Table of Content

20 June 2012, Volume 12 Issue 3

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流动与传递

Gas Velocity Range of Stable Operation in a Gas-Solid Multistage Fluidized Bed with Overflow Standpipes

XU Xu-fei ZHOU Qi ZOU Tao GAO Shi-qiu XU Guang-wen

. 2012, 12(3):  361-368. 

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The variation of gas velocity range of stable operation with major configuration and operating parameters in a gas-solid four-stage fluidized bed with overflow standpipes was studied. The tested parameters included the particle feeding rate, opening ratio and orifice size of gas distributor, inner diameter of overflow standpipe, and type and size of particles. The results showed that the minimal gas velocity (Umin) for stable operation increased with increase in the particle feeding rate, opening ratio of gas distributor and size of the treated particles, while it decreased with increase of the inner diameter of overflow standpipes and was independent of the orifices size of gas distributor. The maximal gas velocity (Umax) of stable operation increased with increase of the particle size and opening ratio and orifices size of gas distributor but decreased with increase of the inner diameter of overflow standpipes. For the tested silica sand and coal particles, Umax increased with increase of the particle feeding rate, but it was almost a constant when the superficial particle velocity was over 1.0×10-4 m/s. The threshold gas velocity ratio (Umax/Umin) of silica sand was about 3 times of that of coal, indicating that the operation flexibility of gas velocity for silica sand was higher than that of coal probably due to the poor particle fluidity of coal with high moisture.

Energy Dissipation Distribution in a Draft Tube-lifted Gas-Solid Air Loop Reactor

SHEN Zhi-yuan YANG Li-jun LIU Meng-xi LU Chun-xi

. 2012, 12(3):  369-375. 

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Based on the energy balance, an energy dissipation rate model of different regions of a draft tube-lifted gas-solid air loop reactor (GSALR) was established. The local particle velocity, bed density and pressure drop were measured in a cold model GSALR and the model parameters were obtained based on the experimental data. The predictions agree with experimental data. The predicted results show that nearly 40% and 30% of the energy dissipation rate occur in the annulus and gas-solid separation regions, while that in the draft tube and gas distributors region is relatively small, reaching a sum of nearly 30%. With increasing of the draft tube gas velocity, the ratio of individual region to global reactor energy dissipation rate decreases for the annulus region, increases for the gas-solid separation region, and basically remains constant for the draft tube and gas distributor affecting regions. Compared with that obtained in an annulus-lifted GSALR, the location of gas distributor has a significant influence on energy dissipation, the flow resistance is smaller in the draft tube-lifted GSALR.

Radial and Axial Distributions of Particle Velocity in a Counter-current Fluidized Bed

LI Zheng-jie DONG Peng-fei SONG Wen-li FAN Chui-gang LI Song-geng LIN Wei-gang

. 2012, 12(3):  376-381. 

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Experiments were carried out in a 90 mm i.d., 7 m high gas upflow and solid downflow fluidized with circulating boiler ash (dp=300 mm) to measure the radial profiles of particle velocity and concentration, and its axial development. The results show that particle velocity is lower both in the center and near the wall in the fully developed region. The maximum particle velocity exists at around r/R=0.85. An empirical formula of particle velocity in the developed region is derived from a number of experimental data. Relative errors between calculated values and experiential data are less than ±11%. Local particle velocity in the region near the bed wall (r/R>0.622) increases along the column. While local particle velocity in the central region (0

Hydrodynamic Modeling on Fluidization Discharging of Particles under U-shape Valve Structure

PENG Li LI Hong-zhong ZHU Qing-shan

. 2012, 12(3):  382-387. 

