SAPO-34 membranes were hydrothermally synthesized using 75 nm-sized SAPO-34 crystals as seed crystals. The SAPO-34 membrane showed a high selectivity to water for water/2-propanol (H2O/IPA) vapor permeation (separation factor > 3200). Selective coke deposition within the pores of SAPO-34 via methanol-to-olefins reaction was applied to examine the effects of zeolitic and non-zeolitic pathways on the separation properties using various SAPO-34 membranes with different qualities. The results imply that H2O molecules are selectively adsorbed and the permeation of IPA is blocked even through the non-zeolitic pores (less than 1 nm) of SAPO-34 membranes. The size and hydrophilicity of non-zeolitic pores are important factors for inhibiting the IPA permeation. (c) 2012 Elsevier B.V. All rights reserved.