Frontiers of Chemical Science and Engineering

ISSN 2095-0179

ISSN 2095-0187(Online)

CN 11-5981/TQ

2015 Impact Factor: 1.043

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Mesoporous zeolites as efficient catalysts for oil refining and natural gas conversion
Jie ZHU, Xiangju MENG, Fengshou XIAO
Front Chem Sci Eng    2013, 7 (2): 233-248.
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Zeolites have been regarded as one of the most important catalysts in petrochemical industry due to their excellent catalytic performance. However, the sole micropores in zeolites severely limit their applications in oil refining and natural gas conversion. To solve the problem, mesoporous zeolites have been prepared by introducing mesopores into the zeolite crystals in recent years, and thus have the advantages of both mesostructured materials (fast diffusion and accessible for bulky molecules) and microporous zeolite crystals (strong acidity and high hydrothermal stability). In this review, after giving a brief introduction to preparation, structure, and characterization of mesoporous zeolites, we systematically summarize catalytic applications of these mesoporous zeolites as efficient catalysts in oil refining and natural gas conversion including catalytic cracking of heavy oil, alkylation, isomerization, hydrogenation, hydrodesulfurization, methane dehydroaromatization, methanol dehydration to dimethyl ether, methanol to olefins, and methanol to hydrocarbons.

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Problems, potentials and future of industrial crystallization
J. Ulrich, P. Frohberg
Front Chem Sci Eng    2013, 7 (1): 1-8.
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This review discusses important research developments and arising challenges in the field of industrial crystallization with an emphasis on recent problems. The most relevant areas of research have been identified. These are the prediction of phase diagrams; the prediction of effects of impurities and additives; the design of fluid dynamics; the process control with process analytical technologies (PAT) tools; the polymorph and solvate screening; the stabilization of non-stable phases; and the product design. The potential of industrial crystallization in various areas is outlined and discussed with particular reference to the product quality, process design, and control. On this basis, possible future directions for research and development have been pointed out to highlight the importance of crystallization as an outstanding technique for separation, purification as well as for product design.

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Where physics meets chemistry: Thin film deposition from reactive plasmas
Andrew Michelmore, Jason D. Whittle, James W. Bradley, Robert D. Short
Front. Chem. Sci. Eng.    2016, 10 (4): 441-458.
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Functionalising surfaces using polymeric thin films is an industrially important field. One technique for achieving nanoscale, controlled surface functionalization is plasma deposition. Plasma deposition has advantages over other surface engineering processes, including that it is solvent free, substrate and geometry independent, and the surface properties of the film can be designed by judicious choice of precursor and plasma conditions. Despite the utility of this method, the mechanisms of plasma polymer growth are generally unknown, and are usually described by chemical (i.e., radical) pathways. In this review, we aim to show that plasma physics drives the chemistry of the plasma phase, and surface-plasma interactions. For example, we show that ionic species can react in the plasma to form larger ions, and also arrive at surfaces with energies greater than 1000 kJ?mol1 (>10 eV) and thus facilitate surface reactions that have not been taken into account previously. Thus, improving thin film deposition processes requires an understanding of both physical and chemical processes in plasma.

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Overcoming oral insulin delivery barriers: application of cell penetrating peptide and silica-based nanoporous composites
Huining HE, Junxiao YE, Jianyong SHENG, Jianxin WANG, Yongzhuo HUANG, Guanyi CHEN, Jingkang WANG, Victor C YANG
Front Chem Sci Eng    2013, 7 (1): 9-19.
Abstract   HTML   PDF (551KB)

