Catalytic property of A(2)(II)B(II)B(VI)O(6) double perovskites (B-VI = Mo, W) for the reduction of nitric oxide with propane in the presence of oxygen

Systematic series of double perovskites containing W and Mo, A(2)(II)B(II)B (VI)O(6) (A(II) = Ba, Sr, Ca; B-II = Mg, Ca, Co, Ni, Cu, Cd; B-VI = W, Mo, W1-xMox) were synthesized, and their catalytic activities for NO-C3H8-O-2 r eaction were investigated. All the oxides crystallized in the ordered doubl e perovskite structure with the rock-salt arrangement of B-II and B-IV cati ons, and the unit cell symmetry was almost exclusively determined by A(II) cations. The double perovskites catalyzed the nonselective reduction of NO into N2O and occasionally N-2 specifically at 600 degrees C in the gaseous mixture of NO (0.44%), C3H8 (0.29%) and O-2 (4.4%). The reduction activity of NO into N2O and N-2 depended on the sort of A(II), B-II, and B-VI cation s, but the effect of B-II cations was the most remarkable. The NO reduction activity increased monotonically with an increase in the enthalpy of forma tion of (BO)-O-II (-Delta H-f(o)), suggesting that the strength of B-II-O b ond or the redox property of B-II ions is of primary importance for the NO reduction activity in the NO-C3H8-O-2 reaction. (C) 2000 Elsevier Science L td. All rights reserved.