Frontiers of Chemical Science and Engineering

ISSN 2095-0179

ISSN 2095-0187(Online)

CN 11-5981/TQ

Postal Subscription Code 80-969

2018 Impact Factor: 2.809

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REVIEW ARTICLE
A review on transport of coal seam gas and its impact on coalbed methane recovery
Geoff G.X. WANG, Xiaodong ZHANG, Xiaorong WEI, Xuehai FU, Bo JIANG, Yong QIN
Front Chem Sci Eng. 2011, 5 (2): 139-161.  
https://doi.org/10.1007/s11705-010-0527-4

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This paper presents a summary review on mass transport of coal seam gas (CSG) in coal associated with the coalbed methane (CBM) and CO2 geo-sequestration enhanced CBM (CO2-ECBM) recovery and current research advances in order to provide general knowledge and fundamental understanding of the CBM/ECBM processes for improved CBM recovery. It will discuss the major aspects of theory and technology for evaluation and development of CBM resources, including the gas storage and flow mechanism in CBM reservoirs in terms of their differences with conventional natural gas reservoirs, and their impact on CBM production behavior. The paper summarizes the evaluation procedure and methodologies used for CBM exploration and exploitation with some recommendations.

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Simulation of bubble column reactors using CFD coupled with a population balance model
Tiefeng WANG
Front Chem Sci Eng. 2011, 5 (2): 162-172.  
https://doi.org/10.1007/s11705-009-0267-5

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Bubble columns are widely used in chemical and biochemical processes due to their excellent mass and heat transfer characteristics and simple construction. However, their fundamental hydrodynamic behaviors, which are essential for reactor scale-up and design, are still not fully understood. To develop design tools for engineering purposes, much research has been carried out in the area of computational fluid dynamics (CFD) modeling and simulation of gas-liquid flows. Due to the importance of the bubble behavior, the bubble size distribution must be considered in the CFD models. The population balance model (PBM) is an effective approach to predict the bubble size distribution, and great efforts have been made in recent years to couple the PBM into CFD simulations. This article gives a selective review of the modeling and simulation of bubble column reactors using CFD coupled with PBM. Bubble breakup and coalescence models due to different mechanisms are discussed. It is shown that the CFD-PBM coupled model with proper bubble breakup and coalescence models and interphase force formulations has the ability of predicting the complex hydrodynamics in different flow regimes and, thus, provides a unified description of both the homogeneous and heterogeneous regimes. Further study is needed to improve the models of bubble coalescence and breakup, turbulence modification in high gas holdup, and interphase forces of bubble swarms.

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Carbon dioxide sequestration in petrochemical industries with the aim of reduction in greenhouse gas emissions
Maryam Takht Ravanchi, Saeed Sahebdelfar, Farnaz Tahriri Zangeneh
Front Chem Sci Eng. 2011, 5 (2): 173-178.  
https://doi.org/10.1007/s11705-010-0562-1

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The mitigation of greenhouse gas emissions to acceptable levels is arguably the greatest environmental challenge these days. Vast utilization of fossil fuels and forest destruction are main causes of CO2 increase in the atmosphere. Carbon dioxide sequestration that consists of separation, transportation and utilization or storage of CO2, is one way for reduction of its emission, in which the most costly section is separation. Different methods can be used for carbon dioxide separation such as absorption, membrane separation, adsorption and cryogenic distillation. Economic, technical and environmental issues should be considered in selection of the technology for particular application. Carbon dioxide concentration, temperature, pressure and flow rate are influential operating parameters in the selection of the appropriate separation method. Nowadays, absorption is the worldwide industrial separation method. New researches are focused on developing new stable solvents and efficient column configuration with suitable internals to minimize pressure drop. Membrane separation and adsorption (PSA type) are other long-term alternatives that can increase separation efficiency and decrease separation cost. The level of energy consumption in various separation methods are in the order: chemical absorption>physical absorption>membrane separation. Because of high investment costs, current separation technologies are suitable for large concentrated sources. In the present paper, different processes for carbon dioxide separation are investigated and compared. Available technologies and commercial plants for CO2 sequestration are provided.