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A hydrodynamic model for the U-valve was proposed based on the Newton's second law to predict solid flow rate under the fluidization discharging mode. During steady discharging, the particles descended in the moving-bed mode in the standpipe, while the particles moved upwards in the fluidization mode in the discharging chamber. A circulating fluidized bed with a U-valve was established and operated to study the performance of the U-valve using silica sand with average diameter of 81.9 mm. Experiments revealed that the solid flow rate increased linearly with the increase of superficial gas velocity. The simulated pressure drop and solid flow rate were in good agreement with those experimental data, e.g. the deviation was ±2% for pressure drop across the discharging chamber, and ±7% for the solid flow rate, demonstrating the validity of proposed algebraic model. Key words: U-valve; discharge under fluidization mode; hydrodynamic modeling; solid

反应与分离

Effects of Surfactants on Seeded Precipitation of Boehmite from Sodium Aluminate Solution

XU Rong-guang WANG Zhi GONG Xu-zhong

. 2012, 12(3):  388-394. 

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The effects of nonionic and anionic surfactants [polyethylene glycol (PEG), polyoxyethylene lauryl ether and sodium dodecylbenzene sulfonate] on boehmite seeded precipitation from sodium aluminate solution were investigated. The results showed that precipitation and agglomeration of crystals were inhibited by sodium dodecylbenzene sulfonate, resulting in refinement of product, the precipitation was intensified and agglomeration of particles was promoted by polyethylene glycol. The largest precipitation rate (32.39%) was obtained with PEG1000 addition of 1 g/L, increased by 8.37%. The best agglomeration efficiency was gained with PEG1000 addition of 5 g/L, and median particle size (D50) of product was 23.86 mm, improved by 4.5%. The analytical results by XRD and TG showed that the crystalline structure of products did not change owing to additive charge, and all products were Al(OH)3 and AlOOH.

Removal of Decabromodiphenyl Ether from TV Set Housing Plastic Waste by Solvolysis Process

PENG Shao-hong ZHAO Xiang-yang LIANG Sha YU Mei

. 2012, 12(3):  395-401. 

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A solvolysis recycling process of waste TV set housing plastic with d-limonene and propanol was developed, the phase distribution characteristics of decabromodiphenyl ether and its influential factors were investigated, the transfer mechanism of decabromodiphenyl ether into the recycled high-impact polystyrene (HIPS) in the course of antisolvent precipitation was analyzed, the measures for reducing the amount of decabromodiphenyl ether to move into recycled HIPS were proposed, the optimum process conditions to separate decabromodiphenyl ether from waste housing plastic were determined by experiments. 87.7% of decabromodiphenyl ether was removed by a tubular centrifuge at 12000 r/min rotation speed and 30℃, when the solution was adjusted to be 20% of TV set housing plastic. After decabromodiphenyl ether particles were dissolved by adding 40 mL d-limonene per 100 mL centrifugate, recycled HIPS particles were precipitated with the same volume of propanol at 50℃. The total polybrominated diphenyl ether concentration of recycled HIPS was reduced to lower than 0.1% and over 99% of decabromodiphenyl ether input successfully removed by this recycling process.

Efficient Crystallization Separation of K2CrO4 and K3VO4 in Alkaline Multi-component System of KOH Medium

YANG Na WANG Shao-na DU Hao QIN Ya-ling ZHENG Shi-li WANG Shao-na

. 2012, 12(3):  402-408. 

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The solubility of KOH-K3VO4-H2O system was determined. Based on the solubility variation of KOH-K3VO4-H2O and KOH-K2CrO4-H2O systems, the separation method of K2CrO4 and K3VO4 by evaporation crystallization and cooling crystallization respectively from KOH-K2CrO4-K3VO4-H2O system was established. Aiming at the digestion liquor obtained by the sub-molten salt decomposition reaction, the effects of process parameters on crystallization separation of K2CrO4 and K3VO4 was studied. The results showed that K2CrO4 was separated when the KOH concentration of digestion liquor was evaporated to 630~670 g/L. The crystallization rate of K2CrO4 was more than 80%, and its purity over 95%. The mother liquor was continuously evaporated, the optimal experimental conditions for the separation of K3VO4 were obtained: KOH concentration 800~850 g/L, temperature from 80℃ to 40℃ with natural cooling, stirring speed 200 r/min, seed load 2%(w). Under the conditions, the crystallization rate of K3VO4 was more than 60%, and its purity over 90%. The solution after the separation of K2CrO4 and K3VO4 was recycled for the sub-molten salt decomposition reaction.

