• Bulletin of the Korean Chemical Society
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• v.35 no.1
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• pp.141-146
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• 2014

A series of bimetallic Cu-Zn/$SiO_2$ catalysts were prepared via thermal decomposition of the as-synthesized $CuZn(OH)_4(H_2SiO_3)_2{\cdot}nH_2O$ hydroxides precursors. This highly dispersed Cu-solid base catalyst is extremely effective for hydrogenation of ethyl acetate to ethanol. The reduction and oxidation features of the precursors prepared by coprecipitation method and catalysts were extensively investigated by TGA, XRD, TPR and $N_2$-adsorption techniques. Catalytic activity by ethyl acetate hydrogenation of reaction temperatures between 120 and $300^{\circ}C$, different catalyst calcination and reduction temperatures, different Cu/Zn loadings have been examined extensively. The relation between the performance for hydrogenation of ethyl acetate and the structure of the Cu-solid base catalysts with Zn loading were discussed. The detected conversion of ethyl acetate reached 81.6% with a 93.8% selectivity of ethanol. This investigation of the Cu-Zn/$SiO_2$ catalyst provides a recently proposed pathway for ethyl acetate hydrogenation reaction to produce ethanol over Cu-solid base catalysts.

• Applied Chemistry for Engineering
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• v.32 no.6
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• pp.599-606
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• 2021

In this study, an experiment and a reaction characteristic study were conducted to enhance the reaction activity of V₂O₅/WO₃/TiO₂ at 300 ℃ or less by adding selenium to the support, in a selective catalytic reduction method using ammonia as a reducing agent to remove nitrogen oxides. Se-TiO₂ and TiO₂ were synthesized using the sol-gel method, and used as a support when preparing V₂O₅/WO₃/TiO₂ and V₂O₅/WO₃/Se-TiO₂ catalysts. The reaction activity of our catalyst was compared with that of a commercial catalyst. The denitration efficiency of the catalyst using TiO₂ prepared by the sol-gel method was lower than that of the catalyst prepared using commercial TiO₂, but was improved by the addition of selenium. Thus, the effect of selenium addition on the catalyst structure was analyzed using BET, XRD, Raman, H₂-TPR, and FT-IR measurements and the effect of the increase in specific surface area by selenium addition and the formation of monomer and complex vanadium species on reaction characteristics were confirmed.

• Clean Technology
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• v.25 no.4
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• pp.296-301
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• 2019

This study was conducted to investigate the characteristics of CO oxidation by NO poisoning in Pt/TiO₂ catalyst prepared by wet impregnation method and calcined at 400 ℃. In order to confirm the NO poisoning effect of the Pt/TiO₂ catalyst, the change of reaction activity was observed when NO was injected during the CO+O₂ reaction where it was ascertained that the CO conversion rate rapidly decreased below 200 ℃. Also, CO conversion was not observed below 125 ℃. Recovery of initial CO conversion was not verified even if NO injection was blocked at 125 ℃. Accordingly, various analyses were performed according to NO injection. First, as a result of the TPD analysis, it was confirmed that NO pre-adsorption in catalyst inhibited CO adsorption and conversion desorption from adsorbed CO to CO₂. When NO was pre-adsorbed, it was confirmed through H₂-TPR analysis that the oxygen mobility of the catalyst was reduced. In addition, it was validated through FT-IR analysis that the redox cycle (Pt²⁺→Pt⁰→Pt²⁺) of the catalyst was inhibited. Therefore, the presence of NO in the Pt/TiO₂ catalyst was considered to be a poisoning factor in the CO oxidation reaction, and it was determined that the oxygen mobility of the catalyst is required to prevent NO poisoning.

