Chemical Looping Combustion of Isopropanol in Aqueous Solution with Fabricated Fe2O3/Al2O3 and Fe2O3/Al2O3/TiO2 Oxygen Carriers

Iron-based oxygen carriers supported on alumina or alumina/titania were fabricated and evaluated for chemical looping combustion of isopropanol (IPA). Hydrogen is the major combustible gas generated by IPA decomposition prior to combustion with oxygen carriers at temperatures above 800 degrees C. Nearly complete combustion (above 95%) of IPA was achieved for experiments conducted with fabricated Fe2O3/Al2O3 and Fe2O3/Al2O3/TiO2 operated at lower inlet IPA flow rates. Carbon deposition during the chemical looping combustion of IPA was minimized using Fe2O3/Al2O3/TiO2 as an oxygen carrier. The reduction of Fe2O3/Al2O3 and Fe2O3/Al2O3/TiO2 by hydrogen was markedly increased with increasing inlet hydrogen concentration (5-20%), and was not obviously influenced by operating temperature (875-925 degrees C). According to the shrinking core model, the mass transfer coefficients (kg) of Fe2O3/Al2O3 and Fe2O3/Al2O3/TiO2 reduction with H-2 were found to be 0.22 and 0.24 mm s(-1), while the effective diffusion diffusivity (De) of Fe2O3/Al2O3 oxygen carriers was more easily depended on the oxygen carrier conversion. The higher reduction conversions obtained for experiments conducted with Fe2O3/Al2O3/TiO2 because it can be further reduced to FeO and Fe; comparing to those with Fe2O3/Al2O3, which is primarily reduced to FeO. Hydrogen molecules are found to diffuse more easily through the FeO product-layer on Fe2O3/Al2O3 than the FeO/Fe product-layer on Fe2O3/Al2O3/TiO2.