• Membrane and Water Treatment
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• v.10 no.5
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• pp.353-360
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• 2019

ZSM-5 membrane was prepared on tubular macroporous ${\alpha}$-alumina support using a different synthesis route. The effects of organic template agent and Si/Al ratio of the synthesis gel on morphology, structure, and separation performance of the ZSM-5 membrane used for dehydration of isopropanol were investigated. High water perm-selectivity ZSM-5 membrane with a thickness of about $3.0{\mu}m$ and a low Si/Al ratio of 10.1 was successfully prepared from organotemplate-free synthesis gel with a molar composition of $SiO_2$ : $0.050Al_2O_3$ : $0.21Na_2O$ : NaF : $51.6H_2O$ at $175^{\circ}C$ for 24 h. The ZSM-5 membrane exhibited high pervaporation performance with a flux of $3.92kg/(m^2{\cdot}h)$ and corresponding separation factor of higher than 10,000 for dehydration of 90 wt.% isopropanol/water mixture at $75^{\circ}C$.

• Korean Chemical Engineering Research
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• v.53 no.4
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• pp.425-430
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• 2015

ZSM-5 crystals grew by hydrothermal synthesis method on the surface of foam type porous silicon carbide ceramics which fabricated by polymer replica method. Oxide layer was developed on the surface of the porous silicon carbide ceramics to induce growth of ZSM-5 from the surface. In this study, hydrothermal synthesis was carried out for 7 h at $150^{\circ}C$ using TEOS, $Al(NO_3){\cdot}9H_2O$ and TPAOH as raw materials in the presence of the porous silicon carbide ceramics. X-ray Powder Diffraction (XRD) and Scanning Electron Microscope (SEM) analyses were confirmed $1{\sim}3{\mu}m$ sized ZSM-5 crystals have grown on the surface of porous silicon carbide ceramics. BET data shows that small pores about $10{\AA}$ size drastically enhanced and surface area increased from $0.83m^2/g$ to $30.75m^2/g$ after ZSM-5 synthesis on the surface of foam type porous silicon carbide ceramics.

• Proceedings of the IEEK Conference
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• 2001.10a
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• pp.610-615
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• 2001

Over 800 thousand tons per year (TPY) agricultural biowastes, such as sugar cane bagasse, sugarcane leaf, rice straw, rice husk and corn leaf, are produced in Taiwan. These biomasses are the major types of agricultural wastes and are abundantly available. However, these biowastes cause disposal and landfill problems. Ossification ashes of the agricultural biowastes containing 70-95 % amorphous silica would make the utilization system of agricultural biowaste ashes become highly economically and environmentally attractive. Experimentally, high crystallinity (99%$^{+}$) zeolites ZSM-5 and ZSM-48 synthesized from the reaction mixtures containing a silica source from ashes of these biowastes gasification were investigated. Tetrapropylammonium bromide (TPABr) and 1,6-diamino-hexane (C$_{6}$ DN) were used as structure-directing agents in syntheses of ZSM-5 and ZSM-48, respectively. X-ray powder diffraction (XRD) and scanning electron microscopy/energy dispersive spectroscopy (SEM/EDX) data indicated that ZSM-5 or ZSM-48 with a high crystallinity can be obtained within 48 hours of crystallization in the high pressure (15-20 atm) autoclave at 393-473 K. The Si/Al ratios of synthetic zeolite products were determined by X-ray fluorescence (XRF) and induced couple plasma/mass spectroscopy (ICP/MS). It was observed that the ZSM-5 crystals a.e composed of hexagonal rod-shaped crystals with typically 8-13 пm in size by SEM. In addition, ZSM-48 crystalline materials are composed of spherical aggregates of needle-shaped or rod-like crystals with typically 2-3 пm in diameter and 6-8 пm in length.h.

• Journal of the Korean Chemical Society
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• v.37 no.3
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• pp.317-326
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• 1993

The acid catalytic reactions of toluene with n-propylalcohol were investigated and the adsorption experiments of dialkylbenzene isomers were carried out at 100$^{\circ}C$ over modified HZSM-5 zeolites. ZSM-5 zeolite was synthesized by the hydrothermal reaction using 4-propylammonium ion, sodium aluminate and colloidal silica etc., and several zeolite catalysts, including H-, K-, Sr-, P-Mg-HZSM-5, H-Y and H-mordenite, were prepared by conventional methods. The main reaction products of toluene with n-propylalcohol over HZSM-5 catalyst include not only xylenes, propyltoluenes, but also ethyltoluenes and high para-selectivity among dialkylbenzene isomers was observed on P-Mg-HZSM-5 zeolite. The diffusion coefficients of various p-dialkylbenzenes are nearly the same, about 1 ${times}$ 10$^{-10}$ cm$^2$/sec and that of m-xylene was about one tenth of o-xylene. These reaction and adsorption characteristics were interpreted in the light of the shape-selectivity related to related to the zeolite pore structure and the zeolitic acidity.

