• 한국세라믹학회지
• /
• 제36권5호
• /
• pp.504-512
• /
• 1999

The high-quality carbon nanofibers were prepared by chemical vapor deposition of gas mixtures of CO-H2 and C3H8-H2 over Fe-Cu and Ni-Cu bimetallic catalysts. The yield and structure of carbon nanofiber produced were altered by the change of catalyst composition and reaction temperature. The high yields were obtained around 500$^{\circ}C$ with e-Cu catalyst and around 700-750$^{\circ}C$ with Ni-Cu catalyst and the relatively higher yields were obtained with the bimetallic catalyst containing 50-90% of Ni and Fe respectively in comparison with the pure metals. The carbon nanofibers produced over the Fe-Cu catalyst at around 500$^{\circ}C$ with the maximum yields had the highest surface ares of 160-200 m2/g around 650$^{\circ}C$ which was slightly lower than the temperature for maximum yields. In order to examine the characteristics of carbon nanofibers as catalyst support Ni and Co metals were supporte on the carbon nanofibers and CO hydrogenation reaction was performed with the catalysts. The particle size distribution of Ni and Co supported over the carbon nanofibers were 6-15 nm and the CO hydrogenation reaction rate with the carbon-nanofiber supported catalysts was much higher than that over the other supports.

• Bulletin of the Korean Chemical Society
• /
• 제13권6호
• /
• pp.605-612
• /
• 1992

Chromium oxide/zirconia catalysts were prepared by dry impregnation of powdered $Zr(OH)_4$ with ($NH_4$)$_2$CrO$_4$aqueous solution. The characterization of prepared catalysts was performed using FTIR, XPS, XRD and DTA methods, and by the measurement of surface area. The addition of chromium oxide to zirconia shifted the transitions of $ZrO_2$ from amorphous to tetragonal phase and from tetragonal to monoclinic phase to higher temperature due to the strong interaction between chromium oxide and zirconia, and the specific surface area of catalysts increased in proportion to the chromium oxide content. Since the $ZrO_2$ stabilizes supported chromium oxide, chromium oxide was well dispersed on the surface of zirconia, and ${\alpha}$-$Cr_2O_3$ was observed only at the calcination temperature above 1173 K. Upon the addition of only small amount of chromium oxide (1 wt% Cr) to $ZrO_2$, both the acidity and acid strength of catalyst increased remarkably, showing the presence of two kinds of acid sites on the surface of $CrO_x$/$ZrO_4$-Bronsted and Lewis.

• 한국대기환경학회지
• /
• 제11권1호
• /
• pp.77-84
• /
• 1995

To prevent or reduce air pollutant from methanol fueled vehicles, methanol oxidation reaction was carried out using a heteropoly acid catalysts. Catalytic activities of catalysts have been experimented at atmospheric pressure in a fixed bed flow reactor. Catalysts were characterized by XRD, IR, thermal analysis, N $H_{3}$-TPD and GC pulse technique. Acidities of catalysts were highly affected by poly-atoms. Methanol conversion was much higher on catalyst with W than on catalyst with Mo as a poly-atoms. With the increase of copper content(X) in C $u_{x}$ $H_{{3-2x}}$PMo catalyst, acidity was decreased and oxidation ability was increased. Methanol conversion and product distribution were affected by the acidity and oxidation ability of catalyst. Especially, supported PdSiW(1wt%) catalyst has a very good methanol conversion and C $O_{2}$ selectivity as high as a commertial 3-way catalyst.t.

• 한국자기공명학회논문지
• /
• 제13권2호
• /
• pp.135-142
• /
• 2009

$^{195}Pt$ NMR measurements were performed to deduce the variation of local density of states at the Fermi energy ($E_F$-LDOS) at the surface of carbonsupported Pt catalysts due to the addition of $Nafion^{(R)}$ ionomer in the metalelectrode-assembly for fuel cells. The results showed that the EF-LDOS at the surface of Pt particles was enhanced by the addition of $Nafion^{(R)}$ ionomers whereas it was uninfluenced in the inner (bulk) part of the Pt particles. This suggests that the effects of ionomers on the electronic states of the Pt particle surface are related to the electrochemical activity of the catalysts.

