• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.21 no.9
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• pp.812-817
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• 2008

A catalytic combustible sensor for LPG/LNG detection was fabricated on $Al_2O_3$ substrate using planar technology. The catalysts of Pd and Pt were added to ${\alpha}$- and ${\gamma}-Al_2O_3$ powders. The mixture of Pt, Pd and $Al_2O_3$ were homogenized by using a three roll mixer. TCR characteristics of Pt heater were optimized with the heat treatment temperature. Sensing properties were investigated as a function of the microstructure of $Al_2O_3$, the gas concentration and the variation of input voltage. ${\alpha}-Al_2O_3$ sintered at 500 $^{\circ}C$ is more suitable as LPG/LNG sensor due to good grain shape and size distribution of about 300 nm than that of ${\gamma}-Al_2O_3$ which is in irregular shape and with a particle size of 5-30 ${\mu}m$. The sensor has shown maximum output voltage of 14 mV for 1000 ppm $C_4H_{10}$ and 3.8 mV for 1000 ppm $CH_4$ at 5.0 V input voltage.

• Journal of Electrochemical Science and Technology
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• v.8 no.1
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• pp.7-14
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• 2017

This study aims to examine the influences of substrates/diffusion layers (DL) and oxygen reduction reaction catalysts ($M_{ORR}$) on the performance of $M_{ORR}/IrO_2$/DL-type bifunctional oxygen electrodes for use in polymer electrolyte membrane (PEM)-type unitized regenerative fuel cells (URFC). The $M_{ORR}/IrO_2$/DL electrodes were prepared via two sequential steps: anodic electrodeposition of $IrO_2$ on various DLs and fabrication of $M_{ORR}$ layers (Pt, Pd, and Pt-Ru) by spraying on $IrO_2/DL$. Experiments using different DLs, with Pt as the $M_{ORR}$, revealed that the roughness factor of the DL mainly determined the electrode performance for both water electrolyzer (WE) and fuel cell (FC) operations, while the contributions of porosity and substrate material were insignificant. When Pt-Ru was utilized as the $M_{ORR}$ instead of Pt, WE performance was enhanced and the electrode performance was assessed by analyzing round-trip efficiencies (${\varepsilon}_{RT}$) at current densities of 0.2 and $0.4A/cm^2$. As a result, using Pt-Ru instead of Pt alone provided better ${\varepsilon}_{RT}$ at both current densities, while Pd resulted in very low ${\varepsilon}_{RT}$. Improved efficiency was related to the additional catalytic action by Ru toward ORR during WE operation.

• Journal of the Korean Wood Science and Technology
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• v.45 no.3
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• pp.278-287
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• 2017

In this study, lignin was efficiently degraded via two-step catalytic cracking process and lignin-oil, char, and gas was produced as lignin degraded products. Three kinds of catalysts (MgO, CaO, and Pt/C) were used in first catalytic cracking step and the highest lignin-oil yield (76.2 wt%) was obtained in Pt/C catalyst with the smallest char formation (4.1 wt%). GC-MS/FID analysis revealed that 18 kinds of monomeric phenols existed in lignin-oil and sum of them was the highest in Pt/C condition (97.8 mg/g lignin). Meanwhile, relatively lower yield of monomeric phenols was produced in MgO and CaO condition because of their absorption on catalysts. Lignin-oil produced over Pt/C was introduced to second catalytic cracking process with porous Pd/activated carbon aerogel catalyst. From this process, four kinds of monomeric phenols such as 4-ethylguaiacol, 4-propylguaiacol, 4-ethylsyringol, 4-propylsyringol were selectively produced at 0.89 - 1.82 wt% level.

