Korean Journal of Chemical Engineering (v.33, #6)
Recent developments in scale-up of microfluidic emulsion generation via parallelization by Heon-Ho Jeong; David Issadore; Daeyeon Lee (1757-1766).
Microfluidics affords precise control over the flow of multiphasic fluids in micron-scale channels. By manipulating the viscous and surface tension forces present in multiphasic flows in microfluidic channels, it is possible to produce highly uniform emulsion droplets one at a time. Monodisperse droplets generated based on microfluidics are useful templates for producing uniform microcapsules and microparticles for encapsulation and delivery of active ingredients as well as living cells. Also, droplet microfluidics have been extensively exploited as a means to enable highthroughput biological screening and assays. Despite the promise droplet-based microfluidics hold for a wide range of applications, low production rate (<<10mL/hour) of emulsion droplets has been a major hindrance to widespread utilization at the industrial and commercial scale. Several reports have recently shown that one way to overcome this challenge and enable mass production of microfluidic droplets is to parallelize droplet generation, by incorporating a large number of droplet generation units (N>>100) and networks of fluid channels that distribute fluid to each of these generators onto a single chip. To parallelize droplet generation and, at the same time, maintain high uniformity of emulsion droplets, several considerations have to be made including the design of channel geometries to ensure even distribution of fluids to each droplet generator, methods for large-scale and uniform fabrication of microchannels, device materials for mechanically robust operation to withstand high-pressure injection, and development of commercially feasible fabrication techniques for three-dimensional microfluidic devices. We highlight some of the recent advances in the mass production of highly uniform microfluidics droplets via parallelization and discuss outstanding issues.
Keywords: Microfluidics; Emulsions; Droplets; Scale-up; Large-scale Integration; Device Fabrication
Dynamic modeling and simulation of reaction, slag behavior, and heat transfer to water-cooling wall of shell entrained-flow gasifier by Cheol-Oong Kim; Ryang-Gyoon Kim; Zelin Wu; Chung-Hwan Jeon (1767-1776).
A mathematical model is developed to simulate a pilot Shell entrained-flow coal gasifier. Submodels of specific structures of the gasifier are established to simulate the complicated gasification process. The model includes the total energy conservation equation and mass conservation equations for the gas components, solid flow, and gas flow. It simulates the influence of the gasifier structure and dimensions and can calculate the effects of changing almost every important operation parameter, e.g., the syngas composition, gasification temperature, carbon conversion ratio, walllayer temperature, and slag mass flow rate. The model can predict the syngas composition under a limited residence time condition. Furthermore, it considers the heat transfer coefficient of each layer of the water wall to calculate its heat loss and temperature. Thus, the model also reflects the influence of performance parameters of the gasifier’s water wall. The slag mass flow rate on the wall is calculated using a slag submodel.
Keywords: Entrained-flow Gasifier; Dynamic Modelling; Simulation; Reaction; Water Wall heat Transfer; Slag Behavior
Electrochemical synthesis of ammonia from water and nitrogen catalyzed by nano-Fe2O3 and CoFe2O4 suspended in a molten LiCl-KCl-CsCl electrolyte by Kwiyong Kim; Chung-Yul Yoo; Jong-Nam Kim; Hyung Chul Yoon; Jong-In Han (1777-1780).
Nano-Fe2O3 and CoFe2O4 were suspended in molten salt of alkali-metal chloride (LiCl-KCl-CsCl) and their catalytic activity in electrochemical ammonia synthesis was evaluated from potentiostatic electrolysis at 600 K. The presence of nanoparticle suspension in the molten chloride resulted in improved production of NH3, recording NH3 synthesis rate of 1.78×10−10 mol s−1 cm−2 and 3.00×10−10 mol s−1 cm−2 with CoFe2O4 and Fe2O3, which are 102% and 240% higher than that without the use of a nanocatalyst, respectively. We speculated that the nanoparticles triggered both the electrochemical reduction of nitrogen and also chemical reaction between nitrogen and hydrogen that was produced from water electro-reduction on cathode. The use of nanocatalysts in the form of suspension offers an effective way to overcome the sluggish nature of nitrogen reduction in the molten chloride electrolyte.
Keywords: Ammonia; Electrochemical Reduction; Molten Salt; Nano-catalysts
Preferential CO oxidation over supported Pt catalysts by Kyung-Won Jeon; Dae-Woon Jeong; Won-Jun Jang; Jae-Oh Shim; Hyun-Suk Na; Hak-Min Kim; Yeol-Lim Lee; Byong-Hun Jeon; Seong-Heon Kim; Jong Wook Bae; Hyun-Seog Roh (1781-1787).
Preferential CO oxidation reaction has been carried out at a gas hourly space velocity of 46,129 h−1 over supported Pt catalysts prepared by an incipient wetness impregnation method. Al2O3, MgO-Al2O3 (MgO=30 wt% and 70 wt%) and MgO were employed as supports for the target reaction. 1 wt% Pt/Al2O3 catalyst exhibited very high performance (X CO >90% at 175 °C for 100 h) in the reformate gases containing CO2 under severe conditions. This result is mainly due to the highest Pt dispersion, easier reducibility of PtO x , and easier electron transfer of metallic Pt. In addition, 1 wt% Pt/Al2O3 catalyst was also tested in the reformate gases with both CO2 and H2O to evaluate under realistic condition.
