We aim to study using QENS the effect of catalyst ageing small molecule (water) mobility in CHA zeolite catalysts used in selective catalytic reduction (SCR) process for emission control technology. QENS measurements will take place at 273, 288, 303 K, and 10 K. The samples will be a fresh CHA catalyst, and a catalyst aged for 200 hours at 523 K in a humid stream, which hydrothermally damages the zeolite framework. The diffusivities obtained using QENS will be compared to macroscopic gravimetry measurements carried out at the Johnson Matthey technology centre (showing significant differences in diffusivity between fresh and aged catalysts) which measure mass transport over larger scales than the nanoscale probed by QENS. We aim to understand the relative importance of nanoscale mobility, and macroscopic mobility in the resulting deactivation of SCR catalysts after the ageing process.