• 한국재료학회:학술대회논문집
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• 한국재료학회 2011년도 추계학술발표대회
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• pp.29.1-29.1
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• 2011

The selective catalytic reduction (SCR) of $MnO_x$ with $NH_3$ is an effective method for the removal of $MnO_x$ from stationary system. The typical catalyst for this method is $V_2O_5-WO_3(MoO_3)/TiO_2$, caused by the high activity and stability. However, This catalyst is active within $300{\sim}400^{\circ}C$ and occurs the pore plugging from the deposition of ammonium sulfate salts on the catalysts surface. It needs to locate the SCR unit after the desulfurizer and electrostatic precipitator without reheating of the flue gas as well as deposition of dust on the catalyst. The manganese oxides supported on titania catalysts have attracted interest because of its high SCR activity at low temperature. The catalytic activity of $MnO_x/TiO_2$ SCR catalyst with different manganese precursors have investigated for low-temperature SCR in terms of structural, morphological, and physico-chemical analyses. The $MnO_x/TiO_2$ were prepared from three different precursors such as manganese nitrate, manganese acetate (II), and manganese acetate (III) by the sol-gel method and then it calcinated at $500^{\circ}C$ for 2 hr. The structural analysis was carried out to identify the phase transition and the change intensity of catalytic activity by various manganese precursors was analyzed by FT-IR and Raman spectroscopy. These different precursors also led to various surface Mn concentrations indicated by SEM. The Mn acetate (III) tends to be more suppressive the crystalline phase (rutile), and it has not only smaller particle size, but also better distributed than the others. It was confirmed that the catalytic activity of MA (III)-$MnO_x/TiO_2$ was the highest among them.

• 대한금속재료학회지
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• 제50권3호
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• pp.201-205
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• 2012

The effects of various manganese precursors for the low-temperature selective catalytic reduction (SCR) of $NO_x$ were investigated in terms of structural, morphological, and physico-chemical analyses. $MnO_x/TiO_2$ catalysts were prepared from three different precursors, manganese nitrate, manganese acetate(II), and manganese acetate(III), by the sol-gel method. The manganese acetate(III)-$MnO_x/TiO_2$ catalyst tended to suppress the phase transition from the anatase structure to the rutile or the brookite after calcination at $500^{\circ}C$ for 2 h. It also had a high specific surface area, which was caused by a smaller particle size and more uniform distribution than the others. The change of catalytic acid sites was confirmed by Raman and FT-IR spectroscopy and the manganese acetate(III)-$MnO_x/TiO_2$ had the strongest Lewis acid sites among them. The highest de-NOx efficiency and structural stability were achieved by using the manganese cetate(III) as a precursor, because of its high specific surface area, a large amount of anatase $TiO_2$, and the strong catalytic acidity.

• 공업화학
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• 제23권1호
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• pp.105-111
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• 2012

본 연구에서는 저온에서 질소산화물 저감효율이 뛰어난 것으로 알려진 망간전구체의 종류에 따른 영향을 고찰하기 위해 초임계수열법으로 합성한 세리아($CeO_2$)와 지르코니아($ZrO_2$)를 담체로 하여 저온 SCR 공정에서의 온도에 따른 활성변화를 비교 분석하였다. Manganese acetate (MA)와 Manganese nitrate (MN), 두 종류 망간전구체의 농도를 영향인자로 고려하여 촉매의 활성변화를 고찰하였다. 활성화된 시료의 특성은 $N_2$ adsorption-desorption, TGA, XRD, XPS를 통해 분석하였고 질소산화물 저감효율을 측정하기 위해 NOx 분석기를 이용하여 De-NOx 실험을 수행하였다. 제조방법에 따라 합성한 촉매의 질소산화물 저감 효율을 분석한 결과 Manganese acetate (MA)를 활성물질로 사용한 촉매가 Manganese nitrate (MN)을 사용한 촉매에 비해 전체적인 온도 영역에서 우수한 질소산화물 저감효율을 보였다. 이는 특성분석 결과를 통해 알 수 있듯이 Manganese acetate (MA)의 주성분인 $Mn_2O_3$가 Manganese nitrate (MN)의 주성분인 $MnO_2$에 비해 높은 산소 이동도를 갖고 담체와의 강한 상호작용을 형성하는 것에 기인한 것으로 보인다.

• Bulletin of the Korean Chemical Society
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• 제34권12호
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• pp.3559-3564
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• 2013

Alumina particles were grafted onto the surface of manganese oxide particles via the coprecipitation process using surfactant and cosurfactant. The phase of Mn/Al salts (Phase I) and the phase of precipitation agent (Phase II) were prepared in aqueous surfactant solution, separately. Phase II was added into Phase I and the reaction was performed to form the precursors of composites through hydrogen bonding between $Mn(OH)_2$ and $Al(OH)_3$ prepared by the reaction of Mn/Al salts with the precipitation agent. The alumina-grafted manganese oxide particles were obtained as a final product after calcination. The concentrations of Al salt and surfactant were varied to investigate their effects on the formation and the crystallinity of composites. In addition, the crystal structure of products could be controlled by changing the calcination temperature. Through thermal analyses, it was found that the thermal stability of manganese oxide was improved by the introduction of alumina on its surface.

