Dec 2008, Volume 2 Issue 4

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  • SUN Ying, ZHU Jiawen, CHEN Kui, ZHU Sheng, XU Jie
    The equilibrium and kinetic characteristics of the adsorption of erythromycin to Sepabeads SP825 were determined. The equilibrium data in a batch system was well described by a Langmuir isotherm. The separation performance was investigated in a fixed-bed system with respect to the adsorption superficial velocity, ionic strength and pH. A mathematical model was used to simulate the mass transfer mechanism, taking film mass transfer, pore diffusion and axial dispersion into account. The model predictions were consistent with the experimental data and were consequently used to determine the mass transfer coefficients.
  • WANG Xia, CHEN Hui, GUO Yanni, SU Yuzhong, WANG Hongtao, LI Jun
    Using the CO2- and N2-assisted atomization processes, the production of ibuprofen/lipid composite microparticles is investigated, in which the lipid includes myristic acid and tripalmitin. The produced composite particles show similar morphology to that of the pure lipids obtained by the same process. In the case of the N2-assisted process, the average size of composite particles is slightly larger than that of the pure lipid particles due to the difficulty of solidification when using N2. In the case of the CO2-assisted process, the average size of composite particles is slightly smaller than that of the pure myristic acid particles, but slightly larger than that of the pure tripalmitin particles. The dissolution study reveals that the drug release from the ibuprofen/myristic acid particles is enhanced in comparison with that of the unprocessed ibuprofen. For the particles produced by the N2-assisted process, the X-ray diffraction (XRD) patterns clearly indicate the encapsulation of ibuprofen into myristic acid. The obtained ibuprofen/tripalmitin composite particles with 5% or 20% of ibuprofen (in mass) evidently show the controlled drug release: only about 20% of the drug is released in 500 min from the ibuprofen/tripalmitin composite particles consisting of 20% ibuprofen prepared by the CO2-assisted process, and the same release is obtained from the ibuprofen/tripalmitin composite particles containing 5% ibuprofen prepared by the N2-assisted process.
  • LU Sumin, MA Youguang, SHEN Shuhua, ZHU Chunying
    The influence of the properties of solid particles in slurry on the absorption of CO2 in the slurry was investigated in a stirred thermostatic reactor. The absorption experiments were carried out in three different slurries consisting of water, cyclohexane and soybean oil, respectively, and three kinds of solid particles (active carbon, active alumina and silica gel) were incorporated into each of the above mentioned slurries separately. The experimental results show that the active carbon particles could enhance the absorption rate of gaseous CO2 in the aqueous slurry, while in the cyclohexane slurry, active carbon particles indicated no the absorption enhancement effect. However, it was observed that the active alumina and silica gel particles could enhance the absorption rate of CO2 in the cyclohexane slurry. These phenomena indicate that the solid particles, which could enhance the gaseous CO2 absorption rate, should possess two properties simultaneously, i.e. they rejected the solvent and had higher adsorption capacity for the solute. The experimental results also show that, as for those solid particles which could enhance the gas absorption rate, the enhancement increased quickly with the increase of solid concentration in slurry at first, and then reached a constant value gradually. It was also found that the enhancement factor was related to the coverage fraction of solid particles on the gas-liquid interface, and due to the reduction of surface fraction with increasing stirred speed, the enhancement factor decreased.
  • WANG Baowei, CAO Xiaolei, YANG Kuanhui, XU Genhui
    Methane coupling to produce C2 hydrocarbons through a dielectric-barrier discharge (DBD) plasma reaction was studied in four DBD reactors. The effects of high voltage electrode position, different discharge gap, types of inner electrode, volume ratio of hydrogen to methane and air cooling method on the conversion of methane and distribution of products were investigated. Conversion of methane is obviously lower when a high voltage electrode acts as an outer electrode than when it acts as an inner electrode. The lifting of reaction temperature becomes slow due to cooling of outer electrode and the temperature can be controlled in the expected range of 60°C–150°C for ensuring better methane conversion and safe operation. The parameters of reactors have obvious effects on methane conversion, but it only slightly affects distribution of the products. The main products are ethylene, ethane and propane. The selectivity of C2 hydrocarbons can reach 74.50% when volume ratio of hydrogen to methane is 1.50.
