Mechanisms of synthesis gas production via thermochemical cycles over La0·3Sr0·7Co0·7Fe0·3O3

Abstract

La0·3Sr0·7Co0·7Fe0·3O3 (LSCF3773) was chosen as an oxygen carrier material for synthesis gas production and synthesized using ethylene-diamine-tetra-acetic acid (EDTA) citrate-complexing method. LSCF exhibited a pure cubic structure where 110 and 100 plane diffractions were active for CO2 splitting, while 111 was more favored by H2O splitting. Overall oxygen storage capacity (OSC) of LSCF was 4072 μmol/gcat. During the reduction process, regular cations (Co4+, Fe4+), polaron cations (Co3+, Fe3+) and localized cations (Co2+, Fe2+) were achieved when the LSCF was reduced at 500, 700 and 900 °C, respectively. The strength of the active sites depended on reduction temperatures. An increase in oxidation temperature enhanced H2 production at temperature ranging from 500 °C to 700 °C while effected CO production at 900 °C. H2O and CO2 was competitively split during the oxidation step, especially at 700 °C. The activation energy of each reaction was ordered as; CO2 splitting > H2O splitting > CO2 adsorption, supporting the above evidence where H2 and CO production were found to increase when the operating temperature was increased.