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SCI和EI收录∣中国化工学会会刊
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Table of Content
28 September 2013, Volume 21 Issue 9
    Recent Advances in Separation of Bioactive Natural Products
    REN Qilong, XING Huabin, BAO Zongbi, SU Baogen, YANG Qiwei, YANG Yiwen, ZHANG Zhiguo
    2013, 21(9):  937-952.  doi:10.1016/S1004-9541(13)60560-1
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    Bioactive natural products are a main source of new drugs, functional foods and food additives. The separation of bioactive natural products plays an important role in transformation and use of biomass. The isolation and purification of bioactive principle from a complex matrix is often inherent bottleneck for the utilization of natural products, so a series of extraction and separation techniques have been developed. This review covers recent advances in the separation of bioactive natural products with an emphasis on their solubility and diffusion coefficients, recent extraction techniques and isolation techniques. This overview of recent technological advances, discussion of pertinent problems and prospect of current methodologies in the separation of bioactive natural products may provide a driving force for development of novel separation techniques.
    Diffusion-controlled Adsorption Kinetics of Surfactant at Air/Solution Interface
    LIU Junji, XU Yun, SUN Hongxiu
    2013, 21(9):  953-958.  doi:10.1016/S1004-9541(13)60562-5
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    For the diffusion-controlled adsorption, the expression of dynamic surface adsorption Γ(t)was obtained by solving the diffusion equation. Two cases, i.e. the short and long time limits, were mainly discussed in this paper. From the measured dynamic surface tension of aqueous surfactant sodium dodecyl sulfate (SDS) solutions at 25℃, the adsorption kinetics of SDS at air/solution interface was studied. It was proved that for both of the short and long time limits, the adsorption process of SDS was controlled by diffusion.
    Three-dimensional Computational Fluid Dynamics Modeling of Two-phase Flow in a Structured Packing Column
    ZHANG Xiaobin, YAO Lei, QIU Limin, ZHANG Xuejun
    2013, 21(9):  959-966.  doi:10.1016/S1004-9541(13)60576-5
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    Characterizing the complex two-phase hydrodynamics in structured packed columns requires a powerful modeling tool. The traditional two-dimensional model exhibits limitations when one attempts to model the detailed two-phase flow inside the columns. The present paper presents a three-dimensional computational fluid dynamics (CFD) model to simulate the two-phase flow in a representative unit of the column. The unit consists of an entire corrugation channel and describes well the real liquid flow conditions. The detailed unsteady two-phase 3D CFD calculations on column packed with Flexipak 1Y were implemented within the volume of fluid (VOF) mathematical framework. The CFD model was validated by comparing the calculated thickness of liquid film with the available experimental data. Special attention was given to quantitative analysis of the effects of gravity on the hydrodynamics. Fluctuations in the liquid mass flow rate and the calculated pressure drop loss were found to be qualitatively in agreement with the experimental observations.
    SEPARATION SCIENCE AND ENGINEERING
    Treatment of Sebacic Acid Industrial Wastewater by Extraction Process Using Castor Oil Acid as Extractant
    XU Hang, ZHOU Quan, WANG Jinfu
    2013, 21(9):  967-973.  doi:10.1016/S1004-9541(13)60546-7
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    Wastewater containing high concentrations of phenol and sodium sulfate is generated in sebacic acid (SA) industry. Castor oil acid, a raw material for producing SA, can be used to extract phenol from wastewater in order to reduce the amount of phenol used in the process and discharge of phenol. The results show that the extraction mechanism is that hydroxyl group of phenol is linked to carboxyl group of castor oil acid by hydrogen bond. The extraction process approaches equilibrium in 30 min. Extraction ratio increases with the increase of sodium sulfate and castor oil acid, and decreases as phenol increases. When the oil-water ratio is 1:3, the optimal distribution coefficient of 40 is obtained. Phenol saturation concentration in castor oil acid is 1.03 mol·L-1 after extraction for 4 times. The equilibrium constant (Kex) at 25℃ is 8.41 and the endothermic enthalpy (ΔH) is 1.513 kJ·mol-1. The Gibbs free energy (ΔG) is -5.277 kJ·mol-1 and the value of ΔS is calculated to be 22.3 J·mol-1·K-1.
