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Table of Content
05 January 2014, Volume 65 Issue 1
    Methanol to propylene process using moving bed technology and its engineering study
    YAN Lixia, JIANG Yuntao, JIANG Binbo, LIAO Zuwei, HUANG Zhengliang, WANG Jingdai, YANG Yongrong, WANG Xieqing
    2014, 65(1):  2-11.  doi:10.3969/j.issn.0438-1157.2014.01.001
    Abstract ( 1168 )   PDF (868KB) ( 685 )  
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    A novel moving bed process for methanol to propylene (MMTP), and conducts engineering analysis for this process were presented. Firstly, according to the principle that the reactor must be matched with reaction catalyst deactivation, the most matching reactor for ZSM-5 catalysts (with mid-level deactivation) is moving bed. Moreover, the MMTP process can not only exert higher propylene selectivity of the catalyst, but also can utilize medium particle circulation rate for reaction and regeneration to serialize and stabilize high yield of propylene process. Secondly, regarding the strong exothermal characteristics of the MMTP reaction, two kinds of processes, fluidized bed one-step operation and fixed bed two-step operation, are compared. Based on the comparison results, it is concluded that the two-step operation of MMTP process can allocate reasonable reaction heat and control product distribution with flexibility. Finally, through integration of heat-exchange network optimization and alcohol-oil refining process, MMTP process owns high propylene yield on the basis of water and energy saving. On the basis of current MMTP process, 10000 t·a-1 propylene technology package design has been completed. In summary, MMTP owns visible competitive advantages both on technique and economics, which has high application potential in industry.
    A review for research on thermodynamics and kinetics of carbon dioxide absorption with organic amines
    CHEN Jian, LUO Weiliang, LI Han
    2014, 65(1):  12-21.  doi:10.3969/j.issn.0438-1157.2014.01.002
    Abstract ( 2305 )   PDF (506KB) ( 1500 )  
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    Carbon capture and storage technology is aimed to solve the problem of global warming mainly caused by increase of atmospheric CO2 level. Amine absorption method, as the most mature technology with economic and technical aspects, is an important technology for CO2 capture. In this review, from the start point of basic reaction mechanism, research works and results on the thermodynamic and kinetic properties of CO2 absorption with amines are summarized, and relationship of CO2 absorption solubility and reaction rates with molecular structures of different types of amines are described. Finally some research directions for thermodynamics and kinetics of CO2 absorption are put forward.
    Manipulating microstructural properties of carbon nanofibers and their applications in catalysis
    SUI Zhijun, LI Ping, ZHOU Jinghong, ZHU Yi'an, De Chen, ZHOU Xinggui
    2014, 65(1):  22-31.  doi:10.3969/j.issn.0438-1157.2014.01.003
    Abstract ( 1367 )   PDF (3610KB) ( 645 )  
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    As a new category of carbonaceous material, carbon nanofiber (CNF) has been extensively studied due to its unique characteristics. CNF is usually classified according to the angle between fiber axis and graphene sheets, that is, platelet, fishbone and tubular CNF. CNF with different microstructures could be synthesized by adjusting the preparation methods. For catalytic chemical vapor deposition method, the structural properties of the as-synthesized CNF are kinetically controlled. The differences of the structure properties of CNF with different microstructures would lead to different ratios of edge/basal atoms and consequently distributions of surface oxygen complex, wettability and other properties. When using CNF as catalyst support, morphologies, particle size distribution, interaction between the CNF support and metal particles and crystal plane orientation could be manipulated, leading to different catalytic performance. CNF has its own catalytic activities as verified by oxidative dehydrogenation of alkanes as solid base catalyst. The activities originate from the existence of heteroatoms on CNF surface, e.g., surface oxygen complexes and doped N. Since the chemistry of CNF surface depends on its microstructure, the great influence of structure properties on their catalytic performance has been evidenced in many researches. CNF with macroscopic shaping could be prepared through several methods. The characteristics of fluid dynamics of a CNF/graphite felt is also reviewed.
    Synthesis of ethylidene norbornene
    XU Huiming, SUN Chunshui, FU Jiansong, XIE Jiaming, SHI Jiale, LIU Xue, ZHANG Yan, SONG Yuexiao, YAO Zhen, CAO Kun
    2014, 65(1):  32-38.  doi:10.3969/j.issn.0438-1157.2014.01.004
    Abstract ( 2561 )   PDF (534KB) ( 1348 )  
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    Regarding to the ongoing demand for poly(ethylene propylene diene monomer) (EPDM), ethylidene norbornene (ENB) as its co-monomer has attracted important attention. In this paper, synthesis mechanism and technology, production status and market trend of ENB are reviewed. The discussion about synthesis processes of ethylidene norbornene is divided into two parts, one is process optimization for side reaction control in the part of vinyl norbornene (VNB) synthesis by Diels-Alder reaction between butadiene and cyclopentadiene obtained from (di)cyclopentadiene by high temperature degradation, the other is influence of different types of catalysts in the VNB isomerization process.
    Calculation of thermodynamic properties for 1:1 electrolyte solutions by square-well chain fluid with variable range-based equation of state
    LUO Zhilin, LI Jinlong, PENG Changjun, LIU Honglai
    2014, 65(1):  39-46.  doi:10.3969/j.issn.0438-1157.2014.01.005
    Abstract ( 943 )   PDF (643KB) ( 306 )  
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    An equation of state (EOS) for square-well chain fluids with variable range was applied to calculate thermodynamic properties of 1:1 aqueous electrolyte solutions. The segment diameter and dispersive energy parameter for 22 ions were fitted by experimental data of the mean ionic activity coefficient and osmotic coefficient of more than 40 aqueous electrolyte solutions, with overall average deviations of 6.03% and 5.83%, respectively. The results showed that the EOS can satisfactorily predict the density of aqueous electrolyte solutions and vapor liquid equilibrium of aqueous electrolyte solutions in wide range of temperature with overall average deviations of 0.22% and 4.69%, respectively. The overall average deviations of the prediction proves the reliability of the model parameters.
    Thermodynamic modeling and process simulation for CO2 absorption into aqueous monoethanolamine solution
    LI Han, CHEN Jian
    2014, 65(1):  47-54.  doi:10.3969/j.issn.0438-1157.2014.01.006
    Abstract ( 1679 )   PDF (958KB) ( 1314 )  
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    A thermodynamic model for monoethanolamine (MEA)-H2O-CO2 was built using the electrolyte non-random two-liquid model. Over twenty parameters were regressed from the vapor pressure and heat capacity data for MEA, data of vapor-liquid equilibrium, heat capacity and heat of mixing for MEA-H2O, and CO2 solubility data for MEA-H2O-CO2 over a wide range of temperature, concentration and CO2 loading. The model was validated by the NMR speciation data and then used to build a process simulation for CO2 absorption/ desorption into 30%(mass) MEA. The simulation results match the pilot plant data in literature. For 30%(mass) MEA solution, when the CO2 removal rate in the absorber is 90%, the reboiler heat duty is the minimum by changing the mass flow ratio of liquid to gas in the absorber. The minimum reboiler heat duty is 3.64 GJ·(t CO2)-1, when the ratio is 2.
