Table of Content

20 October 2006, Volume 6 Issue 5

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流动与传递

The Investigation of Pressure Drop in a Moving Bed

CHEN Yun-hua;ZHU Xue-dong;WU Yong-qiang;ZHU Zi-bin

. 2006, 6(5):  697-702. 

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The pressure drop of gas flowing through the cross-flow moving-bed was investigated in a two-dimension rectangular apparatus. The effects of particles flow rate, superficial gas velocity, formation and development of cavity/raceway and voidage of particles on the pressure drop were investigated experimentally with the operation conditions of 0~1.35 m/s of superficial gas velocity and 0.95~9.68 cm/min of particle velocity. The experimental results show that the particle velocity has little influence on the pressure drop; the phenomena of cavity and pinning occur when the cross-flow velocity is high enough. The development of a cavity or a raceway can cause three types of pressure drop with time, which are stabilization, slight fluctuation and severe fluctuation. The pressure drop of moving-bed can be calculated by Ergun's equation at low velocity of cross-flow gas. Cavity appears in a process cycle of "formation-growing up-collapsing-fluidization" at high gas velocity. On the basis of experimental results, a model for calculating the pressure drop when a cavity occurs and a dimensionless relationship of cavity size is conduced, which agree with the experimental data.

Hydrodynamic Characteristics of QMA Spherosil LS in an Expanded Bed

ZHOU Xiao-ping;SHI Qing-hong;SUN Yan

. 2006, 6(5):  703-707. 

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The bed expansion and size distribution of ion-exchanger, QMA Spherosil LS, were extensively investigated in a glass column (26 mm I.D.) modified by side ports, and the influences of packed bed height, flow velocity and nature of feedstock were discussed. The results suggested that the characteristics of bed expansion could be well described by Richardson-Zaki Equation. The QMA Spherosil LS had a significant size distribution along the axial direction of column, but a relative uniform density. The classification was changed with the packed bed height and flow velocity. Regardless of the interaction between yeast cell and adsorbent, the classification of the adsorbents varied little in the transition from aqueous buffer to biomass containing feedstock.

A Novel Approach for Measuring Gas Holdup through Pressure Fluctuation Signals in Bubble Columns

WANG Guo-feng;YANG Ru;LIU Hui;ZHAGN Xiao-dong;LI Cheng-yue;Li Jian-wei

. 2006, 6(5):  708-712. 

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The time series of fluctuating pressure signals under different experimental conditions were measured by a pressure transducer, and a novel method for measuring gas holdup in bubble column was proposed, namely, the local gas holdup was estimated by resorting to local intermittency measurement (LIM) method and multi-resolution analysis of the time series of fluctuating pressure signals. Firstly, the dominant wavelet scale was determined, which corresponds to the major frequency of power spectral density function (PSDF) of pressure fluctuating signals. Then, signals corresponding to this scale were selected for an intermittent behavior analysis. Consequently, by choosing a proper threshold value on the LIM profile of the major scale detail signal, the gas hold-up was estimated at six radial locations and hence the area average gas hold-up was obtained. A comparison of the gas hold-up values obtained by means of the present LIM analysis and the conventional pressure drop method showed a good agreement, indicating that the larger fluctuations in the column could be attributed to the bubble motions.

Numerical Simulation of Influence of Slit Parameters of Soft-contact Mold on the Distribution of Magnetic Field

ZHANG Lin-tao;WANG En-gang;DENG An-yuan;HE Ji-cheng

. 2006, 6(5):  713-717. 

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The distribution of magnetic field in electromagnetic soft-contact mold with different slit parameters was analyzed through 3-D FEM numerical simulation method. The results show that the cover placed on the top of the mold has little influence on the distribution of magnetic field with or without closed slit. With increment of slit number, the permeability of magnetic field and the maximum value of magnetic flux density become larger. The magnetic flux density becomes more uniform along the circumference. The width of slit has little effect on the distribution of magnetic field. The longer the slit length is, the larger the maximum value of magnetic field is, and the effective acting range of magnetic field becomes larger.

