SAPO-34 membranes had 95-100 higher CO(2) permeances and 9-17 lower CO(2)/CH(4) separation selectivities when their structure-directing templates were removed at 673 K in flowing N(2) or under vacuum instead of in flowing air. The average CO(2) permeance was 8.2 +/- 2 x 10(-7) mol/(m(2) s Pa) during CO(2)/CH(4) separations at 4.6 MPa feed pressure for five membranes whose templates were removed under vacuum. The average CO(2)/CH(4) separation selectivity was 55 +/- 6. Membranes heated in N(2) or under vacuum were white in color, whereas those heated in air were darker. Membrane preparation was reproducible. Temperature-programmed desorption (TPD) and oxidation (TPO) of SAPO-34 crystals showed that more of the templates decomposed and were removed at lower temperature in inert gas than in air or oxygen. Over 90 of the templates were removed by 773 K during TPD in helium, and ethylene was the main decomposition product. In contrast, only 70 of the templates were removed by 773 K during TPO in air or oxygen, and CO(2) and water were the major products When the SAPO-34 crystals were heated in air or oxygen, some of the template, before it decomposed to form ethylene, was oxidized to more stable compounds that were only removed at higher temperatures. (C) 2010 Elsevier By. All rights reserved.
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