    Flow and dispersion performance of gas/ionic liquid systems in microchannels
    TAN Jing, ZHAO Jingjing, XU Jianhong, LUO Guangsheng
    2014, 65(1):  55-60.  doi:10.3969/j.issn.0438-1157.2014.01.007
    Abstract ( 864 )   PDF (1145KB) ( 345 )  
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    Ionic liquids show good prospect in gas-liquid reaction and separation processes. Investigation of flow and dispersion performance of gas/ionic liquid systems is important for the development of technology and devices for gas-liquid dispersion as well as application of ionic liquids in gas-liquid reaction and separation processes. The flow and dispersion performance of N2/[Bmim]BF4 in coaxial annular microchannels was investigated. Flow patterns of bubble-flow, bubble-slug-transition-flow, slug-flow and slug-annular-transition-flow were observed. The influence of gas and liquid flow rates on gas-liquid flow pattern was studied in different microchannels and flow pattern maps were determined accordingly. The effects of gas and liquid flow rates on dispersion size were also investigated. The mechanism was discussed and mathematical models were established to predict the dispersion size in different microchannels.
    Chaotic mixing enhanced by rigid-flexible impeller in stirred vessel
    LIU Zuohua, CHEN Chao, LIU Renlong, TAO Changyuan, WANG Yundong
    2014, 65(1):  61-70.  doi:10.3969/j.issn.0438-1157.2014.01.008
    Abstract ( 933 )   PDF (3521KB) ( 360 )  
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    Flow field in a stirred vessel is usually divided into chaotic and regular mixing regions. It is an alternative way to improve mixing performance and lower the energy consumption by enlarging chaotic mixing region. Reasonable design of impeller is helpful to form appropriate flow condition and to improve the fluid mixing efficiency. Rigid-flexible combination can be designed by flexible body and rigid body with multiple-body motion behavior, intensifying the chaotic mixing. In this study, with the software Matlab, the largest Lyapunov exponent and multi-scale entropy in the tap water mixing system are investigated with double mechanical impellers. The difference between rigid and rigid-flexible impellers is analyzed in mixing performance. Results show that the rigid-flexible impeller enhances fluid movement and the fluid goes into chaotic mixing. At 210 r·min-1,the fluid is chaotic mixing, and the largest Lyapunov exponent is 0.041 for rigid impeller, while it is 0.048 for rigid-flexible impeller. The rigid-flexible impeller could transfer energy effectively and make the energy distribute uniformly. At agitation speed 150 r·min-1, the multi-scale entropy rate of rigid-flexible impeller is similar to that of rigid one at 210 r·min-1. Compared with rigid impeller system, the mixing time is shortened by about 26% with rigid-flexible impeller system. The rigid-flexible impeller could enhance the fluid chaotic mixing and save energy by changing the flow field structure and energy dissipation.
    Flow visualization through channels in plate-and-frame modules
    WANG Tao, ZHAN Xia, LI Jiding
    2014, 65(1):  71-77.  doi:10.3969/j.issn.0438-1157.2014.01.009
    Abstract ( 864 )   PDF (2511KB) ( 584 )  
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    A Perspex test cell was made to observe the flow regime directly in plate-and-frame modules under different conditions. The pressure drops in channels with and without spacer were examined. The critical Reynolds number(Rec) were determined with the correlations for Re and friction factors. The results showed that Rec in the spacer filled channel was much smaller than that in the empty one, indicating that the turbulence regime was reached at lower fluid velocity. The results were verified through the dye injecting method. Channels with different surface roughness, spacer arrangement and spacer porosity were also investigated. Finally, a laboratory scale spiral-wound module was made and a similar pressure drop situation was obtained, which confirms that the method is also suitable for the spiral-wound modules.
    Enhancement of macro-instability in mixer-settler with rigid-flexible impeller
    LIU Zuohua, TANG Qiao, WANG Yundong, SUN Ruixiang, ZHENG Xiongpan, TAO Changyuan
    2014, 65(1):  78-86.  doi:10.3969/j.issn.0438-1157.2014.01.010
    Abstract ( 921 )   PDF (8184KB) ( 376 )  
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    Fluid macro-instability reflects fluid axial energy and mass transfer behavior. To reveal the unsteady flow rule in a mixer-settler with rigid-flexible impeller, oil and water were used as working fluid, and the wavelet analysis and Matlab numerical calculation were adopted to analyze the power spectrum of pressure fluctuation signal in the mixing tank. The influences of rigid-flexible impeller on the frequency of macro-instability were studied, and CFD simulation was adopted to explore the flow field structure in the mixer-settler. Experiments showed that, while the agitation speed (N) of rigid-flexible impeller was lower than 250 r·min-1, the relationship between macro-instability frequency (fMI) and N was linear. When N was higher than 250 r·min-1, much air was sucked into the liquid and fMI disappeared, so the flow field became multi scale structure and resulted in serious emulsification, which was unfavorable for the operation of clarification. Compared with rigid impeller, the rigid-flexible one can enhance the macro-instability and improve the efficiency of fluid mixing and energy transfer. Computational simulation shows that, the rigid-flexible impeller could obviously increase the blade suction ability and axial movement of fluid, realizing efficient mixing and avoiding excessive stirring of the fluid, which is helpful to mixing and clarification.
    Determination of gas-liquid mass transfer coefficient for methanol synthesis under supercritical condition
    LI Jinggang, WU Sicao, LIU Peng, CHENG Zhenmin, ZHOU Zhiming, FANG Yunjin
    2014, 65(1):  87-92.  doi:10.3969/j.issn.0438-1157.2014.01.011
    Abstract ( 1160 )   PDF (602KB) ( 347 )  
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    Gas-liquid mass transfer coefficient for methanol synthesis was determined in a mechanically agitated slurry reactor with paraffin oil as the inert liquid medium and n-hexane as the supercritical medium. The ratio of gas-liquid mass transfer resistance to reaction resistance increased with increasing of catalyst concentration under the reaction condition of temperature 238℃, syngas pressure 3.7 MPa, and space velocity 2744 h-1. As gas-liquid mass transfer was the control step, gas-liquid mass transfer coefficients were obtained by extrapolation. Catalyst concentration had a much bigger effect on gas-liquid mass transfer of CO than that of CO2. Gas-liquid mass transfer coefficients of CO and CO2 in the liquid-phase reaction were 0.161 s-1 and 0.03 s-1 respectively, while they were 0.199 s-1, 0.042 s-1 under supercritical condition. Supercritical fluid is conductive to gas-liquid mass transfer in the three-phase methanol synthesis process.
    Bubble breakup and distribution in asymmetric Y-bifurcating microchannels
    CONG Zhenxia, ZHU Chunying, FU Taotao, MA Youguang
    2014, 65(1):  93-99.  doi:10.3969/j.issn.0438-1157.2014.01.012
    Abstract ( 928 )   PDF (1602KB) ( 379 )  
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    A high-speed camera was used to observe and record bubble breakup and distribution in bifurcating microchannels. Nitrogen and deionized water with 0.3% surfactant sodium dodecyl sulfate (SDS)-glycerol (20%, 40%,50%) were used as dispersed and continuous phases, respectively. Three different flow patterns were observed at the divergence: asymmetric breaking with permanent obstruction,asymmetric breaking with gap and non-breaking regimes. The transition between breakup and non-breakup was studied and compared with existing reports. The effects of flow rates of both phases and physical properties of fluids on the distributions of breaking bubbles were investigated. Both breakup lengths increased with increasing flow rate of gas phase and bubble length, and decreased with increasing liquid viscosity and flow rate. As the flow rate and viscosity of liquid phase increased, the degree of asymmetrical breakup decreased.