反应与分离

Experimental and Theoretical Studies on Desulfurization Efficiency of Dual-alkali FGD System in a RST Scrubber

MO Jian-song;WU Zhong-biao;CHENG Chang-jie;LI Fu-cai;GUAN Bao-hong;ZHAO Wei-rong

. 2006, 6(5):  718-723. 

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The effects of operating parameters on desulfurization efficiency of a dual-alkali FGD process in a rotating-stream-tray (RST) scrubber are investigated. A dimensionless factor, e, is proposed in this study to predict desulfurization efficiency of this dual-alkali FGD system. e represents the desulfurization ability of a dual alkali FGD system, determined by five main operating parameters such as sodium ion concentration, ratio of absorbent flow rate to flue gas flow rate, pH value of absorbent solution, ratio of sulfate ion to total sulfur ion in absorbent solution, and sulfur dioxide concentration of inlet flue gas. The empirical expression for predicting desulfurization efficiency at different temperatures is obtained through the experimental study and theoretical calculation. It provides useful guide for engineering design.

Synthesis of an Ion-sieve Material and Its Adsorption of Lithium from Salt Lake Brine

LI Yan;QI Tao;WANG Li-na;ZOU Xing;ZHANG Yi

. 2006, 6(5):  724-728. 

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Lithium manganese oxide precursor was prepared by hydrothermal reaction of monoclinic type γ-MnOOH with LiOH solution. The ion-sieve material was obtained by acid treatment of the precursor through H+/Li+ ion exchange. The materials of γ-MnOOH, Li-MnO and H-MnO were characterized by XRD and SEM. The adsorption behavior of the ion-sieve material to lithium from salt lake brine was investigated. The ion-sieve material showed a 37 mg/g lithium uptake from salt lake brine with the high ratio of magnesium to lithium, proven to have a large uptake capacity and a high selectivity.

Mechanism and Kinetics of Thermal Decomposition of Bischofite

HUANG Xiao-fang;WU Yu-long;YANG Ming-de;HU Hu-sheng;DANG Jie;ZHANG Jian-an

. 2006, 6(5):  729-733. 

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Reaction mechanism and kinetic behavior of bischofite dehydration were studied by means of the TG-DTA-MS coupling technique and the TG-DTA technique. The results show that there are four steps in the thermal decomposition of bischofite, in the first two steps, four crystallized waters were lost and in the last two steps combined dehydration and hydration took place. The decomposition action of the first step belongs to the R3 mechanism with 3-dimensional phase boundary reaction as the control step, last three steps belongs to the A1 mechanism that Avrami-Erofeev nucleation and nuclei growth as control steps. The apparent active energy of four steps is: 81.13, 125.4, 230.4 and 164.1 kJ/mol respectively, and the frequency factor is 2.95×1010, 2.70×1015, 4.07×1026 and 4.75×1016 s-1 respectively.

Activation Energy for Desorption of Benzene on Modified Activated Carbons

LI Jing;LI Zhong;XI Hong-xia;XIA Qi-bin

. 2006, 6(5):  734-737. 

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This work mainly involves the study of activation energy of benzen desorption on modified activated carbons. Three kinds of activated carbons such as KH560/activated carbon, 1706/activated carbon, and A172/activated carbon were prepared by means of the surface modification of organic silicon alkyl. Temperature-programmed desorption (TPD) experiments were conducted to measure the TPD curves of benzene on the activated carbons and estimate the activation energy for desorption of benzene on the modified activated carbons. The results showed that the activation energy for desorption of benzene on the KH560/activated carbon, 1706/activated carbon and A172/activated carbon separately was 25.968, 23.134 and 18.076 kJ/mol, which were higher than that on unmodified activated carbon, 17.911 kJ/mol. It indicated that the use of organic silicon alkyl to modify the surfaces of activated carbon could improve its adsorption of benzene. The results of inverse gas chromatography (IGC) showed that specific interaction free energy for adsorption of benzene on the activated carbons was negative, which meant that this adsorption was spontaneous, the specific interaction free energy for adsorption of benzene on the modified activated carbons was smaller than that on the unmodified activated carbon, and the smaller the specific interaction free energy, the higher the activation energy required for the desorption of benzene on activated carbon.

