Jun 2008, Volume 2 Issue 2

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  • QI Dongming, YANG Lei, WU Minghua, SHAO Jianzhong, BAO Yongzhong
    A series of “guava-like” silica/polyacrylate nanocomposite particles with close silica content and different grafting degrees were prepared via mini-emulsion polymerization using 3-(trimethoxysilyl)propyl methacrylate (TSPM) modified silica/acrylate dispersion. The silica/polyacrylate composite particles were melt-mixed with unfilled polyacrylate (PA) resin to prepare corresponding silica/polyacrylate molded composites and the dispersion mechanism of these silica particles from the “guava-like” composite particles into polyacrylate matrix was studied. It was calculated that about 110 silica particles were accumulated in the bulk of every silica/polyacrylate composite latex particle. Both the solubility tests of silica/polyacrylate composite latex particles in tetrahydrofuran (THF) and the section transmission electron microscope (TEM) micrographs of silica/polyacrylate molded composites indicated that the grafting degree of silica particles played a crucial role in the dispersion of silica/polyacrylate composite particles into the polyacrylate matrix. When the grafting degree of polyacrylate onto silica was in a moderate range (ca. 20%–70%), almost all of silica particles in these “guava-like” composite particles were dispersed into the polyacrylate matrix in a primary-particle-level. However, at a lower grafting degree, massive silica aggregations were found in molded composites because of the lack of steric protection. At a greater grafting degree (i.e., 200%), a cross-linked network was formed in the silica/polyacrylate composite particles, which prevented the dispersion of composite particles in THF and polyacrylate matrix as primary particles.
  • YUE Hongxia, ZHAO Hongmei, LIU Longjiang, WANG Siping, Ruan Qiong, WANG Tongwen
    The long-chain ionic liquid 1-hexadecyl-3-methylimidazolium chloride (C16mimCl) was used as a template to prepare cerium-doped MCM-48 materials in basic medium by a hydrothermal synthesis procedure. The effect of the amount of Ce salt and C16mimCl/Si on the synthesis were discussed in detail. This mesoporous material exhibits a pore architecture which is cubic Ia3d gyroid and possesses a large surface area and a narrow pore distribution. Cerium in calcined porous framework exists in the form of well-dispersed tetrahedral coordination. The C16mimCl shows a high tendency toward self-aggregation that allows the formation of the cerium-doped gyroid mesostructure by using the appropriate amount of Ce salt.
  • QIANG Liangsheng, MA Jing, CHU Jia, ZHANG Xiaohong
    Fe-doped PbTiO3 (PT) powder and bulk materials were prepared successfully by sol-gel technique and a subsequent sintering process using Fe (C5H5)2 as a dopant agent. The effects of pH and temperature on the Fe-doped PT system were investigated. Thermogravimetry/differential thermal analysis (TG/DTA), X-ray diffraction (XRD) and scanning electron microscopy (SEM) were used to analyze the composition and the microstructure of the PT ceramics. The results indicated that the thermal decomposition of xerogel included three stages: volatilization of adsorption water and organic composition, oxygenolysis of n-butyl and acetate, and transformation of the crystalline phase. Well-stabilized collosol and gel could be obtained at 60°C and pH = 4.5. It was found that PbTiO3, PbFe2O4, and TiO2 crystalline appeared in the Fe-doped PT system when the mass fraction of the dopant Fe was 0.03%. Furthermore, from STM analysis, it could be seen that the grain size of doped PT ceramics was homogeneous and about 1–2 ?m, and the pore of the PT ceramic was small. As a result, the PT ceramic had high tightness.
  • LIU Xiaoye, DAI Gance
    Impregnation rate of thermoplastic resin (polypropylene) in jute fiber mat and influence of relative factors on impregnation were studied, aiming to develop the continuous melt impregnation technique and to investigate the effect of impregnation rate and temperature on processing conditions and mechanical properties of natural fiber mat-reinforced thermoplastics. Influence of pressure on porosity of fiber mat and effect of melt viscosity on impregnation rate were also investigated. The modified capillary rheometer was used as apparatus and experimental data were analyzed based on the one-dimension Darcy’s law. Results showed that at a given pressure, the impregnation rate is inversely proportional to melt viscosity and jute fiber mat has higher porosity than glass fiber mat. The architecture, compressibility, permeability and fiber diameter of jute fiber mat were compared with those of glass fiber mat and their effects on impregnation were discussed further. It could be seen that the average diameter of jute fiber is much bigger; the porosity of jute fiber mat is significantly higher and inner bundle impregnation does not exist in jute fiber mat. Therefore, it is not difficult to understand why the impregnation rate in jute fiber mat is 3.5 times higher and permeability is 14 times greater. Kozeny constants of jute and glass fiber mats calculated based on the capillary model are 2950 and 442, respectively.
