• Proceedings of the Korea Society for Energy Engineering kosee Conference
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• 1999.05a
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• pp.69-74
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• 1999

각종 산업체의 공정에서 혹은 석탄 혹은 석유를 사용하는 화력발전설비에서 다량 발생되는 질소산화물(NOx), 황산화물(SOx)의 배출규제가 점점 강화되어 감에 따라 배출량 절감이 절실히 요구된다. 기존의 배기가스 정화장치는 처리대상에 따라 다양한 방법들이 사용되는데 황산화물의 경우 습식, 반건식, 건식세정법에 의해, 질소산화물은 선택적 촉매환원법(Selective Catalytic Reduction)과 선택적 무촉매환원법(Selective Non Catalytic Reduction)이 널리 이용되고 있다.(중략)

• Clean Technology
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• v.20 no.3
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• pp.269-276
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• 2014

This study was aimed to develop catalytic system for the dry-based reduction of oxidized mercury ($Hg^{2+}$) to elemental mercury ($Hg^0$) which is one of the most important components comprising mercury continuous emission monitoring system (Hg-CEMS). Based on the standard potential in oxidation-reduction reaction, transition metals including Fe, Cu, Ni and Co were selected as possible candidates for catalyst proceeding spontaneous reduction of $Hg^{2+}$ into $Hg^0$. These transition metal catalysts revealed high activity for reduction of $Hg^{2+}$ into $Hg^0$ in the absence of oxygen in reactant gases. However, their activities were greatly decreased in the presence of oxygen, which was attributed to the transformation of transition metals by oxygen to the corresponding transition metal oxides with less catalytic activity for the reduction of oxidized mercury. Hydrogen supplied to the reactant gases significantly enhanced $Hg^{2+}$ reduction activity even in the presence of oxygen. It might be due to occurrence of combustion reaction between $H_2$ and $O_2$ causing the consumption of $O_2$ at such high reaction temperature at which oxidized mercury reduction reaction took place. Because the system showed high activity for $Hg^{2+}$ reduction to $Hg^0$, which was compatible to that of wet-chemistry technology using $SnCl_2$ solution, the catalytic reduction system of Fe catalyst with the supply of $H_2$ could be employed as a commercial system for the reduction of oxidized mercury to elemental mercury.

• Journal of Korean Society for Atmospheric Environment
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• v.18 no.3
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• pp.205-212
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• 2002

The catalytic combustion of benzene, toluene and xylene over Pt-based catalyst was investigated in a fixed bed flow reactor system with atmospheric pressure to recycle the waste industrial catalyst for the processes of removing volatile organic compounds. According to the pretreatment condition, the properties of the waste Pt-based catalyst were characterized by XRD (X-ray diffraction) and BET (Brunauer-Emmett-Toller). In the carte of air pretreatment, 20$0^{\circ}C$ was found to be optimal, and increasing pretreatment temperature resulted in the reduction of the catalytic activity. When Pt-based catalyst pretreated at 20$0^{\circ}C$ by alto was retreated by hydrogen, the catalytic activity increased by increasing treatment temperature. In the case of HNO$_3$aqueous solution pretreatment, the catalytic activity decreased by increasing the concentration of HNO$_3$aqueous solution. The catalytic activity was seen to observe the following sequence : benzene > toluene > xylene.

• Clean Technology
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• v.24 no.1
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• pp.27-34
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• 2018

Catalytic filter has many advantages for the industrial application owing to its bi-functional ability to treat nitrogen oxides and particulate simultaneously. The technical feasibility of using the catalytic filter in the flue gas treatment process will be more promoted if the high porous ceramic sheet filter is utilized. However, it is not easy to prepare the effective catalytic filter using sheet filter as it has less room for catalyst support due to its thin layer. In this study, catalytic filter using a domestic ceramic sheet filter element has been prepared and conducted the experimental evaluation for NO reduction performance. The current sheet filter element shows the low catalytic activity less than 92% conversion for NO concentration 700 ppm at the face velocity $0.02m\;s^{-1}$. This unexpected low catalytic activity seems to be caused by the present of extraordinary large pores from the lack of uniformity in the pore size distribution of the sheet filter. The large pore size of the sheet filter is reduced by composing the smaller powder as its raw material, which presents improvement in NO conversion more than 96%. More improvement is observed showing 98% NO conversion which is applicable to a commercial plant when the catalyst coating layer is expanded by adding the large $TiO_2$ particles during the catalyst preparation. Both of above two methods is regarded as that the broad gates of the larger pores in the coating layer are effectively filled with the proper catalyst. So these results encourage the utilization of sheet filter as a good catalytic filter material with its potential merit of high permeability.

• Applied Chemistry for Engineering
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• v.29 no.1
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• pp.103-111
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• 2018

A plasma-catalytic combined process was used as an attempt to improve the conversion efficiency of nitrogen oxides ($NO_x$) over a wide temperature range ($150{\sim}500^{\circ}C$) to cope with the exhaust gas whose temperature varies greatly. Since the catalytic $NO_x$ reduction is effective at high temperatures where the activity of the catalyst itself is high, the $NO_x$ reduction was carried out without plasma generation in the high temperature region. On the other hand, in the low temperature region, the plasma was created in the catalyst bed to make up for the decreased catalytic activity, thereby increasing the $NO_x$ conversion efficiency. Effects of the types of catalysts, the reaction temperature, the concentration of the reducing agent (n-heptane), and the energy density on $NO_x$ conversion efficiency were examined. As a result of comparative analysis of various catalysts, the catalytic $NO_x$ conversion efficiency in the high temperature region was the highest in the case of the $Ag-Zn/{\gamma}-Al_2O_3$ catalyst of more than 90%. In the low temperature region, $NO_x$ was hardly removed by the hydrocarbon selective reduction process, but when the plasma was generated in the catalyst bed, the $NO_x$ conversion sharply increased to about 90%. The $NO_x$ conversion can be maintained high at temperatures of $150{\sim}500^{\circ}C$ by the combination of plasma in accordance with the temperature change of the exhaust gas.