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RESEARCH ARTICLE
Functional role of ATM in the cellular response to DNA damage
Ming LIU, Wenxiang HU
Front Chem Sci Eng. 2011, 5 (2): 179-187.  
https://doi.org/10.1007/s11705-009-0268-4

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Ataxia-telangiectasia mutated (ATM) plays a key role in regulating the cellular response to ionizing radiation. The tumor-suppressor gene ATM, mutations in which cause the human genetic disease ataxia telangiectasia, encodes a key protein kinase that controls the cellular response to double-stranded breaks. Activation of ATM results in phosphorylation of many downstream targets that modulate numerous damage response pathways, most notably cell cycle checkpoints. Here, we highlight some of the new developments in the field in our understanding of the mechanism of activation of ATM and its signaling pathways, explore whether DNA double-strand breaks are the sole activators of ATM and ATM-dependent signaling pathways, and address some of the prominent, unanswered questions related to ATM and its function. The scope of this article is to provide a brief overview of the recent literature on this subject and to raise questions that could be addressed in future studies.

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REVIEW ARTICLE
Recent advances in the catalytic pyrolysis of biomass
Changwei HU, Yu YANG, Jia LUO, Pan PAN, Dongmei TONG, Guiying LI
Front Chem Sci Eng. 2011, 5 (2): 188-193.  
https://doi.org/10.1007/s11705-010-1015-6

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Biomass is considered as a renewable and alternative resource for the production of fuels and chemicals, since it is the only carbon and hydrogen containing resource that we can find in the world except for fossil resources, capable of being converted to hydrocarbons. The pyrolytic liquefaction of biomass is a promising way to convert biomass to useful products. This paper briefly surveys the present status of the direct catalytic pyrolysis for the liquefaction of biomass. The direct use of catalysts could decrease the pyrolysis temperature, increase the conversion of biomass and the yield of bio-oil, and change the distribution of the pyrolytic liquid products then improve the quality of the bio-oil obtained. The fact that biomass is in solid state present great challenges for its conversion and for the effective use of catalysts due to the bad heat transfer characteristics and bad mass transfer properties. These barriers appeal for the development of a new catalyst and new catalytic process as well as the integration of both. Process design and process intensification are of significant importance in the catalytic conversion of biomass.

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RESEARCH ARTICLE
Investigation of bubble diameter and flow regime between water and dilute aqueous ethanol solutions in an airlift reactor
Baharak SAJJADI, Mostafa Keshavarz MORAVEJI, Reza DAVARNEJAD
Front Chem Sci Eng. 2011, 5 (2): 194-202.  
https://doi.org/10.1007/s11705-010-1019-2

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In this study, the effect of ethanol addition into pure water and its concentration on bubble diameter, gas hold-up and flow regimes were investigated in an airlift reactor. Air and water with ethanol (concentration ranging from 0%–1%, v/v) were as dispersed and continuous phases, respectively. Superficial gas velocity was considered as an effective parameter. Bubble size distribution was measured by photography and picture analysis at various concentrations of ethanol and various velocities of gas. Alcohol concentration enhancement caused bubble diameter to decrease. Furthermore, the bubbles diameter in pure water was nearly 4 times higher than that of ethanol with concentration of 1% (v/v) and also was 3.4 times higher than that of ethanol with concentration of 0.25% (v/v) at the highest aeration gas velocity inlet. For ethanol solutions in lower superficial gas velocity, a homogenous flow regime was observed. This trend continued to inlet gas velocity of about 0.4 cm/s. The transition flow regime occurred after this datum although in pure water, a homogenous flow regime was observed up to a superficial gas velocity of 0.7 cm/s. The gas hold-up in dilute ethanol solutions were more than (around 2 times) that of pure water and increased with increasing concentration of ethanol in those solutions.