Keywords: Preferential CO Oxidation; Pt/Al2O3 ; Dispersion; Reducibility; Electron Transfer
Facile synthesis of TiO2/ZnFe2O4 nanocomposite by sol-gel auto combustion method for superior visible light photocatalytic efficiency by Kalithasan Natarajan; Puspendra Singh; Hari Chand Bajaj; Rajesh Jagannath Tayade (1788-1798).
Photocatalytic composite materials having photon absorption capability in the range of visible light were synthesized by loading TiO2 (5, 10, 15, and 20 wt%) on ferrite nanocomposites by sol-gel auto-combustion method. The synthesized nanocomposites were analyzed using X-ray diffraction, Transmission electron microscopy, diffuse reflectance spectroscopy and N2 adsorption techniques. The generation of photo active hydroxyl radicals for all the synthesized composites was found higher under the irradiation of red LED (RLED irradiation) which was confirmed by degradation of rhodamine B dye under irradiation of RLED. Photocatalytic activity of the synthesized nanocomposites was also carried out under irradiation of ultraviolet (UVLED) and blue (BLED) light emitting diodes, which is comparatively less than for the reaction under red LED irradiation. The operational parameters like catalyst amount, pH and concentration of dye solution were studied and ESI-MS degradation pathway is proposed by analyzing the degraded samples.
Keywords: TiO2 Loading; Zinc Ferrite; Light Emitting Diodes (LEDs); Rhodamine B; Photocatalysis
Enhanced activity of carbon-supported PdCo electrocatalysts toward electrooxidation of ethanol in alkaline electrolytes by Suenghoon Han; Gyu-Sik Chae; Jae Sung Lee (1799-1804).
Carbon-supported Pd and PdCo (1: 2, 1: 1, 2: 1 and 3: 1) catalysts were synthesized by chemical reduction with NaBH4. Their electrochemical properties were investigated by cyclic voltammetry, chronoamperometry and CO stripping voltammetry in alkaline electrolytes, and compared with commercial Pt/C and PtRu(1: 1)/C catalysts. In electrochemical oxidation of ethanol in an alkaline electrolyte, marked improvements in the current density and onset potential were observed by incorporating Co into Pd/C to form PdCo/C alloy electrocatalysts. The best catalyst PdCo (1: 1)/C showed performance superior to the commercial Pt/C or PtRu/C catalysts. It is shown that the incorporated Co facilitates the oxidation of strongly-adsorbed carbonaceous intermediate species on the surface of Pd by forming OH− group and reacts away the intermediates from Pd surface. Thus, PdCo(1: 1)/C catalyst is a promising anode catalyst for direct ethanol fuel cells with alkaline electrolytes.
Keywords: Palladium-cobalt Alloy; Electrocatalysts; Direct Ethanol Fuel Cells; Alkaline Electrolytes
Effects of the ratio of carbon to nitrogen concentration on lipid production by bacterial consortium of sewage sludge using food wastewater as a carbon source by Sang Do Yook; Raul Sanchez Sanchez; Jeong Hyub Ha; Jong Moon Park (1805-1812).
Food wastewater (FWW) and sewage sludge (SS) were used to control the C:N ratio in cultures as a method to increase lipid production by microbial species in SS. FWW and SS were mixed in volumetric ratios (FWW: SS) of 5: 0 (F5), 4: 1 (F4), or 3: 2 (F3). Compared to raw SS, total lipid content production was increased by 263% in F5, 142% in F4, and 111% in F3. These results were caused by increases in the concentrations of triglycerides (TAGs) during lipid enhancement. The fatty acid methyl ester content of TAGs (wt% of extract) was 25.3 in F5, 20.2 in F4 and 13.25 in F3; these were significant improvements over biodiesel production using raw SS. C16:0 fatty acid was mostly converted to C18:1 fatty acid; this is an important result because the proportion of C18:1 strongly influences the quality of biodiesel. This is the first effort to produce biodiesel using FWW instead of synthetic medium as a carbon source. Hence, this study provides a useful solution for treating organic wastes (SS and FWW) simultaneously; this strategy may be an economically viable method for producing biodiesel from organic wastes.
Keywords: Sewage Sludge; Food Wastewater; Lipid; Triacylglycerol (TAG); Fatty Acid Methyl Esters (FAMEs); Biodiesel
Influence of polymeric additives on paraffin wax crystallization in model oils by Taesung Jung; Jong-Nam Kim; Seong-Pil Kang (1813-1822).