    Characteristics of fully developed laminar flow in triangular helical duct
    WANG Cuihua, LIU Shengju, WU Jianhua, LI Yaxia
    2014, 65(1):  100-107.  doi:10.3969/j.issn.0438-1157.2014.01.013
    Abstract ( 1082 )   PDF (903KB) ( 310 )  
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    Based on jackets with triangular flow channels, laminar flow characteristics in triangular helical duct were investigated experimentally and numerically. The simulation results were in good agreement with experimental values. Then the main flow velocity, secondary flow, stream function and vorticity were obtained with numerical method. The distribution of local frictional factor on the boundary of the triangular helical duct was analyzed and compared with that of half-coil helical duct. The results show that the structure of secondary flow is steady two vortices in the range of Dean number and dimensionless curvature ratio. The distribution of local frictional factor along the outer walls differs obviously from that along the inner wall. The mean value of the local frictional factors at the outer walls is 1.54—2.72 times that at the inner wall. With the increase of Dean number and dimensionless curvature ratio, the secondary flow is enhanced and the frictional factors on the outer walls and inner wall increase. For triangular helical ducts with small dimensionless torsion and Dean number, the torsion has little effect on the flow resistance. Compared with the semicircle helical duct with the same area of inner wall, curvature radius, pitch and Reynolds number, the flow resistance in the triangular helical duct is smaller.
    Gas-liquid flow distribution of parallel microchannels
    BAI Lu, ZHU Chunying, FU Taotao, MA Youguang
    2014, 65(1):  108-115.  doi:10.3969/j.issn.0438-1157.2014.01.014
    Abstract ( 1078 )   PDF (2907KB) ( 603 )  
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    The scale-up of microstructured reactor is an essential issue in order to achieve required throughput for industrial application. A high speed camera was used to observe gas-liquid flow pattern and phase distribution in four parallel microchannels. The influence of flow rate and viscosity on flow uniformity was investigated. The experimental liquid phase was deionized water with 0.3%(mass) surfactant sodium dodecyl sulfate (SDS)-glycerol, and the gas phase was nitrogen (N2). Six types of two-phase flow patterns were observed in the parallel microchannels. For the situation of all slug flow in four branch channels, the distribution of bubble length and velocity was studied. At a given gas flow rate, the relative standard deviation (RSD) of bubble length in branch channels increased with increasing liquid flow rate, and the RSD of bubble velocity in branch channels increased with increasing liquid flow rate up to a maximum and then gradually decreased. Non-uniformity of gas phase distribution increased with the increase of liquid flow rate and viscosity, and non-uniformity of liquid phase distribution decreased with the increase of liquid viscosity. The influence of gas flow rate on two-phase distribution was not significant. The study is helpful for the design and optimization of parallel microchannel structure to realize the uniform two-phase distribution.
    Hydrodynamics and mass transfer characteristics of a novel vertical-sheet structured packing
    HU Jianguang, LIU Jiate, YUAN Meng, YU Jianguo, DAI Gance
    2014, 65(1):  116-122.  doi:10.3969/j.issn.0438-1157.2014.01.015
    Abstract ( 1105 )   PDF (613KB) ( 417 )  
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    A novel vertical-sheet structured packing was developed to achieve better performance as compared with conventional structured packings. In order to evaluate hydrodynamics and mass transfer performance of the packing, desorption of oxygen from water was carried out in a packed column with 190 mm internal diameter operated at liquid load of 10—38 m3·m-2·h-1 and F factor of 0.2—3.2 m·s-1·(kg·m-3)0.5. The results show that compared with conventional structured packings with similar specific surface area, the pressure drop and the height of liquid transfer unit of the new packing are lower. The comparisons between the new packing and several improved structured packings with similar specific surface area demonstrate that the capacities of these packings are almost equivalent, while the mass transfer efficiency and pressure drop of the new packing are higher at high liquid load and its pressure drop is lower at low liquid load. For the influence of structure, it is shown that the high mass transfer efficiency of the new packing attributes largely to its novel geometry.
    Axial backmixing of liquid phase in a trickle bed reactor for selective hydrogenation of phenylacetylene
    HU Jiawei, HUANG Binjie, CHENG Zhenmin, ZHOU Zhiming
    2014, 65(1):  123-130.  doi:10.3969/j.issn.0438-1157.2014.01.016
    Abstract ( 1119 )   PDF (885KB) ( 340 )  
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    Recovery of styrene from the C8 fraction of pyrolysis gasoline, a byproduct of steam cracking of naphtha, has been recognized as a very promising approach to meet with increasing demand for styrene, and selective hydrogenation of phenylacetylene is the key reaction during the recovery process. The present study investigated the axial backmixing behaviors of liquid phase in a trickle bed reactor for selective hydrogenation of phenylacetylene. The liquid-phase residence time distribution under various experimental conditions was first measured by using a pulse tracer technique, and then Péclet number and average residence time of liquid phase were determined by the finite element orthogonal collocation method and the Levenberg-Marquardt nonlinear least-squares method. Finally, the effects of operation conditions on axial backmixing of liquid were studied. Liquid backmixing could be reduced by increasing liquid flow rate, gas flow rate, temperature and pressure, but would be exacerbated by increasing particle size.
    2D-QSPR studies on substituting PNP-Cr catalyst systems for highly selective ethylene oligomerization
    TANG Siyang, LIU Zhen, ZHAN Xingwen, CHENG Ruihua, HE Xuelian, LIU Boping
    2014, 65(1):  131-142.  doi:10.3969/j.issn.0438-1157.2014.01.017
    Abstract ( 928 )   PDF (868KB) ( 344 )  
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    1-Hexene and 1-octene are important comonomers for the synthesis of high performance polyolefins. Recently, Cr-bis(diphenylphosphino)amine (PNP-Cr) catalysts show the potential as excellent candidates for highly selective ethylene trimerization/tetramerization. In this work, a series of substituting PNP-Cr catalysts were studied by two-dimensional quantitative structure-property relationship (QSPR) method based on density functional theory (DFT) calculations. The heuristic method (HM) and best multi-linear regression (BMLR) were used for establishing the best linear regression models to describe the relationship between catalyst selectivity and its structure. Both Cr(Ⅰ) and Cr(Ⅱ) active site models for ethylene trimerization/tetramerization were considered. It was found that using self-defined descriptors from DFT calculations could increase the relativity and stability of the models. Monovalent Cr(Ⅰ) center was the most plausible active site for ethylene trimerization, while ethylene tetramerization was most possibly proceeded over divalent Cr(Ⅱ) active site. The skeleton structures of the PNP-Cr system especially a small PNP angle were crucial for achieving excellent catalytic selectivity. Nine new PNP ligands with high selectivity towards ethylene trimerization/tetramerization were predicted based on the best linear regression models providing a good basis for further development of novel catalyst systems with better performance.
    Kinetics of CoCu/SiO2 for synthesis of lower carbon mixed alcohols directly from syngas
    SU Junjie, MAO Wei, YANG Zhen, XU Jing, HAN Yifan
    2014, 65(1):  143-151.  doi:10.3969/j.issn.0438-1157.2014.01.018
    Abstract ( 1564 )   PDF (711KB) ( 455 )  
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    Synthesis of lower carbon mixed alcohols directly from syngas is one of the most promising approaches for utilizing coal resources cleanly and efficiently. The intrinsic kinetics for this reaction, in which the effects of internal and external diffusion had been excluded, was studied over CoCu/SiO2 catalysts prepared by the impregnation method in a fixed-bed reactor at 503—543 K with molar ratios of H2/CO varying from 4 to 0.5. The apparent activation energies and the reaction orders with respect to H2 and CO for products were calculated through power law models. With the combination of chain growth probability and kinetics, the effect of temperature on reaction mechanism was discussed.
