Showing papers in "Korean Journal of Chemical Engineering in 2002"

Room Temperature Ionic Liquids as Replacements for Conventional Solvents - A Review

Abstract: Room temperature ionic liquids are salts that are liquids at ambient temperature. They are excellent solvents for a broad range of polar organic compounds and they show partial miscibility with aromatic hydrocarbons. Typical room temperature ionic liquids have a stable liquid range of over 300 K and have a very low vapor pressure at room temperature. Ionic liquids that are not hydrolyzed show a wide range of solubility in water. These unique properties have suggested that they might be useful as environmentally benign solvents that could replace volatile organic compounds (VOC). By varying the length and branching of the alkane chains of the cationic core and the anionic precursor, the solvent properties of ionic liquids should be able to be tailored to meet the requirements of specific applications to create an almost infinitely set of “designer solvents”. A review of recent applications of ionic liquids is presented along with some results of measurements of liquid-liquid equilibria and partition coefficients with alcohols. The results are compared with predictions based on quantum mechanic calculations.

Fabrication of Highly Ordered Pore Array in Anodic Aluminum Oxide

Abstract: Highly ordered pore array in anodic aluminum oxide was fabricated by anodizing pure aluminum. The order of a pore array was affected by anodizing voltage, electrolyte temperature, and first anodizing time. A regular pore array with mean diameter of 24 nm and interpore distance of 109 nm could be formed by two-step anodization at 40 V., oxalic acid concentration of 0.3 M and electrolyte temperature of 15 ‡C. The measured interpore distance showed linearity with anodizing voltage. The diameter of pores was adjusted by pore widening treatment in a 5 wt% phosphoric acid solution at 30 ‡C after two step anodization. The mechanism of self-arrangement of pores could be explained by the repulsive interaction between the pore walls.

Separation of co2-ch4 and co2-n2 systems using ion-exchanged fau-type zeolite membranes with different si/al ratios

Abstract: FAU-type zeolite membranes with different Si/Al ratios were hydrothermally synthesized on the outer surface of a porous α-Al2O3 support tube. The permeances of the membranes to CO2, CH4 and N2 were then measured at 308 K for single-component and equimolar binary systems. The separation properties were dependent on both the Si/Al ratio and the ion-exchange treatment. For single-component systems, a lower Si/Al ratio resulted in the incorporation of a larger number of Na+ ions. For a CO2-CH4 mixture, both CO2 permeances and CO2/CH4 selectivities were approximately half the values obtained for a binary CO2-N2 mixture. The highest selectivities, obtained using the NaX(1) zeolite membrane, were 28 for CO2/CH4 and 78 for CO2/N2. The RbY, RbX(1) and RbX(2) zeolite membranes showed larger CO2 permeances, compared with those of the original Na-type membranes. Ion-exchange with K+ ions was the most effective for the NaY zeolite membrane in that both the CO2 permeance and the CO2/CH4 selectivity were increased.

A Study of Electrochemical Kinetics of Lithium Ion in Organic Electrolytes

Abstract: Limiting current densities equivalent to the transport-controlling step of lithium ions in organic electrolytes were measured by using a rotating disk electrode (RDE). The diffusion coefficients of lithium ion in the electrolyte of PC/LiClO4, EC : DEC/LiPF6 and EC : DMC/LiPF6 were determined by the limiting current density data according to the Levich equation. The diffusion coefficients increased in the order of PC/LiClO4

Scanning Tunneling Microscopy (STM) and Tunneling Spectroscopy (TS) of Heteropolyacid (HPA) Self-Assembled Monolayers (SAMS): Connecting Nano Properties to Bulk Properties

