Korean Journal of Chemical Engineering (v.33, #5)
Lignocellulosic and marine biomass as resource for production of polyhydroxyalkanoates by Shailesh S. Sawant; Bipinchandra K. Salunke; Tuan Kiet Tran; Beom Soo Kim (1505-1513).
Polyhydroxyalkanoates (PHAs) are considered as sustainable ‘green/bio plastics’ because they have potential to replace their depleting petroleum-based competitors in the recent future. To reach this goal, PHAs must be able to compete with the established petroleum-based plastics in both technical and economic aspects. The current PHA production is based on high-priced substrates of high nutritional value and simple carbon sources such as glucose, sucrose, starch, or vegetable oils. Non-food based carbon-rich complex polysaccharides of lignocellulosic and marine biomass can be used as alternative and suitable feedstock through consolidated bioprocessing (CBP). CBP is a promising strategy that involves the production of lytic enzymes, hydrolysis of biomass, and fermentation of resulting sugars to desired products in a single process step. CBP offers very large cost reductions if microorganisms possessing the abilities are found or microbial processes are developed to utilize substrate and simultaneously produce products. This review focuses on possible available complex polysaccharides of lignocellulosic and marine biomass that can be used as resources to produce PHAs in biorefineries, including CBP.
Keywords: Polyhydroxyalkanoates; Bioplastics; Consolidated Bioprocessing; Lignocellulose; Marine Biomass
Metal hollow sphere electrocatalysts by Jayeeta Chattopadhyay; Tara Sankar Pathak; Daewon Pak; Rohit Srivastava (1514-1529).
Metal micro-/nano hollow spheres have been widely applied in numerous fields during the last decade. This review will only focus on the synthetic strategies to synthesize hollow spherical structures in the enhancement of their electrocatalytic activity, especially the metal hollow spherical materials. We present a comprehensive overview of synthetic strategies for metal hollow spherical structures which have been approached specifically in electrochemical reactions. These synthetic methods are mainly categorized as hard templates, soft templates, sacrificial templates and without templates. The review further includes electrocatalytic approaches of hollow spherical metals in different electrochemical processes, especially the methanol electro-oxidation reaction for methanol fuel cell application and hydrogen and oxygen evolution reactions in water electrolyzer, as metal hollow spherical materials are especially applied in these specific reactions.
Keywords: Metal Hollow Sphere; Synthesis; Electrocatalysts; Methanol Electro-oxidation; Water Electrolyzer
Alkaliphilic lysine decarboxylases for effective synthesis of cadaverine from L-lysine by Seongwook Jeong; Young Joo Yeon; Eun-Gyu Choi; Sungmin Byun; DaeHaeng Cho; Il Kwon Kim; Yong Hwan Kim (1530-1533).
The enzymatic decarboxylation of L-lysine using lysine decarboxylase is a promising biological approach for producing cadaverine, a versatile platform chemical for bio-polyamides. However, due to the problem with elevated pH in the reaction solution during the enzymatic process, it is desirable to use lysine decarboxylases effectively active in alkaline conditions. In this study, the catalytic properties of three lysine decarboxylases from Selenomonas ruminantium (srLDC), Vibrio vulnificus (vvLDC), and Geobacillus thermodenitrificans (gtLDC) were characterized, and the applicability of the enzymes in alkaline conditions was investigated. Among the three enzymes, only vvLDC exhibited effective activity in alkaline pH conditions. The conversion rate of vvLDC was 1.5-fold higher than that of srLDC and 5.3-fold higher than that of gtLDC in pH 9.0. The results indicate that vvLDC is more advantageous than srLDC and gtLDC for the enzymatic conversion of L-lysine to cadaverine in alkaline conditions.
Keywords: Lysine Decarboxylase; L-Lysine; Cadaverine; pH Optimum; Alkaline Conditions
Heat transfer and fluid flow modeling in serpentine microtubes using adaptive neuro-fuzzy approach by Reza Beigzadeh; Marziyeh Hajialyani; Masoud Rahimi (1534-1550).
An adaptive neuro-fuzzy inference system (ANFIS) is applied to predict thermal and flow characteristics in serpentine microtubes. Heat transfer rate and pressure drop were experimentally measured for six serpentine microtubes with different geometrical parameters. Thermal and flow characteristics were obtained in various flow conditions. The ANFIS models were trained using the experimental data to predict Nusselt number (Nu) and friction factor (f) in the studied serpentine microtubes as a function of geometric parameters and flow conditions. The model was validated through testing data set, which were not previously introduced to the developed ANFIS. For Nu prediction, the root mean square error (RMSE), mean relative error (MRE), and absolute fraction of variance (R2) between the predicted results and experimental data were found 0.2058, 1.74%, and 0.9987, respectively. The corresponding calculated values for f were 0.0056, 2.98%, and 0.9981, respectively. The prediction accuracy of the ANFIS models was compared with that of corresponding classical power-law correlations and its advantages are illustrated.
