Prussian blue derived Ca-Fe bifunctional materials for chemical looping CO2 capture and in-situ conversion

Abstract

Chemical looping CO2 capture and in-situ reverse water gas shift (CL-ICCC-RWGS) is a promising way to realize integrated CO2 capture and conversion for responding CO2 emission issue. Most bifunctional materials are performed in a reaction configuration of sorbent-catalyst, however, altering the reaction configuration into a sorbent-oxygen-carrying form by introducing a redox couple would result in a new CL-ICCC-RWGS scheme. In this work, a new integrated CO2 capture and conversion scheme is proposed and experimentally demonstrated by synthesizing a series of Prussian blue derived Ca-Fe bifunctional materials with varying iron loadings and exploring their cyclic capture-conversion reactivity. The bifunctional materials with both Ca and Fe species show CO production during isothermal cycles, since CO2 re-oxidation of metallic iron and reverse water gas shift occur in capture and conversion half-cycles, respectively. FCZ136 exhibits the best averaged CO space time yield (238.25 mmolCO∙s−1∙kgFe2O3−1 and 3.00 mmolCO∙s−1∙kgCaO−1) and CO yield (142.95 molCO∙kgFe2O3−1 and 1.80 molCO∙kgCaO−1) with no deactivation after ten isothermal cycles at 650 °C. This is mainly ascribed to two aspects: (i) high iron dispersion improves CO generation rate, (ii) the presence of two inert promoters (t-ZrO2 and CaZrO3) maintains a superior stability. The result provides a new strategy to design efficient bifunctional material and achieve integrated CO2 capture and conversion.