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Effect of piperazine on the kinetics of carbon dioxide with aqueous solutions of 2-amino-2-methyl-1-propanol
No full textThe absorption of CO2 into aqueous mixtures of 2-amino-2-methyl-1-propanol (AMP) and piperazine was investigated. A wetted-sphere absorption apparatus was used to measure the absorption rate. The absorption rates of CO2 into aqueous solutions of AMP in the range of 0.55-3.35 kmol/m(3) were measured. The experimental temperatures were 303 and 313 K. The zwitterion deprotonation mechanism was used to interpret the kinetic data of aqueous solutions of AMP. The absorption rates of aqueous mixtures of AMP and piperazine were measured. Piperazine concentrations of 0.058, 0.115, and 0.233 kmol/m3 were added for each AMP solution. The apparent reaction rate constants increased with the addition of piperazine. The effect of piperazine on the reaction rate of CO2 with aqueous solutions of AMP consists of the contribution for the zwitterion deprotonation and the direct reaction of piperazine with CO2. The zwitterion deprotonation constants of all bases presented in liquid and the direct reaction rate constant of piperazine were obtained.This work was supported by the Korean Energy
Management Corp., R&D Management Center for Energy
and Resource
Solubilities of carbon dioxide in aqueous mixtures of diethanolamine and 2-amino-2-methyl-1-propanol
No full textThe gas solubility of CO2 has been measured in aqueous mixtures of diethanaolamine and 2-amino-2-methyl-1-propanol at (40, 60, and 80)degrees C and in the pressure range (10 to 300) kPa. The concentrations of the amine mixtures were 6 mass % diethanolamine (DEA) + 24 mass % 2-amino-2-methyl-1-propanol (AMP), 12 mass % DEA + 18 mass % AMP, and 18 mass % DEA + 12 mass % AMP. The solubilities show a systematic change as the composition of the aqueous mixtures varies
Characterization of Sr beta-alumina prepared by sol-gel and spray pyrolysis methods
No full textEu2+ doped beta-alumina, Sr1-xMgAl10O17 Eu-x(2+) (x = 0.01-0.07) were successfully prepared by sol-gel and spray pyrolysis techniques with the same precursor materials. Srbeta-alumina doped with Eu2+ (SrMgAl10O17:Eu2+) prepared from sol-gel method showed three photoluminescence (PL) peaks at 390, 418 and 459 nm after excitation wavelength at 254 nm and one PL peak at 461 nm when excitation was at 365 nm. The same powder was prepared from spray pyrolysis technique showed the six PL peaks at 323, 397, 415, 443, 480 and 508 nm after excitation at 254 nm. Also two PL peaks at 440 and 480 nm were observed after the excitation at 365 nm. These PL peaks were dependent on the excitation wavelength. The effect of different annealing temperatures of sol-gel powders, preparation conditions of spray pyrolysis powders and reduction atmospheres of both sol-gel and spray pyrolysis powders of various compositions of Eu2+ doped Srbeta-alumina were also studied. Both the powders were characterized by scanning electron microscopy, X-ray diffraction and PL techniques and comparison between the two preparation methods. Sol-get prepared powder had eight times higher PL intensity and brightness than the spray pyrolysis prepared powder. The suggested good composition of Srbeta-alumina is Sr0.93MgAl10O17:Eu-0.07 for both sol-gel and spay pyrolysis methods. (C) 2004 Elsevier B.V. All rights reserved.The authors wish to thank the Brain Korea 21 Programme of the Ministry of Science and Technology of South Korea in 2002 for financial support
The synthesis of (Y1-xGdx)(2)O-3 : Eu phosphor particles by flame spray pyrolysis with LiCl flux
No full text(Y1-xGdx)(2)O-3:Eu phosphor particles with dense morphology were prepared by flame spray pyrolysis and the effect of LiCl flux on the crystallinity, morphology, and photoluminescence characteristics of the particles was investigated. All as-prepared particles had monoclinic phase regardless of flux and had different luminescence characteristics from those of commercial Y2O3:Eu particles of cubic phase. The addition of LiCl flux reduced the post-treatment temperature by 300degreesC for phase transformation from the monoclinic phase to the cubic phase. The post-treatment temperature of (Y0.75Gd0.25)(2)O-3:Eu particles for phase transformation decreased from 1100degreesC to 700degreesC when LiCl flux was used. The morphology of the particles was also influenced by the Y/Gd ratio and the LiCl flux. The as-prepared particles had spherical shape and non-aggregation characteristics regardless of Y/Gd ratio and flux. The sphericity of the as-prepared particles prepared without flux was maintained after post-treatment for phase transformation in all Y/Gd ratios. However, LiCl addition promoted the aggregation between product particles. The prepared particles had high photoluminescence intensities comparable to that of the commercial product.This work was supported by a Korea Research Foundation Grant (No. KRF-2000-041-E00351). The Department of Chemical Engineering of KAIST is supported by the BRAIN KOREA 21
program
Formation of ZnO, MgO and NiO nanoparticles from aqueous droplets in flame reactor
