Table of Content

20 December 2007, Volume 7 Issue 6

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流动与传递

Hydrodynamic Characteristics in a Continuous Rotor-Stator Mixer-I. Experimental Investigation

DONG Qiang;NIE Yi-xue;ZHANG Hua-qin;GAO Zheng-ming

. 2007, 7(6):  1055-1059. 

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The hydrodynamic characteristics in a continuous rotor-stator mixer (CRS) with Newtonian and Non-Newtonian fluids were studied experimentally, and three different stators were used in the experiment. The power characteristics and Kolmogorov scale were measured and analyzed. The results show that the power number of stator type 3 is larger than that of stator types 1 and 2, the value is 5.44. The Metzner-Otto constant of CRS is larger than that of normal impellers. The Kolmogorov scale in the CRS is an order of magnitude smaller than that in a traditional stirred tank, so the CRS offers much shorter micro-mixing time than stirred tanks. The results are of importance to the optimization of industrial continuous rotor-stator mixers.

Hydrodynamic Characteristics in a Continuous Rotor-Stator Mixer-II. Numerical Simulation

ZHANG Hua-qin;DONG Qiang;LI Zhi-peng;GAO Zheng-ming

. 2007, 7(6):  1060-1065. 

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The hydrodynamic characteristics in a continuous rotor-stator mixer (CRS) were numerically simulated by using computational fluid dynamics (CFD) package FLUENT 6.2 with the SIMPLE algorithm in this work. The standard k-e model and sliding mesh (SM) method were used in the simulation. The power number NP was constant with variation of Reynolds number Re, and the calculated NP equaled 5.99, the calculation error was 13.7% compared with the experimental value. The hydraulic characteristics under the lower flow rate conditions predicted by CFD are in good agreement with experimental data, though they are unable to be predicted reasonably under the larger flow rates because of the liquid entrainment. The results show that the maximum efficiency of the pumping capacity of CRS is only about 13%, and the power consumption is mainly used for high shear mixing. The predicted flow field and the distribution of shear rate are asymmetric, and each stator slot has a different circulation and re-entrainment pattern as the rotor is passing by the stators, which is in agreement with the literature. The results are of reference to the optimum design of industrial CRS.

Influences of Particle Size and Acoustic Field on Fluidization of SiO2 Ultrafine Particles

LIU Hui-e;GUO Qing-jie;CHEN Shuang;ZHANG Jian;WANG Ming-hua

. 2007, 7(6):  1066-1070. 

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Fluidization behavior of three kinds of SiO2 powder with different sizes and influence of acoustic field were investigated in a 56 mm i.d. glass tube fluidized bed. The average diameters of the three kinds of powder were 5~10 nm (sample 1#), 0.5 mm (sample 2#) and 10 mm (sample 3#), respectively. The particles of samples 1# and 2# could form stable agglomerates under high gas velocity, thus the cohesive force of unit mass was decreased and stable fluidization achieved. However, no stable agglomerates were observed during fluidization of 3# particle sample, which was never fluidized stably. Sound wave could improve the fluidization behavior within a given range of sound frequencies (40~60 Hz) for all the three kinds of powder. The sizes of agglomerates decreased and the minimum fluidization velocities reduced with increasing sound pressure level for 1# and 2# particle samples. Whereas 3# particle sample could never be fluidized smoothly even under sound energy action.

反应与分离

Regeneration of SO2-adsorbed CuO/Al2O3 with H2 and Recovery of Elemental Sulfur

ZHAO You-hua;LIU Zhen-yu;JIA Zhe-hua

. 2007, 7(6):  1071-1076. 

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SO2-adsorbed CuO/Al2O3 can be regenerated with H2 through recycling the tail gas back into the reactor. The temperature-programmed regeneration experiments are carried out in a thermogravimetric analyzer to study Cu and S phase changes during tail gas recycling process. The existence of peaks in the DTG curve at 280 and 330℃, respectively, shows that CuSO4 formed during the SO2 removal transforms to CuO and then Cu, while the result of XPS characterization shows that CuS in the adsorbent is produced by the reaction of SO2 and Cu. An elemental sulfur yield of above 50% can be obtained in the sulfur recovery process at 400℃ with an H2/SO2 molar ratio of 1.5, which shows that CuS formed in the H2 regeneration of CuO/Al2O3 is the catalyst for elemental sulfur production.

Decolorization Ability and Microcosmic Biosorption Process of Reactive Dyes with Fungus Penicillium oxalicum

ZHENG Wen-chai;XIN Bao-ping;GAN Ya-ling;LI Chang-ping

. 2007, 7(6):  1077-1082. 

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The decolorization ability and adsorption process of seven water-soluble reactive dyes, namely Reactive Turquoise Blue KN-G, Reactive Black K-BR, Reactive Turquoise M-GB, Reactive Brilliant Blue M-BR, Reactive Violet K-3R, Reactive Dark Blue K-R and Reactive Turquoise Blue K-GL, with Penicillium oxalicum were studied when the strain was growing in the simulative dye wastewater. It was found from adsorption experiments that the growing Penicillium oxalicum possessed excellent adsorption ability to the reactive dyes. At lower initial dye concentration (200 mg/L), the average decolorization rate of seven dyes reached 93.0%, at higher initial dye concentration (400 mg/L), the decolorization rates of Reactive Turquoise Blue KN-G and Reactive Turquoise M-GB were 99.7% and 99.9% respectively. Spectrophotometric analysis of supernatants and tracing of Cu2+ (which is contained in the dye molecules) concentration in the supernatants indicated that the decolorization of dyes by Penicillium oxalicum biomass involved an adsorption process. Scanning electron microscope (SEM) and transmission electron microscope (TEM) images illustrated that the hyphae of the fungus swelled, the structure of the cell wall was reconstituted and the thickness of the cell wall increased about 10~15 folds. The cell wall played an important role in dye biosorption by growing fungus. It not only offered the major biosorption sites for the dyes, but also provided routeway for the dye molecules to enter the cells.