    Removal of Cu2+ from Aqueous Solutions Using Na-A Zeolite from Oil Shale Ash
    BAO Weiwei, LIU Lu, ZOU Haifeng, GAN Shucai, XU Xuechun, JI Guijuan, GAO Guimei, Zheng Keyan
    2013, 21(9):  974-982.  doi:10.1016/S1004-9541(13)60529-7
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    Na-A zeolite was synthesized using oil shale ash (OSA), which is a solid by-product of oil shale processing. The samples were characterized by various techniques, such as scanning electron microscopy, X-ray diffraction and Brunauer Emmet Teller method. The batch isothermal equilibrium adsorption experiments were performed to evaluate the ability of Na-A zeolite for removal of Cu(II) from aqueous solutions. The effects of operating parameters, such as concentration of copper solutions, adsorbent dosages, pH value of solutions and temperature, on the adsorption efficiency were investigated. The equilibrium adsorption data were fitted with Langmuir and Freundlich models. The maximum adsorption capacity of Na-A zeolite obtained from the Langmuir adsorption isotherm is 156.7 mg·g-1 of Cu(II). The increase of pH level in the adsorption process suggests that the uptake of heavy metals on the zeolite follows an ion exchange mechanism. The batch kinetic data fit the pseudo-second order equation well. The thermodynamic parameters, such as changes in Gibbs free energy (DG), enthalpy (DH) and entropy (DS), are used to predict the nature of the adsorption process. The negative DG values at different temperatures confirm that the adsorption processes are spontaneous.
    SEPARATION SCIENCE AND ENGINEERING
    Experimental and Theoretical Studies of CO2 Absorption Enhancement by Nano-Al2O3 and Carbon Nanotube Particles
    LU Sumin, XING Min, SUN Yan, DONG Xiangjun
    2013, 21(9):  983-990.  doi:10.1016/S1004-9541(13)60550-9
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    The influence of nano-particles on CO2 absorption was studied experimentally in a stirred thermostatic reactor. Nano-Al2O3 and carbon nanotube (CNT) particles which showed different hydrophobic properties were chosen for the investigation. The experimental results were compared with that of micron-size activated carbon (AC) and Al2O3 particles. From the results, no enhancement by micron-size Al2O3 was found, and with the increase of Al2O3 concentration, the enhancement factor decreased. However, nano-Al2O3 showed a weak enhancement for the CO2 absorption. AC and CNT particles all intensified the gas-liquid mass transfer effectively, yet the trend of the enhancement factor with stirring speed for the two particles was different. With increasing stirring speed, the enhancement factor of AC particles was decreased, whereas in CNT suspensions it was increased. The experimental phenomena demonstrated a difference in enhancement mechanism for different size particles. For nano-particles, besides the influence of adsorbability and hydrophobicity, the micro-convection caused by Brownian motion should be also taken into account. Considering the micro-convection effect, a theoretical model was developed to shed light on the absorption enhancement by nano-particles.
    Halloysite Nanotube Composited Thermo-responsive Hydrogel System for Controlled-release
    LIN Xi, JU Xiaojie, XIE Rui, JIANG Mingyue, WEI Jie, CHU Liangyin
    2013, 21(9):  991-998.  doi:10.1016/S1004-9541(13)60572-8
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    Halloysite nanotube-composited thermo-responsive hydrogel system has been successfully developed for controlled drug release by copolymerization of N-isopropylacrylamide (NIPAM) with silane-modified halloysite nanotubes (HNT) through thermally initiated free-radical polymerization. With methylene blue as a model drug, thermo-responsive drug release results demonstrate that the drug release from the nanotubes in the composited hydrogel can be well controlled by manipulating the environmental temperature. When the hydrogel network is swollen at temperature below the lower critical solution temperature (LCST), drug releases steadily from lumens of the embedded nanotubes, whereas the drug release stops when hydrogel shrinks at temperature above the LCST. The release of model drug from the HNT-composited hydrogel matches well with its thermo-responsive volume phase transition, and shows characteristics of well controlled release. The design strategy and release results of the proposed novel HNT-composited thermo-responsive hydrogel system provide valuable guidance for designing responsive nanocomposites for controlled-release of active agents.
    Conversion of Fuel-N to N2O and NOx during Coal Combustion in Combustors of Different Scale
    ZHOU Hao, HUANG Yan, MO Guiyuan, LIAO Ziyu, CEN Kefa
    2013, 21(9):  999-1006.  doi:10.1016/S1004-9541(13)60571-6
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    With focus on investigating the effect of combustor scale on the conversion of fuel-N to NOx and N2O, experiments are carried out in three combustors, including single coal particle combustion test rig, laboratory scale circulating fluidized-bed boiler (CFB) and full scale CFB in this work. For single coal particle combustion, the majority of fuel-N (65%-82%) is released as NOx, while only a little (less than 8%) fuel-N yields N2O. But in laboratory scale CFB, the conversion of fuel-N to N2O is increases, but the conversion of fuel-N to NOx is quite less than that of single coal particle combustion. This is because much char in CFB can promote the NOx reduction by increasing N2O formation. In full scale CFB, both of the conversion of fuel-N to NOx and the conversion of fuel-N to N2O are smaller than laboratory scale CFB.