Wax deposition, precipitation, and gelation make the transport of crude oil in pipelines challenging. The effect of several ethylene copolymers, and small molecules with a long alkyl chain, on wax formation was investigated for n-C32H66 in decane and de-aromatized white oil. Addition of a small amount of EVA (ethylene-co-vinyl acetate) copolymers delayed nucleation by reducing the onset temperature and the wax appearance temperature. They modified the wax crystal-structure and morphology from large plates to tiny particles by adsorbing to the wax surfaces and inhibiting growth. Viscosity and the pour-point were improved by inhibiting the formation of large aggregates. It was demonstrated that the content of vinyl acetate groups in EVA copolymers affected wax crystallization. The small molecules, propylene copolymers, and ethylene copolymers with ethyl acrylate, maleic anhydride, and ethylene glycol showed a weak inhibiting effect. The effect of wax inhibitors was determined by the content and by the type of structure-disturbing groups in the copolymers.
Keywords: Wax; Crystallization; Inhibitors; Nucleation; Crystal Modification; Viscosity
Catalytic oxidation and capture of elemental mercury from simulated flue gas using Mn-doped titanium dioxide by Jingtao Zhi; Xianqun Yu; Jingjing Bao; Xiaoxiang Jiang; Hongmin Yang (1823-1830).
Titanium dioxide (TiO2) and Mn-doped TiO2 (Mn(x)-TiO2) were synthesized in a sol-gel method and characterized by BET surface area analysis, X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). Gasphase elemental mercury (Hg0) oxidation and capture by the Mn-doped TiO2 catalyst was studied in the simulated flue gas in a fixed-bed reactor. The investigation of the influence of Mn loading, flue gas components (SO2, NO, O2, and H2O) showed that the Hg0 capture capability of Mn(x)-TiO2 was much higher than that of pure TiO2. The addition of Mn inhibits the grain growth of TiO2 and improves the porous structure parameters of Mn(x)-TiO2. Excellent Hg0 oxidation performance was observed with the catalyst with 10% of Mn loading ratio and 97% of Hg0 oxidation was achieved under the test condition (120 °C, N2/6%O2). The presence of O2 and NO had positive effect on the Hg0 removal efficiency, while mercury capture capacity was reduced in the presence of SO2 and H2O. XPS spectra results reveal that the mercury is mainly present in its oxidized form (HgO) in the spent catalyst and Mn4+ doped on the surface of TiO2 is partially converted into Mn3+ which indicates Mn and the lattice oxygen are involved in Hg0 oxidation reactions.
Keywords: Elemental Mercury; Mn-doped Titanium Dioxide; Catalytic Oxidation; Removal
The particle size effect of N-doped mesoporous carbons as oxygen reduction reaction catalysts for PEMFC by Ulziidelger Byambasuren; Yukwon Jeon; Dorjgotov Altansukh; Yunseong Ji; Yong-Gun Shul (1831-1836).
The particle size effect of N-doped mesoporous carbon was investigated for ORR activity in acid condition and for issue of a mass transfer and gas diffusion in PEMFCs. As for a non-Pt ORR catalyst, nitrogen (N)-doped ordered mesoporous carbons (OMCs) with a various particle sizes with the range of the average 20, 45 and 75 μm were synthesized by the precursor of polyaniline for the N/C species, and a mesoporous silica template was used for the physical structure for preparation of nitrogen doped OMCs. The N-doped mesoporous carbons are promoted by a transition metal (Fe) to improve catalytic activity for ORR in PEMFCs. All the prepared carbons were characterized by via scanning electron microscopy (SEM), and to evaluate the activities of synthesized doped carbons, linear sweep was recorded in an acidic solution to compare the ORR catalytic activities values for the use in the PEMFC system. The surface area and pore volume were increased as the particles decreased, which was effective for the mass transfer of the reactant for higher activity at the limiting current regions.
Keywords: N-doped Carbons; Ordered Mesoporous Carbons (OMCs); Particle Size; Oxygen Reduction Reaction (ORR); Polymer Electrolyte Membrane Fuel Cell (PEMFC)
CeO2-La2O3/ZSM-5 sorbents for high-temperature H2S removal by Dongjing Liu; Weiguo Zhou; Jiang Wu (1837-1845).
Performance of CeO2-La2O3/ZSM-5 sorbents for sulfur removal was examined at temperature ranging from 500 oC to 700 oC. The sulfur capacity of 5Ce5La/ZSM-5 was much bigger than that of CeO2/ZSM-5. H2 had a negative impact on the sulfidation; however, CO had little influence on sulfur removal. The characterization results showed that CeO2 and La2O3 were well dispersed on ZSM-5 because of the intimate admixing of La2O3 and CeO2, the major sulfidation products were Ce2O2S and La2O2S, the XRD and SEM results revealed that ZSM-5 structure could remain intact during preparation and sulfidation process, the H2-TPR showed that the reducibility of CeO2 can be remarkably enhanced by addition of La.
Keywords: ZSM-5; Rare Earth; Cerium; Sorbent; Desulfurization
Catalytic activity of copper-ceria catalysts supported on different zeolites for CO oxidation by Dong Zhang; Huiping Zhang; Ying Yan (1846-1854).
