• Title/Summary/Keyword: Dealuminated Zeolite

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A Study on Dealumination of NaY Zeolite and its VOCs Adsorption Properties (Dealumination에 의한 NaY zeolite의 개질과 VOCs 흡착특성에 관한 연구)

  • Kang, Shinchoon;Lee, Hwayeol;Park, Yeungho
    • Korean Chemical Engineering Research
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    • v.53 no.3
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    • pp.339-349
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    • 2015
  • In this work, DAY (Dealuminated Y-type) zeolites were prepared to be used as easily regenerable and thermally stable adsorbent substituting activated carbon. NaY zeolites were transformed into DAY zeolites through ion exchange, calcination, steaming, and acid leaching. Calcination temperature and time, and steaming time were changed to increase the Si/Al ratio and maintain crystallinity. Adsorption of VOCs were done for prepared DAY, commercial NaY and Hisiv 1000 in air with relative humidity of 50%. The DAY zeolite prepared by calcination at $520^{\circ}C$ for 4 hrs and steaming for 7 hrs had a same structure and a Si/Al ratio of 80.4. Its adsorption capacity for water vapor was 10% of NaY, indicating its hydrophobicity. Its adsorption capacity for MEK was 0.8 times of Hisiv 1000, that for toluene 1.6 times, and that for EA 1.3 times.

Preparation and Catalytic Properties of Vanadium-Containing MFI Type Zeolite (바나듐 함유 MFI형 제올라이트의 제조 및 촉매적 특성)

  • Kim, Geon Joong;Ko, Wan Suk;Cho, Byung Rin
    • Applied Chemistry for Engineering
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    • v.5 no.2
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    • pp.361-372
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    • 1994
  • Vanadium containing MFI type zeolites have been prepared hydrothermally or by the impregnation method with $NH_4VO_3$ solution after dealumination of HZSM-5. Incorporation of vanadium into the framework of zeolite has been demonstrated by XRD, DTA, FT-IR and ESR analyses. Upon $NH_4VO_3$ impregnation and calcination of dealuminated zeolite, vanadium substitution into the framework could be performed like a hydrothermally synthesized zeolite. Vanadium in zeolite is able to pass redox cycles at high temperatures, and it is shown that vanadium is probably fixed and atomically dispersed in the structure of zeolite. The catalytic benzene hydroxylation, hexanes and alcohols oxidation were used for evaluating the properties of vanadium incorporated MFI zeolite.

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Dealumination of $NH_4Y$-Zeolite to Convert to the Hydrophobic Zeolite by High-Temperature Steam Treatment (소수성 제올라이트로의 변환을 위한 고온 수증기처리에 의한 $NH_4Y$-제올라이트의 탈알루미늄)

  • Kim, Jin-Young;Jeon, Dong-Hwan;Chung, Byung-Hwan;Mo, Se-Young
    • Journal of Korean Society of Environmental Engineers
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    • v.27 no.4
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    • pp.420-430
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    • 2005
  • This study was performed to change the hydrophilic $NH_4Y$-zeolite to the hydrophobic one for removal of VOCs by removing the $Al^{3+}$ in the zeolite-structure to increase the Si/Al ratio, for which the three pelleted $NH_4Y$-zeolite samples were contacted separately with the steam of $400^{\circ}C$, $500^{\circ}C$ and $600^{\circ}C$, respectively, in a stainless steel column for 4 hours. Then extraction of the ex-structure aluminum of the hydrolyzed zeolites with the nitric acids of 0.25, 0.50, 0.75, and 0.10 M at $90^{\circ}C$ in 500 mL-flasks, respectively, according to steam temperature were followed. XRD analysises of the dealuminated zeolites showed that the peaks of the zeolites that had been hydrolyzed with the steams of both $500^{\circ}C$ and $600^{\circ}C$ are distorted more with the increase of the concentration of nitric acid used for extraction of the ex-structure aluminums, however, those hydrolyzed with steam of $400^{\circ}C$ became amorphous phase when treated with the all nitric acids of four concentrations. Also the EDX analysises showed that the BET surface areas and TPVS of the zeolites that had been hydrolyzed with the steam of $600^{\circ}C$ were increased with the concentration of the nitric acid when the nitric acids of 0.25 M and 0.5 M had been used but decreased when the nitric acids of 0.75 M and 1.0 M had been used. These results led to the conclusion that both the $600^{\circ}C$ and $500^{\circ}C$-steam and the 0.5 M-nitric acid are appropriate to change the hydrophilic $NH_4Y$-zeolites to the hydrophobic one, which were proven by the measurement of the benzene and tolune-adsorbing capacities showing the same trend as the BET surface area and TPV The Si/Al ratios and water-adsorbing capacities of the dealuminated zeolites were increased and decreased, respectively, with the concentration of the nitric acids so that it showed that the hydrophobicity is increased.

