• Transactions of the Korean hydrogen and new energy society
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• v.14 no.1
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• pp.69-80
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• 2003

Nickel catalyst has been used for natural gas reforming with carbon dioxide, In this study, catalyst support used was HY zeolite. The optimum loading of Ni in the catalysts was 13 wt%. The effect of promoters, such as Mg, Mn, and K, was also studied. The addition of promoters to Ni catalyst improved the stability of catalysts and carbon deposition on Ni catalyst was suppressed. The reforming reactivity of promoter-added Ni catalyst was higher than that of Ni catalyst without any promoters. SEM, XRD, BET, TGA and FTIR tests were tried to characterize the catalyst structure before and after reaction.

• Applied Chemistry for Engineering
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• v.5 no.1
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• pp.24-29
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• 1994

The zeolite X was prepared from the Korean natural clinoptilolite, which contains some mordenite. Thermal treatment removed the clinoptilolite structure from the ore remaining mordenite. The natural clinoptilolites dealuminated with 2N-8N HCI solution and/or thermal treatment were mixed with NaCl, $NaAlO_2$ and NaOH, and reacted to zeolites X at $95^{\circ}C$ for 12~36 hrs. Maximum yield of NaX was obtained for the reactant mixture of 25 gr of natural zeolite acidtreated with 8 N HCI, together with 3.5g NaCl, 8g $NaAlO_2$ and 50 ml of 6N NaOH at $95^{\circ}C$, for 24 hrs.

• Korean Chemical Engineering Research
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• v.44 no.4
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• pp.329-339
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• 2006

The production of lower olefins from methanol becomes an attractive process because of the rapid increase in crude oil price. This paper reivews the conversion mechanisms of methanol to hydrocarbons over zeolite and SAPO molecular sieve catalysts to understand the formation steps of lower olefins from methanol. The feasibility of the conversion mechanisms such as the direct mechanism based on well-defined intermediates and the hydrocarbon pool mechanism involving hydrocarbon moieties as an active centers is discussed with reepect to the induction period, the selectivity for products and the deactivation phenomena of the methanol conversion. The literature appeered since 1999 for the structure of the hydrocarbon pool and its catalytic role in the methanol conversion are summariged, and the prospect for the methanol-to-olefins process is described.

• Journal of the Korean Chemical Society
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• v.28 no.3
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• pp.194-202
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• 1984

The adsorption properties of organo sulfur compounds on cation exchanged natural zeolites from n-heptane were investigated. The equilibrium adsorbed amounts were dependent upon the exchanged cation and the nature of organo sulfur compounds such as length, volume, electronical structure. The increasing orders of equilibrium adsorbed amounts were thiophene derivatives, disulfide, sulfide mercaptane and thiophene, benzothiaphene, dibenzothiophene. And $Co^{+2}$-zeolite was the most prominent adsorbant. Rate determining step of the adsorption at initial stage was intraparticle diffusion into the transitional pores of zeolite. These adsorption rates were dependent upon the bulkiness of adsorbate. Finally, preadsorbed water didn't affect these adsorption until the cation exchanged natural zeolite contained 2.26${\times}10^{-3}$ mol/g of water. It indicated that water preferentially occupied the micro pores of the cation exchanged natural zeolites.

• Journal of Environmental Science International
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• v.27 no.11
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• pp.975-982
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• 2018

In this study, zeolite (Z-C1) was synthesized using a fusion/hydrothermal method from coal fly ash. The morphological structures of Z-C1 were confirmed to be highly crystalline with a cubic crystal structure. Exchange capacities of $Ca^{2+}$ and $Mg^{2+}$ ions in a single and a mixed solution reached equilibrium within 120 min. The exchange kinetics of these ions were well predicted by the pseudo-second-order rate equation. The exchange isotherms of the $Ca^{2+}$ and $Mg^{2+}$ ions matched the Langmuir isotherm better than the Freundlich isotherm. The maximum cation exchange capacities ($q_m$) obtained by the Langmuir isotherm model were 2.11 mmol/g (84.52 mg/L) and 1.13 mmol/g (27.39 mg/L) for the $Ca^{2+}$ and $Mg^{2+}$ ions, respectively.