Oral insulin delivery has received the most attention in insulin formulations due to its high patient compliance and, more importantly, to its potential to mimic the physiologic insulin secretion seen in non-diabetic individuals. However, oral insulin delivery has two major limitations: the enzymatic barrier that leads to rapid insulin degradation, and the mucosal barrier that limits insulin’s bioavailability. Several approaches have been actively pursued to circumvent the enzyme barrier, with some of them receiving promising results. Yet, thus far there has been no major success in overcoming the mucosal barrier, which is the main cause in undercutting insulin’s oral bioavailability. In this review of our group’s research, an innovative silica-based, mucoadhesive oral insulin formulation with encapsulated-insulin/cell penetrating peptide (CPP) to overcome both enzyme and mucosal barriers is discussed, and the preliminary and convincing results to confirm the plausibility of this oral insulin delivery system are reviewed. In vitro studies demonstrated that the CPP-insulin conjugates could facilitate cellular uptake of insulin while keeping insulin’s biologic functions intact. It was also confirmed that low molecular weight protamine (LMWP) behaves like a CPP peptide, with a cell translocation potency equivalent to that of the widely studied TAT. The mucoadhesive properties of the produced silica-chitosan composites could be controlled by varying both the pH and composition; the composite consisting of chitosan (25 wt-%) and silica (75 wt-%) exhibited the greatest mucoadhesion at gastric pH. Furthermore, drug release from the composite network could also be regulated by altering the chitosan content. Overall, the universal applicability of those technologies could lead to development of a generic platform for oral delivery of many other bioactive compounds, especially for peptide or protein drugs which inevitably encounter the poor bioavailability issues.

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Hierarchically porous materials: Synthesis strategies and emerging applications
Minghui Sun, Chen Chen, Lihua Chen, Baolian Su
Front. Chem. Sci. Eng.    2016, 10 (3): 301-347.
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Great interests have arisen over the last decade in the development of hierarchically porous materials. The hierarchical structure enables materials to have maximum structural functions owing to enhanced accessibility and mass transport properties, leading to improved performances in various applications. Hierarchical porous materials are in high demand for applications in catalysis, adsorption, separation, energy and biochemistry. In the present review, recent advances in synthesis routes to hierarchically porous materials are reviewed together with their catalytic contributions.

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Nano-hydroxyapatite formation via co-precipitation with chitosan-g-poly(N-isopropylacrylamide) in coil and globule states for tissue engineering application
Yang YU, Hong ZHANG, Hong SUN, Dandan XING, Fanglian YAO
Front Chem Sci Eng    2013, 7 (4): 388-400.
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With the excellent biocompatibility and osteoconductivity, nano-hydroxyapatite (nHA) has shown significant prospect in the biomedical applications. Controlling the size, crystallinity and surface properties of nHA crystals is a critical challenge in the design of HA based biomaterials. With the graft copolymer of chitosan and poly(N-isopropylacrylamide) in coil and globule states as a template respectively, a novel composite from chitosan-g-poly(N-isopropylacrylamide) and nano-hydroxyapatite (CS-g-PNIPAM/nHA) was prepared via co-precipitation. Zeta potential analysis, thermogravimetric analysis and X-ray diffraction were used to identify the formation mechanism of the CS-g-PNIPAM/nHA composite and its morphology was observed by transmission electron microscopy. The results suggested that the physical aggregation states of the template polymer could induce or control the size, crystallinity and morphology of HA crystals in the CS-g-PNIPAM/nHA composite. The CS-g-PNIPAM/nHA composite was then introduced to chitosan-gelatin (CS-Gel) polyelectronic complex and the cytocompatibility of the resulting CS-Gel/composite hybrid film was evaluated. This hybrid film was proved to be favorable for the proliferation of MC 3T3-E1 cells. Therefore, the CS-g-PNIPAM/nHA composite is a potential biomaterial in bone tissue engineering.

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Computational fluid dynamics applied to high temperature hydrogen separation membranes
Guozhao JI, Guoxiong WANG, Kamel HOOMAN, Suresh BHATIA, Jo?o C. DINIZ da COSTA
Front Chem Sci Eng    2012, 6 (1): 3-12.
Abstract   HTML   PDF (312KB)

This work reviews the development of computational fluid dynamics (CFD) modeling for hydrogen separation, with a focus on high temperature membranes to address industrial requirements in terms of membrane systems as contactors, or in membrane reactor arrangements. CFD modeling of membranes attracts interesting challenges as the membrane provides a discontinuity of flow, and therefore cannot be solved by the Navier-Stokes equations. To address this problem, the concept of source has been introduced to understand gas flows on both sides or domains (feed and permeate) of the membrane. This is an important solution, as the gas flow and concentrations in the permeate domain are intrinsically affected by the gas flow and concentrations in the feed domain and vice-versa. In turn, the source term will depend on the membrane used, as different membrane materials comply with different transport mechanisms, in addition to varying gas selectivity and fluxes. This work also addresses concentration polarization, a common effect in membrane systems, though its significance is dependent upon the performance of the membrane coupled with the operating conditions. Finally, CFD modeling is shifting from simplified single gas simulation to industrial gas mixtures, when the mathematical treatment becomes more complex.