• Clean Technology
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• v.27 no.1
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• pp.69-78
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• 2021

Vegetable oils, such as palm oil and cashew nut shell liquid (CNSL), are used as major raw materials for bio-diesel in transportation and bio-heavy oil in power generation in South Korea. However, due to the high unsaturation degree caused by hydrocarbon double bonds and a high content of oxygen originating from the presence of carboxylic acid, the range of applications as fuel oil is limited. In this study, hydrotreating to saturate unsaturated hydrocarbons and remove oxygen in mixed bio-oil containing 1/1 v/v% palm oil and CNSL on monometallic catalysts (Ni and Cu) and bimetallic catalysts (Ni-Zn, Ni-Fe, Ni-Cu Ni-Co, Ni-Pd, and Ni-Pt) was perform under mild conditions (T = 250 ~ 400 ℃, P = 5 ~ 80 bar and LHSV = 1 h-1). The addition of noble metals and transition metals to Ni showed synergistic effects to improve both hydrogenation (HYD) and hydrodeoxygenation (HDO) activities. The most promising catalyst was Ni-Cu/��-Al2O3, and in the wide range of the Ni/Cu atomic ratio of 9/1~1/4, the conversion for HYD and HDO reactions of the catalysts were 90-93% and 95-99%, respectively. The tendency to exhibit almost constant reaction activity in these catalysts of different Ni/Cu atomic ratios implies a typical structure-insensitive reaction. The refined bio-oil produced by hydrotreating (HDY and HDO) had significantly lower iodine value, acid value, and kinetic viscosity than the raw bio-oil and the higher heating value (HHV) was increased by about 10%.

• Bulletin of the Korean Chemical Society
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• v.33 no.8
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• pp.2539-2545
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• 2012

In the present study, we suggest a new way to reactivate performance of direct formic acid fuel cell (DFAFC) and explain its mechanism by employing electrochemical analyses like chronoamperometry (CA) and cyclic voltammogram (CV). For the evaluation of DFAFC performance, palladium (Pd) and platinum (Pt) are used as anode and cathode catalysts, respectively, and are applied to a Nafion membrane by catalyst-coated membrane spraying. After long DFAFC operation performed at 0.2 and 0.4 V and then CV test, DFAFC performance is better than its initial performance. It is attributed to dissolution of anode Pd into $Pd^{2+}$. By characterizations like TEM, Z-potential, CV and electrochemical impedance spectroscopy, it is evaluated that such dissolved $Pd^{2+}$ ions lead to (1) increase in the electrochemically active surface by reduction in Pd particle size and its improved redistribution and (2) increment in the total oxidation charge by fast reaction rate of the Pd dissolution reaction.

• International Journal of Automotive Technology
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• v.8 no.6
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• pp.667-674
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• 2007

Various types of NOx storage catalysts for NGV's were designed, manufactured, and tested in this work on a model gas test bench. As in most of other studies on NOx storage catalyst, alkaline earth metal barium(Ba) was used as the NOx adsorbing substance. The barium-based experimental catalysts were designed to contain different amounts of Ba and precious metals at various ratios. Reaction tests were performed to investigate the NOx storage capacity and the NOx conversion efficiency of the experimental catalysts. From the results, it was found that when Ba loading of a catalyst was increased, the quantity of NOx stored in the catalyst increased in the high temperature range over 350. With more Ba deposition, the NOx conversion efficiency as well as its peak value increased in the high temperature range, but decreased in the low temperature range. The best of de-NOx catalyst tested in this study was catalyst B, which was loaded with 42.8 g/L of Ba in addition to Pt, Pd and Rh in the ratio of 7:7:1. In the low temperature range under $450^{\circ}C$, the NOx conversion efficiencies of the catalysts were lower when $CH_4$, instead of either $C_3H_6$ or $C_3H_8$, was used as the reductant.

