• Korean Chemical Engineering Research
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• v.49 no.5
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• pp.664-668
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• 2011

Spherical alumina precursors represented by $AlO_xCl_y(OH)_z$, 30~200 nm in particle diameter, were prepared by partial hydrolysis of $AlCl_3$ vapor in a 500 ml reactor. Investigated on the particle morphology and size were the effects of the reaction time, the stirring speed and the reaction temperature. The particle morphology and size was insensitive to the reaction time in the range 20 to 300 s. The variation of the stirring speed from 0 to 300 and 800 rpm showed that the particle size was the largest at 0 rpm. As the temperature was varied from 180 to 190, 200, $140^{\circ}C$, the particle size showed a maximum at $190^{\circ}C$. By calcination of the as-produced particles at $1,200^{\circ}C$ for 6h with a heating rate of $10^{\circ}C$/min, ${\alpha}$-alumina particles 45 nm in surface area equivalent diameter were obtained. The particle shape after calcination turned wormlike due to sintering between neighboring particles. A rapid calcination at $1400^{\circ}C$ for 0.5 h with a higher heating rate of $50^{\circ}C$/min reduced the sintering considerably. An addition of $SiCl_4$ or TMCTS(2,4,6,8-tetramethylcyclosiloxane) to the $AlCl_3$ reduced the sintering effectively in the calcination step; however, peaks of ${\gamma}$ or mullite phase appeared. An addition of $AlF_3$ to the particles obtained from the hydrolysis resulted in a hexagonal disc shaped alumina particles.

• Journal of the Korean Chemical Society
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• v.7 no.4
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• pp.283-287
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• 1963

The distribution ratio of hydrogen cupferrate in $H_2O-CHCl_3$ system was considered as a function of pH ($HClO_4$), ionic strength ($NaClO_4$), and cupferron concentration in perchloric acid media, respectively. The values were independent upon pH (1.50∼3.00 range) and ionic strength (0.1∼2.00 range), but they increased as increasing the cupferron concentration in the acidic media. At the infinite dilution, the thermodynamic distribution ratio between chloroform and aqueous phase was 120. 0. The activity coefficients of hydrogen cupferrate in chloroform solution were determined by the distribution ratio. This activity coefficient may be calculated by using the empirical equation, $-log\;f_{CHCl3}=0.1285C_{CHCl3}+{7.775C^2}_{CHCl3}$ which represents the experimental data quite well for the solution in 0.1 mole/l order of hydrogen cupferrate concentration.

• Applied Biological Chemistry
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• v.27 no.2
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• pp.112-118
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• 1984

Inverase was entrapped in calcium alginate gel. The immobilized beads had excellent uniform size and configuration. To screen the optimal conditions possessing high enzyme activity, effects of sodium alginate concentration, $CaCl_2$ concentration, and the incubation time of beads in $CaCl_2$ solution during the immobilization procedure were investigated. Immobilized beads prepared from the optimal conditions had 18.8 units per ml of gel, which is equivalent to 68% of the activity of soluble enzyme. Several kinetic parameters were determined: Km value. 143 mM; optimum pH, 4.5; optimum temperature, $50^{\circ}C$. Enzyme loading capacity was 150 mg per 20 ml gel. No significant decrease in sugar conversion was observed during the column operation for 6 days.

• The Plant Pathology Journal
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• v.24 no.3
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• pp.322-327
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• 2008