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Kinetics and thermodynamics of the phosphine adsorption on the modified activated carbon
Bingnan REN
Front Chem Sci Eng. 2011, 5 (2): 203-208.  
https://doi.org/10.1007/s11705-010-0571-0

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The kinetics and the thermodynamics of phosphine (PH3) adsorption on the modified activated carbon have been explained for the adsorption process of PH3. This study investigated the kinetic and thermodynamic properties of PH3 adsorption on the activated carbon impregnated with 5% HCl solution. The thermodynamic properties including PH3 adsorption isotherm and adsorption heat were separately investigated at 20°C, 70°C, 90°C. The results showed that the Freundlich-type isotherm equation described the isotherms well. The adsorption capacity increased with increasing temperature between 20°C and 70°C. Between 70°C and 90°C, the adsorption capacity decreased obviously with increasing temperature. The adsorption capacity reached the maximum at 70°C. By analyzing the results of the kinetics and the thermodynamics, we found that the adsorption of PH3 was dominated by physical adsorption at the lower temperature (20°C). Then with increasing temperature, chemical adsorption gradually dominated in the adsorption process. The adsorption capacity decreased at above 70°C is due to the exothermic effects in the process of adsorption.

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Hydrogen production from methanol through dielectric barrier discharge
Baowei WANG, Xu ZHANG, Haiying BAI, Yijun Lü, Shuanghui HU
Front Chem Sci Eng. 2011, 5 (2): 209-214.  
https://doi.org/10.1007/s11705-010-1018-3

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The hydrogen fuel cell is a promising option as a future energy resource and the production of hydrogen is mainly depended on fossil fuels now. In this paper, methanol reforming to produce H2 through dielectric-barrier discharge (DBD) plasma reaction was studied. Effects of the power supply parameters, reactor parameters and process conditions on conversion of methanol and distribution of products were investigated. The best reaction conditions were following: input power (45 W), material of inner electrode (stainless steel), discharge gap (3.40 mm), length of reaction zone (90.00 mm), dielectric thickness (1.25 mm), and methanol content (37.65%). The highest conversion of methanol and the yield of H2 were 82.38% and 27.43%, respectively.

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Capture of carbon dioxide over porous solid adsorbents lithium silicate, lithium aluminate and magnesium aluminate at pre-combustion temperatures
P. V. Korake, A. G. Gaikwad
Front Chem Sci Eng. 2011, 5 (2): 215-226.  
https://doi.org/10.1007/s11705-010-1012-9

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The capturing process for carbon dioxide over porous solid adsorbents such as lithium silicate, lithium aluminate, and magnesium aluminate at pre- combustion temperatures was studied. Lithium silicate was prepared by the sol gel and solid fusion methods. The lithium silicate adsorbent was characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), nuclear magnetic resonance (NMR), and surface area. The capturing of carbon dioxide over lithium silicate, lithium aluminate, and magnesium aluminate was explored at different experimental conditions such as exposure time, temperature variation, and exposure carbon dioxide pressure. The capturing process for carbon dioxide was investigated over these adsorbents with variation of their metal mole ratios. The effect of the addition of (promoter) sodium, potassium, and cesium in the lithium silicate adsorbent was explored to investigate the variation of the capture of carbon dioxide over these adsorbents.

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Salt-assisted synthesis of tree-like oriented SnO2 nanodendrite
Jinquan SUN, Zifeng YAN, Hongzhi CUI
Front Chem Sci Eng. 2011, 5 (2): 227-230.  
https://doi.org/10.1007/s11705-010-0566-x

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Tree-like SnO2 nanodendrites in large amounts have been prepared through two-step reactions. The nanoparticles used as the precursors have taken aggregation forming tree-like or string of nanodendrtie. The samples were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM) and energy dispersive spectrometer (EDS), respectively. The results showed that molar ratio of the ethanol/distilled water is an important factor for formation of the different dendrite structures. There are different morphologies between tree-like SnO2 nanowhiskers and bunch of SnO2 nanorods. However, they are growing along the [112 ˉ].

