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عنوان فارسی مقاله:
اکسید منگنز مزوپور برای NO2 الحاقی کاتالیزور اکسیداسیون دوده
عنوان انگلیسی مقاله:
Mesoporous manganese oxides for NO2 assisted catalytic soot oxidation
سال انتشار : 2017
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مقدمه انگلیسی مقاله:
1. Introduction
Diesel engines are considered to be the most effective combustion motors, and hence are used for a broad range of technical applications, such as automobiles, locomotives, ships, and power generators [1,2,3]. Despite the high efficiency of diesel engines, diesel particulate matter (DPM) or simply soot is an unsolicited byproduct emitted by diesel exhaust engines. Soot can not only foul the exhaust system, but also cause severe respiratory hazards such as asthma, bronchitis, and lung cancers when inhaled [1–8]. Consequently, emission threshold limits have been established and constantly tightened due to the increased emission of DPM over the last two decades [2,9]. The use of diesel particulate filters (DPFs) to trap DPM is a general post treatment technology to meet the stringent emission standards [6]. However, the DPFs require periodic regeneration, otherwise the backpressurecreated by the loaded DPF may potentially decrease the efficiency of the engine [1,2,4,6,10–12]. The most popular regeneration technique is using a continuous regeneration trap, in which platinum containing catalysts are located upstream in the filter which oxidize the NO emitted by the engine to NO2. The generated NO2 is a better oxidant than O2, and is potentially useful to oxidize DPM at exhaust gas temperatures (200–500 ◦C) [1,2,9,11,13]. In this context, it is very important to identify a promising catalyst which is active for NO2 assisted soot combustion at exhaust gas temperatures. Numerous catalytic materials such as precious metal containing catalysts (i.e., Pt, Ag, Au) [1,5,8,9,14–16], spinels (i.e., ZnAl2O4, CuFe2O4,) [17,18], perovskites (i.e., SrTiO3, MgTiO3) [17], transition metal oxides (i.e., Mn, Cu, Co, Ti, Zr, Ce) [2,19–21], mixed metal oxides (i.e., MnOx CeO2, CoOx CeO2, CuO CeO2, Ce0.5Pr0.5O2) [3,10,11,13,22–24], have been studied over the years. The key factor that determines the activity of catalytic soot oxidation is the transfer of oxygen from its surface to the soot [2,25]. Three basic mechanisms for oxygen transportation are reported for oxide catalysts, (1) a surface redox mechanism – surface oxygens of the catalyst are transferred on to the surface of soot at the sootcatalyst interface, and once transferred, gas phase oxygen fills the resulting vacancies [13,21], (2) a spill-over mechanism – oxygen is first adsorbed on to the surface of the catalyst and undergoes some dissociation forming active oxygen species which are then subsequently transferred onto the surface of soot(catalyst-soot contactis not necessarily required) [21,26], (3) a redox mechanism – catalyst get reduced by transferring bulk oxygen to soot and gets oxidized [2,21]. Nanocrystalline mesoporous materials play a significant role in many applications such as catalysis, electronics, sorption, optics, gas sensors, and magnetics. Catalytic activities of nanocrystalline mesoporous materials are reported to be superior to the nonporous counterparts of the same material due to tunable porosity, surface oxygen vacancies, and large surface areas which promote lattice oxygen mobility [12,27,28–32]. In particular, mesoporous transition metal oxides of Mn, Fe, and Co are recognized for tunable oxidation states which are important in catalyzing redox reactions [31]. However, due to the synthetic limitations of sol-gel chemistry oftransition metal oxides,the successful synthesis of different crystalline phases of mesoporous metal oxides is a tedious process. The circumstances are even more critical for manganese oxides, which can be presentin the range of stable oxides with different oxidation states such as Mn2O3, Mn3O4, polymorphs of MnO2 (-,-,-,-, -, and -), and cation-stabilized octahedral molecular sieves (OMS) [28,30]. In the year 2013, a new series of mesoporous materials [University of Connecticut (UCT) mesoporous materials] was discovered by our group [27]. As an extension of the reported solgel method, a series of different crystalline phases of mesoporous manganese oxides [Mn2O3, -MnO2, and cation-stabilized octahedral molecular sieves (K2-xMn8O16)] using amorphous mesoporous manganese oxide as the precursor, was also successfully synthesized by our group [28,30]. In general, manganese oxides are well known candidates for numerous catalytic applications due to their unique redox properties, low cost, and environment compatibility [30,33,34]. The synthesized mesoporous manganese oxides have shown superior activity both in CO oxidation [28], and methane oxidation [30]. In this work, we report low temperature oxidation of diesel soot in the presence of NO2 using the afore-mentioned mesoporous manganese oxides prepared by the UCT method. 2
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کلمات کلیدی:
Synthesis of Nanostructured Mesoporous Manganese Oxides with ... pubs.acs.org/doi/abs/10.1021/jp110938x by YT Wang - 2011 - Cited by 131 - Related articles Mar 11, 2011 - Nanostructured mesoporous manganese oxides were easily prepared by mixing KMnO4 with ascorbic acid in an aqueous solution under ... Robust Mesoporous Manganese Oxide Catalysts ... - ACS Publications pubs.acs.org/doi/pdf/10.1021/cs501739e by CH Kuo - 2015 - Cited by 59 - Related articles Feb 6, 2015 - Robust Mesoporous Manganese Oxide Catalysts for Water Oxidation .... proper ventilation due to release of toxic NOx gas from the gel. 2.3. Heterogeneous mesoporous manganese oxide catalyst for aerobic ... pubs.rsc.org/-/content/articlehtml/2017/cc/c6cc09095h by K Mullick - 2017 - Cited by 1 Jan 25, 2017 - Mesoporous manganese oxide materials prepared by this method showed .... The presence of the electron withdrawing group –NO2 in the ... Tunable mesoporous manganese oxide for high ... - RSC Publishing pubs.rsc.org/-/content/articlepdf/2016/ta/c5ta07878d by IM Mosa - 2016 - Cited by 11 - Related articles Nov 27, 2015 - mesoporous manganese oxide (Cs-MnOx) synthesized by ..... where nO2 is the number of moles of oxygen produced, Q is the total charge ... Sourav Biswas - Google Scholar Citations scholar.google.com/citations?user=ldaEtdoAAAAJ&hl=en Research Associate, University of Wisconsin - Madison - uconn.edu Robust mesoporous manganese oxide catalysts for water oxidation. CH Kuo, IM ... Mesoporous manganese oxides for NO 2 assisted catalytic soot oxidation. Synthesis of Ordered Mesoporous Manganese Oxides with Various ... https://www.ncbi.nlm.nih.gov/pubmed/26413684 by GO Park - 2015 - Cited by 6 - Related articles J Nanosci Nanotechnol. 2015 Mar;15(3):2441-5. Synthesis of Ordered Mesoporous Manganese Oxides with Various Oxidation States. Park GO, Shon JK, Kim ...
