• Korean Chemical Engineering Research
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• v.50 no.3
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• pp.435-441
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• 2012

The direct conversion of cellulose into polyols in $H_2$ was examined over Pt catalysts supported on various zeolites, viz., mordenite, Y, ferrierite, and ${\beta}$. For comparison, Pt catalysts supported on ${\gamma}-Al_2O_3$, $SiO_2-Al_2O_3$, and $SiO_2$ were also tested. The physical properties of the catalysts were probed with $N_2$ physisorption. The surface acidity was measured with temperature programmed desorption of ammonia ($NH_3$-TPD). The Pt content was quantified with inductively coupled plasma-atomic emission spectroscopy (ICP-AES). The Pt dispersion was determined with CO chemisorptions and transmission electron microscopy (TEM). The conversion of cellulose appeared to be mainly dependent on the reaction temperature and reaction time because it depends on the concentration of $H^+$ ions reversibly formed in hot water. Pt/H-mordenite (20) showed the highest yield to polyols among the tested catalysts. Pt/H-zeolite was superior to Pt/Na-zeolite for this reaction. The polyol yield was dependent on the surface acid density and the external surface area.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.24 no.1
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• pp.15-20
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• 2014

In this research, the geopolymer was fabricated using municipal solid waste incineration ash (denoted as MSWIA) slag and alkali activator, NaOH and its properties were analyzed. Particularly, the effects of NaOH molarity, particle size of MSWIA, and liquid/solids ratio on the compressive strength of geopolymers were investigated. The compressive strength of geopolymers fabricated increased with finer grain size of MSWIA, and optimum value of the liquid/solids ratio was identified as 0.13. As the molarity of the NaOH increased, the compressive strength of geopolymers was increased. Even more the 20 M of NaOH, but the strength was not increased. The calcium aluminum silicate and calcium aluminum silicate hydrate zeolites were generated in the geopolymer fabricated with more than 20 M of NaOH, with some unreacted silica and unknown crystals remained. The highest compressive strength, 163 MPa, of geopolymer was appeared at conditions of curing temperature $70^{\circ}C$, and 20 M of NaOH, indicating that the high concentration of NaOH accelerates the geopolymer reaction and dense microstructure. The high-strength geopolymer fabricated in the present study is expected to contribute significantly to develop the field of cement alternative substances and to improve the recycling rate of MSWIA slag.

• Journal of Korean Society of Environmental Engineers
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• v.27 no.8
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• pp.807-812
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• 2005

This study is to investigate the correlation of pore structures of Zeolite 5As modified with acid and their adsorption capacity of toluene vapor using the dynamic adsorption method. The experimental results showed that the modification with acid allowed more micropores and enlarged the existing pores. Toluene vapor was mainly adsorbed on the surface of pores over $15\;{\AA}$ in diameter. The equilibrium adsorption capacity of toluene vapor of the modified Zeolite 5As was in the range of $15{\sim}70\;mg/g$ and the equilibrium adsorption capacity was increased to f times than that of the Zeolite 5A. The correlation between the total cumulative surface area and the equilibrium adsorption capacity was hard to say linear. The correlation in diameter between the cumulative surface area in the range of over $15\;{\AA}$ and the equilibrium adsorption capacity gate the highest correlation factor of 0.997.

• Proceedings of the Membrane Society of Korea Conference
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• 1997.10a
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• pp.51-52
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• 1997

1. 서론 : 폴리이미드는 우수한 기계적 강도와 열적, 화학적 안정성으로 인해 최근 막분리 재료로 많이 연구 검토되고 있다. 대부분의 폴리이미드는 비교적 높은 선택도를 가지고 있으나 투과계수가 떨어지는 단점을 지니고 있어소 이를 극복하기 위한 많은 연구가 진행되어 왔다. 그 결과 투과계수를 크게 증가시킨 폴리이미드를 함성하였으나 선택도는 감소하여 투과특성의 상위한계를 넘지는 못하였다. 이 한계를 극복하기 의해서 복합잴를 이용하거나 UV, 플라즈마 처리에 의한 고분자막의 수식 등 많은 방법들이 연구되고 있다. 본 연구는 NaX형 제올라이트를 폴리이미드에 혼화시킨 막으로 산소/질소의 분리투과특성의 개선을 시도하였으며, NaX형 제올라이트와 폴리이미드 혼화방법, 혼화비율 등이 기체투과특성에 미치는 영향을 고찰하였다. 본 실험에 사용된 NaX형 제올라이트는 직접 합성하여 사용하였다. 폴리이미드는 2,3,5,6-Tetramethyl-1,4-phenylenediamine(p-TeMPD)과 (3,3,4,4'-dicarboxyphenyl)-hexafluoropropene-dianhydride(6FDA)로 합성한 6FDA-p-TeMPD 폴리이미드를 사용하였고, 그 투과계수는 122Barrer, 선택도$\alpha$$_{N_2/O_2}$ = 3.4이다.