Synthesis of 1-Ethyl-3-methylimidazolium Hydrogen Sulfate and Its Application in the Electrolysis of Aluminum

MA Jiang-hua;LI Yu-ping;LI Hui-quan;ZHANG Yi

. 2007, 7(6):  1083-1088. 

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1-Ethyl-3-methylimidazolium hydrogen sulfate ([EMIM]HSO4) was synthesized with N-methylimidazolium as raw material and characterized by using FT-IR and TG-DTG-DTA and DSC measurements. Some physical properties concerned in aluminum electrolysis, such as density, surface tension, electrical conductivity and viscosity of [EMIM]HSO4, were investigated. The solubility and electrochemical behavior of alumina in [EMIM]HSO4 was studied by using inductively coupled plasma-atomic emission spectrometer (ICP-AES) and cyclic voltammmetry measurements. The results showed that [EMIM]HSO4 was very stable at the temperatures below 270℃, its density and viscosity decreased rapidly with increase of temperature, and molar conductivity reached 2.890 S×cm2/mol at 100℃, demonstrating that [EMIM]HSO4 could be used as electrolyte. The solubility of alumina in [EMIM]HSO4 at 20℃ was 3.81 g/L, suggesting that this system might satisfy the electrolysis of alumina, alumina could be reduced to aluminum at a platinum electrode, with normal deposition at -0.54 V and under potential deposition (UPD) at -0.26 V, and the deposition was a diffusion-controlled process.

Reductive Leaching of Manganese from Low-grade Pyrolusite Using Cane Molasses

SU Hai-feng;SUN Ying-yun;WEN Yan-xuan;TONG Zhang-fa;PEI Rui-nan;XUE Min-hua

. 2007, 7(6):  1089-1093. 

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Manganese leaching from a low-grade pyrolusite was investigated using cane molasses as reducing agent in sulfuric acid medium. Orthogonal and single-factor experiments were employed to examine the influences of concentrations of cane molasses and sulfuric acid, leaching temperature as well as reaction time on the leaching rates of Mn, Fe and Al. And the mechanism of leaching process was also studied. The results showed that high manganese recovery rate with low Fe and Al leaching rates was obtained by analyzing the dissolution of Mn, Fe and Al during the leaching process. The presence of colloidal materials in the cane molasses helped the higher leaching rate of manganese than that obtained by only using pure sucrose and glucose, which had no affection on the dissolution of Fe and Al. The optimal leaching conditions were obtained as 2.35 mol/L H2SO4 and 75 g/L cane molasses for 2 h at 90℃. The leaching rate by this way was 96.7% for Mn, whereas 25.5% for Al and 34.4% for Fe.

Quality Control of 1-Alkyl-3-methylimidazolium Ionic Liquid Precursors with HPLC

ZHANG Yan-qiang;ZHANG Jian-min;CHEN Yu-huan;ZHANG Suo-jiang

. 2007, 7(6):  1094-1098. 

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A high performance liquid chromatography (HPLC) method was proposed to monitor the synthesis and purification of the 1-alkyl-3-methylimidazolium ionic liquid precursors from alkylation of 1-methylimidazole with alkyl halides and determine the purity of final products. The results showed that separation of 1-methylimidazole from the precursors could be obtained under the HPLC performance conditions such as cation exchange column, acetonitrile/KH2PO4 aqueous solution and 209 nm wavelength. The content of unreacted 1-methylimidazole in the precursors could be easily calculated from their corresponding HPLC peak areas with the calibration curve of 1-methylimidazole. The retention times of the 1-alkyl-3-methylimidazolium ionic liquid precursors decreased with their increasing alkyls, and the ionic liquids with the same cation and different anions had almost the same retention times.

过程与工艺

Preparation and Characterization of B-Trichloroborazine and Its Derivatives

WANG Yu;WANG Xi;CAO Wei-liang;SHEN Zhi-xun;WU Yan;WANG Chang-song;ZHANG Wei-gang

. 2007, 7(6):  1099-1106. 

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Crystalline B-trichloroborazine (TCB) was synthesized and purified using Schlenk technique with boron trichloride (BCl3) and ammonium chloride (NH4Cl) as raw materials and chlorobenzene (C6H5Cl) as solvent. Further derivatives of TCB were also obtained by substitution reaction of dimethylamine and TCB, from which high quality BN could be prepared. The results were analyzed using NMR and XRD, and the preparation conditions, experimental apparatus and route of reactions were examined. It was found that the TCB synthesis followed a homogeneous liquid phase reaction mechanism. The yield of TCB could reach above 89% when Hg as catalyst or above 87% by proper extending of reaction time without catalyst. The optimum theoretical plate number of rectification column was estimated as 6 for purification of TCB. The substitution reaction of TCB was simulated at the B3LYP/6-31G* level, the results show that there exists a Cl-B-N-H-Cl tetratomic ring structure in the intermediate state of the substitution reaction. It can also be postulated from the simulation that a mixture of several different products could be produced in the reaction.