    Kinetics of synthesis of hydrogen peroxide directly from H2 and O2 over Pd/HAp catalyst
    OUYANG Like, DA Guojin, TIAN Pengfei, CHEN Tianyuan, XU Jing, HAN Yifan
    2014, 65(1):  152-159.  doi:10.3969/j.issn.0438-1157.2014.01.019
    Abstract ( 1258 )   PDF (874KB) ( 434 )  
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    H2O2 synthesis directly from H2 and O2, as a "green process" and "atomic-economic reaction", is one of the most promising processes for replacing anthraquinone autoxidation process. In this paper, Pd/HAp (hydroxylapatite) catalyst was prepared by the conventional incipient-wetness impregnation method and highly dispersed Pd particles with an average size of 2.5 nm were obtained. Kinetic studies of H2O2 hydrogenation and direct synthesis of H2O2 were performed over a Pd/HAp catalyst and apparent activation energies and reaction orders with respect to H2 and O2 were calculated by power law functional models. Kinetic parameters indicated that the formation of H2O2 was favored at a lower reaction temperatures and higher O2 partial pressure, while higher H2 partial pressure would facilitate H2O formation.
    Activity and stability of nickel based MCM-41 methanation catalysts for production of synthetic natural gas
    ZHANG Jiaying, XIN Zhong, MENG Xin, TAO Miao
    2014, 65(1):  160-168.  doi:10.3969/j.issn.0438-1157.2014.01.020
    Abstract ( 1560 )   PDF (911KB) ( 702 )  
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    Nickel based catalysts with different nickel contents were prepared by the impregnation method with MCM-41, Al2O3 and SiO2 as supports, and catalytic performance was studied in a fixed-bed reactor for the production of synthetic natural gas (SNG). Compared with the Ni/Al2O3 and Ni/SiO2 catalysts, Ni/MCM-41 catalysts with the same nickel content of 10%(mass) showed better catalytic performance with high CO conversion of 100% and CH4 yield of 94.9% at 350℃ under 1.5 MPa with 3:1 molar ratio of H2 to CO and a weight hourly space velocity (WHSV) of 12000 ml·h-1·g-1. The effect of Ni loading on catalytic performance of Ni/MCM-41 catalysts was also investigated. Catalytic activity increased with increasing Ni loading and kept stable with Ni loading of above 10%(mass). 10%Ni/MCM-41 catalyst also exhibited excellent catalytic activity and stability in the catalytic stability test. The catalysts were characterized with X-ray diffraction (XRD), N2 physisorption measurements, thermo gravimetric analysis (TG) and H2 temperature-programmed reduction (H2-TPR). Ni particle size could obviously affect the catalytic performance of Ni/MCM-41 catalysts. Ni/MCM-41 catalyst with 10%(mass) nickel content and appropriate nickel particles of 15.5 nm exhibited good catalytic performance with almost 100% CO conversion and 94.9% CH4 yield.
    Process simulation for synthesis and separation of dibutyl hexahydrophthalate
    LUO Junwen, XU Chunjian, LIANG Changhai, LI Chuang
    2014, 65(1):  169-175.  doi:10.3969/j.issn.0438-1157.2014.01.021
    Abstract ( 1182 )   PDF (690KB) ( 442 )  
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    With inreased critical discussions about potential toxicological effects of phthalates in the mid-nineties, esters of cyclohexane polycarboxylic acids are considered the most promising alternatives to phthalate as plasticizers. Hydrogenation of dibutyl phthalate (DBP) and diisobutyl phthalate (DIBP) using Ni as catalyst was studied by experiment. The products of hydrogenation were respectively dibutyl hexahydrophthalate and diisobutyl hexahydrophthalate. The appropriate reaction conditions for DBP hydrogenation were temperature 130℃, pressure 6.1 MPa and space velocity 1 h-1. The conversion and selectivity of reaction were 99.93% and 92.47% respectively. The appropriate reaction conditions for DIBP hydrogenation were temperature 100℃, pressure 6.1 MPa and space velocity 0.5 h-1. The conversion and selectivity of reaction were 99.70% and 90.42% respectively. Conversion and selectivity were chosen as reaction model parameters, and the synthesis and separation processes of dibutyl hexahydrophthalate and diisobutyl hexahydrophthalate was established by using Aspen Plus software. The purity of product was higher than 99%(mass). Process parameters have important guiding significance to commercialization of hydrogenation of DBP and DIBP.
    Kinetics of synthesis of 1,1,1,3,3-pentachloropropane
    XU Xiaotao, ZHANG Weixing
    2014, 65(1):  176-181.  doi:10.3969/j.issn.0438-1157.2014.01.022
    Abstract ( 1717 )   PDF (514KB) ( 499 )  
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    The telomerization reaction kinetics of synthesis of 1,1,1,3,3-pentachloropropane promoted with iron powder as catalyst precursor and dibutyl phosphate as co-catalyst was studied. The effects of reaction temperature, amount of iron powder and co-catalyst on the reaction were investigated. It was found that the telomerization reaction was of first order and activation energy was 69.15 kJ·mol-1. A reaction kinetic equation was presented. This reaction followed a free radical reaction mechanism in the absence of catalyst, but followed a non-chain redox mechanism in the presence of catalyst.
    Crystal growth and nucleation kinetics of penicillin sulfoxide
    JING Dingding, ZHANG Meijing, WANG Yongli, WANG Jingkang
    2014, 65(1):  182-189.  doi:10.3969/j.issn.0438-1157.2014.01.023
    Abstract ( 1095 )   PDF (993KB) ( 306 )  
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    The crystal growth and nucleation kinetics of penicillin sulfoxide in butyl acetate were studied with Mydlarz & Jones model, which fits the experimental values best. After the model was treated by moment transformation, the crystal growth and nucleation rates were calculated from the crystal size distribution. The parameters in crystallization kinetic functions were obtained with the least square method. The effects of supersaturation ratio, temperature and agitator speed were examined. In conclusion, the crystal growth of penicillin sulfoxide is controlled by surface growth because the growth rate increases greatly with the increase of supersaturation ratio. High agitator speed results in the breakage of penicillin sulfoxide crystals and improves the secondary nucleation. As a result, crystal growth rate decreases and nucleation rate increases with the increase of agitator speed. The study on crystal growth and nucleation kinetics will be beneficial to the industrial production of penicillin sulfoxide.
    Utilization of “instantaneous molecule cluster” hypothesis to predict VLE in CO2 absorption using alkanes
    TANG Zhigang, LI Hongwei, FEI Weiyang, CHEN Jian, GUO Dong, CUI Jingjie
    2014, 65(1):  190-197.  doi:10.3969/j.issn.0438-1157.2014.01.024
    Abstract ( 952 )   PDF (693KB) ( 256 )  
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    In this paper, the hypothesis of "instantaneous molecule cluster" is used to predict the VLE in CO2 absorption using alkanes. It is shown that the predicted values are consistent well with the experimental values in literature, with the linear correlation coefficient larger than 0.95. The results also reveal that the effect of homogenous instantaneous molecule cluster among alkane molecules is the key factor and is more significant than that of homogenous instantaneous molecule cluster among CO2 molecules and that of heterogeneous instantaneous molecule cluster between solvent and CO2 molecules. As carbon chain elongates, formation probability and stability of instantaneous molecule cluster decreases, and absorption capacity increases. The effects of parameters on VLE and their best ranges are also discussed.
