Showing papers in "Korean Journal of Chemical Engineering in 2005"

Gas hydrates: A cleaner source of energy and opportunity for innovative technologies

Abstract: The global energy system is characterized by a gradual de-carbonization and move to cleaner burning technologies: from wood to coal to oil and to natural gas. A final destination characterized by the term“hydrogen economy” is desired. Gas hydrate found in the earth’s crust is considered a source of natural gas that is essentially 100% methane (CH4) gas. Natural gas hydrate estimates worldwide range from 10,000 to 40,000 trillion cubic meters (TCM). Efforts are underway to exploit this resource. These methane hydrates in the earth’s crust also have the potential to be a significant factor in global climate change. Moreover, gas hydrates offer opportunities for the development of innovative technologies (separation of CO2 from CO2/N2 and CO2/H2 mixtures, CO2 sequestration, natural gas transportation and storage and H2 storage). In this work we assess the progress towards exploitation of gas hydrates as a resource for methane (cleaner energy) and summarize the state of the art with respect to the role of gas hydrates in the development of innovative technologies.

Adsorption of heavy metals by brewery biomass

Abstract: In this work, biosorption of lead, copper and cadmium by waste brewery yeast has been studied. The adsorption capacity for lead, copper and cadmium on the biomass increased with the increasing temperature and the maximum uptakes were 0.465 mmolPb/g (96.4 mg/g), 0.769 mmolCu/g (48.9 mg/g) and 0.127 mmolCd/g (14.3 mg/g) at 308 K. The Langmuir isotherm, favorable type, and the pseudo second-order kinetic model represent our experimental data very well. The heat of biosorption was evaluated from the Langmuir isotherm equation, and the biosorption of lead, copper and cadmium was endothermic reaction.

Filtration properties of electrospun ultrafine fiber webs

Abstract: Electrospun fiber webs were prepared at various spinning conditions. The effect of electrospinning parameters on fiber morphology and filtration performance of electrospun webs was investigated. The processing variables considered were only the applied voltage and rotation speed of a drum type collector. The fiber diameter and mean pore size of the electrospun webs decreased with increasing applied voltage and collector speed. Pressure drop and aerosol collection efficiency of the electrospun fiber webs were increased with decreasing fiber and pore size. Additionally, it was found that the filtration performance of the electrospun web was much greater than that of a commercial high efficiency air filter media made of glass fibers.

Influence of ionic liquids on the growth ofEscherichia coli

Abstract: Ionic liquids are compounds that composed only of ions and are liquid at room temperature. Thus, it is normally named room temperature ionic liquid (RTIL). In this study, the application of RTILs to the extractive fermentation of biomaterials was investigated as a substitute of organic solvents. The relative toxicity of the RTILs on the growth ofE. coli was tested. The inhibition of cell growth in the presence of various ionic liquids was measured using solid and liquid culture, and EC50 of each RTILs was calculated. The number of viable and total cells was measured by the number of colonies and optical density, respectively. Effective concentrations of toxicity (EC50) in these tested systems were similar with conventional solvents, such as acetone, acetonitrile, and ethanol. The viability ofE. coli was affected by the polarity and ionic properties of ionic liquids. The resistance of the microorganisms against ionic liquids was different with the cations and anions composing ionic liquids. No general influence of the anionic compound of the ionic liquids was found on toxicity comparing with distinctive influence of cationic moiety.

Simultaneous removal of SO2 and NO by sodium chlorite solution in wetted-wall column

Abstract: The effect of feeding rate of NaClO2 solution, inlet SO2 and NO concentration, [NaClO2]/[SO2+NO] molar ratio (η), L/G ratio and, solution pH on the simultaneous removal of SOx/NOx has been investigated in a wetted-wall column. Both SOx and NOx removal efficiencies are enhanced with the increasing feeding rate of NaClO2 solution and attain a steady state. NOx removal efficiency increases with increasing SO2 concentration, but SOx removal remains unaffected with increasing NO concentration. In an acidic medium, DeSOx and DeNOx efficiency increased with increasing [NaClO2]/[SO2+NOx] molar ratio and attained a steady state. NOx removal starts only after the complete removal of SOx. The excess of NaClO2 does not enhance NOx removal efficiency. Solution pH does not affect the DeSOx and DeNOx efficiency. The maximum SOx and NOx removal efficiencies achieved at the typical operating conditions of commercialized FGD processes are about 100 and 67%, respectively.

