The invention includes an additive for maximizing production of olefins. The additive comprises a ZSM-5 molecular sieve, at least one inorganic oxide, and phosphorus oxide. The ZSM-5 molecular sieve has iron in the framework, and the additive comprises at least 0.5 weight percent iron, as measured as iron oxide, in the molecular sieve framework. The additive is useful for maximizing production of olefins in a FCC process.