The internal and external gas liquid mass transfer limitations in a three-phase spiral string bed minireactor are estimated, using as a model reaction the benzene hydrogenation over a commercial trilobe Ni/gamma-Al2O3 catalyst at elevated pressures and temperatures. A detailed two-phase flow model incorporating liquid volatility, intrinsic catalytic reaction rates, gas liquid mass transfer effects, liquid solid mass transfer effects, internal mass transfer effects, and wetting of the catalytic particles, was used for the simulation of the spiral string bed reactor performance. The benzene intrinsic reaction kinetics was estimated conducting benzene hydrogenation experiments over crushed catalyst particles. The gas liquid mass transfer coefficient was estimated from the data of this study, and the liquid solid mass transfer effects were estimated from data of a previous communication. The proposed correlation for the prediction of gas liquid mass transfer coefficients can describe the gas liquid mass transfer limitations in the spiral string bed reactor at various operating conditions.