  • DONG Yongli, YUAN Fulong, ZHU Yujun, ZHAO Lina, CAI Zhicheng
    CuO/SBA-16 catalysts were prepared by two different routes – the conventional impregnation method and the modified impregnation method with pH adjustment. These catalysts were characterized by X-ray diffraction (XRD), atomic absorption spectrometry (AAS), N2 physisorption and hydrogen temperature programmed reduction (H2-TPR) measurements which reveal that the cubic cage-like (Im3m) pore structure of the parent SBA-16 molecule sieves was well maintained throughout the synthesis. After introduction of Cu, a different CuO dispersion exists on these catalysts. The CuO/SBA-16 prepared by modified impregnation method has a single highly dispersed CuO which is considered as a highly efficient species for hydroxylation of phenol with H2O2. CuO/SBA-16 prepared by the conventional impregnation method shows the presence of bulk CuO species which is undesirable for this reaction.
  • SUN Guida, LI Cuiqing, ZHOU Zhijun, LI Fengyan
    Supported tungsten phosphide catalysts were prepared by temperature-programmed reduction of their precursors (supported phospho-tungstate catalysts) in H2 and characterized by X-ray diffraction (XRD), BET, temperature-programmed desorption of ammonia (NH3-TPD) and X-ray photoelectron spectroscopy (XPS). The reduction-phosphiding processes of the precursors were investigated by thermogravimetry and differential thermal analysis (TG-DTA) and the suitable phosphiding temperatures were defined. The hydrodesulfurization (HDS) and hydrodenitrogenation (HDN) activities of the catalysts were tested by using thiophene, pyridine, dibenzothiophene, carbazole and diesel oil as the feedstock. The TiO2, ?-Al2O3 supports and the Ni, Co promoters could remarkably increase and stabilize active W species on the catalyst surface. A suitable amount of Ni (3%–5%), Co (5%–7%) and V (1%–3%) could increase dispersivity of the W species and the BET surface area of the WP/?-Al2O3 catalyst. The WP/?-Al2O3 catalyst possesses much higher thiophene HDS and carbazole HDN activities and the WP/TiO2 catalyst has much higher dibenzothiophene (DBT) HDS and pyridine HDN activities. The Ni, Co and V can obviously promote the HDS activity and inhibit the HDN activity of the WP/?-Al2O3 catalyst. The G-Ni5 catalyst possesses a much higher diesel oil HDS activity than the sulphided industrial NiW/?-Al2O3 catalyst. In general, a support or promoter in the WP/?-Al2O3 catalyst which can increase the amount and dispersivity of the active W species can promote its HDS and HDN activities.
  • GUO Jintang, ZHANG Hongxin, WANG Bo, YE Yaqin
    The crosslinked polyacrylonitrile (PAN) was synthesized by suspension polymerization using acrylonitrile (ANT) and divinylbenzene (DVB). Effects of a variety of conditions on the polymerization of PAN particle size and stiffness were investigated. Polyketone was prepared by the copolymerization of carbon monoxide (CO) and styrene (ST) catalyzed by PAN resin-supported palladium acetate. The resin-supported catalyst and the copolymerization product were characterized by infrared spectroscopy (IR) and Scanning Electron Microscopy (SEM). Effects of the components of a catalytic system and reaction time on the catalytic activity were studied. The reusability of the resin-supported catalyst was also investigated. Results indicated that the resin-supported catalyst has excellent catalytic property. The yield of polyketone was 6.2348 g when using 1 g of resin and 22.4 mg of palladium acetate.
  • WANG Ruifang, YANG Jialing, SHI Zuoqing, OU Lailiang
    The adsorption effects of several macroporous adsorption resins for gibberellic acid (GA3) were investigated. The dynamic adsorption capacity is 58.38 mg/g dry beads for resin R4 and 96.46 mg/g dry beads for resin R5 which is consistent with the surface area. Aqueous methanol (50%, V/V) is a good eluent and the yield of GA3 is above 95%. The concentration of GA3 could increase five-fold after an adsorption-elution cycle and this is important when considering further crystallization of GA3 in an industrial process.
