ZSM-5 Zeolite Based Additive in FCC Process: A Review on Modifications for Improving Propylene Production

Propylene is a very essential building block in the petrochemical industry. There is a fast growing in its demand that is steadily expanding its market. Fluid catalytic cracking units is the second largest propylene source for petrochemical application. FCC units are primarily used in the production of gasoline. However, refiners have taken advantage with the aim of producing and recovering large amounts of propylene from their Fluid catalytic cracking unit by raising the severity of reaction through riser temperature, installation of a propylene recovery unit and addition of a catalyst that is shape selectivity. ZSM-5 is nowadays used as a very efficient fluid catalytic cracking additive for increasing light olefins production i.e. propylene. This short review will be exclusively focused on ZSM-5-containing additives and look at the main strategies used in the design and modifications of ZSM-5 catalysts to increase the propylene production in the FCC units. The review will highlight the most important and the recent modification methods used in enhancing ZSM-5 performance in the FCC process to maximize the yield of light olefins in general, and in particular that of propylene. These methods include particle size and acidity modification, phosphorus treatment, mesoporous/hierarchical structure creation, incorporation alkali metals and some selected transition metals and introduction of rare-earth metal.