  • WANG Feng, ZHAO Ning, LI Junping, XIAO Fukui, WEI Wei, SUN Yuhan
    A new improved tri-diagonal method was developed for the non-equilibrium stage model of the catalytic distillation by coupling consumptive reaction coefficient. The reactions in the distillation column were divided into generative reaction and consumptive reaction. The non-equilibrium stage model was introduced for the catalytic distillation process of the dimethyl carbonate (DMC) synthesis by urea methanolysis over solid based catalyst, and the improved tri-diagonal method was used to solve the model equations. Comparison of predicted results with experiment data shows that the mean relative error of the yield of DMC was 3.78% under different conditions such as different operating pressures and reaction temperatures. The improved tri-diagonal matrix method could avoid the negative values of the liquid compositions during the calculations and restrain the fluctuation of compositions by slowing down the variations of the values in the iteration. The modeling results show that the improved tri-diagonal method was appropriate for system containing a wide range of boiling point components and a different rate of reactions.
  • WANG Lin, HE Yunliang, WANG Yanfei, BAO Ying, WANG Jingkang
    The green process to recover magnesium chloride from the residue solution of a potassium chloride production plant, which comes from the leach solution of a potash mine in Laos, is designed and optimized. The residue solution contains magnesium chloride above 25 wt-%, potassium chloride and sodium chloride together below 5 wt-% and a few other ions such as Br-, SO42- and Ca2+. The recovery process contains two steps: the previous impurity removal operation and the two-stage evaporation-cooling crystallization procedure to produce magnesium chloride. The crystallized impurity carnallite obtained from the first step is recycled to the potassium chloride plant to recover the potassium salt. The developed process is a zero discharge one and thus fulfills the requirements for green chemical industrial production. The produced magnesium chloride is up to industrial criteria.
  • SONG Jiale, CHEN Lixin, WANG Yazhou, CHEN Weiwei, WANG Rumin
    Photopolymerization of vinyl-containing liquid silizane preceramic monomers copolymerized with thiol monomers, based on a step-growth radical polymerization mechanism, is a novel, rapid, inexpensive and simple technique for producing preceramic structures from liquid precursors. The kinetics of alkyl 3-mercptopropionate-vinyl silizane under UV irradiation is investigated by using real-time Fourier transform infrared (FT-IR) and photo-differential scanning calorimetry (photo-DSC). The experimental results show preliminarily that: (1) about 80% conversion of vinyl group has been achieved in the presence of a low concentration photoinitiator under UV irradiation; (2) by increasing the functionalities of the thiol group, the peak rate of copolymerization increases and the final conversion of the vinyl group decreases; (3) the copolymerization is primarily a bimolecular radical termination process; (4) the copolymerization is first-order, i.e., its rate is proportional to the vinyl group concentration and independent of the concentration of thiol group.
  • QI Dongming, SHAO Jianzhong, WU Minghua, NITTA Kohhei
    A novel phenolic rigid organic filler (KT) was used to modify isotactic polypropylene (iPP). The influence of KT particles on the tensile properties of PP/KT microcomposites was studied by uniaxial tensile test and the morphological structures of the stretched specimens were observed by scanning electron microscopy (SEM) and polarized optical microscopy (POM). We found that the Young’s modulus of PP/KT specimens increased with filler content, while the yield and break of the specimens are related to the filler particles size. The yield stress, the breaking stress and the ultimate elongation of PP/KT specimens were close to those of unfilled iPP specimens when the maximal filler particles size is less than a critical value, which is 7 ?m at a crosshead speed of 10 mm/min and 3 ?m at 200 mm/min, close to that of glass bead but far more than those of other rigid inorganic filler particles. The interfacial interaction was further estimated from yield stress, indicating that KT particles have a moderate interfacial interaction with iPP matrix. Thus, the incorporation of small KT particles can reinforce iPP matrix and simultaneously cause few detrimental effects on the other excellent tensile properties of iPP matrix, due to their organic nature, higher specific area, solid true-spherical shape and the homogenous dispersion of the ROF particles in microcomposites.
  • WU Chunrui, ZHANG Shouhai, YANG Fajie, YAN Chun, JIAN Xigao
    The novel thermal stable composite nanofiltration membranes were prepared through the interfacial polymerization of piperazine and trimesoyl chloride on the poly (phthalazinone ether) ultrafiltration substrate. The effects of polymerization and testing conditions on membrane performance were studied. The surface morphologies of the substrate and the composite membranes were observed by means of scanning electron microscopy (SEM) and atomic force microscopy (AFM). The separation properties of membranes for dyes and salts were tested. The composite membranes show good thermal stability. The rejection for Na2SO4 was kept over 96%, while the flux reached 400 L·m-2·h-1 when it was tested at 1.0 MPa and 80°C. When tested at 1.0 MPa and 60°C, the rejection of the composite membrane for dyes was kept at high level, and the flux reached 180–210 Lm-2·h-1, while the rejection for NaCl was lower than 20%.
