Solid-liquid mass transfer coefficients were determined in three-phase sparged reactors (TPSRs) using benzoic acid dissolution. Experiments were performed in three acrylic column reactors of internal diameter 0.1, 0.2 and 0.3 m respectively, The superficial gas velocities were varied up to 0.35 m s(-1). Using experimental data generated in this work and data reported in the literature for a 0.4-m diameter reactor, the effect of the reactor diameter on the solid-liquid mass transfer coefficient, k(SL), was investigated, It is demonstrated that an empirical approach can be used to determine k(SL) from an appropriate mass transfer correlation useful for the design of TPSRs.