DESONOX catalysts were prepared by (1) precipitation from 0.01 M (NH4)(2)Mo7O24 and M Mg(AcO)(2); (II) coprecipitation of M Mg(NO3)(2), Zn(NO3)(2), and Na4V4O7 on an SM-A4 zeolite; and (III) coprecipitation of M Mg(AcO)(2), Zn(NO3)(2) and Na4V4O7 on SM-A4. The precursors were dried and calcined 12 h/423 K and 4 h/773 K, resp. In (I), Mo and V were 0.0087-0.962 and 0.054-0.493%, resp.; in (II), SM-44, V, and Zn were 0.459-9.812, 1.30-2.25, and 5.11-8.080%, and in (III) 2.94-9.28, 1.66-7.43, and 7.33-31.8%. resp. The sp. surface was (I) 8.1-38.5, (II) 26.3-40.1, (III) 5.2-63.5 m(2)/g. The greater the percentage of V and Mo. the less active and the more active the catalyst, resp.. On the zeolite, Mg(AcO)(2) was favorable to Mg(NO3)(2). Series II and III catalysts removed SO2 in 35% and 55%, resp.