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), CO(2), and CH(4) as well as scanning electron microscopy (SEM), and differential scanning calorimetry (DSC). The H(2)/CH(4) 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 CO(2)/CH(4) and H(2)/CH(4) 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)/CH(4) selectivity of HMA/SAPO-34/PES membrane was 175.8, which was three times as high as the H(2)/CH(4) 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.