Effect of Co/ZSM-5 Zeolite Catalyst on Pyrolysis of Coal in a Spouted Fluidized Bed

ZOU Xian-wu;YAO Jian-zhong;YANG Xue-min;SONG Wen-li;LIN Wei-gang

. 2007, 7(6):  1107-1113. 

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The effect of Co-doped zeolite catalyst, Co/ZSM-5, on the yields and compositions of gas, liquid and solid products from coal pyrolysis was investigated in a spouted fluidized bed. Moreover, the mechanism of Co/ZSM-5 zeolite deactivation and regeneration life was also studied. The results showed that the total conversion rate of coal pyrolysis could be increased by 70% from 550℃ to 600℃ with Co/ZSM-5 zeolite. However, the yields of hexane soluble matters were highest at 600℃. In the hexane soluble matters, the yields of phenol, aliphatic and aromatic groups could be increased up to 203%, 51% and 78%, respectively, at 650℃ with Co/ZSM-5 zeolite. Poisoned Co/ZSM-5 zeolite from carbon deposition could be regenerated by roasting at 500℃, and the reduction of Co/ZSM-5 zeolite activity was less than 5% after 6 regeneration times. The results of catalyst characterization indicated that the cobalt was introduced into ZSM-5 zeolite. Because of its catalytic activity in hydrogenation, cobalt can promote the combination of H· with tar fraction from coal pyrolysis, which decreases the rates of tar fractions forming macromolecule. Therefore, the yield and quality of tar from coal pyrolysis can be improved.

Preparation of Hydrogen through Catalytic Steam Reforming of Bio-oil

WU Ceng;YAN Yong-jie;LI Ting-chen;QI Wei

. 2007, 7(6):  1114-1119. 

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Hydrogen was prepared via catalytic steam reforming of bio-oil which was obtained from fast pyrolysis of biomass in a fluidized bed reactor. Influential factors including temperature, weight hourly space velocity (WHSV) of bio-oil, mass ratio of steam to bio-oil (S/B) as well as catalyst type on hydrogen selectivity and other desirable gas products were investigated. Based on hydrogen in stoichiometric potential and carbon balance in gaseous phase and feed, hydrogen yield and carbon selectivity were examined. The experimental results show that higher temperature favors the hydrogen selectivity by H2 mole fraction in gaseous products stream and it plays an important role in hydrogen yield and carbon selectivity. Higher hydrogen selectivity and yield, and carbon selectivity were obtained at lower bio-oil WHSV. In catalytic steam reforming system a maximum steam concentration value exists, at which hydrogen selectivity and yield, and carbon selectivity keep constant. Through experiments, preferential operation conditions were obtained as follows: temperature 800~850℃, bio-oil WHSV below 3.0 h-1, and mass ratio of steam to bio-oil 10~12. The performance tests indicate that Ni-based catalysts are optional, especially Ni/a-Al2O3 effective in the steam reforming process.

Visible Phase Transition and Degradation Kinetics of Polystyrene in Supercritical Toluene

HUANG Ke;TANG Li-hua;NI Yan-hui;WU Yong-qiang;ZHI Zi-bin

. 2007, 7(6):  1120-1125. 

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A visible micro-reactor was used to study the phase transition of polystyrene degradation in supercritical toluene. Polystyrene could be dissolved into toluene in a few minutes with the temperature increasing. The gas-liquid interface disappeared, companying with the opalescent phenomenon, when the temperature and pressure were slightly higher than the critical point of toluene. Moreover, the properties of thermal degradation and supercritical degradation of polystyrene were studied. The results showed that the conversion rate of polystyrene in supercritical toluene was much higher than that of thermal degradation. Moreover, during the beginning stage of degradation, the molecular weight decreased quickly with producing amounts of small molecular products, while conversion rate of polystyrene of thermal degradation was low. The system of supercritical degradation was a homogenous phase with low density and viscosity, and increased the transmission property, which increased the degradation velocity polystyrene substantially. Polystyrene degradation was a first order reaction. In the temperature range of 330~370℃, the activation energy of thermal degradation was 186.1 kJ/mol, while the activation energy of supercritical degradation was 143.5 kJ/mol due to its homogenous phase of reaction system.

Preparation and Characterization of Mono-disperse Spherical Nickel Particles

HUANG Guo-yong;XU Sheng-ming;XU Gang;LI Lin-yan;CHEN Song-zhe

. 2007, 7(6):  1126-1131. 

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Mono-disperse spherical nickel particles were synthesized by liquid phase reduction method with nickel sulfate as raw material, hydrazine as reductive agent, and sodium hydroxide as adjusting pH value of the solution. The prepared powder samples were characterized by means of X-ray diffraction (XRD), scanning electron microscopy (SEM), thermo-gravimetry (TG) and X-ray photoelectron spectroscopy (XPS). The results indicated that the high purity spherical particles had the face-centered cubic (fcc) crystal structure and their final diameters were between 100 and 400 nm with narrow size distribution. The optimal technological conditions were obtained as that the concentration of Ni2+ was 0.35 mol/L, the ratio [N2H4]/[Ni2+] 4.0, the ratio [NaOH]/[Ni2+] 2.5, and the reaction temperature 80℃. Moreover, the original concentration of nickel controlled the shape, size and agglomeration of the nickel particles, the temperature controlled the reaction rate, and the amounts of NaOH and hydrazine affected the purity of nickel powder.

Effects of Iron Ore Porosity on Its Reduction and Iron Carbide Formation

MA Jiang-hua;LI. Guang-qiang

. 2007, 7(6):  1132-1137. 