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Design, synthesis and HIV-RT inhibitory activity of novel thiazolidin-4-one derivatives
Hua CHEN, Zaihong GUO, Qingmei YIN, Xiaoxu DUAN, Yunjing GU, Xiaoliu LI
Front Chem Sci Eng. 2011, 5 (2): 231-237.  
https://doi.org/10.1007/s11705-010-1022-7

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A series of 2-aryl-3-(4,5,6-trimethylpyrimidin-2-yl) thiazolidin-4-ones (1a1c) and their derivatives bearing a lipophilic substituent, like acetoxy group (3a3c), propionyloxy group (4a4c), methyl (5d and 5e) at C-5 on thiazolidin-4-one ring were designed, synthesized and evaluated for their HIV-RT inhibitory activity. Using self-catalyzed Pummerer reaction, compounds 3a3c and 4a4c were obtained in good yield (63.1%75.2%). Preliminary anti-HIV-RT test of these derivatives indicated that compounds 1a1c, 4b (propionyloxy group at C-5) showed moderate HIV-RT inhibitory activity and compounds 5d and 5e with methyl at C-5 showed a weak HIV-RT inhibitory activity. Structure activity relationship analysis suggested that the substituted groups on C-5 would be unfavorable to anti-HIV-RT activity and that the steric effect might play a critical role in the anti-HIV RT activity.

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Anti-hyperglycemic effect of the polysaccharide fraction isolated from mactra veneriformis
Lingchong WANG, Hao WU, Nian CHANG, Kun ZHANG
Front Chem Sci Eng. 2011, 5 (2): 238-244.  
https://doi.org/10.1007/s11705-010-0002-2

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Total macromolecule extract was obtained from the soft body of Mactra veneriformis by the coupling techniques of decoction and alcohol precipitation. The extract was deproteinized with an ion exchange column, and resulted in the purifying of the crude polysaccharide fraction. It was found by chemical analysis that the crude polysaccharide part is composed of abundant polysaccharides (>95%) and few proteins (<1%). Furthermore, only one type of monosaccharide, glucose, was detected from its hydrolytes by thin-layer chromatography, indicating that the polysaccharides might be analogs of glucosan. The anti-hyperglycemia effects of the crude polysaccharide part were preliminarily investigated using several pharmacological methods in normal and diabetic mice. Animal experimental results showed that the crude polysaccharide fraction exhibited proper glycemia inhibition activity, and 300 mg/kg-weight dose has the optimal effect among all the studied doses. It is concluded that the crude polysaccharide fraction can be explored as a novel health product that possesses potential as an anti-hyperglycemic agent.

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A study on rapid acid chrome black (MB 7) spectrophotometric determination of ClO2 and catalytic degradation of 2,6-dinitro-p-cresol (DNPC) by ClO2
Jing DONG, Huilong WANG
Front Chem Sci Eng. 2011, 5 (2): 245-251.  
https://doi.org/10.1007/s11705-010-1003-x

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Experiments were conducted to investigate the degradation of 2,6-dinitro-p-cresol (DNPC) in the chlorine dioxide (ClO2) catalytic oxidation process. Pure aluminum oxide was used as the catalyst in this process. The degradation of DNPC by ClO2 using aluminum oxide as catalyst was systematically studied by varying the experimental parameters, such as pH values, catalyst dosage, the initial concentration of DNPC and ClO2, reaction time, etc. Under optimal condition (DNPC concentration 39 mg·L-1, ClO2 concentration 0.234 g·L-1, reaction time 15 min, catalyst dosage 4.7 g·L-1 and pH 4.32), almost complete degradation of DNPC can be achieved. The kinetic studies revealed that the ClO2 catalytic oxidation degradation of DNPC followed pseudo-first-order kinetics with respect to both ClO2 and DNPC concentration. The repetitive use of the catalyst was investigated along sequential feed-batch trials. The catalyst performed efficiently after five runs. In addition, a simple and convenient method for the determination of ClO2 in water was developed by using acid chrome black 7 (MB 7) spectrophotometry in this paper.

