A new recycle type continuous flow membrane reactor was constructed to study the operating conditions of membrane reactors and analyze the reported performances of membrane contactors. The operating conditions of the new reactor were as follows: pressure 1-15 bar, temperature 25-170 degrees C, trans-membrane pressures (TMP) from 0.05 to 5 bar, and residence time from 1 to 30 min. The position of the gas-liquid (G-L) interface in the membrane wall was determined by means of controlled precipitation of CaCO3 from a 0.008 M solution of Ca(OH)(2) by a gas mixture containing 1 vol% of CO2 TMP of 0.4, 1.5 and 3.0 bar. It was confirmed that the liquid phase can be selectively displaced from the membrane carrier layer, whereas selective liquid displacement from the filtration layer is still questionable and was not experimentally confirmed. The stability of the physical conditions inside the membrane was checked with gas-liquid mass transport experiments and the catalytic oxidation of formic acid. (C) 2014 Elsevier B.V. All rights reserved