Methanol-to-Hydrocarbons (MTH) is an important industrial reaction. It is thought to work through a 'hydrocarbon pool' mechanism where the hydrocarbons retained within the catalyst pores act both as the activating and deactivating species. It is known that the hydrocarbons retained within the pores increase with time-on-stream and thereby change the diffusional pathways of both reactants and products. During a previous QENS beam time allocation, methanol was used as a probe molecule to study the diffusional constraints of the catalyst pores with increasing reaction time. Due to the high activity of the catalyst, methanol had strong interactions with the acid sites present showing little movement. By using methane as the probe molecule, inert in ZSM5, we will study the diffusional characteristics of an active and a deactivated MTH catalyst.