Extraction of Amino-J Acid from Waste-water by Emulsion Liquid Membrane

PAN Lu-ting

. 2006, 6(5):  738-741. 

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The emulsion liquid membrane technique was used to extract amino-J acid from industrial dye waste-water. The effects of stirring speed, ratio of the emulsion to water (Rew), ratio of the oil to internal phase (Roi) and membrane phase components on the extraction rate were investigated and optimized. The results showed that the extraction rate of amino-J acid approached 97% when the stirring speed was 300 r/min, Rew 1:6, Roi 1:1, trioctylamine (TOA) 3 mL/100 mL kerosene, and methyl-didecyle-alcohol-acrylate (LMA-2) 3 g/100 mL kerosene, respectively. The extraction rate had not changed with the oil phase reused for times.

过程与工艺

Synthesis of Hydroxyapatite and Its Effect on Suspension Polymerization of Methylmethacrylate

HUANG Wei;ZHANG Yu-chuan;XIA Ru

. 2006, 6(5):  742-747. 

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A method of hydroxyapatite (HAP) microcrystal synthesis with neutralization reaction of Ca(OH)2 suspension and H3PO4 solution was studied. With designed orthogonal tests, the effects of temperature, concentration of Ca(OH)2, feeding rate of H3PO4 and amount of sodium dodecylbenzene sulfonate (SDBS) on the morphology and properties of HAP were investigated. Several groups of compound dispersant agents of HAP, polyvinyl alcohol (PVA) and SDBS were prepared, and the effect of each group on the suspension polymerization of methylmethacrylate (MMA) was assessed and compared with each other. The HAP was characterized by FT-IR and TEM. The influences of morphology and size of HAP crystal grains on diameter and size distribution of PMMA were analysed. The results showed that HAP/PVA/SDBS had good effects on suspension polymerization of MMA. It was found that the system of diameter of PMMA increased with increasing acicular degree of HAP, and the diameter of PMMA first increased and then decreased with increasing size of HAP and when the size of HAP was 140 nm×35 nm, the diameter of PMMA reached peak value at 1.41 mm.

Preparation and Stability of Colloidal Liquid Aphrons

HE Yi;WU Zhi-chun;MAO Zai-sha

. 2006, 6(5):  748-752. 

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Colloidal liquid aphrons (CLAs) were prepared using non-ionic and ionic surfactants (mixing speed 900 r/min, PVR=10). The effect of the existence of benzoic acid on the stability of CLAs was investigated when the concentrations of surfactants were the same [the ionic surfactant concentration was 1 g/L, and the non-ionic surfactant concentration was 1.0%(j)]. The experimental results showed that the existence of benzoic acid destructed the stability of several CLAs systems that were very stable when no benzoic acid was added into the oil phase. For the CLAs which were stable whether benzoic acid was added or not, the increase in the concentration of ionic and non-ionic surfactants decreased the average diameter of CLAs. It was also found that the type of ionic surfactant affected the stability of CLAs, when the concentrations of surfactants were kept equal [the ionic surfactant concentration was 1 g/L, and the non-ionic surfactant concentration was 1.0%(φ)], anionic surfactant sodium dodecylsulfate (SDS) and sodium dodecylbenzene sulfonate (SDBS) could be used to prepare stable CLAs, but cationic surfactant hexadecyltrimethyl ammonium bromide (HTAB) could not.

Electrolysis Corrosion Behaviour of NiFe2O4-based Cermet Inert Anode

XI Jin-hui;YAO Guang-chun;LIU Yi-han;ZHANG Xiao-ming

. 2006, 6(5):  758-762. 

