Sep 2007, Volume 1 Issue 3

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  • ZHU Gang, WANG Jinqu, ZHANG Yan, LU Jinming, XIU Jinghai
    ZSM-35 zeolite membranes were prepared on porous stainless steel tubes with silica sol and tetraethoxysilane as silica source, and with 1-butylamine and ethylenediamine as templates, respectively. The characterization of X-ray diffraction (XRD) and scanning electron microscopy (SEM) showed that the membranes prepared with ethylenediamine as the template displayed growth orientation with their crystal planes (h00) parallel to the support surface. The single-component permeability tests of H2, N2 and C3H8 showed that the membranes synthesized with ethylenediamine as the template, compared with those with 1-butylamine as the template, showed relatively higher permeation rates and ideal separation factors, and above their corresponding ideal Knudsen diffusion factors, which might be attributed to the different growth orientation of zeolite membranes synthesized with different templates.
  • XU Jian, LIU Weijun, LIU Honglai, HU Ying
    A simple solution-phase approach has been demonstrated for the large-scale synthesis of silver nanowires with diameters in the range of 15 25 nm, and lengths usually in the range of tens of micrometers. In the presence of gemini surfactant 1,3-bis(cetyldimethylammonium) propane dibromide (16-3-16), the growth of silver could be directed into a highly anisotropic mode to form uniform nanowires with aspect ratios up to about 2,000. X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), energy-dispersive X-ray (EDX), X-ray powder diffraction (XRD), electron diffraction (ED), and UV-vis absorption spectroscopy, were used to characterize the as-prepared silver nanowires, indicating the formation of a highly pure phase, good crystallinity, as well as a uniform diameter.
  • WANG Neng, DING Enyong, CHENG Rongshi
    In order to improve the dispersibility of cellulose nanocrystal (CNC) particles, three different grafted reactions of acetylation, hydroxyethylation and hydroxypropylation were introduced to modify the CNC surface. The main advantages of these methods were the simple and easily controlled reaction conditions, and the dispersibility of the resulting products was distinctly improved. The properties of the modified CNC were characterized by means of Fourier transform infrared spectroscopy (FT-IR), 13C nuclear magnetic resonance (NMR), transmission electron microscopy (TEM) and thermogravimetric analyses (TGA). The results indicated that after desiccation, the modification products could be dispersed again in the proper solvents by ultrasonic treatments, and the diameter of their particles had no obvious changes. However, their thermal degradation behaviors were quite different. The initial decomposition temperature of the modified products via hydroxyethylation or hydroxypropylation was lower than that of modified products via acetylation.
  • WEI Shanshan, ZHANG Yi, XU Jiarui
    PAA/Fe3O4 nanocomposites were prepared by mixing nano-Fe3O4 and polyacrylic acid (PAA) ethanol solution and then evaporating the solvent. The materials were characterized by transmission electron microscope (TEM), Fourier transform infrared spectroscope (FTIR), thermogravimetry analysis (TGA), dynamic ultra-micro hardness tester (DUMHT) and superconducting quantum interference device (SQUID) magnetometer. Results showed that PAA coordinated with nano-Fe3O4 to form a cross-linking structure. The presence of nano-Fe3O4 enhanced the thermal stability of the nanocomposite. The elasticity and hardness of the nanocomposite increased, and the indentation depth reduced with the increase of Fe3O4 content in the composites. The nanocomposites showed superparamagnetic properties at 300 K.