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Fabrication, modification and environmental applications of TiO2 nanotube arrays (TNTAs) and nanoparticles
Front Chem Sci Eng    2012, 6 (1): 112-122.
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Among the semiconductors, titanium dioxide has been identified as an effective photocatalyst due to its abundance, low cost, stability, and superior electronic energy band structure. Highly ordered nanotube arrays of titania were produced by anodization and mild sonication. The band gap energy of the titania nanotube arrays was reduced to 2.6 eV by co-doping with Fe, C, N atoms using an electrolyte solution containing K3Fe(CN)6. The photoconversion of phenol in a batch photoreactor increased to more than 18% based on the initial concentration of phenol by using a composite nanomaterial consisting of titania nanotube arrays and Pt/ZIF-8 nanoparticles. A layer-by-layer assembly technique for the deposition of titania nanoparticles was developed to fabricate air filters for the degradation of trace amounts of toluene in the air and preparation of superhyrophobic surfaces for oil-water separation and anti-corrosion surfaces.

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Nano-confined ammonia borane for chemical hydrogen storage
M. A. WAHAB, Huijun ZHAO, X. D. YAO
Front Chem Sci Eng    2012, 6 (1): 27-33.
Abstract   HTML   PDF (362KB)

There is a great demand for a sufficient and sustainable energy supply. Hence, the search for applicable hydrogen storage materials is extremely important owing to the diversified merits of hydrogen energy. In this regard, ammonia borane (NH3BH3, AB) containing 19.6 wt-% hydrogen has been considered as a promising material for hydrogen storage applications to realize the “hydrogen economy”, but with limits from slow kinetics of hydrogen release and by-product of trace gases such as ammonia and borazine. In this review, we introduce the recent research on AB, regarding to the nanoconfinement effect on improving the kinetics at a relatively low temperature and the prevention/reduction of undesirable gas formation.

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Polyethylene glycol-supported ionic liquid as a highly efficient catalyst for the synthesis of propylene carbonate under mild conditions
Rui YAO, Hua WANG, Jinyu HAN
Front Chem Sci Eng    2012, 6 (3): 239-245.
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The coupling reaction of propylene and CO2 to form propylene carbonate (PC) was promoted by an ionic liquid (IL) covalently bound to polyethylene glycol (PEG). The supported ionic liquid, which has both acidic and basic components, proved to be an active catalyst for PC synthesis under mild conditions. The effects of different cations and anions, reaction temperature, CO2 pressure, and reaction time were investigated. It was demonstrated that the acid group in the catalyst plays an important role in the reaction. With this system, a high PC yield (95%) was achieved under mild conditions (3.0 MPa, 120°C and 4 h) without a co-solvent. In addition, the catalyst was readily recovered and reused. Based on the experimental results, a plausible mechanism for the catalyst was proposed.

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Biodegradable polymethacrylic acid grafted psyllium for controlled drug delivery systems
Ranvijay KUMAR, Kaushlendra SHARMA
Front Chem Sci Eng    2013, 7 (1): 116-122.
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Polymethacrylic acid (PMA) was synthesized on the backbone of psyllium (Psy) by a microwave assisted method to prepare polymeric grafted materials designated as (Psy-g-PMA). Various grades of Psy-g-PMA were prepared by changing the degree of grafting from 35%–58% and the materials were then made into tablets. Swelling and biodegradability studies of the tablets were carried out. Acetyl salicylic acid was incorporated in the various Psy-g-PMA samples and tablets were prepared to study the in vitro drug release in acidic (pH= 4), neutral (pH= 7), and basic (pH= 9) media. In the acidic medium, the swelling was more than 1300%. In addition, the biodegradable Psy-g-PMA had the highest drug release in the acidic medium. This may be attributed to Fickian diffusion since the drug and the medium in which it was released have the same acidic nature.

