With a large specific area, micro-porous membranes in the geometry of hollow fibers become attractive materials for providing an effective contact area between two phases (e.g. liquid-gas and liquid-liquid). In this study, we used hollow fibers as structured packing materials in the propane/propylene distillation. We investigate the effects of morphology and compatibility of hollow fibers on separation efficiency and operation stability in the distillation process. While a hydrophobic micro-porous membrane may seem preferable for this application, an asymmetric membrane with sub-micron pore size on the liquid side may be more suitable for long-term stability of the distillation operation. A stable operation zone without flooding and loading problems is obtained when the pressure drop across the membrane is in a certain ran e. Typically, the high separation efficiency (HTU < 30 cm) is obtained when the tested modules are operated inside this stable zone. Published by Elsevier B.V.