The Chinese Journal of Process Engineering

Gas Holdup in a Bubble Column at Elevated Temperature with Organic Liquid Solutions

HUANG Juan DAI Gan-ce

. 2008, 8(2): 209-216.

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Gas holdup (eg) was studied in a bubble column operated at elevated temperature. The column is 300 mm in diameter and 1.2 m in height, and the distributor has four nozzles with large diameter. The adjusted mixture of acetic acid (the solvent of the reaction) and p-, m-, o-xylene (homologous compound mixture of the reactant) was employed as the liquid phase, considering the oxidation of p-xylene. The experiments were conducted systematically to investigate the influences of superficial gas velocity (Ug), temperature, composition of the organic solutions on eg. The research ranges of superficial gas velocity and temperature were 0.009~0.224 m/s and 11~99℃ respectively. The effect of superficial gas velocity was summed up by eg-Ugn, the value of n varied with temperature, that is, n=0.6 at ambient temperature, n=0.4~0.5 at elevated temperature and 0.2 at the nearing boiling point. There was a transition point at eg-T curve, so the effect of temperature on eg can be classified into two stages, one far from the boiling point and another near to the boiling point. eg was nearly a constant at the first stage and increased significantly at the second. The critical temperature was varied with the superficial gas velocity, it was 90℃ in the range of 0.009~0.045 m/s and 70℃ from 0.072 to 0.18 m/s. As to the effect of the composition of organic liquid solutions, eg increased at first, and decreased when the mass concentration of acetic acid was higher than 80% in tap water-acetic acid system, eg in the acetic acid-xylene solution was lower than that of the water-acetic acid, while solutions had the same acetic acid content, eg in partly soluble water-acetic acid-xylene system was lower than that of the completely soluble system. A gas holdup correlation implicating the effects of various factors was given.

Radial Distribution and Axial Development of Solids Hold-up in the Riser Coupled with Fluidized Bed

WANG De-wu LU Chun-xi

. 2008, 8(2): 217-223.

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A large scale cold model experimental setup of a compound reactor mainly composed of riser and fluidized bed was established according to the olefin reduction technology with auxiliary reactor for FCC naphtha upgrading. The radial distribution of solids hold-up in the riser of the compound reactor was measured in different operating conditions by PV-4A optical fiber density apparatus. The experimental results show that the radial distribution of solids hold-up is the core-annular structure with lower solids hold-up in the center region and higher in the wall region. In the axial direction, the radial local solids hold-up gradually decreases in the particle accelerating region, tends to smooth in the fully-developed region, and then increases in the particle back-mixing region. The radial local solids hold-up decreases with increase of superficial gas velocity or decrease of solids flux. The static bed height of particles in the fluidized bed located atop the riser has effects on the radial distribution of solids hold-up in the back-mixing region, but has little effect on that of particle accelerating and fully-developed regions. The maximum solids hold-up in the particle back-mixing region appears to be close at the non-dimensional radial position f=r/R=0.7, and the axial distributions of radial local solids hold-up in different cross-sections in particle back-mixing region are not similar. According to the analysis of the radial non-uniformity index of local solids hold-up, the uniformity degree of radial distribution of local solids hold-up decreases in the following order: the fully developed region > the back-mixing region > the accelerating region. Furthermore, empirical model for estimating the radial distributions of local solids hold-up in the riser was established based on the experimental data and theoretical analysis. The error between the calculated data of the model and the experimental data is less than 6%.

Fluidization Characteristics of Scrap Printed Circuit Boards Particles with Different Average Sizes

WANG Ming-hua GUO Qing-jie LIU Bao-yong

. 2008, 8(2): 224-229.

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The experiments were carried out in a fluidized bed of 56 mm in diameter and 1600 mm in height to determine the fluidization characteristics of four types of scrap printed circuit board particles with different average sizes. The results show that the fluidization characteristics of scrap printed circuit board particles depend on the average size and type of particles. The scrap printed circuit boards particles, belonging to Geldart A group with strong viscous force, whose fluidization was similar to fluidization of Geldart C, was difficult to fluidize. Whereas, the scrap printed circuit board particles belonging to Geldart B can be fluidized smoothly. Based on the experimental data and the analysis of acting forces, the minimum fluidization velocity is calculated by three correlations. It was found that the minimum fluidization velocities calculated by Ergun Equation approached 94.5%, 114% and 91.8% of the experimental minimum fluidization velocities for the b, c and d particles of Geldart B group. For the scrap printed circuit board particles belonging to Geldart A group, a model of force balance about cohesive particles should be developed to evaluate fluidization characteristics with cohesive particles.

Study on Agglomerate Breaking and Feeding of Superfine Particles in Fluidized Bed

ShaoWu Yin LIU Chuan-ping

. 2008, 8(2): 230-234.

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The agglomerate breaking and feeding of superfine particles in a fluidized bed with 40 mm I.D. were investigated by using superfine silicon particles with 10 mm average diameter as material under addition of coarse particles, vibration and stirring force. The effects of influential factors, including vibration strength, rotational speed of stirrer, diameter and mass percentage of coarse particles, and velocity of nitrogen, on the feeding rate and the ratio of particles to gas were analyzed. With the superfine silicon particles of 10 mm average diameter, the experimental results indicated that the optimal operation conditions for the feeding in fluidized bed were obtained as follows: the rotational speed of stirrer 90 r/min, the frequency of vibration 13.9 Hz, the average diameter of added coarse particles 300 mm, and their added mass percentage 20%. Under the above conditions, the particle agglomerates can be effectively broken, slugging and channeling in the fluidized bed eliminated, and critical fluidization velocity and entrainment velocity lowered. As a result, the feeding effect of superfine particles to the bed can be obviously improved.