Abstract: Nanoscale investigation of Keggin-type heteropolyacid (HPA) self-assembled monolayers (SAMs) was performed by scanning tunneling microscopy (STM) and tunneling spectroscopy (TS) in order to relate surface properties of nanostructured HPA monolayers to bulk redox and acid properties of HPAs. Cation-exchanged, polyatomsubstituted, and heteroatom-substituted HPAs were examined to see the effect of different substitutions. HPA samples were deposited on HOPG surfaces in order to obtain images and tunneling spectra by STM before and after pyridine adsorption. All HPA samples formed well-ordered monolayer arrays, and exhibited negative difference resistance (NDR) behavior in their tunneling spectra. NDR peaks measured for fresh HPA samples appeared at less negative potentials for higher reduction potentials of the HPAs. These changes could also be correlated with the electronegativities of the substituted atoms. Introduction of pyridine into the HPA arrays increased the lattice constants of the two-dimensional HPA arrays by ca. 6 A. Exposure to pyridine also shifted NDR peak voltages of HPA samples to less negative values in the tunneling spectroscopy measurements. The NDR shifts of HPAs obtained before and after pyridine adsorption were correlated with the acid strengths of the HPAs. This work demonstrates that tunneling spectra measured by STM can fingerprint acid and redox properties of HPA monolayers on the nanometer scale.

Triboelectrostatic separation of pvc materials from mixed plastics for waste plastic recycling

Abstract: This study covers the triboelectrostatic separation of Polyvinylchloride (PVC) materials from mixed plastics such as polyethylene terephthalate (PET), polyethylene (PE), polypropylene (PP), and polystyrene (PS). The PVC material generates hazardous hydrogen chloride gas resulting from the combustion in the incinerators. The laboratory scale triboelectrostatic separation system consists of a fluidized-bed tribocharger, a separation chamber, a collection chamber and a controller. Negative and positive surface charges can be imparted to the PVC and PET particles, respectively, due to the difference of triboelectric charging series between the particles in the fluidized-bed tribocharger. They can be separated by passing through an external electric field. A highly concentrated PVC (91.9%) can be recovered with a yield of about 96.1% from the mixture of PVC and PET materials in a single stage of processing. For the removal of PVC from the two-component mixed plastics such as PVC/PET, PVC/PP, PVC/PE or PVC/PS, separation results show the recovery of 96–99% with the pure extract content in excess of 90%. The triboelectrostatic separation system using the fluidized-bed tribocharger shows the potential to be an effective method for removing PVC from mixed plastics for waste plastic recycling.

Phase equilibria and kinetic behavior of co 2 hydrate in electrolyte and porous media solutions: application to ocean sequestration of CO 2

Abstract: Understanding the phase behavior and formation kinetics of CO2 hydrate is essential for developing the sequestration process of CO2 into the deep ocean and its feasibility. Three-phase equilibria of solid hydrate, liquid water, and vapor were determined for aqueous mixtures containing CO2 and NaCl/clay to examine the effect of both ocean electrolytes and sediments on hydrate stability. Due to the capillary effect by clay pores and inhibition effect by NaCl the corresponding hydrate formation pressure appeared to be a little higher than that required for simple and pure hydrate at specified temperature. In addition, the hydrate formation kinetics of carbon dioxide in pure water and aqueous NaCl solutions with or without clay mineral were also measured at various conditions. The formation kinetic behavior was found to be strongly influenced by pressure, temperature and electrolyte concentration. A simplified kinetic model having two adjustable parameters was proposed and the estimated results agreed well with the experimental data.

Characteristics of LDPE pyrolysis

Abstract: Pyrolysis of low-density polyethylene (LDPE) was studied in order to relieve environmental pollution and recover the monomer or fuel. LDPE was thermally decomposed with and without catalyst. First, efficiency of oil production was analyzed according to the variation of reaction conditions such as reaction temperature, types of additives and catalyst, and contacting method. In non-catalytic LDPE pyrolysis, isothermal reaction was almost similar to non-isothermal reaction. Light oil was produced with low reaction temperature (430 °C) in the isothermal reaction, but low heating rate caused light oil production in the non-isothermal reaction. When pyrolyzed polyethylene (PE oil) was applied as an additive, no significant effect showed in the isothermal reaction. In catalytic LDPE pyrolysis (10%NiO/S-A) with additives, efficiency greatly increased especially with polystyrene (PS) addition. It was also found that the molecular weight distribution of product oil could be controlled by applying different additives. When a catalytic reactor was used, the amount of the low molecular weight compound increased as flow rate of thermally decomposed gas was lowered.