Investigation of pore formation for polystyrene electrospun fiber: Effect of relative humidity

Abstract: Electrospinning method uses electrical force to produce a polymer nanofiber from a polymer solution. The surface morphology and the pore formation of e-spun fiber have been studied by many variables that are involved in different polymer concentrations and solvent mixing ratios. Another major factor affecting fiber morphology and size distribution is the relative humidity. The interaction between the relative humidity and the solvent evaporation affects the distribution of electric charge on the surface of the e-spun fiber. The higher the electric density, the thinner the fiber that can be produced in low humidity conditions. The relative humidity and solvent evaporation can create pores on the fiber surface. The pores can be formed under the condition of 30% relative humidity using 100% of THF solvent. The boundary of the pores has expanded and becomes formless due to the agglomeration of each pore, which can decrease the evaporating capacity.

Raney Ni catalysts derived from different alloy precursors Part II. CO and CO2 methanation activity

Abstract: Catalytic activity, in conjunction with reaction mechanism, was studied in the methanation of CO and CO2 on three Raney Ni catalysts derived from different Ni-Al alloys using different leaching conditions. Main products were CH4 and CO2 in CO methanation, and CH4 and CO in CO2 methanation. Any other hydrocarbon products were not observed. Over all catalysts, CO methanation showed lower selectivity to methane and higher activation energy than CO2 methanation. The catalyst derived from alloy having higher Ni content using more severe leaching conditions, namely higher reaction temperature and longer extraction time, showed higher specific activity and higher selectivity to methane both in CO and CO2 methanation. In CO and CO2 methanation on Raney Ni catalyst, catalytic activity was seen to have close relation with the activity to dissociate CO

Characteristics of membrane humidifiers for polymer electrolyte membrane fuel cells

Abstract: Water management plays an important role in obtaining high performance from a polymer electrolyte membrane fuel cell (PEMFC). To reduce the volume and energy consumption of widely-used bubble humidifiers, membrane humidifiers were fabricated by using an ultrafiltration (UF) membrane and Nafion membranes. The performance of the membrane humidifiers was examined as a function of gas flow rate and operating temperature. A single cell was operated using the UF membrane humidifiers exhibiting almost the same performance with that employing bubble humidifiers.

Risk Assessment of Membrane Type LNG Storage Tanks in Korea-based on Fault Tree Analysis

Abstract: For a liquefied natural gas (LNG) storage tank, the greatest concern is for the release of a large amount of LNG or its vapor due to the mechanical failures of main tank and its ancillary equipments or the malfunctions of various hardware components. Nowadays two types of LNG storage tank design, that is, 9%-Ni full containment and membrane concepts, are mostly applied to LNG industry. In Korea the membrane type has been nationally adopted from the beginning step of LNG project because of its higher flexibility in storage capacity comparing to the 9%-Ni type. All the while several huge membrane-type tanks have been built up and operating, the quantified results of risk associated with them has not been systematically delineated. Hence the method of fault tree analysis as a quantitative risk assessment has been here employed to identify and evaluate the risks related to the membrane-type LNG storage tank. Six top events leading greatly to the large release of natural gas are defined as internally induced major accidents and the failure frequencies of these events are calculated by using other sources of process equipment reliability data for the lack of membrane type-specific data.

