In membrane reactive absorption, a gas mixture is contacted with a liquid absorbent in a membrane module to selectively dissolve one or more components from the gas in the liquid, accompanied by a chemical reaction in the liquid phase. The complexity of modeling multiphase systems increases when mass transfer phenomena take place together with chemical reactions. Therefore, it is very important to have reliable mathematical models for process design and scale up, that describe the phenomena involved in the easiest way possible. We propose the separation of propylene-propane gas mixtures in a hollow fiber contactor as a case study. A thorough mathematical model that accounts for the factors influencing the flux through the membrane: (1) gas flux through the membrane pores, (2) kinetic resistances to mass transfer in both fluid phases, and (3) influence of the chemical reaction on the overall kinetics, is reported. First, the model has been validated through the comparison of simulated results with previously reported experimental data. Second, the effect of the module configuration, parallel flow, and cross-flow as well as flow patterns, cocurrent flow, and countercurrent flow on the performance of the separation process is analyzed Process simulation showed that significant improvement of the fluid dynamics can be reached by using a cross flow membrane contactor and the process performance benefits from a countercurrent operating mode.