Radioactive gas tracer measurements conducted during liquid-phase methanol synthesis from syngas in a pilot-scale slurry bubble column at the alternate fuels development unit (AFDU), La Forte have been compared with simulations from two mechanistic reactor models - single-bubble class model (SBCM) and two-bubble class model (TBCM). The model parameters are estimated from an independent sub-model gas and liquid recirculation, and the long-time-averaged slip velocity between the gas and liquid/slurry in the column center can be as high as 50-60 cm/s depending on the operating conditions. Comparison of experimental data with simulation results from the two models indicates that accurate description of interphase gas-liquid mass transfer is crucial to the reliable prediction of tracer responses. Coupled with a correct description of gas and liquid recirculation, the models presented here provides a simple and fundamentally based methodology for design and scale-up of bubble column reactors.