    A Novel γ-Alumina Supported Fe-Mo Bimetallic Catalyst for Reverse Water Gas Shift Reaction
    Abolfazl Gharibi Kharaji, Ahmad Shariati, Mohammad Ali Takassi
    2013, 21(9):  1007-1014.  doi:10.1016/S1004-9541(13)60573-X
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    In reverse water gas shift (RWGS) reaction CO2 is converted to CO which in turn can be used to produce beneficial chemicals such as methanol. In the present study, Mo/Al2O3, Fe/Al2O3 and Fe-Mo/Al2O3 catalysts were synthesised using impregnation method. The structures of catalysts were studied using X-ray diffraction (XRD), Brunauer-Emmett-Teller (BET) method, inductively coupled plasma atomic emission spectrometer (ICP-AES), temperature programmed reduction (H2-TPR), CO chemisorption, energy dispersive X-ray (EDX) and scanning electron microscopy (SEM) techniques. Kinetic properties of all catalysts were investigated in a batch reactor for RWGS reaction. The results indicated that Mo existence in structure of Fe-Mo/Al2O3 catalyst enhances its activity as compared to Fe/Al2O3. This enhancement is probably due to better Fe dispersion and smaller particle size of Fe species. Stability test of Fe-Mo/Al2O3 catalyst was carried out in a fixed bed reactor and a high CO yield for 60 h of time on stream was demonstrated. Fe2(MoO4)3 phase was found in the structures of fresh and used catalysts. TPR results also indicate that Fe2(MoO4)3 phase has low reducibility, therefore the Fe2(MoO4)3 phase significantly inhibits the reduction of the remaining Fe oxides in the catalyst, resulted in high stability of Fe-Mo/Al2O3 catalyst. Overall, this study introduces Fe-Mo/Al2O3 as a novel catalyst with high CO yield, almost no by-products and fairly stable for RWGS reaction.
    PROCESS SYSTEMS ENGINEERING
    Dynamics and Predictive Control of Gas Phase Propylene Polymerization in Fluidized Bed Reactors
    Ahmad Shamiri, Mohamed azlan Hussain, Farouq sabri Mjalli, Navid Mostoufi, Seyedahmad Hajimolana
    2013, 21(9):  1015-1029.  doi:10.1016/S1004-9541(13)60565-0
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    A two-phase dynamic model, describing gas phase propylene polymerization in a fluidized bed reactor, was used to explore the dynamic behavior and process control of the polypropylene production rate and reactor temperature. The open loop analysis revealed the nonlinear behavior of the polypropylene fluidized bed reactor, justifying the use of an advanced control algorithm for efficient control of the process variables. In this case, a centralized model predictive control (MPC) technique was implemented to control the polypropylene production rate and reactor temperature by manipulating the catalyst feed rate and cooling water flow rate respectively. The corresponding MPC controller was able to track changes in the setpoint smoothly for the reactor temperature and production rate while the setpoint tracking of the conventional proportional-integral (PI) controller was oscillatory with overshoots and obvious interaction between the reactor temperature and production rate loops. The MPC was able to produce controller moves which not only were well within the specified input constraints for both control variables, but also non-aggressive and sufficiently smooth for practical implementations. Furthermore, the closed loop dynamic simulations indicated that the speed of rejecting the process disturbances for the MPC controller were also acceptable for both controlled variables.
    A New Tuning Method for Two-Degree-of-Freedom Internal Model Control under Parametric Uncertainty
    Juwari Purwo sutikno, Badhrulhisham Abdul aziz, Chin Sim yee, Rosbi Mamat
    2013, 21(9):  1030-1037.  doi:10.1016/S1004-9541(13)60564-9
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    Internal model control (IMC) yields very good performance for set point tracking, but gives sluggish response for disturbance rejection problem. A two-degree-of-freedom IMC (2DOF-IMC) has been developed to overcome the weakness. However, the setting of parameter becomes a complicated matter if there is an uncertainty model. The present study proposes a new tuning method for the controller. The proposed tuning method consists of three steps. Firstly, the worst case of the model uncertainty is determined. Secondly, the parameter of set point controller using maximum peak (Mp) criteria is specified, and finally, the parameter of the disturbance rejection controller using gain margin (GM) criteria is obtained. The proposed method is denoted as Mp-GM tuning method. The effectiveness of Mp-GM tuning method has evaluated and compared with IMC-controller tuning program (IMCTUNE) as bench mark. The evaluation and comparison have been done through the simulation on a number of first order plus dead time (FOPDT) and higher order processes. The FOPDT process tested includes processes with controllability ratio in the range 0.7 to 2.5. The higher processes include second order with underdamped and third order with nonminimum phase processes. Although the two of higher order processes are considered as difficult processes, the proposed Mp-GM tuning method are able to obtain the good controller parameter even under process uncertainties.