Antifungal activities of natural substrances from Eucalyptus darlympleana, E. globules, E. gunnii and E. unigera were evaluated against postharvest pathogens of kiwifruits, Botrytis cinerea, Botryosphaeria dothidea, and Diaporthe actinidiae, to screen effective natural substances as an alternative to chemical fungicides. Methanol extract of the Eucalyptus trees showed strong antagonistic activity against the pathogenic fungi. Among them, E. unigera and E. darlympleana effectively inhibited mycelial growth of the pathogens. For chemical identification of the antifungal substances, the methanol extract of E. darlympleana leaves was successively partitioned with $CH_2Cl_2$, EtOAc, n-BuOH and $H_2O$. Among the fractions, $CH_2Cl_2$ and n-BuOH showed strong inhibitory activity of mycelial growth of the fungi. Five compounds were isolated from EtOAc and n-BuOH fractions subjected to $SiO_2$ column chromatography. Two phenolic compounds(gallic acid and 3,4-dihydroxybenzoic acid) and three flavonoid compounds(quercetin, quercetin-3-O-$\alpha$-L-rhamnoside, quercetin-3-O-$\beta$-glucoside) were identified by $^1H$-NMR and $^{13}C$-NMR spectroscopy. Among them, only gallic acid was found to be effective in mycelial growth and spore germination of B. cinerea at relatively high concentrations. The results suggest that gallic acid can be a safer and more acceptable alternative to current synthetic fungicides controlling soft rot decay of kiwifruit during postharvest storage.

• Clean Technology
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• v.6 no.1
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• pp.61-69
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• 2000

In this study, generation process and properties of inorganic industrial waste which can be used in cement industry were investigated. The scheme of recycling to use the selected waste as raw materials, mineralizer and flux, admixture and raw materials for special cement was decided and then various experiments were carried out. The experimental results were as follows ; In the use of industrial waste as raw materials, ferrous materials could be substituted by Cu-slag, Zn-slag, electric arc furnace or convertor furnace slag etc., and a siliceous material could be substituted by sand from cast-iron industry. By-products from sugar or fertilizer industry, which has $CaF_2$ as the main component, and jarosite from Zn refinery enabled clinker phases to be formed at lower temperature by $100{\sim}150^{\circ}C$. Adding Cu slag and STS sludge in proper proportion to cement improved properties of cement. Fly ash and limestone powder as admixture had the same effect on cement. As a raw material for special cement, aluminium waste sludge could be used in making ultra early strength cement, which had the compressive strength of $300kg/cm^2$ within 2hours. And two different ashes from municipal incinerator could be raw materials of the cement which was mainly composed of $C_3S$ and $C_{11}A_7{\cdot}CaCl_2$ as clinker phases.

• Clean Technology
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• v.20 no.2
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• pp.108-115
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• 2014

Various metal chlorides and acid catalysts in ionic liquid solvent were investigated to directly convert cellulose into 5-hydroxymethylfurfural (5-HMF). Metal chlorides containing Sn(II), Zn(II), Al(III), Fe(III), Cu(II), and Cr(III) were used and acidic ionic liquid immobilized on silica gel as an acid catalyst and commercial acid catalysts (sulfuric acid, chloric acid, Amberlyst-15,DOWEX50x8) were used for comparison studies. The acid strength and amount of acid catalysts were probed with Hammett indicator. The selectivity and yield of 5-HMF were determined with reaction temperature, reaction time and catalyst ratio. A catalyst containing $CrCl_3-6H_2O$ and $SiO_2-[ASBI]HSO_4$ showed the highest selectivity and it was found that this catalyst had higher activity than commercial solid acid catalysts such as Amberlyst-15 and DOWEX50x8. The selectivity of 5-HMF appeared to be mainly dependent on the acid strength and catalyst ratio, it was found that levulinic acid was produced from 5-HMF by rehydration.

• Bulletin of the Korean Chemical Society
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• v.18 no.2
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• pp.143-149
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• 1997

We have investigated a relationship between conformational preferences of various substituents in monosubstituted cyclohexanes and pertinent torsional parameter values in molecular mechanics calculations. We have manipulated torsional parameters to supply a certain energy difference between gauche and anti conformers, and applied those parameters to monosubstituted cyclohexanes. After investigating 6 different substituents, namely Me, SiH3, F, Cl, Br, and I, MM3 calculations show that (1) the MM3 calculated A values with the current torsional parameters reproduce the available experimental values well, (2) the conformational energy difference between axial and equatorial conformations (the A value) correlates perfectly with the gauche/anti energy differences of the corresponding butane-like fragment (correlation coefficient=l.000), and (3) the A values are essentially twice as the gauche/anti energy differences (slopes=1.86-2.00). On the basis of our analysis, the A values as well as the gauche/anti energy differences are easily calibrated by an adjustment of the relevant torsional parameter. Thus, our technique for tuning the torsional parameters may be of great use in updating molecular mechanics results about conformational preferences whenever a further refinement is necessary.