    Separation and purification of immunoglobulin IgY with hydrophobic charge-induction expanded bed adsorption
    SHI Wei, LIN Dongqiang, YAO Shanjing
    2014, 65(1):  198-204.  doi:10.3969/j.issn.0438-1157.2014.01.025
    Abstract ( 1022 )   PDF (1123KB) ( 322 )  
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    Combining hydrophobic charge-induction chromatography (HCIC) and expanded bed adsorption (EBA), a novel efficient bioseparation process was developed to purify the immunoglobulin IgY from poultry blood. New hydrophobic charge-induction expanded bed adsorbent S-MMI was prepared with 2-mercapto-1-methyl imidazole (MMI) as the HCIC ligands coupled to quartz-densified agarose matrix for EBA. S-MMI had high ligand density (about 105 mmol·g-1) and the saturated adsorption capacity for IgY reached 71.26 mg·ml-1 at pH 7. S-MMI could form perfectly classified fluidization in expanded bed with high stability. Chicken plasma was precipitated with caprylic acid and the supernatant was used as the feedstock for IgY separation. The loading and elution conditions were optimized by packed bed chromatography. The effects of expansion factors in expanded bed were investigated and the separation conditions were optimized. Finally, IgY was purified from pretreated chicken plasma by EBA with high purity of 98.9% and yield of 80.5%. The combination of HCIC and EBA could achieve efficient separation of immunoglobulin from crude feedstock, which provided a new way for the comprehensive utilization of poultry blood resource.
    Effects of inlet size on separation flow field inside hydrocyclone
    WANG Jiangang, ZHANG Yanhong, BAI Zhaoyuan, HUANG Cong, WANG Hualin
    2014, 65(1):  205-212.  doi:10.3969/j.issn.0438-1157.2014.01.026
    Abstract ( 1227 )   PDF (5672KB) ( 461 )  
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    The design of inlet size for hydrocyclone is an effective method to improve separation accuracy. However, for a long term, the study on hydrocylone inlet size is largely dependent on practical experience. Few studies have been on the influence of inlet size on the hydrocyclone flow field. In this article, the flow field inside a 50 mm hydrocyclone is investigated with CFD method. The pressure profile, three-component velocity distribution and secondary vortex structure are analyzed. The results show that the tangential velocity is the component being affected most since it grows apparently, while the axial and radial velocities vary less, which means that the centrifugal factor increases while the separation structure keeps similar. The swirl velocity of the flow in the far side from the inlet is reinforced. The double-peak phenomenon is found in axial velocity and the reduction of inlet size magnifies this effect. In this sense, the flow field with smaller inlet is prone to better separation. However, smaller inlet size facilitates the formation of secondary vortexes and enhances the entrainment of fluid by the injected flow, which may hamper the separation. Thus, the cut-off size will not always decrease with the reduction of inlet size. Moreover, the increase of energy consumption is mostly attributed to the greater local loss in the connection of inlet and cylinder and the formation of more secondary vortexes.
    Concentration distribution of deuterium and oxygen-18 and its influence in heavy-oxygen water separation cascade
    GAO Yunhu, XU Zhihong, YU Zhaojun, FEI Weiyang
    2014, 65(1):  213-219.  doi:10.3969/j.issn.0438-1157.2014.01.027
    Abstract ( 1152 )   PDF (1322KB) ( 466 )  
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    Deuterium and oxygen-18 are enriched in a water distillation system for isotope separation. A new method is proposed to calculate concentration distributions of deuterium and oxygen-18 and the separation factor for oxygen-16 and oxygen-18. The method divides water into four lumps to simplify the complicated isotope exchange reactions. Reactive distillation module of ASPEN PLUS is used to complete the simulation. An example containing five distillation columns cascade indicates that the concentrations of deuterium and oxygen-18 reach 70.7% and 98.0%, respectively. With the increase of deuterium concentration in the last column, the separation factor for oxygen-16 and oxygen-18 αcal approaches αH216O/H218O rather than αD216O/D218O.
    Preparation and lithium adsorption evaluation for spherical ion-sieve granulated by agarose
    LI Chao, XIAO Jiali, SUN Shuying, SONG Xingfu, YU Jianguo
    2014, 65(1):  220-226.  doi:10.3969/j.issn.0438-1157.2014.01.028
    Abstract ( 1193 )   PDF (1720KB) ( 428 )  
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    Spherical Li4Mn5O12 ion-sieve precusor with particle diameter about 2—3 mm was prepared with the Li4Mn5O12 ultrafine powder synthesized by the authors' lab and the agarose granulation process. Agarose was dissolved in deionized water at 90℃. The Li4Mn5O12 ultrafine powder was added to agarose solution and mixed uniformly. Then the mixture was dropped into cold liquid paraffin. Spherical adsorbents were obtained at the bottom of the reactor, which were filtered and cleaned by ethyl acetate, ethanol and deioned water separately. The particles were cross-linked with epichlorohydrin, and then treated with 1 mol·L-1 HCl to obtain the spherical ion-sieve. The effects of concentration of agarose, granulation temperature, concentration of cross-link agent, and cross-link time were studied. It was found that 5% agarose solution, 90℃, epichlorohydrin concentration of 2 ml·g-1, and cross-link time of 6 h were the best condition to prepare the spherical ion-sieve. The lithium ion adsorption capacity of the spherical ion-sieve can reach 4.25 mmol·g-1, which is 75.6% of that of lithium ion sieve powder. The adsorption rate of the spherical ion-sieve is 1.77×10-5 s-1, decreasing one order magnitude compared with that of the powder (3.29×10-4 s-1). The equilibrium lithium adsorption capacity increases apparently with pH value, reaching 5.5 mmol·g-1 at pH 12. The selectivity experiment shows that the prepared lithium ion-sieve presents a highly selectivity for lithium ions. The results show that the spherical ion-sieve is an attractive adsorbent for lithium extraction from brine or seawater.
    Preparation of ternary composite Ca-based material CaO-Ca3Al2O6-MgO for high-temperature CO2 capture
    ZHANG Mingming, PENG Yunxiang, WANG Jin, LI Ping, YU Jianguo
    2014, 65(1):  227-236.  doi:10.3969/j.issn.0438-1157.2014.01.029
    Abstract ( 916 )   PDF (2183KB) ( 361 )  
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    Synthetic sintering-resistant calcium based material for high-temperature CO2 capture was prepared by doping Al2O3 and MgO into CaO using wet chemical method. The synthetic materials with pore structure developed consist of three substances, CaO, Ca3Al2O6 and MgO. Lower mass ratio of Ca3Al2O6/MgO gives smaller grain size of the synthetic material. CO2 capture capacities and cyclic carbonation/calcination (670/900℃) stability were evaluated in thermogravimetric analyzer under the simulated 10%(vol.,the same below) CO2 (90% N2). It is found that the synthetic CaO-Ca3Al2O6-MgO material presents good performance to capture CO2 from the flue gas, and the mass ratio of Ca3Al2O6/MgO has significant effect on CO2 capture performance. Lower mass ratio leads to faster carbonation reaction rate and higher CaO conversion. Moreover, the deactivation mechanism of synthetic material and the anti-sintering mechanism of doping agents were studied through analysis of specific surface area, pore volume, micro morphology, element distribution, phase composition and grain size of CaO-Ca3Al2O6-MgO material after multicycle carbonation/calcination.
