The permeation of a mixture containing H-2, CO2 and water through a zeolite membrane was studied under several operating conditions. The aim was to obtain insight on the feasibility of using such membrane in a zeolite membrane reactor for CO2 hydrogenation to methanol. The effects of total pressure (100-270 kPa), water partial pressure (10-18 kPa) and temperature (160-260 degrees C) were studied. Promising water-permanent gas separation factors were obtained up to 240 degrees C. A surprisingly high water partial pressure was found in the permeate in some cases, which is explained by the radial temperature gradient in the experimental system. The good capability of this zeolite A membrane to selectively separate water vapor makes it a promising material for its use in a zeolite membrane reactor.