Copper-ceria catalysts for CO oxidation supported on 4A, 5A, NaX and NaY zeolites were prepared by incipient wetness impregnation and excess-solution impregnation. Catalysts were characterized by SEM, EDX, XRD, N2 adsorption-desorption, H2-TPR and XPS. Results revealed that the catalysts were greatly affected by zeolites and preparation method. EDX results indicated the metal loading of 4A-ES (5.1 wt% Cu, 15.7 wt% Ce), 5A-ES (5.9 wt% Cu, 19.2% Ce), NaX-ES (11.7wt% Cu, 4.2 wt% Ce) and NaY-ES (11.0 wt% Cu, 7.9 wt% Ce) greatly varied. TPR results suggested that the peak at around 195 °C was presented in NaX-ES and 4A-IW, standing for dispersed copper species that is very active for CO oxidation. The catalytic activity of 4A-ES and NaX-ES was the best among catalysts made by excess-solution impregnation, demonstrated by the lowest T50 at 127 and 129 °C, respectively. The catalytic activity of catalysts made by incipient wetness impregnation was worse than that of catalysts made by excess-solution impregnation, examined by the T50 of 4A-IW and NaX-IW at 128 and 192 °C, respectively.
Keywords: CO Oxidation; Copper-ceria Catalyst; Zeolite; Incipient Wetness Impregnation; Excess-solution Impregnation
Electrochemical degradation of organic dyes with a porous gold electrode by Jieun Kim; Changjoo Yeom; Younghun Kim (1855-1859).
Electrochemical degradation of methylene blue (MB) and rhodamine B (RhB) was studied at porous gold (PAu) electrode in presence of KCl as supporting electrolytes. PAu electrode with three-dimensional porous structure was prepared by paper-based method and used as working electrode. Based on the cyclic voltammetric test, the redox potential of of MB and RhB contained in KCl solution was found and the electrochemical degradation was conducted at fixed applied voltage. The direct oxidation of organic dyes involved using PAu and Pt electrodes, while the indirect electrolysis was mediated by active chlorine electro-generated from KCl solution. The results showed that PAu electrode with porous structure has high electrochemical activity with fast kinetics for the destruction of RhB (0.0448 min-1) and low energy consumption (0.315 kWh/m3), compared to smooth Au foil and reported others. In addition, the durability test for 10 serial degradation showed that PAu electrode has a good reproducibility and high adaptability for practical application.
Keywords: Paper-based Porous Gold; Electrochemical Degradation; Organic Dye; Rhodamine B
Extraction of p-coumaric acid from agricultural residues and separation using ‘sugaring out’ by Pradip B. Dhamole; Shital Chavan; Rashmi G. Patil; Hao Feng; Mahesh Bule; Pallavi Kinninge (1860-1864).
We investigated the extraction of para-coumaric acid (pCA) from different agriculture residues (corn stover, sugarcane bagasse, sorghum stalk, pearl millet stalk, green gram shell, groundnut shell, sesame shell) using sugarcane bagasse alkaline hydrolysis and separation of pCA using sugaring out - a new phase separation method. Primary screening of different feed stocks was by alkaline hydrolysis with 2M NaOH for 6 h at room temperature. Sugarcane baggase resulted into significant amount of pCA (1.1 g/L) and small amount of ferulic acid (FA) (0.23 g/L). The optimized alkaline hydrolysis conditions (2 M NaOH and 16 h) resulted into maximum pCA release of 2.0 g/L. The pCA was separated from alkaline hydrolysate using sugaring out, a two phase separation method that results in aqueous phase and the organic solvent (acetonitrile) phase. Sugaring-out separated more than 90% of the pCA from the alkaline hydrolysate. Results of HPLC using standard pCA and FA showed that the main component of the separated top (organic solvent) phase was pCA rather than FA.
Keywords: p-Coumaric Acid; Alkaline Hydrolysis; Sugaring Out; Agriculture Residue; ATPS
Bio-electrochemical conversion of atmospheric N2 to ammonium using free-living diazotrophs by Il Lae Jung; Young Chan Park; Doo Hyun Park (1865-1871).
The effects of electrochemical reducing power on enrichment, growth, and ammonium production of freeliving diazotrophs from rhizosphere soil were evaluated. Soil bacteria were cultivated in a conventional bioreactor (CBR) and an electrochemical bioreactor (EBR), both containing a neutral red-modified graphite felt (NR-GF) cathode and a platinum anode, but with electricity charged to the EBR only. Temperature gradient gel electrophoresis identified 21 species from rhizosphere soil, and 17 and seven species from the CBR and EBR, respectively, after 40 days of incubation. Six species from the CBR and five species from the EBR were diazotrophs. The bacterial community biomass and the ammonium content in the bacterial culture were, respectively, 1.6 and 2 times higher in the EBR than in the CBR. These results indicate that the electrochemical reducing power generated from the NR-GF may be a driving force in the activation of enrichment, growth, and N2-fixing metabolism of diazotrophs.
