• Bulletin of the Korean Chemical Society
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• v.35 no.1
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• pp.243-249
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• 2014

Three single crystals of fully dehydrated $Co^{2+}$-exchanged zeolite Y (Si/Al = 1.56) were prepared by the exchange of $Na_{75}$-Y ($|Na_{75}|[Si_{117}Al_{75}O_{384}]$-FAU) with aqueous streams 0.05 M in $Co(NO_3)_2$, pH = 5.1, at 294 K for 6 h, 12 h, and 18 h, respectively, followed by vacuum dehydration at 673 K. Their single-crystal structures were determined by synchrotron X-ray diffraction techniques in the cubic space group Fd3m at 100(1) K. They were refined to the final error indices $R_1/wR_2$ = 0.0437/0.1165, 0.0450/0.1228, and 0.0469/0.1278, respectively. Their unit-cell formulas are $|Co_{29.1}Na_{11.8}H_{5.0}|[Si_{117}Al_{75}O_{384}]$-FAU, $|Co_{29.8}Na_{11.0}H_{4.4}|[Si_{117}Al_{75}O_{384}]$-FAU, and $|Co_{30.3}Na_{9.5}H_{4.9}|[Si_{117}Al_{75}O_{384}]$-FAU, respectively. In all three crystals, $Co^{2+}$ ions occupy sites I, I' and II; $Na^+$ ions are also at site II. The tendency of $Co^{2+}$ exchange slightly increases with increasing contact time as $Na^+$ content and the unit cell constant of the zeolite framework decrease.

• Bulletin of the Korean Chemical Society
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• v.33 no.7
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• pp.2369-2377
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• 2012

The gas-phase dehydration of glycerol to acrolein was carried out over silicotungstic acid ($H_4SiW_{12}O_{40}{\cdot}xH_2O$, HSiW) catalysts supported on $SiO_2$, ${\eta}-Al_2O_3$, and silica-aluminas with different Al contents. The HSiW catalysts supported on silica-aluminas showed higher glycerol conversions and acrolein yields during the initial 2 h at $315^{\circ}C$ than did $SiO_2$- and ${\eta}-Al_2O_3$-supported HSiW catalysts. Among the tested catalysts, HSiW/$Si_{0.9}Al_{0.1}O_x$ exhibited the highest space-time yield during the initial 2 h. The loaded HSiW species can change the acid types and suppress the formation of carbonaceous species on Al-rich silica-aluminas. The deactivated HSiW supported on silica-aluminas can be fully regenerated after calcination in air at $500^{\circ}C$. As long as the molar ratio between water and glycerol was in the range of 2-11, the acrolein selectivity increased significantly with increasing water content in the feed, while the surface carbon content decreased owing to the suppression of heavy compounds.

• Bulletin of the Korean Chemical Society
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• v.20 no.7
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• pp.791-795
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• 1999

The crystal structure of a cyclopropane sorption complex of dehydrated fully Ca (2+) -exchanged zeolite X, Ca46Si100Al92O384· 30C3H6 (a = 24.988(4) Å), has been determined by single-crystal X-ray diffraction techniques in the cubic space group Fd3 at 21(1)℃. The crystal was prepared by ion exchange in a flowing stream of 0.05M aqueous Ca(NO3)2 for four days, followed by dehydration at 460℃ and 2×10 (-6) Torr for two days, and exposure to 100 Torr of cyclopropane gas at 21(1)℃. The structure was determined in this atmosphere and refined to the final error indices R1 = 0.068 and R2 = 0.082, with 373 reflections for which I > 3σ (I). In this structure, Ca 2+ ions are located at two crystallographic sites. Sixteen Ca 2+ ions fill the octahedral sites I at the centers of the hexagonal prisms (Ca-O = 2.412(9)Å). The remaining 30 Ca 2+ ions are at sites Ⅱ; each extends 0.46Å into the supercage (an increase of 0.16Å upon C3H6 sorption) where it coordinates to three trigonally arranged framework oxygens at 2.311(8)Å. Each of the 30 cyclopropane molecules was found to complex to Ca 2+ ions at site II by the induced dipole interaction (Ca-C = 2.99(4)Å). All carbon atoms in each cyclopropane molecule are equivalent and equidistant from Ca 2+ ions at site II with which they are associated.

• Bulletin of the Korean Chemical Society
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• v.19 no.10
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• pp.1095-1099
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• 1998