Effect of Dispersed Oil Phases with Different Properties on CO2 Absorption Process

LU Su-min MA You-guang SHEN Shu-hua ZHU Chun-ying

. 2008, 8(2): 235-239.

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The absorption of CO2 into emulsions was investigated using four organic solvents with different properties as dispersed phase, toluene, cyclohexane, n-heptane and n-butanol in a thermostatic reactor. The experimental results show that the absorption rate is closely related to the interfacial properties. When surfactants are not added, the absorption rates of CO2 in the emulsions of toluene, cyclohexane and n-heptane corresponding to their spreading behavior at the gas-liquid interface are: toluene > n-heptane > cyclohexane. Furthermore, a lower absorption rate than that in pure water is observed at low oil volume fraction due to the additional resistance by the spread oil film. The oil volume fractions for toluene, cyclohexane and n-heptane are 0.02, 0.08 and 0.04 respectively at the lowest value of J/J0. The emulsifier promotes the stabilization of the emulsion, however, it increases the resistance of mass transfer due to the adhesion of the surfactants to the gas-liquid and liquid-liquid interfaces, leading to an even lower absorption rate than in the dispersed system without addition of surfactants. Contrary to toluene, cyclohexane and n-heptane, variation of an initial rise following subsequent decline of the absorption rate is found in the partially miscible n-butanol-water system in the range of concentration discussed, and the maximum value of J/J0 coincides with the solubility of n-butanol in water.

Synthesis and Application of Copolymeric Dispersant of Acrylic Acid-Styrene Sulfonic Sodium-Hydroxyethyl Methacrylate

CHEN Zhen REN Tian-rui

. 2008, 8(2): 240-247.

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The copolymeric dispersant of acrylic acid-styrene sulfonic sodium-2-hydroxyethyl methacrylate was synthesized with acrylic acid (AA), styrene sulfonic sodium (SSS) and 2-hydroxyethyl methacrylate (HEMA) as monomers. The effects of the dispersant on dispersion of BaSO4 granules and herbicide atrazine water dispersible granules (WDG) were studied. At the same time, SEM and laser diffraction particle size analyzer were applied to analyze the properties of suspensions. The experimental results showed that the copolymer had an excellent dispersion efficiency when the molar ratio of AA, SSS and HEMA is 4:1:0.6, reaction temperature 70 ℃, 12% of the mass fraction of initiator in total monomers, and reaction time 2 h, the suspension percentage of BaSO4 is 98.99% and that of 75% atrazine WDG 95.47%, being close to that of 75% atrazine WDG comprising Rhodia T36.

Influence of Copolymer of Dodecyl Methacrylate-Acrylic Acid on Transfer of Cu2+ Ions through Emulsion Liquid Membrane

. 2008, 8(2): 248-252.

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The effects of separation conditions of emulsion liquid membrane on the transfer rate of Cu2+ are studied. The membrane is composed of an amphiphilic copolymer of dodecyl methacrylate and acrylic acid [P(DM-AA)], sorbitan monooleate (Span-80), di(2-ethylhexyl) phosphoric acid (HDEHP), kerosene, paraffin oil, and an aqueous H2SO4 solution, which are used as membrane stabilizer, surfactant, carrier, solvent and internal phase, respectively. The results show that the transfer rate of Cu2+ is significantly improved by the steric stabilization of the amphiphilic copolymer. The optimum conditions are determined as follows: P(DM-AA) 3.0%, Span-80 4.0%, HDEHP 3.0%, paraffin oil 6.0%, volumetric ratio of membrane phase to feed phase 1:10, [H+]=1.0 mol/L, contact time 6 min, and stirring rate 200~300 r/min. Moreover, the structure of the emulsion liquid membrane and the mechanism of a coupled counter-transport are also discussed.

Deep Desiliconization of Mid-high Aluminate Concentration Solution with Calcium Sulfate

LI Yu-guo WANG Ya-jing ZHAI Yu-chun

. 2008, 8(2): 253-257.

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The deep desilication of mid-high aluminate concentration solution was investigated with the addition of calcium sulfate dihydrate. The desiliconization efficiency of the Al2O3 concentration (200, 180, and 150 g/L) was affected by the temperature, time, CaSO4×2H2O concentration, molar ratio of alumina to silicon (ak), and stirring speed. Under the conditions of 95℃, ak=1.5, stirring speed of 867 r/min and CCaSO4×2H2O=30 g/L, after 2 h, to the Al2O3 concentration of 200 g/L, the silica module was above 3815, to the Al2O3 concentration of 180 g/L, the silica module was above 4082, and to the Al2O3 concentration of 150 g/L, the silica module was above 4260. The residue was analyzed by XRD technique. The desiliconization mechanism with calcium sulfate dehydrate was also discussed in the text.

Extraction of Rare Earths from Mixed Bastnaesite-Monazite Concentrate by Carbochlorination Reaction with AlCl3 as Defluorinating Agent

YU Xiu-lan WANG Zhi-chang WANG Yong DONG De-qian LIU Jia

. 2008, 8(2): 258-262.

