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Investigation of the oxygen mobility in doped perovskites and its implications on their selectivity as redox catalysts for chemical looping
Keywords: Chemical Looping, Perovskites, Redox Catalysts, Chemical Engineering
Chemical looping (CL) is a concept, which involves the spatial or temporal separation of a desired reaction into sub-reactions with the help of a chemical intermediate. Generally, these chemical intermediates are metal oxides, so-called oxygen carriers (OCs), that are reduced by donating lattice oxygen to a sub-reaction, and that are subsequently re-oxidized during a regeneration step, thus forming a closed loop regarding the overall process. An upcoming, promising field of application for the concept of CL is the production of value-added chemicals, due several of CL’s advantages such as the potential of heat integration, in-situ product separation, and in-situ conversion of by-products to circumvent limitations given by thermodynamic equilibrium.
The main challenge in designing competitive CL processes to produce value-added chemicals is the tendency of the OC to over-oxidize the carbon-based feedstock to COx, which has been linked to the mobility/diffusivity of oxygen in the metal oxide in several studies. Hence, this project aims at improving our understanding of the oxygen release and mobility of doped perovskite (ABO3: A,B = metal cations) metal oxides as OCs and its implications on their selectivity as redox catalysts in chemical looping partial oxidation applications.
Chemical looping (CL) is a concept, which involves the spatial or temporal separation of a desired reaction into sub-reactions with the help of a chemical intermediate. Generally, these chemical intermediates are metal oxides, so-called oxygen carriers (OCs), that are reduced by donating lattice oxygen to a sub-reaction, and that are subsequently re-oxidized during a regeneration step, thus forming a closed loop regarding the overall process. An upcoming, promising field of application for the concept of CL is the production of value-added chemicals, due several of CL’s advantages such as the potential of heat integration, in-situ product separation, and in-situ conversion of by-products to circumvent limitations given by thermodynamic equilibrium.
The main challenge in designing competitive CL processes to produce value-added chemicals is the tendency of the OC to over-oxidize the carbon-based feedstock to COx, which has been linked to the mobility/diffusivity of oxygen in the metal oxide in several studies. Hence, this project aims at improving our understanding of the oxygen release and mobility of doped perovskite (ABO3: A,B = metal cations) metal oxides as OCs and its implications on their selectivity as redox catalysts in chemical looping partial oxidation applications.
As an indicator for the oxygen mobility, the reducibility of the doped perovskites will be assessed by temperature-programmed reduction (TPR). In addition, electrical conductivity relaxation measurements will be carried out to explicitly determine the effect of doping on the oxygen diffusivity within the metal oxide structure. The tendency of the perovskites towards overoxidation of carbonaceous feedstock to CO2 will be evaluated by catalytic experiments in a fixed-bed reactor. To quantify and understand the structural changes caused by doping, the perovskites will be analyzed by powder X-ray diffraction (XRD). Our goal is to correlate the structural changes imposed by doping to the oxygen mobility and ultimately to the catalytic performance of perovskites for partial oxidation reactions.
As an indicator for the oxygen mobility, the reducibility of the doped perovskites will be assessed by temperature-programmed reduction (TPR). In addition, electrical conductivity relaxation measurements will be carried out to explicitly determine the effect of doping on the oxygen diffusivity within the metal oxide structure. The tendency of the perovskites towards overoxidation of carbonaceous feedstock to CO2 will be evaluated by catalytic experiments in a fixed-bed reactor. To quantify and understand the structural changes caused by doping, the perovskites will be analyzed by powder X-ray diffraction (XRD). Our goal is to correlate the structural changes imposed by doping to the oxygen mobility and ultimately to the catalytic performance of perovskites for partial oxidation reactions.