Effects of the Operating Parameters on the Reverse Osmosis-Electrodeionization Performance in the Production of High Purity Water

Abstract: An RO-CEDI (Reverse osmosis-continuous electrodeionization) hybrid process was investigated to pro- duce high purity water. The RO system, with an effective membrane area of 1.1 m 2 , was operated using tap water with conductivity of 64 µs·cm −1 , and the CEDI system experiments were carried out in a cell-pair stack consisting of 3 com- partments. During the parametric study of the RO-CEDI hybrid system, the optimal operating conditions were deter- mined based on the water purity. The electrical resistivity and water dissociation of the ion exchange resins and ion exchange membrane were verified as the key mechanisms of the CEDI system in the water purification. The produced water met the quality requirements as a make-up water in a nuclear power plant with a resistivity of 10-16.7 MΩ·cm.

Two-step growth of ZnO films on silicon by atomic layer deposition

Abstract: Two-step growth of ZnO by atomic layer deposition at low temperatures was performed to grow quality ZnO films on silicon substrates: first, the growth of a buffer layer at 130 ‡C and second, the growth of the main layer at 210 ‡C. Structural and optical properties of the ZnO films deposited on ZnO-buffer/Si(111) were investigated as a function of buffer layer thickness. The films showed a strong UV emission at 380 nm and a weak green emission at 520–570 nm. The ZnO films deposited on a 327 a buffer layer showed overall the best surface morphology and structural and optical properties.

Development of carbon dioxide adsorbents using carbon materials prepared from coconut shell

Abstract: Coconut shell, being a good carbon precursor and having a regular porous structure, was chosen for pro- duction of carbonic materials in this work. Metal doping on the coconut char was used to develop catalytic centers for hydrocarbon cracking and thereby obtain a product with good microporosity. Magnesium, calcium, cobalt, copper and nickel doping on the coconut char was done by soaking the coconut char in the aqueous solutions of the respective metal salt and further calcining. The characterization of the product samples was done by the measurement of surface area, adsorption capacity of CO 2, N2, CH4, and SEM analysis. The micro pore area obtained by using CO 2 adsorption at 298 K was found to be >400 m 2 /g for samples prepared from coconut char impregnated with metal. The adsorption capacity of magnesium-doped sample was found to be 98 mg/g, whereas that for a sample prepared from non-im- pregnated coconut char was 55 mg/g. SEM analysis was conducted to study the morphology and nature of the samples prepared.

Adsorption Isotherm of Ibuprofen on Molecular Imprinted Polymer

Abstract: A molecular imprinted polymer (MIP) using (+)-(S)-2-(4-isobutylphenyl) propionic acid ((+)-(S)-ibuprofen) as the template and 4-vinylpyridine (4-VPY) as the functional monomer was prepared. Chloroform and acetonitrile were used as the porogen with ethylene glycol dimethacrylate (EGDMA) as the crosslinker and 2,2′-azobis(isobutyronitrile) (AIBN) as the initiator. Comparison of ibuprofen adsorption isotherm on molecular imprinted and blank polymers was made by the static method. The adsorption equilibrium data were correlated into the Freundlich, Langmuir, Sips (Langmuir-Freundlich) and Radke-Prausnitz isotherm models, respectively. By a nonlinear regression analysis, the experimental parameters in the equilibrium isotherms were estimated and compared. The calculated data is well fitted with the experimented data. Through the analysis, the ibuprofen imprinted polymer showed higher adsorption ability than blank polymer.

Numerical simulation of the effects of the design feature of a cyclone and the inlet flow velocity on the separation of CO2 particles from a CO2-COF2 mixture

Abstract: In synthesizing COF2 from CO, a considerable amount of CO2 is produced. A method of solidifying CO2 at low temperature and separating CO2 particles from the COF2 gas using a cyclone was designed and the separation efficiency according to the cyclone feature was studied. Optimal sizing and operation conditions of the cyclone were investigated by reviewing the flow velocity profile and the particle trajectory using a numerical analysis with computational fluid dynamics (CFD). The effects of the inlet flow velocity and the ratio of the cyclone diameter to the cone length (D/L) on the recovery efficiency were estimated. Results revealed that the separation efficiency increases with an increase in the ratio of D/L and a decrease in the cyclone size. The recovery efficiency of CO2 increases with the increase in the inlet flow velocity. Based on these results, we could propose a concept and methodology to design the optimal features and sizing of a cyclone suitable for separating solid CO2 from gaseous COF2 at low temperature.