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Kinetic studies of xylan hydrolysis of corn stover in a dilute acid cycle spray flow-through reactor
Hongman ZHANG, Qiang JIN, Rui XU, Lishi YAN, Zengxiang LIN
Front Chem Sci Eng. 2011, 5 (2): 252-257.  
https://doi.org/10.1007/s11705-010-1010-y

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Xylan of corn stover was pretreated with 1%, 2% and 3% (w/w) sulfuric acid at relatively low temperatures (90°C, 95°C and 100°C) in a dilute acid cycle spray flow-through reactor (DCF). The hydrolysis of xylan to its monomeric xylose was modeled by a series of first-order reactions. Both biphasic and Saeman hydrolysis models were applied to fit the experimental data. The results confirmed that the kinetic data of xylan hydrolysis fitted a first-order irreversible reaction model and the experimental data. The reaction rates of xylose monomer formation and degradation were sensitive to catalyst concentration and temperature. Higher catalyst concentration and lower reaction temperature result in high xylose yield. The activation energy for xylose formation and degradation were determined to be 112.9 and 101.0 kJ·mol-1, respectively. Over 90% theoretical xylose obtained from corn stover can be used to produce ethanol, xylitol and fumaric acid by fermentation.

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Morphological and mechanical characterization of a PMMA/CdS nanocomposite
Vishal MATHUR, Manasvi DIXIT, K.S. RATHORE, N. S. SAXENA, K.B. SHARMA
Front Chem Sci Eng. 2011, 5 (2): 258-263.  
https://doi.org/10.1007/s11705-010-1014-7

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Thick film of poly(methyl methacrylate) (PMMA)/CdS nanocomposite have been synthesized by the solution casting process. The nanostructure of the CdS particles has been ascertained through the small angle X-ray scattering (SAXS) technique. The surface morphological characterization of the PMMA/CdS nanocomposite has been done through scanning electron microscopy (SEM) analysis. The variation of mechanical loss factor (Tanδ) with temperature and tensile properties of prepared samples have been studied using Dynamic Mechanical Analyzer (DMA). This study reveals that the glass transition temperature (Tg), Young’s modulus, and fracture energy of the PMMA/CdS nanocomposite are greatly influenced by the existence of interfacial energetic interaction between dispersed CdS nanoparticles and the matrix of PMMA.

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Atomistic simulations for adsorption and separation of flue gas in MFI zeolite and MFI/MCM-41 micro/mesoporous composite
Shengchi ZHUO, Yongmin HUANG, Jun HU, Honglai LIU
Front Chem Sci Eng. 2011, 5 (2): 264-273.  
https://doi.org/10.1007/s11705-010-1007-6

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Adsorption of pure CO2 and N2 and separation of CO2/N2 mixture in MFI zeolite and MFI/MCM-41 micro/mesoporous composite have been studied by using atomistic simulations. Fully atomistic models of MFI and MFI/MCM-41 are constructed and characterized. A bimodal pore size distribution is observed in MFI/MCM-41 from simulated small- and broad-angle X-ray diffraction patterns. The density of MFI/MCM-41 is lower than MFI, while its free volume and specific surface area are greater than MFI due to the presence of mesopores. CO2 is preferentially adsorbed than N2, and thus, the loading and isosteric heat of CO2 are greater than N2 in both MFI and MFI/MCM-41. CO2 isotherm in MFI/MCM-41 is similar to that in MFI at low pressures, but resembles that in MCM-41 at high pressures. N2 shows similar amount of loading in MFI, MCM-41 and MFI/MCM-41. The selectivity of CO2 over N2 in the three adsorbents decreases in the order of MFI>MFI/MCM-41>MCM-41. With increasing pressure, the selectivity increases in MFI and MFI/MCM-41, but decreases in MCM-41. The self-diffusivity of CO2 and N2 in MFI decreases as loading increases, while in MFI/MCM-41, it first increases and then drops.

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16 articles