• Applied Chemistry for Engineering
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• v.27 no.1
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• pp.62-67
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• 2016

In this study, a pellet-type adsorbent was prepared by using the water-treatment sludge as a raw material, and its physical and chemical properties were analyzed through $N_2$-adsorption, XRD, XRF, and $NH_3$-TPD measurements. Adsorption performance for gaseous ammonia and formaldehyde was compared between the pellet-type adsorbents prepared from water-treatment sludge and the impregnated activated carbon. Although the surface area and pore volume of the pellet-type adsorbent produced from water-treatment sludge were much smaller than those of the impregnated activated carbon, the pellet-type adsorbent produced from water-treatment sludge could adsorb ammonia gas even more than that of using the impregnated activated carbon. The pellet-type adsorbent prepared from water-treatment sludge showed a superior adsorption capacity for ammonia which can be explained by chemical adsorption ascribed to the higher amount of acid sites on the pellet-type adsorbent prepared from water-treatment sludge. In the case of formaldehyde adsorption, the impregnated activated carbon was far superior to the adsorbent made from the water-treatment sludge, which can be attributed to the increased surface area of the impregnated activated carbon.

• Proceedings of the KAIS Fall Conference
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• 2012.05a
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• pp.30-32
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• 2012

본 연구에서는 Cu, Mn을 함침 시킨 상용 제올라이트13X 촉매에 CO 산화 전환 반응에 영향을 연구하였다. 촉매 제조는 담지량별로 Cu, Mn을 서로 다른 비율로 물리 혼합하여 상용 제올라이트에 담지하였다. 함침방법은 과잉용액 함침법을 사용하였고, 건조 후 공기분위기에서 소성하여 산화물 형태로 담지하였다. 기본적인 촉매 특성은 X-선 회절분석, 질소흡탈착 등온곡선을 이용하여 기공크기, 기공부피, 비표면적을 구하였으며, FT-IR, 주사현미경, $NH_3$-TPD/TPR, EDX로 특성을 분석하였다. 촉매 산화반응 실험은 고정층 반응기에서 수행하였으며, 외경1/4 inch(내경 4 mm)석영관에 촉매를 중진하고 Gas Chromatograph로 배출가스를 측정하여 Cu-Mn 제올라이트 촉매의 일산화탄소 산화반응을 연구하였다. 일산화탄소 농도, 온도 및 공간속도, Cu-Mn 함량 비율에 따른 산화반응 실험을 수행하여 최적 산화조건과 촉매를 도출하였다.

• Korean Chemical Engineering Research
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• v.51 no.4
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• pp.418-425
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• 2013

The catalytic conversion of ethanol to aromatic compounds ETA was studied over ZSM-5 heterogeneous catalysts. The effect of reaction temperature, weight hourly space velocity (WHSV), and addition of water and methanol, which are the potential impurities of bio-ethanol, on the catalytic performance was investigated in a fixed bed reactor. Commercial ZSM-5 catalysts having different Si/$Al_2$ ratios of 23 to 280 and modified ZSM-5 catalysts by addition of metal (Zn, La, Cu, and Ga) were used for the activity and stability tests in ETA reaction. The catalysts were characterized with ammonia temperature programmed desorption ($NH_3$-TPD) and nitrogen adsorption-desorption techniques. The results of catalytic performance revealed that the optimal Si/$Al_2$ ratio of ZSM-5 is about 50~80 and the selectivity to aromatic compounds decreases in the order of Zn/La > Zn > La > Cu > Ga for the modified ZSM-5 catalysts. Among these catalysts from the ETA reaction, Zn-La/ZSM-5 showed the best catalytic performance for the ETA reaction. The selectivity to aromatic compounds was 72% initially and 56% after 30 h over the catalysts at reaction temperature of $437^{\circ}C$ and WHSV of $0.8h^{-1}$.

• Applied Chemistry for Engineering
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• v.33 no.3
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• pp.328-334
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• 2022

For the study of environmental application of natural zeolites (NZ) and red mud (RM), which are discharged from various industrial fields, the catalytic ozonation of 2-butaone (methyl ethyl ketone, MEK) was performed using the Mn-loaded NZ prepared according to the Mn content of 1, 3, 5, 7, and 10 wt%. By the addition of Mn to NZ, the BET (Brunaure-Emmett-Teller) specific surface area of Mn/NZ catalysts decreased while the ratio of Mn³⁺/[Mn³⁺+Mn⁴⁺] intensively increased. Besides, the addition of Mn component to NZ increased the ratio of adsorbed oxygen (O_adsorbed) toward lattice oxygen (O_lattice), O_adsorbed/O_lattice from 0.076 of NZ to 0.465 of 10 wt% Mn/NZ according to the amount of Mn. It is known that the proportion of two species, Mn³⁺ and O_adsorbed, would greatly affect the catalytic activity. However, the balancing between the paired species, Mn³⁺ vs. Mn⁴⁺ and O_adsorbed vs. O_lattice might be more essential for the catalytic ozonation of MEK at room temperature. Among the Mn-loaded NZ catalysts, the 3 wt% Mn/NZ showed the best activity for the removal of MEK and ozone. The 5, 7, and 10 wt% Mn/NZ catalysts are slightly inferior to the 3 wt% Mn/NZ. Compared to the pristine NZ, the Mn/NZ catalysts showed better activity for the catalytic ozonation of MEK. In addition, the 3 wt% Mn/NZ was confirmed to have the most available acid sites among them by the analysis of NH₃-TPD (temperature programmed desorption). This might be the major reason for the best catalytic activity of 3 wt% Mn/NZ together with the adjusted distribution ratios of Mn³⁺/Mn⁴⁺ and O_adsorbed/O_lattice. Considering the result of 3 wt% Mn/NZ, the 3 wt% Mn/RM was prepared to perform the catalytic activity for the removal of MEK and ozone, but the efficiency of 3 wt% Mn/RM was significantly lower than that of the 3 wt% Mn/NZ.