Keywords: Heat Transfer; Pressure Drop; Serpentine Microtubes; ANFIS; Modeling
Trimetallic catalyst synthesized multi-walled carbon nanotubes and their application for hydrogen storage by Sami Ullah Rather (1551-1556).
Multi-walled carbon nanotubes (MWCNTs) were synthesized by rapid thermal decomposition method using trimetallic catalyst supported MgO. MWCNTs prepared via trimetallic catalyst shows much higher BET specific surface area compared to current monometallic and bimetallic catalyst. As-grown and pristine MWCNTs were found to adsorb nitrogen reversibly and their adsorption uptake exhibits type-II BET isotherm. Existence of small impurities, such as metal and metal oxides present in the MWCNTs, was confirmed by thermogravimetric analysis as well as via energy-dispersive X-ray spectroscopy. An over 10 wt% enhancement of hydrogen storage capacity of as-grown MWCNTs compared to pristine was found to be due to the presence of impurities. Fast kinetics and complete reversibility gives indication that the process responsible for hydrogen adsorption uptake in MWCNTs is physisorption. A linear relation between hydrogen uptake (~0.22 and 0.20 wt%) and equilibrium hydrogen pressure was obtained for both as-grown and pristine MWCNTs.
Keywords: Carbon Nanotube; Physisorption; Decomposition; Trimetallic Catalyst; Chemical Vapor Deposition; Hydrogen Storage
Heterogeneous Fenton degradation of Orange II by immobilization of Fe3O4 nanoparticles onto Al-Fe pillared bentonite by Wenbing Li; Dong Wan; Guanghua Wang; Kun Chen; Qin Hu; Lulu Lu (1557-1564).
A novel catalyst, Fe3O4 nanoparticle decorated Al-Fe pillared bentonite (Fe3O4/Al-Fe-P-B), was prepared by in situ precipitation oxidization method. The catalyst was characterized by SEM, XRD and Raman spectroscopy. The Fe3O4 nanoparticles mainly exist on the surface or enter into the pore of bentonite, with better dispersing and less coaggregation. The catalytic activity of Fe3O4/Al-Fe-P-B was investigated in the degradation of Orange II (OII) by heterogeneous Fenton-like process. The effects of initial concentration of hydrogen peroxide, catalyst loading, temperature and initial pH on the degradation of OII were investigated. The Fe3O4/Al-Fe-P-B showed higher degradation efficiency of OII than bare Fe3O4 or Al-Fe-P-B in the degradation experiment. The enhanced catalytic activity of Fe3O4/Al-Fe-P-B in heterogeneous Fenton system was due to the synergistic effect between Al-Fe-P-B and Fe3O4. The novel catalyst can achieve solid-liquid separation easily by sample magnetic separation and has a good reusability and stability.
Keywords: Magnetic Bentonite; Heterogeneous Catalyst; Degradation; Orange II; Magnetic Separation
Fischer-Tropsch synthesis on the cobalt impregnated catalyst using carbon-coated Ni/SiO2 by Hyun-Mo Koo; Gui Young Han; Jong Wook Bae (1565-1570).
Carbon-coated Ni/SiO2 prepared by dry reforming of CH4 with CO2 was applied for the preparation of the cobalt-based Fischer-Tropsch synthesis (FTS) catalyst with 20 wt%Co to elucidate the metal-support interaction to FTS activity after carbon depositions on the Ni/SiO2. The deposited carbons on the reforming catalyst of Ni/SiO2, which were mainly in the form of filamentous or encapsulated carbons, largely increased CO conversion compared with the fresh Ni/SiO2 without a significant variation of hydrocarbon distributions. The deposited carbons on the Ni/SiO2 play an important role in increasing the reducibility of cobalt oxides due to a mitigated metal-support interaction. The enhanced catalytic activity during FTS reaction is mainly attributed to the proper modification of the Ni/SiO2 surfaces with encapsulated carbons on the exposed nickel surfaces, which largely alters the reducibility of cobalt oxides by reducing the interaction of cobalt particles with the carbon-coated Ni/SiO2 surfaces.
Keywords: Fischer-Tropsch Synthesis (FTS); Cobalt; Ni/SiO2 ; Carbon Deposition from Dry Reforming; Metal-support Interaction
Increasing ethylene production as a high value hydrocarbon in Fischer-Tropsch (FT) reactor: A concept reactor for combining FT with oxidative coupling of methane by Abbas Ghareghashi; Farhad Shahraki; Kiyanoosh Razzaghi; Sattar Ghader; Mohammad Ali Torangi (1571-1589).
