The stabilities and dehydration performances of MER-type zeolite membranes prepared on porous alpha-Al2O3 tubes were determined. The membranes were found to be stable around 573 K and in an acetic acid solution of pH 4, and water permeated through the membrane selectively. The permeation flux and separation factor were 1.9 kg m(-2) h(-1) and 9300, respectively, for an equimolar mixture of ethanol and water at 350 K. Furthermore, the membranes were used for the dehydration of several organic solvents (methanol, n-propanol, i-propanol, and acetone) containing water; it was found that the separation factor increased with the molecular diameter of the organic solvents. In particular, the separation factor for water significantly increased for components with molecular diameters larger than that of ethanol (0.45 nm) because of the similar molecular diameter to the channel diameter of MER-type zeolite (ca. 0.27-0.51 nm). These results suggest that the stability, permeability, and separation performance of the MER-type zeolite membranes are relatively higher than those of the other types of zeolite membranes. (C) 2009 Elsevier B.V. All rights reserved.