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A cermet inert anode of 10%Ag-NiFe2O4/NiO was prepared by powder metallurgical method. The inert anode is a cylinder with 50 mm height and 50 mm diameter. It was applied to aluminium electrolysis testing for 10 h at 960℃ and the current density of 0.8 A/cm2. The behavior of inert anode for aluminium electrolysis in Na3AlF6-5%CaF2-5%Al2O3 was studied. After 10 h electrolysis, the anode was slightly corroded. It was in good condition without tumescence and scaling, which shows that the anode has good corrosion resistance to molten cryolite-based melt. The corrosion rate of the anode was estimated as about 13 mm/a and the purity of the deposited aluminium was 92%~93%. The surface of the inert anode was analyzed using energy-dispersive X-ray microanalysis. The results indicate that non-stoichiometric dissolution of the oxide phase occurred, and Fe2O3 dissolved prior to NiO and entered the electrolyte. The content of oxygen on the surface of the inert anode facing to cathode was more than that of the other side, which indicates that the reaction of O2 releasing is more acute between the two electrodes. A part of released O2 reacted with Ag on the surface of inert anode to produce Ag3O4. The section of the inert anode was also analyzed. It was found that the electrolyte penetrated into the inert anode and reacted with Fe2O3, then the product FeF3 deposited in the interspaces in the anode.

Preparation of Vermiculite Powder with High Expansion and High Quality

HU Guang-suo;LI Zheng-yi;ZHU Yong-ping;ZHANG Wei-gang

. 2006, 6(5):  763-767. 

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Following the previous study on the expansion mechanism of vermiculite originated in Weili, Xinjiang, China, the thermal expansion of the vermiculite was investigated in this work. The results show that individual and cumulative volume expansion ratios increase with increasing of temperature. However, the effect of temperature above 600℃ can be negligible, companied with a very positive effect of fast heating rate which indicates a possibility to utilize such property for producing very high volume expansion vermiculite. Strong scattering of individual expansibility can be explained with the microstructure variation of phlogopite-vermiculite interstratification in the mineral. Thermal analysis confirms that there exist three types of crystallized water combined with metallic ions, such as Ca, Mg and Na during interstratification. Finally, very fine vermiculite powder with thermal conductivity of 0.113~0.115 W/(m·K) was produced, which may be used as high quality thermal insulation material.

Finite Element Analysis on Gibbsite Strength

YE Lu-sheng;CHEN Qi-yuan;YIN Zhou-lan;HUA Shu-gui;LI Wang-xing

. 2006, 6(5):  768-772. 

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The finite element analysis method is applied to study the relationships between the gibbsite crystal overlapped angle and the strength of gibbsite particles. The regularity of the particle size of gibbsite with the strength is calculated. The results show that: (1) The strength of gibbsite is weak when overlapped angle of the crystals is between 60o~80o; (2) When the gibbsite crystals are smaller (about 5 mm), the gibbsite strength becomes better; (3) When the gibbsite crystals are larger (20~40 mm), the gibbsite strength is weaker; (4) The strength of gibbsite particle with different crystal sizes has obvious advantages.

Effect of Coal Type on Coal and Natural Gas Co-gasifying Process

OUYANG Zhao-bin;GUO Zhan-cheng;DUAN Dong-ping;SONG Xue-ping;WANG Zhi

. 2006, 6(5):  773-776. 

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Coal and natural gas co-gasifying process is a new technology to produce synthesis gas based on natural gas steam reforming and coal gasification. A moving bed was used as the reactor in hot simulation experiments. With anthracite, lean and fat coals and coke as the raw materials, the effect of different coal types on the temperature in the flame zone was studied. The effect of coal type on the ingredients of synthesis gas, the methane and steam conversions was investigated in the experiments. With the coals as the raw materials, the results showed that the temperature in the flame zone and the content of active compounds (H2+CO) were higher than those of coke. In addition, the H2/CO ratio of synthesis gas was close to the value calculated by thermodynamic equilibrium. For the crude synthesis gas produced in this work, the content of active compounds is not less than 92%, the rudimental methane less than 2%, and the H2/CO ratio in the range of 1~2. The steam conversion rate is more than 75%, and the methane conversion rate over 90%. The higher ash content of coal is advantageous to the coal and natural gas co-gasifying process. The experimental results have proved that the coal and natural gas co-gasifying process is a new technology to produce synthesis gas suitable to the resource characteristics in China.