The paper proposes a concept configuration of reactors for coupling OCM and FTS, and presents systematic simulation results. FTS section is a combination of fixed bed and membrane fluidized bed reactor, and feed of the FT reactor is supplied by OCM. The reactor configuration is compared with the consecutive reactors of OCM and one fixed bed FT reactor. Effects of CH4/O2 ratio, percent of N2 in the feed, contact time, and input temperature on the yield of ethylene and valuable hydrocarbons are studied. The results show that compared with one FTS reactor configuration, the dual FTS reactor configuration is more effective and thus gives much higher product yields. Furthermore, a main decrease is observed in the formation of CO2 and CH4.
Keywords: Fischer-Tropsch (FT); Oxidative Coupling of Methane (OCM); C2H4 Yield; Fluidized Bed Reactor; Membrane Reactor
Fundamental study of LaMg x Cr1−x O3−δ perovskites nano-photocatalysts: Sol-gel synthesis, characterization and humidity sensing by Benjamin Avila Josephine; Ayyar Manikandan; Vincent Mary Teresita; Susaimanickam Arul Antony (1590-1598).
Nanocrystalline perovskite oxides, LaMg x Cr1−x O3−δ (x=0.0, 0.2, 0.4, 0.6, 0.8 and 1) were prepared by sol-gel method. The samples were characterized by powder X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared (FT-IR) spectroscopy and nitrogen adsorption/desorption isotherms at 77 K, respectively, to identify the structural phases, surface morphology, vibrational stretching frequencies and BET surface area of the samples. Also, it was investigated the humidity sensing characteristics of the samples. The composites were sintered at 800 °C for 5 h and subjected to dc electrical conductivity studies at room temperature. The resistance measurements as a function of relative humidity (RH) in the range of 5-98% were done and the humidity sensing factors (Sf =R5%/R98%) calculated. The activation energy of the compounds were determined from the temperature-dependent electrical conductance experiments in the temperature range of 120-300 °C. LaMgCr-3 (x=0.4) had the highest humidity sensing factor 21407±431, while LaCr-1 (x=0) the lowest sensitivity factor 27.27±2. The response and recovery characteristics were studied for LaMgCr-3, which exhibited good linearity and a very narrow hysteresis loop. The photocatalytic activity of LaMg x Cr1−x O3−δ was investigated by using the photo-decomposition of 4-chlorophenol (4-CP) under UV-visible light. The sample LaMgCr-3 (x=0.4) showed the highest photocatalytic degradation efficiency (93.05%) than other samples, due to their smaller size of particles with higher surface area.
Keywords: Sol-gel Method; Perovskites Oxides; Humidity Sensors; Ceramics; Catalyst
V-promoted Ni/Al2O3 catalyst for synthetic natural gas (SNG) production: Catalyst preparation methodologies by Qing Liu; Fangna Gu; Ziyi Zhong; Guangwen Xu; Fabing Su (1599-1605).
The effect of preparation method on the catalytic performance of V-promoted Ni/Al2O3 catalysts for synthetic natural gas (SNG) production via CO methanation has been investigated. The Ni-V/Al2O3 catalysts were prepared by co-impregnation (CI) method, deposition precipitation (DP) method as well as two sequential impregnation (SI) methods with different impregnation sequence. Among the prepared catalysts, the one prepared by CI method exhibited the best catalytic performance due to its largest H2 uptake and highest metallic Ni dispersion. In a 91h-lifetime test, this catalyst showed high stability at high temperature and weight hourly space velocity. This work demonstrates that the catalytic performance of the V-promoted Ni/Al2O3 catalysts can be improved by carefully controlling the preparation method/conditions.
Keywords: CO Methanation; Synthetic Natural Gas (SNG) Production; Ni/Al2O3 Catalyst; Vanadium Oxide; Preparation Method
Effect of temperature on the electrochemical oxidation of ash free coal and carbon in a direct carbon fuel cell by Duc-Luong Vu; Choong-Gon Lee (1606-1611).
The present study proposes the application of ash-free coal (AFC) as a primary fuel in a direct carbon fuel cell (DCFC) based on a molten carbonate fuel cell (MCFC). AFC was produced by solvent extraction using microwave irradiation. The influence of AFC-to-carbonate ratio (3: 3, 3: 1, 3: 0 and 1: 3 g/g) on the DCFC performance at different temperatures (650, 750 and 850 oC) was systematically investigated with a coin-type cell. The performance of AFC was also compared with carbon and conventional hydrogen fuels. AFC without carbonate (AFC-to-carbonate ratio=3: 0 g/g) gave a comparable performance to other compositions, indicating that the gasification of AFC readily occurred without a carbonate catalyst at 850 oC. The ease of gasification of AFC led to a much higher performance than for carbon fuel, even at 650 oC, where carbon cannot be gasified with a carbonate catalyst.
Keywords: Ash-free Coal; Carbon; Direct Carbon Fuel Cell; Temperature; Molten Carbonate Fuel Cell
Flash spray characteristics of a coal-liquid carbon dioxide slurry by Kangwook Kim; Hakduck Kim; Changyeon Kim; Juhun Song (1612-1619).
