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Park S.M.,Chonnam National University | Jang H.-G.,Chonnam National University | Kim E.S.,Heesung Catalyst Corporation | Han H.-S.,Heesung Catalyst Corporation | Seo G.,Chonnam National University
Applied Catalysis A: General | Year: 2012

The incorporation of zirconia onto the silica supports of platinum catalysts improved the selective reduction of NO by hydrogen in comparison to platinum catalysts supported on silica and alumina. The catalysts were characterized by X-ray diffraction, transmission electron microscopy, the temperature-programmed desorption of ammonia, X-ray photoelectron spectroscopy, and the adsorption of carbon monoxide. Their performances were examined in a flow microreactor and by in situ IR spectroscopy. The incorporation of zirconia onto silica created many strong acid sites and stabilized the dispersed platinum. It aided the adsorption of NO and enhanced the formation of ammonia on the platinum catalysts, even in the presence of excess oxygen. The formation of ammonia from NO and the subsequent removal of NO through reaction with ammonia considerably improved the conversion of NO and the yield of N 2. The presence of zirconia also improved the stability of the supported platinum against hydrothermal treatment. © 2012 Elsevier B.V.


Park S.M.,Chonnam National University | Kim M.-Y.,Chonnam National University | Kim E.S.,Heesung Catalyst Corporation | Han H.-S.,Heesung Catalyst Corporation | Seo G.,Chonnam National University
Applied Catalysis A: General | Year: 2011

Pt-MnOx catalysts without any alkali or transition metals were prepared and their performance in the selective catalytic reduction (SCR) of NO by H2 was examined. Their physicochemical properties were investigated using X-ray diffraction (XRD), extended X-ray adsorption fine structure (EXAFS), and X-ray photoelectron spectroscopy (XPS). The adsorption and removal of NO during H2-SCR were monitored by an in situ FT-IR spectrophotometer. The co-presence of MnO and MnO2 on Pt-MnO x was confirmed by EXAFS and XPS. NO was adsorbed on them as nitrate and nitrite, which were subsequently transformed to NHx species by the introduction of H2. The NHx species adsorbed on the acid sites of manganese oxide were active in the reduction of NO, although a direct reduction by H2 was also possible. The conversion of NO over the Pt(2.0)-MnOx catalyst was maximized to 64% at around 100 °C and fell with further increases in temperature. The N2 yield over the Pt(2.0)-MnOx catalyst was 30% at the same condition, indicating that about a half of NO was converted to N2. On the contrary, the Pt(2.0)/SiO2 catalyst exhibited very low N2 yield, 10%, because N2O was highly produced. The reaction between the hydrogen atoms activated on the platinum and the activated NO on the manganese oxide was considered essential for H2-SCR, and NH3 that formed as an intermediate effectively participated to the selective reduction. © 2011 Elsevier B.V.


Park S.M.,Chonnam National University | Seo G.,Chonnam National University | Yoo Y.S.,Heesung Catalyst Corporation | Han H.-S.,Heesung Catalyst Corporation
Korean Journal of Chemical Engineering | Year: 2010

The adsorption of NO and NO 2 and their subsequent reduction by hydrazine monohydrate (HDM) over Fe-BEA zeolite were investigated using an FT-IR spectrophotometer equipped with an in-situ cell. Although NO and NO 2 molecules were adsorbed on Fe species in an unaltered state, some of them reacted with oxygen atoms, resulting in the adsorption of NO 2 and NO- 3, respectively. The reducing species that had originated from HDM on Fe-BEA selectively reduced these molecules to N 2, while a small amount of N 2O was formed in the reduction of NO by HDM. NO and NO 2 were rapidly reduced by HDM through their adsorbed state even at 150 °C, and Fe species were required for their adsorption and for the formation of reducing species from HDM.


Liu D.,Korea Research Institute of Chemical Technology | Liu D.,Tianjin Polytechnic University | Choi W.C.,Korea Research Institute of Chemical Technology | Kang N.Y.,Korea Research Institute of Chemical Technology | And 4 more authors.
Catalysis Today | Year: 2014

The inter-conversion of light olefins over four types of HZSM-5 based catalysts under cracking conditions was investigated systematically and various methods including XRD, Ar adsorption-desorption, NH3-TPD, 27Al and 31P MAS-NMR were used to characterize the effects of P modification and steaming on ZSM-5. Regardless the types of catalyst, the same behaviors of light olefin inter-conversion were observed only depending on conversion of light olefins. Also, the conversion and selectivity were not influenced by the presence of hydrogen, suggesting that light paraffins were mainly produced from hydrogen transfer during cracking rather than hydrogenation of light olefins. It can be suggested that the inter-conversion of light olefins occurs through oligomerization of light olefins and then re-cracking of the oligomerized products. To guarantee high light olefin yield in catalytic naphtha cracking, it is strongly required to suppress oligomerization of light olefins during catalytic cracking. © 2013 Elsevier B.V. All rights reserved.

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