The diffusion of two series of promoters, linear methyl esters and 4-n-alkyl benzaldehydes, and of methanol in ZSM-5 have been studied using molecular dynamics. Promoter diffusion decreases with increasing alkyl chain length in methyl esters. The much slower diffusing aromatic aldehydes do not show this trend, instead having similar diffusion coefficients irrespective of alkyl chain length. Benzaldehyde itself has the lowest diffusion coefficient of any promoter studied. All studied promoters exhibit a preference for diffusion in the straight pore, which is more pronounced for 4-n-alkyl benzaldehydes. We observed a behaviour previously only seen in approximate sampling of rare events in interactive Molecular Dynamics in Virtual Reality -a molecular '3-point turn'. The diffusion coefficient of methanol is always greater than that of the promoters; the more catalytically active aromatic aldehyde promoters limit methanol diffusion less than the aliphatic ester promoters. This could be critical at low methanol partial pressure, where diffusion of methanol to reaction sites may start to become a limiting factor.