Thermal Stability of Boroaluminosilicate Glass with Rare Earth Doping

NI Ya-ru;LU Chun-hua;ZHANG Yan;ZHANG Qi-tu;XU Zhong-zi

. 2006, 6(5):  777-780. 

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The glass-forming range of rare earth oxide and BaO co-doped Al2O3-B2O3-SiO2 system was explored, and the effect of the rare earth oxide content on glass-forming region was examined firstly. Then the effect of the rare earth oxides content on the glass thermo-stability was analyzed through differential thermal analysis technique. Finally, the glass after heat-treatment near Tx (the temperature at the beginning of exothermic peak formation) formation temperature was analyzed using XRD and TEM/EDS analyses. The results showed that the region of glass-forming range expanded firstly, and then shrank when the rare earth content increased gradually. The glass lacking of transparence after heat treatment near Tx was due to the phase separation, and the rare earth ions mainly distributed in the boron-aluminum rich phase, the higher the glass heat-treatment temperature, the more seriously the glass phase separation occurred. When the glass was heat-treated at a high temperature of 900℃, the diffraction peaks of crystal were very obvious in the XRD spectrum. Through comparing and analyzing, the main crystalline phase might be determined as SmAl2.07(B4O10)O0.6 with the same structure as NdAl2.07(B4O10)O0.6.

Production of Magnesium Powder with a Method of Electromagnetic Vibration Atomizing and Quenching

LIANG Nai-ru;XIE Ping;ZHAO Jun;LIANG Zhi-yong

. 2006, 6(5):  781-783. 

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Magnesium powder was prepared by the method of electromagnetic vibration atomizing and quenching. The molten magnesium was atomized and quenched into the metal powder by the water-cooled plate of the electromagnetic vibration was studied. The grain sizes of Mg powder obtained in the range ≤0.5 mm with a round shape. The influential factors of Mg powder formation such as jetting pressure of the spray nozzle at the crucible bottom, the speed of the rotation dish, the vibration atomizing electromagnetic frequency and power were investigated, and optimized conditions obtained. SEM image shows that Mg particles are in a nearly round shape.

系统与集成

Two-level Optimization Algorithm for Reactor Network Synthesis Based on CSTR

JIN Si-yi;JIA Shu-xiang;YANG Chao-he

. 2006, 6(5):  784-788. 

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The reactor network synthesis problems are commonly complex non-linear programming (NLP) problems, which are difficult to gain global optimal solutions using the traditional optimization approaches. To avoid the above disadvantage, a two-level optimization algorithm was proposed according to the characters of the reactor network model based on continuous stirred-tank reactors (CSTR). By this algorithm, the NLP of the reactor network synthesis is divided into the linear programming in flow rate and reactor volume space, and the stochastic optimization problem in concentration space. As a result the algorithm reduces the scales and difficulties of the problem. Meanwhile, by applying the global optimization algorithm to the concentration space optimization, the probability of obtaining the global optimal solution is improved. The results of the example studies show that the two-level optimization algorithm proposed can give better structure of the reactor network as well as the reactor type and size in the network.

生化工程专栏

Preparation of Chitosan with High Viscosity-average Molecular Weight and High Degree of Deacetylation by Rapid Interim Microwave Heating Method

LI Qiao-xia;SONG Bao-zhen;YANG Zhen-qiu;FAN Hong-lie

. 2006, 6(5):  789-793. 

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Chitosan with high degree of deacetylation (DD=94.5%) and high viscosity-average molecular weight (Mv=1.48′106) was prepared by rapid interim microwave heating method. Influential factors such as particle size of chitin, concentration of sodium hydroxide solution, ratio of liquid to solid, reaction temperature, reaction time and reaction cycle were investigated. 45%(w) sodium hydroxide solution was mixed with 20 g chitin with particle size 250~380 mm by volumetric ratio of liquid to solid 8:1 and reacted for 10 min at 100℃ under microwave (800 W, 2450 MHz). Then, the mixture was treated by washing and drying to obtain chitosan with DD of 72.3% and Mv of 2.06×106. Finally, under the same reaction conditions, this chitosan was treated with 45% NaOH solution under microwave for another 10 min to obtain chitosan with DD of 94.5% and Mv of 1.48×106. Compared with traditional interim electricity heating method, the proposed method not only shortened the reaction time from 5 h to 20 min but also improved the molecular weight from 3.8×105 to 1.48×106 which has close degree of deacetylation. FT-IR and XRD spectra showed that the chitosan with high DD (94.5%) and high Mv (1.48×106) had high crystallinity and order structure and the film made of the chitosan had better properties than the film made from the chitosan with 96.2% DD and 3.8×105 Mv produced by interim electricity heating method.