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The formation process of iron carbide from iron ore by reduction and carburization with 70%H2-30%CH4 gas mixture was studied using thermogravimetric measurement, XRD and EDX analysis. The micropore distribution in the iron ores and their reduced product, iron, was measured. It was observed that the reduction and carburization rates were quite different among the iron ores with different microstructures. The Brazil lump ore, Australia lump ore and South Africa pellet ore can be reduced completely in 50 min, and then carburized. But iron carbide cannot form from the South Africa lump ore, even though it can be reduced to iron in 90 min. The reduction rate of porous iron ore was fast and the structure of formed iron was also porous and abundant in micropores, being favourable to the reaction of carburization. After the reduction, the volume distribution of 0.5~3.5 nm micropores increased doubly, the tendency of the micropore size distribution is similar to that in iron ores, especially, the volume distribution of 3.5~13 nm micropore increased notablely. The micropore size and volume distribution have large effect on the ore reduction rate and the reaction of iron carbide formation.

Effects of Ultrasonic Wave on the Properties and Structure of Cassava Starch

ZHAO Yi-ling;LIAO Dan-kui;ZHANG You-quan;TONG Zhang-fa

. 2007, 7(6):  1138-1143. 

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Cassava starch was treated by ultrasonic wave. The effects of ultrasonic wave on the physicochemical properties, crystal structure, granular morphology, amylose content and thermal properties of cassava starch were investigated respectively. The results indicated that apparent viscosity and shear-thinning nature decreased, and retrogradation increased with increasing ultrasonic treatment time. Starch paste showed higher transparency and lower enzyme resistance when ultrasonic treatment time was less than 2 min. However, continuously increasing ultrasonic treatment time would lead to increasing of transparency and decreasing of enzyme resistance. FT-IR and XRD analysis suggested that ultrasonic wave would not destroy functional groups of starch, but damaged crystal structure, as a result crystallinity decreased. SEM images indicated that more and more starch granules were fractured; many dents and splits were found on the surface of starch granules after ultrasonic treatment. Starch-iodine analysis suggested that ultrasonic wave destroyed amylopectin and starch chains, amylase content increased and degree of polymerization decreased. DSC spectra suggested that gelatinization enthalpy remained the same, but gelatinization temperature rised.

Preparation of Biodiesel from Waste Oil Catalyzed with Brфnsted Acid Ionic Liquid

YI Wu-lang;HAN Ming-han;WU Qin;JIN Yong

. 2007, 7(6):  1144-1148. 

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The preparation of biodiesel from waste oil and methanol catalyzed by a Br?nsted acidic ionic liquid with an alkane sulfonic acid group as catalyst was studied under different reaction conditions. When the molar ratio of methanol to waste oil is 12 and the mass ratio of ionic liquid to oil is 0.02, 86.8% fatty acid methyl ester is obtained in the products after the reaction has taken place at 140℃ for 5 h. Under the same reaction conditions, the ionic liquid has no obvious change of catalytic activity after using 9 times. So the catalyst shows great reusability and good catalytic activity for preparation of biodiesel from waste oil.

Degradation of Methyl Orange by Electrochemical Oxidation with Different Oxide Anodes

WANG Shu-yong;LI Gang

. 2007, 7(6):  1149-1153. 

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The electrochemical oxidation of methyl orange was carried out using Ti/SnO2+Sb2O3 and Ti/SnO2+Sb2O3/PbO2 electrodes as anodes, respectively. The degradation rate, instantaneous current efficiency (ICE) and chemical oxygen demand (COD) were determined for the different electrodes. It is found that the reaction rate of the electrochemical oxidation of methyl orange on the different anodes follows the first-order reaction kinetics, and the apparent rate constants at 25℃ are 0.147 and 2.43×10-2 min-1 for Ti/SnO2+Sb2O3 and Ti/SnO2+Sb2O3/PbO2 anodes, respectively. When the degradation has lasted for 30 min with the Ti/SnO2+Sb2O3 anode, the concentration of methyl orange decreases from 0.305 mmol/L to 4.89×10-3 mmol/L and the conversion rate of methyl orange is 98.4%, while decreases only to 0.14 mmol/L with the Ti/SnO2+Sb2O3/PbO2 anode at same conditions and the conversion is 55.0%. ICE for the Ti/SnO2+Sb2O3 anode is more than that for the Ti/SnO2+Sb2O3 PbO2 anode. The Ti/SnO2+Sb2O3 anode with a higher oxygen evolution potential presents high reaction rate and current efficiency for the elimination of methyl orange.

Effects of Catalysts on Combustion of Pulverized Coal by Synthetical Thermo-gravimetric Analysis

ZHANG Hui;GUO Zhan-cheng;WANG Zhi;XU De-ping

. 2007, 7(6):  1154-1158. 

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The effects of Ce2(CO3)3, CeO2, CaCO3, CaO, four kinds of catalysts, on combustion property of pulverized coal were investigated with a synthetical thermal analyzer, especially the influences of addition content and particle size of Ce2(CO3)3 powder during the combustion process of pulverized coal. The results show that Ce2(CO3)3 powder can increase the combustion process of pulverized coal, and lower its ignition point temperature. The pulverized coal ignition temperature can be reduced about 30℃ when the addition content of Ce2(CO3)3 powder is 1.0%. With the addition content of Ce2(CO3)3 powder increasing and its particle size decreasing, the catalytic effect becomes more eminent when its addition content is less than 1.0%.