Keywords: Bio-electrochemical Reaction; N2 Fixation; Ammonium Production; Diazotrophs
Antihyperglycemic and antioxidant activities of polysaccharide produced from Pleurotus ferulae in streptozotocin-induced diabetic rats by Dubok Choi; YuLan Piao; Sun-Jong Yu; Yeon-Woong Lee; Dong-Hoon Lim; Young-Cheol Chang; Sang-Shin Park; Myung-Koo Lee; Wol-Suk Cha; Don-Sang You; Hoon Cho (1872-1882).
We investigated the antihyperglycemic and antioxidant activities of polysaccharides produced from Pleurotus ferulae mutant in streptozotocin-induced diabetic rats. Blood glucose level in the STZ-induced diabetic rat administered the extract polysaccharides, 250mg/kg b·w/d (EPSG) was 196.97mg/dL, approximately 54.12% less compared to that of the STZ-induced diabetic rats administered 0.9% NaCl solution (NCG). The insulin level in the EPSG was approximately 1.64-fold higher than that in the NCG. HDL and LDL cholesterol levels in the EPSG were 29.15mg/L and 20.35mg/dL, respectively, representing an approximate increase of 69.18% and decrease of 38.52%, respectively. The activities of aspartate aminotransferase (AST) and alanine transferase (ALT) in the EPSG decreased approximately by 49.27 and 50.43%, respectively, while the alkaline phosphatase (ALP) activity decreased by 34.25%, relative to the NCG. Antioxidant activities in the NCG decreased relative to the normal group. In contrast, for EPSG, these values increased relative to the NCG. The malondialdehyde level in the EPSG was 12.95mmol/mg protein, which was approximately 70.64% of that in the NCG. These results suggest that the polysaccharides of Pleurotus ferulae mutant could be developed as potential antidiabetic agents or functional foods for people with a high risk of diabetes mellitus.
Keywords: Pleurotus ferulae ; Antihyperglycemic Activity; Antioxidant Activity; Polysaccharide; STZ-induced Diabetic Rat
A novel CCU approach of CO2 by the system 1,2-ethylenediamine+1,2-ethylene glycol by Bo Guo; Tianxiang Zhao; Feng Sha; Fei Zhang; Qiang Li; Jianbin Zhang (1883-1888).
As a new, effective CO2 fixation system, 1,2-ethylenediamine and 1,2-ethylene glycol (EDA+EG) can efficiently activate CO2 and directly convert it into a novel CO2-storage material (CO2SM) with 46.3% yield. The aqueous CO2SM solution can react with Ca(OH)2-saturated limpid solution to generate morphology-controllable CaCO3 microparticles with additional CO2 bubbling and Ca(OH)2. Additionally, the aqueous EDA+EG solution could be recycled multiple times without significant loss of CO2 capturing and releasing capabilities.
Keywords: CO2 Capture; Storage and Utilization; CO2-storage Material; Absorption-desorption Cycle; CaCO3 Microparticle
Optimization study of a batch chromatographic process based on Amberchrom-CG161C adsorbent for separation of valine from a ternary amino acid mixture by Sungyong Mun (1889-1896).
The optimal design of the batch chromatographic process for separation of valine (product) from isoleucine and leucine (side-products) was carried out by using the relevant optimization tool that was prepared on the basis of an up-to-date genetic algorithm. In such an optimal design, the flow rate, feed size (?feed), eluent gap size (?gap), and product collection time were optimized to maximize the valine productivity of the batch chromatographic process under consideration. The results showed that the valine productivity was governed by the flow rate in the region of low flow rates, whereas it was governed by the Δ gap /Δ feed factor in the region of high flow rates. Finally, the effect of valine yield on the productivity was investigated, followed by providing the proper operating conditions that could be advantageous to both valine productivity and valine yield.
Keywords: Valine Separation; Batch Chromatographic Process; Process Optimization
Thermodynamic and spectroscopic identification of aldehyde hydrates by Hyery Kang; Yun-Ho Ahn; Dong-Yeun Koh; Huen Lee (1897-1902).
-It has been reported that some aldehyde compounds have formed simple sII clathrate hydrates without help-gas molecules, showing a self-forming effect. However, the structure of aldehyde hydrates is quite unstable due to the “gem-diol reaction”. According to the previous studies, the aldehyde hydrate slowly decomposes at atmospheric condition with the conversion of aldehyde to gem-diol. We investigated binary aldehyde (acetaldehyde, propionaldehyde, and isobutyraldehyde)+methane clathrate hydrate with spectroscopic and thermodynamic analyses. Similar to the simple aldehyde hydrate, the binary hydrates also formed a sII hydrate. During the hydrate formation process, we found that most of the aldehydes converted to gem-diols and were then incorporated into the large cages of the sII hydrate. Depending on the equilibrium constant of the gem-diol reaction caused by the molecular structures of the three aldehydes, different phase equilibrium curves of aldehyde+methane hydrates were obtained.
