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Design of High Performance BaO-based Crystals for Chemisorbent and Catalyst 원문보기

  • 저자

    CHEN XUNCAI

  • 학위수여기관

    경희대학교 대학원

  • 학위구분

    국내석사

  • 학과

    화학공학과

  • 지도교수

    Woo-Sik Kim

  • 발행년도

    2015

  • 총페이지

    119 p.

  • 키워드

    BaO-Base crystal;Oxygen chemisorbent;Catalyst;Microsphere;Core-shell structure;

  • 언어

    eng

  • 원문 URL

    http://www.riss.kr/link?id=T13536612&outLink=K  

  • 초록

    In the chapter 2 The high capacity and selectivity of BaO is very attractive for oxygen separation, especially if the thermal properties and oxygen partial pressure during the transition of the BaO-BaO2 reaction cycle can be improved. Therefore, this study synthesized uniform multi-component (BaSrMg)O particles with significantly improved in oxygen-selective chemisorption using a simple method, where the (BaSrMg)O particles are converted from (BaSrMg)CO3 particles. First, Sr2+ is incorporated into BaCO3 particles by co-precipitation, and then Mg2+ is doped into the crystals via re-crystallization, which resulted in homogeneous multi-component (BaSrMg)CO3 particles composed of 52 % (Ba), 6% (Sr), and 42 % (Mg). As a result, the continuous reduction of (BaSrMg)CO3 particles under an H2 atmosphere at 750oC produced porous multi-component (Ba0.52Sr0.06Mg0.42)O particles suitable for O2 separation. The porous multi-component (Ba0.52Sr0.06Mg0.42)O particles with well distributed Ba, Sr, Mg, and O elements in the crystal exhibited a high capacity (2.02 mmol/g) at 700oC owing to the high content and selectivity of BaO in the particles, along with a good thermal stability and high sorption and desorption rates due to the thermal stability of the MgO distributed within the crystals, which prevented the sintering of BaO2 at a high temperature. Another important advantage of the (BaSrMg)O particles for oxygen separation was that the oxygen partial pressure for the transition of the BaO-BaO2 reaction cycle was enhanced from less than 10 % to an O2 concentration of 19.47% at 700 oC due to the incorporation of strontium in the crystal lattice, thereby reducing the energy cost for the release of pure oxygen. The mechanism for improvement of the oxygen partial pressure during the transition of the BaO redox reaction by incorporating strontium was studied based on Raman characterization using 18O labelling. Thus, the production of porous multi-component (BaSrMg)O particles as an oxygen-selective chemisorbent is a significant breakthrough in the development of oxygen separation or enrichment. In the chapter 3 Single-phase multi-component (BaSrMg)CO3 microspheres with a controllable composition were rapidly synthesized in aqueous media via a self-assembly, phase-transformation and agglomeration process. The (BaSrMg)O particles converted from the as-synthesised (BaSrMg)CO3 microspheres showed a high performance in O2 chemisortion or enrichment. In the chapter 4 Alkaline earth metal oxide, (BaSr)O, have attracted significant interest as the oxygen selective material for the large-scale oxygen production from air owing to its high capacity, low cost and the high oxygen partial pressure of transition for the BaO-BaO2 reversible redox reaction. However, their low thermal-abuse tolerance and poor cycle life because of BaO2 sinter and particle structure collaspe, especially at elevated temperature, prohibit their widely use in commerce. Here, we report the design of a high-temperature-stable (BaSr)O-SiO2 core-shell rods with controlled silica shell thicknesses, which were prepared by a modified Stöber method using rod-shaped (BaSr)CO3 single crystal as seed. Inorganic mesoporous silica shells encaged the (BaSr)O cores and the mesopores provided direct access to the (BaSr)O core for O2 molecules made the (BaSr)O-SiO2 particles as the same separation ability as the bare (BaSr)O in oxgyen production. The (BaSr)O-SiO2 core-shell particles would be an important chemisorbent for oxygen separation from air. In the chapter 5 A series of catalysts composed of barium oxide supported on magnesium oxide with various Ba loading has been studied for NO decomposition. However, the flue gas from the stationary power plants and automobile exhausts include much dusts which would easily attach on the surface of catalyst and, thus, reduce the activity of (BaMg)O catalysts. Here, we report the design of a protective model catalytic system that consists of a (BaMg)O core coated with a porous silica shell, which were prepared by a modified Stöber method using (BaMg)CO3 microspheres, the precursor of (BaMg)O, as seed. Inorganic mesoporous silica shells encaged the (BaMg)O cores and the pores provided direct access to the (BaMg)O core for NO molecules made the (BaMg)O-SiO2 catalyst as the same catalytically active as the bare (BaMg)O in NO decomposition. The (BaMg)O-SiO2 core-shell particles would be an important catalyst for NO decomposition in commercial application.


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