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Carbochlorination reaction mechanism was investigated for extraction of rare earths from mixed bastnaesite-monazite concentrate with AlCl3 as defluorination agent. The effects of reaction time, reaction temperature and defluorination agent on the rare earth extractive yield were investigated. The results show that higher yield (93%) can be obtained at 600℃ with AlCl3 as defluorination agent and the rare earth extractive yield can reach 97.4% at 800℃ for 2 h. The dilute hydrochloric acid-insoluble residue obtained by each carbochlorination reaction was analyzed by XRD method. The reaction mechanism of eliminating fluorine and extracting rare earths from mixed bastnaesite-monazite concentrate by carbochlorination reaction with AlCl3 as defluorination agent was discussed.

Synthesis of 1,2-Isopropylidene Glycerol with Cation Exchange Resin Modified by AlCl3

LI Xiao-yan XIAO Guo-min WEI Rui-ping GE Dong-juan

. 2008, 8(2): 263-266.

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Anhydrous AlCl3, cation exchange resin and cation exchange resin modified by AlCl3 were investigated in condensation of glycerol and acetone. As shown in the results of Hammett indicator and pyridine adsorption infrared spectra, the acid strength and catalytic activity of the cation exchange resin were improved after being modified by AlCl3. The highest yield (90.9%) of 1,2-isopropylidene glycerol was obtained under the conditions of molar ratio of glycerol to acetone of 1:3, catalyst concentration of 10%(w), reaction time of 11 h, and 82℃ temperature with the catalyst cation exchange resin modified by AlCl3.

Effects of Polymeric Flocculants on Settlement of Bayer Red Mud Generated from Chinese Diaspore Bauxite

ZHANG Kun-yu HU Hui-ping ZHANG Li-juan CHEN Qi-yuan

. 2008, 8(2): 267-273.

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A systematic investigation on the interaction between Bayer red mud particles generated from Chinese diaspore bauxite and commercial sodium polyacrylate (SPA) or polyacrylamide (PAM) was performed by red mud settling tests, conductivity-pH titration and Ubbelodhe viscosimetric measurement. The results indicate that the treatment with red mud by SPA gives a lower red mud settling rate and lower supernatant turbidity than the treatment with red mud by PAM. There is an optimum polymer dosage of 300 g/t (based on the weight of dry red mud) when red mud slurry is treated by SPA or PAM, so "bridging" adsorption is one of the main interactions between red mud and SPA or PAM. With the increase of NaOH concentration, the hydrolysis degree of PAM dissolved in NaOH solution increases and its molecular weight almost does not change, but the settling rate of red mud treated by it drops rapidly. The settling rate of red mud treated by PAM dissolved in 10 g/L NaOH solution is 0.61 m/h while by PAM dissolved in distilled water it is 1.31 m/h, because the adsorption ability of the hydrolyzed PAM onto red mud surface declines primarily due to the formation of ?CONH2~?COO-~?CONH2 intramolecular hydrogen bond.

Hydrate Formation in a Methane-Tert-butylamine-Water System

LI Dong-liang LIANG De-qing FAN Shuan-shi

. 2008, 8(2): 274-279.

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The formation of hydrate in a methane-tBuNH2 (tert-butylamine)-water system without stirring was studied at 6℃ at different pressures (2.50, 3.50 and 4.50 MPa) and at different initialization reaction quantities (30.0 and 100.0 g). The results showed that the hydrate in this system was pasty, and the reaction rate with CH4 increased when the reaction pressure increased. There is no clear relationship between the reaction pressure and the final CH4 storage capacity (the ratio of volume of CH4 in hydrate to that of initialization reactant at standard condition, mL/mL) while 30.0 g sample was loaded in the reactor, and the final CH4 storage capacity decreased when the reaction pressure increased while 100.0 g sample was loaded in the reactor (5.4 mL/mL at 2.50 MPa, 0.9 mL/mL at 4.50 MPa). Two hydrate structures, Structure VI and Structure II, may form simultaneously in the reaction, and the ratio of the amount of tBuNH2 Structure VI hydrate to that of CH4/tBuNH2 Structure II hydrate may increase in the end of the reaction time, and the methane-tBuNH2-water system at xtBuNH2=9.3% is not suitable to store the CH4 by formation of the hydrate as the maximal CH4 storage capacity is only 5.4 mL/mL. It is considered that hydrate formation mechanism may undergo three steps: contacting and gathering of reactants molecules, forming of hydrate framework, and growing of hydrate.

Morphology Control in Preparation Process of Spherical Manganese Carbonate Particles

SU Hai-feng QU Xiong WEN Yan-xuan TONG Zhang-fa LI Xuan-hai

. 2008, 8(2): 280-284.

