• Bulletin of the Korean Chemical Society
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• 제19권9호
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• pp.942-947
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• 1998

The >$^13C$ NMR spectrum of >$^13CO$ adsorbed on Pd particles varies dramatically depending on dispersion. The spectrum of highly dispersed Pd particles supported on silica is a powder pattern ∼800 ppm wide with a first moment of 410 ppm. A low dispersion sample has a motionally narrowed line centered at 750±30 ppm and only ∼85 ppm full width at half height (FWHH). Over several years, high dispersion samples show an increase in the intensity near 750 ppm. These observations are interpreted as an increase of mobile bridging CO on high dispersion Pd surfaces of particles which resulted from smoothing of the metal particle surfaces in the presence of CO.

• 공업화학
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• 제26권5호
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• pp.575-580
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• 2015

본 연구는 여러 가지 방법에 의해 제조된 Pd/C 촉매의 특성을 질소흡탈착등온선, XRD, FE-TEM 및 CO-chemisorption을 이용하여 확인하였고, 제조된 촉매의 활성을 cyclohexene의 수소화 반응을 통하여 확인하여 제조방법에 따른 촉매의 특성 변화가 촉매 활성에 미치는 영향에 대하여 연구하였다. 각각의 제조방법을 통하여 제조된 Pd/C 촉매의 FE-TEM 분석결과, 이온교환법으로 제조된 촉매의 분산 정도가 매우 우수하며, 폴리올법으로 제조된 촉매의 분산 정도가 매우 낮음을 확인하였다. CO-chemisorption 분석에 의한 분산도 결과 이온교환법, 함침법 및 폴리올법으로 제조된 촉매의 Pd 분산도가 각각 17.55, 13.82% 및 1.35%로 나타나 FE-TEM 결과와 일치함을 확인하였다. 이후 cyclohexene의 수소화반응을 통하여 제조된 촉매의 활성을 확인하였고, 이온교환법으로 제조된 촉매의 cyclohexene의 전환율이 71%로 가장 높음을 확인하였다. 이는 탄소 담지체에 담지된 Pd의 분산도가 반응 활성에 영향을 미쳐 나타난 결과임을 알 수 있었다.

• 공업화학
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• 제25권4호
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• pp.425-429
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• 2014

호기성 벤질 알코올 산화반응용 상용촉매 개발을 위하여 팔라듐이 담지된 차콜 입자를 제조하였다. 특히 촉매의 팔라듐 분산도를 높이기 위해서 상온 이온성액체 중 하나인 [Hmim][$PF_6$]을 기능성 용매로 사용하여 입자를 합성하였다. 다양한 농도의 팔라듐을 함침하여 제조된 입자의 반응성을 측정한 결과 7.5 wt%의 촉매가 가장 우수한 반응 활성과 안정성을 나타내었다. 또한 조촉매로서 다양한 농도의 은입자를 합침하여 촉매를 제조하였다. 동일한 반응조건에서 팔라듐과 은의 질량 비율이 9 : 1인 촉매가 높은 금속 분산도로 인하여 가장 반응성이 우수하였다.

• Bulletin of the Korean Chemical Society
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• 제26권4호
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• pp.563-568
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• 2005

The Pt/C and Pd/C catalysts were prepared from conventional chloride precursors by adsorption or precipitation-deposition methods. Their activities for hydrogenation reactions of cyclohexene and acetophenone were compared with those of commercial catalysts. The Pt/C and Pd/C catalysts obtained from the adsorption procedure reveal higher hydrogenation activity than commercial catalysts and the catalysts prepared by the precipitation-deposition method. Their improved performances are attributed to the decreased metal crystallite sizes of Pt or Pd formed on the active carbon support upon the adsorption of the precursors probably due to the same negative charges of the chloride precursor and the carbon support. Under the preparation conditions studied, the reduction of the supported catalysts using borohydrides in liquid phase is superior to a gas phase reduction by using hydrogen in the viewpoint of particle size, hydrogenation activity and convenience.

• 공업화학
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• 제31권6호
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• pp.674-678
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• 2020

본 연구에서는 상온 조건에서 추가적인 에너지원 없이 H2 산화가 가능한 Pd/TiO2 촉매를 제조하였고, 지지체인 TiO2의 비표면적은 Pd/TiO2 촉매의 H2 산화 반응 성능과 비례하지는 않은 것을 확인하였다. 또한 촉매의 물성 변화에 의한 성능 영향 평가를 위하여 La2O3를 Pd/TiO2 촉매에 첨가하였다. La2O3를 TiO2에 함량별로 첨가하여 Pd/La2O3-TiO2를 제조하였고, CO chemisorption 분석을 진행하였다. Pd/TiO2(G) 촉매의 전환율(14% at 0.5% H2)과 비교하여 Pd/La2O3-TiO2 촉매가 74% 전환율로 5배 이상의 성능 증진이 나타났다. Pd/La2O3-TiO2 촉매는 활성금속인 Pd의 metal dispersion이 클수록 H2 산화반응에 유리한 것으로 분석되었다. 하지만 첨가되는 La2O3가 10%를 초과하게 되면 촉매 성능이 다시 감소하는 것을 알 수 있었다. 마지막으로 Pd/La2O3-TiO2 촉매의 물성이 지배적인 영향을 미치는 것은 주입되는 H2가 0.3~0.5% 농도 조건까지이며, 1% 이상의 H2 농도부터는 물질전달이 촉매 반응속도를 지배하는 것으로 판단된다.