Liquid carbon dioxide (LCO2) could potentially be utilized in coal gasification plants for effectively transporting coal particles, replacing conventional carriers such as water (H2O), particularly in wet-fed gasifiers. However, it is essential to understand the atomization behavior of LCO2 leaving an injector nozzle under both coal-free and coalfed conditions. We examined the atomization behavior of a coal-LCO2 slurry during the throttling process. The injector nozzle was mounted downstream of a high-pressure spray system. The effect of upstream pressure on flash atomization and devolatilization behavior was presented. Compared with the coal-LCO2 mixture, the spray pattern of the coal-water mixture was significantly different, since it evidenced a Rayleigh-type breakup mode. This difference indicates that the coal-water slurry did not transport the coal as effectively as the coal-LCO2 slurry.
Keywords: Coal Gasification; Flashing Spray; Liquid Carbon Dioxide (LCO2); Coal Slurry; Devolatilization
Phenol decomposition in water cathode of DC atmospheric pressure discharge in air by Elena S. Bobkova; Dmitriy S. Krasnov; Alexandra V. Sungurova; Vladimir V. Rybkin; Ho-Suk Choi (1620-1628).
We studied phenol decomposition in aqueous solution under the action of DC discharge at atmospheric pressure in air. The decomposition efficiency was 0.017 molecules per 100 eV. When the kinetics of forming destruction products was studied in detail, the peculiarities of air plasma action were revealed for the first time. Plasma action not only results in the formation of oxygen-containing products, which are usually formed under oxygen plasma action (hydroxyhenols, carboxylic acids, aldehydes), but also the formation of nitro phenols. The treatment is accompanied by hydrogen peroxide formation, a pH decrease, and nitric and nitrous acids formation. We also discussed the possible mechanism of the processes and the role of some active species in chemical transformations after determining some parameters of the discharge.
Keywords: Phenol; Decomposition; Kinetics; Discharge; Decomposition Products; Air
Kinetic, thermodynamic and equilibrium studies on the removal of copper ions from aqueous solutions by natural and modified clinoptilolites by Mehdi Irannajad; Hossein Kamran Haghighi; Eshagh Safarzadeh (1629-1639).
This paper presents the adsorption of Cu(II) ions from aqueous solution on Na and Fe-modified clinoptilolite. The copper adsorption experiments were performed in a batch system considering an optimum contact time of 24 h. Changes in the surfaces and structure were characterized by SEM data. According to the SEM results, it was anticipated that the removal efficiency of Fe-modified clinoptilolite was the highest compared with the natural and Na-modified clinoptilolites. Adsorption of Cu(II) ions by modified clinoptilolites was investigated as a function of the initial Cu(II) concentration, solution pH, and temperature. According to the results, the maximum adsorbed Cu amount onto Fe-modified was 19.40mg/l at the optimum operating condition with a pH value of 5.5 and temperature of 60 °C. According to the thermodynamic evaluations, positive ΔS and negative ΔG were found for the adsorption process showing that the adsorption reaction is a spontaneous process and more favorable at high temperatures. Sorption data have been interpreted in terms of Langmuir and Freundlich, Temkin and Dubinin-Radushkevich. The adsorption equilibrium was best described by the Langmuir adsorption isotherm. In addition, according to the Sips model, the sorption of Cu(II) ions on the Fe-modified clinoptilolite was found to be heterogeneous. The kinetic study showed that the Fe-modified clinoptilolite followed the pseudo-second order model. The results indicated that the clinoptilolite-rich tuff in its iron oxide form could be efficiently used for the removal of copper from aqueous solutions.
Keywords: Copper; Adsorption; Clinoptilolite; Kinetic; Thermodynamic; Isotherm
Synthesis of magnetic Co1−x Ni x Fe2O4/carbon nanotubes with controlled microstructure for adsorption of pentachlorophenol by Chunyue Cui; Mengyuan Sun; Qingzhu Zheng (1640-1646).
Magnetic Co1−x N x Fe2O4/Carbon nanotube (CNTs) nanocomposite was successfully prepared by hydrothermal method and used for the adsorption of pentachlorophenol. The properties of Co1−x N x Fe2O4/CNTs were characterized by scanning and transmission electron microscopy, energy dispersive X-ray spectroscopy, X-ray diffractometry, Brunauer-Emmett-Teller surface area determination, and magnetic measurement. Results showed that the Co1−x N x Fe2O4 nanoparticles with amorphous structure are dispersed uniformly on the CNTs, which enhanced the adsorption capacity. The Co1−x N x Fe2O4/CNTs as a magnetic material are easy to separate from the aqueous solution in magnetic field. The adsorption capacity and magnetization were improved by controlling the Ni content and calcination temperature. In addition, the Co1−x N x Fe2O4/CNTs loaded with pentachlorophenol (PCP) could be regenerated by microwave radiation and the regeneration efficiency reached 110% after six regeneration cycles.