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Monodisperse spherical MnCO3 particles were prepared by low temperature chemical precipitation method using manganese sulfate and ammonium bicarbonate as raw materials, and the diameters of the microspheres were mainly 5~6 mm. The effects of temperature, pH, concentration of MnSO4 and NH4HCO3 on the morphology and size of MnCO3 particles were investigated, and characterized by scanning electron microscope. The growth mechanism of the particles was also discussed. The results show that the solution pH value was the key factor in controlling the morphology of MnCO3 particles. When the pH was decreased from 8.0 to 7.0, the morphology of MnCO3 particles was transformed from cubic to spherical shape. With reducing reaction temperature, the dispersibility of MnCO3 particles became better and their shape also gradually trended towards unification. But the size of the particles became larger. In the experimental range, the morphology and size of MnCO3 particles had no obvious effect when MnSO4 concentration was changed from 0.05 to 0.4 mol/L. It was beneficial to the formation of spherical MnCO3 particles when NH4HCO3 concentration was between 0.1 and 0.3 mol/L. XRD patterns indicated that the precipitates was MnCO3 crystals with trigonal system, calcite crystalloid.

Rapid Synthesis of 5-Substituted-1-acetyl-2-thiohydantoin Derivatives under Microwave Irradiation

ZHOU Jia-dong CAO Fei ZHANG Xiao-long LIN Huan WEI Ping

. 2008, 8(2): 285-289.

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Nine 5-substituted-1-acetyl-2-thiohydantoin derivatives were rapidly synthesized by the reaction of ammonium thiocyanate and a-amino acids using acetic anhydride and acetic acid as mixed solvent under microwave irradiation. The effects of microwave reaction time, microwave reaction temperature, ammonium thiocyanate dosage and acetic anhydride dosage on their yields were examined. The optimum reaction conditions were obtained as follows: 10 mmol a-amino acid, 16 mmol ammonium thiocyanate, 9 mL acetic anhydride (1 mL acetic acid), 100℃, 2 min. Compared with conventional heating method, the reaction time was shortened from 30 to 2 min, and the yield was raised from 55.2%~79.5% to 85.0%~93.0%. The structures of all products were characterized by 1H-NMR, IR spectra and elemental analysis.

Hydrothermal Stability of Sodium 3,5,6-Trichloropyridin-2-ol in Sub- and Supercritical Water

CUI Hong-you YAO De

. 2008, 8(2): 290-294.

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The stability of sodium 3,5,6-trichloropyridin-2-ol (STCP) in water at elevated temperatures has implications for the preparation of STCP by hydrolyzing 2,3,5,6-tetrachloropyridine (TCP) and STCP waste treatment processes. Therefore, thermal stability of STCP was investigated in sub- and supercritical water at 240~400℃, 15~30 MPa and residence time from 2 to 12 min in a continuous tubular reactor. The results show that STCP is stable at 280℃ and 25 MPa, but it begins to decompose with the further rising of the temperature, pressure and residence time. Degradation products had an apparent characteristic absorption peak at 520 nm, which was caused by the keto form for STCP. In addition, the reaction temperature, pressure and different ratios of raw materials for preparing STCP by hydrolyzing TCP were studied under elevated pressures in a batch reactor. The results indicate that hydrolysis temperature is a crucial factor to control the reaction rate. The preferred condition for preparing STCP by TCP hydrolysis is that TCP reacts with NaOH for 3 h with a mole ratio of TCP to NaOH 1:4 at 140℃, reaching a STCP yield of higher than 95% with purity of STCP up to 99%.

Effects of Potassium Chloride Aerosol on Ni-based Monolithic Catalyst for Reforming of Biomass Fuel Gas

GAO Yan WANG Tie-jun WANG Chen-guang WU Chuang-zhi MA Long-long

. 2008, 8(2): 295-299.

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Ni-MgO/g-Al2O3 monolithic catalyst was prepared by a two-step impregnation method. To investigate the deactivation of catalysts by alkali chloride aerosol, a 300 mL/min nitrogen flow containing KCl aerosol particles was led through a catalyst bed at 800℃. The catalysts before and after deposition were characterized by ICP, BET and SEM. The results showed that the activity of the catalysts had decreased due to the reduction of the surface area of the catalyst after deposition of KCl aerosol. Accordingly, the conversion rate of CH4 and H2/CO decreased. Under the reaction condition of biomass fuel gas containing KCl aerosol at 750℃, the conversion rate of CH4 decreased from 87.24% to 32% after 17 h reaction, besides, volumetric fraction in the outlet gas of H2 decreased from 35.09% to 26.74%, that of CO decreased from 33.19% to 29.78%, however, no deactivation appeared under the condition of biomass fuel gas without KCl aerosol.

Preparation of Precipitated Silica Powder from Iron Ore Tailing

YU Hong-hao XUE Xiang-xin YANG Da-wei

. 2008, 8(2): 300-304.

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The preparation of precipitated silica particles via chemical precipitation using iron ore tailing and sodium hydroxide as raw materials was successfully demonstrated. The experimental conditions for synthesizing precipitated silica particles were examined in detail. The phase composition, morphology and structure of the synthesized particles were characterized by X-ray diffraction (XRD), FT-IR spectrometry, scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-ray fluorescence analysis. The SiO2 purity in the precipitated silica product was 92.3%, determined by X-ray fluorescence analysis. The chemical structure of precipitated silica was hydrated silicon oxide through FT-IR analysis. The structure of precipitated silica was amorphous by XRD analysis. The SEM and TEM micrographs showed that the shape of precipitated silica particles was nearly spherical, and their average grain diameter less than 150 nm. The measured results of chemical and physical properties of precipitated silica powder were obtained as followed: the specific surface area was 108 m2/g, pH in the 10% suspending liquid 5.5~6.0, and loss on ignition at 1000℃ was 6.16%. The product could be comparable with the requirements of HG/T 3061-1999 industrial product standard.

