460289 CO2 As a “Soft” Oxidant for Syngas Production Via Chemical Looping
CO2 as a Soft Oxidant for Syngas Production via Chemical Looping
Amey More, Saurabh Bhavsar, Charlie Hansen and Götz Veser
Department of Chemical Engineering, University of Pittsburgh, Pittsburgh, PA
Chemical Looping Combustion is a clean combustion technology, which enables fossil fuel combustion with inherent CO2 capture based on the cyclic oxidation and reduction of an oxygen carrier. While most efforts in chemical looping (CL) are focused on combustion, we previously demonstrated the application of the CL principlethe periodic oxidation and reduction of a metal oxide to couple two independent redox reactionsto the activation of CO2 via reduction to CO . In the present contribution, we investigate and compare CO2 activation via CL in two different operating modes: In the first scheme, CO2 reduction is coupled with CH4 oxidation by using mixtures of Fe and Ni (as alloys or simple physical mixtures) to produce CO and syngas product streams . In the second operating scheme, monometallic Ni carriers are utilized to catalytically crack CH4, producing pure H2 streams. The solid carbon deposits are then burnt off with CO2, overall producing separate CO and H2 product streams.
Supported metal oxide carriers were synthesized, and a combination of thermo-gravimetric analysis (TGA), X-ray diffraction (XRD), and electron microscopy (TEM) was used to identify structure-reactivity correlations for systematic carrier design. Gas phase conversions and selectivities were determined in periodic fixed bed reactor operation. We find that Fe-Ni alloys can indeed show good activity towards both methane activation and CO2 reduction, and that the weak oxidant CO2 allows controlled oxidation of FeNi alloys, which enables selective oxidation of CH4 to syngas. Remarkably, a simple physical mixture of Fe and Ni far exceeds the reactivity of an equivalent alloy carrier, which can be traced back to a synergistic gas-phase coupling between the two carrier fractions. For the second proposed scheme, we find a strong dependence on the support material, which affects particle size and distribution of the active metal species. Overall, our investigations demonstrate the potential of CO2 as a soft oxidant which enables selective oxidation reactions via novel, intensified chemical looping processes.
 M. Najera, et al, Chem. Eng. Res. Des. 89 (2011) 1533; Bhavsar, et al, Chem. Eng. Technol. 35 (2012) 1281; S. Bhavsar and G. Veser, Energy Fuels 27 (2013) 2073; A. More, S. Bhavsar, and G. Veser. Energy Technology (2016) AOP. ADDIN EN.REFLIST
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