Gas–liquid volumetric mass transfer coefficient "kLa " for CH4, CO2, and Ar were experimentally measured at different conditions in a mimicked Fischer–Tropsch (FT) slurry bubble column reactor by using a non-invasive gaseous tracer technique and the axial dispersion model. Results validate the square root relation, between kLa and diffusivity "Dg", that can be used to predict kLa for different species with k La values available in the literature. Additionally, Higbie's penetration theory was adopted along with bubble dynamics parameters estimation to develop a correlation for predicting kLa at wide range of conditions. Current results were used to tune and modify the developed correlation. Predictions of the modified correlation were found to be in line with the findings of previous studies and hence can used to predict kLa for different gases including the syngas (i.e., H2 and CO) at conditions close to FT conditions.