Effect of Membrane Fouling by PVA Addition in Simulated EPS Solution on Cross-flow Filtration

Wang Ge LI Fang WU Liang FU Le-le

. 2012, 12(3):  409-414. 

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The effect of polyvinyl alcohol (PVA) addition on the performance of cross-flow membrane filtration of model extracellular polymeric substances (EPS) solution was studied. Filtrations of model EPS solution with and without PVA were conducted in a cross-flow filtration cell through ultrafiltration (UF) membranes respectively. Hermia modified model was used to check the fouling mechanism by fitting of the experimental data. The results show that the cake filtration model fits to the experimental data the best in UF experiments regardless of addition of PVA, the degree of fitting ranges from 0.891 to 0.994, the adsorption resistance and membrane pollution resistance of the model EPS solution with addition of PVA is higher by half than that of model EPS solution, the specific cake resistance is four times higher, 2.29′1014 and 9.57′1014 m-1 respectively, the sensitivity of flux to the operating pressure is increased with addition of PVA, but the sensitivity to the velocity of the membrane surface reduced.

Separation of Divalent Cobalt and Nickel Ions Using a Synergistic Solvent Extraction System with P507 and Cyanex272

LIU Mei-rong ZHOU Gui-ying WEN Jan-kang

. 2012, 12(3):  415-419. 

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Separation and recovery of divalent nickel and cobalt ions from a bioleaching solution were studied using a synergistic extraction system with P507and Cyanex272. The effects of initial pH value, volumetric ratio of P507 to Cyanex272 (P/C) in organic phase, and ratio of aqueous to organic phase (A/O) on the separation of divalent cobalt and nickel ions were studied. The results showed that the optimal conditions for the separation were: the saponification rate of organic phase 50% and saponification time 30 min, the organic phase composed of 10% [P507:Cyanex272 at 3:2 (volume ratio)], 85% sulphonated kerosene and 5% TBP, A/O 3 to 1 and initial pH value 2.5. In these conditions, the extraction rate of divalent cobalt ion is 92.96%. At the A/O of 2 to 3, turbulence intensity of 225 r/min, time of 4 min, 98.68% of stripping rate of divalent cobalt ion could be obtained with 200 g/L of H2SO4 as the stripping agent, the separation of divalent nickel and cobalt ions was realized under the low initial pH value.

过程与工艺

Optimization of Conditions in Atmospheric Acid Leaching of the Water-leached Residue of Limonitic Laterite after Alkali-roasting

WANG Bao-quan GUO Qiang QU Jing-kui QI Tao

. 2012, 12(3):  420-426. 

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Water-leached residue of limonitic laterite was obtained after Na2CO3-roasting, and its atmospheric leaching behavior was investigated. Thermodynamic calculation was performed to evaluate possible reactions in the leaching process. Hydrochloric acid was chosen as the leaching agent after comparing atmospheric leaching behaviors of elements of the residue in sulfuric and hydrochloric acid, as well as consideration of the treatment options of the leaching liquid and residue. Atmospheric acid leaching experiments were carried out to investigate the effects of mass ratio of acid to residue, mass ratio of liquid to solid, leaching temperature and time on the leaching of water-leached residue of laterite after alkali-roasting. 99.2%(w) Ni, 99.5%(w) Co and 97.8%(w) Fe were leached out at the optimum leaching conditions of mass ratio of acid to residue 1.25, mass ratio of liquid to solid 4, 80℃ and 3 h.

Thermal Decomposition Kinetics of Siderite Ore in Suspension Condition

FENG Zhi-li YU Yong-fu LIU Gen-fan CHEN Wen LV Gang

. 2012, 12(3):  427-432. 