Inhibition of Photocatalytic Activity of Titania Whiskers with Ultraviolet Deposition

Wen Gao-fei;YANG Zhu-hong;LI Wei;FENG Xin;LU Xiao-hua

. 2007, 7(6):  1159-1162. 

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A method for the inhibition of photocatalytic activity of the titania whiskers was reported in the paper. The stability and dispersion behavior of the passivated titania whiskers were studied. The results show that the photocatalytic activity of the passivated titania whiskers is only 10% of fresh titania whiskers, and the stability and dispersion behavior of the passivated titania whiskers are better than those of fresh titania whiskers. Even if calcined or washed by organic solvent and inorganic solvent in ultrasonic cleaner, the photocatalytic activity of the passivated titania whiskers cannot be changed. XRD, SEM and ICP techniques were used to characterize the passivated titania whiskers. The results suggest that the main reason of the inhibition is calcium carbonate deposition on the surface of titania whiskers.

生化工程专栏

Metabolic Flux Analysis of Bacillus licheniformis for Synthesis of b-Mannanase

LIU Zhao-hui;QI Wei;HE Zhi-min

. 2007, 7(6):  1163-1168. 

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Intracellular metabolic activity of Bacillus licheniformis for synthesis of b-mannanase was studied based on metabolic flux analysis (MFA). A metabolic network of Bacillus licheniformis for synthesis of b-mannanase was established, and the metabolic mass balance based stoichiometric model of the above network was also built. The metabolic flux model was solved by using linear programming optimization based on the target functions of the metabolic flux distribution of maximum b-mannanase synthesis and maximum cell density. Furthermore, the maximum theoretical yield of b-mannanase from Bacillus licheniformis was calculated as 57.87%. Finally, five important metabolic nodes in the metabolic network of Bacillus licheniformis were analyzed, and two nodes, ribulose 5-phosphate and oxalacetate, were characterized as non-rigid ones, which would guide us to enhance the productivity of b-mannanase using gene engineering.

Screening of a Lipase with High Enantioselectivity and Its Application in the Resolution of Racemic Ibuprofen

GUO Hua-ying;TANG Liang-hua;SU Min;XUE Jian-ping;XU Xu-ping

. 2007, 7(6):  1169-1174. 

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In order to resolute racemic ibuprofen enantioselectively in organic solvent, a strain of Penicillium expansum TS414 was screened, which could secrete a lipase with perfect enantioselectivity. The main variables affecting the resolution reaction by the lipase were optimized, including water content, temperature, organic solvent, enzyme concentration, structure and concentration of alcohol. Under the optimum conditions of 6.46 mmol/L ibuprofen, 53.3 g/L lipase, 40 mmol/L 1-propanol, 15 mL isooctane, 0.5%(j) water, and 60℃ for 50 h, the total conversion rate and the enantiomeric ratio could reach 42% and 429.63, respectively. The results showed that Penicillium expansum TS414 lipase could be used as a perfect tool enzyme with high enantioselectivity and had a great potential for commercial applications in the resolution of racemic ibuprofen.

Optimization of Biosurfactant-producing Conditions with Bacillus sp. W112 and Characterization of the Biosurfactant

WU Zuo-jun;LI Bao-zhen;YUAN Hong-li

. 2007, 7(6):  1175-1180. 

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A strain of Bacillus sp. was isolated from the oil-water mixture samples of oil field. The fermentation supernatant revealed high surface activity, and the biosurfactant showed high stability against heat, pH and salinity. The optimum conditions of biosurfactant-producing were determined as follows: 30 g/L maltose as carbon substrate, 1.5 g/L mixture of (NH4)SO4+NaNO3 (1:2, volumetric ratio) as nitrogen substrate, temperature 37℃, 100 mL medium in 500 mL total vessel volume, pH 7.0 and 10%(j) inoculums. The biosurfactant was obtained by acid precipitation and chemical extraction method. IR analysis showed that the biosurfactant contained peptide bond and fatty acid bond, which indicated that the biosurfactant was lipopeptide.

A Carbon-controlling Strategy to Enhancement of the Expression for Human IFNb-HSA Fusion Protein with Pichia pastoris

ZHANG Hong-bin;DOU Wen-fang;XU Hong-yu;JIN Jian;LI Hua-zhong;XU Zheng-hong

. 2007, 7(6):  1181-1186. 

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The relationship between the starvation culture and relative cell viability in the growth phase and their effects on the expression of recombinant human IFNb-HSA fusion protein in Pichia pastoris KM71/IH were observed in 5 L fermentor experiments. The results showed that the starvation culture in which glycerol as the solo carbon source was exhausted resulted in the decrease of relative cell viability and expression of recombinant hIFNb-HSA fusion protein. The strategy of mannitol addition in the transition stage not only eliminated the inhibition effect on methanol induction by residual glycerol, but also kept higher relative cell viability (>97%) and then improved the yield of human IFNb-HSA fusion protein. The maximum yield and maximum hIFNb-HSA productivity reached 37.3 mg/L and 0.78 mg/(L×h) respectively, which were 92.3% and 44.4% higher than those in the control.

Expressing Optimization of argE Gene and Mechanism Analysis of Zn2+ Feeding Time and Its Concentration

LI Huan;CHEN Yue;WENG Qiu-ping;ZHU Da-wei;WEI Ping

. 2007, 7(6):  1187-1191. 

