Abstract
A series of novel oxide catalysts, which contain three-dimensionally ordered macroporous (3DOM) and microporous structure, were firstly designed and successfully synthesized by simple method. In the as-prepared catalysts, 3DOM SiO2 is used as support and microporous K-OMS-2 oxide nanoparticles are supported on the wall of SiO2. 3DOM K-OMS-2/SiO2 oxide catalysts were firstly used in soot particle oxidation reaction and they show very high catalytic activities. The high activities of K-OMS-2/SiO2 oxide catalysts can be assigned to three possible reasons: macroporous effect of 3DOM structure for improving contact between soot and catalyst, microporous effect of K-OMS-2 for adsorption of small gas molecules and interaction of K and Mn for activation of gas molecules. The catalytic activities of catalysts are comparable to or even higher than noble metal catalyst in the medium and high temperature range. For example, the T50 of K-OMS-2/SiO2-50, 328 °C, is much lower than those of Pt/Al2O3 and 3DOM Au/LaFeO3, 464 and 356 °C,respectively. Moreover, catalysts exhibited high catalytic stability. It is attributed to that the K+ ions are introduced into the microporous structure of OMS-2 and stabilized in the catalytic reaction. Meanwhile, the K+ ions play an important role in templating and stabilizing the tunneled framework of OMS-2.
Highlights
Soot particles derived from the exhaust of diesel engine are a kind of main source of urban atmospheric particulate matters, which is directly threatening environment and people’s health[1,2]
Noble metal catalysts are very expensive than metal oxide catalysts, which restricts the extensive employment of noble metal catalysts
Different X-ray diffraction (XRD) patterns of as-prepared catalysts indicate that the potassium has been doped into the tunnel structure of OMS-2
Summary
Soot particles derived from the exhaust of diesel engine are a kind of main source of urban atmospheric particulate matters, which is directly threatening environment and people’s health[1,2]. Supporting microporous structure materials on the 3DOM wall structure could enhance the catalytic activity by macroporous effect for soot transmission and microporous effect for adsorption and activation of small gas molecules. Due to changing valence states of Mn species in the OMS-2 and high catalytic activity of K for soot combustion, microporous K-OMS-2, which are formed nanoparticles and supported on 3DOM SiO2, are expected to enhance catalytic performance for soot combustion by macroporous effect, microporous effect, nano-effect and synergistic effect between K and Mn. In this paper, a series of novel oxide catalysts, which contain 3DOM structure in the SiO2 support and microporous structure in the nano-K-OMS-2, were firstly designed and prepared by a very simple method. The as-prepared catalysts exhibit super high catalytic activities for soot combustions owing to macroporous structure for soot transmission and micropore structure for the activation of small molecules (NO, O2). The possible mechanisms of catalysts for soot combustion are discussed based on the results of characterization
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