• Journal of Environmental Science International
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• v.32 no.5
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• pp.343-353
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• 2023

A zeolite material (ZCH) was synthesized from coal fly ash in an HD thermal power plant using a fusion/hydrothermal method. ZCH with high crystallinity could be synthesized at the NaOH/CFA ratio of 0.9. Ion-exchanged ZCH adsorbents for ammonia removal were prepared by ion-exchanging various cation (Cu²⁺, Co²⁺, Fe³⁺, and Mn²⁺) on the ZCH. They were used to evaluate the ammonia adsorption breakthrough curves and adsorption capacities. The ammonia adsorption capacities of the ZCH and ion-exchanged ZCHs were high in the order of Mn-ZCH > Cu-ZCH ≅ Co-ZCH > Fe-ZCH > ZCH according to NH₃-TPD measurements. Mn-ZCH ion-exchanged with Mn has more Brønsted acid sites than other adsorbents. The ion-exchanged Cu²⁺, Co²⁺, Fe³⁺, or Mn²⁺ ions uniformly distributed on the surface or in the pores of the ZCH, and the number of acidic sites increased on the alumina sites to form the crystal structure of zeolite material. Therefore, when the ion-exchanged ZCH was used, the adsorption capacity for ammonia gas increased.

• Analytical Science and Technology
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• v.16 no.5
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• pp.375-390
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• 2003

A single crystal of fully indium-exchanged zeolite A (In-A) was brought into contact with antimony in a fine Pyrex capillary at $350^{\circ}C$ for 6 days. The reaction was monitored by electron-probe X-ray microanalysis (EPXMA). The crystal structure of antimony-sorbed indium-exchanged zeolite A has been determined by single-crystal X-ray diffraction techniques at $21^{\circ}C$ in the cubic space group Pm ${\bar{3}}m$. The crystal structure of $In_8Si_{12}Al_{12}O_{48}{\cdot}(In)_{1.35}(Sb)_{0.7}$ ($a=12.111(2){{\AA}}$, $R_1=0.071$, and $R_2=0.067$) has 8 indium cations, 1.35 indium atoms, and 0.7 antimony atoms per unit cell. Unit cell 1 ($In_8-A{\cdot}In$, 65% of unit cells) contain the $(In_5)^{8+}$ cluster. In unit cell 2 ($In_8-A{\cdot}(In)_2(Sb)_2$, 35% of unit cells), two $(In_3)^{2+}$ cluster and one $(In_3Sb_2)^{7+}$ cluster are found in the large cavity.

• Bulletin of the Korean Chemical Society
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• v.26 no.7
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• pp.1090-1096
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• 2005

$Ag_4Br_4$ nanoclusters have been synthesized in about 75% of the sodalite cavities of fully $K^+$-exchanged zeolite A (LTA). An additional KBr molecule is retained in each large cavity as part of a near square-planar $K_4Br^{3+}$ cation. A single crystal of $Ag_{12}$-A, prepared by the dynamic ion-exchange of $Na_{12}$-A with aqueous 0.05 M $AgNO_3$ and washed with $CH_3OH$, was placed in a stream of flowing 0.05 M KBr in $CH_3OH$ for two days. The crystal structure of the product ($K_9(K_4Br)Si_{12}Al_{12}O_{48}{\cdot}0.75Ag_4Br_4$, a = 12.186(1) $\AA$) was determined at 294 K by single-crystal X-ray diffraction in the space group Pm m. It was refined with all measured reflections to the final error index $R_1$ = 0.080 for the 99 reflections for which $F_o\;{\gt}\;4_{\sigma}\;(F_o)$. The thirteen $K^+$ ions per unit cell are found at three crystallographically distinct positions: eight $K^+$ ions in the large cavity fill the six-ring site, three $K^+$ ions fill the eight-rings, and two $K^+$ ions are opposite four-rings in the large cavity. One bromide ion per unit cell lies opposite a four-ring in the large cavity, held there by two eight-ring and two six-ring $K^+$ ions ($K_4Br^{3+}$). Three $Ag^+$ and three $Br^-$ions per unit cell are found on 3-fold axes in the sodalite unit, indicating the formation of nano-sized $Ag_4Br_4$ clusters (interpenetrating tetrahedra; symmetry $T_d$; diameter ca. 7.9 $\AA$) in 75% of the sodalite units. Each cluster (Ag-Br = 2.93(3) $\AA$) is held in place by the coordination of its four $Ag^+$ ions to the zeolite framework (each $Ag^+$ cation is 2.52(3) $\AA$ from three six-ring oxygens) and by the coordination of its four $Br^-$ ions to $K^+$ ions through six-rings (Br-K = 3.00(4) $\AA$).

