Hydrogen purification using a SAPO-34 membrane

A SAPO-34 membrane separated CO2/H-2 and H-2/CH4 mixtures at feed pressures up to 1.7 MPa. Strong CO2 adsorption inhibited H-2 adsorption and decreased H-2 permeances significantly, especially at low temperatures, so that CO2 preferentially permeated and CO2/H-2 selectivities were higher at low temperatures. At 253 K, CO2/H-2 Separation selectivities were greater than 100 With CO2 permeances of 3 x 10(-8) mol m(-2) s(-1) Pa-1. The CO2/H-2 separation exceeded the upper bounds (selectivity-permeability plot) for polymer membranes. The SAPO-34 membrane separated H-2 from CH4 because CH4 is close to the SAPO-34 pore size and has a lower diffusivity than H-2. The H-2/CH4 separation selectivity had a small maximum with temperature, and decreased slightly with feed pressure and CH4 feed concentration. (C) 2007 Elsevier B.V. All rights reserved.