A simple mathematical analysis on the effect of sand in Cr(VI) reduction using zero valent iron

Abstract: A simple mathematical model was proposed to analyze the enhancement of Cr(VI) reduction when sand materials are added to the zero valent iron (ZVI). Natural decay of Cr(VI) in a control experiment was analyzed by using a zero-order decay reaction. Adsorption kinetics of Cr(VI) to sand was modeled as a first-order reversible process, and the reduction rate by ZVI was treated as a first-order reaction. Natural decay of Cr(VI) was also included in other experiments, i.e., the adsorption to sand, the reduction by ZVI, and both adsorption and reduction when sand and ZVI are present together. The model parameters were estimated by fitting the solution of each model to the corresponding experimental data. To observe the effect of sand addition to ZVI, both adsorption and reduction rate models were considered simultaneously including the natural decay. The solution of the combined model was fitted to the experimental data to determine the first-order adsorption and reduction rate constants when sand as well as ZVI is present. The first-order reduction rate constant in the presence of sand was about 35 times higher than that with ZVI only.

The morphology of electrospun polystyrene fibers

Abstract: Electrospinning is a process of electrostatic fiber formation which uses electrical forces to produce polymer nanofibers from polymer solution. The electrospinning system consists of a syringe feeder system, a collector system, and a high power supplier. The important parameters in the morphology of electrospun polystyrene fibers are concentration, applied voltage, and solvent properties. Higher concentrations of the polymer solution form thicker fibers and fewer beads. When the concentration is 7 wt%, electrospun fibers have an average diameter of 340 nm, but as the concentration of PS increases to 17 wt%, the fiber diameter gradually thickens to 3,610 nm. The fiber morphology under different solvent mixture ratios and solvent mixtures has also been studied.

Synthesis of single phase aragonite precipitated calcium carbonate in Ca(OH)2-Na2CO3-NaOH reaction system

Abstract: The formation behavior of precipitated calcium carbonate polymorphs was investigated in three different supersaturation levels. Because the most easily adjustable and influential variable determining supersaturation is the ion concentration of the major reactants — Ca2+ and CO3 3 2− — the supersaturation can be adjusted by changing the ion concentration of these two ions. At high supersaturation, free energy is necessary for a decrease in nucleation, promoting the formation of a sphere-shaped vaterite, while aragonite and calcite were seen to co-exist at medium supersaturation. At low supersaturation, aragonite was mainly formed by mixing with some calcite. Hence, we considered that lower supersaturation was necessary to obtain a single phase aragonite. Furthermore, we found that the solubility of Ca(OH)2 was decreased with the addition of NaOH by a common ion effect. Thus, it is possible to perform an experiment at a lower Ca2+ concentration. The aragonite was synthesized by adding the Na2CO3 solution to the Ca(OH)2 slurry containing several concentrations of NaOH solution at 75°C and under the addition rate of Na2CO3 at 3 ml/min. The formation yield of calcite decreased when the NaOH concentration was increased. In conclusion, in the case of the reaction of the 2.5 M NaOH solution over 210 minutes, single-phase aragonite with an aspect ratio of 20 was obtained.