• Macromolecular Research
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• v.12 no.1
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• pp.100-106
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• 2004

We have prepared the polymethylene-bridged, dinuciear, half-sandwich constrained geometry catalysts (CGC)［Zr(η$\^$5/:η$^1$-C$\_$9/H$\_$5/SiMe$_2$NCMe$_3$)］$_2$［(CH$_2$)$\_$n/］［n=6(9), n=12(10)］by treating 2 equivalents of ZrCl$_4$with the corresponding tetralithium salts of the ligands in toluene. $^1$H and $\^$13/C NMR spectra of the synthesized complexes provide firm evidence for the anticipated dinuciear structure. In $^1$H NMR spectra, two singlets representing the methyl group protons bonded at the Si atom of the CGC are present at 0.88 and 0.64 ppm, which are considerably downfield positions relative to the shifts of 0.02 and 0.05 ppm of the corresponding ligands. To investigate the catalytic behavior of the prepared dinuciear catalysts, we conducted copolymerizations of ethylene and styrene in the presence of MMAO. The prime observation is that the two dinuclear CGCs 9 and 10 are not efficient for copo-lymerization, which definitely distinguishes them from the corresponding titanium-based dinuclear CGC. These species are active catalysts, however, for ethylene homopolymerization; the activity of catalyst 10, which contains a 12-methylene bridge, is larger than that of 9 (6-methylene bridge), which indicates that the presence of the longer bridge between the two active sites contributes more effectively to facilitate the polymerization activity of the dinuciear CGC. The activities increase as the polymerization temperature increases from 40 to 70$^{\circ}C$. On the other hand, the molecular weights of the polyethylenes are reduced when the polymerization temperature is increased. We observe that dinuciear metallocenes having different-length bridges give different polymerization results, which reconfirms the significant role that the nature of the bridging ligand has in controlling the polymerization properties of dinuclear catalysts.

• Journal of the Korean Wood Science and Technology
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• v.35 no.5
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• pp.93-99
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• 2007

Paulownia coreana inner bark was collected, extracted in 70% acetone, concentrated under reduced pressure and sequentially fractionated using n-hexane, $CH_2Cl_2$, EtOAc and $H_2O$, then freeze dried to give brown powders. A portion of the EtOAc soluble powder was chromatographed on a Sephadex LH-20 column using a serious of aqueous methanol and ethanol-hexane mixture as eluting solvents. Two phenolic acid, $\rho$-courmaric acid and caffeic acid, two isomeric phenylethanoid glycosides, verbascoside and iso-verbascoside, and one epimeric phenylpropanoid glycoside, cistanoside F, were isolated and their structures were elucidated by spectroscopic analysis such as NMR and MS.

• Proceedings of the KIEE Conference
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• 1991.07a
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• pp.174-177
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• 1991

Fluorine-doped $SnO_2\;(SnO_2:F)$ films were prepared in ordinary atmosphere on borosilicate glass substrates using pyrosol deposition method starting from the solutions composed of $SnCl_4-5H_2O-NH_4F-CH_3OH-H_2O-HCl$ in an attempt to develop transparent conductors for use in amorphous silicon (a-Si) solar cello. The deposition rate of films increased with the increase in the content of $H_2O$, whereas it decreased with increasing the content of $CH_3OH$. When air was used as the carrier gas, the lowest electrical resistivity was obtained from a solution having $CH_3OH/H_2O$ mol ratio of about $2{\sim}3$ in the solution. The use of $N_2$ of the same flow rate as the carrier gab resulted always in the high resistive films, but the resistivity of the films decreased continuously with the increase in the content of $H_2O$. The surface morphology and preferred orientation of films were also affected by the solvent composition and the content of HCl in the solution. The room-temperature resistance of the films were fairly stable after heat-treatments up to $600^{\circ}C$.