Economic, Energy and Environment Analysis on Biomass Collection Process

XING Ai-hua LIU Gang WANG Yao WEI Fei JIN Yong

. 2008, 8(2): 305-313.

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The mathematical models simulating the collection cost, energy consumption and environmental pollution of biomass collection process have been established based on the island distribution of straw. The effect of straw compression on collection cost, energy consumption and environmental discharge is discussed for single resource island collection process. The equations for calculating critical collection amount and critical transportation distance are established. The parameter sensitivity analysis for collection cost and energy consumption is investigated respectively. The result shows that collection cost of unit mass straw is proportional to transportation distance and the inverted square root of resource density whether the straw is compressed or not. The collection cost without compression is proportional to the square root of the collection amount, while it decreases first and then increases as the collection amount increases for straw transportation following the compression. The sensitivity analysis shows that transportation fee rate, purchase price and transportation distance are the sensitive parameters for collection cost, which will lead to over ±17% fluctuation of collection cost when these parameters change in ±50%. The ±20% fluctuation of transportation oil consumption per tonne and kilometer and transportation distance will lead to ±17% change for energy consumption.

Numerical Simulation on the Slagging Co-combustion of Coal and Biomass

XiaoHan Wang ZHAO Dai-qing ZENG Xiao-jun

. 2008, 8(2): 314-320.

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Based on the new idea of unification of co-combustion and slagging combustion technologies, the pyrolysis and burning kinetic models of biomass were implanted into the WBSF-PCC (Wall Burning and Slag Flow in Pulverized Coal Combustion) code, which includes several sub-models of particle deposition, wall burning and slag flow. The co-combustion characteristics in a cylindrical combustor with 150 kg/h total feeding rate of coal and wood powder under different mixing ratios were simulated numerically. The results showed that adding wood powder at 25% mass fraction can increase the temperature at the initial stage of combustion, which is helpful to utilize the front space of the combustor; adding wood powder at 25% mass fraction can increase the reaction rate at the initial combustion stage, the coal ignitability is improved, the burnout efficiency is enhanced by about 5% of spatial and deposition particles, which is helpful for coal particles to burn entirely and for combustion devices to minimize its dimensions or sizes. The theoretic analysis in this work has proved that unification of co-combustion and slagging combustion technologies and its industrial application are feasible.

Application of Substance Flow Analysis in Eco-industrial Park Planning

HU Shan-ying CHEN Ding-jiang

. 2008, 8(2): 321-326.

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Carbon element flows in a natural gas chemical industrial park are analyzed in detail and the utilization efficiency of element C is 65.1%. Most loss of element C happens in ammonia syngas production and methanol syngas production. To the processes with low efficiency of element C, causes of resource wasting and potentials of resource saving are identified. Based on the result and combining the planning of an eco-industrial park, a retrofit scheme is proposed. Two measures are adopted, building material flow coupling between processes, which may reduce raw material consumption by using wastes, and improving syngas production technology to raise element C utilization efficiency. The analysis result to element C flows of the retrofit scheme shows that element C utilization efficiency is much increased up to 88.1%, and CO2 emission is obviously reduced.

Preparation of Uniform-sized PELA Microspheres Containing Lysozyme by Membrane Emulsification and Double Emulsion-Solvent Removal Method

LAI Bo WEI Qiang SUN Chun-bao MA Guang-hui SU Zhi-guo

. 2008, 8(2): 327-332.

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Relatively uniform-sized lysozyme-loaded microspheres made of monomethoxy poly(ethylene glycol)-b-poly-DL-lactide (PELA) were prepared by combining premix membrane emulsification and double emulsion-solvent removal method. The effects of polymer composition and organic solvent type on the protein encapsulation efficiency and bioactivity were studied. The results showed that the PELA microspheres could be efficiently prepared by this method, and the coefficient of variation (CV) value of microspheres was less than 20% under the volumetric ratio of oil phase to outer aqueous phase 1:6. This method was universal for different polymer compositions and types of organic solvent. PELA microspheres loading lysozyme were prepared through a W/O/W double emulsion-solvent diffusion method using ethyl acetate as organic solvent. The microspheres had a high protein entrapment rate over 95.7% and full preservation of bioactivity of entrapped lysozyme.

Cultivation of Candida utilis WSH02-08 for Production of Glutathione by Amino Acids Addition Strategy

WU Xiao-yu DU Guo-cheng CHEN Jian

. 2008, 8(2): 333-338.

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The effects of amino acids addition on glutathione production of C. utilis WSH 02-08 were investigated. The results showed that two-step amino acids addition could greatly increase GSH production level. The optimal conditions for two-step amino acids addition strategy were obtained as follows: 4 mmol/L L-cysteine was added after 10 h cultivation, and a mixture of three amino acids (L-glutamic acid, L-cysteine and glycine) was added at 16 h. The optimum concentrations of those three amino acids (8 mmol/L L-glutamic acid, 8 mmol/L L-cysteine and 12 mmol/L glycine) were obtained by orthogonal experiments, GSH concentration and intracellular GSH content reached to 290.1 mg/L and 3.22%. Combining the amino acids addition strategy and high-cell-density cultivation by glucose feeding, 20 mmol/L L-cysteine was added at 36 h, and then the three amino acids (40 mmol/L L-glutamic acid, 40 mmol/L L-cysteine and 60 mmol/L glycine) were added at 45 h, GSH concentration and intracellular GSH content reached to 1725.3 mg/L and 3.29%, which were higher (111.4% and 100.6%) than those of high-cell-density cultivation (816 mg/L and 1.64%).

