• Applied Chemistry for Engineering
• /
• v.9 no.6
• /
• pp.803-810
• /
• 1998

We have studied the catalytic combustion of soot particulate over perovskite-type oxides prepared by malic acid method. The catalysts were modified to enhance the activity by substitution of metal into A or B site of perovskite oxide. In addition, the reaction conditions, such as temperature, $O_2$ concentration, space velocity have been studied. The effect of $SO_2$ pretreatment and water introduced into reactants were also examined. In the $LaCoO_3$ catalyst, the partial substitution of alkali metals into A site enhanced the catalytic activity in the combustion of soot particulate and the activity was shown in the order : Cs>K>Na; In the $La_{0.6}Cs_{0.4}CoO_3 $; catalyst, the substitution of Fe or Mn showed no effect on the ignition temperature. The ignition temperature decreased with increasing $O_2$ concentration and contact time. The introduction of water into reactants feed decreased the ignition temperature and the pretreatment of $SO_2$ showed no effect on the catalytic activity.

• Applied Chemistry for Engineering
• /
• v.10 no.3
• /
• pp.407-414
• /
• 1999

We have studied the reduction of NO by CO over perovskite-type oxides prepared by malic and method. The catalysts were modified to enhance the activity by substitution of metal into A or B site of perovskite oxides. In the $LaCoO_3$ type catalyst, the partial substitution of Sr into A site enhanced the catalytic activity on the conversion of NO at less than $350^{\circ}C$. In the $La_{0.6}Sr_{0.4}Co_{1-x}Fe_xO_3$ catalyst, the partial substitution of Fe or Mn into B site enhanced the conversion of NO, but excess amount of Fe decreased the conversion of NO. In addition, $La_{0.6}Sr_{0.4}Co_{0.8}Fe_{0.2}O_3$ mixed with $SnO_2$ or $MnO_2$ showed the synergy effect on the reduction of NO. The introduction of water into reactants feed decreased the catalytic activity but the deactivation was shown to be reversible. The introduction of $SO_2$ into reactants feed also decreased the catalytic activity.

• Membrane Journal
• /
• v.29 no.3
• /
• pp.173-182
• /
• 2019

Much research has been made for finding new and eco-friendly alternative sources of energy to solve the problems related with the pollution caused by emissions of greenhouse gases such as carbon dioxide as the use of fossil fuels increases worldwide. Among them, fuel cells draws particular interests as an eco-friendly energy generator because only water is obtained as a by-product. Anion exchange membrane-based alkaline fuel cell (AEMFC) that uses anion exchange membrane as an electrolyte is of increased interest recently because of its advantages in using low-cost metal catalyst unlike the PEMFC (potton exchange membrane fuel cell) due to the high-catalyst activity in alkaline conditions. The main properties required as an anion exchange membrane are high hydroxide conductivity and chemical stability at high pH. Recently we reported a chemically crosslinked poly(2-dimethyl-1,4-phenylene oxide) (PPO) by reacting PPO with N,N,N',N'-tetramethyl-1,6-hexanediamine as novel anion exchange membranes. In the current work, we further developed the same crosslinked polymer but having enhanced physicochemical properties, including higher conductivity, increased mechanical and dimensional stabilities by using the PPO with a higher molecular weight and also by increasing the crosslinking density. The obtained polymer membrane also showed a good cell performance.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.19 no.6
• /
• pp.167-175
• /
• 2018

Natural gas is a clean fuel that discharges almost no air-contaminating substances. This study examined the simultaneous reduction of $CH_4$ and NOx of NGOC/LNT catalysts for CNG buses related to the improvement of the $de-CH_4/NOx$ performance, focusing mainly on identifying the additive catalysts, loading of the washcoat, stirring time, and types of substrates. The 3wt. % Ni-loaded NGOC generally exhibited superior $CH_4$ reduction performance through $CH_4$ conversion, because Ni is an alkaline, toxic oxide, and exerts a reducing effect on $CH_4$. A excessively small loading resulted in insufficient adsorption capacity of harmful gases, whereasa too high loading of washcoat caused clogging of the substrate cells. In addition, with the economic feasibility of catalysts considered, the appropriate amount of catalyst washcoat loading was estimated to be 124g/L. The NOx conversion rate of the NGOC/LNT catalysts stirred from $200^{\circ}C$ to $550^{\circ}C$ for 5 hours showed 10-15% better performance than the NGOC/LNT catalysts mixed for 2 hours over the entire temperature range. The NGOC/LNT catalysts exhibitedapproximately 20% higher $de-CH_4$ performance on the ceramic substrates than on the metal substrates.

