Patent ID: 6197719
Filing Date: 2001-03-06
Classification: B01J

Abstract:
A process for the activation of perovskite-structured oxides, represented by a general formula:[A.sub.(1-a) A*.sub.a)].sub.n BO.sub.xwherein A is chemical element or mixture of chemical elements selected from rare earth and other trivalent elements; A* is chemical element or mixture of chemical elements selected from alkali and alkaline earth elements, Pb, Cd, Ag, Cu, Sn and other mono and divalent elements; B is chemical element or mixture of chemical elements selected from Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Y, Nb, Mo and noble metal elements; O is oxygen; a is mole fraction of A* in the mixture of A and A* in the range from 0 to 1; x is an integer having a value of 3 and 4 when n=1 and 2, respectively; by increasing the surface area and/or catalytic activity of said perovskite-structured oxides, the process for the activation of said perovskite-structured oxides comprises:i) treating said perovskite-structured oxide hydrothermally with liquid water with or without containing ammonium hydroxide and/or alkyl ammonium hydroxide at water/perovskite-structured oxide weight ratio above about 0.1 in a closed vessel at a temperature between about 50.degree. C. and about 500.degree. C. under autogenous pressure for a period between 0.1 h and about 100 h and then cooling to room temperature, separating the resulting solid mass by filtration, and drying the said mass, andii) calcining the perovskite-structured oxide treated in step (i) at a temperature between about 300.degree. C. and about 1000.degree. C. in air or inert gas or under vacuum for a period between about 0.1 h and about 100 h.