The present invention relates to a surface modified zeolite adsorbent wherein the surface of said zeolite is modified with a coating comprised of a silicone derived species, said zeolite having a mean crystal size from about 5 to about 10 μm and a skeletal density of ≥1.10 gr./cc. The invention is based on the discovery that larger crystals tend to have higher particle density, and the packing of the larger crystals in agglomeration processes leads to more idealized packing to provide a larger mean-pore diameter. The surface modified adsorbent provides rate selectivity for one gas over others is described. The superior adsorbent has the added convenience of bead forming simultaneously with pore modification as well as having the treatment result in the yielding of high crush strength products.