An improved gas separation PSA process, more particularly for oxygen production, utilizing adsorbents of Type X characterized by high frequency (i.e., cycle times of less than 4 s), bed length to square of mean particle diameter ratio within 200 to 600 mm−1, bed size factor of less than 50 lb/TPDO. The bed length, mean particle size, and cycle time are selected in a range such that axial dispersion becomes an important factor. In this way, low product recovery and high pressure drop (high power consumption) disadvantages often associated with the use of small particles are overcome.