Development of Iron Oxide Carriers for Chemical Looping Combustion Using Sol-Gel

Composite particles with different mass ratios of Fe2O3 and Al2O3 were prepared using a sol-gel method and were examined for use in chemical looping combustion through repeated reduction and oxidation cycles in a packed bed reactor at 850 degrees C Unlike traditional chemical looping combustion which reduces an oxygen carrier in methane and oxidizes it in air, the reducing gas here was a mixture of CO and N-2. Oxidation was performed in a mixture of steam and N-2 to produce H-2, followed by oxidation in air in some cases. The results were as follows (1) For reduction to the FeO phase. unsupported Fe2O3 gave stable conversions over 40 cycles and no Al2O3 support was needed (2) For reduction to the Fe phase over 10 cycles, 10 wt % Al2O3 was sufficient to give stable conversions above 0.9 Over 30-40 cycles, however, the conversion for particles with 10-20 wt % Al2O3 dropped below 0 35. (3) For reduction to the Fe phase over 40 cycles, 40 wt % Al2O3 was replied and gave stable conversions near 0.75. The formation of FeO center dot Al2O3 was confirmed using X-ray diffraction. Steam in N-2, followed by air, is the recommended sequence for oxidizing the composite carriers, since temperature excuisions and agglomeration of particles could be avoided and higher conversions could be achieved