Rheological analysis of the gelation behavior of tetraethylorthosilane/ vinyltriethoxysilane hybrid solutions

Abstract: The gelation behavior of tetraethylorthosilane (TEOS) sol in the presence of a silane coupling agent vinyltriethoxysilane (VTES) was investigated experimentally. Specifically, the gel time and gel structure were analyzed by the rheological multiwave test of Fourier transform mechanical spectroscopy (FTMS) for the mixtures of TEOS/ VTES with various molar ratios at different temperatures. Gelation was accomplished through the sol-gel reactions of the silicon alkoxide TEOS in aqueous acidic solution. The results showed that, at elevated temperatures, the gel point was scattered and obscured by the noise in low frequencies owing to the enhanced thermal agitations. In this case, the statistical method was used to find the exact gel time. The activation energy of gelation and the gel exponent ranged from 25 to 30 kJ/mol and from 0.581 to 0.771, respectively, depending on the TEOS/VTES composition. The fractal dimension was estimated from the gel exponent and indicated the gel structure and that the TEOS/VTES solutions formed a relatively open and coarse gel structure.

Kinetics of cellobiose decomposition under subcritical and supercritical water in continuous flow system

Abstract: The effects of reaction temperature, pressure and residence time were investigated with a flow apparatus Cellobiose decomposition kinetics and products in suband supercritical water were examined at temperatures from 320 to 420 °C at pressures from 25 to 40 MPa, and at residence times within 3 sec Cellobiose was found to decompose via hydrolysis and pyrolysis The yield of desired hydrolysis product, glucose, was the maximum value of 368% at 320 °C, 35 MPa, but the amount of 5-(hydroxymethyl)furfural (HMF), fermentation inhibitor increased too because residence time increased in the subcritical region owing to decrease of reaction rate Meanwhile, though the yield of glucose is low in the supercritical region, the yield of HMF decreased compared with the subcritical region; and at the minimum yield of HMF (380 °C, 25 MPa), the yield of glucose was 214% The decomposition of cellobiose followed first-order kinetics and the activation energy for the decomposition of cellobiose was 5105 kJ/mol at 40MPa

Redox Shuttle Additives for Chemical Overcharge Protection in Lithium Ion Batteries

Abstract: We disclosed that a few kinds of aromatic compounds having thianthrene derivatives with acetyl or other functional groups were stable up to about 4.2-4.3 V against lithium. These materials, called redox shuttle, have lately been employed as a chemical overcharge protection agent that consumes the excess current during battery overcharge. They oxidized above 4 V and worked as redox shuttle when introduced into the electrolyte of a Carbon/LiCoO2 prismatic battery within less than one hour rate (1C). We also studied thermal properties of batteries containing the above-mentioned materials with ARC (Accelerating Rate Calorimeter). We ascertained that the current supplied over the full charge was not stored, but instantly and quite completely consumed in an oxidation-reduction reaction.

A study on fouling mitigation using pulsing electric fields in electrodialysis of lactate containing BSA

Abstract: Fouling tendency in electrodialysis was investigated using the electrochemical and physical properties of the foulants and ion exchange membranes. It was found that bovine serum albumin (BSA), a large molecular weight protein, fouled the AMX membrane irreversibly by deposition on the membrane surface. Electrodialysis experiments of lactate with 1.0 wt% of BSA were performed using the square wave powers at different frequencies to examine the pulsing power influences as a fouling mitigation method, and the results were compared with the data obtained using the DC power. Reduced fouling potentials were observed when the square wave powers were used in the electrodialysis of lactate and confirmed the membrane fouling index for electrodialysis (EDMFI). The pulsing electric fields enhanced the mobility of the charged particles in the fouling layer and decreased the electric resistance of the electrodialysis cell. It was clearly observed that the pulsing electric fields with different frequencies reduced the fouling potentials, and consequently the power consumption was reduced significantly as a fouling mitigation method.