Keywords: Clathrate Hydrate; Aldehyde; Gem-diol; Binary Hydrates; Phase Equilibrium
Experimental verifications of Mpemba-like behaviors of clathrate hydrates by Yun-Ho Ahn; Hyery Kang; Dong-Yeun Koh; Huen Lee (1903-1907).
The exact mechanism of the Mpemba effect of water was recently investigated microscopically and explained on the basis of the cooperative relationship between intramolecular polar-covalent bonds (O-H) and intermolecular hydrogen bonds (O:H). We posited that this relationship might exist in clathrate hydrates since they consist of hydrogen-bonded host water frameworks and enclathrated guest molecules. The formation of tetrahydrofuran (THF) hydrate, which is the simplest clathrate hydrate, was investigated by using differential scanning calorimetry and Raman spectroscopy. THF hydrates show the Mpemba effect at lower initial temperatures, but formation times were delayed at higher initial temperatures because the evaporated THF molecules should be liquefied to correspond to the stoichiometric concentration of guest molecules to form sII clathrate hydrates. However, even though the formation time was delayed at higher initial temperatures, the rates of heat emission during THF hydrate formation, measured in a bulk state, roughly increased as the initial temperature increased. Moreover, we observed that the O: H stretching phonons of water in the THF hydrate showed a blue shift, and the O-H stretching mode showed a redshift as temperature decreased. Both the rate of heat emission and the Raman shift of these two bonds imply that a cooperative relationship between the covalent bond and the hydrogen bond exists in THF hydrate as pure water. The formation kinetics of THF hydrate therefore might depend on its initial temperature, thus showing Mpemba-like behavior.
Keywords: Clathrate Hydrate; THF Hydrate; Mpemba Effect; Initial Temperature; Covalent Bond
Deep desulfurization of fuel gas by adsorption on Cu-impregnated activated carbons in practical conditions by Hoang Phuoc Ho; Palraj Kasinathan; Jaesung Kim; Doohwan Lee; Hee Chul Woo (1908-1916).
Deep desulfurization properties and characteristics of activated carbon (AC) modified by impregnation of CuCl2 were studied using simulated hydrocarbon fuels containing dimethyl sulfide (DMS), tert-butylmercaptan (TBM), and tetrahydrothiophene (THT), the typical organosulfur compounds representing sulfides, thiols, and thiophenes that exist in fuel gases. The pristine AC had limited adsorptive desulfurization performance for a ternary DMS-THT-TBM mixture feed with an early breakthrough of DMS and TBM due to its preferential adsorption of THT. The adsorption of these organosulfur species on the AC surface was intrinsically weak and competing, as indicated by their low desorption activation energies (37-39 kJ mol−1). However, relatively stronger adsorption of THT than the others led to the AC surface gradually being covered by THT through replacement of the initially adsorbed TBM and DMS. The impregnation of CuCl2 on the AC (3.4 atomic % Cu) additionally formed strong and selective adsorption sites for TBM (activation energy=58.6 kJ mol−1) on the AC surface, which gave rise to about three-fold increase in the total breakthrough adsorption capacity for these sulfur species. The structure and physicochemical properties of the adsorbents were characterized by N2 adsorption, x-ray diffraction, x-ray photoelectron spectroscopy, scanning electron microscopy, transmission electron microscopy, thermogravimetric analysis, differential scanning calorimetry, and surface pH measurement. The results suggested that the modulation of adsorption selectivity of the AC surface by CuCl2 impregnation had significant effects on the overall deep desulfurization performance for fuel gases containing multiple organosulfur species in practical conditions.
Keywords: Adsorptive Desulfurization; Activated Carbon; Copper; Fuel Cell; Fuel Processing
Bulk phase behavior of tetra-n-butylammonium bromide hydrates formed with carbon dioxide or methane gas by Sanehiro Muromachi; Yoshitaka Yamamoto; Satoshi Takeya (1917-1921).
We report the bulk phase behavior of ionic clathrate hydrates of tetra-n-butylammonium bromide (TBAB) formed with a common guest substance: CO2 or CH4. We formed the bulk samples by a classical mixing reactor for gas hydrates, and measured them by the powder X-ray diffraction (PXRD). PXRD patterns of the TBAB+(CO2 or CH4) hydrates formed with 0.32 of TBAB mass fraction in the aqueous phase were obtained. They are consistent with the orthorhombic hydrate (Shimada et al., Acta Crystallogr. 2005; Muromachi et al., Chem. Commun. 2014), but not identical with the other stable phase, i.e., the tetragonal TBAB hydrate (Rodionova et al., J. Phys. Chem. B 2013). When the aqueous solutions are under the substantial pressure of CO2 or CH4 gas, TBAB is likely to form the orthorhombic Pmma and/or Imma phases. A question for the bulk orthorhombic TBAB hydrate phase about the scarce gas incorporation is newly proposed.
Keywords: Ionic Clathrate Hydrate; Carbon Dioxide; Methane; Tetra-n-butylammonium Bromide; Powder X-ray Diffraction
Crystallization kinetics for carbon dioxide gas hydrate in fixed bed and stirred tank reactor by Asheesh Kumar; Dishant Khatri; Ju Dong Lee; Rajnish Kumar (1922-1930).