Effects of free ammonia and dissolved oxygen on nitrification and nitrite accumulation in a biofilm airlift reactor

Abstract: The purpose of this research is to find out the effects of free ammonia concentration and dissolved oxygen on nitrification and nitrite accumulation in a biofilm airlift reactor. Free ammonia seriously inhibited the activity of nitrite oxidizers at the concentration higher than 0.1 mg NH3-N/L and it was very effective for nitrite accumulation. Dissolved oxygen limitation in the biofilm also caused nitrite accumulation. Long term inhibition decreased the growth rate for nitrite oxidizers, and ammonia oxidizers were the dominant nitrifiers in the wastewater nitrification. Selective accumulation of ammonia oxidizers in the biofilm could be another reason for nitrite accumulation. Free ammonia inhibited nitrite oxidizers immediately, and adaptation to free ammonia was not observed. Therefore, the optimum con- trol of free ammonia and dissolved oxygen concentration is critical for nitrite accumulation and the strategy can be used for selective accumulation of ammonia oxidizers in a bioreactor system.

Catalytic ozonation of humic acids with Fe/MgO

Abstract: Humic acids were degraded by ozone at room temperature in a stirred tank reactor and a fixed bed reactor with Fe/MgO catalysts. Experimental results show that the ozonation with Fe/MgO induced a significant reduction in UV absorbance of humic acids as compared to ozone alone. Fe/MgO was the most efficient catalyst to degrade humic acids in the presence of ozone. GPC (gel permeation chromatography) showed that the humic acids with high molecular weight could be severely decomposed into organic compounds with low molecular weight on the Fe/MgO catalyst, indicating that humic acids could be catalytically decomposed. The continuous reaction experiments with the palletized catalysts supported that humic acids can be removed by catalysis as well as adsorption.

Influence of Hydrodynamic Parameters on Particle Attrition during Fluidization at High Temperature

Abstract: In a fluidized bed, attrition both increases the number of particles and reduces particle size, which may affect reactor performance, fluidizing properties, operating stability and operating costs. Most fluidized applications are conducted at high temperature, but in the past most attrition correlations were performed at room temperature, so the attrition rate at high temperature could not be predicted. In contrast, this study investigates the attrition rate of flu- idized materials at high temperature. Silica sand was used as the bed material; the operating parameters included tem- perature, particle size, static bed height and gas velocity to assess the attrition rate. Then an appropriate correlation was developed by regression analysis to predict attrition rate at high temperature. Experimental results indicated that the attrition rate increases with increasing temperature. In addition, the particle attrition increased as average particle size decreased because the probability of collision increases with surface area. The attrition rate increased with increasing gas velocity because of increased kinetic stress of particle movement. The actual density and viscosity of air at specific fluidization temperature were modified and an Ar number was introduced to fit our experimental data. The experimen- tal correction agrees with the experimental results, which can predict particle attrition rate at high temperatures.

Adsorption equilibria of reactive dye onto highly polyaminated porous chitosan beads

Abstract: The adsorption of vinyl sulfone type reactive black 5 (RB 5) in aqueous solution onto chitosan beads and cross-linked chitosan beads with glutaraldehyde has been investigated in terms of initial pH and temperature of the solution. The adsorption equilibrium data were correlated with three adsorption models, such as Langmuir, Freundlich and Sips isotherms. Among them, the Freundlich isotherm best fit the data over the entire pH and temperature range of the solution. The adsorption capacity of RB 5 onto chitosan beads and cross-linked chitosan beads increased with decreasing initial pH and with increasing temperature. Equilibrium amount of RB 5 on chitosan beads was greater than that of cross-linked chitosan beads at the same initial pH values. Thermodynamic studies have also been carried out and values of standard free energy (°Gℴ), enthalpy (°Hℴ) and entropy (°Sℴ) were calculated.

Degradation of Pentachlorophenol by an Electroenzymatic Method using Immobilized Peroxidase Enzyme

Abstract: In this study, pentachlorophenol (PCP) was degraded by the electroenzymatic method, which combines the enzymatic catalysis and the electrogeneration of hydrogen peroxide (H2O2). The experiments were conducted in a two-compartment packed-bed reactor using horseradish peroxidase (HRP) immobilized electrode. The highest produc- tion of H2O2 and the current efficiency were observed at −0.4 V vs. Ag/AgCl and a flow rate of 1 mL/min. The highest initial degradation rate and degradation efficiency of PCP were achieved at pH 5 and 25 o C. Under the conditions, the electrolysis was compared with an electrochemical method. The presence of chloride ion indicates that PCP was de- chlorinated at the initial period of degradation. According to the proposed breakdown pathway and the intermediates, the electroenzymatic method showed an improved degradation ability compared to an electrochemical method.

