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Synthesis and Kinetic Study of CeO2 and SiO2 Supported CuO Catalysts for CO Oxidation

Hossain, Shaikh Tofazzel, Hossain
http://rave.ohiolink.edu/etdc/view?acc_num=ysu1526392721561056

Abstract Details

2018, Doctor of Philosophy in Materials Science and Engineering, Youngstown State University, Department of Chemistry.
Shape- and size-controlled CeO2 and SiO2 have been used in many catalysis applications. This research focused on the low-temperature CO oxidation for the automotive exhaust system. After starting a car, it needs to increase the temperature of catalytic converter to achieve full CO conversion. Toxic gas from the car pollutes the environment till the car reaches the required temperature. Thus, the preparation of efficient catalyst is much needed to lower the CO conversion temperature. This work especially focused on the correlation of the effect of catalyst supports’ kind and morphology with their catalytic activity. Copper nitrate and copper carbonate precursors for wet impregnation method and copper nitrate for thermal decomposition method have been used to impregnate CuO onto hydrothermally prepared CeO2 nanorods. Several characterization techniques, such as X-ray diffraction (XRD), Raman spectroscopy, transmission electron microscopy (TEM) and hydrogen temperature programmed reduction (H2-TPR) have confirmed the presence of three different copper species interacting with CeO2 nanorods while forming oxygen vacancies in CeO2 lattice by compensating the charges between copper and cerium. Cu-O-Ce solid solutions and CuO impregnated on CeO2 nanorods catalysts (CuO/CeO2) with various compositions have been prepared using thermal decomposition and hydrothermal methods, to understand the distribution effect of copper species on low temperature CO oxidation. A series of temperature programmed reduction-temperature programmed oxidation (TPR-TPO) thermal cycling studies have been conducted to understand the interactions between three assigned copper species with CeO2 support and the corresponding catalytic performance of the catalysts. The effect of support reducibility and reduction treatment has been studied in SiO2 nanospheres and CeO2 nanorods supported CuOx catalysts on CO oxidation. CuO nanoparticles have been impregnated on SiO2 nanospheres and CeO2 nanorods using thermal decomposition method and then the samples have been oxidized in air at different temperatures (400-600 oC). The sample oxidized at 400 oC has also been further reduced under hydrogen atmosphere to compare the effect of thermal treatment (oxidation vs. reduction treatments) on the catalytic activity. In comparison to SiO2 nanospheres supported CuOx catalysts, both CuO/CeO2 and reduced CuOx/CeO2 catalysts exhibited superior catalytic performance in terms of CO conversion and low-temperature hydrogen consumption. The enhanced activity of CeO2 nanorods supported CuOx catalysts has been correlated strongly to the surface defects on CeO2 nanorods and interfacial structures. In addition, in a novel design of co-supported scaffold structure catalyst, CeO2 nanorods and SiO2 nanospheres have been mixed in various ratios and 10 wt% CuO nanoparticles have been impregnated onto CeO2-SiO2 composite support using thermal decomposition method. Agglomeration of CeO2 nanorods have been stopped by introducing SiO2 nanospheres in the catalyst system, and this design can increase the chance to expose more CeO2 surface to CuO nanoparticles in order to form higher amount of surface defects (incorporation of Cu ions and oxygen vacancies) and lead to higher synergistic interaction between CuO and CeO2. H2 TPR and CO oxidation experiments suggested an enhanced low-temperature catalytic performance for 1:1 ratio mixture of CeO2 and SiO2 due to a strong interfacial interaction among SiO2-CeO2-CuO. For kinetic study, 5%CO-95%He and O2 gases have been used to reduce and oxidize CuO/CeO2 catalyst respectively at a constant temperature of 400 oC (isothermal process). Mathematical formulas for power law, diffusion, nucleation and contraction models have been used to compare with the experimental data collected during the reduction and oxidation process of the catalyst to determine the best fitted reaction mechanism.
Ruigang Wang, PhD (Advisor)
Timothy Wagner, PhD (Advisor)
Clovis Linkous, PhD (Committee Member)
Sherri Lovelace-Cameron, PhD (Committee Member)
Snjezana Balaz, PhD (Committee Member)
211 p.
Chemistry; Materials Science
CeO2; SiO2; interfacial structure; CO oxidation; heterogeneous catalysis

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Citations

  • Hossain, Hossain, S. T. (2018). Synthesis and Kinetic Study of CeO2 and SiO2 Supported CuO Catalysts for CO Oxidation [Doctoral dissertation, Youngstown State University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=ysu1526392721561056

    APA Style (7th edition)

  • Hossain, Hossain, Shaikh Tofazzel. Synthesis and Kinetic Study of CeO2 and SiO2 Supported CuO Catalysts for CO Oxidation. 2018. Youngstown State University, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=ysu1526392721561056.

    MLA Style (8th edition)

  • Hossain, Hossain, Shaikh Tofazzel. "Synthesis and Kinetic Study of CeO2 and SiO2 Supported CuO Catalysts for CO Oxidation." Doctoral dissertation, Youngstown State University, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=ysu1526392721561056

    Chicago Manual of Style (17th edition)

ysu1526392721561056
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This open access ETD is published by Youngstown State University and OhioLINK.