• Clean Technology
• /
• v.18 no.1
• /
• pp.83-88
• /
• 2012

In order to improve the stability of ${\gamma}-Al_2O_3$ on hydrolysis of $SF_6$, the catalytic promoters were investigated in this study. The crystal phase of ${\gamma}-Al_2O_3$ is transformed to their ${\alpha}$-phase during hydrolysis of $SF_6$. Various metal oxides were applied as the promoter material that is Ga, Mg, and Zn and the promoter of 1, 5, and 10 wt% was impregnated over ${\gamma}-Al_2O_3$ by the impregnation method. Specially, it were confirmed in the catalytic activity tests and XRD analysis that ZnO/${\gamma}-Al_2O_3$ catalyst had the high activity for decomposition of $SF_6$ by catalytic hydrolysis and the crystal phase of ZnO promoted ${\gamma}-Al_2O_3$ was not transformed. From these results, it could be known that the stability of ${\gamma}-Al_2O_3$ is enhanced with the catalytic promotion of ZnO impregnated over the surface of catalyst.

• Journal of Sensor Science and Technology
• /
• v.11 no.6
• /
• pp.342-349
• /
• 2002

New formation technique of metal oxide sensing film was proposed m this paper. Silicon wafer with Pt electrodes was used as a substrate for depositing metal Sn film. Metal Sn was deposited in the state of not continuous film but only island state. The samples were prepared to obtain the optimal condition of metal Sn deposition. The resistances of deposited Sn onto Pt electrodes amounted to $1\;k{\Omega}$, $5\;k{\Omega}$, $10\;k{\Omega}$ and $50\;k{\Omega}$, respectively. Also The sample with $1,500\;{\AA}$ thickness of Sn was prepared m order to compare sensing properties between conventional type and proposing type. After deposition of metal Sn, $SnO_2$ was formed by thermal oxidation method for 3 hrs. in $O_2$ ambient at $700^{\circ}C$. Surface morphology, crystal structure and surface roughness of oxidized-sensing film were examined by SEM, XRD, and AFM, respectively. From the results of these analyses, the optimal deposition condition of Sn was that the Pt electrode resistance became $10\;k{\Omega}(300\;{\AA})$. Also, the sensing characteristics of fabricated sensing film for various concentrations of butane, propane and carbon monoxide gases were measured at he operating temperatures of $250^{\circ}C$, $300^{\circ}C$ and $350^{\circ}C$, respectively. Although catalyst as not added to the sensing film, it has exhibited the high sensitivity to all the test gases.

• Transactions of the Korean hydrogen and new energy society
• /
• v.24 no.5
• /
• pp.359-366
• /
• 2013

This work is investigated for the catalytic decomposition of hydrogen iodide (HI). Platinum was used as active material by loading on $ZrO_2-SiO_2$ mixed oxide in HI decomposition reaction. To obtain high and stable conversion of hydrogen iodide in severe condition, it was required to improve catalytic activity. For this reason, a method increasing dispersion of platinum was proposed in this study. In order to get high dispersion of platinum, zirconia was incorporated in silica by sol-gel synthesis. Incorporating zirconia influence increasing platinum dispersion and BET surface area as well as decreasing deactivation of catalysts. It should be able to stably product hydrogen for a long time because of inhibitive deactivation. HI decomposition reaction was carried out under the condition of $450^{\circ}C$ and 1 atm in a fixed bed reactor. Catalysts analysis methods such as $N_2$ adsorption/desorption analysis, X-ray diffraction, X-ray fluorescence, ICP-AES and CO gas chemisorption were used to measurement of their physico-chemical properties.