• 한국신재생에너지학회:학술대회논문집
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• 2011.11a
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• pp.97.2-97.2
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• 2011

Pt-Ru and Pt-Ni bimetallic catalysts were prepared and tested for heavy hydrocarbon reforming. Metals were supported on CGO($Ce_{0.8}Gd_{0.2}O_{2.0-x}$) by incipient wetness method. The prepared catalysts were characterized by Temperature programmed reduction(TPR). Oxidative steam reforming of n-dodecane was conducted to compare the activity of the catalysts. The reforming temperature was varied from $500^{\circ}C$ to $800^{\circ}C$ at fixed $O_2$/C of 0.3, $H_2O$/C of 3.0 and GHSV of 5,000/h.Reduction peaks of metal oxide, surface CGO and bulk CGO were detected. Reduction temperature of metal oxide decreased over the bi-metallic catalysts. It is considered that interaction between metals leads to decrease interaction between metal and oxygen. On the other hands, reduction temperatures of surface CGO were dectected in the order of Pt-Ru > Pt-Ni > Pt. low reduction temperatures of surface CGO indicates the low activation energy for oxygen ion conduction to metal. Oxygen ion conduction is known as de-coking mechanism of ionic conducting supports such as CGO. In activity test, fuel conversion was in the same order of Pt-Ru > Pt-Ni > Pt. Especially, 100% of fuel conversion was obtained over Pt-Ru catalysts at $500^{\circ}C$.

• Applied Chemistry for Engineering
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• v.31 no.6
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• pp.646-652
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• 2020

In this study, an NH3-selective catalytic reduction (SCR) experiment was performed to control NOx in the temperature range of 200~500 ℃. The reaction activity experiment was conducted by varying the firing temperature of Sb/TiO2 when using V/Sb/TiO2 composite as a catalyst. As a result, when the sintering temperature of Sb/TiO2 was 600 ℃, the efficiency was the best, and it was confirmed that the NOx conversion rate was close to 80% at the reaction temperature of 250 ℃. H2-temperature programmed reduction (TPR), X-ray diffraction (XRD), Brunauer-Emmett-Teller (BET), Raman spectroscopy, and X-ray photoelectron spectroscopy (XPS) analyses were employed to derive the cause of the activity enhancement when prepared at different firing temperatures as described above. As a result, when the sintering temperature of Sb/TiO2, which showed an excellent activity, was prepared at 600 ℃, it was confirmed that VSbO4 was generated. This indicates that the non-stoichiometric species of V increased, resulting in the excellent NOx conversion rate of V/Sb/TiO2.

• Korean Chemical Engineering Research
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• v.55 no.5
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• pp.679-684
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• 2017

The influence of catalytic activity on Fe loading methods over Fe/BEA zeolite catalyst in the simultaneous reduction of $N_2O/NO$ has been studied. The Fe/BEA zeolite catalysts were prepared by ion exchange and impregnation. Catalytic tests were carried out in the selective catalytic reduction using ammonia as a reductant to identify the activity of prepared catalysts. The results show that the ion exchanged catalyst exhibited higher NO and $N_2O$ conversions than the impregnated catalysts did. To investigate the difference in catalytic activity, we performed various analyses such as XRD, $H_2-TPR$, $O_2-TPD$ and XPS. It is considered that the increase in the activity of the ion exchange catalyst is due to improved reducibility and increased oxygen desorption rate. In addition, the ion exchange catalyst was found through the XPS analysis that $Fe^{2+}$, which is related to the catalytic activity, is formed about 1.6 times more than the impregnated catalyst.

• Applied Chemistry for Engineering
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• v.32 no.5
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• pp.516-523
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• 2021

A study using selective catalytic reduction (SCR) was conducted in conjunction with ammonia as a reducing agent for controlling nitrogen oxides, a typical secondary inducer of fine dust in the atmosphere. For NH₃-SCR experiments, a commercial catalyst of V/W/TiO₂ only and also V/W-Sb/TiO₂ catalyst with Sb were used, and phosphorous durability was confirmed. As a result of NH₃-SCR experiments, it was confirmed that the addition of Sb to V/W/TiO₂ had durability against phosphorous. In addition, the physical and chemical properties were comparatively analyzed through BET, XPS, H₂-TPR, NH₃-TPD, and FT-IR analysis. From the anaylsis results, when Sb was added to V/W/TiO₂ catalyst, P was also added resulting in the formation of SbPO₄ and the generation of VOPO₄ was suppressed. The phosphorous durability was confirmed by maintaining the redox characteristics of the catalyst before P was added.