Removal of Heavy Metal-Cyanide Complexes by Ion Exchange

Abstract: Simultaneous removal of heavy metal and cyanide ions in an ion exchange column is studied on the basis of formation of metal-cyanide complexes at high pH range. Strong base anion exchange resin beads were contacted with water containing heavy metal (Cu, Cd, Zn) and cyanide ions in semi-fluidized and fluidized beds. Compositions of the heavy metal-cyanide complexes formed for different heavy metal and cyanide concentrations are used to explain the ion exchange behavior. Ion exchange equilibrium data of this study were fitted well with the Langmuir isotherm. The ion exchange capacity of CNas metal complexes increased to about three times that of free cyanide due to higher selectivity of metal complexes on the anion exchange resin. The ion exchange efficiency of the three heavy metalcyanide systems decreases as the concentration ratio of cyanide and heavy metal increases. The regeneration rates of the regenerants used was in the order of NaSCN>NaCN>NaOH, and the regeneration rate of NaOH was substantially lower than other two.

Biosorption Characteristics in the Mixed Heavy Metal Solution by Biosorbents of Marine Brown Algae

Abstract: The biomass of nonliving, dried marine brown algaeU. pinnatifida, H. fusiformis, andS. fulvellum harvested in the sea near Cheju Island, Korea were studied for their sorption ability of copper, zinc, and lead. The metal uptakes by biosorbent materials increased with increasing initial metal concentration and pH in the range of Ci 0.0510 mM. The higher metal uptakes were obtained in the range of pHs 4.0–5.3, 4.0–6.0, and 3.0–6.0 for copper, lead, and zinc, respectively. The metal uptakes by biosorbent materials decreased in the following sequence:U. pinnatifida> H. fusiformis> S. fulvellum. The maximum metal uptake values ofU. pinnatifida for Cu2+, Pb2+, and Zn2+ in the single metal solution are 2.58, 2.6, and 2.08 meq/g in the range of pHs 5.3–4.4, respectively. The metal uptakes by biosorbent materials in the mixed metal solution decreased greatly in comparison to each metal uptake in the single metal solution.

Partial Oxidation of Methane over Nickel Catalysts Supported on Various Aluminas

Abstract: Partial oxidation of methane (POM) was systematically investigated in a fixed bed reactor over 12 wt% Ni catalysts supported on α-A12O3, γ-A12O3 and θ-A12O3 which were prepared at different conditions. Results indicate that the catalytic activity toward POM strongly depends on the BET surface area of the support. All the Ni/ θ-Al2O3 catalysts showed high activity toward POM due to the less formation of inactive NiAl2O4 species, the existence of NiO, species and stable θ-Al2O3 phase. Although Ni/γ-Al2O3 showed the highest activity toward POM, long-time stability cannot be expected as a result of the deterioration of the support at higher temperature, which is revealed from BET results. From the reaction and characterization results, it is inferred that the optimal conditions for the preparation of θ-Al2O3 are 1,173 K and 12 h.

Preparation of L-PLA submicron particles by a continuous supercritical antisolvent precipitation process

Abstract: Submicron particles of L-polylactic acid (L-PLA) without residual solvent were prepared by a continuous supercritical antisolvent (SAS) recrystallization process. Methylene chloride (CH2C12) was used as a carrier solvent of L-PLA. Experiments were performed with changing process parameters such as pressure and temperature at constant concentration. Also, L-PLA initial concentrations in methylene chloride were varied from 0.3 to 4 wt%. The flow rates of CO2 and solution, which were introduced into the precipitator, and nozzle diameter were kept unchanged in all of the experiments. It was found that the SAS process gives fine tuning of particle size and particle size distribution (PSD) by simple manipulations of the process parameters. In all cases of SAS recrystallization experiments, the formed spherical fine particles with a smooth surface were non-agglomerated and free flowing. Mean particle size of the L-PLA microparticles formed was varied from 0.1 to 1 μm by means of adjusting the system pressure and/or temperature.