  • RUN Mingtao, SONG Hongzan, WANG Yingjin, YAO Chenguang, GAO Jungang
    The rheological, phase morphologic, thermal and mechanical properties of poly(trimethylene terephthalate)/metallocene polyethylene (PTT/mPE) blends in the presence of ethylene propylene diene monomer copolymer grafted with maleic anhydride (EPDM-g-MAH) as compatibilizer are studied by means of a capillary rheometer, scanning electron microscopy (SEM), differential scanning calorimetry (DSC) and thermogravimetric analyzer (TGA). Results suggest that the compatibility of PTT/mPE blends is improved greatly after the addition of a compatibilizer. The radius of the dispersed phase in the system decreases greatly when the compatibilizer is added into the blend. When the amount of compatibilizer exceeds 8 wt-%, the size of dispersed phase becomes larger again. This phenomena could be attributed to the higher viscosity of the EPDM-g-MAH phase, which is dispersed more difficulty in the PTT phase of lower viscosity, thus the mixing efficiency is apparently decreased during the melt blending process. Moreover, the melt viscosity of the blend reaches the maximal value in case of 4 wt-% compatibilizer content, above which it would decrease again. This result is associated with the generation of more and bigger dispersed phase inside the bulk phase, thus the grafting efficiency at the interface is decreased, which could result in lower viscosity. The DSC results suggest that the mPE component shows a nucleating effect, and could increase the overall degree and rate of PTT crystallization, while the addition of a compatibilizer might slightly diminish these effects. In addition, the blend with 4 wt-% compatibilizer shows the best thermal stability. Furthermore, the Izod impact strength and the tensile strength at room temperature of the blend are also markedly improved by the addition of a 4 8 wt-% compatibilizer.
  • DU Wen, CHEN Changhua
    Erythromycin biosynthesis is a highly complicated process, which involves both primary metabolism and secondary metabolism. The specific activities of the key enzymes related to glucose metabolism such as hexose kinase (HK), glucose-6-phosphate dehydrogenase (6-PDH), phosphofructokinase (PFK), and isocitrate dehydrogenase (ICD), were determined in Saccharopolyspora erythraea. The specific activities of the enzymes involved in secondary metabolism, such as methylmalonyl-coenzyme A mutase (MCM) and methylmalonyl-coenzyme A transcarboxylase (MCT), were detected as well. Some organic acids contained in fermentation broth were also analyzed. The results show that Co2+ is able to increase erythromycin biosynthesis. It maybe due to Co2+ improving the specific activities of methylmalonyl-coenzyme A mutase and methylmalonyl-coenzyme A transcarboxylase. Meanwhile, it also enhances the flux of the glucose metabolism pathway.
  • XUE Ping, WU Tao
    A heterogeneous chiral catalyst Fe(III)-CS (chitosan) complex/mesoporous molecular sieve SBA-15 (Santa Barbara Amorphous) was prepared. The asymmetric transfer hydrogenations of prochiral acetophenone and 4-methyl-2-pentanone to corresponding chiral alcohols were carried out on Fe-CS/SBA-15 at atmosphere pressure using 2-propanol as hydrogen donor. Effects of Fe content in catalyst, reaction temperature, reaction time and promoter KOH concentration on the conversion of substrates and enantioselectivity were investigated. Fe-CS/SBA-15 with 2.2% mass fraction Fe exhibits considerable enantioselectivity and catalytic activity for the asymmetric transfer hydrogenations of aromatic ketone and aliphatic ketone. Under optimal reaction conditions: KOH concentration 0.03 mol/L, reaction temperature 70ºC and reaction time 4 h, enantiomer excess (ee) of (R)-1-phenylethanol and conversion of acetophenone can reach 87.4% and 27.7%, respectively. Under the above KOH concentration and reaction temperature and reaction time of 8 h, the ee of (R)-4-methyl-2-pentanol and conversion 4-methyl-2-pentanone amounted to 50.2% and 25.5%, respectively.
  • HUANG Qunwu, WANG Yiping, LI Jinhua
    A new method of preparing CuO solar selective absorbing coating for medium temperature is presented. After pretreatment, brass was overlaid with CuO by chemical plating. The effects of reactant concentration, reaction temperature and reaction time on the absorptivity of CuO coating were investigated. The optimized condition of preparing CuO coating was obtained. The CuO coating was analyzed with X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM). In order to prolong the period of use, the CuO coating was protected by TiO2. The experiment shows that the TiO2/CuO coating is more heat-resistant, acid-resistant, and wear resistant than CuO coating, without losing absorptivity markedly. The TiO2 coating can reduce emissivity and protect the CuO coating.