No full textNanoparticles of ZnO, MgO and NiO were produced from droplets of aqueous salt solution in the flame spray pyrolysis reactor. Conventional spray pyrolysis, in which electrical furnace reactor is used, is reported to produce nanoparticles only from acetate precursor. If the reactor pressure is low (similar to60 torr), nitrate salt precursor is also known to produce nanoparticles. In this paper, we report that nanoparticles are produced from nitrate as well as acetate salt precursor solution when propane-oxygen diffusion flame is used to decompose aqueous aerosol droplets. At low flame temperature, however, nanoparticles are not formed and the particle morphology is similar to the morphology produced by the conventional spray pyrolysis. At high flame temperature, nanoparticles are formed, regardless of the salt type. Nanoparticles are formed at lower flame temperature from acetate salts than from nitrate salts. All nanoparticle prepared in this work were fully crystallized and the size measured from transmission electron microscopy images was 30 nm. This size agreed well with the particle size calculated from X-ray diffraction and specific surface area data.The work was partially supported by BRAIN KOREA 21 program and Center for Ultramicrochemical Process Systems sponsored by KOSEF and the authors wish to thank the Ministry of Science and Technology, International JointR&DProject (Korea–UK Science and technology collaboration found; IU-99-005) for supporting this work
Morphological and optical characteristics of Y2O3 : Eu phosphor particles prepared by flame spray pyrolysis
No full textY2O3:Eu phosphor particles were prepared by flame spray pyrolysis and compared with the particles prepared by general spray pyrolysis. The particles prepared by flame spray pyrolysis had a spherical and dense morphology and were finer than the particles prepared by general spray pyrolysis. Flame temperature was an important factor in the preparation of the phosphor particles by flame spray pyrolysis. To obtain Y2O3:Eu particles with a uniformly dense structure, a sufficiently high temperature to form monoclinic phase was required. Too low flame temperature generated nonspherical and hollow particles with cubic phase because the particles did not melt completely, and too high flame temperature of flame generated many nanoparticles due to evaporation. After stepwise post-treatment of as-prepared particles with monoclinic phase and the dense structure, Y2O3:Eu phosphor particles with high brightness and cubic phase were obtained. The Y2O3:Eu phosphor particles prepared by flame spray pyrolysis showed 120% photoluminescence intensity in comparison with the particles prepared by general spray pyrolysis
Optimization of feeding strategy for overproduction of human lipocortin-I in Saccharomyces cerevisiae controlled by the GAL10 promoter
No full textFed-batch fermentation was conducted to overproduce human lipocortin-1 (LC1) in recombinant Saccharomyces cerevisiae controlled by the GAL10 promoter. To optimize the feeding strategy, various fed-batch culture modes were performed with concentrated feed media containing carbon mixtures of galactose (Gal) and glucose (Glu) at three different concentration ratios (Gal:Glu ratios): 9:1, 1:1, 1:9. The cell growth, expression level of LC1, and the plasmid stability were investigated under these fed-batch culture modes, While both glucose and galactose were being fed to the fermenter, the glucose concentration in the culture broth was kept below 1 g/l for efficient gene expression. High cell concentrations of greater than 100 g dry cell weight/l mere achieved with these fed-batch culture modes. A significant amount of intact LC1 was found to be secreted into the culture medium, but proteolytically cleaved products (des1-26-LC1) were also observed in the culture medium. The fed-batch fermentation with the feed medium at a Gal: Glu ratio of 1:1 resulted in the highest LC1 total (intact LC1+des1-26-LC1) concentration of 500 mg/l, which corresponded to 1.73- and 1.83-fold increases over that produced with the media at Gal: Glu ratios of 1:9 and 9:1, respectively
Absorption of Carbon Dioxide into Aqueous Mixtures of 2-Amino-2-Methyl-1-Propanol with Monoethanolamine
No full textSynthesis and properties of Ce1-xGdxO2-x/2 solid solution prepared by flame spray pyrolysis
No full textFlame spray pyrolysis, which produces ultrafine particles, was applied to the synthesis of Ce1-xGdxO2-x/2 solid solutions by substituting Gd from a mole fraction of 0-0.40. The solubility limit of Gd in the Ce1-xGdxO2-x/2 solid solution produced by flame spray pyrolysis was between 0.25 and 0.30, which is consistent with the reported value. The as-prepared Ce1-xGdxO2-x/2 particles had a square morphology and a nanometer range in the equivalent diameter. The small particle size made it possible to reduce the sintering temperature of the Ce1-xGdxO2-x/2 solid solution from 1650 degrees C to 1400 degrees C for the ceria-based solid electrolytes produced by the solid state preparation. The maximum ionic conductivity was achieved when the mole fraction of Gd was 0.25. The mole fraction for the highest ionic conductivity was the same as the particles produced by hydrothermal synthesis. However, the ionic conductivity of the Ce1-xGdxO2-x/2 prepared by the flame spray pyrolysis (1.01 X 10(-2) S/cm at 600 degrees C) was higher than that prepared by the hydrothermal synthesis (7.53 x 10(-3) S/cm at 600 degrees C). (c) 2005 Elsevier Ltd. All rights reserved.Center for Ultramicrochemical Process Systems (CUPS) sponsored by
KOSE
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