    Preparation of Li1.6Mn1.6O4/PVDF membrane and its lithium uptaking
    XIE Lixin, CHEN Xiaomian
    2014, 65(1):  237-243.  doi:10.3969/j.issn.0438-1157.2014.01.030
    Abstract ( 1006 )   PDF (4275KB) ( 724 )  
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    Spinel-type manganese oxide Li1.6Mn1.6O4 was prepared. It was mixed with poly(vinylidene fluoride) (PVDF) and flat membrane was obtained for recovering lithium from lithium-containing waters by a solvent exchange method. After the membrane was treated with an HCl solution it can uptake lithium. A series of experiments for examining its adsorption and reuse were carried out. Results showed that when membrane M-10-55[Li] was treated with 0.5 mol·L-1 HCl solution for 2 h, the lithium extraction reached equilibrium and about 95% lithium was extracted, and the rate of manganese dissolution was about 3.5%. The membrane M-10-55[H] obtained showed good performance in adsorption capacity to Li+ (about 41 mg·g-1), and when used for the fifth time it still had an adsorption capacity of 35 mg·g-1. The membrane can selectively adsorb Li+ better compared with Na+, K+, Mg2+ and Ca2+. It is potential to be used in enrichment and recovery of lithium from seawater and other liquid lithium sources.
    Configuration and analysis of thermally coupled catalytic distillation for C3 alkyne selective hydrogenation
    TIAN He, LUO Yiqing, YUAN Xigang
    2014, 65(1):  244-250.  doi:10.3969/j.issn.0438-1157.2014.01.031
    Abstract ( 947 )   PDF (831KB) ( 420 )  
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    A novel process, thermally coupled catalytic distillation for selective hydrogenation of C3 alkyne into alkene, was proposed. Methylacetylene and propadiene were separated from propylene in propylene column, and converted into propylene at the same time by catalytic hydrogenation. Deethanizer and propylene distillation were thermally coupled by liquid and vapor streams. The proposed process had two advantages: reactive distillation can raise the selectivity of hydrogenation effectively; thermally coupled distillation columns could avoid propylene backmixing in deethanizer and then save energy. Simulation of the process was performed by using Aspen Plus software. Propylene yield increased by 0.74%—2.19%. At the same time, the annual cost for refrigeration was saved by 2.44%—3.61%. The simulation also showed that the novel process was especially suitable for heavy cracking feedstock.
    Optimization of crystallization process of fructose
    XIE Zhiping, SUN Dengqiong, QIN Yanan, REN Riju, GONG Junbo
    2014, 65(1):  251-257.  doi:10.3969/j.issn.0438-1157.2014.01.032
    Abstract ( 1040 )   PDF (907KB) ( 383 )  
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    Mixed solvent (water-ethanol) was screened out for cooling crystallization of fructose. The instrument, Crystalline was used to determine the solubility and metastable zone of fructose in the binary mixed solvent of water-ethanol (mole fraction of water 0.39). The experimental data of solubility were correlated as a function of temperature by using the Apelblat equation. Based on thermodynamic data of fructose crystallization, the cooling crystallization process was designed and optimized, with over 78.2% yield much higher than that by cooling crystallization in aqueous solution and purity higher than 99%. Compared with the commercially available crystalline fructose, the product crystals were of regular shape, high toughness and narrow crystal size distribution. Laser particle size analyzer, Malvern 3000 was used to determine the continuous crystallization kinetics of fructose, and the crystallization kinetics equation was built by the model of population balance equation proposed by Larson and Randolph and was of size-independent growth with particle size larger than 100μm. The exponent of growth rate was bigger than that of nucleation rate and the crystals tended to grow rather than to nucleate in this size range.
    Solvent extraction of erbium(Ⅲ) with P507 in nitric acid solution and its separation from calcium(Ⅱ) and ferrum(Ⅲ)
    NIU Qinglin, WANG Yundong
    2014, 65(1):  258-263.  doi:10.3969/j.issn.0438-1157.2014.01.033
    Abstract ( 1533 )   PDF (616KB) ( 450 )  
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    It is a common practice in rare earth element separation for separating rare earth metals with non-rare earth elements. In this paper, solvent extraction experiments of Er3+ with P507 and saponified P507 in nitric acid solution and its separation from Ca2+ and Fe3+ were performed. The extraction reaction of Er3+ with P507 was determined by graphical method. It was found that increasing saponification degree improved extractability of Er3+. But high degree of saponification led to the decrease of extractability due to Er3+ hydrolysis in aqueous phase. The extractability of Er3+ increased with the increase of initial pH in aqueous phase. When initial pH in aqueous phase was around 2.0, extractability of Er3+ reached a maximum (>95%). The impurities (Ca2+, Fe3+) barely influenced the extractability of Er3+ at the present concentration range. Separation factor of βEr3+/Ca2+ was higher than 10, which indicated that Ca2+ could be effectively removed from Er3+. When initial pH in aqueous phase was around 3.0, separation factor of βEr3+/ Fe3+ was higher than 10 which showed a good separation of Fe3+ from Er3+.
    Extraction of praseodymium(Ⅲ) and neodymium(Ⅲ) in saponified P507-HCl-kerosene system
    LIU Jing, WANG Yundong
    2014, 65(1):  264-270.  doi:10.3969/j.issn.0438-1157.2014.01.034
    Abstract ( 1457 )   PDF (754KB) ( 793 )  
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    The effect of initial aqueous pH, concentration of P507 and saponification degree of P507 was investigated for P507-HCl-kerosene system, not only for individual rare earth elements, but also for both praseodymium(Ⅲ) and neodymium(Ⅲ). Extraction in a membrane dispersion micro-extractor was performed after determining the product formed by saponification reaction and optimized separation conditions. Using membrane dispersion micro-extractor could increase mass transfer rate and shorten reaction time to 2.5 s with similar extraction rate and separation factor achieved by shake flask tests.
    Pervaporation performance of carbon nanotube filled PDMS membranes
    HAN Xiaolong, ZHANG Xingmei, MA Xiaoxun, LI Jiding
    2014, 65(1):  271-278.  doi:10.3969/j.issn.0438-1157.2014.01.035
    Abstract ( 1799 )   PDF (1154KB) ( 627 )  
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    Single wall carbon nanotubes (SWNT), multiwall carbon nanotubes (MWNT) and dodecyltrichlorosilane modified MWNT were incorporated into polydimethylsiloxane (PDMS) for separation of ethanol/water mixture via pervaporation. The pervaporation results showed that separation performance of MWNT/PDMS hybrid membrane was better than that of SWNT/PDMS hybrid membrane. When MWNT/PDMS hybrid membranes were used to separate 5%(mass) ethanol aqueous solution at 40℃, a separation factor of 10.0 and total flux of 206.2 g·(m2·h)-1 were observed. The pervaporation selectivity of MWNT/PDMS membrane could be effectively improved by dodecyltrichlorosilane modification, and the modified MWNT/PDMS hybrid membrane showed a separation factor of 11.3 and total flux of 130.9 g·(m2·h)-1 for 5%(mass) ethanol feed concentration at 40℃.