Fabrication and Thermophysical Characterization of Nano-Porous Silica-Polyurethane Hybrid Aerogel by Sol-Gel Processing and Supercritical Solvent Drying Technique

Abstract: Thermally and mechanically enhanced nanoporous silica-polyurethane hybrid aerogel was synthesized by sol-gel processing and low temperature supercritical CO2 drying. A partially condensed silica solution and a polymeric MDI were used as the raw materials with a tertiary amine as a catalyst and 1,4-dioxiane as a dilution solvent. After the gelation reaction was completed, aged wet hybrid aerogel was dried by a low temperature supercritical CO2 drying technique. Also, thermophysical characteristics such as density, BET surface area, and thermal conductivity as a function of catalyst ratio and aging time of the synthesized hybrid aerogel were analyzed. It was found that, at a fixed target density, the lowest average pore size of the aerogel, 8 nm, was obtained when the catalyst ratio was 0.1 wt.%. Also, at these conditions, the BET surface area showed the highest surface area, 287.3 m2/g. It was found that with decreasing average pore size and with increasing BET surface area, thermal conductivity tends to decrease. At pressure 1 torr, the sample aerogel showed the lowest thermal conductivity, 0.0184 W/mK.

Effect of Recycle and Feeding Method on Batch Reactive Recovery System of Lactic Acid

Abstract: Reactive batch distillation coupling esterification and hydrolysis was studied for the recovery of lactic acid. The analysis of the dynamic behavior of the system showed drastic change of esterification reaction rate in the reboiler due to the difference of volatility and component boilup rate of each species. Methanol recycle and feeding method were investigated as the factors which could control the compoent boilup rate of each species and rate of esterification reaction. The flow rate and composistion of methanol recycle stream was controlled by the temperature of the partial condenser. A temperature slightly higher than the methanol boiling point is optimum as the temperature of the partial condenser. When the temperature of the partial condenser was increased in the initial part of whole batch time and decreased in the latter part, the performance of the system was enhanced, compared with when the partial condenser temperature remained constant. Semibatch operation was compared with batch operation. Continuous feed- ing of methanol enhanced the recovery system performance while continuous feeding of lactic acid aqueous solution deteriorated, compared with batch operation.

Properties of Iron Oxide Particles Prepared in the Presence of Dextran

Abstract: Stable aqueous ferrofluids consisting of superparamagnetic iron oxide particles with nanometer size were prepared by adding aqueous dextran solutions of ferric and ferrous chlorides to ammonium hydroxide. The growth of the core particles was shown to be inhibited by the presence of dextran. Procedures to increase the rate of reaction by varying reaction parameters also inhibited the core growth as long as supply of core material was kept constant. The core particles actually existed in the fluid as chain aggregates, the size of which became smaller with the concentration of dextran by a dense coating of the core particles. The aggregate size was also affected by supplying oxygen in the reaction bath and varying the initial total iron concentration, but it was kept fairly constant with the variation in the other reaction parameters.

Photocatalytic degradation of trichloroethylene over TiO2/SiO2 in an annulus fluidized bed reactor

Abstract: The effects of superficial gas velocity (Ug), wavelength and intensity of ultraviolet (UV) light, oxygen and H2O concentration on the photocatalytic degradation of TCE (Trichloroethylene) over TiO2/SiO2 catalyst have been determined in an annulus fluidized bed photoreactor. The key factor in determining the performance of the annulus fluidized bed photoreactor is found to be an optimum superficial gas velocity (Ug) that provides the optimum UV lighttransmit through the proper size of bubbles in the photoreactor. The degradation efficiency of TCE increases with light intensity but decreases with wavelength of the UV light and H2O concentration in the fluidized bed of TiO2/silica-gel photocatalyst. The optimum concentration of O2 for TCE degradation is found to be approximately 10%. The annulus fluidized bed photoreactor is an effective tool for high TCE degradation with efficient utilization of photon energy.