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Preparation of Cu/ZrO2 catalysts for methanol synthesis from CO2/H2
Xinmei LIU, Shaofen BAI, Huidong ZHUANG, Zifeng YAN
Front Chem Sci Eng    2012, 6 (1): 47-52.
Abstract   HTML   PDF (244KB)

Cu/ZrO2 catalysts for methanol synthesis from CO2/H2 were respectively prepared by deposition coprecipitation (DP) and solid state reaction (SR) methods. There is an intimate interaction between copper and zirconia, which strongly affects the reduction property and catalytic performance of the catalysts. The stronger the interaction, the lower the reduction temperature and the better the performance of the catalysts. Surface area, pore structure and crystal structure of the catalysts are mainly controlled by preparation methods and alkalinity of synthesis system. The conversion of CO2 and selectivity of methanol are higher for DP catalysts than for SP catalysts.

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A thermodynamic study of the removal of HCl and H2S from syngas
Joseph LEE, Bo FENG
Front Chem Sci Eng    2012, 6 (1): 67-83.
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Advanced integrated-gasification combined-cycle (IGCC) and integrated-gasification fuel cell (IFGC) systems require high-temperature sorbents that are capable of removing hydrogen chloride and hydrogen sulfide from coal derived gases to very low levels. HCl and H2S are highly reactive, corrosive, and toxic gases that must be removed to meet stringent environmental regulations, to protect power generation equipment and to control the emissions of contaminants. The thermodynamic behavior of 13 sorbents for the removal of HCl and H2S under various conditions including: initial toxic gas concentration (1–10000 ppm), operating pressure (0.1–11 Mpa), temperature (300 K–1500 K), and the presence of H2O were investigated. The correlation between HCl and H2S was also examined. Thermodynamic calculations were carried out for the reactions of the 13 sorbents using a FactSage 5.2 software package based on free energy minimization. The sorbents, Na2CO3, NaHCO3, K2CO3, and CaO are capable of completely removing chlorine at high temperatures (up to ~1240 K) and at high pressures. Water vapor did not have any significant effects on the dechlorination capability of the sorbents. Nine of the sorbents namely; Cu2O, Na2CO3, NaHCO3, K2CO3, CaO, ZnO, MnO, FeO, and PbO, were determined to have great potential as desulfurization sorbents. Cu2O and ZnO had the best performance in terms of the optimum operating temperature. The addition of water vapor to the reactant gas produces a slightly detrimental effect on most of the sorbents, but FeO exhibited the worst performance with a reduction in the maximum operating temperature of about 428 K. The dechlorination performance of the alkali sorbents was not affected by the presence of H2S in the reactions. However, the desulfurization capability of some sorbents was greatly affected by the presence of HCl. Particularly, the performance of Cu2O was significantly reduced when HCl was present, but the performance of FeO improved remarkably. The thermodynamic results gathered are valuable for the developments of better sorbents.

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Synthesis and properties of PdO/CeO2-Al2O3 catalysts for methane combustion
Xianyun LIU, Jianzhou LIU, Feifei GENG, Zhanku LI, Ping LI, Wanli GONG
Front Chem Sci Eng    2012, 6 (1): 34-37.
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This study focuses on the loading of catalytic materials, e.g., palladium on the surface of supporting materials, with the aim to obtain catalysts with high activity for methane combustion. The catalyst PdO/CeO2-Al2O3 was prepared by impregnation under ultrasonic condition. The effect of different activation methods on the activity of catalysts for methane catalytic combustion was tested. The properties of reaction and adsorption of oxygen species on catalyst surface were characterized by H2-temperature programmed reduction (H2-TPR), and O2-temperature programmed desorption (O2-TPD). Furthermore, the sulfur tolerance and sulfur poisoning mode were investigated. The results indicate that the catalyst PdO/CeO2-Al2O3 activated with rapid activation shows higher activity for methane combustion and better sulfur tolerance. The result of sulfur content analysis shows that there is a large number of sulfur species on the catalyst’s surface after reactivation at high temperature. It proves that the activity of catalysts cannot be fully restored by high-temperature reactivation.

