The effect of low molecular weight additive (LMWA) loading on the gas permeation properties of pure PES and PES/SAPO-34 membranes was investigated. 2-hydroxy 5-methyl aniline (HMA) was selected as LMWA. Membranes were prepared by solvent-evaporation method and annealed above the glass transition temperature (T-g) of PES. They were characterized by single gas permeability measurements of H-2, CO2, and CH4 as well as scanning electron microscopy (SEM), and differential scanning calorimetry (DSC). The H-2/CH4 selectivities of pure PES and SAPO-34/PES membranes were 71.31 and 61.02, respectively. The incorporation of zeolite SAPO-34 to neat PES membranes resulted in higher permeabilities for all gases with slight decrease in CO2/CH4 and H-2/CH4 ideal selectivities compared to pure PES membranes. However, PES/SAPO-34/HMA membranes had significantly higher ideal selectivities than pure PES, PES/SAPO-34, and PES/HMA membranes, for example the H-2/CH4 selectivity of HMA/SAPO-34/PES membrane was 175.8, which was three times as high as the H-2/CH4 selectivity of PES/SAPO-34 membrane. The permeabilities of all the gases through PES/SAPO-34/HMA membranes were also higher than those through PES/HMA membranes. Ternary component membranes revealed better gas permeation performance compared to pure polymeric and binary component membranes. (C) 2010 Elsevier B.V. All rights reserved.