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The cellular location of target gene argE expressed in recombinant BL21(DE3)-pET22b-argE was determined. The effects of Zn2+ effect feeding time and concentration on the biomass production and gene expression product activity were studied. The mechanism of Zn2+ effect was analyzed. The results showed that N-acetylornithine deacetylase coded by argE gene was over expressed and most of it was expressed as insoluble inclusion body, only a little as soluble expression. 1.0 g/L Mg2+ concentration improved both the biomass production and enzyme activity greatly. With different concentrations and feeding times, Zn2+ could bring about different influences. In contrast to the inhibition of feeding Zn2+ at the cultivation beginning, addition of 1.0 mg/L Zn2+ after inducing for 2.5 h with 1.0% lactose reduced the inhibition on the growth and increased the enzyme activity. SDS-PAGE analysis and enzyme activity measurement proved that Zn2+ did not influence the expression rate, but the catalyst site of recombinant NAOase.

Effects of Light Intensity and Fe3+ Concentration on Microcystis aeruginosa Growth and Microcystin Production in a Photobioreactor

ZHANG Yi-feng;KANG Rui-juan;CONG Wei;MA Run-yu

. 2007, 7(6):  1192-1196. 

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The optimal conditions of microcystis aeruginosa cultured in a photobioreactor were established. The effects of light intensity and Fe3+ concentration on Microcystis aeruginosa growth and microcystin production in the photobioreactor were studied. The Fe3+ concentration in the culture medium changed between 0~500 mmol/L. The results showed that the cells growth and microcystin-LR production were both affected by changing Fe3+ concentration and light intensity. Biomass and chlorophyll were limited when Fe3+ concentration was below 0.1 μmol/L and reached the maximum when Fe3+ concentration was 100 μmol/L. Then they both dropped down when Fe3+ concentration was further increased. The maximum production of microcystin-LR was obtained at 10 mmol/L Fe3+ concentration. The effect of light intensity on microcystin-LR production was also studied under the optimal Fe3+ concentration. The results showed that the optimal light intensity for microcystin-LR production was 30 mmol/(m2×s).

Optimization of Culture Medium and Photosynthetic Characteristics of Platymonas subcordiformis

LIU Yuan;CHEN Zhao-an;LU Homg-bin;LIU Chang-fa;JIN Mei-fang;GUO Zhen;ZHANG Wei

. 2007, 7(6):  1197-1201. 

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Uniform design method was applied for culture medium optimization of a marine microalga, Platymonas subcordiformis. Using the uniform design table U10*(108), three key medium ingredients (nitrate-N, phosphate-P, and Tris-HAc buffer) were chosen as optimizing factors. Their effects on the pH variation, photochemical activity of photosystem II (PSII) and light harvesting pigment of microalga cultures were examined. The optimum medium ingredients were obtained as follows: NO3--N 9.5 mmol/L, PO43--P 0.34 mmol/L, Tris-HAc buffer 6.7 mmol/L, under which P. subcordiformis cells could grow efficiently, reaching a density of (8.28±0.51)×106 mL-1 within 15 d. It was found that the buffer Tris-HAc maintained a stable pH value, and high NO3--N level improved the photosynthetic efficiency and growth rate of cells.

Effects of Phenylalanine and Phenylpyruvic Acid on Biosynthesis of Phenyllactic Acid with Lactobacillus sp. SK007

LI Xing-fewng;JIANG Bo;PAN Bei-lei;MU Wan-meng;ZHANG Tao

. 2007, 7(6):  1202-1206. 

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One strain, Lactobacillus sp. SK007, which was isolated from Chinese traditional pickles, could produce the highest phenyllactic acid (PLA) yield (0.55 mmol/L) in the Man-Rogosa-Sharpe (MRS) medium. The PLA production from phenylalanine (Phe) by Lactobacillus sp. SK007 was investigated. It was found that Phe remained 94%, but the intermediate metabolite phenylpyruvic acid (PPA) stayed below the detection level. These results indicated that the transamination of Phe to PPA is a rate-limiting step. The bottleneck was overcome using PPA to replace Phe as substrate. Furthermore, the fermentation conditions of PLA production from PPA by Lactobacillus sp. SK007 were optimized. Under the optimal conditions of 18.3 mmol/L PPA, and 24 h cultivation at 30℃ without shaking, PLA concentration reached 10.25 mmol/L.

Purification and Properties of e-Poly-L-lysine-degrading Enzyme from Kitasatospora sp. MY5-36

FENG Xiao-hai;XU Xiao-ying;YAO zhong;XU Hong

. 2007, 7(6):  1207-1211. 

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A e-poly-L-lysine-degrading (PLD) enzyme from Kitasatospora sp. MY5-36 was purified and characterized. The enzyme was purified through three steps of anion exchange chromatography including DEAE-Sepharose, Source 15Q and Mono Q. The overall purification multiple was 500 with an enzymatic activity recovery rate of 40.7%. As detected by SDS-PAGE and gel filtration chromatography, the PLD enzyme of this strain was composed of two homogeneous subunits. The molecular weight of subunit and holoenzymes were 43.6 and 87.0 kDa, respectively. Its optimal pH value was 7.0 and the optimal temperature 30℃. The activity of PLD enzyme was kept stable when the enzyme was conserved in the temperature range from 20 to 40℃, however, it declined rapidly in the temperature range from 50 to 60℃. The Km value was 0.216 mmol/L and the Vmax 0.112 mmol/(L×min). The PLD enzyme is a kind of metalloenzymes, and can be activated by Co2+ and inhibited by Ca2+.

Fermentation of Acetone and Butanol Coupled with Enzymatic Hydrolysis of Steam Exploded Cornstalk Stover in a Membrane Reactor

LI Dong-min;CHEN Hong-zhang

. 2007, 7(6):  1212-1216. 