• 센서학회지
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• 제20권1호
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• pp.64-69
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• 2011

Porous manganese oxide porous nanostructures were prepared by amino-acid-mediated solvothermal self assembly reaction and subsequent heat treatment at $600^{\circ}C$. When Mn-precursors were heat-treated at $400-550^{\circ}C$, the sensors did not show significant gas responses. In contrast, the manganese oxide heat-treated at $600^{\circ}C$ showed the significant gas responses, that is, the resistance decrease to 100 ppm $C_3H_8$ ($R_a/R_g$ = 2.17, $R_a$ : resistance in air, $R_g$ : resistance in gas) and the resistance increase to 100 ppm $C_2H_5OH$ ($R_g/R_a$ = 1.92). The opposite change of resistance upon exposure to $C_3H_8$ and $C_2H_5OH$ was discussed in relation to the mixed phases of manganese oxides with different valences.

• 한국재료학회:학술대회논문집
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• 한국재료학회 2001년도 추계 학술발표강연 및 논문개요집
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• pp.175-175
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• 2001

• 전기화학회지
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• 제15권3호
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• pp.172-180
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• 2012

리튬이온전지의 양극소재인 $LiMn_2O_4$를 다양한 모양과 크기의 망간산화물 및 망간수산화물 전구체를 사용해서 합성하였다. 첫 번째 단계로 수열합성법이나 침전법을 사용하여 ${\alpha}-MnO_2$, ${\beta}-MnO_2$, $Mn_3O_4$, amorphous $MnO_2$ 및 $Mn(OH)_2$ 등의 전구체를 합성하였고, 두 번째 단계로 이들 전구체로부터 고상법을 사용하여 다양한 형태의 $LiMn_2O_4$를 제조하였다. 합성된 $LiMn_2O_4$의 특성은 주사전자현미경과 XRD Rietveld구조분석을 통해 확인하고, Li coin cell로 조립하여 전극특성을 측정하였다. 500 nm크기의 팔면체(nano-octahedron) $LiMn_2O_4$가 1 C-rate와 50 C-rate에서 각각 107 mAh $g^{-1}$, 99 mAh $g^{-1}$의 높은 전지용량을 나타내며, 다양한 방전전류에서 가장 우수한 전기화학적 특성을 보인다. 3차원 팔면체 결정입자가 1차원 막대모양이나 2차원 판상모양의 다른 형태의 $LiMn_2O_4$보다 구조적 안정성도 우수한 것으로 평가된다. 또한 10 C-rate의 높은 전류로 500회 충 방전이 진행된 후에도 nano-octahedron $LiMn_2O_4$는 단지 5%의 용량감소(95% capacity retention)로 우수한 전극특성을 나타냈다.

• 공업화학
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• 제32권4호
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• pp.483-486
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• 2021

Catalytic ozonation of methyl ethyl ketone (MEK) has been examined over mesoporous MnO_x/Al₂O₃ (MA) catalysts developed by a solvent deficient method using two different manganese precursors including manganese chloride (C) and manganese sulfate (S) at room temperature. The maximum catalytic activities of MA with C (MEK removal efficiency and ozone decomposition of 98.4 and 93.7%, respectively) were higher than those of MA with S (MEK removal efficiency and ozone decomposition of 96 and 68%, respectively). Also the catalytic stability of MA with C was much higher than that of MA with S. The physico-chemical properties of catalysts are well correlated with the activity results, which confirmed that fine dispersion of MnO_x species with high ratios of Mn³⁺/Mn⁴⁺ and more acid sites are attributed to the higher catalyst stability for the MA-C catalyst.

• Bulletin of the Korean Chemical Society
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• 제23권5호
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• pp.679-682
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• 2002

Layered Na0.7[Ni0.05Mn0.95]O2 compounds have been synthesized by a sol-gel method, using glycolic acid as a chelating agent. Na0.7[Ni0.05Mn0.95]O2 precursors w ere used to prepare layered lithium manganese oxides by ion exchange for Na by Li, using LiBr in hexanol. Powder X-ray diffraction shows the layered Na0.7[Ni0.05Mn0.95]O2 has an O3 type structure, which exhibits a large reversible capacity of approximately 190 mA h g-1 in the 2.4-4.5 V range. Na0.7[Ni0.05Mn0.95]O2 powders undergo transformation to spinel during cycling.

• 한국세라믹학회지
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• 제48권5호
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• pp.379-383
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• 2011

This paper presents the synthesis of one-dimensional spinel $LiMn_2O_4$ nanostructures using a facile and scalable two-step process. $LiMn_2O_4$ nanorods with average diameter of 100 nm and length of 1.5 ${\mu}m$ have been prepared by solid-state lithiation of hydrothermally synthesized ${\beta}$-$MnO_2$ nanorods. $LiMn_2O_4$ nanowires with diameter of 10 nm and length of several micrometers have been fabricated via solid-state lithiation of ${\beta}$-$MnO_2$ nanowires. The precursors have been lithiated with LiOH and reaction temperature and pressure have been controlled. The complete structural transformation to cubic phase and the maintenance of 1-D nanostructure morphology have been evaluated by XRD, SEM, and TEM analysis. The size distribution of the spinel $LiMn_2O_4$ nanorods/wires has been similar to the $MnO_2$ precursors. By control of reaction pressure, cubic 1-D spinel $LiMn_2O_4$ nanostructures have been fabricated from tetragonal $MnO_2$ precursors even below $500^{\circ}C$.