• Transactions of the Korean hydrogen and new energy society
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• v.26 no.5
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• pp.423-430
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• 2015

$Cu/ZnO/Al_2O_3$ catalysts for water gas shift (WGS) reaction were synthesized by co-precipitation method with the fixed molar ratio of Cu/Zn/Al precursors as 45/45/10. Copper and zinc precursor were added into sodium carbonate solution for precipitation and aged for 24h. During the aging period, aluminum precursor was added into the aging solution with different time gap from the precipitation starting point: 6h, 12h, and 18h. The resulting catalysts were characterized with SEM, XRD, BET surface measurement, $N_2O$ chemisorption, TPR, and $NH_3$-TPD analysis. The catalytic activity tests were carried out at a GHSV of $27,986h^{-1}$ and a temperature range of 200 to $400^{\circ}C$. The catalyst morphology and crystalline structures were not affected by aluminum precursor addition time. The Cu dispersion degree, surface area, and pore diameter depended on the aging time of Cu-Zn precipitate without the presence of $Al_2O_3$ precursor. Also, the interaction between the active substance and $Al_2O_3$ became more stronger as aging duration, with Al precursor presented in the solution, increased. Therefore, it was confirmed that aluminum precursor addition time affected the catalytic characteristics and their catalytic activities.

• 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.

• Clean Technology
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• v.21 no.2
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• pp.130-139
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• 2015

The NO oxidation process has been applied to improve a removal efficiency of NO included in exhaust gas. In this study, to produce a dry oxidant for the NO oxidation process, the catalytic H₂O₂ decomposition method was proposed. A variety of the heterogeneous solid-acidic Mn-based catalysts were prepared for the catalytic H₂O₂ decomposition and the effect of their physico-chemical properties on the catalytic H₂O₂ decomposition were investigated. The results of this study showed that the acidic sites of the Mn-based catalysts has an influence on the catalytic H₂O₂ decomposition. The Mn-based catalyst having the abundant acidic sites within the wide temperature range in NH₃-TPD shows the best performance for the catalytic H₂O₂ decomposition. Therefore, the NO oxidation efficiency, using the dry oxidant produced by the H₂O₂ decomposition over the Mn-based catalyst having the abundant acidic properties under the wide temperature range, was higher than the others. As a remarkable result, the best performances in the catalytic H₂O₂ decomposition and NO oxidation was shown when the Mn-based Fe₂O₃ support catalyst containing K component was used for the catalytic H₂O₂ decomposition.

• Clean Technology
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• v.28 no.4
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• pp.269-277
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• 2022

With the recent development of the biological enzymatic reaction industry, lactic acid (LA) can be mass-produced from biomass sources. In particular, a catalytic process that converts LA into acrylic acid (AA) is receiving much attention because AA is used widely in the petrochemical industry as a monomer for superabsorbent polymers (SAP) and as an adhesive for displays. In the LA conversion process, NaY zeolites have been previously shown to be a high-activity catalyst, which improves AA selectivity and long-term stability. However, NaY zeolites suffer from fast deactivation due to severe coking. Therefore, the aim of this study is to modify the acid-base properties of the NaY zeolite to address this shortcoming. First, base promoters, Ca ions, were introduced to the NaY zeolites to tune their acidity and basicity via ion exchange (IE) and incipient wetness impregnation (IWI). The IWI method showed superior catalyst selectivity and stability compared to the IE method, maintaining a high AA yield of approximately 40% during the 16 h reaction. Based on the NH₃- and CO₂-TPD results, the calcium salts that impregnated into the NaY zeolites were proposed to exit as an oxide form mainly at the exterior surface of NaY and act as additional base sites to promote the dehydration of LA to AA. The NaY zeolites were further treated with KOH before calcium impregnation to reduce the total acidity and improve the dispersion of calcium through the mesopores formed by KOH-induced desilication. However, this KOH treatment did not lead to enhanced AA selectivity. Finally, calcium loading was increased from 1wt% to 5wt% to maximize the amount of base sites. The increased basicity improved the AA selectivity substantially to 65% at 100% conversion while maintaining high activity during a 24 h reaction. Our results suggest that controlling the basicity of the catalyst is key to obtaining high AA selectivity and high catalyst stability.