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Enzymatic hydrolysis of steam-exploded cornstalk stover in a membrane reactor coupled with fermentation of acetone and butanol by Clostridium acetobutylicum AS1.132 was investigated. A butanol yield of 0.14 g/g (cellulose+hemicellulose) and the maximum butanol productivity of 0.31 g/(L×h) were obtained with the dilution rate of 0.075 h-1. The butanol yield per unit enzymes was 0.0039 g/IU which was 1.5 times as much as that by batch fermentation and the cost of enzymes decreased greatly. The ratio of butanol, acetone and ethanol was 65.3:24.3:10.4. The conversion rates of cellulose and hemicellulose were 72% and 80%, respectively. The inhibition of enzymatic hydrolysate on cellulase which could be used circularly was lightened greatly. Enzymatic hydrolysate was fed into the fermentor continuously to keep the concentration of solvent low, as a result, the inhibition of solvent, especially butanol, on microbial activity was effectively eliminated, and the fermentation cycle became longer.

Energy-produced Components in Calotropis gigantea

LI Rui;ZENG Jian-li;WANG Xiao-dong;ZHAO Bing;WANG Yu-chun

. 2007, 7(6):  1217-1220. 

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The energy-produced components in Calotropis gigantean, a plant growing in saline and alkaline land, have been systematically investigated. According to the results from GC-MS analysis, there are alkyl hydrocarbons from C7H16 to C44H90 in the plant juice. The content of C21H44 in the total alkyl hydrocarbons is the highest as 52.98%, the contents from C7H16 to C17H36 and from C29H60 to C44H90 are 10.28% and 37.45% respectively. The content of total alkyl hydrocarbons is 0.02%~0.03% in the juice and 0.01%~0.015% in the entire plant. Based on the national standard examination of coals, for whole plant, the results show ash content 8.12%, the volatile matter 68.82%, gross calorific value 17.93 MJ/kg, sulfur content only 0.55%, the total content of carbon and hydrogen 49.51% which is higher than that of Calotropis procera reported. In the plant, total cellulose is the highest in the stem and lowest in the bark, the saponification values of the bark is the highest, the contents of polysaccharide and protein are higher than those of juice.

材料工程专栏

A Novel Ni/C Composite Powder and Its Derived Thermal Sprayed Coating

WU Jiu-ling;LI Zeng;ZHANG Wei-gang

. 2007, 7(6):  1221-1228. 

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Ni/C composite particles consisting of mesophase carbon microbeads (MCMB) coated with a metal layer of nickel are produced and studied. When the new particles and their derived coating are compared with the normal ones, a great difference between them has been found. At the same time, the chemical stability of the coating is also studied by oxidation in air at 400℃ for various periods of time, as well as catalysis of nickel on the oxidation of graphite. A suitable coating can be obtained from the new spherical particles with less energy consumption and under more loose operation conditions. Hardness variation of the derived coating is kept within 30%, which is much smaller compared with the normal Ni/C coating. It is found that the maximum hardness appears after heating for 20 h, and then the hardness steps down to a steady value. During the oxidation, the increased mass of the mixture of nickel and graphite reaches its maximum, 0.25% between 25~28 h, which differs from the mass change that would occur under the assumption that nickel should have no effect on the oxidation of graphite.

Preparation, Structure and Soot Oxidation Performance of Nano-scaled Perovskite-type La1-xKxCoO3 Catalyst

LIU Shu-mo;WEI Ji-ying;JIANG Feng;ZUO Min;CAI Bing

. 2007, 7(6):  1229-1235. 

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Diesel engines are currently facing serious challenges to reduce exhaust pollution, especially the particulate soot, which is harmful to human beings. Simultaneous removal of NOx and soot has been studied for the past two decades and perovskite-type LaMO3 (M= Co, Mn) proved to be an effective catalyst. In this work, a series of nanostructured K+-doped perovskite-type La1-xKxCoO3 catalysts were prepared by sol-gel method using sucrose as complex agent. The influences of K+ doping and high temperature calcining on the structure and soot oxidation activity of the catalyst were studied by XRD and TPR techniques. The results indicated that nanostructured perovskite catalyst with single phase formed at the temperature higher than 600℃, and it showed much higher activity for soot oxidation in the mixed gas of NO and O2. K+ could be inserted into perovskite lattices, enhancing the phase transformation from cubic to rhombohedral structure. The resulting phase was more stable at high temperatures. The catalyst of La0.90K0.10CoO3 (about 30 nm) calcined at 700℃ with rhombohedral structure exhibited the highest activity for soot oxidation in 0.5% NO and 5% O2, which led to the low Tig and Tend as 240 and 387℃ respectively, almost 200℃ lower than the temperature of soot combustion without the catalyst. In the reaction system of soot-NO-O2, both the crystal structure and particle size of the perovskite catalysts were most influential, and the rhombohedral structure together with small size perhaps was beneficial to soot oxidation.

Photoelectrochemical Investigation of K2Ti6O13 Thin Film Prepared by Sol-Gel Method

HU Yu-yan;QIAN Qing-hua;LI Wei;LIU Chang;FENG Xin;LU Xiao-hua

. 2007, 7(6):  1236-1242. 

