Adsorption separation of H₂, CO₂, CH₄ , CO and N₂ by zeolites

Abstract

This experiment studies studies hydrogen purification by cryogenic adsorption. Effect of zeolite molecular sieves, temperature, bead size, inlet pressure and ratio of zeolite/alumina were studied. Life time of adsorbents was also investigated. The characterization of each zeolite was determined by XRD. Zeolite were studied are 3A, 4A, 5A, 13X and beta at the temperature of -196℃, 0℃ and ambient (25℃). The inlet pressure are 5, 10, 15, 20 bar g. Bead size are 1-2 and 2.5-5 mm. The ratio of alumina:zeolite are 9:3 and 5:7 by weight. Life time of adsorbents were studied by repeating 4 times of calcinations at 300℃, 3 hours for zeolite and 180℃, 3 hours for alumina. Then compare purity of hydrogen after each adsorption cycle. Feed gases are standard mixed gas composed of 10.1% CO, 9.9% CO₂, 10.1% CH₄, 10.0% N₂, 59.8% H₂ and hydrogen industrial grade. According to the results, beta zeolite has a good adsorbtion ability for CO₂, CH₄, CO and N₂ respectively. The suitable inlet pressure is 10 barg and the temperature at purify tank -196℃. The pellet size is 2.5-5 mm. and the ratio of alumina:zeolite is 9:3. When this condition was applied to, hydrogen industrial grade as a feed gas, hydrogen purity would be increased up to 99.9999%. This adsorbent was test to reuse. After four times of adsorption cycles, this adsorbent can be reused without a significant changing in H₂ purity.