Diffusion of ammonia within zeolites is of great interest due to applications in the selective catalytic reduction (SCR) reaction in fuel exhausts, reducing harmful NOx compounds to nitrogen. Though this system has been studied previously with small pore zeolites (showing that the presence of a counter ion affects ammonia diffusivity), a real system involves the presence of hydrocarbons in the catalyst which competitively diffuse with ammonia. This proposal aims to measure the effect of the presence of a long and short alkane (deuterated to remove their signal) on the diffusion of ammonia in commercial SCR catalyst zeolite Beta. The metal free zeolite is chosen because counter ion presence was shown previously to affect diffusion. Two loadings of the alkane will be chosen (1 mol/uc and 3 mol/uc) to judge the affect of both concentration and chain length in hindering ammonia diffusion.