De-SOx catalyst: the role of iron in iron mixed solid solution spinels, MgO.cntdot.MgAl2-xFexO4

This paper discusses the iron mixed solid solution spinels, MgO {center dot} MgAl{sub 2{minus}x}Fe{sub x}O{sub 4}, prepared by the coprecipitation method, and the role of iron in these spinels examined for the de-SO{sub x} chemistry. The iron in the mixed spinels exhibited a dual function, namely, the catalytic oxidation of SO{sub 2} to SO{sub 3} and the dramatic lowering of the sulfate reduction temperature. In short, the iron mixed solid solution spinels performed much better as a de-SO{sub x} catalyst than their single solid solution counterpart without iron, Ce/MgO {center dot} MgAl{sub 2}O{sub 4}. The fractional substitution of the Al atom in the spinel structure (x {le} 0.4) resulted in overcoming a drawback of sulfur accumulation inherent in the solid solution spinel. Sulfur tends to build up rather quickly in the de-SO{sub x} cycle test with the solid solution spinel catalyst without iron. The iron mixed solid solution spinels impregnated with cerium, Ce/MgO {center dot} MgAl{sub 2{minus}x}Fe{sub x}O{sub 4}, displayed an even better de-SO{sub x} function and an excellent steam stability as well.