Keywords: Carbon Nanotubes Co1−x N x Fe2O4 ; Adsorption; Regeneration
Effects of surfactants on the preparation of TiO2 nanoparticles in microwave-assisted sol-gel process and their photocatalytic activity by Inseok Jang; Hui Jun Leong; Seong-Geun Oh (1647-1652).
Nanosized TiO2 particles were prepared through facile sol-gel reaction by using microwave-assisted method. To investigate the effects of surfactants on the formation of TiO2, various additives (PVP, Triton X-100 and P123) were employed. The diameter of synthesized titania spheres could be controlled from 105 to 380 nm. The TiO2 particles prepared with P123 triblock copolymer showed large surface area and high pore volume. It was attributed to the fact that the pore site, where the surfactant template initially existed, was generated upon calcination process. The characteristics of prepared TiO2 nanoparticles were analyzed by using FE-SEM, TEM, XRD, FT-IR and N2 adsorption-desorption. As an application of prepared composites for water treatment, their photocatalytic performances for the degradation of methylene blue dye were examined by using UV-vis spectrophotometer under room light irradiation. The prepared TiO2 particles with Triton X-100 and P123 exhibited higher performance for methylene blue photo-degradation than that of P25. It was attributed to the effects of large specific surface area and high porosity.
Keywords: Surfactant; TiO2 ; Surface Area; Photocatalytic Activity
Plasma treatment of multi-walled carbon nanotubes for lipase immobilization by Xun Cao; Rui Zhang; Wei-min Tan; Ce Wei; Jing Wang; Ze-meng Liu; Ke-quan Chen; Ping-kai Ouyang (1653-1658).
Plasma-modified multiwalled carbon nanotubes (MWNTs) were used as a support to immobilize lipase. The effects of vacuum plasma treatment power, vacuum plasma treatment time, immobilization temperature, immobilization time, and initial protein concentration of the lipase on the amount of lipase immobilized and on the subsequent activity of the immobilized lipase were investigated. The results showed that the adsorption capacity of the plasma-modified MWNTs could reach 0.15 g/g and that the maximal enzyme activity of the immobilized lipase was 520U/g under optimized conditions. Fourier transform infrared (FTIR) analysis and transmission electron microscopy (TEM) were used to characterize the properties of the plasma-modified MWNTs and plasma-modified MWNTs-lipase, and the results showed that the lipase was successfully immobilized on the plasma-modified MWNTs. Also, the MWNTs-lipase produced an esterification rate of approximately 47% in the synthesis of polyethylene glycol (PEG)-aliphatic esters.
Keywords: Plasma-modified; Multiwalled Carbon Nanotubes; Lipase; Esterification
Antibacterial and in vivo reactivity of bioactive glass and poly(vinyl alcohol) composites prepared by melting and sol-gel techniques by Salha Boulila; Hassane Oudadesse; Hafed Elfeki; Rim Kallel; Bertrand Lefeuvre; Mostafa Mabrouk; Slim Tounsi; Dhekra Mhalla; Amany Mostafa; Khansa Chaabouni; Fatma Makni-Ayedi; Allal Barroug; Tahia Boudawara; Abdelfattah Elfeki (1659-1668).
Bioactive glass particle is used in the repair of bone defects. This material undergoes a series of surface in vivo reactions, which leads to osteointegration. We evaluated the effect of the bioactive glass synthesis, sol-gel (BG(S)) versus melting (BG(M)), associated with polyvinyl-alcohol (PVA) on in vivo bioactivity with biochemical parameters, liver-kidney histological structure and antibacterial in vitro activity. These composites were testified in many bacteria and implanted in ovariectomized rat. The serum and organs (liver and kidney) of all groups, control and treated rats, were collected to investigate the side effects of our composites, BG(S)-PVA and BG(M)-PVA, in comparison with control and ovariectomized rats. Also, the implants, before and after implantation, were prepared for analysis using physicochemical techniques such as Fourier transform infrared spectroscopy and X-ray diffraction. Our results have shown the stability of natremia, kaliemia, calcemia and phosphoremia. The histological structures of liver and kidney in implanted rats are intact compared to control and ovariectomized rats. BG(S)-PVA is characterized by a higher antibacterial effect on negative and positive gram bacteria than BG(M)-PVA. The physicochemical results have confirmed a progressive degradation of BG(S)-PVA and BG(M)-PVA, while replacing the implant by an apatite layer. But this bioactivity of BG(S)-PVA is faster than BG(M)-PVA. We can therefore confirm, on the one hand, the biocompatibility of our two implants and, on the other hand, the beneficial effect of sol-gel synthesis technique versus melting, both on the antibacterial effect and on the rapid formation of layer hydroxyapatite, and consequently on osteogenesis.