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The sol-gel method was used to prepare potassium hexatitanate and titania thin films on indium-tin oxide (ITO) substrate by dip-coating. With this method, the connection between K2Ti6O13 film and ITO glass substrate was strong and maintained a good electrical contact. Electrochemical method combined with ultraviolet-visible light absorption spectrometry was used to ascertain the electronic band structure of K2Ti6O13 film. TiO2 film was used to verify the feasibility of this method and compared with K2Ti6O13 film as a reference system of structure and performance characteristic. The results show that the band gap energy of K2Ti6O13 film electrode estimated from the ultraviolet spectrum was 3.05 eV which is lower than that of K2Ti6O13 particle (3.45 eV) and TiO2 film (3.22 eV). K2Ti6O13 film possessed visible light response capability. The lower edge of the conduction band of the potassium hexatitanate was approximately -0.77 V (vs. NHE) lower than that of anatase (-0.61 V vs. NHE), which indicates that K2Ti6O13 film electrode possesses stronger reducibility. The potassium hexatitanate had the feasibility of hydrogen production from water photolysis. The electrochemical measurement also reveals that K2Ti6O13 is a stable photocatalyst with effective separation of photogenerated charge carriers. Consequently, the K2Ti6O13 film is a promising material in the field of hydrogen manufacturing with visible light.

Preparation and Anti-coking Property of SiO2/S Coating on HP40 Tube

ZHOU Jian-xin;XU Hong;ZHANG Li;LIU Jing-lei;QI Xue-gui;PENG Bo

. 2007, 7(6):  1243-1248. 

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SiO2/S coating was prepared on the inner surface of an HP40 tube using dimethyldisulfide and tetraethylorthosilicate by atmospheric pressure chemical vapor deposition (APCVD) to alleviate catalytic coking on the inner surface of radiant tube for ethylene production in petrochemical plants. The comparative coking experiments with the coated and uncoated HP40 tubes were carried out under the same cracking conditions. SiO2/S coating was compact and had excellent anti-coking property. The coke on the coated HP40 tube was about 22% of that on the uncoated HP40 tube, and only small granular coke was deposited on the coated HP40 tube. However, the filamentous coke formed on the uncoated HP40 tube. The thermal stability of SiO2/S coating was satisfactory at cracking temperature, and the anti-coking property of SiO2/S coating was still over 60% after 3 coking and decoking cycles.

Visual Study on the Formation of Naproxen Particles with Different Morphologies

JIN Kang-kang;CHENG Jing;WEN Li-xiong;CHEN Jian-feng

. 2007, 7(6):  1249-1253. 

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A new technology was proposed to visually study the crystallization morphologies of naproxen particles synthesized by reaction-precipitation. The effects of surfactant type and concentration, naproxen concentration and reacting temperature on the morphology and size of the synthesized naproxen particles were investigated, and the growth mechanism of particles was discussed briefly. It was found that needle-like, spherical, butterfly-like and rod-like crystals of naproxen particles could be obtained respectively in the presence of Tween-80, PVP, Karomic-90 or CMC. Naproxen concentration, surfactant concentration and reacting temperature could also influence the particle size significantly.

Photocatalytic Activity of Zn-doped TiO2 Nanocrystals Synthesized by Diffusion Flame Combustion

ZHAO Yin;LI Chun-zhong;LIU Xiu-hong;SHI Li-yi

. 2007, 7(6):  1254-1258. 

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Zinc-doped TiO2 nanocrystals were synthesized by diffusion flame method with titanium tetrachloride and zinc aceetylacetonate as raw materials, and their structures were characterized by XRD, ICP-AES and XPS. The catalytic activity of Zn-doped TiO2 nanocrystals on photodegradation of Rhodamine B was investigated under UV light irradiation and the mechanism was elaborated to demonstrate the improved photocatalytic activity of Zn-doped TiO2 nanocrystals. It is found that dopant Zn2+ ions are mostly located on the surface of TiO2 nanoparticle, and small ZnO nuclei dispersing randomly on the anatase TiO2 surface form, which has less effect on the crystalline phase and particle size. The best photocatalytic activity of 0.21%(mol) Zn-doped TiO2 nanoparticles is attributed to the enhancement of electron and hole segregation because of the difference in the energy band positions of TiO2 and ZnO.

Preparation of Microfiltration Carbon Membrane by Pyrolysis of Phenol-Formaldehyde Resin

WEI Wei;HU Hao-quan;QIN Guo-tong;YOU Long-bo

. 2007, 7(6):  1259-1262. 

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The microfiltration carbon membrane was prepared by pyrolysis of novolac phenol-formaldehyde resin. The effects of carbonization conditions, including carbonization temperature, heating rate, holding time and protective gas flow rate, and activation conditions on the carbon membrane properties were systematically investigated. The mass loss during carbonization was characterized by thermogravimetric analysis. The gas bubble pressure method was used to determine the pore size distribution of the carbon membrane. The results indicate that the gas permeation rate and the mean pore size of carbon membrane decrease with the increase of carbonization temperature. The gas permeation rate decreases from 1.84′10-5 mol/(m2×s×Pa) to 1.14′10-5 mol/(m2×s×Pa) and the mean pore size decreases from 0.61 mm to 0.54 mm with the carbonization temperature from 650℃ to 950℃. The carbon membrane carbonized at 350℃ shows the lowest strength. Above 350℃, high carbonization temperature results in high strength carbon membrane. The heating rate, holding time and protective gas flow rate have little effect on the carbon membrane properties. Activation of carbon membrane with CO2 increases the pore size of membrane. With CO2 content increasing from 12.5% to 50%, the gas permeation rate increases from 7.0′10-5 mol/(m2×s×Pa) to 1.68′10-4 mol/(m2×s×Pa) and the mean pore size increases from 1.54 mm to 1.96 mm.