• Korean Chemical Engineering Research
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• v.60 no.4
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• pp.620-629
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• 2022

By varying various experimental conditions such as heating rate, molar hourly space velocity (MHSV), and nitridation reaction temperature, vanadium oxynitride was prepared through temperature programmed reduction/nitridation reaction (TPRN) of vanadium pentoxide and ammonia, and characterization were performed. In order to investigate the physico-chemical properties of the prepared catalyst, N₂ adsorption-desorption analysis, X-ray diffraction analysis (XRD), hydrogen temperature programmed reduction (H₂-TPR), temperature programmed oxidation (TPO), ammonia temperature programmed desorption (NH₃-TPD), transmission electron microscopy (TEM) was performed. Transformation of V₂O₅ with 5 m² g^-1 low specific surface area by reduction at 340 ℃ to V₂O₃ showed a high specific surface area value of 115 m² g^-1 by micropore formation. As the nitridation temperature increased beyond that, the specific surface area continued to decrease due to sintering. The nitridation reaction variable that had the greatest influence on the specific surface area was the reaction temperature, and the x + y value of VN_xO_y of a single phase approached from 1.5 to 1.0 as the nitridation reaction temperature increased. At a high reaction temperature of 680 ℃, the cubic lattice constant a was VN. close to the value. At 680 ℃, the highest nitridation temperature among the experimental conditions, the ammonia conversion rate was 93%, and no deactivation was observed.

• Korean Chemical Engineering Research
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• v.60 no.3
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• pp.459-467
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• 2022

Redispersion of Pt-Sn particles in Pt, PtSn catalyst which have been sintered by high temperature hydrogen reduction was investigated using oxygen treatment with various temperatures. The aim of this study was to understand the relationship between the catalytic activity for propane dehydrogenation reaction and the change in the physicochemical properties of the catalyst. X-ray diffraction analysis (XRD), CO pulse chemisorption, and H₂ temperature programmed reduction (H₂-TPR) were performed to investigate the state of active metal and interactions between particles of redispersed catalyst. It was confirmed that the dispersion and particle size of platinum, the crystal phase of the catalyst, and the reduction behavior were changed according to the oxygen treatment. As for the catalytic activity in propane dehydrogeantion, sintered PtSn catalyst treated with oxygen at 500 ℃ showed best activity and recovery of initial activity. It was confirm that catalyst after oxygen treatment at 500 ℃ showed high dispersion of Pt and decreased particle size as the results of CO pulse chemisorption and XRD of catalyst, and thus the redispersion of PtSn particles in sintered catalyst was occurred. Catalytic activity was recovered due to redispersion using oxygen treatment, and the activity recovery of the PtSn catalyst was higher than that of Pt catalyst.

• 한국신재생에너지학회:학술대회논문집
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• 2010.06a
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• pp.230.2-230.2
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• 2010

천연가스 수증기 개질 반응에 사용되는 펠릿 촉매의 단점인 열 및 물질 전달 제한, 낮은 effectiveness factor, 압력강화와 channeling 등의 문제점을 해결 하고자 모노리스 형태의 금속 구조체 촉매를 본 연구에 적용 하였다. Fecralloy 재질의 금속 구조체에 Ni 촉매를 워시코팅 (wash coating) 하여 제조 하였으며, 이를 천연가스 수증기 개질 반응에 적용하여 수소를 생산하였다. 실험 조건으로는 S/C ratio를 3으로 고정하여 온도를 $600^{\circ}C{\sim}800^{\circ}C$로 변화 시켰으며, GHSV $3000{\sim}30000h^{-1}$에서 진행 되었다. 구조체 촉매 코팅에 사용된 Ni 촉매의 BET, TPR, H2-chemisorption, SEM, EDS의 특성분석을 수행 하였다. 온도별 테스트에서 모노리스 형태의 금속 구조체 촉매가 펠릿 형태의 촉매에 비해 우수한 열전달 효과로 인해 낮은 퍼니스 온도와 높은 반응 활성을 나타내었으며, GHSV 변화에 따른 성능평가 결과도 15wt% $Ni/MgAl_2O_4$펠릿 촉매와 비교하여 금속 구조체 촉매가 높은 활성을 보였다.