This study investigated the effect of annealing time and temperature on gas separation performance of mixed matrix membranes (MMMs) prepared from polyethersulfone (PES), SAPO-34, and 2-hydroxy 5-methyl aniline (HMA). A postannealing period at 120 degrees C for a week extensively increased the reproducibility and stability of MMMs, but for pure PES membranes no postannealing was necessary for stable and reproducible performance. The effect of operation temperature was also investigated. The permeabilities of H-2, CO2, and CH4 increased with increasing permeation temperature from 35 degrees C to 120 degrees C, yet CO2/CH4 and H-2/CH4 selectivities decreased. PES/SAPO-34/HMA ternary and PES/SAPO-34 binary MMMs exhibited the highest ideal selectivity and permeability values at all temperatures, respectively. For H-2/CO2 pair, when temperature increased from 35 degrees C to 120 degrees C, selectivity increased from 3.2 to 4.6 and H-2 permeability increased from 8 to 26.5 Barrer for ternary MMM, demonstrating the advantage of using this membrane at high temperatures. The activation energies were in the order of CH4 > H-2 > CO2 for all membranes. PES/SAPO-34/HMA membrane had activation energies higher than that of PES/SAPO-34 membrane, suggesting that HMA acts as a compatibilizer between the two phases. (C) 2014 Wiley Periodicals, Inc.