    Interactions between sodium caprylate and bovine serum albumin in mixed-mode adsorption
    YUAN Xiaoming, LIN Dongqiang, WANG Chenwei, YAO Shanjing
    2014, 65(1):  279-284.  doi:10.3969/j.issn.0438-1157.2014.01.036
    Abstract ( 895 )   PDF (602KB) ( 415 )  
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    Mixed-mode chromatography is a new technology for the purification of immunoglobulin (IgG). Previous researches indicated that a certain concentration of sodium caprylate (NaCA) could significantly reduce the adsorption of serum albumins and improve the efficiency of mixed-mode chromatography. With MEP HyperCel resin and bovine serum albumin (BSA) as the model, the interactions between NaCA and BSA were investigated by static adsorption and isothermal titration calorimetry (ITC) in the present work. The influences of concentration of NaCA, pH, salt addition and temperature were discussed. The static adsorption experiments showed that the adsorption capacities of BSA and IgG firstly decreased and then increased with increasing NaCA concentration. The influence of NaCA on BSA was much obvious than IgG. ITC analysis indicated that the interactions between NaCA and BSA were quite stronger than those for IgG, and the hydrophobic force dominated the NaCA-BSA interactions. With NaCA addition, the adsorption of BSA decreased with increasing pH value or temperature, and different salts showed varying impacts. ITC analysis also demonstrated that the NaCA-BSA interactions were influenced by pH, salt addition and temperature. In general, ITC results were consistent with those of adsorption experiments, which demonstrated that ITC could be used to evaluate the interactions between small molecule and protein, then study the mechanism of specific additive on protein adsorption.
    Synthesis of heat-integrated water allocation network considering non-isothermal mixing
    LIU Zuming, LUO Yiqing, YUAN Xigang
    2014, 65(1):  285-291.  doi:10.3969/j.issn.0438-1157.2014.01.037
    Abstract ( 1164 )   PDF (477KB) ( 370 )  
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    The design of heat-integrated water allocation network has become a recent research direction. However, most current models do not treat non-isothermal mixing directly in the water network in order to avoid nonlinearity. Therefore, the number of streams increases dramatically when designing heat exchanger network. In order to manage this problem, a new kind of water network model that considers non-isothermal mixing is developed and combined with the LP transshipment model to perform simultaneous optimization of water and heat integration. Non-isothermal mixing is introduced to improve the water network's energy performance and reduce the complexity of designing heat exchanger network by decreasing stream number. A detailed heat exchanger network to satisfy the targeted water and utility consumption can be designed adequately by the principles of pinch method. The results show that the new model not only targets the optimal water and utility consumption but also obtains a much simpler heat exchanger network. This is from a practical application point of view highly valuable.
    Electro-reductive conversion of 5-nitrobenzimidazolone to 5-aminobenzimidazolone on copper mesh cathode
    NIU Dongfang, WANG Haiyang, YU Qiuyan, ZHANG Xinsheng
    2014, 65(1):  292-297.  doi:10.3969/j.issn.0438-1157.2014.01.038
    Abstract ( 728 )   PDF (626KB) ( 278 )  
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    5-aminobenzimidazolone was prepared by electro-reduction of 5-nitrobenzimidazolone on copper mesh cathode. The electrochemical behavior was studied on Cu micro-electrode by cyclic voltammetry, and the result indicated that the electrochemical reduction of 5-nitrobenzimidazolone was an irreversible reaction controlled by diffusion. Influence of some key factors (such as nature of cathode material, current density, temperature and passed charge) on this reaction was investigated. Under the optimized condition, the yield of 5-aminobenzimidazolone reached 93%. The yield of 5-aminobenzimidazolone could still be maintained at about 93% after the catholyte was continuously recycled 10 times, corresponding to the effect of fresh catholyte.
    Scale and corrosion inhibition performance of tobacco rob extract
    GUO Yong, WANG Hefang, LIU Zhiyong
    2014, 65(1):  298-304.  doi:10.3969/j.issn.0438-1157.2014.01.039
    Abstract ( 824 )   PDF (758KB) ( 332 )  
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    The effect of different extraction methods on scale inhibition of tobacco rob extract was studied. The extract had good inhibition performance for calcium carbonate, calcium sulfate and calcium phosphate. The scale inhibition mechanism was studied with IR, XRD and SEM. The extract had good scale inhibition performance for deposition because of collaborative features of chelation function and distortion function. The method of rotary coupon test and polarization curve were used to study corrosion inhibition mechanism of tobacco rob extract. The extractor was an anodic corrosion inhibitor for carbon steel. The tobacco rob extract was an environment-friendly water treatment agent with excellent biodegradability.
    Refolding of recombinant pig liver esterase inclusion bodies in vitro assisted by thiol-carrying latex particles
    HUANG Shoukun, GUAN Yixin, YU Hongwei, YAO Shanjing
    2014, 65(1):  305-312.  doi:10.3969/j.issn.0438-1157.2014.01.040
    Abstract ( 902 )   PDF (1112KB) ( 282 )  
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    Pig liver esterase (PLE) has been widely used in many fields, such as kinetic resolutions, desymmetrizations of prochiral substrates, and synthesis of nucleosides. Recombinant expression of the γ-isoenzyme of PLE (γ-PLE) in Escherichia coli can avoid the undesirable presence of several PLE isoenzymes in commercial production and interfering influence of other hydrolases, but γ-PLE expressed in Escherichia coli is usually in the form of insoluble inclusion bodies which should be refolded in vitro to recover its biological activity. Three kinds of thiol-carrying latex particles SG-DTT with different concentrations of sulphydryl groups (6.1 μmol·g-1, 25.2 μmol·g-1 and 143.4 μmol·g-1) were synthesized, and then used to assist refolding of γ-PLE in vitro. The effects of particle concentration, pH, refolding temperature and urea concentration on the refolding process were investigated. It was shown that refolding should be carried out under suitable redox environment and particles with higher concentration of sulphydryl groups were more effective. The final γ-PLE activity could achieve as high as 1885 U·L-1 when γ-PLE concentration was 1000 μg·ml-1, increased by 72% than that without the particles. All results above demonstrated that thiol-carrying latex particles could assist γ-PLE refolding by attacking disul?de bonds in misfolded protein to form correct pairing through thiol/disul?de exchange reactions and inhibiting intermolecular interactions, which presented an alternative way to facilitate refolding of proteins with disulfide bonds in vitro.
    Model of charge/discharge operation for all-vanadium redox flow battery
    LI Minghua, FAN Yongsheng, WANG Baoguo
    2014, 65(1):  313-318.  doi:10.3969/j.issn.0438-1157.2014.01.041
    Abstract ( 1338 )   PDF (1652KB) ( 659 )  
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    All-vanadium redox flow battery (VRFB) is one of rechargeable batteries. The battery can be charged and discharged by valence change of vanadium ions. The electrolytic solution of redox flow battery is circulated by pumps between battery cells and tanks. The characteristics of output voltage is influenced by chemical reaction, electrolytic solution flow, and electrical circuit. However, there is little research in consideration of the above interactions. Therefore, a model based on the above facts was established. Simulation results were compared with experimental results. The validity of the model was checked by comparison. Furthermore, simulation was performed to study the relation ship between charging/discharging currents and battery capacity. A peak of battery capacity was observed with change of current. The model was appropriate and simulation expressed the experimental result correctly. It is expected that this model will give a useful indicator to design and control of the battery.