• Bulletin of the Korean Chemical Society
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• 제35권7호
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• pp.1979-1984
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• 2014

We have developed an efficient method to generate highly active Pd and PdO nanoparticles (NPs) dispersed on graphene and graphene oxide (GO) by an impregnation method combined with thermal treatments in $H_2$ and $O_2$ gas flows, respectively. The Pd NPs supported on graphene (Pd/G) and the PdO NPs supported on GO (PdO/GO) demonstrated excellent carbon-carbon cross-coupling reactions under a solvent-free, environmentally-friendly condition. The morphological and chemical structures of PdO/GO and Pd/G were fully characterized using X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and transmission electron microscopy (TEM). We found that the remarkable reactivity of the Pd/G and PdO/GO catalysts toward the cross-coupling reaction is attributed to the high degree of dispersion of the Pd and PdO NPs while the oxidative states of Pd and the oxygen functionalities of graphene oxide are not critical for their catalytic performance.

• Bulletin of the Korean Chemical Society
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• 제34권7호
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• pp.2099-2104
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• 2013

We present here an efficient and simple method for preparation of highly active Pd heterogeneous catalyst (CNT-Pd), specifically by reaction of dichlorobis(triphenylphosphine)palladium ($Pd(PPh_3)_2Cl_2$) with thiolated carbon nanotubes (CNTs). The as-prepared CNT-Pd catalysts demonstrated an excellent catalytic activity for the carbon-carbon (C-C) cross-coupling reactions (i.e. Suzuki, Stille, and decarboxylative coupling reactions) under mild conditions. The CNT-Pd catalyst could easily be removed from the reaction mixture; additionally, in the decarboxylative coupling of iodobenzene and phenylpropiolic acid, it showed a six-times recyclability, with no loss of activity. Moreover, once its activity had decreased by repeated recycling, it could easily be reactivated by the addition of phosphine ligands. The remarkable recyclability of the decarboxylative coupling reaction is attributable to the high degree of dispersion of Pd catalysts in CNTs. Aggregation of the Pd catalysts is inhibited by their strong adhesion to the thiolated CNTs during the chemical reactions, thereby permitting their recycling.

• 한국전기전자재료학회논문지
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• 제20권11호
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• pp.959-964
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• 2007

To investigate the influence of partial discharge(PD) distribution characteristics due to various defects on the power cable joints interface, we used the K-means clustering method. As the result of PD number(n) distribution analyzing on $\Phi-n$ graph, the phase angle($\Phi$) of cluster centroid shifted to $0^{\circ}\;and\;180^{\circ}$ increasing with applying voltage. It was confirmed that the PD quantify(q) and euclidean distance of centroid were increased with applying voltage from the centroid distribution analyzing of $\Phi-q$ plane. The dispersion degree was increased with calculated standard deviation of the $\Phi-q$ cluster centroid. The PD number and mean value on $\Phi-q$ graph were some different by electric field concentration with defect types.

• 한국주조공학회지
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• 제37권4호
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• pp.101-107
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• 2017

This study investigated the effect of Pd on the microstructure, tensile and creep properties of Mg-4Al-2Sn (AT42) alloy at a high temperature for transportation-related industrial applications. AT42-xPd (x = 0, 1 and 2 wt. %) alloys were prepared using a permanent mould casting method. The microstructures of the as-cast alloys were characterized by the presence of the intermetallic phases $Mg_{17}Al_{12}$, $Mg_2Sn$ and $Al_4Pd$. The addition of Pd was found to improve the tensile properties of AT42 at room and at elevated temperatures, and to increase the creep resistance at elevated temperatures. A small amount of Pd could markedly improve the tensile properties of AT42 by means of grain-refinement and the dispersion of secondary phase strengthening. Moreover, the thermally stable phase $Al_4Pd$ effectively improves the creep resistance of AT42 due to the strengthened grain boundaries and the suppressed formation of $Mg_{17}Al_{12}$.

• Bulletin of the Korean Chemical Society
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• 제34권5호
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• pp.1441-1444
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• 2013

Hetero-dimer anions of naphthalene (Np), anthracene (An), phenanthrene (Ph) and pyrene (Py) were investigated using the time-of-flight mass spectrometer (TOF-MS), anion photoelectron spectroscopy (PES) and theoretical calculation. There are two possible geometries with their electron affinity (EA) difference: parallel displaced (PD) and T-shaped. Dispersion force plays a key role in PD structure with the formation of a new anionic core while ${\pi}$-hydrogen interaction plays a key role in T-shaped structure with the monomer anionic core. The optimized structures and charge distributions can simply be explained by the relative difference of EA.