Zeolites are porous framework materials that have active catalytic sites inside narrow channels. Unwanted reactions create coke in the pores which may block access to the active sites. We want to use quasielastic neutron scattering measurements to determine how a model reactant moves in pores with different amounts of coke. This will demonstrate how coke affects the access of the reactant to the active sites and help in designing more robust catalysts for cleaner fuel production.