  • LIU Zhenfa, WANG Yanji, GAO Yuhua, ZHANG Lihui
    Polyaspartic acid (PASP) composite, a scale inhibitor, was prepared from PASP, itaconic acid–acrylic acid–acrylic ester (IA-AA-AE) terpolymer and 2-phosphonobutane- 1,2,4-tricarboxylic acid (PBTCA). The scale inhibition of PASP composite and the effect of its synergism with a magnetic field on scale inhibition were investigated. Calcium carbonate crystals in scale samples were characterized by means of SEM and XRD. The static and dynamic experiments show that the chelating function of PASP composite for Ca2+ can be enhanced by synergism with a magnetic field. Under Ca2+ 650 mg/L, HCO3- 1,300 mg/L and PASP composite 4 mg/L, the scale inhibition rate of PASP composite in magnetic water can increase by 10% in static state and by 20% in dynamic experiments. Scanning electron microscope (SEM) and X-ray diffraction (XRD) results show that calcite and aragonite can be completely transformed into vaterite by using PASP composite.
  • WANG Jingang, HU Jinbang, WANG Daobin, DUAN Zhenya
    A kinetic model of the pozzolanic reaction for the preparation of flue gas desulfurizers from fly ash and Ca(OH)2 was deduced on the basis of solid phase reaction kinetic theory. Kinetic expressions and parameters were obtained and verified by experiment. A comparison of calculated results with experimental results showed that precision in kinetic expressions was good. The apparent reaction rate constants of the pozzolanic reaction could be raised by increasing the specific surface area of fly ash and the hydration temperature, and by using a suitable additive.
  • CAI Jun, WANG Li, TONG Lige, SUN Shufeng, WU Ping
    This paper presents a novel method that uses the interception effect of gradient magnetic field on oxygen molecules to realize enrichment. The use of two opposite magnetic poles of two magnets at a certain distance forms a magnetic space having a field intensity gradient near its borders. When air injected into the magnetic space outflows from the magnetic space via its borders, oxygen molecules in the air will experience the interception effect of the gradient magnetic field, but nitrogen molecules will outflow from the magnetic space without hindrance. Thus, continuous oxygen enrichment is realized. The enrichment degree of oxygen reaches 0.65% when the inlet and outlet air flows are 40 mL/min and 20 mL/min, respectively, and the gas temperature is 298 K and the maximal product of magnetic flux density and its gradient is 563 T2/m (the distance between two magnetic poles is 1 mm). When the gas temperature rises to 343 K, the enrichment degree drops to 0.32%; and when the maximal product of magnetic flux density and field intensity gradient drops to 101 T2/m (the distance between two magnetic poles is 4 mm), the enrichment degree drops to 0.23%. The experimental results show that there is an optimal ratio between the inlet air flow and the outlet air flow. Under the experimental conditions in this paper, the value is about 2.0. It is demonstrated that the method presented in this paper can continuously enrich oxygen and has a higher enrichment degree than other oxygen-enrichment methods using magnetic separation.
  • WEN Lixiong, WANG Qing, ZHENG Tianyuan, CHEN Jianfeng
    In this study, two different methods were applied to disperse hollow silica nanoparticles (HSNP); one employed polyethylenimine (PEI) as the dispersant during the synthesis processes for preparing HSNP, while the other added PEI into suspensions of the prepared HSNP and used milling treatment to achieve the desired dispersion. It was found that adding PEI during the synthesis process of HSNP had no noticeable improvement in the dispersion, while adding PEI into suspensions of the prepared HSNP and utilizing milling treatment resulted in remarkable dispersion improvement. Therefore, the latter was chosen as the method in dispersing HSNP suspensions. The adsorption of PEI on the surface of HSNP and the stability of the aqueous suspensions was investigated. The results indicated that the adsorption of PEI on the surface of HSNP would increase the repulsive energy among particles, hence reducing the agglomeration of HSNP and improving the stability of the aqueous suspensions. The change of HSNP’s ζ potential after adding PEI and the relationship between the adsorbed amount of PEI and pH were also investigated.
