Fluidised Catalytic Cracking (FCC) units (shown below) are one of the major conversion units in modern petrochemical refineries. ZSM-5 additives. These are used in FCC units to convert gasoline (mainly gasoline olefins) into lighter C3 and C4 olefins (propene and butenes). Propene is a key feedstock for downstream petrochemical industry and plays a major role in a variety of polypropene products in the market. There is a global supply shortage of propene and improving propene yields from FCC units is seen as one strategy for meeting that supply gap. This proposal, and a parallel INS proposal, aims to understand how steam dealumination of ZSM-5 (which generates the working catalyst) modifies the diffusion of a model long-chain alkene reactant (1-octene) and the product, propene.