Effect of temperature, oxidant and catalyst loading on the performance of direct formic acid fuel cell

Abstract: We investigated the effect of temperature, oxidant and catalyst loading on the performance of direct formic acid fuel cell (DFAFC). When oxidant was changed from air to oxygen, the power density was increased to 17.3 mW/ cm2 at 25 ‡C. The power density of DFAFC operated with oxygen showed a maximum value of 40.04 mW/cm2 with the temperature rise from room temperature to 70 °C. The highest power density of DFAFC using air was observed for Pt-Ru black catalyst with loading of 8 mgPt/cm2 at room temperature. At 70 ‡C; however, the performance of catalyst with the loading of 4 mgPt/cm2 was higher than that of 8 mgPt/cm2. The DFAFC, operated with oxygen and catalyst of 4 mgPt/cm2 loading, showed the best performance at all temperature range. The enhancement of cell performance with an increase of catalyst loading is believed to come from an increase of catalyst active sites. However, operated at higher temperature or with oxygen, the cell with higher catalyst loading showed lower performance than expected. It is speculated that the thick catalyst layer inhibits the proton transport.

Extraction of lipids and cholesterol from squid oil with supercritical carbon dioxide

Abstract: The oil obtained from waste squid viscera consists of multi-compounds such as EPA, DHA and other valuable polyunsaturated fatty acids. The refining of this squid oil, using supercritical carbon dioxide plus ethanol, was performed in a semi-continuous flow extractor at 8 to 17 MPa and 25 to 50 °C. When 1.5% w/w ethanol was added to the solvent, the solubility of lipids was increased by up to 50% over the neat CO2 value. The extraction curves indicated mass transfer to be solubility limited. Cholesterol was co-extracted with the lipids but, with its lower solubility, less than 54% appeared in the refined oil. The results of the carbon dioxide/multi-compound squid oil system at applied to the extraction conditions were correlated with the mole fraction of the cholesterol and the density of the pure solvent.

On the Origin of Electrodeposition Mechanism of ZnO on ITO Substrate

Abstract: Zinc oxide (ZnO) was potentiostatically deposited on indium tin oxide (ITO) substrates. Comparing of the theoretical mass/charge ratio with experimental value measured by in-situ electrochemical quartz crystal microbal- ance, the origin of deposition mechanism of ZnO could be explained as follows: (i) surface pH enhancement due to the adsorption of hydroxide ion; (ii) the formation of intermediate species (i.e., zinc hydroxide (Zn(OH) + ); (iii) ZnO deposition with production of water. Ex-situ morphological and structural analyses by scanning electron microscope and X-ray diffraction strongly supported the deposition mechanism of ZnO. This also showed that hexagonal shaped ZnO islands were first formed on ITO cathode and grew into compact ZnO films, and the formation behaviour of ZnO was clearly explained via analysis of the profile of measured current.

Pt-V2O5-WO3/TiO2 catalysts supported on SiC filter for NO reduction at low temperature

Abstract: The catalytic filter, V2O5-WO3-TiO2 supported on a ceramic filter, is known as a promising material for treating particulates and NO x simultaneously at optimum temperatures around 320°C. In order to improve its catalytic activity at low temperatures, the effect of Pt addition on the catalytic filter has been investigated. Catalytic filters, Pt-V2O5-WO3-TiO2/SiC, were prepared by co-impregnation of Pt, V, and W precursors on TiO2 coated-SiC filter by vacuum aided-dip coating. The Pt-added catalytic filter shifted the optimum working temperature from 280–330°C (for the non Pt-impregnated filter) to 180–230°C, providing N x slip concentration less than 20 ppm for the treatment of 700 ppm NO at a face velocity of 2 cm/s with the same value over the non Pt-added catalytic filters. The promotional effect following the addition of Pt is believed to result from electrical modification of the catalyst maintaining a high electron transfer state. Ammonia oxidation was also observed to be dominant above the optimal temperature for SCR.