Cryopreservation of Cistanche deserticola Callus

GE Feng;WANG Xiao-dong;ZHAO Bing;WANG Yu-chun

. 2006, 6(5):  794-798. 

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A simple and optimized cryopreservation process was applied to Cistanche deserticola callus. To obtain optimal results, the callus was pre-cultured on B5 medium supplemented 6% (j) dimethyl sulfoxide (DMSO) and then treated with a vitrification solution at 25℃ for 20 min before immersion in liquid nitrogen. The vitrification solution contained 30% (j) glycerol, 15% (j) ethylene glycol, 10% (j) DMSO and 0.5 mol/L sucrose. After cryopreservation and rapid thawing in a water bath at 30℃, the callus was washed with 1.0 mol/L sucrose solution at 25℃. The survival rate of callus was 86% under the above cryopreservation process. After the cryopreserved callus was cultured on B5 medium for five months, the content and production of PeG were 97% and 95% of those in the non-frozen callus.

Lipase-catalyzed Production of Biodiesel from Several Oils in a Novel Reaction Medium

LI Li-lin;DU Wei;LIU De-hua;LI Ze-bo;WANG Li

. 2006, 6(5):  799-803. 

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Tert-butanol was adopted as a reaction medium for lipase-catalyzed methanolysis of oils for biodiesel production, in which both the negative effects caused by excessive methanol and by-product glycerol could be eliminated. The optimum conditions of methanolysis of rapeseed oil were as follow: tert-butanol/oil (volumetric ratio) 1:1, methanol/oil (molar ratio) 4:1, 3% Lipozyme TLIM and 1% Novozym 435 based on oil weight, 35℃, 130 r/min and 12 h. The highest biodiesel yield was 95% and the lipases could be reused 200 cycles without obvious loss of their activity. The technology was further tested in a pilot plant and the product was up to the biodiesel standards of US (ASTM PS121-99) and Germany (DINE51606). Furthermore, soybean oil, tung oil, cottonseed oil, sapium fat and acidified waste oil were also explored for biodiesel production, and lipases also showed good stability in tert-butanol reaction medium.

Effect of By-products on Cell Growth and Biosynthesis of 1,3-Propanediol by Klebsiella pneumoniae

ZHANG Yan-ping;LIU Ming;DU Chen-yu;SHEN Jin-yu;CAO Zhu-an

. 2006, 6(5):  804-808. 

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Biosynthesis of 1,3-propanediol attracted much attention recently. The cell growth and biosynthesis of 1,3-propanediol by Klebsiella pneumoniae tended to be ceased in the latter phase of anaerobic culture. The effect of environmental factors was studied in this work. It was indicated that the main by-product ethanol was the key inhibitor. Addition of 4 g/L ethanol in the culture medium would restrain the cell growth and 1,3-propanediol formation. By addition of 8 g/L ethanol, the maximum specific rates of cell growth and 1,3-propanediol biosynthesis, the maximum concentrations of biomass and 1,3-propanediol were decreased by 21.6%, 22.1%, 59.6% and 33.5% respectively. The inhibition potentials of other by-products on the anaerobic growth of K. pneumoniae were also detected. It was shown that the cell growth was inhibited obviously with 2 g/L acetic acid, yet it would not be affected even with 5 g/L 2,3-butanediol or 10 g/L lactic acid.

Optimization of Fermentation Conditions of High Yield and High Molecular Weight Hyaluronic Acid

CHENG Xia;LIU Deng-ru;CHEN Jian;DU Guo-cheng

. 2006, 6(5):  809-813. 