Immobilization of Povidone-Iodine on Silica Gel Particles and Sterilization Activity

LIU Qing GAO Bao-jiao YANG Ying

. 2008, 8(2): 339-344.

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N-vinyl pyrrolidone (NVP) was grafted on silica gel particles, resulting in the grafted particles of poly(pyrrolidone)/SiO2 (PVP/SiO2). The complexation reaction between PVP/SiO2 and iodine was conducted in ethanol as solvent. The immobilization of povidone-iodine on SiO2 was realized, and the functional particles of PVP-I2/SiO2 were obtained. The effects of various influential factors on the complexation reaction were examined. The structure and composition of the functionalized particles of PVP-I2/SiO2 were characterized with Fourier transform infrared spectrum and chemical analysis method. The sterilization property of PVP-I2/SiO2 was studied with Escherichia coil as a disease-leading bacterium and the method of live bacteria plate counting. The experimental results show that the suitable temperature for the complexation reaction is 60℃, and the complexation degree increases with the increase of iodine concentration. At 60℃ a maximum complexation degree of 0.16%(w) is obtained as iodine is dissolved in ethanol in saturated state. The PVP-I2/SiO2 particles have strong sterilization activity. Their sterilization rate can reach 100% as they contact with the cell suspension, which has a concentration of 1′109 CFU/mL, only at a dosage of 5 g/L and for 3 min. TTC-dehydrogenase determination and measurement of extracellular DNA and RNA have fully verified the sterilization mechanism of PVP-I2/SiO2.

Effect of Plasmid Distribution Gene parDE on the Stability of Formate Dehydrogenase NADH Regeneration System

ZHANG Gang YANG Guang LI Chun CAO Zhu-an

. 2008, 8(2): 345-349.

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The recombinant bacterium F6 was constructed with the recombinant plasmid pDK7-fdh-parDE which contained the genes parDE and fdh. While the FY and F-1 were constructed with the recombinant plasmids pDK6-fdh and pMAL-p2X-fdh only containing fdh, respectively. K. oxytoca M5al is the initial bacterium of F6, FY and F-1. The effect of parDE on plasmid stability and FDH (formate dehydrogenase) enzyme activity was also studied. It was shown that 93% F-1 and 78% FY lost the plasmids while only 3% F6 lost the plasmids after 160 generations. Furthermore, the FDH specific enzyme activity of F6 decreased from 2.82 to 2.77 U/mg, only 1.77% decreased, while the enzyme activity of FY decreased significantly from 2.69 to 2.02 U/mg, and F-1 decreased from 2.63 to 1.33 U/mg, close to the enzyme activity of M5al after 160 generations. It was indicated that the recombinant bacteria with the parDE had obvious advantage on plasmid stability, and FDH enzyme activity was higher than the recombinant bacteria without the parDE.

Hydrolytic Model of Chitosanases Produced with Aspergillus CJ22-326

CHEN Xiao-e FANG Xu-bo YU Hui XIA Wen-shui

. 2008, 8(2): 350-354.

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Hydrolytic model of two chitosanases of chitosan, ChiB and ChiA, separated and purified from a culture filtrate of Aspergillus CJ22-326, was investigated. The experimental results on the viscosity changes of reaction solution and analysis of enzymatic hydrolysis products by TLC and HPLC showed that ChiB was an endo-type cleavage enzyme. ChiB decreased the viscosity of reaction solution significantly, hydrolyzed b-(1,4) glucosidic bond of chitosan at random. Using chitooligosaccharides as substrates, ChiB acted on GlcN?GlcN and did not act on GlcNAc?GlcNAc glucosidic bond. Chitooligosaccharides with the degree of polymerization below 5 could not be hydrolyzed by ChiB. Hydrolysis products of chitopentose were chitobiose and chitotriose. The latter was the main product of chitohexaose hydrolysis. ChiA was an exo-type amino-glucosidase which mainly cleaved glucosamine residue from non-reducing end of chitosan or chitooligosaccharides. ChiA acted only on GlcN?GlcN and GlcN?GlcNAc glucosidic bonds.

Synthesis of Fatty Acid Ethyl Esters from Soybean Oil by Immobilized Lipase from Candida sp. 99-125

HOU Ji-xian LU Ji-ke NIE Kai-li WANG Fang TAN Tian-wei

. 2008, 8(2): 355-358.

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The objective of the work was to study the enzymatic production of fatty acid ethyl esters (FAEEs) which were synthesized from soybean oil and ethanol by the immobilized lipase Candida sp. 99-125. The effects of different conditions such as water content, solvent content, enzyme amount and temperature on the esterification reaction were studied for optimizing the process. With a three-stepwise addition of ethanol into the reaction system, the maximum yield of FAEEs of 96.8% was obtained after 12 h under the following optimized conditions: 12.5%(w) water, based on the weight of soybean oil, 3 mL/g n-hexane as solvent, 20%(w) lipase and temperature 40℃. Moreover, the immobilized lipase could be used continuously for 14 batches with high yield of FAEEs over 70%.