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Low temperature synthesis of visible light responsive rutile TiO2 nanorods from TiC precursor
John TELLAM, Xu ZONG, Lianzhou WANG
Front Chem Sci Eng    2012, 6 (1): 53-57.
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A nano-structured TiO2 with rutile phase was synthesized by using the hydrothermal method from a titanium carbide (TiC) nano-powder precursor at low temperature to produce a stable visible light responsive photocatalyst. The rutile phase was formed at temperature as low as 100°C, and both synthesis time and temperature affected its formation. The rutile particles showed a faceted nano-rod structure, and were tested for absorption and photo-degradation ability under visible light. Particles with shorter synthesis times showed higher visible light absorption and corresponding photo-degradation ability, while those synthesized at lower temperatures had lower, but still evident, degradation ability under visible light.

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The dehydration behavior and non-isothermal dehydration kinetics of donepezil hydrochloride monohydrate (Form I)
Tiantian LIU, Yuanyuan RAN, Bochao WANG, Weibing DONG, Songgu WU, Junbo GONG
Front Chem Sci Eng    2014, 8 (1): 55-63.
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Powders of donepezil hydrochloride monohydrate (Form I) underwent isomorphic dehydration, losing 3% w/w water between 90% and 10% relative humidity (RH) without changing its powder X-ray pattern. Below 10% RH, additional dehydration occurred in conjunction with a reversible phase transition between the monohydrate state and a dehydrated state, with a 4.0% w/w loss to 0% RH. A combination of methods was used to understand the structural changes occurring during the desolvation process, including dynamic vapor sorption measurements, thermal analysis and powder X-ray diffraction. Form I showed the characteristics of the channel hydrate, whose non-isothermal dehydration behavior proceeds in two steps: (1) the loss of non-crystalline water adsorbed on the surface, and (2) the loss of one crystalline water in the channel. Dehydrated Form I is structurally similar to the monohydrate Form I. According to the heat of fusion and the crystal density criteria, the two crystal forms belonged to the univariant system, and the anhydrate (Form III) is stable. The dehydration kinetics was achieved from the TG-DTG curves by both the Achar method and the Coats-Redfern method with 15 frequently cited basic kinetic models. The dynamic dehydration processes for steps 1 and 2 were best expressed by the Zhuralev-Lesokin-Tempelman equation, suggesting a three-dimensional diffusion-controlled mechanism.

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Investigation of the preparation methodologies of Pd-Cu single atom alloy catalysts for selective hydrogenation of acetylene
Xinxiang Cao,Arash Mirjalili,James Wheeler,Wentao Xie,Ben W.-L. Jang
Front. Chem. Sci. Eng.    2015, 9 (4): 442-449.
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Galvanic replacement, co-impregnation and sequential impregnation have been employed to prepare Pd-Cu bimetallic catalysts with less than 1 wt-% Cu and ca. 0.03 wt-% Pd for selective hydrogenation of acetylene in excess ethylene. High angle annular dark field-scanning transmission electron microscopy (HAADF-STEM) and H2 chemisorption results confirmed that Pd-Cu single-atom alloy structures were constructed in all three bimetallic catalysts. Catalytic tests indicated that when the conversion of acetylene was above 99%, the selectivity of ethylene of these three single atom alloy catalysts was still more than 73%. Furthermore, the single atom alloy catalyst prepared by sequential incipient wetness impregnation was found to have the best stability among the three procedures used.