• Bulletin of the Korean Chemical Society
• /
• 제35권12호
• /
• pp.3535-3541
• /
• 2014

Bisphenol A is considered as pollutant, because it is toxic and hazardous to living organisms even at very low concentrations. Biological oxidation used for removing this organic from waste water is not suitable and consequently application of catalytic wet oxidation has been considered as one of the best options for treating bisphenol A. We have developed Fe/SBA-15, Ni/SBA-15 and Fe-Ni/SBA-15 as heterogeneous catalysts using the advanced impregnation method for oxidation of bisphenol A in water. The catalysts were characterized with physico-chemical characterization methods such as, powder X-ray diffraction (PXRD), FT-IR measurements, N2 adsorption-desorption isotherm, thermo-gravimetric analysis (TGA), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and inductively coupled plasma optical emission spectroscopy (ICP-OES) analysis. This work illustrates activity of the catalysts for heterogeneous catalytic degradation reaction revealed with excellent conversion and recyclability. The degradation products identified were not persistent pollutants. GC-MS analysis identified the products: 2,4-hexadienedioic acid, 2,4-pentadienic acid and isopropanol or acetic acid. The leachability study indicated that the catalysts release very little metals to water. Therefore, the possibility of water contamination through metal leaching was almost negligible.

• 한국신재생에너지학회:학술대회논문집
• /
• 한국신재생에너지학회 2011년도 추계학술대회 초록집
• /
• pp.97.2-97.2
• /
• 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 $500^{\circ}C$.

• 멤브레인
• /
• 제2권1호
• /
• pp.49-58
• /
• 1992

Functionalized organic polymers have been used as supports for heterogenized homogeneous catalytic process[1]. Sprcific advantages of using these resins as support reagents have been reviewed[2-4]. These include: -ease of by-product separation from the main reaction product usuallyby simple filtration. -prevention of intermolecular reaction of reactive species or functional groups by simulating high dilution conditions[5]. -utility of the "fish-hook" principle in which a minor component in fished out of a large excess substrate by the insoluble polymer[6]. -the possibility of reusing recovered reagents as well as eliminating the use of volatile or noxious substances[7]. Catalysis by ion-exchange membranes is perhaps one of the latest examples of the use of a polymer-supported species. Conceptually, catalysts on membrane supports offer several possible advantages over traditional powder type systems. They are: (1) Membranes immobilize the catalyst, preventing agglomeration. (2) Filtration is unnecessary for the catalyst separation and so complete catalyst recovery is facilitated. (3) Catalytyic and separation processes can be combined, allowing membrane supported catalysts for the continous flow reactors. reactors.

• Bulletin of the Korean Chemical Society
• /
• 제27권5호
• /
• pp.789-792
• /
• 2006

• 한국전기화학회:학술대회논문집
• /
• 한국전기화학회 2003년도 연료전지심포지움 2003논문집
• /
• pp.225-228
• /
• 2003

• 한국재료학회지
• /
• 제21권3호
• /
• pp.180-185
• /
• 2011

This study is aimed to increase the activity of cathodic catalysts for PEMFCs(Polymer Electrolyte Membrane Fuel Cells). we investigated the temperature effect of 20wt% Pt/C catalysts at five different temperatures. The catalysts were synthesized by using chemical reduction method. Before adding the formaldehyde as reducing agent, process was undergone for 2 hours at the room temperature (RT), $40^{\circ}C$, $60^{\circ}C$, $80^{\circ}C$ and $100^{\circ}C$, respectively. The performances of synthesize catalysts are compared. The electrochemical oxygen reduction reaction (ORR) was studied on 20wt% Pt/C catalysts by using a glassy carbon electrode through cyclic voltammetric curves (CV) in a 1M H2SO4 solution. The ORR specific activities of 20wt% Pt/C catalysts increased to give a relative ORR catalytic activity ordering of $80^{\circ}C$ > $100^{\circ}C$ > $60^{\circ}C$ > $40^{\circ}C$ > RT. Electrochemical active surface area (EAS) was calculated with cyclic voltammetry analysis. Prepared Pt/C (at $80^{\circ}C$, $100^{\circ}C$) catalysts has higher ESA than other catalysts. Physical characterization was made by using X-ray diffraction (XRD) and transmission electron microscope (TEM). The TEM images of the carbon supported platinum electrocatalysts ($80^{\circ}C$, $100^{\circ}C$) showed homogenous particle distribution with particle size of about 2~3.5 nm. We found that a higher reaction temperature resulted in more uniform particle distribution than lower reaction temperature and then the XRD results showed that the crystalline structure of the synthesized catalysts are seen FCC structure.