Preparation of a Fe-modified Polyacrylonitrile Fibrous Photocatalyst and Its Application in Degradation of Reactive Red MS

DONG Yong-chun DU Fang MA Han-xiao HAN Zhen-bang CAO Ya-nan

. 2008, 8(2): 359-365.

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A modified Fe-polyacrylonitrile fibrous photocatalyst (Fe-PAN) was prepared by a reaction between PAN fibers containing amidoxime group and ferric chloride at room temperature and characterized using SEM, XRD and FT-IR techniques, and then used as a heterogeneous catalyst for the photocatalytic degradation of Reactive Red MS in water. Some factors affecting the degradation of Reactive Red MS such as catalyst dosage, catalyst loading (CFe-PAN) and solution pH were investigated with respect to the decoloration rate. Additionally, the photocatalytic degradation of Reactive Red MS was examined by UV-Vis spectrometry. The results indicated that amidoxime groups from PAN fibers were able to ligate ferric ions in solution, and increasing amidoxime groups or ferric ion concentration led to the high CFe-PAN catalysts. Moreover, increasing catalyst dosage and CFe-PAN significantly accelerated the dye degradation. Fe-PAN catalyst showed high photocatalytic activity at pH≤6.0 solution, however, its activity was reduced insignificantly at alkaline medium. Photocatalytic degradation of Reactive Red MS in the presence of Fe-PAN catalyst followed the pseudo-first order kinetics, and increasing catalyst dosage and CFe-PAN also enhanced the degradation rate constant.

Preparation and Properties of Water-borne Cationic Polyurethane

Ni Zhong Qiaolong Yuan

. 2008, 8(2): 366-371.

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Water-borne cationic polyurethanes were synthesized by five polyesters and polyethers glycol, four diisocyanates and hydrophilic chain-extender, N-methyl diethanol amine, with different polymerization processes. The results showed that the addition polymerization process of the introduction of the diisocyanate into the mixture of polyol and hydrophilic chain-extender was appropriate, and the stable water-borne cationic polyurethane was prepared. The properties of cationic polyurethane emulsions and their films dispersed at 35℃ were better than that at 70℃. Especially, the tensile strength of the sample could be increased much more 3 times when the cationomer was dispersed in 35℃. The research results on the content of hydrophilic chain-extender and hard segment in cationic polyurethane indicated that the particle size of cationic polyurethane latex was decreased and the stability of the latex was augmented with increase of the addition of the hydrophilic chain-extender when the content of hard segment got to 30%(w) upwards, and the tensile strength of the cationic polyurethane film was also increased. The thermal analysis of the cationic polyurethane elucidated that the ordered structures of the hard and soft segments in the cationic polyurethane film were destroyed when the content of hard segment reached up to 40%(w), and that the glass transition temperature of the cationic polyurethane film was more than 15℃.

Fabrication and Characterization of C/PTFE Cathode for Hydrogen Peroxide Synthesis through Alkaline Fuel Cell Reactor

SONG Tian-shun XU Fu-yuan CHEN Ying-wen SHEN Shu-bao

. 2008, 8(2): 372-377.

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A fabricating method of C-polytetraflouroethylene cathode, C/PTFE, for hydrogen peroxide synthesis through alkaline fuel cell reactor was studied, and the primary influential factors of fabrication were investigated. The performances of cathodes at different fabricating conditions were evaluated by the voltage-current curve, concentration curve of H2O2 and AC impendence diagram. The results showed that cathode performances were much affected by the pressure, carbon content and PTFE content in the flattening layer. When the pressure was 10.0 MPa, carbon content 0.2 g, and PTFE content 50%, the maximum current and high output of H2O2 were produced, and the concentration of H2O2 reached 56 mmol/L after 2.5 h.

Preparation of Foam Glass-ceramic from Oil Shale Residue

FEBG Zong-yu XUE Xiang-xin

. 2008, 8(2): 378-383.

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Foam glass-ceramic was prepared with oil shale residue as major raw material, adding other auxiliary materials. The effects of various factors on the properties of foam glass-ceramics were analyzed. The results showed that the optimal contents of both foaming agent calcium carbonate and stabilizing agent sodium phosphate were 4% and 6% respectively. The optimal process conditions of heat treatment were obtained as follows: the foaming temperature of 1080℃, foaming time of 15 min, and heating rate of 14℃/min. The foaming and crystallization processes of samples were completed after heat treatment including preheating, sintering, foaming, stabilizing and annealing. In addition, the foaming process needed higher temperature and was held in a short time. The samples were transformed into foam glass-ceramic as shown by the analysis of XRD, SEM and FT-IR. The primary crystallization phase was augite, and the minor crystallization phase anorthite. These crystals formed in fibroid minicrystal structure, and complected one another. Compared with related materials, the properties of foam glass-ceramic integrated the advantages of high mechanical strength and light weight, heat preservation, and thermal insulation.

Structure and Magnetism of Fe Nanowires Array Prepared by Electrochemical Deposition with AAO Template

GU Feng LI Chun-zhong

. 2008, 8(2): 384-388.

