Process for preparing a catalyst suitable for the treatment of exhaust gases from internal combustion engines

A process for producing a catalyst that contains at least one refractory inorganic oxide, which is .alpha.-alumina, .gamma.-alumina, .DELTA.-alumina, eta-alumina, theta-alumina, kappa-alumina, rho-alumina, chi-alumina, silica, a silica-alumina, a zeolite, a silica-magnesia, titanium oxide, zirconium oxide, or a mixture thereof;

• at least one iron oxide;
• at least one cerium oxide;
• at least one catalytically active metal A from Group VIB, VIIB, VIII or IB of the Periodic System;
• and optionally at least one compound of metal B from Group IA, IIA, IVB, or rare earths having atomic numbers 57-71 inclusive, all deposited in the form of a porous layer on a ceramic or metal substrate, said process comprising:
• (a), in an atomizing device having an inlet and an outlet, atomizing an aqueous suspension of at least one powder of said refractory inorganic oxide, at least one soluble cerium salt, at least one soluble iron salt, optionally at least one portion of at least one insoluble compound and/or at least one soluble salt of said metal B, and optionally at least one portion of at least one metal A that has been previously deposited by impregnation of at least one of a precursor thereof on at least one of the solid constituents that are present, so as to recover a powder, and optionally calcining the resultant powder;
• (b) transferring the resultant powder from step (a) back into suspension while optionally adding said compound of metal B, as well as, optionally at least one bonding agent and optionally at least one mineral acid or organic acid;
• (c) coating a ceramic or metal substrate with the suspension obtained in step (b);
• (d) calcining the coated substrate from step (c);
• (e) impregnating said coated and calcined substrate with any remainder or all of said precursor of metal A;
• and
• (f) heat-activating said coated, calcined, and impregnated substrate obtained from (e).