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Methanation of carbon dioxide: an overview
Wei WANG, Jinlong GONG
Front Chem Sci Eng    2011, 5 (1): 2-10.
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Although being very challenging, utilization of carbon dioxide (CO2) originating from production processes and flue gases of CO2-intensive sectors has a great environmental and industrial potential due to improving the resource efficiency of industry as well as by contributing to the reduction of CO2 emissions. As a renewable and environmentally friendly source of carbon, catalytic approaches for CO2 fixation in the synthesis of chemicals offer the way to mitigate the increasing CO2 buildup. Among the catalytic reactions, methanation of CO2 is a particularly promising technique for producing energy carrier or chemical. This article focuses on recent developments in catalytic materials, novel reactors, and reaction mechanism for methanation of CO2.

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Removal of copper ions from aqueous solution by adsorption using LABORATORIES-modified bentonite (organo-bentonite)
Front Chem Sci Eng    2012, 6 (1): 58-66.
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Equilibrium, kinetic and thermodynamic aspects of the adsorption of copper ions from an aqueous solution using linear alkylbenzene sulfonate (LABORATORIES) modified bentonite (organo-bentonite) are reported. Modification of bentonite was performed via microwave heating with a concentration of LABORATORIES surfactant equivalent to 1.5 times that of the cation exchange capacity (CEC) of the raw bentonite. Experimental parameters affecting the adsorption process such as pH, contact time and temperature were studied. Several adsorption equations (e.g., Langmuir, Freundlich, Sips and Toth) with temperature dependency were used to correlate the equilibrium data. These models were evaluated based on the theoretical justifications of each isotherm parameter. The Sips model had the best fit for the adsorption of copper ions onto organo-bentonite. For the kinetic data, the pseudo-second order model was superior to the pseudo-first order model. Thermodynamically, the adsorption of copper ions occurs via chemisorption and the process is endothermic (ΔH0>0), irreversible (ΔS0>0) and nonspontaneous (ΔG0>0).

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Ultrasound-mediated targeted microbubbles: a new vehicle for cancer therapy
Junxiao YE, Huining HE, Junbo GONG, Weibing DONG, Yongzhuo HUANG, Jianxin WANG, Guanyi CHEN, Victor C YANG
Front Chem Sci Eng    2013, 7 (1): 20-28.
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With the hope of overcoming the serious side effects, great endeavor has been made in tumor-targeted chemotherapy, and various drug delivery modalities and drug carriers have been made to decrease systemic toxicity caused by chemotherapeutic agents. Scientists from home and abroad focus on the research of targeted microbubbles contrast agent, and the use of the targeted ultrasound microbubble contrast agent can carry gene drugs and so on to the target tissue, as well as mediated tumor cell apoptosis and tumor microvascular thrombosis block, etc., thus plays the role of targeted therapy. Recent studies have elucidated the mechanisms of drug release and absorption, however, much work remains to be done in order to develop a successful and optimal system. In this review, we summarized the continuing efforts in understanding the usage of the ultrasound triggered target microbubbles in cancer therapy, from release mechanism to preparation methods. The latest applications of ultrasound-triggered targeted microbubbles in cancer therapy, especially in gene therapy and antiangiogenic cancer therapy were discussed. Moreover, we concluded that as a new technology, ultrasound–triggered targeted microbubbles used as drug carriers and imaging agents are still energetic and are very likely to be translated into clinic in the near future.

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Recovery of waste heat in cement plants for the capture of CO2
Ruifeng DONG, Zaoxiao ZHANG, Hongfang LU, Yunsong YU
Front Chem Sci Eng    2012, 6 (1): 104-111.
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Large amounts of energy are consumed during the manufacturing of cement especially during the calcination process which also emits large amounts of CO2. A large part of the energy used in the making of cement is released as waste heat. A process to capture CO2 by integrating the recovery and utilization of waste heat has been designed. Aspen Plus software was used to calculate the amount of waste heat and the efficiency of energy utilization. The data used in this study was based on a dry process cement plant with a 5-stage preheater and a precalciner with a cement output of 1 Mt/y. According to the calculations: 1) the generating capacity of the waste heat recovery system is 4.9 MW. 2) The overall CO2 removal rate was as high as 78.5%. 3) The efficiency of energy utilization increased after the cement producing process was retrofitted with this integrated design.

