Methane/Nitrogen Gas Separation over the Zeolite Clinoptilolite by the Selective Adsorption of Nitrogen

Abstract

N 2 diffuses into the structural pores of clinoptilolite 10 3 to 10 4 times faster than does CH 4 . Thus internal surfaces are kinetically selective for N 2 adsorption. Some clino samples are more effective at N 2 /CH 4 separation than others and this property was correlated with the zeolite surface cation population. An incompletely exchanged clino containing doubly charged cations appears to be the most selective for N 2 . Using a computer-controlled pressure swing adsorption apparatus, several process variables were studied in multiple cycle experiments. These included feed composition and rates, and adsorber temperature, pressure and regeneration conditions. N 2 diffusive flux reverses after about 60 seconds, but CH 4 adsorption continues. This causes a decay in the observed N 2 /CH 4 separation. Therefore, optimum process conditions include rapid adsorber pressurization and short adsorption/desorption/regeneration cycles.