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Investigation of active sites and reaction networks in catalytic hydrogen production: steam reforming of lower alkanes and the water-gas shift reaction

Natesakhawat, Sittichai
http://rave.ohiolink.edu/etdc/view?acc_num=osu1110209339

Abstract Details

2005, Doctor of Philosophy, Ohio State University, Chemical Engineering.
Steam reforming (SR) of hydrocarbons and water-gas shift (WGS) are of importance in hydrogen generation technologies due to recent attention focusing on fuel cells. Current research efforts have focused on catalyst development to improve activity, selectivity, and stability under a realistic range of operating conditions. Although coke formation is a major concern for Ni-based catalysts when used for hydrocarbon steam reforming, their low cost and long-proven performance warrants further investigation. Moreover, hydrogen and fuel cell technologies will greatly benefit from innovative high-temperature shift (HTS) catalyst formulations that can overcome some serious drawbacks (i.e., low activity at low temperatures, sintering of magnetite (Fe3O4), a pyrophoric nature, and the harmful effects of Cr6+ on human health). In this Ph.D. study, lanthanide-promoted Ni/Al2O3 catalysts and Fe-based catalysts promoted with first row transition metals were synthesized by a modified sol-gel technique and a coprecipitation method, respectively. The effect of synthesis variables on the catalyst properties (i.e., BET surface area, reducibility, crystallite size, crystal structure, oxidation states, adsorption/desorption behavior, and surface intermediates during the reaction) and, in turn, on the catalytic performance in SR of lower alkanes and the WGS reaction has been investigated. Catalysts were characterized by BET surface area and pore size distribution measurements, temperature-programmed desorption/reduction/oxidation (TPD/TPR/TPO), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS), static chemisorption, transmission electron microscopy (TEM), thermogravimetric analysis (TGA). The introduction of small amounts (2 wt%) of Ce and Yb in sol-gel Ni/Al2O3 catalysts improves SR activity significantly by enhancing Ni surface area, reducibility of Ni species, and Ni sintering resistance. In addition, the incorporation of Ce in Ni/Al2O3 catalysts results in the reduction of carbon dissolution/diffusion through nickel crystallites, thus preventing catalyst deactivation by coke formation. Formulations of highly active and Cr-free HTS catalysts can be achieved by adding both Al and Cu. The activity of Fe-based catalysts is strongly related to catalyst reducibility, magnetite crystallite size, and redox characteristics. More detailed characterization has provided additional insights into phase transformations, surface intermediates, and reaction/deactivation mechanisms, giving further evidence of the modification of the properties and performance of catalysts through optimized synthesis.
Umit Ozkan (Advisor)
Engineering, Chemical
catalyst; STEAM REFORMING; Ni/Al2O3; STEAM; REFORMING; Ni-2; Catal

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Citations

  • Natesakhawat, S. (2005). Investigation of active sites and reaction networks in catalytic hydrogen production: steam reforming of lower alkanes and the water-gas shift reaction [Doctoral dissertation, Ohio State University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=osu1110209339

    APA Style (7th edition)

  • Natesakhawat, Sittichai. Investigation of active sites and reaction networks in catalytic hydrogen production: steam reforming of lower alkanes and the water-gas shift reaction. 2005. Ohio State University, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=osu1110209339.

    MLA Style (8th edition)

  • Natesakhawat, Sittichai. "Investigation of active sites and reaction networks in catalytic hydrogen production: steam reforming of lower alkanes and the water-gas shift reaction." Doctoral dissertation, Ohio State University, 2005. http://rave.ohiolink.edu/etdc/view?acc_num=osu1110209339

    Chicago Manual of Style (17th edition)

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This open access ETD is published by The Ohio State University and OhioLINK.