The phase change from germ nuclei to growth nuclei and subsequent volume transformation in a crystallization process was modeled by Avrami equations. The phase change during the hydrate formation was fitted with the classical Avrami model by utilizing gas uptake data. The idea is to understand the difference in growth behavior of hydrate crystals when in small pores compared to a stirred tank reactor which does not pose any physical restrictions to hydrate growth. The parameters n and k of the Avrami equation were determined explicitly for CO2 hydrate formation.
Keywords: Gas Hydrates; Avrami Equation; Kinetics; Fixed Bed; CO2 Capture & Sequestration
Ultrasonic/microwave synergistic synthesis of well-dispersed hierarchical zeolite Y with improved alkylation catalytic activity by Xiaoqin Fu; Xiaoli Sheng; Yuming Zhou; Zhiwei Fu; Shuo Zhao; Zewu Zhang; Yiwei Zhang (1931-1937).
Well-dispersed hierarchical zeolite Y, structure-directed by ionic liquid 1-methyl-3-[3'-(trimethoxysilyl) propyl] imidazolium chloride, was synthesized for the first time using a novel ultrasonic/microwave synergistic synthesis (UMSS). The time required for the synthesis of zeolite Y by UMSS method was remarkably reduced to 6 h instead of 24 h under conventional hydrothermal conditions. The structures of all samples were characterized by XRD, BET, FT-IR, SEM and TEM. The results clearly demonstrated that the UMSS is a promising strategy to achieve zeolite Y with improved crystallinity, large BET surface area, bulky mesopore volume, well-dispersed morphology, small zeolite nanoparticle. The catalytic activity of hierarchically micro-mesoporous zeolite Y was evaluated by using the alkylation of o-xylene with styrene. Mesoporous zeolite Y synthesized by UMSS method showed significantly higher catalytic activity, stability and reusability, compared with conventional hydrothermal synthesis. It might be ascribed to its large mesoporous volume, small crystal nanoparticle and high surface area, minimizing the diffusion length as the reactant molecules diffuse into the pores, and correspondingly the products diffuse out of zeolites. This study suggests that UMSS method is a good alternative for the synthesis of micro-mesoporous zeolite Y, which may be of remarkable benefit for industrial applications.
Keywords: Micro-mesoporous Zeolite Y; Ionic Liquid; Ultrasonic/Microwave Synergistic Synthesis; Conventional Synthesis Method; Alkylation
Effects of additives on the mechanical and thermal properties of epoxy-based nanocomposites produced using sonication by YoonKook Park; Chun-Hyung Cho (1938-1941).
Epoxy nanocomposites were synthesized in the presence of hydroxyapatite with the aid of an ultrasonicator. In general, as the amount of hydroxyapatite increased from 0wt% to 10wt%, the mechanical properties of the hydroxyapatite-containing nanocomposite were enhanced. The mechanical properties of the nanocomposite were significantly enhanced by the simple addition of 10 wt% of hydroxyapatite. Specifically, the storage modulus of the 10 wt% hydroxyapatite-containing nanocompsote was 3.2GPa, which is 46% higher compared to that of the pristine epoxy nanocomposite. The glass transition temperature of hydroxyapatite-containing nanocomposites generally decreased by few degrees in Celsius. To investigate the effect of additives on the mechanical properties of the epoxy-based nanocomposite, nanocomposites were synthesized using both montmorillonite and tellurium dioxide instead of hydroxyapatite. Intrestingly, both additive-based nanocomposite materials resulted in an increase in the storage modulus while the glass transition temperature decreased. These results demonstrate that the addition of few wt% of all three additives (hydroxyapatite, montmorillonite, and tellurium dioxide) can enhance the mechanical properties of epoxy-based nanocomposites.
Keywords: Epoxy; Hydroxyapatite; Montmorillonite; Tellurium Dioxide; Nanocomposite
Crystal growth of ionic semiclathrate hydrate formed at interface between CO2+N2 gas mixture and tetrabutylammonium bromide aqueous solution by Hiroaki Hayama; Hotaka Akiba; Yuki Asami; Ryo Ohmura (1942-1947).
This study reports a visual observation of the formation and growth of ionic semiclathrate hydrate on the surface of a Tetrabutylammonium bromide (TBAB) aqueous solution and CO2+N2 gas mixture. The composition of CO2+N2 gas mixture was 20: 80. The experimental temperature range was from 280 K to 290 K, under the pressures of 2.3MPa and 4.7MPa, at w TBAB =0.10 and w TBAB =0.40, where wTBAB denotes the mass fraction of TBAB in the aqueous solution. At w TBAB =0.40, the hydrate crystals were initially observed to grow within the droplet, and followed by lateral growth at the droplet surface; but at w TBAB =0.10, the hydrate crystals grew exclusively in the liquid phase and did not cover the droplet surface. Two types of different crystals with different sizes were clearly observed.
