Catalytic properties of dispersed iron oxides Fe 2 O 3 /MO 2 (M = Zr, Ce, Ti and Si) for sulfuric acid decomposition reaction: Role of support

Abstract Supported iron oxides have been established as an important class of catalyst for high temperature sulfuric acid decomposition. With an objective to elucidate the role of support in modifying the overall catalytic properties of dispersed iron oxide catalysts, a series of supported iron oxide based catalysts, Fe 2 O 3 (15 wt%)/MO 2 (M = Zr, Ce, Ti and Si), synthesized by adsorption-equilibrium method, is investigated for sulfuric acid decomposition reaction. The structure of dispersed iron oxide phases largely depended on the nature of the support oxide as revealed by the XRD and Mossbauer studies. α-Fe 2 O 3 is found to be present as a major phase on ZrO 2 and CeO 2 support while e-Fe 2 O 3 was the major phase on silica supported iron oxide. On the other hand, presence of mixed oxide Fe 2 TiO 5 was revealed over TiO 2 support. Strong dispersed metal oxide-support interactions inhibited the total reduction of the dispersed phase on SiO 2 and TiO 2 as compared to complete reduction of dispersed iron oxide on CeO 2 and ZrO 2 supports during temperature programmed reduction upto 1000 °C. The order of catalytic activity at a temperature of ∼750 °C is observed as Fe 2 O 3 /SiO 2  > Fe 2 TiO 5 /TiO 2  > Fe 2 O 3 /ZrO 2  > Fe 2 O 3 /CeO 2 , while at higher temperatures of ∼900 °C the SO 2 yield is found to be comparable for all catalysts. A relationship between the rate of sulfate decomposition and catalytic activity is established through detailed TG-DTA investigations of sulfated catalyst and support. Considerable influence of the support oxide on the composition, structure, redox properties, morphology and catalytic activities of the active iron oxide dispersed phase has been observed. Thus, the support oxides operate as a critical component in the complex supported metal oxide catalysts and these findings might influence the design and development of future high temperature sulfuric acid decomposition catalysts.