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Novel Perovskite-based electro-catalysts for Oxidative Dehydrogenation (ODH) of Ethane in an Electrochemical Membrane Reactor

Fuller, Anshuman
http://rave.ohiolink.edu/etdc/view?acc_num=osu1439880541

Abstract Details

2015, Doctor of Philosophy, Ohio State University, Chemical Engineering.
The alkane oxidative dehydrogenation (ODH) reaction can be used to make valuable olefins such as ethylene (C2H4) from raw materials such as ethane (C2H6); however the process is weighed down by low selectivity issues since there is a tendency to form CO2. Conducting this reaction in a membrane reactor allows for the possibility of controlling the reaction up until the olefin step. The setup of this non-traditional reactor is similar to that of a solid oxide fuel cell (SOFC), but instead of obtaining power electric current is intentionally supplied to regulate the oxidant amount to the alkane. The main aim was to develop active and selective catalysts that can be used to catalyze ethane ODH in this novel reactor at T < 600oC, with a special focus on La-doped strontium titanate perovskites. Prior to the electro-catalytic testing, a variety of sealants, both commercial and lab-made, were investigated. The glass sealant from Schott, GM31107™, was found to work best for our system exhibiting the lowest air leaks, highest compatibility with the reactor components and also good reproducibility. La-doped strontium titanates having the formula LaxSr1-xTiO3±d (x= 0.0, 0.1, 0.2, 0.3, 0.4 and 0.5) were synthesized using a modified Pechini method. Their bulk, surface and electronic properties were characterized using N2 physisorption, ambient and controlled-environment X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), infrared (IR) spectroscopy, X-ray absorption spectroscopy (XAS) and electronic conductivity measurements. In addition to testing these catalysts in the electrochemical membrane reactor, fixed-bed reaction testing was also done to understand their ability to activate ethane. The incorporation of La3+ over Sr2+ in the LaxSr1-xTiO3±d seemed to moderately increase the Lewis acidity of the surface under oxidizing conditions, as observed in fixed-bed catalytic studies and methanol adsorption experiments. Electronic conductivity experiments showed that the materials were indeed redox stable and that reduction conditions, such as temperature and environment, affected the conductivity of higher La-doped samples. Efforts were made to improve ethylene selectivity by incorporating Cl into the structure (LaxSr1-xTiO3±dCls (x= 0.1, 0.2, 0.3, 0.4)), which did show promising results. Fixed-bed catalytic tests displayed a clear improvement in ethylene selectivity due to Cl incorporation into the structure, while decreasing COx production and O2 consumption for all the Cl-doped titanates indicating enhanced ODH activity. The addition of Cl did, however, decrease the electronic conductivity of the titanates under anode conditions, but they were still above the benchmark requirement of 1 S/cm under reducing conditions. Despite the lower conductivity, the La0.2Sr0.8TiO3±dCls catalyst outperformed all the samples tested in the electro-catalytic ethane ODH tests by exhibiting higher ethylene productivity and selectivity. Subsequently, metal dopants including Pt, Pd, V and Mo were also impregnated onto the La0.2Sr0.8TiO3±dCls anode to investigate changes in the ethylene selectivity. The noble metal dopants Pt and Pd did show moderate improvements in C2H4 selectivity unlike the V and Mo impregnated anodes which acted as inhibitors for the ODH reaction and preferred to completely oxidize the C2H6 to CO2.
Umit Ozkan (Advisor)
Andre Palmer (Committee Member)
Anne Co (Committee Member)
Chen Gu (Committee Member)
252 p.
Chemical Engineering

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Citations

  • Fuller, A. (2015). Novel Perovskite-based electro-catalysts for Oxidative Dehydrogenation (ODH) of Ethane in an Electrochemical Membrane Reactor [Doctoral dissertation, Ohio State University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=osu1439880541

    APA Style (7th edition)

  • Fuller, Anshuman. Novel Perovskite-based electro-catalysts for Oxidative Dehydrogenation (ODH) of Ethane in an Electrochemical Membrane Reactor. 2015. Ohio State University, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=osu1439880541.

    MLA Style (8th edition)

  • Fuller, Anshuman. "Novel Perovskite-based electro-catalysts for Oxidative Dehydrogenation (ODH) of Ethane in an Electrochemical Membrane Reactor." Doctoral dissertation, Ohio State University, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=osu1439880541

    Chicago Manual of Style (17th edition)

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