Mixed solld solutions magnesium-alumina spinel catalyst, MgAl2O4 ·xAl2O3·yMgO (0< x<9, 0< y <5), using to reduce the SOx emission from the fluid catalytic cracking units (FCCU), were prepared by coprecipitation method. It was found that a "volcano" type curve relation between the lattice parameter (a) and the composition of the spinel existed. The activity decreases as the value of x in the alumina excess spinel increases from 1 to 9, and increases as the value of y increases in the magnesium-rich spinel until up to 1, if y >1, the activity decreases which was due to MgO and spinel coekist in the catalyst. The results of reduction-oxidation (red-ox) cycle tests showed that introducing rare earth cerium to spinel could improve the de-SOx activity. Of all the catalysts, 0.1Ce/MgAl2O4· MgO is a promising catalyst which has the highest activity.30% propane as reducing gas is superior to 30% H2.