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To analyze the influences of temperature and atmosphere on the siderite ore, isothermal decomposition experiments of siderite ore in the dilute phase suspension condition were conducted. The experimental results showed that the peak concentration of CO in the off-gas came out 5~10 s later than that of CO2, and the magnetization rate of FeO was sped up obviously between 600 and 650℃ and a maximum speed appeared at around 700℃. With the increase of concentration of CO2 in the atmosphere, the decomposition rate of siderite ore was reduced and the magnetization rate of FeO increased first, and then both showed a tendency to a limit at the concentration of 16% CO2. The shrinking sphere model with surface reaction rate controlling mechanism best fitted to the experiment data in the suspension condition while the reaction-order model F1 was best for that in the non-isothermal thermogravimetric analysis.

生化工程专栏

Preparation of Gigaporous P(MMA-MAA) Microspheres by Two-step Emulsification, Emulsion Ripening and Solvent Extraction

CHEN Song-fei WANG Qi-bao SU Zhi-guo MA Guang-hui GAO Fei

. 2012, 12(3):  433-439. 

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P(MMA-MAA) was used as the major component of particle material and amphiphilic polymer PELA as a complementary material. Gigaporous poly(methyl methacrylate-methacrylic acid) [P(MMA-MAA)] microspheres with flow-through pores with the diameters from submicron to micron scale were prepared by two-step emulsification, emulsion ripening and solvent extraction. The influential parameters on final morphology were particularly investigated, including the polymer component, ripening time and osmotic gradient. Under the optimum preparation conditions of P(MMA-MAA) concentration 100 g/L, PELA amount 40 g/L, PVA concentration in W2 25 g/L, NaCl concentration in W1 1%~5 g/L and emulsion ripening time 0~30 min, the microspheres with pore size at micron scale and porosity of 95% were obtained. The formation mechanism of gigapores was discussed with consideration of the evolution behavior of double-emulsion system. The rigidity of microspheres could be improved by cross-linking after the formation of porous particles.

Casin Immobilization and Enzymolysis Behaviors at Different Solid-Aqueous Interfaces by Quartz Crystal Microbalance

FENG Xiao-yi QIN Pei-yong GE Jia WANG Ping; MA Guang-hui SU Zhi-guo GAO Fei ZHANG Song-ping

. 2012, 12(3):  440-446. 

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A quartz crystal microbalance (QCM) with dissipation monitoring was used to characterize the adsorption and subsequent trypsin-catalyzed hydrolysis of casin molecules at several typical interfaces, including Au, SiO2 and polystyrene coated chip surfaces. The results showed that a high non-specific adsorption amount of 127.9 ng/cm2 was observed for casin on polystyrene chip surface, while no apparent adsorption occurred on native Au and SiO2 chips. After activation and modification, casin was covalently immobilized on Au and SiO2 chip surfaces with the amounts of 178 and 1718 ng/cm2, respectively. The subsequent enzymolysis of attached casin by injection of typsin was also monitored using QCM. After trypsin treatment, casin molecules and its hydrolysate peptide adsorbed on polystyrene surface could be efficiently removed with surfactant, without trypsin pre-treatment, however, only 36% of the adsorbed casin was removed by surfactant. A method for measuring activity of trypsin at solid-aqueous interfaces was developed. The measured specific hydrolytic activities of trypsin for immobilized casin on Au and SiO2 chip surfaces are 0.010 and 0.157 U/mg, respectively, which was lower than that for free casin in solution with the specific activity of 17.8 U/mg.

Preparation of Thermo-sensitive Microspheres by Premix Membrane Emulsification for Immobilization of Trypsin

QIN Jia LI Chun-ping WANG Yu-xia MA Guang-hui

. 2012, 12(3):  447-453. 

