• Applied Chemistry for Engineering
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• v.31 no.1
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• pp.57-60
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• 2020

An acetaldehyde, a representative food waste odor, was decomposed using a hybrid system comprised of a non-thermal plasma and catalyst at an ambient temperature under high humidity. A five wt.% Mn was impregnated on two differently structured microporous zeolites, namely Beta and ZSM-5, with a different molar ratio of SiO₂/Al₂O₃. Under high humidity conditions, the acetaldehyde degradation was higher in zeolites with the high ratio of SiO₂/Al₂O₃. Among studied catalysts, a five wt.% Mn/Beta (SiO₂/Al₂O₃ = 300) showed the highest acetaldehyde removal activity owing to its high hydrophobicity and reducibility. During long term stability test using the same catalyst for 110 hours, the acetaldehyde removal activity was relatively well-maintained.

• Applied Chemistry for Engineering
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• v.4 no.3
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• pp.488-496
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• 1993

Natural zeolites have recently been the subject of intensive research due to their versatilities in possible industrial applications. Among several different types of domestic natural zeolites, clinoptilolite, is one of the highly prospective domestic natural zeolites. However, it is always possible for heulandite, the isostructure of clinoptilolite, to coexist with clinoptilolite. Unfortunately, heulandite is thermally very unstable restricting its application to industrial process. In this paper, the effects of ion exchanges and heat-treatments on the thermal stability for domestic natural zeolite, heulandite are described. Two different ion-exchanging experiments were carried out followed by heat-treatments at different temperatures. X-ray, IR and AA spectroscopic analyses showed the enhancements in thermal stabilities of heulandite by $Na^+$ cation exchanges.

• Journal of Environmental Science International
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• v.12 no.12
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• pp.1321-1327
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• 2003

Two different kinds of cases, with and without addition of noncrystalline silica to the Hadong kaolin were studied to obtain useful information on the synthesis of zeolite. The research was carried out to investigate the formation area and the crystalized degree of zeolite according to a synthetic time, the water content of raw material mixture, KOH concentration, and stirring intensity. In the case of without addition of noncrystalline silica to the Hadong kaolin and the low concentration range of KOH, the structure of the kaolin was not changed. However, when the mole ratio of K2O/SiO$_2$ in natural kaolin was increased, Linde-L zeolite and unknown structure of kaolins, U-1 and U-2 were produced. While in the high concentration range of KOH, the unknown structure of kaolins, U-6 and U-2, were produced and the production rate of U-6 was increased with the increased of K2O/SiO$_2$ mole ratio. In the case of with addition of noncrystalline silica to the Hadong kaolin and treatment with KOH hydrothermal processing, ZSM-5, ZSM-35, and Linde-L zeolites and the mixture of unknown structure of zeolites, U-1, U-2, U-3, and U-4, were obtained. Both cases demonstrated that the synthesis of zeolite from the Hadong kaolin was highly influenced by KOH concentration of raw material mixture.

• Journal of Environmental Science International
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• v.11 no.1
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• pp.75-83
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• 2002

The removal performance of copper ion was studied using Na-P1 zeolites synthesized from Jeju scoria. The scoria which is found in large amounts in Jeju Island, was sampled at four regions, Jeju-shi Bonggae-dong(A). Pukcheju-gun Hanlim-eup Sangmyong-ri Mangoreum(B), Pukcheju-gun Hanlim-eup Keumag-ri(C) and Namcheju-gun Andeok-myun Dongkwang-ri(D). Synthetic Na-P1 zeolites used in this study were more effective than natural zeolite and scoria for the removal of copper ion. The removal performances of copper ion decreased in the order of Na-P1(D) > Na-P1(C) > Na-P1(B) > Na-P1(A) among Na-P1 synthesized from the scoria according to region. These results showed the same trend with cation exchange capacity(CEC) for each synthetic zeolite, i.e., the synthetic Na-P1 zeolite with a higher CEC showed a higher removal performance. The effective diffusion coefficients of copper ion by synthetic Na-P1 zeolites were one hundred and ten times higher than those by a pure zeolite 4A and the zeolite A synthesized from coal fly ash, respectively.

• Journal of Environmental Science International
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• v.21 no.12
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• pp.1463-1468
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• 2012

The purpose of this work is to study the desorption characteristics of water vapor on zeolites saturated with water vapor. Three kinds of zeolite; zeolite 3A, zeolite 4A, and zeolite 5A were used as adsorbent. The desorption experiments with several different temperatures in the range of $90{\sim}150^{\circ}C$ and several different flow rates in the ranges of 0~0.4 L/min on zeolite bed were carried out. The desorption ability of water vapor was most effective on zeolite 5A among the compared zeolites. The higher the desorption temperature of water vapor was, the faster the desorption velocity was. The desorption ability of water vapor with an air supply was higher than that without an air supply. The most appropriate air flow rate was considered as 0.1 L/min.