Solid Circulation Characteristics in an Internally Circulating Fluidized Bed with Orifice-Type Draft Tube

Abstract: Effects of superficial gas velocities to a draft tube, to an annulus section and particle size on the solid circulation rate (G,) have been determined in an internally circulating fluidized bed (0.28 m I.D. × 2m high) with an orifice type draft tube. The solid circulation rate from the draft tube to an annulus section increases with increasing gas velocities to the draft tube(U d ) and annulus section (Ua) and consequent increase in pressure drop across the orifice (ΔPor). However, the values ofG s decrease by 7–21% with increasing particle size from 86 to 288 μm. The pressure drop across the orifice increases with increasingU d andU a . However, ΔPor decreases by 5–23% with increasing particle size. To predictG s in an internally circulating fluidized bed, a correlation is proposed as a function of ΔPor

Performance evaluation of electrodewatering system for sewage sludges

Abstract: A laboratory-scale electrodewatering system, incorporating an electric field as an additional driving force to conventional pressure dewatering, has been developed to decrease the water content of sludges generated in wastewater treatment. Consisting of a piston-type filter press, a power supply and a data acquisition system, the electrodewatering system’s performance was evaluated as a function of applied pressure, applied voltage, sludge type and filtration time. Experiments were carried out using sewage sludges with the electric field up to 120 V/cm and pressure ranging from 98.1 to 392.4 kPa. Electrodewatering involving a combination of electric field and pressure enhances both the dewatering rate and final dewatered volume. The final water content of sewage sludges in the electrodewatering system can be reduced to 62 wt%, as compared to 78 wt% achieved with the pressure filtration alone. The electrodewatering system shows the potential to be an effective method for reducing the water content in sludges.

Removal of Phenolic Compounds by Electro-assisted Advanced Process for Wastewater Purification

Abstract: Electro-assisted advanced process was developed for wastewater treatment of phenolic compounds. A series of correlative experiments were carried out: the degradation of phenol by the advanced electrochemical oxidation process, the degradation of chlorophenol by the photo-electrocatalysis, and the degradation of chlorophenol by pair electrodes. It was found that phenol and chlorophenol could be removed rapidly and effectively at initial concentra- tion of 100-400 mg L -1 , current density of 3.2-27.5 mA cm -2 , and applied voltage of 2-5 V. The combination of elec- trocatalytic and UV radiation greatly accelerated the removal efficiency. The dechlorination of chlorophenol could be achieved under cathodic reduction so that it could be further oxidized more quickly and completely. The mechanism of dechlorination was proposed to be the indirect dechlorination by atomic hydrogen. The electro-assisted advanced processes were suitable for the treatment of the phenolic compounds.

A unique way to make ultra low sulfur diesel

Abstract: SK Corporation has developed a new process, SK HDS Pretreatment process that enables the refiners to produce economically ultra-low-sulfur-diesel of below 10 ppm. This technology is based on the adsorptive removal of nitrogen containing compounds (NCC) from the feedstock to conventional hydrodesulfurization (HDS) units. The NCC is known to interfere with the activity of HDS catalysts. In the SK HDS Pretreatment Process, the feedstock to the HDS unit is pretreated, and 90% or more of NCC in the feedstock is removed, resulting in higher desulfurization in a conventional HDS unit. It was found that the degree of improvement in HDS is proportional to the degree of NCC removal. SK HDS Pretreatment Process is a cost-effective method for refineries to choose for 10 ppm ULSD production.

Removal of zinc ions in wastewater by electrodialysis

Abstract: To obtain useful data for treatment of the wastewater discharged from zinc electroplating processes, we investigated the effects of operating parameters, such as the initial concentration of dilute solution, the flow velocity and the applied voltage, on removal rate of Zn2+ in the model solutions using an electrodialysis system. Zinc ions in the solutions were effectively removed by the electrodialyzer with CMX cation exchange membranes and AMX anion exchange membranes. The initial concentration of dilute solution, the flow velocity and the applied voltage strongly affected the performance of the electrodialysis system. As the initial concentration of dilute solution, the flow velocity and the applied voltage were increased, the removal ratio was increased. The energy consumption was increased as the initial concentration of dilute solution and the applied voltage were increased, whereas the effect of the flow velocity on the energy consumption was negligible.