• Bulletin of the Korean Chemical Society
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• v.28 no.1
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• pp.41-48
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• 2007

Large colorless single crystals of sodium zeolite X, stoichiometry |Na80 |[Si112Al80O384]-FAU, with diameters up to 200 μm and Si/Al = 1.41 have been synthesized from gels with the composition of 2.40SiO2 : 2.00NaAlO2 : 7.52NaOH : 454H2O : 5.00TEA. One of these, a colorless octahedron about 200 μm in cross-section has been treated with aqueous 0.1 M KNO3 for the preparation of K+-exchanged zeolite X. The crystal structure of |K80|[Si112Al80O384]-FAU per unit cell, a = 24.838(4) A, dehydrated at 673 K and 1 × 10-6 Torr, has been determined by single-crystal X-ray diffraction techniques in the cubic space group Fd at 294 K. The structure was refined using all intensities to the final error indices (using only the 707 reflections for which Fo > 4σ (Fo)) R1 = 0.075 (based on F) and R2 = 0.236 (based on F2). About 80 K+ ions per unit cell are found at an unusually large number of crystallographically distinct positions, eight. Eleven K+ ions are at the centers of double 6-rings (D6Rs, site I; K-O = 2.492(6) A and O-K-O (octahedral) = 88.45(22)o and 91.55(22)o). Site-I' position (in the sodalite cavities opposite D6Rs) is occupied by five K+ ions per unit cell; these K+ ions are recessed 1.92 A into the sodalite cavities from their 3-oxygen planes (K-O = 2.820(19) A, and O-K-O = 78.6(6)o). Twety-three K+ ions are found at three nonequivalent site II (in the supercage) with occupancies of 5, 9, and 9 ions; these K+ ions are recessed 0.43 A, 0.75 A, and 1.55 A, respectively, into the supercage from the three oxygens to which it is bound (K-O = 2.36(13) A, 2.45(13) A, and 2.710(13) A, O-K-O = 116.5(20)o, 110.1(17)o, and 90.4(6)o, respectively). The remaining sixteen, thirteen, and twelve K+ ions occupy three sites III' near triple 4-rings in the supercage (K-O = 2.64(3) A, 2.94(3) A, 2.73(5) A, 2.96(6) A, 3.06(4) A, and 3.08(3) A).

• Korean Chemical Engineering Research
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• v.51 no.5
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• pp.531-535
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• 2013

The effect of heat-treatment temperature on the activity of catalysts was studied by investigating $N_2O$ decomposition reaction in Fe ion-supported BEA Zeolite. As a result of $N_2O$ decomposition reaction experiment, $N_2O$ decomposition activity significantly decreased as heat-treatment temperature of Fe/BEA catalyst increased. the shape and size of the particles of Fe/BEA catalyst following the rise of heat-treatment temperature did not display a significant change. But following the rise of the heat-treatment temperature, its surface area was significantly reduced. Also it was confirmed that as the heat-treatment temperature rose, the crystallization of ${\beta}$ structure was greatly reduced. And as heat-treatment temperature rose, while SiO structure either increased or did not exhibit much change, the structure of Fe bonded with lattice structure was speculated to decrease. From the stated results, it was concluded that the increase of heat-treatment temperature became the cause of the declined activity of catalysts by destruction of its ${\beta}$ structure of bonding aluminium and Fe atoms.