(771e) CO2 As a “Soft” Oxidant for Syngas Production Via Chemical Looping | AIChE

(771e) CO2 As a “Soft” Oxidant for Syngas Production Via Chemical Looping


More, A. - Presenter, University of Pittsburgh
Bhavsar, S., US DOE-National Energy Technology Laboratory, Pittsburgh
Hansen, C., University of Pittsburgh
Veser, G., University of Pittsburgh

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


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
principle”—the periodic oxidation and reduction of a metal oxide to couple two
independent redox reactions—to the activation of CO2 via reduction
to CO [1]. 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 [2]. 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.

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 Fe–Ni 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
(2016) AOP.


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