Novel evaluation method for the water-in-oil (W/O) emulsion stability by turbidity ratio measurements

Abstract: The turbidity ratio method of evaluating the stabilities of water-in-oil emulsions has been established with two wavelengths (450 and 850 nm) by taking the intensity ratio of two beams The slopes of turbidity ratio of several water-in-oil emulsions with time were calculated to evaluate the emulsion stabilities at different HLB (Hydrophilie-Lipophile Balance), the amounts of emulsifiers, and water contents The results of the turbidity ratio technique were consistent with the amount of phase separation of emulsions incubated for 30 days at room temperature From the turbidity ratio measurements, we determined that the required HLB of diesel oil was about 60, and that the stability of emulsion increased with the amount of emulsifier The increasing amount of the water showed a negative effect on emulsion stability Finally, this method provides a useful tool for the quick evaluation of the required HLB and the condition of emulsification throughout this study

Water Enhanced Solubilities of Succinic Acid in Reactive Extraction Using Tertiary Amines/Alcohols Systems

Abstract: Tertiary amines were used as the extradants for reactive extraction in alcohol diluents. Equilibrium and hydration data for various alcohol diluents and tertiary amines were obtained. From these data, the effect of coextracted water on extractability was investigated. For the measurement of the water-enhanced solubilities of succinic acid, the sensitivity index was introduced. The amount of coextracted water into organic phase was increased with the chain length of alcohol diluents. However, the water-enhanced solubility of succinic acid was almost constant with the chain length of alcohol diluents. The sensitivity indices were proportional to the chain length of tertiary amines; thus, the water-enhanced solubilities of succinic acid were increased.

Steam Gasification of an Australian Bituminous Coal in a Fluidized Bed

Abstract: To produce low calorific value gas, Australian coal has been gasified with air and steam in a fluidized bed reactor (0.1 m-I.D◊1.6 m-high) at atmospheric pressure. The effects of fluidizing gas velocity (2-5 U f/Umf), reaction temperature (750-900 o C), air/coal ratio (1.6-3.2), and steam/coal ratio (0.63-1.26) on gas composition, gas yield, gas calorific value of the product gas and carbon conversion have been determined. The calorific value and yield of the product gas, cold gas efficiency, and carbon conversion increase with increasing fluidization gas velocity and reaction temperature. With increasing air/coal ratio, carbon conversion, cold gas efficiency and yield of the product gas increase, but the calorific value of the product gas decreases. When steam/coal ratio is increased, cold gas efficiency, yield and calorific value of the product gas increase, but carbon conversion is little changed. Unburned carbon fraction of cyclone fine decreases with increasing fluidization gas velocity, reaction temperature and air/coal ratio, but is nearly constant with increasing steam/coal ratio. Overall carbon conversion decreases with increasing fluidization velocity and air/ coal ratio, but increases with increasing reaction temperature. The particle entrainment rate increases with increasing fluidization velocity, but decreases with increasing reaction temperature.

Simulation of the aromatic recovery process by extractive distillation

Abstract: The NFM (N-formylmorpholine) extractive distillation process is used for the purpose of recovering aromatics, such as benzene, toluene, and xylene. The thermodynamic equation used in the simulation is the NRTL equation, and NRTL interaction binary parameters were obtained by experimental data. The missing thermodynamic properties are predicted by group contribution method. Simulation results of the extractive distillation column were in good agreement with the operation data.

Synthesis of Mesoporous γ-Alumina through Pre- and Post-hydrolysis Methods

Abstract: Two methods of pre- and post-hydrolysis are suggested for the preparation of mesoporous aluminas. These techniques were developed based on the control of the reaction rates of hydrolysis of aluminium precursors. The characteristics of the resulting materials, such as pore uniformities, porosity and crystalline shape, were investigated. Results show that these methods allow one to prepare tailor-made mesoporous aluminas at an ambient temperature.