DE-SOX CATALYST - AN XRD STUDY OF MAGNESIUM ALUMINATE SPINEL AND ITS SOLID-SOLUTIONS

A systematic X-ray diffraction study was undertaken to characterize the stoichiometric spinel (MgAl2O4), alumina excess spinel (MgAl2O4.xAl2O3), and magnesia excess spinel (MgAl2O4.yMgO). A Vegard's plot, lattice parameter vs the composition of these solid solutions, reveals that, in alumina excess spinel, a continuous solid solution (x = 0-infinity) exists, while, in magnesia excess material, the solid solution is limited to y = 0-1. When y = 1, a solid solution assumes the composition of MgAl2O4.MgO. If y > 1, both periclase and stoichiometric spinel (MgAl2O4) phases coexist. The SO(x) removal activity of various hydrothermally stable cerium oxide containing solid solution spinels was evaluated. In the magnesia excess solid solutions, SO(x) removal activity increased as MgO increased and reached maximum at y = 1, which is the CeO2/MgAl2O4.MgO system. This catalyst in the most widely used SO(x) reduction catalyst today.