Transformation of Korean Natural Zeolite to Faujasite NaX (한국산 천연 제올라이트로부터 제올라이트 NaX로의 전환)

  • Park, Yun-Hee;Ha, Baik-Hyon
    • 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.

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Adsorption Characteristics of Nitrogen monoxide over Dealuminated and Alkali/Alkaline-earth Metal ion Exchanged Y-Zeolites (탈알루미늄 및 알칼리/알칼리토금속 양이온을 교환한 Y형 제올라이트의 NO흡착 특성)

  • Kim, Cheol-Hyun;Lee, Chang-Seop
    • Journal of the Korean Institute of Gas
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    • v.9 no.4 s.29
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    • pp.17-25
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    • 2005
  • The dealuminated and alkali/alkaline-earth metal exchanged Y-zeolites were prepared as a catalyst. Elemental compositions and structures of the prepared catalysts were analyzed by the various spectroscopic techniques such as inductively coupled plasma-atomic emission spectroscopy(ICP-AES), X-ray fluorescence(XRF) and X-ray diffraction(XRD), and the desorption behaviors of adsorbed species on the catalyst surfaces were investigated via NO-TPD experiment. Comparing with the composition of the starting material of NaY zeolite, the magnitudes of Si/Al ratio in catalytic materials were increased after dealumination. The Si/Al ratio of catalytic materials after dealumination followed by Cs and Ba cation exchange were additionally decreased. Dealumination to catalysts induced a destruction of basic frame due to a detachment of aluminum, which results in reducing framework structure, while increasing non-framework structure. This phenomenon becomes more serious with increasing time of steam treatment and even more significant for the cation exchanged catalysts. In NO-TPD experiments, the desorption peaks of NO which indicates an activity point of catalysts shifted to the low temperature region after dealumination and cation exchange. The desorption peaks of the NO-TPD profiles taken after steam treatment also shifted to the low temperature region as the steam treatment time increased. In dealuminated and cation exchanged Y-zeolites, the catalytic activities were more influenced by exchanged cation and the formation of non-framework structure.

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Reactions of n-Butane of Pd-Zeolite Y Catalyst (Pd-Zeolite Y 촉매에서의 n-Butane의 반응)

  • Chon Hakze;Oh Seung Mo
    • Journal of the Korean Chemical Society
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    • v.23 no.3
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    • pp.161-164
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    • 1979
  • The effect of acidity and the metal surface area of the Pd loaded zeolite catalysts; prepared from $Ca^{2+}-,\;La^{3+}-,\;NH_4^+-$exchanged Y and dealuminated HY was studied for the reaction of n-butane. The amount of strong acid site determined by the temperature programmed desorption of ammonia increased in the order NaY < CaY < LaY. Total amount of acid site decreased with increasing degree of dealumination, but the portion of strong acid site increased with increasing $SiO_2/Al_2O_3$ ratio. The effective metal surface area determined by the CO adsorption technique was large for those zeolite catalysts having strong acidity. It was found that conversion of n-butane was strongly dependent on the acidity and the effective metal surface area of the catalysts. The fact that the conversion of n-butane was proportional to the effective metal surface area suggests that the dehydrogenation by metallic component is the primary step in the reaction of n-butane.

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Reactions of m-Xylene over Mordenite Catalysts (모더나이트 촉매에서의 m-크실렌의 반응)

  • C. H. Yune;B. J. Ahn;Hakze Chon
    • Journal of the Korean Chemical Society
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    • v.25 no.1
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    • pp.26-29
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    • 1981
  • Reactions of m-xylene were studied in a fixed-bed type micropulse reactor over cation-exchanged dealuminated mordenite and zeolite Y catalysts. Over H-mordenite catalysts higher catalyst pretreatment temperature as well as dealumination resulted in the increase of the formation of disproportionation product. $Ba^{2+}- and Mg^{2+}-$exchanged mordenite catalysts showed the shape selectivity in the disproportionation reaction of m-xylene, that is, the formation of trimethylbenzene decreasing sharply as the degree of cation exchange increased.