  • LI Aixiang, LU Zaijun, LÜ Zijian
    Well-defined comb-like branched polymers having one branch in each repeating unit have been successfully synthesized by the coupling reaction of living polystyrene (PS) and polyisoprene (PI) anions with 1, 1-diphenylethenyl (DPE) groups along PS backbone prepared via atom transfer radical polymerization (ATRP) of 4-vinylbenzyloxy benzophenone (Sc) followed by Wittig reaction. The resulting comb-like branched polymers were characterized by IR, 1H-NMR, gel permeation chromatography (GPC) and static light scattering (SLS) in detail. The effect of living chains and DPE group molar ratio on grafting efficiency was discussed. The results show the coupling reaction of living chains and DPE groups was highly effective, and the coupling efficiency can be controlled via the feed molar ratios of living chains and DPE groups. Moreover, the effect of molecular weights of backbone (PSe) and PSLi or PILi on grafting efficiency was also discussed. The results show that when excess living polymers were used, the almost quantitative grafting efficiency could be achieved.
  • XU Xiaohui, LIU Xiaoyun, ZHOU Chengjun, ZHUANG Qixin, HAN Zhewen
    A novel series of polybenzazoles with rigid-rod benzoxazole cycle and soft methylene segment was designed and synthesized via solution condensation polymerizations from 4,6-diamino-1,3-benzenediol diphosphate, terephthalic acid and aliphatic dicarboxylic acid. The structures of polybenzazoles were characterized by means of FT-IR, 1H NMR and Wide-angle X-ray diffraction (WAXRD). All the polymers show excellent thermal stability and the Tds was above 471°C. The intrinsic viscosities [?] of the polymers ranged from 0.8 to 0.9. The UV-Vis absorption peaks of the polymers in MSA were blue-shifted from 429 nm for PBO to 291 nm for PBOC7, and the Stokes shifts in PL spectra enlarged.
  • LIU Weidong, ZHU Baoku, XIE Shuhui, XU Zhikang
    Using poly(amic acid) (PAA) as a precursor followed by thermal imidization, the polyimide/barium titanate composite films were successfully prepared by a direct mixing method and in situ process. The influence of processing factors, such as particle size, distribution mode and polymerization method on dielectric properties was studied. Results revealed that the dielectric constant (?) of the composite film increased by using bigger fillers or employing in situ polymerization and bimodal distribution. When the composite film containing 50 Vol-% of BaTiO3 with size in 100 nm was prepared via in situ process, its dielectric constant reached 45 at 10 kHz.
  • XU Yunlong, TAO Lili, MA Hongyan, HUANG Huaqing
    LiFePO4/C cathode materials were synthesized by a combination of co-precipitation and microwave heating using polyethylene glycol (PEG) as a carbon resource and the influence of microwave heating time on the structure and electrochemical performance of the materials was also discussed. The samples were characterized by X-ray diffraction (XRD), TEM, particle-size analysis and constant current charge-discharge experiment. The results show that the LiFePO4/C heated for 9 min has a pure olive-type phase and excellent electrochemical performance. The initial discharge capacities of this sample are 154.3, 139.7, 123.9 mAh/g at the rates 0.1C, 0.2C, 1C at room temperature, respectively, and after 20 cycles remain 152.3, 134.3, 118.5 mAh/g, respectively.
  • LIU Feng, XIAO Jianhua, REN Weihua, HU Jun, LIU Honglai
    Poly(triphenylamine-p-phenylenevinylene)s with two different end-groups were obtained through a Wittig polycondensation. The structures of two copolymers were characterized. Ultraviolet and visible spectroscopy (UV-Vis) and photoluminescence (PL) spectra show the end-capped polymer emits intensive green light in both solution and film state. Their applications in the detection of nitro compounds were investigated, and the results show high fluorescence quenching sensitivity of the end-capped polymer towards o-nitrotoluene (o-NT). When the concentration of o-NT was 21.5 × 10-3 mol/L, the fluorescence quenching reached 96%. Additionally, after the exposure of polymer film in three different quenchers such as dinitrotoluene (DNT), p-nitrobenzoquinone (p-BQ) and p-nitrotoluene (p-NT) for 600 s, its fluorescence quenching reached 93.6%, 11.5% and 77.9%, respectively. This kind of polymer has great advantages in preparation and may find applications in the detection of nitro explosives.