Keywords: Antibacterial; Bioactivity; Biocompatibility; Bioactive Glass; Melting; Sol-gel
Production of polyhydroxyalkanoates by batch and fed-batch cultivations of Bacillus megaterium from acid-treated red algae by Bassam Alkotaini; Hyunseok Koo; Beom Soo Kim (1669-1673).
Polyhydroxyalkanoates (PHAs) are linear polyesters synthesized by microbial fermentation of various substrates. PHAs are accumulated in microbial cells in order to store carbon and energy for future use. We used acid-pre-treated red alga (Gelidium amansii) as a cheap, abundant carbon source to produce PHA via batch and fed-batch cultivation of Bacillus megaterium KCTC 2194. After acid treatment of 10% (w/v) G. amansii, 25.5 g/L galactose, 3.6 g/L glucose, 6 g/L 5-HMF, and 1.05 g/L levulinic acid were formed. In batch culture at pH 7, the dry cell weight (DCW) and PHA content increased to 5.5 g/L and 51.4%, respectively. The cell concentration was enhanced by fed-batch cultivation using two feeding strategies: pH-stat and intermittent feeding. When the pH-stat feeding strategy was employed to add concentrated hydrolysate to the fermentor, DCW increased to 8.2 g/L, with 53.2% PHA content. When concentrated hydrolysate was fed using the intermittent feeding strategy, higher DCW (10.1 g/L) was obtained, along with a slight increase of PHA content to 54.5%. This study demonstrates that red algae could be used after simple acid treatment, to produce PHA without steps for enzymatic hydrolysis and inhibitor removal.
Keywords: Polyhydroxyalkanoates; PHA; Red Algae; Gelidium amansii ; Bacillus megaterium ; Fed-batch Cultivation
Intelligent identification of the flow regimes of two-component particles in a fluidized bed with the optimized fuzzy c-means clustering algorithm by Heng Wang; Zhaoping Zhong; Xiaoyi Wang; Feihong Guo (1674-1680).
Flow regime identification is important in the application of fluidized beds. This paper provides a method for deciding flow regime number by objective criterion. The optimized fuzzy c-means clustering algorithm was used to cluster the flow regime classification of two-component particles in a fluidized bed. The genetic algorithm was applied to optimize the initial center clusters of fuzzy c-means clustering. Hilbert-Huang transform was applied to analyze pressure fluctuation signals and extract the characteristic parameters. Three clusters were found and respectively ascribed to three flow regimes: bubbling bed, slugging bed, and turbulent bed. A multilayer neural network was used to train and test the identification system of the flow regimes. The identification accuracies of bubbling bed, slugging bed, and turbulent bed can reach 91.67%, 92.85%, and 91.30%, respectively.
Keywords: Fluidization; Flow Regime Identification; Fuzzy C-means Clustering; Two-component Particles; Hilbert-Huang Transform
Mathematical modeling of supercritical carbon dioxide extraction of methyl eugenol from tuberose flowers by Probir Kumar Ghosh; Paramita Bhattacharjee (1681-1691).
Methyl eugenol-rich extracts from dried tuberose flowers (Polianthes tuberosa L.) of Calcutta single variety were obtained using supercritical carbon dioxide (SC-CO2) extraction. The optimized conditions for highest yield of methyl eugenol were 50 °C, 300 bar, 135 min with 1 L min−1 flow rate of gaseous CO2. Solubilities of methyl eugenol under different SC-CO2 extraction conditions were evaluated by Hildebrand solubility parameter and Chrastil equation. The extraction curve of methyl eugenol followed plug flow model. Steady state extraction occurred up to 100min, followed by unsteady state. Release of methyl eugenol from tuberose flowers followed first-order kinetics (Peppas model) and non-Fickian diffusion. Packed bed characterization was carried out using dimensionless numbers of mass transfer, considering steady and unsteady states of extraction. These findings could be used in the development of the pilot plant and commercial scale extraction of methyl eugenol from floral matrices.
Keywords: Supercritical carbon dioxide; Tuberose; Methyl eugenol; Solubility; Dimensionless numbers
Densities and surface tensions of binary mixtures of biodiesel, diesel, and n-butanol by Hongya Yue; Zhigang Liu (1692-1697).
Density and surface tension have been measured for mixtures of biodiesel+n-butanol, biodiesel+diesel, and diesel+n-butanol over the entire concentration range at 283.15 K and 293.15 K and atmospheric pressure, with the combined expanded uncertainties of 1.32 kg·m−3 and 1%, receptively. Densities were determined by a single-sinker densimeter; surface tensions were measured using the surface laser light scattering method. The experimental data showed that densities and surface tensions decreased as temperature increased. The excess surface tensions and excess densities were all negative, and further fitted to the Redlich-Kister equation.