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A study on the synthesis and crystal growth of the MFI type zeolite, silicalite under highgravity (고중력에서 MFI 형 Zeolite 인 Silicalite 결정의 합성 및 성장에 관한 연구)

  • Kim, Wha-Jung;Lee, Joon
    • Applied Chemistry for Engineering
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    • v.2 no.2
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    • pp.97-107
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    • 1991
  • Highly-siliceous dealuminated zeolite, silicalite(end member of ZSM-5) was synthesized from a batch composition of 2.55 $Na_2O-5.0$ TPABr-$100SiO_2-2800H_2O $ at $180^{\circ}C$ and at times ranging from one to seven days of reaction time. Autoclaves containing the synthesis mixture were centrifuged within the specially-equipped convection oven to provide an elevated gravitational force field like 30 and 50 G. Tests were also conducted at normal gravity. For synthesis performed under elevated gravities, average and maximum crystal sizes were substantially greater than those synthesized under normal gravity and product yields were also found to be affected by elevated gravity ; that is, product yields were substantially enhanced under elevated gravity from 4 % to 55 % with respect to normal gravity. The average crystal sizes of silicalite synthesized at normal gravity were 50 to $70{\mu}m$ over an entire range of reaction time, one to seven days while the average crystal sizes synthsized under elevated gravities, 30 and 50 G, were 160 to $190{\mu}m$ respectively. For the elevated gravity, in particular, two separate nucleations and growths were observed. For examples, at 50G, large crystals of $200{\mu}m$ were produced through the second growing stage after 5 days of reaction following the rapid first growing stage where fairly large crystals of $135{\mu}m$ were produced only in 2 days of reaction. The maximum crystal sizes obtained through the above two growing stages were 190 and $300{\mu}m$, respectively. A discussion of how elevated gravity affects nucleation, growth, yield and crystal size of silicalite is presented.

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Catalytic Cracking of Triphenylmethane on Alumina Mixed with Mordenite Formed Secondary Pore (2차세공이 형성된 모더나이트와 알루미나를 혼합한 촉매상에서 Triphenylmethane의 분해반응)

  • Lee, Kyong-Hwan;Choi, Jun-Woo;Ha, Baik-Hyon
    • Applied Chemistry for Engineering
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    • v.8 no.6
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    • pp.1048-1053
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    • 1997
  • Modified mordenites by HF treatement, which have different $SiO_2/Al_2O_3$ ratio, and those mixed with $\gamma$-alumina are prepared and used for catalytic cracking of triphenylmethane(TPM) in micro-activity tester(MAT). Dealumination of mordenites decreased the acid content but developed secondary mesopores. The conversion and the selectivity of benzene over modified mordenites with the mesopores were increased. However, for the further dealuminated mordenites, they decreased due to the destruction of pore structure and low acid amount. Accordingly, the maximum cracking activity and the maximum selectivity of benzene were obtained about 17 $SiO_2/Al_2O_3$ ratio of modified mordenites. The modified mordenites mixed with alumina enhanced the cracking activity of TPM compared with the pure mordenites. It can be explained that TPM is cracked at active sites with in large pores of alumina firstly and further cracked into small molecules in zeolite pores as step mechanism of catalytic cracking.

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Adsorption Characteristics of Nitrogen Monoxide on Y-type and ZSM-5 Zeolites Exchanged with Alkali/Alkaline-earth Metal Cation (알칼리/알칼리토금속 양이온을 치환한 Y형 및 ZSM-5 제올라이트의 NO 흡착 특성)

  • Kim, Cheol Hyun;Lee, Chang Seop
    • Applied Chemistry for Engineering
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    • v.16 no.6
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    • pp.857-864
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    • 2005
  • Dealuminated and alkali/alkaline-earth metal exchanged Y-type and ZSM-5 zeolites were prepared as catalytic materials. Comparing with the composition of starting material, the magnitude of Si/Al ratio was increased after dealumination and cation exchange process. The ratio of Si/Al on surface was appeared to be larger than that in bulk. The destruction of basic frame in catalysts observed was understood to be due to a detachment of aluminum, which results in reducing framework while increasing non-framework. This phenomenon becomes more serious with increasing time of steam treatment and even more significant for the cation exchanged catalysts. The desorption peaks of the NO-TPD profiles taken after dealumination and cation exchanged Y-type and ZSM-5 zeolites shifted to the low temperature region. It was also found that the longer the steam treatment time, the degree of shift toward low temperature region was increased. The catalytic activities are dependent on the nature of cation exchanged, the ratio of Si/Al and the ratio of framework/non-framework by a change in basic frame.