  • YUAN Yi, WANG Yanming, YU Yaoting
    Dendritic polymers are three-dimensional, highly ordered compounds formed by reiterative reaction sequences, and via discrete stages referred to as generations. To study the spacer effect of low density lipoprotein (LDL) adsorbent, we linked dendrimer polyamidoamine (PAMAM) generation 1 (G1), generation 3 (G3) and generation 5 (G5) to cellulose beads, respectively, and then determined the adsorption proportion of the adsorbents with PAMAM decorated with taurine. The result shows that the spacer with activated multi-points could efficiently improve the adsorption capacity of the adsorbent.
  • LIU Zhaohui, QI Wei, WU Weina, LIU Yue, HE Zhimin
    The effects of some sugars (glucose, mannose, fructose, sucrose and chitosan) and polyols (glycol, glycerol and sorbitol) as protective additive on the thermostability of ?-mannanase were studied. The optimal reaction temperatures of ?-mannanase and the thermodynamics and the deactivation kinetics with or without additives were also investigated. The experimental results show that sucrose, chitosan and sorbitol could apparently improve the thermal stability of ?-mannanase when their concentration was kept at 2 g/L. The optimal combination additive proportion was sucrose: chitosan : sorbitol = 1 : 2 : 2 (molar ratio) using the orthogonal experimental design. The sucrose, chitosan, glycerol, sorbitol and the combination additive might increase the optimal reaction temperature from 50°C to about 60°C due to their good protection effect. The thermal deactivation curves of ?-mannanase accorded with the kinetic rules of first order reaction, and the corresponding kinetic and thermodynamic parameters were calculated. Meanwhile, the protective mechanism of the additives against deactivation of enzyme was also discussed.
  • LAN Wenjian, MO Linfeng, LI Houjin, CAI Chuanghua, ZHOU Yipin, YAO Junhua
    New marine bacterium Zooshikella sp. SY01, producer of prodigiosin, was isolated from the seawaters of Sanya Bay. The culture conditions of this bacterium were investigated. Zooshikella sp. SY01 was cultured in 2216E media which contained tryptophan, histidine, lactonic acid, camphor, limonene, casein, diphenyl guanidine, coumarin and 1,3-dinitrobenzene, respectively. After 5 days cultivation, the extracts of different culture broths were detected by direct infusion mass spectroscopy using positive ESI mode. As the results, tryptophan, histidine and casein didn’t show any observable influences on the biosynthesis of prodigiosin. Lactonic acid, camphor, limonene, diphenyl guanidine, coumarin could inhibit the bacterium growth and prodigiosin biosynthesis to a certain extent, slower the culture broth to turn red. However, 1, 3-dinitrobenzene inhibited the bacteria to produce prodigiosin completely. MS data suggested that various metabolites with chemodiversity were produced in different culture media. In particular, a series of high-molecular-weight compounds with high relative abundances were observed in the medium containing limonene. To further optimize the culture condition, more new prodigiosin analogues and lead compounds can be obtained and the goal of “one strain-many compounds” can be achieved.
  • LUO Peng, YANG Chuanmin, LIU Zhong, WANG Gaosheng
    Although simultaneous saccharification and fermentation (SSF) has been investigated extensively, the optimum condition for SSF of wheat straw has not yet been determined. Dilute sulfuric acid impregnated and steam explosion pretreated wheat straw was used as a substrate for the production of ethanol by SSF through orthogonal experiment design in this study. Cellulase mixture (Celluclast 1.5 l and ?-glucosidase Novozym 188) were adopted in combination with the yeast Saccharomyces cerevisiae AS2.1. The effects of reaction temperature, substrate concentration, initial fermentation liquid pH value and enzyme loading were evaluated and the SSF conditions were optimized. The ranking, from high to low, of influential extent of the SSF affecting factors to ethanol concentration and yield was substrate concentration, enzyme loading, initial fermentation liquid pH value and reaction temperature, respectively. The optimal SSF conditions were: reaction temperature, 35°C; substrate concentration, 100 g·L-1; initial fermentation liquid pH, 5.0; enzyme loading, 30 FPU·g-1. Under these conditions, the ethanol concentration increased with reaction time, and after 72 h, ethanol was obtained in 65.8% yield with a concentration of 22.7 g·L-1.
