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Dispersion of “guava-like” silica/polyacrylate
nanocomposite particles in polyacrylate matrix
QI Dongming, YANG Lei, WU Minghua, SHAO Jianzhong, BAO Yongzhong
Frontiers of Chemical Engineering in China - Selected Publications from Chinese Universities. 2008, 2 (2): 127-134.
https://doi.org/10.1007/s11705-008-0033-0
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.
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Preparation and microstructure analysis of Fe-doped
PbTiO ceramic
QIANG Liangsheng, MA Jing, CHU Jia, ZHANG Xiaohong
Frontiers of Chemical Engineering in China - Selected Publications from Chinese Universities. 2008, 2 (2): 140-144.
https://doi.org/10.1007/s11705-008-0021-4
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.
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Synthesis, characterization and hydrotreating
performance of supported tungsten phosphide catalysts
SUN Guida, LI Cuiqing, ZHOU Zhijun, LI Fengyan
Frontiers of Chemical Engineering in China - Selected Publications from Chinese Universities. 2008, 2 (2): 155-164.
https://doi.org/10.1007/s11705-008-0038-8
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.
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Hydrogen production by catalytic gasification
of cellulose in supercritical water
GUAN Yu, PEI Aixia, GUO Liejin
Frontiers of Chemical Engineering in China - Selected Publications from Chinese Universities. 2008, 2 (2): 176-180.
https://doi.org/10.1007/s11705-008-0026-z
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.
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Visbreaking of heavy petroleum oil catalyzed
by SO/ZrO solid super-acid doped with Ni or Sn
JING Ping, LI Qingbiao, HAN Mei, SUN Daohua, JIA Lishan, FANG Weiping
Frontiers of Chemical Engineering in China - Selected Publications from Chinese Universities. 2008, 2 (2): 186-190.
https://doi.org/10.1007/s11705-008-0035-y
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.
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Modeling and simulation of biomass air-steam
gasification in a fluidized bed
KONG Xiaoying, WU Chuangzhi, YUAN Zhenhong, MA Longlong, CHANG Jie, LÜ Pengmei
Frontiers of Chemical Engineering in China - Selected Publications from Chinese Universities. 2008, 2 (2): 209-213.
https://doi.org/10.1007/s11705-008-0039-7
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.
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Recombinant aspartate aminotransferase-catalyzed
synthesis of L-4-fluorophenylalanine
CHEN Meijuan, JIA Honghua, CHEN Yongsheng, JIANG Min, WEI Ping
Frontiers of Chemical Engineering in China - Selected Publications from Chinese Universities. 2008, 2 (2): 220-223.
https://doi.org/10.1007/s11705-008-0041-0
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.
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Preliminary study on preparation of cell-free system for protein expression
CHEN Haiqin, XU Zhinan, WANG Cheng, CEN Peilin, LIAO Yuhua
Frontiers of Chemical Engineering in China - Selected Publications from Chinese Universities. 2008, 2 (2): 224-229.
https://doi.org/10.1007/s11705-008-0029-9
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.
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