• Journal of the Korean Applied Science and Technology
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• v.21 no.3
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• pp.231-237
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• 2004

Ga-MFI was synthesized by a hydrothermal process at atmospheric pressure. The effect of mole ratios of reactants on crystallization was also investigated thoroughly. The characteristics of synthesized Ga-MFI was compared with ZSM-5. The synthesis of Ga-MFI was carried out with five different mole-compositions of $\underline{a}SiO_2-\underline{b}Ga_2O_3-\underline{c}Na_2O-\underline{d}TPA_2o-\underline{e}H_2O$. The synthesized Ga-MFI and ZSM-5 were characterized by XRD and FT-IR. The inorganic cation ($Na^+$) and water played an important role in crystallinity and the organic cation ($TPA^+$) as a template played a great influence on yields. With the increase in the amount of $Ga^{3+}$, crystallization time was increased. With a fixed $SiO_2/Ga_2O_3$ ratio of 400, the optimum reaction condition was obtained at $H_2O/SiO_2$=30${\sim}$35, $Na_2O/SiO_2$=0.5${\sim}$0.6, and $TPA_2O/Na_2O$=1${\sim}$1.25. In these cases, the crystallinity and yield were more than 95% and 90%, respectively. By comparing IR spectrum of Ga-MFI with those of ZSM-5 and silicalite, it was found that Ga-MFI showed a unique peak at 970 $cm^{-1}$, which may be used to identify Ga-MFI from ZSM-5 and silicalite.

• Korean Chemical Engineering Research
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• v.56 no.6
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• pp.909-913
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• 2018

A hydrocarbon trap (HT) plays an important role of controlling vehicle emissions in the so-called cold emission period by holding hydrocarbons until three way catalysts (TWCs) are thermally activated. In this study, we have investigated the adsorption characteristics of cation (H, La, K, and Ag)-exchanged ZSM-5 zeolites for hydrocarbons (propylene, n-butane, and toluene) by DFT (density functional theory)-based computational chemistry. Cation exchange is to improve the hydrothermal stability of zeolites and their adsorption capacity, thereby rendering cation-exchanged zeolites promising materials for HT. The idea of cluster approximation makes the calculation of adsorption energies superbly efficient in computation. The results showed that Ag-exchanged ZSM-5 would be the best for the adsorption of all three adsorbates, without often encountered Ag oxidation in experiments. Besides, the hydrothermal stability of La-exchanged ZSM-5 was confirmed from the change of geometrical parameters by cation exchange, and it showed good adsorption capacity for propylene and toluene. Hydrogen-exchanged ZSM-5 was also good for hydrogen adsorption, but had poor hydrothermal stability.

• Bulletin of the Korean Chemical Society
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• v.32 no.5
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• pp.1703-1708
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• 2011

ZSM-5-$SO_3H$ efficiently catalyzed the one-pot three-component Mannich reaction of aldehydes, anilines, and ketones. ${\beta}$-Aminocarbonyl compounds were obtained in reasonable yields and excellent stereoselectivities when the reaction was carried out at room temperature under solvent-free conditions. Simple experimental conditions and product isolation procedure makes this protocol potential for the development of clean and environment-friendly strategy for the synthesis of ${\beta}$-amino-ketones. The catalyst was recovered and reused for subsequent runs.

• Journal of the Korean Chemical Society
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• v.33 no.2
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• pp.177-184
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• 1989

Acidic properties of ZSM-5 zeolite catalysts were investigated by temperature-programmed desorption technique and ir spectroscopy. Ammonia t.p.d. pattern of HZSM-5 showed three different states, designated as ${\alpha}$,${\beta}$ and ${\gamma}$. The amount of ${\gamma}$-state decreased with increasing $SiO_2/Al_2O_3$ ratio, and upon cation-exchanging with alkali cations. From the ir adsorption spectra of absorbed pyridine and the reaction study of toluene alkylation, the ${\gamma}$-state could be explained to be due to the strong Bronsted acid sites of H-ZSM-5. Also they showed that the interaction between alkali cation-exchanged ZSM-5 and bases, i.e. $NH_3$ and pyridine, was increasing with decreasing the size of cations.

• Bulletin of the Korean Chemical Society
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• v.25 no.5
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• pp.681-686
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• 2004

Ti-ZSM-5 prepared by secondary synthesis, from the reaction of H-ZSM-5 with vapor phase $TiCl_4$, was characterized with several physicochemical techniques including FT-IR and UV/VIS-DRS. It was found that zeolite structure, surface area and pore volume did not change, and the framework aluminum could not be replaced by titanium atom during the secondary synthesis of Ti-ZSM-5. The incorporation of titanium into the framework might be due to reaction of $TiCl_4$with the silanol groups associated with defects or surface sites. The formation of extra-framework titanium could not be avoided, unless the samples were further treated by water vapor at 550 $^{\circ}C$ or higher temperature. High temperature steam treatment of Ti-ZSM-5 prepared by chemical vapor deposition with $TiCl_4$was efficient to prevent the formation of non-framework titanium species. Ti-ZSM-5 zeolites prepared in this work contained only framework titanium species and exhibited improved catalytic property close to TS-1 prepared by hydrothermal synthesis.

• Journal of Energy Engineering
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• v.6 no.1
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• pp.26-33
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• 1997

Highly crystalline Cu-ZSM5 was prepared without using organic templates. Several ion exchange treatments between Na$\^$＋/ and Cu$\^$2＋/ brought about excess loading of copper ions on the ZSM5 zeolite and the resultant zeolite was active for the decomposition of NO. This indicates that the copper ions excessively loaded on the ZSM5 zeolite are effective for the NO decomposition. When oxygen was added to a reactants, the conversion of NO decreased. NO, O$_2$TPD experiments explained that the active sites for NO decomposition and the adsorption sites of O$_2$, were the same. O$_2$, at the surface of ZSM5 zeolite was desorbed incompletely after pretreatment at 500$^{\circ}C$, and CU-ZSM5 pretreated with H$_2$at 500$^{\circ}C$ showed promoted activity at the start of reaction. Thus, it seems clear that O$_2$, adsorbed ai the surface of catalyst inhibits the catalytic activity.