A highly flexible and efficient Monte Carlo lattice dynamics (MCLD) code has been developed which takes as input data characterising the microdynamics of the adsorbate molecule within the zeolite framework. Molecular dynamics (MD) and grand canonical Monte Carlo (GCMC) simulations are used to determine a physically realistic distribution of adsorption sites within the zeolite and their relative energies of interaction with the adsorbate of interest, these sites are then identified with the lattice sites used in the MCLD simulation. In this paper the method is applied to ethane and ethene adsorbed in silicalite. Variable temperature NMR relaxometry experiments are performed to provide and constrain the input data for the MCLD simulations. Excellent agreement between simulated and measured single- and binary-component adsorption isotherms is obtained and the results are interpreted in terms of the relative rate of site desorption of the two species within the zeolite framework.