Reactivity of oxygen ions in mixed oxides in dehydrogenation of propane

Salvatore Davide Crapanzano

Research output: ThesisPhD Thesis - Research UT, graduation UT

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Abstract

Propane pulse experiments are used as a method to select suitable oxides as oxygensupplier for operation of catalytic dense membrane reactor (CDMR) in oxidativedehydrogenation of propane. Ba0.5Sr0.5Co0.8Fe0.2O3-d (BSCF), La2NiO4+d (LN),La2Ni0.9V0.1O4.15+d (LNV-10) and PrBaCo2O5+d (PBC) powders were used as modelcatalysts to explore the catalytic properties of surfaces in terms of activity and selectivity.Furthermore, as propane pulses induce variation of the oxidation degree by slowlyreducing the powdered oxide, crucial information on the effect of variation of the oxygencontent (i.e. the oxidation degree) in the samples on reactivity and selectivity is obtained.PBC and BSCF are not suitable for CDMR because the former showed low selectivity toC3H6 and the latter adsorbs CO2 by forming carbonates. LN and LNV-10 are promisingmaterials for membrane application, provided that they are operated in the optimalwindow of reduction degree. LNV-10 has shown a constant level of C3H6 productionwithin a broad window of oxidation degree (over-stoichiometric oxygen d < 0.03) at 550°C, while the performance of LN catalyst deteriorated drastically towards CO, CH4 andcoke after just a few pulses. This is because in the case of LN, the activation of latticeoxygen caused the formation of Ni metal, responsible for production of CO and coke,mainly. Contrary, only over-stoichiometric oxygen (d) is activated in LNV-10, whichshowed promising selectivities to olefins. Additionally, LNV-10 has demonstratedstructure stability and reversibility during oxidation-reduction cycles at 550 °C. Testing LN, BSCF and PBC membranes during steady-state experiments revealed thatthe permeation rate was higher than the reaction rate. Therefore, it was reasonable toassume that intermediate adsorbed oxygen species (O2-, O22-, and O-) were present andpossibly responsible for CO2 formation, decreasing the selectivity. In the case of LNV-10, the presence of intermediate adsorbed oxygen species was excluded butunfortunately, the contribution of the LNV-10 membrane on converting propane was verysmall although it showed higher yield to olefins at 550 °C.
Original languageEnglish
Awarding Institution
  • University of Twente
Supervisors/Advisors
  • Lefferts, Leon, Supervisor
Award date28 May 2010
Place of PublicationEnschede
Publisher
Print ISBNs90-365-3038-5
DOIs
Publication statusPublished - 28 May 2010

Keywords

  • METIS-267251

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