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Thermo-sensitive poly(N-isopropyl acrylamide-co-acrylic acid) [P(NIPAM-co-AAc)] microspheres with narrow size distribution were successfully prepared by premix membrane emulsification at room temperature. The results show that the mean diameter of microspheres was 5.2 mm, their polydispersity index as low as 0.0323. The temperature-responsive behaviors of prepared microspheres were characterized. It was confirmed that the lower critical solution temperature (LCST) of P(NIPAM-co-AAc) microspheres decreased with addition of hydrophilic monmer. The higher the monmer amount, the lower the LCST of P(NIPAM-co-AAc) microspheres. The LCST of P(NIPAM-co-AAc) microspheres increased with more addition of N,N￠-methylenebisacrylamide. The respond time increased with addition of hydrophilic monmer. Trypsin was covalently immobilized onto the microspheres. The result showed that when the concentrations of 1-ethyl-3-(3-dimethylaminopropyl)-carbodiimide hydrochloride, trypsin and PBS were 0.9 mg/mL, 1.8 mg/mL and 70 mmol/L, the optimal value of trypsin loading and activity yield, 276.10 mg/g and 75.07% respectively, was reached. The highest activity of immobilized trypsin was obtained at pH 8 and 37℃.

Pharmacology Efficacy in vitro of PTX-PLGA Microspheres and Surface Modified PTX-PLGA Microspheres by Quaternized Chitosan

CAI Ming-ming WANG Lian-yan; LV Pi-ping MA Guang-hui Zhu Bao-cheng

. 2012, 12(3):  454-459. 

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Poly(dl-lactic-co-glycolic acid) (PLGA) microspheres containing PTX and surface modified PTX-PLGA microspheres with HTCC were prepared by premix membrane emulsification combined with solvent evaporation. Then the corresponding effects on surface morphology, loading and encapsulation efficiencies, release profile and antitumor activity in vitro were systematically investigated. The results showed that the mean diameter of PTX-loaded HTCC-PLGA microspheres was 882 nm, the loading and encapsulation efficiencies were 5.15% and 70.46%, and the cumulative release rate in vitro for 22 d was 70.17%, which had little difference from PTX-loaded PLGA microspheres. However, PTX-loaded HTCC-PLGA microspheres showed positive surface charge as +36.7 mV and PLGA was -14.8 mV. The intracellular PTX incubated with PTX-loaded PLGA and PLGA-HTCC microspheres was 5.6 and 9.7 times as much as that of Taxol?, and HTCC-PLGA microspheres showed lower cell viability than PLGA microspheres. Therefore, PTX-loaded HTCC-PLGA microspheres were the potential delivery system for insoluble drug PTX.

Chitosan-based Intelligent Charge-reversed System for High Efficiency Delivery of Paclitaxel

MA Yu-feng LV Pi-ping YUE Zhan-guo WEI Wei MA Guang-hui YU Rong

. 2012, 12(3):  460-465. 

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After modification by tris(2-aminoethyl) amine (TAEA) and 2,3-dimethylmaleic anhydride (DMMA), chitosan nanoparticles (CNP) were endowed with intelligent charge-reversal ability. The fabricated system (CNP-TAEA-DMMA- nanoparticles) was then loaded with insoluble anticancer drug paclitaxel (PTX), and the drug delivery efficiency was tested in vivo. The results showed that PTX-CNP-TAEA-DMMA- nanoparticles were negatively charged (-11 mV) at normal tissue circumstance (pH 7.4) and rarely internalized by J774.1 cells, exhibiting stealth effect to macrophages. Once reaching the cancer site, those nanoparticles could intelligently transform to positive charge (+5 mV) by the low-pH microenvironment in tumor tissue, which could improve tumor cell uptake and accordingly increase the drug concentration at the lesion site. Compared with commercial PTX formulation, the nanoparticles possessed superior biocompatibility and better cytotoxicity (the value of half inhibitory concentration was decreased to 4.09 from 11.3 mg/mL), holding a great potential as efficient anti-cancer drug carrier.

