• 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.

• Korean Chemical Engineering Research
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• v.44 no.4
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• pp.356-362
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• 2006

The $SO_2$ reduction using CO and $H_2$ over Sn-Zr based catalysts was performed in this study. Sn-Zr based catalysts with Sn/Zr molar ratio (0/1, 1/4, 1/1, 2/1, 3/1, 1/0) were prepared by the precipitation and co-precipitation method. The effect of the temperature on the reaction characteristics of the $SO_2$ reduction with a reducing agent such as $H_2$ and CO was investigated under the conditions of space velocity of $10,000ml/g_{-cat.}h$, $([CO(or\;H_2)]/[SO_2])$ of 2.0. As a result, the activity of Sn-Zr based catalysts were higher than $SnO_2$ and $ZrO_2$. The reactivity for the $SO_2$ reduction with CO was higher than that with $H_2$, and sulfur yield in the $SO_2$ reduction by $H_2$ was higher than that by CO. The reactivity for the $SO_2$ reduction with $H_2$ was increased with the reaction temperature regardless of Sn-Zr based catalyst with a Sn/Zr molar ratio. $SnO_2-ZrO_2$ (Sn/Zr=1/4) had highest activity at $550^{\circ}C$, in the $SO_2$ reduction with $H_2$ and $SO_2$ conversion of 94.4％ and sulfur yield of 66.4％ were obtained at $550^{\circ}C$. On the other hand, in the $SO_2$ reduction by CO, the reactivity was decreased with the increase over $325^{\circ}C$. At the optimal temperature of $325^{\circ}C$, $SO_2$ conversion and sulfur yield were about 100％ and 99.5％, respectively, in the $SO_2$ reduction over $SnO_2-ZrO_2$ (Sn/Zr=3/1). Also, the $SO_2$ reduction using syngas with $CO/H_2$ ratio over $SnO_2-ZrO_2$ (Sn/Zr=2/1) was performed in order to investigate the application possibility of the simulated coal gas as the reductant in DSRP. As a result, the reactivity of the $SO_2$ reduction using syngas with $CO/H_2$ ratio was increased with increasing the CO content of syngas. Therefore, it could be known that DSRP using the simulated coal gas over Sn-Zr based catalyst is possible to be realized in IGCC system

• Applied Chemistry for Engineering
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• v.18 no.2
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• pp.155-161
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• 2007

In this study, the reactivity of a $SnO_2-ZrO_2$(Sn/Zr = 2/1) catalyst for $SO_2$ reduction by CO was investigated in order to optimize the various reaction conditions such as temperature, gas hourly space velocity (GHSV), and [CO]/[$SO_2$] molar ratio. The reaction temperature in the range of $300{\sim}550^{\circ}C$, space velocity in the range of $5000{\sim}30000cm^3/[g_{-cat}{\cdot}h]$ and [CO]/[$SO_2$] molar ratio in the range of 1.0~4.0 were employed. The optimum temperature, GHSV, and [CO]/[$SO_2$] molar ratio were determined to be $325^{\circ}C$, $10000cm^3/[g_{-cat}{\cdot}h]$, and 2.0, respectively; under these conditions, $SO_2$ conversion was over 99% and sulfur selectivity was over 95%. In addition, the effect of $H_2O$ content on the $SO_2$ reduction by CO was also investigated. As the $H_2O$ content increased from 2 vol% up to 6 vol%, the reactivity and sulfur selectivity decreased. In case of 2 vol% $H_2O$ content, the reaction temperature and [CO]/[$SO_2$] molar ratio were varied in the range of $300{\sim}400^{\circ}C$ and 1.0~3.0. The optimum temperature and [CO]/[$SO_2$] molar ratio were $340^{\circ}C$ and 2.0, respectively under which $SO_2$ conversion and sulfur selectivity were about 90% and 87%, respectively.

• Journal of Korean Society of Environmental Engineers
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• v.22 no.12
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• pp.2263-2273
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• 2000

Catalytic wet air oxidation of acetic acid over Mn-Ce based catalysts deposited on various supports ($SiO_2$, $TiO_2$, $ZrO_2$), $ZrSiO_4$, $ZrO_2(10wt%)/TiO_2$) have been carried out in high pressure microreactors. Also, promotional effects by small addition(O.5~1.0 wt%) of p-type semiconductors (CoO, $Ag_2O$, SnO) have been investigated. From the screening tests for initial activity ranking, both Mn(2.8)-Ce(7.2 wt%) and Ru(O.4)Mn(2.7)-Ce(6.9 wt%) supported on $TiO_2$ were selected as the promising reference candidates. In $Mn-Ce/TiO_2$ reference catalyst, addition of small amount of each p-type semiconductor (Co, Sn and Ag) resulted in activity promotional effect and the degree of the increase was in the following order: Co> Ag > Sn. Especially, $Mn-Ce/TiO_2$ promoted with 0.5 wt% Co gave the 2.6 folds activity increase compared to the reference case attributing to the surface area increase as well as synergy effect. In $Ru-Mn-Ce/TiO_2$ reference catalyst, only Co(1.0 wt%) promoted case showed a little reaction rate increase.

• 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.

• Journal of the Korea Institute of Military Science and Technology
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• v.7 no.2 s.17
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• pp.81-87
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• 2004

Semiconductor thick film gas sensors based on tin oxide are fabricated and their gas response characteristics are examined for four simulant gases of chemical warfare agent (CWA)s. The sensing materials are prepared in three different sets. 1) The Pt or Pd $(1,\;2,\;3\;wt.\%)$ as catalyst is impregnated in the base material of $SnO_2$ by impregnation method.2) $Al_2O_3\;(0,\;4,\;12,\;20\;wt.\%),\;In_2O_3\;(1,\;2,\;3\;wt.\%),\;WO_3\;(1,\;2,\;3\;wt.\%),\;TiO_2\;(3,\;5,\;10\;wt.\%)$ or $SiO_2\;(3,\;5,\;10\;wt.\%)$ is added to $SnO_2$ by physical ball milling process. 3) ZnO $(1,\;2,\;3,\;4,\;5\;wt.\%)$ or $ZrO_2\;(1,\;3,\;5\;wt.\%)$ is added to $SnO_2$ by co-precipitation method. Surface morphology, particle size, and specific surface area of fabricated sensing films are performed by the SEM, XRD and BET respectively. Response characteristics are examined for simulant gases with temperature in the range 200 to $400^{\circ}C$, with different gas concentrations. These sensors have high sensitivities more than $50\%$ at 500ppb concentration for test gases and also have shown good repetition tests. Four sensing materials are selected with good sensitivity and stability and are fabricated as a sensor array A sensor array Identities among the four simulant gases through the principal component analysis (PCA). High sensitivity is acquired by using the semiconductor thick film gas sensors and four CWA gases are classified by using a sensor array through PCA.