• Korean Chemical Engineering Research
• /
• v.47 no.1
• /
• pp.96-104
• /
• 2009

In order to lower a reaction temperature with high conversions for simultaneous catalytic reduction of NO and $N_2O$ over Pd-Rh supported mixed metal oxide honeycomb catalysts, $H_2$ or CO was utilized as a reductant. When using the reductants, the effects of reaction conditions were examined in NO and $N_2O$ conversions, where reaction temperatures, concentrations of the reductants and oxygen and the concentration ratio of $N_2O$ to NO were varied. In using $H_2$ reductant, larger than 50% of NO and $N_2O$ conversions was observed at the temperatures below $200^{\circ}C$ in absence of $O_2$. In using CO reductant, NO and $N_2O$ conversions increased from the temperatures higher than $200^{\circ}C$ and $300^{\circ}C$, respectively. However, in use of both reductants, NO and $N_2O$ conversions decreased with increasing oxygen concentration. As a result, $H_2$ reductant could reduce simultaneously NO and $N_2O$ at relatively lower reaction temperature than CO. Also, NO and $N_2O$ conversions were less influenced by using $H_2$ reductant than CO one. Concentration ratio between NO and $N_2O$ did not affect their conversions regardless the type of reductants. Pretreatment of the catalyst in $H_2$ was more effective in simultaneous reduction of NO and $N_2O$ at low reaction temperature than that in $O_2$.

• Journal of the Korean Electrochemical Society
• /
• v.12 no.2
• /
• pp.189-195
• /
• 2009

$\beta-Ga_{2}O_{3}$ nanorods were synthesized by chemical vapor deposition method using nickel-oxide nanoparticle as a catalyst and gallium metal powder as a source material. The average diameter of nanorods was around 160 nm and the average length was $4{\mu}m$. Also, we confirmed that the synthesis of nanorods follows the vapor-solid growth mechanism. From the results of X-ray diffraction and HR-TEM observation, it can be found that the synthesized nanorods consisted of a typical core-shell structure with single-crystalline $\beta-Ga_{2}O_{3}$ core with a monoclinic crystal structure and an outer amorphous gallium oxide layer. Li/$\beta-Ga_{2}O_{3}$ nanorods cell delivered capacity of 867 mAh/g-$\beta-Ga_{2}O_{3}$ at first discharge. Although the Li/$\beta-Ga_{2}O_{3}$ nanorods cell showed low coulombic efficiency at first cycle, the cell exhibited stable cycle life property after fifth cycle.

• KEPCO Journal on Electric Power and Energy
• /
• v.2 no.2
• /
• pp.285-291
• /
• 2016

In chemical-looping combustion, pure oxygen is transferred to fuel by solid particles called as oxygen carrier. Chemical-looping combustion process usually utilizes a circulating fluidized-bed process for fuel combustion and regeneration of the reduced oxygen carrier. The performance of an oxygen carrier varies with the active metal oxide and the raw support materials used. In this work, spraydried Mn-based oxygen carriers were prepared with different raw support materials and their physical properties and oxygen transfer performance were investigated to determine that the raw support materials used are suitable for spray-dried manganese oxide oxygen carrier. Oxygen carriers composed of 70 wt% $Mn_3O_4$ and 30 wt% support were produced using spray dryer. Two different types of $Al_2O_3$, ${\gamma}-Al_2O_3$ and ${\alpha}-Al_2O_3$, and $MgAl_2O_4$ were applied as starting raw support materials. The oxygen carrier prepared from ${\gamma}-Al_2O_3$ showed high mechanical strength stronger than commercial fluidization catalytic cracking catalyst at calcination temperatures below $1100^{\circ}C$, while the ones prepared from ${\alpha}-Al_2O_3$ and $MgAl_2O_4$ required higher calcination temperatures. Oxygen transfer capacity of the oxygen carrier prepared from ${\gamma}-Al_2O_3$ was less than 3 wt%. In comparison, oxygen carriers prepared from ${\alpha}-Al_2O_3$ and $MgAl_2O_4$ showed higher oxygen transfer capacity, around 3.4 and 4.4 wt%, respectively. Among the prepared Mn-based oxygen carriers, the one made from $MgAl_2O_4$ showed superior oxygen transfer performance in the chemical-looping combustion of $CH_4$, $H_2$, and CO. However, it required a high calcination temperature of $1400^{\circ}C$ to obtain strong mechnical strength. Therefore, further study to develop new support compositions is required to lower the calcination temperature without decline in the oxygen transfer performance.