PCR-DGGE Analysis of Microbial Community during Bioleaching Process of Waste Printed Wire Boards by Acidophilic Bacteria

ZHANG Ting ZHU Neng-wu CHENG Dan WU Ping-xiao

. 2012, 12(3):  466-471. 

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The mixed culture of acidophilic bacteria was used as the inoculant to bioleach waste printed wire boards. Meanwhile, bacteria in different leaching phases (0, 5, 24 and 60 h) were sampled, and denaturing gradient gel electrophoresis (DGGE) analysis of polymerase chain reaction (PCR)-amplified 16Sr RNA genes was used to evaluate the change of microbial community structure during the bioleaching process. The results showed that the mixed culture of acidophilic bacteria could bioleach 96.36 % copper from the boards in 48 h. The analysis of the bands selected from the DGGE gel revealed that the sequences of seven bands (Z1~Z7) had over 99% sequence similarity with Acidithiobacillus ferrooxidans. It meant that the seven strains were all clustered to Acidithiobacillus ferrooxidans genus. The relative abundance of Z1 to Z7 in the four samples was not changed significantly. Meanwhile, Z3 showed the highest relative abundance during the whole bioleaching process, which was 72.70%, 82.90%, 79.00% and 85.80%, respectively. Therefore, the microbial community structure changed a little bit during the bioleaching, which always consisted of Acidithiobacillus ferrooxidans strains and was dominated by strain Z3.

Immobilization of Lipase on PVDF-SiO2 Composite Microspheres

TAN Yan-li WANG Yu-jun SUN Hai-tao LUO Guang-sheng

. 2012, 12(3):  472-477. 

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Polyvinylidene fluoride (PVDF)-SiO2 composite microspheres enveloping SiO2 were prepared by phase transition process and used as carrier to immobilize Candida rugosa lipase (CRL). It is found that CRL immobilized on PVDF or PVDF-SiO2 composite microspheres has a large loading. As to PVDF-SiO2 composite microspheres, with the increase of SiO2 amount, both the loading and recovery rate of activity increase. When the mass ratio of PVDF to SiO2 is 1:1, they have the maximal loading of 200 mg/g and the maximal recovery rate of activity of 50.98%, the PVDF-SiO2 composite microspheres are the optimized carrier in the experiment. Comparing PVDF-SiO2 composite with SiO2, the former is superior in filtration and has no pollution on substrate solution.

Removal of Auto-growth Inhibitors of Spirulina platensis and Model Analysis

WAMG Li-meng LIU Ming XUE Sheng-zhang CONG Wei LU Yun-ming

. 2012, 12(3):  478-483. 

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A long-term used culture medium of Spirulina platensis was treated with different adsorbents, and they were screened in removal of the contained inhibitors via comparison of specific growth rate of Spiruina platensis in different adsorption-treated culture media. The concentrations of polysaccharide, organic acid and protein in culture medium before and after adsorption were compared, and the one with the largest concentration disparity was extracted to test its inhibition effect on Spirulina platensis growth. In addition, model analysis was carried out on the adsorption process. The results showed that the auto-growth inhibitor of Spirulina platensis was extracellular polysaccharide, and the adsorption treated culture medium by macro-porous adsorption resin S-8 could reduce extracellular polysaccharide content by 62% and simultaneously increased the specific growth rate by 39.4%, compared with the non-treatment medium. For the adsorption process of polysaccharide by S-8, 30 min was sufficient for equilibrium, pseudo-second-order and Boyd film diffusion model fitted well with the kinetic data, with linear correlation coefficients of 0.9991 and 0.9374, respectively.

Thermochemical Catalytic Liquefaction of the Cyanobacteria from Dianchi Lake in Sub- and Supercritical Ethanol, and Properties of Bio-oil

CHEN Xiao-ping BAO Gui-rong WANG Hua LI Fa-she LI Xiu-feng DU Wei

. 2012, 12(3):  484-488. 