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Advancement in materials for energy-saving lighting devices
Tak H. KIM, Wentai WANG, Qin LI
Front Chem Sci Eng    2012, 6 (1): 13-26.
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This review provides a comprehensive account of energy efficient lighting devices, their working principles and the advancement of these materials as an underpinning to the development of technology. Particular attention has been given to solid state lighting devices and their applications since they have attracted the most interest and are the most promising. Solid state lighting devices including white light emitting diodes (LEDs), organic LEDs (OLEDs), quantum-dot LEDs (QLEDs) and carbon-dot LEDs (CLEDs) are promising energy efficient lighting sources for displays and general lighting. However there is no universal solution that will give better performance and efficiency for all types of applications. LEDs are replacing traditional lamps for both general lighting and display applications, whereas OLEDs are finding their own special applications in various areas. QLEDs and CLEDs have advantages such as high quantum yields, narrow emission spectra, tunable emission spectra and good stability over OLEDs, so applications for these devices are being extended to new types of lighting sources. There is a great deal of research on these materials and their processing technologies and the commercial viability of these technologies appears strong.

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Advances and perspectives in catalysts for liquid-phase oxidation of cyclohexane
Hui LI, Yuanbin SHE, Tao WANG
Front Chem Sci Eng    2012, 6 (3): 356-368.
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The latest progress and developments in catalysts for the oxidation of cyclohexane are reviewed. Catalytic systems for the oxidation of cyclohexane including metal supported, metal oxides, molecular sieves, metal substituted polyoxometalates, photocatalysts, organocatalysts, Gif systems, metal-organic catalysts and metalloporphyrins are discussed with a particular emphasis on metalloporphyrin catalytic systems. The advantages and disadvantages of these methods are summarized and analyzed. Finally, the development trends in the oxidation technology of cyclohexane are examined.

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Fe3O4 encapsulated mesoporous silica nanospheres with tunable size and large void pore
Tingting LIU, Lihong LIU, Jian LIU, Shaomin LIU, Shi Zhang QIAO
Front Chem Sci Eng    2014, 8 (1): 114-122.
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Magnetic Fe3O4 and mesoporous silica core-shell nanospheres with tunable size from 110–800 nm were synthesized via a one step self-assembly method. The morphological, structural, textural, and magnetic properties were well-characterized by scanning electron microscopy, transmission electron microscopy, X-ray diffraction, N2 adsorption-desorption and magnetometer. These nanocomposites, which possess high surface area, large pore volume and well-defined pore size, exhibit two dimensional hexagonal (P6mm) mesostructures. Interestingly, magnetic core and mesoporous silica shell nanocomposites with large void pore (20 nm) on the shell were generated by increasing the ratio of ethanol/water. Additionally, the obtained nanocomposites combined magnetization response and large void pore, implying the possibility of applications in drug/gene targeting delivery. The cell internalization capacity of NH2-functionalized nanocomposites in the case of cancer cells (HeLa cells) was exemplified to demonstrate their nano-medicine application.

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Effective regeneration of thermally deactivated commercial V-W-Ti catalysts
Xuesong SHANG, Jianrong LI, Xiaowei YU, Jinsheng CHEN, Chi HE
Front Chem Sci Eng    2012, 6 (1): 38-46.
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An effective method for the regeneration of thermally deactivated commercial monolith SCR catalysts was investigated. Two types of regenerated solutions, namely NH4Cl (1 mol/L) and dilute H2SO4 (0.5 mol/L), were employed to treat the used catalyst. The effects of temperature and the regeneration process on the structural and textural properties of the catalysts were determined by X-ray diffraction, scanning electron microscopy, N2 adsorption/desorption, elemental analysis and Fourier transform infrared spectroscopy. The results suggest that the anatase phase of the used catalyst is maintained after exposure to high temperatures. Some of the catalytic activity was restored after regeneration. The catalyst regenerated by aqueous NH4Cl had a higher activity than that of the catalyst treated by dilute H2SO4. The main reason is that the NH3 generated from the decomposition of NH4Cl at high temperatures can be adsorbed onto the catalyst which promotes the reaction. The aggregated V2O5 were partially re-dispersed during the regeneration process, and the intrinsic oxidation of ammonia with high concentrations of O2 is a factor that suppresses the catalytic activity.