  • GUAN Yu, PEI Aixia, GUO Liejin
    Cellulose, one of the important components of biomass, was gasified in supercritical water to produce hydrogen-rich gas in an autoclave which was operated batch-wise under high-pressure. K2CO3 and Ca(OH)2 were selected as the catalysts (or promoters). The temperature was kept between 450°C and 500°C while pressure was maintained at 24–26 MPa. The reaction time was 20 min. Experimental results showed that the two catalysts had good catalytic effect and optimum amounts were observed for each catalyst. When 0.2 g K2CO3 was added, the hydrogen yield could reach 9.456 molkg-1 which was two times of the H2 amount produced without catalyst. When 1.6 g Ca(OH)2 was added, the H2 yield was 8.265 molkg-1 which is lower than that obtained using K2CO3 as catalyst but is still 1.7 times that achieved without catalyst. Comparing with the results obtained using K2CO3 or Ca(OH)2 alone, the use of a combination of K2CO3 and Ca(OH)2 could increase the H2 yield by up to 2.5 times that without catalyst and 25% and 45% more than that obtained using K2CO3 and Ca(OH)2 alone, respectively. It was found that methane was the dominant product at relatively low temperature. When the temperature was increased, the methane reacts with water and is converted to hydrogen and carbon dioxide.
  • LI Jia, ZOU Jijun, ZHANG Xiangwen, GUO Wei, MI Zhentao
    Suspensoid of HZSM-5 or HY zeolites mixed with a self-made ceramic-like binder was coated on the inner wall of a tubular reactor by gas-aided fluid displacement technology. The coated zeolites were characterized by means of X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR) and scanning electron microscopy (SEM). The coating thickness is 10–20 ?m and the particle size of the zeolites is in the range of 1–5 ?m. In the coated reactor, cracking of endothermic fuels including n-dodecane and aviation fuel RP-3 was carried out separately under supercritical conditions at 600°C and 625°C to investigate their heat sinks and conversion of catalytic reactions. For the reaction catalyzed by HY(25% mass fraction) coating, the heat sink capacity of n-dodecane are 815.7 and 901.9 kJ/kg higher than that of the bare tube at 600°C and at 625°C, respectively. Conversion of n-dodecane also increases from 42% to 60% at 600°C and from 66% to 80% at 625°C. The coated zeolite can significantly inhibit the carbon deposition during supercritical cracking reactions.
  • JING Ping, LI Qingbiao, HAN Mei, SUN Daohua, JIA Lishan, FANG Weiping
    SO42-/ZrO2 solid super-acid catalysts (SZ) doped with Ni2+ or Sn2+ (Ni2+/SZ, Sn2+/SZ) were prepared for catalytic visbreaking of heavy petroleum oil from Shengli oil field. The visbreaking reactions were carried out at 240°C and 3–4 MPa for 24 h using a heavy petroleum oil to catalyst mass ratio of 100 : 0.05. The effect of water content on viscosity of heavy petroleum oil was also investigated. Both catalysts can promote thermolysis of heavy petroleum oil and the viscosity was reduced from 0.319 Pa·s to 0.135 Pa·s for Ni2+/SZ and 0.163 Pa·s for (Sn2+/SZ) with visbreaking rates of 57.7% and 48.9%, respectively. After visbreaking, the saturated hydrocarbon content increased while aromatics, resin, asphaltene, sulfur and nitrogen content decreased. The presence of water was disadvantageous to visbreaking of heavy petroleum oil.
  • ZHONG Li, REN Wei, GUO Wenjing
    A pilot scale test of advanced treatment of ethene wastewater by ozonization was carried out for industrial water reuse. Effects of different operating conditions on COD degradation, such as wastewater flow rate, ozonized gas flow rate, operating voltage of ozonizer and two ozone generation means, using pure oxygen or air, was investigated. The results show that the increase of ozonizer operating voltage, the decrease of wastewater flow rate and the suitable ozonized gas flow rate improve the removal of COD in wastewater and that ozone generated respectively from air and pure oxygen can effectively remove COD of ethene wastewater to meet the industrial water reuse criterion.
  • ZHANG Tengyun, FAN Hongbo, ZHONG Li, CHUANG Karl
    The synthesis of nonaqueous peracetic acid in acetone by acetaldehyde oxidation was carried out in a tubular packed reactor. The influencing factors of the reacting system including packing material, oxygen carrier, and reactor configuration were investigated. The results show that porous materials are inappropriate for peracetic acid synthesis and only non porous material with appropriate surface area can provide good peracetic acid selectivity and yield. Among the six kinds of packing material investigated, SA-5118 is the best one. As oxidizing gas, pure oxygen is superior to air. The optimum length-to-inner diameter ratio of the reactor is about 40. Under the proper reaction conditions, the highest peracetic acid yield of 84.15% and the highest selectivity of 93.34% can be achieved which indicates that the novel reacting system is effective and economical for nonaqueous peracetic acid production.