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Direct liquefaction of the cyanobacteria from Dianchi Lake in ethanol under the sub- and supercritical conditions was carried out in an autoclave. The influences of reaction temperature, reaction time, catalyst loading, ratio of cyanobacteria to ethanol on the liquefaction were investigated. The results show that the optimal conditions are reaction temperature 270℃, reaction time 40 min, concentration of catalyst SO42-/ZrO2 2%, ratio of cyanobacteria to ethanol 1:15 g/mL. Under these conditions, the liquefaction conversion rate reaches 87.46% and the yield of bio-oil is 63.32%. The analysis by FT-IR and GC-MS indicates that the bio-oil is a complex mixture with palm ethyl as the main constituent.

材料工程专栏

Effects of Supports and Promoter Ag on Pd Catalysts for Selective Hydrogenation of Acetylene

ZHU Shu-ying HOU Rui-jun WANG Tie-feng

. 2012, 12(3):  489-496. 

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SiO2, a-Al2O3, g-Al2O3, ZrO2 and CeO2 were used as supports and Ag as promoter to study their effects on Pd catalysts for selective hydrogenation of acetylene. The catalysts were prepared by impregnated synthesis and characterized by XRD, BET and TEM. The catalytic reaction was carried out in a fixed-bed reactor. Overall, the low specific surface area supports were better to increase the ethylene selectivity at high conversion rate of acetylene. Among the four Pd catalysts on low specific surface area supports, the catalyst on low specific surface area SiO2 (LSA-SiO2) retained a high ethylene selectivity even at complete conversion, while the other catalysts showed significant decrease in the selectivity at complete conversion. The performance of Pd/LSA-SiO2 was important to decrease the loss of ethylene in selective hydrogenation of trace acetylene in ethylene. Addition of Ag to Pd/LSA-SiO2 significantly decreased the formation of ethane, C4 alkenes and green oil, and improved the ethylene selectivity to 90% when Pd:Ag=1:1 and 1:3(w). When the ratio of Pd to Ag was above 1, the activity of Pd-Ag bimetallic catalyst was similar to that of Pd monometallic catalyst, and the selectivity of ethylene increased with increasing of amount of Ag. When the ratio of Pd to Ag was below 1, the activity of bimetallic catalyst decreased with increasing of amount of Ag, while the selectivity of ethylene was kept unchanged. The optimum temperature was 200~230℃ for 0.02%(w)Pd-0.02%(w)Ag/LSA-SiO2 to give a high ethylene selectivity and low formation of green oil.

Fabrication of Electrophoretic Particles by Polymer Encapsulation and Characterization of Their Dispersion Stability Using UV Transmittance Method

SUN Shi-wei REN Jun; MENG Xian-wei; TANG Fang-qion;g

. 2012, 12(3):  497-503. 

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Black pigment nanoparticles were modified with a series of monomers with different polarities by radical grafting polymerization, and the effects of these polymer coating layers on the dispersion stability of copper chromite nanoparticles used in electrophoretic medium were examined by transmittance method. The results show that the stabilization time of particles in nonaqueous medium at least has increased 5 times after polymer modification, and the longer the side chain of monomer, the stabler the particles. When the monomer with an alkyl chain containing more than 4 carbon atoms, the corresponding polymer layers will impart good dispersibility to particles. The final black/white electrophoretic display has a response time of less than 1 s and contrast of (4~5):1 under a bias voltage of 5 V. The present results will provide a guideline for polymer modification of electrophoretic particle and theoretical foundation for improving electrophoretic medium stability and lifetime of electrophoretic display.

Preparation of High Infrared Reflective Chromic Oxide Green Pigment from Potassium Chromate by Hydrogen Reduction Calcination

ZHOU Zhen LI Ping ZHANG Hong-ling XU Hong-bin WANG Shao-na

. 2012, 12(3):  504-509. 