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Molecular level simulations on multi-component systems —a morphology prediction method
Front Chem Sci Eng    2013, 7 (1): 49-54.
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The crystal morphology grown from a solution composed of an organic solvent, solute and additive can be predicted reliably by a computational method. Modeling the supersaturated solution as liquid phase is achieved by employing commercial software. The molecular composition of this solution is a required input parameter. The face specific diffusion coefficient of the solid (crystal surface) and liquid (solution) system is determined using the molecular dynamics procedure. The obtained diffusion coefficient is related to the specific face growth rate via the attachment energy of the pure morphology. The significant improvements are achieved in the morphology prediction because the investigation on the face growth rates in a complex growth environment (as multi-component solutions with additives) can be carried out based on the diffusion coefficients.

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Modeling of coal swelling induced by water vapor adsorption
Zhejun PAN
Front Chem Sci Eng    2012, 6 (1): 94-103.
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Gas adsorption-induced coal swelling is a well-know phenomenon. Coal swelling or shrinkage by adsorption or desorption of water vapor has not been well understood but has significant implications on gas drainage process for underground coal mining and for primary and enhanced coalbed methane production. Decreased matrix moisture content leads to coal shrinkage and thus the change of cleat porosity and permeability under reservoir conditions. Unlike gas adsorption in coal which usually forms a single layer of adsorbed molecules, water vapor adsorption in the coal micropores forms multilayer of adsorbed molecules. In this work, a model has been developed to describe the coal swelling strain with respect to the amount of moisture intake by the coal matrix. The model extended an energy balance approach for gas adsorption-induced coal swelling to water vapor adsorption-induced coal swelling, assuming that only the first layer of adsorbed molecules of the multilayer adsorption changes the surface energy, which thus causes coal to swell. The model is applied to describe the experimental swelling strain data measured on an Australian coal. The results show good agreement between the model and the experimental data.

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Application of membrane separation technology in post-combustion carbon dioxide capture process
Mo LI,Xiaobin JIANG,Gaohong HE
Front. Chem. Sci. Eng.    2014, 8 (2): 233-239.
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Membrane separation technology is a possible breakthrough in post-combustion carbon dioxide capture process. This review first focuses on the requirements for CO2 separation membrane, and then outlines the existing competitive materials, promising preparation methods and processes to achieve desirable CO2 selectivity and permeability. A particular emphasis is addressed on polyimides, poly (ethylene oxide), mixed-matrix membrane, thermally-rearranged polymer, fixed site carrier membrane, ionic liquid membrane and electrodialysis process. The advantages and drawbacks of each of materials and methods are discussed. Research threads and methodology of CO2 separation membrane and the key issue in this area are concluded

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Purification of L-asparaginase II by crystallization
Front Chem Sci Eng    2013, 7 (1): 37-42.
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Here a case study of L-asparaginase II out of a recombinant Escherichia coli is presented. The target protein was obtained by simple cell disintegration and acetone precipitation. The L-asparaginase II has been crystallized in three different forms in the following microbatch crystallization. The rod-shaped crystals (~400 μm edge length) were obtained at either 8°C or 22°C after 17 h by addition of PEG6000. The rectangular-shaped crystals were obtained after further recrystallization of the rod-shaped crystals. The rhombic-shaped crystals formed at 8°C after 12 days when cold ethanol was used instead of PEG6000. All crystallizations were performed in tris-acetate buffer (50 mmol·L-1, pH 5.1). By crystallization, the specific activity of L-asparaginase II has increased 5-fold. The protein content and the purity of the crystals were evaluated by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE). The more concentrated L-asparaginase II out of an extract mixture and the presence of only less minor proteins after crystallization demonstrates that crystallization is an effective and mild method to purify the target protein. The single crystal X-ray diffraction pattern reveals that the crystals are proteins and the X-ray powder diffraction (XRPD) pattern shows clearly that the crystals forming in PEG6000 and ethanol have different crystal structures.

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