The crystal structure of an acetylene sorption complex of dehydrated fully Mn(Ⅱ)-exchanged zeolite X, Mn46Si100Al92O384·30C2H2 (a=24.705(3) Å) has been determined by single-crystal X-ray diffraction techniques. The structure was solved and refined in the cubic space group Fd3 at 21(l) ℃. The complex was prepared by dehydration at 380 ℃ and 2 x 10-6 Torr for 2 days, followed by exposure to 300 Torr of acetylene gas for 2 h at 24 ℃. The structure was refined to the final error indices, R1=0.060 and R2=0.054 with 383 reflections for which I > 3σ(Ⅰ). In the structure, Mn2+ ions are located at two different crystallographic sites; sixteen Mn2+ ions at site I are located at the centers of the double six rings and thirty Mn2+ ions are found at site Ⅱ in the supercage, respectively. Each of these latter Mn2+ ions is recessed ca. 0.385(2) Å into the supercage from its three-oxygen plane. Thirty acetylene molecules are sorbed per unit cell. Each Mn2+ ion at site Ⅱ lies on a threefold axis in the supercage of the unit cell, close to three equivalent trigonally arranged zeolite framework oxygen atoms (Mn(Ⅱ)-O=2.135(9) Å) and symmetrically to both carbon atoms of a C2H2 molecules. At these latter distances, the Mn(Ⅱ)-C interactions are weak (Mn(Ⅱ)-C=2.70(5) Å), probably resulting from electrostatic attractions between the divalent cations and the polarizable π-electron density of the acetylene molecules.

• Clinical and Experimental Pediatrics
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• v.57 no.7
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• pp.304-309
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• 2014

Benign convulsion with mild gastroenteritis (CwG) is a type of afebrile seizure that occurs in children. CwG is defined as a convulsion in a previously healthy child with no known central nervous system infection or encephalopathy, accompanying mild diarrhea without fever, electrolyte imbalance, or moderate to severe dehydration. Convulsions in CwG are characterized by multiple brief episodes of generalized or focal seizures. Although the etiology and pathophysiology have yet to be fully explained, many pathogenic mechanisms have been proposed including the possibility of direct invasion of the central nervous system by a gastrointestinal virus such as rotavirus or the possibility of indirect influence by the production and effects of certain mediators. The electroencephalogram findings are benign and long-term antiepileptic treatment is typically not required. Long-term prognosis has been favorable with normal psychomotor development. This review provides a general overview of CwG with the goal of allowing physicians practicing in the field of pediatrics to better recognize this unique entity and, ultimately, to minimize unnecessary evaluation and treatment.

• Journal of the Korean Chemical Society
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• v.33 no.4
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• pp.357-365
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• 1989

The positional parameters of framework atoms, cations, and water molecules in hydrated and dehydrated $Mg_4Na_4-A$, $Ca_6-A$, $Zn_5Na_2-A$ and $Co_4Na_4-A$ were determined by the optimization technique using some potential energy functions and VAIOA optimization program. Upon dehydration, cations in hydrated states move toward the framework oxygens of 6 rings. Frameworks of fully dehydrated zeolite A are more stable than those of fully dehydrated divalent cation exchanged Zeolite A. There are three different kinds of water molecules in divalent cation exchanged Zeolite A; W(III) (water molecules having hydrogen bonds), W(II) (water molecules associated with $Na^+$ ions), and W(I) (water molecules associated with divalent cations). Three different DTA endothermic peaks were observed corresponding to the dehydration of three different kinds of water molecules in divalent cation exchanged Zeolite A.

• Bulletin of the Korean Chemical Society
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• v.13 no.1
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• pp.70-74
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• 1992

Two crystal structures of ethylene (a= 12.272(2) ${\AA}$) and acetylene (a = 12.245(2) ${\AA}$) sorption complexes of dehydrated fully $Ca^{2+}$-exchanged zeolite A have been determined by single crystal X-ray diffraction techniques in the cubic space group, Pm3m at $21(1)^{\circ}C$. Their complexes were prepared by dehydration at $360^{\circ}C$ and $2{\times}10^{-6}$ Torr for 2 days, followed by exposure to 200 Torr of ethylene gas and 120 Torr of acetylene gas both at $24^{\circ}C$, respectively. The structures were refined to final R (weighted) indices of 0.062 with 209 reflections and 0.098 with 171 reflections, respectively, for which I > 3${\sigma}$(I). The structures indicate that all six $Ca^{2+}$ ions in the unit cell are associated with 6-oxygen ring of the aluminosilicate framework. Four of these extend somewhat into the large cavity where each is coordinated to three framework oxide ions and an ethylene molecule and/or an acetylene molecule. The carbon to carbon distance in ethylene sorption structure is 1.48(7) ${\AA}$ and that in acetylene sorption structure 1.25(8) ${\AA}$. The distances between $Ca^{2+}$ ion and carbon atom are 2.87(5) ${\AA}$ in ethylene sorption structure and 2.95(7) ${\AA}$ in acetylene sorption structure. These bonds are relatively weak and probably formed by the electrostatic attractions between the bivalent $Ca^{2+}$ ions and the polarizable ${\pi}$-electron density of the ethylene and/or acetylene molecule.