• 한국신재생에너지학회:학술대회논문집
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• 2009.11a
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• pp.524-526
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• 2009

바이오디젤은 식물성 기름이나 동물성 지방과 같은 재생 가능한 원료로부터 전이에스테르화 반응을 통해 생산되는 대체 연료이다. 본 연구에서는 NaX 제올라이트 촉매에 염기성 물질인 KOH를 담지한 후 소성온도에 따라 제조된 촉매를 사용하여 바이오디젤 제조 특성을 조사하였다. 제조된 촉매의 결정구조와 성분을 분석하기위해 XRD, SEM 을 이용하였으며, 표면적을 측정하기 위해 BET 를 사용하였다. 실험결과 소성온도가 $500^{\circ}C$일 때 30wt% KOH/NaX 제올라이트 촉매내 K 함량이 가장 높았고, 이때 70%이상의 높은 바이오디젤 수율을 얻을 수 있었다.

• 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.

• Korean Chemical Engineering Research
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• v.47 no.4
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• pp.488-494
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• 2009

Zeolite 4A was prepared by new synthesis method, 2-step crystallization, for enhancement of oil absorption capacity. Vietnamese sand and $NaAlO_2$ solution from natural bauxite were used as raw materials in stead of conventional cullet and $Al(OH)_3$ to reduced the processing cost. Some dissolved organics in $NaAlO_2$ solution were removed by activated carbon. Synthetic method was progressed by 1) reacting the raw materials at $55^{\circ}C$, 4 hr with the ratio of Si/Al to 1.15, and 2) reacting at $65^{\circ}C$, 5 hr with reducing the ratio of Si/Al to 0.98. New method can easily control the particle size, aggregation, surface polarity, and enhanced the whiteness of the products. The prepared zeolite 4A shows excellent oil absorption capacity(O.A.C>50 ml/100 g) as well as equal value with calcium ion exchange capacity, and proves the 2-step crystallization is the economic and effective process for the preparation of zeolite 4A.

• Korean Journal of Materials Research
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• v.10 no.3
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• pp.191-198
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• 2000

A serpentine mineral was treated in hydrochloric acid solution to obtain amorphous silica residue with high surface area. The highly porous silica with aluminum hydroxide and sodium hydroxide was hydrothermally reacted in an autoclave. A numerous experiments were performed in terms of reaction time, temperature, alkalinity, and calcinations temperature. As a result, a ZSM-5 zeolite of the highest crystallinity was produced under such conditions as $^170{\circ}C$ of the reaction temperature, 24 hours of the reaction time, and $11.7Na_2O{\cdot}Al_2O_3{\cdot}90SiO_2{\cdot}3510H_2O{\cdot}10.8(TPA)_2O$ the composition along with 3 hours of the calcinations at $600^{\circ}C$.

• Journal of the Mineralogical Society of Korea
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• v.4 no.2
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• pp.99-107
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• 1991

Three fully dehydrated fully Rb+-exchanged zeolite A single crystals have been prepared by the reduction of all Na+ ions in dehydrated Na12-A by rubidium vapor at various experimental conditions (220 $\leq$ T $\leq$ 33$0^{\circ}C$, 2 $\leq$ t $\leq$24 hours, and 0.1 $\leq$ PRb $\leq$ 1.1 Torr). Their structures were determined by single-crystal X-ray diffraction methods in the space group {{{{ RHO }}m3m (a=12.245(3) A) at 22(1)$^{\circ}C$. In these structures 12.6(2) to 13.5(2) Rb species are found per unit cell, more than the 12 Rb+ ions needed to balance the anionic charge of the zeolite framework, indication that the sorption of Rb0 has occurred. In each structure, three Rb+ ions per unit cell are located at the centers of 8-rings. Beyond that, the fractional occupancies observed are simply explained by two unit cell arrangments. In one, two Rb+ ions are in the sodalite unit near opposite 6-rings, six are in the large cavity near 6-ring, and one is in the large cavity near a 4-ring. In the other, three Rb species in the sodalite cavity (forming a triangle 3.7 A on an edge) each bond (3.4 A) through a 6-ring to an Rb species in the large cavity to give an (Rb6)4+ cluster of symmetry 3m (C3V). Five additional Rb+ ions fill the remaining large-cavity 6-ring sites.

• Analytical Science and Technology
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• v.15 no.6
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• pp.540-549
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• 2002

The arrangement of encapsulated Ar atoms in the molecular-dimensioned cavities of fully dehydrated zeolite A of unit-cell composition $Cs_3Na_8HSi_{12}Al_{12}O_{48}$ ($Cs_3$-A) has been studied crystallographically to probe the confinement effect of guest species in microporous environment. Atoms of Ar were encapsulated in the cavities of $Cs_3$-A by treatment with 410 atm of Ar at $400^{\circ}C$ for two days, followed by cooling at room temperature. The crystal structure of $Cs_3Na_8H$-A(4Ar) ($P_e$ = 410 atm, $a=12.245(2){\AA}$, $R_1=0.0543$, and $R_2=0.0552$) has been determined by single crystal X-ray diffraction technique in the cubic space group $Pm\bar{3}m$ at 21 (1) $^{\circ}C$ and 1 atm. Encapsulated Ar atoms are distributed in three crystallographic distinct positions: 1.5 Ar atoms per unit cell opposite 6-rings, 1.5 opposite four-rings in the large cavity, and finally 1.0 in the sodalite-unit. The possible structures of argon clusters, such as $Ar_2$, $Ar_3$, and $Ar_4$, are proposed.