Copolymerization of Phenyl Glycidyl Ether with Carbon Dioxide Catalyzed by Ionic Liquids

Abstract: The copolymerization of phenyl glycidyl ether (PGE) and carbon dioxide was performed without any solvent in the presence of ionic liquid as catalyst. The reaction was carried out in a batch autoclave reactor. The carbonate content of polycarbonate was affected by the structure of imidazolium salt ionic liquid; the one with the cation of bulkier alkyl chain length and with more nucleophilic anion showed better reactivity. However, the yield of carbon dioxide addition decreased when hexyl or octyl containing ionic liquids were used in place of butyl group in 1-alkyl-3-methyl imidazolium salts. The carbonate content and turnover number (TON) of the polycarbonate increased as the reaction temperature increased from 40 to 80 ‡C. However, the carbonate content decreased with increasing reaction time.

Compositional and structural identification of natural gas hydrates collected at site 1249 on ocean drilling program leg 204

Abstract: In contrast to the structural studies of laboratory-grown gas hydrate, this study has been performed on naturally grown clathrate hydrates from the sea floor. The PXRD pattern of natural gas hydrate shows that the sample had a structure I hydrate. The13C NMR spectrum was obtained for the natural gas hydrate sample in order to identify the cage occupancy of guest molecules and determine the hydration number. The NMR spectrum reveal that the natural gas hydrates used in this study contain only methane with no noticeable amount of other hydrocarbons. The existence of two peaks at different chemical shifts indicates that methane molecules are encapsulated in both large and small cages. In addition, Raman spectroscopic analysis is also carried out to identify natural hydrates and compared with the NMR results. Investigating the composition and structure of natural gas hydrates is essential for applying natural gas hydrates as a novel energy source.

Flammability studies of benzene and methanol with various vapor mixing ratios at 150°C

Abstract: Both benzene and methanol are important raw materials in petrochemical industries worldwide. However, with increased demand in the past few years, the fire and explosion hazards from both benzene and methanol under abnormal conditions have increased rapidly with the demand. This study investigated the flammability characteristics of a binary solution for the mixture of benzene and methanol at various vapor-mixing ratios (100/0, 75/25, 50/50, 25/75, 0/100 vol%) under 150°C, 760 and 1,520 mmHg by using a 20 Liter Spherical Explosion Vessel. Such work leads to specific safety-related property parameters, including upper explosion limit (UEL), lower explosion limit (LEL), minimum oxygen concentration (MOC), maximum explosion pressure (P max ), maximum rate of explosion pressure rise (dP/dt) max , and gas or vapor explosion constant (K g ). Along with the results which show that the UEL, Pmax, and Kg all increased with the pressure and oxygen concentration, a triangular flammability diagram was also established. This all serves to elucidate the potential hazards when vapors of different flammable chemicals are mixed.

Gas permeation properties in a composite mesoporous alumina ceramic membrane

Abstract: In this study, the effect of different chemical interactions on the gas permeation properties were investigated in the composite mesoporous ceramic membrane prepared with γ-alumina on the surface of a macroporous ceramic membrane. In the permeation results, the gas permeance of the strongly adsorbing gas species increased in the mesoporous ceramic membranes. It is considered that the permeation of the adsorbing gas species increased through preferential adsorption on the membrane pore surface. It was shown in this study that the modified mesoporous ceramic membrane could increase the permeation performance in the presence of the adsorbing gas species due to the surface diffusion mechanism.