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A high infrared reflective chromium oxide green pigment was prepared by a hydrogen reduction calcination method. The maximum reflectance of Cr2O3 reached 70%. The influential factors on the reflectance such as reduction product, CrOOH, Cr(OH)3, temperature, and dopants TiO2 and P2O5 were studied. It was found that the reflectivity of Cr2O3 was improved by the calcination temperature and doping of TiO2 and P2O5. When the calcination temperature reached 1150℃, the reflectance of Cr2O3 was 60%, at this temperature, the reflectance reached 70% when the Cr2O3 was doped with P2O5 and TiO2 under the enhancement of KCrPO7 and (Cr,Ti)2O3 phase formation.

Stabilizing Function of Water Steam for Reactive Components in the Regeneration Process of Cu-Bi Bimetallic Catalyst Used in Synthesis of Vinyl Chloride

JIA Jin-chao LUO Guo-hua LI Xiao-gang ZHOU Kai WEI Fei

. 2012, 12(3):  510-515. 

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Addition of water steam into regeneration process was applied to enhance the performance of Cu-Bi catalyst in the reaction of acetylene hydrochlorination, and the stability of the catalyst was tested by multiple reaction-regeneration cycles. The results showed that compared with traditional regeneration method by air only which could lead 95% loss of reactive components in just 6 h regeneration cycles, the process involving water steam could transform bismuth chloride formed on the catalyst surface in the reaction process into bismuth phosphate which possesses excellent thermal stability. After 15 h regeneration cycles, only 20% Bi was lost, and the initial reactivity of the catalyst could still be recovered, which can make its industrial application possible.

Preparation and Characterization of Sn-doped ZnO Particles with Low Infrared Emissivity

ZHAO Liang ZHU Yong-ping

. 2012, 12(3):  516-521. 

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Sn-doped ZnO particles were successfully synthesized by chemical co-precipitation method. Their morphology, phase, microstructure and infrared emissivity were characterized. The results show that the Sn-doped ZnO particles are of ellipsoid shape, their crystalline structure changed with thermal process temperature, the optimal thermal process temperature and Sn-doped proportion are 1000℃ and 15%, respectively, the minimum emissivity values are 0.42, 0.28, 0.46 and 0.48 corresponding to the infrared wavelengths of 0~∞, 3~5, 8~14 and 14~20 mm, which indicates that the Sn-doped ZnO particles have the application potential as low infrared emissivity material.

Preparation and Catalytic Activity of H4SiW12O40/TiO2

ZHOU Hua-feng LIU Yu-ping ZHANG Li-qing

. 2012, 12(3):  522-526. 

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Two kinds of H4SiW12O40/TiO2 were synthesized by impregnation and sol-gel methods respectively with meseporous titania. Their structures were characterized by IR, TGA-DSC and N2 adsorption?desorption. Their catalytic activities in synthesis of tri-butyl citrate were studied. The results show that the H4SiW12O40/TiO2 synthesized by sol-gel method shows good catalytic activity and reusability in synthesis of tri-butyl citrate. The conversion rate of citric acid reaches 86.49% in 260 min when H4SiW12O40/TiO2(sol-gel) is reused in six times.

综述

Research Advances in Directly Heated Cracking of Hydrocarbonsby Heat Carrier Gas-I. Pyrolysis Apparatuses and Techniques

JING Xiao-dong ZHAO Yue-hong WEN Hao XU Zhi-hong

. 2012, 12(3):  527-540. 

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Recent advances in directly heated cracking using heat carrier gas together with the wide applications in industry are reviewed, focusing on the composition, operating conditions, product yields and the progress of pyrolysis apparatuses of directly heated cracking using heat carrier gas. In addition, the decoking techniques, mechanism and kinetics of hydrocarbons pyrolysis are also summarized up. Finally, the outlook for the future development of directly heated cracking using heat carrier gas is provided and a conclusion is drawn that directly heated cracking using superheated steam produced by combustion of hydrogen and oxygen as heat carrier gas will be one of the most promising techniques for it has the advantages of high feedstock and products flexibility, higher heat efficiency, and lower CO2 emission, and production of synthesis gas by coupling the decoking and pyrolysis processes.