A multifunctional additive for maximizing yield of light olefins and LPG, with a tolerance to contaminant metals. Maximization of the referenced properties is accomplished through the use of a zeolite treated with a phosphorus source, calcined and impregnated with a rare earth salt. The process for preparation of the referenced catalyst includes the following steps: preparation of a precursor containing a zeolite that is selective of olefins with a source of phosphorus; placement of a source of phosphorus in this precursor through calcination; deposition of rare earth salts on the surface of the additive for maximizing the yield of light olefins and LPG that forms; and drying the multifunctional additive formed.