  • BAN Jingyang, YU Jianliang, ZHANG Xu, TAN Tianwei
    In this work, the ethanol production from sweet sorghum residue was studied. Sweet sorghum residue was hydrolyzed with phosphoric acid under mild conditions. The liquid hydrolysate was fermented by Pachysolen tannophilus, and the hydrolysis residue was fermented by the simultaneous saccharification and fermentation (SSF) using Saccharomyces cerevisiae with cellulase (60 FPU/g dry materials). Orthogonal experiments were carried out to investigate the effects of main reaction condition factors, such as temperature, acid concentration, time and dry-matter content, on the reducing sugar yield. The results show that the optimal reaction conditions should be 120°C, 80 g/L, 80 min and 10%, respectively. Under these conditions, 0.3024 g reducing sugar/g dry material was obtained. The liquid hydrolysate was then fermented by P.tannophilus with the highest ethanol concentration of 14.5 g/L. At a water-insoluble solid concentration of 5%, 5.4 g/L ethanol was obtained after 12 h of SSF. The total ethanol yield was 0.147 g/g dry material, which would be beneficial for the application of ethanol production from sweet sorghum residue.
  • WANG Qian, YAO Zhong, XUN Zhijing, XU Xiaoying, XU Hong, WEI Ping
    Since ?-glutamyltranspeptidase (GGT) especially catalyses the transfer of the ?-glutamyl moiety to a variety of amino acids and short peptides, GGT has important practical value for enzymatic synthesis of ?-glutamyl compounds. In this paper, the GGT produced from Bacillus subtilis NX-2 was purified by a combination of ammonium sulfate fractionation and ion exchange chromatography, and the properties of purified GGT were investigated. At the conditions of pH 10.0, D-glutamine (D-Gln)/L-tryptophan (L-Trp) with a molar ratio of 5 : 7, a temperature 40°C and a reaction time of 4 h, a higher conversion rate of 42% was obtained. According to the time course, the catalytic mechanism of enzymatic synthesis of ?-D-glutamyl-L-tryptophan (?-D-Gln-L-Trp) was discussed. It was demonstrated that the GGT can catalyze not only the reaction of transpeptidation, but also the irreversible hydrolysis of the products which results in the decrease of the yield of the products. The affinity parameter of GGT to D-Gln (Km) was 5.08 mmol·L-1 and the maximum reaction rate of transpeptidation (rmax) was determined as 0.034 mmol·min-1·L-1, while the affinity parameter of GGT to ?-D-Gln-L-Trp (Km) was 2.267 mmol·L-1, and the maximum reaction rate of hydrolysis (rmax) was 0.012 mmol·min-1·L-1.
  • LU Chunxi, LI Ruxin, SHI Mingxian, LIU Xiancheng
    The gas flow field and the separation efficiency of a novel fluid catalytic cracking (FCC) riser terminal device, named as Super Short Quick Separator (SSQS), were studied. On the basis of above investigations, a section-lateral-mixing separation model was proposed, which included both the effect of inertia and structure of gas outlet on particles capture. After final modification, the results predicted with this model could be in good agreement with the cold experimental data. According to this model, the separation efficiency of SSQS is mainly influenced by the difference between the arc radius and the center pipe radius as well as the magnitude of particle tangential velocity.
  • WANG Rui, YANG Song, YIN Shitao, SONG Baoan, BHADURY Pinaki S., XUE Wei, TAO Shuwei, JIA Zhaohui, LIU Da, GAO Liang
    The preparation and regeneration conditions of the identified catalyst X/Y/MgO/?-Al2O3 with high catalytic activity were studied and optimized. The biodiesel was prepared by transesterification of Jatropha curcas seed oil produced in Guizhou with methanol at its reflux temoerature in the presence of X/Y/MgO/?-Al2O3 . The pilot plant tests were carried out in a 100 L reaction vessel. Both average yield and fatty acid methyl esters (FAME) content reached more than 96.50% under the optimum reaction conditions of the pilot plant tests designed with an oil/methanol molar ratio of 1 : 10, catalyst concentration of 1.00%, and reaction time of 3 h at reflux temperature. In addition, analysis shows that the quality of biodiesel meets the standard EN 14214.
  • WANG Yuxin, LIU Congmin, ZHOU Yaping
    Activated carbon with high specific surface area and considerable mesopores was prepared from bamboo scraps by phosphoric acid activation. The effect of activation conditions was studied. Under the conditions of impregnating bamboo with 80% H3PO4 at 80°C for 9 days and activation at 500°C for 4 h, the prepared activated carbon had the highest mesopore volume of 0.67 cm3/g, a specific surface area of 1567 m2/g, and the mesopore ratio reached 47.18%. The study on adsorption isotherms of CH4, CO2, N2 and O2 on the activated carbon were carried out at 298 K. The considerable difference in the adsorption capacity between CO2 and the other gases was observed, which would be of interest for the adsorptive separation/purification of gaseous CO2 from its mixtures, especially from mixtures with N2 and/or O2.