Keywords: Clathrate Hydrate; Crystal Growth; Carbon Capture; Crystal Morphology; Tetrabutylammonium Bromide
Electrochemical study of Magnetite-CH composite carbon paste modified electrode by Al. Kavitha; Kumanan Bharathi Yazhini (1948-1953).
Magnetite nanoparticles were synthesized by coprecipitation and characterized. The average particle size was 22-50 nm by XRD and AFM. Chitosan was prepared from crab shells and characterized. Magnetite-chitosan composite carbon paste modified electrode was prepared and characterized by using XRD, FT-IR and SEM technique. The electrochemical responses of this Magnetite-CH composite electrode were studied in potassium ferrocyanide/KCl system using cyclic voltammetry and electrochemical impedance spectroscopy. The cyclic voltammetric and EIS studies indicated better electron transfer of magnetite-CH composite (3: 1) carbon paste modified electrodes compared to bare, magnetite, chitosan composite electrodes. The surface parameters like surface coverage (τ), Diffusion coefficient (D0), and rate constant (kS) were studied. The shelf-life of the developed electrode system is about 12 weeks under refrigerated conditions.
Keywords: Magnetite; Chitosan; Nanocomposite; Carbon Paste; Modified Electrode
Colloidal dispersion gels based on sulfonated polyacrylamide and chromium triacetate for harsh-environment by Ehsan Alvand; Jamal Aalaie; Mahmood Hemmati; Vali Ahmad Sajjadian (1954-1963).
The aim of this study was to outline the preparation of colloidal dispersion gels (CDGs) based on sulfonated polyacrylamide (SPA) and chromium triacetate and investigating their stability in harsh conditions. The effect of crosslinker, polymer concentration, salinity, and gelation time and temperature on the formation, rheological behavior and size distribution of CDGs and also their thermo-chemical stabilities were investigated. It was found that the shear viscosity and size of CDGs decreased with increasing of preparation time. Dynamic light scattering and scanning electron microscopy evaluations showed that the size of CDGs particles decreased with increasing of the Cr3+ concentration. In addition, SPA solution had yield stress, while CDGs did not. The elevation of temperature inhibits while the salinity does not disturb the formation of CDGs. In the systems with lower polymer concentration, CDGs were formed. Conversely, in the systems with higher polymer concentration, bulk gels were formed. After aging, CDG sample had a minimal viscosity loss, indicating its exceptional thermo-chemical stability.
Keywords: Colloidal Dispersion Gel; Sulfonated Polyacrylamide; Aging; Yield Stress; Oil Recovery
HMF synthesis in aqueous and organic media under ultrasonication, microwave irradiation and conventional heating by Naser Esmaeili; Mohammad Jalal Zohuriaan-Mehr; Hossein Bouhendi; Gholam Bagheri-Marandi (1964-1970).
5-Hydroxymethyl furfural (HMF) is known as a noteworthy platform in a biorefinery concept. HMF was prepared via fructose dehydration in aqueous and organic media, using three methods, i.e., conventional heating, ultrasonication and microwave irradiation. Water, methyl isobutyl ketone (MIBK), methyl ethyl ketone and ethyl acetate were used as media for HCl-catalyzed synthesis of HMF. FTIR and 1H-NMR spectroscopies were used for analysis. The synthesis yield and selectivity were investigated to optimize variables such as fructose concentration, catalyst dosage, temperature, irradiation power, solvent, and the reaction atmosphere. It was found that the yield in the organic media was superior to that of the aqueous ones. In addition, nitrogen atmosphere favored higher yield than air, due to lack of HMF oxidation. As conclusion, the highest yields of the conventional, ultrasonicated and microwave-assisted reactions were 87, 53, and 38%, respectively. In the reactions ultrasonically promoted, the reaction time scale was highly reduced from hours to minutes. The yield was varied with treatment times, so that ultrasonication was recognized to be the best approach in terms of yield, while the microwave method was the fastest one. Selectivity varied from 60 to 90% depending the reaction media and promotion method.
Keywords: Hydroxymethyl Furfural; Synthesis; Ultrasonication; Microwave Irradiation; Fructose Dehydration
Extremely flexible organic-inorganic moisture barriers by Se Hee Lim; Seung-Woo Seo; Haksoo Lee; Heeyeop Chae; Sung Min Cho (1971-1976).
Organic/inorganic multilayer structures were fabricated for extreme flexibility as well as enhanced moisturebarrier property. The organic and inorganic layers for the structures were formed by plasma polymerization and atomic layer deposition, respectively. The layers were grown alternately to form the organic/inorganic multilayer structures on a plastic substrate. To accomplish extreme flexibility of the barriers, ultra-thin aluminum oxide layers were grown by the atomic layer deposition and sandwiched by a flexible plasma-polymer layer. The moisture-barrier films were then confirmed to retain the initial barrier property even after 10,000 times of bending at a radius as small as 3mm when the barrier structure was located at a neutral plane.
Keywords: Moisture Barrier; Atomic Layer Deposition; Plasma Polymerization; Bending Radius