Using membrane reactor integrated with water vapor permselective membrane, the Sabatier reaction for the methanation of carbon dioxide with hydrogen, CO2+4H(2) double left right arrow CH4+2H(2)O, was investigated. The reaction experiments were carried out under the conditions of superficial space velocity 0.030-0.123 s(-1), molar ratio of H-2 to CO2 in the feed gas, 1-5, operating pressure 0.2 MPa absolute, and temperature 480-719 K. The conversion was increased about 18% in maximum with the membrane. Theoretical equations for Sabatier reaction with and without membrane were derived and applied to analyze the experimental data of CO2 conversion.