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The effects of initial glucose concentration, agitation speed and aeration rate on hyaluronic acid (HA) production by Streptococcus zooepidemicus WSH24 were investigated in batch culture. The agitation speed had the most pronounced effect on HA yield and molecular weight. Under the condition of 200 r/min, the HA yield, YHA/C and molecular weight could reach 5.3 g/L, 0.13 g/g and 1.88×106 Da, respectively. When the initial glucose concentration was 65.8 g/L, the HA yield, YHA/C and molecular weight reached 5.9 g/L, 0.17 g/g and 1.90×106 Da, respectively. The aeration rate also affected HA fermentation. HA yield and molecular weight were higher at aeration rate of 1.2 L/(min·L) than those at 0.5 L/(min·L).

Sucrose-added Fed-batch Culture for 1,11-Dicarboxylic Acid Production by Candida tropicalis and Recombinant Candida tropicalis Strain

GAO Hong;LIU Ming;HUANG Ying-ming;HUA Yu-tao;CAO Zhu-an

. 2006, 6(5):  814-817. 

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Candida tropicalis strain F10-1 and its recombinant strain CZ-15 can be used for 1,11-dicarboxylic acid (DCA13) production, and in CZ-15, one copy of carnitine acetyltransferase (CAT) genes is disrupted. The sucrose-added fed-batch fermentation of F10-1 and CZ-15 was studied. The results showed that the optimal feeding time and the optimal sucrose concentration were different for F10-1 and CZ-15. By feeding sucrose in the acid production stage, for F10-1 and CZ-15, the acid production was increased by 25.0% and 23.4%, reaching 99.5 and 108.1 g/L, and the alkane conversion rate was increased by 35.5% and 28.6%, respectively.

Production of (R)-Mandelic Acid by Asymmetric Degradation of the Racemate with Brevibacterium sp. CCSYU10011

ZHANG Hui;XU Yan

. 2006, 6(5):  818-821. 

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(R)-mandelic acid is a useful chiral synthon for the production of various pharmaceutical. In order to prepare (R)-mandelic acid from rac-mandelic acid, Brevibacterium sp. CCSYU10011 was screened from various microorganisms, of which the resting cells could convert the racmate to (R)-isomer. The process of bioconversion showed that the microorganism asymmetricly degraded (S)-mandelic acid from the racemate and (R)-mandelic acid was maintained. The factors affecting biotransformation efficiency were investigated, including temperature, pH, substrate concentration and cell biomass. Under the optimal conditions, 48.7% yield and 99% enantiomeric excess value were obtained.

材料工程专栏

Novel Cathode Material for Direct Carbon Fuel Cell

ZHAO Li;ZHU Qing-shan

. 2006, 6(5):  822-826. 

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The effect of Ni-CeO2 cathodes on the performance of direct carbon fuel cell (DCFC) was studied. The performances of DCFC with different Ni-CeO2 cathodes generating relatively high current density and power density were reported. The results showed that DCFC using the Ni-CeO2 cathode produced the maximum current and power densities of 474 mA/cm2 and 108 mW/cm2 at 630℃, respectively, the fuel conversion efficiency was 70% at the current density of 50 mA/cm2. The DCFC using Ni-CeO2 cathode produced the maximum current and power densities of 328 mA/cm2 and 72 mW/cm2 at 500℃, respectively. XRD and SEM were employed in the cathode characterization. Some features of the cathodes which might greatly contribute to the increase in DCFC performance were discussed.

Studies on Au/TiO2 Catalyst for Hydrogen Production from Methanol Steam Reforming

CUI Bing-bing;XU Xin;LUO Guo-hua;TONG Ze-min;CHEN De

. 2006, 6(5):  827-831. 

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A series of Au/TiO2 catalysts were prepared by the deposition-precipitation method and characterized by XRD and TEM. The influences of gold loading, calcination temperature and promoter on the catalytic activity of Au/TiO2 catalysts for the hydrogen production from methanol steam reforming were studied. The results show that the catalyst prepared under the conditions of 5% Au loading, 100℃ drying without calcination, and addition NiO promoter exhibits the best activity. According to the TEM observation, addition of NiO promoter could improve the dispersion of nanometer TiO2 support, and gold particles become smaller.

