Abstract: A perovskite-type catalyst consists essentially of a metal oxide composition. The metal oxide composition is represented by the general formula A.sub.1-x B.sub.x MO.sub.3, in which A is a mixture of elements originally in the form of single phase mixed lanthanides collected from bastnasite; B is a divalent or monovalent cation; M is at least one element selected from the group consisting of elements of an atomic number of from 23 to 30, 40 to 51, and 73 to 80; a is 1 or 2; b is 3 when a is 1 or b is 4 when a is 2; and x is a number defined by 0.ltoreq.x<0.5.

Abstract: A perovskite-type catalyst consisting essentially of a metal oxide composition. The metal oxide composition is represented by the general formula A.sub.a-x B.sub.x M0.sub.b, in which A is a mixture of elements originally in the form of single phase mixed lanthanides collected from Bastnasite; B is a divalent or monovalent cation; M is at least one element selected from the group consisting of elements of an atomic number of from 23 to 30, 40 to 51, and 73 to 80; a is 1 or 2; b is 3 when a is 1 or b is 4 when a is 2; and x is a number defined by 0.ltoreq.x<0.7. Methods for preparing the perovskite-type catalyst are also described.

Abstract: Disclosed herein is an emission control system including an air pretreatment system for enhancing the ability of air passing therethrough to absorb moisture, a humidification chamber having an inlet and an outlet, the inlet being attached to the air pretreatment system, the pretreated air passing from the air pretreatment system into the inlet and through the humidification chamber so that it is humidified at a consistently controllable rate in its passage through the humidification chamber to and out of the outlet.