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Ce掺杂的OMS-2催化剂上二甲醚催化燃烧性能的研究   总被引:2,自引:0,他引:2       下载免费PDF全文
通过氧化还原法合成了氧化锰八面体分子筛(OMS-2),而后浸渍负载一定量的Ce 。 采用TG-DSC、XRD、低温氮气吸附脱附、TEM、FT-IR、Uv-vis、O2-TPD、H2-TPR以及XPS等技术对制备材料的结构和氧化还原性能进行了表征,考察了催化剂的二甲醚催化燃烧反应性能。结果表明,低掺杂量的Ce高度分散在OMS-2中;高含量时存在独立的CeO2。光谱测试结果表明,Ce的掺杂并未对OMS-2的晶型产生影响。XPS结果表明,Ce的掺杂会提高OMS-2中晶格氧的量。 O2-TPD 和H2-TPR 结果表明,制备的催化剂具有比较丰富的氧物种,低温下易还原,因而在二甲醚催化燃烧中表现出了良好的催化活性和热稳定性。起燃温度在160℃左右,完全燃烧温度在170℃左右,反应产物仅有二氧化碳和水,并且反应后催化剂晶型保持不变,没有积炭产生。  相似文献
2.
采用不同方法制备了一系列氧化锰八面体分子筛(OMS-2)催化剂,考察了制备方法对其低温NH3-SCR催化性能的影响,并采用BET、XRD、Raman、H2-TPR、XPS和TEM等手段对催化剂的物化性质进行表征。结果表明,OMS-2催化剂在50~150℃时其低温SCR活性明显优于MnOx催化剂,OMS-2催化剂在120℃时NOx转化率接近100%。此外,不同的制备方法对OMS-2催化剂的SCR脱硝活性影响明显。其中,固相法制备的OMS-2催化剂的SCR活性最佳。H2-TPR测试结果表明,OMS-2更容易发生氧化还原反应,MnOx还原峰对应的温度较高。XRD、TEM和XPS分析结果表明,低结晶度和高分散性的无定形催化剂有利于低温SCR反应,较高的表面晶格氧和无定形MnO2物种是OMS-2催化剂具有优异低温SCR活性的主要原因。  相似文献
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We report geometries and vertical excitation energies for the red and green chromophores of the DsRed.M1 protein in the gas phase and in the solvated protein environment. Geometries are optimized using density functional theory (DFT, B3LYP functional) for the isolated chromophores and combined quantum mechanical/molecular mechanical (QM/MM) methods for the protein (B3LYP/MM). Vertical excitation energies are computed using DFT/MRCI, OM2/MRCI, and TDDFT as QM methods. In the case of the red chromophore, there is a general blue shift in the excitation energies when going from the isolated chromophore to the protein, which is caused both by structural changes and by electrostatic interactions with the environment. For the lowest ππ* transition, these two factors contribute to a similar extent to the overall DFT/MRCI shift of 0.4 eV. An enlargement of the QM region to include active‐site residues does not change the DFT/MRCI excitation energies much. The DFT/MRCI results are closest to experiment for both chromophores. OM2/MRCI and TDDFT overestimate the first vertical excitation energy by 0.3–0.5 and 0.2–0.4 eV, respectively, relative to the experimental or DFT/MRCI values. The experimental gap of 0.35 eV between the lowest ππ* excitation energies of the red (cis‐acylimine) and green (trans‐peptide) forms is well reproduced by DFT/MRCI and TDDFT (0.32 and 0.37 eV, respectively). A histogram spectrum for an equal mixture of the two forms, generated by OM2/MRCI calculations on 450 snapshots along molecular dynamics trajectories, matches the experimental spectrum quite well, with a gap of 0.23 eV and an overall blue shift of about 0.3 eV. DFT/MRCI appears as an attractive choice for calculating excitation energies in fluorescent proteins, without the shortcomings of TDDFT and computationally more affordable than CASSCF‐based approaches. © 2009 Wiley Periodicals, Inc. J Comput Chem, 2010  相似文献
4.
The development of green and efficient catalysts for peroxymonosulfate (PMS) activation and organic pollutants degradation has received widespread attention. In this study, the hybrid CaCO3/OMS‐2 catalysts were prepared by a simple precipitation approach and characterized by X‐ray powder diffraction, N2 adsorption–desorption, scanning electron microscopy, transmission electron microscopy, X‐ray photoelectron spectroscopy and cyclic voltammetry. It was found that deposition of CaCO3 on OMS‐2 surface can weaken the Mn‐O bond by formation of Ca‐O‐Mn bond. The interactions between CaCO3 and OMS‐2 significantly enhanced Acid Orange 7 degradation in the presence of PMS with a pseudo‐first‐order kinetic constant of 0.21 min−1, which was much higher than those of OMS‐2 (0.026 min−1) and CaCO3 (0.021 min−1). The CaCO3/OMS catalysts were also much more efficient than other reported OMS‐2 hybrid catalysts, and could be performed over a wide solution pH and for other organic dyes degradation. Sulfate and hydroxyl radicals were formed from the oxidation of low valent manganese species by PMS as the active species in the system. This study can provide a simple method for the design of efficient manganese‐based hybrids for wastewater remediation via PMS activation.  相似文献
5.
毕秀茹  孟旭  赵培庆 《分子催化》2020,34(5):462-474
氧化锰八面体分子筛具有优异的氧化性、离子交换性和导电性等性能,被广泛应用于环保、半导体、有机合成等诸多领域。由于体相存在混合价态Mnn+和丰富的表面缺陷空位,使该分子筛同O2或H2O2等绿色氧化剂之间容易发生快速电子转移,活化绿色氧化剂,近年来作为非均相催化剂和功能性载体应用于有机分子的清洁合成中,表现出优异的催化活性、反应选择性和结构稳定性。本文综述了近年来OMS-2催化剂在有机分子清洁氧化合成中,及作为具有电子转移介质性能的载体材料的研究进展,并对未来发展提出了展望。  相似文献
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