• Journal of Korean Society for Atmospheric Environment
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• v.13 no.1
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• pp.91-98
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• 1997

Y-zeolite and ${\gamma}$-Al$_2$O$_3$ were used as supports on CO and $C_3$H$_{6}$ oxidation for diesel emission control. The catalysts composed of Pd and Pt as active components were wash coated on honeycomb type ceramic substrate. The oxidation of CO and $C_3$H$_{6}$ was carried out over prepared honeycomb in a fixed bed continuous reactor in the temperature range of 20$0^{\circ}C$~50$0^{\circ}C$ and 20,000 GHSV (h$^{-1}$ ). Surface area of Y-zeolite was larger than that of ${\gamma}$-Al$_2$O$_3$ due to channel structure of Y-zeolite. Therefore, high conversion of CO and $C_3$H$_{6}$ could be obtained because of good dispersion of active metals over Y-zeolite. The honeycomb used Y-zeolite as a support showed higher $C_3$H$_{6}$ conversion than that of ${\gamma}$-Al$_2$O$_3$ due to better cracking and isomerization activity of Y-zeolite. PdPt catalyst showed high conversion of CO and $C_3$H$_{6}$ at low temperature region, 20$0^{\circ}C$~30$0^{\circ}C$, for their synergy effects. PdPt/Y-Zeolite catalyst could achieve more than 80％ conversion of $C_3$H$_{6}$ at 30$0^{\circ}C$. The use of Y-zeolite as a support increased CO and $C_3$H$_{6}$ conversion, and decreased SO$_2$ conversion very effectively. Y-zeolite found to have a good adaptability as a support for the diesel emission after treatment system.

• Journal of Korean Society for Atmospheric Environment
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• v.23 no.6
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• pp.699-707
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• 2007

This study was carried out to investigate the reaction characteristics of corona/catalyst hybrid $DeNO_x$ process. The experiments were performed by using the multi-staged pin-to-hole type corona reactor which is enable to control the pin-to-hole gap and to insert the catalyst. Also, used for this study, were catalysts which commercially used Pt, Pd and $TiO_2$, and oxygen and hydrocarbon ($C_2H_4$) as reagents. In the syn-gas test, at high temperatures in the range of $100{\sim}200^{\circ}C$, the corona-only $DeNO_x$ process did not reduce the $NO_x$ concentration effectively. However in the presence of ethylene and oxygen as reagents, the $NO_x$ removal efficiency was better at these high temperatures than corona-only $DeNO_x$ process. In addition, coronal catalyst hybrid process with $TiO_2$ showed more efficiency of $NO_x$ removal than Pt and Pd catalyst, because the $TiO_2$ catalyst was more active than Pt and Pd catalyst to converse the $NO_2$ to $HNO_3$. Furthermore, at the condition of real diesel exhaust gas, the $DeNO_x$ efficiency of corona/catalyst hybrid process was not good at higher reaction temperature and plasma density.

• Transactions of the Korean Society of Automotive Engineers
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• v.3 no.2
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• pp.95-101
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• 1995

Experiments have been conducted to investigate the characteristics of formaldehyde and nitrous oxide formation from the catalytic reaction of methane. Catalysts used in the experiment were Pd. Pd/Pt/Rh loaded on ${\gamma}-Al_2O_3$ and ${\gamma}-Al_2O_3-La_2O_3$ monolith. In the catalytic reaction of methane. as the concentration of NO, $O_2$ and $CH_4$ increased, the formaldehyde emission was increased. The concentration of $N_2O$ increased as NO and CO increased. It was also found that the formaldehyde emission was produced by the gas reaction of methane in high temperature above 950K.

• Journal of Sensor Science and Technology
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• v.3 no.3
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• pp.9-15
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• 1994

Catalytic combustible gas sensors were fabricated by using ${\gamma}-Al_{2}O_{3}$ with large surface area and noble metal catalysts. The optimum conditions for ${\gamma}-Al_{2}O_{3}$ fabrication were investigated by DT/TGA and XRD analyses and it was found that fabricated ${\gamma}-Al_{2}O_{3}$ had superior value as surface area of $215.5m^{2}/g$. Gas sensors were manufactured and tested to inflammable gases by using Pt coil as a heater and temperature sensing part, fine ${\gamma}-Al_{2}O_{3}$ powder as a bead material and Pt, Pd noble metal powder as a catalyst. From the results, fabricated sensor showed good sensitivity to LPG and LNG of 20mV/l000ppm, 6.5mV/l000ppm respectively.