  • WEN Zhen, DANG Zhi, ZHU Zhixin, ZONG Minhua
    The solubilization behavior of methyl orange as a solvation probe in multiple systems composed of supercritical carbon dioxide, surfactants and co-solvents, is studied. It is concluded that some surfactants, such as sodium bis-(2-ethylhexyl) sulfosuccinate (AOT) and isooctyl phenol polyethoxylate (TX-10), could form reverse micelles in supercritical carbon dioxide under the action of butanol. The formation of reverse micelles is a spontaneous process thermodynamically. Specifically for the nonionic surfactant TX-10, the formation of reverse micelles is dependent on the entropy increase in the system, while for the anionic surfactant AOT, the micellization is mainly dominated by the increase in enthalpy at higher temperatures, but by the increase in entropy at lower temperatures.
  • LIU Yingxin, WEI Zuojun, CHEN Jixiang, ZHANG Jiyan
    Using tetraethyl orthosilicate (TEOS) as the precursor of silica, the silica aerogel and xerogel, which were used as supports of nickel-based catalysts for liquid hydrogenation of m-dinitrobenzene to m-phenylenediamine, were prepared by the sol-gel method combined with supercritical drying (SCD) and conventional drying, respectively. Then, a series of nickel-based catalyst samples supported on these supports were prepared by the incipient wetness impregnation method with an aqueous solution of nickel nitrate as well as lanthanum nitrate as impregnation liquids. Based on the characterization results of nitrogen adsorption-desorption (BET), X-ray diffraction (XRD), temperature programmed reduction (TPR), temperature-programmed desorption of hydrogen (H2-TPD), and catalytic activity evaluation, the physico-chemical properties and catalytic performances of the catalysts were investigated. The results show that the nickel crystallites on the binary nickel catalyst using silica aerogel as support are of smaller particle size. However, compared with the sample supported on silica xerogel, the nickel catalyst supported on the silica aerogel exhibits lower activity and selectivity for the hydrogenation of m-dinitrobenzene because it has a lesser amount of active sites and weaker absorption ability to reactants caused by sintering of the nickel crystallites. The addition of promoter La2O3 could increase the activity and selectivity of the catalysts. Among all the nickel-based catalyst samples prepared, the La2O3 promoted ternary nickel-based catalyst supported on silica xerogel exhibits the highest activity and selectivity for the hydrogenation of m-dinitrobenzene to m-phenylenediamine, which could be attributed to its highest active surface area and appropriate absorption strength to reactants. Over this promising catalyst, the conversion of m-dinitrobenzene and the yield of m-phenylenediamine could reach 97.0% and 93.1%, respectively, under proper reaction conditions of hydrogen pressure 2.6 MPa, temperature 373 K, and reaction time 1 h.
  • SUN Xuewen, ZHAO Suoqi, LI Hui
    Alkylation of benzene with propylene was carried out with FeCl3-chloro-butyl-pyridine (FeCl3-[bpc]) ionic liquid as catalyst to obtain cumene. Significant improvements in propylene conversion and cumene selectivity under mild reaction conditions were attained by modification of the catalyst with HCl. Under 20ºC, 0.1 MPa, reaction time 5 min, mole ratio of benzene to propylene 10:1 and mass ratio of FeCl3-[bpc] to benzene 1:100, conversion of propylene can increase from 83.60% to 100.00% and selectivity of cumene can increase from 90.86% to 98.47%. If reaction is carried out in following two stages, the result will be very good. At the initial stage of the reaction, alkylation is the main reaction and a higher conversion of propylene is obtained at a lower temperature. At the later stage of the reaction, transalkylation is the main reaction and selectivity to cumene can be increased by appropriately raising the reaction temperature.
  • ZHANG Fumin, GUO Maiping, GE Hanqing, WANG Jun
    An environmentally benign method for the synthesis of heteropoly acids H3+nPMo12 nVnO40·xH2O (PMoVn, n = 1−3) was developed by the reaction of an aqueous slurry which contained stoichiometric amounts of MoO3, V2O5 and H3PO4. Characterization of the as-synthesized catalysts with inductively coupled plasma (ICP) elemental analysis, thermogravimetry (TG), X-ray diffraction (XRD) and infrared (IR) spectroscopy indicated that V ions substituted for Mo ions in Keggin-type phosphomolybdic acid. The as-synthesized samples were found to be an efficient catalyst for the hydroxylation of benzene which was carried out in a mixed solvent of acetonitrile and acetic acid with aqueous hydrogen peroxide as oxidant. PMoV2 exhibi ted the highest benzene conversion of 34.5% with phenol selectivity of 100%.