Keywords: Surface Tension; Surface Laser Light Scattering Method; Biodiesel; Diesel; n-Butanol; n-Butanol
Calculation of solubility of N-ethylcarbazole in ethanol+petroleum ether mixtures at various temperatures by Abolghasem Jouyban; William Eugence Acree Jr. (1698-1705).
Published solubility data for N-ethylcarbazole dissolved in binary (ethanol+petroleum ether) solvent mixtures has been reanalyzed by using the combined nearly ideal binary solvent/Redlich-Kister (CNIBS/R-K) and Jouyban- Acree models. The CIBS/R-K model was found to describe the observed solubility data to within an overall absolute mean deviation of 1.7%. Slightly larger mean deviations of approximately 6.6% were noted for the Jouyban-Acree model. Mathematical expressions are derived for predicting the solubility N-ethylcarbazole dissolved in binary (ethanol+petroleum ether) solvent mixtures as a function of both temperature and binary solvent composition.
Keywords: N-ethylcarbazole; Solubility Predictions; Binary Solvent Mixtures
Tuning magnetism via selective injection into ice-like clathrate hydrates by Youngjune Park; Dong-Yeun Koh; Joonghoe Dho; Sun-Hwa Yeon; Huen Lee (1706-1711).
Clathrate hydrates exhibit unique intermolecular interactions between host-guest and guest-guest molecules because they have 3-dimensional superstructures consisting of the sublattices created by hydrogen-bonded water molecules that form cage-like frameworks in which guest molecules can be incorporated. Lattice engineering or molecular engineering using a selective injection of specific guest molecules into these sublattices can be exploited to tune the physicochemical properties of guest molecules or to create new functional materials. Here, we report distinctive intermolecular behavior of oxygen molecules that are selectively inserted in a structure-II type superstructure consisting of a tetrahedral sublattice by the small 512 water cages and a diamond-like sublattice by the large 51264 cages. Pure O2 clathrate hydrate and binary THF+O2 clathrate hydrate were synthesized, and their magnetism and heat capacity were measured at low temperature conditions. These results strongly suggest that the magnetic property of the oxygen molecule is largely varied with the formation of a 3-dimensional superstructure by the injection of O2 into the water frameworks.
Keywords: Clathrate; Gas Hydrate; Oxygen; Magnetism; Tetrahydrofuran
One-dimensional approaches for methane hydrate production by CO2/N2 gas mixture in horizontal and vertical column reactor by Yeobum Youn; Minjun Cha; Minchul Kwon; Juwoon Park; Yutaek Seo; Huen Lee (1712-1719).
The recovery of methane gas from methane hydrate bearing sediments was investigated by using a continuous stream of a CO2 and N2 gas mixture. A long cylindrical high-pressure reactor was designed to demonstrate the recovery of methane from methane hydrate bearing sediments, and the injection rate of the gas mixture was controlled to monitor the amount of recovered methane from methane hydrates. The recovery efficiency of methane gas from methane hydrates is inversely proportional to the flow rate of the CO2 and N2 gas mixture. Methane hydrates were synthesized by using two different sediments, having particle size distributions of 75 to 150 μm and 45 to 90 μm with the same porosity, and the recovery efficiency of methane from methane hydrates was also monitored. We confirmed that there is no significant difference in the replacement characteristics by using these two different sediments. Horizontal and vertical flows of the CO2 and N2 gas mixture were applied to monitor the effect of flow direction on replacement characteristics. We also confirmed that a similar amount of methane was recovered in horizontal and vertical flows of the CO2 and N2 gas mixture at the same flow rate. The present study may help in establishing the process variables for recovering methane gas from methane hydrate bearing sediments in offshore conditions.
Keywords: Methane Hydrate; Sediments; Flow Rate; Flow Direction; Recovery Efficiency; Particle Size
Effect of sorbitan monostearate concentration on the thermal, mechanical and drug release properties of oleogels by Sai Sateesh Sagiri; Uvanesh Kasiviswanathan; Gauri Shankar Shaw; Meenakshi Singh; Arfat Anis; Kunal Pal (1720-1727).
The current study describes the effect of the concentration of Span 60 (gelator) on the properties of oleogels. Mustard oil was chosen as the representative vegetable oil. Microscopy showed that an increase in the gelator concentration resulted in the increase in the gelator network density. Thermal studies (crystallization kinetics and differential scanning calorimetry) indicated a 2-stage crystallization process. An increase in the gelator proportion resulted in the increase in the compatibility amongst the oleogel components. The formation of gelator network was governed by the interaction amongst the hydroxyl groups of Span 60. A variation in the gelator proportion resulted in the alteration in the d-spacing, crystallite size and lattice strain. The variation in the above-mentioned properties was found to affect the viscoelastic properties of the oleogels as was predicted from the Weichert model. The drug release studies suggested that the drug diffusion due to the gelator network relaxation during drug release was predominant as compared to the Fickian diffusion. The results suggested that it is possible to alter not only the release profile of drugs but also the physical properties (of the oleogels) by tailoring the gelator concentration.