• Clean Technology
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• v.20 no.3
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• pp.212-217
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• 2014

In order to regenerate the sulfidated desulfurization sorbent, oxygen is used as the oxidant agent on the regeneration process. The small amount of oxygen un-reacted in regeneration process is flowed into direct sulfur recovery process. However, the reactivity for $SO_2$ reduction can be deteriorated with the un-reacted oxygen by various reasons. In this study, the deactivation effects of un-reacted oxygen contained in the off-gas of regeneration process flowed into direct sulfur recovery process of hot gas desulfurization system were investigated. Sn-Zr based catalysts were used as the catalyst for $SO_2$ reduction. The contents of $SO_2$ and $O_2$ contained in the regenerator off-gas used as the reactants were fixed to 5.0 vol% and 4.0 vol%, respectively. The catalytic activity tests with a Sn-Zr based catalyst were for $SO_2$ reduction performed at $300-450^{\circ}C$ and 1-20 atm. The un-reacted oxygen oxidized the elemental sulfur produced by $SO_2$ catalytic reduction and the conversion of $SO_2$ was reduced due to the production of $SO_2$. However, the temperature for the oxidation of elemental sulfur increased with increasing pressure in the catalytic reactor. Therefore, it was concluded that the decrease of reactivity at high pressure is occurred by catalytic deactivation, which is the re-oxidation of lattice oxygen vacancy in Sn-Zr based catalyst with the un-reacted oxygen on the catalysis by redox mechanism. Meanwhile the un-reacted oxygen oxidized CO supplied as the reducing agent and the temperature in the catalyst packed bed also increased due to the combustion of CO. It was concluded that the rapidly increasing temperature in the packed bed can induce the catalytic deactivation such as the sintering of active components.

• 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.

• Clean Technology
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• v.27 no.3
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• pp.207-216
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• 2021

Major anthropogenic emissions of elemental mercury (Hg⁰) occur from coal-fired power plants, and the emissions can be controlled successfully using NH₃-SCR (selective catalytic reduction) systems with catalysts. Although the catalysts can easily convert the gaseous mercury into Hg²⁺ species, the reactions are greatly dependent on the flue gas constituents and SCR conditions. Numerous deNO_xing catalysts have been proposed for considerable reduction in power plant mercury emissions; however, there are few studies to date of elemental mercury oxidation using SCR processes with MW- and full-scale coal-fired boilers. In these flue gas streams, the chemistry of the mercury oxidation is very complicated. Coal types, deNO_xing catalytic systems, and operating conditions are critical in determining the extent of the oxidation. Of these parameters, halogen element levels in coals may become a key vehicle for obtaining better Hg⁰ oxidation efficiency. Such halogens are Cl, Br, and F and the former one is predominant in coals. The chlorine exists in the form of salts and is transformed to gaseous HCl with a trace amount of Cl₂ during the course of coal combustion. The HCl acts as a very powerful promoter for high catalytic Hg⁰ oxidation; however, this can be strongly dependent on the type of coal because of a wide variation in the chlorine contents of coal.

• Proceedings of the Korean Vacuum Society Conference
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• 2010.08a
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• pp.304-304
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• 2010

The study on the catalytic oxidation of carbon monoxide (CO) to carbon dioxide ($CO_2$) using the noble metals has long been the interest subject and the recent progress in nanoscience provides the opportunity to develop new model systems of catalysts in this field. Of the noble metal catalysts, we selected ruthenium (Ru) as metal catalyst due to its unusual catalytic behavior. The size of colloid Ru NPs was controlled by the concentration of Ru precursor and the final reduction temperatures. For catalytic activity of CO oxidation, it was found that the trend is dependent on the size of Ru NPs. In order to explain this trend, the surface oxide layer surrounding the metal core has been suggested as the catalytically active species through several studies. In this poster, we show the influence of surface oxide on Ru NPs on the catalytic activity of CO oxidation using chemical treatments including oxidation, reduction and UV-Ozone surface treatment. The changes occurring to UV-Ozone surface treatment will be characterized with XPS and SEM. The catalytic activity before and after the chemical modification were measured. We discuss the trend of catalytic activity in light of the formation of core-shell type oxide on nanoparticles surfaces.

• Journal of Environmental Science International
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• v.14 no.7
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• pp.669-674
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• 2005

Catalytic combustion of toluene was investigated on $CuOx/SnO_2-ZrO_2\;CuOx/SnO_2\;CuOx/ZrO_2$ catalysts prepared by impregnation. Characteristics of catalysts loaded on binary support and single support were observed by TPR, TPO, XRD, XPS techniques. The results on catalytic combustion showed that binary supports improve the activity of copper in the combustion of toluene. The reason for high catalytic activity on toluene combustion of $CuOx/SnO_2-ZrO_2$ catalyst was ascribed to oxidation$\cdot$reduction activity at low temperatures and stability of oxidation state after reduction.