    Molecular simulation of outer surface charge on water transport through double-wall carbon nanotube
    CHEN Qile, KONG Xian, LU Diannan, LIU Zheng
    2014, 65(1):  319-327.  doi:10.3969/j.issn.0438-1157.2014.01.042
    Abstract ( 895 )   PDF (2184KB) ( 381 )  
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    The effects of the outer surface charge on the water transport behavior inside double-wall carbon nanotube (DWCNT) were examined using molecular dynamic simulation. It is shown that the bipolar dipole orientation of water molecules inside charged DWCNT prohibits the flipping of whole water chains, stabilizing the hydrogen bonds from these fluctuations and thus accelerating the water flux, compared to the neutral DWCNT. On the other hand, the introduction of electrostatic interactions between CNT and water molecules reduces the free energy barrier of water entry, which also enhances water flux. Above simulation results provide a molecular insight into the water transport through CNT, which is helpful for the design of CNT based materials and devices for water purification.
    Mixed-amine functionalized SBA-15 for CO2 adsorption
    JING Yu, WEI Li, WANG Yundong, YU Yanmei
    2014, 65(1):  328-336.  doi:10.3969/j.issn.0438-1157.2014.01.043
    Abstract ( 1056 )   PDF (1212KB) ( 851 )  
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    To achieve an economical and effective approach of CO2 capture, design of novel adsorbents for post-combustion CO2 adsorption has important significance. To improve CO2 adsorption capacity, two methods of wet impregnation and surface grafting have been used recently. "Mixed-amine" concept was proposed and these two methods were combined in this paper. 3-Aminopropyltrimethoxysilane (APTS) was first grafted onto the surface of SBA-15 and then polyethylenimine (PEI) was impregnated into the space of pores. This novel adsorbent possessed a very high density of amine groups. The structural property, CO2 adsorption capacity and amine efficiency of mixed-amine functionalized SBA-15 with different ratios of APTS and PEI were investigated. The CO2 adsorption result showed that the performance of mixed-amine functionalized SBA-15 depended on kinetic diffusion. SBA-15-(APTS-0.5-PEI-50), SBA-15-(APTS-1.0-PEI-50) and SBA-15-(APTS-2.0-PEI-30) could be identified as potential adsorbents at 75℃. The amine efficiency of mixed-amine functionalized SBA-15 was between purely impregnated and grafted ones.
    Electric field-assisted preparation of aligned MWCNTs/polystyrene composite membranes for enhanced gas separation performance
    LI Xuewa, ZHAO Shixiong, WU Bin, AN De, WANG Yuxin
    2014, 65(1):  337-345.  doi:10.3969/j.issn.0438-1157.2014.01.044
    Abstract ( 1178 )   PDF (53787KB) ( 3139 )  
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    Incorporation of particulate fillers in a membrane matrix has been proven effective in improving the separation performance of the membrane. This study explored the possibility of casting fillers embedded membranes with the assistance of alternating electric field to further improve the membrane performance in gas separation. Composite membranes with varying contents of multi-walled carbon nanotubes (MWCNTs) dispersed in polystyrene (PS) were prepared. In order to align the MWCNTs in the membrane, an alternating electric field of 2000 V·cm-1, 1 Hz was vertically applied on the pre-membrane solution until the solvent was evaporated completely. Electro-casting achieved not only vertical alignment but also more uniform dispersion of MWCNTs in the membrane matrix. The electro-cast composite membranes showed higher permeability of both carbon dioxide and methane, but the increment of the former was higher than the latter, resulting in improved selectivity of the membrane.
    Preparation and characterization of organic-inorganic hybrid flexible silica aerogel
    QU Kang, PU Qun, SHAN Guorong
    2014, 65(1):  346-351.  doi:10.3969/j.issn.0438-1157.2014.01.045
    Abstract ( 1134 )   PDF (5606KB) ( 535 )  
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    Monolithic silica aerogels were prepared via supercritical fluid drying of methanol gels, which were obtained using the sol-gel co-precursor method with methyltrimethoxysilane (MTMS) and tetraethoxysilane (TEOS) as precursors, methanol as solvent, oxalic acid and ammonia as catalysts. The microstructure, specific surface area, pore size distribution, bending and compressibility, and thermal stability of silica aerogels were studied by scanning electron microscopy, nitrogen adsorption/desorption tests, and thermogravimetric analysis. The properties of the silica aerogels, prepared with different mole ratios of MTMS/TEOS, varied obviously. The silica aerogel, prepared with mole ratio of MTMS/TEOS at 8/1, was a flexible material with density of 0.11 g·cm-3, porosity of 94.2%, specific surface area of 693.3 m2·g-1, maximal bending angle of 92°, maximal compression ratio of 41.2% and compression spring-back of 100%.
    Ag-TiO2 porous thin film and its superhydrophilic properties under visible light
    SUN Lin, SHAN Guorong, PAN Pengju
    2014, 65(1):  352-357.  doi:10.3969/j.issn.0438-1157.2014.01.046
    Abstract ( 873 )   PDF (4436KB) ( 689 )  
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    Superhydrophilic Ag-TiO2 thin films were prepared by the sol-gel method using titanium-n-butoxide as TiO2 precursor, silver nitrate as silver source, poly(ethylene glycol) (PEG2000) as structure directing agent. As-prepared composite thin films were characterized by X-ray diffraction, X-ray photoelectronic spectroscopy, scanning electron microscopy and atom force microscopy. The superhydrophilicity of Ag-TiO2 thin films with different Ag and PEG2000 contents were evaluated in terms of static water contact angle, wetting time and long-term stability. Ag-doping significantly improved response to visible light and shortened wetting time, and porous surface with high roughness favored long-term superhydrophilicity. The Ag-TiO2 thin films with 10% Ag doping and 5% PEG2000 content showed excellent superhydrophilic properties under natural light conditions. Water droplets could fully spread on the surface within 0.2 second with static water contact angle of 0°. Superhydrophilicity was maintained for more than 30 d when the thin films were stored in dark place. Superhydrophilic properties were enhanced when the films were irradiated under visible light. The composite Ag-TiO2 thin films showed excellent anti-fogging effect.
    Preparation of hierarchical porous carbons from vinylidene chloride-based block copolymers
    YANG Jie, PU Qun, BAO Yongzhong
    2014, 65(1):  358-364.  doi:10.3969/j.issn.0438-1157.2014.01.047
    Abstract ( 1125 )   PDF (4436KB) ( 325 )  
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    A series of triblock copolymers consisting of vinylidene chloride polymer and polystyrene (PS) blocks (PS-b-PVDC-b-PS) were prepared via reversible addition-fragmentation chain transfer (RAFT) living radical polymerization, and were further heat-treated to obtain hierarchical porous carbons with micro-and meso-pores directly. The structures of triblock copolymers were characterized with GPC and NMR, and the result demonstrated that the prepared PS-b-PVDC-b-PS exhibited number average molecular weight greater than 6000 and narrow molecular weight distributions (PDI<1.5). The thermogravimetric analysis of triblock copolymers showed two weigh loss peaks, corresponding to thermal degradation of PS and PVDC blocks, respectively. The morphology and pore structure of the resulted porous carbons were characterized with SEM and N2 absoprtion analysis. PVDC block acted as a good kind of carbon precursor capable of forming micro-pores, and the micro-dispersed PS block acted as a meso-pore extender to generate meso-pores. Carbon yields decreased and average pore diameters increased as the content of PS in triblock copolymers increased. The greatest Brunauer-Emmett-Teller surface area (839 m2·g-1), mesoporsity degree (54%) and average pore size (2.02 nm) were achieved as triblock copolymer with PS/PVDC molar ratio of 4.3 was used as precursor.