Stress and Strength Analysis of Al(OH)3 Grains

YIN Zhou-lan;HUA Shu-gui;YE Lu-sheng;CHEN Qi-yuan;LI Wang-xing

. 2006, 6(5):  832-836. 

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Based on the SEM morphology of the gibbsite grains used in China￠s alumina industry, the finite element analysis method was applied to study the relations between the position and number of filling crystals and the strength of gibbsite grains. It has been discovered that the strength of gibbsite grains is strengthened with small filling crystals. The optimum position of filling is 75% of the length of the gap. The increase of the number of the filling crystals will improve the strength of the grains. When the gap varies from 1 to 2 mm, the larger the gap, the smaller the grain strength. Therefore, the finite element analysis can be used to evaluate the strength of the products of Al(OH)3 from the SEM morphology of the gibbsite grains.

Ball Milling Process and Its Effect on Hydrogen Adsorption Storage of MWNTS

YAO Yun-jin;ZHANG Su-ping;YAN Yong-jie

. 2006, 6(5):  837-840. 

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The effect of mechanical ball milling with different time on the hydrogen adsorption behavior of the multi-wall carbon nanotubes (MWNTs) was studied. The microstructure characteristics of MWNTs before and after ball milling were examined by transmission electron microscope (TEM) and X-ray diffraction (XRD). The results showed that ball milling could break MWNTs, shorten their length, open the tips of the tubes, and increased their surface defects and specific surface area at the same time. After ball milling for 12 h, the hydrogen storage capacity of MWNTs increased from 1.60% to 2.55%. The enhancement of hydrogen adsorption might result from the increase of defects and surface area of the MWNTs caused by ball milling.

Synthesis of Zinc Oxide Nanobelts in Aqueous Solution of Ethylene Diamine

JIANG Da;ZHAI Yu-chun;CHEN YUan-tao;GONG Rui;ZHANG Wei

. 2006, 6(5):  841-844. 

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Zinc oxide nanobelts were synthesized in aqueous solution of ethylene diamine by solvothermal synthesis and characterized at the same time. The width and length of zinc oxide nanobelts are 20~30 nm and 500~600 nm respectively. Zinc oxide nanobelts were prepared through dissolution-crystallization mechanism. Ethylene diamine bonding was a key factor in synthesis of zinc oxide nanobelts, and the oriented growth of zinc oxide was controlled by the quantity of sodium hydroxide.

Formation of CdS Nanoparticles on Polymer Spheres Coated with Polyelectrolyte/Dendrimer Multilayers

GUO Fei;ZHU Yi-hua;YANG Xiao-ling

. 2006, 6(5):  845-848. 

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Core-shell microspheres with polyelectrolyte multilayers were fabricated by electrostatic self-assembly of three kinds of polyelectrolyte, such as polyamidoamine (PAMAM), poly(diallyldimethylammonium chloride) (PDADMAC) and poly(4-styrenesulfonate) (PSS). Core-shell microspheres with CdS/polyelectrolyte multilayers were prepared by deposition and adsorption of CdS on the polyelectrolyte multilayers, and the CdS nanoparticles were formed in solution or polyelectrolyte layer, the formed core-shell microspheres had stable photoluminescence property. TEM was used to characterize the shape of core-shell microspheres and photonic properties of core-shell microspheres with CdS/polyelectrolyte multilayers were analyzed by UV-Vis reflectance and photoluminescence spectra.

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A Review on Bioleaching Mechanism and Electrochemistry of Arsenic-bearing Gold Ores

LI Hai-bo;CAO Hong-bin;ZHANG Guang-ji;ZHANG Yi;FANG Zhao-heng

. 2006, 6(5):  849-856. 

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The bioleaching of arsenic-bearing refractory gold ores offers an effective pretreatment technology, which is an environmentally friendly process and able to improve the gold recovery. In the present article, the chemical reaction mechanism, leaching kinetics, biochemistry, electrochemistry and process intensifying technologies occurring in the bioleaching process of sulfide minerals are reviewed.