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A two-step electrochemical anodizing approach was introduced to prepare porous anodic aluminum oxide (AAO) membrane in sulfuric acid solution. The SEM image shows that the pore diameter is 20 nm, interpore spacing 50 nm and pore density 4.5×1010 pores/cm2. Ordered Fe nanowire arrays embedded in AAO template have been fabricated by pulse voltage electrodeposition of Fe into the pores of AAO. The Rietveld results show that the preferred orientation of those nanowires with diameter of 20 nm is crystal plane of Fe (110) and preferred orientation factor is 0.30. The easy magnetization axis of this system is perpendicular to the membrane. When the outer magnetic field is perpendicular to the membrane, the squareness is as high as 0.914, and coercivity 1656 Oe.

Preparation and Optical Properties of ZnO Nano- and Micro-crystals with Different Morphologies

ZHOU Li-min WANG Yi-ping GUANG Qun-wu LIU Shi-rong

. 2008, 8(2): 389-393.

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ZnO nano- and micro-crystals with various morphologies including hexagonal columns, brush-like assemblies, hexagonal cones and inverted cone pairs were prepared by a solvothermal method. The effects of different solvents and pH levels on ZnO morphology were investigated. X-ray powder diffraction analysis indicated that all ZnO products had wurtzite crystal structure. The results of scanning electron microscopy and transmission electron microscopy showed that ZnO had the diameters in the range of 100 nm~15 mm and the lengths of 150 nm~60 mm. Moreover, ZnO morphology was greatly influenced by solvents as well as pH values. The UV-Vis absorbance spectra showed that ZnO crystal samples had the similar excitonic character with the absorption peak at 375 nm. The photoluminescence spectra showed a strong UV peak at 385 nm and a broad green emission peak at 505 nm, respecitively. These results indicated that ZnO products had excellent optical properties and high crystal quality.

Synthesis of Fe3O4 Microspheres with Hollow Structure by Soft Template Method

YU Ling-jie YUAN Fang-li WANG Xi

. 2008, 8(2): 394-398.

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Fe3O4 microspheres with hollow structure were prepared by the glycol solvothermal method using FeCl3×6H2O and NH4Ac as reactants. The structure, morphology and magnetism property of synthesized Fe3O4 were characterized using XRD, SEM, TEM and VSM. The effects of reaction time and temperature on the morphology of product were also studied. It is revealed that 200℃ and 12 h were suitable synthetic parameters for the particles with morphology being uniform and high dispersion at an average size about 400 nm. The product obtained exhibits a ferromagnetic behavior with saturation magnetization value of 73.51 emu/g. It is not only a simple but also effective approach to synthesize Fe3O4 microspheres with hollow structures in one step using ammonia bubbles generated in situ as soft template.

Preparation and Characterization of Tin-Graphite Composite Material with Carbothermal Reduction

WU Feng LI Yan-hong WU Chuan BAI Ying

. 2008, 8(2): 399-403.

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Tin-graphite composite material was prepared by carbothermal reduction method from SnO2 and graphite in Ar atmosphere. The material was characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). Electrochemical lithium insertion- extraction character of the material was determined by constant current charge-discharge, slow scanning cyclic voltammetry (CV), and electrochemical impedance spectrometry (EIS) methods. The results of XRD and SEM show that spherical metallic Sn particles reduced from SnO2 are separated in graphite. The initial lithium insertion-extraction special capacities of the material can reach to 887 and 615 mA×h/g respectively, and initial Coulombic efficiency 69%. Even after 15 cycles, tin-graphite composite material still shows high extraction special capacities as 387 mA×h/g, the high capacity retention at the 15th cycle as 63% and an excellent cycle performance with only 2.5% capacity loss per cycle.

Investigation on Time-dependent Performance of Membrane Electrode for Ozone Production

. 2008, 8(2): 404-408.

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The solid polymer electrolyte composite membrane electrode was prepared by using Nafion membrane, lead dioxide and carbon-supported platinum as the electrolyte, anodic and cathodic catalyst, respectively. Morphology and structure studies of the membrane electrode with scanning electron microscopy and X-ray diffraction showed that with ozone production for 220 h, there was about 6% a-PbO2 in the lead dioxide anode. Meanwhile, the bonding structure of anode became loose and there were a lot of re-crystallized nano-sized particles on the surface of anode. The current efficiency of ozone evolution on the electrode decreased, and its voltage increased with time. It was found that the main reason for the degradations was change in morphology and structure of catalyst layer caused by recrystallization of lead dioxide, and the other reason was change in structure of lead dioxide induced by reduction of Pb2+ to Pb4+. With 180 h running of the electrode，the voltage and current efficiency of the electrode became steady, the reason might be the structure of anodic catalyst layer tending to remain stable.

Research Progress in Fixation and Transformation of CO2 Using Ionic Liquids

YUAN Xiao-liang ZHANG Yan-qiang LAN Ling YAN Li-jun ZHANG Suo-jiang

. 2008, 8(2): 409-416.

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Research progress in application of CO2 fixation and transformation using ionic liquids (ILs) has been systematically discussed. There are three kinds of CO2 fixation using ILs according to structures of ionic liquids and mechanism of fixation, which are CO2 fixation using common ILs, CO2 fixation using task-specific ILs and fixation-conversion of CO2 using ILs. The mechanism of CO2 fixation using common ionic liquids is physical absorption and that of task-specific ILs is chemical process, while fixation and conversion of CO2 using ILs will be a good way from flue gas to new chemicals. Design and synthesis of high effective task-specific ILs to achieve the goal of fixation and conversion of CO2 will be a key step applied in CO2 fixation.

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