• Bulletin of the Korean Chemical Society
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• v.19 no.11
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• pp.1222-1227
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• 1998

The crystal structure of a benzene sorption complex of fully dehydrated Cd2+-exchanged zeolite X, Cd46Si100Al92O384·43C6H6 (a=24.880(6) Å), has been determined by single-crystal X-ray diffraction techniques in the cubic space group Fd3 at 21 ℃. The crystal was prepared by ion exchange in a flowing stream of 0.05 M aqueous Cd(NO3)2 for 3 d, followed by dehydration at 400 ℃ and 2 x 10-6 Torr for 2 d, followed by exposure to about 92 Torr of benzene vapor at 22 ℃. The structure was determined in this atmosphere and refined to the final error indices R1=0.054 and Rw=0.066 with 561 reflections for which I > 3σ(I). In this structure, Cd2+ ions are found at four crystallographic sites: eleven Cd2+ ions are at site 1, at the centers of the double six-oxygen rings; six Cd2+ ions lie at site I', in the sodalite cavity opposite to the double six-oxygen rings; and the remaining 29 Cd2+ ions are found at two nonequivalent threefold axes of unit cell, sites Ⅱ' (in the sodalite cavity ) and site Ⅱ (in the supercage) with occupancies of 2 and 27 ions, respectively. Each of these Cd2+ ions coordinates to three framework oxylkens, either at 2.173(13) or 2.224(10) Å, respectively, and extends 0.37 Å into the sodalite unit or 0.60 Å into the supercage from the plane of the three oxygens to which it is bound. The benzene molecules are found at two distinct sites within the supercages. Twenty-seven benzenes lie on threefold axes in the large cavities where they interact facially with the latter 27 site-Ⅱ Cd2+ ions (Cd2+-benzene center=2.72 Å; occupancy=27 molecules/32 sites). The remaining sixteen benzene molecules are found in 12ring planes; occupancy=16 molecules/16 sites. Each hydrogen of these sixteen benzenes is ca. 2.8/3.0 Å from three 12-ring oxygens where each is stabilized by multiple weak electrostatic and van der Waals interactions with framework oxygens.

• Bulletin of the Korean Chemical Society
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• v.33 no.10
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• pp.3303-3310
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• 2012

Two single crystals of fully dehydrated partially $Li^+$-exchanged zeolite X were prepared by the exchange of Na-X, $Na_{92}Si_{100}Al_{92}O_{384}$ (Si/Al = 1.09), with $Li^+$ using aqueous 0.1 M $LiNO_3$ at 293 (crystal 1) and 333 K(crystal 2), followed by vacuum dehydration at 623 K and $1{\times}10^{-6}$ Torr for 2 days. Their structures were determined by single-crystal synchrotron X-ray diffraction techniques in the cubic space group $Fd{\overline{3}}$ at 100(1) K. Their structures were refined using all intensities to the final error indices (using the 1281 and 883 reflections for which ($F_o$ > $4{\sigma}(F_o)$) $R_1/R_2$ = 0.075/0.244 and 0.074/0.223 for crystals 1 and 2, respectively. Their compositions are seen to be ${\mid}Li_{86}Na_6{\mid}[Si_{100}Al_{92}O_{384}]$-FAU and ${\mid}Li_{87}Na_5{\mid}[Si_{100}Al_{92}O_{384}]$-FAU, respectively. In crystal 1, 17 $Li^+$ ions per unit cell are at site I', 15 another site I', 30 at site II, and the remaining 16 at site III; 2 $Na^+$ ions are at site II and the remaining 4 at site III'. In crystal 2, 32 and 30 $Li^+$ ions per unit cell fill sites I' and II, respectively, and the remaining 25 at site III'; 2 and 3 $Na^+$ ions are found at sites II and III', respectively. The extent of $Li^+$ exchange increases slightly with increasing ion exchange temperature from 93% to 95%.

• Journal of the Korean Applied Science and Technology
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• v.22 no.3
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• pp.204-211
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• 2005

The structure of nitrogen adsorption complex of fully dehydrated $Cd^{2+}$ ion exchanged zeolite-X, $|Cd_{46}(N)_{18}|[Si_{100}Al_{92}O_{384}]$, was determined in the cubic space group $Fd\overline{3}$ at 21(1) $^{\circ}C$ [a = 24.863(4) ] by single crystal X-ray diffraction analysis. The crystal was prepared by ion exchange in a flowing steam of 0.05 M aqueous solution $Cd(NO_3)_2$ : $Cd(O_2CCH_3)_2$ = 1:1 for five days, followed by dehydration at $500^{\circ}C$ and $2{\times}10^{-6}$ Tor. for two days, and exposured to 100 Tor. zeolitically dry nitrogen gas at 21(1) $^{\circ}C$. The structure was determined in atmosphere, and was refined within $F_0$ > $4{\sigma}(F_0)$ using reflection for which the final error can appear in indices $R_1$ = 0.097 and $wR_2$ = 0.150. In this structure, $Cd^{2+}$ ions occupied four crystallographic sites. Nine $Cd^{2+}$ ions filled the octahedral site I at the centers of hexagonal prisms (Cd-O = 2.452(16) ${\AA}$). Eight $Cd^{2+}$ ions filled site I' (Cd-O = 2.324(19) ${\AA}$). The remaining 29 $Cd^{2+}$ ions are found at two nonequivalent sites II (in the supercages) with occupancy of 11 and 18 ions. Each of these $Cd^{2+}$ ions coordinated to three framework oxygens, either at 2.159(15) or 2.147(14) ${\AA}$, respectively. Eighteen nitrogen molecules were adsorbed per unit cell and three per supercage.