Keywords: Oleogels; Mustard Oil; Biocompatibility; Span 60; Controlled Drug Delivery
Structural identification of DClO4 clathrate hydrates: Neutron powder diffraction analysis by Kyuchul Shin; Minjun Cha; Wonhee Lee; Huen Lee (1728-1735).
Acid clathrate hydrates which do not contain hydrogen fluoride impurities are believed to include several vacancy sites in the host lattice for protonation of the framework. In this work, the crystal structures of a DClO4· 5.5D2O solid at various temperatures were identified by the direct space method and Rietveld refinement of the neutron powder diffraction patterns. A position change of vacancy sites accompanying the shift of ClO 4 − guest ions in the 51262 cavity toward the center of the cavity from the edge of the hexagonal face was observed at about 180 K, and this phenomenon is expected to result in weakened host proton-guest anion interactions and to induce a phase transition related to the proton conduction behavior of the DClO4 clathrate. The present findings explain the proton dynamics of the hydrogen fluoride-free acid clathrate hydrates and provide a better understanding of the nature of guest-host interactions occurring on ion-doped hydrate materials.
Keywords: Clathrate; Hydrate; Neutron Powder Diffraction
Anticorrosive properties of olive oil polyurethanamide/ZnO biocomposite coatings by Manawwer Alam; Naser Mohammed Alandis; Eram Sharmin; Fahmina Zafar; Mohammad Asif Alam (1736-1742).
Olive oil based polyurethanamide/ZnO biocomposites were prepared by energy efficient microwave irradiation technique. The biocomposites showed good coating properties: scratch resistance, impact resistance, adhesion and flexibility retention. The corrosion studies carried out by potentiodynamic polarization measurements exhibit inhibition efficiency of 99.99% in 5% NaCl, 99.99% in 3.5% HCl, and 99.94% tap water, respectively. The overall approach is significant as it focuses on the utilization of vegetable oil, a sustainable material, polyurethanamide, synthesized through an energy efficient technique, at lower temperature, in lower reaction time, promoting value addition through simple chemistry. The coatings provide corrosion protection by barrier action.
Keywords: Olive Oil; Polyurethane; Coatings; ZnO; Potentiodynamic
Superhydrophobic, flexible and gas-permeable membrane prepared by a simple one-step vapor deposition by Bo Ra Kim; Dae Han Kim; Young Dok Kim (1743-1748).
We demonstrate the fabrication of superhydrophobic, flexible and gas-permeable membranes by a simple one-step process consisting only of thermal evaporation of a fluid polydimethylsiloxane (PDMS) polymer, without the use of any other chemicals such as curing agents or solvents of PDMS. As a substrate for the PDMS coating, a stainless steel mesh approx. 100 μm thick was used, which is flexible and becomes superhydrophobic after PDMS coating, attaining a water contact angle above 160°. The flexible mesh remained gas-permeable upon superhydrophobic coating, since PDMS evenly coated each strand of the metal mesh, and the vacancies between wires remained unclogged upon coating. The mechanical and chemical stability of the superhydrophobic, flexible and gas-permeable membrane is demonstrated herein.
Keywords: Superhydrophobicity; Chemical Vapor Deposition; Polydimethylsiloxane; Gas Permeability; Flexibility
Generation of micro- and nano-bubbles in water by dissociation of gas hydrates by Tsutomu Uchida; Kenji Yamazaki; Kazutoshi Gohara (1749-1755).
Gas hydrate crystals have a structure in which one molecule is enclathrated in a cage of water molecules. When such a crystal dissociates in water, each enclathrated molecule, generally vapor at standard temperature and pressure, directly dissolves into the water. After the solution is supersaturated, excess gas molecules from further dissociation start forming small bubbles called micro- and nano-bubbles (MNBs). However, it is difficult to identify such small bubbles dispersed in liquid because they are smaller than a microscope's optical resolution. To confirm the formation of MNBs after gas hydrate dissociation, we used a transmission electron microscope (TEM) to analyze freeze-fracture replicas of CH4-hydrate dissociation solution. The TEM images indicate the existence of MNBs in the solution, with a number concentration similar to that from a commercially supplied generator. Raman spectroscopic measurements on the CH4-hydrate dissociated solution were then used to confirm that the MNBs contain CH4 vapor, and to estimate experimentally the inner pressure of the CH4 MNBs. These results suggest that the dissociation of gas hydrate crystals in water is a simple, effective method to obtain MNB solution. We then discuss how such MNBs may play a key role in the memory effect of gas-hydrate recrystallization.
Keywords: Microbubble; Nanobubble; Gas Hydrate Dissociation; Freeze Fracture Replica; Bubble Pressure; Memory Effect