reactor
    Wenxin JI,Ming ZENG,Hongbin CONG,Zonglu YAO,Haibo MENG,Lixin ZHAO
    2019, 53 (3):  46-58.  doi: 10.3969/j.issn.1673-5854.2019.03.007
    Abstract ( 656 )   HTML ( 1712209946 )   PDF (1653KB) ( 1041 )   Save

    Biomass pyrolysis is an important way to realize the energy utilization of biomass, and it is of great significance to solve the increasingly serious energy problems. This paper focused on the research status of several typical biomass pyrolysis reactors, and listed several new pyrolysis reactors which were recently developed, and the working principle, advantages and disadvantages of different types of pyrolysis reactors were summarized. The catalytic pyrolysis technology and biomass raw material pretreatment technology were reviewed. It was concluded that the research on the development of new high-efficiency, high-activity pyrolysis catalysts and the basic theory of raw material pretreatment technology were the future research directions of bio-pyrolysis.

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    Research Progress on Hemicellulose and Its Reducing Sugar Extraction by Hot-water Prehydrolysis
    Chenggong XU,Jinlong CUI,Zhiwei CHEN,Guibao GUO
    2019, 53 (3):  59-66.  doi: 10.3969/j.issn.1673-5854.2019.03.008
    Abstract ( 567 )   HTML ( 29345 )   PDF (829KB) ( 802 )   Save

    Hemicellulose and its reducing sugar can be effectively extracted by hot-water prehydrolysis from biomass. The role of hemicellulose has important impact in various fields. The research results of hemicellulose and its reducing sugar extraction by hot-water prehydrolysis at home and abroad in recent ten years were reviewed. The reaction rule of hemicellulose during the hot-water prehydrolysis were analyzed. The advantages and disadvantages of this method were expounded. The research progress and the development tendency of this method were carefully summarized.

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