  • JIANG Qi, CHENG Jiye, GAO Zhiqin
    Solid base catalysts for the direct synthesis of dimethyl carbonate (DMC) from carbon dioxide, methanol, and propylene oxide were prepared by loading KCl and K2CO3 on the surface of La2O3, Y2O3, CeO2 and Nd2O3. The catalysts were characterized by thermogravimetric analysis (TGA) and X-ray diffraction (XRD) techniques. The catalytic activities were efficiently influenced by the preparation conditions. The optimal loading amount of K2CO3 is 17.6% (mass) for KCl-K2CO3/Y2O3 and 22.2% for other catalysts. Supports affected the activity of catalyst. KCl-K2CO3/Nd2O3 exhibited the highest activity. The activity of KCl-K2CO3/Y2O3 increased with the increase of calcination temperature in the range of 800ºC–900ºC. The formation of KYO2, Y3O4Cl or YOX species probably promoted the catalysts.
  • ZHAO Yongxian, SHAO Huafeng, WANG Bo, YAO Wei, HUANG Baochen
    With TiCl4/MgCl2 (Ti) and Al(i-Bu)3 (Al) as catalysts, the thermoplastic copolymer of 1-butene(Bt) and 1-hexene(He) was synthesized successfully. The effects of Bt/He, Ti/(He+Bt), Al/Ti, temperature and reaction time on conversion, catalyst efficiency(CE), intrinsic viscosity([η]) and insoluble content were studied. The copolymer was analyzed with Fourier transform-infrared (FTIR) and nuclear magnetic resonance (1H-NMR). Results showed that the optimal polymerization conditions were: He/Bt = 0.25, temperature 40ºC–50ºC, Al/Ti = 400–500, Ti/(Bt+He) = 3×10-5-4*times;10-5, time 4 h. Intrinsic viscosity was found to increase with increasing Ti/(Bt+He) and decreasing Al/Ti and polymerization temperature. When the molar content of He, Al/Ti and polymerization temperature increased, the insoluble content in CH2Cl2 of copolymers decreased. When Ti/(Bt+He) and reaction time increased, the insoluble content in CH2Cl2 of copolymers also increased. The crystallization and stereoregularity of poly(1-butene) decreased with the addition of He.
  • ZHANG Yatao, FAN Lihai, ZHANG Lin, CHEN Huanlin
    In this paper, the removal of trace carbon dioxide from closed spaces through membrane process and biotransformation are introduced in detail. These methods include the microalgae photobioreactor, membrane microalgae photobioreactor, supported liquid membrane, membrane gas-liquid contactor, hydrogel membrane, and enzyme membrane bioreactor. The advantages and disadvantages of these methods are compared. It is found that higher CO2 removal efficiency can be obtained in biotransformation and membrane process. However, a large volume and high energy consumption are needed in biotransformation, while the low permeability and stability must be solved in the membrane process.
  • WANG Lijun, CHENG Youwei, WANG Qinbo, LI Xi
    The process of p-xylene liquid phase oxidation to produce purified terephthalic acid (PTA) involves a series of liquid phase radical reactions, chemical absorption, reactive crystallization, and evaporation. A commercial PTA production flow sheet includes a number of unit operations, which construct a complex process system. In this paper, a review of research and development (R&D) works on PTA process carried out in Zhejiang University during recent years is introduced. The works cover the oxidation and crystallization kinetics, gas-liquid mass transfer and evaporation, reactor modeling, database development, novel reactor design, process modeling, simulation, and optimization. The author emphasizes the viewpoint through this case study that chemical reaction engineering should be developed to process system engineering to extend its scope, and particular attention should be paid on reactor and process modeling.