  • LU Yangcheng, WU Yingxin
    To control the morphology of cellulose membranes used for separation, they were prepared by the NMMO method using water, methanol, ethanol and their binary solution as coagulation baths. Morphologies of the surface and cross section of dry membranes were observed. The pore structure parameters of wet membranes were determined. By comparison, the process and mechanism of pore formation in dry membranes were suggested, and the relativity of cellulose crystal size to average pore diameter in wet membranes and their influences were discussed. The results show that the morphology of dry membranes is clearly varied with coagulation baths, while the porosity of wet membranes is almost constant. Porous structures can appear in the compact region of dry membranes due to swelling from water. These pores have a virtual effect on the average pore diameter of wet membranes. By changing the composition of coagulation baths, the microstructure of cellulose membranes in a dry or wet environment can be adjusted separately.
  • KONG Xiaoying, WU Chuangzhi, YUAN Zhenhong, MA Longlong, CHANG Jie, LÜ Pengmei
    By considering the features of fluidized-bed reactors and the kinetic mechanism of biomass gasification, a steady-state, isothermal, one-dimensional and two-phase mathematical model of biomass gasification kinetics in bubbling fluidized beds was developed. The model assumes the existence of two phases – a bubble and an emulsion phase – with chemical reactions occurring in both phases. The axial gas dispersion in the two phases is accounted for and the pyrolysis of biomass is taken to be instantaneous. The char and gas species CO, CO2, H2, H2O, CH4 and 8 chemical reactions are included in the model. The mathematical model belongs to a typical boundary value problem of ordinary differential equations and its solution is obtained by a Matlab program. Utilizing wood powder as the feedstock, the calculated data show satisfactory agreement with experimental results and proves the effectiveness and reliability of the model.
  • CHEN Miaocan, ZHAO Ling, LIU Tao, WU Jiangwei, YUAN Weikang
    The solubility of CO2 in solid-state PET was measured using a pressure-decay method. In order to calculate the solubility of CO2 in the amorphous region of PET, the crystallinity of solid state PET dissolved in CO2 at different pressures and temperatures was measured by differential scanning calorimetry (DSC). The solubility increases with increasing pressure and it follows a linear relationship and obeys Henry’s law when the pressure is below 8 MPa. The effect of temperature on solubility is weak and the solubilities at different temperatures are almost the same under low pressures. At higher pressure, the solubility decreases with an increase in temperature. The solubility of CO2 in the amorphous region of PET at 373.15 K, 398.15 K and 423.15 K was correlated with the Sanchez-Lacombe equation of state with a maximal correlation error of 6.69%.
  • CHEN Meijuan, JIA Honghua, CHEN Yongsheng, JIANG Min, WEI Ping
    L-4-Fluorophenylalanine (FPhe) was prepared from 4-fluorophenylpyruvate (FPPA) catalyzed by aspartate aminotransferase (Asp-AT) of the recombinant E. coli BL21-pET/aspC. After 12 h enzymatic reaction, the FPPA conversion was over 90% and the yield of FPhe could be above 85% under the following optimal conditions: 37°C, pH value range of 5.0–8.0, 5.5 mass ratio of cell to FPPA, 0.6% (w/v) of Tween 80, 7.08 g/L FPPA, and 1.6 of molar ratio of L-Asp to FPPA.
  • CHEN Haiqin, XU Zhinan, WANG Cheng, CEN Peilin, LIAO Yuhua
    In the new era of “Omics”, the traditional techniques of protein expression in vivo can not come up with the exponential increase of genetic information. The cell-free protein synthesis system provides a new strategy of protein expression with advantages of rapid, convenient and high-throughput expression. The preparation of cell extracts, the optimization of substrate concentrations and the energy regeneration system are the key factors for the successful construction of cell-free protein expression system. In this work, the cell extract was prepared from RNase I- defective strain E. coli A19. The cell growth phase, the pressure for cell disruption and the storage condition of cell extracts were optimized. Meanwhile, the optimal substrate concentrations and the energy regeneration system were selected. Under the optimized conditions, the green fluorescent protein (GFP) reporter gene was expressed in the E. coli cell-free system with high expression level (Ca. 154 ?g/mL) which was 29 times higher than the expression level before optimization.