Thermochemical CO2 splitting reaction with supported La(x)A(1-x)Fe(y)B(1-y)O(3) (A = Sr, Ce, B = Co, Mn; 0 <= x, y <= 1) perovskite oxides

An efficient redox material for two-step thermochemical CO2 splitting reaction requires high chemical yield at relatively low reduction temperature. Herein, the oxides with perovskite structure of formula La(x)A(1-x)Fe(y)B(1-y)O(3) (A = Sr, Ce, B = Co, Mn; 0 <= x, y <= 1) start to release O-2 at 800 degrees C and the largest O-2 production is 11.8 ml/g(perovskite) at 1300 degrees C. However, for these unsupported La(x)A(1-x)Fe(y)B(1-y)O(3) materials, the CO production is low in spite of high reduction yield. ZrO2, Al2O3 and SiO2 are thus considered as supports to disperse La(x)A(1-x)Fe(y)B(1-y)O(3) materials and different supports induce great differences in the reaction activity. By A-site or B-site substitution of LaFeO3, the O-2 releasing temperature has fallen from 1230 degrees C to 800-950 degrees C and the CO production is enhanced 2-3 times. LaFe0.7Co0.3O3 (25 wt%)/SiO2 shows the highest reaction activity among these investigated materials with the O-2 production of 4.0 ml/g(material) (16.0 ml/g(perovskite)) and CO production of 7.6 ml/g(material) (30.4 ml/g(perovskite)) when it is reduced at 1300 degrees C and re-oxidized at 1100 degrees C, and the activity is relatively stable even after 10 cycles of the reaction. By contrast, the CO production is 4.5 ml/g for CeO2 when it is reduced at 1400 degrees C. The estimated activation energy for the reduction step of LaFe0.7Co0.3O3 (25 wt%)/SiO2 is around 89-149 KJ/mol according to different models. The CO generation step of LaFe0.7Co0.3O3 (25 wt%)/SiO2 is mainly controlled by bulk diffusion (D1) at 1000 degrees C and then it turns to first order surface reaction (F1) at 1100 degrees C. (C) 2014 Elsevier Ltd. All rights reserved