• 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 the Korean Ceramic Society
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• v.33 no.9
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• pp.1064-1072
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• 1996

The synthetic conditions and characteristics of ZSM-5 type zeolites (ZSM-5/silicalite) for the preparation of the zeolite composite membranes for gas separation were investigated. ZSM-5 zeolites could be synthesized by the hydrothermal treatment of the mixture of colloidal silica sol aluminum nitrate sodium hydroxide and TPABr at a temperature range of 150-17$0^{\circ}C$ in the autoclave. Silicalties were done from the solution of water glass water and TPABr. Their crystalline structures transformed from orthorhombic to monoclinic from and their pore structures of three-dimensional channels were opened as TPABr filling channels was burned off at the calcination temperature of 50$0^{\circ}C$. The specific surface area of the calcined zeolite was about 360 m3/g and its surface property was hydrophobic. Crystal sizes of ZSM-5 and silicalite were 0.5-1.0${\mu}{\textrm}{m}$ and 8-10${\mu}{\textrm}{m}$ respectively having no change due to the calcination. In particular the shape and the size of the ZSM-5 type zeolite were sensitively varied with silica sources and concentrations of reaction solutions/sols.

• Journal of the Mineralogical Society of Korea
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• v.27 no.1
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• pp.41-51
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• 2014

The four natural zeolites collected in Pohang and Gyeongju area, Kyungsangbuk-do, Korea, were characterized by XRD, XRF, DTA, TGA, and CEC analysis. The primary species of these zeolite are heulandite, modenite, illite, and illite in Kuryongpo (Ku), Pohang (Po), Yangbuk-A (Ya-A), and Yangbuk-B (Ya-B) samples. The XRF analysis showed that the four zeolites contain Si, Al, Na, K, Mg, Ca, and Fe. Cation exchange capacity of Kuryongpo (Ku) zeolite was the highest compared to other zeolites. The adsorption capacities of Cs and Sr in the four natural zeolites were compared at $25^{\circ}C$. On the basis of adsorption data Langmuir and Freundlich adsorption isotherm model were confirmed. The equilibrium process was descried well by Langmuir isotherm model. This study shows that Ya-A zeolite is the most efficient for the $Cs^+$ and $Sr^{2+}$ ion adsorption compared to the other natural zeolites.

• Bulletin of the Korean Chemical Society
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• v.30 no.6
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• pp.1274-1284
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• 2009

Single crystals of fully dehydrated and fully $Ca^{2+}$-exchanged zeolites A (|$Ca_6$|[$Si_{12}Al_{12}O_{48}$]-LTA) and X (|$Ca_{46}$| [$Si_{100}Al_{92}O_{384}$]-FAU) were brought into contact with Te in fine pyrex capillaries at 623 K and 673 K, respectively, for 5 days. Crystal structures of Te-sorbed $Ca^{2+}$-exchanged zeolites A and X have been determined by single-crystal X-ray diffraction techniques at 294 K in the cubic space group Pm$\overline{3}$ m (a = 12.288(2) $\AA$) and Fd $\overline{3}$ (a = 25.012(1) $\AA$), respectively. The crystal structures of pale red-brown |$Ca_6Te_3$|[$Si_{12}Al_{12}O_{48}$]-LTA and black coloured |$Ca_{46}Te_8$| [$Si_{100}Al_{92}O_{384}$]-FAU have been refined to the final error indices of $R_1/wR_2\;=\;0.1096/0.2768\;and\;R_1/wR_2$ = 0.1054/ 0.2979 with 204 and 282 reflections for which $F_o\;>\;4{\sigma}(F_o)$, respectively. In the structure of |Ca6Te3|[$Si_{12}Al_{12}O_{48}$]- LTA, 6 $Ca^{2+}$ ions per unit cell were found at one crystallographic positions, on 3-fold axes equipoints of opposite 6-rings. In |$Ca_{46}Te_8$|[$Si_{100}Al_{92}O_{384}$]-FAU, 46 $Ca^{2+}$ ions per unit cell were found at four crystallographically distinct positions: 3 $Ca^{2+}$ ions at Ca(1) fill the 16 equivalent positions of site I, 21 $Ca^{2+}$ ions at Ca(2) fill the 32 equivalent positions of site I’, 10 and 12 $Ca^{2+}$ ions at Ca(3) and Ca(4), respectively, fill the 32 equivalent positions of site II. The Te clusters are stabilized by interaction with cations and framework oxygen. In sodalite units, Te-Te distances of 2.86(10) and 2.69(4) $\AA$ in zeolites A and X, respectively exhibited strong covalent properties due to their interaction with $Ca^{2+}$ ions. On the other hand, in large cavity and supercage, those of 2.99(3) and 2.76(11) $\AA$ in zeolites A and X, respectively, showed ionic properties because alternative ionic interaction was formed through framework oxygen at one end and $Ca^{2+}$ cations at the other end.

• Korean Chemical Engineering Research
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• v.45 no.6
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• pp.547-553
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• 2007

The catalytic cracking of n-octane over FER, MFI, MOR and BEA zeolites was studied by the protolytic cracking mechanism in order to understand the effect of pore structure of zeolites on their product composition and deactivation. The selectivities for $C_3$ and $C_3{^=}$ were high over the zeolites with medium pores due to additional cracking, while those for $C_4$ and $C_4{^=}$, the initial products, were high over the zeolites with large pores. MFI zeolite showed slow deactivation due to small carbon deposit, while FER zeolite with small pores deactivated rapidly with severe carbon deposit. The deactivation of BEA zeolite was slow even with a large amount of carbon deposit, but MOR zeolite showed a rapid deactivation even with a small amount of carbon deposit. The conversion measured along with the time on stream on these zeolite catalysts was simulated by a mechanism based on the simplified reaction path of n-octane cracking and the deactivation related to the pore blockage by carbon deposit.