    PROCESS SYSTEMS ENGINEERING
    Soft Sensor for Inputs and Parameters Using Nonlinear Singular State Observer in Chemical Processes
    XU Feng, WANG Yeye, LUO Xionglin
    2013, 21(9):  1038-1047.  doi:10.1016/S1004-9541(13)60570-4
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    Chemical processes are usually nonlinear singular systems. In this study, a soft sensor using nonlinear singular state observer is established for unknown inputs and uncertain model parameters in chemical processes, which are augmented as state variables. Based on the observability of the singular system, this paper presents a simplified observability criterion under certain conditions for unknown inputs and uncertain model parameters. When the observability is satisfied, the unknown inputs and the uncertain model parameters are estimated online by the soft sensor using augmented nonlinear singular state observer. The riser reactor of fluid catalytic cracking unit is used as an example for analysis and simulation. With the catalyst circulation rate as the only unknown input without model error, one temperature sensor at the riser reactor outlet will ensure the correct estimation for the catalyst circulation rate. However, when uncertain model parameters also exist, additional temperature sensors must be used to ensure correct estimation for unknown inputs and uncertain model parameters of chemical processes.
    Volumetric and Transport Properties of Aqueous NaB(OH)4 Solutions
    ZHOU Yongquan, FANG Chunhui, FANG Yan, ZHU Fayan,
    2013, 21(9):  1048-1056.  doi:10.1016/S1004-9541(13)60561-3
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    Density, pH, viscosity, conductivity and the Raman spectra of aqueous NaB(OH)4 solutions precisely measured as functions of concentration at different temperatures (293.15, 298.15, 303.15, 313.15 and 323.15 K) are presented. Polyborate distributions in aqueous NaB(OH)4 solution were calculated, covering all the concentration range, B(OH)4- is the most dominant species, other polyborate anions are less than 5.0%. The volumetric and the transport properties were discussed in detail, both of these properties indicate that B(OH)4- behaves as a structure-disordered anion.
    Production of Poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) by Recombinant Pseudomonas stutzeri 1317 from Unrelated Carbon Sources
    WEI Xiaoxing, LIU Feng, JIAN Jia, WANG Ruiyan, CHEN Guoqiang,
    2013, 21(9):  1057-1061.  doi:10.1016/S1004-9541(13)60549-2
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    Synthetic biology promises to simplify the construction of metabolic pathways by assembling the detached modules of the whole pathway. This gives new approaches for the microbial production of industrial products such as polyhydroxyalkanoates (PHA). In this study, to produce poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) (PHBHHx) by Pseudomonas stutzeri 1317 from unrelated carbon sources such as glucose, the phaC1-phaZ-phaC2 operon of P. stutzeri 1317 was knocked out to generate the PHA deficient mutant P. stutzeri 1317LF. Then three modules containing phaCAhAReBRe, phaCAhBReGPp and phaCAhPAh were introduced into P. stutzeri 1317LF separately. The shake flask results indicated that the precursor supply and PHA synthase activity were the vital factors for the PHBHHx accumulation of P. stutzeri 1317LF. Furthermore, the PHBHHx accumulation of the recombinants from different carbon resources were performed. The highest PHBHHx content was 23.7%(by mass) with 58.6%(by mole) 3HB fraction. These results provide basis for further improving the PHBHHx accumulation of P. stutzeri from unrelated carbon sources.
    Ammonium Ion Adsorption and Settleability Improvement Achieved in a Synthetic Zeolite-Amended Activated Sludge
    Emilia Otal, Luís F. Vilches, Yolanda Luna, Rodrigo Poblete, Juan M. García-Maya, Constantino Fernández-Pereira
    2013, 21(9):  1062-1068.  doi:10.1016/S1004-9541(13)60566-2
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    Municipal wastewater treatment plants typically exhibit two classic problems: high ammonium concentration in water after conventional biological treatment and, in some cases, poor activated sludge sediment ability. Potential solutions to these problems were investigated by adding a synthetic zeolite obtained from coal fly ash to different steps of activated sludge treatment. The experimental results for ammonium removal fit well with the theoretical adsorption isotherms of the Freundlich model with a maximum adsorption capacity of 13.72 mg·g-1. Utilization of this kind of zeolite to improve activated sludge sediment ability is studied for the first time in this work. It is found that the addition of the zeolite (1 g·L-1) to an activated sludge with settling problems significantly enhances its sediment ability and compact ability. This is confirmed by the sludge volume index (SVI), which was reduced from 163 ml·g-1 to 70 ml·g-1, the V60 value, which was reduced from 894 ml·L-1 to 427 ml·L-1, and the zeta potential (ζ), which was reduced from -19.81 mV to -14.29 mV. The results indicate that the addition of this synthetic zeolite to activated sludge, as an additional waste management practice, has a positive impact on both ammonium removal and sludge settleability.