Pulsed field gradient (PFG) NMR measurements have been conducted to measure self-diffusion coefficients of gases within porous media. Analysis of these microscopic data with the use of a previously developed long-range diffusion model has enabled us to accurately predict breakthrough curves for transport through packed-bed adsorption columns, and the length of unused bed (LUB). This methodology enables the evaluation of mass-transfer coefficients without the complications associated with transient sorption experiments, that is, heat effects, and thereby offers a reasonable alternative to conventional breakthrough experimentation for the evaluation of mass-transfer coefficients, and LUB for large-scale unit operations. (C) 2004 American Institute of Chemical Engineers.